分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： We construct charged black hole solutions with hyperscaling violation in the infrared(IR) region in Einstein-Maxwell-Dilaton-Axion theory and investigate the temperature behavior of the ratio of holographic shear viscosity to the entropy density. When translational symmetry breaking is relevant in the IR, the power law of the ratio is testi ed numerically at low temperature T, namely, =s T , where the values of exponent coincide with the analytical results. We also nd that the exponent is not a ected by irrelevant current, but is reduced by the relevant current.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： Recent progress in holographic approach makes it more transparent that each conductivity can be decomposed into the coherent contribution due to momentum relaxation and the incoherent contribution due to intrinsic current relaxation. In this paper we investigate this decomposition in the framework of Einstein-Maxwell-Dilaton theory. We derive the perturbation equations which are decoupled for a large class of background solutions, and then obtain the analytic results of conductivity with slow momentum relaxation in low frequency approximation, which is consistent with the known results from memory matrix techniques.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We investigate the holographic DC and Hall conductivity in massive Einstein-Maxwell-Dilaton (EMD) gravity. Two special EMD backgrounds are considered explicitly. One is dyonic Reissner-Nordstro╩-AdS (RN-AdS) geometry and the other one is hyperscaling violation AdS (HV-AdS) geometry. We find that the linear-T resistivity and quadratic-T inverse Hall angle can be simultaneously achieved in HV-AdS models, providing a hint to construct holographic models confronting with the experimental data of strange metal in future.
分类： 物理学 >> 核物理学 提交时间： 2016-09-06
摘要： We introduce a Weyl term into the Einstein-Maxwell-Axion theory in four dimensional spacetime. Up to the first order of the Weyl coupling parameter γ, we construct charged black brane solutions without translational invariance in a perturbative manner. Among all the holographic frameworks involving higher derivative gravity, we are the first to obtain metal-insulator transitions (MIT) when varying the system parameters at zero temperature. Furthermore, we study the holographic entanglement entropy (HEE) of strip geometry in this model and find that the second order derivative of HEE with respect to the axion parameter exhibits maximization behavior near quantum critical points (QCPs) of MIT. It testifies the conjecture in 1502.03661 and 1604.04857 that HEE itself or its derivatives can be used to diagnose quantum phase transition (QPT).
分类： 物理学 >> 核物理学 提交时间： 2016-09-05
摘要： In this paper we investigate the ratio of shear viscosity to entropy density, η/s, in hyperscaling violating geometry with lattice structure. We show that the scaling relation with hyperscaling violation gives a strong constraint to the mass of graviton and usually leads to a power law of temperature, η/s∼Tκ. Remarkably, we find the exponent κ can be greater than two such that the new bound for viscosity raised inarXiv:1601.02757 is violated. Our above observation is testified by constructing specific solutions with UV completion in various holographic models. Finally, we compare the boundedness of κ with the behavior of entanglement entropy and conjecture a relation between them.
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