特征为2的有限域上对称矩阵方程解的计数公式及q超几何级数表达

设Fq是有q＝2t个元的有限域.本文利用Fq上奇异辛几何和奇异伪辛几何理论,给出当A,C是Fq上对称矩阵时,Fq上适合XAXT＝C的解存在的充要条件以及秩k的解X和解X的个数的明显公式,并且用q超几何级数简化表达解数公式．     

对称群上Cayley图的条件匹配排除数

一个图的条件匹配排除数是最少的边的数量,使得从图中删除这些边后形成的图既没有孤立点,也没有完美匹配和几乎完美匹配.条件匹配排除数是衡量网络在边故障情况下的鲁棒性的参数之一.本文给出了对称群上Cayley图的条件匹配排除数.     

联立Pell方程组x~2-ay~2=1和y~2-bz~2=1的解数

设a,b是正整数.我们研究了联立Pell方程组x~2-ay~2=1,y~2-bz~2=1的正整数解(x,y,z)的个数.本文利用Bennett关于联立Padé逼近的一个结果,证明了该方程组至多只有两组正整数解(x,y,z),从而改进了Bennett(1998),袁平之(2004)等人的结论.     

Pell方程组x2-ay2=1和 z2-by2=1的解数

设a,b是不同的正整数,本文证明了当max(a,b)＞10126时,Pell方程组x2-ay2=1和z2-by2=1至多有2组正整数解(x,y,z).     

矩阵方程AXB=C有D对称解的充要条件及通解

本文利用矩阵对的广义奇异值分解研究矩阵方程AXB=C有D对称解的充分必要必要条件,并给出了通解的表达式。     

矩阵方程AXAT=C的对称斜反对称解

设A∈Rm×n,C∈Rm×m给定,利用矩阵的广义奇异值分解和对称斜反对称矩阵的性质,得到了矩阵方程(1)AXAT=C存在对称斜反对称解的充要条件和通解表达式;证明了若方程(1)有解,则一定存在唯一极小范数解,并给出了极小范数解的具体表达式和求解步骤.     

On Explicit Formulas for the Number of Solutions to the Equation (x1+...+xn)2 =ax1...xn in a Finite Field

We consider the equation of the title in a finite field of q elements. Assuming certain relations between n and q, we obtain explicit formulas for the number of solutions to this equation.     

Locally Symmetric Connections on Complex Hypersurfaces with Type Number 1

We characterize – by describing in local coordinates their sections – the transversal bundles which on the complex hypersurface with type number 1 induce locally symmetric connections.     

矩阵方程AXAT=C的对称斜反对称解

设A∈R^m×n,C∈R^m×m给定,利用矩阵的广义奇异值分解和对称斜反对称矩阵的性质,得到了矩阵方程(1)AXA^T=C存在对称斜反对称解的充要条件和通解表达式;证明了若方程(1)有解,则一定存在唯一极小范数解,并给出了极小范数解的具体表达式和求解步骤.     

广义Ramanujan-Nagell方程x~2+D~m=p~n的解数

设a是正整数,D=3a2+1,P=4a2+1,其中p是素数.本文证明了:如果a不是4的倍数,则除了当(D,p)=(4,5)时方程x2+Dm=pn恰有3组正整数解(x,m,n)=(1,1,1),(3,2,2),(11,1,3)以外,该方程恰有2组正整数解(x,m,n)=(a,1,1)和(8a3+3a,1,3).     

On Symmetric Association Schemes with k 1=3

In this paper, we have a classification of primitive symmetric association schemes with k ₁ = 3.     

On the Equation xp + y q = z r : A Survey

Let p, q and r be three integers 2. During the last ten years many new ideas have emerged for the study of the Diophantine equation x + y = z. This study is divided into three parts according whether (p, q, r) = is negative, zero or positive. For instance, if we have (p, q, r) < 0, this study is closely connected to the theory of modular representations of dimension 2 in finite characteristic. The approach of associating to this equation Galois representations given by the division points of elliptic curves is very efficient. The aim of this paper is to present this circle of ideas and the known results concerning this equation.     

On the Number of Nilpotents in the Partial Symmetric Semigroup

Abstract

In this note, we obtain and discuss formulae for the total number of nilpotent partial and nilpotent partial one–one transformations of a finite set.     

The Bisymplectomorphism Group of a Bounded Symmetric Domain

We determine the group of diffeomorphisms of a bounded symmetric domain, which preserve simultaneously the hyperbolic and the at symplectic form. *Research partially supported by GNSAGA (INdAM) and MIUR of Italy; MIUR Project “Geometric Properties of Real and Complex Manifolds” (PRIN05). **Research partially supported by GNSAGA (INdAM) and MIUR of Italy; MIUR Project “Geometric Properties of Real and Complex Manifolds” (PRIN05). ***Part of this work was done in July 2007 during a visit of G. Roos at Politecnico di Torino; visit supported by GNSAGA (INdAM) and MIUR of Italy; MIUR Project “Geometric Properties of Real and Complex Manifolds: (PRIN05).     

Conjugacy in Permutation Representations of the Symmetric Group

Although the conjugacy classes of the general linear group are known, it is not obvious (from the canonic form of matrices) that two permutation matrices are similar if and only if they are conjugate as permutations in the symmetric group, i.e., that conjugacy classes of S _n do not unite under the natural representation. We prove this fact, and give its application to the enumeration of fixed points under a natural action of S _n  × S _n . We also consider the permutation representations of S _n which arise from the action of S _n on ordered tuples and on unordered subsets, and classify which of them unite conjugacy classes and which do not.     

广义Ramanujan-Nagell方程x~2-D=3~n的解数

设D是不能被3整除的正整数.本文证明了:当D>1012时,如果Pell方程U2-DV2=-1有解(U,V),则方程x2-D=3n至多有2组正整数解(x,n).     

Chromatic Polynomials and the Symmetric Group

In this paper we give first a new combinatorial interpretation of the coefficients of chromatic polynomials of graphs in terms of subsets of permutations. Motivated by this new interpretation, we introduce next a combinatorially defined polynomial associated to a directed graph, and prove that it is related to chromatic polynomials. These polynomials are a specialization of cover polynomials of digraphs.I am grateful to the Swiss National Science Foundation for its partial financial supportFinal version received: June 25, 2003