Number Theory Seminar

Seminar information archive ~09/27Next seminarFuture seminars 09/28~

Date, time & place Wednesday 17:00 - 18:00 056Room #056 (Graduate School of Math. Sci. Bldg.)
Organizer(s) Naoki Imai, Yoichi Mieda

Seminar information archive

2007/10/10

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
James Lewis (University of Alberta)
Abel-Jacobi Maps Associated to Algebraic Cycles I

[ Abstract ]
This talk concerns the Bloch cycle class map from the higher Chow groups to Deligne cohomology of a projective algebraic manifold. We provide an explicit formula for this map in terms of polylogarithmic type currents.

2007/09/19

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
Gereon Quick (Universitaet Muenster)
Etale cobordism
[ Abstract ]
We define and study a new candidate of etale topological cohomology theories for schemes over a field of abritrary characteristic: etale cobordism. As etale K-theory is related to algebraic K-theory, etale cobordism is related to algebraic cobordism of Voevodsky and Levine/Morel. It shares some nice properties of topological theories, e.g. it is equipped with an Atiyah-Hirzebruch spectral sequence from etale cohomology. We discuss in particular a comparison theorem between etale and algebraic cobordism after inverting a Bott element and, finally, we give an outlook to further possible applications of this theory.

2007/09/12

15:00-18:00   Room #117 (Graduate School of Math. Sci. Bldg.)
E. Lau (Univ. of Bielefeld) 15:00-15:45
Classification of p-divisible groups by displays and duality
T. Zink (Univ. of Bielefeld) 16:00-16:45
Applications of the theory of displays
E. Looijenga (Univ. of Utrecht) 17:00-18:00
Presentation of mapping class groups from algebraic geometry
[ Abstract ]
A presentation of the mapping class group of a genus g surface with one hole is due to Wajnryb with later improvements due to M. Matsumoto. The generators are Dehn twists defined by 2g+1 closed curves on the surface. The relations involving only two Dehn twists are the familiar Artin relations, we show that those involving more than two can be derived from algebro-geometry considerations.

2007/08/27

16:30-17:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Steven Zucker (Johns Hopkins大学)
The reductive Borel-Serre motive

2007/07/18

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
梶原 健 (横浜国立大学)
Tropical toric varieties

2007/07/11

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
Andreas Rosenschon (University of Alberta)
Algebraic cycles on products of elliptic curves over p-adic fields

2007/06/27

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
Stephen Lichtenbaum (Brown University)
The conjecture of Birch and Swinnerton-Dyer is misleading
[ Abstract ]
All values of zeta and L-functions at integral points should be given in terms of products and quotients of Euler characteristics, and the order of the zeroes and poles at these
points should be given by the sum and difference of the ranks of
corresponding finitely generated abelian groups.

2007/05/09

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
宮崎 直 (東京大学大学院数理科学研究科)
$(g,K)$-module structures of principal series representations
of $Sp(3,R)$

2007/05/02

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
長谷川 泰子 (東京大学大学院数理科学研究科)
Cohen-Eisenstein series and modular forms associated to imaginary quadratic fields

2007/04/25

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
津嶋 貴弘 (東京大学大学院数理科学研究科)
Localized Characteristic Class and Swan Class

2007/04/11

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
斎藤 毅 (東京大学大学院数理科学研究科)
l進層の暴分岐と特性サイクル

2007/01/31

15:15-18:45   Room #117 (Graduate School of Math. Sci. Bldg.)
Dennis Eriksson (東大数理/Paris) 15:15-16:15
Towards a proof of a metrized Deligne-Riemann-Roch theorem
小林 真一 (名古屋大学多元数理) 16:30-17:30
CM楕円曲線の超特異点における2変数p進L関数
(A two variable p-adic L-function for CM elliptic curves at supersingular primes)
Frans Oort (Utrecht) 17:45-18:45
Irreducibility of strata and leaves in the moduli space of abelian varieties

