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GR: Fachverband Gravitation und Relativitätstheorie

GR 6: BH Physics I

GR 6.3: Vortrag

Mittwoch, 2. April 2025, 12:05–12:25, ZHG008

Wave optical imaging by a point-source scattering for a TNdS black hole — •Felix Willenborg^{1, 2}, Dennis Philipp^{1, 2}, and Claus Lämmerzahl^{1, 2} — ¹Zentrum für angewandte Raumfahrt und Mikrogravitation (ZARM), University of Bremen, 28359 Bremen, Germany — ²Gauss-Olbers Center, c/o ZARM, University of Bremen, 28359 Bremen, Germany

The Taub-NUT spacetime is a curious solution of the Einstein’s vacuum field equation due to the presence of conical singularities and their different interpretations for NUT charges N ≠ 0. Gravitational lensing maps have shown the twisting of a background for light- and time-like geodesics, as well as the observation of the conical singularity in the Bonnor interpretation.

Several methods offer a theoretical description of these observations. Already mentioned are ray-optical methods by geodesics or the calculation of the scattering by the so-called amplification factor F by the description of time-delays t_d. In our work, we describe the calculation by a full wave equation using the Teukolsky equation, which allows access to all frequencies. To obtain fully analytical solutions, a small cosmological constant is considered, generalising the solution to Taub-NUT-de Sitter (TNdS). We observe the scattering of a monochromatic point source to an observer at a larger distance from the black hole. Afterwards, we briefly discuss the method and present results for Schwarzschild-de Sitter at very low frequencies in a wave-optical approach as a simple model. Finally, we present results for TNdS and how these change with the parameter variation.

Keywords: Bonnor and Misner interpretation; Taub-NUT-de Sitter; TNdS; wave optical image; scattering