关于矩阵乘法的一个算法的时间复杂度

两个n阶非负整数方阵相乘,常规算法的时间复杂度为O(n³),文献[1]提出一个“运算次数”为O(n²)的“最佳”算法,本文根据算法分析理论得出此算法的时间复杂度不低于O(n³log₂ⁿ),因而比常规算法的运算量还大.     

连分数与类数及其他

本文用连分数给出虚二次域的类数公式,见文中的定理4.结合Hirzebruch和zagier的结果(定理5),就完全了用连分数给出虚二次域的类数公式的结果.另外还讨论了一类虚二次域类数的可除性,即有 定理6.设l,q均为正整数,且q≥2.如0>△=1-4q^l为无平方因子整数,则l除尽虚二次域(Q(△^1/2)的类数. 文献[6]中,用了代数几何方法证明了当l为奇素数时的情形,本文只用初等方法.最后,文中给出了一个实二次域类数的初等公式.     

有限可换主理想环上模理论可判定性及其复杂性

本文利用初等等价的工具，引用Ｅｈｅｎｆｅｕｃｈｔ Ｇａｍｅ理论，证明了有限可换主理想环上模的理论是可判定的，并且判定过程的计算复杂性上界为２^ｃｎ２．     

关于矩阵乘法的一个改进算法的时间复杂度

两个ｎ阶非负整数方阵相乘,常规算法的时间复杂度为Ｏ（ｎ^３）,文献［１］提出一个“运算次数”为Ｏ（ｎ²）的“最佳”算法,文献［２］对此算法做了进一步研究,提出三种改进策略．本文根据算法分析理论,得出改进后的算法的时间复杂度仍不低于Ｏ（ｎ^３ｌｏｇｎ）,因而其阶仍高于常规算法的运算量的阶．     

三角形重心的一个向量性质的另证及推广

文[1]类比文[2]用高等几何方法(仿射几何法)给出了三角形重心的另一个向量性质(即性质1).本文将给出性质1的初等证法并推广之.     

算术平均值与几何平均值不等式的推广

利用初等对称多项式得出算术平均值与几何平均值不等式的推广形式,并给出[1]中的一个猜想不等式的证明.     

齐型空间上的BMO函数

本文初等而又简单地证明了如下事实。设f是齐型空间X上函数,使这里k∈Z⁺,(log⁺)^k是k次对数重叠,S遍历X中所有的球,则f∈BMO。并且因此建立了Baernstein定理在n维实、复球上的一个类似。     

负相协随机变量的指数不等式

该文给出了一些负相协随机变量的指数不等式.这些不等式改进了由Jabbari和Azarnoosh^[4]及Oliveira^[7] 所得到的相应的结果.利用这些不等式对协方差系数为几何下降情形, 获得了强大数律的收敛速度为n^-1/2(log log n)^1/2(log n)^2.这个收敛速度接近独立随机变量的重对数律的收敛速度, 而Jabbari和Azarnoosh^[4]在上述情形下得到的收敛速度仅仅为n^-1/3(log n)^5/3.     

Bonnesen等周不等式的一个初等证明

本文给出Bonnesen等周不等式的一个初等证明,它不涉及积分几何理论,浅显易懂.     

常曲率平面上一域包含另一域的充分条件

本文研究了常曲率平面X^κ中一域包含另一域的包含问题.利用积分几何中包含测度理论及对称等周亏格,得到了X^κ中一域包含另一域的充分条件,并给出X^κ中等周不等式的一个简化证明.     

Counting bitangents with stable maps

This paper is an elementary introduction to the theory of moduli spaces of curves and maps. As an application to enumerative geometry, we show how to count the number of bitangent lines to a projective plane curve of degree d by doing intersection theory on moduli spaces.     

