A Probe of Planck Energy Physics

Large scale voids are a very prominent feature in recent redshift surveys: here we attempt an explanation in terms of a first order phase transition occurring during the slow roll epoch of a two field inflation, a process where one field drives the slow roll while the other undergoes quantum tunneling through a potential barrier. The ensuing bubble like perturbations – nucleated at a number of e-folds N ≈ 55 before reheating – are thought to be the precursors of the voids we observe today, while the zero-point fluctuations of the inflaton are the small, Gaussian perturbations seen by COBE on the large angular scales. If this is so, primordial bubbles must have left a trace on the CMB, unless Silk damping and/or early reionization have erased it. We predict this imprint to have power on small angular scales, ≈ 10 arcmin or ≈ ≈ 1000. Therefore the physics at the Planck energy may be tested astronomically both indirectly through the large scale structure and directly through the forthcoming high resolution MAP and Planck satellites.