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Topic

Black holes immersed in a magnetic field: the case of the Ernst-Wild geometry

Department of Physics and Astronomy

Date & location

• Friday, April 17, 2026
• 9:00 A.M.
• Clearihue Building, Room B017

Examining Committee

Supervisory Committee

• Dr. Adam Ritz, Department of Physics and Astronomy, ̽��ϵ�� (Supervisor)
• Dr. Pavel Kovtun, Department of Physics and Astronomy, UVic (Member)
• Dr. Cornelia Bohne, Department of Chemistry, UVic (Outside Member)

External Examiner

• Prof. Eric Poisson, Department of Physics, University of Guelph

Chair of Oral Examination

• Dr. Stan Dosso, School of Earth and Ocean Sciences, UVic

Abstract

This thesis explores how magnetic fields surrounding black holes influence the signals we observe from them - both in gravitational waves and in direct images. Although most theoretical models treat black holes as isolated objects in vacuum, real astrophysical black holes can exist in magnetized environments. These magnetic fields can subtly alter the behaviour of light and gravitational waves near the black hole and therefore affect what our detectors and telescopes record. The first part of the thesis focuses on the visual signature of magnetized black holes - their photon rings and shadows - using numerical backwards ray tracing. It was found that rotation and magnetic fields act in competing ways, one flattening and the other stretching the observed shadow, and that these effects are directly connected to the same oscillation modes that govern gravitational wave ringdown. The second part of the thesis studies how a magnetic field modifies the vibrations of a rotating black hole following a binary black hole merger. Using analytical expansions and numerical techniques, I calculated how the characteristic oscillation frequencies change in the presence of a weak magnetic field and tested these effects within the LIGO-Virgo-KAGRA ringdown analysis pipeline pyRing. This provides the first quantitative estimate of how surrounding magnetospheres could bias the measurement of black hole mass and spin from gravitational wave data. Together, these results link two powerful observational windows - gravitational waves and black hole imaging - within a single theoretical framework that accounts for magnetized environments.