A note on the ranks of 2 × 2 × 2 and 2 × 2 × 2 × 2 tensors

Using rank-1 reduction formula and the vector space spanned by the real rank-1 matrices, we present a different way to show that the maximum possible rank of the 2?×?2?×?2 tensors over the real field is 3. Following, we obtain that the maximum rank of the 2?×?2?×?2?×?2 tensors over the real field is less than or equal to 5 and propose another way to show that the maximum rank of the 2?×?2?×?2?×?2 tensors over the complex field is 4, except one special case.     

2×2 Hermite矩阵几何

设D是有对合a→的除环, 假设是D的真子域并且含在D的中心域中. 指出: 如果D的特征不等于2, 则D是F上可离二次扩域或者是F上广义四元数除环; 如果D的特征等于2, 则D是F上可离二次扩域, 因此迹映射Tr:D→F,恒为满射,从而已有的 Hermite矩阵几何的基本定理中关于D的假设(ii)可以删去. 万哲先已经证明了当D为域时2×2 Hermite矩阵几何的基本定理. 继续证明了当D为特征不等于2的广义四元数除环时,D上2×2 Hermite矩阵几何的基本定理.     

环F_2+uF_2+u~2F_2上循环码的Gray距离

定义了环R=F2+uF2+u2 F2(u3=0)到F32的一个新的Gray映射.首先介绍环R上奇长度的循环码的挠码,给出了各阶挠码的生成多项式.利用一阶挠码与二阶挠码确立了R上奇长度的循环码的Gray距离.     

利用|z_1 z_2|~2 |z_1-z_2|~2=2|z_1|~2 2|z_2|~2解题

关于复数模的有关性质之一有公式|z_1 z_2|~2 |z_1-z_2|~2=2|z_1|~2 2|z_2|~2其几何意义是:平行四边形两对角线的平方和等于四边平方和,利用它解决一类有关复数模的问题不但有效,而且解题过程简单,方法新颖。例1 已知|z 3 4i|~2 |z-3-4i|~2=80求|z|:并说明z点的轨迹表示的图形。分析若设z=x yi代入已知整理,则会步骤冗长,利用     

On the classification of nonsingular 2×2×2×2 hypercubes

As a first step in the classification of nonsingular 2×2×2×2 hypercubes up to equivalence, we resolve the case where the base field is finite and the hypercubes can be written as a product of two 2×2×2 hypercubes. (Nonsingular hypercubes were introduced by D. Knuth in the context of semifields. Where semifields are related to hypercubes of dimension 3, this paper considers the next case, i.e., hypercubes of dimension 4.) We define the notion of ij-rank (with 1 ≤ i < j ≤ 4) and prove that a hypercube is the product of two 2×2×2 hypercubes if and only if its 12-rank is at most 2. We derive a ‘standard form’ for nonsingular 2×2×2×2 hypercubes of 12-rank less than 4 as a first step in the classification of such hypercubes up to equivalence. Our main result states that the equivalence class of a nonsingular 2×2×2×2 hypercube M of 12-rank 2 depends only on the value of an invariant δ ₀(M) which derives in a natural way from the Cayley hyperdeterminant det₀ M and another polynomial invariant det M of degree 4. As a corollary we prove that the number of equivalence classes is (q + 1)/2 or q/2 depending on whether the order q of the field is odd or even.     

求1~2 2~2 3~2 … n~2的一种方法

因为每个三角形数阵各数字之和=12 22 32 … n2．每个三角形数阵共有(1 n)n/2 个数．现将三个三角形数阵平移使其重合,则重合后每个小圆圈内三数和为2n 1,所以重     

也谈Pell方程x~2-2y~2=1和y~2-DZ~2=4的公解

本文证明了:若D为奇数且最多含有3个互不相同的素因数时,Pell方程x~2-2y~2=1和y~2-Dz~2=4的公解仅有非平凡解(x,y,z)=(17,12,2)(D=35);(x,y,z)=(19601,13860,26)(D=29×41×239)。这个结论加强了Mohanty和Ramasamy以及陈建华的结论。     

环$F_2 uF_2 u^2F_2$上的循环码及自对偶码

We give the structures of a cyclic code over ring
R = F2 ＋ uF2 ＋ u^2F2 = {0, 1,u, u^2,v, v^2,uv, v^3},
where u^3 = 0, of odd length and its dual code. For the cyclic code, necessary and sufficient conditions for the existence of self-dual code are provided.     

