Deletion-Star Ceilings and a 1.28249… Lower Bound for Cost-Preserving Single-Source Unsplittable Flows

Sergey Nikolenko

Nikolenko constructs a 17-terminal common-point instance proving the universal cost-preserving unsplittable-flow constant is at least 1.282494797984843521. A 3/2 congestion ceiling applies only to common-point cells of complement mass two.

Sources for this record

What was already known

Goemans’ factor-one conjecture had been refuted at 16/15; the earlier planar lower bound was about 1.139747. Alfredo De la Fuente later improved this 17-terminal line to 1.28260069012508836.

AI involvement AI-led

Nikolenko framed and wrote the theory and credits GPT-5.6 Sol, Claude Fable 5 and Claude Opus 5 with the construction search, certificates and much theory. De la Fuente’s later refinement is separate human work.

The author expressly credits models with the construction search and much theory development, and says the work was predominantly theirs; it does not document an autonomous session.

Importance Notable

The construction substantially raised the general lower bound and clarified some restricted upper bounds.

Limitations

The 1.282494 value is no longer the numerical record; the restricted ceilings do not bound all instances. Complete checking of those analytic ceilings is not documented.

Technical verification Partial

Exact machine checks cover the 17-terminal lower-bound certificate, all 131,072 routings, and sample/exhaustive tests of parts of the restricted-class theory. The source does not document a complete proof check of every analytic ceiling in this combined assessment.

Formal checking

Raw-arc path rediscovery, exhaustive routing enumeration, exact rational hull certificate and finite theorem tests

Checker
Nikolenko project’s independently written verifier scripts
Scope
The 17-terminal lower bound and finite certificate; selected restricted-class checks
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

Nikolenko explains the common-point two-order reduction, record witness and deletion-star residual, including why its ceilings do not bound the universal constant.

Correction and publication history

2026-10-18 · publication

The construction substantially raised the general lower bound and clarified some restricted upper bounds.

Read this published revision