Definitions for M-theory
A generalized theory of eleven-dimensional supergravity that attempts to unify the five superstring theories
Origin: Abbreviation of membrane.
In theoretical physics, M-theory is an extension of string theory in which 11 dimensions of spacetime are identified as 7 higher-dimensions + the 4 common dimensions. Proponents believe that the 11-dimensional theory unites all five 10 dimensional string theories and supersedes them. Though a full description of the theory is not known, the low-entropy dynamics are known to be supergravity interacting with 2- and 5-dimensional membranes. This idea is the unique supersymmetric theory in 11 dimensions, with its low-entropy matter content and interactions fully determined, and can be obtained as the strong coupling limit of type IIA string theory because a new dimension of space emerges as the coupling constant increases. Drawing on the work of a number of string theorists, Edward Witten of the Institute for Advanced Study suggested its existence at a conference at USC in 1995, and used M-theory to explain a number of previously observed dualities, initiating a flurry of new research in string theory called the second superstring revolution. In the early 1990s, it was shown that the various superstring theories were related by dualities which allow the description of an object in one super string theory to be related to the description of a different object in another super string theory. These relationships imply that each of the super string theories is a different aspect of a single underlying theory, proposed by Witten, and named "M-theory".