Paper IX visual guide · Visual 23 of 23

A derivative weight can cost one digit of root precision

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Original section in the visual-guide PDF · Original visual source

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Compare the linear equations \(F(x)=3x=0\) and \(G_A(x)=3x+3^A=0\), where \(A\ge2\). Their coefficient difference has \(3\)-adic valuation \(A\), but their roots differ by

\[ x_A-0=-3^{A-1},\qquad v_3(x_A)=A-1. \]
One digit of precision is lost in root displacement
Original figure from the retained vector PDF.

Reading the figure

For the displayed exponents two through seven, coefficient precision is the exponent, while root displacement precision is one less. Both lines rise with slope one. The derivative has valuation one, and the source derives the loss exactly from the two linear equations.

Recorded root displacement
ExponentRootCoefficient valuationDisplacement valuation
2-321
3-932
4-2743
5-8154
6-24365
7-72976
Selectable labels from the original PDF

Native PDF text retains the figure’s extraction order. Equations and data tables above provide the reading order.

2
3
4
5
6
7
A in 3x + 3^A
1234567
3-adic valuation
coefficient precision
root displacement precision

Original vector figure PDF · Full-size image

The derivative has valuation one. Solving the correction equation divides by three, so one digit of coefficient precision is lost in root displacement. The calculation is exact for every displayed \(A\) and also follows immediately from the two linear equations.

This example explains why weighted lifting and deformation estimates track a Jacobian loss rather than silently treating every invertible derivative over \(\mathbb Q_p\) as a unit over \(\mathbb Z_p\). A valuation-zero derivative would not incur this particular loss. Nonlinear systems additionally require their stated neighborhood, residual, and right-inverse hypotheses.

Reproducibility. The eight examples use exact rational and integer arithmetic in tools/worked_examples.py. The release record states the executed finite ranges. This atlas adds no Lean endpoint and changes no formal claim in the companion.

Source and conversion record

The full edition has 23 sections and 20 figures, including eight worked examples. The older visual README describes 15 sections and 12 figures. Original wording, equations and finite-check scope are retained. Descriptions and data tables are reading aids. This conversion renders existing figure PDFs without rebuilding TeX, running the mathematical generators, auditing proofs or compiling Lean.

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