Cosmology and Fundamental Physics

This award funds the research activities of a postdoc at Tufts University who will be working under the direction of Professors Mark Hertzberg and Ken Olum. Our universe may contain a network of cosmic strings, microscopically thin objects of astronomical length that may arise from the breaking of symmetries associated with the fundamental laws of elementary particle physics. In this project, the PIs will develop a new simulation of axion strings. Axions are a leading candidate for the mysterious dark matter that makes up most of the matter of the universe, but in many scenarios the connection between the axion properties and the resulting dark matter depends on the dynamics associated with a cosmological epoch of axion strings. In another project, the PIs will compare and contrast the success of various theoretical models of the Big Bang. To do this, they intend to perform a mix of semi-analytical work and numerical simulations. Research in this area advances the national interest by promoting the progress of science in one of its most fundamental directions: the search for new physics beyond the Standard Model of particle physics and an improved understanding of the early universe. The project is also intended to have broader impacts through the training of a postdoctoral researcher, and the results of this project will be broadly disseminated through journal publications and made available to the public on the World Wide Web. More technically, the computational code developed at the Tufts Institute of Cosmology will be used to study gravitational effects on strings and will be extended to simulate axion strings as Nambu strings coupled to a Kalb-Ramond field. Also, the PIs intend to examine the correspondence between simulations of field theory on a lattice and simulations of Nambu (infinitely thin) strings. This will lead to a more accurate computation of axion dark matter properties, and thereby help to determine whether axions are the source of the observed dark matter. Furthermore, the work on evolving inhomogeneous initial states will involve detailed numerical scalar field and gravitational simulations/calculations, with initial conditions drawn from a range of probability distributions. 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.