Name: Mar Bastero-Gil
 Institution: Department of Theoretical Physics and the cosmos
 Title: Non-linear metric perturbation enhancement of primordial   gravitational waves
 Key Words: inflation, gravitational waves, preheating
 Abstract: We present the evolution of the full set of Einstein equations 
during preheating after inflation. We study a generic supersymmetric model of hybrid inflation, integrating fields and metric fluctuations in a 3-dimensional lattice.  We take initial conditions  consistent with Eintein's constraint equations.  The induced preheating of the  metric fluctuations is not large enough to backreact onto the fields, but preheating of the scalar modes does affect the evolution of vector and tensor modes. In particular, they do enhance the induced stochastic background of gravitational waves during preheating, giving an energy density  in general an order of magnitude larger than that obtained by
evolving the  tensors fluctuations in an homogeneous background metric. This enhancement can improve the expectations for detection by planned gravitational waves observatories.