On the role of interactions in trans-sonically flowing atomic condensates

TL;DR

This paper investigates how interactions influence the behavior of flowing atomic condensates with horizons, revealing that observed density modulations are mainly due to linear interference rather than collective effects, supported by numerical and analytical methods.

Contribution

It provides a combined numerical and analytical analysis showing interactions are not essential for density modulations, challenging previous interpretations of black-hole lasing phenomena.

Findings

Density modulations are primarily due to linear interference of atomic waves.

Interactions are not necessary for the observed density patterns.

Analytical solutions using Airy wavefunctions support the interference interpretation.

Abstract

We provide a joint numerical-analytical study of the physics of a flowing atomic Bose-Einstein condensate in the combined presence of an external trap and a step potential which accelerates the atoms out of the condensate creating a pair of neighbouring black- and white- hole horizons. In particular, we focus on the rapidly growing density modulation pattern that appears in the supersonic region, an experimentally observed feature that was related to black-hole lasing phenomena. A direct assessment of the role of interactions in this process suggests an interpretation of the experimental data in terms of linear interference of atomic waves rather than collective effects. Our conclusions are further supported by an analytical solution of the Schrodinger equation in terms of Airy wavefunctions.