**AbstractHistory and Philosophy of Physics Research Seminar**

Time and Place: Tuesdays from 4.15pm to 5:45pm, Institute of Philosophy (Main building of the University of Bonn, Room 1.070).

Schedule for the Summer Semester 2019:

**2.4.2019: Tushar Menon (Oxford)**

Title: “Clocks and chronogeometry: Rotating spacetimes and the relativistic null hypothesis”

Title: “Clocks and chronogeometry: Rotating spacetimes and the relativistic null hypothesis”

Abstract: Recent work in the physics literature demonstrates that, in particular classes of rotating spacetimes, physical light rays do

*not,*in general, traverse null geodesics. In this talk, I discuss the philosophical significance of this result, both for the clock hypothesis in particular, for a recent purported demonstration of its validity for light clocks, and for the operational meaning of the metric field in General Relativity. (This talk is based on joint work with James Read and Niels Linnemann)

**9.4.2019: Tilman Sauer (Mainz)**

Title: The History of Distant Parallelism Revisited

Abstract: In the years from 1928 to 1931, Einstein tried to base a unified field theory on the geometry of teleparallism, i.e. on a space-time geometry determined by a tetrad field that defines both a spatially-flat connection of distant parallelism as well as a metric field with an associated Levi-Civita connection. Unaware of prior mathematical work on this topic by Roland Weitzenböck, Elie Cartan, and others, Einstein looked for field equations for the tetrad field that would comprise both the gravitational field and the Maxwell field. In the talk I will reconsider this episode in the light of contemporary correspondence with mathematicians and physicists as well as unpublished manuscripts.

**16.4.2019: No seminar**

23.4.2019: Dennis Lehmkuhl (Bonn)

23.4.2019: Dennis Lehmkuhl (Bonn)

Title: The Einstein-Weyl correspondence and geodesic motion

Abstract: In 1918, Hermann Weyl and Albert Einstein exchanged almost two dozen letters. In the majority of them, they focus on comparing general relativity (GR) with Weyl’s unified field theory. The latter is based on a generalisation of pseudo-Riemannian geometry that we now call Weyl geometry. One of the most interesting aspects of this correspondence is the discussion of the motion of test particles in GR as compared to Weyl’s theory. I will first outline the different positions advocated by Weyl and Einstein and the arguments they name in their favour. In the 1920s, Einstein and Weyl then independently argued that the geodesic motion of test particles in GR could be derived rather than assumed. In 1975, Geroch and Jang provided a new type of proof for such a `geodesic theorem’. I will argue that the Geroch-Jang theorem can be generalised to Weyl geometry if the latter is decoupled from the project of a unified field theory, and that it can then shed new light on the positions advocated by Einstein and Weyl in the 1910s and 1920s. (This is joint work with Erhard Scholz.)

**30.4.2019: Florian Boge (Wuppertal)**

Title: Quantum Information vs. Epistemic Logic: An Analysis of the Frauchiger-Renner Theorem

**7.5.2019: Joshua Rosaler (RWTH Aachen)**

Title: The Geometry of Reduction: Weaving the Model Patchwork of Modern Physics

**14.5.2019: TBA**

21.5.2019: No seminar

21.5.2019: No seminar

**28.5.2019: Jeroen van Dongen (Amsterdam)**

Title: TBA

**4.6.2019: Carina Prunkl (Oxford)**

Title: TBA

**11.6.2019: No seminar (Pentecost)**

**18.6.2019: Radin Dardashti (Wuppertal)**

Title: TBA

**25.6.2019: Martin King (Bonn)**

Title: TBA

**2.7.2019: TBA**