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Sergei Lukyanov

Publications and source records attributed to Sergei Lukyanov.

7 recordsLinked to original sources
arXiv2017

Dimer correlation amplitudes and dimer excitation gap in spin-1/2 XXZ and Heisenberg chains

Correlation functions of dimer operators, the product operators of spins on two adjacent sites, are studied in the spin-$\frac{1}{2}$ XXZ chain in the critical regime. The amplitudes of the leading oscillating terms in the dimer correlation functions are determined with high accuracy as functions of the exchange anisotropy parameter and the external magnetic field, through the combined use of bosonization and density-matrix renormalization group methods. In particular, for the antiferromagnetic Heisenberg model with SU(2) symmetry, logarithmic corrections to the dimer correlations due to the marginally-irrelevant operator are studied, and the asymptotic form of the dimer correlation function is obtained. The asymptotic form of the spin-Peierls excitation gap including logarithmic corrections is also derived.

cond-mat.str-el↗
arXiv2013

Classical Conformal Blocks and Painleve VI

We study the classical c\to \infty limit of the Virasoro conformal blocks. We point out that the classical limit of the simplest nontrivial null-vector decoupling equation on a sphere leads to the Painleve VI equation. This gives the explicit representation of generic four-point classical conformal block in terms of the regularized action evaluated on certain solution of the Painleve VI equation. As a simple consequence, the monodromy problem of the Heun equation is related to the connection problem for the Painleve VI.

hep-th↗
arXiv2011

Critical values of the Yang-Yang functional in the quantum sine-Gordon model

The critical values of the Yang-Yang functional corresponding to the vacuum states of the sine-Gordon QFT in the finite-volume are studied. Two major applications are discussed: (i) generalization of Fendley-Saleur-Zamolodchikov relations to arbitrary values of the sine-Gordon coupling constant, and (ii) connection problem for a certain two-parameter family of solutions of the Painleve III equation.

hep-th↗
arXiv2002

Long-distance asymptotics of spin-spin correlation functions for the XXZ spin chain

We study asymptotic expansions of spin-spin correlation functions for the XXZ Heisenberg chain in the critical regime. We use the fact that the long-distance effects can be described by the Gaussian conformal field theory. Comparing exact results for form factors in the XYZ and sine-Gordon models, we determine correlation amplitudes for the leading and main sub-leading terms in the asymptotic expansions of spin-spin correlation functions. We also study the isotropic (XXX) limit of these expansions.

hep-th↗
arXiv1994

Bosonization of ZF Algebras: Direction Toward Deformed Virasoro Algebra

These lectures were prepared to be presented at A.A. Belavin seminar on CFT at Landau Institute for Theoretical Physics. We review bosonization of CFT and show how it can be applied to the studying of representations of Zamolodchikov-Faddeev (ZF) algebras. In the bosonic construction we obtain explicit realization of chiral vertex operators interpolating between irreducible representations of the deformed Virasoro algebra. The commutation relations of these operators are determined by the elliptic matrix of IRF type and their matrix elements are given in the form of the contour integrals of some meromorphic functions.

hep-th↗