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when toggle format what by license comment
Apr 19, 2019 at 15:56 history edited Hao Chen CC BY-SA 4.0
deleted 1 character in body
Apr 19, 2019 at 14:54 history edited Hao Chen CC BY-SA 4.0
append acknowledgement
Apr 18, 2019 at 22:41 answer added Dmitri Panov timeline score: 2
Apr 18, 2019 at 16:25 comment added Hao Chen @OlegEroshkin You are right. As I regard $\mathbb{S}^2$ as compactification of $\mathbb{R}^2$, I mean the winding number of $f(C)$ in $\mathbb{S}^2 \setminus \infty$. It is now clarified in the question.
Apr 18, 2019 at 16:24 history edited Hao Chen CC BY-SA 4.0
clarify the meaning of winding number
Apr 18, 2019 at 16:07 comment added Oleg Eroshkin What is the "winding number" for the loop in $S^2$ around 0? The sphere minus one point is contractible. You need to remove two points to have a nontrivial homotopic invariant.
Apr 18, 2019 at 15:27 comment added Hao Chen @wojowu this can be fixed by compactify $\mathbb{R}^n$ to $\mathbb{S}^n$. I updated the question accordingly.
Apr 18, 2019 at 15:24 history edited Hao Chen CC BY-SA 4.0
R→S
Apr 18, 2019 at 15:20 comment added Wojowu Let $f$ be the standard projection and $C$ be a flat circle. $f^{-1}(0)$ is a line going through the center of the circle and contains no curve linked to $C$.
Apr 18, 2019 at 13:45 history asked Hao Chen CC BY-SA 4.0