The landmark detection of gravitational waves (GWs) emitted by black-hole and neutron-star binaries has opened a new era in physics, giving access to hitherto unexplored systems. In parallel to their countless astrophysical applications, these discoveries open new avenues to explore fundamental physics.
These new challenges call for a multidisciplinary, cross-cutting effort at the interface of different communities. Recently, specific initiatives to connect affine subareas (e.g. nuclear and GW astrophysics or black-hole and particle physics) were established, but lack the required depth and stability.
With the GWPFP initiative, we propose to support and train the next generation of leaders in GW physics, who will be able to communicate across a spectrum of sub-fields. This is instrumental to maximize the benefit from theoretical developments and from the wealth of data, now available from current (LIGO/Virgo/KAGRA) and soon to be taken by future (LISA, Einstein Telescope, Cosmic Explorer) GW interferometers, radio and X-ray observatories (e.g., Event Horizon Telescope, NICER, GRAVITY, Athena, eXTP), cosmological observations by the JWST, and from particle accelerators facilities (e.g., CERN, GSI/FAIR).