Editing String theory (section)

=== Compatibility with dark energy ===
It remains unknown whether string theory is compatible with a metastable, positive [[cosmological constant]].
Some putative examples of such solutions do exist, such as the model described by Kachru ''et al''. in 2003.<ref>{{cite journal |last1=Kachru |first1=Shamit |last2=Kallosh |first2=Renata |last3=Linde |first3=Andrei |last4=Trivedi |first4=Sandip P. |title=de Sitter Vacua in String Theory |journal=[[Phys. Rev. D]] |date=2003 |volume=68 |issue=4 |page=046005 |doi=10.1103/PhysRevD.68.046005 |arxiv=hep-th/0301240 |bibcode=2003PhRvD..68d6005K |s2cid=119482182 | issn=0556-2821 }}</ref> In 2018, a group of four physicists advanced a controversial conjecture which would imply that [[Swampland (physics)|no such universe exists]]. This is contrary to some popular models of [[dark energy]] such as [[Lambda-CDM model|Λ-CDM]], which requires a positive vacuum energy. However, string theory is likely compatible with certain types of [[quintessence (physics)|quintessence]], where dark energy is caused by a new field with exotic properties.<ref>{{cite web |last1=Wolchover |first1=Natalie |title=Dark Energy May Be Incompatible With String Theory |url=https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/ |website=[[Quanta Magazine]] |publisher=Simons Foundation |access-date=2 April 2020 |date=9 August 2018 |archive-date=15 November 2020 |archive-url=https://web.archive.org/web/20201115210807/https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/ |url-status=live }}</ref>