All proofs
Project-declaredLean 4.32.0 · mathlib@81a5d257c8e4

D Lp Norm ddconv le d Lp Norm dddconv

dLpNorm_ddconv_le_dLpNorm_dddconv

Plain-language statement

For a complex-valued function and a nonzero even integer nn, discrete self-convolution has no larger LnL^n norm than discrete self-difference-convolution: ffnffn\|f*f\|_n\le\|f\mathbin{\circleddash}f\|_n.

Exact Lean statement

lemma dLpNorm_ddconv_le_dLpNorm_dddconv (hn₀ : n ≠ 0) (hn : Even n) (f : G → ℂ) :
    ‖f ∗ᵈ f‖_[n] ≤ ‖f ○ᵈ f‖_[n]

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma dLpNorm_ddconv_le_dLpNorm_dddconv (hn₀ : n  0) (hn : Even n) (f : G  ℂ) :    ‖f ∗ᵈ f‖_[n]  ‖f ○ᵈ f‖_[n] := by  refine le_of_pow_le_pow_left₀ hn₀ (by positivity) ?_  have h := pow_le_pow_left₀ (by positivity) (cLpNorm_conv_le_cLpNorm_dconv hn₀ hn f) n  rw [conv_eq_smul_ddconv, dconv_eq_smul_dddconv] at h  have h' : (Fintype.card G : )⁻¹ * (Fintype.card G : )⁻¹ ^ n * ‖f ∗ᵈ f‖_[n] ^ n       (Fintype.card G : )⁻¹ * (Fintype.card G : )⁻¹ ^ n * ‖f ○ᵈ f‖_[n] ^ n := by    simpa [cLpNorm_pow_eq_card_inv_mul_dLpNorm_pow hn₀, dLpNorm_nnqsmul, mul_pow,      mul_assoc, mul_left_comm, mul_comm] using h  have hpos : 0 < (Fintype.card G : )⁻¹ * (Fintype.card G : )⁻¹ ^ n := by positivity  nlinarith
Project
Arithmetic Progressions Almost Periodicity
License
Apache-2.0
Commit
afafc42a5326
Source
APAP/Prereqs/FourierTransform/Convolution.lean:46-56

Reuse this declaration

Bring the exact result into your workflow

The import identifies the source module. Your project still needs the pinned package dependency shown on this page.

What this badge means

This completion status comes from the project or community source. It has not yet been represented here as an independent rebuild and axiom audit.

Continue in this project

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.

View proof record
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.

View proof record
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.

View proof record