OAI/Computability/MaxCut/Encoding/KMSKernelOrbitsFourier.lean

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Basis-invariant matrix functions have constant actual Fourier coefficients on kernel fibers. This uses ambient automorphism transitivity proved from the first isomorphism theorem, followed by the exact change-of-basis identity for the normalized trace-character transform.

  1. theorem OAI.MaxCutGames.Inverse.KMSKernelOrbitsFourier.coefficient_eq_of_ker_eq line 28

    Source documentation

    Actual coefficients depend on the kernel, not on the chosen embedding of the quotient into the basis-index space. No coefficient-invariance premise is assumed beyond the original function's basis invariance.

    theorem coefficient_eq_of_ker_eq (f : (E →ₗ[F2] F) → ℝ)
        (hf : IsBasisInvariant f) (S T : F →ₗ[F2] E) (hker : S.ker = T.ker) :
        linearCoeff f S = linearCoeff f T := by
    …