Cardinal.exists_uncountable_fiber

∀ {β α : Type u} (f : β → α), Cardinal.mk α < Cardinal.mk β → ∀ [Uncountable β], ∃ a, Uncountable ↑(f ⁻¹' {a})

A function whose domain's cardinality is uncountable and strictly greater than its codomain's has an uncountable fiber.

Defined in: Mathlib.SetTheory.Cardinal.Pigeonhole
Cited by: 0 results in Mathlib
Foundations: Depth 106 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes: Uncountable

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