Tree independence number I. (Even hole, diamond, pyramid)-free graphs

Abstract

The tree-independence number tree-$\hat{I}\pm$, first defined and studied by Dallard, Milanič and Štorgel, is a variant of treewidth tailored to solving the maximum independent set problem. Over a series of papers, Abrishami et al. developed the so-called central bag method to study induced obstructions to bounded treewidth. Among others, they showed that, in a certain superclass $\mathcal{C}$ of (even hole, diamond, pyramid)-free graphs, treewidth is bounded by a function of the clique number. In this paper, we relax the bounded clique number assumption, and show that $\mathcal{C}$ has bounded tree-$\hat{I}\pm$. Via existing results, this yields a polynomial time algorithm for the maximum independent set problem in this class. Our result also corroborates, for this class of graphs, a conjecture of Dallard, Milanič and Štorgel that in a hereditary graph class, tree-$\hat{I}\pm$ is bounded if and only if the treewidth is bounded by a function of the clique number.

17 pages. arXiv admin note: text overlap with arXiv:2203.06775