Primordial Bubbles within Primordial Bubbles

Two consecutive, distinct episodes of phase transition occurring during inflation may nucleate two generations of bubbles, one inside the other. We design a model of inflation that realizes this sequence and yields bubble spectra that are bimodal and tunable functions of phenomelogical parameters in turn combinations of microphysical parameters. We argue in favor of a tuning of the parameters such that the outer and earlier generation of bubbles becomes hundreds of Mpc/h in diameter (like the local Hubble bubbles of the literature) whereas the inner and later generation becomes tens of Mpc/h in diameter (like the observed large scale voids).