Searcharxiv⌕ Search

arXiv subjects

Jin Li

Publications and source records attributed to Jin Li.

At least 307 records · Page 17Linked to original sources
arXiv2015

Nonlinear Electromagnetic Quasinormal Modes and Hawking Radiation of A Regular Black Hole with Magnetic Charge

Based on a regular exact black hole (BH) from nonlinear electrodynamics (NED) coupled to General Relativity, we investigate its stability of such BH through the Quasinormal Modes (QNMs) of electromagnetic (EM) field perturbation and its thermodynamics through Hawking radiation. In perturbation theory, we can deduce the effective potential from nonlinear EM field. The comparison of potential function between regular and RN BHs could predict their similar QNMs. The QNMs frequencies tell us the effect of magnetic charge $q$, overtone $n$, angular momentum number $l$ on the dynamic evolution of NLED EM field. Furthermore we also discuss the cases near extreme condition of such magnetically charged regular BH. The corresponding QNMs spectrum illuminates some special properties in the near-extreme cases. For the thermodynamics, we employ Hamilton-Jacobi method to calculate the near-horizon Hawking temperature of the regular BH and reveal the relationship between classical parameters of black hole and its quantum effect.

gr-qc↗
arXiv2015

Exothermic isospin-violating dark matter after SuperCDMS and CDEX

We show that exothermic isospin-violating dark matter (IVDM) can make the results of the latest CDMS-Si experiment consistent with recent null experiments, such as XENON10, XENON100, LUX, CDEX, and SuperCDMS, whereas for the CoGeNT experiment, a strong tension still persists. For CDMS-Si, separate exothermic dark matter or isospin-violating dark matter cannot fully ameliorate the tensions among these experiments; the tension disappears only if exothermic scattering is combined with an isospin-violating effect of f_n/f_p=-0.7. For such exothermic IVDM to exist, at least a new vector gauge boson (dark photon or dark Z') that connects SM quarks to Majorana-type DM particles is required.

hep-ph↗
arXiv2014

Generalized Hamming Weights of Irreducible Cyclic Codes

The generalized Hamming weight (GHW) $d_r(C)$ of linear codes $C$ is a natural generalization of the minimum Hamming distance $d(C)(=d_1(C))$ and has become one of important research objects in coding theory since Wei's originary work [23] in 1991. In this paper two general formulas on $d_r(C)$ for irreducible cyclic codes are presented by using Gauss sums and the weight hierarchy $\{d_1(C), d_2(C), \ldots, d_k(C)\}$ $(k=\dim C)$ are completely determined for several cases.

cs.IT↗
arXiv2014

Study of the material photon and electron background and the liquid argon detector veto efficiency of the CDEX-10 experiment

The China Dark Matter Experiment (CDEX) is located at the China Jinping underground laboratory (CJPL) and aims to directly detect the WIMP flux with high sensitivity in the low mass region. Here we present a study of the predicted photon and electron backgrounds including the background contribution of the structure materials of the germanium detector, the passive shielding materials, and the intrinsic radioactivity of the liquid argon that serves as an anti-Compton active shielding detector. A detailed geometry is modeled and the background contribution has been simulated based on the measured radioactivities of all possible components within the GEANT4 program. Then the photon and electron background level in the energy region of interest (<10^-2 events kg-1 day-1 keV-1 (cpkkd)) is predicted based on Monte Carlo simulations. The simulated result is consistent with the design goal of CDEX-10 experiment, 0.1 cpkkd, which shows that the active and passive shield design of CDEX-10 is effective and feasible.

physics.ins-det↗
arXiv2014

Lorentz Invariance Violation and Modified Hawking Fermions Tunneling from Black Strings

Recently the modified Dirac equation with Lorentz invariance violation has been proposed, which would be helpful to resolve some issues in quantum gravity theory and high energy physics. In this paper, the modified Dirac equation has been generalized in curved spacetime, and then fermion tunneling of black strings is researched under this correctional Dirac field theory. We also use semi-classical approximation method to get correctional Hamilton-Jacobi equation, so that the correctional Hawking temperature and correctional black hole's entropy are derived.

hep-th↗
arXiv2013

A background simulation method for cosmogenic nuclides inside HPGe detectors for rare event experiments

Cosmogenic nuclides inside germanium detectors contribute background noise spectra quite different from ordinary external sources. We propose and discuss a nuclide decay and level transition model based on graph theory to understand the background contribution of the decay of cosmogenic nuclides inside a germanium crystal. In this work, not only was the level transition process, but the detector response time was also taken into consideration to decide whether or not to apply coincidence summing-up. We simulated the background spectrum of the internal cosmogenic nuclides in a germanium detector, and found some unique phenomena caused by the coincidence summing-up effect in the simulated spectrum. Thus, the background spectrum of each cosmogenic nuclide can be quantitatively obtained.

