談話会・数理科学講演会

過去の記録 ~04/19次回の予定今後の予定 04/20~

担当者 足助太郎,寺田至,長谷川立,宮本安人(委員長)
セミナーURL https://www.ms.u-tokyo.ac.jp/seminar/colloquium/index.html

2019年10月25日(金)

15:30-16:30   数理科学研究科棟(駒場) 123号室
Yves Benoist 氏 ( CNRS, Paris-Sud)
Arithmeticity of discrete subgroups (英語)
[ 講演概要 ]
By a theorem of Borel and Harish-Chandra,
an arithmetic group in a semisimple Lie group is a lattice.
Conversely, by a celebrated theorem of Margulis,
in a higher rank semisimple Lie group G
any irreducible lattice is an arithmetic group.

The aim of this lecture is to survey an
arithmeticity criterium for discrete subgroups
which are not assumed to be lattices.
This criterium, obtained with Miquel,
generalizes works of Selberg and Hee Oh
and solves a conjecture of Margulis. It says:
a discrete irreducible Zariski-dense subgroup
of G that intersects cocompactly at least one
horospherical subgroup of G is an arithmetic group.