Tight bounds for powers of Hamilton cycles in tournaments

نویسندگان

چکیده

A basic result in graph theory says that any n-vertex tournament with in- and out-degrees larger than n−24 contains a Hamilton cycle, this is tight. In 1990, Bollobás Häggkvist significantly extended by showing for fixed k ε>0, sufficiently large n, all tournaments degrees at least n4+εn contain the k-th power of cycle. Up until now, there has not been progress on determining more accurate error term degree condition, neither understanding how n should be Bollobás-Häggkvist theorem. We essentially resolve both these questions. First, we show if are n4+cn1−1/⌈k/2⌉ some constant c=c(k), then particular, order to guarantee square one only needs additive term. also present construction which, modulo well known conjecture Turán numbers complete bipartite graphs, shows must n1−1/⌈(k−1)/2⌉, which matches our upper bound even k. For odd k, believe lower can improved. Indeed, k=3, n4+Ω(n1/5) no cube addition, results imply theorem already holds n=ε−Θ(k), best possible.

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ژورنال

عنوان ژورنال: Journal of Combinatorial Theory, Series B

سال: 2023

ISSN: ['0095-8956', '1096-0902']

DOI: https://doi.org/10.1016/j.jctb.2022.10.002