Group_Action_on_Sets_with_k_Elements
Provedfinite-setsgroup-actionsgroup-theoryproofwiki
Let be a finite group whose identity is . Let \Bbb S = \set {S \subseteq G: \card S = k}, that is, the set of all of subsets of which have exactly elements. Let act on by the rule This is a group action, and where denotes the stabilizer of by .
Preamble
import Mathlib.Analysis.Complex.Basic
Formal statement
theorem Group_Action_on_Sets_with_k_Elements {G : Type _} [Group G] [Fintype G] [DecidableEq G] (k : ℕ) (S : Finset G) (hS : S.card = k) (g : G) : (Finset.image (fun x => g * x) S).card = k := by sorrySource