Open Research Index

Fischer's 24-vertex zero-forcing counterexample

John Fairfax-Ball

Palomar Registrypalomar/PALOMAR-2026-09-20-000009Sep 20, 2026math.COscore 0

A Lean 4 formalization of Mikko Fischer's explicit connected 24-vertex subcubic graph with independence number 9 and zero-forcing number 11. The formalization verifies the exact graph and both numerical invariants, yielding an existential counterexample to the proposed bound Z(G) <= alpha(G) + 1 for connected graphs of maximum degree at most 3.

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