Dynamics of the quantum vacuum: Cosmology as relaxation to the equilibrium state

Abstract

The behavior of the gravitating vacuum energy density in an expanding universe is discussed. A scenario is presented with a step-wise relaxation of the vacuum energy density. The vacuum energy density moves from plateau to plateau and follows, on average, the steadily decreasing matter energy density. The current plateau with a small positive value of the vacuum energy density (effective cosmological constant) may result from a still not equilibrated contribution of the light massive neutrinos to the quantum vacuum.

Reconsidering a higher-spin-field solution to the main cosmological constant problem

“…(5.16) of Ref. [7] (and reiterated in the review [10]), the present value of this quantity ½Ã þðt now Þ would be of the order of the experimental value à ðexpÞ $ ðmeVÞ 4 .…”

“…1 Very briefly, q-theory aims to give the proper macroscopic description of the Lorentz-invariant quantum vacuum where a (Planck-scale) cosmological constant à has been canceled dynamically by appropriate microscopic degrees of freedom (see the original article [6] for further details and also the brief review [10]). Typically, there are one or more of these Lorentz-invariant vacuum variables (denoted by q, with or without additional suffixes) to characterize the thermodynamics of this static physical system in equilibrium.…”

“…Inspiration for this model was obtained from previous work by Volovik and one of the present authors on the so-called q-theory approach [6][7][8][9] to the main cosmological constant problem (a one-page review of q-theory can be found in Appendix A of Ref. [10] and a ultrabrief summary will be given in the Footnote of Sec. II A).…”

Vacuum Energy Decay from a q-Bubble

“…A in Ref. [10]), the dynamical process of equilibration of the vacuum towards the full equilibrium is still under investigation. The previously obtained results [6] concern the decay of an initially homogeneous high-energy state emerging immediately after the Big Bang.…”

Cosmological bootstrap

“…In other approach, the cosmological constant relaxes by gradually passing different regions of its potential, i.e. by moving from a plateau to plateau [32].…”