Paul Townsend

Paul Kingsley Townsend (born 3 March 1951) is a British theoretical physicist, specializing in general relativity, supersymmetry, string/M-theory, solitons, and cosmology. He was elected a Fellow of the Royal Society in 2000.

Quotes

 * It is argued that the type IIA 10-dimensional superstring theory is actually a compactified 11-dimensional supermembrane theory in which the fundamental supermembrane is identified with the soltionic membrane of 11-dimensional supergravity. The charged extreme black holes of the 10-dimensional type IIA string theory are interpreted as the Kaluza-Klein modes of 11-dimensional supergravity and the dual sixbranes as the analogue of Kaluza-Klein monopoles. All other p-brane solutions of the type IIA superstring theory are derived from the 11-dimensional membrane and its magnetic dual fivebrane soliton.


 * In the case of parallel multi D-branes there can be open strings with one end on one brane and the other end on another brane. Classically, such a string has a minimum energy proportional to the distance between the branes. Supersymmetry ensures that this remains true quantum-mechanically, so additional massless states can appear only when two or more D-branes coincide.
 * (quote from pages 12–13)


 * To get the string of string theory, you have to imagine taking a violin string and just keep pulling on the two ends. Now, if you keep pulling, what happens of course is that the waves on the string move along at a certain speed which depends on the tension with which you pull it. And if you keep pulling on the violin string of course a real one will break. But if you imagine that you keep pulling, then at some point the speed of the waves on the string will increase indefinitely. But not of course indefinitely because there's a fundamental limit which is the speed of light. So when you've reached the point where you pull on your violin strings and you've stretched it to the point where actually the waves on it are now moving at the speed of light, then you have a very strange material and that material is the string of string theory. In a way the branes are essentially the same material but just more extended.
 * (quote at 1:25 of 4:12)