Ostap Chervak
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Registered User
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Interests:
Ramsey theory, General Topology, Asymptotic Topology, Dimension Theory, Algebraic Topology, Commutative rings, Set Theory, Forcing, General Number Theory
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May 9 |
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Bijection from $\mathbb{R}$ to $\mathbb{R^2}$ How can you do the second step? I don't see an imediate way of building a bijection between $\mathbb{R}$ and $\mathbb{R}\setminus\mathbb{Q}$ |
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May 4 |
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Awfully sophisticated proof for simple facts This prove shows that there exist a field with 83 elements |
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Jan 31 |
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Colloquial catchy statements encoding serious mathematics A city is compact if you can fire all except finite number of policemen patrolling the city |
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Jan 23 |
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nontrivial theorems with trivial proofs Note that this indeed is a generalization: original Euclid's proof uses $I=\emptyset$ |
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Jan 19 |
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Magic trick based on deep mathematics Any hints on solving this problem? |
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Jan 19 |
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What is the field with one element? "F_un mathematics" spin off exists, it's just isn't a website |
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Jan 17 |
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What are the most misleading alternate definitions in taught mathematics? And how to define paracompactness then? If you define it in terms of decompositions of unit you lose conection with compactness |
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Jan 16 |
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Estimate on radical of $2^n \pm 1$ deleted 143 characters in body |
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Jan 15 |
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Estimate on radical of $2^n \pm 1$ $2^n + 1 = (2^n + 1) \rightarrow 2^n+1 \leq rad (1\times 2\times (2^n+1))^2 \rightarrow 2rad(2^n+1) \geq \sqrt{2^n+1} $ Thank you, quid, sorry for that |
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Jan 15 |
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Is there a (standard) name for $\bar{A}\setminus A$? If space is compact you may use the word "remainder" |
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Jan 15 |
revised |
Estimate on radical of $2^n \pm 1$ deleted 2 characters in body |
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Jan 15 |
revised |
Estimate on radical of $2^n \pm 1$ added 165 characters in body; deleted 2 characters in body; added 6 characters in body |
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Jan 15 |
asked | Estimate on radical of $2^n \pm 1$ |
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Jan 12 |
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Mochizuki’s proof and Siegel zeros something may be clear while not being clearly clear |
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Jan 4 |
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Awfully sophisticated proof for simple facts Irrartionality of $\pi$ uses infinitude of primes, so proofs by zeta function are all circular – |
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Jan 2 |
awarded | ● Popular Question |
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Dec 31 |
answered | Old books still used |
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Dec 5 |
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A profinite group which is not its own profinite completion? In fact $G/H$ is an ultrapower of $T$ but ultrapower of finite set is isomorphic to it. |
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Dec 4 |
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Why is there no Borel function mapping every countable set of reals outside itself? Existence of non-measurables is equivalent to $\aleph_1 \leq |\mathbb {R}|$ |
