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  • Springer  (21,061)
  • International Union of Crystallography  (3,844)
  • Periodicals Archive Online (PAO)
  • 2000-2004  (24,905)
  • 2002  (24,905)
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  • 2000-2004  (24,905)
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  • 1
    Electronic Resource
    Electronic Resource
    Some experimental and theoretical studies on the Mn magnetic moment in Y ( Ni 1 - x Mn x ) 2 B 2 C (2002)
    Springer
    The European physical journal 25 (2002), S. 307-311 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.25.Jb Electronic structure – 75.10.Lp Band and itinerant models – 75.30.Hx Magnetic impurity interactions – 74.25.Ha Magnetic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The magnetic moment of the Mn impurities was obtained from magnetization measurements of Y ( Ni 1 - x Mn x ) 2 B 2 C as a function of the concentration x less than 0.15. Using the coherent potential approximation and starting from 3 d density of states, obtained from the first principles calculations, the magnetic moments are obtained within a two sublattice model. For adequately estimated values of the Coulomb interactions U, the position of the energy level of Mn and adopting values for the intersublattice hybridization term, a qualitative agreement with the observed experimental data is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020035
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  • 2
    Electronic Resource
    Electronic Resource
    The September 11 attack: A percolation of individual passive support (2002)
    Springer
    The European physical journal 26 (2002), S. 269-272 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 89.75.Hc Networks and genealogical trees – 05.50.+q Lattice theory and statistics (Ising, Potts, etc.) – 87.23.Ge Dynamics of social systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A model to terrorism is presented using the theory of percolation. Terrorism power is related to the spontaneous formation of random backbones of people who are sympathetic to terrorism but without being directly involved in it. They just don't oppose in case they could. In the past such friendly-to-terrorism backbones have been always existing but were of finite size and localized to a given geographical area. The September 11 terrorist attack on the US has revealed for the first time the existence of a world wide spread extension. It is argued to have result from a sudden world percolation of otherwise unconnected and dormant world spread backbones of passive supporters. The associated strategic question is then to determine if collecting ground information could have predict and thus avoid such a transition. Our results show the answer is no, voiding the major criticism against intelligence services. To conclude the impact of military action is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020089
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  • 3
    Electronic Resource
    Electronic Resource
    Element-specific magnetic long- and short-range order and competing interactions in Gd x Eu 1 - x S (2002)
    Springer
    The European physical journal 26 (2002), S. 273-289 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.25.+z Spin arrangements in magnetically ordered materials (including neutron and spin-polarised electron studies, synchrotron-source X-ray scattering, etc.). – 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) – 78.70.Ck X-ray scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report on an investigation of the magnetic properties of Gd x Eu 1 - x S mixed crystals with compositions in the range of 0.6 〈 x 〈 1. For the two samples Gd 0.8 Eu 0.2 S and Gd 0.73 Eu 0.27 S a long-range antiferromagnetic order was observed at low temperatures. Element-specific measurements exhibited a different temperature dependence of the reduced sublattice magnetisation of the two magnetic species. A model calculation and Monte Carlo simulations revealed that the different temperature dependence is due to frustration effects. These frustration effects lead to a breakdown of the long-range order for higher europium contents. For the Gd 0.67 Eu 0.33 S-sample we were able to observe a short-range antiferromagnetic order with correlation lengths of a few 10Å with X-ray resonance exchange scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020090
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  • 4
    Electronic Resource
    Electronic Resource
    Generation of 3rd and 5th harmonics in a thin superconducting film by temperature oscillations and isothermal nonlinear current response (2002)
    Springer
    The European physical journal 26 (2002), S. 291-296 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.) – 74.40.+k Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.) – 74.76.-w Superconducting films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The generation of harmonics of the voltage response is considered when an AC current is applied through a superconducting film above Tc. It is shown that almost at all temperatures the mechanism of the temperature oscillations created by the AC current and the temperature dependence of the resistance dominates over the isothermal nonlinear electric conductivity. Only in a narrow critical region close to Tc the latter is essential for the generation of the harmonics. A detailed investigation of harmonics generation provides an accurate method for measuring the thermal boundary conductance between the film and the insulating substrate. The critical behaviour of the third harmonic will give a new method for the determination of the lifetime of metastable Cooper pairs above Tc. The comparison of the calculated fifth harmonics of the voltage with the experiment is proposed as an important test for the applicability of the employed theoretical models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020091
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  • 5
    Electronic Resource
    Electronic Resource
    The asymptotic behaviour of the exact and approximative ν = 1/2   Chern-Simons Green's functions (2002)
    Springer
    The European physical journal 26 (2002), S. 307-318 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.) – 73.43.-f Quantum Hall effects – 71.27.+a Strongly correlated electron systems; heavy fermions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We consider the asymptotic behaviour of the Chern-Simons Green's function of the ν = 1/ system for an infinite area in position-time representation. We calculate explicitly the asymptotic form of the Green's function of the interaction free Chern-Simons system for small times. The calculated Green's function vanishes exponentially with the logarithm of the area. Furthermore, we discuss the form of the divergence for all τ and also for the Coulomb interacting Chern-Simons system. We compare the asymptotics of the exact Chern-Simons Green's function with the asymptotics of the Green's function in the Hartree-Fock as well as the random-phase approximation (RPA). The asymptotics of the Hartree-Fock Green's function correspondence well with the exact Green's function. In the case of the RPA Green's function we do not get the correct asymptotics. At last, we calculate the self consistent Hartree-Fock Green's function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020094
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  • 6
    Electronic Resource
    Electronic Resource
    Probing electron-phonon coupling in high-Tc superconductors by site-selective isotope substitution (2002)
    Springer
    The European physical journal 26 (2002), S. 323-328 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 63.20.Kr Phonon-electron and phonon-phonon interactions – 74.25.Kc Phonons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We consider changes in the electron-phonon coupling in high-T c cuprates caused by site-selective oxygen isotope substitution. Contrary to the total substitution, the site-selective replacement influences the coupling constant for each phonon mode due to the induced changes in the phonon eigenvectors. The relative changes for some modes can be larger than 100%. The measured properties sensitive to these changes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020096
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  • 7
    Electronic Resource
    Electronic Resource
    MO analysis of macroscopic supercurrent flow in MgB 2 (2002)
    Springer
    The European physical journal 26 (2002), S. 297-300 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.70.-b Superconducting materials (excluding high-Tc compounds) – 74.50.+r Proximity effects, weak links, tunneling phenomena, and Josephson effects – 74.80.-g Spatially inhomogeneous structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present results from an extended magneto-optical (MO) analysis of two samples cut from high-density pellets of MgB2. The first sample was studied in order to show that no matter how large the sample is and despite the bulk granularity, the material enters into a critical state in a crystal-like fashion. The second sample was chosen for the quantitative analysis. A numerical approach based on an inverted 2D Biot-Savart model was used to calculate the current paths across the homogeneous polycrystalline bulk, as well as in the vicinity and across some morphological defects. Local current densities in the homogeneous part were estimated as a function of the applied magnetic field at different temperatures, in three regimes: below full penetration, at full penetration and above full penetration, respectively. A hypothesis of interpretation of the apparent absence of magnetic granularity inside the polycrystalline microstructure is presented. It is related to a critical state likely reached by a network of strongly coupled Josephson junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020092
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  • 8
    Electronic Resource
    Electronic Resource
    Calculation of partial structure factors of a less-simple binary alloy (2002)
    Springer
    The European physical journal 26 (2002), S. 319-322 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.25.Mv Liquid metals and alloys – 61.20.-p Structure of liquids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The partial static structure factors, using the Faber-Ziman (FZ) theory, have been calculated for Ag-In alloy. For 20% Ag at 623 K and 70% Ag at 973 K, the interionic pair potential based on the Bretonnet-Silbert (BS) formalism are calculated and the hard sphere diameters for the component elements are estimated from the potential profile using the linearised Weeks-Chandler-Andersen (LWCA) method. The average number densities are calculated on the assumption that the atomic volumes are simply additive. The calculated structure factors are compared with the experimental values. The partial structure factors for Ag-Ag at 20% Ag and In-In at 70% Ag appear to be slightly out of phase with the calculated values particularly in large q-region. From the calculations it appears that this discrepancy is related to the process of derivation of the experimental structure factors from the total one, and the Ag-In alloy can be described by a mixture of hard spheres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020095
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  • 9
    Electronic Resource
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    Intercalation and high temperature superconductivity of fullerides (2002)
    Springer
    The European physical journal 26 (2002), S. 3-6 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.70.Wz Fullerenes and related materials – 74.72.-h High-Tc compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Intercalation of polyatomic molecules into a superconductor can drastically affect the properties of the compound. A mechanism responsible for a large increase in T c for such systems is proposed. It explains the recent remarkable observation of high T c superconductivity in the hole-doped C60/CHX3 (X≡Cl, Br) compounds and the large shift in their T c upon Cl↦Br substitution. The increase in T c is due to contribution to the pairing arising from the interaction of electrons with the vibrational manifold of the molecule. The proposed mechanism opens up the possibility to observe a site-selective isotope effect. We also suggest that intercalating CHI3 would further increase the critical temperature to T c≃ 140 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020058
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  • 10
    Electronic Resource
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    Giant moments of Fe and Co on and in rubidium aaand potassium films (2002)
    Springer
    The European physical journal 26 (2002), S. 7-11 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions – 71.20.Dg Alkali and alkaline earth metals – 73.50.-h Electronic transport phenomena in thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Thin quench-condensed films of Rb and K are covered with 1/100 of a mono-layer of Fe or Co. Then the impurities are covered with several atomic layers of the host. The magnetization of the films is measured by means of the anomalous Hall effect (AHE). The magnetization follows a Brillouin function with a magnetic moment of more than 10 Bohr magnetons for bulk Co and Fe impurities. These moments are much larger than the moments of the atomic configurations of Fe and Co and suggest enhanced magnetic moments of the impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020059
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  • 11
    Electronic Resource
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    Strain effect on transport properties of SrRuO 3 films grown by laser MBE (2002)
    Springer
    The European physical journal 26 (2002), S. 23-28 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 81.15.Fg Laser deposition – 75.70.Ak Magnetic properties of monolayers and thin films – 81.40.Jj Elasticity and anelasticity, stress-strain relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Transport properties of SrRuO3 thin films were studied as a function of the epitaxial strain. SrRuO3 films were grown on (100) SrTiO3 substrates by the Pulsed Laser Deposition technique equipped with Reflection High Energy Electrons Diffraction (RHEED). Samples thickness has been varied from a few unit cells to above 1000 Å while monitoring RHEED intensity oscillations. In thicker films epitaxial strain was found to be progressively relaxed. SrRuO3 relaxed films (thickness 1000 Å) show metallic behavior for the whole temperature range with a ferromagnetic ordering at about 150 K. For thinner films, ferromagnetic ordering occurs at progressively lower temperatures, until in films thinner than 400 Å it disappears. Films thinner than 80 Å show a semiconducting behavior at low temperatures. Our results provide direct evidence of the crucial role of the strain effect for conducting and magnetic properties of SrRuO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020061
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  • 12
    Electronic Resource
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    Persistence distributions in a conserved lattice gas with absorbing states (2002)
    Springer
    The European physical journal 26 (2002), S. 75-79 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.70.Ln Nonequilibrium and irreversible thermodynamics – 05.50.+q Lattice theory and statistics (Ising, Potts, etc.) – 05.65.+b Self-organized systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Extensive simulations are performed to study the persistence behavior of a conserved lattice gas model exhibiting an absorbing phase transition from an active phase into an inactive phase. Both the global and the local persistence exponents are determined in two and higher dimensions. The local persistence exponent obeys a scaling relation involving the order parameter exponent of the absorbing phase transition. Furthermore we observe that the global persistence exponent exceeds its local counterpart in all dimensions in contrast to the known persistence behavior in reversible phase transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020068
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  • 13
    Electronic Resource
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    Renormalization group treatment of the scaling properties of finite systems with subleading long-range interaction (2002)
    Springer
