Reputation
32,393
Next tag badge:
96/100 score
20/20 answers
Badges
3 71 153
Impact
~956k people reached

2d
comment Is it possible to have a research career while checking the proof of every theorem that you cite?
Trivial comment: this depends on how you define the word "check".
Apr
30
comment From Weyl groups to Weyl groupoids?
I would normally choose morphisms to be automorphisms seen as elements of $GL(\mathfrak{g})$ instead of exponentials - this is not a big deal as long as you work over the real or complex numbers. To get a Weyl group, you consider a groupoid whose objects are Cartan subalgebras, together with the obvious functor from $\mathcal{W}$. Fibers are naturally W-torsors.
Apr
24
comment q-product semiring
The paper you link has a discussion of generalized distributivity in section 4.2, but it requires a modification of the addition operation.
Apr
24
comment q-product semiring
You can also set $z=y$ to find that $2f(x,y) = x + 2y - 1$, which is not symmetric in $x$ and $y$.
Apr
24
comment Rational points
If $G$ is an anisotropic torus, your characterization of $k$-points is a bit off.
Apr
23
comment origin of analogy “primes as the atoms of number theory/ arithmetic”
This is not an analogy - "indivisible object" is the original meaning of "atom", and primes are multiplicatively indivisible.
Apr
18
comment Notation clash between a representation and spectral radius
$\pi$ and $\sigma$ are often used for representations. Really, you should feel free to use almost any letter for a representation.
Apr
17
comment Generalization of the fiber changing trick for principal bundles?
First, choose a trivialization of $E \to B$, then use the same gluing laws with $G$ replaced by $F$.
Apr
11
comment Examples of math hoaxes/interesting jokes published on April Fool's day?
Joro: Permission for minor edits is implicitly expected on MathOverflow, and is part of the design of the site. Please do not admonish users for doing so.
Apr
11
comment On the symmetric group of 2^n elements
It looks like $X_k^n$ is empty whenever $2^{k-1} > n$. Am I mistaken?
Apr
5
comment Representations of Calkin algebra
I think the correct spelling is "Calkin".
Apr
5
comment Defining smooth manifolds without homeomorphisms
I think do Carmo's differential geometry text uses sets instead of topological spaces to introduce manifolds. At some point, he adds the conditions of Hausdorff and second-countable in order to prove interesting theorems. This is analogous to the situation in the algebraic geometry world, where schemes are not assumed to be separated, but varieties are.
Apr
1
revised Self-dual vertex algebras
reclassify
Apr
1
comment Self-dual vertex algebras
You are unlikely to find an explicit formula that fits the generality of your question. Do you have some generators and their OPEs available?
Mar
29
revised Finding eigenvalues of an 'almost-tridiagonal' circulant matrix
minor correction
Mar
26
awarded  Popular Question
Mar
26
awarded  Nice Answer
Mar
25
comment Useful, non-trivial general theorems about morphisms of schemes
EGA 4 vol. 4 Corollary 17.11.4 expresses this as a necessary and sufficient criterion for a map to be smooth at a point.
Mar
24
comment Are the positive multiplicative group and the additive group of the field of algebraic numbers isomorphic?
@ArturoMagidin I think cardinality is not quite enough in the countable case. Perhaps the existence of an infinite set of independent elements would help.
Mar
23
revised Where does a math person go to learn quantum mechanics?
Updated link