RUI: Probing Gauge Extensions of the Standard Model with Primordial Gravitational Waves

This award funds the research activities of Professor Bartosz Fornal at Barry University, Miami, FL. The first detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015 marked the beginning of a new era in gravitational wave astronomy. Although thus far only signals from black hole and neutron star mergers have been observed, many cosmological processes that occurred within a fraction of a second after the Big Bang are expected to have produced a stochastic gravitational-wave signal continuously passing through us today, carrying information about the physics at the earliest times. This primordial gravitational-wave background may hold the key to discovering the fundamental laws governing nature at the highest energies, understanding how matter in the Universe came to dominate over antimatter, and uncovering the nature of dark matter. As a result, research in this area advances the national interest by promoting the progress of science in one of its most fundamental directions: the discovery and understanding of new physical law. In his research, Professor Fornal will develop new strategies for using gravitational-wave observations to test particle-physics theories with extended symmetries at high energies that address outstanding questions in fundamental physics. This project is also envisioned to have significant broader impacts. Professor Fornal will involve undergraduate students in his research, providing them with the necessary skills and experience to become future researchers. They will present their research results at conferences and meetings of the American Physical Society, providing valuable opportunities for scientific exchange and career development. Professor Fornal will also develop new course curricula based on the results of this research, as well as conduct outreach activities at local schools and organize events for the general public. More technically, Professor Fornal and his students will investigate gravitational wave signatures of early-Universe symmetry-breaking phase transitions within the framework of well-motivated beyond-Standard Model theories with extended gauge structures. Particular attention will be given to additional spectral features arising from domain-wall annihilation and symmetry-restoring phase transitions during reheating. The research will encompass models with gauged baryon and lepton number, grand unification, and gauged flavor symmetries. The models considered will accommodate dark matter, explain the matter-antimatter asymmetry of the Universe, include mechanisms for generating neutrino masses, and shed light on the reheating epoch. The predicted signals will be explored through multi-messenger astrophysical observations, creating new synergies between particle physics, gravitational-wave astronomy, and astrophysics while helping guide the optimal design of future gravitational-wave detectors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.