Mathematics and Physics Wiki
Register
Advertisement
String Theory
All Roads Lead to String Theory (Polchinski)
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


Featured

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

StringDualities

Dualities between the 5 string theories



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

  1. 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.
  2. Sen, Ashok (1996). "Unification of String Dualities". Nucl.Phys.Proc.Suppl. 58 (6): 5-19. http://arxiv.org/pdf/hep-th/9609176.pdf.
  3. Townsend, Paul (1996). "Brane Surgery". Nucl.Phys.Proc.Suppl. 58 (6): 163-175. http://arxiv.org/pdf/hep-th/9512219v3.pdf.
  4. Duff, Michael. "The Theory Formerly known as Strings". http://arxiv.org/pdf/hep-th/9608117v3.pdf.
  5. Susskind, Leonard; Banks, T., Fischler, W., Shenker, S.. M Theory as a Matrix model: A conjecture. http://arxiv.org/pdf/hep-th/9610043v3.pdf.
Advertisement