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

Abstract

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 excitationssolitons 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.

Analogy between freezing lakes and the cosmic radiation era

“…Specifically, factors such as the presence/absence of impurities in the water and their nature and concentration, the atmospheric temperature and its variation in time, the temperature at the bottom of the "lake" (in practice, a deep tank), the lack of winds, and the depth of the "lake" can all be controlled in a laboratory setting. The equipment necessary to conduct an analogue gravity experiment bsed on the physics of water is common in cold laboratories studying snow and ice, while the equipment required is not sophisticated in comparison with that used in conventional analogue gravity in which black holes, cosmological spacetimes, and curved space phenomena such as Hawking radiation, su-perradiance, and false vacuum decay require the use of Bose-Einstein condensates [22][23][24][25]61], ultracold atoms [62], optical systems [63,64], or at least very finely controlled water flows and vortices (e.g., [65][66][67][68]). Likewise, the experimental study of the analogy between freezing lakes and cosmology would require a much simpler laboratory setting than it would be necessary to study the analogy between cosmology and large geological systems such as glaciers and beaches, which also exhibit analogies with cosmology [26,27].…”

“…By introducing This equation is analogous to the Friedmann equation of relativistic cosmology for a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe filled with blackbody radiation, as discussed in the next section. Indeed, the Friedmann equation, which resembles an energy conservation equation for a conservative mechanical system, lends itself to analogy with equations arising in the study of many different and completely unrelated physical systems, ranging from particles in one-dimensional motion [15]- [19] to optical systems [20,21], condensed matter systems [22][23][24][25], the transverse profiles of glacial valleys [20,21,26], and equilibrium beach profiles [27].…”

Superradiant scattering in fluids of light

“…Given the conserved current, one can integrate it over an annular sub-region with boundary instead of all space. The resulting relation ∂ t region rdr J 0 + J 1 boundary (t) = 0 (39) tells us that as long as J 1 is zero at the boundary the total charge in the integrated region is conserved. For example, when a wavepacket moves across the boundary the total charge in the region will change, and that change is governed by (39).…”

Optical characterisation of micro-fabricated Fresnel zone plates for atomic waveguides

“…While ring-guided ultracold atom interferometers have long been a goal [19,22], actual rotation metrology has only been achieved very recently [23,24]. Atom waveguides, in particular rings, are also of great interest outside inertial sensing for a variety of fundamental physics experiments including dimensionality [25,26], cosmological phenomena [27], and superfluidity [28].…”