Higgs-dilaton cosmology: From the early to the late Universe

Abstract

We consider a minimal scale-invariant extension of the standard model of particle physics combined with unimodular gravity formulated in. This theory is able to describe not only an inflationary stage, related to the standard model Higgs field, but also a late period of dark-energy domination, associated with an almost massless dilaton. A number of parameters can be fixed by inflationary physics, allowing us to make specific predictions for any subsequent period. In particular, we derive a relation between the tilt of the primordial spectrum of scalar fluctuations, n s, and the present value of the equation of state parameter of dark energy (DE), wDE0. We find bounds for the scalar tilt, n s<0.97, the associated running, -0.0006 <0.0033, which will be critically tested by the results of the Planck mission. For the equation of state of dark energy, the model predicts wDE0>-1. The relation between n s and wDE0 allows us to use the current observational bounds on n s to further constrain the dark-energy equation of state to 0<1+wDE0<0.02, which is to be confronted with future dark-energy surveys. © 2011 American Physical Society.