Using Two Measures Theory to Approach Bags and Confinement

TL;DR

This paper explores a two-measure theory incorporating a dilaton field to model bags and confinement, demonstrating how scale invariance breaking leads to different vacuum phases with normal and confining gauge dynamics.

Contribution

It introduces a novel two-measure framework with scale invariance and spontaneous symmetry breaking to differentiate inside and outside bag regions.

Findings

Inside bags, gauge dynamics is non-confining.

Outside bags, gauge dynamics is confining.

The model exhibits phases with different vacuum energy densities.

Abstract

We consider the question of bags and confinement in the framework of a theory which uses two volume elements $\sqrt{-{g}}d^{4}x$ and $\Phi d^{4}x$, where $\Phi $ is a metric independent density. For scale invariance a dilaton field $\phi$ is considered. Using the first order formalism, curvature ($\Phi R$ and $\sqrt{-g}R^{2}$) terms, gauge field term($\Phi\sqrt {- F_{\mu \nu}^{a}\, F^{a}_{\alpha\beta}g^{\mu\alpha}g^{\nu\beta}}$ and $\sqrt{-g} F_{\mu \nu}^{a}\, F^{a}_{\alpha\beta}g^{\mu\alpha}g^{\nu\beta}$) and dilaton kinetic terms are introduced in a conformally invariant way. Exponential potentials for the dilaton break down (softly) the conformal invariance down to global scale invariance, which also suffers s.s.b. after integrating the equations of motion. The model has a well defined flat space limit. As a result of the s.s.b. of scale invariance phases with different vacuum energy density appear. Inside the bags the gauge dynamics is normal, that is non confining, while for the outside, the gauge field dynamics is confining.