  The formation of protostellar disks is still a mystery, largely due to the
difficulties in observations that can constrain theories. For example, the 3D
alignment between the rotation of the disk and the magnetic fields (B-fields)
in the formation environment is critical in some models, but so far impossible
to observe. Here, we study the possibility of probing the alignment between
B-field and disk rotation using ``polarization holes'' (PHs). PHs are widely
observed and are caused by unresolved B-field structures. With ideal
magnetohydrodynamic (MHD) simulations, we demonstrate that different initial
alignments between B-field and angular momentum (AM) can result in B-field
structures that are distinct enough to produce distinguishable PHs. Thus PHs
can potentially serve as probes for alignments between B-field and AM in disk
formation.
