不添辅助线证明Steiner-Lehmer定理并将其推广

1Steiner-Lehmer定理的源流及新证Steiner-Lehmer定理即如下的定理1.定理1如果一个三角形的两条内角平分线相等,则该三角形是等腰三角形.这虽然是个初等几何中的定理,其名气却非常响亮.1840年在C.L.Lahmus给C.F.Sturm(1803-1855)的信中,向他请教这一命题的证明.后者也没能给出证明,就在数学界广泛征解.当时得到了几种证法,但都是间接证明,也都比较繁琐.此后100多年来,寻找其简洁的直接证明一直     

Morley定理的更简证明

近年 ,我们对 Morley定理的研究日深 ,证明日简 ,本文给出一个仅用几行文字的证明 ,供大家赏析 .Morley定理　如图 1,任意△ ABC每两个内角相邻的三等分角线的交点构成正△ DEF.图 1　　　　　　　　　图 2证明　如图 1,设 A =3α,B =3β,C =3γ,如图 2 ,又构造凹六边形A′F′B     

T样条函数空间的局部支集基

Schumaker，L.L.在其名著《Spline Function；Basic Theory》中第九章给出了Tchebysheff样条函数空间的局部支集基定理，可惜其证明却是错的，本文给出了上述定理的正确证明。     

齐次函数的一个仿射球定理

本文研究了相关齐次函数的仿射球定理.利用Hopf极大值原理,对任意给定的带凹性条件的初等对称曲率问题,获得了此类仿射球定理.特别地,这也给出了Deicke齐次函数定理的一个新证明.     

抽象代数中一条著名定理的简捷证明

群论中有一条重要的定理自由Abel群F的任意两组基具有相同的势。常见文献上的证明都比较冗长。Thomas W.Hungerford的著作、《Alsbra》在第72页上只给出证明概要,已占一定篇幅。本文将作出一个既简短又详细的巧妙证法。     

Fermat小定理的集合论证明

在初等数论里 ,Fermat小定理是个很基本的结果 ,具有广泛的应用 .为方便计 ,我们先给出这个定理 .Fermat小定理　设 p为素数 ,a为任意不能被 p整除的自然数 ,则ap-1≡ 1　 (modp) .用最初等的话说 ,ap-1除以 p的余数恒等于 1.在学过最基本的同余知识后 ,即可给出这个结论的证明 ,这在任何数论或代数入门书上都能找出 .如果有了“群”的概念 ,就可以看出Fermat小定理是有限群的一种基本特征 .现在我们从集合论的角度给出Fermat小定理的一种证明 ,它仅仅需要一点最基本的计数技巧 .定理　设 p是一个素数 ,a是任意一个自然数 ,则ap ≡a　 (mo…     

齐次函数的一个仿射球定理（英文）

本文研究了相关齐次函数的仿射球定理.利用Hopf极大值原理,对任意给定的带凹性条件的初等对称曲率问题,获得了此类仿射球定理.特别地,这也给出了Deicke齐次函数定理的一个新证明.     

Fibonacci数列模p~r的周期性研究

对任意素数p、正整数r,Fibonacci数列{Fn}对pr取模构成一个数列{an}.若{Fn}的最小正周期为T,则{an}的最小正周期为pr-1T,首次提出该定理,并用数学归纳法进行了证明.此外对任意正整数m,不加证明地给出了{Fmod m}的周期性定理.     

二项式定理的概率论证法

应用广泛的二项式定理除了可用数学归纳法证明外,还可用组合分析或数学分析等方法分别证明之。本文给出一个完全只用初等概率论的知识的方法来证明二项式定理。 定理:设a,b里任意实数,n是正整数,     

《圆锥曲线焦点弦的一个性质》一文的补充和推广

在文 [1 ]中给出如下结论 :定理 1　设AB ,CD是圆锥曲线过焦点F的两动弦 ,弦端点连线AC ,BD交于点M ,则M的轨迹是圆锥曲线的相应准线 .本文对文 ( 1)的证明做些补充并给出定理1的推广形式 .1　补充在文 [1]中给出的定理 1的证明 ,其实是仅证出点M一定在准线上 ,还应补证 :准线上任意一点M ,都存在过焦点的两条弦AB ,CD使AC ,BD的交点为M .补充如下 :设点M( ρ0 ,θ0 )是圆锥曲线E的准线l:ρcosθ=-p上任意一点 ,过点M做直线AC交E于A( ρ1 ,θ1 ) ,C( ρ2 ,θ2 ) ,延长AF ,CF分别交E于B( ρ1 ′,θ1 π) ,D( ρ2 ′,θ2 π)…     

PBW deformations of quadratic monomial algebras

A result of Braverman and Gaitsgory from 1996 gives necessary and sufficient conditions for a filtered algebra to be a Poincaré-Birkhoff-Witt (PBW) deformation of a Koszul algebra. The main theorem in this paper establishes conditions equivalent to the Braverman-Gaitsgory Theorem to efficiently determine PBW deformations of quadratic monomial algebras. In particular, a graphical interpretation is presented for this result, and we discuss circumstances under which some of the conditions of this theorem need not be checked. Several examples are also provided. Finally, with these tools, we show that each quadratic monomial algebra admits a nontrivial PBW deformation.     

