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seen Jul 16 at 15:10

Jul
9
accepted Defining algebras over noncommutative rings
Jul
9
comment Defining algebras over noncommutative rings
I'm still trying to digest the monoidal category concept, but the list of axioms looks like what I need, thank you. Can we say more about what a "natural" monoidal structure is, and why the bimodules have one but the left modules don't?
Jul
3
comment Irrationality measure.
Can you post some of the proposed definitions so we can evaluate them?
Jul
2
awarded  Curious
Jun
29
revised Ideals of infinite product rings
incorporated feedback, expanded
Jun
28
comment Defining algebras over noncommutative rings
Thanks, fixed now.
Jun
28
revised Defining algebras over noncommutative rings
clarified: two-sided algebra has ring structure
Jun
28
asked Defining algebras over noncommutative rings
Jun
23
awarded  Yearling
Jun
7
comment Does a four-variable analog of the Hall-Witt identity exist?
We could formulate a more general question like this. A permutation $\pi$ on the set $S$ induces a permutation $F(\pi)$ on the free group $F(S)$. If $\pi$ is a cycle on a set $S$ with $n$ elements, what are the nontrivial $\gamma \in F(S)$ such that $\prod_{i=1}^n F(\pi)^i(\gamma) = 1$?
Jun
7
comment For what categories do category algebras exist?
I have some questions about the "Finitary incidence algebras" paper (from 2008, not the quasiorder one), but my e-mail to you bounced...
May
31
comment generalization of bijection proof
Maybe "partitions with no values divisible by $k$" and "partitions with no $k$-tuples of the same value", for $k > 2$? I think we need to know more about what kind of generalization you're looking for.
May
31
comment Column or row of a matrix?
I don't know of a standard notation for either the rows or columns, except maybe $M_{i*}$ and $M_{*j}$.
May
31
revised For what $x$ and $y$, the sum of the factorials of $x$ and $y$ equals 10 factorial?
tag was confusing
May
31
suggested suggested edit on For what $x$ and $y$, the sum of the factorials of $x$ and $y$ equals 10 factorial?
May
31
comment generalization of bijection proof
I think you're well on your way to a proof here. You've outlined a map from the distinct partitions to the odd partitions. Now you have to show that that map is one-to-one and onto. The easiest way is to find an inverse map: given an odd partition, how would you get back to the corresponding distinct partition?
May
30
comment Example of non-abelian partially ordered group
More info on Math Overflow at What's a non-abelian totally ordered group?, especially in Rolfsen's Ordered Groups and Topology. The simplest example of a nonabelian group with a total order appears to be the free group on two generators, but the proof is not obvious.
May
30
comment Example of non-abelian partially ordered group
This is clearly a useful example (upvoted).
May
29
comment maximum nonattacking black and white queens on infinite chessboard
I'm not quite following the part about the blank row, but this looks like a nice way to fill a (roughly) 7-by-7 rectangle, then tile the plane with a grid of these rectangles. That sounds like a density around $3/49$ rather than $3/7$.
Feb
23
revised maximum nonattacking black and white queens on infinite chessboard
add example, clarify "nonattacking"