Talks by Alberto Nicolis

Effective field theories for hydrodynamical systems

Abstract

I will review EFT techniques that have been developed recently for dealing with the infrared dynamics of ordinary fluids and of superfluids. Gravity does not play an essential role in the construction (though it can be added straightforwardly to the system), yet certain applications resemble very closely the EFT approach to gravity wave emission by binary systems. I will describe in some detail one such application, as well as a possible application to cosmology.

Galilean Genesis

Abstract We propose a novel cosmological scenario, in which standard inflation is replaced by an expanding phase with a drastic violation of the Null Energy Condition (NEC): \dot H >> H^2. The model is based on the recently introduced Galileon theories, which allow NEC violating solutions without instabilities. The unperturbed solution describes a Universe that is asymptotically Minkowski in the past, expands with increasing energy density until it exits the regime of validity of the effective field theory and reheats.

Solid Inflation

Abstract I will describe a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations.