An Annotated List Of Thirty-Three ΛCDM Issues

This post summarizes 33 issues with the ΛCDM "Standard Model of Cosmology" all in one place with annotations to sources discussing each of these issues, but in no particular order.

Some of these issues may someday be convincingly refuted. But, others have been identified repeatedly by independent groups of scientists and have been known for a long time without a satisfactory resolution and have grown stronger as better data has become available. Counting ideas is always a slippery matter and there is room to argue that I should have lumped some of these together or that I should have split some of them up into sub-issues. One can also legitimately argue that some of these are apples and oranges because they involved different kinds of issues. But, collectively, they provide a robust challenge to the ΛCDM model's correctness.

* the wrong gravitational lensing around galaxies in clusters 

(see Massimo Meneghetti, et al., "An excess of small-scale gravitational lenses observed in galaxy clusters" 369 (6509) Science 147-1351 (September 11, 2020). DOI: 10.1126/science.aax5164)

* KIDS evidence of less clumpy structure than predicted 

(see the KIDS website).

* the Hubble tension 

(see, e.g., Adam G. Riess, et al., "A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team" arXiv:2112.04510 (December 8, 2021)).

* the wrong DM halo shapes in galaxies 

(see, e.g., James S. Bullock, Michael Boylan-Kolchin, "Small-Scale Challenges to the ΛCDM Paradigm" (July 13, 2017, last updated September 2, 2019), Pengfei Li, Federico Lelli, Stacy McGaugh, James Schombert, "A comprehensive catalog of dark matter halo models for SPARC galaxies" (January 28, 2020). arXiv 2001.10538; Zhao-Qiang Shen, Guan-Wen Yuan, Cheng-Zi Jiang, Yue-Lin Sming Tsai, Qiang Yuan, Yi-Zhong Fan, "Exploring dark matter spike distribution around the Galactic centre with stellar orbits" arXiv:2303.09284 (March 16, 2023) (To be submitted to MNRAS), Mariia Khelashvili, Anton Rudakovskyi, Sabine Hossenfelder, “Dark matter profiles of SPARC galaxies: a challenge to fuzzy dark matter” arXiv:2207.14165 (July 28, 2022); Nicolas Loizeau, Glennys R. Farrar, “Galaxy rotation curves disfavor traditional and self-interacting dark matter halos, preferring a disk component or ad-hoc Einasto function” arXiv 2105:00119 (April 30, 2021); Daniel B Thomas, Michael Kopp, Katarina Markovič, "Using large scale structure data and a halo model to constrain Generalised Dark Matter" arXiv:1905.02739 (May 7, 2019 last updated May 4, 2020) https://doi.org/10.1093/mnras/stz2559; Marie Korsaga, et al., “GHASP: an Hα kinematics survey of spiral galaxies – XII. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using Rc-band photometry” (September 17, 2018); Theodorus Maria Nieuwenhuizen “Subjecting dark matter candidates to the cluster test” (October 3, 2017); Lin Wang, Da-Ming Chen, Ran Li “The total density profile of DM halos fitted from strong lensing” (July 31, 2017); James S. Bullock, Michael Boylan-Kolchin, “Small-Scale Challenges to the ΛCDM Paradigm” arXiv 1707.04256 (July 13, 2017, last updated September 2, 2019); Davi C. Rodrigues, Antonino del Popolo, Valerio Marra, Paulo L. C. de Oliveira, "Evidences against cuspy dark matter halos in large galaxies" arXiv:1701.02698 (January 10, 2017, last revised 13 June 13, 2017) (accepted in MINRAS) and P.L. Biermann, H.J. de Vega, N.G. Sanchez, "Highlights and Conclusions of the Chalonge Meudon workshop 2012: warm dark matter galaxy formation in agreement with observations" arXiv:1305.7452 (May 31, 2013 last revised June 26, 2013))

* excessively tight DM-ordinary matter correlations 

(see, e.g., Paolo Salucci, "The distribution of dark matter in galaxies" (November 21, 2018) (60 pages, 28 Figures ~220 refs. Invited review for The Astronomy and Astrophysics Review), Antonino Del Popolo et al., "Correlations between the Dark Matter and Baryonic Properties of CLASH Galaxy Clusters" (August 6, 2018), https://arxiv.org/abs/2008.04052, and Man Ho Chan, "Two mysterious universal dark matter-baryon relations in galaxies and galaxy clusters" arXiv:2212.01018 (December 2, 2022) (Accepted in Physics of the Dark Universe), Xuejian Shen, Thejs Brinckmann, David Rapetti, Mark Vogelsberger, Adam Mantz, Jesús Zavala, Steven W. Allen, "X-ray morphology of cluster-mass haloes in self-interacting dark matter" arXiv:2202.00038 (January 31, 2022, last revised November 1, 2022) (accepted by MNRAS); Aidan Zentner, Siddharth Dandavate, Oren Slone, Mariangela Lisanti, “A Critical Assessment of Solutions to the Galaxy Diversity Problem” arXiv:2202.00012 (January 31, 2022); Lorenzo Posti, S. Michael Fall “Dynamical evidence for a morphology-dependent relation between the stellar and halo masses of galaxies” arXiv:2102.11282 (February 22, 2021) (Accepted for publication in A&A); Camila A. Correa, Joop Schaye, "The dependence of the galaxy stellar-to-halo mass relation on galaxy morphology" arXiv:2010.01186 (October 2, 2020) (accepted for publication in MNRAS); Paolo Salucci, Nicola Turini, Chiara Di Paolo, "Paradigms and Scenarios for the Dark Matter Phenomenon" arXiv:2008.04052 (August 10, 2020); Paolo Salucci and Nicola Turini, “Evidences for Collisional Dark Matter In Galaxies?” (July 4, 2017); and Edo van Uitert, et al., “Halo ellipticity of GAMA galaxy groups from KiDS weak lensing” (October 13, 2016), Zhixing Li, Hong Guo, Yi Mao, “Theoretical Models of the Atomic Hydrogen Content in Dark Matter Halos” arXiv:2207.10414 (July 21, 2022)(distributions of hydrogen in interstellar space are also inconsistent with a dark matter particle that interacts only via gravity)

* the unexpected relationship between DM proportion and galaxy shape 

(see, e.g., David Winters, Alexandre Deur, Xiaochao Zheng, "New Analysis of Dark Matter in Elliptical Galaxies" arXiv:2207.02945 (July 6, 2022) (published at 518 (2) MNRAS 2845-2852 (2023)); arXiv:2010.01186, and arXiv:2004.05905))

* satellite galaxies in the galactic plane 

(see, e.g., Marcel S. Pawlowski, Pavel Kroupa "The Milky Way's Disk of Classical Satellite Galaxies in Light of Gaia DR2" arXiv (November 12, 2019) (Accepted for publication in MNRAS))

* too few satellite galaxies 

(see James S. Bullock, Michael Boylan-Kolchin, "Small-Scale Challenges to the ΛCDM Paradigm" (July 13, 2017, last updated September 2, 2019) arXiv 1707.04256)

* the unexpected relationship between bulge mass and number of satellite galaxies 

(see 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); Dark matter can't explain bulge formation in galaxies: Alyson M. Brooks, Charlotte R. Christensen, "Bulge Formation via Mergers in Cosmological Simulations" (12 Nov 2015))

* the wrong predicted halo mass function 

(see https://arxiv.org/abs/1911.00517)

* impossible early galaxies 

(see, e.g., Labbé, I., van Dokkum, P., Nelson, E. et al. "A population of red candidate massive galaxies ~600 Myr after the Big Bang." Nature (February 22, 2023). https://doi.org/10.1038/s41586-023-05786-2 (open access version available at https://arxiv.org/abs/2207.12446) Manoj K. Yennapureddy, Fulvio Melia, "A Cosmological Solution to the Impossibly Early Galaxy Problem" (March 19, 2018) and https://arxiv.org/abs/2002.11129))

