Particle creation due to tachyonic instability in relativistic stars

TL;DR

This paper investigates how tachyonic instability in relativistic stars causes exponential vacuum energy growth, leading to particle creation in the final state, independent of the rate of spacetime change.

Contribution

It demonstrates that tachyonic instability results in particle creation even in the adiabatic limit, a novel insight into quantum effects in dense astrophysical objects.

Findings

Vacuum energy density grows exponentially during instability

Particle creation occurs even with slow spacetime changes

Final particle amount depends on instability duration

Abstract

Dense enough compact objects were recently shown to lead to an exponentially fast increase of the vacuum energy density for some free scalar fields properly coupled to the spacetime curvature as a consequence of a tachyonic-like instability. Once the effect is triggered, the star energy density would be overwhelmed by the vacuum energy density in a few milliseconds. This demands that eventually geometry and field evolve to a new configuration to bring the vacuum back to a stationary regime. Here, we show that the vacuum fluctuations built up during the unstable epoch lead to particle creation in the final stationary state when the tachyonic instability ceases. The amount of created particles depends mostly on the duration of the unstable epoch and final stationary configuration, which are open issues at this point. We emphasize that the particle creation coming from the tachyonic instability will occur even in the adiabatic limit, where the spacetime geometry changes arbitrarily slowly, and therefore is quite distinct from the usual particle creation due to the change in the background geometry.