title: Landau dynamics of a grey soliton in a trapped condensate.
abstract: It is shown that grey soliton dynamics in a one-dimensional trap can be treated within the framework of the local density approximation as Landau dynamics of a quasiparticle. A soliton of arbitrary amplitude moves in the trapping potential without deformation of its density profile as a particle of mass 2m. The dynamics in the local density approximation is shown to be consistent with the perturbation theory for dark solitons. Dynamics of a vortex ring in a trap is discussed qualitatively.
authors.affiliation: Centro de Física Teórica e Computacional, Universidade de Lisboa, Complexo Interdisciplinar, Avenida Professor Gama Pinto 2, Lisboa 1649-003, Portugal.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Konotop
authors.forename: Lev
authors.initials: L
authors.lastname: Pitaevskii