Particles, Strings and Gravity in a Dynamical Universe

This award funds the research activities of Professors Mina Aganagic, Raphael Bousso, and Petr Horava at the University of California at Berkeley.

In the first two decades of this century, we have witnessed dramatic progress in our understanding of the fundamental laws of the Universe from the shortest to the largest scales, firmly based on the principles of quantum mechanics (which describes the subatomic world) and general relativity (which describes gravitational forces acting at large distance scales). While string theory may represent the dominant paradigm for unifying these two principles, many important puzzles and open questions still remain.

Professors Aganagic, Bousso, and Horava will attempt to provide answers to some of these open questions and puzzles, with the goal of deepening our understanding of the quantum-mechanical Universe. Specifically, these professors will investigate the properties of quantum-mechanical theories of gravity by using the newly found connection between such theories and the rapidly developing interdisciplinary field of science known as "quantum information theory", as well as by using more traditional methods that have been successful in describing all the non-gravitational forces in nature.

The results of this research are expected to have implications for the puzzles associated with the quantum-mechanical behavior of black holes, possible short-distance generalizations of Einstein's general theory of relativity, and the structure of the evolving Universe at largest distances. In addition, Professors Aganagic, Bousso, and Horava will work on the relations of string theory and quantum gravity to pure mathematics.

Such research is expected to have a broad impact not only in particle physics and cosmology, but also in neighboring areas of physics and beyond. This research thereby advances the national interest by promoting the progress of science in its most fundamental form. The universal nature of this research also serves as an excellent vehicle for supporting the education of young researchers (students and postdoctoral scholars), and provides a natural platform for further increasing diversity and inclusion in science.

More specifically, Professor Aganagic will develop her program of categorifying quantum knot invariants using little string theory in six dimensions and its low-energy limit known as Theory X. She will also pursue categorification of Chern-Simons gauge theory on general three-manifolds. Professor Bousso will expand the AdS/CFT holographic dictionary by studying the kink transform.

He will examine the Euclidean path integral in semiclassical quantum gravity, using his recently proposed gravity/ensemble duality. In addition, he will attempt to strengthen the Quantum Focussing Condition, and will revisit the notorious measure problem in the landscape cosmology of string theory. Professor Horava will apply nonrelativistic completions of relativistic quantum field theories to the puzzles of technical naturalness (such as the Higgs mass hierarchy problem and the cosmological constant problem).

He will work to identify new classes of short-distance completions of relativistic supersymmetric Yang-Mills gauge theories in higher dimensions, using nonrelativistic Aristotelian supersymmetry at short distances. He will use the recently discovered topological nonrelativistic quantum gravity of Perelman's Ricci flow to study puzzles of quantum gravity, such as topology-changing transitions and quantum completeness.

He will study string theory in its covariant formulation in the novel regime far from equilibrium, as described by the Schwinger-Keldysh formalism.

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.