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Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Xian Z.,CAS Institute of High Energy Physics | Zhou Z.,CAS Institute of High Energy Physics
Journal of High Energy Physics | Year: 2016

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. We find the exponent κ can be greater than two such that the new bound for viscosity raised in [7] 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. © 2016, The Author(s).


Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Ling Y.,University of Chinese Academy of Sciences | Xian Z.,CAS Institute of High Energy Physics | Zhou Z.,CAS Institute of High Energy Physics
Chinese Physics C | Year: 2017

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 verified numerically at low temperature T, namely, η/s ∼ T κ, where the values of exponent κ coincide with the analytical results. We also find that the exponent κ is not affected by irrelevant current, but is reduced by the relevant current. © Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.


Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Ling Y.,University of Chinese Academy of Sciences | Liu P.,CAS Institute of High Energy Physics | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

In this note we remark that the butterfly effect can be used to diagnose the phase transition of superconductivity in a holographic framework. Specifically, we compute the butterfly velocity in a charged black hole background as well as anisotropic backgrounds with Q-lattice structure. In both cases we find its derivative to the temperature is discontinuous at critical points. We also propose that the butterfly velocity can signalize the occurrence of thermal phase transition in general holographic models. © 2017 The Authors


Zhang J.,Shanghai University | Jiang Y.,Shanghai University | Jiang Y.,Shanghai Key Laboratory of High Temperature Superconductors | Jiang Y.,Key Laboratory for Astrophysics
Laser Physics | Year: 2016

By treating the hopping parameter as a perturbation, with the help of cumulant expansion and the re-summing technique, the one-particle Green's function of a spin-1 Bose system in a honeycomb optical lattice is calculated analytically. By the use of the re-summed Green's function, the quantum phase diagrams of the system in ferromagnetic cases as well as in antiferromagnetic cases are determined. It is found that in antiferromagnetic cases the Mott insulating states with even filling factor are more robust against the hopping parameter than that with odd filling factor, in agreement with results via other different approaches. Moreover, in order to illustrate the effectiveness of the re-summed Green's function method in calculating time-of-flight pictures, the momentum distribution function of a honeycomb lattice spin-1 Bose system in the antiferromagnetic case is also calculated analytically and the corresponding time-of-flight absorption pictures are plotted. © 2016 Astro Ltd.


Lan S.,Beijing Normal University | Tian Y.,University of Chinese Academy of Sciences | Tian Y.,Shanghai Key Laboratory of High Temperature Superconductors | Zhang H.,Beijing Normal University | Zhang H.,Vrije Universiteit Brussel
Journal of High Energy Physics | Year: 2016

Abstract: Motivated by the various indications that holographic superfluid is BCS like at the standard quantization but BEC like at the alternative quantization, we have implemented the alternative quantization in the dynamical holographic superfluid for the first time. With this accomplishment, we further initiate the detailed investigation of quantum turbulence in finite temperature BEC by a long time stable numerical simulation of bulk dynamics, which includes the two body decay of vortex number caused by vortex pair annihilation, the onset of superfluid turbulence signaled by Kolmogorov scaling law, and a direct energy cascade demonstrated by injecting energy to the turbulent superfluid. All of these results share the same patterns as the holographic superfluid at the standard quantization, thus suggest that these should be universal features for quantum turbulence at temperatures order of the critical temperature. © 2016, The Author(s).


Cui X.,Shanghai University | Feng Z.,Shanghai University | Feng Z.,Shanghai Key Laboratory of High Temperature Superconductors | Jin Y.,Shanghai University | And 7 more authors.
Journal of Applied Crystallography | Year: 2015

AutoFP, a highly automated software toolkit, has been developed to improve the extent of automation of the widely used Rietveld refinement program FullProf [Rodríguez-Carvajal (1993). Physica B, 192, 55-69]. An expert system algorithm is used as the control layer to simulate the manual process when FullProf is used to perform Rietveld refinement. This enables the program to complete the Rietveld refinement highly automatically. It is shown that the expert system algorithm is a good choice for automating Rietveld refinement. The programming interface is available for advanced users to implement their own acquired experience of refinement or add new Rietveld refinement engines to AutoFP. AutoFP can be also used as an automated Rietveld refinement engine by other programs. AutoFP is an open-source software package developed in Python, and it is user friendly, easy to learn and easy to use. © 2015 International Union of Crystallography.


