This evidence, if established more definitively, is a strong blow to basically all dark matter particle theories and a useful data point to distinguish different gravity based explanations of dark matter phenomena.
We use a new deprojection formula to infer the gravitational potential around isolated galaxies from weak gravitational lensing. The results imply circular velocity curves that remain flat for hundreds of kpc, greatly extending the classic result from 21 cm observations. Indeed, there is no clear hint of a decline out to 1 Mpc, well beyond the expected virial radii of dark matter halos. Binning the data by mass reveals a correlation with the flat circular speed that closely agrees with the Baryonic Tully-Fisher Relation known from kinematic data. These results apply to both early and late type galaxies, indicating a common universal behavior.
Tobias Mistele, Stacy McGaugh, Federico Lelli, James Schombert, Pengfei Li, "Indefinitely Flat Circular Velocities and the Baryonic Tully-Fisher Relation from Weak Lensing" arXiv:2406.09685 (June 14, 2024) (accepted for publication in ApJL).
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Primordial Black Holes with QCD Color Charge
Elba Alonso-Monsalve and David I. Kaiser
Phys. Rev. Lett. 132, 231402 – Published 6 June 2024
Physics logo See synopsis: Colorful Primordial Black Holes
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Abstract
We describe a realistic mechanism whereby black holes with significant QCD color charge could have formed during the early Universe. Primordial black holes (PBHs) could make up a significant fraction of the dark matter if they formed well before the QCD confinement transition. Such PBHs would form by absorbing unconfined quarks and gluons and hence could acquire a net color charge. We estimate the number of PBHs per Hubble volume with near-extremal color charge for various scenarios and discuss possible phenomenological implications.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.231402
Not convincing at all. Net QCD color charge would be completely unprecedented and there is just no positive evidence for any primordial black holes, let alone a significant number of them that survive to the present.
The behavior of a black hole with net color charge seems theoretically interesting. I have a feeling it would be connected by color flux to the other particles of the quark-gluon plasma from which it was formed, and that the flux lines would be broken by pair creation which would lead to color-neutralization of the black hole. But this should be argued for, in a more rigorous way.
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