Soft Gravitons Screen Couplings in de Sitter Space

Who: Hiroyuki Kitamoto (KEK)
When: Monday, August 27, 2012 at 14:15
Where: U49D

The scale invariance of the quantum fluctuations in de Sitter space leads to the appearance of de Sitter symmetry breaking infra-red logarithms in the graviton propagator. We investigate how virtual gravitons of the super-horizon scale affect the local dynamics of matter fields at sub-horizon scale. We show that the IR logarithms do not spoil Lorentz invariance in scalar, Dirac and gauge field theories. The leading IR logarithms can be absorbed by time dependent wave function renormalization factors. In the interacting field theory with λϕ4, Yukawa and gauge interactions, we find that the couplings become time dependent with definite scaling exponents. We argue that the relative scaling exponents of the couplings are gauge invariant and physical as we can use the evolution of a coupling as a physical time.

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