Exploring the similarities of the dS/CFT and AdS/CFT correspondences

The dS/CFT correspondence differs from its AdS/CFT counterpart in some ways, yet is strikingly similar to it in many others. For example, both involve CFTs defined on connected spaces (despite the fact that the conformal boundary of de Sitter space is not connected), and both impose constraints on scalar masses (Strominger's bound for de Sitter, and the Breitenlohner-Freedman bound for anti-de Sitter). We argue that these similarities can be explored and exploited using a slight extension of the Euclidean approach to AdS/CFT. The methods are particularly compatible with Hull's embedding of de Sitter space in a timelike T-dual version of M-theory. (C) 2002 Elsevier Science B.V. All rights reserved.