This award funds the research activities of Professor Matthew B. Kleban at New York University.
Recent years have witnessed many profound discoveries in particle physics and cosmology. Gravitational waves from merging black holes were recently detected for the first time, confirming a prediction of Einstein's theory of general relativity and opening an unprecedented new window into the physics of strong gravity and extreme states of matter. Similarly, the Large Hadron Collider discovered the Higgs particle, although this discovery does not suggest any way of solving certain issues such as the so-called "hierarchy problem" or provide any clear hint of what physics exists at shorter distance scales. Likewise, there is strong evidence for dark energy, which is responsible for the accelerated rate of expansion of the current universe, and for cosmic inflation, a period of explosive expansion just after the Big Bang. Yet this evidence tells us little about the underlying physical origin of either phenomenon. A breakthrough in understanding the meaning of these recent profound discoveries would promote the progress of science in a fundamental way, revealing new laws of nature and helping to explain the origin and fate of our universe. Research in this direction thus advances the national interest by furthering the development of basic science within the United States. As part of his research, Professor Kleban will investigate the theoretical consequences of Einstein's theory of general relativity in exotic situations, such as during rapid cosmic expansion and near black holes. He will also study how to understand the effects of quantum mechanics in such situations. Further, he will study the physics of hypothetical particles called "axions" that could play a key role in explaining certain mysterious features of the Standard Model of particle physics. Professor Kleban's work is also envisioned to have broader impacts in the form of public lectures and interviews, and in inspiring and training undergraduate and graduate physics students at New York University. Professor Kleban will also train and aid in the professional development of a postdoctoral researcher who will participate in this research.
More technically, Professor Kleban will study the theory of axion landscapes, making use of the techniques he recently developed to push forward our understanding of the cosmology of such theories. He will continue his work on extending a "no-hair theorem" for de Sitter spacetime with inhomogeneous initial conditions in classical general relativity and the problem of initial conditions in inflationary cosmology. Lastly, he will study string theory in three-dimensional anti-de Sitter spacetime at a special string-scale radius of curvature, where the theory appears to undergo a phase transition from a phase dominated by black holes to one dominated by long strings.
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.