Guo M.,Beijing Normal University | Lan S.,Beijing Normal University | Niu C.,Gwangju Institute of Science and Technology | Tian Y.,University of Chinese Academy of Sciences | And 3 more authors.
Classical and Quantum Gravity | Year: 2016

In this note, we have addressed various issues on zero temperature holographic superfluids. First, inspired by our numerical evidence for the equality between the superfluid density and particle density, we provide an elegant analytic proof for this equality by a boost trick. Second, using not only the frequency domain analysis but also the time domain analysis from numerical relativity, we identify the hydrodynamic normal modes and calculate out the sound speed, which is shown to increase with the chemical potential and saturate to the value predicted by the conformal field theory in the large chemical potential limit. Third, the generic non-thermalization is demonstrated by the fully nonlinear time evolution from a non-equilibrium state for our zero temperature holographic superfluid. Furthermore, a conserved Noether charge is proposed in support of this behavior. © 2016 IOP Publishing Ltd.


Xia H.,Shanghai University | Xia H.,Shanghai Key Laboratory of High Temperature Superconductors | Chen J.,Shanghai University | Chen J.,Shanghai Key Laboratory of High Temperature Superconductors | And 3 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

The Doppler effect is a fundamental physical phenomenon observed for waves propagating in vacuum or various media, commonly gaseous or liquid. Here, we report on the occurrence of a Doppler effect in a solid medium. Instead of a real object, a topological soliton, i.e., a magnetic domain wall (DW) traveling in a current-carrying ferromagnetic nanowire, plays the role of the moving wave source. The Larmor precession of the DW in an external field stimulates emission of monochromatic spin waves (SWs) during its motion, which show a significant Doppler effect, comparable to the acoustic one of a train whistle. This process involves two prominent spin-transfer-torque effects simultaneously, the current-driven DW motion and the current-induced SW Doppler shift. The latter gives rise to an interesting feature, i.e., the observed SW Doppler effect appears resulting from a stationary source and a moving observer, contrary to the laboratory frame. © 2016 American Physical Society.


Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Liu P.,CAS Institute of High Energy Physics | Wu J.-P.,Bohai University | Wu J.-P.,Shanghai Key Laboratory of High Temperature Superconductors
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

The entanglement exhibits extremal or singular behavior near quantum critical points (QCPs) in many condensed matter models. These intriguing phenomena, however, still call for a widely accepted understanding. In this paper we study this issue in holographic framework. We investigate the connection between the holographic entanglement entropy (HEE) and the quantum phase transition (QPT) in a lattice-deformed Einstein-Maxwell-Dilaton theory. Novel backgrounds exhibiting metal-insulator transitions (MIT) have been constructed in which both metallic phase and insulating phase have vanishing entropy density in zero temperature limit. We find that the first order derivative of HEE with respect to lattice parameters exhibits extremal behavior near QCPs. We propose that it would be a universal feature that HEE or its derivatives with respect to system parameters can characterize QPT in a generic holographic system. Our work opens a window for understanding the relation between entanglement and the QPT from a holographic perspective. © 2016 American Physical Society.


Wu J.-P.,Bohai University | Wu J.-P.,Shanghai Key Laboratory of High Temperature Superconductors
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

In this letter, we systematically explore the holographic (non-)relativistic fermionic spectrum without/with dipole coupling dual to Born-Infeld anti-de Sitter (BI-AdS) black hole. For the relativistic fermionic fixed point, this holographic fermionic system exhibits non-Fermi liquid behavior. Also, with the increase of BI parameter γ, the non-Fermi liquid becomes even "more non-Fermi". When the dipole coupling term is included, we find that the BI term makes it a lot tougher to form the gap. While for the non-relativistic fermionic system with large dipole coupling in BI-AdS background, with the increase of BI parameter, the gap comes into being again. © 2016 The Author.

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