Gravitational Bose-Einstein Condensation of Vector/Hidden Photon Dark Matter

TL;DR

This paper investigates the gravitational Bose-Einstein condensation of massive vector fields, revealing how correlation between components affects condensation time and the potential for solitons to acquire spin.

Contribution

It introduces a numerical study of vector field condensation, comparing results to scalar cases and exploring the effects of component correlation on condensation dynamics.

Findings

Condensation time depends on component correlation.

Fully correlated vector fields condense as quickly as scalars.

Vector solitons can gain net spin angular momentum.

Abstract

We study the gravitational Bose-Einstein condensation of a massive vector field in the kinetic regime and the non-relativistic limit using non-linear dynamical numerical methods. Gravitational condensation leads to the spontaneous formation of solitons. We measure the condensation time and growth rate, and compare to analytical models in analogy to the scalar case. We find that the condensation time of the vector field depends on the correlation between its different components. For fully correlated configurations, the condensation time is the same as that for a scalar field. On the other hand, uncorrelated or partially correlated configurations condense slower than the scalar case. As the vector soliton grows, it can acquire a net spin angular momentum even if the total spin angular momentum of the initial conditions is zero.