Almost all cographs have a cospectral mate

Fuente: arXiv
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Main Authors: Wang, Wei, Huang, Ximei
Format: Preprint
Published: 2025
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author Wang, Wei
Huang, Ximei
author_facet Wang, Wei
Huang, Ximei
contents Complement-reducible graphs (or cographs) are the graphs formed from the single-vertex graph by the operations of complement and disjoint union. By combining the Johnson-Newman theorem on generalized cospectrality with the standard tools in the asymptotic enumeration of trees, we show that almost all cographs have a cospectral mate. This result can be viewed as an analogue to a well-known result by Schwenk, who proved that almost all trees have a cospectral mate.
format Preprint
id arxiv_https___arxiv_org_abs_2507_16730
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Almost all cographs have a cospectral mate
Wang, Wei
Huang, Ximei
Combinatorics
05C50
Complement-reducible graphs (or cographs) are the graphs formed from the single-vertex graph by the operations of complement and disjoint union. By combining the Johnson-Newman theorem on generalized cospectrality with the standard tools in the asymptotic enumeration of trees, we show that almost all cographs have a cospectral mate. This result can be viewed as an analogue to a well-known result by Schwenk, who proved that almost all trees have a cospectral mate.
title Almost all cographs have a cospectral mate
topic Combinatorics
05C50
url https://arxiv.org/abs/2507.16730