Gravity from symmetry breaking phase transition

TL;DR

This paper explores a novel mechanism where gravity emerges from a symmetry-breaking phase transition involving fermionic fields, leading to gauge bosons, Higgs modes, and gravitational waves, inspired by superfluid $^3$He.

Contribution

It proposes a new scenario for gravity emergence through fermionic vacuum symmetry breaking, connecting it to superfluid $^3$He phenomena and predicting gravitational waves.

Findings

Gravity arises from fermionic vacuum symmetry breaking.

6 gauge bosons absorb NG modes and become massive.

Presence of two massless gravitational waves.

Abstract

The paper is devoted to the memory of Dmitry Diakonov. We discuss gravity emerging in the fermionic vacuum as suggested by Diakonov 10 years ago in his paper "Towards lattice-regularized Quantum Gravity". Gravity emerges in the phase transition. The order parameter in this transition is the tetrad field, which appears as the bilinear composite of the fermionic fields. This symmetry breaking gives 6 Nambu-Goldstone modes; 6 gauge bosons in the spin-connection fields, which absorb 6 NG modes and become massive gauge bosons; and 6 Higgs fields. The similar scenario of the symmetry breaking with appearance of the $5+1$ Higgs gravitons takes place in the B-phase of superfluid $^3$He. While in $^3$He-B these Higgs modes are all massive, in the GR these Higgs collective modes give rise to two massless gravitational waves.