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151.
Y. Ōno R. Bulla A.C. Hewson 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):375-384
The Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized
dynamical mean-field theory recently developed by Bulla and Potthoff. The phase boundary of the metal-insulator transition
is obtained analytically as a function of the on-site Coulomb interaction at the d-orbital, the charge-transfer energy between the d- and p-orbitals and the hopping integrals between p-d, d-d and p-p orbitals. The result is in good agreement with the numerical results obtained from the exact diagonalization method.
Received 5 October 2000 and Received in final form 8 December 2000 相似文献
152.
We propose a new and simple estimating equation for the parameters in median regression models with designed censoring variables, and then apply the empirical log likelihood ratio statistic to construct confidence region for the parameters. The empirical log likelihood ratio statistic is shown to have a standard chi-square distribution, which makes this method easy to implement. At the same time, another empirical log likelihood ratio statistic is proposed based on an existing estimating equation and the limiting distribution of the empirical likelihood ratio statistic is shown to be a sum of weighted chi-square distributions. We compare the performance of the empirical likelihood confidence region based on the new estimating equation, with that based on the existing estimating equation and a normal approximation method by simulation studies. 相似文献
153.
Stefano Longhi 《Annalen der Physik》2023,535(11):2300291
Strongly-correlated systems in non-Hermitian models are an emergent area of research. Herein, a non-Hermitian Hubbard model is considered, where the single-particle hopping amplitudes on the lattice are not reciprocal, and provide exact analytical results of the spectral structure in the two-particle sector of Hilbert space under different boundary conditions. The analysis unveils some interesting spectral and dynamical effects of purely non-Hermitian nature and that deviate from the usual scenario found in the single-particle regime. Specifically, a spectral phase transition of the Mott-Hubbard band on the infinite lattice is predicted as the interaction energy is increased above a critical value, from an open to a closed loop in complex energy plane, and the dynamical dissociation of doublons, i.e., instability of two-particle bound states, in the bulk of the lattice, with a sudden revival of the doublon state when the two particles reach the lattice edge. Particle dissociation observed in the bulk of the lattice is a clear manifestation of non-Hermitian dynamics arising from the different lifetimes of single-particle and two-particle states, whereas the sudden revival of the doublon state at the boundaries is a striking burst edge dynamical effect peculiar to non-Hermitian systems with boundary-dependent energy spectra, here predicted for the first time for correlated particles. 相似文献
154.
A lattice random walk model based on particles scattering on discrete lattice of homogenous space is introduced. The discrete Green's function (DFG) for two-dimensional and three-dimensional lattice random walk of photon is found and proved by mathematical induction. The convolution theorem of photon lattice random walk is presented. They can be used with the method of images to calculate the photon density distribution in semi-infinite and finite slab homogenous turbid media such as tissue. 相似文献
155.
An effective Hamiltonian of the two-dimensional antiferromagnetic Heisenberg model is derived by using the Holstein-Primakoff transformation. Three nonlinear coupled partial equations of motion are obtained. In the long-wavelength approximation, these equations, are reduced to the envelope function equations by the method of multiple scales. The amplitude functions satisfy the nonlinear Schrodinger equation. Introducing an inverse scatteriag transformation, the single-, two- and multi-soliton solutions in the two-dimensional antiferromagnetic Heisenberg model are investigated. 相似文献
156.
MA YuQiang 《理论物理通讯》1999,31(4):537-542
We propose a soluble quantum spherical XY ferromagnet with a random field in the boson space. We obtain a general expression of the critical temperat ure Tc below which the ordered ferromagnet phase appears. The Imry-Ma result concerning the lower critical dimension dc = 4 is recovered, and the critical exponents near the critical temperature Tc are calculated. We show that the random-field fluctuations rather than the quantum fluctuations dominate the phase transition and critical behavior of the system. The entropy vanishes as Td/2 at low temperatures, contrary to the classical spherical model. 相似文献
157.
158.
John F. Nagle 《Journal of statistical physics》1985,38(3-4):531-540
It has been suggested that some lattice models of polymers, especially ones that incorporate more realistic excluded volume interactions extending to further neighbors, may be subject to gridlock. A model is defined to have the property of gridlock if it cannot melt at any temperature unless a density decrease is allowed. Classical theories of polymer melting are incompatible with the property of gridlock. This paper proves rigorously that a two-dimensional square-lattice model of polymer chains that have nearest-neighbor excluded volume interactions (called the X1S model) has the gridlock property. The proof uses elementary concepts from graph theory. Also, different interpretations of the X1S model are given in terms of real polymers. This leads to a discussion of a number of different classes of melting depending upon whether the intramolecular rotameric energies and the attractive intermolecular energies are antagonistic to or supportive of the melting transition. 相似文献
159.
Ananias M. Mariz Constantino Tsallis E. L. Albuquerque 《Journal of statistical physics》1985,40(3-4):577-592
We study the phase diagram for the Ising Model on a Cayley tree with competing nearest-neighbor interactionsJ
1 and next-nearest-neighbor interactionsJ
2 andJ
3 in the presence of an external magnetic field. To perform this study, an iterative scheme similar to that appearing in real space renormalization group frameworks is established; it recovers, as particular cases, previous works by Vannimenus and by Inawashiroet al. At vanishing temperature, the phase diagram is fully determined, for all values and signs ofJ
2/J
1 andJ
3/J
2; in particular, we verify that values ofJ
3/J
2 high enough favor the paramagnetic phase. At finite temperatures, several interesting features (evolution of reentrances, separation of the modulated region into two disconnected pieces, etc.) are exhibited for typical values ofJ
2/J
1 andJ
3/J
2.Partially supported by the Brazilian Agencies CNPq and FINEP. 相似文献
160.
G. Pawłowski 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):471-479
The extended Hubbard model in the atomic limit (AL-EHM) on a square lattice with periodic boundary conditions is studied with
use of the Monte Carlo (MC) method. Within the grand canonical ensemble the phase and order-order boundaries for charge orderings
are obtained. The phase diagrams include three types of charge ordered phases and the nonordered phase. The system exhibits
very rich structure and shows unusual multicritical behavior.
In the limiting case of tij=0, the EHM is equivalent to the pseudospin model with single-ion anisotropy
, exchange interaction W in an effective magnetic field
. This classical spin model is analyzed using the MC method for the canonical ensemble. The phase diagram is compared with
the known results for the Blume-Capel model. 相似文献