Cosmology seminar: Kei Yamamoto: Inflation with a Gauge-kinetic Coupling and Multiple Vector Fields

Models of inflation where the scalar inflaton is coupled to a gauge field
have attracted attention recently due to their potential observational
consequences including statistical anisotropy, gravitational waves and
non-Gaussianity. I will talk about its extension to multiple vector degrees
of freedom. It is shown that the anisotropic single field configuration is
generically unstable and the gauge fields dynamically distribute themselves
so as to minimize the anisotropy in the attractor state. In the special
case of completely isotropic inflation with a non-vanishing triad of
background gauge fields, two-point correlation functions for scalar
curvature and gravitational wave are computed. The gauge fields give rise
to a slight red tilt in the spectra and tend to suppress the
tensor-to-scalar ratio.