Lefschetz–Verdier Trace Formula and a Generalization of a Theorem of Fujiwara

The goal of this paper is to generalize a theorem of Fujiwara (Deligne’s conjecture) to the situation appearing in a joint work [KV] with David Kazhdan on the global Langlands correspondence over function fields. Moreover, our proof is more elementary than the original one and stays in the realm of ordinary algebraic geometry, that is, does not use rigid geometry. We also give a proof of the Lefschetz–Verdier trace formula and of the additivity of filtered trace maps, thus making the paper essentially self-contained. The work was supported by the Israel Science Foundation (Grant No. 555/04) Received: May 2005 Accepted: August 2005     

Cantor尘的Hausdorff测度的初等证明

本文从自相似集的几何性质出发 ,用初等的方法得到了 Cantor尘的 Hausdorff测度 .     

An axiomatic analysis of the Droz-Farny Line Theorem

We analyze an elementary theorem of Euclidean geometry, the Droz-Farny Line Theorem, from the point of view of the foundations of geometry. We start with an elementary synthetic proof which is based on simple properties of the group of motions. The proof reveals that the Droz-Farny Line Theorem is a special case of the Theorem of Goormatigh which is, in turn, a special case of the Counterpairing Theorem of Hessenberg. An axiomatic analysis in the sense of Hilbert [14] and Bachmann [2] leads to a study of different versions of the theorems (e.g., of a dual version or of an absolute version, which is valid in absolute geometry) and to a new axiom system for the associated very general plane absolute geometry (the geometry of pencils and lines). In the last section the role of the theorems in the foundations of geometry is discussed.     

Bend, break and count

This paper gives a formula for the number of members of a given ‘nice’ family of rational curves on a surface passing through the appropriate number of general points, expressing this number in terms of reducible members of the family. Similar formulae have been obtained previously using methods of quantum cohomology, but the present method is by contrast completely elementary, relying merely on some simple geometry on ruled surfaces.     

Topological projective geometries

A concept of topological projective geometry is defined, which in contrast to the definitions given in [Mi] and [SÖ] does not contain any dimensional restrictions. Besides elementary properties it is shown in this paper that these topological geometries always possess a coordinatization over a uniquely determined topological division ring if the dimension is finite.Dedicated to Prof. Dr. Hanfried Lenz on his 70^th birthday     

一类初等微分几何定理机器证明的算法与实现

空间曲面上的曲线论是初等微分几何的重要部分．作者提出了一种以外微分运算和向量计算为主要工具,可以进行有关曲面上曲线局部性质的定理机器证明的算法．该算法结合了曲面上的活动标架,曲面上曲线的测地标架和曲线自身的Frenet标架,在Maple 9下得到实现．对20个例子进行的测试表明,由该算法生成的自动证明简短可读．     

On the realization of symmetries in quantum mechanics

The aim of this paper is to give a simple, geometric proof of Wigner’s theorem on the realization of symmetries in quantum mechanics that clarifies its relation to projective geometry. Although several proofs exist already, it seems that the relevance of Wigner’s theorem is not fully appreciated in general. It is Wigner’s theorem which allows the use of linear realizations of symmetries and therefore guarantees that, in the end, quantum theory stays a linear theory. In the present paper, we take a strictly geometrical point of view in order to prove this theorem. It becomes apparent that Wigner’s theorem is nothing else but a corollary of the fundamental theorem of projective geometry. In this sense, the proof presented here is simple, transparent and therefore accessible even to elementary treatments in quantum mechanics.     

On the realization of symmetries in quantum mechanics

The aim of this paper is to give a simple, geometric proof of Wigner’s theorem on the realization of symmetries in quantum mechanics that clarifies its relation to projective geometry. Although several proofs exist already, it seems that the relevance of Wigner’s theorem is not fully appreciated in general. It is Wigner’s theorem which allows the use of linear realizations of symmetries and therefore guarantees that, in the end, quantum theory stays a linear theory. In the present paper, we take a strictly geometrical point of view in order to prove this theorem. It becomes apparent that Wigner’s theorem is nothing else but a corollary of the fundamental theorem of projective geometry. In this sense, the proof presented here is simple, transparent and therefore accessible even to elementary treatments in quantum mechanics.