报告人：Hongbin Sun  Assistant Professor (Rutgers University)

报告时间：2020年6月13日08：30-10：00 

直播平台：ZOOM房间号：会议 ID：274 175 4144  密码：930643

直播链接：https://cernet.zoom.com.cn/j/2741754144?pwd=TzRiV0gwT2l0NU1CRWtmODlpRUdrZz09

报告内容摘要：For a (finitely generated) subgroup of a (finitely generated) group, we will consider two properties of this subgroup: the separability of this group and its subgroup distortion. The separability of a subgroup measures whether the property of an element not lying in this subgroup is visible by taking some finite quotient. We will give a characterization on whether a subgroup of a 3-manifold group is separable. The subgroup distortion compares the intrinsic and extrinsic geometry of a subgroup. For an arbitrary subgroup of a 3-manifold group, we prove that the subgroup distortion can only be linear, quadratic, exponential and double exponential. It turns out the subgroup separability and subgroup distortion are closed related for subgroups of 3-manifold groups. The subgroup distortion part is joint work with Hoang Nguyen (at BICMR).