* the EDGES 21 cm result 

(see https://www.nature.com/articles/nature25792)

* evidence for an external field effect 

(see https://arxiv.org/abs/2009.11525)

* evidence that the universe is not homogeneous and isotropic 

(see, e.g., arXiv:2009.14826)

* no dark matter galaxies 

(see Isabel M.E. Santos-Santos, et al., "Baryonic clues to the puzzling diversity of dwarf galaxy rotation curves" (November 20, 2019) (submitted to MNRAS) and Maria Luisa Buzzo, Duncan A. Forbes, Jean P. Brodie, Steven R. Janssens, Warrick J. Couch, Aaron J. Romanowsky, Jonah S. Gannon, "The large-scale structure of globular clusters in the NGC 1052 group" arXiv:2303.16375 (March 29, 2023) (Accepted for publication in MNRAS))

* lack of X-ray emissions in low surface brightness galaxies 

(see https://arxiv.org/abs/1906.05867)

* there are too few galaxy clusters 

(see https://arxiv.org/abs/1902.10837)

* it gets globular cluster formation wrong 

(see Peter Creasey, et al., "Globular Clusters Formed within Dark Halos I: present-day abundance, distribution and kinematics" (June 28, 2018) and Scarpa et al., "Globular Clusters as a Test for Gravity in the Weak Acceleration Regime" (2006) https://arxiv.org/abs/astro-ph/0601581)

* it doesn't explain apparent wide binary star discrepancies 

(see Hernandez et al., "Wide binaries as a critical test for Gravity theories" (2012) https://arxiv.org/abs/1205.5767)

* colliding clusters are too common and too fast 

(see, e.g., Jounghun Lee, Eiichiro Komatsu, "Bullet Cluster: A Challenge to LCDM Cosmology" (May 22, 2010) (published in Astrophysical Journal 718 (2010) 60-65 and "A massive blow for ΛCDM - the high redshift, mass, and collision velocity of the interacting galaxy cluster El Gordo contradicts concordance cosmology" Asencio, E. et al., 2021MNRAS.500.5249A); Sandor M. Molnar, Tom Broadhurst. "A Hydrodynamical Solution For The “Twin-Tailed” Colliding Galaxy Cluster “El Gordo”. The Astrophysical Journal, 2015; 800 (1): 37 DOI: 10.1088/0004-637X/800/1/37)

* the cosmic coincidence problem 

(see, e.g., https://arxiv.org/abs/1410.2509)

* dark energy measurement issues 

(see, e.g., Jacques Collins, et al., "Evidence for Anisotropy of cosmic acceleration", 631 Astronomy and Astrophysics L13 (November 20, 2019) DOI: https://doi.org/10.1051/0004-6361/201936373 and Peter A. Milne, Ryan J. Foley, Peter J. Brown, Gautham Narayan. "The Changing Fractions of Type IA Supernova NUV–Optical Subclasses With Redshift: The Astrophysical Journal, 2015; 803 (1): 20 DOI: 10.1088/0004-637X/803/1/20)

* the wrong predicted DM halo size scaling exponent in clusters 

(see Yong Tian, Han Cheng, Stacy S. McGaugh, Chung-Ming Ko, Yun-Hsin Hsu "Mass-Velocity Dispersion Relation in MaNGA Brightest Cluster Galaxies" arXiv:2108.08980 (August 20, 2021) (published in 24 The Astrophysical Journal Letters 917))

* mean separation of void galaxies and KBC void prediction problems 

(see Saeed Tavasoli, "Void Galaxy Distribution: A Challenge for ΛCDM" arXiv:2109.10369 (September 21, 2021) (Accepted in ApJ Letter) DOI: 10.3847/2041-8213/ac1357 and "The KBC void and Hubble tension contradict ΛCDM on a Gpc scale" Haslbauer, M. et al., 2020MNRAS.499.2845H)

* structure growth and other cosmological parameter tensions 

(see, e.g., the paper in the OP and Elcio Abdalla, et al., "Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies" arXiv:2203.06142 (March 11, 2022); Nhat-Minh Nguyen, Dragan Huterer, Yuewei Wen, "Evidence for suppression of structure growth in the concordance cosmological model" arXiv:2302.01331 (February 2, 2023))

* inconsistent with Chandrasekhar dynamical friction 

(see https://archive.ph/wEVQ0)

* spiral galaxy thickness is too thin relative the the predicted value in ΛCDM 

(see "The High Fraction of Thin Disk Galaxies Continues to Challenge ΛCDM Cosmology" Haslbauer, M., et al., 2022ApJ...925..183H)

* predicts too low early star formation efficiency 

(see Deng Wang, Yizhou Liu, "JWST high redshift galaxy observations have a strong tension with Planck CMB measurements" arXiv:2301.00347 (January 1, 2023))

* insufficient satellites of satellites 

(see https://arxiv.org/abs/2303.03025)

* evidence that feedback effects needed to fit models to reality are too weak to fill that function 

(see https://arxiv.org/abs/2303.02929 and Lin Wang, Da-Ming Chen, Ran Li, "Baryon effects on the dark matter halos constrained from strong gravitational lensing" arXiv:1706.03324 (June 11, 2017) (accepted in MINRAS).)

* non-detection of DM particles by myriad means shrinking their possible parameter space in a manner that taking all available data collectively rules out many solutions to some of these issues 

(see, e.g., https://arxiv.org/abs/2011.10431, compiling exclusions mostly from the Particle Data Group https://dispatchesfromturtleisland.blogspot.com/2020/10/current-experimental-exclusions-on-bsm.html,

Shyam Balaji, Divya Sachdeva, Filippo Sala, Joseph Silk, "Dark Matter spikes around Sgr A* in γ-rays" arXiv:2303.12107 (March 21, 2023). https://www.nature.com/articles/s41586-018-0739-1,

Dicong Liang, Lijing Shao, "Improved bounds on the bosonic dark matter with pulsars in the Milky Way" arXiv:2303.05107 (March 9, 2023),

https://arxiv.org/abs/2010.07559, https://arxiv.org/pdf/1408.3583.pdf, https://arxiv.org/abs/1501.00907, https://arxiv.org/abs/1709.02304,

https://arxiv.org/abs/1709.02222, https://arxiv.org/abs/1709.01930, https://arxiv.org/abs/1710.01375, https://arxiv.org/abs/1510.01516,

https://arxiv.org/abs/1710.06488, https://arxiv.org/abs/1708.05681,

https://arxiv.org/abs/1708.04630, https://arxiv.org/abs/1707.01632,

https://arxiv.org/abs/1708.04858,

https://arxiv.org/abs/1301.4984,

https://arxiv.org/abs/1612.00457,

https://arxiv.org/abs/1504.01195,

https://arxiv.org/pdf/1305.7452v2.pdf,

Paolo Salucci and Nicola Turini, "Evidences for Collisional Dark Matter In Galaxies?" (July 4, 2017),

Torsten Bringmann, et al., "Strong constraints on self-interacting dark matter with light mediators" (December 2, 2016),

https://arxiv.org/abs/1504.06576,

Alyson Brooks, "Re-Examining Astrophysical Constraints on the Dark Matter Model" (July 28, 2014),

Dark matter distributions have to closely track baryon distributions, even though there is no viable mechanism to do so: Edo van Uitert, et al., "Halo ellipticity of GAMA galaxy groups from KiDS weak lensing" (October 13, 2016),

