Temperature of nonextensive systems: Tsallis entropy as Clausius entropy

The problem of the temperature in nonextensive statistical mechanics is studied. Considering the first law of thermodynamics and a “quasi-reversible process”, it is shown that the Tsallis entropy becomes the Clausius entropy if the inverse of the Lagrange multiplier, β, associated with the constraint on the internal energy is regarded as the temperature. This temperature is different from the previously proposed “physical temperature” defined through the assumption of divisibility of the total system into independent subsystems. A general discussion is developed about the role of the Boltzmann constant in generalized statistical mechanics based on an entropy, which, under the assumption of independence, is nonadditive.