Cosmological Phonon Collider

The expansion of the universe spontaneously breaks time translation by selecting a preferred reference frame. As a consequence, very much like a superfluid at zero temperature, the low-energy description of single field inflation can be organised in terms of the associated Goldstone mode of the broken symmetry (aka the phonon). Similar to particle colliders, if we were to scatter sound waves, the presence of additional heavy fields coupled to the medium would manifest as distinct peaks in the cross-section of the phonons. In this talk, I introduce a cosmological version of this idea, in which the imprints of additional heavy particles during inflation are encoded in the late time boundary correlators of the Goldstone boson. I discuss various phenomenological consequences of this setup for the primordial bispectrum and trispectrum.