29,743 reputation
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bio website math.tsukuba.ac.jp/~carnahan
location 筑波市, Japan
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visits member for 5 years, 2 months
seen 4 hours ago
I think this is a neat project.

Dec
14
comment Why do sporadic simple groups have so few conjugacy classes?
An equivalent question is, why do sporadic simple groups lack small representations?
Dec
12
answered A kind of Discrete Fourier Transform
Dec
12
reviewed Leave Open Dihedral subgroups of $\mathrm{PSL}_2(\mathbb{F}_q)$
Dec
12
reviewed Close Clarification about Joyal's notation
Dec
12
comment What is the etale fundamental group of Spec Z((x))?
There is a non-trivial automorphism of $\mathbb{Z}((x^{1/2}))$.
Dec
12
revised Number of singular fibers in families of hypersurfaces
edited tags
Dec
11
comment Decomposing quasi-finite separated group schemes
The last question has a negative answer, because you don't have any hypotheses that distinguish $0$ from any other point in the disk. You may want to specify that the pullback of $G$ to the punctured disk is étale, or something.
Dec
11
comment A kind of Discrete Fourier Transform
Your general DFT is just the restriction of an $N$-tuple of DFTs along the diagonal. That is, you really have a more general DFT: $$MGDFT_z(\ell,k)=\frac{1}{N}\sum_{j=0}^{N-1}z_{\ell,j} \omega^{-kj}$$ which is invertible, but you are forgetting most of the information by setting $k=\ell$. MGDFTs appear in many places, since they are just vector-valued DFTs. I have never seen an application of the GDFT by itself - you can certainly prove elementary properties like norm bounds by passing to the MGDFT, but if you don't tell us what sort of specific results you seek it is difficult to say more.
Dec
11
comment Most dispersed set of points in a disk?
@GerryMyerson You might as well turn your comment into an answer, since we are unlikely to see anything better in the near future.
Dec
10
comment Link between Virasoro algebra and Heisenberg algebra
See also mathoverflow.net/questions/16392/…
Dec
9
awarded  Enlightened
Dec
9
awarded  Nice Answer
Dec
3
reviewed Close totally disconnected sets and homeomorphisms
Dec
3
reviewed Reopen Affine communication lemma and finite limits in the category of rings
Dec
3
comment Relationship between Verma modules and delta functions
This seems to be a restatement of a theorem of Beilinson and Bernstein that gives an equivalence of categories between monodromic $D$-modules on the flag variety and representations of $G$. You can write generating elements of the $D$-modules as distributions corresponding to highest-weight vectors.
Dec
2
comment Can these two proofs of the parametrization of pythagorean triples be unified?
The second proof also appears on this site: mathoverflow.net/a/10903/121
Dec
1
reviewed Close How can we join two points with a small ruler?
Dec
1
comment The resolution of which conjecture/problem would advance Mathematics the most?
@JosephO'Rourke I don't think the list order is indicative of anything. After all, P vs NP is "número tres" at claymath.org/millennium-problems .
Nov
30
comment Affine communication lemma and finite limits in the category of rings
My best guess at your intention is that you want to prove that certain properties of affine schemes are Zariski-local in nature, and you are asking how to eliminate certain repetitive aspects of the standard arguments. Is that correct?
Nov
29
reviewed Close Affine communication lemma and finite limits in the category of rings