【报告题目】：Loop Quantum Gravity Signatures with EHT Observables of Rotating Black Holes via Strong Gravitational Lensing
【报 告 人】：Sushant Ghosh TooKumar教授，Jamia Millia Islamia
【报告时间】：6月20日10:30
【报告地点】：29幢414
【报告摘要】：We investigate strong gravitational lensing by loop quantum gravity (LQG)-motivated rotating black holes (LMRBH), which depend on an extra parameter apart from mass , rotation and admit four classes: BH-I (one horizon), BH-II (two horizons), BH-III (three horizons), and NH (no horizon). We find that increasing the parameter increases the photon orbit radius, critical impact parameter, deflection angle, and angular position , while reducing angular separation and increasing relative magnitude for prograde motion and opposite for retrograde motion. Taking Sgr A* and M87* as lenses, we have ranges (16.4-39.8) and (12.33-29.9) as, while ranges (0.008-0.376) and (0.006-0.282) as, respectively. Deviations from Kerr reach up to as and as for , and 7.683 and as for M87*. The relative magnitude of LMRBH satisfies . Whereas time delays for Sgr A* and M87* can reach and minutes. Within , most of the BH-I and BH-II parameter space agrees with EHT observational data, while BH-III is largely ruled out and NH is completely excluded.
我们研究了由环量子引力（LQG）启发的旋转黑洞（LMRBH）产生的强引力透镜效应。这类黑洞除质量M和旋转参数a之外，还依赖于一个额外参数l，并分为四类：BH-I（一个视界）、BH-II（两个视界）、BH-III（三个视界）和NH（无视界）。我们发现，参数l增大时，顺行运动的光子轨道半径、临界碰撞参数、偏转角和角位置θ_∞均增大，角分离s减小，相对星等r_mag增大；而对于逆行运动，情况则相反。以Sgr A和M87为透镜天体时，θ_∞的范围分别为（16.4–39.8）μas和（12.33–29.9）μas，而s的范围分别为（0.008–0.376）μas和（0.006–0.282）μas。与Kerr黑洞的偏差在Sgr A情况下可达10.22μas（θ_∞）和0.241μas（s），在M87情况下可达7.683μas和0.181μas。LMRBH的相对星等满足r_mag∈（0.047, 1.54）。而Sgr A和M87的时间延迟分别可达约23.26分钟和约33261.8分钟。在1σ置信水平内，BH-I和BH-II的大部分参数空间与EHT观测数据一致，而BH-III大部分被排除，NH则完全被排除。
【报告人简介】：Professor Sushant G. Ghosh is Professor and Director at the Centre for Theoretical Physics (CTP), Jamia Millia Islamia, New Delhi, with over three decades of academic and research experience. He previously served as the University’s first Director (Research) and founding Director of MCARS, and was an Associate Professor at BITS Pilani, Dubai Campus. His research focuses on gravitation and astrophysics, particularly rotating black holes, black hole shadows, gravitational lensing, and related areas of theoretical and computational astrophysics. He has published over 200 peer-reviewed research papers. He received the Visitor’s (President of India) Award for Research in 2015. He is a Fulbright Fellow (2018). His work has earned wide international recognition, including ranking No. 1 globally in Black Hole Research by ScholarGPS (2023, 2025; No. 2 in 2024), inclusion in Stanford’s Top 2% Scientists list (2020–2025), and seven IOP Publishing Top Cited Paper Awards. He is an honorary professor at the University of KwaZulu-Natal, South Africa, and a visiting associate at IUCAA, Pune.
