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Tensor bounds on the hidden universe

Seminar
Monday, 05.11.2018 14:00

Speakers: Subodh Patil (Niels Bohr Institute, Copenhagen, Denmark)
Place: Seminar room n. 226, Institute of Physics, Pod Vodárenskou věží 1, Prague 8
Presented in English
Organisers: Department of Particle Theory and Phenomenology
In this talk, we present an amusing observation that primordial gravitational waves, if ever observed, can be used to bound the hidden field content of the universe. This is because a large number of hidden fields can resum to potentially observable logarithmic runnings for the graviton two-point function in the context of single field inflation, courtesy of a `large N' expansion. This allows one to translate ever more precise bounds on the tensor to scalar consistency relation into bounds on the hidden field content of the universe, with potential implications for phenomenological constructions that address naturalness with a large number of species. Along the way, we'll review how the cutoff for an EFT that includes gravity changes as we incorporate matter, identifying two distinct scales for gravity. We'll also need to address certain subtleties regarding loop corrections on cosmological backgrounds, especially with regards to the correct implementation of dimensional regularization.