# A Rapidly Expanding Bose-Einstein Condensate: An Expanding Universe in the Lab

We study the dynamics of a supersonically expanding, ring-shaped Bose-Einstein condensate both experimentally and theoretically. The expansion redshifts long-wavelength excitations, as in an expanding universe. After expansion, energy in the radial mode leads to the production of bulk topological excitations—solitons and vortices—driving the production of a large number of azimuthal phonons and, at late times, causing stochastic persistent currents. These complex nonlinear dynamics, fueled by the energy stored coherently in one mode, are reminiscent of a type of “preheating” that may have taken place at the end of inflation.

*A Rapidly Expanding Bose-Einstein Condensate: An Expanding Universe in the Lab*; S. Eckel, A. Kumar, T. Jacobson, I. B. Spielman, and G. K. Campbell; Phys. Rev. X **8** 021021 (2018). doi:10.1103/PhysRevX.8.021021

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.8.021021