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It was first shown by Cameron and Ku that the group $G=Sym(n)$ has the strict EKR property. Then Godsil and Meagher presented an entirely different proof of this fact using some algebraic properties of the symmetric group. A similar method…

Combinatorics · Mathematics 2013-12-02 Bahman Ahmadi

A subset in a group $G \leq Sym(n)$ is intersecting if for any pair of permutations $\pi,\sigma$ in the subset there is an $i \in \{1,2,\dots,n\}$ such that $\pi(i) = \sigma(i)$. If the stabilizer of a point is the largest intersecting set…

Combinatorics · Mathematics 2013-11-28 Bahman Ahmadi , Karen Meagher

In this paper we consider the derangement graph for the group $\textrm{PSU}(3,q)$ where $q$ is a prime power. We calculate all eigenvalues for this derangement graph and use these eigenvalues to prove that $\textrm{PSU}(3,q)$ has the…

Combinatorics · Mathematics 2017-08-29 Karen Meagher

In the recent years, the generalization of the Erd\H{o}s-Ko-Rado (EKR) theorem to permutation groups has been of much interest. A transitive group is said to satisfy the EKR-module property if the characteristic vector of every maximum…

Combinatorics · Mathematics 2024-04-17 Cai Heng Li , Venkata Raghu Tej

A set of permutations $\mathcal{F}$ of a finite transitive permutation group $G\leq \operatorname{Sym}(\Omega)$ is \emph{intersecting} if any pair of elements of $\mathcal{F}$ agree on an element of $\Omega$. We say that $G$ has the…

Combinatorics · Mathematics 2021-11-11 Roghayeh Maleki , Andriaherimanana Sarobidy Razafimahatratra

In this paper we prove an Erd\H{o}s-Ko-Rado-type theorem for intersecting sets of permutations. We show that an intersecting set of maximal size in the projective general linear group PGL(3,q), in its natural action on the points of the…

Combinatorics · Mathematics 2013-10-10 Karen Meagher , Pablo Spiga

In this paper we introduce a new way of measuring the robustness of Erd\H{o}s--Ko--Rado (EKR) Theorems on permutation groups. EKR-type results can be viewed as results about the independence numbers of certain corresponding graphs, namely…

Combinatorics · Mathematics 2025-02-21 Karen Gunderson , Karen Meagher , Joy Morris , Venkata Raghu Tej Pantangi , Mahsa N Shirazi

Let $S_n$ be the symmetric group on $n$ points. Deza and Frankl [M. Deza and P. Frankl, On the maximum number of permutations with given maximal or minimal distance, J. Combin. Theory Ser. A 22 (1977) 352--360] proved that if ${\cal F}$ is…

Combinatorics · Mathematics 2011-07-19 Jun Guo , Kaishun Wang

We prove that every 2-transitive group has a property called the EKR-module property. This property gives a characterization of the maximum intersecting sets of permutations in the group. Specifically, the characteristic vector of any…

Combinatorics · Mathematics 2022-07-13 Karen Meagher , Peter Sin

Let $G=\text{GL}_n(q)$ be the general linear group over the finite field $\mathbb{F}_q$ of $q$ elements, and let $k$ be an algebraically closed field of characteristic $r >0$ such that $r$ does not divide $q(q-1)$. In 1999, Cline, Parshall,…

Representation Theory · Mathematics 2020-10-06 Veronica Shalotenko

Let G=PGL(2,q) be the projective general linear group acting on the projective line P_q. A subset S of G is intersecting if for any pair of permutations \pi,\sigma in S, there is a projective point p in P_q such that p^\pi=p^\sigma. We…

Combinatorics · Mathematics 2010-10-22 Karen Meagher , Pablo Spiga

The classical Erd\H os-Ko-Rado theorem states that if $k\le\floor{n/2}$ then the largest family of pairwise intersecting $k$-subsets of $[n]=\{0,1,...,n\}$ is of size ${{n-1}\choose{k-1}}$. A family of $k$ subsets satisfying this pairwise…

Combinatorics · Mathematics 2012-04-12 Patricia A. Carey , Anant P. Godbole

Consider the general linear group, which is not connected but rather has two connected components, the matrices with positive determinant and the ones with negative determinant. Consider the Iwasawa decomposition of its special linear…

Representation Theory · Mathematics 2014-04-23 Kahar El-Hussein

We give a proof of the Erd\H{o}s-Ko-Rado Theorem using the Borel Fixed Point Theorem from algebraic group theory. This perspective gives a strong analogy between the Erd\H{o}s-Ko-Rado Theorem and (generalizations of) the Gerstenhaber…

Combinatorics · Mathematics 2024-11-06 Russ Woodroofe

A subset $Y$ of the general linear group $\operatorname{GL}(n,q)$ is called $t$-intersecting if $\operatorname{rk}(x-y)\le n-t$ for all $x,y\in Y$, or equivalently $x$ and $y$ agree pointwise on a $t$-dimensional subspace of…

Combinatorics · Mathematics 2023-06-28 Alena Ernst , Kai-Uwe Schmidt

Let a finite group $G$ act transitively on a finite set $X$. A subset $S\subseteq G$ is said to be {\it intersecting} if for any $s_1,s_2\in S$, the element $s_1^{-1}s_2$ has a fixed point. The action is said to have the {\it weak…

Group Theory · Mathematics 2014-12-15 Mohammad Bardestani , Keivan Mallahi-Karai

As we all know, many interesting and important codes are obtained by modifying or combining existing codes. In this paper, we focus on generalized Roth-Lempel (in short, GRL) codes and define a class of extended codes, i.e., the extended…

Information Theory · Computer Science 2025-08-19 Zhonghao Liang , Qunying Liao

The Erd\H{o}s--Ko--Rado (EKR) theorem and its generalizations can be viewed as classifications of maximum independent sets in appropriately defined families of graphs, such as the Kneser graph $K(n,k)$. In this paper, we investigate the…

Combinatorics · Mathematics 2024-06-25 Karen Gunderson , Karen Meagher , Joy Morris , Venkata Raghu Tej Pantangi , Mahsa N. Shirazi

A theorem of Elekes and Szab\'{o} recognizes algebraic groups among certain complex algebraic varieties with maximal size intersections with finite grids. We establish a generalization to relations of any arity and dimension, definable in:…

Logic · Mathematics 2023-03-07 Artem Chernikov , Ya'acov Peterzil , Sergei Starchenko

In this paper we study twisted conjugacy classes and the $R_{\infty}$-property for classical linear groups. In particular, we prove that the general linear group ${\rm GL}_n(K)$ and the special linear group ${\rm SL}_n(K)$ possess…

Group Theory · Mathematics 2012-02-01 T. R. Nasybullov
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