Thermodynamics of nuclear condensates and phase transitions in white dwarfs

TL;DR

This paper investigates the phase transitions of helium in white dwarf stars, revealing a sequence of superconducting and normal states, with implications for the star's ground state and thermodynamic behavior.

Contribution

It provides a detailed analysis of helium thermodynamics in white dwarfs, identifying phase transitions and their relation to stellar states, using a specific approximation for electron screening.

Findings

First order transition between two superconducting phases

Second order transition to the normal state

Crystalline state remains the ground state at relevant densities

Abstract

We study the thermodynamics of helium at densities relevant for white dwarf physics. We find evidence that, as the temperature is increased, there is first a first order transition between two superconducting phases followed by a second order transition to the normal state. These transitions occur, for realistic densities, at temperatures below the crystallization temperature and the crystalline state is likely to remain as the true ground state of the system. The calculations are performed with a screening but non-dynamical electron background and we comment on the impact of this and other approximations to our result.