Gravity seminars 2022

October 11, 2022	Harald Pfeiffer [he, his] Group-leader, Max-Planck-Institute for Gravitational Physics, Potsdam Professor, University of Potsdam Title: Frontiers in numerical relativity: Binary black holes with eccentricity and at high mass-ratios Abstract: Binary black hole simulations are essential to analyse gravitational wave signals and to deepen our understanding of the behavior of Einstein's theory of general relativity in strongly nonlinear and dynamic situations. After a brief survey of the past impact of NR on gravitational wave astronomy, this talk will focus on recent progress in two frontiers of numerical relativity: First, binaries with eccentricity, including the case of unbound scattering encounters. And second, the quest to cover the full mass-ratio range from comparable masses to extreme mass-ratios.
November 8, 2022	Tanja Hinderer, Utrecht Title: Probing subatomic physics with gravitational waves from neutron star binary inspirals Abstract: The gravitational waves from merging binary systems carry unique information about the nature and internal structure of compact objects. This is of key interest for neutron stars, whose material is compressed by their tremendous gravity to supra-nuclear densities, where novel phases of matter emerge. I will describe examples of the interplay of matter with strong-field gravity and recent progress in modeling the resulting characteristic signatures in the gravitational waves from binary systems. I will also highlight new insights gained from recent gravitational-wave discoveries, and conclude with an outlook onto the remaining challenges and exciting prospects for the next years, as gravitational-wave science continues to move towards an era of precision physics. Slides can be found here
November 15, 2022	Pippa Cole, Amsterdam Title: Disks, spikes and clouds: distinguishing between black hole binary environments with LISA Abstract: LISA, the space-based gravitational wave detector, is due to fly in the mid 2030s. An entire new frequency range will be opened up for discovering gravitational wave sources, including intermediate and extreme mass ratio black hole binaries which will remain in band for up to weeks, months or even years. This offers an exciting new avenue for fundamental physics discoveries because the environment of the binaries will have an effect on the gravitational waveform over this long period of time, and we will be able to measure the properties of the environments from the gravitational wave observations alone. I will show that we can measure the parameters of not only baryonic environments such as accretion disks, but also the properties of dark matter spikes or clouds of scalar fields if they are present around the binaries. I will demonstrate that we can distinguish between different environments with a Bayesian model comparison approach and argue the importance of including environmental effects in waveform modelling. This is so that we don't miss the opportunity to learn about the nature of dark matter or the structure of accretion disks, but crucially also so that we don't infer biased parameters by assuming that the system is inspiralling through vacuum. Slides can be found here
November 29, 2022	Jan Steinhoff, AIE Potsdam Title: Gravitational waves from a particle physics perspective Abstract: Continuing the success of gravitational wave observations requires a large effort on improving their theoretical predictions in the next decade, in order to keep their accuracy on par with improvements of the detectors. This requires innovations on the methods by which gravitational waves from compact binaries are calculated. In this talk, we focus on approaches to analytic, perturbative predictions for relativistic binaries inspired by high-energy physics. In this area, effective field theories are highly useful and scattering amplitudes (the primary observable) can be calculated very efficiently using novel tools. These methods can indeed be applied the classical binaries and their gravitational waves. We give a basic introduction to the ideas of these approaches and recent progress. Slides can be found here
December 13, 2022	Neil Cornish, Montana State University Title: The challenge and promise of the LISA gravitational wave observatory. Abstract: Next decade will see the launch of the ESA-NASA Laser Interferometer Space Antenna (LISA) gravitational wave observatory. LISA will open up the source-rich milli-Hertz region of the gravitational wave spectrum which is thought to contain tens of millions of sources, mostly galactic binaries, along with dozens of massive black hole binaries, extreme mass ratio inspirals and stellar remnant black hole binaries. There is also the interesting prospect of detecting stochastic signals from processes in the early universe, such as first order phase transitions and primordial magnetic fields. Extracting this rich bounty will be very challenging since the long duration of the signals means that they will all be superimposed in the data, and on these long timescales, the instrument noise likely to vary and to contain many gaps and disturbances. I will describe some of the efforts to address this issue, and show new results from the first global fit pipeline applied to simulated LISA data.

The Niels Bohr International Academy (NBIA)

Gravity seminars 2022