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Nonpositively Curved Almost Hermitian Metrics on Product of Compact Almost Complex Manifolds

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Acta Mathematica Sinica,English Series 2015年第1期31卷 61-70页

作者： Chengjie YU department of Mathematics Shantou University

In this paper, we give a classification of almost Hermitian metrics with nonpositive holo- morphic bisectional curvature on a product of compact almost complex manifolds. This generalizes previous results of Zheng [Ann. of Math. （2）, 137（3）, 671-673 （1993）] and the author [Proc. Amer. Math. Soc., 139（4）, 1469-1472 （2011）].

关键词： Almost-Hermitian manifold holomorphic bisectional curvature nonpositive curvature

Non-parametric reconstruction of dark energy and cosmic expansion from the Pantheon compilation of type Ia supernovae

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Chinese Physics C 2019年第7期43卷 103-111页

作者： Hai-Nan Lin Xin Li Li Tang department of Physics Chongqing University

The equation of state(EoS) of dark energy plays an important role in the evolution of the universe and has attracted considerable interest in the recent years. With the progress in observational technique, a precise constraint on the EoS of dark energy can be obtained. In this study, we reconstruct the EoS of dark energy and cosmic expansion using Gaussian processes(GP) from the most up-to-date Pantheon compilation of type Ia supernovae(SNe Ia),which consists of 1048 finely calibrated SNe Ia. The reconstructed EoS of dark energy has a large uncertainty owing to its dependence on the second-order derivative of the construction. Adding the direct measurements of Hubble parameters H(z) as an additional constraint on the first-order derivative can partially reduce the uncertainty;however, it is still not sufficiently precise to distinguish between the evolving and the constant dark energy. Moreover, the results heavily rely on the prior of the Hubble constant H0. The H0 value inferred from SNe+ H(z) without prior is H0= 70.5 ± 0.5 km s^-1 Mpc^-1. Moreover, the matter density ΩM has a non-negligible effect on the reconstruction of dark energy. Therefore, more accurate determinations on H0 and ΩM are required to tightly constrain the EoS of dark energy.

关键词： cosmology dark energy type Ia supernovae

Assessment of widely used methods to derive depositional ages from detrital zircon populations

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Geoscience Frontiers 2019年第4期10卷 1421-1435页

作者： Daniel S.Coutts William A.Matthews Stephen M.Hubbard department of Geoscience University of Calgary

The calculation of a maximum depositional age(MDA)from a detrital zircon sample can provide insight into a variety of geological ***,the impact of sample size and calculation method on the accuracy of a resulting MDA has not been *** use large populations of synthetic zircon dates(N≈25,000)to analyze the impact of varying sample size(n),measurement uncertainty,and the abundance of neardepositional-age zircons on the accuracy and uncertainty of 9 commonly used MDA calculation ***,a new method,the youngest statistical population is *** each method,500 samples of n synthetic dates were drawn from the parent population and MDAs were *** mean and standard deviation of each method ove r the 500 trials at each n-value(50-1000,in increments of 50)were compa red to the known depositional age of the synthetic population and used to compare the methods quantitatively in two simulation *** first simulation scenario varied the proportion of near-depositional-age grains in the synthetic *** second scenario varied the uncertainty of the dates used to calculate the *** sample size initially decreased the mean residual error and standard deviation calculated by each *** higher n-values(>~300 grains),calculated MDAs changed more slowly and the mean resid ual error increased or decreased depending on the method *** the p roportion of near-depositional-age grains and lowering measurement uncertainty decreased the number of measurements required for the calculated MDAs to stabilize and decreased the standard deviation in calculated MDAs of the 500 *** of the two simulation scenarios show that the most successful way to increase the accuracy of a calculated M DA is by acquiring a large number of low-uncertainty measurements(300300)approach is used if the calculation of accurate MDAs are key to research *** acquisition method s,such as high-to moderate-precision m

关键词： Detrital zircon Maximum depositional age Geochronology Basin chronology LA-ICP-MS

Linear forms, algebraic cycles, and derivatives of L-series

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Science China Mathematics 2019年第11期62卷 2401-2408页

作者： Shouwu Zhang department of Mathematics Princeton University

In this note, we state some refinements of conjectures of Gan-Gross-Prasad and Kudla concerning the central derivatives of L-series and special cycles on Shimura varieties. The analogues of our formulation for special values of L-series are written in terms of invariant linear forms on automorphic representations defined by integrations of matrix coefficients.

