Decay of Vacuum Energy

TL;DR

The paper investigates how interacting massive fields on a fixed de Sitter background can render the vacuum an inverse-population medium that supports stimulated radiation, potentially driving explosive particle production. It compares propagator choices (Bunch-Davies vs in/out vs in/in) and spacetime manifolds (hyperboloid vs centaur) to reveal how instability and barrier-crossing effects arise, including an obstructions to Wick rotation and dimension-dependent imaginary parts of the effective action. By deriving a kinetic equation for mode occupations and highlighting infrared divergences, it shows a possible finite-time blow-up in particle numbers, signaling strong back reaction and the need for a dynamical treatment of curvature. Collectively, the work motivates the concept of a cosmic-laser mechanism that could deplete curvature and address the cosmological constant problem while outlining the major theoretical challenges in fully incorporating back reaction and nonperturbative effects.

Abstract

This paper studies interacting massive particles on the de Sitter background. It is found that the vacuum acts as an inversely populated medium which is able to generate stimulated radiation. Without back reaction (not considered in this paper) this effect leads to the explosion. It is expected that the proposed "cosmic laser" mechanism depletes the curvature and may help to solve the cosmological constant problem.