Difference between revisions 147178451 and 147178452 on dewiki

{{Unreferenced|date=December 2007}}

{{string-theory}}
{{see|string theory}}

'''Superstring theory''' is an attempt to explain all of the [[Elementary particle|particles]] and [[fundamental force]]s of nature in one theory by modeling them as vibrations of tiny [[supersymmetry|supersymmetric]] strings. It is considered one of the most promising candidate theories of [[quantum gravity]]. Superstring theory is a shorthand for '''supersymmetric string theory'&(contracted; show full)

{{unsolved|physics|Is [[string theory]], superstring theory, or [[M-theory]], or some other variant on this theme, a step on the road to a "[[theory of everything]]," or just a blind alley?}}

== Number of superstring theories ==

Theoretical physicists were troubled by the existence of five separate string theories. This has been solved by the [[second superstring revolution]] in the 
[[1990s]] during which the five string theories were discovered to be different limits of a single underlying theory: [[M-theory]].
{| border="1" cellpadding="1" cellspacing="1" bordercolorlight="#666699" bordercolordark="#666699" bgcolor="#CCFFCC" mm_noconvert="TRUE"
|- bgcolor="#FFFFFF"
! colspan="3" class="dark" | String Theories
|-
! class="dark" | Type
(contracted; show full)
|-
! bgcolor="#FFCCCC" class="dark" | HE
| align="CENTER" class="dark" | 10
| bgcolor="#FFFFCC" class="dark" | [[Supersymmetry]] between forces and matter, with closed strings only, no [[tachyon]], [[heterotic]], meaning right moving and left moving strings differ, group symmetry is [[E8 (mathematics)|''E''<sub>8</sub>
&times;×''E''<sub>8</sub>]] 
|}

The five consistent superstring theories are:
* The [[type I string]] has one supersymmetry in the ten-dimensional sense (16 supercharges). This theory is special in the sense that it is based on unoriented [[open string|open]] and [[closed string]]s, while the rest are based on oriented closed strings.
* The [[type II string]] theories have two supersymmetries in the ten-dimensional sense (32 supercharges). There are actually two kinds of type II strings called type IIA and type IIB. They differ mainly in the fact that the IIA theory is non-[[chirality (physics)|chiral]] (parity conserving) while the IIB theory is chiral (parity violating).
* The [[heterotic string]] theories are based on a peculiar hybrid of a type I superstring and a bosonic string. There are two kinds of heterotic strings differing in their ten-dimensional [[gauge group]]s:  the heterotic [[E8 (mathematics)|''E''<sub>8</sub>&times;×''E''<sub>8</sub>]] string and the heterotic [[special orthogonal group|SO(32)]] string. (The name heterotic SO(32) is slightly inaccurate since among the SO(32) [[Lie group]]s, string theory singles out a quotient Spin(32)/Z<sub>2</sub> that is not equivalent to SO(32).)

(contracted; show full)[[it:Teoria delle superstringhe]]
[[ja:超弦理論]]
[[pl:Teoria superstrun]]
[[ru:Теория суперструн]]
[[sl:Teorija superstrun]]
[[sv:Supersträngteori]]
[[fi:Supersäieteoria]]
[[zh:超弦理論]]