Particle-like solutions in the generalized SU(2) Proca theory

TL;DR

This paper explores particle-like solutions in a modified gravity theory with SU(2) symmetry, revealing new features like negative energy regions and potential stability, extending the concept of gauge boson stars.

Contribution

It is the first study of astrophysical properties of the generalized SU(2) Proca theory, identifying new solutions and stability features not present in Einstein-Yang-Mills theory.

Findings

Discovered solutions with negative effective energy density.

Found globally charged solutions in certain parameter regions.

Indicated potential for stable solutions absent in Einstein-Yang-Mills theory.

Abstract

The generalized SU(2) Proca theory is a vector-tensor modified gravity theory where the action is invariant under both diffeomorphisms and global internal transformations of the SU(2) group. This work constitutes the first approach to investigate the physical properties of the theory at astrophysical scales. We have found solutions that naturally generalize the particle-like solutions of the Einstein-Yang-Mills equations, also known as gauge boson stars. Under the requirement that the solutions must be static, asymptotically flat, and globally regular, the t'Hooft-Polyakov magnetic monopole configuration for the vector field rises as one viable possibility. The solutions have been obtained analytically through asymptotic expansions and numerically by solving the boundary value problem. We have found new features in the solutions such as regions with negative effective energy density and imaginary effective charge. We have also obtained a new kind of globally charged solutions for some region in the parameter space of the theory. Furthermore, we have constructed equilibrium sequences and found turning points in some cases. These results hint towards the existence of stable solutions which are absent in the Einstein-Yang-Mills case.