Exact expectation values of local fields in quantum sine-Gordon model

We propose an explicit expression for vacuum expectation values of the exponential fields in the sine-Gordon model. Our expression agrees both with semi-classical results in the sine-Gordon theory and with perturbative calculations in the Massive Thirring model. We use this expression to make new predictions about the large-distance asymptotic form of the two-point correlation function in the XXZ spin chain.Comment: 18 pages, harvmac.tex, 2 figure

Expectation values of boundary fields in the boundary sine-Gordon model

We propose an explicit expression for vacuum expectation values of the boundary field e^{ia\phi_{B}} in the boundary sine-Gordon model with zero bulk mass. This expression agrees with known exact results for the boundary free energy and with perturbative calculations.Comment: 7 pages, harvmac.te

Expectation values of local fields in Bullough-Dodd model and integrable perturbed conformal field theories

Exact expectation values of the fields e^{a\phi} in the Bullough-Dodd model are derived by adopting the ``reflection relations'' which involve the reflection S-matrix of the Liouville theory, as well as special analyticity assumption. Using this result we propose explicit expressions for expectation values of all primary operators in the c<1 minimal CFT perturbed by the operator \Phi_{1,2} or Phi_{2,1}. Some results concerning the $\Phi_{1,5}$ perturbed minimal models are also presented.Comment: 27 pages, harvmac.tex, one epsf figur

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.Comment: 19 pages, 5 figures; references adde

Integrable Quantum Field Theories in Finite Volume: Excited State Energies

We develop a method of computing the excited state energies in Integrable Quantum Field Theories (IQFT) in finite geometry, with spatial coordinate compactified on a circle of circumference R. The IQFT ``commuting transfer-matrices'' introduced by us (BLZ) for Conformal Field Theories (CFT) are generalized to non-conformal IQFT obtained by perturbing CFT with the operator $\Phi_{1,3}$. We study the models in which the fusion relations for these ``transfer-matrices'' truncate and provide closed integral equations which generalize the equations of Thermodynamic Bethe Ansatz to excited states. The explicit calculations are done for the first excited state in the ``Scaling Lee-Yang Model''.Comment: 54 pages, harvmac, epsf, TeX file and postscript figures packed in a single selfextracting uufile. Compiles only in the `Big' mode with harvma