# Particle Physics Seminar

## "Implications of Cosmological Observations for History of Early Universe"

#### Presented by Ghazal Geshnizjani, University of Waterloo/ Perimeter Institute for Theoretical Physics

Wednesday, April 22, 2015, 3:00 pm — Building 510 Room 2-160

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 Ï‰ âˆ 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.

Hosted by: Morgan May

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