|
Calendar of Physics Talks Vienna
| Gravitational memory effects for particles and wave packets (Vienna Theory Lunch Seminar) |
| Speaker: | Marius Oancea (Universität Wien) |
| Abstract: |
Gravitational waves can generally influence the dynamics of test objects with which they interact. Changes in the relative dynamics of test objects can persist even after the gravitational wave has passed and spacetime is again flat. These are generally referred to as gravitational memory effects, since the properties of the passing gravitational wave remain encoded in the relative dynamics of test objects. In this talk, I will discuss gravitational memory effects in plane wave spacetimes for different classes of test objects: particles following geodesics, spinning particles with non-geodesic motion, and test scalar fields. For all these objects, memory effects are encoded into a set of four memory tensors that depend on the gravitational wave profile. Joint work with Abraham Harte, Thomas Mieling, and Florian Steininger.
[[part of https://lunch-seminar.univie.ac.at ]] |
| Date: | Tue, 07.05.2024 |
| Time: | 12:30 |
| Duration: | 75 min |
| Location: | TU Wien: Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room DB10E11 |
| Contact: | Florian Lindenbauer |
| Cosmic rays in jets of Active Galactic Nuclei |
| Speaker: | Anita Reimer (University of Innsbruck) |
| Abstract: | Gamma rays, high-energy neutrinos and cosmic rays impinging on Earth signal the existence of environments in the Universe that allow acceleration of particle populations into the extremely energetic regime. Jets of Active Galactic Nuclei (AGN) - powerful relativistic matter streams emanating from the core of distant galaxies that host supermassive black holes - are among the most numerous persistent source populations in the high-energy gamma-ray sky, and are considered prime candidate sources of the ultra-high-energy cosmic rays (UHECRs) observed on Earth.
In this presentation I will discuss aspects of the survival, workings, possible signatures and role of UHECRs in various environments that jets of AGN offer. |
| Date: | Tue, 07.05.2024 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Erwin-Schroedinger-Hoersaal, Boltzmanngasse 5, 5. Stock |
| Contact: | S. Plaetzer |
| Initial data sets with vanishing mass are contained in pp-waves. |
| Speaker: | Seven Hirsch (IAS) |
| Abstract: | Abstract: Isolated gravitational systems such as stars, galaxies and black holes are modeled by asymptotically flat initial data sets. In 1981 Schoen-Yau and Witten showed that such initial data sets with vanishing energy must be contained in Minkowski space. We show that if such initial data sets have vanishing mass, they must be contained in pp-wave spacetimes. This is based upon joint work with Yiyue Zhang from UCI. |
| Date: | Wed, 08.05.2024 |
| Time: | 13:45 |
| Duration: | 60 min |
| Location: | via zoom |
| Contact: | Piotr T. Chrusciel |
|