On the classification of triply-transitive strongly-regular graphs
Fuente:
arXiv
Gespeichert in:
| Hauptverfasser: | , , |
|---|---|
| Format: | Preprint |
| Veröffentlicht: |
2025
|
| Schlagworte: | |
| Online-Zugang: | |
| Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
| _version_ | 1866918098310791168 |
|---|---|
| author | Herman, Allen Maleki, Roghayeh Razafimahatratra, Andriaherimanana Sarobidy |
| author_facet | Herman, Allen Maleki, Roghayeh Razafimahatratra, Andriaherimanana Sarobidy |
| contents | Let $Γ= (Ω,E)$ be a strongly-regular graph with adjacency matrix $A_1$, and let $A_2$ be the adjacency matrix of its complement. For any vertex $ω\in Ω$, we define $E_{0,ω}^*$ $E_{1,ω}^*$ and $E_{2,ω}^*$ to be respectively the diagonal matrices whose main diagonal is the row corresponding to $ω$ in the matrices $I, A_1$, and $A_2$. The Terwilliger algebra of $Γ$ with respect to the vertex $ω\in Ω$ is the subalgebra $T_ω= \left\langle I,A_1,A_2,E_{0,ω}^*,E_{1,ω}^*,E_{2,ω}^* \right\rangle$ of the complex matrix algebra $\operatorname{M_{|Ω|}}(\mathbb{C})$. The algebra $T_ω$ contains the subspace $T_{0,ω} = \operatorname{Span}\left\{ E_{i,ω}^*A_jE_{k,ω}^*: 0\leq i,j,k\leq 2 \right\}$.
In addition, if $G = \AutΓ$, then $T_ω$ is a subalgebra of the centralizer algebra $\tilde{T}_ω= \End{G_ω}{\mathbb{C}^Ω}$.
The strongly-regular graph $Γ=(Ω,E)$ is triply transitive if $Γ$ is vertex transitive and $T_{0,ω} = T_ω= \tilde{T}_ω$, for any $ω\in Ω$. In this paper, we classify all triply transitive strongly-regular graphs that are not isomorphic to the collinearity graph of the polar space $O_{6}^-(q)$, where $q$ is a prime power, or the affine polar graph $\vo_{2m}^\varepsilon(2)$, where $m\geq 1$ and $\varepsilon = \pm 1$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_14320 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On the classification of triply-transitive strongly-regular graphs Herman, Allen Maleki, Roghayeh Razafimahatratra, Andriaherimanana Sarobidy Combinatorics Rings and Algebras 05E30, 20B05, 51E99 Let $Γ= (Ω,E)$ be a strongly-regular graph with adjacency matrix $A_1$, and let $A_2$ be the adjacency matrix of its complement. For any vertex $ω\in Ω$, we define $E_{0,ω}^*$ $E_{1,ω}^*$ and $E_{2,ω}^*$ to be respectively the diagonal matrices whose main diagonal is the row corresponding to $ω$ in the matrices $I, A_1$, and $A_2$. The Terwilliger algebra of $Γ$ with respect to the vertex $ω\in Ω$ is the subalgebra $T_ω= \left\langle I,A_1,A_2,E_{0,ω}^*,E_{1,ω}^*,E_{2,ω}^* \right\rangle$ of the complex matrix algebra $\operatorname{M_{|Ω|}}(\mathbb{C})$. The algebra $T_ω$ contains the subspace $T_{0,ω} = \operatorname{Span}\left\{ E_{i,ω}^*A_jE_{k,ω}^*: 0\leq i,j,k\leq 2 \right\}$. In addition, if $G = \AutΓ$, then $T_ω$ is a subalgebra of the centralizer algebra $\tilde{T}_ω= \End{G_ω}{\mathbb{C}^Ω}$. The strongly-regular graph $Γ=(Ω,E)$ is triply transitive if $Γ$ is vertex transitive and $T_{0,ω} = T_ω= \tilde{T}_ω$, for any $ω\in Ω$. In this paper, we classify all triply transitive strongly-regular graphs that are not isomorphic to the collinearity graph of the polar space $O_{6}^-(q)$, where $q$ is a prime power, or the affine polar graph $\vo_{2m}^\varepsilon(2)$, where $m\geq 1$ and $\varepsilon = \pm 1$. |
| title | On the classification of triply-transitive strongly-regular graphs |
| topic | Combinatorics Rings and Algebras 05E30, 20B05, 51E99 |
| url | https://arxiv.org/abs/2507.14320 |