# Riemann isometry vs Euclidean bi-Lipschitz mapping

Assume that $\gamma$ is a rectifiable Jordan curve in the complex plane of length $2\pi$. Then there exists a Riemann isometry $f$ between $\gamma$ and the unit circle $T$. My question is, does this isometry provides the minimal constant of bi-Lipschitz mappings (w.r.t. euclidean metric) between $\gamma$ and $T$ (provided that the last set is non-empty).

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I guess that by the "constant" of a bi-Lipschitz mapping, you mean its distortion, right? –  Benoît Kloeckner Jun 7 '13 at 13:50

Imagine a curve which pass very close to itself say at the points $A$ and $B$, but both arcs from $A$ to $B$ are nearly round and both have length near $\pi$. If you map it isometrically, the distortion is very bad for $A$ and $B$ and you can decrease distortion by shrinking the image of one of the arcs.