Heat and generalized Clausius entropy of nonextensive systems

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Macroscopic nonextensive thermodynamics is studied without recourse to microscopic statistical mechanics. It is shown that if entropy is nonextensive, the concept of physical temperature introduced through the generalized zeroth law of thermodynamics necessarily leads to modifications of the first law of thermodynamics and some of thermodynamic relations including Clausius definition of thermodynamic entropy. It is also shown, by applying this generalized Clausius entropy to a composite nonextensive system, how the nonextensive entropy and the quantity of heat consistently behave in an arbitrary thermodynamic process. An important point emerging from this is that the entropy coefficient, which connects the microscopic and macroscopic concepts, cannot be removed from the macroscopic nonextensive theory. This fact suggests that nonextensivity may require atomism for macroscopic thermodynamics at a logical level.