Locate annihilation boundaries between matter and antimatter domains

Determine whether annihilation boundaries between matter domains and antimatter domains exist in the Universe and, if so, identify them through analyses of the diffuse gamma-ray background and the cosmic microwave background radiation.

Background

The paper discusses that primordial antimatter could persist in isolated regions, potentially producing observable signatures where matter and antimatter domains meet. It highlights two observational fronts—diffuse gamma-ray background (DGRB) and cosmic microwave background (CMB)—as probes that could reveal such domain boundaries.

The authors note that the locations or even existence of these annihilation boundaries are not established, and non-observations to date mainly set upper bounds on antimatter abundance.