Friday, July 29, 2022

No Dark Matter Particle Model Fits The Data Well

MOND, and other gravitational theories for explaining dark matter phenomena in galaxies that reproduce the radial acceleration relations (RAR), accurately reproduce the dynamics of the SPARC galaxies, the largest catalog of observational data regarding galaxy rotation curves. See, e.g., Pengfei Li, Federico Lelli, Stacy McGaugh, James Schormbert, "Fitting the Radial Acceleration Relation to Individual SPARC Galaxies" arXiv (February 28, 2018).

But, none of the standard shaped dark matter particle halos does that, and "fuzzy dark matter" can't reproduce this result for a consistent set of fuzzy dark matter particle properties.
Stellar and gas kinematics of galaxies are a sensitive probe of the dark matter distribution in the halo. The popular fuzzy dark matter models predict the peculiar shape of density distribution in galaxies: specific dense core with sharp transition to the halo. Moreover, fuzzy dark matter predicts scaling relations between the dark matter particle mass and density parameters. 
In this work, we use a Bayesian framework and several dark matter halo models to analyse the stellar kinematics of galaxies using the Spitzer Photometry and Accurate Rotation Curves database. We then employ a Bayesian model comparison to select the best halo density model. 
We find that more than half of the galaxies prefer the fuzzy dark model against standard dark matter profiles (NFW, Burkert, and cored NFW). While this seems like a success for fuzzy dark matter, we also find that there is no single value for the particle mass that provides a good fit for all galaxies.
Mariia Khelashvili, Anton Rudakovskyi, Sabine Hossenfelder, "Dark matter profiles of SPARC galaxies: a challenge to fuzzy dark matter" arXiv:2207.14165 (July 28, 2022).

Unknown Unknowns

This article discusses an important methodological issue of wide interdisciplinary importance: how to deal with "unknown unknowns" so as not to be overconfident about scientific results, without throwing out the baby with the bathwater and retreating to a nihilist position that we know nothing. 

It demonstrates an approach to estimating the uncertainty of results even though we don't know the precise sources of the uncertainties, including possible researcher fraud.
Uncertainty quantification is a key part of astronomy and physics; scientific researchers attempt to model both statistical and systematic uncertainties in their data as best as possible, often using a Bayesian framework. Decisions might then be made on the resulting uncertainty quantification -- perhaps whether or not to believe in a certain theory, or whether to take certain actions. 
However it is well known that most statistical claims should be taken contextually; even if certain models are excluded at a very high degree of confidence, researchers are typically aware there may be systematics that were not accounted for, and thus typically will require confirmation from multiple independent sources before any novel results are truly accepted. 
In this paper we compare two methods in the astronomical literature that seek to attempt to quantify these `unknown unknowns' -- in particular attempting to produce realistic thick tails in the posterior of parameter estimation problems, that account for the possible existence of very large unknown effects. 
We test these methods on a series of case studies, and discuss how robust these methods would be in the presence of malicious interference with the scientific data.
Peter Hatfield, "Quantification of Unknown Unknowns in Astronomy and Physics" arXiv:2207.13993 (July 28, 2022).

Tuesday, July 26, 2022

Belle II Does Not See Lepton Universality Violations In Select B Meson Decays

A new search for lepton universality violations by the Belle II collaboration did not find any sign of lepton universality violations. As the introduction to the new paper explains:
The decays B → K`+` −, where ` stands for an electron or a muon, are flavor-changingneutral-current processes. Being governed by a b → s quark-level transition, these decays are forbidden at tree level in the standard model (SM) of particle physics, but can proceed through b → s`+` − loop amplitudes at lowest order. Various SM extensions predict new particles that contribute to the processes, altering the values of observables from their SM predictions. These possibilities make B → K`+` − decays a sensitive probe for beyond-the-SM physics. 
One of the key predictions of the SM is that the coupling strengths of electroweak gauge bosons to charged leptons e, µ, and τ are the same, a property known as lepton-flavor universality (LFU). Accordingly, the ratio of branching fractions of B → Kµ+µ − to B → Ke+e − decays, called RK, is expected to be close to unity. A recent measurement of RK by the LHCb Collaboration reported a 3.1σ discrepancy with respect to its SM prediction in the range of dilepton mass squared q^2 ∈ (1.1, 6.0) GeV^2/c^4. On the other hand, the measurements reported by the Belle experiment are consistent with both the SM and the LHCb result, albeit with significantly less precision compared to the latter. 
In this report, we describe measurements of branching fractions B (B → J/ψK), LFU ratios 
RK(J/ψ) = B (B → J/ψ(µ +µ −)K)/ B (B → J/ψ(e +e −)K), (1) 
and isospin asymmetries 
AI = Γ[B0 → J/ψ(` +` −)K0 ] − Γ[B+ → J/ψ(` +` −)K+] Γ[B0 → J/ψ(` +` −)K0 ] + Γ[B+ → J/ψ(` +` −)K+] , (2) 
performed using data recorded by the Belle II experiment. 
In contrast to suppressed, charmless B → K`+` − decays, the B → J/ψ(` +` −)K decays involve a favored b → c tree-level transition. Hence, contributions from beyond-the-SM physics are expected to have a negligible impact. 
Since the branching fraction of B → J/ψ(` +` −)K is two orders of magnitude larger than that of B → K`+` − decays and both channels share the same final-state particles, the former decays constitute an excellent control sample for studies of the latter. Therefore, the measurement of RK (J/ψ) and its consistency with unity would be a strong validation of the future RK measurement in the charmless counterpart of B → K`` decays. Throughout the report, charge conjugate processes are implicitly included.

