时间：2026年10月9日(星期五)，14:00-15:00
地点：E14-301
主讲人：Yang CAO, Shandong University
报告主题：New step in strong approximation for linear algebraic groups
报告摘要：The classical theory of strong approximation for linear algebraic groups, developed by Kneser, Prasad, and Platonov in the 1960s, only consider the semi-simple simply connected case; the series works by Colliot-Thelene, Xu, Harari, and Demarche extended these results to more general groups, which necessarily needed cohomological obstructions. In this talk, I will present new approaches to strong approximation that avoid to use the abstract notion of cohomological obstruction. I will discuss two recent results:
1) (joint work with Yijin Wang) almost strong approximation for general linear algebraic group (open question of Rapinchuk and Tralle);
2) (joint work with Zhizhong Huang and Runlin Zhang) arithmetic purity of strong approximation for semi-simple simply connected case (open question of Wittenberg).
