The Standard Model of Cosmology a.k.a. LambdaCDM model a.k.a. Concordance Model of Cosmology, doesn't predict the tight relationship between the distribution of star in galaxies and the location of dark matter inferred from the dynamics and lensing in the vicinity of those stars.

Another thing which is observed, but not predicted by the Concordance Model is the fairly strong correlation between a galaxy's bulge size and its number of satellite galaxies. But, that structure is also present in the data. A new paper confirms that there is a correlation and that the Concordance Model doesn't predict its existence.

There is a correlation between bulge massof the three main galaxies of the Local Group (LG), i.e. M31, Milky Way (MW), and M33,and the number of their dwarf spheroidal galaxies. A similar correlation has also been reported for spiral galaxies with comparable luminosities outside the LG. These correlations do not appear to be expected in standard hierarchical galaxy formation.In this contribution, and for the first time, we present a quantitative investigation of the expectations of the standard model of cosmology for this possible relation using a galaxy catalogue based on the Millennium-II simulation. Our main sample consists of disk galaxies at the centers of halos with a range of virial masses similar to M33, MW, and M31. For this sample, we find an average trend (though with very large scatter) similar to the one observed in the LG; disk galaxies in heavier halos on average host heavier bulges and larger number of satellites. In addition,we study sub-samples of disk galaxies with very similar stellar or halo masses (but spanning a range of 2-3 orders of magnitude in bulge mass) and find no obvious trend in the number of satellites vs. bulge mass. We conclude that while for a wide galaxy mass range a relation arises (which seems to be a manifestation of the satellite number - halo mass correlation), for a narrow one there is no relation between number of satellites and bulge mass in the standard model.Further studies are needed to better understand the expectations of the standard model for this possible relation.

B. Javanmardi, M. Raouf, H. G. Khosroshahi, S. Tavasoli, O. Müller, A. Molaeinezhad, "The number of dwarf satellites of disk galaxies versus their bulge mass in the standard model of cosmology" (November 21, 2018) (accepted in The Astrophysical Journal).

This is quite powerful, despite a firstly thin data set to establish the correlation that exists in the real world, because it is a problem with lambdaCDM that is independent of its inaccurate expectations about where dark matter is located. A new paper continuing this line of research is the following one:

Yingjie Jing, et al., "The dark matter deficit galaxies in hydrodynamical simulations" (November 22, 2018).Low mass galaxies are expected to be dark matter dominated even within their centrals.Recently two observations reported two dwarf galaxies in group environment with very little dark matter in their centrals. We explore the population and origins of dark matter deficit galaxies (DMDGs) in two state-of-the-art hydrodynamical simulations, the EAGLE and Illustris projects.For all satellite galaxies withM∗>109 M⊙ in groups withM200>1013 M⊙ , we find that about5.0% of them in the EAGLE, and3.2% in the Illustris are DMDGs with dark matter fractions below50% inside two times half-stellar-mass radii. We demonstrate that DMDGs are highly tidal disrupted galaxies; and because dark matter has higher binding energy than stars, mass loss of the dark matter is much more rapid than stars in DMDGs during tidal interactions.If DMDGs were confirmed in observations, they are expected in current galaxy formation models.

Another problem, somewhat related to the unexpected structure in inferred dark matter distributions, is that a very large swath of the parameter space of particles that interact with Standard Model matter non-gravitationally has been excluded experimentally, but the tight alignment of stars and inferred dark matter distributions implies that if dark matter is real that it has to have non-trivial, non-gravitational interactions with stars and other ordinary matter. Truly "sterile" dark matter which doesn't interact with anything non-gravitationally, which would be "collisionless", as lambdaCDM assumes that dark matter comes close to, has basically been ruled out experimentally.

In addition to these two relatively independent problems, lambdaCDM also has a problem with its chronology of the moderately early universe. This gives rise to the "Impossible Early Galaxies" problem, and to 21cm radiation wavelength lines that fail to show the behavior expected in a world with dark matter at roughly the end of the "radiation era".

While correlation is not causation, most strong correlations in nature have a cause of some kind. Figuring out which set is the cause and which is the effect can be difficult, or can even be a category error. But, there is almost always some reason for the relationship.

Because the Concordance Model fails to explain multiple independent phenomena that show correlations, it is probably wrong. Not wildly totally wrong, because it does get lots of things that we can confirm with astronomy at very large scales right. But, significantly, deeply flawed.

It only took the one flaw to convince me that something was amiss with the Concordance Model. But, lots of people who are less skeptical of lambdaCDM than I am, are going to start looking for alternatives as multiple, significant, seemingly independent breaks between the Concordance Model and observed reality emerge.

