  Black-hole accretion systems are known to possess several distinct modes (or
spectral states), such as low/hard state, high/soft state, and so on. Since the
dynamics of the corresponding flows is distinct, theoretical models were
separately discussed for each state. We here propose a unified model based on
our new, global, two-dimensional radiation-magnetohydrodynamic simulations. By
controlling a density normalization we could for the first time reproduce three
distinct modes of accretion flow and outflow with one numerical code. When the
density is large (model A), a geometrically thick, very luminous disk forms, in
which photon trapping takes place. When the density is moderate (model B), the
accreting gas can effectively cool by emitting radiation, thus generating a
thin disk, i.e., the soft-state disk. When the density is too low for radiative
cooling to be important (model C), a disk becomes hot, thick, and faint; i.e.,
the hard-state disk. The magnetic energy is amplified within the disk up to
about twice, 30%, and 20% of the gas energy in models A, B, and C,
respectively. Notably, the disk outflows with helical magnetic fields, which
are driven either by radiation pressure force or magnetic pressure force, are
ubiquitous in any accretion modes. Finally, our simulations are consistent with
the phenomenological alpha-viscosity prescription, that is, the disk viscosity
is proportional to the pressure.
