  We numerically study the origin of the multi-armed spiral structure observed
in the circumnuclear gaseous mini-disks of nearby galaxies. We show that the
presence of dust in such disks and its interaction with the gravitationally
stable gaseous component leads to the development of a multi-armed spiral
structure. As a particular example, we study the formation of the multi-armed
spiral pattern in the mini-disk of the galaxy NGC 4736, for which the
observational data for the rotation and the density distribution are available.
We find that the multi-armed spiral structure grows in the stable gaseous
mini-disk of NGC 4736 if the gas-to-dust ratio is about 5-20 percent. We also
demonstrate that together with the dust concentration, the important factor for
the development of instability is the size of the dust grains. A nonlinear
multi-armed spiral pattern develops in the stable gaseous disk with sizes of
grains larger than one micron. If future observations confirm the presence of a
large amount of dust in the mini-disks of galaxies, this will pinpoint the
mechanism of the formation of the multi-armed spiral structure in them.
