Gravity-Induced Vacuum Dominance

Abstract

It has been widely believed that, except in very extreme situations, the influence of gravity on quantum fields should amount to just small, subdominant contributions. This view seemed to be endorsed by the seminal results obtained over the last decades in the context of renormalization of quantum fields in curved spacetimes. Here, however, we argue that this belief is false by showing that there exist well-behaved spacetime evolutions where the vacuum energy density of free quantum fields is forced, by the very same background spacetime, to become dominant over any classical energy-density component. By estimating the time scale for the vacuum energy density to become dominant, and therefore for backreaction on the background spacetime to become important, we argue that this (infrared) vacuum dominance may bear unexpected astrophysical and cosmological implications.

Quantization of unstable linear scalar fields in static spacetimes

“…(41) -see Appendix A. Even tough restrictive, these conditions can be satisfied at least for massive scalar particles in Minkowski spacetime subject to scalar potential wells [8] and for non-minimally coupled scalar fields in static spacetimes curved by classical matter [1]. The former example resembles the SSW instability, while the latter has a realization in the spacetime of compact objects [2].…”

“…Here we are particularly concerned with the tachyonic-like instability analyzed in Ref. [1]. There it was argued that it is possible for a neutral, non-minimally coupled scalar field to become unstable when subject to gravitational fields generated by realistic classical-matter distributions.…”

Quantum versus classical instability of scalar fields in curved backgrounds

“…See Refs. [1][2][3][4] for a complete discussion on the "vacuum awakening effect" (and Ref. [11] for a rigorous discussion on the quantization of unstable linear fields in globally static spacetimes).…”

“…References [1][2][3][4] analyzed the case of a quantum fieldΦ, which satisfies Eq. (1), being stable on ðR 4 ; η ab Þ but unstable on ðR 4 ; g ab Þ.…”

“…It was shown that certain well-behaved spacetimes can induce an exponential growth of the vacuum energy density of some nonminimally coupled free scalar fields [1]. Particular astrophysically inspired realizations of this mechanism were explored in Refs.…”