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This paper is devoted to the study of $2$-designs with $\lambda\ge (r,\lambda)^2$ admitting a flag-transitive automorphism group $G$. The group $G$ has been shown to be point-primitive of either almost simple or affine type. In this paper,…

Combinatorics · Mathematics 2025-11-19 Junchi Zhang , Jianbing Lu , Meizi Ou

In this article, we study $2$-designs with $\gcd(r,\lambda)=1$ admitting a flag-transitive almost simple automorphism group with socle a finite simple exceptional group of Lie type. We obtain four infinite families of such designs and…

Group Theory · Mathematics 2020-04-06 Seyed Hassan Alavi

In this article, we study $2$-designs with $\gcd(r, \lambda)=1$ admitting a flag-transitive automorphism group. The automorphism groups of these designs are point-primitive of almost simple or affine type. We determine all pairs…

Group Theory · Mathematics 2019-09-19 Seyed Hassan Alavi , Mohsen Bayat , Ashraf Daneshkhah

In this paper, we completely classify the non-trivial 2-(v,k,3) designs admitting an almost simple, flag-transitive automorphism group with socle PSL(2,q).

Combinatorics · Mathematics 2025-12-25 Hongxue Liang , Zhihui Liu , Alessandro Montinaro

The classification of the $2$-designs with $\lambda=2$ admitting a flag-transitive automorphism groups with socle $PSL(2,q)$ is completed by settling the two open cases in \cite{ABDT}. The result is achieved by using conics and hyperovals…

Combinatorics · Mathematics 2024-05-01 Alessandro Montinaro , Yanwei Zhao , Zhilin Zhang , Shenglin Zhou

The symmetric $2$-$(v,k,\lambda )$ designs, with $k>\lambda \left(\lambda-3 \right)/2$, admitting a flag-transitive, point-imprimitive automorphism group are completely classified: they are the known $2$-designs with parameters…

Combinatorics · Mathematics 2022-12-20 Alessandro Montinaro

Let $\mathcal{D}$ be a non-trivial quasi-symmetric $2$-design with two block intersection numbers $x=0$ and $2\leq y\leq10$, and suppose that $G$ is an automorphism group of $\mathcal{D}$. If $G$ is flag-transitive and point-primitive, then…

Combinatorics · Mathematics 2025-06-13 Jianbing Lu

In this article, we investigate symmetric 2-designs of prime order admitting a flag-transitive automorphism group G. Recently, the authors proved that the automorphism group G of this type of designs must be point-primitive, and is of…

Group Theory · Mathematics 2023-07-26 Z. W. Lu , S. L. Zhou

In this article, we study $2$-$(v,k,\lambda)$ designs $\mathcal{D}$ with $\lambda$ prime admitting flag-transitive and point-primitive almost simple automorphism groups $G$ with socle $T$ a finite exceptional simple group or a sporadic…

Group Theory · Mathematics 2025-05-09 Seyed Hassan Alavi , Ashraf Daneshkhah , Alessandro Montinaro

In this article, we investigate $2$-$(v,k,\lambda)$ designs with $\gcd(r,\lambda)=1$ admitting flag-transitive automorphism groups $G$. We prove that if $G$ is an almost simple group, then such a design belongs to one of the seven infinite…

Group Theory · Mathematics 2020-08-11 Seyed Hassan Alavi , Ashraf Daneshkhah , Fatemeh Mouseli

In this article, we study $2$-designs with prime replication number admitting a flag-transitive automorphism group. The automorphism groups of these designs are point-primitive of almost simple or affine type. We determine $2$-designs with…

Group Theory · Mathematics 2019-08-16 Seyed Hassan Alavi , Mohsen Bayat , Jalal Choulaki , Asharf Daneshkhah

Non-trivial $2$-$(k^{2},k,\lambda )$ designs, with $\lambda \mid k$, admitting a flag-transitive almost simple automorphism group are classified.

Group Theory · Mathematics 2022-03-18 Alessandro Montinaro

This paper is devoted to the classification of all flag-transitive point-primitive non-trivial $2$-$(v, k, \lambda)$ designs with the alternating group $A_n$($n \le 10$) as the socle of their automorphism groups, and 87 different designs…

Combinatorics · Mathematics 2025-08-29 Delu Tian , Qianfen Liao , Zhilin Zhang

In this article, we study flag-transitive automorphism groups of non-trivial symmetric $(v, k, \lambda)$ designs, where $\lambda$ divides $k$ and $k\geq \lambda^2$. We show that such an automorphism group is either point-primitive of affine…

Group Theory · Mathematics 2019-01-15 Seyed Hassan Alavi , Ashraf Daneshkhah , Narges Okhovat

In this article, we investigate symmetric $(v,k,\lambda)$ designs $\mathcal{D}$ with $\lambda$ prime admitting flag-transitive and point-primitive automorphism groups $G$. We prove that if $G$ is an almost simple group with socle a finite…

Group Theory · Mathematics 2020-09-14 Seyed Hassan Alavi , Mohsen Bayat , Ashraf Daneshkhah

In this paper, we present a classification of $2$-designs with $\gcd(r,\lambda)=1$ admitting flag-transitive automorphism groups. If $G$ is a flag-transitive automorphism group of a non-trivial $2$-design $\mathcal{D}$ with…

In this article, we study symmetric designs admitting flag-transitive, point-imprimitive almost simple automorphism groups with socle sporadic simple groups. As a corollary, we present a classification of symmetric designs admitting…

Group Theory · Mathematics 2023-07-12 Seyed Hassan Alavi , Ashraf Daneshkhah

In this paper we show that a flag-transitive automorphism group $G$ of a non-trivial $2$-$(v,k,\lambda)$ design with $\lambda\geq (r, \lambda)^2$ is not of product action type. In conclusion, $G$ is a primitive group of affine or almost…

Group Theory · Mathematics 2023-04-19 Huiling Li , Zhilin Zhang , Shenglin Zhou

It is shown that, apart from the smallest Ree group, a flag-transitive automorphism group $G$ of a $2$-$(k^{2}, k, \lambda)$ design D, with $\lambda \mid k$, is either an affine group or an almost simple classical group. Moreover, when $G$…

Combinatorics · Mathematics 2022-03-18 Alessandro Montinaro , Eliana Francot

This paper determined all pairs $(\mathcal{D},G)$ where $\mathcal{D}$ is a non-symmetric 2-$(v,k,\lambda)$ design with $(r,\lambda)=1$ and $G$ is the almost simple flag-transitive automorphism group of $\mathcal{D}$ with an exceptional…

Combinatorics · Mathematics 2019-07-16 Yongli Zhang , Shenglin Zhou
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