a corresponding D2-brane crossing a D6-brane. Yet, the D6-brane is connected to these other branes by dualities. Thus, at least naively it appears that application of supergravity dualities can transform the solutions of [@GM] into ones in which D6-branes do in fact admit flux from other branes. Nevertheless, finding the mechanism through which this works, or what alternative resolution string theory provides remains a puzzle to be solved by further study of D6-branes.

Confinement and Charge quantization {#confine}
===================================

We now turn to a related puzzle [@half] which, though we will use 6-branes in its study, is most easily stated in terms of D0- and D8-branes. Consider for example a system with a single D0-brane and a single D8-brane and suppose that the boundary conditions are such that the ten-form Ramond-Ramond gauge field takes the symmetric values $\pm 1/2$ of the fundamental quantum on either side of the D8-brane domain wall. Then, the brane-source charge arguments above (or, equivalently the arguments of [@PS; @BGL] in type IIA supergravity [@Romans] and the arguments of [@Lif; @BDG; @DFK; @K; @HoWu; @dA; @OSZ] in related contexts) lead to the conclusion that exactly 1/2 of a fundamental string must end on the D0-brane. While 