New and Refurbished Directions Beyond the Standard Model

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This award funds the research activities of a postdoctoral research associate working in the research group of Professor Lisa Randall at Harvard University.Recent decades have seen significant advances in particle physics. Yet many issues stubbornly remain that seem to require new ingredients or new ways of thinking. Among these problems is the so-called "hierarchy problem" of particle physics --- i.e., the question of why gravity is as weak as it is. There are also problems concerning the energy density of the Universe --- problems which directly affect how quickly the universe expanded immediately after the big bang and how quickly it appears to be accelerating in its expansion today. As part of her research, Professor Randall considers theories in which there are extra spacetime dimensions beyond those of width, height, and depth. Such extra dimensions provide a new arena in which these and other issues may be addressed. Research in this area thus serves the national interest by enhancing our understanding of the fundamental operation of the universe. This research is also expected to have significant broader impacts. Studies of extra dimensions not only provide deeper insights into current ideas of particle physics but also offer a rich territory ideal for the training of junior physicists entering the field, such as postdoctoral fellows and students. This research will also provide ideas that the public enjoys learning about, and which Professor Randall will include in her ongoing public lectures. More technically, this research will involve new features that appear within the context of theories with extra spacetime dimensions. In particular, how does the stabilization mechanism essential to achieving the cosmology of the three observed spatial dimensions change the low energy theory that describes what we see? Already there exist examples, ultimately based on a string theory model, where gravitational constraints from an extra dimension were essential and needed to be included in the analysis. As part of this project Professor Randall and her colleagues will study how this extra ingredient can be relevant for achieving the consistency of the theory and fixing the size of an extra dimension.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.