Can a relativistic MOND theory fit clusters and the CMB without dark matter?
In plain words
MOND explains galaxy rotation well but still leaves missing mass in galaxy clusters and has trouble with the pattern of the cosmic microwave background. The question is whether any complete version of the theory fixes this without adding unseen matter.
Precise statement
In MOND, galaxy clusters retain a mass discrepancy of a factor $\sim 2$ in their cores, and the Bullet Cluster shows lensing mass offset from the gas. Determine whether a relativistic MOND theory (for example the aether-scalar-tensor theory AeST of Skordis and Zlosnik, 2021) simultaneously fits cluster hydrostatic and lensing masses, the CMB acoustic peaks and the matter power spectrum with only baryons and standard neutrinos. Answer yes with an explicit joint fit, or no for AeST and its published generalizations by showing that the cluster and CMB fits cannot both be met.
What would settle it
Joint fits of a fully specified relativistic MOND theory to Planck and ACT CMB spectra, galaxy clustering and cluster lensing profiles.
Status in the literature
AeST reproduces the Planck temperature spectrum and the linear matter power spectrum (2021); a joint fit including cluster masses and lensing has not been demonstrated.