BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Aristotelis Panagiotopoulos (Kurt Gödel Research Center\, Univers ity of Vienna) DTSTART:20240430T080000Z DTEND:20240430T100000Z DTSTAMP:20260417T072446Z UID:3cqfs/16 DESCRIPTION:Title: I ncompleteness Theorems for Observables in General Relativity\nby Arist otelis Panagiotopoulos (Kurt Gödel Research Center\, University of Vienna ) as part of Tricontinental Quantum Fundamentals Seminar\n\n\nAbstract\nOn e of the biggest open problems in mathematical physics has been the proble m of formulating a complete and consistent theory of quantum gravity. Some of the core technical and epistemological difficulties come from the fact that General Relativity (GR) is\, fundamentally\, a geometric theory and\ , as such\, it oughts to be `generally covariant'\, i.e. invariant under c hange of coordinates by the arbitrary diffeomorphism of the ambient manifo ld. The Problem of Observables is a famous instance of the difficulties th at general covariance brings into quantization: no non-trivial diffeomorph ism-invariant quantity has ever been reported on the collection of all spa cetimes.\n\nIt turns out that there is a good reason for this! In a recent joint work with Marios Christodoulou and George Sparling we employ method s from Descriptive Set Theory (DST) in order to show that no complete obse rvables for full GR can be Borel definable. In other words\, the problem o f observables is to `analysis' what the Delian problem was to `straightedg e and compass'. This talk will provide a gentle introduction to the main c oncepts of DST\, where they come from\, and how they connect to the proble m of observables. We will then discuss the aforementioned Incompleteness T heorem\, as well as the next steps in a research program that aims to furt her uncover this new connection between theoretical physics and DST.\n LOCATION:https://researchseminars.org/talk/3cqfs/16/ END:VEVENT END:VCALENDAR