Nash-Williams' conjecture for triangle decompositions

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Let GG be a K3K_3-divisible graph, meaning that 33 divides e(G)e(G) and 22 divides dG(v)d_G(v) for every vertex vv, with nn vertices and minimum degree δ(G)\delta(G). A K3K_3-decomposition is a partition of the edges of GG into edge-disjoint triangles.

Nash-Williams' conjecture. If GG is K3K_3-divisible and

δ(G)≥34n,\delta(G) \geq \frac{3}{4}n,

then, for sufficiently large nn, GG admits a K3K_3-decomposition.

This is the central extremal conjecture in design theory. The paper presents a proof of the associated fractional conjecture, while the integral statement remains the target motivating the work.

References

Primary source

Michelle Delcourt and Luke Postle, “A Proof of Nash-Williams' Conjecture”, arXiv:2606.11178 (2026).

Additional references

13 papers in this index state this conjecture (2012–2026). The statement above is taken from the most recent of them; the others are arXiv:2512.04071, arXiv:2508.20819, arXiv:2008.00926, arXiv:1908.11076, arXiv:1808.06956, arXiv:1711.03382, arXiv:1507.04985, arXiv:1503.08191, arXiv:1402.2739, arXiv:1306.0342, arXiv:1212.4667, arXiv:1205.1558.

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