  We studied the effects of rotation on standing accretion shock instability
(SASI) by performing three-dimensional hydrodynamics simulations. Taking into
account a realistic equation of state and neutrino heating/cooling, we prepared
a spherically symmmetric and steady accretion flow through a standing shock
wave onto a proto-neutron star (PNS). When the SASI entered the nonlinear
phase, we imposed uniform rotation on the flow advecting from the outer
boundary of the iron core, whose specific angular momentum was assumed to agree
with recent stellar evolution models. Using spherical harmonics in space and
Fourier decompositions in time, we performed mode analysis of the nonspherical
deformed shock wave to observe rotational effects on the SASI in the nonlinear
phase. We found that rotation imposed on the axisymmetric SASI did not make any
spiral modes and hardly affected sloshing modes, except for steady l=2, m=0
modes. In contrast, rotation imposed on the non-axisymmetric flow increased the
amplitude of spiral modes so that some spiral flows accreting on the PNS were
more clearly formed inside the shock wave than without rotation. The amplitudes
of spiral modes increased significantly with rotation in the progressive
direction.
