Ribbons on the Cosmic Background Radiation Sky: A Powerful Test of a Baryon Symmetric Universe

If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the cosmic background radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width θ_w∼0.1°separated by angle θ_w∼1°(L/100h_-1Mpc) L is the characteristic domain size) and with distortion parameter y≈10^-6. Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric.