Cosmological Bootstrap in Slow Motion

Abstract: Inflation can be viewed as a natural particle collider through which we can learn about physics at very short distances. In this talk, I study the physics of the cosmological phonon collider: I uncover the imprints of heavy particles during inflation on the correlators of the Goldstone boson of the broken time diffeomorphism during inflation. I show that the reduced speed of sound for the Goldstone allows new types of footprints of heavy fields to emerge. In particular, I will demonstrate that the exchange of supersonic, massive fields that are still lighter than Hubble divided by the speed of sound induces characteristic resonances in the soft limit of the bispectrum. This signal is vividly distinct from the standard squeezed limit oscillations associated with particle creation in de Sitter. Throughout, I use and extend the cosmological bootstrap techniques derived from locality, unitarity, and analyticity in order to analytically compute the desired exchange diagrams.