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1

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The classical equivalent-neighbor XXZ model: Exact results for dynamic correlation functions (1990)

Liu, Jian-Min ; Müller, Gerhard

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 67 (1990), S. 5489-5491

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The dynamics of the classical XXZ model with uniform interaction is nonlinear for N≥2 spins and nonintegrable for N≥3. However, the nonlinearities disappear in the thermodynamic limit N→∞, and the spin autocorrelation functions can be determined exactly for infinite temperature. The function 〈Szi(t)Szi〉 exhibits a Gaussian decay to a nonzero constant, and the function 〈Sxi(t)Sxi〉 decays algebraically to zero or like a Gaussian, depending on the type (easy axis or easy plane) and amount of uniaxial anisotropy.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.345860

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2

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Deterministic and stochastic spin diffusion in classical Heisenberg magnets : The 5th Joint MMM−Intermag Conference (1991)

Liu, Jian-Min ; Srivastava, Niraj ; Viswanath, V. S. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 70 (1991), S. 6181-6183

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: This computer simulation study provides further evidence that spin diffusion in the one-dimensional classical Heisenberg model at T=∞ is anomalous: 〈Sj(t)⋅Sj〉 ∼t−α1 withα1 (approximately-greater-than)1/2. However, the exponential instability of the numerically integrated phase-space trajectories transforms the deterministic transport of spin fluctuations into a computationally generated stochastic process in which the global conservation laws are still satisfied to high precision. This may cause a crossover in 〈Sj(t)⋅Sj〉 from anomalous spin diffusion (α1 (approximately-greater-than) 1/2) to normal spin diffusion (α1 = 1/2) at some characteristic time lag that depends on the precision of the numerical integration.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.350037

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3

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Universality classes of dynamical behavior (abstract) : The 5th Joint MMM−Intermag Conference (1991)

Liu, Jian-Min ; Müller, Gerhard

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 70 (1991), S. 6187-6187

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: In studies of dynamic correlation functions the focus is, in general, on their long-time asymptotic behavior and the singularity structure of the associated spectral densities. It turns out that the analysis of the same dynamic correlation functions from a quite different perspective is equally useful and revealing. The focus of our study is on the properties of spectral densities at high frequencies, specifically their decay law, expressible asΦ0(large-closed-square)ω(large-closed-square) ∼exp(large-closed-square) − ω2(large-closed-square)λ(large-closed-square), in terms of a characteristic exponent λ. That decay law governs the growth rate of the sequence of recurrents which determine the relaxation function in the continued-fraction representation. The value of λ contains valuable information on the underlying dynamical processes taking place in the system, which, in some sense, is complementary to that inferred from the singularity structure of spectral densities. A detailed study of the dynamics of various quantum and classical spin models has prompted us to introduce the concept of "universality class'' for a classification of dynamical behavior on the basis of the characteristic exponent λ. For the equivalent-neighbor XYZ model1 we are able to demonstrate four different prototype universality classes: λ=0 (compact support), λ=1 (Gaussian decay), λ=2 (exponential decay), λ=3 (stretched exponential decay), which can be interpreted in terms of basic notions of classical dynamics. Finally, we present the exact T=∞ dynamic correlation functions for a two-sublattice Heisenberg antiferromagnet with uniform intersublattice interaction and zero intrasublattice interaction.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.350013

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4

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Two-magnon excitations in quantum spin chains (1988)

Liu, Jian-Min ; Bonner, Jill C.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 63 (1988), S. 4144-4146

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Quantum spin chains of higher spin are interesting in the case of both ferromagnets and antiferromagnets. They comprise a wide range of model types—Bethe–Ansatz integrable, nonintegrable, and with limited integrability. It is not well appreciated that the two-magnon (two-body) problems is always solvable, by Bethe–Ansatz and Green's-function techniques, regardless of the integrability character of the entire model, with interesting implications in the context of solitons and bound solitons. Chubukov and Kveschenko have suggested using the two-magnon problem in a test for integrability and claim to find additional classes of integrable spin chains for s=1 and s= (3)/(2) . Here we investigate this situation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.340522

