2023/09/13 by Scott Melville, Melville, Scott, Guilherme L. Pimentel +1 · 2 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2309.07092
We define an S-matrix for massive scalar fields on a fixed de Sitter spacetime, in the expanding patch co-ordinates relevant for early Universe cosmology. It enjoys many of the same properties as its Minkowski counterpart, for instance: it is insensitive to total derivatives and field redefinitions in the action; it can be extracted as a particular "on-shell" limit of time-ordered correlation functions; and for low-point scattering, kinematics strongly constrains its possible structures. We present explicit formulae relating the usual observables - in-in equal-time correlators and wavefunction coefficients at the conformal boundary - to S-matrix elements. Finally, we discuss some of the subtleties in extending this S-matrix to light fields (in the complementary series).