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Atlas.DifferentialAnalysis.code.SchwartzSeminorms

noncomputable def TemperedDistributions.japaneseBracket {E : Type u_4} [NormedAddCommGroup E] (x : E) :

The Japanese bracket ⟨x⟩ = √(1 + ‖x‖²) on a normed space, a smooth weight comparable to 1 + ‖x‖.

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    The Japanese bracket is nonnegative: 0 ≤ ⟨x⟩.

    The Japanese bracket is bounded above by 1 + ‖x‖: ⟨x⟩ ≤ 1 + ‖x‖.

    Reverse comparison: 1 + ‖x‖ ≤ √2 · ⟨x⟩.

    Monotone power version: ⟨x⟩^k ≤ (1 + ‖x‖)^k.

    Reverse power comparison: (1 + ‖x‖)^k ≤ (√2)^k · ⟨x⟩^k.

    theorem TemperedDistributions.weighted_norm_le_sup_seminorm {𝕜 : Type u_1} [NormedField 𝕜] {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] {K k n : } (hk : k K) (hn : n K) (f : SchwartzMap E F) (x : E) :
    (1 + x) ^ k * iteratedFDeriv n (⇑f) x 2 ^ K * ((Finset.Iic (K, K)).sup fun (m : × ) => SchwartzMap.seminorm 𝕜 m.1 m.2) f

    Each weighted derivative norm (1 + ‖x‖)^k · ‖∂^n f(x)‖ is bounded by 2^K times the supremum of Schwartz seminorms of order at most K.

    The monomial weighted norm ‖x‖^k · ‖∂^n f(x)‖ is bounded by the weighted norm (1 + ‖x‖)^k · ‖∂^n f(x)‖.

    noncomputable def TemperedDistributions.weightedCkNorm {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] (K n : ) (f : SchwartzMap E F) :

    The weighted C^k norm of a Schwartz function: the infimum of constants c ≥ 0 bounding (1 + ‖x‖)^K · ‖∂^n f(x)‖ uniformly in x.

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      The set of bounds defining weightedCkNorm K n f is nonempty, using Schwartz decay.

      The set of bounds defining weightedCkNorm K n f is bounded below by 0.

      Pointwise bound: each value (1 + ‖x‖)^K · ‖∂^n f(x)‖ is dominated by weightedCkNorm K n f.

      theorem TemperedDistributions.weightedCkNorm_le_sup_seminorm {𝕜 : Type u_1} [NormedField 𝕜] {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] {K n : } (hn : n K) (f : SchwartzMap E F) :
      weightedCkNorm K n f 2 ^ K * ((Finset.Iic (K, K)).sup fun (m : × ) => SchwartzMap.seminorm 𝕜 m.1 m.2) f

      weightedCkNorm K n f ≤ 2^K · sup_{m ≤ (K,K)} seminorm_m f.

      theorem TemperedDistributions.seminorm_le_weightedCkNorm {𝕜 : Type u_1} [NormedField 𝕜] {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] {K k n : } (hk : k K) (f : SchwartzMap E F) :

      Reverse comparison: any Schwartz seminorm of order (k, n) with k ≤ K is bounded by weightedCkNorm K n f.

      The maximum of weightedCkNorm K n f over derivative orders n ≤ K.

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        Individual weightedCkNorm K n f is bounded by the supremum weightedCkNormSup K f when n ≤ K.

        theorem TemperedDistributions.seminorm_le_weightedCkNormSup {𝕜 : Type u_1} [NormedField 𝕜] {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] {K k n : } (hk : k K) (hn : n K) (f : SchwartzMap E F) :

        Schwartz seminorms with k, n ≤ K are bounded by weightedCkNormSup K f.

        theorem TemperedDistributions.weightedCkNormSup_le_sup_seminorm {𝕜 : Type u_1} [NormedField 𝕜] {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] (K : ) (f : SchwartzMap E F) :
        weightedCkNormSup K f 2 ^ K * ((Finset.Iic (K, K)).sup fun (m : × ) => SchwartzMap.seminorm 𝕜 m.1 m.2) f

        weightedCkNormSup K f ≤ 2^K · sup_{m ≤ (K,K)} seminorm_m f.

        noncomputable def TemperedDistributions.monomialDerivNormSum {𝕜 : Type u_1} [NormedField 𝕜] {E : Type u_2} [NormedAddCommGroup E] [NormedSpace E] {F : Type u_3} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] (K : ) (f : SchwartzMap E F) :

        The sum of all Schwartz seminorms of order at most (K, K) applied to f.

