RR Electric Magnetic Dirac Pairing Convention

For a mutually electric/magnetic RR pair associated with a Dp and D$(6-p)$, $0\le p\le 6$, $p\mathrm{\ne }3$, write the independent field-strength kinetic term as $-\frac{{\alpha }_p}{2}\int F_{p+2}\wedge \ast F_{p+2}$, where ${\alpha }_p>0$ is its kinetic normalization. The adopted massless Type IIA and Type IIB bulk actions give ${\alpha }_p=(2{\kappa }_0^2{)}^{-1}$ for the independent RR forms; the same normalization is used for their dual fields. In the source normalization of Type II Dp Brane DBI WZ Action, set the electric and magnetic charge units to $q_e={\mu }_p$ and $q_m={\mu }_{6-p}$. Adopt the Dirac lattice $\frac{q_e{q}_m}{{\alpha }_p}=2\pi n,n\in \mathbb{Z}\mathrm{.}$ Thus the dimensionless source-normalized Dp pairing is $2{\kappa }_0^2{\mu }_p{\mu }_{6-p}=2\pi n$; a pair with product $2\pi$ is the minimal nonzero Dirac unit. This is a quantization postulate, not a consequence of local supergravity Bianchi identities alone. It does not derive global RR flux quantization. The Type IIB self-dual five-form case at $p=3$ requires a separate treatment and is not inferred from this convention.

Polchinski, Chaudhuri, and Johnson, Lecture IV §4.1

Polchinski, §2