Wen-Li Yang

Off-diagonal Bethe ansatz solution of the XXX spin-chain with arbitrary boundary conditions

Employing the off-diagonal Bethe ansatz method proposed recently by the present authors, we exactly diagonalize the XXX spin chain with arbitrary boundary fields. By constructing a functional relation between the eigenvalues of the transfer matrix and the quantum determinant, the associated T-Q relation and the Bethe ansatz equations are derived

Off-Diagonal Bethe Ansatz and Exact Solution of a Topological Spin Ring

A general method is proposed for constructing the Bethe ansatz equations of integrable models without U(1) symmetry. As an example, the exact spectrum of the XXZ spin ring with a Möbius-like topological boundary condition is derived by constructing a modified T-Q relation based on the functional connection between the eigenvalues of the transfer matrix and the quantum determinant of the monodromy matrix. With the exact solution, the elementary excitations of the topological XX spin ring are discussed in detail. It is found that the excitation spectrum indeed shows a nontrivial topological nature.

Q-operator and T–Q relation from the fusion hierarchy

We propose that the Baxter Q-operator for the spin-1/2 XXZ quantum spin chain is given by the j -> infinity limit of the transfer matrix with spin-j (i.e., (2j + 1)-dimensional) auxiliary space. Applying this observation to the open chain with general (non-diagonal) integrable boundary terms, we obtain from the fusion hierarchy the T-Q relation for generic values (i.e., not roots of unity) of the bulk anisotropy parameter. We use this relation to determine the Bethe ansatz solution of the eigenvalues of the fundamental transfer matrix. This approach is complementary to the one used recently to solve the same model for the roots of unity case. (c) 2005 Elsevier B.V. All rights reserved.

Off-diagonal Bethe ansatz solutions of the anisotropic spin-1/2 chains with arbitrary boundary fields

The anisotropic spin-1/2 chains with arbitrary boundary fields are diagonalized with the off-diagonal Bethe ansatz method. Based on the properties of the R-matrix and the K-matrices, an operator product identity of the transfer matrix is constructed at some special points of the spectral parameter. Combining with the asymptotic behavior (for XXZ case) or the quasi-periodicity properties (for XYZ case) of the transfer matrix, the extended T-Q ansatzes and the corresponding Bethe ansatz equations are derived

On the second reference state and complete eigenstates of the open XXZ chain

The second reference state of the open XXZ spin chain with non-diagonal boundary terms is studied. The associated Bethe states exactly yield the second set of eigenvalues proposed recently by functional Bethe Ansatz. In the quasi-classical limit, two sets of Bethe states give the complete eigenstates of the associated Gaudin model.

Exact solution of the XXZ Gaudin model with generic open boundaries

The XXZ Gaudin model with generic integrable boundaries specified by generic non-diagonal K-matrices is studied. The commuting families of Gaudin operators are diagonalized by the algebraic Bethe ansatz method. The eigenvalues and the corresponding Bethe ansatz equations are obtained

Off-Diagonal Bethe ansatz for exactly solvable models

Overview.- The algebraic Bethe ansatz.- The periodic anisotropic spin-1/2 chains.- The spin-1/2 torus.- The spin-1/2 chain with arbitrary boundary fields.- The one-dimensional Hubbard model.- The nested off-diagonal Bethe ansatz.- The hierarchical off-diagonal Bethe Ansatz.- The Izergin-Korepin model.

State transition induced by higher-order effects and background frequency.

The state transition between the Peregrine rogue wave and W-shaped traveling wave induced by higher-order effects and background frequency is studied. We find that this intriguing transition, described by an exact explicit rational solution, is consistent with the modulation instability (MI) analysis that involves a MI region and a stability region in a low perturbation frequency region. In particular, the link between the MI growth rate and the transition characteristic analytically demonstrates that the localization characteristic of transition is positively associated with the reciprocal of the zero-frequency growth rate. Furthermore, we investigate the case for nonlinear interplay of multilocalized waves. It is interesting that the interaction of second-order waves in the stability region features a line structure rather than an elastic interaction between two W-shaped traveling waves.

Spin-1/2 XYZ model revisit: General solutions via off-diagonal Bethe ansatz

The spin-1/2 XYZ model with both periodic and anti-periodic boundary conditions is studied via the off-diagonal Bethe ansatz method. The exact spectra of the Hamiltonians and the Bethe ansatz equations are derived by constructing the inhomogeneous T Q relations, which allow us to treat both the even N (the number of lattice sites) and odd N cases simultaneously in a unified approach

Exact solution of the A(n-1)((1)) trigonometric vertex model with non-diagonal open boundaries

The A(n-1)((1)) trigonometric vertex model with generic non-diagonal boundaries is studied. The double-row transfer matrix of the model is diagonalized by algebraic Bethe ansatz method in terms of the intertwiner and the corresponding face-vertex relation. The eigenvalues and the corresponding Bethe ansatz equations are obtained.