Cosmology

Cosmology and particle physics are deeply interrelated. Among the common problems are dark energy, dark matter and baryon asymmetry of the Universe. We discuss these problems in general terms, and concentrate on several particular hypotheses. On the dark matter side, we consider weakly interacting massive particles and axions/axion-like particles as cold dark matter, sterile neutrinos and gravitinos as warm dark matter. On the baryon asymmetry side, we discuss electroweak baryogenesis as a still-viable mechanism. We briefly describe diverse experimental and observational approaches towards checking these hypotheses. We then turn to the earliest cosmology. We give arguments showing that the hot stage was preceded by another epoch at which density perturbations and possibly primordial gravity waves were generated. The best guess here is inflation, which is consistent with everything we know of density perturbations, but there are alternative scenarios. Future measurements of the properties of density perturbations and possible discovery of primordial gravity waves have strong potential in this regard.