Zobrazeno 1 - 10
of 177
pro vyhledávání: '"Devillers, Alice"'
Autor:
Devillers, Alice, Kamčev, Nina, McKay, Brendan, Catháin, Padraig Ó, Royle, Gordon, Van de Voorde, Geertrui, Wanless, Ian, Wood, David R.
There are finitely many graphs with diameter $2$ and girth 5. What if the girth 5 assumption is relaxed? Apart from stars, are there finitely many triangle-free graphs with diameter $2$ and no $K_{2,3}$ subgraph? This question is related to the exist
Externí odkaz:
http://arxiv.org/abs/2406.00246
Autor:
Alavi, Seyed Hassan, Amarra, Carmen, Daneshkhah, Ashraf, Devillers, Alice, Praeger, Cheryl E.
It was shown in 1989 by Delandtsheer and Doyen that, for a $2$-design with $v$ points and block size $k$, a block-transitive group of automorphisms can be point-imprimitive (that is, leave invariant a nontrivial partition of the point set) only if $v
Externí odkaz:
http://arxiv.org/abs/2404.11241
We consider $2$-designs which admit a group of automorphisms that is flag-transitive and leaves invariant a chain of nontrivial point-partitions. We build on our recent work on $2$-designs which are block-transitive but not necessarily flag-transitiv
Externí odkaz:
http://arxiv.org/abs/2401.13885
An $H$-decomposition of a graph $\Gamma$ is a partition of its edge set into subgraphs isomorphic to $H$. A transitive decomposition is a special kind of $H$-decomposition that is highly symmetrical in the sense that the subgraphs (copies of $H$) are
Externí odkaz:
http://arxiv.org/abs/2308.07684
More than $30$ years ago, Delandtsheer and Doyen showed that the automorphism group of a block-transitive $2$-design, with blocks of size $k$, could leave invariant a nontrivial point-partition, but only if the number of points was bounded in terms o
Externí odkaz:
http://arxiv.org/abs/2303.11655
Publikováno v:
Innov. Incidence Geom. 20 (2023) 135-175
The sets of primitive, quasiprimitive, and innately transitive permutation groups may each be regarded as the building blocks of finite transitive permutation groups, and are analogues of composition factors for abstract finite groups. This paper ext
Externí odkaz:
http://arxiv.org/abs/2212.02574
Autor:
Devillers, Alice, Praeger, Cheryl E.
In this paper we develop several general methods for analysing flag-transitive point-imprimitive $2$-designs, which give restrictions on both the automorphisms and parameters of such designs. These constitute a tool-kit for analysing these designs an
Externí odkaz:
http://arxiv.org/abs/2208.12455
Publikováno v:
J. Algebraic Combin. 57 (2023), 515-524
A graph is called odd if there is an orientation of its edges and an automorphism that reverses the sense of an odd number of its edges, and even otherwise. Pontus von Br\"omssen (n\'e Andersson) showed that the existence of such an automorphism is i
Externí odkaz:
http://arxiv.org/abs/2204.01947
The Johnson graph $J(v, k)$ has as vertices the $k$-subsets of $\mathcal{V}=\{1,\ldots, v\}$, and two vertices are joined by an edge if their intersection has size $k-1$. An \emph{$X$-strongly incidence-transitive code} in $J (v, k)$ is a proper vert
Externí odkaz:
http://arxiv.org/abs/2202.06237
We study point-block incidence structures $(\mathcal{P},\mathcal{B})$ for which the point set $\mathcal{P}$ is an $m\times n$ grid. Cameron and the fourth author showed that each block $B$ may be viewed as a subgraph of a complete bipartite graph $\m
Externí odkaz:
http://arxiv.org/abs/2201.01143