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Calendar of Physics Talks Vienna
| Speaker: | Claudia de Rham (Imperial College London) |
| Abstract: | In standard effective field theories, the notion of causality is intrinsically linked with that of subluminality and with a set of positivity constraints to be imposed on the low-energy scattering amplitudes. I will highlight how the presence of gravity leads to a more subtle relation between causality, (sub)luminality and positivity bounds. These considerations are relevant for putting constraints on cosmological and gravitational effective field theories and I will provide explicit criteria to be satisfied so as to ensure causality and a standard high energy completion in gravitational effective field theories. |
| Date: | Tue, 25.05.2021 |
| Time: | 16:00 |
| Duration: | 60 min |
| Location: | https://tuwien.zoom.us/j/95482849369?pwd=SkU2WU5hMVJBQWsyVlFXRlRvQlIvdz09 |
| Contact: | Céline Zwikel |
| The dynamics and statics of floating bodies (joint work with B.Schmidt) |
| Speaker: | Robert Beig (Univ. Vienna) |
| Abstract: | Bodies floating in still water are subject to the laws of rigid body mechanics combined with Archimedes' principle. We write down the equations governing their dynamics. These equations take the form of a Hamiltonian system similar to, but richer in structure than, the well-known heavy top. The sometimes surprising equilibrium configurations of floating bodies have attracted interest from the times of Archimedes up until today. The stability properties of equilibria have essentially been known since the 18th century and extensively used in naval architecture and by glaciologists studying icebergs. We give a precise statement of these stability criteria and an elementary proof of nonlinear stability under time evolution. |
| Date: | Thu, 27.05.2021 |
| Time: | 15:00 |
| Duration: | 30 min |
| Location: | https://univienna.zoom.us/j/6540036841?pwd=SytyVkZJZzNyRG9lMm13ejlHeHRRUT09 |
| Contact: | Piotr Chrusciel, David Fajman |
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