Explain the origin of the Universe’s matter–antimatter asymmetry

Develop a successful mechanism for the creation of primordial protons, neutrons, and electrons—baryogenesis and leptogenesis—that accounts for the observed surplus of matter over antimatter in the Universe.

Background

The paper reviews Sakharov’s conditions (baryon number violation, C and CP violation, and departure from thermal equilibrium) and notes that, within the Standard Model, these effects are insufficient by several orders of magnitude to generate the observed baryon asymmetry.

Thus, identifying a viable baryogenesis/leptogenesis mechanism remains an outstanding challenge in particle physics and cosmology.