The distribution of radio galaxies and quasars that are observed is inconsistent the the Standard Model of Cosmology which asserts that at a sufficiently large scale the universal should look essentially the same in all directions aside from a correction based upon our vantage point of observation.
We present the first joint analysis of catalogs of radio galaxies and quasars to determine if their sky distribution is consistent with the standard ΛCDM model of cosmology. This model is based on the cosmological principle, which asserts that the universe is isotropic and homogeneous on large scales, so the observed dipole anisotropy in the cosmic microwave background (CMB) must be attributed to our local peculiar motion.
We test the null hypothesis that there is a dipole anisotropy in the sky distribution of radio galaxies and quasars consistent with the motion inferred from the CMB, as is expected for cosmologically distant sources. Our two samples, constructed respectively from the NRAO VLA Sky Survey and the Wide-field Infrared Survey Explorer, are systematically independent and have no shared objects.
Using a completely general, two dimensional definition of the p-value that accounts for correlation between the found dipole amplitude and its directional offset from the CMB dipole, the null hypothesis is independently rejected with p=7.9×10^−3 and p=9.9×10^−6 for the radio galaxy and quasar samples, respectively, corresponding to 2.7σ and 4.4σ significance. The joint significance, using sample size-weighted Z-scores, is 5.2σ. We show that the radio galaxy and quasar dipoles are consistent with each other and find no evidence for any frequency dependence of the amplitude.
Nathan Secrest, et al., "A Challenge To The Standard Cosmological Model", arXiv:2206.05624 (June 11, 2022).
does MOND better fits the observations
ReplyDeleteToy model MOND doesn't address the issue. MOND is only applicable in weak fields where astronomers and cosmologists typically use a Newtonian approximation, up to the galaxy length scale.
ReplyDeleteThis is an inherently relativistic issue at the maximal scale that it is possible to observe (basically, a collective measurement of all examples of a particular type of object in the entire sky), so many billions of light years, as opposed to thousands of light years.
There are two basic predictions of LambdaCDM that are tested: (1) that the universe as a whole is isotropic, which means basically that it is spherically symmetrical in the sense that the distribution of stars isn't statistically distinguishable in one direction relative to another (something we already know that LambdaCDM does not produce at the galaxy and galaxy group scale where contrary to theory we find galaxies aligned in a preferred plane rather than randomly over all spherical coordinates), and (2) that the universe is homogeneous at large enough scales, when in fact, the bubble-like or web-like structure of the universe persists up to the largest observable scales (in addition to being non-isotropic which is necessarily non-homogeneous at the largest scales), which implies that rather than being washed out as the universe expands, that the random inhomogeneity of the very early universe due to random quantum (and non-quantum) fluctuations is magnified as the universe expands.
While cosmological inflation theories are not part of LambdaCDM this result also tends to disfavor cosmological inflation, one of the main justifications for which is that smooths out deviations from isotropic and homogeneous structures that might otherwise be magnified as the universe expands.
Now, to be fair, one of the reasons that LambdaCDM assumes isotropy and homogeneity, is simply a matter of mathematical convenience. It is much easier to calculate analytical solutions to the history of the universe in a model with those assumptions (i.e. directly calculate a prediction with calculus) because you can do your calculations for a single light cone from a time near the Big Bang and then by symmetry assume that your calculations will hold in all directions, rather than because there are particularly strong theoretical motivations for these properties to be important. And, while it is an oversimplification, to get a mere 2.7 sigma statistical significance for the deviation from radio galaxies takes all 508,144 radio galaxies in a survey area making up 27% of the sky, and to get the 4.4 sigma significance for the quasar sample takes 98% of the 1.6 million quasars observed in a survey area making up 51% of the sky. The deviations from the LambdaCDM predictions are too subtle to observe at a statistically significant level, for example, in a sample of say 10,000 objects in 5% of the sky. So, the assumptions are sufficient to make good first order approximations, even though they ultimately don't hold experimentally, for a model that purports to describe all sorts of properties of the universe, with only about seven independent degrees of freedom.
But, while these are good convenience assumptions for a simple minimal model that is only a first order approximation, these assumptions are a problem if you take them too seriously as many cosmologists and astrophysicists do, because if you try to reverse engineer laws of physics and properties of dark matter and dark energy phenomena from the LambdaCDM model including these assumptions what you will come up with is qualitatively different (e.g. will tend to produce the wrong form of the relative equations) from laws of physics and properties of dark matter and dark energy that can actually reproduce what we observe.
Correction: "(e.g. will tend to produce the wrong form of the RELEVANT equations)"
ReplyDeleteIncidentally, while this is beyond the domain of applicability of toy model MOND (as opposed to one of the several general relativistic approximations of it) and while Deur's work hasn't really been worked out to make a prediction in this context, it is very likely that Deur's approach would perform better.
ReplyDeleteThis is because one of the core insights of Deur's work is that phenomena like dark matter and dark energy arise from plain vanilla General Relativity in cases where there is a lack of spherically symmetry which leads to gravitational field self-interactions that are far from negligible at the quite large scale of galaxies that are not spherically symmetric and galaxy clusters (which end up acting like a bunch of two point systems between member galaxies in the clusters), both of which are ubiquitous in real life.
The notion that these non-spherically symmetrical effects at galaxy and galaxy cluster scales might also encourage non-spherically symmetric structure in the universe as a whole, while it doesn't follow directly from this reality, is certainly more plausible and likely to follow in Deur's analysis than in conventional GR which simply doesn't even look at how and why non-spherically symmetric systems are so prone to arise at this scale.
interesting.
ReplyDeletein this paper,
MONG: An extension to galaxy clusters
Louise Rebecca (1,2), Arun Kenath (2), C Sivaram (3) ((1) Department of Physics, Christ Junior College, (2) Department of Physics and Electronics, CHRIST (Deemed to be University), (3) Indian Institute of Astrophysics)
The presence of dark matter, though well established by indirect evidence, is yet to be observed directly. Various dark matter detection experiments running for several years have yielded no positive results. In view of these negative results, we had earlier proposed alternate models by postulating a minimum gravitational field strength (minimum curvature) and a minimum acceleration. These postulates led to the modified Newtonian dynamics and modified Newtonian gravity (MONG). The observed flat rotation curves of galaxies were also accounted for through these postulates. Here we extend these postulates to galaxy clusters and model the dynamical velocity-distance curve for a typical cluster such as the Virgo cluster. The radial velocities of galaxies in the Virgo cluster are also obtained through this model. Observations show an inconsistency in the Hubble flow at a mean cluster distance of 17 Mpc, which is expected in regions of high matter density. This decrease in velocity is predicted by our model of modified gravity (MONG). The radial velocity versus distance relation for galaxies in the Virgo cluster obtained using MONG is in agreement with observations.
Comments: 9 pages, 2 figures, 21 equations
Subjects: General Relativity and Quantum Cosmology (gr-qc)
Cite as: arXiv:2205.12793 [gr-qc]
which was published
has been published in
https://www.worldscientific.com/worldscinet/mpla
https://www.worldscientific.com/doi/10.1142/S021773232250078X
page 3
they add both gravitational self-energy and dark energy to the poison equation to give rise to a MOND like physics
the gravitational self-energy sounds like Deur,
but they also add cosmological constant with reference 5-7
@neo
ReplyDeleteSaw and bookmarked the MONG paper. I'll probably read it in depth at some point. I agree that it is similar to Deur's approach and might even actually be basically the same thing, but the MONG theory is less well developed and fleshed out so I haven't put in the time to do that yet.