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Joseph O'Rourke
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Here is a function $f(x,y)$ which is 0 inside the square $C=[\pm1,\pm1]$, and outside that square has value equal to the Euclidean distance $d( p, C )$ from $p=(x,y)$ to the boundary of $C$. [I am trying to follow Pietro's suggestion, as far as I understand it.] It is not rotationally symmetric (but it is centrally symmetric). Are its gradient descent paths geodesics? I think so...
GradientSquare http://cs.smith.edu/%7Eorourke/MathOverflow/GradientSquare.jpg

Joseph O'Rourke
  • 150.8k
  • 36
  • 358
  • 958