  The specific heat and the compressibility for the integrable t-J model are
calculated showing Luttinger liquid behavior for low temperatures. A
Trotter-Suzuki mapping and the quantum transfer matrix approach are utilized.
Using an algebraic Bethe ansatz this method permits the exact calculation of
the free energy and related quantities. A set of just two non-linear integral
equations determining these quantities is studied for various particle
densities and temperatures. The structure of the specific heat is discussed in
terms of the elementary charge as well as spin excitations.
