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Timeline for radius of tubular neighborhood

Current License: CC BY-SA 3.0

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Mar 10, 2017 at 9:42 history edited CommunityBot
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Oct 26, 2012 at 17:39 comment added Liviu Nicolaescu Let me write it in a different way $x(t)=e^{-t}\cos t$ $y(t)=e^{-t}\sin t$, $t\in [0,2\pi N]$. As $t$ runs in the interval $[0,2\pi N]$ the point $(x(t),y(t))$ keeps on orbiting around the origin, while the distance to the origin decays exponentially to $0$. But I know believe it may not be a counterexample to your conjecture.
Oct 26, 2012 at 16:28 comment added Jay so.. that is an extra restriction on $\theta \in [0, 2\pi]$? :)
Oct 26, 2012 at 15:33 comment added Liviu Nicolaescu If it decreases going one way along the curve, it increases going the other way. The example of a spiral given in polar coordinates by the equation $r=e^{-\theta}$, $0\leq \theta \leq 2\pi N$, may provide a counterexample to your conjectured formula. It seems plausible that if the curve is the $C^2$-boundary of a convex domain then the largest tubular radius is the inverse of the maximal curvature.
Oct 26, 2012 at 15:13 comment added Jay Thanks a lot! Maybe that is what I want: if the curvature of the curve is always decreasing, then the radius of the tubular neighborhood is given by the injective radius of (left) end point, it seems true, right?
Oct 26, 2012 at 12:33 comment added Pietro Majer actually this is exactly what the OP is saying...
Oct 26, 2012 at 12:17 history edited Liviu Nicolaescu CC BY-SA 3.0
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Oct 26, 2012 at 12:00 history answered Liviu Nicolaescu CC BY-SA 3.0