    The European physical journal 26 (2002), S. 89-99 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 64.60.-i General studies of phase transitions – 64.60.Fr Equilibrium properties near critical points, critical exponents – 75.40.-s Critical-point effects, specific heats, short-range order
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The finite size behavior of the susceptibility, Binder cumulant and some even moments of the magnetization of a fully finite O(n) cubic system of size L are analyzed and the corresponding scaling functions are derived within a field-theoretic ɛ-expansion scheme under periodic boundary conditions. We suppose a van der Waals type long-range interaction falling apart with the distance r as r - (d + σ), where 2 〈 σ 〈 4, which does not change the short-range critical exponents of the system. Despite that the system belongs to the short-range universality class it is shown that above the bulk critical temperature T c the finite-size corrections decay in a power-in-L, and not in an exponential-in-L law, which is normally believed to be a characteristic feature for such systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020070
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  • 14
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    Hydrodynamic vector potentials (2002)
    Springer
    The European physical journal 26 (2002), S. 121-132 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.20.Ft Instability of shear flows – 47.27.Cn Transition to turbulence – 47.11.+j Computational methods in fluid dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Solving the Navier-Stokes equation for incompressible fluids is greatly simplified by the solution of the vorticity equation. To accomplish this for three-dimensional flows requires vector potentials. These potentials are not only useful to take care of the incompressibility. Their modes are suitable also as test functions since the familiar Galerkin procedure does not work. The new method is checked by examples with known results and its relation to the classical approach with the stream function is clarified. The principle demonstration, however, concerns the transition to turbulence in plane shear flows. A simple layer of long rolls with axes parallel to the basic flow incites the transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020073
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  • 15
    Electronic Resource
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    On adiabatic N-soliton interactions and trace identities (2002)
    Springer
    The European physical journal 29 (2002), S. 237-241 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 42.65.Tg Optical solitons – 02.30.Ik Integrable systems – 45.20.J Hamiltonian mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We compare the Hamiltonian properties of the N-soliton solutions of the NLSE in the adiabatic approximation and show how it matches the Hamiltonian formulation for the complex Toda chain which describes the adiabatic N-soliton interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00293-7
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  • 16
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    Effect of phase shift in shape changing collision of solitons in coupled nonlinear Schrödinger equations (2002)
    Springer
    The European physical journal 29 (2002), S. 249-254 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 42.65.Tg .Optical solitons – 02.30.Ik .Integrable systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Soliton interactions in systems modelled by coupled nonlinear Schrödinger (CNLS) equations and encountered in phenomena such as wave propagation in optical fibers and photorefractive media possess unusual features: shape changing intensity redistributions, amplitude dependent phase shifts and relative separation distances. We demonstrate these properties in the case of integrable 2-CNLS equations. As a simple example, we consider the stationary two-soliton solution which is equivalent to the so-called partially coherent soliton (PCS) solution discussed much in the recent literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00295-5
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  • 17
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    Hedgehog production in spatially correlated noise (2002)
    Springer
    The European physical journal 29 (2002), S. 269-271 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 11.27.+d Extended classical solutions; cosmic strings, domain walls, texture – 05.70.Fh Phase transitions: general studies – 67.40.Vs Vortices and turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The production of topological defects during a quench in a φ4 model is investigated. The influence of a spatially correlated noise on defect production in two and three dimensions is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00299-1
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  • 18
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    Off-center Li ions: solid state rotators described by Mathieu's nonlinear-oscillator equation (2002)
    Springer
    The European physical journal 29 (2002), S. 273-277 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.72.-y Defects and impurities in crystals; microstructure – 71.38.-k Polarons and electron-phonon interactions – 76.30.Mi Color centers and other defects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Substitutional impurity ions in crystals are known to displace off-center and to perform hindered rotations around the ideal lattice positions. The vibronic theory to describe both the off-center displacements and the hindered rotations by a single angular equation incorporates terms up to 3rd order in the off-center displacement coordinates. When the rotation is confined to a single plane, the corresponding vibronic equation is equivalent to Mathieu's equation. Extending our earlier work, we derive here the dipole-dipole coupling to take into account cooperative phenomena. We also derive the optical absorption band arising from dipolar transitions across “Mexican Hat” surfaces, and we show that hindered rotations gives rise to magnetic moments quantized in rotational bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00300-1
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  • 19
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    Crowdion dynamics in a nonuniformly deformed three-dimensional crystal (2002)
    Springer
    The European physical journal 29 (2002), S. 285-289 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 63.20.Ry Anharmonic lattice modes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The problem of crowdion motion is formulated and analyzed as a dynamical problem of a three-dimensional crystal lattice formed by atoms of several kinds, which interact with each other by means of short-range pair potentials. It is explained that in order for the the crowdion excitations of the close-packed atomic rows to be distinguishable against the background of small dynamic deformations of the crystal as a whole, the microscopic parameters of the crystal structure must meet certain stated requirements. The equation of motion of a crowdion in an arbitrary elastic strain field of the crystal is derived in the Lagrangian formalism. Expressions are obtained which relate the effective mass and the rest energy of a crowdion with the geometric and force parameters of the crystal lattice.
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    URL: http://dx.doi.org/10.1140/epjb/e2002-00302-y
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  • 20
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    Standing wave instabilities, breather formation and thermalization in a Hamiltonian anharmonic lattice (2002)
    Springer
    The European physical journal 29 (2002), S. 279-283 
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    ISSN: 1434-6036
    Keywords: PACS. 63.20.Ry Anharmonic lattice modes – 45.05.+x General theory of classical mechanics of discrete systems – 05.45.-a Nonlinear dynamics and nonlinear dynamical systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Modulational instability of travelling plane waves is often considered as the first step in the formation of intrinsically localized modes (discrete breathers) in anharmonic lattices. Here, we consider an alternative mechanism for breather formation, originating in oscillatory instabilities of spatially periodic or quasiperiodic nonlinear standing waves (SWs). These SWs are constructed for Klein-Gordon or Discrete Nonlinear Schrödinger lattices as exact time periodic and time reversible multibreather solutions from the limit of uncoupled oscillators, and merge into harmonic SWs in the small-amplitude limit. Approaching the linear limit, all SWs with nontrivial wave vectors (0 〈 Q 〈 π) become unstable through oscillatory instabilities, persisting for arbitrarily small amplitudes in infinite lattices. The dynamics resulting from these instabilities is found to be qualitatively different for wave vectors smaller than or larger than π/2, respectively. In one regime persisting breathers are found, while in the other regime the system thermalizes.
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    URL: http://dx.doi.org/10.1140/epjb/e2002-00301-0
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  • 21
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    Soliton dynamics in chiral molecular chains with first- and third-neighbour interactions (2002)
    Springer
    The European physical journal 29 (2002), S. 291-294 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 63.20.Ry Anharmonic lattice modes – 78.20.Ek Optical activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate the propagation and interaction of solitons associated with circularly polarized vibrations in gyrotropic media. The chirality of the structure yields different dispersion laws and hence different phase and group velocities for the left- and right-handed modes. The helical arrangement of the monomers is modelled through first- and third-neighbour interactions. The dynamics of the excitations is governed by a system of coupled discrete nonlinear Schrödinger equations which is studied both analytically and numerically. Depending on the initial conditions and the interaction constants, different evolutionary patterns are obtained corresponding to unbound or bound one- and two-soliton solutions. The results can be applied to the process of energy transfer in helical polymers.
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    URL: http://dx.doi.org/10.1140/epjb/e2002-00303-x
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  • 22
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    Lattice effects in the quasiparticle dynamics and kinetics (2002)
    Springer
    The European physical journal 29 (2002), S. 295-300 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.60.-k Transport processes – 05.20.-y Classical statistical mechanics – 41.20.-q Applied classical electromagnetism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In this work we present a full selfconsistent set of nonlinear equations which unifies the nonlinear elasticity theory equations, the Boltzmannn transport theory and the Maxwell equations for quasiparticles with arbitrary dispersion laws in nonstationarily deformed crystals with arbitrary (but linear) constitutive relations. Transformations to replace the Galilean ones are obtained, the quasiparticle mechanics in a Hamiltonian form is deduced, and a Boltzmann-type transport equation (valid in the whole Brillouin zone) is derived. The theory may be applied to metals, semiconductors, quantum crystals, low-dimensional structures etc.
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    URL: http://dx.doi.org/10.1140/epjb/e2002-00304-9
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  • 23
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    Exciton-polariton solitary waves (2002)
    Springer
    The European physical journal 29 (2002), S. 301-304 
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    ISSN: 1434-6036
    Keywords: PACS. 71.36.+c Polaritons – 71.35.-y Excitons and related phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Effects of the exciton and polariton dispersions and the nonlinear exciton and photon interactions on the properties of polariton solitons in molecular crystals are investigated. Higher-order terms and phase-modulation (chirp) are taken into account. Bright- and dark-soliton solutions of the resulting modified nonlinear Schrödinger (NLS) equation are presented. Nonlinearity- and dispersion-induced critical points on the polariton dispersion curve are obtained, separating regions with different solutions.
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    Non-linear dynamics of spinodal decomposition (2002)
    Springer
    The European physical journal 29 (2002), S. 305-309 
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    ISSN: 1434-6036
    Keywords: PACS. 05.45.Yv Solitons – 47.20.Ky Nonlinearity – 47.54.+r Pattern selection; pattern formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We develop a new technique describing the non linear growth of interfaces. We apply this analytical approach to the one dimensional Cahn-Hilliard equation. The dynamics is captured through a solvability condition performed over a particular family of quasi-static solutions. The main result is that the dynamics along this particular class of solutions can be expressed in terms of a simple ordinary differential equation. The density profile of the stationary regime found at the end of the non-linear growth is also well characterized. Numerical simulations are compared in a satisfactory way with the analytical results through three different fitting methods and asymptotic dynamics are well recovered, even far from the region where the approximations hold.
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    Elasticity and shape equation of a liquid membrane (2002)
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    The European physical journal 29 (2002), S. 317-322 
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    ISSN: 1434-6036
    Keywords: PACS. 87.16.Dg Membranes, bilayers, and vesicles
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    Topics: Physics
    Notes: Abstract: The density of the elastic energy of a deformed membrane in a liquid state is calculated. The thermodynamic equilibrium of its different parts is taken into account. The shape equation of a closed membrane is deduced. The quantity which keeps its value, when the variations of the energy of the system are calculated, is not the area of the deformed membrane, but its area in the flat tension free state. Because of this, additional terms appear in the second variation around the stable state. The case of a lipid bilayer and its fluctuations is examined for both free and blocked exchange of molecules between the monolayers, comprising the bilayer.
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    An advected-field method for deformable entities under flow (2002)
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    The European physical journal 29 (2002), S. 311-316 
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    ISSN: 1434-6036
    Keywords: PACS. 87.16.Dg Membranes, bilayers, and vesicles – 47.55.Dz Drops and bubbles – 87.17.Jj Cell locomotion; chemotaxis and related directed motion
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    Topics: Physics
    Notes: Abstract: We study dynamics of a deformable entity (such as a vesicles under hydrodynamical constraints). We show how the problem can be solved by means of Green's functions associated with the Stokes equations. A gauge-field invariant formulation makes the study of dynamics efficient. However, this procedure has its short-coming. For example, if the fluids are not Newtonian, then no Green's function is available in general. We introduce a new approach, the advected field one, which opens a new avenue of applications. For example, non-Newtonian entities can be handled without additional deal. In addition problems like budding, droplet break-up in suspensions, can naturally be treated without additional complication. We exemplify the method on vesicles filled by a fluid having a viscosity contrast with the external fluid, and submitted to a shear flow. We show that beyond a viscosity contrast (the internal fluid being more viscous), the vesicle undergoes a tumbling bifurcation, which has a saddle-node nature. This bifurcation is known for blood cells. Indeed red cells either align in a shear flow or tumble according to whether haematocrit concentration is high or low.
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    Complexifications and real forms of Hamiltonian structures (2002)
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    The European physical journal 29 (2002), S. 177-181 
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    ISSN: 1434-6036
    Keywords: PACS. 02.30.Ik Integrable systems – 02.40.Tt Complex manifolds – 45.20.Jj Lagrangian aaand Hamiltonian mechanics
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    Topics: Physics
    Notes: Abstract: We consider generalizations of the standard Hamiltonian dynamics to complex dynamical variables and introduce the notions of real Hamiltonian form in analogy with the notion of real forms for a simple Lie algebra. Thus to each real Hamiltonian system we are able to relate several nonequivalent ones. On the example of the complex Toda chain we demonstrate how starting from a known integrable Hamiltonian system (e.g. the Toda chain) one can complexify it and then project onto different real forms.
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    On the rational solutions of the Knizhnik-Zamolodchikov equation (2002)
    Springer
    The European physical journal 29 (2002), S. 183-187 
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    ISSN: 1434-6036
    Keywords: PACS. 11.25.Hf Conformal field theory, algebraic structures – 02.20.Uw Quantum groups – 11.30.Ly Other internal and higher symmetries
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    Topics: Physics
    Notes: Abstract: We present some new results on the rational solutions of the Knizhnik-Zamolodchikov (KZ) equation for the four-point conformal blocks of isospin I primary fields in the SU (2) k Wess-Zumino-Novikov-Witten (WZNW) model. The rational solutions corresponding to integrable representations of the affine algebra (2) k have been classified in [#!MST!#,#!ST!#]; provided that the conformal dimension is an integer, they are in one-to-one correspondence with the local extensions of the chiral algebra. Here we give another description of these solutions as specific braid-invariant combinations of the so called regular basis introduced in [#!STH!#] and display a new series of rational solutions for isospins I = k + 1,  k ∈ N corresponding to non-integrable representations of (2) k .
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    CEF nature of the magnetic excitations in ordered HoNi B C (2002)
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    The European physical journal 29 (2002), S. 377-384 
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    ISSN: 1434-6036
    Keywords: PACS. 74.70.Dd Ternary, quaternary and multinary compounds – 75.10.Dg Crystal-field theory and spin Hamiltonians – 78.70.Nx Neutron inelastic scattering
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    Topics: Physics
    Notes: Abstract: The magnetic excitations in the antiferromagnetic phase of HoNi2B2C are studied by inelastic neutron scattering on single crystals for the first time. Spectra measured at constant T = 2 K along symmetry directions of the reciprocal space are well explained in terms of crystal electric field (CEF) magnetic excitons within the J = 8 ground state multiplet of Ho3+. Very modest bandwidth with planar energy dispersion describes the magnetic exciton dynamics. A perturbative model approach consisting of the CEF states in the effective exchange mean-field provides a simple but applicable characterization of the experimental observations. The microscopic determination of the relevant exchange parameters is discussed in connection with previous works on the subject.
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    Ultrametricity between states at different temperatures in spin-glasses (2002)
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    The European physical journal 29 (2002), S. 425-435 
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    ISSN: 1434-6036
    Keywords: PACS. 75.10.Nr Spin-glass and other random models
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    Topics: Physics
    Notes: Abstract: We prove the existence of correlations between the equilibrium states at different temperatures of the multi-p-spin spherical spin-glass models with continuous replica symmetry breaking: there is no chaos in temperature in these models. Furthermore, the overlaps satisfy ultrametric relations. As a consequence the Parisi tree is essentially the same at all temperatures with lower branches developing when lowering the temperature. We conjecture that the reference free energies of the clusters are also fixed at all temperatures as in the generalized random-energy model.
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    Lagrangian and Eulerian velocity intermittency (2002)
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    The European physical journal 29 (2002), S. 357-358 
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    ISSN: 1434-6036
    Keywords: PACS. 47.27.Gs Isotropic turbulence; homogeneous turbulence
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    Topics: Physics
    Notes: Abstract: Usual turbulence experiments, based on the Taylor hypothesis, differ from true Eulerian measurements. This is the origin of the apparent discrepancy between a recent two point correlation analysis and the multiplicative cascade picture. Indeed, both Eulerian and Lagrangian observations perfectly agree with this picture.
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    The CPA solution of the anomalous Lyapunov exponent for disordered binary chains (2002)
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    The European physical journal 29 (2002), S. 437-440 
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    ISSN: 1434-6036
    Keywords: PACS. 75.10.Hk Classical spin models – 78.30.Ly Disordered solids – 71.23.-k Electronic structure of disordered solids
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    Topics: Physics
    Notes: Abstract: The Coherent Potential Approximation (CPA) self-consistent equation is calculated for a binary disordered chain introducing a simple transformation. The transformation reduces the CPA equation to a cubic polynomial whose complex roots are related to the Green function and their relation to the complex Lyapunov exponent is also established. This solution fruitfully captures essential aspects of the well-known anomalous scaling behaviors in a different and advantageous way. It is found that the anomalous behavior is strongly effected by the nature of these roots. A small disorder expansion is carried out for comparison with the previous weak disorder calculations. We found that the CPA reproduced the anomalous behavior of the exact calculations.
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    Application of percolation theory to current transfer in granular superconductors (2002)
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    The European physical journal 29 (2002), S. 359-367 
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    ISSN: 1434-6036
    Keywords: PACS. 64.60.Ak Renormalization-group, fractal, and percolation studies of phase transitions – 74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.) – 4.80.Bj Granular, melt-textured, and amorphous superconductors; powders
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    Notes: Abstract: We investigate the description of current transfer in polycrystalline superconductors by percolation theory and its limitations. Various computer models that have been proposed are reviewed and related to the experimental and theoretical framework. While some conductor properties can be well described by percolation theory and models, we argue that a conceptual gap exists between experiment and theory. This gap has to be bridged by finding relations between electromagnetic and statistical parameters. We derive various such relations and compare them with recent simulation data. In particular, we suggest a new scaling law between the two fundamental variables “current” and “probability”.
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    High field transport properties of La Sr CuO epitaxial thin films (2002)
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    The European physical journal 29 (2002), S. 369-375 
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    ISSN: 1434-6036
    Keywords: PACS. 74.25.Fy Transport properties – 74.25.jb Electronic structure
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    Notes: Abstract: We have studied the temperature dependent resistivity ρ( T ) of La2-xSrxCuO4 epitaxial thin films in the doping range 0.045 ⩽ x ⩽ 0.25 in pulsed magnetic fields up to 50 T. The zero-field resistivity ρ( T ) of these samples in the pseudogap regime, can be scaled onto one single universal curve in a broad temperature range by using a linear transformation of both temperature and resistivity. The high field data ρ( T ) reveal a metal to insulator transition (MIT) at low temperatures, well into the overdoped regime. For samples having k F l 〈 1, with kF the Fermi wave vector and l the mean free path, this low temperature insulating behavior of the resistivity is described by the variable range hopping conductivity (VRH). For samples with k F l 〉 1, the divergence follows ρ( T ) ∼ ln (1/ T ) or a power law, depending upon the Sr-content. We further found that the residual conductivity at the minimum in ρ( T ), appearing due to the MIT, follows a linear behavior with respect to the Sr-content. It is argued that the unusual MIT in compounds with k F l 〉 1, is most probably associated with the pseudogap and the behavior of charge stripes at low temperatures.
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    Dynamics of modulated and composite aperiodic crystals (2002)
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    The European physical journal 29 (2002), S. 385-398 
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    ISSN: 1434-6036
    Keywords: PACS. 61.44.-n Semiperiodic solids – 63.20.Dj Phonon states and bands, normal modes, and phonon dispersion – 61.12.-q Neutron diffraction and scattering
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    Topics: Physics
    Notes: Abstract: We compare within an unifying formalism the dynamical properties of modulated and composite aperiodic (incommensurate) crystals. We discuss the concept of inner polarization and we define an inner polarization parameter β that distinguishes between different acoustic modes of aperiodic crystals. Although this concept has its limitations, we show that it can be used to extract valuable information from neutron coherent inelastic scattering experiments. Within certain conditions, the ratio between the dynamic and the static structure factors at various Bragg peaks depends only on β. We show how the knowledge of β for modes of an unknown structure can be used to decide whether the structure is composite or modulated. The same information can be used to predict scattered intensity within unexplored regions of the reciprocal space, being thus a guide for experiments.
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    The 1D Hubbard model within the Composite Operator Method (2002)
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    The European physical journal 29 (2002), S. 399-417 
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    ISSN: 1434-6036
    Keywords: PACS. 71.10.Fd Lattice fermion models (Hubbard model, etc.) – 71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.) – 71.27.+a Strongly correlated electron systems; heavy fermions
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    Topics: Physics
    Notes: Abstract: Although effective for two dimensional (2D) systems, some approximations may fail in describing the properties of one-dimensional (1D) models, which belong to a different universality class. In this paper, we analyze the adequacy of the Composite Operator Method (COM), which provides a good description of many features of 2D strongly correlated systems, in grasping the physics of 1D models. To this purpose, the 1D Hubbard model is studied within the framework of the COM by considering a two-pole approximation and a paramagnetic ground state. The local, thermodynamic and single-particle properties, the correlation functions and susceptibilities are calculated in the case of half filling and arbitrary filling. The results are compared with those obtained by the Bethe ansatz (BA) as well as by other numerical and analytical techniques. The advantages and limitations of the method are analyzed in detail.
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    Cellular oscillator with a small number of particles (2002)
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    The European physical journal 29 (2002), S. 485-489 
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    ISSN: 1434-6036
    Keywords: PACS. 05.10.Ln Monte Carlo methods – 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion – 05.65.+b Self-organized systems – 87.17.-d Cellular structure and processes
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    Notes: Abstract: To illustrate complex spatio-temporal effects which are possible in cellular reactions with a small number of particles, we present Monte Carlo simulations of the formation of oscillatory spark-like patterns in a model completely stochastic Ca+2 oscillator. Our analysis shows that in order to observe such patterns the minimum average number of Ca+2 ions in the cytosol may be as low as about 50.
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    Magnetism of alloyed models of Cr(Mn) V and Mn Cr overlayers on V (001) substrates (2002)
    Springer
    The European physical journal 29 (2002), S. 497-501 
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    ISSN: 1434-6036
    Keywords: PACS. 75.70.Ak Magnetic properties of monolayers and thin films
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    Topics: Physics
    Notes: Abstract: The magnetism is calculated for substitutional alloyed of Crx(Mnx)V1-x monolayers (MLs) and CrxMn1-x on V (001) surface with a variety of concentrations (x = 0.25, 0.50 and 0.75). The substitutional surface alloys were treated by an artificial super cell construction. Parallel magnetic ordering is obtained for all the considered structures. The surface net magnetization increases in terms of Cr (Mn) concentration in Crx(Mnx)V1-x/V (001) system, while no serious variations occur in CrxMn1-x/V (001). Vanadium atoms at the interfacial layers acquire appreciable magnetic moments antiferromagneticlly (AF) coupled with the surface moments.
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    Diffusion theory of spin injection through resistive contacts (2002)
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    The European physical journal 29 (2002), S. 513-527 
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    Keywords: PACS. 72.25.Hg Electrical injection of spin polarized carriers – 72.25.Mk Spin transport through interfaces
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    Topics: Physics
    Notes: Abstract: Insertion of a resistive contact between a ferromagnetic metal and a semiconductor microstructure is of critical importance for achieving efficient spin injection into a semiconductor. However, the equations of the diffusion theory are rather cumbersome for the junctions including such contacts. A technique based on deriving a system of self-consistent equations for the coefficients of spin injection, γ, through different contacts are developed. These equations are concise when written in the proper notations. Moreover, the resistance of a two-contact junction can be expressed in terms of γ's of both contacts. This equation makes calculating the spin valve effect straightforward, allows to find an explicit expression for the junction resistance and to prove that its nonequilibrium part is positive. Relation of these parameters to different phenomena like spin-e.m.f. and the contact transients is established. Comparative effect of the Coulomb screening on different parameters is clarified. It is also shown that the spin non-conservation in a contact can have a dramatic effect on the non-equilibrium resistance of the junction.
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    Magnetization and neutron scattering studies of the pressure effect on the magnetic transition in Er Y Co (2002)
    Springer
    The European physical journal 29 (2002), S. 547-552 
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    ISSN: 1434-6036
    Keywords: PACS. 75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) – 75.25.+z Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.) – 74.62.Fj Pressure effects – 61.12.-q Neutron diffraction and scattering
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    Topics: Physics
    Notes: Abstract: Neutron powder diffraction was employed to study the pressure effect on the magnetic transition in the pseudobinary Laves-phase compound Er0.57Y0.43Co2 and to determine the magnetic moments of the Er- and Co-subsystems. Our studies reveal that the onset of long-range magnetic order for both the localized 4 f (Er) and itinerant 3 d (Co) electron moments appears at about the same temperature at ambient pressure. The pressure effect on Tc is found to be negative and equal for both sublattices, namely T c / p ∼ - 0.4 K/kbar. The values of the magnetic moments of the Er and the Co ions are found = 5.40±0.15μ B /atom, = 0.50±0.07μ B /atom and 5.35±0.15μ B /atom, 0.37±0.09μ B /atom, for p = 0 and 6 kbar, respectively. Our experimental results give evidence for short-range magnetic order formation at temperatures already above Tc and for a coexistence short- and long-range order below Tc down to 4 K.
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    SrRuO based heterostructures grown by pulsed laser deposition (2002)
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    The European physical journal 29 (2002), S. 561-566 
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    ISSN: 1434-6036
    Keywords: PACS. 81.15.Fg Laser deposition – 61.10.Kw X-ray reflectometry (surfaces, interfaces, films) – 68.55.Ac Nucleation and growth: microscopic aspects
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    Topics: Physics
    Notes: Abstract: In this report we demonstrate that high quality epitaxial heterostructures, based on metallic SrRuO3 and insulating SrTiO3 individual blocks a few unit cells thick, can be grown in a purely 2D, layer-by-layer mode, using pulsed laser deposition with in situ reflection high energy electron diffraction (RHEED) diagnostics. The thickness of each constituent block can be controlled at the level of a single unit cell. A detailed investigation carried out at the synchrotron facility, ESRF, by various X-ray techniques has demonstrated that each intensity oscillation of the RHEED specular spot corresponds strictly to the growth of a single perovskite unit cell, either SrRuO3 or SrTiO3. Furthermore, we show that, in these structures, the interfaces between the different constituent blocks are very sharp with a roughness of only one unit cell.
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    Balance-equation approach to impact ionization induced by an intense terahertz radiation: Application to InAs/AlSb heterojunctions (2002)
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    The European physical journal 29 (2002), S. 553-559 
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    ISSN: 1434-6036
    Keywords: PACS. 73.50.Fq High-field and nonlinear effects – 72.10.-d Theory of electronic transport; scattering mechanisms – 72.20.-i Conductivity phenomena in semiconductors and insulators
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    Topics: Physics
    Notes: Abstract: We have extended the balance equations to account for conduction-valence interband impact ionization (II) process induced by an intense terahertz (THz) electromagnetic irradiation in semiconductors, and applied them to study the II effect on electron transport and electron-hole pair generation-recombination rate in THz-driven InAs/AlSb heterojunctions (HJ). As many as needed multiphoton channels are self-consistently taken into account for yielding a given accuracy. The time evolution of transport state including THz-radiation-induced II process are monitored in details by an extensive time-dependent analysis. Two different physical stages, the quasi-steady state and the complete steady-state, are clearly identified from the present calculations. Intersubband electron transfer rate and net electron-hole generation rate are derived as functions of the THz radiation strength E ac for various radiation frequencies from f ac = 0.42 to 6 THz at lattice temperatures T = 6 K. It's indicated that the THz radiation with a larger E ac or a lower f ac, has a stronger effect on electron transport and II process. Qualitative agreement is obtained between the calculated electron-hole generation rate and the available experimental data for InAs/AlSb HJ's at T = 6 K.
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    The role of pinning and instability in a class of non-equilibrium growth models (2002)
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    The European physical journal 29 (2002), S. 567-576 
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    ISSN: 1434-6036
    Keywords: PACS. 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion – 64.60.Ht Dynamic critical phenomena – 05.70.Ln Nonequilibrium and irreversible thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the dynamics of a growing crystalline facet where the growth mechanism is controlled by the geometry of the local curvature. A continuum model, in (2+1) dimensions, is developed in analogy with the Kardar-Parisi-Zhang (KPZ) model is considered for the purpose. Following standard coarse graining procedures, it is shown that in the large time, long distance limit, the continuum model predicts a curvature independent KPZ phase, thereby suppressing all explicit effects of curvature and local pinning in the system, in the “perturbative” limit. A direct numerical integration of this growth equation, in 1+1 dimensions, supports this observation below a critical parametric range, above which generic instabilities, in the form of isolated pillared structures lead to deviations from standard scaling behaviour. Possibilities of controlling this instability by introducing statistically “irrelevant" (in the sense of renormalisation groups) higher ordered nonlinearities have also been discussed.
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    Birth and long-time stabilization of out-of-equilibrium coherent structures (2002)
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    The European physical journal 29 (2002), S. 577-591 
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    Keywords: PACS. 05.20.-y Classical statistical mechanics – 05.45.-a Nonlinear dynamics and nonlinear dynamical systems
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    Notes: Abstract: We study an analytically tractable model with long-range interactions for which an out-of-equilibrium very long-lived coherent structure spontaneously appears. The dynamics of this model is indeed very peculiar: a bicluster forms at low energy and is stable for very long time, contrary to statistical mechanics predictions. We first explain the onset of the structure, by approximating the short time dynamics with a forced Burgers equation. The emergence of the bicluster is the signature of the shock waves present in the associated hydrodynamical equations. The striking quantitative agreement with the dynamics of the particles fully confirms this procedure. We then show that a very fast timescale can be singled out from a slower motion. This enables us to use an adiabatic approximation to derive an effective Hamiltonian that describes very well the long time dynamics. We then get an explanation of the very long time stability of the bicluster: this out-of-equilibrium state corresponds to a statistical equilibrium of an effective mean-field dynamics.
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    Separable-entangled frontier in a bipartite harmonic system (2002)
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    The European physical journal 29 (2002), S. 605-611 
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    ISSN: 1434-6036
    Keywords: PACS. 03.65.Bz Foundations, theory of measurement, miscellaneous theories (including Aharonov-Bohm effect, Bell inequalities, Berry's phase) – 03.67.-a Quantum information – 05.20.-y Classical statistical mechanics – 05.30.-d Quantum statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We consider a statistical mixture based on that of two identical harmonic oscillators which is characterized by four parameters, namely, the concentrations (x and y) of diagonal and nondiagonal bipartite states, and their associated thermal-like noises (T/α and T, respectively). The fully random mixture of two spins 1/2 as well as the Einstein-Podolsky-Rosen (EPR) state are recovered as particular instances. By using the conditional nonextensive entropy as introduced by Abe and Rajagopal, we calculate a bound for the separable-entangled frontier. Although this procedure is known to provide a necessary but in general not sufficient condition for separability, it does recover, in the particular case x = T = 0 ( ∀α), the 1/3 exact result known as Peres' criterion. The x = 0 frontier remarkably resembles to the critical line associated with standard diluted ferromagnetism where the entangled region corresponds to the ordered one and the separable region to the paramagnetic one. The entangled region generically shrinks for increasing T or increasing α.
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    Envelope solitons induced by high-order effects of light-plasma interaction (2002)
    Springer
    The European physical journal 29 (2002), S. 613-618 
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    ISSN: 1434-6036
    Keywords: PACS. 52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.) – 52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma – 52.35.Sb Solitons; BGK modes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The nonlinear coupling between light beams and non-resonant ion density perturbations in a plasma is considered, taking into account the relativistic particle mass increase and the light beam ponderomotive force. A pair of equations comprising a nonlinear Schrödinger equation for light beams and a driven (by the light beam pressure) ion-acoustic wave response is derived. It is shown that the stationary solutions of our nonlinear equations can be represented in the form of a bright and dark/gray soliton for the one-dimensional problem. We also present numerical results which exhibit that our bright soliton solutions are stable exclusively for the values of the parameters compatible with our theory.
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    Genetic Algorithms as a tool in the study of aperiodic order, with application to the case of X-Ray diffraction spectra of GaAs-AlAs multilayer heterostructures (2002)
    Springer
    The European physical journal 29 (2002), S. 619-628 
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    ISSN: 1434-6036
    Keywords: PACS. 02.50.-r Probability theory, stochastic processes, and statistics – 05.90.+m Other topics in statistical physics, thermodynamics, and nonlinear dynamical systems – 61.10.-i X-ray diffraction and scattering – 61.43.-j Disordered solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present the first application of Genetic Algorithms to the analysis of data from an aperiodically ordered system, high resolution X-Ray diffraction spectra from multilayer heterostructures arranged according to a deterministic or random scheme. This method paves the way to the solution of the “inverse problem”, that is the retrieval of the generating disorder from the investigation of the spectra of an unknown sample having non crystallographic, non quasi-crystallographic order.
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    Inelastic relaxation and noise temperature in S/N/S junctions (2002)
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    The European physical journal 29 (2002), S. 629-633 
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    ISSN: 1434-6036
    Keywords: PACS. 74.50.+r Proximity effects, weak links, tunneling phenomena, and Josephson effects – 74.80.Fp Point contacts; SN and SNS junctions – 73.50.Td Noise processes and phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We studied electronic relaxation in long diffusive superconductor/normal metal/superconductor (S/N/S) junctions by means of current noise and transport measurements down to very low temperature (100mK). Samples with normal metal lengths of 4, 10 and 60μm have been investigated. In all samples the shot noise increases very rapidly with the voltage. This is interpreted in terms of enhanced heating of the electron gas confined between the two S/N interfaces. Experimental results are analyzed quantitatively taking into account electron-phonon interaction and heat transfer through the S/N interfaces. Transport measurements reveal that in all samples the two S/N interfaces are connected incoherently, as shown by the reentrance of the resistance at low temperature. The complementarity of noise and transport measurements allows us to show that the energy dependence of the reentrance at low voltage is essentially due to the increasing effective temperature of the quasiparticles in the normal metal.
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    Resonant enhancement of charge transfer through surface states (2002)
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    The European physical journal 29 (2002), S. 635-639 
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    ISSN: 1434-6036
    Keywords: PACS. 73.20.At Surface states, band structure, electron density of states – 73.40.-c Electronic transport in interface structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A model is proposed that treats electrons at surfaces as a combination of two-dimensional and three-dimensional degrees of freedom. This yields a simple formula for the surface state induced resonant enhancement of the transfer of electrons through a surface. The model also yields analytic approximations for the transition between two-dimensional and three-dimensional distance laws in the correlations between electrons in surface states.
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    Thermal instability of a rotating saturated porous medium heated from below and submitted to rotation (2002)
    Springer
    The European physical journal 29 (2002), S. 641-647 
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    ISSN: 1434-6036
    Keywords: PACS. 47.20.Bp Buoyancy-driven instability – 44.25.+f Natural convection – 47.27.Te Convection and heat transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In this work, we study the problem of onset of thermal convection in a rotating saturated porous medium heated from below. The effect of rotation is restricted to the Coriolis force, neglecting thus the centrifugal effects, the porous medium is described by Brinkman's model. The linear eigenvalue problem is solved by means of a modified Galerkin method. The behavior of the critical temperature gradient is discussed in terms of various parameters of the system for both stationary and overstable convections. Finally a weakly nonlinear analysis is provided to derive amplitude equations and to study the onset of Küppers-Lortz instability.
