arXiv subjects

Jie Wang

Publications and source records attributed to Jie Wang.

At least 631 records · Page 35Linked to original sources

arXiv2016

Toric P-Difference Varieties

In this paper, we introduce the concept of P-difference varieties and study the properties of toric P-difference varieties. Toric P-difference varieties are analogues of toric varieties in difference algebra geometry. The category of affine toric P-difference varieties with toric morphisms is shown to be antiequivalent to the category of affine P[x]-semimodules with P[x]-semimodule morphisms. Moreover, there is a one-to-one correspondence between the irreducible invariant P-difference subvarieties of an affine toric P-difference variety and the faces of the corresponding affine P[x]-semimodule. We also define abstract toric P-difference varieties associated with fans by gluing affine toric P-difference varieties. The irreducible invariant P-difference subvarieties-faces correspondence is generalized to abstract toric P-difference varieties. By virtue of this correspondence, a divisor theory for abstract toric P-difference varieties is developed.

math.RA↗

arXiv2016

Large-scale Collaborative Imaging Genetics Studies of Risk Genetic Factors for Alzheimer's Disease Across Multiple Institutions

Genome-wide association studies (GWAS) offer new opportunities to identify genetic risk factors for Alzheimer's disease (AD). Recently, collaborative efforts across different institutions emerged that enhance the power of many existing techniques on individual institution data. However, a major barrier to collaborative studies of GWAS is that many institutions need to preserve individual data privacy. To address this challenge, we propose a novel distributed framework, termed Local Query Model (LQM) to detect risk SNPs for AD across multiple research institutions. To accelerate the learning process, we propose a Distributed Enhanced Dual Polytope Projection (D-EDPP) screening rule to identify irrelevant features and remove them from the optimization. To the best of our knowledge, this is the first successful run of the computationally intensive model selection procedure to learn a consistent model across different institutions without compromising their privacy while ranking the SNPs that may collectively affect AD. Empirical studies are conducted on 809 subjects with 5.9 million SNP features which are distributed across three individual institutions. D-EDPP achieved a 66-fold speed-up by effectively identifying irrelevant features.

cs.LG↗

arXiv2016

The cold dark matter content of Galactic dwarf spheroidals: no cores, no failures, no problem

We examine the dark matter content of satellite galaxies in Lambda-CDM cosmological hydrodynamical simulations of the Local Group from the APOSTLE project. We find excellent agreement between simulation results and estimates for the 9 brightest Galactic dwarf spheroidals (dSphs) derived from their stellar velocity dispersions and half-light radii. Tidal stripping plays an important role by gradually removing dark matter from the outside in, affecting in particular fainter satellites and systems of larger-than-average size for their luminosity. Our models suggest that tides have significantly reduced the dark matter content of Can Ven I, Sextans, Carina, and Fornax, a prediction that may be tested by comparing them with field galaxies of matching luminosity and size. Uncertainties in observational estimates of the dark matter content of individual dwarfs have been underestimated in the past, at times substantially. We use our improved estimates to revisit the `too-big-to-fail' problem highlighted in earlier N-body work. We reinforce and extend our previous conclusion that the APOSTLE simulations show no sign of this problem. The resolution does not require `cores' in the dark mass profiles, but, rather, relies on revising assumptions and uncertainties in the interpretation of observational data and accounting for `baryon effects' in the theoretical modelling.

astro-ph.GA↗

arXiv2016

Difference Index of Quasi-Prime Difference Algebraic Systems

This paper is devoted to studying difference indices of quasi-prime difference algebraic systems. We define the quasi dimension polynomial of a quasi-prime difference algebraic system. Based on this, we give the definition of the difference index of a quasi-prime difference algebraic system through a family of pseudo-Jacobian matrices. Some properties of difference indices are proved. In particular, an upper bound of difference indices is given. As applications, an upper bound of the Hilbert-Levin regularity and an upper bound of orders for difference ideal membership problem are deduced.

math.AC↗

arXiv2016

Difference Index of Quasi-regular Difference Algebraic Systems

This paper is devoted to studying difference indices of quasi-regular difference algebraic systems. We give the definition of difference indices through a family of pseudo-Jacobian matrices. Some properties of difference indices are proved. In particular, a Jacobi-type upper bound for the sum of the order and the difference index is given. As applications, an upper bound of the Hilbert-Levin regularity and an upper bound of the order for difference ideal membership problem are deduced.

math.AC↗

arXiv2016

Determination of the hyperfine coupling constant of cesium 7S1/2 state

We report the hyperfine splitting (HFS) measurement of cesium (Cs) 7S1/2 state by optical-optical double-resonance spectroscopy in the 6S1/2-6P3/2-7S1/2 (852 nm + 1470 nm) ladder-type system. The HFS frequency calibration is performed by employing a phase-type waveguide electro-optic modulator together with a stable confocal Fabry-Perot cavity. From the measured HFS between F"= 3 and F"= 4 manifolds of Cs 7S1/2 state [HFS = 2183.273(37) MHz], we have determined the magnetic dipole hyperfine coupling constant [A = 545.818(09) MHz], which is in good agreement with the previous work but much more accurate.