2006/12/20

16:30-18:45   Room #117 (Graduate School of Math. Sci. Bldg.)
Anna Cadoret (RIMS/JSPS) 16:30-17:30
On the profinite regular inverse Galois problem
[ Abstract ]
Given a field $k$ and a (pro)finite group $G$, consider the
following weak version of the regular inverse Galois problem:
(WRIGP/$G$/$k$) \\textit{there exists a smooth geometrically
irreducible curve $X_{G}/k$ and a Galois extension $E/k(X_{G})$
regular over $k$ with group $G$.} (the regular inverse Galois
problem (RIGP/$G$/$k$) corresponding to the case
$X_{G}=\\mathbb{P}^{1}_{k}$). A standard descent argument shows that
for a finite group $G$ the (WRIGP/$G$/$k$) can be deduced from the
(RIGP/$G$/$k((T))$). For
profinite groups $G$, the (WRIGP/$G$/$k((T))$) has been proved for
lots of fields (including the cyclotomic closure of characteristic $0$
fields) but the descent argument no longer works.\\\\
\\indent Let $p\\geq 2$ be a prime, then a profinite group
$G$ is said to be \\textit{$p$-obstructed} if it fits in a profinite group extension
$$1\\rightarrow K\\rightarrow G\\rightarrow G_{0}\\rightarrow 1$$
with $G_{0}$ a finite group and $K\\twoheadrightarrow
\\mathbb{Z}_{p}$. Typical examples of such profinite groups $G$ are
universal $p$-Frattini covers of finite $p$-perfect groups or
pronilpotent projective groups.\\\\
\\indent I will show that the (WRIGP/$G$/$k$) - even under
its weaker formulation: (WWRIGP/$G$/$k$) \\textit{there exists a
smooth geometrically irreducible curve $X_{G}/k$ and a Galois
extension $E/k(X_{G}).\\overline{k}$ with group $G$ and field of
moduli $k$.} - fails for the whole class of $p$-obstructed profinite
groups $G$ and any field $k$ which is either a finitely generated
field of characteristic $0$ or a finite field of characteristic
$\\not= p$.\\\\
\\indent The proof uses a profinite generalization of the cohomological obstruction
for a G-cover to be defined over its field of moduli and an analysis of the constrainsts
imposed on a smooth geometrically irreducible curve $X$ by a degree $p^{n}$
cyclic G-cover $X_{n}\\rightarrow X$, constrainsts which are too rigid to allow the
existence of projective systems $(X_{n}\\rightarrow
X_{G})_{n\\geq 0}$ of degree $p^{n}$ cyclic G-covers
defined over $k$. I will also discuss other implicsations of these constrainsts
for the (RIGP).
Eric Friedlander (Northwestern) 17:45-18:45
An elementary perspective on modular representation theory

2006/12/06

16:30-18:45   Room #117 (Graduate School of Math. Sci. Bldg.)
Vincent Maillot (Jussieu/京大数理研) 16:30-17:30
New applications of the arithmetic Riemann-Roch theorem
Don Blasius (UCLA) 17:45-18:45
Zariski Closures of Automorphic Galois Representations

2006/11/01

16:30-18:45   Room #117 (Graduate School of Math. Sci. Bldg.)
G.Bayarmagnai (東大数理) 16:30-17:30
Essential dimension of some finite group schemes
Jacques Tilouine (パリ北大学) 17:45-18:45
Overconvergent Siegel modular forms
[ Abstract ]
We recall what is known and what is conjectured on p-adic families of overconvergent Siegel modular forms. We show how this relates to a Fontaine-Mazur type conjecture on the classicality of certain overconvergent Siegel forms of genus 2. We explain few results known in this direction.

2006/10/25

17:00-18:00   Room #117 (Graduate School of Math. Sci. Bldg.)
平之内 俊郎 (九州大学)
Extensions of truncated discrete valuation rings ( 田口雄一郎先生との共同研究 )
[ Abstract ]
局所体の拡大とその付値環の或る商である"truncated" dvrの拡大の圏を比較する. 不分岐拡大と剰余体の拡大が一対一対応するのと同じ様に, 分岐に関する条件を加えれば,局所体と "truncated" dvr の拡大の圏が同値になる (Deligne).
今回は, 古典的な(上付き)分岐群の代わりにAbbes-斎藤による分岐群を用いて分岐に関する条件を与える. そして,この分岐群の Rigid 幾何的解釈を踏襲する事でDeligneの定理の剰余体が非完全な場合への一般化が得られる事を述べる.

2006/10/18

16:30-18:45   Room #117 (Graduate School of Math. Sci. Bldg.)
Fabrice Orgogozo (東大数理・Ecole Polytechnique de Paris) 16:30-17:30
p-dimension of henselian fields: an application of Ofer Gabber's algebraization technique
Kim Minhyong (Purdue大学・京大数理研) 17:45-18:45
Fundamental groups and Diophantine geometry

2006/09/06

16:30-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
Bas Edixhoven (Univ. of Leiden)
Computation of the mod l Galois representations associated to Delta

2006/08/25

16:30-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
A. Marmora (パリ北大・東大/学振)
p-adic local constants

2006/07/12

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
桜井 真 (東京大学理学系研究科)
Beilinson-Drinfeld chiral algebra, geometric Langlands program and open Gromov-Witten invariants
[ Abstract ]
都合により、とりやめになりました。

2006/06/28

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
原下秀士 (北海道大学・学振)
Configuration of the central streams in the moduli of abelian varieties

2006/06/07

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
廣惠 一希 (東京大学大学院数理科学研究科)
Hecke-Siegel's pull back formula for the Epstein zeta function with spherical

2006/05/24

16:30-18:45   Room #117 (Graduate School of Math. Sci. Bldg.)
Kai Köehler (Düesseldorf 大学) 16:30-17:30
Quaternionic analytic torsion and arithmetic geometry
Thomas Geisser (南カリフォルニア大学) 17:45-18:45
Duality via cycle complexes

2006/04/26

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
伴 克馬 (東京大学大学院数理科学研究科)
Differential Operators of Rankin-Cohen-Ibukiyama Type for Automorphic Forms of Several Variables

2006/04/19

16:30-17:30   Room #117 (Graduate School of Math. Sci. Bldg.)
谷口 隆 (東京大学大学院数理科学研究科)
Distributions of discriminants of cubic algebras

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