Deformations of Quadratic Algebras with Antisymmetric Relations

A finitely generated quadratic algebra with antisymmetric generating relations is called a weakly symmetric algebra. The automorphism group and Calabi–Yau property of a Poincaré–Birkhoff–Witt (PBW)-deformation of a weakly symmetric algebra are discussed. It is shown that the Calabi–Yau property of a PBW-deformation of a weakly symmetric algebra is equivalent to that of the corresponding augmented PBW-deformation under some mild conditions.     

Skew Clifford algebras

We introduce a generalization, called a skew Clifford algebra, of a Clifford algebra, and relate these new algebras to the notion of graded skew Clifford algebra that was defined in 2010. In particular, we examine homogenizations of skew Clifford algebras, and determine which skew Clifford algebras can be homogenized to create Artin-Schelter regular algebras. Just as (classical) Clifford algebras are the Poincaré-Birkhoff-Witt (PBW) deformations of exterior algebras, skew Clifford algebras are the ${\mathbb{Z}}_2$-graded PBW deformations of quantum exterior algebras. We also determine the possible dimensions of skew Clifford algebras and provide several examples.     

限制李超代数的诱导模

In this paper we first prove the PBW theorem for reduced universal enveloping algebras of restricted Lie superalgebras. Then the notion of an induced module is introduced and the dimension formula of induced modules is established. Finally, using the results above, we obtain a property of induced modules pertaining to automorphisms of Lie superalgebras and isomorphisms of modules.     

Gr?bner–Shirshov Basis of Derived Hall Algebra of Type A_n

We know that in Ringel–Hall algebra of Dynkin type, the set of all skew commutator relations between the iso-classes of indecomposable modules forms a minimal Gr?bner–Shirshov basis,and the corresponding irreducible elements forms a PBW type basis of the Ringel–Hall algebra. We aim to generalize this result to the derived Hall algebra DH(A_n) of type A_n. First, we compute all skew commutator relations between the iso-classes of indecomposable objects in the bounded derived category D~b(A_n) using the Auslander–Reiten quiver of D~b(A_n), and then we prove that all possible compositions between these skew commutator relations are trivial. As an application, we give a PBW type basis of DH(A_n).     

Presenting Schur Algebras as Quotients of the Universal Enveloping Algebra of gl2

We give a presentation of the Schur algebras S _Q (2,d) by generators and relations, in fact a presentation which is compatible with Serre's presentation of the universal enveloping algebra of a simple Lie algebra. In the process we find a new basis for S _Q (2,d), a truncated form of the usual PBW basis. We also locate the integral Schur algebra within the presented algebra as the analogue of Kostant's Z-form, and show that it has an integral basis which is a truncated version of Kostant's basis.     

素特征的“李定理”

设L为代数闭域F上有限维李代数,著名的李定理说:若char F=0,则L为可解当且仅当L的任一有限维不可约模为1维的.在这里特征为0及模为有限维两个条件都是本质的.(1)若charF=P>0,则L为交换当且仅当L的任一(有限维)不可约模为1维的;(2)若char F=0,则L为交换当且仅当L的任一(有限维或无限维)不可约模为1维的; (3)若char F=P>7,L为李代数(限制李代数),则L为可解当且仅当L的任一不可约模(限制模)的维数为p的幂.     

Endoprimal distributive lattices are endodualisable

L. Márki and R. Pöschel have characterised the endoprimal distributive lattices as those which are not relatively complemented. The theory of natural dualities implies that any finite algebraA on which the endomorphisms of A yield a duality on the quasivariety is necessarily endoprimal. This note investigates endodualisability for finite distributive lattices, and shows, in a manner which elucidates Márki and Pöschel's proof, that it is equivalent to endoprimality.Presented by A. F. Pixley.     

A strong constructive version of engel's theorem

We examine two problems in the computational theory of Lie algebras. First, we prove a constructive version of Engel's theorem: if L is a finite-dimensional Lie algebra that is not nilpotent, we show how to construct an element x in L such that the linear transformation ad x is not nilpotent. No special assumptions about the underlying field are needed. Second, as an important application of the first result, we give an algorithm for the construction of a Cartan subalgebra of a finite-dimensional Lie algebra. This solves the problem of finding a totally constructive proof of the existence of a Cartan subalgebra, posed by Beck, Kolman, and Stewart in the paper "Computing the Structure of a Lie Algebra". Our proofs are ordinary mathematical proofs that do not employ the general law of excluded middle. The advantage of this approach to mathematics is that our proofs, which are not burdened or obscured by the details of a particular programming language, can nevertheless be routinely turned into computer programs     

The centralizer of an element in a Lie algebra of type L

In this paper, we investigate the Lie algebra L(A, α, δ) of type L and obtain the respective sufficient conditions for L(A, α,δ) to be semisimple, and for Z(ω) = Fω as well, where 0 ≠ ω ∈ L(A, α, δ) and Z(ω) is the centralizer of ω.