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Spin diffusion in classical Heisenberg magnets with uniform, alternating, and random exchange : 38th Annual Conference ion Magnetism and Magnetic Materials (1994)

Srivastava, Niraj ; Liu, Jian-Min ; Viswanath, V. S. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 75 (1994), S. 6751-6753

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: We have carried out an extensive simulation study for the spin autocorrelation function at T=∞ of the one-dimensional classical Heisenberg model with four different types of isotropic bilinear nearest-neighbor coupling: uniform exchange, alternating exchange, and two kinds of random exchange. For the long-time tails of all but one case, the simulation data seem incompatible with the simple ∼t−1/2 leading term predicted by spin diffusion phenomenology.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.356842

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6

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Large scale peculiar velocities of galaxies

Xiang Shou-Ping ; Cheng Fu-Zhen ; Liu Jian-Min

Amsterdam : Elsevier

Chinese Astronomy and Astrophysics 15 (1991), S. 121-130

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ISSN: 0275-1062

Keywords: Cosmology-Large scale structure-Galaxies

Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Topics: Physics

Type of Medium: Electronic Resource

URL: http://linkinghub.elsevier.com/retrieve/pii/0275-1062(91)90054-2

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7

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Influence of saturable absorber on critical phenomenon analogies in single mode laser driven by external coherent field (1984)

Liu, Jian-Min

Springer

The European physical journal 57 (1984), S. 85-90

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ISSN: 1434-6036

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The influence of the existence of absorbing atoms in a laser cavity on the critical exponents of abrupt transitions between steady states in the system of single mode onephoton laser driven by an external coherent field is discussed. An isolated threshold when $$\bar \sigma = \bar \sigma _0 ,\bar \sigma = - \kappa \bar \gamma _ \bot S/\bar N|\bar g|^2 (\bar S - S)$$ ,and a kind of threshold when , where $$\bar \sigma $$ is the pump parameter of the absorbing atoms, is obtained. The asymptotic forms of the families of potential functions for the system near these threshold are also found. The well-known scaling hypothesis in the general homogeneous function form is shown to be a characteristic of these asymptotic families. Four threshold exponents, β, δ, γ′ and α′ and four threshold amplitudes,B, D, Γ′ andA′, near each of these thresholds, are obtained. The threshold exponents near each threshold obey the scaling laws of critical phenomena, while the corresponding amplitudes obey the definite relations between exponents and amplitudes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01679930

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8

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Resection of meningiomas with implantable microwave coagulation (1996)

Zhou, Xiao-ping ; Xie, Qi-liang ; Liu, Jian-min ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Bioelectromagnetics 17 (1996), S. 85-88

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ISSN: 0197-8462

Keywords: brain tumor ; coagulation ; bleeding ; hemostasis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Physics

Notes: Implantable microwave coagulation was used to perform resection on 62 patients that had intracranial meningiomas. When 20-60 W microwave power was applied for 15 s, the temperature at the center of the tumor tissue was 43-63°C; 30 mm from the center, the temperature was under 40°C. Histological changes in the center of the tumor showed coagulative necrosis, diminished nuclei, and obliterated blood vessels. The changes at 10-20 mm from the center of the tumor showed coagulative necrosis and degeneration and, 30-50 mm from the center of the tumor, showed normal cell morphology after microwave coagulation. The thermal field in brain tumor has an effective diameter of about 40 mm. No side effects on the normal brain tissues were observed. The amount of blood loss during the operation was minimal while the meningioma was coagulated, especially when the meningioma was located at the skull base or in the parasagittal or cerebral convexity region. After microwave coagulation, the entire tumor could easily be removed. Among the 62 surgically treated cases, gross total tumor excision was 85%. No postoperative complications occurred after microwave coagulation, and there was no operative mortality in the series. We believe that this new technique has the advantage of simplicity, less blood loss, and smooth postoperative procedures. Hemostatic effects during the operation are satisfactory, and blood transfusion can be reduced by 50-60%. © 1996 Wiley-Liss, Inc.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

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