# Xiao Liu - University of Chinese Academy of Sciences, Beijng

## Contact Details

NameXiao Liu |
||

AffiliationUniversity of Chinese Academy of Sciences, Beijng |
||

CityBeijing |
||

CountryChina |
||

## Pubs By Year |
||

## Pub CategoriesPhysics - Optics (10) High Energy Physics - Phenomenology (8) Computer Science - Computer Vision and Pattern Recognition (6) Solar and Stellar Astrophysics (5) Astrophysics of Galaxies (4) Nuclear Theory (4) Quantum Physics (3) Mathematics - Information Theory (3) Computer Science - Information Theory (3) High Energy Physics - Experiment (3) Nuclear Experiment (2) Statistics - Methodology (2) Mathematics - Optimization and Control (2) Statistics - Applications (2) Computer Science - Learning (2) Computer Science - Networking and Internet Architecture (2) Physics - Mesoscopic Systems and Quantum Hall Effect (2) High Energy Physics - Theory (1) Instrumentation and Methods for Astrophysics (1) Computer Science - Data Structures and Algorithms (1) Cosmology and Nongalactic Astrophysics (1) Statistics - Machine Learning (1) Quantitative Biology - Neurons and Cognition (1) Physics - Biological Physics (1) Computer Science - Cryptography and Security (1) General Relativity and Quantum Cosmology (1) Computer Science - Distributed; Parallel; and Cluster Computing (1) Mathematics - Algebraic Geometry (1) Mathematical Physics (1) Mathematics - Mathematical Physics (1) Computer Science - Computation and Language (1) Computer Science - Neural and Evolutionary Computing (1) Computer Science - Information Retrieval (1) Physics - Physics and Society (1) Physics - Other (1) |

## Publications Authored By Xiao Liu

We investigate the process $B_c^+\to B_s^0\pi^+\pi^0$ via $B\bar{K}^*$ rescattering. The kinematic conditions for triangle singularities are perfectly satisfied in the rescattering diagrams. A resonance-like structure around the $B\bar{K}$ threshold, which we denote as $X(5777)$, is predicted to be present in the invariant mass distribution of $B_s^0 \pi^+$. Read More

Sparse coding (SC) is an automatic feature extraction and selection technique that is widely used in unsupervised learning. However, conventional SC vectorizes the input images, which breaks apart the local proximity of pixels and destructs the elementary object structures of images. In this paper, we propose a novel two-dimensional sparse coding (2DSC) scheme that represents the input images as the tensor-linear combinations under a novel algebraic framework. Read More

Sparse coding (SC) is an unsupervised learning scheme that has received an increasing amount of interests in recent years. However, conventional SC vectorizes the input images, which destructs the intrinsic spatial structures of the images. In this paper, we propose a novel graph regularized tensor sparse coding (GTSC) for image representation. Read More

The search engine is tightly coupled with social networks and is primarily designed for users to acquire interested information. Specifically, the search engine assists the information dissemination for social networks, i.e. Read More

Sometimes the early star formation can be found in cold and dense molecular clouds, such as infrared dark cloud (IRDC). Considering star formation often occurs in clustered condition, HII regions may be triggering a new generation of star formation, so we can search for initial stage of massive star formation around HII regions. Based on that above, this work is to introduce one method of how to search for initial stage of massive star formation around HII regions. Read More

We present a sample of quasars discovered in the area of Galactic Anti-Center (GAC) of $150^{\circ} \leq l \leq 210^{\circ}$ and $|b| \leq 30^{\circ}$, based on the LAMOST Data Release 3 (DR3). The sample contains 151 spectroscopically confirmed quasars. Among them 80 are newly discovered with the LAMOST. Read More

Can one hear the shape of a drum? was proposed by Kac in 1966. The simple answer is NO as shown through the construction of iso-spectral domains. There already exists 17 families of planar domains which are non-isometric but display the same spectra of frequencies. Read More

