On automorphisms of digraphs without symmetric cycles
نویسنده
چکیده
A digraph is a symmetric cycle if it is symmetric and its underlying graph is a cycle. It is proved that if D is an asymmetric digraph not containing a symmetric cycle, then D remains asymmetric after removing some vertex. It is also showed that each digraph D without a symmetric cycle, whose underlying graph is connected, contains a vertex which is a common fixed point of all automorphisms of D.
منابع مشابه
Consistent Cycles in Graphs and Digraphs
Let Γ be a finite digraph and let G be a subgroup of the automorphism group of Γ. A directed cycle ~ C of Γ is called G-consistent whenever there is an element of G whose restriction to ~ C is the 1-step rotation of ~ C. Consistent cycles in finite arc-transitive graphs were introduced by Conway in one of his public lectures. He observed that the number of G-orbits of G-consistent cycles of an ...
متن کاملAutomorphism Group of a Possible 2-(121, 16, 2) Symmetric Design
Let D be a symmetric 2-(121, 16, 2) design with the automorphism group of Aut(D). In this paper the order of automorphism of prime order of Aut(D) is studied, and some results are obtained about the number of fixed points of these automorphisms. Also we will show that |Aut(D)|=2p 3q 5r 7s 11t 13u, where p, q, r, s, t and u are non-negative integers such that r, s, t, u ? 1. In addition we prese...
متن کاملVertex Removable Cycles of Graphs and Digraphs
In this paper we defined the vertex removable cycle in respect of the following, if $F$ is a class of graphs(digraphs) satisfying certain property, $G in F $, the cycle $C$ in $G$ is called vertex removable if $G-V(C)in in F $. The vertex removable cycles of eulerian graphs are studied. We also characterize the edge removable cycles of regular graphs(digraphs).
متن کامل0n removable cycles in graphs and digraphs
In this paper we define the removable cycle that, if $Im$ is a class of graphs, $Gin Im$, the cycle $C$ in $G$ is called removable if $G-E(C)in Im$. The removable cycles in Eulerian graphs have been studied. We characterize Eulerian graphs which contain two edge-disjoint removable cycles, and the necessary and sufficient conditions for Eulerian graph to have removable cycles h...
متن کاملVertex-transitive digraphs with extra automorphisms that preserve the natural arc-colouring
In a Cayley digraph on a group G, if a distinct colour is assigned to each arc-orbit under the left-regular action of G, it is not hard to show that the elements of the left-regular action of G are the only digraph automorphisms that preserve this colouring. In this paper, we show that the equivalent statement is not true in the most straightforward generalisation to G-vertex-transitive digraph...
متن کامل