Counting Small Induced Subgraphs: Hardness of Symmetry-Based Properties
Abstract
Jerrum and Meeks (TOCT, JCSS 2015) introduced the counting problems for fixed graph properties : Given an input graph and , count the -vertex subsets such that the induced subgraph satisfies . For recursively enumerable , it is known that is either #W[1]-hard or fixed-parameter tractable. A direct classification depending on however still remains open. In particular, the status was open for the property of graphs without nontrivial automorphisms, also mentioned in a very recent survey on parameterized counting by Roth (Comput.~Sci.~Rev.~2026). This is a natural property that evades all currently known techniques for proving #W[1]-hardness, including a general toolkit based on Fourier analysis that was very recently introduced by Curticapean and Neuen (SODA~2025). In this paper, we show that counting induced -vertex graphs without nontrivial automorphisms is #W[1]-hard by constructing ``clique scaffolds'', i.e., problem-specific restrictions of the property that enable a reduction from the -clique problem. More generally, we show that for every finite group , counting -vertex induced subgraphs with automorphism group is #W[1]-hard.
Keywords
Cite
@article{arxiv.2606.31803,
title = {Counting Small Induced Subgraphs: Hardness of Symmetry-Based Properties},
author = {Radu Curticapean and Mingjun Liu},
journal= {arXiv preprint arXiv:2606.31803},
year = {2026}
}