Speaker
Description
The early appearance of supermassive black holes motivates the question of whether dark matter can contribute to their rapid growth. In this talk, I will present a loss-cone framework for collisionless cold dark matter capture by early black hole seeds. The calculation combines a relativistic capture boundary with orbit-averaged angular-momentum diffusion and a quasi-static treatment of the evolving halo distribution and potential. I will compare stellar relaxation, gravitational scattering by primordial black holes, and phenomenological refilling by triaxial or chaotic centrophilic orbits. Stellar relaxation produces negligible growth in the adopted benchmark, whereas primordial black holes can substantially enhance capture in sufficiently compact halos. Efficient non-spherical refilling can produce rapid early growth, but the available phase-space reservoir is eventually depleted and the black hole mass saturates. Fixed-background calculations therefore overestimate sustained growth, especially in the full-loss-cone limit. By contrast, a TNG50-calibrated NFW profile at redshift (z=20) gives negligible growth even under optimistic refilling assumptions. These results suggest that collisionless dark matter capture is not a generic solution to early supermassive black hole growth, but may provide a significant, non-radiative contribution in rare compact environments with efficient angular-momentum refilling.