Breaking the sound barrier in AdS/CFT

Abstract

It has been conjectured that the speed of sound in holographic models with UV fixed points has an upper bound set by the value of the quantity in conformal field theory. If true, this would set stringent constraints for the presence of strongly coupled quark matter in the cores of physical neutron stars, as the existence of two-solar-mass stars appears to demand a very stiff Equation of State. In this article, we present a family of counterexamples to the speed of sound conjecture, consisting of strongly coupled theories at finite density. The theories we consider include $\mathcal{N}=4$ super Yang-Mills at finite R-charge density and non-zero gaugino masses, while the holographic duals are Einstein-Maxwell theories with a minimally coupled scalar in a charged black hole geometry. We show that for a small breaking of conformal invariance, the speed of sound approaches the conformal value from above at large chemical potentials.

41 pages, 8 figures. Published version

References in corpus (23)

• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Chiral effective field theory and nuclear forces
• Cold Quark Matter
• Neutron matter at next-to-next-to-next-to-leading order in chiral effective field theory
• Sound velocity bound and neutron stars
• Deconfinement and Gluon Plasma Dynamics in Improved Holographic QCD
• A holographic critical point
• Cold Nuclear Matter In Holographic QCD
• Holographic Nuclear Physics
• Baryon Number-Induced Chern-Simons Couplings of Vector and Axial-Vector Mesons in Holographic QCD
• A bound on the speed of sound from holography
• D3-D7 Quark-Gluon Plasmas at Finite Baryon Density
• Holographic Responses of Fermion Matter
• Holography and the speed of sound at high temperatures
• Dense Holographic QCD in the Wigner-Seitz Approximation
• Zero Sound in Strange Metallic Holography
• Supersymmetric Charged Clouds in AdS_5
• Correlated stability conjecture revisited
• (Super)Yang-Mills at Finite Heavy-Quark Density
• Explicit flavor symmetry breaking and holographic compact stars
• Alternative large Nc baryons and holography

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