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Abstract :
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.
Biography:
I graduated from the School of Electrical and Computer Engineering in Athens, Greece before moving to MIT for my PhD.
I got my PhD in 2014 with Alan Guth and David Kaiser working on inflation.I was a Fortner postdoctoral fellow at the University of Illinois at Urbana-Champaign (2014-1017) After that, I had a joint postdoctoral position between Nikhef (Amsterdam)
and Leiden University, in the Netherlands. Since September 2020, I am a "La Caixa" Junior Leader Fellow at the Institute for High Energy Physics of Barcelona, where I'm leading my own group.
Zoom：https://zoom.com.cn/j/61122254297
Password： 123456
Video review：https://vshare.sjtu.edu.cn/open/39b383f94711f50293d502e76b69b35d