In theoretical
physics, Mtheory is a
new limit of string theory in which 11 dimensions of spacetime may be identified. Because the
dimensionality exceeds the dimensionality of five superstring theories in 10 dimensions, it was originally believed that the
11dimensional theory is more fundamental and unifies all string theories (and
supersedes them). However, in a more modern understanding, it is another, sixth
possible description of physics of the full theory that is still called "string
theory." Though a full description of the theory is not yet known, the
lowentropy dynamics are known to be supergravity
interacting with 2 and 5dimensional membranes.
This theory is the unique supersymmetrical theory in eleven dimensions, with
its lowentropy 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 (including Ashoke
Sen, Chris Hull, Paul Townsend, Micheal Duff and John
Schwart), Edwrad Witten of the Institute for Advanced
Study suggested its existence at a conference at USC in 1995, and used
Mtheory to explain a number of previously observed dualities, sparking a flurry of new research in
string theory called the second superstring revolution.
According to Witten and others, the M in Mtheory could stand for
master, mathematical, mother, mystery,
membrane, magic, or matrix. Witten reluctantly admits the M
in Mtheory can also stand for murky because the level of understanding
of the theory is so primitive. Yet other physicists
in jest suggest it is an anagram by flipping the M to a W to stand for
Witten. However, originally the letter was taken from membrane, but since
Witten was more skeptical about membranes than his colleagues, he just kept the
"M". Later, he let the meaning be a matter of taste for the user of the word
"Mtheory".
In the early 1990s, it was shown that the various superstring theories were
related by dualities, which allow physicists to relate the description of an
object in one super string theory 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 "Mtheory".
Mtheory is not yet complete; however it can be applied in many situations
(usually by exploiting string theoretic dualities). The theory of electromagnetism was
also in such a state in the mid19th century; there were separate theories for
electricity and magnetism and, although they were known to be related, the exact
relationship was not clear until James Clerk Maxwell published his equations, in his 1864 paper A
Dynamical Theory of the Electromagnetic Field. Witten has suggested that a general
formulation of Mtheory will probably require the development of new
mathematical language. However, some scientists have questioned the tangible
successes of Mtheory given its current incompleteness, and limited predictive
power, even after so many years of intense research.
In late 2007, Bagger, Lambert
and Gustavsson set off renewed interest in Mtheory with the discovery of a candidate
Lagrangian description of coincident M2branes, based on a nonassociative
generalization of Lie Algebra, Nambu 3 algebra or Filipov 3algebra. Practitioners hope the BaggerLambert
Gustavsson action (BLG action) will provide the longsought microscopic description of
Mtheory.
