DOI: 10.1140/epjc/s10052-026-15884-w ISSN: 1434-6052

Phonon dynamics in spherically-curved analog-gravity Bose–Einstein condensates

J. Austin Chunn, Ruotong Zhai, Daniel E. Sheehy
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Abstract

We study the low energy phonon dynamics of a Bose–Einstein condensate (BEC) with a density profile that is equivalent, via a coordinate transformation, to phonons traveling in a “spherical” curved spacetime that realizes the Friedman–Lemaître–Robertson–Walker (FLRW) metric. The metric of this BEC is characterized by its curvature

$$\kappa $$ κ
and a time-dependent scale factor a ( t ),  with an increase in the latter corresponding to an expansion of the analog FLRW universe. We study the propagation of classical phonons in such BECs, finding that a sudden change in the scale factor induces ripples in the wave motion. In addition, we study quantum phonon creation (or vacuum amplification) due to the scale-factor modification and quantify their entanglement.

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