Strong students write paper in ´Lenshouse´

A group of the Strong PhD students, Juno Chan, Conor Dyson, Jaime Redondo-Yuste, and Luka Vujeva, along with a master's student, Matilde Garcia, set out on a research retreat in order to produce a paper in just one week. Inspired by Niels Bohr’s trips to his summerhouse in Tisvilde, they rented a summerhouse through KU Feriefond and worked intensively in a cabin in the woods north of Copenhagen for one week. The students produced a research paper now under review that introduces novel results and lays forward the path for modeling gravitational lensing by ultra-compact objects using black hole perturbation theory: Lensing and wave optics in the strong field of a black hole.

Gravitational waves are produced during the violent mergers of black holes and other ultra-compact objects. By detecting these waves, physicists hope to gain new insights into the astrophysics of black holes and explore the frontiers of fundamental physics. However, their creation and detection are only part of the story. Before reaching our detectors on Earth, these waves must first traverse the universe. As they travel, gravitational waves interact with large-scale structures and strongly gravitating systems, causing distortions that imprint the history of their journey. This phenomenon is known as gravitational wave lensing. Most research in this field has focused on lensing in the Newtonian regime, where gravity is weak. However, recent interest has emerged in understanding distortions that occur in the strong-field regime—what happens when the lens itself is a black hole?

In their paper, the students seek to answer this question, and they also made use of the Black Hole Perturbation Toolkit (https://bhptoolkit.org/index.html), an open-access code written by physicists (some of whom are members of the strong group), designed for easily applying methods in black hole perturbation theory. Notably, the students' paper on Lensing and wave optics in the strong field of a black hole became the 200th publication to cite the toolkit, marking a major milestone in the code’s history, which was shared on the social media platform Bluesky here: https://bsky.app/profile/bhptoolkit.bsky.social.