  We construct an effective gauge field theory model describing a 2D quantum
antiferromagnet in the flux phase ground state. Due to period doubling the
number of gauge fields is four rather than the naively expected single one.
These additional gauge fields correspond to field configurations in which the
flux is staggered, which should be taken into account to enforce single
occupancy within the magnetic unit cell. We calculate a new type of quantum
anomaly, present in such a model. In particular this leads to a generalized
local flux hypothesis, which is tested numerically.
