共查询到20条相似文献,搜索用时 15 毫秒
1.
《Nuclear Physics B》1995,455(3):724-758
The form-factor bootstrap approach is used to compute the exact contributions in the large-distance expansion of the correlation function 〈σ(x)σ(0)〉 of the two-dimensional Ising modeliin a magnetic field at T = Tc The matrix elements of the magnetization operator σ,(x) present a rich analytic structure induced by the (multi-)) scattering processes of the eight massive particles of the model. The spectral representation series has a fast rate of convergence and perfectly agrees with the numerical determination of the correlation function. 相似文献
2.
The transition of liquid 3He to the superfluid B phase in aerogel at T=0 is considered. It is shown that in a magnetic field, the quantum phase transition with respect to pressure is split in
two. The amount of splitting δP is estimated. The components of the superfluid density tensor are calculated near the critical pressures.
Zh. éksp. Teor. Fiz. 115, 754–762 (February 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
3.
The existence of a spontaneous magnetization in the three-dimensional Ising model in a weak random magnetic field (RFIM) is investgated. Following Imry and Ma, we consider the energy change, E, from the fully aligned ferromagnetic state caused by flipping all the spins inside a connected surface, . It is proved rigorously that with high probability, E is positive forall enclosing the origin. Under the unproven assumption that the expectation value of the spin at one site is weakly correlated with the random fields at far away sites (which is true if surfaces within surfaces can be ignored) it follows that the three-dimensional RFIM has a spontaneous magnetization at low temperatures. The proof works for all dimensions greater than two, providing support for the conjecture that two is the lower critical dimension.Work supported in part by NSF grant No. DMR 8100417. 相似文献
4.
5.
We study the ferromagnetic random-field Ising model on random
graphs of fixed connectivity z (Bethe lattice) in the presence of an
external magnetic field H. We compute the number of single-spin-flip
stable configurations with a given magnetization m and study the
connection between the distribution of these metastable states in the H-m plane
(focusing on the region where the number is exponentially large) and
the shape of the saturation hysteresis loop obtained by cycling the
field between - and + at T=0. The annealed complexity A(m,H) is
calculated for z=2,3,4 and the quenched complexity Q(m,H) for
z=2. We prove explicitly for z=2 that the contour
Q(m,H)=0 coincides with the saturation loop. On the other hand, we show that
A(m,H) is irrelevant for describing, even qualitatively, the observable hysteresis properties of the system. 相似文献
6.
7.
We find the asymptotic decrease of correlations <
A +y
,
B
>,yZ
v
+1, |y|, in the Ising model at high temperatures. For the case when monomials
A
and
B
both are odd, using the saddle-point method, we find the asymptotics of the correlations for any dimension . For even monomials
A
,
B
we formulate a general hypothesis about the form of the asymptotics and confirm it in two cases: (1) =1 and the vectory has an arbitrary direction, (2)y is directed along a fixed axis and arbitrary . Here we use besides the saddle-point method, some arguments from scattering theory. 相似文献
8.
《Physics letters. A》1998,246(6):505-510
Ising models obeying Glauber dynamics in a temporally oscillating magnetic field are analyzed. In the context of stochastic resonance, the response in the magnetization is calculated by means of both a mean-field theory with linear-response approximation, and the time-dependent Ginzburg-Landau equation. Analytic results for the temperature and frequency dependent response, including the resonance temperature, compare favorably with simulation data. 相似文献
9.
E. Barouch 《Physica D: Nonlinear Phenomena》1980,1(3):333-337
We demonstrate that the partition function of the 2-dimensional Ising model in the presence of a magnetic field can be expressed in terms of the distributions of the prime numbers in closed form. 相似文献
10.
11.
Numerical results up to the 42nd order of replica-symmetry breaking (RSB) are used to predict the singular structure of the Sherrington-Kirkpatrick spin glass at T=0. We confirm predominant single parameter scaling and derive corrections for the T=0 order function q(a), related to a Langevin equation with pseudotime 1/a. a=0 and a=infinity are shown to be two critical points for infinity-RSB, associated with two discrete spectra of Parisi block size ratios, attached to a continuous spectrum. Finite-RSB-size scaling, associated exponents, and T=0-energy are obtained with unprecedented accuracy. 相似文献
12.
