Quark Virtuality and QCD Vacuum Condensates

Based on the Dyson-Schwinger equations (DSEs) in the ‘rainbow‘ approximation, we investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, we calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λu,d^2 0.7 GeV^2 for u, d quarks, and λs^2=1.6 GeV^2 for s quark. Our theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions.     

非奇异单圈图的刻划

边数等于顶点个数的连通图称为单圈图.本文修正了文献[1]中关于奇异单圈图的充要条件,并且利用该条件证明了文献[2]中一个关于非奇异单圈图的猜想.     

Evolution of Shower Parton Distributions in a Jet from Quark Recombination Model

The evolution of shower parton distributions in a jet is investigated in the framework of a quark recombination model. The distributions are parameterized and the Q^2 dependence of the parameters is given by polynomials of In Q^2 for a wide range of Q^2     

Raman spectroscopic study of ceramic Sr2Bi4Ti5O18

Raman spectra of ceramic Sr2Bi4Ti5O18 （SBTi5） are reported to consist of four different Raman bands. Temperature-dependent spectra reveal the relationship between the lattice vibration and the material＇s structure. There appears a relatively large change in structure of the material at about 273K, The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum （FWHM）, which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464cm^-1 indicate that the latter phonon mode is more anharmonic than the former one.     

Cntinuity of Some Classes of Functions Related to Degenerate Parabolic Equations and Its Applications

We study some classes of functions satisfying the assumptions similar to but weaker than those for the classical B2 function classes used in the research of quasi-linear parabolic equations as well as the ones used in the research of degenerate parabolic equations including porous medium equationsl.Comsequently,we prove that a function in such a class is continuous.As an application,we obtain the estimate for the continuous modulus of the solutions of a few degenerate parabolic equations in divergence form,including the anisotropic porous equations.     

良紧性的特征与网式Alexander子基引理

紧性是拓扑学中最重要的概念之一.自从1968年C.L.Chang提出Fuzzy拓扑空间的概念以来,人们就试图将这一概念推广到Fuzzy拓扑学中,提出了各种Fuzzy紧性.相比之下,还是王国俊提出的良紧性有较多的优点,比较理想,从而很快获得人们的承认.对良紧性进行各种等价刻划,不论对良紧性本身的研究还是对后继工作都是很重要的.事实上,正是对良紧性的几何刻划导致了这种紧性在L-Fuzzy拓扑空间中的推广.本文中,我们将对L-Fuzzy拓扑空间中的良紧性给出几个等价刻划,在此基础上,我们建立了良紧性的所谓网式Alexander子基引理,从而更加简捷地证明了良紧性的Tychonoff定理而不借助良紧性的几何特征.     

有关Kegel猜测的若干结果

Kegel曾经提出如下猜测:若环R可以表示为它的两个局部幂零子环S、T之和,即有R=S+T,问R是否必是局部幂零的?本文证明:若Kegel猜测不真,则必存在一个本原环可以表示为它的两个局部幂零子环之和.另外,还得到两个与Kegel猜测有关的很有趣的结果.     

具有性质(G'_k)的Wakamatsu倾斜模

本文引进了具有性质(G'k)的Wakamatsu倾斜模的概念,并用同调有限子范畴的性质对其进行了刻画．     

一维准周期结构声子晶体透射性质的研究

提出了一维准周期结构的声子晶体模型.对弹性波通过该一维准周期结构声子晶体的透射系数进行了数值计算，并与周期结构的透射系数进行了比较.计算结果表明，弹性波通过一维准周期结构声子晶体时，同样会有带隙的出现，且带隙所在频率范围与周期结构的情形完全一样，不同的是在准周期结构声子晶体中，带隙内有很强的局域共振模.对此局域模性质的研究有助于声波或弹性波滤波器的制作. 关键词： 准周期结构 声子晶体 局域化     

Can Quintessence Be the Rolling Tachyon？

In the light of the recent works by Sen(hep-th/o203211,hep-th/0203265,hep-th/0204143)and Gibbons(hepth/0204008),we present a phase-plane analysis on the cosmology containing a rolling tachyon field in a potential resulting from string theory.we show that there is no stable point on the phase-plane,which indicates that there is a coincidence problem if we consider the tachyon as a candidate for quintessence.Furthermore,we also analyse the phase-plane of the cosmology cotaining a rolling tachyon field for an exactly solvable toy potential in which the critical point is stable.Therefore,it is possible for the rolling tachyon to be a candidate for quintessence if we give up the strict constraint on the potential or find a more appropriate effective potential for the tachyon from M/String theory.