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Hamiltonian Cycles for Finite Weyl Groupoids

Takato Inoue, Hiroyuki Yamane

Abstract

Let $Γ({\mathcal{W}})$ be the Cayley graph of a finite Weyl groupoid ${\mathcal{W}}$. In this paper, we show an existence of a Hamitonian cycle of $Γ({\mathcal{W}})$ for any ${\mathcal{W}}$. We exatctly draw a Hamiltonian cycle of $Γ({\mathcal{W}})$ for any (resp. some) irreducible ${\mathcal{W}}$ of rank three (resp. four). Moreover for the irreducible ${\mathcal{W}}$ of rank three, we give a second largest eigenvalue of the adjacency matrix of $Γ({\mathcal{W}})$, and know if $Γ({\mathcal{W}})$ is a bipartite Ramanujan graph or not.

Hamiltonian Cycles for Finite Weyl Groupoids

Abstract

Let be the Cayley graph of a finite Weyl groupoid . In this paper, we show an existence of a Hamitonian cycle of for any . We exatctly draw a Hamiltonian cycle of for any (resp. some) irreducible of rank three (resp. four). Moreover for the irreducible of rank three, we give a second largest eigenvalue of the adjacency matrix of , and know if is a bipartite Ramanujan graph or not.
Paper Structure (17 sections, 27 theorems, 56 equations)

This paper contains 17 sections, 27 theorems, 56 equations.

Key Result

Theorem 1.2

(Rapaport-Strasser (1959) SR59, see alsoPR06) Let $G$ be a finite group generated by three elements $a$, $b$, $c$ of $G\setminus\{e\}$ with $a^2=b^2=c^2=abab=e$. Let $Z:=\{\{x,xy\}|x\in G, y\in\{a,b,c\}\}$. Then there exists a Hamiltonian cycle for $\Gamma(G,Z)$.

Theorems & Definitions (50)

  • Definition 1.1
  • Theorem 1.2
  • Theorem 1.3
  • Definition 2.1
  • Definition 2.2
  • Definition 2.3
  • Lemma 2.4
  • Proposition 2.5
  • Lemma 2.6
  • proof
  • ...and 40 more