Self-gravitating vector dark matter

We derive the nonrelativistic limit of a massive vector field. We show that the Cartesian spatial components of the vector behave as three identical, noninteracting scalar fields. We find classes of spherical, cylindrical, and planar self-gravitating vector solitons in the Newtonian limit. The gravitational properties of the lowest-energy vector solitons-the gravitational potential and density field-depend only on the net mass of the soliton and the vector particle mass. In particular, these self-gravitating, ground-state vector solitons are independent of the distribution of energy across the vector field components and are indistinguishable from their scalar-field counterparts. Fuzzy vector dark matter models can therefore give rise to halo cores with observational properties that are identical to the ones in scalar fuzzy dark matter models. We also provide novel hedgehog vector soliton solutions which cannot be observed in scalar-field theories. The gravitational binding of the lowest-energy hedgehog halo is about 3 times weaker than the ground-state vector soliton. Finally, we show that no spherically symmetric solitons exist with a divergence-free vector field.

Automated summary

This study explores the nonrelativistic limit of a massive vector field, showing that the vector's spatial components behave as identical, noninteracting scalar fields. Various self-gravitating vector solitons in different geometries are found in the Newtonian limit, with gravitational properties depending on mass and particle mass. Ground-state vector solitons exhibit similarities to their scalar counterparts, and novel hedgehog vector soliton solutions are proposed, with weaker gravitational binding compared to the ground-state vector soliton. Additionally, the absence of spherically symmetric solitons with a divergence-free vector field is demonstrated.