  We count the BPS states of strings in uniform 3-form fluxes, using
supersymmetric quantum mechanics derived from the kappa-symmetric action for
D-branes. This problem is relevant to the stringy physics of warped
compactifications. We work on a type IIB T^6/Z_2 orientifold with imaginary
self-dual, quantized, 3-form flux. Ignoring the orientifold projection, the
number of short multiplets living on a single string is the square of the units
of 3-form flux present on the torus; the orientifold removes roughly half of
the multiplets. We review the well-known case of a superparticle on T^2 as an
pedagogical example.
