A subset $B$ of a group $G$ is called a difference basis of $G$ if each element $g\in G$ can be written as the difference $g=ab^{-1}$ of some elements $a,b\in B$. The smallest cardinality $|B|$ of a difference basis $B\subset G$ is called the difference size of $G$ and is denoted by $Δ[G]$. The fraction $ð[G]:=Δ[G]/{\sqrt{|G|}}$ is called the difference characteristic of $G$. We prove that for every $n\in\mathbb N$ the dihedral group $D_{2n}$ of order $2n$ has the difference characteristic $\sqrt{2}\leð[D_{2n}]\leq\frac{48}{\sqrt{586}}\approx1.983$. Moreover, if $n\ge 2\cdot 10^{15}$, then $ð[D_{2n}]<\frac{4}{\sqrt{6}}\approx1.633$. Also we calculate the difference sizes and characteristics of all dihedral groups of cardinality $\le80$.
Combinatorial transfer: a new method for constructing infinite families of nonabelian difference sets, partial difference sets, and relative difference sets
On minimal product-one sequences of maximal length over Dihedral and Dicyclic groups
设$G$是一个有限群.对于$G$上的序列,我们指的是来自$G$的项的有限无序序列,其中允许重复,并且如果它的项可以被排序使得它们的乘积等于$G$的单位元,则我们说它是乘积1序列。大达文波特常数$\mathsf D (G)$是最小乘积1序列的最大长度,即不能分解为两个非平凡乘积1序列的乘积1序列。给出了二面体群和双循环群上长度为$\mathsf D (G)$的所有极小积1序列的明确刻画。基于这些刻画,我们研究了这些群上的积一序列么半群的长度集的并。
Computation of small reflective and dihedral Ramsey numbers
Faculty of Electronic Engineering, University of Niš(尼什大学电子工程学院);Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska(普里莫尔斯卡大学数学、自然科学和信息技术学院)
Reed College(里德学院);University of Michigan(密歇根大学);Amherst College(阿默斯特学院);Princeton University(普林斯顿大学);Williams College(威廉姆斯学院);University of Wisconsin, Madison(威斯康星大学麦迪逊分校);University of Texas at Austin(德克萨斯大学奥斯汀分校)