Massive particles in D-brane models ?

[Dilatino]

How does a zero separation of parallel D-branes give mass to the particles that correspond to strings stretched between them?

Is there a scalar field corresponding to the separation of the D-branes which takes the role of a higgs field, or how does it work?

 

[Ben Niehoff]

Parallel D-branes have modes that correspond to strings stretched between the branes.

At zero separation, these open string modes are massless, because the strings have zero length.

At non-zero separation, these modes become massive, because the strings have nonzero length (and the string tension is a constant).

This is directly analogous to the Higgs mechanism. In the worldvolume theory on the branes, it corresponds to breaking gauge symmetry due to a vev of a scalar field, and the gauge boson acquiring a mass.