Anisotropies in the Cosmic Microwave Background
There are small variations in temperature in the CMB, as well as the signs of polarization along curved lines. My explanation for that is that we are seeing the remnants of overlapping blast waves from the early annihilation period. Even though the actual blast waves do not overlap (they push against each other, expanding the voids), the polarization curves reflect overlapping spheres. It is the radiation given off by the original blasts that overlap each other.