Supports for Outerplanar and Bounded Treewidth Graphs
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| Format: | Preprint |
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2025
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| _version_ | 1866909642223779840 |
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| author | Raman, Rajiv Singh, Karamjeet |
| author_facet | Raman, Rajiv Singh, Karamjeet |
| contents | We study the existence and construction of sparse supports for hypergraphs derived from subgraphs of a graph $G$. For a hypergraph $(X,\mathcal{H})$, a support $Q$ is a graph on $X$ s.t. $Q[H]$, the graph induced on vertices in $H$ is connected for every $H\in\mathcal{H}$.
We consider \emph{primal}, \emph{dual}, and \emph{intersection} hypergraphs defined by subgraphs of a graph $G$ that are \emph{non-piercing}, (i.e., each subgraph is connected, their pairwise differences remain connected).
If $G$ is outerplanar, we show that the primal, dual and intersection hypergraphs admit supports that are outerplanar. For a bounded treewidth graph $G$, we show that if the subgraphs are non-piercing, then there exist supports for the primal and dual hypergraphs of treewidth $O(2^{tw(G)})$ and $O(2^{4tw(G)})$ respectively, and a support of treewidth $2^{O(2^{tw(G)})}$ for the intersection hypergraph. We also show that for the primal and dual hypergraphs, the exponential blow-up of treewidth is sometimes essential.
All our results are algorithmic and yield polynomial-time algorithms (when the treewidth is bounded). The existence and construction of sparse supports is a crucial step in the design and analysis of PTASs and/or sub-exponential time algorithms for several packing and covering problems. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_05039 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Supports for Outerplanar and Bounded Treewidth Graphs Raman, Rajiv Singh, Karamjeet Combinatorics Discrete Mathematics We study the existence and construction of sparse supports for hypergraphs derived from subgraphs of a graph $G$. For a hypergraph $(X,\mathcal{H})$, a support $Q$ is a graph on $X$ s.t. $Q[H]$, the graph induced on vertices in $H$ is connected for every $H\in\mathcal{H}$. We consider \emph{primal}, \emph{dual}, and \emph{intersection} hypergraphs defined by subgraphs of a graph $G$ that are \emph{non-piercing}, (i.e., each subgraph is connected, their pairwise differences remain connected). If $G$ is outerplanar, we show that the primal, dual and intersection hypergraphs admit supports that are outerplanar. For a bounded treewidth graph $G$, we show that if the subgraphs are non-piercing, then there exist supports for the primal and dual hypergraphs of treewidth $O(2^{tw(G)})$ and $O(2^{4tw(G)})$ respectively, and a support of treewidth $2^{O(2^{tw(G)})}$ for the intersection hypergraph. We also show that for the primal and dual hypergraphs, the exponential blow-up of treewidth is sometimes essential. All our results are algorithmic and yield polynomial-time algorithms (when the treewidth is bounded). The existence and construction of sparse supports is a crucial step in the design and analysis of PTASs and/or sub-exponential time algorithms for several packing and covering problems. |
| title | Supports for Outerplanar and Bounded Treewidth Graphs |
| topic | Combinatorics Discrete Mathematics |
| url | https://arxiv.org/abs/2504.05039 |