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Question: Given a smooth, convex, closed surface. How would one find points on it with the property: the average of the geodesic distances from that point to all other points on the surface (the distance is of course, measured along the surface) is to be minimum/maximum?

Guesses: The point which minimizes the average geodesic distance from itself to all other points on the surface is one of the local minima of the Gaussian curvature; likewise, a local maximum of the Gaussian curvature will be the point that maximizes the average Gaussian distance.

Note: not sure if the global minimum and maximum of Gaussian curvature necessarily give the desired points. If that is indeed the case, if the closed and convex surface is polyhedral, the maximizing point would be that vertex where the sum of angles at that vertex of the faces meeting there would be the least. That the global maximum of curvature gives max average distance looks doubtful - in view of the fact that for a polygonal region, the longest diagonal need not begin from the vertex of the region with least angle.

Further query: Like the 4-vertex theorem, are there theorems on the minimum numbers of local extrema of Gaussian curvature on a 2D surface?

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    $\begingroup$ Just a rephrasing. If the surface is a convex polyhedron $P$, you are asking for the most compact source unfolding, which is obtained from a source $x$ by cutting the cut locus $C(x)$ and unfolding $P$ to the plane. $\endgroup$ Commented Jun 2, 2021 at 20:29
  • $\begingroup$ Thanks very much for the pointer to cut locus and unfolding! A naive guess for the source for the most compact source unfolding for a convex polyhedron would be: the source lies on the medial axis of one of the polygonal faces - maybe it is even one among the centers of the largest circles drawable on the faces. $\endgroup$ Commented Jun 3, 2021 at 11:33
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    $\begingroup$ I think an appropriate question is: Which source point $x$ leads to the source unfolding with the minimum-radius circumscribing circle? I believe this can be calculated in $O(n^4)$ time, but there is no nice characterization theorem lurking here (which is what you are seeking). That's just my hunch. $\endgroup$ Commented Jun 3, 2021 at 21:45
  • $\begingroup$ Thanks. Can you clarify if minimizing (maximizing) the radius of the circumscribing circle of the source unfolding automatically ensures that the average distance to a point on the surface from the source is also minimized (maximized)? And not sure if the source is always the center of the circumscribing circle. $\endgroup$ Commented Jun 4, 2021 at 11:34
  • $\begingroup$ No, there could be no relation between the circumcircle and the average distance. I find the min circumcircle a natural (and computable) measure of compactness. $\endgroup$ Commented Jun 4, 2021 at 11:42

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