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arXiv · 0905.0903

A bound on the speed of sound from holography

Aleksey Cherman·Thomas D. Cohen·Abhinav Nellore
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Abstract

We show that the squared speed of sound v_{s}^{2} is bounded from above at high temperatures by the conformal value of 1/3 in a class of strongly coupled four-dimensional field theories, given some mild technical assumptions. This class consists of field theories that have gravity duals sourced by a single scalar field. There are no known examples to date of field theories with gravity duals for which v_{s}^{2} exceeds 1/3 in energetically favored configurations. We conjecture that v_{s}^{2}=1/3 represents an upper bound for a broad class of four-dimensional theories.

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Aleksey Cherman, Thomas D. Cohen, Abhinav Nellore. 2009-05-06. A bound on the speed of sound from holography. https://doi.org/10.1103/physrevd.80.066003

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