C Lp Norm dft indicator one pow
cLpNorm_dft_indicator_one_pow
Plain-language statement
The -th Fourier moment of the indicator of a finite set equals its order- additive energy: . This is the standard bridge between Fourier norms and additive tuple counts.
Exact Lean statement
lemma cLpNorm_dft_indicator_one_pow [MeasurableSpace G] [DiscreteMeasurableSpace G] (n : ℕ)
(s : Finset G) : ‖dft 𝟭_[(s : Set G)]‖ₙ_[↑(2 * n)] ^ (2 * n) = boringEnergy n sFormal artifact
Lean source
lemma cLpNorm_dft_indicator_one_pow [MeasurableSpace G] [DiscreteMeasurableSpace G] (n : ℕ) (s : Finset G) : ‖dft 𝟭_[(s : Set G)]‖ₙ_[↑(2 * n)] ^ (2 * n) = boringEnergy n s := by obtain rfl | hn := n.eq_zero_or_pos · simp refine Complex.ofReal_injective ?_ calc _ = ⟪dft (𝟭_[(s : Set G)] ∗ᵈ^ n), dft (𝟭_[s] ∗ᵈ^ n)⟫ₙ_[ℂ] := ?_ _ = ⟪𝟭_[(s : Set G), ℂ] ∗ᵈ^ n, 𝟭_[s] ∗ᵈ^ n⟫_[ℂ] := wInner_cWeight_dft _ _ _ = _ := ?_ · rw [cLpNorm_pow_eq_expect_norm (by positivity)] simp_rw [pow_mul', ← norm_pow _ n, Complex.ofReal_expect, Complex.ofReal_pow, ← Complex.conj_mul', wInner_cWeight_eq_expect, inner_apply', dft_iterConv_apply] · simp only [wInner_one_eq_sum, RCLike.inner_apply, boringEnergy_eq, Complex.ofReal_mul, Complex.ofReal_sum, sq, Complex.ofReal_iterConv, (((isSelfAdjoint_indicator_one _).iterConv _).apply _).conj_eq, Complex.ofReal_comp_indicator_one]- Project
- Arithmetic Progressions Almost Periodicity
- License
- Apache-2.0
- Commit
- afafc42a5326
- Source
- APAP/Prereqs/Energy.lean:53-68
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Related declarations
Add Dissociated boring Energy le
AddDissociated.boringEnergy_le
Project documentation
If a finite set is additively dissociated, then its order- additive energy is at most , where is the project's Chang constant. This is the quantitative dissociated-set estimate used in the proof of Chang's lemma.
Source project: Arithmetic Progressions Almost Periodicity
Person-level attribution pending.
Linfty almost periodicity
AlmostPeriodicity.linfty_almost_periodicity
Project documentation
An almost-periodicity theorem. Under the small-growth hypothesis , and for nonempty finite sets , there is a set of translations with . Every changes the normalized convolution by at most in .
Source project: Arithmetic Progressions Almost Periodicity
Person-level attribution pending.
Linfty almost periodicity boosted
AlmostPeriodicity.linfty_almost_periodicity_boosted
Plain-language statement
A boosted almost-periodicity estimate. Under , it finds a large set , with the stated lower bound , such that averaging the target convolution against the -fold convolution of changes it by at most in .
Source project: Arithmetic Progressions Almost Periodicity
Person-level attribution pending.