Making massive spin-2 particles from gravity during inflation

The phenomenon of cosmological gravitational particle production (CGPP) occurs during and after inflation as light fields “feel” the cosmological expansion and their mode functions evolve non-adiabatically. CGPP is a compelling and minimal explanation for the origin of dark matter, which might only interact gravitationally, as well as other cosmological relics. Various studies have explored CGPP for massive particles with spin up to 3/2, and by doing so, identified interesting and unexpected features such as quantum interference effects and “catastrophic” production of high-momentum modes. In this presentation, I will describe how CGPP arises for massive spin-2 particles in the context of bigravity. I’ll discuss the implications for massive spin-2 particles as a dark matter candidate and related issues including the avoidance of ghost instabilities (FRW-generalized Higuchi bound).