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| bio | website | |
|---|---|---|
| location | ||
| age | ||
| visits | member for | 2 years, 4 months |
| seen | 3 mins ago | |
| stats | profile views | 4,151 |
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Apr 12 |
answered | Deformation retraction: special case of homotopy equivalence? |
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Apr 12 |
comment |
Deformation retraction: special case of homotopy equivalence? Impossible because if $Im(id_X) \subset A$ then it's not the $id$ function. Oh. Just realised my mistake: I can still have a homotopy.... arrgh Now I'm annoyed with myself for making the same mistake for the $n$-th time. Thanks for your patience! |
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Apr 12 |
asked | Deformation retraction: special case of homotopy equivalence? |
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Apr 11 |
accepted | Proof of Urysohn's lemma — dyadic rationals |
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Apr 6 |
accepted | Question about notation / terminology |
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Apr 6 |
asked | Proof of Urysohn's lemma — dyadic rationals |
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Apr 4 |
comment |
Common algorithm with an order of Θ(2^n) @Didier Piau: right, thanks! |
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Apr 4 |
answered | Common algorithm with an order of Θ(2^n) |
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Apr 4 |
answered | Confused about notation of $\sin^2 \theta$ |
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Apr 4 |
answered | where to go for help solving specific math problems |
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Apr 4 |
comment |
Show that $\mathbb{R}^2$ is not homeomorphic to $\mathbb{R}^2 \setminus\{(0,0)\}$ @Christian Blatter: I'm sorry but I think this doesn't answer my question satisfactorily. Could you give me a mathematically rigorous argument why it is not enough? To me arguing like I argued in my answer above is a proof by contradiction, so it seems rigorous to me. |
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Apr 4 |
comment |
Show that $\mathbb{R}^2$ is not homeomorphic to $\mathbb{R}^2 \setminus\{(0,0)\}$ @Christian Blatter: Many thanks for pointing this out. I'm a beginner in this subject, so may I ask: why is it not enough to argue that any homotopy would go through $(0,0)$? |
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Apr 4 |
comment |
casting out nines: division why the down vote? |
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Apr 4 |
revised |
Show that $\mathbb{R}^2$ is not homeomorphic to $\mathbb{R}^2 \setminus\{(0,0)\}$ added 30 characters in body |
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Apr 4 |
answered | Show that $\mathbb{R}^2$ is not homeomorphic to $\mathbb{R}^2 \setminus\{(0,0)\}$ |
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Apr 3 |
accepted | Superscript wedge on an $R$-module |
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Apr 3 |
comment |
Superscript wedge on an $R$-module Thank you so much! I didn't know what to search for because I didn't know it was called 'dual'. |
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Apr 3 |
revised |
Superscript wedge on an $R$-module edited body; added 12 characters in body |
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Apr 3 |
comment |
Superscript wedge on an $R$-module @Qiaochu: sorry, that was a typo, it should've said page 3! |
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Apr 3 |
asked | Superscript wedge on an $R$-module |
