String Theory | ||
---|---|---|
All Roads Lead to String Theory (Polchinski) | ||
Prior to the First Superstring Revolution
| ||
Early History | S-Matrix Theory Regge Trajectory | |
Bosonic String Theory | Worldsheet String Bosonic String Theory String Perturbation Theory Tachyon Condensation | |
Supersymmetric Revolution | Supersymmetry RNS Formalism GS Formalism BPS | |
Superstring Revolutions
|
||
First Superstring Revolution | GSO Projection Type II String Theory Type IIB String Theory Type IIA String Theory Type I String Theory Type H String Theory Type HO String Theory Type HE String Theory |
|
Second Superstring Revolution | T-Duality D-Brane S-Duality Horava-Witten String Theory M-Theory Holographic Principle N=4 Super-Yang-Mills Theory AdS CFT BFSS Matrix Theory Matrix String Theory (2,0) Theory Twistor String Theory F-Theory String Field Theory Pure Spinor Formalism |
|
After the Revolutions
| ||
Phenomenology | String Theory Landscape Minimal Supersymmetric Standard Model String Phenomenology | |
This article is or was once a featured article on the Mathematics and Physics Wiki, which generally indicates a relatively well-written, or interesting article. |
M-Theory is basically a strongly-coupled theory in 11 dimensions from which other String Theoryies can be derived from.
Motivation
Dualities
In the Second Superstring Revolution, it was realised that the ordinary 5 String Theoryies were connected by 2 dualities, namely T-Duality and S-Duality/. To be specific, these dualities can be portrayed on a map as you can see in the image here.
This means that some of these String Theoryies are in fact equivalent, so that there are really just 2 distinct String Theoryies, the Type IIA String Theory, and the Type HE String Theory.
At strong coupling (take the S-Dual), these become the Townsend String Theory and the Horava-Witten String Theory, respectively. Various physicists, including Edward Witten, Ashok Sen, Nathan Seiberg, etc., postulated (see for example, [1], [2] [3]) that these two String Theoryies are actually a \new theory, which came to be known as M-Theory compactified on a circle, and a line segment, respectively. This is also when Michael Duff coined the term "The Theory Formerly known as Strings" [4].
Branes
While this is certnaily not proclaimable to be a motivation for M-Theory, it is worth stating here that the fundamental objects of M-Theory are not Strings, but actually 2-Branes and 5-Branes. This was not such a great surprise, because D-Branes already existed in ordinary String Theories.
Supergravity
Following the "Dualities" section, it is obvious that M-Theory needs to be an 11-Dimensional theory. Now, 11-Dimensional Supergravity is of course, an 11-Dimensional Theory. Various Supergravity Theoryies, including Supergravity, for example, are low-energy limits of Superstring Theoryies. Thus, it was therefore perceived as possible, that 11-Dimensional Supergravity lies in the low-energy limit of M-Theory/ .
Non-Perturbative Formulation
- Main Article: BFSS Matrix Theory
The non-perturbative formulation of M-Theory is BFSS Matrix Theory [5].
References
- ↑ Witten, Edward (1996). "Five-Branes and M-Theory on an orbifold". Nucl.Phys.B 463 (6): 382-397. http://arxiv.org/pdf/hep-th/9512219v3.pdf.
- ↑ Sen, Ashok (1996). "Unification of String Dualities". Nucl.Phys.Proc.Suppl. 58 (6): 5-19. http://arxiv.org/pdf/hep-th/9609176.pdf.
- ↑ Townsend, Paul (1996). "Brane Surgery". Nucl.Phys.Proc.Suppl. 58 (6): 163-175. http://arxiv.org/pdf/hep-th/9512219v3.pdf.
- ↑ Duff, Michael. "The Theory Formerly known as Strings". http://arxiv.org/pdf/hep-th/9608117v3.pdf.
- ↑ Susskind, Leonard; Banks, T., Fischler, W., Shenker, S.. M Theory as a Matrix model: A conjecture. http://arxiv.org/pdf/hep-th/9610043v3.pdf.