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location Penn State, University Park, PA
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Jan
14
awarded  Nice Answer
Dec
13
awarded  ag.algebraic-geometry
Dec
12
comment Mumford-Tate groups of products of Hodge structures
Yes, you are right: please see my counterexample below.
Dec
12
answered Mumford-Tate groups of products of Hodge structures
Dec
12
answered can all CM types be realized by Jacobians?
Nov
17
comment When are K-automorphisms of the n-torsion of an elliptic curve E/K liftable to K-endomorphisms of E?
It seems to me that for elliptic curves the question (for non-CM) elliptic curves $E$ about the Galois image in $Aut(E[p])$ was raised by Serre in his (already mentioned) 1972 Inventiones paper. Some partial (but very important) results in this direction were obtained recently by Yuri Bilu and Pierre Parent annals.math.princeton.edu/2011/173-1/p13 .
Nov
13
comment Mumford-Tate groups of products of Hodge structures
As far as I know, Mumford-Tate groups are never semisimple.
Nov
8
comment When are K-automorphisms of the n-torsion of an elliptic curve E/K liftable to K-endomorphisms of E?
Dear Stefan, you are welcome. As far as I know, nobody stated it as a conjecture for $d>1$.
Nov
7
answered When are K-automorphisms of the n-torsion of an elliptic curve E/K liftable to K-endomorphisms of E?
Oct
1
awarded  Nice Answer
Sep
30
awarded  Yearling
Jun
25
awarded  Revival
Jun
7
awarded  Necromancer
Mar
14
comment Does the Manin-Drinfeld theorem hold over number fields?
You are welcome. Actually, since the end of 1960th all major Russian mathematical journals (Izvestija, MatSbornik, Uspekhi, Functional Analysis, MatZametki, . . .) are translated into English.
Mar
14
answered Does the Manin-Drinfeld theorem hold over number fields?
Mar
12
revised Tate conjecture for abelian varieties over a finitely generated extension of an algebraically closed field
the statement was clarified, improved formatting
Mar
12
revised Tate conjecture for abelian varieties over a finitely generated extension of an algebraically closed field
fixed grammar
Mar
12
answered Tate conjecture for abelian varieties over a finitely generated extension of an algebraically closed field
Feb
26
answered Smooth projective varieties of Picard number one
Feb
25
answered An abelian Hodge-Tate representation lands in a torus