Postdoc at the University of Copenhagen

Sep
24
awarded Autobiographer
Sep
24
awarded Autobiographer
Sep
24
awarded Autobiographer
Jun
21
comment Set up router with my laptop, now the laptop can't see it
I didn't really see anything helpful for improving my question in "How to ask." I did research, but obviously I didn't find anything related to wireless networks vanishing for just one device. My question is specific and assuming it has an answer it should be clear-cut. That said, I updated the question with information from the script in Wild Man's comment. Let me know if any other information would be helpful.
Jun
21
awarded Editor
Jun
21
revised Set up router with my laptop, now the laptop can't see it
added 74 characters in body
Jun
20
asked Set up router with my laptop, now the laptop can't see it
Jun
5
comment A pointless circle in HoTT
What is your definition of "inhabited by"?
Jun
4
comment Source of quotation about the waste-baskets of physicists
Well to have been more accurately (R.I.P.)
May
5
comment Is GL2( R ) - > PGL2( R ) surjective?
In general the map will be surjective when Pic(R) is trivial. Brian Conrad's homework on group schemes walks you through this to a certain extent. If R as a Dedekind domain you can think of the elements of $PGL_n(R)$ as being pseudomatrices of fractional ideals all of whose $n$-fold products which go into the determinant are principal. If the class group is trivial, then all the entries have to be principal anyway and you're left with a standard matrix in $GL_n(R)$ up to unit multiple in $R$.
Apr
24
comment Spicing up Riemann surfaces course (revised)
What's so bland about Riemann Surfaces that requires spicing up?
Apr
12
answered Quadratic twist of an elliptic curve given by non-Weierstrass model
Apr
10
comment Canonical lifts from $\mathbb F_q$ and CM-theory
I have two references in mind: 1) Messing's book shows how if $A_{/k}$ is an ordinary abelian variety then the Serre-Tate Canonical lift $\mathcal{A}_{W(k)}$ admits an isomorphism $End_k(A) \cong End_{W(k)}(\mathcal{A})$. 2) Deligne's Inventiones paper "Varieties Abeliennes Ordinaires..." shows how the choice of embedding $W(k) \hookrightarrow \mathbf{C}$ doesn't change anything. He therefore shows an equivalence of categories between ordinary abelian varieties over a finite field vs $\mathbf{C}$ whose details escape me at the moment but the paper is 3 pages so you should read it anyway :)
Apr
1
comment Etale covers of a hyperelliptic curve
You're right. I still think there's a way to say that if $Y$ was also Galois then there's a way to break it up into a composite cover with $X$ in the middle but I don't really have any evidence for that.
Apr
1
revised Etale covers of a hyperelliptic curve
edit: removed previous edit
Apr
1
revised Etale covers of a hyperelliptic curve
added 273 characters in body
Apr
1
answered Etale covers of a hyperelliptic curve
Mar
12
comment Connections between Riemann hypothesis for curves over finite fields and Ramanujan property for graphs
For Ramanujan graphs coming Cayley graphs I don't know the exact story, but using Brandt matrices you can get Ramanujan graphs out of the dual graphs of certain Shimura curves. Pete Clark has some "rambling notes" on this subject here math.uga.edu/~pete/ramanujanrevisited.pdf and I covered some smaller cases in a course I taught a year ago.
Feb
24
answered Trouble with pgfplots and ubuntu
Feb
24
comment Trouble with pgfplots and ubuntu
I saw that these were indeed pretty old so I upgraded them as in askubuntu.com/questions/163682/… but kile is still using the 2009 repositories and nothing has changed.
1 2 3 4 5