View source for FRW/CFT duality

{{Short description|Duality between FRW models and conformal field theory}}
{{more citations needed|date=September 2011}}
In [[physics]], the '''Friedmann–Robertson–Walker/conformal field theory-duality''' or '''FRW/CFT duality'''<ref>
{{cite journal
| last1        = Yasuhiro
| first1       = Sekino
| authorlink1  = Yasuhiro Sekino
| last2        = Susskind
| first2       = Leonard
| authorlink2  = Leonard Susskind
| date         = 28 Oct 2009
| title        = Census Taking in the Hat: FRW/CFT Duality.
| journal      = Phys. Rev.
| volume       = 80
| issue        = 8
| series       = D
| pages        = 083531
| doi          = 10.1103/PhysRevD.80.083531
| url          = http://prd.aps.org/abstract/PRD/v80/i8/e083531
|arxiv = 0908.3844 |bibcode = 2009PhRvD..80h3531S | s2cid = 18616546
}}
</ref><ref>
{{cite journal
| last1        = Bousso
| first1       = Raphael
| authorlink1  = Raphael Bousso
| last2        = Susskind
| first2       = Leonard
| authorlink2  = Leonard Susskind
| date         = 22 Jul 2011
| title        = The Multiverse Interpretation of Quantum Mechanics
| arxiv          = 1105.3796
| doi=10.1103/PhysRevD.85.045007
| volume=85
| issue=4
| journal=Physical Review D
| page = 045007
| bibcode=2012PhRvD..85d5007B
| s2cid = 118507872
}}
</ref> is a conjectured duality for [[Friedmann–Lemaître–Robertson–Walker metric|Friedmann–Robertson–Walker metric]] inspired by the [[AdS/CFT correspondence]]. It assumes that the [[cosmological constant]] is exactly zero, which is only the case for models with exact unbroken [[supersymmetry]]. Because the energy density does not approach zero as we approach spatial infinity, the metric is not [[asymptotically flat]]. This is not an asymptotically cold solution.

==Overview==
In [[eternal inflation]], our universe passes through a series of phase transitions with progressively lower cosmological constant. Our current phase has a cosmological constant of size <math>10^{-123}</math>, which is conjectured to be [[metastable]] in [[string theory]]{{citation needed|date=February 2014}}. It is possible our universe might tunnel into a supersymmetric phase with an exactly zero cosmological constant. In fact, any particle in eternal inflation will eventually terminate in a phase with exactly zero or negative cosmological constant. The phases with negative cosmological constant will end in a [[Big Crunch]]. [[Stephen Shenker]] and [[Leonard Susskind]] called this the '''census taker's hat'''.<ref>{{Cite journal |last=Susskind |first=Leonard |date=2009 |editor-last=Zanelli |editor-first=Jorge |editor2-last=Henneaux |editor2-first=Marc |title=The Census Taker's Hat |url=https://link.springer.com/chapter/10.1007/978-0-387-87499-9_16 |journal=Quantum Mechanics of Fundamental Systems: The Quest for Beauty and Simplicity |language=en |location=New York, NY |publisher=Springer |pages=1–53 |doi=10.1007/978-0-387-87499-9_16 |isbn=978-0-387-87499-9}}</ref>

The conformal compactification of the terminal phase has a [[Penrose diagram]] shaped like a hat for [[future null infinity]]. A Euclidean Liouville quantum field theory is assumed to reside there. The null coordinate corresponds to the running of the [[renormalization group]].

The terminal phase has an ever-expanding FRW metric in which the average energy density goes to zero.

== References ==

{{reflist}}

{{Quantum gravity}}

{{DEFAULTSORT:FRW CFT duality}}
[[Category:Quantum gravity]]
[[Category:Leonard Susskind]]
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