A phase of ultra slow-roll during inflation, characterized by a transient decrease in the inflaton field velocity, is known to generate large curvature perturbations on small scales that could later seed the formation of a significant population of primordial black holes. In this talk, we discuss how non-Gaussianities can arise from the non-linear relation between curvature perturbations and...
We will discuss the negative gradient flow of an energy functional of Spin(7)-structures on compact 8-manifolds. The energy functional is the L2-norm of the torsion of the Spin(7)-structure. We will talk about the short-time existence and uniqueness of solutions to the flow. We will also explain how this negative gradient flow is the most general flow of Spin(7)-structures.
