Concavity, Response Functions and Replica Energy [article]

Alessandro Campa, Lapo Casetti, Ivan Latella, Agustín Pérez-Madrid, Stefano Ruffo
2018 Entropy   pre-print
In nonadditive systems, like small systems or like long-range interacting systems even in the thermodynamic limit, ensemble inequivalence can be related to the occurrence of negative response functions, this in turn being connected with anomalous concavity properties of the thermodynamic potentials associated to the various ensembles. We show how the type and number of negative response functions depend on which of the quantities E, V and N (energy, volume and number of particles) are
more » ... d in the ensemble. In particular, we consider the unconstrained ensemble in which E, V and N fluctuate, physically meaningful only for nonadditive systems. In fact, its partition function is associated to the replica energy, a thermodynamic function that identically vanishes when additivity holds, but that contains relevant information in nonadditive systems.
doi:10.3390/e20120907 pmid:33266631 pmcid:PMC7512492 arXiv:1810.11309v1 fatcat:aug2t53atzdo5dhamdnbbr7vaa