The induced subgraph order on unlabelled graphs
The electronic journal of combinatorics, Tome 13 (2006)
A differential poset is a partially ordered set with raising and lowering operators $U$ and $D$ which satisfy the commutation relation $DU-UD=rI$ for some constant $r$. This notion may be generalized to deal with the case in which there exist sequences of constants $\{q_n\}_{n\geq 0}$ and $\{r_n\}_{n\geq 0}$ such that for any poset element $x$ of rank $n$, $DU(x) = q_n UD(x) + r_nx$. Here, we introduce natural raising and lowering operators such that the set of unlabelled graphs, ordered by $G\leq H$ if and only if $G$ is isomorphic to an induced subgraph of $H$, is a generalized differential poset with $q_n=2$ and $r_n = 2^n$. This allows one to apply a number of enumerative results regarding walk enumeration to the poset of induced subgraphs.
DOI :
10.37236/1155
Classification :
06A07
Mots-clés : differential poset, unlabelled graphs, walk enumeration, poset of induced subgraphs
Mots-clés : differential poset, unlabelled graphs, walk enumeration, poset of induced subgraphs
@article{10_37236_1155,
author = {Craig A. Sloss},
title = {The induced subgraph order on unlabelled graphs},
journal = {The electronic journal of combinatorics},
year = {2006},
volume = {13},
doi = {10.37236/1155},
zbl = {1110.06008},
url = {http://geodesic.mathdoc.fr/articles/10.37236/1155/}
}
Craig A. Sloss. The induced subgraph order on unlabelled graphs. The electronic journal of combinatorics, Tome 13 (2006). doi: 10.37236/1155
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