On the commuting graph of some non-commutative rings with unity

Subject Areas : History and biography

F.  Ramezani ¹ (Department of Basic science , Imam Khomeini International University, Qazvin, Iran)
E.  Vatandoost ² (Department of Basic science , Imam Khomeini International University, Qazvin, Iran)

Received: 2016-10-02 Accepted : 2017-01-20 Published : 2016-01-20

Keywords: Commuting graphs, non-commutative rings, non-connected graphs,

Abstract :

‎‎Let $R$ be a non-commutative ring with unity‎. ‎The commuting graph‎ of $R$ denoted by $\Gamma(R)$‎, ‎is a graph with a vertex set‎‎$R\setminus Z(R)$ and two vertices $a$ and $b$ are adjacent if and only if‎$ab=ba$‎. ‎In this paper‎, ‎we investigate non-commutative rings with unity of order $p^n$ where $p$ is prime and $n \in \lbrace 4,5 \rbrace$‎. It is shown that‎, ‎$\Gamma(R)$ is the disjoint union of complete graphs‎. Finally‎, ‎we prove that there are exactly five commuting‎‎graphs of non-commutative rings with unity up to twenty vertices and they are $3K_2,3K_4,7K_2‎, ‎K_2 \cup 2K_6$ and $4K_2 \cup K_6$‎.

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