Ratio of shear viscosity to entropy density in generalized theories of gravity

Journal Article · Thu Jan 15 04:00:00 EST 2009 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.79.021901· OSTI ID:21259767

Brustein, Ram; Medved, A J. M. ^[1]

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1. Department of Physics, Ben-Gurion University, Beer-Sheva 84105 (Israel)

Near the horizon of a black brane solution in anti-de Sitter space, the long-wavelength fluctuations of the metric exhibit hydrodynamic behavior. For Einstein's theory, the ratio of the shear viscosity of near-horizon metric fluctuations {eta} to the entropy per unit of transverse volume s is {eta}/s=1/4{pi}. We propose that, in generalized theories of gravity, this ratio is given by the ratio of two effective gravitational couplings and can be different than 1/4{pi}. Our proposal confirms that {eta}/s is equal to 1/4{pi} for any theory that can be transformed into Einstein's theory, such as F(R) gravity. Our proposal also implies that matter interactions--except those including explicit or implicit factors of the Riemann tensor--will not modify {eta}/s. The proposed formula reproduces, in a very simple manner, some recently found results for Gauss-Bonnet gravity. We also make a prediction for {eta}/s in Lovelock theories of any order or dimensionality.

• OSTI ID: 21259767
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 2 Vol. 79; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COUPLING
DE SITTER GROUP
DENSITY
EINSTEIN FIELD EQUATIONS
ENTROPY
FLUCTUATIONS
FORECASTING
GRAVITATION
INTERACTIONS
MATHEMATICAL SOLUTIONS
SIMULATION
VISCOSITY
WAVELENGTHS