Sourcing curvature modes with entropy perturbations in non-singular bouncing cosmologies

The observed temperature fluctuations in the cosmic microwave background can be traced back to primordial curvature modes that are sourced by adiabatic and/or entropic matter perturbations. In this paper, we explore mechanism context of non-singular bouncing cosmologies. We show naturally generated during `graceful exit,' i.e., when smoothing slow contraction phase ends and universe enters bounce stage. Here, key role is played kinetic energy components come dominate density drive evolution towards cosmological bounce.