What:	Mass stream and Cusp relation
Who:	Dr. Li Guoliang (Argelander Institute for Astronomy Bonn University)
When:	Wednesday morning, Dec. 9th, 11:00 a.m.
Where:	Room 327, Office Block, 2 West Beijing Road (PMO, CAS) Welcome to attend ( PMO Academic committee & academic circulating committee)

abstract：The statistic of cusp relation from observation provides a very strong constraint on the abundance of substructure in lens while the previews research shows that the observation needs much more substructures than N-body simulation can provide. This has been a challenge to the structure formation theory in the CDM cosmology for a long time . In this talk, I'll show how the disrupted substructure, mass stream, can violate the cusp relation and this will provide a possible way to weaken that discrepancy between observation and theoretical predication.