I know that D$p$ branes are branes with $p$ spatial dimension with satisfying Dirichlet boundary condition. I want to confirm the following things.

First, I heard the D-branes are massive, and these massive D-branes is well described in $Ads$ geometry. Is it right? Why D-branes are massive?

In some context, D-branes are related with M branes. What is M-brane? Is it just some object describes in M-theory? I also heard M5 brane is related with D4 brane with some manipulation(dimensional reduction).

In the process of reading some papers, interestingly, M branes are also related with NS branes. What is NS-brane? Is it just some object describe in NS sector?

Is all branes are related with each other? What i mean is D brane and M branes seems have some similarity and M branes and NS brane have some relation. So there might be some relation about D-branes and NS branes.


1 Answer 1


When you try writing a quantu, theory of strings, you get supergravity in the classical limit. Branes are just solitonic solutions to those supergravity theories.

You can classify string/brane theories based on the type of SUGRA theory you get in the classical limit. That gives you four kinds in (9+1)dim and M-theory in (10+1)dim, all related by various kinds of dualities.

  • NS5 brane and all the D branes are branes in Type2 theories.
  • M-branes are just the solitonic solutions supported by SUGRA in (10+1)d. When you reduce that theory on a circle, you get Type2a (which is the same as Type2b, up to T-duality) so the M5 and M2 branes reduce to the various D-branes you know. Further, acting on the D5 by an S-duality will give you the NS5.

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