110 research outputs found
Hyperelliptic jacobians and projective linear Galois groups
In his previous paper (Math. Res. Letters 7(2000), 123--132) the author
proved that in characteristic zero the jacobian of a hyperelliptic curve
has only trivial endomorphisms over an algebraic closure of
the ground field if the Galois group of the irreducible polynomial
is either the symmetric group or the alternating group
. Here is the degree of .
In math.AG/0003002 we extended this result to the case of certain ``smaller''
Galois groups. In particular, we treated the infinite series and .
In the present paper we prove that has only trivial endomorphisms over
if the set of roots of could be identified with the
-dimensional projective space over a finite field
of odd characteristic in such a way that , viewed as its permutation
group, becomes either the projective linear group or the
projective special linear group . Here we assume that
.Comment: LaTeX2e, 8 pages. We include a discussion of the characteristic
cas
Polynomials in one variable and ranks of certain tangent maps
We study a map that sends a monic degree n complex polynomial f(x) without
multiple roots to the collection of n values of its derivative at the roots of
f(x). We give an answer to a question posed by Ju.S. Ilyashenko.Comment: Remark 3.5 has been corrected/update
Homomorphisms of abelian varieties
We discuss Galois properties of points of prime order on an abelian variety
that imply the simplicity of its endomorphism algebra. Applications to
hyperelliptic jacobians are given. In particular, we improve some of our
earlier results.Comment: 23 pages, to appear in the Proceedings of ``Arithmetic, Geometry and
Coding Theory - 9" conference (Luminy, May 2003
Absolutely simple Prymians of trigonal curves
Using Galois Theory, we construct explicitly absolutely simple (principally
polarized) Prym varieties that are not isomorphic to jacobians of curves even
if we ignore the polarizations. Our approach is based on the previous papers
math/0610138 [math.AG] and math/0605028 [math.AG] .Comment: 12 page
Abelian varieties over fields of finite characteristic
The aim of this paper is to extend our old results about Galois action on the
torsion points of abelian varieties to the case of (finitely generated) fields
of characteristic 2.Comment: 18 pages. Some typos have been correcte
Division by 2 on hyperelliptic curves and jacobians
Let be an algebraically closed field of characteristic different from 2,
a positive integer, a degree polynomial with coefficients
in and without multiple roots, the corresponding genus
hyperelliptic curve over and the jacobian of . We identify with
the image of its canonical embedding into (the infinite point of goes
to the zero point of ). For each point there are
points . We describe explicitly the Mumford
represesentations of all . The rationality questions for
are also discussed.Comment: 24 pages. We added results concerning the absence of torsion points
of certain order on certain subvarieties of hyperelliptic jacobian
Hyperelliptic jacobians and \U_3(2^m)
In his previous paper (Math. Res. Letters 7(2000), 123--132) the author
proved that in characteristic zero the jacobian of a hyperelliptic curve
has only trivial endomorphisms over an algebraic closure of
the ground field if the Galois group of the irreducible polynomial
is either the symmetric group or the alternating group
. Here is the degree of . In math.AG/0003002 we extended this
result to the case of certain ``smaller'' Galois groups. In particular, we
treated the infinite series and . In this paper we do the case of Gal(f)=\U_3(2^m) and
Jordan groups and elliptic ruled surfaces
We prove that an analogue of Jordan's theorem on finite subgroups of general
linear groups holds for the groups of biregular automorphisms of elliptic ruled
surfaces. This gives a positive answer to a question of Vladimir L. Popov.Comment: 14 page
Division by 2 on odd degree hyperelliptic curves and their jacobians
Let be an algebraically closed field of characteristic different from 2,
a positive integer, a degree polynomial with coefficients
in and without multiple roots, the corresponding genus
hyperelliptic curve over K, and the jacobian of . We identify with
the image of its canonical embedding into (the infinite point of goes
to the identity element of ). It is well known that for each there are exactly elements such that
. M. Stoll constructed an algorithm that provides
Mumford representations of all such , in terms of the Mumford
representation of . The aim of this paper is to give explicit
formulas for Mumford representations of all such , when
is given by in terms of
coordinates . We also prove that if then does not contain
torsion points with order between and .Comment: 18 pages. The paper overlaps with arXiv:1606.05252 and
arXiv:1807.0700
Hyperelliptic jacobians and modular representations
In his previous paper (Math. Res. Letters 7(2000), 123--132) the author
proved that in characteristic zero the jacobian of a hyperelliptic curve
has only trivial endomorphisms over an algebraic closure of the
ground field if the Galois group of the irreducible polynomial
is either the symmetric group or the alternating group
. Here is the degree of .
In the present paper we extend this result to the case of certain ``smaller''
Galois groups. In particular, we treat the case when or 12 and
is the Mathieu group or respectively. The infinite series
and are also
treated.Comment: The paper will appear in Texel volume "Moduli of abelian varieties"
(Texel Island 1999), Birkh\"ause
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