Koszul Differential Graded Algebras and BGG Correspondence II

The concept of Koszul differential graded （DG for short） algebra is introduced in [8]. Let A be a Koszul DG algebra. If the Ext-algebra of A is finite-dimensional, i.e., the trivial module Ak is a compact object in the derived category of DG A-modules, then it is shown in [8] that A has many nice properties. However, if the Ext-algebra is infinite-dimensional, little is known about A. As shown in [15] （see also Proposition 2.2）, Ak is not compact if H（A） is finite-dimensional. In this paper, it is proved that the Koszul duality theorem also holds when H（A） is finite-dimensional by using Foxby duality. A DG version of the BGG correspondence is deduced from the Koszul duality theorem.     

THEORETICAL ANALYSIS OF A HIGH-MACH-NUMBER DILUTE INELASTIC GAS IMPINGING ON A SURFACE

We consider a problem of a 2-dimensional high-Mach-number dilute inelastic gas originating from infinity impinging on an oblique surface of infinite length. By analyzing probabilities of particle-particle collisions, we derive an analytical formula for the mean force experienced by the surface when the system is dilute. We also derive conditions for the validity of our theory.     

INFINITELY MANY SOLUTIONS FOR ELLIPTIC SYSTEMS WITH STRONGLY INDEFINITE VARIATIONAL STRUCTURE

Based on the multiplicity results of Benci and Fortunato [4], we consider some elliptic systems with strongly indefinite quadratic part, and establish the existence of infinitely many nontrivial solutions in a suitable family of products of fractional Sobolev spaces.     

具无穷时滞的Lotka-Volterra捕食系统的生存分析

研究了具有无穷时滞具有m个捕食者和n个食饵的的Lotka-Volterra非自治系统,主要利用比较定理得到了系统内生物种群持续生存的充分条件.     

一类无穷区间上具有积分边界条件的分数阶微分方程的正解存在性

研究一类无穷区间上具有积分边界条件的分数阶微分方程边值问题.先构造Green函数,并讨论相关性质,再利用压缩映象原理及单调迭代法,讨论此类边值问题的正解存在性,建立了若干正解存在定理.     

半无穷区间上具有共振的序列分数阶微分方程积分边值问题的可解性

本文研究半无穷区间上具有共振的分数阶微分方程积分边值问题.通过构造适当的Banach空间及算子,利用迭合度理论和Mawhin连续性定理获得上述边值问题解的存在性结论,推广了前人的结果.     

一类七次多项式微分系统的中心条件与赤道极限环分支

研究了一类七次系统无穷远点的中心条件与赤道极限环分支问题.通过将实系统转化为复系统研究,给出了计算无穷远点奇点量的递推公式,并在计算机上用Mathematica推导出该系统无穷远点前14个奇点量,进一步导出了无穷远点成为中心的条件和14阶细焦点的条件,在此基础上得到了七次系统无穷远点分支出12个极限环的一个实例.     

Banach空间中无穷区间上n阶非线性脉冲微分-积分方程初值问题的整体解

利用Banach不动点定理，通过逐步求解方法，在较宽松的条件下，给出了Banach空间中无穷区间上n阶非线性脉冲微分-积分方程初值问题的整体解的存在定理，对最近出现的结果作了重要推广，并举例说明了本文结果的应用．     

绝对值方程算例分析

分别给出了绝对值方程存在唯一解的算例、存在2~n个解的算例、存在无穷多个解的算例以及无解的算例,并分析了这些算例中矩阵奇异值的特点.     

瑕积分的收敛性与Lebesgue可积性

瑕积分的收敛性与Lebesgue可积性之间具有密不可分的关系.首先详细证明了瑕积分收敛定理,然后说明无穷积分的收敛定理与瑕积分的收敛定理是等价的,最后利用两条定理的等价性给出一个应用.