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We call a map proper if the inverse image of quasi-compact sets are quasi-compact sets.(Add the Hausforff axiom if convient) Is there example for such a map not be a closed map?

(If the spaces are locally compact Hausdorff, any proper map would be closed.)

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It’s not necessarily true without some separation axioms. Let $\tau_D$ be the discrete topology on $X=\{0,1\}$, and let $\tau_I$ be the indiscrete topology on $X$. Then the identity map from $\langle X,\tau_D\rangle$ to $\langle X,\tau_I\rangle$ is continuous and proper but not closed. You can replace replace $\tau_I$ by the Sierpiński topology, which is $T_0$, and still have an example.

Brian M. Scott
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    Ah you're back! Haven't seen you around for a bit! P.S. Thanks for all the help you gave me a bit ago! – DanZimm Oct 10 '14 at 04:25
  • @DanZimm: You’re welcome! Yes, it’s been almost a year; I expect to be back for a while, though perhaps not so active as before. – Brian M. Scott Oct 10 '14 at 04:27
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    Ah fair, hope all is well! Since you're on now I'll see if I have any good topology questions ;) – DanZimm Oct 10 '14 at 04:32