Upcoming CfAR Seminars
TBA
Past Seminars
Feb 22, 2023. 12:45pm in Room X131
Speaker: Mikołaj Korzyński (Center for Theoretical Physics, Polish Academy of Sciences)
Title: Redshift and position drift in general relativity
Abstract: I will discuss the redshift and the position drifts in general relativity, i.e. the temporal variations of the redshift and the position on the sky of a light source, as registered by an arbitrary observer. Recall that the redshift is simply the difference between the photon's energy as measured by the light source in its rest frame and by the observer. With the recent advancements in astrometry, the drifts of distant sources are likely to become important observables in cosmology in the near future. In my lecture I will present the derivation of exact relativistic formulas, containing automatically all possible light propagation and kinematical effects. I will discuss their physical consequences and possible applications to the gravitational lensing theory, cosmology and pulsar timing.
Feb 8, 2023. 1pm in Room X131
Speaker: Nils Anderson (University of Southampton)
Title: Modelling non-equilibrium aspects of neutron star mergers
Abstract: Neutron star mergers involve a lot of messy (not particularly well understood) physics. Many of the key issues involve non-equilibrium aspects. For example, it was recently demonstrated that deviations from beta equilibrium impact on the fine-print details of the merger gravitational-wave signal. In addition, we need to account for turbulence. Both problems are tricky to formulate in general relativity. Framing the discussion in the context of state-of-the-art merger simulations, I will summarise recent progress in formulating a suitable large-eddy scheme for turbulence and the emerging understanding of bulk viscosity in neutron star mergers. I will provide suggestive evidence that these developments are required for modelling merger signals for next generation detectors like the Einstein Telescope and the Cosmic Explorer.
Speaker: Mikołaj Korzyński (Center for Theoretical Physics, Polish Academy of Sciences)
Title: Redshift and position drift in general relativity
Abstract: I will discuss the redshift and the position drifts in general relativity, i.e. the temporal variations of the redshift and the position on the sky of a light source, as registered by an arbitrary observer. Recall that the redshift is simply the difference between the photon's energy as measured by the light source in its rest frame and by the observer. With the recent advancements in astrometry, the drifts of distant sources are likely to become important observables in cosmology in the near future. In my lecture I will present the derivation of exact relativistic formulas, containing automatically all possible light propagation and kinematical effects. I will discuss their physical consequences and possible applications to the gravitational lensing theory, cosmology and pulsar timing.
Feb 8, 2023. 1pm in Room X131
Speaker: Nils Anderson (University of Southampton)
Title: Modelling non-equilibrium aspects of neutron star mergers
Abstract: Neutron star mergers involve a lot of messy (not particularly well understood) physics. Many of the key issues involve non-equilibrium aspects. For example, it was recently demonstrated that deviations from beta equilibrium impact on the fine-print details of the merger gravitational-wave signal. In addition, we need to account for turbulence. Both problems are tricky to formulate in general relativity. Framing the discussion in the context of state-of-the-art merger simulations, I will summarise recent progress in formulating a suitable large-eddy scheme for turbulence and the emerging understanding of bulk viscosity in neutron star mergers. I will provide suggestive evidence that these developments are required for modelling merger signals for next generation detectors like the Einstein Telescope and the Cosmic Explorer.