Yale University

Co-Investigators

Eugene Lim,

*Yale University*

Liam McAllister,

*Princeton University*

Project Title

Possible Pasts in the Multiverse

Project Summary

The suggestion that our observable universe may be a single "pocket" in an infinite "multiverse" is one of the most profoundly exciting - and unsettling - possibilities offered by modern cosmology. However, attempts to calculate the probability of finding oneself inside a given type of pocket universe often yield ambiguous answers, which depend critically on the choice of coordinate system in the multiverse. This proposal tackles this problem by examining only quantities that can be computed without reference to any explicit coordinate system, and without making direct comparisons between hypothetical observers who could only communicate by using signals that travel faster than light. Secondly, much of theoretical support for the multiverse comes from the string landscape. This is a massively complicated, multidimensional surface with a vast number of valleys and paths - each of which represents a possible past for our (or any other) universe. The second goal of this proposal is to compute the properties of the landscape that follow directly from its dimensionality, as opposed to following from explicitly stringy considerations.

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