Editing Randall–Sundrum model (section)

{{Short description|Extra-dimensional model of the universe}}
{{Redirect|Warp factor|the concept in [[Star Trek]]|Warp drive (Star Trek)}}
In [[physics]], '''Randall–Sundrum models''' (RS) (also called '''5-dimensional warped geometry theory''') are [[Mathematical model|model]]s that describe the world in terms of a [[warped geometry|warped-geometry]] higher-dimensional [[universe]], or more concretely as a 5-dimensional [[anti-de Sitter space]] where the [[elementary particle]]s (except the [[graviton]]) are localized on a (3&nbsp;+&nbsp;1)-[[dimension]]al [[Membrane (M-Theory)|brane]] or branes.

The two models were proposed in two articles in 1999 by [[Lisa Randall]] and [[Raman Sundrum]] because they were dissatisfied with the [[Universal extra dimension|universal extra-dimensional]] models then in vogue. Such models require two fine tunings; one for the value of the [[Brane cosmology|bulk]] [[cosmological constant]] and the other for the brane [[tension (physics)|tensions]]. Later, while studying RS models in the context of the [[AdS/CFT correspondence|anti-de Sitter / conformal field theory (AdS/CFT) correspondence]], they showed how it can be dual to [[Technicolor (physics)|technicolor model]]s.

The first of the two models, called '''RS1''', has a finite size for the extra dimension with two branes, one at each end.<ref>{{cite journal
 |last=Randall |first=Lisa |author2=Sundrum, Raman
 |year=1999
 |title=Large Mass Hierarchy from a Small Extra Dimension
 |journal=[[Physical Review Letters]]
 |volume=83 |issue=17 |pages=3370&ndash;3373
 |doi=10.1103/PhysRevLett.83.3370 |bibcode=1999PhRvL..83.3370R
 |arxiv = hep-ph/9905221 }}</ref> The second, '''RS2''', is similar to the first, but one brane has been placed infinitely far away, so that there is only one brane left in the model.<ref>{{cite journal
 |last=Randall |first=Lisa |author2=Sundrum, Raman
 |year=1999
 |title=An Alternative to Compactification
 |journal=Physical Review Letters |volume=83 |issue=23 |pages=4690–4693 |arxiv = hep-th/9906064 |bibcode=1999PhRvL..83.4690R|doi=10.1103/PhysRevLett.83.4690|s2cid=18530420 }}</ref>