Simon Birrer, Adam Amara, and Alexandre Refregier, "Lensing substructure quantification in RXJ1131-1231: A 2 keV lower bound on dark matter thermal relict mass" (January 31, 2017),

Lin Wang, Da-Ming Chen, Ran Li "The total density profile of DM halos fitted from strong lensing" (July 31, 2017),

https://arxiv.org/pdf/1704.01832.pdf,

http://iopscience.iop.org/article/10.1088/1742-6596/718/3/032008/pdf)

* it has made few ex ante predictions that have turned out to be true

(see, e.g. https://tritonstation.com/2020/05/05/predictive-power-in-science/)

* gravitational alternatives to DM have made many accurate ex ante predictions and solve some of the other problems 

(see, e.g. A. Deur, "A possible explanation for dark matter and dark energy consistent with the Standard Model of particle physics and General Relativity" (2017), J. W. Moffat and M. H. Zhoolideh Haghighi, "Modified gravity (MOG) can fit the acceleration data for the cluster Abell 1689" (16 Nov 2016), Nils Wittenburg, Pavel Kroupa and Benoit Famaey "The formation of exponential disk galaxies in MOND." (February 5, 2020) Astrophysical Journal, http://arxiv.org/abs/2002.01941, Constantinos Skordis, Tom Złosnik, "A new relativistic theory for Modified Newtonian Dynamics" arXiv (June 30, 2020), Francesco Sylos Labini, et al., "Mass models of the Milky Way and estimation of its mass from the GAIA DR3 data-set" arXiv:2302.01379 (February 2, 2023) (accepted for publication in The Astrophysical Journal)).

An April Fool's Day Preprint

For much of February 2023, the world was in panic as repeated balloon-like unidentified flying objects (UFOs) were reported over numerous countries by governments that often responded with military action. As a result, most of these craft either escaped or were destroyed, making any further observation of them nearly impossible. These were not the first time balloon-like objects have loomed over Earth, nor are they likely to be the last. This has prompted us to push for a better understanding of UFOs. 

First we demonstrate that the distribution of balloon incidents and other UFO reports are consistent with being drawn from the same geographic distribution, and further that both of these distributions are consistent with the areas of the Earth that feature the jet stream. 

Second we show that there are more UFO sightings during meteor showers, as we would expect if meteor showers, already a known source of extraterrestrial material, are being used to provide some manner of distraction to help alien craft enter the Earth's atmosphere without drawing undue attention. These links between alleged balloon incidents, UFO reports, and meteor showers establish a transport pipeline for alien craft from interplanetary and possibly interstellar space to the Earth's surface.

Michael B. Lund, "UFOs: Just Hot Air or Something Meteor?" arXiv:2303.17103 (April 1, 2023) (submission for Saturday's Acta Prima Aprilia). 

An Observed Relationship Between Quark Masses And Mixings

Maybe its a coincidence, maybe there is something to it. It was simple and interesting enough to mention, in any case. The lack of a clear relationship or similarity between the four different formulas used is not very encouraging, however.

Boris Altshuler, "Quark mixing angles and weak CP-violating phase vs quark masses: potential approach" arXiv:2303.16568 (March 29, 2023) (substantial text overlap with arXiv:2210.09780).

The Trouble With GR GEM Effects To Explain Flat Rotation Curves

It has been clear for a long time that gravitomagnetism (GEM) effects in General Relativity (GR) do not explain dark matter phenomena like flat galaxy rotation curves. One paper which I discussed in another recent paper goes beyond that and I'll analyze it when I have a chance at greater depth. But, this paper's conclusion that a lack of GEM effects to explain dark matter precludes at GR effects to address dark matter phenomena isn't well supported. 

The flatness of galaxy rotation curves at large radii is generally considered to be a significant piece of evidence in support of the existence of dark matter. Several studies have claimed that post-Newtonian corrections to the Newtonian equations of galaxy dynamics remove the need for dark matter. A few recent studies have examined these claims, and identified errors in their reasoning. 

We add to this critique by giving what we consider to be particularly simple and transparent description of the errors made in these post-Newtonian calculations, some of which were of a rather technical nature, others more fundamental, e.g. the loss of the correct relativistic scaling, promoting small corrections to order unity changes. 

Our work reinforces the orthodoxy that post-Newtonian effects are indeed too small to significantly alter galactic rotation curves, and will hopefully serve as a useful guide for others, pointing out subtle errors that one might inadvertently make in such calculations.

Kostas Glampedakis, David Ian Jones, "Pitfalls in applying gravitomagnetism to galactic rotation curve modelling" arXiv:2303.16679 (March 29, 2023).

More Data About A Pair Of Dark Matter Free Galaxies

The two galaxies with no inferred dark matter in the NGC 1052 group, DF2 and DF4 are explained by the external field effect in the MOND paradigm, and tidal stripping is often resorted to explain them in a dark matter particle paradigm, although this paper also calls attention to a new "mini-bullet cluster" hypothesis. 

A new article takes a closer look at the large scale structure of the group to provide further data to analyze the source of these anomalous galaxies and does not reach any conclusions, although it tends to disfavor tidal stripping over a mini-Bullet Cluster or modified gravity hypothesis.

Prompted by the many controversial claims involving the NGC 1052 group, including that it hosts two dark matter-free galaxies with overluminous and monochromatic globular cluster (GC) systems, here we map out the large-scale structure (LSS) of GCs over the entire group. 

To recover the LSS, we use archival optical CFHT imaging data. We recover two GC density maps, one based on universal photometric properties of GCs from simple stellar population models, and one based on the properties of spectroscopically confirmed GCs in DF2 and DF4 (the two dwarf galaxies with overluminous GC populations). Both selection methods reveal overdensities around the massive galaxies in the group, as well as around NGC 1052 itself, that are coincident with the positions of previously identified stellar streams and tidal features. No intragroup GCs are found connecting these structures to any of the dwarf galaxies. We find, however, two other dwarfs in the group hosting GC systems. These include RCP32 with 2 GCs with ages equivalent to the GCs around NGC 1052, and DF9 with 3 GCs with ages similar to the GCs around DF2 and DF4. 

We conclude that the GC distribution in the group does not strongly support any formation scenario in particular. It favours, nonetheless, scenarios relying on galaxy-galaxy interactions and on the coeval formation of GCs around the DM-free dwarf galaxies. These may include the recently proposed bullet-dwarf formation, as well as high-redshift tidal dwarf galaxy models.

Maria Luisa Buzzo, Duncan A. Forbes, Jean P. Brodie, Steven R. Janssens, Warrick J. Couch, Aaron J. Romanowsky, Jonah S. Gannon, "The large-scale structure of globular clusters in the NGC 1052 group" arXiv:2303.16375 (March 29, 2023) (Accepted for publication in MNRAS).

The introduction to the paper explains:

The NGC 1052 group has been the topic of intense debate over several years due to claims that it hosts dark matter (DM)-free low-surface brightness (LSB) dwarf galaxies (van Dokkum et al. 2018, 2019). This came as a surprise since both dwarf (Strigari et al. 2008b,a) and LSB galaxies (de Blok & McGaugh 1997) are believed to be some of the most DM-dominated galaxies in the universe. This is because their gravitational potentials are too weak to counteract the outward pressures of stellar feedback, resulting in decreased star formation efficiencies. 

