Theory HEP Seminar

Cutting rule for in-in correlators and cosmological collider

Yohei Ema

CERN

Cosmological correlators, observed through the structures of the universe, contain rich information on the physics of the early universe. However, in general, the calculation of the cosmological correlators is quite involved due to the loss of the time translation invariance. In this talk, I derive a cutting rule for equal-time in-in correlators, including cosmological correlators, which decomposes diagrams into fully retarded functions and cut-propagators consisting of Wightman functions. Our derivation relies only on basic assumptions such as unitarity and, therefore, holds for theories with arbitrary particle contents and local interactions at any loop order. As an application, we show that non-local cosmological collider signals, particle production signals in the correlators, arise solely from cut-propagators under the assumption of microcausality. The cut factorizes the conformal time integrals, simplifying practical calculations.