This award supports research in relativity and relativistic astrophysics, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. Gravitational waves are ripples in the fabric of spacetime caused by the violent acceleration of extremely compact objects, like black holes and neutron stars smashing together billions of light-years away, or exotic processes in the very early universe. Detecting the primordial stochastic gravitational-wave background is one of the most ambitious goals of gravitational-wave astronomy. This persistent signal that permeates all space encodes information about even earlier moments in the Universe’s history than those we can currently probe with traditional electromagnetic telescopes. The primordial background is likely too weak to be detected with the current LIGO-Virgo-KAGRA instruments that routinely observe gravitational waves from black hole and neutron star mergers, but it could lie within the reach of proposed next-generation detectors. However, even with improved data, existing analysis methods are insufficient for disentangling the contributions of the weak background from the much louder foreground of gravitational waves from compact-object mergers. This project focuses on developing a novel method for detecting the primordial background in the presence of the foreground from merger signals. This award also provides training in data analysis and science communication to the students involved, and to the broader loca