September 27, 10:15 in E204   

David Mulryne, (Queen Mary, University of London, UK)


Evolution of non-Gaussianity in multi-field models

The study of the statistics of perturbations produced by inflation has the power to tell us much about the inflationary potential, and hence the physics of the very early universe. In complex multi-field models, however, extracting information about the potential from observation is extremely difficult. I will discuss some recent work which is a step towards this goal. The work is concerned with how the non-linearity parameter fnl, which parametrises the three-point function, can evolve during multi-field inflation. Particular features in the inflationary potential lead to a particular sign of fnl as it evolves, and tuning the initial conditions on these features leads to a large but transitory magnitude. Ultimately we should consider the value of fnl at an adiabatic limit, when it becomes constant, and I further discuss the conditions needed for fnl to be large at that time if the limit is reached "naturally". I show that for concrete models of inflation numerical techniques often become essential to reliably calculate the value of fnl at an adiabatic limit, and give a number of explicit examples, including axion potentials, inflection potentials and the hybrid potential.