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  • Articles  (1,049)
  • Springer  (1,049)
  • International Union of Crystallography (IUCr)
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  • 2020-2024
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  • European Physical Journal C  (521)
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  • Articles  (1,049)
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Publisher
  • Springer  (1,049)
  • International Union of Crystallography (IUCr)
  • Springer Nature
  • Taylor & Francis
Years
  • 2020-2024
  • 2010-2014  (1,049)
  • 2000-2004
  • 1980-1984
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  • 1
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    Off-diagonal deformations of kerr black holes in Einstein and modified massive gravity and higher dimensions (2014)
    Springer
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    Publication Date: 2014-12-23
    Description: We find general parameterizations for generic off-diagonal spacetime metrics and matter sources in general relativity (GR) and modified gravity theories when the field equations decouple with respect to certain types of nonholonomic frames of reference. This allows us to construct various classes of exact solutions when the coefficients of the fundamental geometric/physical objects depend on all spacetime coordinates via corresponding classes of generating and integration functions and/or constants. Such (modified) spacetimes display Killing and non-Killing symmetries, describe nonlinear vacuum configurations and effective polarizations of cosmological and interaction constants. Our method can be extended to higher dimensions which simplifies some proofs for embedded and nonholonomically constrained four-dimensional configurations. We reproduce the Kerr solution and show how to deform it nonholonomically into new classes of generic off-diagonal solutions depending on 3–8 spacetime coordinates. Certain examples of exact solutions are analyzed and they are determined by contributions of a new type of interactions with sources in massive gravity and/or modified f(R,T) gravity. We conclude that by considering generic off-diagonal nonlinear parametric interactions in GR it is possible to mimic various effects in massive and/or modified gravity, or to distinguish certain classes of “generic” modified gravity solutions which cannot be encoded in GR.
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  • 2
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    Confinement and screening in tachyonic matter (2014)
    Springer
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    Publication Date: 2014-12-21
    Description: In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of ‘anti-screening’ in a medium with exotic dielectric. We show that tachyon matter behaves like in an exotic way whose associated dielectric function modifies the Maxwell equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to the condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance, which is associated with a screening phase.
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  • 3
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    On the four-dimensional formulation of dimensionally regulated amplitudes (2014)
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    Publication Date: 2014-12-18
    Description: Elaborating on the four-dimensional helicity scheme, we propose a pure four-dimensional formulation (FDF) of the \(d\) -dimensional regularization of one-loop scattering amplitudes. In our formulation particles propagating inside the loop are represented by massive internal states regulating the divergences. The latter obey Feynman rules containing multiplicative selection rules which automatically account for the effects of the extra-dimensional regulating terms of the amplitude. We present explicit representations of the polarization and helicity states of the four-dimensional particles propagating in the loop. They allow for a complete, four-dimensional, unitarity-based construction of \(d\) -dimensional amplitudes. Generalized unitarity within the FDF does not require any higher-dimensional extension of the Clifford and the spinor algebra. Finally we show how the FDF allows for the recursive construction of \(d\) -dimensional one-loop integrands, generalizing the four-dimensional open-loop approach.
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  • 4
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    Polytropic equation of state and primordial quantum fluctuations (2014)
    Springer
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    Publication Date: 2014-12-18
    Description: We study the primordial Universe in a cosmological model where inflation is driven by a fluid with a polytropic equation of state \(p = \alpha \rho + k\rho ^{1 + 1/n}\) . We calculate the dynamics of the scalar factor and build a Universe with constant density at the origin. We also find the equivalent scalar field that could create such an equation of state and calculate the corresponding slow-roll parameters. We calculate the scalar perturbations, the scalar power spectrum, and the spectral index.
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  • 5
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    Search of wormholes in different dimensional non-commutative inspired space-times with Lorentzian distribution (2014)
    Springer
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    Publication Date: 2014-12-18
    Description: In this paper we ask whether the wormhole solutions exist in different dimensional noncommutativity-inspired spacetimes. It is well known that the noncommutativity of the space is an outcome of string theory and it replaced the usual point-like object by a smeared object. Here we have chosen the Lorentzian distribution as the density function in the noncommutativity-inspired spacetime. We have observed that the wormhole solutions exist only in four and five dimensions; however, in higher than five dimensions no wormhole exists. For five dimensional spacetime, we get a wormhole for a restricted region. In the usual four dimensional spacetime, we get a stable wormhole which is asymptotically flat.
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  • 6
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    Different critical points of chiral and deconfinement phase transitions in (2 + 1)-dimensional fermion–gauge interacting model (2014)
    Springer
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    Publication Date: 2014-12-17
    Description: Based on the truncated Dyson–Schwinger equations for fermion and massive boson propagators in QED \(_3\) , the fermion chiral condensate and the mass singularities of the fermion propagator via the Schwinger function are investigated. It is shown that the critical point of the chiral phase transition is apparently different from that of the deconfinement phase transition and in Nambu phase the fermion is confined only for small gauge-boson mass.
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  • 7
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    Constraints on the $$\mathbf {\omega \pi }$$ ω π form factor from analyticity and unitarity (2014)
    Springer
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    Publication Date: 2014-12-17
    Description: Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic \(\omega \pi \) form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we derive upper and lower bounds on the modulus of the \(\omega \pi \) form factor in the elastic region. The results provide a significant check on those obtained with standard dispersion relations, confirming the existence of a disagreement with experimental data in the region around \(0.6\, \text {GeV}\) .
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  • 8
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    The NUHM2 after LHC Run 1 (2014)
    Springer
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    Publication Date: 2014-12-17
    Description: We make a frequentist analysis of the parameter space of the NUHM2, in which the soft supersymmetry (SUSY)-breaking contributions to the masses of the two Higgs multiplets, \(m^2_{H_{u,d}}\) , vary independently from the universal soft SUSY-breaking contributions \(m^2_0\) to the masses of squarks and sleptons. Our analysis uses the MultiNest sampling algorithm with over \(4 \times 10^8\) points to sample the NUHM2 parameter space. It includes the ATLAS and CMS Higgs mass measurements as well as the ATLAS search for supersymmetric jets +  \({/\!\!E}_T\) signals using the full LHC Run 1 data, the measurements of \(\mathrm{BR}(B_s \rightarrow \mu ^+\mu ^-)\) by LHCb and CMS together with other B-physics observables, electroweak precision observables and the XENON100 and LUX searches for spin-independent dark-matter scattering. We find that the preferred regions of the NUHM2 parameter space have negative SUSY-breaking scalar masses squared at the GUT scale for squarks and sleptons, \(m_0^2 〈 0\) , as well as \(m^2_{H_u} 〈 m^2_{H_d} 〈 0\) . The tension present in the CMSSM and NUHM1 between the supersymmetric interpretation of \((g-2)_\mu \) and the absence to date of SUSY at the LHC is not significantly alleviated in the NUHM2. We find that the minimum \(\chi ^2 = 32.5\) with 21 degrees of freedom (dof) in the NUHM2, to be compared with \(\chi ^2/\mathrm{dof} = 35.0/23\) in the CMSSM, and \(\chi ^2/\mathrm{dof} = 32.7/22\) in the NUHM1. We find that the one-dimensional likelihood functions for sparticle masses and other observables are similar to those found previously in the CMSSM and NUHM1.
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  • 9
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    Lepton flavor violation in flavored gauge mediation (2014)
    Springer
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    Publication Date: 2014-12-17
    Description: We study the anatomy and phenomenology of lepton flavor violation (LFV) in the context of flavored gauge mediation (FGM). Within FGM, the messenger sector couples directly to the MSSM matter fields with couplings controlled by the same dynamics that explains the hierarchies in the SM Yukawas. Although the pattern of flavor violation depends on the particular underlying flavor model, FGM provides a built-in flavor suppression similar to wave function renormalization or SUSY partial compositeness. Moreover, in contrast to these models, there is an additional suppression of left–right flavor transitions by third-generation Yukawas that in particular provides an extra protection against flavor-blind phases. We exploit the consequences of this setup for lepton flavor phenomenology, assuming that the new couplings are controlled by simple \(U(1)\) flavor models that have been proposed to accommodate large neutrino mixing angles. Remarkably, it turns out that in the context of FGM these models can pass the impressive constraints from LFV processes and leptonic electric dipole moments (EDMs) even for light superpartners, therefore offering the possibility of resolving the longstanding muon \(g-2\) anomaly.
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  • 10
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    Analysis of generalized ghost pilgrim dark energy in non-flat FRW universe (2014)
    Springer
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    Publication Date: 2014-12-17
    Description: This work is based on pilgrim dark energy conjecture which states that phantom-like dark energy possesses the enough resistive force to preclude the formation of black hole. The non-flat geometry is considered which contains the interacting generalized ghost pilgrim dark energy with cold dark matter. Some well-known cosmological parameters (evolution parameter ( \(\omega _{\Lambda }\) ) and squared speed of sound) and planes ( \(\omega _{\Lambda }\) – \(\omega _{\Lambda }'\) and statefinder) are constructed in this scenario. The discussion of these parameters is totally done through pilgrim dark energy parameter ( \(u\) ) and interacting parameter ( \(d^2\) ). It is interesting to mention here that the analysis of evolution parameter supports the conjecture of pilgrim dark energy. Also, this model remains stable against small perturbation in most of the cases of \(u\) and \(d^2\) . Further, the cosmological planes correspond to \(\Lambda \) CDM limit as well as different well-known dark energy models.
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