12,027 reputation
340111
bio website mit.edu/~darij/www
location Karlsruhe (home), Munich (until summer 2011), Cambridge/MA (2011-)
age 26
visits member for 5 years, 5 months
seen 14 mins ago
I'm just here for asking stupid questions.

1d
comment Most harmful heuristic?
Both of your points are true. It is a good idea to bring up the Jordan normal form before the theory of modules over a PID, but it is not at all necessary to teach its proof and the algorithm before the general case of a PID.
May
20
revised Newton polyhedron and product of ideals
added 4 characters in body; edited title
May
18
awarded  Necromancer
May
16
awarded  Favorite Question
May
11
reviewed Leave Open Fixed point theorem in ordered spaces
May
11
reviewed Leave Open Why is the evaluation map of sheaves injective
May
11
reviewed Close Orbits of a cyclic group on the powerset
May
11
reviewed Leave Open Question about Eigenvalues of group elements
May
11
reviewed Leave Open Representations of Hamilton's real/complex quaternions algebra
May
11
revised What are some examples of colorful language in serious mathematics papers?
added 55 characters in body
May
6
comment Reference for Hopf algebra applications to Feynman diagrams
Alessandra Frabetti is a name that comes to my mind, but I am as far from understanding this subject as one can be.
May
5
comment Combinatorial polynomials from general diagram fillings?
These $P$-partition enumerators and their generalizations are the subject of several papers by Malvenuto and Reutenauer, e.g., arXiv:1407.0476v2, arXiv:0905.3508v1, and "Plethysm and conjugation of quasi-symmetric functions". One thing that generalizes very well from the classical case are formulas for the coproduct and the antipode (in the Hopf algebra $\operatorname{QSym}$). I am trying to write an expository paper about this for a year now...
May
5
comment What are some examples of interesting uses of the theory of combinatorial species?
Very nice -- worth an edit of the post, I guess.
May
4
reviewed Approve How to prove the following determinant identity?
May
4
comment scalar multiple of Young symmetrizer
Ah! You want the general $n_x$. Sorry.
May
4
comment scalar multiple of Young symmetrizer
The $n_\lambda$ is the product of the hook lengths of $\lambda$. Combine Lemma 4.42 with Theorem 4.53 in arxiv.org/abs/0901.0827v5. (That said, I hope Fulton/Harris also have a proof of this somewhere.)
May
3
comment What are some examples of interesting uses of the theory of combinatorial species?
Does your recent arXiv preprint with Westbury warrant an update of this post?
Apr
30
awarded  Necromancer
Apr
30
comment Antisymmetrization of the Hochschild cocycle
You are right about homology vs. cohomology, though -- these are different problems. Sorry!
Apr
29
comment Antisymmetrization of the Hochschild cocycle
$b^2 = 0$ does not hold with the wrong signs; check the case $n = 0$.