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Bin Chen

Publications and source records attributed to Bin Chen.

At least 595 records · Page 33Linked to original sources
arXiv2018

Holographic subregion complexity under a thermal quench

We study the evolution of holographic subregion complexity under a thermal quench in this paper. From the subregion CV proposal in the AdS/CFT correspondence, the subregion complexity in the CFT is holographically captured by the volume of the codimension-one surface enclosed by the codimension-two extremal entanglement surface and the boundary subregion. Under a thermal quench, the dual gravitational configuration is described by a Vaidya-AdS spacetime. In this case we find that the holographic subregion complexity always increases at early time, and after reaching a maximum it decreases and gets to saturation. Moreover we notice that when the size of the strip is large enough and the quench is fast enough, in $AdS_{d+1}(d\geq3)$ spacetime the evolution of the complexity is discontinuous and there is a sudden drop due to the transition of the extremal entanglement surface. We discuss the effects of the quench speed, the strip size, the black hole mass and the spacetime dimension on the evolution of the subregion complexity in detail numerically.

hep-th↗
arXiv2018

Entanglement Entropy in $T\overline{T}$-Deformed CFT

In this paper, we study the entanglement entropy of a single interval on a cylinder in two-dimensional $T\overline{T}$-deformed conformal field theory. For such case, the (Rényi) entanglement entropy takes a universal form in a CFT. We compute the correction due to the deformation up to the leading order of the deformation parameter in the framework of the conformal perturbation theory. We find that the correction to the entanglement entropy is nonvanishing in the finite temperature case, while it is vanishing in the finite size case. For the deformed holographic large $c$ CFT, which is proposed to be dual to a AdS$_3$ gravity in a finite region, we find the agreement with the holographic entanglement entropy via the Ryu-Takayanagi formula. Moreover, we compute the leading order correction to the Rényi entropy, and discuss its holographic picture as well.

hep-th↗
arXiv2018

Magnetic Reconnection Null Points as the Origin of Semi-relativistic Electron Beams in a Solar Jet

Magnetic reconnection, the central engine that powers explosive phenomena throughout the Universe, is also perceived as one of the principal mechanisms for accelerating particles to high energies. Although various signatures of magnetic reconnection have been frequently reported, observational evidence that links particle acceleration directly to the reconnection site has been rare, especially for space plasma environments currently inaccessible to $\textit{in situ}$ measurements. Here we utilize broadband radio dynamic imaging spectroscopy available from the Karl G. Jansky Very Large Array to observe decimetric type III radio bursts in a solar jet with high angular ($\sim$20$''$), spectral ($\sim$1 %), and temporal resolution (50 milliseconds). These observations allow us to derive detailed trajectories of semi-relativistic (tens of keV) electron beams in the low solar corona with unprecedentedly high angular precision ($<0''.65$). We found that each group of electron beams, which corresponds to a cluster of type III bursts with 1-2-second duration, diverges from an extremely compact region ($\sim$600 km$^2$) in the low solar corona. The beam-diverging sites are located behind the erupting jet spire and above the closed arcades, coinciding with the presumed location of magnetic reconnection in the jet eruption picture supported by extreme ultraviolet/X-ray data and magnetic modeling. We interpret each beam-diverging site as a reconnection null point where multitudes of magnetic flux tubes join and reconnect. Our data suggest that the null points likely consist of a high level of density inhomogeneities possibly down to 10-km scales. These results, at least in the present case, strongly favor a reconnection-driven electron acceleration scenario.

astro-ph.SR↗
arXiv2018

A Study of Deep Feature Fusion based Methods for Classifying Multi-lead ECG

An automatic classification method has been studied to effectively detect and recognize Electrocardiogram (ECG). Based on the synchronizing and orthogonal relationships of multiple leads, we propose a Multi-branch Convolution and Residual Network (MBCRNet) with three kinds of feature fusion methods for automatic detection of normal and abnormal ECG signals. Experiments are conducted on the Chinese Cardiovascular Disease Database (CCDD). Through 10-fold cross-validation, we achieve an average accuracy of 87.04% and a sensitivity of 89.93%, which outperforms previous methods under the same database. It is also shown that the multi-lead feature fusion network can improve the classification accuracy over the network only with the single lead features.

