Review: Recent Advances in Beyond the Standard Model Cosmology

Introduction: The standard cosmological model incorporates concepts like inflation, baryosynthesis, and dark matter/energy, which are believed to extend Beyond the Standard Model (BSM) of fundamental physics. The paper explores various BSM cosmological features, which include signals that challenge the standard ΛCDM cosmology. These signals are discussed in the context of their potential to reduce the number of viable cosmological models, thus helping to refine our understanding of the universe’s underlying physics.

Key Topics Covered:

1. Dark Atom Signatures in Direct Dark Matter Searches:
   • The DAMA/NaI and DAMA/LIBRA experiments have shown positive results for dark matter detection, which contrast with the negative results from other experiments. (The DAMA/NaI experiment investigated the presence of dark matter particles in the galactic halo by exploiting the model-independent annual modulation signature, and DAMA/LIBRA is also dark matter detector. Both are located underground in Italy. ) This has led to the exploration of non-WIMP (Weakly Interacting Massive Particles) interpretations, particularly the dark atom hypothesis.
   • Dark atoms, consisting of stable particles with multiple charges, could explain the positive results observed. These atoms interact with ordinary matter through nuclear forces, which might explain why they evade detection by conventional WIMP searches.
2. Axion-Like Particle (ALP) Models:
   • The paper delves into the role of ALPs as candidates for dark matter. These particles emerge from the breaking of global U(1) symmetry and behave like cold dark matter during the growth of cosmic structures.
   • The study explores how ALP-induced primordial inhomogeneities could lead to the formation of structures like primordial black holes (PBHs) and could contribute to the recently discovered Stochastic Gravitational Wave Background (SGWB) and the early galaxy formation observed by the James Webb Space Telescope (JWST).
3. Primordial Inhomogeneities from ALP Physics:
   • ALPs could create large inhomogeneities in the early universe, potentially leading to the formation of PBHs and contributing to cosmic phenomena like gravitational waves and early galaxy formation.
   • The potential for these inhomogeneities to result in closed domain walls and eventually wormholes or baby universes is also discussed, providing a possible link between ALP physics and recent cosmological observations.
4. Antimatter Domains in a Baryon Asymmetrical Universe:
   • The paper touches on the possibility of antimatter domains within the universe, which could have survived from the early universe due to inhomogeneous baryosynthesis.
   • These domains might explain the existence of antimatter in the form of large structures, like globular clusters, within the Milky Way, potentially detectable through future cosmic ray experiments.

Conclusion: The paper highlights several open problems and potential avenues for future research within the realm of BSM cosmology. The discussion emphasizes the need for further exploration of dark atom models, ALP physics, and antimatter domains to refine our understanding of the universe and its fundamental physics.