English
IsSemisimple(restrict f hp) is equivalent to a lattice-theoretic condition about q ≤ p and existence of r with certain disjointness and joins.
Русский
IsSemisimple(ограничение f hp) эквивалентно условию на решётке: для каждого q ≤ p существует r и пр. условия.
LaTeX
$$$$ \\text{IsSemisimple}(\\mathrm{restrict} f hp) \\iff \\forall q \\in invtSubmodule, q \\le p \\rightarrow \\exists r \\le p, r \\in invtSubmodule f \\land Disjoint(q,r) \\land q \\sqcup r = p. $$$$
Lean4
theorem isSemisimple_iff : f.IsSemisimple ↔ ∀ p ∈ invtSubmodule f, ∃ q ∈ invtSubmodule f, IsCompl p q := by
simp [isSemisimple_iff']