Speaker
Description
In this talk, I introduce a novel relationship between cosmological correlators and flat space Feynman diagrams in momentum space. Focusing on Witten diagrams in de Sitter space with heavy internal lines and light external legs, I introduce the Massive Flat Space (MFS) limit. In this limit, (i) the external energies entering the bulk-to-boundary propagators are sent to zero, (ii) the mass of the internal heavy lines is sent to infinity, while (iii) the product of the external energies and the mass remains fixed. Under these conditions, I derive a master equation that expresses the (off-shell) n-point correlator in the MFS limit as a contact diagram in de Sitter space, with a vertex factor corresponding to the amputated n-point graph in flat space. As a non-trivial application of this master equation, I provide analytical solutions to the one-loop bubble diagrams that contribute to inflationary correlators, in scenarios where the inflaton perturbations exhibit a reduced speed of sound.
