Weighted coordinate norm and its reduction to a plain coordinate norm
DefinitionHlawkaSchatten_DiagonalConstruction_WeightedCoordinatesTwo total definitions describe weighted coordinate power functionals for real and real vectors indexed by an arbitrary finite type. In the positive-exponent range, nonnegative weights can be absorbed into a rescaling of the coordinates. The ordinary unweighted functional is a norm in the range .
weightedNorm attaches a real weight (nonnegative in use) to each coordinate before summing:
reweight rescales each coordinate of by the corresponding weight raised to the power :
By a theorem in the same source module, for whenever every , where is the finite coordinate power functional (DiagonalConstruction.lpNorm); and for the all-ones weight. A further theorem shows that, for fixed and , is concave on the nonnegative weights.
import Mathlib.Analysis.Convex.SpecificFunctions.Pow
import Mathlib.Analysis.InnerProductSpace.Basic
import Mathlib.Analysis.InnerProductSpace.Dual
import Mathlib.Analysis.Normed.Lp.PiLp
import Mathlib.Analysis.SpecialFunctions.Pow.Continuity
/-
Copyright (c) 2026 Ezzeri Esa. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Ezzeri Esa
-/
/-! # Concavity under common coordinate reweighting -/
namespace HlawkaSchatten.DiagonalConstruction
variable {ι : Type*} [Fintype ι]
noncomputable def weightedNorm (p : ℝ) (x w : ι → ℝ) : ℝ :=
(∑ i, w i * |x i| ^ p) ^ (1 / p)
noncomputable def reweight (p : ℝ) (w x : ι → ℝ) : ι → ℝ :=
fun i ↦ w i ^ (1 / p) * x i
end HlawkaSchatten.DiagonalConstruction
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