Seminarium Kosmologia i Fizyka Cząstek

String axions which are protected by shift symmetries give rise to flat directions in the potential well-suited for inflation. In supergravity, axions arise in combination with saxions as components of complex scalar fields. Successful single-field inflation requires that all saxions (moduli) decouple during the inflationary epoch. When embedded in string theory, this seems to necessitate a very high supersymmetry breaking scale as considered in the models of (F-term) axion monodromy. I will show that high-scale supersymmetry breaking generically induces non-decoupling effects which dominate the inflaton potential in the region of parametric control. This conclusion cannot be evaded through an approximate no-scale cancellation as it appears in the Large Volume Scenario. As a possible alternative to axion monodromy, I will discuss natural inflation. I will show that in natural inflation, the saxions can be decoupled by Hubble mass terms during the inflationary epoch. This implies that supersymmetry can be broken at the low (TeV) scale. The mechanism requires the presence of two axions, where the second axion simultaneously solves the problem of the trans-Planckian decay constant via the alignment mechanism. This talk is based on arXiv:1501.05812 and arXiv:1503.01777.