Current observations of astrophysical black holes only confirm the GR predictions at the order of the horizon size, with no direct implications regarding physics immediately outside the horizon. On the other hand, near-horizon corrections might be fundamental to understanding the mysterious features of black holes. In this talk, I will discuss the possibility of not quite black holes (horizonless ultracompact objects) being the endpoint of gravitational collapse. Theoretically, I will talk about an interesting candidate and its implication for black hole physics and particle physics. Observationally, gravitational wave echoes may provide a smoking gun signal for such objects in general, especially when strong deviations occur at a microscopic distance (say Planck scale) outside of the macroscopic objects. I will talk about the recent progress made in searches for echoes. Also, the possibility of primordial ultracompact objects as dark matter will be mentioned.  

Bio: Jing Ren is currently an associate professor at Theoretical Physics Division of Institute of High Energy Physics, Chinese Academy of Sciences. She obtained her PhD in 2014 from Tsinghua University and was a postdoc at University of Toronto from 2014 to 2018. She works mainly in theoretical particle physics and the interface with gravity. Her recent research interests include new physics beyond the Standard Model and General Relativity, black hole physics and gravitational waves, dark matter physics and detection.