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          The supremum of Schwartz seminorms over Iic (K, K) is bounded by their sum.

          Cardinality of Iic (K, K) in ℕ × ℕ equals (K + 1)^2.

          The order |α| = ∑ αᵢ of a multi-index α : Fin m → ℕ.

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            def MultiIndexBridge.tupleToMultiIndex {m n : } (σ : Fin nFin m) :
            Fin m

            From a tuple σ : Fin n → Fin m build the multi-index counting fibers of σ.

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              The total order of tupleToMultiIndex σ equals n, the length of the tuple.

              noncomputable def MultiIndexBridge.multiIndexDirections {m : } (β : Fin m) :

              Canonical tuple of unit direction vectors corresponding to a multi-index β, indexed by Fin |β|.

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                Each entry of multiIndexDirections β is a standard basis vector.

                Each direction vector in multiIndexDirections β has norm at most one.

                def MultiIndexBridge.realMonomial {m : } (α : Fin m) (x : EuclideanSpace (Fin m)) :

                The real monomial x^α = ∏ᵢ (xᵢ)^(αᵢ) associated to a multi-index α.

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                  |x^α| ≤ ‖x‖^{|α|} for any multi-index α.

                  noncomputable def MultiIndexBridge.multiIndexPartialDeriv {m : } {F : Type u_1} [NormedAddCommGroup F] [NormedSpace F] (β : Fin m) (f : EuclideanSpace (Fin m)F) (x : EuclideanSpace (Fin m)) :
                  F

                  The mixed partial derivative ∂^β f(x) of order β, expressed via the iterated Fréchet derivative applied to the canonical direction tuple.

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                    ‖∂^β f(x)‖ ≤ ‖D^{|β|} f(x)‖ where D^k is the iterated Fréchet derivative.

                    The iterated Fréchet derivative norm of a Schwartz function is bounded by the sum over tuples of the corresponding mixed partial derivative norms.

                    |x^α| · ‖D^{|β|} f(x)‖ is bounded by the Schwartz seminorm of order (|α|, |β|).

                    theorem MultiIndexBridge.norm_le_sum_abs {m : } (x : EuclideanSpace (Fin m)) :
                    x i : Fin m, |x.ofLp i|

                    The Euclidean norm is bounded by the sum of coordinate absolute values: ‖x‖ ≤ ∑ |xᵢ|.

                    theorem MultiIndexBridge.norm_pow_le_sum_coord_pow {m : } (x : EuclideanSpace (Fin m)) (k : ) :
                    x ^ (k + 1) m ^ k * i : Fin m, |x.ofLp i| ^ (k + 1)

                    Power-of-norm bound: ‖x‖^(k+1) ≤ m^k · ∑ |xᵢ|^(k+1) for x ∈ ℝ^m.

                    def MultiIndexBridge.coordMultiIndex {m : } (k : ) (i : Fin m) :
                    Fin m

                    Single-coordinate multi-index: k at position i, zero elsewhere.

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                      The order of the single-coordinate multi-index coordMultiIndex k i equals k.

                      |xᵢ|^k = |x^{coordMultiIndex k i}|: a coordinate power matches the corresponding monomial.

                      The finset of all multi-indices α : Fin m → ℕ with each αᵢ ≤ K.

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                        theorem MultiIndexBridge.mem_boundedMultiIndices_iff {m : } (α : Fin m) (K : ) :
                        α boundedMultiIndices m K ∀ (i : Fin m), α i K

                        Membership criterion: α ∈ boundedMultiIndices m K ↔ ∀ i, αᵢ ≤ K.

                        If the total order of α is at most K, then each coordinate is at most K.

                        Cardinality: there are (K + 1)^m multi-indices with each coordinate bounded by K.

                        Multi-indices α with total order |α| ≤ K.

