Is there a "most perfect fluid" consistent with quantum field theory?

Abstract

It was recently conjectured that the ratio of the shear viscosity to entropy density, $\eta /s$, for any fluid always exceeds $\hslash /(4\pi k_B)$. This conjecture was motivated by quantum field theoretic results obtained via the AdS/CFT correspondence and from empirical data with real fluids. A theoretical counterexample to this bound can be constructed from a nonrelativistic gas by increasing the number of species in the fluid while keeping the dynamics essentially independent of the species type. The question of whether the underlying structure of relativistic quantum field theory generically inhibits the realization of such a system and thereby preserves the possibility of a universal bound is considered here. Using rather conservative assumptions, it is shown here that a metastable gas of heavy mesons in a particular controlled regime of QCD provides a realization of the counterexample and is consistent with a well-defined underlying relativistic quantum field theory. Thus, quantum field theory appears to impose no lower bound on $\eta /s$, at least for metastable fluids.

4 pages; typos corrected and references added in new version

References in corpus (16)

• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Shear viscosity of strongly coupled N=4 supersymmetric Yang-Mills plasma
• Holography and hydrodynamics: diffusion on stretched horizons
• Universality of the shear viscosity in supergravity
• Hadronic dissipative effects on elliptic flow in ultrarelativistic heavy-ion collisions
• From AdS/CFT correspondence to hydrodynamics. II. Sound waves
• Coupling constant dependence of the shear viscosity in N=4 supersymmetric Yang-Mills theory
• Perfect Fluidity of the Quark Gluon Plasma Core as Seen through its Dissipative Hadronic Corona
• Hydrodynamics of R-charged black holes
• The Hydrodynamics of M-Theory
• Shear viscosity from R-charged AdS black holes
• Viscosity of gauge theory plasma with a chemical potential from AdS/CFT correspondence
• The shear viscosity of gauge theory plasma with chemical potentials
• The Viscosity Bound Conjecture and Hydrodynamics of M2-Brane Theory at Finite Chemical Potential
• Cold Strongly Coupled Atoms Make a Near-perfect Liquid
• The Letter "s" (and the sQGP)

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• QCD Viscosity to Entropy Density Ratio in the Hadronic Phase
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• Lovelock theories, holography and the fate of the viscosity bound
• The Shear Viscosity in Anisotropic Phases
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• Fluid Dynamics and Viscosity in Strongly Correlated Fluids
• Hydrodynamics of spacetime and vacuum viscosity
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• A sticky business: the status of the conjectured viscosity/entropy density bound
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• On the universality of AdS${}_2$ diffusion bounds and the breakdown of linearized hydrodynamics
• Hydrodynamics with conserved current via AdS/CFT correspondence in the Maxwell-Gauss-Bonnet gravity
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• Viscosity of an ideal relativistic quantum fluid: A perturbative study
• Is an Ultra-Cold Strongly Interacting Fermi Gas a Perfect Fluid?
• The first order hydrodynamics via AdS/CFT correspondence in the Gauss-Bonnet gravity
• Transport Coefficients from Extremal Gauss-Bonnet Black Holes
• Temperature Effect on Shear and Bulk Viscosities of QCD Matter
• How Perfect a Gluon Plasma Can Be in Perturbative QCD?
• Universal relations of transport coefficients from holography
• On the violation of the holographic viscosity versus entropy KSS bound in non relativistic systems
• Viscosity bound for anisotropic superfluids in higher derivative gravity
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• Chiral restoration effects on the shear viscosity of a pion gas
• Dissipative Properties and Isothermal Compressibility of Hot and Dense Hadron Gas using Non-extensive Statistics
• Shear Viscosities from Kubo Formalism in a large-$N_{\mathrm{c}}$ Nambu--Jona-Lasinio Model
• $\eta /s$ at finite coupling
• Shear viscosity and Strong-Coupling Corrections in the BCS-BEC crossover Regime of an Ultracold Fermi Gas
• Shear viscosity of strongly interacting fermionic quantum fluids
• Nuclear and Quark Matter at High Temperature
• One-loop corrections to $\eta /s$ in AdS${}_4$/CFT${}_3$
• Ratio of viscosity to entropy density in a strongly coupled one-component plasma
• Viscosity for Anisotropic Reissner Nordström Blackbranes
• Gravity/Fluid Correspondence and Its Application on Bulk Gravity with $U(1)$ Gauge Field
• Shear viscosity over entropy density ratio with extended quasi-particles
• Shear Viscosity in Weakly Coupled N-Component Scalar Field Theories
• Kovtun-Son-Starinets Conjecture and Effects of Mass Imbalance in the Normal State of an Ultracold Fermi Gas in the BCS-BEC Crossover Region
• Gauge-String Dualities and Some Applications
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• Resurrecting the Strong KSS Conjecture