星空在线,星空在线(中国)前沿讲坛第102讲（2022年第30讲）

报告人：岳瑞宏 扬州大学 教授

报告时间：2022年9月16日（周五）下午 15:00-16:00

报告地点：龙赛理科楼北楼228会议室

报告题目：QNM、有效势与黑洞回声

报告摘要：In this talk, I will discuss the some characters of quasi-normal modes (QNM) in gravity back ground. The an external source can influence the perturbation behavior, and may further drive the system to experience new perturbation modes. We also prove that a single discontinuity in the effective potential, no matter how insignificant it is, will appreciably modify the asymptotic behavior of the QNM. Besides, we proceed further that a discontinuity planted into the metric furnishes an alternative mechanism for the black hole echoes, which may correspond to an uneven matter distribution inside the surrounding halo. The period of the echoes is shown to related to the asymptotic spacing between successive poles along the real axis in the frequency domain.

星空在线,星空在线(中国)前沿讲坛第103讲（2022年第31讲）

报告人：范恩贵 复旦大学 教授

报告时间：2022年9月16日（周五）下午 16:00-17:00

报告地点：龙赛理科楼北楼228会议室

报告题目：The defocusing NLS equation with nonzero background: Large-time asymptotics in a solitonless region

报告摘要：Consider initial value problem for the defocusing NLS equation with nonzero background. In the soliton region |x/t|<2, Cuccagna and Jenkins obtained soliton resolution for the defocusing NLS equation; In the solitonless region |x/t|>2, we give lare time asymptotics for the defocusing NLS equation.