title: Thermal collapse of a granular gas under gravity.
abstract: Free cooling of a gas of inelastically colliding hard spheres represents a central paradigm of kinetic theory of granular gases. At zero gravity the temperature of a freely cooling homogeneous granular gas follows a power law in time. How does gravity, which brings inhomogeneity, affect the cooling? We combine molecular dynamics simulations, a numerical solution of hydrodynamic equations and an analytic theory to show that a granular gas cooling under gravity undergoes thermal collapse: it cools down to zero temperature and condenses on the bottom of the container in a finite time.
authors.affiliation: Bioengineering Department, University of California, San Diego, La Jolla, California 92093-0402, USA.
authors.forename: Dmitri
authors.initials: D
authors.lastname: Volfson
authors.forename: Baruch
authors.initials: B
authors.lastname: Meerson
authors.forename: Lev S
authors.initials: LS
authors.lastname: Tsimring