Topic: Superradiant instabilities of massive bosons around exotic compact objects

Speaker: Postdoc Mai Zhanfeng (Peking University)

Moderator: Associate Professor Li Pengcheng

Report time: 10:00 a.m. on Friday, November 3, 2023

Address: Academic Lecture Hall, Room 213, 2nd Floor, Physics Building (Building 18)

Welcome teachers and students to attend!

School of Physics and Photonics

October 23, 2023

Abstract: Superradiantly unstable ultralight particles around a classical rotating black hole (BH) can form an exponentially  growing bosonic cloud,  which have been shown to provide an astrophysical probe to detect ultralight particles and constrain their mass.  However, the classical BH picture has been questioned,  and different theoretical alternatives have been proposed. Exotic compact objects (ECOs) are horizonless alternatives to  BHs featuring a reflective surface (with a reflectivity K) in place of the event horizon. In this talk,  I will talk about the superradiant instabilities around ECOs,  particularly focusing on the influence of the boundary reflection. The calculation for the growth rate of superradiant  instabilities around ECOs shows that the result can be related to the BH case by a correction factor with fruitful  physical significance. Additionally,  I shall talk about the time evolution of superradiant instabilities and find that the boundary reflection can either  shorten or prolong the growth timescale. As a result,  the boundary reflection alters the superradiance exclusion region on the Regge plane,  potentially affecting constraints on the mass of ultralight particles. For a mildly reflective surface,  the exclusion region is not substantially changed,  while significant effects from the boundary reflection can occur for an extreme reflectivity.

About the speaker: Mai Zhanfeng is an assistant researcher/postdoctoral fellow at the Kaiwei Institute of Astronomy and Astrophysics, Beijing University. Graduated from Physics Xiangqin Innovative Class of South China Normal University in 2015. Graduated from Beijing Normal University in 2018. He received his PhD from Tianjin University in 2022. His main research interests are black hole physics and its application to gravitational waves, especially the application of quasi-regular modes of black holes and superradiant instability to gravitational waves. In Physical Review D, Science China Physics, Mechanics & Astronomy, European Physical Journal C, Physics Letter B, 13 articles were published in the Journal of High Energy Physics, including 6 first authors and 2 corresponding authors. Currently, he is in charge of a special theoretical physics fund of the National Natural Science Foundation of China.