cs.CV↗
arXiv2018

Broad Non-Gaussian Fe XXIV Line Profiles in the Impulsive Phase of the 2017 September 10 X8.3 class Flare Observed by Hinode/EIS

We analyze the spectra of high temperature \fexxiv~lines observed by \emph{Hinode}/EIS during the impulsive phase of the X8.3--class flare on September 10, 2017. The line profiles are broad, show pronounced wings, and clearly depart from a single Gaussian shape. The lines can be well fitted with $κ$ distributions, with values of $κ$ varying between~$\approx$1.7 to 3. The regions where we observe the non-Gaussian profiles coincide with the location of high-energy ($\approx$100--300 keV) HXR sources observed by \emph{RHESSI}, suggesting the presence of particle acceleration or turbulence, also confirmed by the observations of a non-thermal microwave sources with the \emph{Expanded Owens Valley Solar Array} (EOVSA) at and above the HXR looptop source. We also investigate the effect of taking into account $κ$ distributions in the temperature diagnostics based on the ratio of the \fexxiii~263.76~Å~and \fexxiv~255.1~Å~EIS lines. We found that these lines can be formed at much higher temperatures than expected (up to log($T$\,[K])\,$\approx$\,7.8), if departures from Maxwellian distributions are taken into account. Although larger line widths are expected because of these higher formation temperatures, the observed line widths still imply non-thermal broadening in excess of ~200\,\kps. The non-thermal broadening related to HXR emission is better interpreted by turbulence rather than chromospheric evaporation.

astro-ph.SR↗
arXiv2018

Microwave and Hard X-Ray Observations of the 2017 September 10 Solar Limb Flare

We report the first science results from the newly completed Expanded Owens Valley Solar Array (EOVSA), which obtained excellent microwave imaging spectroscopy observations of SOL2017-09-10, a classic partially-occulted solar limb flare associated with an erupting flux rope. This event is also well-covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in hard X-rays (HXRs). We present an overview of this event focusing on microwave and HXR data, both associated with high-energy nonthermal electrons, and discuss them within the context of the flare geometry and evolution revealed by extreme ultraviolet (EUV) observations from the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory (SDO/AIA). The EOVSA and RHESSI data reveal the evolving spatial and energy distribution of high-energy electrons throughout the entire flaring region. The results suggest that the microwave and HXR sources largely arise from a common nonthermal electron population, although the microwave imaging spectroscopy provides information over a much larger volume of the corona.

astro-ph.SR↗
arXiv2018

Object-Aware Guidance for Autonomous Scene Reconstruction

To carry out autonomous 3D scanning and online reconstruction of unknown indoor scenes, one has to find a balance between global exploration of the entire scene and local scanning of the objects within it. In this work, we propose a novel approach, which provides object-aware guidance for autoscanning, for exploring, reconstructing, and understanding an unknown scene within one navigation pass. Our approach interleaves between object analysis to identify the next best object (NBO) for global exploration, and object-aware information gain analysis to plan the next best view (NBV) for local scanning. First, an objectness-based segmentation method is introduced to extract semantic objects from the current scene surface via a multi-class graph cuts minimization. Then, an object of interest (OOI) is identified as the NBO which the robot aims to visit and scan. The robot then conducts fine scanning on the OOI with views determined by the NBV strategy. When the OOI is recognized as a full object, it can be replaced by its most similar 3D model in a shape database. The algorithm iterates until all of the objects are recognized and reconstructed in the scene. Various experiments and comparisons have shown the feasibility of our proposed approach.

