On possible uniform Turán densities
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866908359156826112 |
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| author | King, Dylan Piga, Simón Sales, Marcelo Schülke, Bjarne |
| author_facet | King, Dylan Piga, Simón Sales, Marcelo Schülke, Bjarne |
| contents | Given a family of $3$-graphs $\mathcal{F}$, the uniform Turán density $π_{\therefore}(\mathcal{F})$ is defined as the infimum $d\in[0,1]$ for which any sufficiently large uniformly $d$-dense $3$-graph - that is, a $3$-graph which has edge-density at least $d$ on all linearly sized subsets - contains a copy of some $F \in \mathcal{F}$. Let $Π_{\therefore,\text{fin}}$ denote the set of all possible uniform Turán densities of finite families. Erdős, Hajnal, and Rödl introduced a family of constructions for lower bounds on uniform Turán densities called palette constructions. We show that $Π_{\therefore,\text{fin}}$ contains every $d$ that is obtained as the uniform density of an optimized palette construction. A corollary of this is that $Π_{\therefore,\text{fin}}$ contains the set of Lagrangians of $3$-graphs and includes irrational numbers. Our work complements a recent result of Lamaison, which states that every value in $Π_{\therefore,\text{fin}}$ can be approximated by uniform densities of palette constructions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_21220 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On possible uniform Turán densities King, Dylan Piga, Simón Sales, Marcelo Schülke, Bjarne Combinatorics 05C65 Given a family of $3$-graphs $\mathcal{F}$, the uniform Turán density $π_{\therefore}(\mathcal{F})$ is defined as the infimum $d\in[0,1]$ for which any sufficiently large uniformly $d$-dense $3$-graph - that is, a $3$-graph which has edge-density at least $d$ on all linearly sized subsets - contains a copy of some $F \in \mathcal{F}$. Let $Π_{\therefore,\text{fin}}$ denote the set of all possible uniform Turán densities of finite families. Erdős, Hajnal, and Rödl introduced a family of constructions for lower bounds on uniform Turán densities called palette constructions. We show that $Π_{\therefore,\text{fin}}$ contains every $d$ that is obtained as the uniform density of an optimized palette construction. A corollary of this is that $Π_{\therefore,\text{fin}}$ contains the set of Lagrangians of $3$-graphs and includes irrational numbers. Our work complements a recent result of Lamaison, which states that every value in $Π_{\therefore,\text{fin}}$ can be approximated by uniform densities of palette constructions. |
| title | On possible uniform Turán densities |
| topic | Combinatorics 05C65 |
| url | https://arxiv.org/abs/2504.21220 |