Nonthermal Supermassive Dark Matter

Can Supermassive Black Holes alter Cold Dark Matter cusps through accretion?

We present some simple models to determine whether or not the accretion of cold dark matter by supermassive black holes is astrophysically important. Contrary to some claims in the literature, we show that supermassive black holes cannot significantly alter a power law density cusp via accretion, whether during mergers or in the steady state.

Supermassive black holes in scalar field galaxy halos

Ultralight scalar fields provide an interesting alternative to WIMPS as halo dark matter. In this paper we consider the effect of embedding a supermassive black hole within such a halo, and estimate the absorption probability and the accretion rate of dark matter onto the black hole. We show that the accretion rate would be small over the lifetime of a typical halo, and hence that supermassive ...

Dark Matter Accretion into Supermassive Black Holes

Upper and Lower Bounds on Gravitational Entropy

The gravitational entropy of the Universe is large and subtle to calculate. A lower bound is well known from supermassive black holes at the centers of galaxies, but the remainder is harder to pin down. A parametric model of clumped matter entropy is provided. We suggest a new upper bound due to dark matter halos, that is far below the holographic bound, yet above that for the supermassive blac...

Formation of Supermassive Black Holes: Simulations in General Relativity

There is compelling evidence that supermassive black holes exist. Yet the origin of these objects, or their seeds, is still unknown. We discuss several plausible scenarios for forming the seeds of supermassive black holes. These include the catastrophic collapse of supermassive stars, the collapse of relativistic clusters of collisionless particles or stars, the gravothermal evolution of dense ...