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Colloquium: Black Hole Entropy, Entanglement, and the Einstein Equation

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Ted Jacobson, University of Maryland
When
15 October 2015 from 4:00 PM to 5:00 PM
Where
117 Osmond Laboratory
Contact Name
Eugenio Bianchi
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Black hole entropy was originally introduced by Bekenstein in 1972 to save the second law. He inferred that the black hole entropy should equal the horizon area in Planck units, which is now generally believed to measure quantum vacuum entanglement across the horizon. But why is this entanglement entropy finite? And why does classical gravity "know" about it? I will give a picturesque answer to the first question, and will attempt to answer the second by explaining how the Einstein equation might follow from the hypothesis that entanglement entropy in any "small" geodesic ball of fixed volume is maximized in the vacuum. Along the way the ancestral stories of Planck's black body entropy and Bekenstein's black hole entropy will be recalled, to inspire and remind us of the curious paths that  progress can take in physics, and of the key role that puzzling over the foundations of  thermodynamics has played.

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