Regular Fuzzy Dark Matter Black Holes and Their Horizon Structure

Abstract

We construct regular, horizon-admitting compact objects supported entirely by a self-gravitating dark-matter fluid, in the one-parameter curvature-gravity family $f(R)=R+βR^n$. Working with the Einasto density profile, we derive the anisotropic fluid field equations for a static, spherically symmetric metric and obtain the exact General Relativity limit under a de~Sitter-type equation of state, in which the central singularity is replaced by a regular de~Sitter core and the solution is either a horizonless droplet or a black hole with one or two Killing horizons, depending on a single rescaled-mass parameter. We compute the resulting Hawking temperature and geodesic effective potential, and -- exploiting the linearity of the $β=0$ field equation -- solve the curvature correction perturbatively in closed form for general $n$, showing that its sign and radial shape are genuinely model-dependent by direct comparison at fixed $β$ between $n=2$ (Starobinsky) and $n=3$ (cubic) gravity. We repeat the construction for a non-local equation of state and confirm the resulting droplets are curvature-regular via the Kretschmann scalar. Finally, replacing the Einasto profile with the cored Burkert profile preserves the qualitative regularity mechanism but, because the Burkert halo lacks a finite total mass, produces a horizon structure with inner and outer radii separated by nearly three orders of magnitude -- a genuine physical distinction between two comparably realistic dark-matter models.