Speaker: Jerome Quintin, McGill University

Abstract:  I will review the idea behind the matter bounce scenario as an alternative to inflation and highlight two of its problems: its instability with respect to anisotropies and its large tensor-to-scalar ratio. I will present two tentative resolutions to the latter in which curvature perturbations are effectively enhanced, but I will argue that these approaches are not viable because they always lead to the production of large non-Gaussianities. I will then show that a more robust resolution (to both problems) would be to consider a theory in which the graviton has a non-trivial mass, but I will also discuss the limitations of such a theory.