Break the 3 log n depth barrier for explicit functions

Establish a depth lower bound strictly larger than 3 log n for some explicit Boolean function against fan-in-2 AND/OR/NOT circuits (De Morgan formulas).

Background

The strongest current lower bounds for depth of circuits computing explicit functions are (3−o(1))·log n. The paper improves depth lower bounds under additional restrictions on the top of the circuit but emphasizes that surpassing 3·log n in the unrestricted model is still unknown.

Proving any bound strictly exceeding 3·log n in the standard model would represent significant progress toward the long-term P versus NC^1 goal.