Năstase, Horaţiu [UNESP]2020-12-122020-12-122019-01-01Fundamental Theories of Physics, v. 197, p. 249-261.2365-64250168-1222http://hdl.handle.net/11449/200479In the last chapter, we considered T-duality for closed strings. Now we start off by considering T-duality for open strings, and see that it will lead to D-branes. Then, we define the low energy supergravity limits of string theory, the strong coupling limit of string theory known as M-theory, and finally show that all the various incarnations of string theory are related into a single duality web, as facets of the same unique theory.249-261engCapítulo de livro10.1007/978-3-030-15077-8_212-s2.0-85085195657