Connecting inflation to cosmological magnetic fields and neutrino masses
Nordita Astrophysics seminars
Thursday 11 October 2018
to 17:30 at
122:026, Nordita West
Evangelos I. Sfakianakis (Nikhef, Amsterdam & Leiden University)
Axions are attractive candidates for theories of large-field inflation that are capable of generating observable primordial gravitational wave backgrounds. These fields enjoy shift-symmetries that protect their role as inflatons from being spoiled by coupling to unknown UV physics. This symmetry also restricts the couplings of these axion fields to other matter fields. At lowest order, the only allowed interactions are derivative couplings to gauge fields and fermions. These derivative couplings lead to the biased production of fermion and gauge-boson helicity states during and after inflation. I will discuss preheating in natural inflation models that are derivatively coupled to Abelian gauge-fields.
For an axion coupled to U(1) gauge fields preheating is efficient for a wide range of parameters. In certain cases the inflaton is seen to transfer all its energy to the gauge fields within a few oscillations. Identifying the gauge field as the hypercharge sector of the Standard Model can lead to the generation of cosmologically relevant magnetic fields. Interestingly gauge boson production can also seed leptogenesis. The details depend on the properties of neutrinos, providing correlated observables connecting inflationary dynamics to BSM physics.