# Particle production in an expanding universe?

I was reading this interesting article which talks about particle production in an expanding universe.

Usually this process is proposed to have occurred in the early universe, when the expansion was in the inflationary phase and it was so powerful that matter was created in particle production mechanisms.

However, can particles be produced in an accelerating expanding universe like our current one? Can particles be produced by the universe's expansion with the current conditions of our own one?

• If the rate is absurdly small, is the right answer “yes”? Sep 25 at 3:47
• Matter production is assumed to have happened after inflation, not during it. When inflation ends, the inflaton field starts oscillating, and through these oscillations the matter particles can be produced (energy is transferred from inflaton to matter).
– Kosm
Sep 25 at 13:24

You get an approach to a finite de Sitter temperature $$T=\hbar H/2\pi k_B\approx 2.67\cdot 10^{-30}$$ K in a universe expanding forever due to a cosmological constant, and this does produce a very meagre stream of particles as excitations of the fields. So this is something that likely happens in our universe in the standard $$\Lambda$$CDM cosmology.