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    Super-slippery carbon nanotubes (2002)
    Springer
    The European physical journal 25 (2002), S. 131-134 
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    ISSN: 1434-6036
    Keywords: PACS. 61.48.+c Fullerenes and fullerene-related materials – 62.20.Qp Tribology and hardness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The friction between the walls of multi-wall carbon nanotubes is shown to be extremely low in general, with important details related to the specific choice of the walls. This is governed by a simple expression revealing that the phenomenon is a profound consequence of the specific symmetry breaking: super-slippery sliding of the incommensurate walls is a Goldstone mode. Three universal principles of tribology, offering a recipe for lubricant selection are emphasized.
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    Electronic structure of Pu monochalcogenides and monopnictides (2002)
    Springer
    The European physical journal 25 (2002), S. 139-146 
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    ISSN: 1434-6036
    Keywords: PACS. 71.27.+a Strongly correlated electron systems; heavy fermions – 71.28.+d Narrow-band systems; intermediate-valence solids – 71.15.Nc Total energy and cohesive energy calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The electronic and magnetic properties of Pu monopnictides and monochalcogenides, PuX (X = N, P, As, Sb, Bi, O, S, Se, Te, Po), are studied using the self-interaction-corrected local spin-density approximation. This approach allows for an integer number of f-states to be localized, while the remaining f-electron degrees of freedom are available for band formation. By varying the relative proportions of localized and delocalized f-states, the energetically most favourable (groundstate) configuration can be established. We show that the experimental data can be interpreted in terms of the coexistence of both localized and delocalized f-states.
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    Structure and magnetic properties of epitaxial cobalt islands (2002)
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    The European physical journal 25 (2002), S. 167-176 
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    ISSN: 1434-6036
    Keywords: PACS. 75.50.Tt Fine-particle systems; nanocrystalline materials – 75.30.Gw Magnetic anisotropy – 75.60-d Domain effects, magnetization curves, and hysteresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Growth, structural and magnetic properties of cobalt island structures grown by molecular beam epitaxy on 4 nm thick island shaped Ru buffers are studied. The islands are characterized by a narrow distribution of sizes, and are separated on average by spacing of around one hundred nanometers. Growth of the islands into continuous films is found to proceed in three well defined stages, and corresponding magnetic behaviors are identified. The particles formed in the first stage of growth appear to be similar in shape and size, and their magnetic behavior suggest the presence of superparamagnetism. Particles in the second stage of growth are ferromagnetic and display a reorientation transition of their magnetization out of the film plane, consistent with that seen in patterned magnetic dot arrays. Particles coalesce in the last stage of growth and magnetic properties of continuous films are observed.
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    Electronic structure and metal-insulator transition in SrTi 1 - x Ru xO 3 (2002)
    Springer
    The European physical journal 25 (2002), S. 203-208 
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    ISSN: 1434-6036
    Keywords: PACS. 79.60.Bm Clean metal, semiconductor, and insulator surfaces – 78.70.Dm X-ray absorption spectra – 71.30.+h Metal-insulator transitions and other electronic transitions
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    Topics: Physics
    Notes: Abstract: We studied the changes in the electronic structure of SrTi1-xRuxO3 across the metal-insulator transition. The parent compound, SrTiO3, is a well known diamagnetic insulator; whereas the doped compound, SrTi1-xRuxO3, becomes a ferromagnetic metal above x C = 0.35. The techniques used in the study were photoemission (PES) and O 1 s X-ray absorption (XAS) spectroscopy. The experimental spectra were analyzed in terms of band structure and Hubbard model calculations. The PES and XAS spectra of SrTi1-xRuxO3 show the Ru 4 d bands growing in the band gap of SrTiO3 . The analysis in terms of the Hubbard model indicates that the Ti 3 d and Ru 4 d bands are mostly decoupled. This suggests that the metal-insulator transition is a percolation transition like that of metals embedded in a rare gas matrix. Electron correlation effects are present in this system, but they do not seem to play a major role in the transition.
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    Effect of lattice fluctuations on the quantum phase transition in a one-dimensional commensurate system (2002)
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    The European physical journal 25 (2002), S. 299-306 
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    ISSN: 1434-6036
    Keywords: PACS. 71.38.-k Polarons and electron-phonon interactions – 71.30.+h Metal-insulator transitions and other electronic transitions – 71.45.Lr Charge-density-wave systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The effect of quantum lattice fluctuations on the properties of quantum phase transition in a one-dimensional commensurate system near and at criticality is studied. The nonadiabatic effect due to finite phonon frequency 〉 0 are treated through an energy-dependent electron-phonon scattering function introduced in a unitary transformation. By using the Green's function perturbation theory we have shown that our theory gives a good description of the effect of quantum lattice fluctuations: (1) At the criticality, when the coupling constant g2 decreases or the phonon frequency increases the lattice distortion and the gap in the fermionic spectrum decreases gradually; at some critical value g c 2 or ( )c, the system becomes gapless and the lattice distortion disappears. (2) The calculated density of states do not have the inverse-square-root singularity but have a peak with a significant tail below the peak. (3) At the criticality our approach successfully describes the classical-quantum crossover. In the classical region the adiabatic mean-field parameters may strongly be renormalized by nonadiabatic corrections, and in the quantum region the phase transition is of the signature of a Kosterlitz-Thouless transition. (4) Away from the criticality the critical exponents for the energy gap and the ordering parameter have been calculated.
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    Transition to plastic motion as a critical phenomenon and anomalous interface layer of a 2D driven vortex lattice (2002)
    Springer
    The European physical journal 25 (2002), S. 313-317 
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    ISSN: 1434-6036
    Keywords: PACS. 64.60.Ht Dynamic critical phenomena – 74.60.Ge Flux pinning, flux creep and flux-line lattice dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The dynamic transition between ordered flow and plastic flow is studied for a two-dimensional driven vortex lattice, in the presence of sharp and dense pinning centers, from numerical simulations. For this system, which does not show smectic ordering, the lattice exhibits a first order transition from a crystal to a liquid, shortly followed by the dynamical transition to plastic flow. The resistivity provides a critical order parameter for the latter, and critical exponents are determined in analogy with a percolation transition. At the boundary between a pinned region and an unpinned one, an anomalous layer is observed, where the vortices are more strongly pinned than in the bulk.
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    Directed transport of an asymmetric particle pair induced by non-equilibrium conditions (2002)
    Springer
    The European physical journal 25 (2002), S. 345-350 
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    ISSN: 1434-6036
    Keywords: PACS. 05.60.Cd Classical transport – 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion – 87.16.Nn Motor proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The hopping motion of a classical bounded pair of two particles along a chain is investigated. It is shown that in the asymmetric case of the system dynamics including excited states which differ from the respective ground states by the barrier to be overcome by one of the two particles, the over- and underpopulation of these excited states leads to a directed motion of the particle pair. Thereby, overpopulation results in one direction of motion, whereas underpopulation results in the opposite direction, and the mean velocity is determined by the amount of over-resp. underpopulation. For small deviations from equilibrium, the system exhibits linear response well known from other ratchet-type models. Possible generalizations and applications are discussed.
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    Microscopic theory of non local pair correlations in metallic F/S/F trilayers (2002)
    Springer
    The European physical journal 25 (2002), S. 373-389 
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    ISSN: 1434-6036
    Keywords: PACS. 74.50.+r Proximity effects, weak links, tunneling phenomena, and Josephson effects – 74.80.Dm Superconducting layer structures: superlattices, heterojunctions, and multilayers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We consider a microscopic theory of F/S/F trilayers with metallic or insulating ferromagnets. The trilayer with metallic ferromagnets is controlled by the formation of non local pair correlations among the two ferromagnets which do not exist with insulating ferromagnets. The difference between the insulating and ferromagnetic models can be understood from lowest order diagrams. Metallic ferromagnets are controlled by non local pair correlations and the superconducting gap is larger if the ferromagnetic electrodes have a parallel spin orientation. Insulating ferromagnets are controlled by pair breaking and the superconducting gap is smaller if the ferromagnetic electrodes have a parallel spin orientation. The same behavior is found in the presence of disorder in the microscopic phase variables and also in the presence of a partial spin polarization of the ferromagnets. The different behaviors of the metallic and insulating trilayers may be probed in experiments.
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    Minority opinion spreading in random geometry (2002)
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    The European physical journal 25 (2002), S. 403-406 
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    ISSN: 1434-6036
    Keywords: PACS. 89.75.Hc Networks and genealogical trees – 05.50.+q Lattice theory and statistics (Ising, Potts, etc.) – 87.23.Ge Dynamics of social systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The dynamics of spreading of the minority opinion in public debates (a reform proposal, a behavior change, a military retaliation) is studied using a diffusion reaction model. People move by discrete step on a landscape of random geometry shaped by social life (offices, houses, bars, and restaurants). A perfect world is considered with no advantage to the minority. A one person-one argument principle is applied to determine locally individual mind changes. In case of equality, a collective doubt is evoked which in turn favors the Status Quo. Starting from a large in favor of the proposal initial majority, repeated random size local discussions are found to drive the majority reversal along the minority hostile view. Total opinion refusal is completed within few days. Recent national collective issues are revisited. The model may apply to rumor and fear propagation.
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    Coherent transport in disordered metals: zero dimensional limit (2002)
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    The European physical journal 30 (2002), S. 5-8 
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    ISSN: 1434-6036
    Keywords: PACS. PACS 73.23.-b Electronic transport in mesoscopic systems – PACS 73.63.-b Electronic transport in mesoscopic or nanoscale materials and structures
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    Topics: Physics
    Notes: Abstract: We consider non-equilibrium transport in disordered conductors. We calculate the interaction correction to the current for a short wire connected to electron reservoirs by resistive interfaces. In the absence of charging effects we find a universal current-voltage-characteristics. The relevance of our calculation for existing experiments is discussed as well as the connection with alternative theoretical approaches.
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    Effective action approach to the Leggett's mode in two-band superconductors (2002)
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    The European physical journal 30 (2002), S. 45-51 
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    ISSN: 1434-6036
    Keywords: PACS. 74.20.Fg BCS theory and its development – 11.10.Wx Finite-temperature field theory
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    Topics: Physics
    Notes: Abstract: We investigate a collective excitation (Leggett's mode) corresponding to small fluctuations of the relative phase of two condensates in two-band superconductor using the effective “phase only” action. We consider the possibility of observing Leggett's mode in MgB2 superconductor and conclude that for the known at present values of the two-band model parameters for MgB2 Leggett's mode arises above the two-particle threshold.
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    Coexistence of superconductivity and ferromagnetism in ferromagnet/superconductor proximity structures (2002)
    Springer
    The European physical journal 30 (2002), S. 33-38 
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    ISSN: 1434-6036
    Keywords: PACS. 74.50.+r Proximity effects, weak links, tunneling phenomena, and Josephson effects – 74.80.Fp Point contacts; SN and SNS junctions – 74.80.-g Spatially inhomogeneous structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The Nambu spinor Green's function approach is applied to calculating the density of states (DOS) and superconducting order parameter in normal-metal/insulator/ferromagnet/superconductor (NM/I/FM/SC) junctions. It is found that the s-wave superconductivity and ferromagnetism can coexist near the FM/SC interface, which is induced by proximity effect. On the SC side, the spin-dependent DOS appears both within and without the energy gap. On the FM side, the superconducting order parameter displays a damped oscillation and the DOS exhibits some superconducting behavior. The calculated result for the DOS in FM for “0 state” and “π state” can reproduce recent tunneling spectra in Al/Al2O3/PdNi/Nb tunnel junctions.
