  We present high-contrast H-band polarized intensity (PI) images of the
transitional disk around the young solar-like star GM Aur. The near-infrared
direct imaging of the disk was derived by polarimetric differential imaging
using the Subaru 8.2-m Telescope and HiCIAO. An angular resolution and an inner
working angle of 0."07 and r~0."05, respectively, were obtained. We clearly
resolved a large inner cavity, with a measured radius of 18+/-2 au, which is
smaller than that of a submillimeter interferometric image (28 au). This
discrepancy in the cavity radii at near-infrared and submillimeter wavelengths
may be caused by a 3-4M_Jup planet about 20 au away from the star, near the
edge of the cavity. The presence of a near-infrared inner is a strong
constraint on hypotheses for inner cavity formation in a transitional disk. A
dust filtration mechanism has been proposed to explain the large cavity in the
submillimeter image, but our results suggest that this mechanism must be
combined with an additional process. We found that the PI slope of the outer
disk is significantly different from the intensity slope obtained from
HST/NICMOS, and this difference may indicate the grain growth process in the
disk.
