If $S$ is a subset of an abelian group $G$, the polychromatic number of $S$ in $G$ is the largest integer $k$ so that there is a $k-$coloring of the elements of $G$ such that every translate of $S$ in $G$ gets all $k$ colors. We determine the polychromatic number of all sets of size 2 or 3 in the group of integers mod n.
If $G$ is a graph and $\mathcal{H}$ is a set of subgraphs of $G$, we say that an edge-coloring of $G$ is $\mathcal{H}$-polychromatic if every graph from $\mathcal{H}$ gets all colors present in $G$ on its edges. The $\mathcal{H}$-polychromatic number of $G$, denoted $\operatorname{poly}_\mathcal{H} (G)$, is the largest number of colors in an $\mathcal{H}$-polychromatic coloring. In this paper we determine $\operatorname{poly}_\mathcal{H} (G)$ exactly when $G$ is a complete graph on $n$ vertices, $q$ is a fixed nonnegative integer, and $\mathcal{H}$ is one of three families: the family of all m…
In a recent paper, Grau et al. (2017) studied the zero divisor graphs of the ring of Lipschitz integers modulo $n$, and computed the domination number of the undirected zero divisor graph of the ring of Lipschitz integers modulo $n$. But the case $n$ is a power of prime numbers remained open. In this note, this problem is solved. We also show the automorphism group of the zero divisor graph of the ring of Lipschitz integers modulo $2^s$.
The study of graph drawings on 2-surfaces is an active area of mathematical research. Our main results are criteria for integer and modulo 2 embeddability of graphs to surfaces.
The work considers an equivalence relation in the set of all $n\times m$ matrices with entries in the set $[p]=\{ 0,1,\ldots , p-1 \}$. In each element of the factor-set generated by this relation, we define the concept of canonical matrix, namely the minimal element with respect to the lexicographic order. We have found a necessary and sufficient condition for an arbitrary matrix with entries in the set $[p]$ to be canonical. For this purpose, the matrices are uniquely represented by ordered n-tuples of integers.
Domination polynomial of co-maximal graphs of integer modulo ring
School of Mathematics and Statistics, Shandong University of Technology(山东理工大学数学与统计学院);School of Mechanical Engineering, Shandong University of Technology(山东理工大学机械工程学院)
A universal sequence of integers generating balanced Steinhaus figures modulo an odd number
在本文中,我们部分地解决了一个公开的问题,由于J. C. Molluzzo在1976年提出了一个正整数$n$模的平衡Steinhaus三角形的存在性,即包含$\mathbb{Z}/n\mathbb{Z}$的所有元素的Steinhaus三角形具有相同的重数。对于每一个奇数$n$,通过线性元胞自动机生成杨辉三角形模$n$,在$\mathbb{Z}/n\mathbb{Z}$中建立一个轨道,其中包含无穷多个平衡Steinhaus三角形.在$\mathbb{Z}/n\mathbb{Z}$中,这个轨道是从一个称为通用序列的整数序列中得到的。证明了在$n$是奇素数幂的情况下,对于至少$2/3$的容许大小,存在平衡的Steinhaus三角形.其他平衡的斯坦豪斯图形,如斯坦豪斯三角形、广义杨辉三角形、帕斯卡三角形或菱形,也出现在通用序列模$n$奇数的轨道上。我们证明了平衡广义杨辉三角形的存在性至少$2/3$的容许大小,在$n$是一个奇素数的权力的情况下,和平衡菱形的存在性的所有容许的大小,在$n$是一个平方免费的奇数。
A Kakeya set $S \subset (\mathbb{Z}/N\mathbb{Z})^n$ is a set containing a line in each direction. We show that, when $N$ is any square-free integer, the size of the smallest Kakeya set in $(\mathbb{Z}/N\mathbb{Z})^n$ is at least $C_{n,ε} N^{n - ε}$ for any $ε$ -- resolving a special case of a conjecture of Hickman and Wright. Previously, such bounds were only known for the case of prime $N$. We also show that the case of general $N$ can be reduced to lower bounding the $\mathbb{F}_p$ rank of the incidence matrix of points and hyperplanes over $(\mathbb{Z}/p^k\mathbb{Z})^n$.
Thomassen, in 1983, conjectured that for a positive integer $k$, every $2$-connected non-bipartite graph of minimum degree at least $k + 1$ contains cycles of all lengths modulo $k$. In this paper, we settle this conjecture affirmatively.
Given a constant $α>0$, an $n$-vertex graph is called an $α$-expander if every set $X$ of at most $n/2$ vertices in $G$ has an external neighborhood of size at least $α|X|$. Addressing a question posed by Friedman and Krivelevich in [Combinatorica, 41(1), (2021), pp. 53--74], we prove the following result: Let $k>1$ be an integer with smallest prime divisor $p$. Then for $α>\frac{1}{p-1}$ every sufficiently large $α$-expanding graph contains cycles of length congruent to any given residue modulo $k$. This result is almost best possible, in the following sense: There exists an absolute constant…
Given a prime $p$ and a positive integer $k$, let $\mathrm{M}_{n}(\mathbb{Z}/p^{k}\mathbb{Z})$ be the ring of $n \times n$ matrices over $\mathbb{Z}/p^{k}\mathbb{Z}$. We consider the number of solutions $X \in \mathrm{M}_{n}(\mathbb{Z}/p^{k}\mathbb{Z})$ to the polynomial equation $P(X) = 0$, where $P(t)$ is a monic polynomial in $(\mathbb{Z}/p^{k}\mathbb{Z})[t]$ whose reduction modulo $p$ is square-free over the finite field $\mathbb{F}_{p}$ of $p$ elements. Noting that $P(X) = 0$ if and only if $\mathrm{cok}(P(X)) \simeq (\mathbb{Z}/p^{k}\mathbb{Z})^{n}$, we give a conjectural generalization …
For a positive integer $\ell$, let $b_{\ell}(n)$ denote the number of $\ell$-regular partitions of a nonnegative integer $n$. Motivated by some recent conjectures of Keith and Zanello, we establish infinite families of congruences modulo $2$ for $b_3(n)$ and $b_{21}(n)$. We prove a specific case of a conjecture of Keith and Zanello on self-similarities of $b_3(n)$ modulo $2$. We next prove that the series $\sum_{n=0}^{\infty}b_9(2n+1)q^n$ is lacunary modulo arbitrary powers of $2$. We also prove that the series $\sum_{n=0}^{\infty}b_9(4n)q^n$ is lacunary modulo $2$.