Gauge coupling unification and nonequilibrium thermal dark matter

Area of Science:

• Cosmology
• Particle Physics
• Astroparticle Physics

Background:

• The origin of dark matter remains a significant mystery in cosmology.
• Existing models often rely on dark matter being in thermal equilibrium with the early universe.
• Inflationary reheating is a crucial epoch for particle production in the early universe.

Purpose of the Study:

• To investigate a non-thermal production mechanism for dark matter.
• To explore models with an extra U(1) gauge symmetry for dark matter generation.
• To connect dark matter production with gauge coupling unification.

Main Methods:

• Studying a model with an extra U(1) gauge symmetry broken at an intermediate scale.
• Utilizing a massive mediator particle with a mass above the reheating scale.
• Analyzing the dark matter abundance via the relation T(RH)^3 / M(int)^4.

Main Results:

• A viable dark matter candidate is identified as a standard model singlet charged under the extra U(1).
• The model allows for gauge coupling unification at a higher grand unification scale.
• The dark matter abundance is determined by the reheating temperature and intermediate scale, independent of thermal equilibrium.

Conclusions:

• The proposed non-thermal dark matter production mechanism is consistent with gauge coupling unification.
• The model predicts specific relationships between the reheating temperature and the intermediate symmetry breaking scale.
• This framework offers a new perspective on dark matter origins, linking it to grand unified theories.