Editing M-theory (section)

{{short description|Framework of superstring theory}}
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{{For introduction|Introduction to M-theory}}
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'''M-theory''' is a theory in [[physics]] that unifies all [[Consistency|consistent]] versions of [[superstring theory]]. [[Edward Witten]] first conjectured the existence of such a theory at a [[string theory]] conference at the [[University of Southern California]] in 1995. Witten's announcement initiated a flurry of research activity known as the [[second superstring revolution]]. Prior to Witten's announcement, string theorists had identified five versions of superstring theory. Although these theories initially appeared to be very different, work by many [[physicists]] showed that the theories were related in intricate and nontrivial ways. Physicists found that apparently distinct theories could be unified by mathematical transformations called [[S-duality]] and [[T-duality]]. Witten's conjecture was based in part on the existence of these dualities and in part on the relationship of the string theories to a [[field theory (physics)|field theory]] called [[eleven-dimensional supergravity]].

Although a complete formulation of M-theory is not known, such a formulation should describe two- and five-dimensional objects called [[branes]] and should be approximated by eleven-dimensional supergravity at low [[energies]]. Modern attempts to formulate M-theory are typically based on [[matrix theory (physics)|matrix theory]] or the [[AdS/CFT correspondence]]. According to Witten, M should stand for "magic", "mystery" or "membrane" according to taste, and the true meaning of the title should be decided when a more fundamental formulation of the theory is known.<ref name="Duff 1996, sec. 1">Duff 1996, sec. 1</ref>

Investigations of the mathematical structure of M-theory have spawned important theoretical results in physics and mathematics. More speculatively, M-theory may provide a framework for developing a [[theory of everything|unified theory]] of all of the [[fundamental force]]s of nature. Attempts to connect M-theory to experiment typically focus on [[compactification (physics)|compactifying]] its [[extra dimension]]s to construct candidate models of the four-dimensional world, although so far none have been verified to give rise to physics as observed in [[high-energy physics]] experiments.