String compactification, generalized geometry, and 4D physics

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).A broad program of research is proposed to elucidate the geometrical structure that underlies the internal dimensions of string theory, and to overcome key obstacles to extracting 4D particle physics from this geometry. The two main areas that will be investigated are warped compactifications and generalized geometry. Three additional areas include global embeddings of local models of particle physics, the string theory LHC inverse problem, and a cosmological model in which conventional string theory vacua arise from a more symmetric phase in the past. Intellectual Merit: Nearly all compactifications of string theory currently under sudy are warped compactifications. It is proposed to apply string duality to derive the precise effect of warping in the reduction to 4D, and to check nonperturbative corrections to warped compactifications. The first project is essential for reliably computing perturbative mass spectra in string theory models. The second will increase confidence in recent nonperturbative mechanisms for moduli stabilization and for the generation of hierarchically small Majorana neutrino masses and mu-terms. Another critical ingredient in moduli stabilization and inflationary scenarios is internal magnetic flux, now generalized to nongeometric flux. The nongeometric flux radically alters our understanding of the internal geometry by destroying the usual 6D interpretation of the extra dimensions as a manifold. A set of strategies is outlined to more precisely characterize compactifications with generalized flux, and to extract the 4D physics of D-branes in this background. Of the remaining three proposed projects, two further advance the goal of connecting string theory to 4D physics at the scale soon to be probed at the LHC. The last project provides a concrete realization of a long speculated idea that conventional string theory vacua describe a symmetry breaking phase of a more symmetric underlying theory. Broader Impacts: The PI brings the exciting frontiers of string theory and elementary particle physics to Bryn Mawr College. Supervised research will foster diversity in science and engineering, by building on Bryn Mawr's strong tradition of individualized research mentoring of talented undergraduate women (a quarter of whom are students of color) and coeducational graduate students, with a proven track record of recruitment and retention. The Ph.D. program, as a feeder to the faculties of regional liberal arts colleges, expands research activity in high energy physics. The plan exploits existing infrastructure: departmental colloquia, the Tri-College PACT seminar, and connections to the University of Pennsylvania. The PI will initiate a Theory Lunch and a visitor program tailored to the needs of a high energy theory program at a thriving liberal arts college.