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 http://www.slac.stanford.edu/spires/find/hep/www?j=PHLTA,B188,58" [Broken] 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"?