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The Ohio State University

Project Title

What is an event?

Project Summary

We are used to thinking of space as being made of points in three dimensions. Einstein taught us a century ago that we should instead think in terms of events, which are points in four dimensional spacetime. But once we include effects of quantum mechanics, we find that it is not so easy to define the notion of an event, since spacetime has quantum fluctuations. What then should replace the notion of an event? It turns out that the idea of events must be completely altered; what happens at an event in classical relativity must be described in very indirect ways in quantum gravity. In particular, in string theory, the effects at one event have to be encoded in large nonlocal matrices in a `dual' theory which has no gravity. More interestingly, the spacetime inside a black hole emerges as an approximate dual description of an even larger physical system: the space of all states of the black hole. This picture of the black hole interior arises from the fuzzball paradigm, which resolves Hawking's well known `information paradox' in string theory by showing that black holes swell up into `fuzzballs' that have, strictly speaking, no horizon or singularity.

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