dorsal/arxiv
View SchemaOn generalized Tur\'{a}n problems for expansions
| Authors | Junpeng Zhou, Xiamiao Zhao, Xiying Yuan |
|---|---|
| Categories | |
| ArXiv ID | 2601.09244vv1 |
| URL | https://arxiv.org/abs/2601.09244 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
Given a graph $F$, the $r$-expansion $F^r$ of $F$ is the $r$-uniform hypergraph obtained from $F$ by inserting $r-2$ new distinct vertices in each edge of $F$. Given $r$-uniform hypergraphs $\cH$ and $\cF$, the generalized Tur\'{a}n number, denoted by $\ex_r(n,\cH,\cF)$, is the maximum number of copies of $\cH$ in an $n$-vertex $r$-uniform hypergraph that does not contain $\cF$ as a subhypergraph. In the case where $r=2$ (i.e., the graph case), the study of generalized Tur\'{a}n problems was initiated by Alon and Shikhelman [\textit{J. Combin. Theory Series B.} 121 (2016) 146--172]. Motivated by their work, we systematically study generalized Tur\'{a}n problems for expansions and obtain several general and exact results. In particular, for the non-degenerate case, we determine the exact generalized Tur\'{a}n number for expansions of complete graphs, and establish the asymptotics of the generalized Tur\'{a}n number for expansions of the vertex-disjoint union of complete graphs. For the degenerate case, we establish the asymptotics of generalized Tur\'{a}n numbers for expansions of several classes of forests, including star forests, linear forests and star-path forests.
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"abstract": "Given a graph $F$, the $r$-expansion $F^r$ of $F$ is the $r$-uniform hypergraph obtained from $F$ by inserting $r-2$ new distinct vertices in each edge of $F$. Given $r$-uniform hypergraphs $\\cH$ and $\\cF$, the generalized Tur\\\u0027{a}n number, denoted by $\\ex_r(n,\\cH,\\cF)$, is the maximum number of copies of $\\cH$ in an $n$-vertex $r$-uniform hypergraph that does not contain $\\cF$ as a subhypergraph. In the case where $r=2$ (i.e., the graph case), the study of generalized Tur\\\u0027{a}n problems was initiated by Alon and Shikhelman [\\textit{J. Combin. Theory Series B.} 121 (2016) 146--172]. Motivated by their work, we systematically study generalized Tur\\\u0027{a}n problems for expansions and obtain several general and exact results. In particular, for the non-degenerate case, we determine the exact generalized Tur\\\u0027{a}n number for expansions of complete graphs, and establish the asymptotics of the generalized Tur\\\u0027{a}n number for expansions of the vertex-disjoint union of complete graphs. For the degenerate case, we establish the asymptotics of generalized Tur\\\u0027{a}n numbers for expansions of several classes of forests, including star forests, linear forests and star-path forests.",
"arxiv_id": "2601.09244",
"authors": [
"Junpeng Zhou",
"Xiamiao Zhao",
"Xiying Yuan"
],
"categories": [
"math.CO"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "On generalized Tur\\\u0027{a}n problems for expansions",
"url": "https://arxiv.org/abs/2601.09244",
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