The Shear Viscosity in Anisotropic Phases

Jain, Sandeep; Samanta, Rickmoy; Trivedi, Sandip P.

doi:10.48550/arxiv.1506.01899

Cited by 15 publications

(27 citation statements)

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“…For instance, the anisotropic shear viscosity η /s ≤ η ⊥ /s = 1/4π always decreases as the magnitude of the source of anisotropy (a magnetic field or a nontrivial bulk axion profile) increases; indeed, this is the main topic of Ref. [157]. On the other hand, the anisotropic drag force in the transverse plane is larger than in the direction of the magnetic field, which is the opposite behavior found in the Einstein-axion-dilaton model for an axion driven anisotropy 36 [131].…”

Section: Discussionmentioning

confidence: 99%

Momentum transport in strongly coupled anisotropic plasmas in the presence of strong magnetic fields

et al. 2016

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We present a holographic perspective on momentum transport in strongly coupled, anisotropic non-Abelian plasmas in the presence of strong magnetic fields. We compute the anisotropic heavy quark drag forces and Langevin diffusion coefficients and also the anisotropic shear viscosities for two different holographic models, namely, a top-down deformation of strongly coupled N = 4Super-Yang-Mills (SYM) theory triggered by an external Abelian magnetic field, and a bottomup Einstein-Maxwell-dilaton (EMD) model which is able to provide a quantitative description of lattice QCD thermodynamics with (2 + 1)-flavors at both zero and nonzero magnetic fields. We find that, in general, energy loss and momentum diffusion through strongly coupled anisotropic plasmas are enhanced by a magnetic field being larger in transverse directions than in the direction parallel to the magnetic field. Moreover, the anisotropic shear viscosity coefficient is smaller in the direction of the magnetic field than in the plane perpendicular to the field, which indicates that strongly coupled anisotropic plasmas become closer to the perfect fluid limit along the magnetic field. We also present, in the context of the EMD model, holographic predictions for the entropy density and the crossover critical temperature in a wider region of the (T, B) phase diagram thathas not yet been covered by lattice simulations. Our results for the transport coefficients in the phenomenologically realistic magnetic EMD model could be readily used as inputs in numerical codes for magnetohydrodynamics.

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Section: Discussionmentioning

confidence: 99%

Momentum transport in strongly coupled anisotropic plasmas in the presence of strong magnetic fields

et al. 2016

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“…From the Kaluza-Klein reduction, we know that the offdiagonal components of the metric, whose perturbations carry spin 1, induce gauge fields in the dimensionally reduced theory. Jain et al argued that the conductivity of these gauge fields, is proportional to the spin-1 viscosity components η xiz,xiz [12], which motivates us to conjecture that the dc electrical conductivities obeys a universal lower bound in anisotropic systems.…”

Section: Examplesmentioning

confidence: 99%

“…We thus have shear viscosities η xiz,xiz , which are defined by the metric fluctuations h xiz . Such metric components carry spin 1 with respect to the SO(d − 2) symmetries [12]. Although the spin-2 components of the shear viscosity tensor in the x i − x j plane satisfy the KSS bound, the shear force in the x i − z plane, which is related to the spin-1 metric components, can violates it.…”

Section: Introductionmentioning

confidence: 99%

Universality of DC electrical conductivity from holography

Sin

2017

Physics Letters B

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We propose a universal formula of dc electrical conductivity in rotational-and translationalsymmetries breaking systems via the holographic duality. This formula states that the ratio of the determinant of the dc electrical conductivities along any spatial directions to the black hole area density in zero-charge limit has a universal value. As explicit illustrations, we give several examples elucidating the validation of this formula: We construct an anisotropic black brane solution, which yields linear in temperature for the in-plane resistivity and insulating behavior for the out-of-plane resistivity; We also construct a spatially isotropic black brane solution that both the linear-T and quadratic-T contributions to the resistivity can be realized.

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“…[8] additionally hold the point of view that the viscoelastic nature of the mechanical response in materials as the physical reason is responsible for the bound violation. Different from the slight violation caused by higher derivative gravity, great impact can result from anisotropic models for strongly coupled N = 4 Super-Yang-Mills plasma derived from type-IIB supergravity as another example in Einstein gravity [22][23][24][25][26][27][28], whose anisotropic background is based on the solution given and analyzed in [29] and [30]. Ref.…”

Section: Introductionmentioning

confidence: 99%

Shear viscosity to entropy density ratio in higher derivative gravity with momentum dissipation

Wang

2016

Phys. Rev. D

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We investigate η/s in linear scalar fields modified Gauss-Bonnet theory that breaks translation invariance. We first calculate η/s both analytically and numerically and show its relationship with temperature in log-log plot. Our results show that η/s ∼ T 2 at low temperatures. The causality is also considered in this work. We then find that causality violation still happens in the presence of the linear scalar field and we suggest there is a Gauss-Bonnet coupling dependent lower limit for the effective mass of the graviton. If the effective mass of the graviton is big enough, then there will be no causality violation and hence no constraints for the Gauss-Bonnet coupling.

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The Shear Viscosity in Anisotropic Phases

Cited by 15 publications

References 0 publications

Momentum transport in strongly coupled anisotropic plasmas in the presence of strong magnetic fields

Momentum transport in strongly coupled anisotropic plasmas in the presence of strong magnetic fields

Universality of DC electrical conductivity from holography

Shear viscosity to entropy density ratio in higher derivative gravity with momentum dissipation

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