Orthogonal non-Gaussianities from Dirac-Born-Infeld Galileon inflation
Renaux-Petel, Sébastien (DAMTP, University of Cambridge)

We consider the relativistic extension of the Galileon model. We derive the conditions under which this model can sustain a phase of quasi de-Sitter expansion. We analyze the linear perturbations about a homogeneous cosmological solution and demonstrate the existence of a critical background energy density above which cosmological fluctuations become ghosts. Finally, in the inflationary context, we show that this is the first concrete early Universe model where the orthogonal shape can be the dominant contribution to the primordial non-Gaussianities.