Kawarabayashi–Picasarri-Arrieta Reed-type conjecture for digraphs

Let DD be a digraph. Define its maximum geometric-mean degree by

Δ~(D)=maxvV(D)d(v)d+(v),\widetilde{\Delta}(D)=\max_{v\in V(D)}\sqrt{d^-(v)d^+(v)},

let ω(D)\overset{\leftrightarrow}{\omega}(D) be its biclique number, and let χ(D)\vec{\chi}(D) be its dichromatic number. Kawarabayashi–Picasarri-Arrieta conjecture.

χ(D)12(Δ~(D)+1+ω(D)).\vec{\chi}(D) \leq \left\lceil \frac{1}{2}\big(\widetilde{\Delta}(D)+1+\overset{\leftrightarrow}{\omega}(D)\big)\right\rceil.

This is a directed analogue of Reed's conjecture. The source records an intermediate result with an error parameter, but does not state that the conjecture itself is resolved.

Sources & referencesView supporting material

Primary source

Ararat Harutyunyan, Ken-ichi Kawarabayashi, Lucas Picasarri-Arrieta and Gil Puig i Surroca, “(Δ-1)-dicolouring of digraphs”, arXiv:2507.10266 (2025).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.