Cold Dark Matter Based on an Analogy with Superconductivity

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.