Documentation

LeanPool.Superdiffusion.Algsuperdiff.Section3.Provider.Diffusivity.ApproximateRecurrence.LocalizationFluctuationStationarity

LocalizationFluctuationStationarity #

Ported from scottnarmstrong/Superdiffusion at 7f20476385d4af418f110303085ad0740c9eba46. Module imports, support namespace and local option directives adapted for Lean Pool.

The stationarity half #

  1. geometric -- state the per-cell bound at the cell's own scale-m ancestor. This is LocalizationFluctuationAncestor, proved;
  2. probabilistic -- transport the annealed fourth moment from that ancestor back to cu_m by stationarity, "which the manuscript uses silently".

This module performs step 2.

The route #

Every scale-m triadic cube is an integer translate of cu_m (eq_translateCube_originCube_of_scale), and the cutoff-sample law is invariant under every real translation (Cutoff.map_translateCutoffSample_cutoffSampleLaw, Cutoff.coefficientCutoffLaw_stationary_real). What is missing between those two facts is the per-cube covariance of the coarse matrices of the actual cutoff family: CoarseGraining's

reduce the covariance of the two multiscale ellipticity constants to exactly the per-cube identities

  |b(3^n z + R; a_omega)|            = |b(R; a_{tau_v omega})| ,
  |sigma_*^{-1}(3^n z + R; a_omega)| = |sigma_*^{-1}(R; a_{tau_v omega})| ,

for every descendant R of cu_m at depth n, where v = 3^m z is the physical shift and a_omega = coefficientCutoffTriadicCoeffFamily M L omega. coarseBlockMatrix_coefficientCutoff_translateCube proves both at once, at the level of the coarse block matrix, by the chain

  A(cu(3^n z + R); a_omega)  =  A(open(3^n z + R); cutoff_omega)         (Ch02 = CoarseGraining)
                              =  A(v + open(R); cutoff_omega)             (geometry)
                              =  A(open(R); translate_v cutoff_omega)     (translation)
                              =  A(open(R); cutoff_{tau_v omega})         (Cutoff.Symmetry)
                              =  A(cu(R); a_{tau_v omega}) .

Note that the physical shift 3^n z * 3^{m-n} = 3^m z is the same at every depth n, which is precisely what the CoarseGraining hypothesis needs.

What is proved #

Binders #

Everything through gaugedEllipticitySum_scale_eq_originCube is pathwise and unconditional apart from the typing binders and the cube-scale identification hT : T.scale = m; no measure, no model gate and no moment occurs. The two transport statements add one binder, hmeas, the a.e.-strong measurability in the sample of the observable being integrated -- the analytic side condition of the change of variables, on the very object the moment is formed from. It is not a smallness, normalization or moment assumption, and it is stated at the origin cube, i.e. at the carrier the frozen theorem already speaks about.

Scope #

There is no sorry.

References #

Geometry: the open realization of a translated cube #

Unconditional. The open realization of translateCube w S is the translate of the open realization of S by the physical shift w * 3^{S.scale}.

Unconditional. Every scale-m triadic cube is the integer translate of cu_m by its own index.

The two coarse block matrices agree #

Unconditional. The Chapter-2 coarse block matrix of a cube coefficient object is the CoarseGraining coarse block matrix of its underlying coefficient field on the open cube.

This is the content of coarseBlockMatrix_cubeSet_eq_ch02_coarseBlockMatrix_of_aelocallyUniformlyEllipticField without its A packaging: the cutoff family is not built through triadicCoeffFamilyOfA, so that statement does not apply to it.

The per-cube covariance of the coarse block matrix of the actual cutoff family. Translating the cube by w and translating the sample by the physical shift w * 3^{S.scale} produce the same coarse block matrix.

Unconditional: the only inputs are the geometry step, CoarseGraining's translation identity for coarseBlockMatrix and the exact commutation Cutoff.coefficientCutoff_translateCutoffSample.

The physical shift does not move with the depth #

Unconditional. A depth-n descendant of a cube of scale m, translated by descendantTranslationShift n z, moves by the physical shift 3^m z, which does not depend on n.

The gauged ellipticity sum is covariant #

The pathwise covariance, at an arbitrary scale-m cube. Unconditional apart from the scale identification hT.

The change of variables in the sample #

The translation change of variables on the cutoff-sample law.

Conditional on hg, the a.e.-strong measurability of the integrand -- the analytic side condition of the change of variables.

The transport #

The stationarity half. The annealed fourth moment of the gauged ellipticity sum at any scale-m cube equals the one at cu_m, where Frozen.Section3.coarse_ellipticity_bounds lives.

Conditional on the scale identification hT and on hmeas, the a.e.-strong measurability in the sample of the observable at the origin cube. Nothing about the model, the gauge or the exponent is assumed.

The transport at the ancestor carrier of LocalizationFluctuationAncestor. The annealed fourth moment of the gauged ellipticity sum at a mesoscopic cell's own scale-m ancestor is the one at cu_m. Together with LocalizationFluctuationAncestor.doubledPoincareEllipticityFactor_sq_le_recurrenceAncestor this closes the carrier mismatch.

Conditional on hm : R.scale <= m (the ancestor exists) and on hmeas.