Exploring Fundamental Physics Across Cosmic History: Early- and Late-Time Acceleration, Dark Matter, and Gravitation

This award funds the research activities of Professor Mark Hertzberg at Tufts University. Cosmology provides a powerful means to address fundamental questions in physics beyond the Standard Model. With no direct evidence for new physics at particle colliders, astronomical observations offer a complementary avenue for answering these questions. Perhaps the most significant questions are: what fundamental interactions took place in the early and late universe? What are the constituents of the universe, including the dark matter and dark energy? The project will investigate specific sub-topics within these important questions by firstly developing theoretical models and then comparing to cosmological and astrophysical data. This research therefore advances the national interest by pursuing fundamental questions of high significance. The project will have broader impacts. It will involve graduate and undergraduate students, who will play an important role in analyzing models and performing computational work; this will help them develop essential research skills. Professor Hertzberg will also actively advance these topics within the larger community. More technically, Professor Hertzberg will examine new models of cosmic acceleration involving ultralight scalar fields, and compare to cosmological data, including DESI. He will also explore and constrain possible new long-range forces between dark matter provided by light mediators. Finally, he will also constrain corrections to general relativity treated as an effective field theory using theoretical arguments and observations, including gravitational waves. 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.