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Theorems · Theorem · category theory

CategoryTheory.PreGaloisCategory.lt_card_fiber_of_mono_of_notIso

∀ {C : Type u₁} [inst : CategoryTheory.Category.{u₂, u₁} C] (F : CategoryTheory.Functor C FintypeCat)
  [inst_1 : CategoryTheory.PreGaloisCategory C] [CategoryTheory.PreGaloisCategory.FiberFunctor F] {X Y : C} (f : X ⟶ Y)
  [CategoryTheory.Mono f], ¬CategoryTheory.IsIso f → Nat.card (F.obj X).obj < Nat.card (F.obj Y).obj

Along a mono that is not an iso, the cardinality of the fiber strictly increases.

Defined in
Mathlib.CategoryTheory.Galois.Basic
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Foundations
Depth 95 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
CategoryTheory.CategoryCategoryTheory.PreGaloisCategoryCategoryTheory.PreGaloisCategory.FiberFunctorCategoryTheory.Mono

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