ProvedPartialAI co-developed
(Record lower bound only. The sub-2 ceiling is the codimension-two case and does not bound the record ladder (k=17 has complement mass 11). 4/3 and 2 are conjectures; the proved gap is [1.28249, 2].)
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For a single-source unsplittable flow, find the optimal universal additive constant s.t. every feasible fractional flow with arc costs should admit an unsplittable routing with and on every arc. Goemans conjectured ; this was disproved in July 2026 by a separate seven-vertex counterexample with critical constant (see the Dinitz–Garg–Goemans entry), leaving the optimal open.
Lower bound: a seventeen-terminal common-point interval instance certifies
Upper bounds: the paper proves the first unconditional ceiling below 2, but for the codimension-two case only, at complement mass . The record cells lie outside it — the instance has — so that ceiling does not bound the record ladder. Two figures are conjectures rather than results: as the supremum of critical constants over common-point cells, approached but not attained and not an extrapolation from the ladder (Conjecture 1.1, Theorem 5.1), and for the universal constant itself (Conjecture 1.2). The proved gap remains .
Posed by Dinitz, Garg, Goemans, 1999Open 27yModel GPT-5.6 Sol, Claude Fable 5, Claude Opus 5 (OpenAI, Anthropic)Solved 2026-07-31