An unconditional whole-basis geometric lower bound #
The existing fixed polynomial-time family requires more than
(gateCoefficient - ε)n gates over the signed unbounded AND/OR/XOR basis, where
gateCoefficient = (1+2c)/(1+c) and c = 1 - H₂(1/4). This is approximately
1.15876032857. There is no sparsity, depth, fanout, or fan-in hypothesis.
The proof combines affine restrictions in the tradition of Demenkov--Kulikov with one-way communication accounting in the tradition of Roychowdhury--Orlitsky--Siu. The hard family is the already checked Chattopadhyay--Liao construction. No claim of historical priority is part of the theorem.
theorem
Algebraic.Cutwidth.Aggregate.Geometry.sourceReductionHardFamily_eventually_lt_size
{ε : ℝ}
(hε : 0 < ε)
:
∀ᶠ (n : ℕ) in Filter.atTop, ∀ (c : Circuit Aggregate.Geometry.signature n 1),
(c.Computes Aggregate.Geometry.interpretation fun (x : Fin n → Bool) (x_1 : Fin 1) =>
Extractor.sourceReductionHardFamily n x) →
(gateCoefficient - ε) * ↑n < ↑c.size
The same explicit family is gate-hard above coefficient one for arbitrary-depth signed unbounded AND/OR/XOR circuits, including every binary Boolean operation.