Subventions et des contributions :

Subvention ou bourse octroyée s'appliquant à plus d'un exercice financier. (2017-2018 à 2022-2023)

The overall theme of my research proposal is to test fundamental physics with new cosmological observations. Observational and experimental cosmology have over the past years entered a ``golden age''. Experiments have produced high precision maps of the temperature distribution of the cosmic microwave background (CMB). High quality CMB polarization maps will become available over the next five years. Data concerning the structure of the universe on large scales as seen from new optical telescopes is accumulating at a rapid rate. 21cm redshift surveys will provide a new window to probe this structure. Canada is playing an important role in these observational efforts (e.g. Prof. Matt Dobbs at McGill). I plan to study ways to use this exciting new data to probe aspects of high energy physics. One avenue of research which I plan to pursue is to search for signals of topological defects such as cosmic strings in new observational windows. Topological defects are predicted in many particle physics models beyond the Standard Model, and in this case inevitably arise in the early universe and persist to the present time. Looking for signals of such defects in cosmological observations is a way to probe particle physics which is complementary to accelerator studies. We will work out the specific signals of strings in various observational windows and develop statistical tools with which the signals can be seen when they are embedded in background noise.

The seeds for the structures which are observed in the cosmos were laid down in the very early universe at energies where new fundamental physics is expected to be operational. The expansion of space is a cosmological microscope which lets us probe fundamental physics with cosmological experiments. The data about the early universe is encoded in cosmological fluctuations which propagate to the present time. I plan to use fundamental principles of superstring theory to develop an understanding of the very early universe at the highest energy scales. Our past work on ``string gas cosmology" indicates that the picture of the early universe will be radically different from what naive extrapolation of convention particle physics-based cosmology would yield. What is missing is a consistent dynamical description of the early phase. One of the goals of our work is to provide an improved dynamical picture of the very early universe based on string theory. An improved understanding of the very early universe will generate new and more consistent realizations of inflation, but may also lead to alternative early universe scenarios with specific predictions for cosmological observations.

I also plan to work on new dark energy models based on theories with axions, on inflationary reheating, on the back-reaction of cosmological perturbations, and on the stabilization of embedded defects via plasma effects.