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                          noncomputable def MultiIndexBridge.monomialDerivSupNorm {F : Type u_2} [NormedAddCommGroup F] [NormedSpace F] {m : } (α β : Fin m) (f : SchwartzMap (EuclideanSpace (Fin m)) F) :

                          The monomial-mixed-derivative sup norm: the infimum of c ≥ 0 with |x^α| · ‖∂^β f(x)‖ ≤ c for all x.

                          Instances For

                            The set of bounds in monomialDerivSupNorm is nonempty, using Schwartz decay.

                            The set of bounds in monomialDerivSupNorm is bounded below by 0.

                            Pointwise: |x^α| · ‖∂^β f(x)‖ ≤ monomialDerivSupNorm α β f.

                            theorem MultiIndexBridge.monomialDerivSupNorm_le_bound {F : Type u_2} [NormedAddCommGroup F] [NormedSpace F] {m : } (α β : Fin m) (f : SchwartzMap (EuclideanSpace (Fin m)) F) {M : } (hMp : 0 M) (hM : ∀ (x : EuclideanSpace (Fin m)), |realMonomial α x| * multiIndexPartialDeriv β (⇑f) x M) :

                            Any uniform pointwise bound M dominates monomialDerivSupNorm α β f.

                            monomialDerivSupNorm α β f is bounded by the Schwartz seminorm of order (|α|, |β|).

                            noncomputable def MultiIndexBridge.bookMultiIndexNorm {F : Type u_2} [NormedAddCommGroup F] [NormedSpace F] {m : } (K : ) (f : SchwartzMap (EuclideanSpace (Fin m)) F) :

                            The book-style multi-index norm: sum of monomialDerivSupNorm α β f over all |α|, |β| ≤ K.

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                              theorem MultiIndexBridge.seminorm_le_bookMultiIndexNorm {𝕜 : Type u_1} [NormedField 𝕜] {F : Type u_2} [NormedAddCommGroup F] [NormedSpace F] [NormedSpace 𝕜 F] [SMulCommClass 𝕜 F] {m : } [Nonempty (Fin m)] {j n K : } (hj : j K) (hn : n K) (f : SchwartzMap (EuclideanSpace (Fin m)) F) :
                              (SchwartzMap.seminorm 𝕜 j n) f m ^ (2 * K) * bookMultiIndexNorm K f

                              Reverse comparison: each Schwartz seminorm seminorm j n f with j, n ≤ K is at most m^{2K} · bookMultiIndexNorm K f.

                              Combined comparison: monomialDerivNormSum K f ≤ (K + 1)^2 · m^{2K} · bookMultiIndexNorm K f.

                              Equivalence of weightedCkNormSup and bookMultiIndexNorm up to constants depending on K and m.

                              Decomposition of a Euclidean vector into the sum v = ∑ᵢ vᵢ · eᵢ over the standard basis.

                              theorem MultiIndexBridge.multilinear_basis_expansion {F : Type u_2} [NormedAddCommGroup F] [NormedSpace F] {m n : } (M : ContinuousMultilinearMap (fun (x : Fin n) => EuclideanSpace (Fin m)) F) (v : Fin nEuclideanSpace (Fin m)) :
                              M v = σ : Fin nFin m, (∏ k : Fin n, (v k).ofLp (σ k)) M fun (k : Fin n) => EuclideanSpace.single (σ k) 1

                              Expansion of a continuous multilinear map M in the standard basis: M v = ∑_σ (∏ₖ v_k (σ k)) · M (e_{σ k}).

                              The ⟨x⟩^K-weighted C^k norm of a Schwartz function: the infimum of c ≥ 0 bounding ⟨x⟩^K · ‖∂^n f(x)‖ uniformly.

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                                The set of bounds for japaneseBracketCkNorm K n f is nonempty.

                                The set of bounds for japaneseBracketCkNorm K n f is bounded below by 0.

                                Pointwise: ⟨x⟩^K · ‖∂^n f(x)‖ ≤ japaneseBracketCkNorm K n f.

                                The supremum of japaneseBracketCkNorm K n f over n ≤ K.

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                                  Corollary 7.2 (Melrose): equivalence of the Japanese-bracket weighted C^K norm and the book multi-index norm up to constants C₁, C₂ > 0.