763 reputation
410
bio website andreaferretti.it
location Bonn, Germany
age
visits member for 4 years
seen Jul 22 at 10:08

Aug
6
comment Does set $\mathbb{R}^+$ include zero?
I tend to use $\mathbb{R}_{> 0}$ or $\mathbb{R}_{\geq 0}$ and avoid that notation altogether.
Aug
6
comment Yoneda-Lemma as generalization of Cayley`s theorem?
I don't think that there is such an established notion. I meant it in an intuitive sense. For groups, you associate to $g$ the map which sends $h$ to $gh$. So $g$ is determined by how it acts on other elements. For a category, you associate to $A$ the functor which sends $B$ to $Hom(B, A)$, and $A$ is determined by these $Hom$ sets. I will see if I can come up with a suitable notion of action which makes this precise.
Aug
6
answered Yoneda-Lemma as generalization of Cayley`s theorem?
Aug
5
revised Thin categories and graphs (isomorphism of categories)
added 8 characters in body
Aug
5
comment Thin categories and graphs (isomorphism of categories)
There should be { brackets, but they are lost in the formatting. On MO one can avoid that by using backticks (`) around formulas, but here it does not work. Any other workaround?
Aug
5
answered Thin categories and graphs (isomorphism of categories)
Aug
4
answered How to describe the Galois group of the compositum of all quadratic extensions of Q?
Aug
3
answered Good Physical Demonstrations of Abstract Mathematics
Aug
3
comment Applications for the class equation from group theory
Wow, now we have $\LaTeX$!! :-)
Aug
3
revised Applications for the class equation from group theory
added 95 characters in body
Aug
2
answered Why should I care about fields of positive characteristic?
Jul
27
revised Why is compactness in logic called compactness?
added 549 characters in body
Jul
27
answered Why is compactness in logic called compactness?
Jul
27
awarded  Supporter
Jul
27
answered Applications of class number
Jul
27
awarded  Editor
Jul
27
awarded  Teacher
Jul
27
revised Applications for the class equation from group theory
added 1018 characters in body
Jul
27
answered Applications for the class equation from group theory