Overview of "The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology"
This paper by Pavel Kroupa scrutinizes the current standard model of cosmology (SMoC), focusing on the implications of dark matter (DM) in structure formation and dynamics, particularly in dwarf galaxies. The author challenges the prevailing dark matter paradigm by presenting observational data and logical arguments, suggesting alternative explanations for observed cosmic phenomena.
Kroupa's central thesis is articulated through the "Dual Dwarf Galaxy Theorem," which posits that if the SMoC is valid, two distinct types of dwarf galaxies must exist: type A, which are dark matter-dominated, and type B, which are dynamically formed tidal dwarf galaxies (TDGs) devoid of dark matter. The existence of only one observable type—arguably type B—is used to question the validity of the SMoC.
Critical Analysis of Dwarf Galaxies
The paper examines the properties and distribution of dwarf galaxies, particularly the satellites of the Milky Way (MW). Observations show that these satellites do not align with the expected isotropy and mass distribution predicted by the dark matter hypothesis. Instead, they form a Vast Polar Structure (VPOS) around the MW, suggestive of a phase-space correlation expected if they were TDGs formed in galactic interactions. Furthermore, the Baryonic Tully-Fisher (BTF) relation is observed for TDGs, contradicting the notion that it is a haLLMark of dark matter-dominated galaxies.
Theoretical and Observational Challenges
Kroupa highlights several inconsistencies within the SMoC:
- Missing Satellites and Isotropy: The observed paucity of satellite galaxies and their anisotropic distribution challenge the predicted dark matter sub-halo formation.
- Baryonic Tully-Fisher Relation: The alignment of TDGs with the BTF relation suggests a commonality in rotational dynamics that contradicts the dark matter model, which would predict deviation for non-dark matter-dominated systems.
- Phase-Space Distribution: The VPOS comprising satellites, young halo globular clusters, and tidally induced streams presents a coherent structure unlikely to arise from accretion of dark matter sub-haloes.
Alternative Explanations: Milgromian Dynamics
Kroupa discusses Milgromian dynamics (MOND) as a potential alternative to the dark matter paradigm. MOND, modifying Newtonian dynamics at low accelerations, accounts for galactic rotation curves and the MDA correlation without invoking dark matter. Recent developments embed MOND within relativistic frameworks, offering a coherent cosmological model alternative that addresses both galactic dynamics and large-scale structure formation.
Implications and Future Research
The paper's implications are profound, questioning the very existence of dark matter as envisioned in the SMoC and urging the consideration of modified gravity theories. Future research directions include:
- Empirical verification of MOND across various cosmic scales.
- Comprehensive surveys of satellite systems around different galaxy types to test the bulge-satellite correlation.
- High-resolution simulations in a Milgromian universe to explore structure formation and the emergence of VPOS-like arrangements.
In sum, Kroupa's paper challenges the bedrock assumptions of the SMoC, advocating for a reevaluation of dark matter's role in cosmology and supporting modified dynamic theories as plausible explanations for observed cosmic phenomena.