A cosmological constant from degenerate vacua

TL;DR

This paper proposes that the small positive cosmological constant can be explained by a theory with multiple degenerate vacua that are quantum mechanically unstable, with our universe residing in one such metastable state.

Contribution

It introduces a novel explanation for the cosmological constant based on degenerate vacua and quantum tunneling, supported by an example involving topological vacua in gauge theories.

Findings

The small vacuum energy density can result from metastable degenerate vacua.

Quantum tunneling between vacua can account for the observed cosmological constant.

The framework connects topological features in gauge theories to cosmological observations.

Abstract

Under the hypothesis that the cosmological constant vanishes in the true ground state with lowest possible energy density, we argue that the observed small but finite vacuum-like energy density can be explained if we consider a theory with two or more degenerate perturbative vacua, which are unstable due to quantum tunneling, and if we still live in one of such states. An example is given making use of the topological vacua in non-Abelian gauge theories.