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Project-declaredLean 4.32.0 · mathlib@81a5d257c8e4

W Inner one cft

wInner_one_cft

Plain-language statement

Parseval-Plancherel identity for the discrete Fourier transform.

Exact Lean statement

@[simp] lemma wInner_one_cft (f g : G → ℂ) : ⟪cft f, cft g⟫_[ℂ] = ⟪f, g⟫ₙ_[ℂ]

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
@[simp] lemma wInner_one_cft (f g : G  ℂ) : ⟪cft f, cft g⟫_[ℂ] = ⟪f, g⟫ₙ_[ℂ] := by  classical  unfold cft  simp_rw [wInner_one_eq_sum, wInner_cWeight_eq_expect, inner_apply', map_expect, map_mul,    starRingEnd_self_apply, expect_mul, mul_expect,  expect_sum_comm,    mul_mul_mul_comm _ (conj <| f _),  sum_mul,  AddChar.inv_apply_eq_conj,  map_neg_eq_inv,     map_add_eq_mul, AddChar.sum_apply_eq_ite]  simp [add_neg_eq_zero, card_univ, Fintype.card_ne_zero, NNRat.smul_def]
Project
Arithmetic Progressions Almost Periodicity
License
Apache-2.0
Commit
afafc42a5326
Source
APAP/Prereqs/FourierTransform/Compact.lean:50-57

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Related declarations

Project-declaredLean 4.32.0

Add Dissociated boring Energy le

AddDissociated.boringEnergy_le

Project documentation

If a finite set ss is additively dissociated, then its order-nn additive energy is at most CnnnsnC^n n^n |s|^n, where CC is the project's Chang constant. This is the quantitative dissociated-set estimate used in the proof of Chang's lemma.

additive combinatoricsarithmetic progressionsFourier analysis

Source project: Arithmetic Progressions Almost Periodicity

Person-level attribution pending.

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Project-declaredLean 4.32.0

Linfty almost periodicity

AlmostPeriodicity.linfty_almost_periodicity

Project documentation

An LL^\infty almost-periodicity theorem. Under the small-growth hypothesis σ[A,S]K\sigma[A,S]\le K, and for nonempty finite sets B,CB,C, there is a set of translations TT with TK4096L(C/B)/ε2S|T|\ge K^{-4096\lceil\mathcal L(|C|/|B|)\rceil/\varepsilon^2}|S|. Every tTt\in T changes the normalized convolution μA1BμC\mu_A*1_B*\mu_C by at most ε\varepsilon in LL^\infty.

additive combinatoricsarithmetic progressionsFourier analysis

Source project: Arithmetic Progressions Almost Periodicity

Person-level attribution pending.

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Project-declaredLean 4.32.0

Linfty almost periodicity boosted

AlmostPeriodicity.linfty_almost_periodicity_boosted

Plain-language statement

A boosted LL^\infty almost-periodicity estimate. Under σ[A,S]K\sigma[A,S]\le K, it finds a large set TT, with the stated lower bound TK4096L(C/B)k2/ε2S|T|\ge K^{-4096\lceil\mathcal L(|C|/|B|)\rceil k^2/\varepsilon^2}|S|, such that averaging the target convolution against the kk-fold convolution of μT\mu_T changes it by at most ε\varepsilon in LL^\infty.

additive combinatoricsarithmetic progressionsFourier analysis

Source project: Arithmetic Progressions Almost Periodicity

Person-level attribution pending.

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