Spontaneous symmetry breaking in Loop Quantum Gravity

TL;DR

This paper explores how spontaneous symmetry breaking can be modeled within Loop Quantum Gravity, comparing it to the Proca field case, and introduces a new scalar field representation that simplifies constraint solving.

Contribution

It demonstrates a novel approach to incorporating spontaneous symmetry breaking in Loop Quantum Gravity using a new scalar field representation that simplifies the constraint equations.

Findings

Hamiltonians are similar with an extra scalar field in symmetry breaking

The scalar field operator is self-adjoint with a continuous spectrum

New representation enables explicit solutions to some constraints

Abstract

In this paper we investigate the question how spontaneous symmetry breaking works in the framework of Loop Quantum Gravity and we compare it to the results obtained in the case of the Proca field, where we were able to quantise the theory in Loop Quantum Gravity without introducing a Higgs field. We obtained that the Hamiltonian of the two systems are very similar, the only difference is an extra scalar field in the case of spontaneous symmetry breaking. This field can be identified as the field that carries the mass of the vector field. In the quantum regime this becomes a well defined operator, which turns out to be a self adjoint operator with continuous spectrum. To calculate the spectrum we used a new representation in the case of the scalar fields, which in addition enabled us to rewrite the constraint equations to a finite system of linear partial differential equations. This made it possible to solve part of the constraints explicitly.