Hosted by: Morgan May

I will argue that any theory of early universe that matches cosmological observations should include a phase of accelerated expansion (i.e. inflation) or it has to break at least one of the following tenets of classical general relativity: Null Energy Conditions (NEC), sub-luminal signal propagation, or sub-Planckian energy densities. This proof extends to a large class of theories with higher (spatial) derivative or non-local terms in the action as well. Interestingly, only theories in the neighbourhood of Lifshitz points with ω ∝ k^0 and k^3 are excluded from the proof. I will also discuss in what sense detecting primordial gravitational waves is a smoking gun for inflation.