Particle decays and stability on the de Sitter universe

Understand

We study particle decay in de Sitter space-time as given by first order perturbation theory in a Lagrangian interacting quantum field theory.

• We study in detail the adiabatic limit of the perturbative amplitude and compute the "phase space" coefficient exactly in the case of two equal particles produced in the disintegration.
• We show that for fields with masses above a critical mass $m_c$ there is no such thing as particle stability, so that decays forbidden in flat space-time do occur here.
• The lifetime of such a particle also turns out to be independent of its velocity when that lifetime is comparable with de Sitter radius.