The construction of large-scale quantum networks relies on the development of practical quantum repeaters. Many approaches have been proposed with the goal of outperforming the direct transmission of photons, but most of them are inefficient or difficult to implement with current technology. Here, we present a protocol that uses a semi-hierarchical structure to improve the entanglement distribution rate while reducing the requirement of memory time to a range of tens of milliseconds. Read More

From biosystem to complex system,the study of life is always an important area. Inspired by hyper-cycle theory about the evolution of non-life system, we study the metabolism, self-replication and mutation behavior in the Internet based on node entity, connection relationship and function subgraph--motif--of network topology. Firstly a framework of complex network evolution is proposed to analyze the birth and death phenomena of Internet topology from January 1998 to August 2013. Read More

The low temperature properties of glass are distinct from those of crystals due to the presence of poorly understood low-energy excitations. The tunneling model proposes that these are atoms tunneling between nearby equilibria, forming tunneling two level systems (TLSs). This model is rather successful, but it does not explain the remarkably universal value of the mechanical dissipation $Q^{-1}$ near 1 kelvin. Read More

The low-tubal-rank tensor model has been recently proposed for real-world multidimensional data. In this paper, we study the low-tubal-rank tensor completion problem, i.e. Read More

Weather radar echoes, correlated in both space and time, are the most important input data for short-term precipitation forecast. Motivated by real datasets, this paper is concerned with the spatio-temporal modeling of two-dimensional radar reflectivity fields from a sequence of radar images. Under a Lagrangian integration scheme, we model the radar reflectivity data by a spatio-temporal conditional autoregressive process which is driven by two hidden sub-processes. Read More

This paper investigates the modeling of an important class of degradation data, which are collected from a spatial domain over time; for example, the surface quality degradation. Like many existing time-dependent stochastic degradation models, a special random field is constructed for modeling the spatio-temporal degradation process. In particular, we express the degradation at any spatial location and time as an additive superposition of two stochastic components: a dynamic spatial degradation generation process, and a spatio-temporal degradation propagation process. Read More

We quantify the dependence of the single-shot ablation threshold on the angle of incidence and polarization of a femtosecond laser beam, for three dissimilar solid-state materials: a metal, a dielectric and a semiconductor. Using the constant, linear value of the index of refraction, we calculate the laser fluence transmitted through the air-material interface at the point of ablation threshold. We show that, in spite of the highly nonlinear ionization dynamics involved in the ablation process, the so defined transmitted threshold fluence is universally independent of the angle of incidence and polarization of the laser beam for all three material types. Read More

We investigate the possible rescattering effects which may contribute to the process $B^+\to J/\psi\phi K^+$. It is shown that the $D_{s}^{*+}D_{s}^-$ rescattering via the open-charmed meson loops, and $\psi^\prime \phi$ rescattering via the $\psi^\prime K_1$ loops may simulate the structures of $X(4140)$ and $X(4700)$, respectively. However, if the quantum numbers of $X(4274)$ ($X(4500)$) are $1^{++}$ ($0^{++}$), it is hard to to ascribe the observation of $X(4274)$ and $X(4500)$ to the $P$-wave threshold rescattering effects, which implies that $X(4274)$ and $X(4500)$ could be genuine resonances. Read More

A key challenge in fine-grained recognition is how to find and represent discriminative local regions. Recent attention models are capable of learning discriminative region localizers only from category labels with reinforcement learning. However, not utilizing any explicit part information, they are not able to accurately find multiple distinctive regions. Read More

The modular invariants of a family of semistable curves are the degrees of the corresponding divisors on the image of the moduli map. The singularity indices were introduced by G. Xiao to classify singular fibers of hyperelliptic fibrations and to compute global invariants locally. Read More

This paper introduces the visually informed embedding of word (VIEW), a continuous vector representation for a word extracted from a deep neural model trained using the Microsoft COCO data set to forecast the spatial arrangements between visual objects, given a textual description. The model is composed of a deep multilayer perceptron (MLP) stacked on the top of a Long Short Term Memory (LSTM) network, the latter being preceded by an embedding layer. The VIEW is applied to transferring multimodal background knowledge to Spatial Role Labeling (SpRL) algorithms, which recognize spatial relations between objects mentioned in the text. Read More

