Thermodynamics of the dissipative two-state system: A Bethe-ansatz study

The thermodynamics of the dissipative two-state system is calculated exactl y for all temperatures and level asymmetries for the case of Ohmic dissipat ion. We exploit the equivalence of the two-state system to the anisotropic Kondo model and extract the thermodynamics of the former by solving the the rmodynamic Betheansatz equations of the latter. The universal scaling funct ions for the specific heat C-alpha(T) and static dielectric susceptibility chi(alpha)(T) are extracted for all dissipation strengths 0<alpha<1. The lo garithmic corrections to these quantities at high temperatures are found in the Kondo limit alpha-->1(-), whereas for alpha<1 we find the expected pow er law temperature dependences with the powers being functions of the dissi pative coupling a. The low-temperature behavior is always that of a Fermi l iquid. [S0163-1829(99)06519-4].