I believe the Belle paper consistent with the SM referenced is this one.

The bottom line result is that:

This makes it increasingly more difficult to come up with a model that sees lepton universality violations in the circumstances where they are observed, while not seeing them where they are not observed to high precision, even though this doesn't directly contradict the previous indications of lepton universality violations at the LHCb experiment at the Large Hadron Collider.

The paper and its abstract are as follows:

Belle II Collaboration, "Measurements of the branching fraction, isospin asymmetry, and lepton-universality ratio in B→J/ψK decays at Belle II" arXiv:2207.11275 (July 22, 2022).

Dark Side Doesn't Find Dark Matter Either

The DarkSide-50 direct dark matter detection experiment bridges most of the mass gap between LZ and XENONnT experiment dark matter searches previously discussed. 

A trio of papers report that it too has not seen any signal of dark matter, greatly constraining the parameter space of any dark matter candidates that interact with ordinary matter even much weaker than that of a neutrino.

We report on the search for dark matter WIMPs in the mass range below 10 GeV/c^2, from the analysis of the entire dataset acquired with a low-radioactivity argon target by the DarkSide-50 experiment at LNGS. The new analysis benefits from more accurate calibration of the detector response, improved background model, and better determination of systematic uncertainties, allowing us to accurately model the background rate and spectra down to 0.06 keV(er). A 90% C.L. exclusion limit for the spin-independent cross section of 3 GeV/c^2 mass WIMP on nucleons is set at 6×10^−43 cm^2, about a factor 10 better than the previous DarkSide-50 limit. This analysis extends the exclusion region for spin-independent dark matter interactions below the current experimental constraints in the [1.2,3.6] GeV/c^2 WIMP mass range.
The DarkSide-50 Collaboration, "Search for low-mass dark matter WIMPs with 12 ton-day exposure of DarkSide-50" arXiv:2207.11966 (July 25, 2022).

Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c^2 mass dark matter. 

We present new constraints for sub-GeV/c^2 dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12306 ± 184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c^2. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below 3.6 GeV/c^2.
The DarkSide-50 Collaboration, "Search for dark matter-nucleon interactions via Migdal effect with DarkSide-50" arXiv:2207.11967 (July 25, 2022).
We present a search for dark matter particles with sub-GeV/c^2 masses whose interactions have final state electrons using the DarkSide-50 experiment's (12306 ± 184) kg d low-radioactivity liquid argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section σ¯(e), the axioelectric coupling constant g(Ae), and the dark photon kinetic mixing parameter κ. We also set the first dark matter direct-detection constraints on the mixing angle |Ue4|^2 for keV sterile neutrinos.
The DarkSide-50 Collaboration, "Search for dark matter particle interactions with electron final states with DarkSide-50" arXiv:2207.11968 (July 25, 2022).

More On Impossible Early Galaxies

As previously noted, the James Webb Space Telescope (JWST) has seen the earliest detected galaxies, far earlier than should be possible in the LambdaCDM Standard Model of Cosmology. 

A new paper spells out how the JWST improves on the Hubble Space Telescope in capabilities to see such galaxies and recognizes that the "impossible early galaxies" problem is a severe one for the LambdaCDM paradigm. 

