Excited State TBA and Functional Relations in Spinless Fermion Model

抄録

The excited state thermodynamic Bethe ansatz (TBA) equations for the spinless Fermion model are presented by the quantum transfer matrix (QTM) approach. We introduce a more general family called T-functions and explore functional relations among them (T-system) and their certain combinations (Y-system). From their analytical property, we derive a closed set of non linear integral equations which characterize the correlation length of ‹ c_j^†c_i› at any finite temperatures. Solving these equations numerically, we explicitly determine the correlation length, which accurately coincides with previous results.