Equivalence of the 3/5 and 2/5 5-cycle double cover bounds

Let GG be a bridgeless graph, and let a 55-cycle double cover be a collection C=(E0,,E4){\cal C}=(E_0,\ldots,E_4) of five cycles in which every edge belongs to exactly two cycles. Equivalence conjecture for strengthened 5-cycle double covers. The conjecture asserting that every bridgeless graph admits such a cover with

E035E(G)|E_0|\geq \frac{3}{5}|E(G)|

is equivalent to the conjecture asserting that every bridgeless graph admits such a cover with

E025E(G).|E_0|\geq \frac{2}{5}|E(G)|.

The paper says that the 2/52/5 formulation is equivalent to the ordinary 5-cycle double cover conjecture and proposes the equivalence with the strengthened formulation. It remains open.

Sources & referencesView supporting material

Primary source

Giuseppe Mazzuoccolo and Vahan Mkrtchyan, “Expanding vertices to triangles in cubic graphs”, arXiv:2504.19201 (2025).

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