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mitchell porter
May2-11, 03:28 AM
P: 757
Just speaking classically, de Sitter space has a spacelike conformal boundary, anti de Sitter has a timelike conformal boundary, and Minkowski space has a lightlike conformal boundary. (When I say the AdS boundary is timelike, I mean it has a timelike direction - it has spacelike directions too.) Also, of course, the bulk theories all have Lorentzian signature, classically.

I read somewhere that results in AdS can sometimes be analytically continued to results in dS by way of working in Euclidean signature in the AdS boundary theory, but the dS "results" had problems as usual - maybe they were purely formal expressions; I forget the details.