A Memoriam of Bernd Schmidt

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In Memoriam of Bernd Schmidt

On 10th January 2023 Bernd Schmidt passed away. He is survived by his wife Christa Pauler and daughters Katrin and Nikola Schmidt.

Bernd was an influential scientist whose work covered many of the aspects of general relativity which are nowadays called Mathematical Relativity. He started his research career at Hamburg University, where Pascual Jordan led an illustrious group which produced, among many others, Juergen Ehlers, Engelbert Schuecking and Rainer K. Sachs. A modern version of his 1996 diploma thesis was published in 1991 as “Existence and Properties of Spherically Symmetric Static Fluid Bodies with a Given Equation of State”, co-authored with Alan Rendall. His first published paper in 1967 on “Isometry Groups with Surface-Orthogonal Trajectories” is important for understanding the geometry of spherically symmetric spacetimes and forms the basis for the treatment in Appendix B of the celebrated Hawking-Ellis monograph. The subject of spherical symmetry in general relativty remained close to Bernd’s interest throughout his life. Bernd’s 1972 paper on the bundle (or b-) boundary also plays a key role in description of singularities of Chapter 8 in the Hawking-Ellis monograph.

When Juergen Ehlers undertook the call to create a relativity group at the Max Planck Institute for Physics and Astrophysics in Munich, he recruited Bernd to join him. Bernd remained with this group through its relocation, first at Garching and finally at Golm. In 1995, with Ehlers, Bernard Schutz and Helmut Friedrich, Bernd became a founding member of the Albert Einstein Institute at Golm, the Max Planck Institute devoted to Gravitation. Starting in 1995, he was instrumental in assisting the founding Directors in designing and staffing the new Institute. After his retirement in 2007 he moved back to Munich, where he continued research until his death. Bernd recently presented a talk in Golm on the history of the Institute. In the week following his return to Munich he became afflicted with a fatal brain abscess.

Bernd’s research contributions are striking in their breadth. The subjects range from purely geometric topics such as spacetime isometry groups and the theory of connections, to subjects of physical importance such as spacetime singularities, the asymptotic structure of the gravitational field, exact solutions of the Einstein equations, mathematical cosmology, stellar oscillations, relativistic elasticity, quasi-normal modes and aspects of numerical relativity.

His comprehensive Living Review with Kostas Kokkatas on “Quasi-Normal modes of Stars and Black Holes” has provided an important resource for numerous perturbation studies which have been a main topic in relativistic astrophysics. In particular, the review has gained particular importance from the recent observations of gravitational waves from binary inspirals, where quasi-normal modes dominate the final ringdown of the waveform. His work on boost-symmetric spacetimes with Jiri Bicak, and the analysis of various aspects of the asymptotic structure of spatial and null infinity has led to a number of important advances. Thanks to his more recent work with Robert Beig, elasticity has now become an interesting new area of research in mathematical general relativity. Their collaboration continued until Bernd’s last publication, “Mechanics of Floating Bodies” (2021).

Bernd was insightful and perceptive in both research and friendship. Many mathematical relativists were drawn to the Albert Einstein Institute for long visits because of Bernd’s presence. A great many colleagues in this community will share our appreciation of his advice, professional support and research input. His clarity of thought and friendly help went beyond his own specialties and spanned all aspects of general relativity. This was immediately apparent to those who benefited from interacting with him and was perhaps his most important contribution to the field.

Abhay Ashtekar, Robert Beig, Jeff Winicour