Paper III visual guide · Visual 12 of 24 · MODEL D / AN EXACT REVERSIBLE TRIANGLE

Measure the mismatch at its base

Traditional paper: Theorem 5.10 (p. 13), Section 9 (p. 20)

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Original plate in the visual-guide PDF · Original atlas source

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Retain the reversible scalar model with forward values \(2,3,5\) and all reverse values given by inverses. Two routes from chart \(0\) to chart \(2\) multiply the input by \(6\) and \(5\), respectively. The additive discrepancy equals the original input.

A scalar triangle and repeated loop transport
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Reading the drawing

The dashed direct edge is a specified comparison map. The accompanying table records exact rational loop iterates rather than an analytic convergence assertion.

Drawing labels and data 21 labels

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  • \(0\)
  • \(1\)
  • \(2\)
  • \(2\)
  • \(3\)
  • \(5\)
  • reverse of direct edge: \(1/5\)
  • forward routes: 5 versus 6
  • loop input \(1\) returns \(6/5\)
  • \(0\)
  • \(1\)
  • \(1\)

\(\frac{6}{5}\)

  • \(2\)

\(\frac{36}{25}\)

  • \(3\)

\(\frac{216}{125}\)

  • \(4\)

\(\frac{1296}{625}\)

  • loops
  • returned value

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Evidence note from the source edition

The dashed direct edge is a specified comparison map, not a missing edge. The table shows the exact effect of traversing the same loop repeatedly. These are rational values of this example, not an analytic convergence claim.

The defect lives at the target of the forward routes:

\[ \Delta_{2,1,0}=3\cdot2-5=1. \]

The holonomy lives back at chart \(0\):

\[ H_{2,1,0}=5^{-1}\cdot3\cdot2=\frac65, \qquad H-I=\frac15=\Gamma_{0\leftarrow2}\Delta. \]

For input \(5\), the direct output and the output after two steps are \(25\) and \(30\). Returning by \(1/5\) gives \(5\) and \(6\). The target discrepancy of \(5\) has become a base discrepancy of \(1\). The types and locations of these differences matter even in an example in one dimension.

Because the return map is invertible, it cannot turn a nonzero defect into zero. This is the mechanism behind \(\Delta=0\Longleftrightarrow H=I\) in the reversible interface.

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Holonomy compares paths after both have been returned to the same base fiber. It is the transported mismatch, not an untyped difference between outputs in different charts.

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