front page: the zeta ball card mentions the Wick turn

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FAqjv3n4yABxvJPJHFRhVA

index.html

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       <h2>Zeta ball · four turns</h2>
-      <p>One sphere, dragged by hand or turned by its three struts. Stand it up for the base case — 0 at the floor, ∞ at the lamp, and 0, 1, ∞, −1 a quarter turn apart, so 1 is half way to ∞ — then tip it through four stops whose shadows are the charts s/(1 − s), 2s − 1 (zeta’s orientation), 1 − 1/s (Li) and 1/(1 − 2s). The slide runs the touching point round the critical circle, and dragging the ball moves the sliders. Live ζ or ξ on the ball and on the floor, the six frame points under both names, the zeros as beads, and 3b1b’s grid as the ball’s own latitude–longitude, bent by η.</p>
+      <p>One sphere, dragged by hand or turned by its three struts. Stand it up for the base case — 0 at the floor, ∞ at the lamp, and 0, 1, ∞, −1 a quarter turn apart, so 1 is half way to ∞ — then tip it through four stops whose shadows are the charts s/(1 − s), 2s − 1 (zeta’s orientation), 1 − 1/s (Li) and 1/(1 − 2s). The slide runs the touching point round the critical circle, and dragging the ball moves the sliders. Then the Wick turn: multiply on one side only, p ↦ e<sup>iθ</sup>p, and the ball swells through the lamp into the plane (the lamp’s shadow), turns inside out, flattens into the plane projected from ½, and comes home — the four corners of the quaternion explorable, with q₁ = e<sup>iθ</sup>q and q₂ = q̄ read out. Live ζ or ξ on the ball and on the floor, the six frame points under both names, the zeros as beads, and 3b1b’s grid as the ball’s own latitude–longitude, bent by η.</p>
       <span class="go">open explorer →</span>
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     <a class="card" href="strut/">