  We present the first numerical result of fully general relativistic
axisymmetric simulations for the collapse of a rotating high-entropy stellar
core to a black hole and an accretion disk. The simulations are performed
taking into account the relevant microphysics. We adopt as initial condition a
spherical core with constant electron fraction ($Y_e = 0.5$) and entropy per
baryon $s$ = 8 $k_B$, and angular velocity is superimposed. In the early phase,
the core collapses in a homologous manner. Then, it experiences a weak bounce
due to the gas pressure of free nucleons. Because the bounce is weak, the core
collapses eventually to a black hole. Subsequent evolution depends on initial
angular velocity. When the rotation is not fast, a geometrically thin (but
optically thick) accretion disk is formed, and shock waves are formed in the
inner part of the disk. For the moderately rotating case, the thin accretion
disk expands eventually to be a geometrically thick torus after sufficient
accumulation of the thermal energy generated at the shocks. Furthermore,
convection occurs inside the torus. Neutrino luminosities vary violently with
time because of the convective motion. For the rapidly rotating case, by
contrast, a geometrically thick torus is formed soon after the black hole
formation, and convective activity is weak due to the presence of epicyclic
mode.
