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Feb
22
comment When is matrix multiplication commutative?
Here's an example why this condition is not neccesary: Take any non-diagonalizable matrix $A$. It will always commute with the unit matrix $1$, but $A$ and $1$ are clearly not simultaneously diagonalizable.
Feb
12
comment When is matrix multiplication commutative?
It's not neccesary, AFAICT. I can't think of a counter-example right know, though.
Jan
31
awarded  Revival
Jan
22
comment $f(x) \in R[X]$ irreducible $\Rightarrow (f(x))$ ideal?
Just to make sure: Do you mean by $(f)$ the ideal generated by $f$?
Jan
11
comment Powers of $2\times 2$ matrices, such that $A^n = I$
Do you know about rotation matrices?
Dec
19
awarded  Caucus
Sep
30
awarded  Explainer
Sep
25
awarded  Nice Answer
Sep
13
comment What is a polynomially bounded function?
Your argument would be correct if, say, $2^x-1$ was actually a polynomial. But by definition, a polynomial is of the form $a_n x^n + a^{n-1} x^{n-1} + \cdots + a_0$ for some parameters $a_0, \ldots, a_n$, and $2^x-1$ is not of this form.
Sep
13
revised What is a polynomially bounded function?
Not particularly computer science-related, texified
Sep
2
reviewed Approve spectral-graph-theory tag wiki excerpt
Aug
2
reviewed Approve Finding the volume of $(x-4)^2+y^2 \leqslant 4$
Aug
2
reviewed Reject Finitely generated ideal in Boolean ring; how do we motivate the generator?
Jul
6
comment Help with function proof
Indeed, my bad. Ignore my previous comment.
Jul
6
comment Help with function proof
@CameronWilliams: If you prefer, write $\mathbb{N}_0$. My natural numbers start at 0.
Jul
6
comment Help with function proof
To everybody trying to show a proof: Please make sure that what you want to prove is actually correct. In particular, consider $A = B = \mathbb{N}$, $f(x) = 0$, $Y = 2\mathbb{N}$ (the set of even numbers).
Jul
6
comment Who named “Quotient groups”?
Skimming the paper, Hölder uses the term "Faktorgruppe" (factor group), and refers to an expression "factor of composition" that he attributes to Jordan.
May
31
comment How to extend an existing orthogonal set of vectors?
Would guessing a linearly independent vector and then taking the orthogonal part work? You can make a vector orthogonal to a given set of vectors using methods similar to Gram-Schmidt...
Apr
26
reviewed Reject Uniform convergence of $\sum_{k=1}^\infty \frac{1}{k^{1+x}}$
Apr
21
reviewed Approve Estimating the integrated Tchebychev function and calculating its error