dorsal/arxiv
View SchemaThe maximum number of triangles in graphs without the square of a path
| Authors | Yichen Wang, Ervin Győri |
|---|---|
| Categories | |
| ArXiv ID | 2601.09454vv1 |
| URL | https://arxiv.org/abs/2601.09454 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
The generalized Tur\'an number for $H$ of $G$, denoted by $\ex(n,H,G)$, is the maximum number of copies of $H$ in an $n$-vertex $G$-free graph. When $H$ is an edge, $\ex(n,H,G)$ is the classical Tur\'an number $\ex(n,G)$. Let $P_k$ be the path with $k$ vertices. The square of $P_k$, denoted by $P_k^2$, is obtained by joining the pairs of vertices with distance at most two in $P_k$. The Tur\'an number of $P_k^2$, $\ex(n, P_k^2)$, was determined by several researchers. When $k=3$, $P_3^2$ is the triangle and $\ex(n, P_3^2)$ is well-known from Mantel's theorem. When $k=4$, $\ex(n, P_4^2)$ was solved by Dirac in a more general context. When $k=5,6$, the problem was solved by Xiao, Katona, Xiao, and Zamora. For general $k \ge 7$, the problem was solved by Yuan in a more general context. Recently, Mukherjee determined the generalized Tur\'an number $\ex(n, K_3, P_5^2)$. In this paper, we determine the exact value of $\ex(n, K_3, P_6^2)$ and characterize all the extremal graphs for $n \ge 11$.
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"abstract": "The generalized Tur\\\u0027an number for $H$ of $G$, denoted by $\\ex(n,H,G)$, is the maximum number of copies of $H$ in an $n$-vertex $G$-free graph. When $H$ is an edge, $\\ex(n,H,G)$ is the classical Tur\\\u0027an number $\\ex(n,G)$. Let $P_k$ be the path with $k$ vertices. The square of $P_k$, denoted by $P_k^2$, is obtained by joining the pairs of vertices with distance at most two in $P_k$.\n The Tur\\\u0027an number of $P_k^2$, $\\ex(n, P_k^2)$, was determined by several researchers. When $k=3$, $P_3^2$ is the triangle and $\\ex(n, P_3^2)$ is well-known from Mantel\u0027s theorem. When $k=4$, $\\ex(n, P_4^2)$ was solved by Dirac in a more general context. When $k=5,6$, the problem was solved by Xiao, Katona, Xiao, and Zamora. For general $k \\ge 7$, the problem was solved by Yuan in a more general context.\n Recently, Mukherjee determined the generalized Tur\\\u0027an number $\\ex(n, K_3, P_5^2)$. In this paper, we determine the exact value of $\\ex(n, K_3, P_6^2)$ and characterize all the extremal graphs for $n \\ge 11$.",
"arxiv_id": "2601.09454",
"authors": [
"Yichen Wang",
"Ervin Gy\u0151ri"
],
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"math.CO"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "The maximum number of triangles in graphs without the square of a path",
"url": "https://arxiv.org/abs/2601.09454",
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