cs.GR↗
arXiv2018

Charge-tuneable biexciton complexes in monolayer WSe$_{2}$

Multi-exciton states such as biexcitons, albeit theoretically predicted, have remained challenging to identify in atomically thin transition metal dichalcogenides so far. Here, we use excitation-power, electric-field and magnetic-field dependence of photoluminescence to report direct experimental evidence of two biexciton complexes in monolayer tungsten diselenide: the neutral and the negatively charged biexciton. We demonstrate bias-controlled switching between these two states, we determine their internal structure and we resolve a fine-structure splitting of 2.5 meV for the neutral biexciton. Our results unveil multi-particle exciton complexes in transition metal dichalcogenides and offer direct routes to their deterministic control in many-body quantum phenomena.

cond-mat.mes-hall↗
arXiv2018

Dynamics of coherence-induced state ordering under Markovian channels

We study the dynamics of coherence-induced state ordering under incoherent channels, particularly four specific Markovian channels: $-$ amplitude damping channel, phase damping channel, depolarizing channel and bit flit channel for single-qubit states. We show that the amplitude damping channel, phase damping channel, and depolarizing channel do not change the coherence-induced state ordering by $l_1$ norm of coherence, relative entropy of coherence, geometric measure of coherence, and Tsallis relative $α$-entropies, while the bit flit channel does change for some special cases.

quant-ph↗
arXiv2018

Einstein-Gauss-Bonnet Black Rings at Large $D$

We study the black ring solution in the Einstein-Gauss-Bonnet (EGB) theory at large $D$. By using the $1/D$ expansion in the near horizon region we derive the effective equations for the slowly rotating black holes in the EGB theory. The effective equations describe the non-linear dynamics of various stationary solutions, including the EGB black ring, the slowly rotating EGB black hole and the slowly boosted EGB black string. By different embeddings we construct these stationary solutions explicitly. By performing the perturbation analysis of the effective equations, we obtain the quasinormal modes of the EGB black ring. We find that thin EGB black ring becomes unstable against non-axisymmetric perturbation.Furthermore, we numerically evolve the effective equations in a particular case to study the final state of the instability, and find that the thin black ring becomes the stable non-uniformblack ring at late time, which gives a relative strong evidence to support the conjecture given in [arXiv:1510.02200].

hep-th↗
arXiv2018

Greybody factors for Spherically Symmetric Einstein-Gauss-Bonnet-de Sitter black hole

We study the greybody factors of the scalar fields in spherically symmetric Einstein-Gauss-Bonnet-de Sitter black holes in higher dimensions. We derive the greybody factors analytically for both minimally and non-minimally coupled scalar fields. Moreover, we discuss the dependence of the greybody factor on various parameters including the angular momentum number, the non-minimally coupling constant, the spacetime dimension, the cosmological constant and the Gauss-Bonnet coefficient in detail. We find that the non-minimal coupling may suppress the Hawking radiation, while the Gauss-Bonnet coupling could enhance the radiation.

hep-th↗
arXiv2018

Holographic Mutual Information of Two Disjoint Spheres

We study quantum corrections to holographic mutual information for two disjoint spheres at a large separation by using the operator product expansion of the twist field. In the large separation limit, the holographic mutual information is vanishing at the semiclassical order, but receive quantum corrections from the fluctuations. We show that the leading contributions from the quantum fluctuations take universal forms as suggested from the boundary CFT. We find the universal behavior for the scalar, the vector, the tensor and the fermionic fields by treating these fields as free fields propagating in the fixed background and by using the 1/n prescription. In particular, for the fields with gauge symmetries, including the massless vector boson and massless graviton, we find that the gauge parts in the propagators play indispensable role in reading the leading order corrections to the bulk mutual information.

hep-th↗
arXiv2018

Holographic Turbulence in Einstein-Gauss-Bonnet Gravity at Large $D$

We study the holographic hydrodynamics in the Einstein-Gauss-Bonnet(EGB) gravity in the framework of the large $D$ expansion. We find that the large $D$ EGB equations can be interpreted as the hydrodynamic equations describing the conformal fluid. These fluid equations are truncated at the second order of the derivative expansion, similar to the Einstein gravity at large $D$. From the analysis of the fluid flows, we find that the fluid equations can be taken as a variant of the compressible version of the non-relativistic Navier-Stokes equations. Particularly, in the limit of small Mach number, these equations could be cast into the form of the incompressible Navier-Stokes equations with redefined Reynolds number and Mach number. By using numerical simulation, we find that the EGB holographic turbulence shares similar qualitative feature as the turbulence from the Einstein gravity, despite the presence of two extra terms in the equations of motion. We analyze the effect of the GB term on the holographic turbulence in detail.

hep-th↗
arXiv2018

Fingerprint template protection using minutia-pair spectral representations

Storage of biometric data requires some form of template protection in order to preserve the privacy of people enrolled in a biometric database. One approach is to use a Helper Data System. Here it is necessary to transform the raw biometric measurement into a fixed-length representation. In this paper we extend the spectral function approach of Stanko and Skoric [WIFS2017], which provides such a fixed-length representation for fingerprints. First, we introduce a new spectral function that captures different information from the minutia orientations. It is complementary to the original spectral function, and we use both of them to extract information from a fingerprint image. Second, we construct a helper data system consisting of zero-leakage quantisation followed by the Code Offset Method. We show empirical data which demonstrates that applying our helper data system causes only a small performance penalty compared to fingerprint authentication based on the unprotected spectral functions.

cs.CR↗
arXiv2018

Notes on modified trace distance measure of coherence

We investigate the modified trace distance measure of coherence recently introduced in [Phys. Rev. A 94, 060302(R) (2016)]. We show that for any single-qubit state, the modified trace norm of coherence is equal to the $l_{1}$-norm of coherence. For any $d$-dimensional quantum system, an analytical formula of this measure for a class of maximally coherent mixed states is provided. The trade-off relation between the coherence quantified by the new measure and the mixedness quantified by the trace norm is also discussed. Furthermore, we explore the relation between the modified trace distance measure of coherence and other measures such as the $l_{1}$-norm of coherence and the geometric measure of coherence.

quant-ph↗
arXiv2018

Ordering states with various coherence measures

Quantum coherence is one of the most significant theories in quantum physics. Ordering states with various coherence measures is an intriguing task in quantification theory of coherence. In this paper, we study this problem by use of four important coherence measures -- the $l_1$ norm of coherence, the relative entropy of coherence, the geometric measure of coherence and the modified trace distance measure of coherence. We show that each pair of these measures give a different ordering of qudit states when $d\geq 3$. However, for single-qubit states, the $l_1$ norm of coherence and the geometric coherence provide the same ordering. We also show that the relative entropy of coherence and the geometric coherence give a different ordering for single-qubit states. Then we partially answer the open question proposed in [Quantum Inf. Process. 15, 4189 (2016)] whether all the coherence measures give a different ordering of states.

quant-ph↗
arXiv2018

Asymmetric Cryptography with Physical Unclonable Keys

Secure communication is of paramount importance in modern society. Asymmetric cryptography methods such as the widely used RSA method allow secure exchange of information between parties who have not shared secret keys. However, the existing asymmetric cryptographic schemes rely on unproven mathematical assumptions for security. Further, the digital keys used in their implementation are susceptible to copying that might remain unnoticed. Here we introduce a secure communication method that overcomes these two limitations by employing Physical Unclonable Keys (PUKs). Using optical PUKs realized in opaque scattering materials and employing off-the-shelf equipment, we transmit messages in an error-corrected way. Information is transmitted as patterned wavefronts of few-photon wavepackets which can be successfully decrypted only with the receiver's PUK. The security of PUK-Enabled Asymmetric Communication (PEAC) is not based on any stored secret but on the hardness of distinguishing between different few-photon wavefronts.

physics.optics↗