Frankl’s conjecture# Frankl’s Conjecture at 0.38234553336670271 Every nontrivial finite union-closed family has an element in more than 38.2345% of its sets. The conjecture asks for 50%; the stronger exact bound here is checked in Lean. Matrix mortality# Matrix mortality Can a nonempty product of given integer matrices be zero? Definitions, decidability table, and small-matrix undecidability proofs.