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We describe a new class of maximal cliques, with a vector space structure, of Cayley graphs defined on the additive group of a field. In particular, we show that in the cubic Paley graph with order $q^3$, the subfield with $q$ elements…

Combinatorics · Mathematics 2022-08-16 Chi Hoi Yip

A well-known conjecture due to van Lint and MacWilliams states that if $A$ is a subset of $\mathbb{F}_{q^2}$ such that $0,1 \in A$, $|A|=q$, and $a-b$ is a square for each $a,b \in A$, then $A$ must be the subfield $\mathbb{F}_q$. This…

Combinatorics · Mathematics 2022-08-30 Shamil Asgarli , Chi Hoi Yip

We show the maximality of subfields as cliques in a special family of Cayley graphs defined on the additive group of a finite field. In particular, this confirms a conjecture of Yip on generalized Paley graphs.

Combinatorics · Mathematics 2023-08-30 Chi Hoi Yip

There is a conjecture that the second largest maximal cliques in Paley graphs of square order $P(q^2)$ have size $\frac{q+\epsilon}{2}$, where $q \equiv \epsilon \pmod 4$, and split into two orbits under the full group of automorphisms…

Combinatorics · Mathematics 2024-10-08 Huye Chen , Sergey Goryainov , Cong Hu

We prove that a family of pseudo-Paley graphs of square order obtained from unions of cyclotomic classes satisfies the Erd\H{o}s-Ko-Rado (EKR) module property, in a sense that the characteristic vector of each maximum clique is a linear…

Combinatorics · Mathematics 2023-01-02 Shamil Asgarli , Sergey Goryainov , Huiqiu Lin , Chi Hoi Yip

We study maximal cliques in the collinearity graphs of Desarguesian nets, give some structural results and some numerical information. In particular, we show for Desarguesian nets that the set consisting of a point $x$ together with all its…

Combinatorics · Mathematics 2026-04-28 Andries E. Brouwer , Sergey Goryainov , Leonid Shalaginov , Chi Hoi Yip

It is known that Paley graphs of square order have the strict-EKR property, that is, all maximum cliques are canonical cliques. Peisert-type graphs are natural generalizations of Paley graphs and some of them also have the strict-EKR…

Combinatorics · Mathematics 2024-06-21 Sergey Goryainov , Chi Hoi Yip

We derive an asymptotic formula for the number of solutions in a given subfield to certain system of equations over finite fields. As an application, we construct new families of maximal cliques in generalized Paley graphs. Given integers…

Number Theory · Mathematics 2024-12-02 Greg Martin , Chi Hoi Yip

The celebrated Erd\H{o}s-Ko-Rado (EKR) theorem for Paley graphs (of square order) states that all maximum cliques are canonical in the sense that each maximum clique arises from the subfield construction. Recently, Asgarli and Yip extended…

Combinatorics · Mathematics 2024-02-02 Chi Hoi Yip

For a given graph $H$, its subdivisions carry the same topological structure. The existence of $H$-subdivisions within a graph $G$ has deep connections with topological, structural and extremal properties of $G$. One prominent example of…

Combinatorics · Mathematics 2023-08-22 Seonghyuk Im , Jaehoon Kim , Younjin Kim , Hong Liu

Let $q$ be an odd power of a prime $p$, and $S \subset \mathbb{F}_q^*$ such that $S=-S$ and $S/S \neq \mathbb{F}_q^*$. We show that the clique number of the Cayley graph $\operatorname{Cay}(\mathbb{F}_q^+,S)$ is at most…

Combinatorics · Mathematics 2025-11-26 Chi Hoi Yip

Let $GP(q,d)$ be the $d$-Paley graph defined on the finite field $\mathbb{F}_q$. It is notoriously difficult to improve the trivial upper bound $\sqrt{q}$ on the clique number of $GP(q,d)$. In this paper, we investigate the connection…

Number Theory · Mathematics 2022-03-25 Chi Hoi Yip

We investigate the number of maximal cliques, i.e., cliques that are not contained in any larger clique, in three network models: Erd\H{o}s-R\'enyi random graphs, inhomogeneous random graphs (also called Chung-Lu graphs), and geometric…

Combinatorics · Mathematics 2024-11-27 Thomas Bläsius , Maximillian Katzmann , Clara Stegehuis

Let $p$ be a prime, let $q=p^n$, and let $D\subseteq \mathbb{F}_q^\ast$. A celebrated result of Carlitz and McConnel states that if $D$ is a proper subgroup of $\mathbb{F}_q^\ast$, and $f:\mathbb{F}_q\to\mathbb{F}_q$ is a function such that…

Number Theory · Mathematics 2026-04-07 Maosheng Xiong , Chi Hoi Yip

Let GP$(q^2,m)$ be the $m$-Paley graph defined on the finite field with order $q^2$. We study eigenfunctions and maximal cliques in generalised Paley graphs GP$(q^2,m)$, where $m \mid (q+1)$. In particular, we explicitly construct maximal…

Combinatorics · Mathematics 2023-08-30 Sergey Goryainov , Leonid Shalaginov , Chi Hoi Yip

We determine new upper bounds for the clique numbers of strongly regular graphs in terms of their parameters. These bounds improve on the Delsarte bound for infinitely many feasible parameter tuples for strongly regular graphs, including…

Combinatorics · Mathematics 2019-01-31 Gary R. W. Greaves , Leonard H. Soicher

In this paper we find new maximal cliques of size $\frac{q+1}{2}$ or $\frac{q+3}{2}$, accordingly as $q\equiv 1(4)$ or $q\equiv 3(4)$, in Paley graphs of order $q^2$, where $q$ is an odd prime power. After that we use new cliques to define…

Combinatorics · Mathematics 2021-03-02 Sergey Goryainov , Vladislav V. Kabanov , Leonid Shalaginov , Alexandr Valyuzhenich

We prove that the clique number of the Paley graph is at most $\sqrt{p/2} + 1$, and that any supposed additive decompositions of the set of quadratic residues can only come from co-Sidon sets.

Number Theory · Mathematics 2020-05-07 Brandon Hanson , Giorgis Petridis

In this paper, we study the order of a maximal clique in an amply regular graph with a fixed smallest eigenvalue by considering a vertex that is adjacent to some (but not all) vertices of the maximal clique. As a consequence, we show that…

Combinatorics · Mathematics 2020-12-18 Gary R. W. Greaves , Jack H. Koolen , Jongyook Park

The well-known Van Lint--MacWilliams' conjecture states that if $q$ is an odd prime power, and $A\subseteq \mathbb{F}_{q^2}$ such that $0,1 \in A$, $|A|=q$, and $a-b$ is a square for each $a,b \in A$, then $A$ must be the subfield…

Combinatorics · Mathematics 2026-01-21 Chi Hoi Yip
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