Cosmological tests of fundamental physics

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We live in a golden age of cosmology. The next generation of optical and radio telescopes will complete the detailed 3D map of the structure in the universe, revealing its evolution through multiple epochs. Upcoming cosmic microwave background (CMB) experiments will produce high quality polarization maps potentially confirming the quantum origin of the initial inhomogeneities that seeded formation of stars and galaxies. Canadian astronomers are actively involved in these efforts. My proposal is inspired by the opportunities presented by the upcoming experiments for resolving some of the long-standing puzzles in particle physics and cosmology, such as the nature of dark matter and dark energy. My group is in a good position to solidify its leading role in designing and applying new tests of fundamental physics, while working in close partnership with observational teams. The research program I propose is broadly grouped into two main themes: One focuses on the dynamics of the late time universe and includes studies of dark energy, cosmological test of general relativity and alternative theories of gravity. The other will concern the early universe and using cosmology as a laboratory for testing particle physics. With dark matter and dark energy making up 95% of the energy content of the universe, and with general relativity only weakly tested over cosmological times and distances, there is a considerable interest in developing and testing alternative theories of gravity. My group will develop theoretical frameworks and numerical tools that, in addition to testing specific theories of dark energy and modified gravity, will answer a set of important qualitative questions in as model-independent way as possible. Such questions would include whether dark energy density remains constant in time, whether the equivalence principle holds on cosmological scales and if there are interactions between the dark components. Our work will build on existing long term collaborations with team members of upcoming surveys such as DESI, Euclid and LSST. The expanding universe acts as a microscope revealing physics at energies beyond the reach of particle accelerators. CMB has been our key source of information that will eventually be complemented by gravitational wave (GW) observations from future experiments such as LISA. This proposal includes studying the phase transitions that took place in the early universe, along with their relics, such as primordial magnetic fields and cosmic strings, and their characteristic CMB and GW signatures. I will also study axion strings and their decay into dark matter. My work in this area will form part of my contribution to the CMB-S4 collaboration. The SFU Cosmology Group, with its combined expertise in theory, statistics, computing and data analysis, provides a stimulating environment for developing and testing new ideas, and unique opportunities for training HQP in areas of active international interest.