Structure of the vacuum in the quantum sine-Gordon model

Zou Bo-Xia, Jun Yan, Tao Wang

Lawrence J. Landau

Constantin Babenko

This PhD thesis addresses the problem of the calculation of the one point functions (1PF) in integrable two-dimensional quantum field theories. A method for their calculation has been developed in the context of the sine-Gordon Theory. The integrability of the model was used to build a basis of local operators to describe the six-vertex model. This basis, called fermionic, is interesting because the vacuum expectation values of its operators are expressed in terms of determinants and the fermionic structure can be extended to the continuous limit in order to characterize local operators in the CFT. In this thesis, we continue to work on this approach, aiming to generalize the fermionic basis to the supersymmetric sine-Gordon model (ssG). We derived scaling equations governing the thermodynamics of the ssG theory, reproducing the BLZ generating function. Then, we described the integrable structure of the ssG model using the fermion-current basis. We focused on the fermionic part and calculated its one point functions. These results were verified with a different approach based on the reflection relations.

Sergei L. Lukyanov, Alexander B. Zamolodchikov

We propose an explicit expression for vacuum expectation values 〈eiaϕ〉 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.

Satoshi Takada, Susumu Misawa

Giovanni Feverati

In this thesis, we review recent progresses on Nonlinear Integral Equation approach to finite size effects in two dimensional integrable quantum field theories, with emphasis to Sine-Gordon/Massive Thirring model and restrictions to minimal models perturbed by $Φ_{1,3}$. Exact calculations of the dependence of energy levels on the size are presented for vacuum and many excited states.