I will review some important challenges for theoretical cosmology, focusing on the trans-Planckian problem for inflation and the anisotropy problem for matter bounce and ekpyrosis, and I will discuss some recent work exploring particular aspects of these problems.
I will argue why we need to remain objective about the physics of the early universe and explore different scenarios. In particular, I will present a cosmological bounce model based on Cuscuton gravity that does not have any ghosts or curvature instabilities. I will then discuss if Cuscuton bounce can provide an alternative to inflation for generating near scale-invariant scalar perturbations....
Different theories of the very early universe that can explain our observations of the cosmic microwave background are presented. The current paradigm - inflationary cosmology - has received much attention, but it is not the only theoretically viable explanation; indeed, several alternative scenarios exist. It thus bares the question: how can we discriminate between the various theories, both...
