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.
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)‖.
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.
weightedCkNorm K n f is nonnegative.
Pointwise bound: each value (1 + ‖x‖)^K · ‖∂^n f(x)‖ is dominated by weightedCkNorm K n f.
weightedCkNorm K n f ≤ 2^K · sup_{m ≤ (K,K)} seminorm_m 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.
Schwartz seminorms with k, n ≤ K are bounded by weightedCkNormSup K f.
weightedCkNormSup K f ≤ 2^K · sup_{m ≤ (K,K)} seminorm_m f.
The sum of all Schwartz seminorms of order at most (K, K) applied to f.
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monomialDerivNormSum K f is nonnegative.
The supremum of Schwartz seminorms over Iic (K, K) is bounded by their sum.
weightedCkNormSup K f ≤ 2^K · monomialDerivNormSum K f.
Reverse comparison: monomialDerivNormSum K f ≤ (K + 1)^2 · weightedCkNormSup K f.
The total order of tupleToMultiIndex σ equals n, the length of the tuple.
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.
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.
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|).
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.
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.
Membership: α ∈ totalOrderBoundedMultiIndices m K ↔ |α| ≤ K.
coordMultiIndex k i belongs to totalOrderBoundedMultiIndices m K when k ≤ K.
tupleToMultiIndex σ belongs to totalOrderBoundedMultiIndices m K whenever n ≤ K.
The monomial-mixed-derivative sup norm: the infimum of c ≥ 0 with |x^α| · ‖∂^β f(x)‖ ≤ c for all x.
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The set of bounds in monomialDerivSupNorm is nonempty, using Schwartz decay.
The set of bounds in monomialDerivSupNorm is bounded below by 0.
monomialDerivSupNorm α β f is nonnegative.
Pointwise: |x^α| · ‖∂^β f(x)‖ ≤ monomialDerivSupNorm α β f.
Any uniform pointwise bound M dominates monomialDerivSupNorm α β f.
monomialDerivSupNorm α β f is bounded by the Schwartz seminorm of order (|α|, |β|).
The book-style multi-index norm: sum of monomialDerivSupNorm α β f over all |α|, |β| ≤ K.
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bookMultiIndexNorm K f is nonnegative.
Comparison: bookMultiIndexNorm K f ≤ ((K + 1)^m)^2 · monomialDerivNormSum 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.
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.
japaneseBracketCkNorm K n f is nonnegative.
Pointwise: ⟨x⟩^K · ‖∂^n f(x)‖ ≤ japaneseBracketCkNorm K n f.
japaneseBracketCkNorm K n f ≤ weightedCkNorm K n f.
Reverse: weightedCkNorm K n f ≤ (√2)^K · japaneseBracketCkNorm K n f.
The supremum of japaneseBracketCkNorm K n f over n ≤ K.
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japaneseBracketCkNormSup K f ≤ weightedCkNormSup K f.
Reverse: weightedCkNormSup K f ≤ (√2)^K · japaneseBracketCkNormSup K f.
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.