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Oct 29 at 11:18 answer added Jason Starr timeline score: 4
Oct 27 at 10:52 comment added Jason Starr No, that is not correct. Consider a union of two linear three-planes intersecting in the origin (in affine six-space). Let $Z$ be the singleton set of the origin. This scheme is not $\text{S}_2$, even though the open complement of $Z$ is $\text{S}_2$.
Oct 27 at 1:32 history asked Junpeng Jiao CC BY-SA 4.0