Existence and decay of traveling waves for the nonlocal Gross-Pitaevskii equation

TL;DR

This paper proves the existence, decay, and analyticity of dark soliton solutions in a nonlocal Gross-Pitaevskii equation modeling Bose gases with nonlocal interactions, covering almost all subsonic speeds.

Contribution

It establishes the existence of dark solitons for a broad class of nonlocal interactions and subsonic speeds using variational methods and a priori estimates.

Findings

Existence of dark solitons for almost all subsonic speeds.

Exponential decay and analyticity of the solitons.

Existence in the entire subsonic regime for specific potentials.

Abstract

We consider the nonlocal Gross-Pitaevskii equation that models a Bose gas with general nonlocal interactions between particles in one spatial dimension, with constant density far away. We address the problem of the existence of traveling waves with nonvanishing conditions at infinity, i.e. dark solitons. Under general conditions on the interactions, we prove existence of dark solitons for almost every subsonic speed. Moreover, we show existence in the whole subsonic regime for a family of potentials. The proofs rely on a Mountain Pass argument combined with the so-called "monotonicity trick", as well as on a priori estimates for the Palais-Smale sequences. Finally, we establish properties of the solitons such us exponential decay at infinity and analyticity.