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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.

The asymptotic safety paradigm is currently emerging as a highly promising idea for Beyond-Standard-Model physics with key progress in asymptotically safe quantum gravity and asymptotically safe matter models. The last years have seen not only the development of asymptotically safe gravity-matter models but also the discovery of asymptotically safe beyond Standard Model matter models that are under control in perturbation theory. New exciting avenues in (astro) particle physics are now waiting to be explored. For example although the nature of dark matter is a long-standing riddle it is a fact that experimental searches have so far not provided any direct clues but have instead come up with ever more stringent constraints on theoretically preferred regions of parameter space for dark-matter-models. Thus the key to unraveling this riddle could be a new theoretical paradigm to guide model builders. This workshop aims at exploring whether asymptotic safety can be a candidate for this new paradigm. We aim to bring together experts on phenomenological models and quantum gravity to probe both the theoretical viability and empirical signatures of asymptotically safe extensions of the standard model that include gravity. To facilitate a highly productive meeting that can trigger new collaborations each talk will be followed up by 15-20 minutes discussion time. Further each day of the workshop will feature a dedicated discussion session. Participants will be encouraged to contribute questions for the discussion both before as well as during the workshop. The last day of the workshop will conclude with a roadmap discussion during which all participants will be given the opportunity to propose concrete suggestions for follow-up work that might lead into future joint projects.

What can you do with a Physics degree?  Plenty although the reality is that most people being trained in physics at the undergraduate graduate or even postdoctoral levels aren't aware of the broad spectrum of opportunities available to them.  The problem solving skills necessary to succeed in physics are sought after in a wide range of technology financial and industrial sectors. This day will bring together current students and postdocs in theoretical physics with former students who have found great success in a wide range of different areas from startups to big companies finance and even bestselling novels.  Many of them were affiliated with Perimeter Institute and chose their career paths over opportunities in academia.  Through a combination of talks and panel sessions this day will showcase the many career possibilities available to young physicists steps they can take to explore these options and how to avoid the inevitable pitfalls. Lunch will be provided and there will ample opportunities to ask questions and network.

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.

The goal of the workshop is to foster interaction between researchers working on the S-matrices of conventional strings and on ambitwistor strings.  The workshop will exploit synergies between the two frameworks and identify the current key questions in the fields and areas that can benefit from collaboration. The program of the workshop will be tailored to questions and problems raised by the participants in the run-up to the event. The goal is to spend most of the time on collaborative discussions in order to exchange expertise and to attempt to resolve questions during the workshop. A list of such problems can be found below and this will be extended by the participants in the run-up to the meeting. To obtain ambitwistor integrands and Bern-Carrasco-Johansson (BCJ) numerators for multiloop amplitudes and to connect with superstring worldsheet correlators. To develop fully nonlinear approaches by working on curved backgrounds both for application to AdS/CFT and to problems in perturbative gravity and gauge theory on nontrivial backgrounds. To understand the twistor and ambitwistor geometry underpinning both conventional and ambitwistor strings including the geometry of soft limits infrared structure and its links with formulations at null infinity. To explore mathematical structures behind the integrals of conventional and ambitwistor strings (positive geometries and canonical forms twisted (co)-cycle etc.)

Our universe is of astonishing simplicity: almost all physical observations can in principle be described by a few theories that have short mathematical descriptions. But there is a field of computer science which quantifies simplicity namely algorithmic information theory (AIT). In this workshop we will discuss emerging connections between AIT and physics some of which have recently shown up in fields like quantum information theory and thermodynamics. In particular AIT and physics share one goal: namely to predict future observations given previous data. In fact there exists a gold standard of prediction in AIT called Solomonoff induction which is also applied in artificial intelligence. This motivates us to look at a broader question: what is the role of induction in physics? For example can quantum states be understood as Bayesian states of belief? Can physics be understood as a computation in some sense? What is the role of the observer i.e. the agent that is supposed to perform the predictions? These and related topics will be discussed by a diverse group of researchers from different disciplines.

Foil theories sometimes called mathematically rigorous science fiction describe ways the world could have been were it not quantum mechanical. Our understanding of quantum theory has been deepened by contrasting it with these alternatives. So far observers in foil theories have only been modeled implicitly for example via the recorded probabilities of observing events. Even when multi-agent settings are considered these agents tend to be compatible in the classical sense that they could always compare their observations. Scenarios where agents and their memories are themselves modeled as physical systems within the theory (and could in particular measure each other as in Wigner's friend experiment) have not yet been considered. In this workshop we will investigate which foil theories allow for the existence of explicit observers and whether they allow for paradoxes in multi-agent settings such as those found in quantum theory. We will also investigate which interpretations of quantum theory would equally well interpret the foil theories and which interpretations are truly quantum. We will gain a deeper understanding of how this can happen by discussing appropriate definitions observers in these theories and seeing how such observers learn about their environment.

Scientific inquiry in the 21st century is beset with inefficiencies: a flood of papers not read theories not tested and experiments not repeated; a narrow research agenda driven by a handful of high-impact journals; a publishing industry that turns public funding into private profit; the exclusion of many scientists particularly in developing countries from cutting-edge research; and countless projects that are not completed for lack of skilled collaborators. These are all symptoms of a major communication bottleneck within the scientific community; the channels we rely on to share our ideas and findings especially peer-reviewed journal articles and conference proceedings are inadequate to the scale and scope of modern science. The practice of open research doing science on a public platform that facilitates collaboration feedback and the spread of ideas addresses these concerns. Open-source science lowers barriers to entry catalyzing new discoveries. It fosters the real-time sharing of ideas across the globe favoring cooperative endeavor and complementarity of thought rather than wasteful competition. It reduces the influence of publishing monopolies enabling a new credit attribution model based on contributions made rather than references accrued. Overall it democratizes science while creating a new standard of prestige: quality of work instead of quantity of output. This workshop will bring together a diverse group of researchers from fields as diverse as physics biology computer science and sociology committed to open-source science. Together we will review the lessons learnt from various pioneering initiatives such as the Polymath project and Data for Democracy. We will discuss the opportunity to build a new tool similar to the software development platform GitHub to enable online collaborative science. We will consider the challenges associated with the adoption of such a tool by our peers and discuss ways to overcome them. Finally we will sketch a roadmap for the actual development of that tool.