Showing items related by title, author, creator and subject.

• The spectral excess theorem for graphs with few eigenvalues whose distance- 2 or distance-1-or-2 graph is strongly regular 

  Dalfó, Cristina; Fiol, Miguel Angel; Koolen, Jack (Taylor & Francis, 2018-07-13)

  We study regular graphs whose distance-2 graph or distance-1-or-2 graph is strongly regular. We provide a characterization of such graphs Γ (among regular graphs with few distinct eigenvalues) in terms of the spectrum and ...

• A general method to obtain the spectrum and local spectra of a graph from its regular partitions 

  Dalfó, Cristina; Fiol, Miguel Angel (International Linear Algebra Society, 2020-07-12)

  It is well known that, in general, part of the spectrum of a graph can be obtained from the adjacency matrix of its quotient graph given by a regular partition. In this paper, a method that gives all the spectrum, and also ...

• Spectra and eigenspaces from regular partitions of Cayley (di)graphs of permutation groups 

  Dalfó, Cristina; Fiol, Miguel Angel (Elsevier, 2020)

  In this paper, we present a method to obtain regular (or equitable) partitions of Cayley (di)graphs (that is, graphs, digraphs, or mixed graphs) of permutation groups on n letters. We prove that every partition of the ...