On q-power cycles in cubic graphs

International audienceIn the context of a conjecture of Erdős and Gyárfás, we consider, for any $q ≥ 2$, the existence of q-power cycles (i.e. with length a power of q) in cubic graphs. We exhibit constructions showing that, for every $q ≥ 3$, there exist arbitrarily large cubic graphs with no q-power cycles. Concerning the remaining case $q = 2$ (which corresponds to the conjecture of Erdős and Gyárfás), we show that there exist arbitrarily large cubic graphs whose only 2-power cycles have length 4 only, or 8 only

Minimal unavoidable sets of cycles in plane graphs

A set $S$ of cycles is minimal unavoidable in a graph family $\cal{G}$ if each graph $G \in \cal{G}$ contains a cycle from $S$ and, for each proper subset $S^{\prime}\subset S$, there exists an infinite subfamily $\cal{G}^{\prime}\subseteq\cal{G}$ such that no graph from $\cal{G}^{\prime}$ contains a cycle from $S^{\prime}$. In this paper, we study minimal unavoidable sets of cycles in plane graphs of minimum degree at least 3 and present several graph constructions which forbid many cycle sets to be unavoidable. We also show the minimality of several small sets consisting of short cycles

On q-Power Cycles in Cubic Graphs

In the context of a conjecture of Erdős and Gyárfás, we consider, for any q ≥ 2, the existence of q-power cycles (i.e., with length a power of q) in cubic graphs. We exhibit constructions showing that, for every q ≥ 3, there exist arbitrarily large cubic graphs with no q-power cycles. Concerning the remaining case q = 2 (which corresponds to the conjecture of Erdős and Gyárfás), we show that there exist arbitrarily large cubic graphs whose all 2-power cycles have length 4 only, or 8 only