A-B transition in superfluid $^3$He and cosmological phase transitions

TL;DR

This paper investigates the A-B phase transition in superfluid helium-3 as an analog for early universe cosmological phase transitions, highlighting discrepancies with classical nucleation theory and exploring rapid intrinsic nucleation mechanisms.

Contribution

It combines experimental and theoretical studies of the superfluid $^3$He A-B transition, applying cosmological simulation techniques to understand nucleation mechanisms beyond classical theory.

Findings

Classical nucleation theory fails to predict the A-B transition lifetime.

Experimental evidence suggests a rapid, intrinsic nucleation mechanism.

Simulation methods from cosmology aid in understanding superfluid phase transitions.

Abstract

First order phase transitions in the very early universe are a prediction of many extensions of the Standard Model of particle physics and could provide the departure from equilibrium needed for a dynamical explanation of the baryon asymmetry of the Universe. They 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 of Cahn-Hilliard and Langer, due to Coleman and Linde. The high purity and precise control of pressure and temperature achievable in the laboratory made the first-order A to B transition of superfluid $^3$He an ideal for test of classical nucleation theory. As Leggett and others have noted the theory fails dramatically. The lifetime of the metastable A phase is measurable, typically of order minutes to hours, far faster than classical nucleation theory predicts. If the nucleation of B phase from the supercooled A phase is due to a new, rapid intrinsic mechanism that would have implications for first-order cosmological phase transitions as well as predictions for gravitational wave (GW) production in the early universe. Here we discuss studies of the AB phase transition dynamics in $^3$He, both experimental and theoretical, and show how the computational technology for cosmological phase transition can be used to simulate the dynamics of the A-B transition, support the experimental investigations of the A-B transition in the QUEST-DMC collaboration with the goal of identifying and quantifying the mechanism(s) responsible for nucleation of stable phases in ultra-pure metastable quantum phases.