1,963 research outputs found
A note on pentavalent s-transitive graphs
AbstractA graph, with a group G of its automorphisms, is said to be (G,s)-transitive if G is transitive on s-arcs but not on (s+1)-arcs of the graph. Let X be a connected (G,s)-transitive graph for some s≥1, and let Gv be the stabilizer of a vertex v∈V(X) in G. In this paper, we determine the structure of Gv when X has valency 5 and Gv is non-solvable. Together with the results of Zhou and Feng [J.-X. Zhou, Y.-Q. Feng, On symmetric graphs of valency five, Discrete Math. 310 (2010) 1725–1732], the structure of Gv is completely determined when X has valency 5. For valency 3 or 4, the structure of Gv is known
The heptagon-wheel cocycle in the Kontsevich graph complex
The real vector space of non-oriented graphs is known to carry a differential
graded Lie algebra structure. Cocycles in the Kontsevich graph complex,
expressed using formal sums of graphs on vertices and edges, induce
-- under the orientation mapping -- infinitesimal symmetries of classical
Poisson structures on arbitrary finite-dimensional affine real manifolds.
Willwacher has stated the existence of a nontrivial cocycle that contains the
-wheel graph with a nonzero coefficient at every
. We present detailed calculations of the differential of
graphs; for the tetrahedron and pentagon-wheel cocycles, consisting at and of one and two graphs respectively, the cocycle condition
is verified by hand. For the next, heptagon-wheel cocycle
(known to exist at ), we provide an explicit representative: it
consists of 46 graphs on 8 vertices and 14 edges.Comment: Special Issue JNMP 2017 `Local and nonlocal symmetries in
Mathematical Physics'; 17 journal-style pages, 54 figures, 3 tables; v2
accepte
Distance-regular Cayley graphs with small valency
We consider the problem of which distance-regular graphs with small valency
are Cayley graphs. We determine the distance-regular Cayley graphs with valency
at most , the Cayley graphs among the distance-regular graphs with known
putative intersection arrays for valency , and the Cayley graphs among all
distance-regular graphs with girth and valency or . We obtain that
the incidence graphs of Desarguesian affine planes minus a parallel class of
lines are Cayley graphs. We show that the incidence graphs of the known
generalized hexagons are not Cayley graphs, and neither are some other
distance-regular graphs that come from small generalized quadrangles or
hexagons. Among some ``exceptional'' distance-regular graphs with small
valency, we find that the Armanios-Wells graph and the Klein graph are Cayley
graphs.Comment: 19 pages, 4 table
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