Abstract
We establish that massive complex Abelian vector fields (mass μ) can form gravitating solitons, when minimally coupled to Einstein's gravity. Such Proca stars (PSs) have a stationary, everywhere regular and asymptotically flat geometry. The Proca field, however, possesses a harmonic time dependence (frequency w), realizing Wheeler's concept of geons for an Abelian spin 1 field. We obtain PSs with both a spherically symmetric (static) and an axially symmetric (stationary) line element. The latter form a countable number of families labelled by an integer m∈Z+. PSs, like (scalar) boson stars, carry a conserved Noether charge, and are akin to the latter in many ways. In particular, both types of stars exist for a limited range of frequencies and there is a maximal ADM mass, Mmax, attained for an intermediate frequency. For spherically symmetric PSs (rotating PSs with m=1,2,3), Mmax≃1.058MPl2/μ (Mmax≃1.568,2.337,3.247MPl2/μ), slightly larger values than those for (mini-)boson stars. We establish perturbative stability for a subset of solutions in the spherical case and anticipate a similar conclusion for fundamental modes in the rotating case. The discovery of PSs opens many avenues of research, reconsidering five decades of work on (scalar) boson stars, in particular as possible dark matter candidates.
Highlights
According to the latest cosmological data [1], ∼ 26% of the Universe’s energy content is dark matter (DM)
Despite its success in modeling structure formation, some shortcomings of the weakly interactive massive particles (WIMPs) DM model arise in small scales, such as the “missing satellite” [3,4] and the “cuspy core” [5] problems. These issues may eventually be solved within the WIMP paradigm; but they suggest considering alternative models
An analogous conclusion holds for Proca stars (PSs), as we show by considering their linear radial perturbations
Summary
Richard Brito a,∗, Vitor Cardoso a,b, Carlos A.R. Herdeiro c, Eugen Radu c a CENTRA, Departamento de Física, Instituto Superior Técnico – IST, Universidade de Lisboa – UL, Avenida Rovisco Pais 1, 1049, Lisboa, Portugal b Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2J 2W9, Canada c Departamento de Física da Universidade de Aveiro and CIDMA, Campus de Santiago, 3810-183 Aveiro, Portugal article info. We establish that massive complex Abelian vector fields (mass μ) can form gravitating solitons, when minimally coupled to Einstein’s gravity. Such Proca stars (PSs) have a stationary, everywhere regular and asymptotically flat geometry. We obtain PSs with both a spherically symmetric (static) and an axially symmetric (stationary) line element The latter form a countable number of families labelled by an integer m ∈ Z+. PSs, like (scalar) boson stars, carry a conserved Noether charge, and are akin to the latter in many ways Both types of stars exist for a limited range of frequencies and there is a maximal ADM mass, Mmax, attained for an intermediate frequency. The discovery of PSs opens many avenues of research, reconsidering five decades of work on (scalar) boson stars, in particular as possible dark matter candidates
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