physics.ins-det↗
arXiv2013

Dirac quasinormal modes in spherically symmetric regular black holes

Using the WKB approximation, massless and massive Dirac quasinormal modes (QNMs) are studied in spherically symmetric regular spacetimes. We analyze the relationships between QNM frequencies and the parameters (angular momentum number $l$, magnetic monopole charge $β$ and the mass of the field $m$), and discuss the extreme charge of magnetic monopole $β_{e}$ for spherically symmetric regular black holes (BHs). Furthermore, we apply an expansion method to expand QNMs in inverse powers of $L=l+1/2$, and confirm good precision with $l>n$. Finally, we improve traditional finite difference method to be available in massive Dirac case, and illuminate the dynamical evolution of massive Dirac field.

gr-qc↗
arXiv2013

Measurement of Cosmic Ray Flux in China JinPing underground Laboratory

China JinPing underground Laboratory (CJPL) is the deepest underground laboratory presently running in the world. In such a deep underground laboratory, the cosmic ray flux is a very important and necessary parameter for rare event experiments. A plastic scintillator telescope system has been set up to measure the cosmic ray flux. The performance of the telescope system has been studied using the cosmic ray on the ground laboratory near CJPL. Based on the underground experimental data taken from November 2010 to December 2011 in CJPL, which has effective live time of 171 days, the cosmic ray muon flux in CJPL is measured to be (2.0+-0.4)*10^(-10)/(cm^2)/(s). The ultra-low cosmic ray background guarantees CJPL's ideal environment for dark matter experiment.

physics.ins-det↗
arXiv2013

The CDEX-1 1 kg Point-Contact Germanium Detector for Low Mass Dark Matter Searches

The CDEX Collaboration has been established for direct detection of light dark matter particles, using ultra-low energy threshold p-type point-contact germanium detectors, in China JinPing underground Laboratory (CJPL). The first 1 kg point-contact germanium detector with a sub-keV energy threshold has been tested in a passive shielding system located in CJPL. The outputs from both the point-contact p+ electrode and the outside n+ electrode make it possible to scan the lower energy range of less than 1 keV and at the same time to detect the higher energy range up to 3 MeV. The outputs from both p+ and n+ electrode may also provide a more powerful method for signal discrimination for dark matter experiment. Some key parameters, including energy resolution, dead time, decay times of internal X-rays, and system stability, have been tested and measured. The results show that the 1 kg point-contact germanium detector, together with its shielding system and electronics, can run smoothly with good performances. This detector system will be deployed for dark matter search experiments.

physics.ins-det↗
arXiv2013

Introduction of the CDEX experiment

Weakly Interacting Massive Particles (WIMPs) are the candidates of dark matter in our universe. Up to now any direct interaction of WIMP with nuclei has not been observed yet. The exclusion limits of the spin-independent cross section of WIMP-nucleon which have been experimentally obtained is about 10^{-7}pb at high mass region and only 10^{-5}pb} at low mass region. China Jin-Ping underground laboratory CJPL is the deepest underground lab in the world and provides a very promising environment for direct observation of dark matter. The China Dark Matter Experiment (CDEX) experiment is going to directly detect the WIMP flux with high sensitivity in the low mass region. Both CJPL and CDEX have achieved a remarkable progress in recent two years. The CDEX employs a point-contact germanium semi-conductor detector PCGe whose detection threshold is less than 300 eV. We report the measurement results of Muon flux, monitoring of radioactivity and Radon concentration carried out in CJPL, as well describe the structure and performance of the 1 kg PCGe detector CDEX-1 and 10kg detector array CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of the CDEX-1, CDEX-10 and the future CDEX-1T detectors.

physics.ins-det↗
arXiv2013

Strain-induced topological insulator phase transition in HgSe

Using ab initio electronic structure calculations we investigate the change of the band structure and the nu_0 topological invariant in HgSe (non-centrosymmetric system) under two different type of uniaxial strain along the [001] and [110] directions, respectively. Both compressive [001] and [110] strain leads to the opening of a (crystal field) band gap (with a maximum value of about 37 meV) in the vicinity of Gamma, and the concomitant formation of a camel-back- (inverse camel-back-) shape valence (conduction) band along the direction perpendicular to the strain with a minimum (maximum) at Gamma. We find that the Z_2 invariant nu_0=1, which demonstrates conclusively that HgSe is a strong topological insulator (TI). With further increase of the strain the band gap decreases vanishing at a critical strain value (which depends on the strain type) where HgSe undergoes a transition from a strong TI to a trivial (normal) insulator. HgSe exhibits a similar behavior under a tensile [110] uniaxial strain. On the other hand, HgSe remains a normal insulator by applying a [001] tensile uniaxial strain. Complementary electronic structure calculations of the non-polar (110) surface under compressive [110] tensile strain show two Dirac cones at the Gamma point whose spin chiral states are associated with the top and bottom slab surfaces.

cond-mat.mtrl-sci↗
arXiv2012

New and conventional bottomonium states

Recent progress on the bottomonium states is reported. This talk briefly reviews the observation of $h_b(1P), h_b(2P), Z_{b1}^+, Z_{b2}^+$ states, transition of $h_b(nP)\to η_b(mS)γ$ and new studies on the $η_b(2S)$ state. Other $η$ and $π^+π^-$ transitions of $Υ(nS)$ are also discussed.

