Cold Dark Matter Based on an Analogy with Superconductivity

TL;DR

This paper proposes a new cold dark matter candidate based on fermion condensates analogous to superconductivity, with distinctive thermal history and potential observable signatures in cosmic microwave background and large scale structure.

Contribution

It introduces a novel dark matter model involving fermion pairs undergoing a phase transition, linking condensed matter physics with cosmological dark matter theories.

Findings

Fermions behave like radiation at high temperatures and decouple via a critical phase transition.

The condensate decays slightly faster than standard dark matter predictions, offering testable observational signatures.

Frustrated phase transition in massive fermions leaves a residual dark energy component.

Abstract

We present a novel candidate for cold dark matter consisting of condensed Cooper pairs in a theory of interacting fermions with broken chiral symmetry. Establishing the thermal history from the early radiation era to the present, the fermions are shown to behave like standard radiation at high temperatures, but then experience a critical era decaying faster than radiation, akin to freeze-out, which sets the relic abundance. Through a second-order phase transition, fermion-antifermion pairs condense and the system asymptotes toward zero temperature and pressure. By the present era, the nonrelativistic, massive condensate decays slightly faster than in the standard scenario--a unique prediction that may be tested by combined measurements of the cosmic microwave background and large scale structure. We also show that in the case of massive fermions, the phase transition is frustrated, and instead leaves a residual, long-lived source of dark energy.