title: Semiphenomenological model for gas-liquid phase transitions.
abstract: We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value T(s) depending on the gas density. It is further shown that, even if T is only marginally lower than T(s), the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with T(s) being the temperature of saturated vapor and the high-density clusters representing liquid droplets.
authors.affiliation: Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland.
authors.forename: E S
authors.initials: ES
authors.lastname: Benilov
authors.affiliation: Departamento de Física, CCCEE, Universidade da Madeira, Largo do Município, 9000 Funchal, Portugal.|Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
authors.forename: M S
authors.initials: MS
authors.lastname: Benilov