Modified gravity theories that seek to explain dark matter (including efforts to explain dark matter with non-Newtonian General Relativistic effects) generically result in earlier galaxy formation than in LambdaCDM.
On July 13, 2022, NASA released to the whole world the data obtained by the James Webb Space Telescope (JWST) Early Release Observations (ERO). These are the first set of science-grade data from this long-awaited facility, marking the beginning of a new era in astronomy. Many critical questions unanswered in the past several decades now see the hope of being addressed. JWST will push the redshift boundary far beyond what has been reached by the Hubble Space Telescope (HST), and in so doing it will lead to the understanding of how the first luminous objects - first stars and first galaxies - were formed in the early universe. 
The red wavelength cut-off at 1.6 micron limits HST to redshift around 11, which is when the age of the universe was only ~420 million years. The NIRCam instrument, the most sensitive camera onboard JWST, extends to 5 micron and will allow for the detection of early objects only several tens of million years after the Big Bang should they exist. 
Among the JWST ERO targets there is a nearby galaxy cluster SMACS 0723-73, which is a massive cluster and has been long recognized as a good "cosmic telescope" to amplify the background, far-away galaxies through its gravitational lensing effect. The NIRCam field-of-view is large enough that the ERO observations have covered not only the cluster but also a flanking field not boosted by gravitational lensing. JWST is so sensitive that the flanking field also sees far beyond HST. 
Here we report the result from our search of candidate galaxies at redshift larger than 11 using these ERO data. We have a total of 88 such candidates spreading over the two fields, some of which could be at redshifts as high as 20. Neither the high number of such objects found nor the high redshifts they reside at are expected from the previously favored predictions.
Haojing Yan, et al., "First Batch of Candidate Galaxies at Redshifts 11 to 20 Revealed by the James Webb Space Telescope Early Release Observations" arXiv:2207.11558 (July 23, 2022).

Another paper also discusses the finds and suggests that JWST may be approaching the limits of finding the oldest galaxies because the oldest galaxies found by the JWST also appear to be very young galaxies.
One of the main goals of the JWST is to study the first galaxies in the Universe. We present a systematic photometric analysis of very distant galaxies in the first JWST deep field towards the massive lensing cluster SMACS0723. As a result, we report the discovery of two galaxy candidates at z∼16, only 250 million years after the Big Bang. We also identify two candidates at z∼12 and 11 candidates at z∼10−11. 
Our search extended out to z≲21 by combining color information across seven NIRCam and NIRISS filters. By modelling the Spectral Energy Distributions (SEDs) with EAZY and BEAGLE, we test the robustness of the photometric redshift estimates. While their intrinsic (un-lensed) luminosity is typical of the characteristic luminosity L∗ at z>10, our high-redshift galaxies typically show small sizes and their morphologies are consistent with disks in some cases. The highest-redshift candidates have extremely blue UV-continuum slopes −3<β<−2.5, young ages ∼10−100 Myr, and stellar masses log(M⋆/M⊙)=8.4−8.8 inferred from their SED modeling which indicate a rapid build-up of their stellar mass. Our search clearly demonstrates the capabilities of JWST to uncover robust photometric candidates up to very high redshifts, and peer into the formation epoch of the first galaxies.
Hakim Atek, et al., "Revealing Galaxy Candidates out to z∼16 with JWST Observations of the Lensing Cluster SMACS0723" arXiv:2207.12338 (July 25, 2022).

Yet another paper looks at early galaxies seen by the JWST at arXiv:2207.12356.

Monday, July 25, 2022

XENON1T Signal Not Supported By XENONnT

I have been arguing since the results came out that the XENON1T "signals" of dark matter aren't reliable because it didn't adequately control for background effects. The new and improved next generation version of the same experiment supports my conclusion.

The new XENONnT dark matter exclusion complements that of LZ. The LZ experiment is looking for dark matter with traditional WIMP model masses. The XENONnT experiment is looking for dark matter with masses typical of warm dark matter models, and other highly energetic lighter dark matter candidates like axion-like particles (ALPs). Both see no signal to high precisions.

Slide 26 compares the XENON1T excess with the new XENONnT result, and it's clear it was not a real signal. Probably some tritium contamination, maybe just a statistical fluctuation, but certainly not new physics.