关键词： linear forms algebraic cycles derivatives L-series

Projections on Weak*-closed Subspace of Dual Banach Algebras

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Acta Mathematica Sinica,English Series 2012年第3期28卷 477-486页

作者： Ali GHAFFARI department of Mathematics Semnan University

Our first purpose in this paper is to provide necessary conditions for a weak＊-closed translation invariant subspace in the semigroup algebra of a locally compact topological foundation semigroup to be completely complemented. We give conditions when a weak＊-closed left translation invariant subspace in Ma,（S）＊ of a compact cancellative foundation semigroup S is the range of a weak＊-weak＊ continuous projection on M~,（S）＊ commuting with translations. Let G be a locally compact group and A be a Banach G-module. Our second purpose in this paper is to study some projections on A＊ and /3（A＊） which commutes with translations and convolution.

关键词： Amenability Banach algebras completely cancellative foundation semigroup projections semigroup algebras weak*-closed subspace weak*-operator topology

Properties of the free energy density using the principle of maximum conformality

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Chinese Physics C 2018年第8期42卷 59-64页

作者：步时吴兴刚申建明曾军 department of Physics Chongqing University

We present a detailed study on the properties of the free energy density at high temperature by applying the principle of maximum conformality（PMC）scale-setting method within effective field *** PMC utilizes the renormalization group equation recursively to identify the occurrence and pattern of the non-conformal{βi}-terms,and determines the optimal renormalization scale at each *** analysis shows that a more accurate free energy density up to gs^5-order level without renormalization scale dependence can be achieved by applying the *** also observe that by using a smaller factorization scale around the effective parameter m E,the PMC prediction is consistent with the lattice QCD prediction derived at low temperature.

关键词： perturbative QCD free energy density renormalization QCD high-order corrections

Mass transfer and possible third-body effect on the period variations of the near-contact binary CN And

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Research in Astronomy and Astrophysics 2019年第8期19卷 3-10页

作者： Jin-Ting Cai Yun-Xia Yu Ke Hu Fu-Yuan Xiang department of Physics Xiangtan University

We present a period analysis of the near-contact binary CN And using all available times of light minima. It is revealed that the orbital period exhibits a long-term decrease as well as a small-amplitude cyclic oscillation. This result suggests that the secular period decrease at the rate of d P/dt =-1.4017 ×10-7 d yr-1 is caused by a combination of mass transfer and angular momentum loss due to magnetic braking. The periodic variation with an amplitude of A = 0.0036 d and a period of Pmod = 28.3542 yr should be rooted in the light-time effect of a third body, rather than cyclic magnetic activity.

关键词： stars:binaries:close stars:binaries:eclipsing stars:individual:CN And

Integrability and Solutions of the (2+1)-Dimensional Broer-Kaup Equation with Variable Coefficients

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Communications in Theoretical Physics 2012年第9期58卷 387-392页

作者：王路华贺劲松 department of Mathematics Ningbo University

The integrability of the （2＋l）-dimensional Broer-Kaup equation with variable coefficients （VCBK） is verified by finding a transformation mapping it to the usual （2＋l）-dimensional Broer-Kaup equation （BK）. Thus the solutions of the （2＋1）-dimensional VCBK are obtained by making full use of the known solutions of the usual （2＋1）dimensional IRK. Two new integrable models are given by this transformation, their dromion-like solutions and rogue wave solutions are also obtained. Further, the velocity of the dromion-like solutions can be designed and the center of the rogue wave solutions can be controlled artificially because of the appearance of the four arbitrary functions in the transformation.

关键词： (2+l)-dimensional Broer Kaup equation with variable coefficients integrability (2+1)-dimen-sional Broer-Kaup equation dromion-like rogue wave

Applications of new affine invariant for polytopes

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Applied Mathematics and Mechanics(English Edition) 2008年第2期29卷 273-278页

作者：杨柳何斌吾 department of Mathematics Shanghai University

To study the Schneider＇s projection problem, Lutwak, Yang and Zhang recently introduced a new .affine invariant functional U（P） for convex polytopes in R^n. In the paper, we obtain the analytic expression of the affine-invariant U（P） defined on a specific subclass of origin-symmetric convex polytopes in Rn and give an application of U（P） to the Lp-Minkowski problem.

关键词： convex polytope affine invariant Minkowski problem volume