Ketil Tveiten
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Registered User
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May 3 |
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Pathological Examples of Dimension Why don't you post these answers as comments to the relevant posts? |
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Apr 24 |
awarded | ● Civic Duty |
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Apr 23 |
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Can I use both of setbuilder notations in one article? I have sometimes seen semicolon used instead of colon or vertical bar, but I very much prefer the bar anyway, even if it gets ugly. |
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Apr 12 |
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Is there a deep reason for the fecundity of involutions? Alexandre: I suppose the thing I object to is the word "omnipresent". Observing lots of examples of $\mathbb{Z}/2$-symmetry does not mean that it is somehow a fundamental thing, it only means that $\mathbb{Z}/2$-symmetry is a thing we are good at recognising. Most objects (or living things) in nature don't have any symmetry at all, and in a similar way, most objects in mathematics have no symmetry, it's just that we tend to work with those objects that are nice enough that we can do something with them, and having some kind of low-order symmetry is an easy way to be nice. |
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Apr 9 |
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Additive functors and Derived Categories An example of a "useful" composition of left and right derived functors is the direct image of D-modules, which is a $R\pi_*$ applied to a derived tensor product. |
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Apr 5 |
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Is there a deep reason for the fecundity of involutions? I don't like this answer. If we understand well how to use hammers, we are going to notice a lot of nails, but that doesn't mean nails are somehow truly ubiquitous or favoured by the gods, it just means that we recognise them when we see them. Bonus points to anyone who makes good use of Jellyfish Algebras, btw. |
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Mar 7 |
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Any other definition for algebraic number than the root of algebraic equation? Perhaps the OP is looking for some other characterisation of algebraic numbers than "is the root of a monic rational polynomial"? |
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Feb 26 |
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Does the Čech cohomology always yield long exact sequences from short ones? The nlab page for derived functors nlab.mathforge.org/nlab/show/derived+functor talks about Kan extensions, though I'm not competent enough to decide if that helps you. |
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Feb 12 |
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D-affine morphisms and composition Is there any reason why you don't define it in terms of the derived direct image $f_+$? That would seem to be the natural thing to do from a $D$-module perspective... |
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Jan 31 |
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why are subextensions of Galois extensions also Galois? I can't see how the question wasn't answered in the Stackexchange thread. Try reading it again, and consulting your Galois theory textbook? |
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Jan 30 |
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Picture of a 3 dimensional amoeba. The first link is broken, should be en.wikipedia.org/wiki/Amoeba_(mathematics). |
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Jan 30 |
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Is there a standard name for functions of the form $x^\alpha p(x)$, where $p(x)$ is a polynomial? added 500 characters in body |
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Jan 29 |
asked | Is there a standard name for functions of the form $x^\alpha p(x)$, where $p(x)$ is a polynomial? |
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Jan 10 |
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D-module that is coherent as O-module You could also check J.E. Björk, Analytic D-modules and their applications, he spells out the coherence stuff in a little more detail. Might be hard to find a copy, though. |
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Jan 10 |
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D-module that is coherent as O-module deleted 32 characters in body |
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Jan 10 |
answered | D-module that is coherent as O-module |
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Dec 25 |
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Smallest sphere intersecting lines in R^3 How is $max(x,-x)$ not convex? |
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Dec 6 |
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Area Under Generalized Parabolas and Hyperbolas without Calculus. I don't understand, what's the purpose of a method that only works if you know the answer beforehand? |
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Dec 6 |
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Covering maps in real life that can be demonstrated to students @Brian Rushton: Think of cutting a paper Möbius strip (aka. paper-strip-glued-with-a-half-twist) along the midline. You get the paper-strip-glued-with-a-twist, which is the required nonstandard cylinder embedding. |
