New Sufficient Conditions for Linear-Sized Epsilon-Nets and $(p,2)$-Theorems
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| Format: | Preprint |
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2025
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| _version_ | 1866912798978605056 |
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| author | Keller, Chaya Smorodinsky, Shakhar |
| author_facet | Keller, Chaya Smorodinsky, Shakhar |
| contents | An $ε$-net theorem for a hypergraph upper bounds the minimum size of a vertex set that pierces all $ε$-heavy hyperedges. A $(p,2)$-theorem bounds from above the minimum size of a vertex set that pierces all hyperedges, in terms of the maximum size of a set of pairwise disjoint hyperedges. Numerous works studied $ε$-net theorems and $(p,2)$-theorems that guarantee the existence of small-sized piercing sets.
We focus on the question: In which settings the asymptotically smallest possible piercing sets -- i.e., $ε$-nets of size $O(\frac{1}ε)$ and piercing sets of size $O(p)$ in $(p,2)$-theorems, are guaranteed? We obtain several sufficient criteria for the existence of such linear $ε$-net theorems and $(p,2)$-theorems that unveil interesting connections to graph theory and improve and generalize several previous results. Most notably, we exhibit an unexpected relation of $ε$-nets to the classical Zarankiewicz's problem in graph theory. We show that a linear bound in the Zarankiewicz-type problem that asks for the maximum size of a bipartite graph with no copy of $K_{2,t}$, implies a linear $ε$-net theorem for the corresponding neighborhood hypergraph. We also show that hypergraphs with a hereditarily linear-sized Delaunay graph admit an almost linear $(p,2)$-theorem, and deduce that incidence hypergraphs of non-piercing regions in the plane admit a linear $(p,2)$-theorem, significantly improving previous results on such hypergraphs.
Our work presents a landscape of sufficient conditions for the existence of linear $ε$-net theorems and $(p,2)$-theorems, with complex interrelations between them. Many of the interrelations are still unknown and call for future research. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_07269 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | New Sufficient Conditions for Linear-Sized Epsilon-Nets and $(p,2)$-Theorems Keller, Chaya Smorodinsky, Shakhar Combinatorics Computational Geometry 52A37 An $ε$-net theorem for a hypergraph upper bounds the minimum size of a vertex set that pierces all $ε$-heavy hyperedges. A $(p,2)$-theorem bounds from above the minimum size of a vertex set that pierces all hyperedges, in terms of the maximum size of a set of pairwise disjoint hyperedges. Numerous works studied $ε$-net theorems and $(p,2)$-theorems that guarantee the existence of small-sized piercing sets. We focus on the question: In which settings the asymptotically smallest possible piercing sets -- i.e., $ε$-nets of size $O(\frac{1}ε)$ and piercing sets of size $O(p)$ in $(p,2)$-theorems, are guaranteed? We obtain several sufficient criteria for the existence of such linear $ε$-net theorems and $(p,2)$-theorems that unveil interesting connections to graph theory and improve and generalize several previous results. Most notably, we exhibit an unexpected relation of $ε$-nets to the classical Zarankiewicz's problem in graph theory. We show that a linear bound in the Zarankiewicz-type problem that asks for the maximum size of a bipartite graph with no copy of $K_{2,t}$, implies a linear $ε$-net theorem for the corresponding neighborhood hypergraph. We also show that hypergraphs with a hereditarily linear-sized Delaunay graph admit an almost linear $(p,2)$-theorem, and deduce that incidence hypergraphs of non-piercing regions in the plane admit a linear $(p,2)$-theorem, significantly improving previous results on such hypergraphs. Our work presents a landscape of sufficient conditions for the existence of linear $ε$-net theorems and $(p,2)$-theorems, with complex interrelations between them. Many of the interrelations are still unknown and call for future research. |
| title | New Sufficient Conditions for Linear-Sized Epsilon-Nets and $(p,2)$-Theorems |
| topic | Combinatorics Computational Geometry 52A37 |
| url | https://arxiv.org/abs/2507.07269 |