hep-ex↗
arXiv2012

First observation of $B_s^0\to J/ψη$ and $B_s^0\to J/ψη'$

We report first observations of $B_s^0\to J/ψη$ and $B_s^0\to J/ψη'$. The results are obtained from 121.4 fb^{-1} of data collected at the $Υ(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We obtain the branching fractions Br(B_s^0\to J/ψη)= [5.10\pm 0.50(stat.)\pm 0.25(syst.)^{+1.14}_{-0.79}(N_{B_s^(*)\bar B_s^(*))] \times 10^{-4}, and Br(B_s^0\to J/ψη')=[3.71\pm 0.61(stat.)\pm 0.18(syst.)^{+0.83}_{-0.57}(N_{B_s^(*)\bar B_s^(*))] \times 10^{-4}. The ratio of the two branching fractions is measured to be $\frac{Br(B_s\to J/ψη')}{Br(B_s\to J/ψη)} = 0.73\pm 0.14(stat.)\pm 0.02(syst.)$.

hep-ex↗
arXiv2011

Simple Regenerating Codes: Network Coding for Cloud Storage

Network codes designed specifically for distributed storage systems have the potential to provide dramatically higher storage efficiency for the same availability. One main challenge in the design of such codes is the exact repair problem: if a node storing encoded information fails, in order to maintain the same level of reliability we need to create encoded information at a new node. One of the main open problems in this emerging area has been the design of simple coding schemes that allow exact and low cost repair of failed nodes and have high data rates. In particular, all prior known explicit constructions have data rates bounded by 1/2. In this paper we introduce the first family of distributed storage codes that have simple look-up repair and can achieve arbitrarily high rates. Our constructions are very simple to implement and perform exact repair by simple XORing of packets. We experimentally evaluate the proposed codes in a realistic cloud storage simulator and show significant benefits in both performance and reliability compared to replication and standard Reed-Solomon codes.

cs.IT↗
arXiv2011

Dynamics of 2D Stochastic non-Newtonian fluids driven by fractional Brownian motion

A 2D Stochastic incompressible non-Newtonian fluids driven by fractional Bronwnian motion with Hurst parameter $H \in (1/2,1)$ is studied. The Wiener-type stochastic integrals are introduced for infinite-dimensional fractional Brownian motion. Four groups of assumptions, including the requirement of Nuclear operator or Hilbert-Schmidt operator, are discussed. The existence and regularity of stochastic convolution for the corresponding additive linear stochastic equation are obtained under each group of assumptions. Mild solution are then obtained for the non-Newtonian systems by the modified fix point theorem in the selected intersection space. When the domain is square, the random dynamical system generated by non-Newtonian systems has a random attractor under some condition on the spectrum distribution of the corresponding differential operator.

math-ph↗
arXiv2011

Dynamics of stochastic non-Newtonian fluids driven by fractional Brownian motion with Hurst parameter $H \in (1/4,1/2)$

In this paper we consider the Stochastic isothermal, nonlinear, incompressible bipolar viscous fluids driven by a genuine cylindrical fractional Bronwnian motion with Hurst parameter $H \in (1/4,1/2)$ under Dirichlet boundary condition on 2D square domain. First we prove the existence and regularity of the stochastic convolution corresponding to the stochastic non-Newtonian fluids. Then we obtain the existence and uniqueness results for the stochastic non-Newtonian fluids. Under certain condition, the random dynamical system generated by non-Newtonian fluids has a random attractor.

math.DS↗
arXiv2011

Optimal Repair of MDS Codes in Distributed Storage via Subspace Interference Alignment

It is well known that an (n,k) code can be used to store 'k' units of information in 'n' unit-capacity disks of a distributed data storage system. If the code used is maximum distance separable (MDS), then the system can tolerate any (n-k) disk failures, since the original information can be recovered from any k surviving disks. The focus of this paper is the design of a systematic MDS code with the additional property that a single disk failure can be repaired with minimum repair bandwidth, i.e., with the minimum possible amount of data to be downloaded for recovery of the failed disk. Previously, a lower bound of (n-1)/(n-k) units has been established by Dimakis et. al, on the repair bandwidth for a single disk failure in an (n,k) MDS code . Recently, the existence of asymptotic codes achieving this lower bound for arbitrary (n,k) has been established by drawing connections to interference alignment. While the existence of asymptotic constructions achieving this lower bound have been shown, finite code constructions achieving this lower bound existed in previous literature only for the special (high-redundancy) scenario where $k \leq \max(n/2,3)$. The question of existence of finite codes for arbitrary values of (n,k) achieving the lower bound on the repair bandwidth remained open. In this paper, by using permutation coding sub-matrices, we provide the first known finite MDS code which achieves the optimal repair bandwidth of (n-1)/(n-k) for arbitrary (n,k), for recovery of a failed systematic disk. We also generalize our permutation matrix based constructions by developing a novel framework for repair-bandwidth-optimal MDS codes based on the idea of subspace interference alignment - a concept previously introduced by Suh and Tse the context of wireless cellular networks.

cs.IT↗