Two galaxies claimed to be largely DM-free within their stellar components, NGC 1052-DF2 and NGC 1052-DF4 (DF2 and DF4, hereafter), were also found to have extremely extended sizes (effective radius, 𝑅e > 1.5 kpc) for their surface brightnesses, being better classified as ultra-diffuse galaxies (UDGs). Additionally, they were found to host a population of ultra-luminous globular clusters (GCs) (van Dokkum et al. 2018, 2019; Shen et al. 2021). All of these peculiar properties are accompanied by the fact that the galaxies are very close in projection, but far away from each other in line-of-sight tip of the red giant branch (TRGB) distance (2 Mpc, Shen et al. 2021). The puzzle created by these complications has culminated in skepticism about the DM-free nature of these galaxies (Trujillo et al. 2019; Montes et al. 2020) and have also led to the development of simulations and theoretical methods to understand the possible formation pathways of such galaxies. Assuming that it is not a coincidence that the galaxies share such unusual properties while being so close in proximity, a common formation scenario for them must simultaneously explain: 1) their lack of DM, 2) their large sizes and 3) the presence of overluminous GCs. 

One of the most commonly proposed scenarios involves tidal stripping by a more massive galaxy (Ogiya 2018; Macciò et al. 2021; Jackson et al. 2021; Ogiya et al. 2021; Moreno et al. 2022). This scenario potentially explains the DM depletion (Haslbauer et al. 2019) and extended sizes of the galaxies, and it is expected to leave behind a trail of stripped GCs, but so far it is not capable of explaining the overluminous GC population around DF2 and DF4. 

Alternatively, Trujillo-Gomez et al. (2021), attempting to explain both the low DM content and the peculiar GC systems, proposed that the galaxies were formed by a combination of an early, intense burst of star-formation that creates a rich GC system with a top-heavy GC luminosity function (GCLF), and feedback that expands the galaxy. The expansion leads to an LSB galaxy residing in a diffuse DM ‘core’ creating the illusion of a DM-free galaxy. While it is an interesting possibility, this model also implies that all GC-rich LSB galaxies or ultra-diffuse galaxies should have unusual GCLFs and be DM-poor – in contradiction to the observations (e.g., Toloba et al. 2018; Saifollahi et al. 2022; Gannon et al. 2022, 2023). 

Recently, Silk (2019), Shin et al. (2020) and Lee et al. (2021) have proposed that DM-free galaxies with overluminous GCs could form in a ‘mini bullet cluster’ event (Clowe et al. 2006), where a high-speed collision in the host group would be able to separate baryonic- and dark-matter. These studies were the first ones capable of explaining aspects of the DM depletion and GC population, although not the spatial distribution of gas and GCs. van Dokkum et al. (2022a), building on this scenario, suggested that not only DF2 and DF4 were formed in the aftermath of this high-speed interaction, but also seven to nine other dwarf galaxies in the NGC 1052 group. The collision would have happened ∼8 Gyr ago, separating the baryonic and DM content of the progenitor galaxies. As a result, the gas would have formed a trail of DM-free galaxies (forming a near-linear distribution in projection) along with many massive GCs, while the DM itself would lie at the ends of the trail in two DM-dominated galaxies (see van Dokkum et al. 2022a, figure 1). This scenario can potentially explain all of the unusual properties of these galaxies, but it makes strong predictions. One of the most important predictions is that all of the galaxies in the trail (except the DM-dominated ones), as well as any formed GCs, should have the same ages and metallicities –hence, colours– since they would have been formed by the same process, from the same material and at the same time.

Later in the discussion section that article states:

The bullet-dwarf collision scenario makes the prediction that any GCs formed in the interaction should have small variations in colour and all be consistent with an age of ∼8 Gyr. The model suggests that the metallicities of the sources should be similar, but does not predict any specific value as it does for the ages. Previous studies, none the less, have shown that DF2 and DF4 have stellar metallicities of [𝑍/H] ∼ −1.1 dex (Fensch et al. 2019a; Buzzo et al. 2022). If the other galaxies/GCs were formed from the same material, there is an expectation that they would have the similar metallicities. The GC colours and the stellar body of DF2 and DF4 were shown to meet these expectations (Buzzo et al. 2022; van Dokkum et al. 2022b). Apart from DF2 and DF4, only RCP32 and DF9 are found to host GC populations (both with 𝑁GC ≤ 3). No intragroup structure was identified along the bullet trail, which naturally raises the question of why the collision would form a trail of galaxies, but only a portion of them would have enough gas to form several and mostly overluminous GCs. 

The finding of two GCs around RCP32 (one of the DM-dominated dwarfs) with colours similar to those of the progenitor galaxy (NGC 1052) and three GCs around DF9 with equivalent colours (within the uncertainties) to those of DF2 and DF4 GCs are consistent with the predictions of the scenario. . . . 

Thus, some of our findings seem to be broadly consistent with the bullet collision, namely: 1) The GC system around RCP32 has stellar populations similar to those of the progenitor galaxy. 2) The GC system around DF9 has populations similar to those of the GCs around DF2 and DF4. 3) The predicted number of GCs around DF9 (3.6) is consistent with the finding of 3 GCs around it. 4) The lack of GCs around other dwarfs is consistent with the prediction that their GC numbers are smaller than 1. While these aspects may be broadly consistent with the scenario, the lack of constraints on the formation histories of any of the other galaxies in the trail prevents us from conclusively adhering to this scenario. . . . 

Since the first claim that the galaxies in the NGC 1052 group could be dark matter-free, the most prominent model to explain their formation relied on tidal stripping by a more massive galaxy (e.g., Ogiya 2018; Ogiya et al. 2021; Moreno et al. 2022). Such models were shown to successfully explain the lack of DM and the presence of GCs in the galaxies, but even using different simulations, they were not able to create GCs as massive as the ones seen in DF2 and DF4. 

Tidal stripping models, additionally, are expected to leave a trail of stripped GCs between the stripped dwarf galaxy and the massive host (Lee et al. 2010), but such structures are not seen in any of our LSS maps. 

On the other hand, GC streams and other GC LSS structures are observed all around NGC 1052, indicating recent interactions between NGC 1052, NGC 1047 and NGC 1402, as suggested by Müller et al. (2019b). Thus, tidal stripping could explain the connections found between the massive galaxies in the group, but do not seem to have any connection with the dwarfs.

Models that are alternative to the existence of dark matter may also be suitable explanations for the existence of these DM-free galaxies (e.g., MOND; Kroupa et al. 2012). They have been proposed as possible formation pathways for DF2 by Kroupa et al. (2018) and for DF4 by Müller et al. (2019a). These models, however, do not make predictions about the globular cluster population of the galaxies nor about their stellar populations, thus, they are more difficult to test with this study. They remain a possibility to be further developed and tested.

The conclusion of the article states:

In this work, we investigated the large scale structure of GCs in the NGC 1052 group in order to test the level of agreement of different formation scenarios proposed for the dwarf galaxies in the group with the recovered GC LSS. These include the ‘bullet-dwarf’ scenario, high-redshift tidal dwarf galaxies, tidal stripping and modified gravity models. Using CFHT data in the 𝑢, 𝑔 and 𝑖 bands, we select two sets of GC candidates: one based on SSP models consistent with GCs in general, with a typical range in age of 8−14 Gyr and metallicity of −2.2 < [𝑍/H] < −0.0 dex; and a second narrower one based on the properties of spectroscopically confirmed GCs around DF2 and DF4. We subtracted the GC system of NGC 1052 to be able to see smaller overdensities around all LSB galaxies and any intragroup GC structures. The distribution of GCs around NGC 1052 was modelled to be larger than normal for an early-type galaxy of its mass, reaching a GC number radius of 10.8 galaxy effective radii. If the GC system of NGC 1052 is separated into red and blue GCs, these extend out to 8.8 and 13.2 𝑅e, respectively. The GCs around NGC 1052 have an average colour that correspond to an age of 11.2 ± 1.6 Gyr and [𝑍/H]= −0.8 ± 0.3 dex. 

