Four Lectures on M-theory
P. K. Townsend
TL;DR
These lectures argue that M-theory unifies the five D=10 superstring theories as different limits or vacua of an 11D framework. The approach uses membranes and fivebranes in 11D, with compactifications and dualities mapping to the known 10D theories and their D-brane spectra, while 11D supergravity emerges as the low-energy limit at strong coupling. The discussion highlights how RR branes and dualities (T-duality, S-duality, SL(2,Z)) arise naturally from M-theory, and outlines proposed non-perturbative definitions, such as the BFSS matrix model, that capture membrane dynamics. Collectively, the work presents a cohesive brane-based picture in which quantum gravity, gauge theories, and string theories are interwoven in a single, higher-dimensional framework.
Abstract
Synopsis: (i) how superstring theories are unified by M-theory; (ii) how superstring and supermembrane properties follow from the D=10 and D=11 supersymmetry algebras; (iii) how D=10 and D=11 supergravity theories determine the strong coupling limit of superstring theories; (iv) how properties of Type II p-branes follow from those of M-branes.