We study the polyhedral structure of the static probabilistic lot-sizing problem and propose valid inequalities that integrate information from the chance constraint and the binary setup variables. We prove that the proposed inequalities subsume existing inequalities for this problem, and they are facet-defining under certain conditions. In addition, we show that they give the convex hull description of a related stochastic lot-sizing problem. Read More

Fine-grained recognition is challenging due to its subtle local inter-class differences versus large intra-class variations such as poses. A key to address this problem is to localize discriminative parts to extract pose-invariant features. However, ground-truth part annotations can be expensive to acquire. Read More

We investigate the invariant mass distributions of $B_s\pi$ via different rescattering processes. Because the triangle singularity (TS) could be present for a very broad incident energy region, it can be expected that the TS peaks may simulate the resonance-like bump $X(5568)$ observed by the D0 collaboration. The highly process-dependent characteristic of TS mechanism offers a criterion to distinguish it from other dynamic mechanisms. Read More

We investigate the reaction $\pi^- p \to \pi^- J/\psi p$ via the open-charm hadron rescattering diagrams. Due to the presence of the triangle singularity (TS) in the rescattering amplitudes, the TS peaks can simulate the pentaquark-like resonances arising in the $J/\psi p$ invariant mass distributions, which may bring ambiguities on our understanding of the nature of the exotic states. Searching for the heavy pentaquark in different processes may help us to clarify the ambiguities, because of the highly process-dependent characteristic of the TS mechanism. Read More

We performed a multiwavelength study toward infrared dark cloud (IRDC) G34.43+0.24. Read More

Within the Dyson-Schwinger equations (DSEs) framework, a gluon propagator model incorporating quark's feedback through operator product expansion (OPE) is introduced to investigate the QCD phase diagram in the temperature--chemical-potential ($T-\mu$) plane. Partial restoration of chiral symmetry at zero temperature and finite temperature are both studied, suggesting a first order phase transition point on the $\mu$ axis and a critical end point at $(T_E,\mu_E)/T_c = (0.85,1. Read More

Cloud computing provides scientists a platform that can deploy computation and data intensive applications without infrastructure investment. With excessive cloud resources and a decision support system, large generated data sets can be flexibly 1 stored locally in the current cloud, 2 deleted and regenerated whenever reused or 3 transferred to cheaper cloud service for storage. However, due to the pay for use model, the total application cost largely depends on the usage of computation, storage and bandwidth resources, hence cutting the cost of cloud based data storage becomes a big concern for deploying scientific applications in the cloud. Read More

**Category:**Physics - Optics

In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed into the appropriate band gaps structures by the two-dimensional function photonic crystals. Read More

We investigate the processes $e^+e^-$$\to$$\gamma J/\psi\phi$, $\gamma J/\psi\omega$ and $\pi^0 J/\psi\eta$ to search for the charmnium-like states with hidden $s\bar{s}$, such as $Y(4140)$, $Y(4274)$, $X(4350)$ and $X(3915)$. These processes will receive contributions from the charmed-strange meson rescatterings. When the center-of-mass energies of the $e^+e^-$ scatterings are taken around the $D_{s0}(2317)D_s^{*}$, $D_{s1}(2460)D_s$ or $D_{s1}(2460)D_s^{*}$ threshold, the anomalous triangle singularities can be present in the rescattering amplitudes, which implies a non-resonance explanation about the resonance-like structures. Read More

Discovery of novel topological orders of condensed matters is of a significant interest in both fundamental and applied physics due to the associated quantum conductance behaviors and unique symmetry-protected backscattering-immune propagation against defects, which inspired similar fantastic effects in classical waves system, leading to the revolution of the manipulation of wave propagation. To date, however, only few theoretical models were proposed to realize acoustic topological states. Here, we theoretically and experimentally demonstrate a two dimensional acoustic topological insulators with acoustic analogue of quantum spin Hall Effect. Read More