The GC map based on SSP colours revealed overdensities in the centre of the group, around NGC 1052 itself, and GC systems around the giant galaxies in the group. The overdensities around NGC 1052 coincide with the positions of pre-identified stellar streams and LSB features in the group, indicating past tidal interactions. The GC map based on the properties of spectroscopically confirmed GCs around DF2 and DF4 also revealed overdensities in the centre of the group, in the same positions as the previously identified stellar streams. Reassuringly, the GC systems of DF2 and DF4 themselves were also found. They have an average age of 9.1 ± 0.8 Gyr and [𝑍/H]= −1.2 ± 0.2 dex, being thus younger and less metal-enriched than NGC 1052. No prominent intragroup GC structures were found in any map. On the other hand, GC systems were identified around four dwarf galaxies in the group: DF2 and DF4, as already known, but also RCP32 with 2 GCs and DF9 with 3 GCs. The average age of the GCs around RCP32 is consistent with the age of the GCs around NGC 1052, while the GCs around DF9 are consistent, within the uncertainties, with the colours of DF2/DF4 GCs. 

If we assume a bullet-like formation and that all of the galaxies in the supposed trail share the averaged specific frequency of DF2 and DF4 –the trail galaxies with most GCs per unit luminosity (𝑆𝑁 =14.6)– we predict a total number of GCs throughout the trail of 𝑁GC = 42.3 ± 4.7. Our predictions indicate that the number of GCs around DF9 is 𝑁GC = 3.6 ± 1.2, which is consistent with our finding of 3 GCs. All of the other galaxies in the trail were found to have a combined predicted number of GCs smaller than 2. These predictions are consistent with the lack of GCs found in any of the other trail galaxies or in the intragroup medium. In addition, the colours (thus, stellar populations) of the GCs found around DF9 are similar to the ones around DF2 and DF4 and, thus, meet the stellar population expectations of the scenario. On the other hand, the GCs around RCP32 have equivalent ages to the GCs around NGC 1052 itself, which is consistent with the expectation that this DM-dominated dwarf would host the primordial GCs coming from the progenitor galaxy. While this scenario has many aspects of agreement with the recovered GC LSS, the lack of conclusive evidence on the properties of any of the other trail galaxies makes it hard to reach any definite conclusions on their formation scenario. 

We discuss how TDGs formed at high-redshifts (0.5 < 𝑧 < 2), when merger and star formation rates were higher, may be able to explain the overluminous population of GCs found in the galaxies. As they would have been formed at high-𝑧, the metallicities and ages of the GCs may be consistent with the ones observed in this study. TDG models, however, at low or high-redshift, do not seem to be able to explain the 2 Mpc distance between the two DMfree dwarf galaxies in the group, as this mode of formation predicts that the galaxies will live within about one or two hundred kpc from their progenitors. Thus, although promising, models of highredshift TDGs need further exploration in order to correctly explain the physical separation of the galaxies. 

We discuss how tidal stripping models are unlikely to explain the dwarf galaxies in the group, as they cannot explain the overluminous GCs in the galaxies. We suggest, however, that tidal stripping could be taking place around the massive galaxies in the group, such as NGC 1052, NGC 1047 and NGC 1042, as stellar streams and tidal features are observed connecting these galaxies and are key imprints of this type of interaction. Additionally, we argue that modified gravity models remain as a possibility to explain these DM-free galaxies, but as they do not make any predictions on the stellar populations or GC systems of the galaxies, they are more difficult to test with our study. 

We conclude that the GC distribution in the group does not conclusively point to any formation scenario in particular, but it favours models relying on galaxy-galaxy interactions and on the coeval formation of dwarfs and their GC systems. These include the recently proposed bullet-dwarf formation, as well as tidal dwarf galaxy models. Both scenarios need further exploration and adjustments to be fully compatible with the GC LSS observed in the group.

Are There Outlier Ultra Diffuse Galaxies?

Most ultra-diffuse galaxies don't deviate significantly from the baryonic Tully-Fisher scaling relation which is a good fit to all individual galaxies (there is a similar but different relationship that exists in galaxy clusters). 

But a new paper with the largest sample size that can be compared to the baryonic Tully-Fisher scaling relation does identify some hydrogen gas rich outlier ultra-diffuse galaxies, but that the outlier galaxies tend to obey narrower original Tully-Fisher scaling relation. 

In the MOND paradigm, the baryonic Tully-Fischer relation flows trivially from the gravity modifications that MOND contains, and outliers from the baryonic Tully-Fisher relation can arise due to an external field effect, or because a galaxy is not in equilibrium. 

In Deur's paradigm, the gravitational effects of spherically symmetric interstellar gas can be parsed from the effects of non-spherically symmetric clusters of stars, as illustrated by his analysis of the Bullet Cluster. This kind of analysis could be relevant to gas rich galaxies.

In the dark matter particle paradigm, outliers could be explained by tidal stripping, or because of random variation in dark matter halo sizes associated with a galaxy that may be muted for larger galaxies due to the law of averaged over multiple galaxy mergers involving in assembling larger galaxies.

The paper conjectures that it may be related to the hydrogen fraction of these galaxies but doesn't reach a firm conclusion regarding the cause of these outliers (which is sensible given that there isn't a firm consensus on the source of the baryonic Tully-Fisher or the original Tully-Fischer scaling relationships).

The baryonic Tully-Fisher relation (BTFR), which connects the baryonic mass of galaxies with their circular velocities, has been validated across a wide range of galaxies, from dwarf galaxies to massive galaxies. Recent studies have found that several ultra-diffuse galaxies (UDGs) deviate significantly from the BTFR, indicating a galaxy population with abnormal dynamical properties. However, such studies were still confined within a small sample size. In this study, we used the 100% complete Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) to investigate the BTFR of 88 HI-rich UDGs (HUDGs), which is the largest UDG sample with dynamical information. We found that the HUDGs form a continuous distribution in the BTFR diagram, with high-velocity galaxies consistent with normal dwarf galaxies at 1 σ level, and low-velocity galaxies deviating from the BTFR, in line with that reported in the literature. We point out that the observed deviation may be subject to various selection effects or systemic biases. Nevertheless, we found that the significance of the deviation of HUDGs from the BTFR and TFR are different, i.e., they either deviate from the BTFR or from the TFR. Our result indicates that a high-gas fraction may play an important role in explaining the deviation of HUDGs from BTFR.

Hui-Jie Hu, Qi Guo, Zheng Zheng, Hang Yang, Chao-Wei Tsai, Hong-Xin Zhang, Zhi-Yu Zhang, "Global dynamic scaling relations of HI-rich ultra-diffuse galaxies" arXiv:2303.16232 (March 28, 2023) (accepted for publication in ApJL).

Another experimental test of galaxy properties is this preprint:

In this paper, we use SPARC's HSBs, and LSBs galaxies to verify two issues. 

The first one is related to one claim of Donato D09, namely: is the DM surface density (DMsd) a constant universal quantity, equal to log(Σ/M⊙pc−2)=2.15±0.2, or does it depend on the baryon surface density of the system? 

The second one, is based on a MOND prediction that for HSBs the DMsd is constant, and equal to log(Σ/M⊙pc−2)=2.14, while for LSBs the surface density is not constant and takes values that are smaller than for HSBs and D09 prediction Milgrom 2009. 

We find that HSBs shows a constant DMsd vs magnitude as in D09, and a constant DMsd vs Σeff as in MOND prediction, for HSBs with Σeff>200L⊙/pc2, and Σeff>300L⊙/pc2. However, the value of the DMsd is larger, Σ≃2.61 (in the case of the DMsd-magnitude with Σeff>300L⊙/pc2), and Σ≃2.54 (in the case of the surface DMsd-surface brightness with Σeff>200L⊙/pc2). This value slightly depends on the threshold to determine wheter a galaxy is HSB. 

