Showing papers by "Rafael I. Nepomechie published in 1994"
TL;DR: The model is conformally invariant and has central charge $c_{vir} = 2$ when one of these parameters is zero, and the Bethe Ansatz equations admit an infinite number of solutions with lowest energy.
Abstract: We consider a two-parameter (c\ifmmode\bar\else\textasciimacron\fi{},c\ifmmode \tilde{}\else \~{}\fi{}) family of quantum integrable isotropic Hamiltonians for a chain of alternating spins of spin s=1/2 and s=1. We determine the thermodynamics for low-temperature T and small external magnetic field H, with T\ensuremath{\ll}H. In the antiferromagnetic (c\ifmmode\bar\else\textasciimacron\fi{}g0,c\ifmmode \tilde{}\else \~{}\fi{}g0) case, the model has two gapless excitations. In particular, for c\ifmmode\bar\else\textasciimacron\fi{}=c\ifmmode \tilde{}\else \~{}\fi{}, the model is conformally invariant and has central charge ${\mathit{c}}_{\mathrm{vir}}$=2. When one of these parameters is zero, the Bethe ansatz equations admit an infinite number of solutions with lowest energy.
63 citations
TL;DR: In this paper, the boundary matrix for the open antiferromagnetic spin $1/2$ isotropic Heisenberg chain with boundary magnetic fields was calculated using an extension of the Korepin-Andrei-Destri method.
Abstract: We calculate the boundary $S$ matrix for the open antiferromagnetic spin $1/2$ isotropic Heisenberg chain with boundary magnetic fields. Our approach, which starts from the model's Bethe Ansatz solution, is an extension of the Korepin-Andrei-Destri method. Our result agrees with the boundary $S$ matrix for the boundary sine-Gordon model with $\beta^2 \rightarrow 8\pi$ and with ``fixed'' boundary conditions.
42 citations
TL;DR: In this paper, an expression for the eigenvalues of the transfer matrix for the open quantum spin chain associated with the fundamental representation of $A^{(2)}_{2n} was proposed.
Abstract: We propose an expression for the eigenvalues of the transfer matrix for the $U_q(B_n)$-invariant open quantum spin chain associated with the fundamental representation of $A^{(2)}_{2n}$. By assumption, the Bethe Ansatz equations are ``doubled'' with respect to those of the corresponding closed chain with periodic boundary conditions. We verify that the transfer matrix eigenvalues have the correct analyticity properties and asymptotic behavior. We also briefly discuss the structure of the eigenstates of the transfer matrix.
22 citations
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09 Feb 1994
TL;DR: In this paper, the excitations and matrix of an integrable isotropic antiferromagnetic quantum spin chain of alternating spin 1/2 and spin 1 were determined.
Abstract: We determine the excitations and $S$ matrix of an integrable isotropic antiferromagnetic quantum spin chain of alternating spin 1/2 and spin 1 There are two types of gapless one-particle excitations: the usual spin 1/2 (``spinor'') kink, and a new spin 0 (``scalar'') kink Remarkably, the scalar-spinor scattering is nontrivial, yet the spinor-spinor scattering is the same as if the scalar kinks were absent Moreover, there is no scalar-scalar scattering
18 citations