bio  website  stankewicz.net 

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Postdoc at the University of Bristol
2h

revised 
Endomorphism algebras of abelian surfaces with real multiplication
added 10 characters in body 
7h

awarded  Curious 
19h

asked  Endomorphism algebras of abelian surfaces with real multiplication 
Jan 19 
awarded  Yearling 
Nov 6 
awarded  Popular Question 
Nov 6 
awarded  Necromancer 
Sep 24 
awarded  Autobiographer 
Jun 5 
comment 
A pointless circle in HoTT
What is your definition of "inhabited by"? 
Jun 4 
comment 
Source of quotation about the wastebaskets 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 nonWeierstrass model 
Apr 10 
comment 
Canonical lifts from $\mathbb F_q$ and CMtheory
I have two references in mind: 1) Messing's book shows how if $A_{/k}$ is an ordinary abelian variety then the SerreTate 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. 
Jan 27 
awarded  Necromancer 
Jan 19 
awarded  Yearling 