三群体2×2×2非对称演化博弈稳定性分析

针对目前三方演化博弈的稳定性研究不足这一问题,利用复制动态方程构建了一般化的三维动力系统,首先讨论了单群体策略演化趋势,接着根据李雅普诺夫稳定性理论分析了系统的渐进稳定性,并结合单群体策略的演化趋势对系统稳定性作了深入研究。研究表明:严格纯策略纳什均衡是ESS,不严格纯策略纳什均衡是线性策略收敛(自定义概念),所有类型的混合策略纳什均衡均为鞍点,共同划分了ESS的吸引域,并证明了零特征值非ESS定理,以及ESS不共边定理,在此基础上给出了N维双策略系统中ESS的最多个数。最后,设计了六组经典算例,首先结合研究结果分析了算例,接着对算例进行系统仿真,仿真结果与理论分析一致,为演化博弈的进一步研究提供借鉴与启发。     

环F_2+uF_2+u~2F_2上线性码的MacWilliams恒等式

记R=F_2+uF_2+u~2F_2,定义了环R上码字的李重量分布的概念,构造了从R~n到F_2~(3n)的Gray映射φ.通过对环R上线性码及其对偶码生成矩阵的研究,证明了环R上线性码及其对偶码的Gray象是F_2上的对偶码.利用域F_2上线性码及其对偶码的重量分布关系,得到了环R上线性码及其对偶码关于李重量分布的MacWilliams恒等式.     

用((a b)/2)~2≤(a~2 b~2)/2解题两例

对于a、b∈R,易知(a b/2)2≤a2 b2/2恒成立,此不等式反映了任意两个实数的和与这两个数的平方和的大小关系,巧用这一不等式可以妙解一些数学不等关系的问题．请看以下两例: 1．比较大小例1试比较2~(1/2) 3~(1/2) 4~(1/2)与30~(1/2)的大小．解∵(a b/2)2≤a2 b2/2,     

马达加斯加2

狮子亚历史斯是丛林之王,这里的丛林指的是喧嚣的城市丛林,而非茂密的野生丛林。在纽约中央公园里的动物园,他算得上是吸引游客的头号明星。     

2×2算子矩阵的逆

设H和K为复的无限维可分Hilbert空间．本文利用算子的几何结构着重研究了Hilbert空间H(?)K上的2×2算子矩阵的逆,给出了一些有意义的结果．     

L~2(R~2)中2进变元低通滤波器

一维2进低通滤波器在一维多分辨分析(MRA)小波的构造和拓扑性质研究中起到重要作用.对于高维小波,其生成要依赖于某个扩张矩阵,所以构造比较复杂.该文讨论由一致矩阵2I_2(2002)生成的MRA小波的低通滤波器(称作2进双变量滤波器.利用2进双变量滤波器乘子完全刻画了2进双变量滤波器,并且证明了所有2进双变量滤波器集合在L~2(T~2)范数拓扑下是道路连通的结论.     

Diophantine方程y~2=px(x~2+2)

设p是大于3的奇素数.本文证明了:当p≡5或7(mod 8)时,方程y~2=px(x~2+2)无正整数解(x,y);当p≡1(mod 8)时,该方程至多有1组解;当p≡3(mod 8)时,该方程至多有2组解.     

The rank of a 2 × 2 × 2 tensor

As computing power increases, many more problems in engineering and data analysis involve computation with tensors, or multi-way data arrays. Most applications involve computing a decomposition of a tensor into a linear combination of rank-1 tensors. Ideally, the decomposition involves a minimal number of terms, i.e. computation of the rank of the tensor. Tensor rank is not a straight-forward extension of matrix rank. A constructive proof based on an eigenvalue criterion is provided that shows when a 2?×?2?×?2 tensor over ? is rank-3 and when it is rank-2. The results are extended to show that n?×?n?×?2 tensors over ? have maximum possible rank n?+?k where k is the number of complex conjugate eigenvalue pairs of the matrices forming the two faces of the tensor cube.     

环F_2+uF_2+u~2F_2上线性码的广义Gray像

摘要:引入了环F_2+uF_2+u~2F_2与F_2之间的广义Gray映射,利用环F_2+uF_2+u~2F_2上线性码的生成矩阵得出了广义Gray像φ(C)的生成矩阵,证明了F_2+uF2+u2F2上线性码自正交码的广义Gray像仍为自正交码和F_2+uF_2+u~2F_2上循环码的广义Gray像是F_2上的准循环码.