Quantum infra-red effects in de Sitter space (through Skype)

Quantum field theory in de Sitter space is necessary to investigate
physics in the past and present exponentially expanding universes from
a microscopic view point. In particular, we focus on the quantum
effects at the super-horizon scale. It is because there is a dS
symmetry breaking mechanism and physical quantities may acquire time
dependence as quantum effects.

Gravitational field is an attractive candidate which induces such
infra-red effects. I talk mainly about our recent works of soft
graviton effects on the local dynamics of matter fields at the
sub-horizon scale. We show that soft gravitational effects do not
spoil Lorentz invariance in scalar, Dirac and gauge field theories. In
the interacting field theory with quartic, Yukawa and gauge
interactions, we find that the effective couplings are time dependent
and the evolutions are physical as their relative scaling exponents
are gauge invariant.