DARK MATTER AND SELF-INTERACTING DARK MATTER (SIDM) THEORY

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TAG: GS 3: SCIENCE AND TECHNOLOGY

THE CONTEXT: Dark matter remains one of the most enigmatic components of the universe, constituting a substantial portion (around 85%) of its mass. However, its elusive nature—being nonluminous and undetectable via traditional means—has made it a challenging puzzle for astrophysicists and cosmologists.

The Dark Matter Conundrum

• Nature of Dark Matter:
  • Unlike normal matter, dark matter doesn’t interact via electromagnetic forces, making it invisible to telescopes and difficult to directly observe.
• The Cold Dark Matter Theory (CDM):
  • Prevailing theories, such as the CDM paradigm, suggest that dark matter particles are collisionless, influencing cosmic structure formation through gravitational effects.

Puzzles in Astrophysics

• High-Density Dark Matter Halo in Massive Elliptical Galaxies:
  • Observations of strong gravitational lensing revealed a high-density dark matter halo, challenging the expectations set by the CDM theory.
• Ultra-Diffuse Galaxies with Extremely Low Densities:
  • Conversely, ultra-diffuse galaxies exhibit remarkably low luminosity and dispersed distributions, posing another challenge to the CDM theory.

Introducing SIDM as a Solution

• Self-Interacting Dark Matter (SIDM) Theory:
  • SIDM proposes that dark matter particles interact through a dark force, allowing for self-collisions, particularly near the center of galaxies.
• Research Led by Hai-Bo Yu:
  • A team led by Professor Hai-Bo Yu from the University of California, Riverside, conducted a study exploring SIDM’s potential to address these astrophysical puzzles.

Simulations and Findings

• High-Resolution Simulations:
  • The research team conducted high-resolution simulations of cosmic structure formation incorporating strong dark matter self-interactions.
• Heat Transfer and Halo Density:
  • SIDM simulations revealed that self-interactions lead to heat transfer within halos, diversifying their central densities compared to their CDM counterparts.
• Reconciling Opposite Extremes:
  • SIDM’s ability to explain both high-density halos and ultra-diffuse galaxies challenges the limitations of the CDM paradigm.

Implications and Future Prospects

• Challenges to CDM Paradigm:
  • The puzzles presented by observations of different galactic structures pose challenges for the traditional CDM theory.
• SIDM as a Compelling Candidate:
  • SIDM emerges as a compelling candidate to reconcile these extremes, presenting a more intricate and dynamic view of dark matter.
• Encouraging Further Studies:
  • The team hopes their work encourages more investigations in this area, particularly leveraging upcoming astronomical observatories’ data, such as the James Webb Space Telescope and the Rubin Observatory.
• Significance of Observational Probes and Simulations:
  • This study underscores the significance of utilizing astrophysical observations and sophisticated simulations to understand dark matter’s properties and behaviour.

Conclusion

• The study by Hai-Bo Yu and collaborators sheds light on the potential of SIDM to address the discrepancies observed in the distribution and density of dark matter within different galactic structures.
• By challenging the prevailing CDM paradigm, this research paves the way for a deeper understanding of dark matter’s complexities, urging further exploration and investigation in this intriguing field.

SOURCE: https://phys.org/news/2023-12-dark-theory-puzzles-astrophysics.html