Concrete squared partitions on the line and on slow-coordinate grids #
Integer translates of one compactly supported smooth bump are normalized by the square root of their locally finite sum of squares. Every object below is constructed; no partition-of-unity or derivative-bound hypothesis is assumed.
A smooth locally finite sum is smooth. This elementary version uses finite sums on neighborhoods, so no uniform convergence premise is needed.
One fixed bump: equal to one on [-1/2,1/2], positive on (-1,1).
Equations
- NavierStokes.SquaredPartition.bump = { rIn := 1 / 2, rOut := 1, rIn_pos := NavierStokes.SquaredPartition.bump._proof_1, rIn_lt_rOut := NavierStokes.SquaredPartition.bump._proof_2 }
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A finite product of locally finite families is locally finite, with the whole tuple as index.
Product mask, given by ∏ j, gridMask δ (k j) (x j).
Equations
- NavierStokes.SquaredPartition.productMask δ k x = ∏ j : Fin d, NavierStokes.SquaredPartition.gridMask δ (k j) (x j)
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Compact smooth profiles have a finite bound at every fixed derivative order.
Full Fréchet jets of a translated rescaling cost one inverse scale per derivative, with no dependence on the translation.
A single compact annular profile; its zero extension is smooth at zero.
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Integer Q, given by (2 : ℝ) ^ (-(n : ℝ)).
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- NavierStokes.SquaredPartition.integerQ n = 2 ^ (-↑n)
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Dyadic local finiteness holds on the positive q domain. The supports
accumulate at zero, so no global local-finiteness claim is made there.
After any chosen starting band, the retained bands partition the smaller
active range 0<q≤Q_N. In particular one can retain only n≥4.
The actual three-coordinate partition at slow mesh S_n^(-3).
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Every fixed jet costs the fixed power S^(3m), uniformly in all grid nodes.
The manuscript's three physical-to-slow coordinate rescalings.
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Physical slow mask, given by slowMask n k (slowCoordinates D n x).
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The constructed masks fit inside the exact enlarged boxes already colored
in SlotColoring, for either pulse sign.
Label mask, given by dyadicMask (n : ℤ) p.1 * slowMask n k p.2.
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The exact normalized squared partition obtained by multiplying dyadic and
slow-grid masks; any lower band cutoff can be imposed by shrinking q.