Feldmann Denis
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Registered User
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French math teacher (undergraduate level, CPGE), Ecole Normale Supérieure (Ulm, prom 1967) ; lots of other interests (see my website)
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Jan 26 |
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What is the difference between a function and a morphism? Don't you really mean "whose domain is $A$ and range $B$" ? (then, of course, you have to think of the objects of your category as sets). But of course, the answer is negative, as different morphisms can correspond to the same function. |
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Jan 23 |
asked | Translation of a non-standard analysis formulation |
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Jan 21 |
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Toroidality testing Well, you can check if they dont have as minor one of the 16000 already known obstructions (for not too large graphs, this is less absurd than it sounds...) |
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Jan 21 |
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Examples of “exotic” induction "Proofs from the Book" gives the nice ($P(1)$ and ($P(n)$ implies $P(2n)$) and ($P(n)$ implies $P(n−1)$)) implies $\forall n, P(n)$ as a way to prove the general inequality between geometric and arithmetic mean (due to Artin, or perhaps Cauchy) – Feldmann Denis 0 secs ago |
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Jan 7 |
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Have discovered a recursive formula for Prime Density - is this known? Something is very wrong here.If any formula of this shape was correct, it would give a fast way to calculate $\pi(x)$. Check it for not too small values of $n$... |
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Dec 20 |
revised |
Aronszajn trees and the transfinite subway another puzzle |
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Dec 20 |
asked | Aronszajn trees and the transfinite subway |
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Dec 15 |
asked | Positive results coming from paradoxes |
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Dec 1 |
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Are grothendieck universes enough for the foundations of category theory? Actually, the Grothendieck axiom of universe U is much stronger than existence of a strongly inaccessible cardinal, being equivalent to the exoistence of a proper class of inaccessibles (but it is weaker than the existence of a 1-inaccessible cardinal) |
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Nov 30 |
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Counterpart of Weierstrass theorem And I cannot resist to add a reference to the <a href="en.wikipedia.org/wiki/Long_line"; rel="nofollow">long line</a>, locally isomorphic to R, sequentially compact, but not compact. |
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Nov 26 |
answered | Examples where adding complexity made a problem simpler |