Recently, a suspicion arose that the free electrons in planetary nebulae (PNe) and HII regions might have non-thermal energy distributions. In this scenario, a kappa index is introduced to characterize the electron energy distributions, with smaller kappa values indicating larger deviations from Maxwell-Boltzmann distributions. Assuming that this is the case, we determine the kappa values for a sample of PNe and HII regions by comparing the intensities of [OIII] collisionally excited lines and the hydrogen Balmer jump. Read More

**Category:**Physics - Optics

Under the action of pump light, the conventional photonic crystal can be turned into function photonic crystal. In the paper, we have designed optical triode with one-dimensional function photonic crystal, and analyzed the effect of period number, medium thickness and refractive index, incident angle, the irradiation way and intensity of pump light on the optical triode magnification. We obtain some valuable results, which shall help to optimal design optical triode. Read More

Asteroseismology allows for deriving precise values of surface gravity of stars. The accurate asteroseismic determinations now available for large number of stars in the Kepler fields can be used to check and calibrate surface gravities that are currently being obtained spectroscopically for a huge numbers of stars targeted by large-scale spectroscopic surveys, such as the on-going Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Galactic survey. The LAMOST spectral surveys have obtained a large number of stellar spectra in the Kepler fields. Read More

In collaborative recommendation systems, privacy may be compromised, as users' opinions are used to generate recommendations for others. In this paper, we consider an online collaborative recommendation system, and we measure users' privacy in terms of the standard differential privacy. We give the first quantitative analysis of the trade-offs between recommendation quality and users' privacy in such a system by showing a lower bound on the best achievable privacy for any non-trivial algorithm, and proposing a near-optimal algorithm. Read More

Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by Duan-Lukin-Cirac-Zoller protocol, many improved quantum-repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multi-photons (multi-photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Read More

The arrangement of the fiber positioning units in LAMOST focal plane may lead to the collisions during the fiber allocation. To avoid these collisions, the soft protection system has to abandon some targets located in the overlapped field of the adjacent fiber units. In this paper, we firstly analyzed the probability of the collisions between fibers and inferred their possible reasons. Read More

**Affiliations:**

^{1}YNAO,

^{2}PKU,

^{3}YNAO,

^{4}PKU, KIAA,

^{5}YNAO

**Category:**Astrophysics of Galaxies

The study of kiloparsec-scale dual active galactic nuclei (AGN) will provide important clues to understand the co-evolution between the host galaxies and their central supermassive black holes undergoing a merging process. We present long-slit spectroscopy of the J0038$+$4128, a kiloparsec-scale dual AGN candidate discovered by Huang et al. recently, using the Yunnan Faint Object Spectrograph and Camera (YFOSC) mounted on Li-Jiang 2. Read More

We compute the $N=2$ R\'enyi entanglement entropy of two intervals at equal time in a circle, for the theory of a 2d compact complex free scalar at finite temperature. This is carried out by performing functional integral on a genus 3 ramified cover of the torus, wherein the quantum part of the integral is captured by the four point function of twist fields on the worldsheet torus, and the classical piece is given by summing over winding modes of the genus 3 surface onto the target space torus. The final result is given in terms of a product of theta function and certain multi-dimensional theta function. Read More

The quantum entangled degrees of entangled states become smaller with the transmission distance increasing, how to keep the purity of quantum entangled states is the puzzle in quantum communication. In the paper, we have designed a new type entanglement degrees amplifier by one-dimensional photonic crystal, which is similar as the relay station of classical electromagnetic communication. We find when the entangled states of two-photon and three-photon pass through photonic crystal, their entanglement degrees can be magnified, which make the entanglement states can be long range propagation and the quantum communication can be really realized. Read More

In this paper, we have proposed the compound structure of one-dimensional photonic crystal (PC), which includes series connection and parallel connection PC. We have studied the transmission characteristics of series connection and parallel connection PC, and obtained some new results. In addition, we have proved the series connection one-dimensional PC can realize the logical AND operation, and the parallel connection one-dimensional PC can realize the logical OR operation. Read More

