Addario-Berry–Havet–Linhares Sales–Reed–Thomassé density conjecture

Let $k\in\mathbb N$, let $D$ be a digraph, and let $T$ be an antidirected tree with $k$ edges. Addario-Berry et al.'s conjecture. Every digraph $D$ with more than $(k-1)|V(D)|$ edges contains every antidirected $k$-edge tree. The bound is necessary by examples described in the survey; the conjecture is the proposed sharp density threshold and remains open in the stated generality.