Collapse threshold for a cosmological Klein Gordon field

Understand

Oscillating scalar fields are useful to model a variety of matter components in the universe.

• One or more scalar fields participate in the reheating process after inflation, while at much lower energies scalar fields are robust dark matter candidates.
• Pertaining structure formation in these models, it is well known that inhomogeneities of the Klein-Gordon field are unstable above the characteristic De Broglie wavelength.
• In this paper we show that such instability implies the existence of a threshold amplitude for the collapse of primordial fluctuations.