Many Triangles with Few Edges

Bibliographic Details
Title: Many Triangles with Few Edges
Authors: Kirsch, R., Radcliffe, A. J.
Source: Electronic Journal of Combinatorics, Volume 26, Issue 2 (2019), P2.36
Publication Year: 2017
Collection: Mathematics
Subject Terms: Mathematics - Combinatorics
More Details: Extremal problems concerning the number of independent sets or complete subgraphs in a graph have been well studied in recent years. Cutler and Radcliffe proved that among graphs with $n$ vertices and maximum degree at most $r$, where $n = a(r+1)+b$ and $0 \le b \le r$, $aK_{r+1}\cup K_b$ has the maximum number of complete subgraphs, answering a question of Galvin. Gan, Loh, and Sudakov conjectured that $aK_{r+1}\cup K_b$ also maximizes the number of complete subgraphs $K_t$ for each fixed size $t \ge 3$, and proved this for $a = 1$. Cutler and Radcliffe proved this conjecture for $r \le 6$. We investigate a variant of this problem where we fix the number of edges instead of the number of vertices. We prove that $aK_{r+1}\cup \mathcal{C}(b)$, where $\mathcal{C}(b)$ is the colex graph on $b$ edges, maximizes the number of triangles among graphs with $m$ edges and any fixed maximum degree $r\le 8$, where $m = a \binom{r+1}{2} + b$ and $0 \le b < \binom{r+1}{2}$.
Document Type: Working Paper
Access URL: http://arxiv.org/abs/1709.06163
Accession Number: edsarx.1709.06163
Database: arXiv
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