181,014 research outputs found
All finite transitive graphs admit self-adjoint free semigroupoid algebras
In this paper we show that every non-cycle finite transitive directed graph
has a Cuntz-Krieger family whose WOT-closed algebra is . This
is accomplished through a new construction that reduces this problem to
in-degree -regular graphs, which is then treated by applying the periodic
Road Coloring Theorem of B\'eal and Perrin. As a consequence we show that
finite disjoint unions of finite transitive directed graphs are exactly those
finite graphs which admit self-adjoint free semigroupoid algebras.Comment: Added missing reference. 16 pages 2 figure
Two families of graphs that are Cayley on nonisomorphic groups
A number of authors have studied the question of when a graph can be
represented as a Cayley graph on more than one nonisomorphic group. The work to
date has focussed on a few special situations: when the groups are -groups;
when the groups have order ; when the Cayley graphs are normal; or when the
groups are both abelian. In this paper, we construct two infinite families of
graphs, each of which is Cayley on an abelian group and a nonabelian group.
These families include the smallest examples of such graphs that had not
appeared in other results.Comment: 6 page
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