Is there physical content in D Branes?

[arivero]

I am having a hard time to see how/if D Branes are physics, at all.

We are told that it is the modern notation for Chan Paton charges. But then Marcus and Sagnotti, in the unique paper I have found on the topic, seem to think different

Reference
Group Theory from Quarks at the Ends of Strings. (http://www.slac.stanford.edu/spires/find/hep/www?j=PHLTA,B188,58)
Neil Marcus (UC, Berkeley & LBL, Berkeley) , Augusto Sagnotti (Rome U.,Tor Vergata & INFN, Rome) . UCB-PTH-86/27, LBL-22076, ROM2F-86/015, Oct 1986. 10pp.
Published in Phys.Lett.B188:58,1987.

Is there any good work relating D-branes to "charges at the end of strings"?

[nrqed]

I am having a hard time to see how/if D Branes are physics, at all.

We are told that it is the modern notation for Chan Paton charges. But then Marcus and Sagnotti, in the unique paper I have found on the topic, seem to think different

Reference
Group Theory from Quarks at the Ends of Strings. (http://www.slac.stanford.edu/spires/find/hep/www?j=PHLTA,B188,58)
Neil Marcus (UC, Berkeley & LBL, Berkeley) , Augusto Sagnotti (Rome U.,Tor Vergata & INFN, Rome) . UCB-PTH-86/27, LBL-22076, ROM2F-86/015, Oct 1986. 10pp.
Published in Phys.Lett.B188:58,1987.

Is there any good work relating D-branes to "charges at the end of strings"?

Are you specifically interested in string theory as applied to a theory of QCD or string theory in general (as a theory of everything)?

The need for branes in superstring theory goes beyond the introduction of gauge indices. I think that what Polchinski showed was that branes are required as elementary constituents in addition to strings. Introducing Chan-Paton factors at the end of open strings which end on branes can be done in order to introduce gauge groups but as far as I know, branes do not require Chan Paton factors (I mightbe wrong).

In any case, have you look at Zwiebach? He gives a nice introduction.