I, of course, think (although I can't personally rigorously prove it) that pretty much all of the flaws of lambdaCDM exist because we have misunderstood some important second and third order quantum gravitational effects that matter in very weak gravitational fields in very high mass systems. My very strong intuition is that, in reality, there is both no dark matter and no dark energy, apart of fields of Standard Model fundamental particles and gravitons. But, I don't expect that paradigm shift to spread all that quickly, unless a rising star popularizes a solution of that kind of a mass scale within the physics and physics journalism communities.

Meanwhile, another promising modified gravity theory has emerged.

Meanwhile, another promising modified gravity theory has emerged.

We have recently shown that the baryonic Tully-Fisher (BTF) and Faber-Jackson (BFJ) relations imply that the gravitational "constant" G in the force law vary with acceleration a as 1/a. Here we derive the converse from first principles. First we obtain the gravitational potential for all accelerations and we formulate the Lagrangian for the central-force problem. Then action minimization implies the BTF/BFJ relations in the deep MOND limit as well as weak-field Weyl gravity in the Newtonian limit. TDimitris M. Christodoulou, Demosthenes Kazanas, "Gravitational Potential and Nonrelativistic Lagrangian in Modified Gravity with Varying G" (November 21, 2018).he results show how we can properly formulate a nonrelativistic conformal theory of modified dynamics that reduces to MOND in its low-acceleration limit and to Weyl gravity in the opposite limit. An unavoidable conclusion is that a0, the transitional acceleration in modified dynamics, does not have a cosmological origin and it may not even be constant among galaxies and galaxy clusters.

Further afield and mostly unrelated is the possibility that lots of the filamentary large scale structure of the universe could be driven by magnetism, which is usually assumed to be negligible and not influential in interstellar space. But, maybe not:

Evidence repeatedly suggests thatcosmological sheets, filaments and voids may be substantially magnetised today. The origin of magnetic fields in the intergalactic medium is however currently uncertain.We discuss a magnetogenesis mechanism based on the exchange of momentum between hard photons and electrons in an inhomogeneous intergalactic medium. Operating near ionising sources during the epoch of reionisation, it is capable of generating magnetic seeds of relevant strengths over scales comparable to the distance between ionising sources. Furthermore, when the contributions of all ionising sources and the distribution of gas inhomogeneities are taken into account, it leads, by the end of reionisation, to a level of magnetisation that may account for the current magnetic fields strengths in the cosmic web.

Mathieu Langer, Jean-Baptiste Durrive "Magnetising the Cosmic Web during Reionisation" (November 22, 2018).

MORE INTERESTING PAPERS (NO TIME TO FORMAT THEM, A RICH LOAD OF PAPERS TODAY FOR SOME REASON, PERHAPS A PRE-THANKSGIVING RUSH TO WRAP STUFF UP):

arXiv:1811.09197 [pdf, other]

Large-scale redshift space distortions in modified gravity theories

César Hernández-Aguayo, Jiamin Hou, Baojiu Li, Carlton M. Baugh, Ariel G. Sánchez

Comments: 18 pages, 11 figures, submitted to MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Measurements of redshift space distortions (RSD) provide a means to test models of gravity on large-scales. We use mock galaxy catalogues constructed from large N-body simulations of standard and modified gravity models to measure galaxy clustering in redshift space. We focus our attention on two of the most representative and popular families of modified gravity models: the Hu \& Sawicki f(R) gravity and the normal branch of the DGP model. The galaxy catalogues are built using a halo occupation distribution (HOD) prescription with the HOD parameters in the modified gravity models tuned to match with the number density and the real-space clustering of {\sc boss-cmass} galaxies. We employ two approaches to model RSD: the first is based on linear perturbation theory and the second models non-linear effects on small-scales by assuming standard gravity and including biasing and RSD effects. We measure the monopole to real-space correlation function ratio, the quadrupole to monopole ratio, clustering wedges and multipoles of the correlation function and use these statistics to find the constraints on the distortion parameter, β. We find that the linear model fails to reproduce the N-body simulation results and the true value of β on scales $s < 40\Mpch$, while the non-linear modelling of RSD recovers the value of β on the scales of interest for all models. RSD on large scales (s≳20-$40\Mpch$) have been found to show significant deviations from the prediction of standard gravity in the DGP models. However, the potential to use RSD to constrain f(R) models is less promising, due to the different screening mechanism in this model,

arXiv:1811.09222 [pdf, ps, other]

Beyond the Standard models of particle physics and cosmology

Maxim Yu. Khlopov

Comments: Prepared for Proceedings of XXI Bled Workshop "What comes beyond the Standard models?"

