This award funds the research activities of Professors John Donoghue, Ben Heidenreich, and Lorenzo Sorbo at the University of Massachusetts, Amherst.<br/><br/>One of the most pressing questions in theoretical physics concerns the search for a theory (or theories) that can unite quantum mechanics and gravity, as well as strategies to probe its validity. Professor Donoghue's and Professor Heidenreich’s research use different techniques to explore the theoretical aspects of quantum gravity: Professor Donoghue, by studying its implications at relatively low energies, and Professor Heidenreich, by determining general properties that any theory of quantum gravity should satisfy. Professor Sorbo studies how such a theory (as well as other theories) might have left observable effects during the early evolution of the Universe. This project will also have important broader impacts. Graduate students will be involved in this research, so that junior physicists can be trained to do research in this field. Profs. Donoghue, Heidenreich and Sorbo will also create online pedagogical material, organize workshops and provide outreach to grade school audiences.<br/><br/>More technically, Professor Donoghue will investigate novel aspects of the effective field theory treatment of quantum general relativity. Professor Heidenreich will investigate quantum gravity through the swampland program, with a focus on stringent tests of foundational ideas such as the absence of global symmetries and constraints on the spectrum of particles and branes, and on the properties of moduli space. Professor Sorbo will explore various aspects of inflationary phenomenology, with a focus on processes of particle creation during inflation, especially in the regime where the created particles strongly affect the background.<br/><br/>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.