Gravitational Universe: Challenges and Opportunities

Gravitational Universe: Challenges and Opportunities The landmark detection of gravitational waves (GWs) emitted by merging black-hole and neutron-star binaries has opened a new era in physics, giving us access to the strong-field regime of the gravitational interaction.

The wealth of data coming from current and future GW detectors (such as 3G, LISA, PTA) will provide an opportunity to challenge current paradigms, exploring fundamental physics from an entirely new perspective, and eventually finding new physics.

In this new observational window, we could learn that general relativity is not adequate to describe the strong-field regime of gravity; new fundamental fields beyond the standard model, or new kinds of compact objects, could challenge current understanding of dark matter and dark energy.In order to reach these results, the impressive experimental effort put in place will not be sufficient if not accompanied by a similar effort by the theoretical and the data-analysis communities.

Severe theoretical and conceptual problems need to be overcame before the new generation of detectors is operating.

On one hand, we need to develop new data-analysis algorithms, to extract meaningful results from the impressive amount of data which will be delivered.

On the other hand, we need to develop theoretical models of GW sources which do not assume the standard theories and paradigms which we want to test, in order to perform non-biased tests and to use observational results to address fundamental problems.

It is of utmost importance that scientists with different expertise and addressing different challenges exchange their views and learn from each other’s problems.

The proposed studies can be loosely classified into four groups with considerable overlap: i) Perturbation techniques in general relativity and beyond ii) Non-linear simulations of binary compact objects beyond general relativity iii) GWs from the dark universe iv) Data analysis for GW experiments