Year: 2020
Type: article
Abstract: The unconstrained ensemble describes completely open systems in which energy, volume and number of particles fluctuate. Here we show that not only equilibrium states can exist in this ensemble, but also that completely open systems can undergo first-order phase transitions. This is shown by studying a modified version of the Thirring model with attractive and repulsive interactions and with particles of finite size. The model exhibits first-order phase transitions in the unconstrained ensemble, at variance with the analogous model with point-like particles. While unconstrained and grand canonical ensembles are equivalent for this model, we found inequivalence between the unconstrained and isothermal–isobaric ensembles. By comparing the thermodynamic phase diagram in the unconstrained case with that obtained in the isothermal–isobaric ensemble, we show that phase transitions under completely open conditions for this model are different from those in which the number of particles is fixed, highlighting the inequivalence of ensembles.
Authors: Alessandro Campa, Lapo Casetti, Ivan Latella, Stefano Ruffo
Institutions: Istituto Superiore di Sanità, Arcetri Astrophysical Observatory, Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, University of Florence, Universitat de Barcelona, Scuola Internazionale Superiore di Studi Avanzati, Institute for Complex Systems, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, National Research Council
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2982633374