Cosmological Bardeen-Cooper-Schrieffer condensate as dark energy

Abstract

We argue that the occurrence of late-time acceleration can conveniently be described by first-order general relativity covariantly coupled to fermions. Dark energy arises as a Bardeen-Cooper-Schrieffer condensate of fermions which forms in the early universe. At late times, the gap and chemical potential evolve to have an equation of state with effective negative pressure, thus naturally leading to acceleration.

17 pages, 3 figures. v2: discussion improved, figure and references added, results unchanged; v3: typo and figure corrections of the erratum included