Vector Dark Matter Halo: From Polarization Dynamics to Direct Detection

TL;DR

This paper explores the polarization dynamics of vector dark matter in galaxy halos through simulations, revealing how initial conditions affect halo formation, polarization distribution, and implications for direct detection of dark photons.

Contribution

It introduces a detailed numerical analysis of vector dark matter polarization evolution, linking initial conditions to halo structure and detection prospects, which is a novel approach in dark matter research.

Findings

VDM forms halos and Proca stars from various initial conditions.

Polarization density fluctuations mirror matter density.

Partially polarized states conserve total polarization with core-periphery polarization exchange.

Abstract

This study investigates the characteristic polarization formation and evolution of vector dark matter (VDM) in the outer halo of galaxies. By employing numerical simulations, we analyze the behavior of VDM under different initial conditions -- homogeneous, isotropic, and partially polarized. The simulations solve the Schr\"odinger-Poisson equations, examining the spin density distribution and its evolution during gravitational collapse and halo formation. Our results reveal that VDM forms halos and central Proca stars from homogeneous and isotropic conditions, with the polarization density fluctuation amplitude mirroring VDM matter density. In scenarios with no initial polarization, spin density remains stable in the halo core but fluctuates in outer regions. Partially polarized initial conditions lead to a conservation of total polarization, with increased core polarization resulting in opposite polarization in the periphery. We examine the novel consequences of the partially polarized state for direct detection of dark photons, i.e., VDM kinetically mixed with ordinary photons.