DE / EN

**History 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will reconsider this episode in the light of contemporary correspondence with mathematicians and physicists as well as unpublished manuscripts.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: History and Philosophy of the Black Hole Information Paradox

Abstract: The black hole ‘information paradox’ was introduced by Stephen Hawking in 1976. It suggested that the evaporation of a quantum black hole could not be in agreement with familiar unitary evolution laws of quantum mechanics. We present the history of the ensuing debate and place the contributions of various actors within the context of the various cultures of theory from which they originated. Why was Hawking’s position originally not considered controversial, and was opposition, in particular of Dutch theorist Gerard `t Hooft, quickly dismissed? Attention will further be given to the role of string theory entropy counts in debates on the paradox of the mid-1990s. Among these is the derivation of the Bekenstein-Hawking entropy for a certain D-brane system by Andrew Strominger and Cumrun Vafa. Was the result indeed accepted as strongly suggestive of unitary evolution scenarios, as Strominger and Vafa contended? This is related to an ontological question: had the states of a black hole indeed been counted?

**4.6.2019: Carina Prunkl (Oxford)**

Title: TBA

**11.6.2019: No seminar (Pentecost)**

**18.6.2019: Radin Dardashti (Wuppertal)**

Title: The Empirical Progress of Non-Empirical Science

Abstract: Many theories in fundamental physics are being developed and assessed non-empirically for several decades now, but have not yet been tested experimentally. This situation may not change in the foreseeable future and may suggest that this field of research is doomed to not make scientific progress. May we, however, consider these developements as theoretical progress? If yes, theoretical progress in what sense? Are these developments of any relevance for empirical progress? I will evaluate the answers that various philosophical accounts of scientific progress provide for this question, discuss their shortcomings and propose an account which allows to make sense of scientific progress in the absence of experiments.

**25.6.2019: Martin King (Bonn)**

Title: TBA

**2.7.2019: TBA**

The following conferences are currently co-organized by members of the group:

- 22-24 May 2019: International Conference on Simplicities and Complexities, at the University of Bonn

For more philosophy of physics events taking place in Bonn, please see here.