Timeline for An ordinal invariant for spaces based on a hierarchy of closed sets from z-sets
Current License: CC BY-SA 2.5
7 events
| when toggle format | what | by | license | comment | |
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| Jan 29, 2011 at 20:34 | comment | added | David Feldman | Thanks both, right, I garbled my own question. Think I've improved it now. | |
| Jan 29, 2011 at 20:21 | history | edited | David Feldman | CC BY-SA 2.5 |
edited title; added 323 characters in body
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| Jan 29, 2011 at 16:21 | history | edited | Andrés E. Caicedo | CC BY-SA 2.5 |
added 6 characters in body
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| Jan 29, 2011 at 9:47 | answer | added | Not Mike | timeline score: 2 | |
| Jan 29, 2011 at 9:17 | comment | added | Not Mike | For any normal space $X$ we have $\\{\\{x\\}: x\in X\\} \subset H(1)$ so $\bigcup_{\lambda\le1} H(\lambda)$ must contain $\\{\\{x\\}: x\in X\\}$ and every point of $X$. So the hierarchy is degenerate, and I don't think what you intended. | |
| Jan 29, 2011 at 9:14 | comment | added | Joel David Hamkins | Won't $X$ itself be in every family, since it is the zero set of the constant zero function? And in this case, we add it back in at each step. Could you explain? Also, in (1) you haven't described $H(0)$ as a family of sets, and in (2) you are taking the union of families, which would be a family, but I think you intend to take the union of the sets in that union family---could you clarify? | |
| Jan 29, 2011 at 7:11 | history | asked | David Feldman | CC BY-SA 2.5 |