The Bethe-Salpeter amplitudes of the bound states formed by two scalar particles with unequal masses are analyzed in the massive scalar particle exchange ladder model. The norms of the amplitudes are calculated numerically, and it is confirmed that the norm vanishes for the bound state corresponding to the complex eigenvalue of the coupling constant. The behaviour of the Bethe-Salpeter amplitud...

A quantum algebra invariant integrable closed spin 1 chain is introduced and analysed in detail. The Bethe ansatz equations as well as the energy eigenvalues of the model are obtained. The highest weight property of the Bethe vectors with respect to Uq(sl(2)) is proved. PACS Nos. 03.65.Fd 05.50+q 75.10.Jm Running Title Closed spin 1 XXZ chain e-mail [email protected] e-mail [email protected] ...

We consider the six-vertex model with domain wall boundary conditions. We choose the inhomogeneities as solutions of the Bethe Ansatz equations. The Bethe Ansatz equations have many solutions, so we can consider a wide variety of inho-mogeneities. For certain choices of the inhomogeneities we study arrow correlation functions on the horizontal line going through the centre. In particular we obt...

The ground-state phases of a one-dimensional SU~4! spin-orbital Hamiltonian in a generalized external field are studied on the basis of the Bethe-ansatz solution. Introducing three Landé g factors for spin, orbital, and their products in the SU~4! Zeeman term, we systematically discuss various symmetry breakings. The magnetization versus external field is evaluated by solving the Bethe-ansatz e...

We show how to derive exact boundary S matrices for integrable quantum field theories in 1+1 dimensions using lattice regularization. We do this calculation explicitly for the sine-Gordon model with fixed boundary conditions using the Bethe ansatz for an XXZtype spin chain in a boundary magnetic field. Our results agree with recent conjectures of Ghoshal and Zamolodchikov, and indicate that the...

We present the thermodynamic Bethe ansatz as a way to factorize the partition function of a 2d field theory, in particular, a conformal field theory and we compare it with another approach to factorization due to K. Schoutens which consists of diagonalizing matrix recursion relations between the partition functions at consecutive levels. We prove that both are equivalent, taking as examples the...

We prove that the regular Bethe ansatz eigenvectors of the XXZ spin chain at roots of unity are the highest weight vectors of the sl2 loop algebra. Here the variable q is related to the XXZ coupling parameter ∆ by ∆ = (q + q−1)/2, and it is given by a root of unity: q2N = 1. It follows that the regular Bethe state gives the highest weights of the Drinfeld generators of Uq(L(sl2)). Thus, we can ...

We study the finite size scaling of the spin stiffness for the one-dimensional s = 1 2 quantum antiferromagnet as a function of the anisotropy parameter ∆. Previous Bethe ansatz results allow a determination of the stiffness in the thermodynamic limit. The Bethe ansatz equations for finite systems are solvable even in the presence of twisted boundary conditions, a fact we exploit to determine t...

The instantaneous Bethe–Salpeter equation, derived from the general Bethe–Salpeter formalism by assuming that the involved interaction kernel is instantaneous, represents the most promising framework for the description of hadrons as bound states of quarks from first quantum-field-theoretic principles, that is, quantum chromodynamics. Here, by extending a previous analysis confined to the case ...

A Ward-Takahashi identity preserving Bethe-Salpeter kernel can always be calculated explicitly from a dressed-quark-gluon vertex whose diagrammatic content is enumerable. We illustrate that fact using a vertex obtained via the complete resummation of dressed-gluon ladders. While this vertex is planar, the vertex-consistent kernel is nonplanar and that is true for any dressed vertex. In an exemp...