Four Lectures on Asymptotically Flat Riemannian Manifolds -- Lectures on Linear Stability of Rotating Black Holes -- The Bianchi Classication of the Three-Dimensional Lie Algebras and Homogeneous Cosmologies and the Mixmaster Universe -- The Physics of LIGO–Virgo -- Generation of Initial Data for General-Relativistic Simulations of Charged Black Holes -- BMS Symmetries and Holography: An Introductory Overview -- Relativity of Observer Splitting Formalism and Some Astrophysical Applications -- Some Remarks on a New Exotic Spacetime for Time Travel by Free Fall -- Schwarzschild Spacetime Under Generalised Gullstrand–Painlevé Slicing -- Crystal Spacetimes with Discrete Translational Symmetry -- Electrogeodesics and Extremal Horizons in Kerr-Newman (anti-)de Sitter -- Hearing the Nature of Compact Objects -- Minisuperspace Quantisation via Conditional Symmetries. .