Black hole formation via gas-dynamical processes
  Understanding the formation of earliest supermassive black holes is a
question of prime astrophysical interest. In this chapter, we focus on the
formation of massive black holes via gas dynamical processes. The necessary
requirement for this mechanism are large inflow rates of about 0.1 solar mass
per year. We discuss how to obtain such inflow rates via an isothermal collapse
in the presence of atomic hydrogen cooling, and the outcome of such a collapse
from three dimensional cosmological simulations in subsection 2.2. Alternatives
to an isothermal direct collapse are discussed in subsection 3 which include
trace amounts of metals and/or molecular hydrogen. In the end, we briefly
discuss future perspectives and potential detection of massive black hole seeds
via upcoming missions.