physics.atom-ph↗

arXiv2016

Monomial Difference Ideals

In this paper, basic properties of monomial difference ideals are studied. We prove the finitely generated property of well-mixed difference ideals generated by monomials. Furthermore, a finite prime decomposition of radical well-mixed monomial difference ideals is given. As a consequence, we prove that every strictly ascending chain of radical well-mixed monomial difference ideals in a difference polynomial ring is finite, which answers a question raised by E. Hrushovski in the monomial case. Moreover, the Alexander Duality for monomial ideals is generalized to the monomial case.

math.AC↗

arXiv2016

A combined model for pseudorapidity distributions in Cu-Cu collisions at BNL-RHIC energies

The charged particles produced in nucleus-nucleus collisions come from leading particles and those frozen out from the hot and dense matter created in collisions. The leading particles are conventionally supposed having Gaussian rapidity distributions normalized to the number of participants. The hot and dense matter is assumed to expand according to the unified hydrodynamics, a hydro model which unifies the features of Landau and Hwa-Bjorken model, and freeze out into charged particles from a space-like hypersurface with a proper time of Tau_FO . The rapidity distribution of this part of charged particles can be derived out analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against the experimental data performed by BNL-RHIC-PHOBOS Collaboration in different centrality Cu-Cu collisions at sqrt(s_NN)=200 and 62.4 GeV, respectively. The model predictions are in well consistent with experimental measurements.

nucl-th↗

arXiv2016

Scalable Information Inequalities for Uncertainty Quantification

In this paper we demonstrate the only available scalable information bounds for quantities of interest of high dimensional probabilistic models. Scalability of inequalities allows us to (a) obtain uncertainty quantification bounds for quantities of interest in the large degree of freedom limit and/or at long time regimes; (b) assess the impact of large model perturbations as in nonlinear response regimes in statistical mechanics; (c) address model-form uncertainty, i.e. compare different extended models and corresponding quantities of interest. We demonstrate some of these properties by deriving robust uncertainty quantification bounds for phase diagrams in statistical mechanics models.

cs.IT↗

arXiv2016

Toric Difference Variety

In this paper, the concept of toric difference varieties is defined and four equivalent descriptions for toric difference varieties are presented in terms of difference rational parametrization, difference coordinate rings, toric difference ideals, and group actions by difference tori. Connections between toric difference varieties and affine N[x]-semimodules are established by proving the correspondence between the irreducible invariant difference subvarieties and the faces of the N[x]-submodules and the orbit-face correspondence. Finally, an algorithm is given to decide whether a binomial difference ideal represented by a Z[x]-lattice defines a toric difference variety.

cs.SC↗

arXiv2016

Discovery of an ultra-diffuse galaxy in the Pisces-Perseus supercluster

We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.4 degrees in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (mu_V = 24.8 mag/arcsec), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (R_e(V) = 12 arcsec) and proximity (15 arcmin) to the well-known dwarf spheroidal galaxy And II. Its red color (V-I = 1.0), shallow Sersic index (n_V=0.68), and the absence of detectable H-alpha emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6-meter telescope (V_h=5450 +/- 40 km/s) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (~78 Mpc), DGSAT I would have an R_e ~ 4.7 kpc and M_V ~-16.3$. Its properties resemble those of the ultra-diffuse galaxies recently discovered in the Coma cluster. DGSAT I is the first case of these rare ultra-diffuse galaxies found in this galaxy cluster. Unlike the ultra-diffuse galaxies associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

astro-ph.GA↗

arXiv2016

Investigation of two-color magneto-optical trap with cesium 6S1/2-6P3/2-7S1/2 ladder-type system

A novel cesium (Cs) two-color magneto-optical trap (TC-MOT), which partially employs the optical radiation forces due to photon scattering of the 6P3/2 (F'=5) - 7S1/2 (F"=4) excited-state transition in the Cs 6S1/2 - 6P3/2 - 7S1/2 (852 + 1470 nm) ladder-type system, has been proposed and experimentally investigated. One of the three pairs of 852 nm cooling/trapping beams (CTBs) in a conventional Cs MOT is replaced with a pair of the 1470 nm CTBs (type-I) or with one 852 nm CTB plus another counter-propagating 1470 nm CTB (type-II). Both the type-I and type-II Cs TC-MOTs can cool and trap atoms on both the red- and blue-detuning sides of the two-photon resonance. The Cs TC-MOT demonstrated in this work may have applications in the background-free detection of cooled and trapped atoms, and the photon-pair sources compatible with the ensemble-based quantum memory and the long-distance quantum communication via optical fiber.

physics.atom-ph↗

arXiv2015

A combined model for the pseudorapidity distributions in p-p collisions at center-of-mass energies from 23.6 to 7000 GeV

