Subdegree Cosmic Microwave Background Anisotropies from Inflationary Bubbles

It is well known that processes of first order phase transitions may haveoccurred in the inflationary era. If one or more occurred well before the endof inflation, the nucleated bubbles are stretched to large scales and theprimordial power spectrum contains a scale dependent non-Gaussian componentprovided by the remnants of the bubbles. We predict the anisotropies in thecosmic microwave background (CMB) induced by inflationary bubbles. We build ageneral analytic model for describing a bubbly perturbation; we evolve eachFourier mode using the linear theory of perturbations from reheating untildecoupling; we get the CMB anisotropies by considering the bubbly perturbationintersecting the last scattering surface. The CMB image of an inflationarybubble is a series of concentric isothermal rings of different color (sign of$\delta T/T$) on the scale of the sound horizon at decoupling ($\le 1^{o}$ inthe sky); the resulting anisotropy is therefore strongly non-Gaussian. The meanamplitude of $\delta T/T$ for a bubble of size $L$ follows the known estimatesfor linear perturbations, $\delta T/T\simeq\delta\rho /\rho\cdot(L/H^{-1})^{2}$. In particular, bubbles with size corresponding to the seeds ofthe observed large scale voids (tens of comoving Mpc) induce an interestingpattern of CMB anisotropies on the sub-degree angular scale, to be furtherinvestigated and compared with the forthcoming high resolution CMB mapsprovided by the MAP and the Planck experiments.Comment: 10 pages, 5 postscript figures, accepted by Ap.