I am studying Strominger's paper, "Open p-branes" [arXiv:hep-th/9512059v1]. On page 5, referring to the 6-dimensional $(0,2)$ theory on the M5-brane of M-Theory, he says

Since this is a chiral theory it is not possible for extra massless fields to appear when the fivebrane positions coincide.

Yes, the 6d $(0,2)$ theory (in modern parlance the $(2,0)$ theory) is chiral, but why does *that* mean no extra massless fields will appear when the fivebranes coincide?

I know that the NS5-brane of Type-IIA string theory carries a self-dual antisymmetric tensor, and not a gauge field (in contrast to a D$p$-brane or even an NS5-brane of Type-IIB), so when parallel NS5-branes in Type-IIA become coincident, one does not get enhanced gauge symmetries but rather a critical point with tensionless strings. I guess if you compactify the M5-brane along a transverse direction, you should get the Type-IIA NS5-brane with $(1,1)$ worldvolume supersymmetry. So the type-IIA NS5-brane has a nonchiral worldvolume theory.

Is he referring to some general result that if the worldvolume theory on a brane is chiral, a stack of such branes will not produce extra massless fields?

This post imported from StackExchange Physics at 2016-10-23 22:31 (UTC), posted by SE-user leastaction