English
The Birkhoff embedding is the order-embedding sending a to the pair (Iic a, supIrred Iic a).
Русский
Встраивание Биркгоффа — это отображение-встраивание, отправляющее a в пару (Iic a, supIrred Iic a).
LaTeX
$$supIrredLowerSet : α ↪o { s : LowerSet α // SupIrred s }$$
Lean4
/-- The **Birkhoff Embedding** of a finite partial order as sup-irreducible elements in its
lattice of lower sets. -/
def supIrredLowerSet : α ↪o { s : LowerSet α // SupIrred s }
where
toFun a := ⟨Iic a, supIrred_Iic _⟩
inj' _ := by simp
map_rel_iff' := by simp