Speaker
Description
We develop a fully relativistic formulation for the evolution of a dark
sector containing fermions coupled to a light scalar field in an arbitrary cosmological background characterised by equation of state parameter w. Treating the fermions as a degenerate Fermi gas decoupled from the background cosmic fluid, and assuming a Yukawa-type coupling with the scalar we show that the scalar dynamics select branches that minimise the effective fermion mass. We identify two broad regimes: a scaling regime, in which the scalar oscillates around a value which minimises fermions effective mass, and the coupled sector redshifts approximately as radiation, and an asymptotic regime, in which the field evolves towards configurations where the fermions recover their bare mass.