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

The modern Standard cosmological model of inflationary Universe and baryosynthesis deeply involves particle theory beyond the Standard model (BSM). Inevitably, models of BSM physics lead to cosmological scenarios beyond the Standard cosmological paradigm. Scenarios of dark atom cosmology in the context of puzzles of direct and indirect dark matter searches, of clusters of massive primordial black holes as the source of gravitational wave signals and of antimatter globular cluster as the source of cosmic antihelium are discussed.

arXiv:1811.09578 (cross-list from physics.gen-ph) [pdf, ps, other]
arXiv:1811.09308 [pdf, ps, other]
arXiv:1811.09179 [pdf, ps, other]
arXiv:1811.09262 [pdf, ps, other]
arXiv:1811.09378 [pdf, other]

Bound on the graviton mass from Chandra X-ray cluster sample

Sajal Gupta, Shantanu Desai

Comments: 5 pages, 1 figure

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

MORE INTERESTING PAPERS (NO TIME TO FORMAT THEM, A RICH LOAD OF PAPERS TODAY FOR SOME REASON, PERHAPS A PRE-THANKSGIVING RUSH TO WRAP STUFF UP):

arXiv:1811.09197 [pdf, other]

Large-scale redshift space distortions in modified gravity theories

César Hernández-Aguayo, Jiamin Hou, Baojiu Li, Carlton M. Baugh, Ariel G. Sánchez

Comments: 18 pages, 11 figures, submitted to MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Measurements of redshift space distortions (RSD) provide a means to test models of gravity on large-scales. We use mock galaxy catalogues constructed from large N-body simulations of standard and modified gravity models to measure galaxy clustering in redshift space. We focus our attention on two of the most representative and popular families of modified gravity models: the Hu \& Sawicki f(R) gravity and the normal branch of the DGP model. The galaxy catalogues are built using a halo occupation distribution (HOD) prescription with the HOD parameters in the modified gravity models tuned to match with the number density and the real-space clustering of {\sc boss-cmass} galaxies. We employ two approaches to model RSD: the first is based on linear perturbation theory and the second models non-linear effects on small-scales by assuming standard gravity and including biasing and RSD effects. We measure the monopole to real-space correlation function ratio, the quadrupole to monopole ratio, clustering wedges and multipoles of the correlation function and use these statistics to find the constraints on the distortion parameter, β. We find that the linear model fails to reproduce the N-body simulation results and the true value of β on scales $s < 40\Mpch$, while the non-linear modelling of RSD recovers the value of β on the scales of interest for all models. RSD on large scales (s≳20-$40\Mpch$) have been found to show significant deviations from the prediction of standard gravity in the DGP models. However, the potential to use RSD to constrain f(R) models is less promising, due to the different screening mechanism in this model,

arXiv:1811.09222 [pdf, ps, other]

Beyond the Standard models of particle physics and cosmology

Maxim Yu. Khlopov

Comments: Prepared for Proceedings of XXI Bled Workshop "What comes beyond the Standard models?"

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

The modern Standard cosmological model of inflationary Universe and baryosynthesis deeply involves particle theory beyond the Standard model (BSM). Inevitably, models of BSM physics lead to cosmological scenarios beyond the Standard cosmological paradigm. Scenarios of dark atom cosmology in the context of puzzles of direct and indirect dark matter searches, of clusters of massive primordial black holes as the source of gravitational wave signals and of antimatter globular cluster as the source of cosmic antihelium are discussed.

Bound on the graviton mass from Chandra X-ray cluster sample

Sajal Gupta, Shantanu Desai

Comments: 5 pages, 1 figure

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

## 6 comments:

I'm sympathetic to MOND myself, but Ethan Siegal and Sean Carroll points out that both gravitational lensing and the third peak in the CMB "proves" dark matter or some type exists.

I think that galaxies obey MOND and modified gravity, so there's no dark matter except neutrinos and black holes within a galaxy, and dark matter in the form of micro black holes exist outside of galaxies to form clusters and filaments.

micro black holes may have dissipated by the time of the 21cm signal.

Ethan Siegal and Sean Carroll are wrong on that point, even though toy model MOND doesn't do those things. Indeed, I've cited a paper or two at this blog that demonstrates that it is possible in principle to create a third peak in the CMB with a modified gravity theory, and there is absolutely no reason why modified gravity that creates the appearance of DM (as, e.g. MOND does) would not give rise to corresponding gravitational lensing effects.

It is also worth noting that while lambdaCDM proves that there should be a third peak, the height of the third peak is an experimentally measured parameter of the theory and not a prediction. So, that is less impressive proof than it seems. LambdaCDM is the most parsimonious model to explain cosmology scale phenomena, but we can basically say with certainty now that it is not correct. So, we'll have to find some other model to explain what we see.

