Functional Integrals and Variational-Cumulant Expansion in sine-Gordon-Thirring Model

Zou Bo-Xia, Jun Yan, Tao Wang

Jun Yan, Baolin Li

Masatoshi Imada, Kazuo Hida, M. Ishikawa

C. Destri

Jun Yan

The free energy in 1D sine-Gordon-Thirring model with impurity coupling is studied by means of functional integrals and variational-cumulant expansion methods. Two variational parameters are introduced to evaluate free energy and statistical averages. It is shown that the non-perturbation method of functional integrals can be applied to strong-coupling range of fermion systems.

Jun Yan

The free energy at low temperature in 1D sine-Gordon–Thirring model with impurity coupling is studied by means of functional integrals method. For massive free sine-Gordon–Thirring model, free energy is obtained from perturbation expansion of functional determinant. Moreover, the free energy of massive model is calculated by use of an auxiliary Bose field method.