Title
Local Wl Invariance And Hidden Shades Of Regularity
Abstract
The k-dimensional Weisfeiler-Leman algorithm is a powerful tool in graph isomorphism testing. For an input graph G, the algorithm determines a canonical coloring of s-tuples of vertices of G for each s between 1 and k. We say that a numerical parameter of s-tuples is k-WL-invariant if it is determined by the tuple color. As an application of Dvorak's result on k-WL-invariance of homomorphism counts in the case of k = 2, we spot some non-obvious regularity properties of strongly regular graphs and related graph families. For example, if G is a strongly regular graph, then the number of 7-paths between vertices x and y in G depends only on whether or not x and y are adjacent (this is true also for shorter paths but no longer true for 8-paths). Likewise, the number of cycles of length 7 passing through a vertex x in G is the same for every x (where the length 7 is also optimal). (c) 2021 Elsevier B.V. All rights reserved.
Year
DOI
Venue
2021
10.1016/j.dam.2021.08.037
DISCRETE APPLIED MATHEMATICS
Keywords
DocType
Volume
Strongly regular graphs, Distance-regular graphs, Subgraph and homomorphism counts, Weisfeiler-Leman algorithm, Constituent graphs of association schemes
Journal
305
ISSN
Citations 
PageRank 
0166-218X
0
0.34
References 
Authors
0
3
Name
Order
Citations
PageRank
Fuhlbrück Frank100.34
Johannes Köbler2316.83
Verbitsky Oleg300.34