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 Φ1,3​. Exact calculations of the
dependence of energy levels on the size are presented for vacuum and many
excited states.Comment: PhD thesis, 96 pages, 28 figure