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    Quantitative roughness of sputtered Fe-Cr superlattices (2002)
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    The European physical journal 30 (2002), S. 17-23 
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    ISSN: 1434-6036
    Keywords: PACS. 68.35.Ct Interface structure and roughness – 68.65.Cd Superlattices – 68.37.Lp Transmission electron microscopy (TEM) – 61.10.Eq X-ray scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We obtained quantitative values of all significant parameters describing the roughness of Fe-Cr superlattices, both in the lateral and growth directions, by statistical analysis of energy-filtered transmission electron microscopy images using cross section samples. These results are in good agreement with the complementary low-angle X-ray scattering measurements. The interface roughness of sputtered Fe-Cr superlattices was changed systematically by varying Ar-pressure during the growth and the number of the bilayers. By scaling local window size we obtained the dependence of the saturated roughness and its correlation lengths in both the lateral and growth directions. The roughness and its correlation lengths (lateral and perpendicular) increase with pressure. However correlation length in the lateral is constant with bilayer index for low-pressure sputtered samples
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    Electronic topological transitions and phase stability in the fcc Al-Zn alloys (2002)
    Springer
    The European physical journal 30 (2002), S. 57-66 
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    ISSN: 1434-6036
    Keywords: PACS. 71.23.-k Electronic structure of disordered solids – 71.18.+y Fermi surface: calculations and measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report on a detailed investigation of the phase equilibria and the Fermi surface in the Al-Zn system. Our calculation are based on the density functional theory and we use the linear muffin-tin orbital method and the Green's function technique. The calculated free energies of alloy formation exhibit the existence of a miscibility gap between the alloys containing approximately 10 and 55 at.% of Zn, in agreement with the phase diagram of the Al-Zn system. Seven electronic topological transitions (ETT) were found in Al-Zn system within the stability range of the fcc solid solution. A relation between these ETT and the phase stability of the fcc Al-Zn solid solutions is established. We show that extremum points on the concentration dependencies of the thermodynamic properties of Al-Zn alloys can be explained by band-filling effects.
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    Coulomb excitation of 72 30Zn42 (2002)
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    The European physical journal 14 (2002), S. 1-5 
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    ISSN: 1434-601X
    Keywords: PACS. 25.70.De Coulomb excitation – 23.20.-g Electromagnetic transitions
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract: The reduced transition probability B(E2: 01 +→ 2+) of 72Zn has been measured for the first time by Coulomb excitation at intermediate energy. The result B(E2: 01 +→ 2+) = 1740±210 e2fm4, corresponds to the deformation parameter β2 of 0.23, in close agreement with expectations derived from the neighboring nucleus 73Zn. A discussion of the evolution of the N = 40 sub-shell closure as a function of Z is presented.
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    A role of the axial-vector mesons on the photon production in heavy-ion collisions and their relevant decays (2002)
    Springer
    The European physical journal 14 (2002), S. 87-93 
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    ISSN: 1434-601X
    Keywords: PACS. 13.25.Jx Decays of other mesons – 13.30.Eg Hadronic decays – 25.75.Dw Particle and resonance production – 25.70.-z Low and intermediate energy heavy-ion reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A role of the axial-vector mesons, such as K1 and a1, on the emitted-photon spectrum in hot hadronic matter is studied through the channels πρ→a 1→πγ and Kρ→K 1→Kγ. Both channels could be dominant over the region lower than E γ∼ 0.5 GeV, while the role of the K1 meson is diminished in the higher E γ region. This study is carried out with an SU L(3) ⊗SU R(3) effective chiral Lagrangian which includes vector and axial-vector mesons systematically and explains well their hadronic and radiative decays simultaneously.
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    Enhanced excitation of giant pairing vibrations in heavy-ion reactions induced by weakly bound projectiles (2002)
    Springer
    The European physical journal 14 (2002), S. 37-42 
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    ISSN: 1434-601X
    Keywords: PACS. 21.60.Ev Collective models – 25.60.Je Transfer reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The use of radioactive ion beams is shown to offer the possibility to study collective pairing states at high excitation energy, which are not usually accessible with stable projectiles because of large energy mismatch. In the case of two-neutron stripping reactions induced by 6He, we predict a population of the giant pairing vibration in 208Pb or 116Sn with cross-sections of the order of a millibarn, dominating over the mismatched transition to the ground state.
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    Stability and instability of a hot and dilute nuclear droplet (2002)
    Springer
    The European physical journal 14 (2002), S. 43-51 
    Details
    ISSN: 1434-601X
    Keywords: PACS. 21.60.Ev Collective models – 21.65.+f Nuclear matter – 25.70.Mn Projectile and target fragmentation – 25.70.Pq Multifragment emission and correlations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Results on dissipative isoscalar modes of a hot and dilute nuclear droplet are presented. As compared to the adiabatic limit (part I), realistic dissipation yields a substantial reduction of the growth rates for all unstable modes, while the area of spinodal instability in the (ϱ,T)-plane remains unchanged. The qualitative features of multifragmentation through spinodal decomposition as obtained in the adiabatic limit are not significantly affected by dissipation.
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    On the difference between proton and neutron spin-orbit splittings in nuclei (2002)
    Springer
    The European physical journal 14 (2002), S. 29-36 
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    ISSN: 1434-601X
    Keywords: PACS. 21.60.Cs Shell model – 21.10.Pc Single-particle levels and strength functions – 21.60.Jz Hartree-Fock and random-phase approximations – 24.10.Jv Relativistic models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The latest experimental data on nuclei at 132Sn permit us for the first time to determine the spin-orbit splittings of neutrons and protons in identical orbits in this neutron-rich doubly magic region and compare the case to that of 208Pb. Using the new results, which are now consistent for the two neutron-rich doubly magic regions, a theoretical analysis defines the isotopic dependence of the mean-field spin-orbit potential and leads to a simple explicit expression for the difference between the spin-orbit splittings of neutrons and protons. The isotopic dependence is explained in the framework of different theoretical approaches.
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    URL: http://dx.doi.org/10.1140/epja/iepja1393
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    Light-charged-particle evaporation from hot 31P nucleus at E*∼ 60 MeV (2002)
    Springer
    The European physical journal 14 (2002), S. 53-61 
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    ISSN: 1434-601X
    Keywords: PACS. 24.60.Dr Statistical compound-nucleus reactions – 25.70.Gh Compound nucleus – 25.70.Jj Fusion and fusion-fission reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The inclusive energy spectra of light charged particles, such as, α, p, d and t, evaporated from the hot 31P nucleus at an excitation energy E *∼ 60 MeV, have been measured at various angles. The compound nucleus 31P has been populated using two different entrance channel configurations; i.e., 7Li (47 MeV) + 24Mg and 19F (96 MeV) + 12C reactions, leading to the same excitation energy of the compound system. It has been observed that the spectra obtained in the 7Li (47 MeV) + 24Mg reaction follow the standard statistical-model prediction with a spherical configuration of the compound nucleus. But, the spectra obtained in the 19F (96 MeV) + 12C reaction deviate from similar predictions of the statistical model both on higher- as well as on lower-energy sides. Considerable deformation was required to be incorporated in the calculation in order to reproduce the measured-energy spectra in this case. Dynamical trajectory model calculations were not found to play any significant role in explaining the differences in behaviour between the two cases under study. The observed discrepancy has been attributed to the difference in the angular-momentum distributions of the compound nuclei formed in the two reactions.
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    The Z = 82 shell closure in neutron-deficient Pb isotopes (2002)
    Springer
    The European physical journal 14 (2002), S. 23-28 
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    ISSN: 1434-601X
    Keywords: PACS. 21.10.Dr Binding energies and masses – 21.60.Jz Hartree-Fock and random-phase approximations – 27.70.+q 150 ?A? 189 – 27.80.+w 190 ?A? 219
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Recent mass measurements show a substantial weakening of the binding-energy difference δ2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms of deformed ground states of Hg and Po isotopes.
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    Quark-hadron duality and the nuclear EMC effect (2002)
    Springer
    The European physical journal 14 (2002), S. 105-112 
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    ISSN: 1434-601X
    Keywords: PACS. 13.60.Hb Total and inclusive cross-sections (including deep-inelastic processes) – 13.40.Gp Electromagnetic form factors – 14.20.Dh Protons and neutrons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Recent data on polarized proton knockout reactions off 4He nuclei suggest a small but nonzero modification of proton electromagnetic form factors in medium. Using model-independent relations derived on the basis of quark-hadron duality, we relate the medium modification of the form factors to the modification at large x of the deep-inelastic structure function of a bound proton. This places strong constraints on models of the nuclear EMC effect which assume a large deformation of the intrinsic structure of the nucleon in medium.
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    Kink solutions of the classical transverse field Ising chain (2002)
    Springer
    The European physical journal 25 (2002), S. 53-60 
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    ISSN: 1434-6036
    Keywords: PACS. 05.45.Yv Solitons – 75.10.Hk Classical spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate stationary and travelling wave solutions of the classical one-dimensional transverse field Ising model. Results are given on the existence, shape and stability of kink solutions and periodic solutions. We review recent analytical results (e.g., the proof of existence of a one-parameter family of stationary kink solutions and the proof of existence of travelling wave kink solutions with nonzero velocity c≠ 0) and extend them by the use of numerical methods. Small oscillations arising in the tails of travelling kink solutions are investigated numerically. In the end, stability analysis puts some light on pinning effects.
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    Coexistence of ferromagnetism and superconductivity in Cu-rich lanthanum Cu-oxides (2002)
    Springer
    The European physical journal 25 (2002), S. 19-23 
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    ISSN: 1434-6036
    Keywords: PACS. 74.72.Dn La-based cuprates – 74.25.Ha Magnetic properties – 74.90.+n Other topics in superconductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We have measured the zero field and field cooled magnetization of the lightly oxygen doped Cu-rich La2CuO 4 + δ in a wide temperature range (5 K to 350 K). The data together with the evolution of the magnetic hysteresis loop suggest that the ferromagnetism with Curie temperature of 280 K coexists with superconductivity below the transition temperature ∼ 34 K. The coexistence occurs in the hole-rich clusters of size ? 150 nm, which are electronic phase separated from the hole-poor antiferromagnetic background.
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    Correlation between growth of high-index faces, relative growth rates and crystallographic structure of crystal (2002)
    Springer
    The European physical journal 25 (2002), S. 61-68 
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    ISSN: 1434-6036
    Keywords: PACS. 81.10.Aj Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: According to contemporary crystal growth theories, crystals are bound by low-index faces which are the most slowly growing. However, high-index faces are observed in crystal habits more and more often. In this paper the growth of high-index faces is analysed from a crystallographic perspective. It is shown that the crystallographic structure of a given crystal, expressed by the trigonometric function of appropriate interfacial angles, influences to great degree the crystallisation process and the morphology of crystals, in particular the behaviour of high-index faces. Additionally, it is concluded that at particular crystallographic structure of a crystal, a given high-index face may exist in the habit and develop its size, although it grows much faster than the neighbouring faces.
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    Scattering of vortex pairs in 2D easy-plane ferromagnets (2002)
    Springer
    The European physical journal 25 (2002), S. 89-100 
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    ISSN: 1434-6036
    Keywords: PACS. 75.10.Hk Classical spin models – 75.70.Kw Domain structure (including magnetic bubbles) – 05.45.Yv Solitons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Vortex-antivortex pairs in 2D easy-plane ferromagnets have characteristics of solitons in two dimensions. We investigate numerically and analytically the dynamics of such vortex pairs. In particular we simulate numerically the head-on collision of two pairs with different velocities for a wide range of the total linear momentum of the system. If the momentum difference of the two pairs is small, the vortices exchange partners, scatter at an angle depending on this difference, and form two new identical pairs. If it is large, the pairs pass through each other without losing their identity. We also study head-tail collisions. Two identical pairs moving in the same direction are bound into a moving quadrupole in which the two vortices as well as the two antivortices rotate around each other. We study the scattering processes also analytically in the frame of a collective variable theory, where the equations of motion for a system of four vortices constitute an integrable system. The features of the different collision scenarios are fully reproduced by the theory. We finally compare some aspects of the present soliton scattering with the corresponding situation in one dimension.
