A New Relativistic Generalization Of MOND (And More)

This six page article is just a conference paper summary of a much more involved modified gravity theory and its implications. The abstract is silent on how well it handles galaxy cluster physics, which deviate (in a quite systemic way) from simple toy-model MOND theories, or the Hubble tension.

We propose an alternative scalar-tensor theory based on the Khronon scalar field labeling a family of space-like three-dimensional hypersurfaces. This theory leads to modified Newtonian dynamics (MOND) at galactic scales for stationary systems, recovers GR plus a cosmological constant in the strong field regime, and is in agreement with the standard cosmological model and the observed cosmic microwave background anisotropies.

Luc Blanchet, Constantinos Skordis, "Khronon-Tensor theory reproducing MOND and the cosmological model" arXiv:2507.00912 (July 1, 2025) (Contribution to the 2025 Gravitation session of the 59th Rencontres de Moriond).

A fuller explanation of the theory can be found here.

Another lengthy paper by P. S. Bhupal Dev et al., examines the constraints dark matter-neutrino interactions which are very strict.

We present a comprehensive analysis of the interactions of neutrinos with the dark sector within the simplified model framework. We first derive the exact analytic formulas for the differential scattering cross sections of neutrinos with scalar, fermion, and vector dark matter (DM) for light dark sector models with mediators of different types. We then implement the full catalog of constraints on the parameter space of the neutrino-DM and neutrino-mediator couplings and masses, including cosmological and astrophysical bounds coming from Big Bang Nucleosynthesis, Cosmic Microwave Background, DM and neutrino self-interactions, DM collisional damping, and astrophysical neutrino sources, as well as laboratory constraints from 3-body meson decays and invisible Z decays. 

We find that most of the benchmarks in the DM mass-coupling plane adopted in previous studies to get an observable neutrino-DM interaction effect are actually ruled out by a combination of the above-mentioned constraints, especially the laboratory ones which are robust against astrophysical uncertainties and independent of the cosmological history. 

To illustrate the consequences of our new results, we take the galactic supernova neutrinos in the MeV energy range as a concrete example and highlight the difficulties in finding any observable effect of neutrino-DM interactions. 

Finally, we identify new benchmark points potentially promising for future observational prospects of the attenuation of the galactic supernova neutrino flux and comment on their implications for the detection prospects in future large-volume neutrino experiments such as JUNO, Hyper-K, and DUNE. We also comment on the ultraviolet-embedding of the effective neutrino-DM couplings.