title: Negative specific heat in the canonical statistical ensemble.
abstract: According to thermodynamics, the specific heat of Boltzmannian short-range interacting systems is a positive quantity. Less intuitive properties are instead displayed by systems characterized by long-range interactions. In that case, the sign of specific heat depends on the considered statistical ensemble: Negative specific heat can be found in isolated systems, which are studied in the framework of the microcanonical ensemble; on the other hand, it is generally recognized that a positive specific heat should always be measured in systems in contact with a thermal bath, for which the canonical ensemble is the appropriate one. We demonstrate that the latter assumption is not generally true: One can, in principle, measure negative specific heat also in the canonical ensemble if the system under scrutiny is non-Boltzmannian and/or out-of-equilibrium.
authors.affiliation: Dipartimento di Fisica, Università di Trieste, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Staniscia
authors.forename: A
authors.initials: A
authors.lastname: Turchi
authors.forename: D
authors.initials: D
authors.lastname: Fanelli
authors.forename: P H
authors.initials: PH
authors.lastname: Chavanis
authors.forename: G
authors.initials: G
authors.lastname: De Ninno