International Light Cone Advisory Committee


Algebras and Observers

by Edward Witten (Institute for Advanced Study)

In ordinary quantum mechanics, we consider the observer to be external to the system under study, but in the context of gravity, this is not possible in general, because everything gravitates. After some general discussion of what notion of an ``algebra of observables'' makes sense in the context of gravity, I will give de Sitter space as an example in which it is necessary to explicitly include an observer and the observer's gravity in the description.

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