Gravitational waves from non-abelian gauge fields during inflation

Wednesday 18 May 2022, 4:00pm to 5:00pm


Online (MS Teams)

Open to

Alumni, Postgraduates, Public, Staff, Undergraduates


Registration not required - just turn up

Event Details

Cosmology seminar

I will introduce a class of inflationary models, where inflation is driven exclusively or in part by non-abelian gauge fields. I will describe how the spectrum of density fluctuations and gravitational waves is computed, and show that these models can produce observationally viable spectra, if the gauge symmetry is spontaneously broken by a Higgs sector. The background gauge field texture violates parity, resulting in a chiral gravitational wave spectrum. This arises due to an exponential enhancement of one polarization of the spin-2 fluctuation of the gauge field. Higgsed Chromo-Natural Inflation and related models can produce observable gravitational waves at inflationary energy scales well below the GUT scale.

If the axion and gauge fields constitute a spectator sector, they will not be responsible for the scalar perturbations but can nevertheless produce detectable gravitational waves. In this case, I will show how different classes of potentials arising in various string theory constructions lead to distinct GW templates. In the case of a modulated (axion monodromy) potential, the GW signal acquires characteristic oscillations which can be in principle probed by future observations of CMB B-modes, e.g. with LiteBIRD. This opens a unique window into “hearing” the shape of String-related axion potentials. Finally, I will show a connection with inflationary leptogenesis.


Evangelos Sfakianakis (Instituto de Física de Altas Energías, Barcelona)

Contact Details

Name Samuel Sanchez Lopez