Documentation

LeanPool.NavierStokesAndEuler.NavierStokes.TorusAverages

Actual torus and native-coordinate averages #

The integer covering is treated as an actual surjective additive homomorphism of the compact torus. Haar invariance is a conclusion, not an assumption.

Concentration of actual pulse covariance columns #

We use r = sqrt L, so that a slot has length r^2. Pointwise Gaussian bounds on the fundamental component and an actual compactly supported cutoff give mass of order r and first centered moment of order r^2. Division by the mass then gives a direction error of order 1/r.

Smooth positive covariance solves #

For an actual real two-by-two matrix and target, the signed areas in Cramer's rule give an explicit strict cone. On that cone, the inverse solution and its positive square roots depend smoothly on smooth input data. A compact family has a uniform positive lower bound and a uniform tolerance for perturbing both the matrix and the target.

No assertion here supplies smoothness or error estimates for the manuscript's integrated columns. No assertion concerns extension through a zero-amplitude edge, where the strict cone hypotheses fail.

Two signed covariance slots #

The finite-dimensional algebra underlying Lemma 8.7 and equation (29) of the candidate manuscript. In the orthonormal (N,K) coordinates, the two normalized columns are (-a,-b) and (-a,b), with positive column scales. A target (-m,t) lies strictly between them precisely when |a*t| < b*m.

The actual integrated columns in the manuscript include approximation errors. This file does not identify those columns with the exact model, or prove the Gaussian, parameter-derivative, or flat-edge estimates.

Covariance amplitudes across an exponential-flat edge #

The normalized matrix and target are actual smooth functions with an explicit strict cone. Columns are then multiplied by edge κᵢ, and the target by edge σ. Exact inverse and square-root identities exhibit a positive remaining exponential whenever κᵢ < σ; in particular the squared-factor convention κᵢ = 2 λᵢ is covered by λᵢ < σ / 2.

The coefficient quotients are proved smooth from these formulas. Their smoothness across the singular matrix at the edge is not assumed.

theorem NavierStokes.PulseCovariance.normalizedMatrix_entry_error {r a A b B c₀ u E : } (pulses : SignedPulsePair r a A b B c₀ u E) (hE : 0 E) (i j : Fin 2) :
|normalizedMatrix pulses i j - signedModel c₀ u i j| (E + (|c₀| + 1) * |u| * concentrationConstant a A b B) / r

Lattice periodization and its actual integral #

Native coordinates and the determinant prefactor #

The real-cosine factor in Lemma 8.7 #