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Vladimir E. Korepin

Publications and source records attributed to Vladimir E. Korepin.

47 records · Page 3Linked to original sources
arXiv1995

Dual Field Approach to Correlation Functions in the Heisenberg Xxz Spin Chain

We study zero temperature correlation functions of the spin-$1\over 2$ Heisenberg XXZ model in the critical regime $-1< Δ\leq 1$ in a magnetic field by means of the {\tenit Dual Field Approach}. We show for one particular example how to derive determinant representations for correlation functions and how to use these to embed the correlation functions in integrable systems of integro-difference equations (IDE). These IDE are associated with a Riemann-Hilbert problem.

solv-int↗
arXiv1994

$η$-pairing as a mechanism of superconductivity in models of strongly correlated electrons

We consider extended versions of the Hubbard model which contain additional interactions between nearest neighbours. In this letter we show that a large class of these models has a superconducting ground state in arbitrary dimensions. In some special cases we are able to find the complete phase diagram. The superconducting phase exist even for moderate repulsive values of the Hubbard interaction $U$.

cond-mat↗
arXiv1994

Differential equation for a correlation function of the spin-${1\over2}$ Heisenberg chain

We consider the probability to find a string of $x$ adjacent parallel spins in the antiferromagnetic ground state of the model (in a magnetic field). We derive a system of integro-difference equations which define this probability. This system is completely integrable, it has Lax representation and a corresponding Riemann-Hilbert problem. The quantum correlation funtion is a $τ$-function of this system.

cond-mat↗
arXiv1994

Correlation Function of the Spin-1/2 XXX Antiferromagnet

We consider a special correlation function in the isotropic spin-$\half$ Heisenberg antiferromagnet. It is the probability of finding a ferromagnetic string of (adjacent) spins in the antiferromagnetic ground state. We give two different representations for this correlation function. Both of them are exact at any distance, but one becomes more effective for the description of long distance behaviour, the other for the description of short distance behaviour.

cond-mat↗
arXiv1993

SU(2)xSU(2) Invariant Scattering Matrix of the Hubbard Model

We consider the one-dimensional half-filled Hubbard model. We show that the excitation spectrum is given by the scattering states of four elementary excitations, which form the fundamental representation of $SU(2)\times SU(2)$. We determine the exact two-particle Scattering matrix, which a solution of the Yang-Baxter equation and reflects the $SO(4)$ symmetry of the model. The results for repulsive and attractive Hubbard model are related by an interchange of spin and charge degrees of freedom.

cond-mat↗
arXiv1993

Scattering Matrix and Excitation Spectrum of the Hubbard Model

We consider the one-dimensional Hubbard model at half filling. We show that both excitation spectrum and S-matrix are determined by the SO(4) symmetry of the model. The complete set of excitations is given by the scattering states four elementary excitations, which form the fundamental representation of SO(4). We evaluate the exact S-matrix, which satisfies the Yang-Baxter relation. The results for the repulsive and attractive Hubbard model are related by an interchange of spin and charge degrees of freedom.

cond-mat↗
arXiv1993

Spectrum of Low-Lying Excitations in a Supersymmetric Extended Hubbard Model

We continue the study of the $u(2|2)$-supersymmetric extension of the Hubbard model in one dimension. We determine the excitation spectrum at zero temperature even in the sectors where the ground states are $u(2|2)$-descendants of Bethe states. The excitations include spinons, holons, electrons, localons (local electrons pairs, moving coherently through the lattice) and their bound states. The spectra are found to be very different for repulsive and attractive on-site interaction. We also study the thermodynamics of the model.

cond-mat↗
arXiv1992

New Exactly Solvable Model of Strongly Correlated Electrons Motivated by High T_c Superconductivity

We present a new model describing strongly correlated electrons on a general $d$-dimensional lattice. It differs from the Hubbard model by interactions of nearest neighbours, and it contains the $t$-$J$ model as a special case. The model naturally describes local electron pairs, which can move coherently at arbitrary momentum. By using an $η$-pairing mechanism we can construct eigenstates of the hamiltonian with off-diagonal-long-range-order (ODLRO). These might help to relate the model to high-$T_c$ superconductivity. On a one-dimensional lattice, the model is exactly solvable by Bethe Ansatz.

cond-mat↗
arXiv1992

A New Solution of the Supersymmetric TJ Model by Means of the Quantum Inverse Scattering Method

We construct the enveloping fundamental spin model of the t-J hamiltonian using the Quantum Inverse Scattering Method (QISM), and present all three possible Algebraic Bethe Ansätze. Two of the solutions have been previously obtained in the framework of Coordinate Space Bethe Ansatz by Sutherland and by Schlottmann and Lai, whereas the third solution is new. The formulation of the model in terms of the QISM enables us to derive explicit expressions for higher conservation laws.

hep-th↗