Peer-reviewedCC BY 4.0The Electronic Journal of Combinatorics
Unexpectedly, a Symmetry on Unlabeled Graphs
Abstract
We exhibit the joint symmetric distribution of the following two parameters on the set of unlabeled simple connected graphs with n vertices. The first parameter is the maximal number of leaves attached to a vertex. The second parameter is the size of the largest set of vertices sharing the same closed neighborhood minus $1$. Apparently, this is the first example of a natural non-trivial equidistribution of graph parameters on unlabeled simple connected graphs with a fixed set of vertices. Our proof is enumerative, using the theory of species. Exhibiting an explicit bijection interchanging the two parameters remains an open problem.
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BibTeX
@article{furnsinn2026unexpectedly,
title = {{Unexpectedly, a Symmetry on Unlabeled Graphs}},
author = {Florian Fürnsinn and Moritz Gangl and Martin Rubey},
journal = {The Electronic Journal of Combinatorics},
year = {2026},
month = nov,
doi = {10.37236/15312},
url = {https://www.combinatorics.org/ojs/index.php/eljc/article/view/v33i4p32},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Unexpectedly, a Symmetry on Unlabeled Graphs
AU - Florian Fürnsinn
AU - Moritz Gangl
AU - Martin Rubey
PY - 2026
DA - 2026/11/06
JO - The Electronic Journal of Combinatorics
DO - 10.37236/15312
UR - https://www.combinatorics.org/ojs/index.php/eljc/article/view/v33i4p32
AB - We exhibit the joint symmetric distribution of the following two parameters on the set of unlabeled simple connected graphs with n vertices. The first parameter is the maximal number of leaves attached to a vertex. The second parameter is the size of the largest set of vertices sharing the same closed neighborhood minus $1$. Apparently, this is the first example of a natural non-trivial equidistribution of graph parameters on unlabeled simple connected graphs with a fixed set of vertices. Our proof is enumerative, using the theory of species. Exhibiting an explicit bijection interchanging the two parameters remains an open problem.
SN - 1077-8926
ER -