The projective general unitary group is the quotient group
of the general unitary group
by its group center.
The group center consists of the scalar
matrices
for which
, where
is the
identity matrix.
Therefore,
For a finite group ,
denotes its group order.
In particular,
The quotient group has a faithful group action on the subset of projective space
represented by nonzero vectors satisfying
, where
is the preserved Hermitian form.
The projective image of the special
unitary group is the projective
special unitary group, which is a normal subgroup
of
.