MOND still looks respectable good compared to various dark matter particle models in the SPARC database of galaxies.
The observed rotation velocities of spiral galaxies at large scales exceed those predicted by their baryonic components, motivating the need for dark matter (DM) or Modified Newtonian Dynamics (MOND). We fit the rotation curves of 147 late-type galaxies from the SPARC database, using a suite of models including Cold Dark Matter (CDM) models with and without baryonic feedback, Warm DM, Fuzzy DM, and MOND. We also combine SPARC kinematics with weak-lensing data to extend the mean rotation curves to ~1 Mpc. On a galaxy-by-galaxy basis, the inner SPARC rotation curves marginally favour CDM models with baryonic feedback, although accounting for the uncertainties in distances and inclinations increases the degeneracy among DM-based models and MOND. All DM models predict host halo masses larger than abundance-matching expectations, with only the CDM model with baryonic feedback reducing the scatter around the mean luminosity-halo mass relation. MOND is able to reproduce the flatness of the mean galactic rotation curves on scales up to 1 Mpc, providing stellar mass-to-light ratios within observational uncertainties. In contrast, all DM models, without the contribution of mass external to the bound halo, struggle to explain the flat rotation curves. The inclusion of the current weak-lensing data tends to favour MOND over DM models, at least at the largest scales. Future observations from BIG-SPARC, the Square Kilometre Array, and most importantly, upcoming weak-lensing surveys such as EUCLID and Rubin will provide more stringent and independent tests of these competing frameworks.
Amy Smith, et al., "Dark Matter and MOND successes and degeneracies in reproducing SPARC rotation curves and weak lensing data" arXiv:2610.33157 (October 23, 2026) (Accepted at MNRAS).
Triton Station also has a new post comparing dark matter particle theories and MOND. The summary is as follows:
could you or Mitchell comment on
ReplyDeleteClosing the Loop: from EPRL-FK spinfoams to Regge dynamics
Matteo Bruno, Pietro Donà, Gowrisankar Sreeram
We study the semiclassical limit of the EPRL-FK model on a fixed simplicial complex. We ask what additional condition is needed for its variational principle to reproduce the equations of motion of Regge calculus, the standard discretization of General Relativity. This limit differs and complements the definition of the semiclassical regime in which, for suitable boundary states and a sufficiently refined simplicial complex, spinfoam amplitudes approximate gravitational transition amplitudes to a prescribed accuracy. We recast the EPRL-FK model in wedge-holonomy variables and identify geometric closure as the missing condition. We prove that imposing geometric closure as an additional constraint alongside local flatness allows us to reconstruct curved geometries. On a regular, nondegenerate Lorentzian branch with spacelike tetrahedra, these constraints define a surface equivalent to the space of length-Regge geometries, modulo gauge. The wedge action restricted to this surface becomes the Regge action, and variations tangent to this surface yield the length-Regge equations. We propose a way to implement geometric closure directly in the spinfoam amplitude. With this additional constraint, the EPRL-FK model is equivalent to Regge calculus in its semiclassical regime on a fixed simplicial complex.
Comments: 48 pages, 11 figures v2 - Added more references, modified the Introduction and the Abstract to reflect this addition that complements the analysis
Subjects: General Relativity and Quantum Cosmology (gr-qc)
Cite as: arXiv:2609.37179 [gr-qc]
does this means that EPRL-FK mode spinfoam equivalent to Regge calculus Regge calculus is standard discretization of General Relativity that so EPRL-FK mode spinfoam succeeds in 4d General Relativity
The paper looks interesting, but I don't have the time to review and analyze it in depth. I spent last week on vacation in Cancun, almost entirely offline, and then skimmed the week's worth of arXiv preprints this week upon returning.
ReplyDeletedo you think if spinfoam dynamics is equivalent to Regge calculus in its semiclassical regime and Regge calculus is the standard discretization of General Relativity that spinfoam dynamics is equivalent to General Relativity?
ReplyDelete