Large Grants
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Previous Programs

2016 Physics of the Observer
2016 Awardees

2015 The Physics of What Happens
2015 Awardees

2013 Physics of Information
2013 Awardees

2010 The Nature of Time
2010 Awardees

2008 Foundational Questions in Physics and Cosmology
2008 Awardees

2006 Foundational Questions in Physics and Cosmology
2006 Awardees

Samir Mathur
The Ohio State University

Project Title

What is an observer?

Project Summary

The notion of an observer has been a puzzling one since the advent of quantum mechanics. This issue becomes more vexing when we come to gravity. An observer who falls into a black hole cannot make measurements on things outside, and an observer who stays outside cannot see things inside the hole. Do we now have two different wavefunctions, one for the inside and one for the outside? Or does the Hilbert space contain events that can never be seen by a given observer? With string theory we now have a paradigm where we can address this question. One finds that black holes are ‘fuzzballs’, with no horizon. Thus we do not have a region inside the horizon which can disconnect the different classes of observers. Now the question is: do cosmological horizons behave the same way as the black hole horizon? In that case, quantum gravity would give a completely new notion of an observer: the entire wavefunction will get automatically limited to the domain which can be see by the observer. But if cosmological horizons are different, then we would not be able to implement this philosophy. This proposal seeks to resolve this issue.

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