Revisiting Separators in String Graphs, Region Intersection Graphs, and Induced-Minor-Free Graphs

James Davies, Paweł Rzążewski, Jack Spalding-Jamieson, Bartosz Walczak

The AI-origin improvement in Appendix B gives non-expansive line embeddings with O(log h) average distortion for the stated vertex-weighted metrics of connected graphs excluding the one-subdivision of K_h as an induced minor. The paper derives balanced separators of size O(h log h √m) for the corresponding m-edge graphs.

Sources for this record

What was already known

The paper’s base embedding bound has O(h²) loss. The AI-origin terminal-set peeling argument improves that dependence to O(log h). The paper’s repairs to earlier separator results are separate human contributions.

AI involvement AI-centered

The authors explicitly credit GPT-5.6 Sol with devising the initial improvement in Appendix B. They substantially simplified its presentation; the underlying human baseline and repairs remain separately credited.

Importance Notable

Improves a parameter dependence in graph separators and metric embeddings; the retained contribution is Appendix B, not the whole paper.

Limitations

The existential statements are formally checked; the paper’s polynomial-time construction claims are outside the selected formal checking scope. The repository README omits an h factor in one separator summary: the exact Lean bound contains √(|V(H)|+|E(H)|) and agrees with O(h log h √m) for the paper’s forbidden subdivision.

Technical verification Formal (Lean)

The authors report Lean verification of the existential statements, with independently separated and human-checked definitions/statements. The pinned exact improved theorem retains the graph-size/edge factor. The exact check execution date is not supplied; the paper date is retained separately.

Formal checking

The authors report Lean verification of the existential statements, with independently separated and human-checked definitions/statements. The pinned exact improved theorem retains the graph-size/edge factor.

Checker
Authors’ Lean 4 formalization
Scope
Existential non-expansive embeddings and balanced separator bounds, with exact forbidden-induced-minor and vertex-weighted metric definitions; not polynomial running time.
Basis
Reported by the linked checker
Evidence source

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

Human understanding Full

Davies, Rzążewski, Spalding-Jamieson and Walczak explain the central terminal-set peeling argument and its separator consequence in Appendix B, after simplifying the AI-origin improvement.

Correction and publication history

2026-10-19 · publication

Added this sourced contribution with its stated scope, AI attribution, checking evidence and research limits.

Read this published revision