Editing Quantum field theory (section)

===Other developments===
The 1970s saw the development of non-perturbative methods in non-Abelian gauge theories. The [['t Hooft–Polyakov monopole]] was discovered theoretically by 't Hooft and [[Alexander Markovich Polyakov|Alexander Polyakov]], [[flux tube]]s by [[Holger Bech Nielsen]] and [[Poul Olesen]], and [[instanton]]s by Polyakov and coauthors. These objects are inaccessible through perturbation theory.{{r|shifman|page1=4}}

[[Supersymmetry]] also appeared in the same period. The first supersymmetric QFT in four dimensions was built by [[Yuri Golfand]] and [[Evgeny Likhtman]] in 1970, but their result failed to garner widespread interest due to the [[Iron Curtain]]. Supersymmetry theories only took off in the theoretical community after the work of [[Julius Wess]] and [[Bruno Zumino]] in 1973,{{r|shifman|page1=7}} but to date have not been widely accepted as part of the Standard Model due to lack of experimental evidence.<ref name="Wolchover">{{cite journal |last=Wolchover |first=Natalie |title=Supersymmetry Fails Test, Forcing Physics to Seek New Ideas |journal=Quanta Magazine |date=November 20, 2012 |url=https://www.quantamagazine.org/20121120-as-supersymmetry-fails-tests-physicists-seek-new-ideas/}}</ref>

Among the four fundamental interactions, gravity remains the only one that lacks a consistent QFT description. Various attempts at a theory of [[quantum gravity]] led to the development of [[string theory]],{{r|shifman|page1=6}} itself a type of two-dimensional QFT with [[conformal symmetry]].<ref name="polchinski1" /> [[Joël Scherk]] and [[John Henry Schwarz|John Schwarz]] first proposed in 1974 that string theory could be ''the'' quantum theory of gravity.<ref>{{cite arXiv |last=Schwarz |first=John H. |author-link=John Henry Schwarz |eprint=1201.0981 |title=The Early History of String Theory and Supersymmetry |class=physics.hist-ph |date=2012-01-04 }}</ref>