General Relativistic Polarized Proca Stars

TL;DR

This paper investigates the stability of polarized Proca stars, massive vector field configurations influenced by general relativity, revealing conditions under which they remain stable or collapse into black holes, with polarization affecting their stability threshold.

Contribution

The study provides the first numerical analysis of the stability of polarized Proca stars in general relativity, comparing linear, circular, and hedgehog-like configurations.

Findings

Stable configurations are achievable for certain initial compactness levels.

Circularly polarized stars can withstand higher compactness before collapsing.

Collapse to black holes occurs at higher compactness for polarized stars than for hedgehog configurations.

Abstract

Massive vector fields can form spatially localized, non-relativistic, stationary field configurations supported by gravitational interactions. The ground state configurations (p-solitons/vector solitons/dark photon stars/polarized Proca stars) have a time-dependent vector field pointing in the same spatial direction throughout the configuration at any instant of time, can carry macroscopic amounts of spin angular momentum, and are spherically symmetric and monotonic in the energy density. In this paper, we include general relativistic effects, and numerically investigate the stability of compact polarized Proca stars (linear and circularly polarized) and compare them to hedgehog-like field configurations (with radially pointing field directions). Starting with approximate field profiles of such stars, we evolve the system numerically using 3+1 dimensional numerical simulations in general relativity. We find that these initial conditions lead to stable configurations. However, at sufficiently large initial compactness, they can collapse to black holes. We find that the initial compactness that leads to black hole formation is higher for circularly polarized stars (which carry macroscopic spin angular momentum), compared to linearly polarized ones, which in turn is higher than that for hedgehog configurations.