Write $\mathcal{ C}(G)$ for the cycle space of a graph $G$, $\mathcal{ C}_\kappa(G)$ for the subspace of $\mathcal{ C}(G)$ spanned by the copies of the $\kappa$-cycle $C_\kappa$ in $G$, $\mathcal{ T}_\kappa$ for the class of graphs satisfying $\mathcal{ C}_\kappa(G)=\mathcal{ C}(G)$, and $\mathcal{ Q}_\kappa$ for the class of graphs each of whose edges lies in a $C_\kappa$. We prove that for every odd $\kappa \geq 3$ and $G=G_{ n,p}$, \[\max_p \, \Pr(G \in \mathcal{ Q}_\kappa \setminus \mathcal{ T}_\kappa) \rightarrow 0;\] so the $C_\kappa$'s of a random graph span its cycle space as soon as they cover its edges. For $\kappa=3$ this was shown by DeMarco, Hamm and Kahn (2013).
Categories: math.CO