Complete Solution of a Supersymmetric Extended Hubbard Model

We show that the recently constructed exact solution of the $SU(2|2)$ extended Hubbard model on a one-dimensional lattice provides a complete set of $4^L$ eigenstates of the hamiltonian, where $L$ is the length of the lattice.Comment: 16 pages, LaTex, PUPT-1420, CERN-TH.6982/9

Relationship between single-particle excitation and spin excitation at the Mott Transition

An intuitive interpretation of the relationship between the dispersion relation of the single-particle excitation in a metal and that of the spin excitation in a Mott insulator is presented, based on the results for the one- and two-dimensional Hubbard models obtained by using the Bethe ansatz, dynamical density-matrix renormalization group method, and cluster perturbation theory. The dispersion relation of the spin excitation in the Mott insulator is naturally constructed from that of the single-particle excitation in the zero-doping limit in both one- and two-dimensional Hubbard models, which allows us to interpret the doping-induced states as the states that lose charge character toward the Mott transition. The characteristic feature of the Mott transition is contrasted with the feature of a Fermi liquid and that of the transition between a band insulator and a metal.Comment: 6 pages, 2 figures, to appear in JPS Conf. Pro

Determinant formula for the six-vertex model with reflecting end

Using the Quantum Inverse Scattering Method for the XXZ model with open boundary conditions, we obtained the determinant formula for the six vertex model with reflecting end.Comment: 10 page

Bethe ansatz solution of the Osp(1∣2n)Osp(1|2n) invariant spin chain

We have applied the analytical Bethe ansatz approach in order to solve the $Osp(1|2n)$ invariant magnet. By using the Bethe ansatz equations we have calculated the ground state energy and the low-lying dispersion relation. The finite size properties indicate that the model has a central charge $c=n$.Comment: 9 page

Algebraic properties of an integrable t-J model with impurities

We investigate the algebraic structure of a recently proposed integrable $t-J$ model with impurities. Three forms of the Bethe ansatz equations are presented corresponding to the three choices for the grading. We prove that the Bethe ansatz states are highest weight vectors of the underlying $gl(2|1)$ supersymmetry algebra. By acting with the $gl(2|1)$ generators we construct a complete set of states for the model.Comment: 20 pages, LaTe

Applications of Massive Integrable Quantum Field Theories to Problems in Condensed Matter Physics

We review applications of the sine-Gordon model, the O(3) non-linear sigma model, the U(1) Thirring model, and the O(N) Gross--Neveu model to quasi one-dimensional quantum magnets, Mott insulators, and carbon nanotubes. We focus upon the determination of dynamical response functions for these problems. These quantities are computed by means of form factor expansions of quantum correlation functions in integrable quantum field theories. This approach is reviewed here in some detail.Comment: 150 pages, 35 figures, published in the I. Kogan Memorial Volume by World Scientifi

Effects of thermal phase fluctuations in a 2D superconductor: an exact result for the spectral function

We consider the single particle spectral function for a two-dimensional clean superconductor in a regime of strong critical thermal phase fluctuations. In the limit where the maximum of the superconducting gap is much smaller than the Fermi energy we obtain an exact expression for the spectral function integrated over the momentum component perpendicular to the Fermi surface.Comment: 4 pages, 3 figures. References added, figures improve

Violations of the String Hypothesis in the Solutions of the Bethe Ansatz Equations in the XXX-Heisenberg

We study the equations for the quasi-momenta which characterize the wave-functions in the Bethe ansatz for the XXX-Heisenberg model. We show in a simple analytical fashion, that the usual ``string hypothesis" incorrectly predicts the number of real solutions and the number of complex solutions for $N>21$ in the sector with two spins flipped, confirming the work of Essler et al. Two complex pair solutions drop out and form two additional real pair solutions. We also introduce a new set of variables which allows the equations to be written as a single polynomial equation in one variable. We consider in some detail the case of three spins flipped.Comment: 18 pages. revised to amplify credit, in plain tex with macropackage psbox (available from the net