13.
We identify the correct field operators which correspond to the order and disorder variables of the D = 2 Ising model. After infinite resummations we obtain equality between our correlation functions and the correlation functions of McCoy, Tracy and Wu [4]. 相似文献
14.
S.-W. Son H. Jeong J. D. Noh 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):431-437
We propose a method to determine the community
structure of a complex network. In this method the ground state
problem of a ferromagnetic random field Ising model is considered
on the network with the magnetic field Bs = +∞, Bt =
-∞, and Bi≠s,t=0 for a node pair s and t. The
ground state problem is equivalent to the so-called maximum flow
problem, which can be solved exactly numerically with the help of
a combinatorial optimization algorithm. The community structure is
then identified from the ground state Ising spin domains for all
pairs of s and t. Our method provides a criterion for the
existence of the community structure, and is applicable equally
well to unweighted and weighted networks. We demonstrate the
performance of the method by applying it to the Barabási-Albert
network, Zachary karate club network, the scientific collaboration
network, and the stock price correlation network.
(Ising, Potts, etc.) 相似文献
15.
16.
O. V. Alekseev 《JETP Letters》2012,95(4):201-205
A particular modification of the free-field representation of the form factors in the Bullough-Dodd model is considered. The
two-particles minimal form factors are excluded from the construction. As a consequence, a convenient representation for the
multiparticle form factors has been obtained, recurrence relations between them have been established, and their properties
have been studied. The proposed construction is used to obtain the free-field representation of the lightest particles form
factors in the Φ1, 2 perturbed minimal models. The Ising model in a magnetic field is considered as a significant example. The results obtained
in the framework of the proposed free-field representation are in agreement with the corresponding results obtained by solving
the bootstrap equations. 相似文献
17.
The effect of a zero-centered Gaussian random magnetic field distribution on the phase transition properties of the anisotropic quantum Heisenberg model has been investigated on a honeycomb lattice within the framework of effective field theory (EFT) for a two-spin cluster (which is abbreviated as EFT-2). Particular attention has been devoted to investigation of the effect of the anisotropy in the exchange interaction on a system with Gaussian random magnetic field distribution. The variation of the critical temperature with the randomness parameter (i.e., the width of the distribution) has been obtained for several anisotropy parameters. Critical Gaussian distribution width values, which make the critical temperature zero, have been obtained. Moreover, it has been concluded that all critical temperatures are of second order, and that reentrant behavior does not exist in the phase diagrams. 相似文献
18.
J. M. G. Amaro de Matos A. E. Patrick V. A. Zagrebnov 《Journal of statistical physics》1992,66(1-2):139-164
An approach to the definition of infinite-volume Gibbs states for the (quenched) random-field Ising model is considered in the case of a Curie-Weiss ferromagnet. It turns out that these states are random quasi-free measures. They are random convex linear combinations of the free product-measures shifted by the corresponding effective mean fields. The conditional self-averaging property of the magnetization related to this randomness is also discussed.This paper is dedicated to Robert A. Minlos on the occasion of his 60th birthday. 相似文献
19.
FeAl alloys in their disordered structural phase have been investigated through an Ising model where besides exchange interactions between nearest-neighbors Fe atoms, a superexchange interaction mediated by Al atoms is also taken into account. The model has been approximately treated according to the effective field theory. Although the phase diagram, as a function of Al concentration, is similar to the one previously obtained from Bogoliubov variational approach for the free energy, a different behavior for the superexchange interaction is achieved, which can also be physically accepted for this system. 相似文献
20.
T. Morita 《Physica A》1979,98(3):566-572
We study the random Ising model in the pair approximation of the cluster variation method. We show that the distribution function of the effective field is determined either by a reducibility condition of the distribution function of two sites to that of one site or by a stationarity condition of the averaged free energy. 相似文献