Talks

Experiments and observations over the last decade and a half have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.

I will discuss the appeal of pseudo-Goldstone bosons (pGBs) for the generation of scales in Early Universe cosmology. In particular, I will demonstrate how in Goldstone Inflation a pGB inflaton can solve the hierarchy problem of inflation (the tension between the Lyth bound and the inflationary scale as preferred by CMB anisotropies), while avoiding the problems with trans-Planckian scales that are typically associated with related models. A simple model based on the coset SU(4)/Sp(4) realises both the Higgs doublet and an inflaton singlet as Goldstone modes. A single setup can then give rise to Goldstone Inflation and the dynamical generation of the electroweak scale through a composite Higgs, thus also addressing the EW hierarchy problem. I will discuss perturbative reheating in this model, and show how it naturally connects to both EW physics and a UV completion. If time permits I will address our current studies on non-perturbative reheating and the possibility of electroweak baryogenesis in this setup. 

I describe an inflation model that can generate a cosmological magnetic seed field of nG strength on Mpc length scales today that could explain observed few microG large-scale galactic magnetic fields. I also summarize some of the extensions of this model that have been developed over the last two decades, as well as open questions about such models.