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Ask zeta functions associated with small graphs

$W^+_\Gamma$ and $W^-_\Gamma$

In the paper

Rossmann, Voll: Groups, graphs, and hypergraphs: average sizes of kernels of generic matrices with support constraints. Mem. Amer. Math. Soc. 294 (2024), no. 1465, vi+120 pp. (preprint),

for each (finite simple) graph $\Gamma$, bivariate rational generating functions $W_\Gamma^\pm(q,t) \in \mathbf Q(q,t) \cap \mathbf Q(q)[\![t]\!]$ are defined. These generating functions encode average sizes of kernels in modules of (anti-)symmetric matrices with support constraints defined by $\Gamma$. The package Zeta for SageMath includes an implementation of an algorithm for explicitly computing $W_\Gamma(q,t)$. The following lists of the rational functions $W_\Gamma^\pm(q,t)$ for all graphs with at most $7$ vertices were computed using Zeta. In the lists, an “ask[±] zeta function” refers to an instance of $W_\Gamma^\pm(q,t)$. These functions are provided as SageMath input and, for graphs with at most six vertices, also rendered using MathJax.

Description of graphs SageMath input Rendered using MathJax
At most 5 vertices W_1-5_inline.html W_1-5_inline_latex.html
At most 5 vertices (connected graphs only) W_1-5_connected_inline.html W_1-5_connected_inline_latex.html
6 vertices W_6_inline.html W_6_inline_latex.html
6 vertices (connected graphs only) W_6_connected_inline.html W_6_connected_inline_latex.html
7 vertices W_7.html
7 vertices (connected graphs only) W_7_connected.html

In the files above, graphs are specified using the graph6 format. Plots were created using SageMath.

$W^\sharp_\Gamma$

In the paper

Rossmann, Voll: Ask zeta functions of joins of graphs. (preprint),

we introduced the rational functions $W^\sharp_\Gamma(q,t)$. Letting $\hat\Gamma$ denote the reflexive closure of $\Gamma$, we have $W^\sharp_\Gamma(q,t) = W^\pm_{\hat\Gamma}(q,t)$. The following list contains the rational functions $W_\Gamma^\sharp(q,t)$ for all graphs with at most $7$ vertices.

Description of graphs SageMath input Rendered using MathJax
At most 5 vertices asks_1-5.html asks_1-5_latex.html
At most 5 vertices (connected graphs only) asks_1-5_connected.html asks_1-5_connected_latex.html
6 vertices asks_6.html asks_6_latex.html
6 vertices (connected graphs only) asks_6_connected.html asks_6_connected_latex.html
7 vertices asks_7.html
7 vertices (connected graphs only) asks_7_connected.html

Author: Tobias Rossmann. Last modified: 15 May 2025