Neutrinos can't possible be dark matter. There aren't enough of them, they aren't heavy enough, and they are too "hot" to form large scale structure.

There is no evidence whatsoever that there have ever been micro-black holes and none have ever been seen. Indeed, given the theoretical limit on the smallest size a primordial black hole could be given evaporation from the time of the Big Bang (which is the only time that they could have formed) to the present, and the scales at which we can affirmatively rule out primordial black holes as a component of dark matter, there is very little parameter space left. I strongly suspect that they will find nothing.

"Neutrinos can't possible be dark matter. There aren't enough of them, they aren't heavy enough, and they are too "hot" to form large scale structure."

this is probably true. but large scale structure formation is different under MOND than in lamda cdm.

under lamda cdm, neutrinos are too hot to form large scale structure, but that is assuming GR holds

"There is no evidence whatsoever that there have ever been micro-black holes and none have ever been seen. Indeed, given the theoretical limit on the smallest size a primordial black hole could be given evaporation from the time of the Big Bang (which is the only time that they could have formed) to the present, and the scales at which we can affirmatively rule out primordial black holes as a component of dark matter, there is very little parameter space left. I strongly suspect that they will find nothing."

as astrophysics grad student on not even wrong said that the mainstream majority of actual astrophysicists accept the third peak explanation as some form of dark matter, it's not just Siegel and Sean Carroll's fringe opinion. it's the mainstream consensus.

no cold dark matter candidate of any kind has yet been identified

there is a list of possible candidates for dark matter, and on this list is micro-black holes.

https://www.livescience.com/62235-dark-matter-primordial-black-holes.htmlhttps://www.space.com/25691-dark-matter-black-hole-atoms.html

the papers i've seen ruling out primordial black holes as a component of dark matter posit black holes with sun sized masses or larger, not planck scale masses, using gravitational lensing

and perhaps micro-black holes evaporated by the time of the 21 cm signal, giving rise to a baryon only explanation, so that again, none are seen.

"as astrophysics grad student on not even wrong said that the mainstream majority of actual astrophysicists accept the third peak explanation as some form of dark matter, it's not just Siegel and Sean Carroll's fringe opinion. it's the mainstream consensus."

A third peak is definitely consistent with some form of dark matter, and the dark matter paradigm is still the leading view in the physics community. I certainly do not want to in any way suggest that Siegel or Sean Carroll's view is a fringe opinion.

But, the fact that it is consistent with some form of dark matter does not "prove" that there is dark matter. To the extent that they say that dark matter is the only possible explanation of the third peak they are simply wrong, no matter how many of their peers agree.

"the papers i've seen ruling out primordial black holes as a component of dark matter posit black holes with sun sized masses or larger, not planck scale masses, using gravitational lensing"

The maximum mass of primordial black holes is from gravitational lensing. The lower limit on their mass is from straightforward calculations of the amount of mass loss that would occur from Hawking radiation over 13.8 billion years.

I reviewed those limits in a 2016 post here: https://dispatchesfromturtleisland.blogspot.com/2016/09/machos.html

"The sweet spot is 10^22 kilograms, which is a bit less than the mass of the Moon (which is 7*10^22 kilograms), plus or minus, which would imply a typical primordial black hole with an event horizon radius of even less than 8.4 millimeters.""

Hawking radiation implies a minimum primordial black hole mass of 10^12 kg. This is on the order of the same mass as Deimos, a moon of the planet Mars with a radius of about 6 km.

"perhaps micro-black holes evaporated by the time of the 21 cm signal, giving rise to a baryon only explanation, so that again, none are seen."

If they evaporate by the time of the 21 cm signal, then lambdaCDM falls apart. There are very strong experimental limits on minimum dark matter lifetime, in a dark matter paradigm. lambdaCDM assumes that the dark matter mass of the universe is approximately constant at all times.

Oops. Deimos is 1000 times the mass of the smallest possible black hole (unit confusion). So, a better comparison would be a 600 meter radius asteroid.

i'm not aware of any non-DM explanation of the third peak, even stacy mcgaugh in his latest post says as much.

there are papers that suggest hawking radiation emitted by a primordial black hole decays until there is a remnant. similar to a cold white dwarf. this remnant could still exist in some theories and be dark matter.

"If they evaporate by the time of the 21 cm signal, then lambdaCDM falls apart. There are very strong experimental limits on minimum dark matter lifetime, in a dark matter paradigm. lambdaCDM assumes that the dark matter mass of the universe is approximately constant at all times."

the links i provided suggest of primordial black holes that are atomic in mass, not asteroid. and that they are the end stage of hawking radiation.

the constraints you provided on primordial black holes have a lot more mass than this, and is based on gravitational lensing.

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