General Physics Colloquium and Parratt Lecture, Professor Gretchen Campbell, NIST and University of Maryland, College Park

Title:  A Supersonically expanding Bose-Einstein Condensate: An expanding universe in the lab 

Host: Erich Mueller

Abstract:  At ultralow temperatures, quantum degenerate gases take the form of quantum fluids, which are many-body, interacting forms of matter that behave as quantum-coherent superfluids. These quantum fluids support long-lived collective excitations, which have applications in both the study of fundamental physics questions, and possibly, for the creation of new types of quantum-matter based devices and sensors.  Here I will discuss recent experiments with our quantum fluid: A ring-shaped Bose-Einstein Condensate (BEC). The massive scale of the universe makes the experimental study of cosmological inflation difficult. This has led to an interest in developing analogous systems using table top experiments. One possible system for such simulations is an expanding atomic quantum gas. In recent experiments, we have modeled the basic features of an expanding universe by drawing parallels with both expanding and contracting ring-shaped BEC.  The BEC can be thought of as a vacuum for phonons, and used in analogy to the quantum field proposed to have driven the expansion of the early universe, and phonons are the analogue to photons in our expanding universe.   In theoretical models of the expanding universe, relativistic scalar fields are attenuated by “Hubble friction”, which results from the dilation of the underlying metric. By contrast, in a contracting universe this pseudo-friction leads to amplification. In recent experiments, we experimentally measured both Hubble attenuation and amplification in expanding and contracting ring-shaped Bose-Einstein condensates, in which phonons are analogous to cosmological scalar fields.