The Feedback-Exponent Conjecture for bounded minimum feedback vertex number

From papers

Let k01k_0\geq 1 be an integer. For a graph HH, write ex(n,H)\operatorname{ex}(n,H) for its Turán number, and call a rational number r[1,2]r\in[1,2] realizable as a Turán exponent if there is a graph HH such that

ex(n,H)=Θ(nr).\operatorname{ex}(n,H)=\Theta(n^r).

The minimum feedback vertex number (FVN) of a graph is the minimum number of vertices whose removal makes the graph acyclic. Feedback-Exponent Conjecture. There exists a rational number p/q[1,2]p/q\in[1,2] that cannot be realized as the Turán exponent of any bipartite graph whose minimum FVN is at most k0k_0.

This conjecture asks whether bounded minimum feedback vertex number restricts the rational exponents realizable by bipartite graphs. It is motivated by the Rational Exponent Conjecture of Erdős and Simonovits and by examples showing that, for bipartite graphs with minimum FVN 22, the Turán exponent is not determined solely by the minimum cycle length; the status of the proposed restriction is not established in the supplied text.

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Sources & referencesView supporting material

Primary source

Xiao-Chuan Liu and Xu Yang, “On Turán Number of Graphs with Small Minimum Feedback Vertex Numbers”, arXiv:2607.07157 (2026).

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