In this paper, we have proposed a new compound structure one-dimensional photonic crystal, which include series connection, parallel connection and positive and negative feedback compound structure photonic crystal. We have studied their transmission characteristics and obtained some new results, which should be help to design new type optical devices, such as optical amplifier, photonic crystal laser and so on. Read More

Existing deep convolutional neural networks (CNNs) have shown their great success on image classification. CNNs mainly consist of convolutional and pooling layers, both of which are performed on local image areas without considering the dependencies among different image regions. However, such dependencies are very important for generating explicit image representation. Read More

Wireless sensor networks are widely adopted in military, civilian and commercial applications, which fuels an exponential explosion of sensory data. However, a major challenge to deploy effective sensing systems is the presence of {\em massive missing entries, measurement noise, and anomaly readings}. Existing works assume that sensory data matrices have low-rank structures. Read More

Relic gravitational waves (RGWs) generated in the early Universe form a stochastic GW background, which can be directly probed by measuring the timing residuals of millisecond pulsars. In this paper, we investigate the constraints on the RGWs and on the inflationary parameters by the observations of current and potential future pulsar timing arrays. In particular, we focus on effects of various cosmic phase transitions (e. Read More

In this paper we introduce an equation of state (EOS) of quark matter within the framework of Dyson-Schwinger equations (DSEs) to study the structure of compact stars. The smooth crossover from hadronic matter to quark matter in the hybrid star is studied. We compare different strategies to obtain crossover EOSs and find a new way to construct two-solar-mass hybrid stars with even a relatively soft quark EOS, while earlier works show that the quark EOS should be stiff enough to support a massive hybrid star. Read More

**Affiliations:**

^{1}Peking University

**Category:**Solar and Stellar Astrophysics

We present empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs of luminosity classes IV and V and for giants of luminosity classes II and III, based on a collection from the literature of about two hundred nearby stars with direct effective temperature measurements of better than 2.5 per cent. The calibrations are valid for an effective temperature range 3,100 - 10,000 K for dwarfs of spectral types M5 to A0 and 3,100 - 5,700 K for giants of spectral types K5 to G5. Read More

In this paper, we have firstly proposed a new one-dimensional varied-time photonic crystals, i.e., the refractive indices of media $A$ and $B$ are the time functions. Read More

**Category:**Physics - Optics

In this paper, we have firstly proposed a new one-dimensional variable frequency photonic crystals (VFPCs), and calculated the transmissivity and the electronic field distribution of VFPCs with and without defect layer, and considered the effect of defect layer and variable frequency function on the transmissivity and the electronic field distribution. We have obtained some new characteristics for the VFPCs, which should be help to design a new type optical devices. Read More

In this paper, we have studied the quantum transmission characteristics of one-dimensional photonic crystal with and without defect layer by the quantum theory approach, and compared the calculation results of classical with quantum theory. We have found some new quantum effects in the one-dimensional photonic crystal. When the incident angle $\theta=0$, there is no quantum effect. Read More

Indoor localization is a supporting technology for a broadening range of pervasive wireless applications. One promis- ing approach is to locate users with radio frequency fingerprints. However, its wide adoption in real-world systems is challenged by the time- and manpower-consuming site survey process, which builds a fingerprint database a priori for localization. Read More

We propose to study the pentaquark candidates of $P_c^+(4380)$ and $P_c^+(4450)$ in $J/\psi$ photoproduction and look for further experimental evidence for their nature. Since the photoproduction process does not satisfy the so-called "anomalous triangle singularity" condition their presence in $J/\psi$ photoproduction would conclude that they should be genuine states and provide further evidence for their existence. Read More

Recent experimental and theoretical studies show that energy efficiency, which measures the amount of information processed by a neuron with per unit of energy consumption, plays an important role in the evolution of neural systems. Here, we calculated the information rates and energy efficiencies of the Hodgkin-Huxley (HH) neuron model at different temperatures in a noisy environment. We found that both the information rate and energy efficiency are maximized by certain temperatures. Read More