Cold atoms stay cool

Lewis R. B. Picard

Masatoshi Kajita

As an introduction, the states of atoms and molecules are introduced. At room temperature, gaseous atoms and molecules move very fast. We imagine that the gaseous phase is transformed to liquid or solid phase by cooling, but it is possible only with high density of atoms and molecules. With low densities, atoms and molecules also stay in the gaseous state at low temperature. Research using cold atoms and molecules, trapped by electric or magnetic field, give important information to develop new physics.

Christopher J. Foot

José Tito Mendonça

We discuss the Schrödinger–Newton (SN) equation in the context of cold atom physics. For that purpose, we establish the wave-kinetic equation equivalent to the SN equation, which stays valid in different physical scenarios relevant to cold atoms. They include: (1) the usual scenario of matter confined in a self-gravitating field, (2) atomic molasses, confined and cooled by laser beams in a magneto-optical trap (MOT), (3) Bose–Einstein condensates, with or without long range dipolar interactions, and (4) electron states in a quantum plasma. We show that these different systems can be described by a formally identical equation, and they also manifest similar elementary excitations. The wave-kinetic equation is obtained by following the well-known Wigner–Moyal procedure, allowing the representation of quantum states in a classical phase-space. It is particularly well suited to discuss kinetic properties associated with Landau damping, as shown. We also consider generalisation of the SN equation onto the relativistic domain, and its impact on the proposed wave-kinetic description.