Abstract
The D6-brane spectrum of type IIA vacua based on twisted
tori 
6 and RR background fluxes is analyzed. In
particular, we compute the torsion factors of Hn(6,
) and describe the effect that they have on D6-brane
physics. For instance, the fact that H3(6,) contains N subgroups explains why RR tadpole
conditions are affected by geometric fluxes. In addition, the presence
of torsional (co)homology shows why some D6-brane moduli are lifted,
and it suggests how the D-brane discretum appears in type IIA flux
compactifications. Finally, we give a clear, geometrical understanding
of the Freed-Witten anomaly in the present type IIA setup, and discuss
its consequences for the construction of semi-realistic flux vacua.
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