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    Rotating superconductors: Ginzburg-Landau equations (2002)
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    The European physical journal 25 (2002), S. 25-30 
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    ISSN: 1434-6036
    Keywords: PACS. 74.20.De Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) – 74.25.Bt Thermodynamic properties – 74.25.Ha Magnetic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Superconductors put into rotation develope a spontaneous internal magnetic field (the “London field”). In this paper Ginzburg Landau equations for order parameter, field, and current distributions for superconductors in rotation are derived. Two simple examples are discussed: the massive cylinder and the “Little and Parks geometry”: a thin film of superconducting material deposited on a cylinder of normal material. A dependence of T c on rotational frequency is predicted. The magnitude of the effect is estimated and should be observable.
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    Evaluation of forces in magnetic materials by means of energy and co-energy methods (2002)
    Springer
    The European physical journal 25 (2002), S. 31-38 
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    ISSN: 1434-6036
    Keywords: PACS. 41.20.-q Applied classical electromagnetism – 41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems – 05.70.-a Thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The evaluation of the total force of magnetic origin acting upon a body in a stationary magnetic field is often carried out using the so-called magnetic energy (or co-energy) method, which is based on the derivation of the magnetic energy (or co-energy) with respect to a virtual rigid displacement of the considered body. The application of this method is usually justified by resorting to the energy conservation principle, written in terms both of electrical and of mechanical quantities. In this paper we shall re-examine the whole matter in the context of classical thermodynamics, in order to obtain a more comprehensive and general proof of the validity of the energy (or co-energy) approach and to point out its limitations. Two typical configurations will be discussed; in the first one, the field sources are represented by conducting bodies carrying free currents, whereas in the second one a permanent magnet creates the driving field. All magnetic materials are assumed to be non-hysteretic and permanent magnets are represented by means of the well-known linear model in the second quadrant of the (B,H) plane.
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    Wilson's renormalization group applied to 2D lattice electrons in the presence of van Hove singularities (2002)
    Springer
    The European physical journal 25 (2002), S. 69-87 
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    ISSN: 1434-6036
    Keywords: PACS. 71.10.Fd Lattice fermion models (Hubbard model, etc.) – 71.10.Hf Non-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systems – 74.72.-h High-Tc compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The weak coupling instabilities of a two dimensional Fermi system are investigated for the case of a square lattice using a Wilson renormalization group scheme to one loop order. We focus on a situation where the Fermi surface passes through two saddle points of the single particle dispersion. In the case of perfect nesting, the dominant instability is a spin density wave but d-wave superconductivity as well as charge or spin flux phases are also obtained in certain regions in the space of coupling parameters. The low energy regime in the vicinity of these instabilities can be studied analytically. Although saddle points play a major role (through their large contribution to the single particle density of states), the presence of low energy excitations along the Fermi surface rather than at isolated points is crucial and leads to an asymptotic decoupling of the various instabilities. This suggests a more mean-field like picture of these instabilities, than the one recently established by numerical studies using discretized Fermi surfaces.
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    Photoconductance of a one-dimensional quantum dot (2002)
    Springer
    The European physical journal 25 (2002), S. 115-122 
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    ISSN: 1434-6036
    Keywords: PACS. 71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.) – 73.63.Kv Quantum dots – 73.50.Pz Photoconduction and photovoltaic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The ac-transport properties of a one-dimensional quantum dot with non-Fermi liquid correlations are investigated. It is found that the linear photoconductance is drastically influenced by the interaction. While for weak interaction it shows peak-like resonances, in the strong interaction regime it assumes a step-like behavior. In both cases the photo-transport provides precise informations about the quantized plasmon modes in the dot. Temperature and voltage dependences of the sideband peaks are treated in detail. Characteristic Luttinger liquid power laws are found.
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    Comparison study of energy bands and Wannier-Mott excitons in mixed Zn(P As ) and Zn Cd P crystals (2002)
    Springer
    The European physical journal 28 (2002), S. 37-43 
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    ISSN: 1434-6036
    Keywords: PACS. 71.35.-y Excitons and related phenomena – 74.62.Dh Effects of crystal defects, doping aaand substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Excitonic absorption, reflection and photoluminescence spectra of mixed Zn(P1-xAsx)2 crystals over the full range of x ( 0 ? x ? 1) and Zn1-xCdxP2 crystals at 0 ? x ? 0.05 have been studied at low temperatures (1.8 K). The decrease of the energy gap in Zn(P1-xAsx)2 at the increase of x occurs slightly sublinearly. The rydbergs of excitonic series in this crystals decrease as well, and the dependences Ry ( x ) for all series are strongly superlinear at small x. In Zn1-xCdxP2 crystals the energy gap and rydbergs decrease at the increase of x (at 0 ? x ? 0.05) as well. The dependences of Eg and Ry on x are considerably stronger in Zn(P1-xAsx)2 than in Zn1-xCdxP2. At the increase of x the half-width of excitonic absorption lines increases monotonically in both type crystals that is evidence of the increasing role of fluctuations of crystal potential.
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    Modeling generalized stacking faults in Au using the tight-binding potential combined with a simulated annealing method (2002)
    Springer
    The European physical journal 28 (2002), S. 45-48 
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    ISSN: 1434-6036
    Keywords: PACS. 61.72.Nn Stacking faults and other planar or extended defects – 71.15.Nc Total energy and cohesive energy calculations
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    Topics: Physics
    Notes: Abstract: The tight-binding potential combined with a simulated annealing method is used to study the generalized stacking fault (GSF) structure and corresponding energy of gold. The potential is chosen to fit band structures and total energies from a set of first-principle calculations [Phys. Rev. B 54, 4519 (1996)]. It is found that the relaxed stacking fault energy (SFE) and unstable SFE are equal to 46 and 102 mJ/m2, respectively, and are in good agreement with first principles calculations and experiment. In addition, the structure properties of the relaxed GSF of metal Au are also presented.
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    Landau-Fermi liquid analysis of the 2D t-t' Hubbard model (2002)
    Springer
    The European physical journal 28 (2002), S. 61-70 
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    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We calculate the Landau interaction function f (k,k') for the two-dimensional t-t' Hubbard model on the square lattice using second and higher order perturbation theory. Within the Landau-Fermi liquid framework we discuss the behavior of spin and charge susceptibilities as function of the onsite interaction and band filling. In particular we analyze the role of elastic umklapp processes as driving force for the anisotropic reduction of the compressibility on parts of the Fermi surface.
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    Similarities between the t-J and Hubbard models in weakly correlated regimes (2002)
    Springer
    The European physical journal 28 (2002), S. 49-54 
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    ISSN: 1434-6036
    Keywords: PACS. 71.10.-w Theories and models of many-electron systems – 71.10.Fd Lattice fermion models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present a comparative study of the Hubbard and t - J models far away from half-filling. We show that, at such fillings the t - J Hamiltonian can be seen as an effective model of the repulsive Hubbard Hamiltonian over the whole range of correlation strength. Indeed, the | t/U| ∈ 0, + ∞ range of the Hubbard model can be mapped onto the finite range | J/t| ∈ 2, 0 of the t - J model, provided that the effective exchange parameter J is defined variationally as the local singlet-triplet excitation energy. In this picture the uncorrelated limit U = 0 is associated with the super-symmetric point J = - 2| t| and the infinitely correlated U = + ∞ limit with the usual J = 0 limit. A numerical comparison between the two models is presented using different macroscopic and microscopic properties such as energies, charge gaps and bond orders on a quarter-filled infinite chain. The usage of the t - J Hamiltonian in low-filled systems can therefore be a good alternative to the Hubbard model in large time-consuming calculations.
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    Breakdown of waves described by exact solutions of the Thomas-Fermi model (2002)
    Springer
    The European physical journal 28 (2002), S. 71-74 
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    ISSN: 1434-6036
    Keywords: PACS. 03.75.Fi Phase coherent atomic ensembles; quantum condensation phenomena 04. General relativity and gravitation – 03.65.Ge Solutions of wave equations: bound states – 02.70.Ns Molecular dynamics and particle methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The dynamics of large localized repulsive clouds is examined by means of exact non-stationary solutions of the one-dimensional Thomas-Fermi model. The nonlinear flattening of the cloud peak, the wave breakdown at the cloud peripheries, and the condensate velocity distributions are thus described. Our solutions, which can contain an arbitrary amount of free parameters, show the nonlinear evolution of an arbitrary initial wave form. A unique procedure for analyzing these solutions is presented. The difference between our breakdown matter wave solutions and the well known Riemann shock waves is stressed.
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    Magnetic interaction in Mg, Ti, Nb doped manganites (2002)
    Springer
    The European physical journal 28 (2002), S. 75-80 
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    ISSN: 1434-6036
    Keywords: PACS. 75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) – 75.30.Vn Colossal magnetoresistance – 75.30.Et Exchange and superexchange interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: An effect of Mn substitution with Me=Mg2+, Ti4+, Nb5+ in manganites has been investigated by preparing La0.7Sr0.3(Mn1-xMex)O3 and La1-xSrx(Mn1 - x/2Nbx/2)O3 series. It was established that substitution of manganese with magnesium up to x = 0.16 leads to a collapse of a long-range ferromagnetic order whereas La0.7Sr0.3(Mn 3 + 0.85Nb 5 + 0.15)O3 is ferromagnet with T C = 123 K and exhibits a large magnetoresistance below Curie point despite an absence of four-valent manganese. Hypothetical magnetic phase diagrams are constructed for La0.7Sr0.3(Mn1-xMex)O3 and La1-xSrx(Mn1 - x/2Nbx/2)O3. Our results show that Mn3+-O-Mn3+ exchange interaction is ferromagnetic in the orbitally disordered manganites as well as an increase of Mn4+ content above 50% from a total amount of manganese ions leads to formation of a spin glass state due to a competition between antiferromagnetic Mn4+-O-Mn4+ and ferromagnetic Mn3+-O-Mn4+(Mn3+) superexchange interactions.
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    Switching current noise and relaxation of ferroelectric domains (2002)
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    The European physical journal 28 (2002), S. 81-89 
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    ISSN: 1434-6036
    Keywords: PACS. 77.80.Dj Domain structure; hysteresis – 77.80.Fm Switching phenomena – 05.40.Ca Noise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We simulate field-induced nucleation and switching of domains in a three-dimensional model of ferroelectrics with quenched disorder and varying domain sizes. We study (1) bursts of the switching current at slow driving along the hysteresis loop (electrical Barkhausen noise) and (2) the polarization reversal when a strong electric field was applied and back-switching after the field was removed. We show how these processes are related to the underlying structure of domain walls, which in turn is controlled by the pinning at quenched local electric fields. When the depolarization fields of bound charges are properly screened we find that the fractal switching current noise may appear with two distinct universal behaviors. The critical depinning of plane domain walls determines the universality class in the case of weak random fields, whereas for large randomness the massive nucleation of domains in the bulk leads to different scaling properties. In both cases the scaling exponents decay logarithmically when the driving frequency is increased. The polarization reverses in the applied field as a power-law, while its relaxation in zero field is a stretch exponential function of time. The stretching exponent depends on the strength of pinning. The results may be applicable for uniaxial relaxor ferroelectrics, such as doped SBN:Ce.
