Identifier
Values
['A',1] => ([],1) => ([],1) => ([(0,1)],2) => 1
['A',2] => ([(0,2),(1,2)],3) => ([(1,2)],3) => ([(0,3),(1,2),(1,3),(2,3)],4) => 1
['B',2] => ([(0,3),(1,3),(3,2)],4) => ([(2,3)],4) => ([(0,4),(1,4),(2,3),(2,4),(3,4)],5) => 2
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Description
The number of odd automorphisms of a graph.
Let $D$ be an arbitrary orientation of a graph $G$. Then an automorphism of $G$ is odd, if it reverses the orientation of an odd number of edges of $D$.
The graphs on $n$ vertices without any odd automorphisms are equinumerous with the number of non-isomorphic $n$-team tournaments, see [2].
The odd automorphisms of the complete graphs are precisely the even permutations.
Map
incomparability graph
Description
The incomparability graph of a poset.
Map
cone
Description
The cone of a graph.
The cone of a graph is obtained by joining a new vertex to all the vertices of the graph. The added vertex is called a universal vertex or a dominating vertex.
Map
to root poset
Description
The root poset of a finite Cartan type.
This is the poset on the set of positive roots of its root system where $\alpha \prec \beta$ if $\beta - \alpha$ is a simple root.