2,934 research outputs found
One dimensional model for doubly degenerate electrons
A Hubbard-like model with SU(4) symmetry for electrons with two-fold orbital
degeneracy is studied extensively. Exact solution in one dimension is derived
by means of Bethe ansatz, where the sites are supposed to be occupied by at
most two electrons. The features of ground state and excited states for
repulsive coupling are shown. For finite N number of electrons, the
configurations of quantum numbers are given explicitly and the spectra of
excitations are obtained by solving the Bethe-ansatz equation numerically. For
infinite N, the ground state and various kinds of low-lying excitations are
obtained on the basis of thermodynamics limit.Comment: Revtex, 21 pages including 9 figures, PRB versio
Numerical and Monte Carlo Bethe ansatz method: 1D Heisenberg model
In this paper we present two new numerical methods for studying thermodynamic
quantities of integrable models. As an example of the effectiveness of these
two approaches, results from numerical solutions of all sets of Bethe ansatz
equations, for small Heisenberg chains, and Monte Carlo simulations in
quasi-momentum space, for a relatively larger chains, are presented. Our
results agree with those obtained by thermodynamics Bethe ansatz (TBA) and
Quantum Transfer Matrix (QTM).Comment: 8 pages, 6 figure
A New Phase Transition Related to the Black Hole's Topological Charge
The topological charge of AdS black hole is introduced in
Ref.[1,2], where a complete thermodynamic first law is obtained. In this paper,
we investigate a new phase transition related to the topological charge in
Einstein-Maxwell theory. Firstly, we derive the explicit solutions
corresponding to the divergence of specific heat and determine
the phase transition critical point. Secondly, the curve and curve
are investigated and they exhibit an interesting van der Waals system's
behavior. Critical physical quantities are also obtained which are consistent
with those derived from the specific heat analysis. Thirdly, a van der Waals
system's swallow tail behavior is observed when in the
graph. What's more, the analytic phase transition coexistence lines are
obtained by using the Maxwell equal area law and free energy analysis, the
results of which are consistent with each other.Comment: 11 pages, 5 figure
Thermodynamics of SU(2) bosons in one dimension
On the basis of Bethe ansatz solution of two-component bosons with SU(2)
symmetry and -function interaction in one dimension, we study the
thermodynamics of the system at finite temperature by using the strategy of
thermodynamic Bethe ansatz (TBA). It is shown that the ground state is an
isospin "ferromagnetic" state by the method of TBA, and at high temperature the
magnetic property is dominated by Curie's law. We obtain the exact result of
specific heat and entropy in strong coupling limit which scales like at low
temperature. While in weak coupling limit, it is found there is still no
Bose-Einstein Condensation (BEC) in such 1D system.Comment: 7 page
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