de Sitter space and Holography

de Sitter space and Holography de Sitter space and Holography

hep.physics.uoc.gr
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13.07.2015 Views

For example• In static coordinates:l 2 P(X,X ′ ) = −√(r 2 − l 2 )(r ′2 − l 2 ) cosh t − t′l+ rr ′ cos Θwhere Θ is the geodesic distance of two points on the unitS d−2 .• In planer coordinates:l 2 P(X,X ′ ) = −l 2 cosh t − t′l+ 1 2 e−t−t′ l δ ij (x i − y i )(x j − y j )Consider a scalar field in dS spaceS = − 1 ∫d d x √ −g[(∇φ) 2 + m 2 φ 2 ]2The Green function G(X,Y ) = 〈0|φ(X)φ(Y )|0〉 obeys(∇ 2 − m 2 )G(X,Y ) = 0Since dS space is maximally symmetric, the Green functiondepends on X and Y only through P(X,Y ).26

For any function f(P) one can seel 2 (∇ 2 − m 2 )f(P) = (1 − P 2 ) d2 f df− PddP2dP − m2 l 2 fTherefore one has[(1 − P 2 ) d2dP 2 − Pd ddP − m2 l 2 ]G(P(X,Y )) = 0Which as solution in terms of hypergeometric functionsG = const.F(h + , h − , d 2 , 1 + P2)whereh ± = 1 [(d − 1) ± √ ](d − 1)22 − 4m 2 l 2Since the above equation is symmetric under P → −P thereis another solutionG = const.F(h + , h − , d 2 , 1 − P2)One parameter family of dS invariant Green functioncorresponding to a linear combination of these solutions.G α (X,Y ) = 〈α|φ(X)φ(Y )|α〉27

For example• In static coordinates:l 2 P(X,X ′ ) = −√(r 2 − l 2 )(r ′2 − l 2 ) cosh t − t′l+ rr ′ cos Θwhere Θ is the geo<strong>de</strong>sic distance of two points on the unitS d−2 .• In planer coordinates:l 2 P(X,X ′ ) = −l 2 cosh t − t′l+ 1 2 e−t−t′ l δ ij (x i − y i )(x j − y j )Consi<strong>de</strong>r a scalar field in dS <strong>space</strong>S = − 1 ∫d d x √ −g[(∇φ) 2 + m 2 φ 2 ]2The Green function G(X,Y ) = 〈0|φ(X)φ(Y )|0〉 obeys(∇ 2 − m 2 )G(X,Y ) = 0Since dS <strong>space</strong> is maximally symmetric, the Green function<strong>de</strong>pends on X <strong>and</strong> Y only through P(X,Y ).26

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