In the case of LSBs, for Σeff<100L⊙/pc2, and Σeff<25L⊙/pc2, the surface density vs magnitude, for lower magnitudes, is approximately equal to that predicted by D09, but several galaxies, for magnitude M>−17, have smaller values than those predicted by D09. The DMsd vs Σeff shows a similar behavior in qualitative, but not quantitative, agreement with MOND predictions. 

In summary, in the case of HSBs both D09 and MOND are in qualitative, but not quantitative, agreement with the data. In the case of LSBs D09 is mainly in disagreement with the data, and MOND only in qualitative agreement with them.

Antonino Del Popolo, "SPARC HSBs, and LSBs, the surface density of dark matter haloes, and MOND" arXiv:2303.16658 (March 29, 2023) (Physics of the Dark Universe Volume 40, May 2023, 101203).

Swahili Origins

Swahili ethnogenesis is quite recent and was a Persian Muslim and African hybrid civilization that was roughly contemporaneous with the Norman Conquest of England, the Gypsy migration from India, Leif Erikson's establishment of Viking outposts in eastern Canada, the Viking era in Europe, the Icelandic Commonwealth, the linguistic conversion of Hungary to the current Hungarian language, a major Native American city near where Saint Louis is today, and other notable historical events around Y1K. 

A long history of mercantile trade along the eastern shores of Africa left its mark on the DNA of ancient Swahili people.

A new analysis of centuries-old bones and teeth collected from six burial sites across coastal Kenya and Tanzania has found that, around 1,000 years ago, local African women began having children with Persian traders — and that the descendants of these unions gained power and status in the highest levels of pre-colonial Swahili society.

The findings help elucidate the foundations of Swahili civilization, and suggest that long-told origin stories, passed down through generations of Swahili families, may be more truthful than many outsiders have presumed.

“The genetics corroborate the Swahili people’s own history that they tell about themselves, not what others were saying about them,” said Esther Brielle, a geneticist and postdoctoral fellow at Harvard who led the DNA analysis with her adviser, David Reich.

The researchers published their findings on Wednesday in the journal Nature.

The Swahili Coast is a narrow strip of land that stretches some 2,000 miles along the Eastern African seaboard — from modern-day Mozambique, Comoros and Madagascar in the south, to Somalia in the north. In its medieval heyday, the region was home to hundreds of port towns, each ruled independently, but with a common religion (Islam), language (Kiswahili) and culture.

Many towns grew immensely wealthy thanks to a vibrant trading network with merchants who sailed across the Indian Ocean on the monsoon winds. Middle Eastern pottery, Asian cloths‌‌ and other luxury goods came in. African gold, ivory and timber‌‌ went out — along with a steady flow of enslaved people, who were shipped off and sold across the Arabian Peninsula and Persian Gulf. (Slave trading later took place between the Swahili coast and Europe as well.)

. . .

At first, most scholars thought that the civilization, with its lavish mosques and ornate housewares, must have been the achievement of a foreign ruling class that established outposts in East Africa. But over the past 40 years, archaeologists, linguists and historians have come to see Swahili society as predominantly homegrown — with outside elements adopted over time that had only a marginal impact.

That African-centric version of Swahili roots never sat well with the Swahili people themselves, though.

They generally preferred their own origin story, one in which princes from present-day Iran (then known as Persia) sailed across the Indian Ocean, married local women and enmeshed themselves into East African society. Depending on the narrative source, that story dates to around 850 or 1000 — the same period during which genetic mixing was underway, according to the DNA analysis.

“It’s remarkably spot on,” said Mark Horton, an archaeologist at the Royal Agricultural University of England who has worked on the Swahili coast for decades.

“This oral tradition was always maligned,” added George Abungu, an archaeologist and former director-general of the National Museums of Kenya (who, like Dr. Horton, was not involved in the genetic analysis). “Now, with this DNA study, we see there was some truth to it.”

The ancient DNA study is the largest of its kind from Africa, involving 135 skeletons dating to late-medieval and early-modern times, 80 of which have yielded analyzable DNA.

From the New York Times. 

Another Observational Tension With The ΛCDM Model (And Recap Of CDM Fails)

I didn't recognize the implications of this paper for the ΛCDM Model when I saw the abstract in passing when the preprint was released a couple of months ago. Hat tip to Madeleine Birchfield for flagging it. 

The paper argues that the predicted value of the growth index in the ΛCDM Model, that measures the growth of large scale structure, is in strong (4.2 sigma) tension with observations, given the model's measured parameters.

This adds one more observational challenge to the roughly 33 other independent observational challenges to the ΛCDM Model which are already known detailed in previous posts at this blog:

* January 25, 2021 (summarizing the main known observational challenges know to me on that date including compact gravitational lensing in clusters, KIDS evidence of less clumpy structure than predicted, Hubble tension, the wrong DM halo shapes, excessively tight DM-ordinary matter correlations, the unexpected relationship between DM proportion and galaxy shape, satellite galaxies in the galactic plane, too few satellite galaxies, unexpected relationship between bulge mass and number of satellite galaxies, the halo mass function, impossible early galaxies, the EDGES 21 cm result, evidence for an external field effect, the universe is not homogeneous and isotropic, no dark matter galaxies, lack of X-ray emissions in low surface brightness galaxies, there are too few galaxy clusters, it gets globular cluster formation wrong, doesn't explain apparent wide binary star discrepancies, colliding clusters are too common and too fast, the cosmic coincidence problem, dark energy measurement issues, non-detection of DM particles by myriad means shrinking their possible parameter space, few ex ante predictions, gravitational alternatives to DM have made ex ante predictions and solve some of the other problems), 

* February 23, 2021 (missing satellites), 

* March 17, 2021 (the EDGES 21 cm result), 

*August 23, 2021 (DM scaling exponent in clusters), 

* September 23, 2021 (mean separation of void galaxies), 

* December 21, 2021 (Hubble tension), 

* March 11, 2022 (questioning one possible observational conflict from the EDGES 21 cm result), 

* March 14, 2022 (Hubble, structure growth and other cosmological parameter tensions), 

* July 15, 2022 (Chandrasekhar dynamical friction, satellite galaxies plane, cluster collisions, Hubble tension/KBC void, spiral galaxy thickness, impossible early galaxies), 

* July 26, 2022 (impossible early galaxies),

* January 3, 2023 (early star formation efficiency), 

* February 2, 2023 (impossible early galaxies),

* March 2, 2023 (impossible early galaxies),

* March 7, 2023 (satellites of satellites and weak feedback effects), and

* March 17, 2023 (ruling out predicted NFW spike at center of Milky Way).

We present evidence for a suppressed growth rate of large-scale structure during the dark-energy dominated era.

Modeling the growth rate of perturbations with the ``growth index'' γ, we find that current cosmological data strongly prefer a higher growth index than the value γ=0.55 predicted by general relativity in a flat ΛCDM cosmology.

Both the cosmic microwave background data from Planck and the large-scale structure data from weak lensing, galaxy clustering, and cosmic velocities separately favor growth suppression. When combined, they yield γ=0.633+0.025−0.024, excluding γ=0.55 at a statistical significance of 3.7σ. The combination of f σ(8) and Planck measurements prefers an even higher growth index of γ=0.639+0.024−0.025, corresponding to a 4.2σ-tension with the concordance model.

In Planck data, the suppressed growth rate offsets the preference for nonzero curvature and fits the data equally well as the latter model. A higher γ leads to a higher matter fluctuation amplitude S(8) inferred from galaxy clustering and weak lensing measurements, and a lower S(8) from Planck data, effectively resolving the S(8) tension.

Nhat-Minh Nguyen, Dragan Huterer, Yuewei Wen, "Evidence for suppression of structure growth in the concordance cosmological model" arXiv:2302.01331 (February 2, 2023).

Adult Life Expectancy Gains Came Surprisingly Early In Europe

The real breakthroughs in life expectancy came very late, starting in earnest after 1800 CE with major breakthroughs that reduced maternal, infant, and child deaths mostly due to breakthroughs related to the germ theory of disease, antibiotics, vaccines, and sanitation in medical work including labor and delivery. 

But the lives of nobles who managed to live to adulthood started to get significantly longer, starting around 1000 CE in Northwest Europe.

I analyze the adult age at death of 115,650 European nobles from 800 to 1800. Longevity began increasing long before 1800 and the Industrial Revolution, with marked increases around 1400 and again around 1650. Declines in violent deaths from battle contributed to some of this increase, but the majority must reflect other changes in individual behavior. There are historic spatial contours to European elite mortality; Northwest Europe achieved greater adult lifespans than the rest of Europe even by 1000 AD.

Neil Cummins, "Lifespans of the European Elite, 800–1800" 77(2) Journal of Economic History 406-439 (June 12, 2017) (open access).

The introductory body text of the article notes that:

Although individual level demographic data before 1538 is sparse we have abundant evidence of the lives of the European nobility. This analysis exploits recent mass digitization of family trees to examine trends in elite adult lifespan over the millennium between 800 and 1800. The majority of the sample are from Northwest Europe, but there is substantial representation from all across Europe. Understanding that the sample is heavily skewed, and that this skew changes over time, I have four principle findings.

First, plague, which afflicted Europe 1348–1700, killed nobles at a much lower rate than it did the general population. 

Second there were significant declines in the proportion of male deaths from battle violence, mostly before 1550. I am able to estimate, from the timing of deaths within the year, the fraction of males who died violently in each epoch. Before 1550, 30 percent of noble men died in battle. After 1550, it was less than 5 percent.

Third finding there was a common upwards trend in the adult lifespan of nobles even before 1800. But this improvement was concentrated in two periods. Around 1400, and then again around 1650, there were relatively sudden upwards movements in longevity. In England and Wales, for example, the average age at death of noble adults increased from 48 for those born 800–1400, to 54 for 1400–1650, and then 56 for 1650–1800. This rise is independent of the fall in violent battle deaths. 

Finally, I find that there were regional differences in elite adult lifespan favoring Northwest Europe, that emerged around 1000 A.D. While average lifespan in England in 1400 was 54, in Southern Europe, as well as in Central and Eastern Europe, it was only 50. The cause of this geographic “effect” is unknown.

The total sample from 800-1800 CE was as follows:

The most elite title was Emperor (rank 1) of which there are 94 in the final adult lifespan subsample analyzed in this article.

There are 843 Kings (rank 2) and 422 Grand/Archdukes (rank 3); 1,598 dukes, 683 prince/prince-electors, 4,787 Earls and Counts, 2,262 Marquesses and Margraves, 986 Viscounts, 6,444 Barons and Lords, 5,968 Baronets and 3,321 Knights constitute ranks 4–11.

Esquires and Gentlemen along with other lesser noble titles, 1,795 persons, were assigned to group 12.

A “Geographic’” title (rank 13) was one of the 699 cases where a person was listed as “of” a certain specific location.

There were 69 military titles such as Captain and Colonel (rank 14) and 692 religious titles (rank 15, including 12 popes and 533 nuns).

Occupational titles accounted for 1,343 (rank 16) and 83,644 had no suffix (rank 17). Those with no suffix represented the non-titled family members of the elite family trees.

Observations Relevant To Dark Matter And Dark Energy Phenomena

Stepping back from any solution, here are some observations about dark matter phenomena and dark energy phenomena.

1. Dark matter phenomena appear to be fully determined from the distribution of ordinary matter to the limits of experimental precision and our ability to calculate theoretically expected relationships.

2. Dark matter phenomena are only discernible in extremely weak gravitational fields; dynamics in stronger gravitational field can be fully described with Newtonian gravity with general relativity adjustments near very large compact masses and for very fast moving objects.

3. The magnitude of dark energy phenomena at any one place is much weaker than the magnitude of dark matter phenomena.

4. The form of a gravitational pull that would produce flat rotation curves in spiral galaxies is consistent with dimensional reduction from a sphere to a disk of gravitational pull.

5. Alignment of celestial bodies in a plane is expected when there is dimensional reduction of gravitational pull.

6. The more spherically symmetric an agglomeration of matter is the weaker the apparent dark matter phenomena that it exhibits.

7. Galactic clusters exhibit a greater magnitude of dark matter phenomena than galaxies do.

8.  Some ultra-diffuse galaxies show an immense amount of dark matter-like effects, while others show almost none. Those that exhibit almost none are in locations where an external field effect is one possible explanation and tidal stripping of dark mater is another. In general, there is strong statistical evidence for an external field effect.

9. There is no credible evidence for the existence of, and there are no credible theoretical predictions to suggest, that there are any hadrons other than protons and bound neutrons which are stable for more than even a microsecond.

10. If dark matter particles of 1 GeV mass to 1000 GeV mass exist, they have a cross-section of interaction with ordinary matter that is millions to billions of times weaker than neutrinos which interact only via the weak force and gravity. All known fundamental particles have the same magnitude of weak force charge. The mass range at which interactions with ordinary matter are weaker than neutrinos extends below 1 GeV.

11. If dark matter particles of 1000 to 100,000 GeV exist, they have a cross-section of interaction with ordinary matter that is weaker than any force other than the weak force.

12. Dark matter particles with masses of asteroid scale or larger do not account for a significant share of dark matter phenomena.

13. No black holes with masses less than what would be produced by a stellar collapse have been observed. Primordial black holes cannot be a sole explanation of dark matter phenomena.

14. Parameter fitting for self-interacting dark matter theories to a Yukawa force model produce an interaction strength on the same order of magnitude as electromagnetism but with a limited range suggestive of a force carrying boson with a mass on the order of a pion.

15. Inferred dark matter particle halo shapes rarely correspond to an NFW distribution which is what would be expected from a collisionless particle with a mass too large to have significant quantum effects.

16. Galaxies form significantly earlier than would be predicted in a cold dark matter particle cosmology, but this observation is consistent with many gravitational explanations of dark matter phenomena.

17. It is possible in multiple ways to reproduce the cosmic background radiation amplitude peaks with a gravitational as opposed to a dark matter explanation.

18. The aggregate magnitude of dark matter phenomena in the universe is about half of the aggregate magnitude of dark energy phenomena in the universe.

19. Dark energy phenomena are only observed at scales of at least intergalactic distances.

20. General relativity with a cosmological constant (one form of dark energy) does not globally conserve mass-energy.

21. There is strong observational evidence that if dark matter particles exist they are stable on the time frame of the age of the universe, or are created and destroyed in indiscernible interaction that are in near perfect equilibrium.

22. There is evidence from simulations that neither collisionless warm dark matter, nor self-interacting dark matter that has no interactions with ordinary matter can explain observed dark matter phenomena.

23. Gravitational lensing of light is consistent with general relativity or a massless graviton, but is inconsistent with a massive graviton.

24. Gravitational waves travel at a speed consistent with the speed of light and limited to a tiny deviation from the speed of light.

25. There is no credible evidence of sterile neutrinos that oscillate with active neutrinos.

26. Cosmology evidence strongly suggests that there are only three flavors of neutrinos that are consistent with the cosmology definition of a neutrino.

27.  Collisions between galaxies and galaxy clusters happen more often and at higher velocities than predicted by a LambdaCDM model.

28. The radial acceleration relation holds for galaxies of all observed sizes (except for the small number of "no dark matter" ultra-diffuse galaxies where an external field effect could be present).

29. No mechanism sufficient to produce "feedback" effects necessary to make the LambdaCDM model work in simulations has been observed in specific instance.

30. There are strong, but not conclusive hints that dark energy has not been constant over time and that the Hubble constant has not, in fact, been constant over time. The Hubble constant as estimated from the cosmic background radiation pattern appears smaller then than it is in recent billions of years from multiple kinds of observations.

31. Efforts to detect axions or axion-like particles have so far failed to see any, and the "strong CP problem" has multiple proposed solutions that do not rely on axions.

32. There is no positive experimental evidence of supersymmetry.

33. There is no positive evidence of any non-Standard Model Higgs boson.

34. Hot dark matter particles (e.g. thermal freeze out dark matter with masses on the order of neutrino masses) are ruled out observationally.

An Interesting Gravity Calculation

The study is an interesting exercise in evaluating gravitational pulls and quantifying the energy of the gravitational field at a very abstract theoretical level in a system that is not spherically symmetric. The shape dependence is also notable.

The problem of mutual gravitational energy W(mut) for a system of two homogeneous prolate spheroids, whose symmetry axes are on the same line, is set and solved. The method of equigravitating elements is applied, where the external potentials of three-dimensional spheroids are represented by the potentials of one-dimensional inhomogeneous focal rods. The solution of the problem is reduced to the integration of the potential of one rod over the segment of the second rod. As a result, the expression W(mut) for two prolate spheroids can be obtained in a finite analytic form through elementary functions. The force of attraction between the spheroids is found. The function W(mut) is also represented by a power series in eccentricity of the spheroids. Possible applications of the obtained results are discussed.

B.P. Kondratyev, V.S. Kornoukhov, E.N. Kireeva "Mutual gravitational energy of homogeneous prolate spheroids. Collinear case" arXiv:2303.13892 (March 24, 2023) (227 Publications of the Pulkovo Observatory 77-85 (2022)).

More Analysis of Emergent Gravity

Verlinde's Emergent Gravity posits that gravity is not a fundamental force and instead arises from entropy and entanglement. It has had some stumbles, contradicting observations in its original form, but there have been efforts to revive it such as this intriguing paper.                                

We disclose a close correspondence between Verlinde's Emergent Gravity (VEG) theory and the non-local gravity theories. Such non-local effects can play crucial role at small distances as well as in large scale structures. In particular, we argue that the emergent gravity effectively is a manifestation of the entanglement entropy and can modify Newton's law of gravity as well as address the flat rotation curves of spiral galaxies. 

In the cosmological setup, we have considered three different models for the apparent dark matter density. 

In the first model, we have found that Friedmann equations get modified due to the presence of the apparent dark matter (DM) in such a way that Newton's constant of gravity shifts as G→G(N)=G(1+ζ), where ζ is a dimensionless small parameter. This modification basically coincides with the modified gravity (MOG) theory. Using the flat rotating curves we estimate ζ∼10^−7. 

Interestingly enough, for such a model, we find out that by rescaling the radial coordinate, r, the curvature space constant, k, and the scale factor of the universe, a, the effect of apparent DM can change the geometry of the universe and can shift the curvature space constant as k⋆=k(1−ζ). 

Finally, we study a more realistic model applied to the whole universe with evolving densities and we address the Hubble tension problem in the context of Verlinde's emergent gravity using the look-back time quantity.

Kimet Jusufi, Ahmad Sheykhi, Salvatore Capozziello, "Apparent dark matter as a non-local manifestation of emergent gravity" arXiv:2303.14127 (March 23, 2023).

A New ATLAS W Boson Mass Measurement

The ATLAS experiment at the Large Hadron Collider (LHC) has made a new measurement of the W boson mass (actually just a reanalysis of 2011 data) with high precision (via a post at the Physics Forums). 

While the W boson mass is a free parameter in the Standard Model of Particle Physics, it is also has a functional relationship to other free parameters in the Standard Model including the electromagnetic and weak force coupling constants, the Z boson mass, and to a much smaller extent, the Higgs boson and top quark masses, that can assist in finding a global electroweak fit to the value of this parameter. Specifically:

In the Standard Model, the W boson mass is closely related to the strength of the electroweak interactions and the masses of the heaviest fundamental particles, including the Z boson, the top quark and the Higgs boson. In this theory, the particle is constrained to weigh 80354 million electronvolts (MeV), within an uncertainty of 7 MeV. . . .

In its new study, ATLAS reanalysed its 2011 sample of W bosons, improving the precision of its previous measurement. The new W boson mass, 80360 MeV with an uncertainty of 16 MeV, is 10 MeV lower than the previous ATLAS result and 16% more precise. The result is in agreement with the Standard Model.

The new measurement if close to the global fit value, and to past precision measurements, while it is far from an outlier result derived from a reanalysis of the CDF experiment at the Tevatron collider (which ceased to operate long ago). 

The outlier CDF value is inconsistent at the two sigma level with all of the other W boson mass measurements that are outstanding from LEP experiments, from the D0 experiment at the Tevatron collider, from the LHCb experiment, and from ATLAS. All of the other W boson mass measurements, unlike the CDF value, also overlap the global electroweak fit value.

This outlier status is probably due to a flawed analysis of the old data by CDF.

A 16th Century Warfare Fail In Mexico

Tenochtitlan was the capital of the Aztec empire and probably the largest city in the Americas at the time that Spanish Conquistadors arrived in the New World. It was located roughly where Mexico City is today. It fell to the Spanish in 1521 CE.

Ultimately, the conquistador military fail described above didn't make much of a difference. The city fell anyway. Still, technologically, the Spanish edge over the Aztecs in 1521 CE was modest. 

But European diseases to which the indigenous people had no immunity and which the Spanish didn't understand well enough to spread intentionally if they'd wanted to do so, was the decisive factor. 

In the case of the Aztecs, in particular, the Aztec deaths were mostly due to Salmonella, based upon examination of bodies in mass graves in Mexico. Small pox was the biggest Old World disease leading to mass death, often before Europeans arrived, in much of the rest of the Americas.

New Dark Matter Parameter Constraints From Our Galaxy's Central Black Hole

A new study puts upper bounds on the cross-section of interaction of dark matter particles at masses up to 100,000 GeV (i.e. up to masses about a hundred times greater than the masses that can be probed with direct dark matter detectors and particle accelerators), based upon observations from the vicinity of the Milky Way's central black hole, under various assumptions, including the not very well justified assumption that the dark matter particle can annihilate.

The limits at lower masses aren't nearly as stringent of those from existing experiments, and the limits at higher masses still don't rule out cross-sections of interaction as strong as those of neutrinos. But these are some of the strongest constraints to date for hypothetical dark matter particles with masses from 1,000 to 100,000 GeV.

Of course, for a variety of reasons that I won't reiterate in this post, in all likelihood, the phenomena attributed to dark matter have a gravitational cause of some kind, and are not actually due to the gravitational pull of dark matter particles of the type tested for in this paper.

We use H.E.S.S. γ-ray observations of Sgr A* to derive novel limits on the Dark Matter (DM) annihilation cross-section. 

We quantify their dependence on uncertainties i) in the DM halo profile, which we vary from peaked to cored, and ii) in the shape of the DM spike around Sgr A*, dynamically heated by the nuclear star cluster. For peaked halo profiles and depending on the heating of the spike, our limits are the strongest existing ones for DM masses above a few TeV. Our study contributes to assessing the influence of the advancements in our knowledge of the Milky Way on determining the properties of DM particles.

Shyam Balaji, Divya Sachdeva, Filippo Sala, Joseph Silk, "Dark Matter spikes around Sgr A* in γ-rays" arXiv:2303.12107 (March 21, 2023).