Form-factors of exponential fields in the sine-Gordon model

An integral representation for form-factors of exponential fields in the sine-Gordon model is proposed.Comment: 8 pages, harvmac.tex, added the formula (25) for two soliton form-factors at the reflectionless point

Correlation amplitude for the XXZ spin chain in the disordered regime

We proposed an analytical expression for the amplitude defining the long distance asymptotic of the correlation function .Comment: 5 pages, harvmac.tex, one epsf figur

Particle-Field Duality and Form Factors from Vertex Operators

Using a duality between the space of particles and the space of fields, we show how one can compute form factors directly in the space of fields. This introduces the notion of vertex operators, and form factors are vacuum expectation values of such vertex operators in the space of fields. The vertex operators can be constructed explicitly in radial quantization. Furthermore, these vertex operators can be exactly bosonized in momentum space. We develop these ideas by studying the free-fermion point of the sine-Gordon theory, and use this scheme to compute some form-factors of some non-free fields in the sine-Gordon theory. This work further clarifies earlier work of one of the authors, and extends it to include the periodic sector.Comment: 17 pages, 2 figures, CLNS 93/??

Form-factors of the sausage model obtained with bootstrap fusion from sine-Gordon theory

We continue the investigation of massive integrable models by means of the bootstrap fusion procedure, started in our previous work on O(3) nonlinear sigma model. Using the analogy with SU(2) Thirring model and the O(3) nonlinear sigma model we prove a similar relation between sine-Gordon theory and a one-parameter deformation of the O(3) sigma model, the sausage model. This allows us to write down a free field representation for the Zamolodchikov-Faddeev algebra of the sausage model and to construct an integral representation for the generating functions of form-factors in this theory. We also clear up the origin of the singularities in the bootstrap construction and the reason for the problem with the kinematical poles.Comment: 16 pages, revtex; references added, some typos corrected. Accepted for publication in Physical Review

On the Finite Temperature Formalism in Integrable Quantum Field Theories

Two different theoretical formulations of the finite temperature effects have been recently proposed for integrable field theories. In order to decide which of them is the correct one, we perform for a particular model an explicit check of their predictions for the one-point function of the trace of the stress-energy tensor, a quantity which can be independently determined by the Thermodynamical Bethe Ansatz.Comment: 12 pages, corrected some typos and an equatio

Explicit Construction of Spin 4 Casimir Operator in the Coset Model SO^(5)1×SO^(5)m/SO^(5)1+m \hat{SO} (5)_{1} \times \hat{SO} (5)_{m} / \hat{SO} (5)_{1+m}

We generalize the Goddard-Kent-Olive (GKO) coset construction to the dimension 5/2 operator for $\hat{so} (5)$ and compute the fourth order Casimir invariant in the coset model $\hat{SO} (5)_{1} \times \hat{SO} (5)_{m} / \hat{SO} (5)_{1+m}$ with the generic unitary minimal $c < 5/2$ series that can be viewed as perturbations of the $m \rightarrow \infty$ limit, which has been investigated previously in the realization of $c= 5/2$ free fermion model.Comment: 11 page

One-point functions in integrable quantum field theory at finite temperature

We determine the form factor expansion of the one-point functions in integrable quantum field theory at finite temperature and find that it is simpler than previously conjectured. We show that no singularities are left in the final expression provided that the operator is local with respect to the particles and argue that the divergences arising in the non-local case are related to the absence of spontaneous symmetry breaking on the cylinder. As a specific application, we give the first terms of the low temperature expansion of the one-point functions for the Ising model in a magnetic field.Comment: 10 pages, late