All parallel chip-firing games with 2|E|−|V| < |σ| < 2|E| have period 2

Daniel Wang, Nathan Lannan

For every finite connected simple graph G=(V,E), a parallel chip-firing game with 2|E|−|V|<|σ|<2|E| has eventual minimal period two and activity one half.

Sources for this record

What was already known

Ji, Li and Wang conjectured this strict chip-count band. It was known for trees, cycles, complete graphs and complete bipartite graphs, but not every connected graph.

AI involvement AI-led

Wang and Lannan credit GPT-5.6-Sol with the Section 3 proof. They verified the argument and wrote the exposition; Ji and Li assisted with review.

The authors attribute the proof of the general middle-stair theorem to GPT-5.6-Sol; session independence is not established.

Importance Notable

Proves the conjecture for all finite connected simple graphs.

Limitations

Wang and Lannan report verifying the model-found proof, but do not describe their checking protocol.

Technical verification Formal (human)

The authors expressly say they verified the resulting Section 3 argument for Theorem 1.2; this is a source-reported completed human proof check.

Formal checking

The authors expressly say they verified the resulting Section 3 argument for Theorem 1.2; this is a source-reported completed human proof check.

Checker
Daniel Wang and Nathan Lannan
Scope
Theorem 1.2: period two in the strict middle chip-count band on every connected simple graph
Basis
Reported by the linked checker
Evidence source

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

Human understanding Full

The human-authored proof explains prefix heights, waiting rounds, edge charges and complement configurations, then derives period two from alternating firing sequences.

Correction and publication history