General Relativity & Quantum Cosmology

There has been a surge of interest in indefinite causal structure the idea that cause and effect can no longer be sharply distinguished.  Motivated both by experimentation with quantum switches and quantum gravity there can be situations in which there is no matter-of-the-fact as to what the causal structure of spacetime is.  This meeting will bring together workers in Quantum Foundations and Quantum Gravity in both theoretical experimental physics to discuss the state of the art of current research and set new directions for this emerging subdiscipline.

Understanding the small-scale structure of spacetime is one of the biggest challenges faced by  modern theoretical physics. There are many different attempts to solve this problem and they reflect the diversity of approaches to quantum gravity. This workshop will bring together researchers from a wide range of quantum gravity approaches and give them an opportunity to exchange ideas and gain  new insights.

This cross-disciplinary workshop gathers theorists who have been working on novel approaches to understanding the structure of the Standard Model and its link to cosmology and gravity. It follows the previous Simplicity I and II workshops at Princeton University (2014) and Fermilab (2016) and will be a small informal meeting with plenty of room for discussions.

We are entering an exponentially growing phase of gravitational-wave (GW) astronomy excitingly represented by the Nobel Prize in Physics last year - only two years after the first detection. The successful multi-messenger detection of binary neutron star merger in last August has triggered increasing interests to probe the neutron star post-merger gravitational radiations as they will give more decisive and informative description of the post-merger object itself and the GW/electromagnetic emission mechanism. As the post-merger GWs mainly lie in the 1kHz-4kHz band it becomes necessary and important to think about possible third-generation GW detectors that are primarily sensitive to the high frequency band.  In this workshop we shall focus on possible science case and detector configuration for kHz high-frequency detectors. We will have several invited talks while leaving more time for free discussions. We hope this workshop can serve as a seed for much broader discussions in the GW astronomy community and help promote high frequency detectors as one of the development directions of third-generation GW detectors.

Black hole superradiance is a fascinating process in general relativity and a unique window on ultralight particles beyond the standard model. Bosons -- such as axions and dark photons -- with Compton wavelengths comparable to size of astrophysical black holes grow exponentially to form large clouds spinning down the black hole in the process and produce monochromatic continuous gravitational wave radiation. In the era of gravitational wave astronomy and increasingly sensitive observations of astrophysical black holes and their properties superradiance of new light particles is a promising avenue to search for new physics in regimes inaccessible to terrestrial experiments. This workshop will bring together theorists data analysts and observers in particle physics gravitational wave astronomy strong gravity and high energy astrophysics to explore the signatures of black hole superradiance and to study the current and future possibilities of searching for new particles with black holes.