Early formation and rapid growth of supermassive black holes

Determine the physical mechanisms that enable supermassive black holes to form at early cosmic times and grow to extremely large masses, consistent with current observational constraints.

Background

In discussing the entropy budget of the observable universe, the authors note that supermassive black holes (SMBHs) dominate the non-horizon entropy. Typical SMBHs have masses around 10^8 solar masses and entropies near 10^93, contributing about 10^105 to the total entropy.

The existence of very massive SMBHs at early times remains puzzling, and understanding their formation and growth is identified as a major open problem in astrophysics.