2022-08-29

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Cosmology and the AB transition in superfluid helium 3 †

Speaker: Mark Hindmarsh †

The extreme purity and precise control of pressure and temperature achievable in the laboratory
make the superfluid Helium-3 AB transition ideal for testing the theory of first order phase transitions in the early Universe.
Such a phase transition, which appears naturally in many extensions of the Standard Model of particle physics,
could provide the departure from equilibrium needed for a dynamical explanation of the baryon asymmetry of
the Universe. It could also produce gravitational waves of a frequency observable by
future space-based detectors such as the Laser Interferometer Space Antenna (LISA).

All calculations of the gravitational wave power spectrum rely on a relativistic version
of the classical nucleation theory, due to Coleman and Linde.
Yet when the A phase of superfluid He-3 is supercooled, the B phase appears far faster than
classical nucleation theory would predict. If the appearance of B phase is due to a new
rapid intrinsic mechanism, gravitational wave production could be rendered negligible.

I discuss how the nucleation rate influences gravitational wave production
at a first order phase transition in the early Universe, and make quantitive analogies with
the AB transition. I outline future experiments designed to eliminate extrinsic
nucleation mechanisms, and how they can be used to test cosmological nucleation theory.