报告题目1：Images and flares of geodesic hotspots around a Kerr black hole
报告人1：郭敏勇副教授（北京师范大学）
报告题目2: Krylov complexity for operator growth
报告人2：范仲英讲师（广州大学）
主持人：訾铁光
报告时间：2024年5月17日（星期五）下午15:30-16:30
报告地点：物理楼（18号楼）二楼220会议室
欢迎广大师生参加!
物理与光电学院
2024年5月10日
报告1摘要：In this study, we develop a numerical method to generate images on an observer’s screen, formed by radiation from hotspots on any timelike orbits outside a black hole. This method uses the calculation of fractional numbers, enabling us not only to produce the overall image but also to distinguish between primary, secondary, and higher-order images. Building upon this, we compute the images of hotspots from eight potential types of geodesic timelike orbits outside a Kerr black hole, summarizing the properties of both the overall and individual order images. Furthermore, we calculate the centroid motion and lightcurve. Notably, we observe flare phenomena across all orbit types and classify these flares into three categories based on the Doppler and gravitational redshift effects.
报告人1简介：
郭敏勇，副教授，2014年本科毕业于北京科技大学，2019年博士毕业于北京师范大学，期间2017年至2019年在加拿大圆周理论物理研究所联合培养。2019年至2021年5月在北京大学高能中心做博士后。2021年5月至今在北京师范大学物理学系工作。目前从事黑洞图像、引力的全息性质等方面的研究。目前已发表研究论文40余篇，累计被引用1600余次。
报告2摘要：Krylov complexity was recently introduced to describe Heisenberg evolution of Hermitian operators for many body systems. It provides a new tool to probe chaotic dynamics, in addition to conventional quantities such as the out-of-time-order-correlators. In this talk, I will introduce aspects of Krylov complexity, including the Lanczos algorithm, a universal relation between Krylov complexity and the operator entropy and the complexity algebra. In particular, the complexity algebra connects three distinct aspects of operator growth: i) the symmetry of Heisenberg evolution; ii) the quantum limit on the growth rate of complexity; iii) analytical solutions to Heisenberg evolution.
报告人2简介：范仲英，2015年毕业于北京师范大学物理系，获博士学位。毕业后加入北京大学高能中心任博士后研究员。2017年加入广州大学。主要研究领域为引力理论、黑洞物理和规范引力对偶。