A new upper bound on the dimer constant of ℤ³

Qidong He

A diagonal transfer-layer family gives an upper bound for the cubic-lattice dimer constant. Its (m,n)=(5,5), p=2 exact finite computation yields ℓ₃≤0.452130.

Sources for this record

What was already known

Lundow’s earlier published upper bound was 0.457547. Csikvári’s matching-polynomial inequality and Friedland–Schneider’s spectral-radius result were existing ingredients.

AI involvement AI-centered

GPT-5.6 Sol Ultra suggested the diagonal transfer-layer idea and its link to Csikvári’s inequality. Qidong He developed the proof, compressed computation and Java implementation.

The acknowledged model contribution is the retained diagonal-layer/Csikvari connection on which the improved upper bound rests.

Importance Notable

Improves the published upper bound for the three-dimensional dimer constant.

Limitations

This is an upper bound, not the exact constant. The specified exact computation is reported, but the program and full analytic argument have no documented independent replay.

Technical verification Partial

The paper reports arbitrary-precision integer vector updates and exact cross-multiplication for the (5,5), p=2 finite bound, with upward rounding to six decimals. This checks the numeric part on specified inputs; no completed independent check of the full transfer-layer theorem or program replay is documented.

Independent checking

Matrix-free sector iteration with arbitrary-precision integer vector updates and exact ratio comparison, followed by upward decimal rounding

Checker
Qidong He's Java implementation
Scope
Finite (m,n)=(5,5), p=2 ratio bound yielding ell_3 <= 0.452130 under Corollary 3.4
Basis
Reported by the linked checker
Evidence source

Human understanding Full

He explains how diagonal layers, Csikvari's inequality, symmetry compression and monotone spectral-radius ratios yield the bound. The unexplained preference for near-square section sizes is a side observation, not a gap in the central mechanism.

Correction and publication history