Matter antimatter and dark matter
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Matter, Antimatter, and Dark Matter: A Comprehensive Overview
Matter-Antimatter Asymmetry in the Universe
The universe exhibits a significant asymmetry between matter and antimatter, a phenomenon that has intrigued scientists for decades. Observational evidence suggests that the early universe had a matter-antimatter imbalance, leading to the predominance of matter we observe today . This asymmetry is believed to have originated from processes in the early universe, such as baryogenesis, which dynamically generated more matter than antimatter . Theoretical models, including those involving spacetime torsion and the Einstein-Cartan-Sciama-Kibble theory of gravity, propose mechanisms where fermions and antifermions decay asymmetrically due to differences in energy levels at high densities, contributing to the observed matter-antimatter imbalance .
Antimatter as a Dark Matter Candidate
Antimatter has also been proposed as a candidate for dark matter. One intriguing concept is antimatter macroscopic dark matter (macros), which interacts with ordinary matter primarily through annihilation with large cross-sections. While various observations have constrained parts of the anti-macro parameter space, significant regions, especially those involving nuclear-dense objects, remain unexplored . Additionally, experiments have placed direct constraints on the interaction of antiprotons with axion-like dark matter particles, suggesting that antimatter could play a role in the dark matter puzzle Smorra2019Carosi2019.
The Role of Dark Matter in the Universe
Dark matter constitutes a significant portion of the universe's mass, yet its microscopic properties remain elusive. It is estimated that dark matter makes up about 27% of the universe's energy density, vastly outweighing the 5% attributed to ordinary matter . Various theories propose that dark matter could interact with antimatter differently than with matter, potentially linking the matter-antimatter asymmetry to dark matter properties . For instance, the interaction of ultralight axion-like particles with antiprotons has been studied to understand these potential differences .
Theoretical Models Connecting Matter, Antimatter, and Dark Matter
Several theoretical models attempt to explain the connections between matter, antimatter, and dark matter. One such model involves the interference of tree-level diagrams, where the imaginary part of the Breit-Wigner propagator for an unstable mediator plays a crucial role. This model suggests that the real part of the neutral component of an inert doublet could serve as a cold dark matter candidate, linking the evolution of dark matter relic density with baryon asymmetry . Another model proposes that interactions between ordinary and mirror matter in the early universe could co-generate baryon asymmetries, leading to phenomena such as neutron-antineutron oscillations .
Conclusion
The interplay between matter, antimatter, and dark matter remains one of the most fascinating and complex topics in modern physics. While significant progress has been made in understanding the matter-antimatter asymmetry and exploring antimatter as a dark matter candidate, many questions remain unanswered. Ongoing research and experiments continue to probe these mysteries, offering the potential for groundbreaking discoveries that could reshape our understanding of the universe.
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