Editing Heterotic string theory (section)

{{Short description|Physics concept of subatomic structure}}
{{About|string theory|heterosis in biology|Heterosis}}
{{String theory|cTopic=Theory}}
In [[string theory]], a '''heterotic string''' is a closed string (or loop) which is a hybrid ('heterotic') of a [[superstring]] and a [[bosonic string]]. There are two kinds of heterotic superstring theories, the heterotic SO(32) and the heterotic E<sub>8</sub>&nbsp;×&nbsp;E<sub>8</sub>, abbreviated to '''HO''' and '''HE'''. Apart from that there exist seven more heterotic string theories which are not [[supersymmetric]] and hence are only of secondary importance in most applications.<ref>{{Cite book |last=Polchinski |first=Joseph |title=String Theory: Superstring Theory and Beyond |publisher=Cambridge University Press |year=1998 |isbn=9780521633048 |volume=2 |pages=55-59 |language=English}}</ref> Heterotic string theory was first developed in 1985 by [[David Gross]], [[Jeffrey A. Harvey|Jeffrey Harvey]], [[Emil Martinec]], and [[Ryan Rohm]]<ref>{{cite journal | last1=Gross | first1=David J. | last2=Harvey | first2=Jeffrey A. | last3=Martinec | first3=Emil | last4=Rohm | first4=Ryan | title=Heterotic String | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=54 | issue=6 | date=1985-02-11 | issn=0031-9007 | doi=10.1103/physrevlett.54.502 | pages=502–505| pmid=10031535 | bibcode=1985PhRvL..54..502G }}</ref> (the so-called "Princeton string quartet"<ref>{{cite web|author=Dennis Overbye|author-link=Dennis Overbye|url=https://www.nytimes.com/2004/12/07/science/07stri.html?pagewanted=2&fta=y|title=String theory, at 20, explains it all (or not)|work=The New York Times|date=2004-12-07|access-date=2020-03-15}}</ref>), in one of the key papers that fueled the [[first superstring revolution]].