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    The role of OH ions in the stabilization of F colour centres in LiF (2002)
    Springer
    The European physical journal 28 (2002), S. 91-101 
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    ISSN: 1434-6036
    Keywords: PACS. 77.22.Ej Polarisation and depolarisation – 42.55.Rz Doped insulator lasers and other solid state lasers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Thermally Stimulated Depolarisation Current (TSDC) and optical methods are applied to a range of alkali-fluoride crystals in order to establish a model for the stable F 2 + - like colour centres in LiF:OH-. The experimental results for LiF:OH- suggest that the OH- defects are partially destroyed under ionising irradiation or during crystal growth. The low-temperature dielectric relaxation signals in LiF:OH- and LiF:Mg2+,OH- are attributed to highly interacting hydroxide ions and products of their destruction located in extended lattice defects. In LiF:OH-, in contrast to other alkali halides, the results advocate for a defect-structure model, which considers a neutral defect (ND, probably O2 or H2) sited at the anion vacancy of the O2--V a + dipole and which possibly is the “nucleus” for the F 2 + centre. The proposed F 2 + (ND, O-) model seems to better explain the dielectric results, compared to the older F 2 + (O2-) and F 2 + (O-) models. The estimate for the electric dipole moment derived from the experimental TSDC bands, gives a value for the F 2 + - like centre in LiF:OH- between those of the F 2 + (O-) and F 2 + (O2-) defects, in good agreement with the proposed F 2 + (ND,O-) model. The reduction of the activation energy barrier of the (re)orientation process of the Mg2+V c - (OH-) complexes in LiF:Mg2+,OH-, and the low-temperature shift of their TSDC band, compared to the single Mg 2 + V c - peak in LiF:Mg2+, are tentatively ascribed to an increase in the crystal-lattice parameters owing to the presence of OH- and/or products of its destruction.
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    Characterization of Bernstein modes in quantum dots (2002)
    Springer
    The European physical journal 28 (2002), S. 111-115 
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    ISSN: 1434-6036
    Keywords: PACS. 73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic aaand nanoscale systems – 73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The dipole modes of non-parabolic quantum dots are studied by means of their current and density patterns as well as with their local absorption distribution. The anticrossing of the so-called Bernstein modes originates from the coupling with electron-hole excitations of the two Landau bands which are occupied at the corresponding magnetic fields. Non-quadratic terms in the potential cause an energy separation between bulk and edge current modes in the anticrossing region. On a local scale the fragmented peaks absorb energy in complementary spatial regions which evolve with the magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00206-x
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    Floating Wigner molecules and possible phase transitions in quantum dots (2002)
    Springer
    The European physical journal 28 (2002), S. 117-120 
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    ISSN: 1434-6036
    Keywords: PACS. 73.20.Qt Electron solid – 73.21.La Quantum dots – 73.22.Gk Broken symmetry phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A floating Wigner crystal differs from the standard one by a spatial averaging over positions of the Wigner-crystal lattice. It has the same internal structure as the fixed crystal, but contrary to it, takes into account rotational and/or translational symmetry of the underlying jellium background. We study properties of a floating Wigner molecule in few-electron spin-polarized quantum dots, and show that the floating solid has the lower energy than the standard Wigner crystal with fixed lattice points. We also argue that internal rotational symmetry of individual dots can be broken in arrays of quantum dots, due to degenerate ground states and inter-dot Coulomb coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00207-9
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    Current and shot noise in two capacitively coupled single electron transistors with an atomic sized spacer (2002)
    Springer
    The European physical journal 28 (2002), S. 121-128 
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    ISSN: 1434-6036
    Keywords: PACS. 73.23.Hk Coulomb blockade; single-electron tunnelling – 73.40.Gk Tunnelling – 73.50.Td Noise processes and phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized, which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance. An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise) are responsible for a strong enhancement of the current noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00208-8
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    Growth and addition in a herding model (2002)
    Springer
    The European physical journal 28 (2002), S. 129-132 
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    ISSN: 1434-6036
    Keywords: PACS. 02.50.cw Probability theory – 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion – 89.75Hc. Networks and genealogical trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A model of herding is introduced which is exceptionally simple, incorporating only two phenomena, growth and addition. At each time step either (i) with probability p the system grows through the introduction of a new agent or (ii) with probability q = 1 - p a free agent already in the system is added at random to a group of size k with rate Ak. Two versions of the model, A k = k and A k = 1, are solved and in both versions we find two different types of behaviour. When p 〉 1/2 all the moments of the distribution of group sizes are linear in time for large time and the group distribution is power-law. When p 〈 1/2 the system runs out of free agents in a finite time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00209-7
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    Zero bias anomaly in the density of states of low-dimensional metals (2002)
    Springer
    The European physical journal 28 (2002), S. 29-36 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.10.Pm Fermions in reduced dimensions – 71.23.-k Electronic structure of disordered solids – 71.30.+h Metal-insulator transitions and other electronic transitions – 72.15.Rn Localization effects (Anderson or weak localization)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We consider the effect of Coulomb interactions on the average density of states (DOS) of disordered low-dimensional metals for temperatures T and frequencies ω smaller than the inverse elastic life-time 1/τ. Using the fact that long-range Coulomb interactions in two dimensions (2d) generate ln2-singularities in the DOS ν(ω) but only ln-singularities in the conductivity σ(ω), we can re-sum the most singular contributions to the average DOS via a simple gauge-transformation. If σ(ω) 〉 0, then a metallic Coulomb gapν(ω) ∝ |ω|/e 4 appears in the DOS at T = 0 for frequencies below a certain crossover frequency Ω 2 which depends on the value of the DC conductivity σ(0). Here, - e is the charge of the electron. Naively adopting the same procedure to calculate the DOS in quasi 1d metals, we find ν(ω) ∝ (|ω|/Ω 1)1/2exp(- Ω 1/|ω|) at T = 0, where Ω 1 is some interaction-dependent frequency scale. However, we argue that in quasi 1d the above gauge-transformation method is on less firm grounds than in 2d. We also discuss the behavior of the DOS at finite temperatures and give numerical results for the expected tunneling conductance that can be compared with experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00210-2
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    Predictions for high-energy real and virtual photon–photon scattering from color dipole BFKL–Regge factorization (2002)
    Springer
    The European physical journal 22 (2002), S. 637-646 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. High-energy virtual photon–virtual photon scattering can be viewed as an interaction of small size color dipoles from the beam and target photons, which makes $\gamma^{*}\gamma^{*}, \gamma^{*}\gamma$ scattering at high energies (LEP, LEP200 and NLC) an indispensable probe of the short distance properties of the QCD pomeron exchange. Based on the color dipole representation, we investigate the consequences for the $\gamma^{*}\gamma^{*},\gamma^{*}\gamma$ scattering of the incorporation of asymptotic freedom into the BFKL equation which makes the QCD pomeron a series of isolated poles in the angular momentum plane. The emerging color dipole BFKL–Regge factorization allows us to relate in a model-independent way the contributions of each BFKL pole to $\gamma^{*}\gamma^{*},\gamma^{*} \gamma$ scattering and DIS off protons. Numerical predictions based on our early works on the color dipole BFKL phenomenology of DIS on protons are in good agreement with the experimental data on the photon structure function $F_{2\gamma}$ and the most recent data on the $\gamma^*\gamma^*$ cross section $\sigma^{\gamma^*\gamma^*}(Y)$ from the OPAL and L3 experiments at LEP200. We discuss the role of non-perturbative dynamics and predict a pronounced effect of the Regge-factorization breaking due to large unfactorizable non-perturbative corrections to the perturbative vacuum exchange. We comment on the salient features of the BFKL–Regge expansion for $\gamma^{*}\gamma^{*},\gamma^{*}\gamma$ scattering including the issue of the decoupling of subleading BFKL poles and the soft plus rightmost hard BFKL pole dominance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100804
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    Charmless hadronic decays of B mesons to a pseudoscalar and a tensor meson (2002)
    Springer
    The European physical journal 22 (2002), S. 683-694 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We study two-body charmless hadronic decays of B mesons to a pseudoscalar meson (P) and a tensor meson (T) in the frameworks of both flavor SU(3) symmetry and generalized factorization. Certain ways to test the validity of the generalized factorization are proposed, based on the flavor SU(3) analysis. We present a set of relations between a flavor SU(3) amplitude and the corresponding amplitude in the generalized factorization which bridge both approaches in $B \rightarrow PT$ decays. The branching ratios and CP asymmetries are calculated using the full effective Hamiltonian including all the penguin operators and the form factors obtained in the non-relativistic quark model of Isgur, Scora, Grinstein and Wise. We identify the decay modes in which the branching ratios and CP asymmetries are expected to be relatively large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100826
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    $\bar{B}^0$ decays to $D^{(*)0} \eta$ and $D^{(*)0}\eta^\prime$ (2002)
    Springer
    The European physical journal 22 (2002), S. 677-681 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We consider the hadronic B decays $\bar{B}^0\to D^{0} \eta, \bar{B}^0\to D^{*0} \eta, \bar{B}^0\to D^{0} \eta^\prime$ , $\bar{B}^0\to D^{*0} \eta^\prime$ in the framework of a quark-flavour basis and factorization. The formalism allows one to compute the decays to the $\eta$ meson and to relate them to those of the $\eta^\prime$ . Measuring the branching ratios of these processes may shed light on the nature of the $\eta$ – $\eta^\prime$ mixing. On the experimental side, only upper limits on the branching ratios are known at present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100837
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    Unitarity constraints and role of geometrical effects in deep-inelastic scattering and vector meson electroproduction (2002)
    Springer
    The European physical journal 22 (2002), S. 667-675 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Deep-inelastic scattering at low x and elastic vector meson electroproduction are analyzed on the basis of the s-channel unitarity extended to off-shell particle scattering. It appeared that the role of unitarity is important, but contrary to the case of on-shell scattering it does not rule out a power-like behavior of the total cross sections. We discuss the behavior of the total cross section of virtual photon–proton scattering in the geometrical approach and obtain the result that the exponent of the power-like energy dependence of $\sigma^{\mathrm{{tot}}}_{\gamma^* p}$ is related to the constituent quark interaction radius. The mass effects and energy dependence of vector meson electroproduction are discussed along with the angular distributions at large momentum transfers in these processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100843
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    Quark–antiquark potentials from a scalar field in SU(2) YM (2002)
    Springer
    The European physical journal 23 (2002), S. 145-147 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A generalized Dick model with a potential term is discussed. The solution originating from a static, point-like, color source is found to have a confining part. A comparison with a wide spectrum of phenomenological quark–antiquark potentials is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100849
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    The first three pomerons... (2002)
    Springer
    The European physical journal 23 (2002), S. 135-143 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A model of a three pomeron contribution to high energy elastic pp and $\bar p p$ scattering is proposed. The data are well described for all momenta ( $0.01\le |t|\le 14.$ GeV $^2$ ) and energies ( $8.\le s^{1/2}\le 1800.$ GeV) ( $\chi^2/{\mathrm{d.o.f.}}=2.60$ ). The model predicts the appearance of two dips in the differential cross-section which will be measured at LHC. The parameters of the pomeron trajectories are $\alpha(0)_{{\mathbb{P}}_1}=1.058, \alpha'(0)_{{\mathbb{P}}_1}=0.560 {\mathrm{GeV}}^{-2};$ $\alpha(0)_{{\mathbb{P}}_2}=1.167, \alpha'(0)_{{\mathbb{P}}_2}=0.273 {\mathrm {GeV}}^{-2};$ $\alpha(0)_{{\mathbb{P}}_3}=1.203, \alpha'(0)_{{\mathbb{P}}_3}=0.094 {\mathrm{GeV}}^{-2}$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100838
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    Transverse mass distributions of neutral pions from $^{208}$ Pb-induced reactions at 158 $\cdot A$ GeV (2002)
    Springer
    The European physical journal 23 (2002), S. 225-236 
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    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected 158 $\cdot A$ GeV Pb + Pb, and Pb + Nb collisions. The distributions cover the range $0.5 \mathrm{GeV}/c^2 \le m_T - m_0 \le 4 \mathrm{GeV}/c^2$ . The change of the spectral shape and the multiplicity with centrality is studied in detail. In going from p+p to semi-peripheral Pb+Pb collisions there is a nuclear enhancement increasing with transverse mass similar to the well known Cronin effect, while for very central collisions this enhancement appears to be weaker than expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100886
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