Ultra-compact Objects of Non-minimally Coupled Dark Matter

TL;DR

This paper explores the theoretical existence of ultra-compact, horizonless dark matter objects resulting from non-minimal coupling to gravity, analyzing their properties, particle orbits, and gravitational lensing effects.

Contribution

It demonstrates that non-minimal coupling can produce stable, regular dark matter objects with unique gravitational features, expanding the understanding of possible compact dark matter configurations.

Findings

Non-minimal coupling induces anisotropic pressure supporting ultra-compact objects.

Orbits of particles around these objects are characterized and analyzed.

Gravitational lensing creates a pseudo-shadow effect around the objects.

Abstract

In the framework of a collisionless dark matter fluid which is non-minimally coupled to gravity, we investigate the existence and properties of static, spherically symmetric solutions of the general relativistic field equations. We show that the non-minimal coupling originates an (anisotropic) pressure able to counteract gravity and to allow the formation of regular, horizonless ultra-compact objects of dark matter (NMC-UCOs). We then analyze the orbits of massive and massless particles in the gravitational field of NMC-UCOs, providing some specific example and a general discussion in terms of phase portraits. Finally, we study the gravitational lensing effects around NMC-UCOs, and effectively describe these in terms of a pseudo-shadow.