Exact form factors in (1 + 1)-dimensional field theoretic models with soliton behaviour

Isomorphism of critical and off-critical operator spaces in two-dimensional quantum field theory

“…zero-particle) state. The form factors satisfy a set of functional equations taking into account the spin s Φ of the operator, the monodromy properties under analytic continuation in rapidity space and the pole singularities associated to bound states and annihilation processes [5,6]. For the Lee-Yang model these equations read…”

“…Indeed, integrable massive theories are solved on-shell, through the determination of the exact S-matrix, and any information about the operators needs to be extracted from the particle dynamics. The monodromy properties and the singularity structure provide a set of equations [5,6] for the matrix elements of the operators on asymptotic states (form factors) which have the S-matrix as their only input, and whose space of solutions is expected to coincide with the operator space of the theory.…”

First-order phase transitions and integrable field theory. The dilute q-state Potts model

“…These models are integrable, in the sense that the S-matrix which determine their on-shell physics in 1 + 1 dimensions can be computed exactly [2]. The solvability of the models extends off-shell through the possibility of exact determination of the matrix elements of local operators on the asymptotic states [3,4], which in turn leads to the evaluation of correlation functions in the form of spectral series.…”

Matrix elements of the operator in integrable quantum field theory

“…Moving off-shell means evaluating the matrix elements (form factors) of the operators on the asymptotic particle states; if this is achieved the correlators can be expressed as spectral sums. The simplifications of the dynamics allow to prescribe the analytic properties of the form factors through a set of functional equations whose only input is the S-matrix [3,4]. A solution of these equations, i.e.…”