New bounds for double covers of the discrete box {0,1,2}^d

Patrick White

For exact double covers of {0,1,2}^d by proper subboxes, Patrick White’s model-origin modular and line-rigidity argument gives f(4)≥19, f(5)≥33 and the unconditional bound f(6)≥60.

Sources for this record

What was already known

Before White’s paper only the volume lower bound was known generally, while the Leader–Milićević–Tan question asked if f(d)≥2^d. Earlier constructed upper bounds included 82 at d=6 and an asymptotic constant 1.28; the question remains open from d=6 onward.

AI involvement AI-centered

White chose the problem and questions and checked the work; he credits Claude and GPT-5.5 with the modular refinement and crossing lemma.

Specific retained mathematical ideas, including the decisive crossing lemma, are credited to the models, with White directing and checking.

Importance Notable

Provides the first lower bounds beyond volume counting, settles the proposed 2^d threshold through d=5 and raises the d=6 bound past the profile-method limit of 57.

Limitations

The 2^d question remains open from d=6 onward. The d=4 and d=5 corollaries use the separately computed base value f(3)=11. The paper’s upper constructions have separate checking scope.

Technical verification Formal (Lean 4 / mathlib kernel and exact finite computation)

The assessed f(6)≥60 bound is reported as an unconditional Lean 4 theorem with standard axioms only. White also reports independent finite computation, but no separate human hand-check of the argument is documented. The f(4), f(5) corollaries assume f(3)≥11, supplied by separate exhaustive computation.

Formal checking

Lean theorem f6_ge_60_unconditional, no hypotheses or nonstandard axioms

Checker
Lean 4/mathlib formalization reported by Patrick White
Scope
Unconditional f(6)≥60 lower bound
Basis
Reported by the linked checker
Evidence source

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

Human understanding Full

White explains the line-rigidity, crossing and aggregation mechanism and why profile-only methods stop at 57.

Correction and publication history

2026-10-18 · publication

Provides the first lower bounds beyond volume counting, settles the proposed 2^d threshold through d=5 and raises the d=6 bound past the profile-method limit of 57.

Read this published revision