English
There is a top element on β given by topβ = l(topα) provided by the adjunction, ensuring top(β) is above all β-elements.
Русский
Существует верхний элемент в β, заданный как topβ = l(topα), обеспечиваемый аксиомой сопряженности.
LaTeX
$$$$ \text{top}_{β} = l(\text{top}_{α}), \; \text{le}_{β}(x, \text{top}_{β}) \text{ holds for all } x. $$$$
Lean4
/-- Lift the top along a Galois insertion -/
abbrev liftOrderTop [Preorder α] [OrderTop α] (gi : GaloisInsertion l u) : OrderTop β
where
top := gi.choice ⊤ <| le_top
le_top := by simp only [gi.choice_eq];
exact fun b =>
(gi.le_l_u b).trans
(gi.gc.monotone_l le_top)
-- See note [reducible non-instances]