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#### Universal Formula for the Holographic Speed of Sound

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1702.00017.pdf

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(Publisher version), 418KB

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##### Citation

Anabalon, A., Andrade, T., Astefanesei, D., & Mann, R. (2018). Universal Formula
for the Holographic Speed of Sound.* Physics Letters B,* *781*,
547-552. doi:10.1016/j.physletb.2018.04.028.

Cite as: https://hdl.handle.net/11858/00-001M-0000-002C-A986-B

##### Abstract

We consider planar hairy black holes in five dimensions with a real scalar
field in the Breitenlohner-Freedman window and show that is possible to derive
a universal formula for the holographic speed of sound for any mixed boundary
conditions of the scalar field. As an example, we locally construct the most
general class of planar black holes coupled to a single scalar field in the
consistent truncation of type IIB supergravity that preserves the $SO(3)\times
SO(3)$ R-symmetry group of the gauge theory. We obtain the speed of sound for
different values of the vacuum expectation value of a single trace operator
when a double trace deformation is induced in the dual gauge theory. In this
particular family of solutions, we find that the speed of sound exceeds the
conformal value. Finally, we generalize the formula of the speed of sound to
arbitrary dimensional scalar-metric theories whose parameters lie within the
Breitenlohner-Freedman window.