In p-p collisions, the produced charge particles consist of two leading particles and those frozen out from the hot and dense matter created in collisions. The two leading particles are respectively in the projectile and target fragmentation region, which, in this paper, are conventionally supposed to have Gaussian rapidity distributions. The hot and dense matter is assumed to expand according to the unified hydrodynamics, a hydro model which unifies the features of Landau and Hwa-Bjorken model, and freeze out into charged particles from a space-like hypersurface with a fixed proper time of Tau_FO. The rapidity distribution of this part of charged particles can be derived out analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against the experimental data performed in a wide now available center-of-mass energy region from 23.6 to 7000 GeV. The model predictions are in well consistent with experimental measurements.

nucl-th↗

arXiv2015

Distinguishing general relativity and $f(R)$ gravity with the gravitational lensing Minkowski functionals

We explore the Minkowski functionals of weak lensing convergence map to distinguish between $f(R)$ gravity and the general relativity (GR). The mock weak lensing convergence maps are constructed with a set of high-resolution simulations assuming different gravity models. It is shown that the lensing MFs of $f(R)$ gravity can be considerably different from that of GR because of the environmentally dependent enhancement of structure formation. We also investigate the effect of lensing noise on our results, and find that it is likely to distinguish F5, F6 and GR gravity models with a galaxy survey of $\sim3000$ degree$^2$ and with a background source number density of $n_g=30~{\rm arcmin}^{-2}$, comparable to an upcoming survey dark energy survey (DES). We also find that the $f(R)$ signal can be partially degenerate with the effect of changing cosmology, but combined use of other observations, such as the cosmic microwave background (CMB) data, can help break this degeneracy.

astro-ph.CO↗

arXiv2015

On $Q$-Tensors

One of the central problems in the theory of linear complementarity problems (LCPs) is to study the class of $Q$-matrices since it characterizes the solvability of LCP. Recently, the concept of $Q$-matrix has been extended to the case of tensor, called $Q$-tensor, which characterizes the solvability of the corresponding tensor complementarity problem -- a generalization of LCP; and some basic results related to $Q$-tensors have been obtained in the literature. In this paper, we extend two famous results related to $Q$-matrices to the tensor space, i.e., we show that within the class of strong $P_0$-tensors or nonnegative tensors, four classes of tensors, i.e., $R_0$-tensors, $R$-tensors, $ER$-tensors and $Q$-tensors, are all equivalent. We also construct several examples to show that three famous results related to $Q$-matrices cannot be extended to the tensor space; and one of which gives a negative answer to a question raised recently by Song and Qi.

math.OC↗

arXiv2015

Online aging study of high rate MRPC

With the constant increase of accelerator luminosity, the rate requirements of the MRPC detectors become important. In the same time, aging problem of the detector has to be studied meticulously. An online aging test system is set up in our Lab. The setup of the system is described and the purpose is to study the performance stability during the long time running under high luminosity environment. The high rate MRPC has been irradiated by X-ray for 36 days and accumulated charge density reached 0.1C/cm2. No obvious performance degradation is observed for the detector.

physics.ins-det↗

arXiv2015

SPEC application for achieving inelastic X-ray scattering experiment in the SSRF

In order to carry out inelastic X-ray scattering (IXS) experiment at BL15U1 beamline of Shanghai Synchrotron Radiation Facility (SSRF), the data acquisition and control system based on SPEC software has been developed. The IXS experimental method needs linkage control of monochromator, silicon drift detector (SDD) and ionization chamber on continuous segment-scan mode with variable step size, and gains the data of energy, spectrum and light intensity synchronously. A method is presented for achieving this function which was not realized only by using SSCAN of Experimental Physics and Industrial Control System (EPICS). This paper shows work details including control system description, SPEC configurations for EPICS devices, macro definitions and applications in the BL15U1. An IXS experiment was executed by using the SPEC control system, its results prove that the method is feasible to perform the experiment.

physics.ins-det↗

arXiv2015

Research on the secondary electron yield of tizrv-pd thin film coatings

In particle accelerators, the build-up of electron cloud may have important influence on beam quality. Especially for the positron and proton accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. A secondary electron emission (SEE) measurement system has been designed and used to study the SEE of palladium (Pd), TiZrV and TiZrV-Pd with an independently adjustable energy from 50 eV to 5 keV. Here, we obtained the characteristics of the SEE from Pd, TiZrV and TiZrV-Pd film coatings with different thickness under ultrahigh-vacuum (UHV) conditions. Moreover, the maximum secondary electron yield (SEY), δmax, of the Pd, TiZrV and TiZrV-Pd film coatings under different primary electron doses were obtained, respectively. Finally, the variation of the secondary electron yield with the incident electron energy will be discussed for Pd, TiZrV and TiZrV-Pd thin film coatings. Low SEY is a new advantage of TiZrV-Pd films, besides high H2 absorption ability and prolonging the lifetime of TiZrV film, which will be of great value in the design of beam screen for Super Proton-Proton Collider (SPPC).

physics.acc-ph↗