More Observational Analysis Of Dark Matter Phenomena

A new paper notes a subtle, but quite general, flaw of conventional dark matter models, by comparing a little studied feature of actual hydrogen gas distributions that are observed with the distributions predicted by one of the leading dark matter simulations.
Atomic hydrogen (H I) gas, mostly residing in dark matter halos after cosmic reionization, is the fuel for star formation. Its relation with properties of host halo is the key to understand the cosmic H I distribution. In this work, we propose a flexible, empirical model of H I-halo relation. In this model, while the H I mass depends primarily on the mass of host halo, there is also secondary dependence on other halo properties. We apply our model to the observation data of the Arecibo Fast Legacy ALFA Survey (ALFALFA), and find it can successfully fit to the cosmic H I abundance (ΩHI), average H I-halo mass relation ⟨MHI|Mh⟩, and the H I clustering. The best fit of the ALFALFA data rejects with high confidence level the model with no secondary halo dependence of H I mass and the model with secondary dependence on halo spin parameter (λ), and shows strong dependence on halo formation time (a1/2) and halo concentration (cvir). 
In attempt to explain these findings from the perspective of hydrodynamical simulations, the IllustrisTNG simulation confirms the dependence of H I mass on secondary halo parameters. However, the IllustrisTNG results show strong dependence on λ and weak dependence on cvir and a1/2, and also predict a much larger value of H I clustering on large scales than observations. This discrepancy between the simulation and observation calls for improvements in understanding the H I-halo relation from both theoretical and observational sides.
Zhixing Li, Hong Guo, Yi Mao, "Theoretical Models of the Atomic Hydrogen Content in Dark Matter Halos" arXiv:2207.10414 (July 21, 2022).

An analysis finds that modified gravity theories, generally are a better fit to the character of the data than dark matter particle or modified inertia theories. It is one of the rare papers to compare modified inertia theories to modified gravity theories.
Mass discrepancy in galaxies invokes dark matter, or alternatively modification of gravity or inertia. These theoretical possibilities may be distinguished by the statistical relation between the centripetal acceleration of particles in orbital motion and the expected Newtonian acceleration for the observed distribution of baryons in galaxies. Here predictions of cold dark matter halos, modified gravity, and modified inertia are compared and tested by a statistical sample of rotation curves of galaxies. 
Modified gravity under an estimated mean external field correctly predicts the observed statistical relation of accelerations. Cold dark matter halos predict systematically deviating relations and modified inertia is inconsistent with the apparently seen difference between the inner and outer parts. All aspects of rotation curves are most naturally explained by modified gravity.
Kyu-Hyun Chae, "Distinguishing Dark Matter, Modified Gravity, and Modified Inertia by the Inner and Outer Parts of Galactic Rotation Curves" arXiv:2207.11069 (July 22, 2022).

Thursday, July 21, 2022

The Testimony Of 14,000 Year Old Ancient DNA From SW China

In Xiaoming Zhang et al., "A Late Pleistocene human genome from Southwest China" (2022), the authors discuss their analysis of 14,000 year old ancient DNA from a woman at the Red Deer Cave named Mengzi Ren (MZR). (I tip my hat to Bernard's blog and to Razib who together alerted me to this paper.) I previously blogged this find, before ancient DNA analysis was available, on December 18, 2015.

Her "mosaic" of seemingly partially archaic bone features suggested that she might be an archaic hominin-modern human hybrid in Southwest China. 

As was the case with seemingly archaic featured remains in South America that were later genotyped to be ordinary indigenous Americans genetically, the reality was less flashy and was largely paradigm affirming. 

The results disfavor the late persistence of archaic hominins in mainland Asia, and demand a non-genetic explanation for her seemingly archaic features, as she is genetically a typical Southeast and southern East Asian anatomically modern human.

Perhaps the most novel conclusion of the paper is that it substantiates a strong genetic affinity between the Red Deer Cave people of Southwest China ca. 14,000 years ago, and the main founding population of the Americas which broke away from Asia at roughly the same time or a few thousand years earlier.


Her mtDNA was a now extinct basal branch of mtDNA M9, a non-African modern human mtDNA clade, that is fairly closely related to the mtDNA M9 clades that are common in China's interior and central Asia (and to a lesser extent in the rest of China). Her mtDNA deviates by just one mutation from the mtDNA M9 root.

In island Southeast Asia and Vietnam, in contrast, mtDNA E which is also a basal branch of mtDNA M is more common.

Autosomal DNA

She is definitively an anatomically modern human based upon her autosomal DNA, which is close on a PCA chart of overall genetic similarity to Hoabinhian hunter-gatherers who occupied Southeast Asia and adjacent regions in China from sometime in the Upper Paleolithic, a.k.a. Late Pleistocene, era until about 2000 BCE.  

There has been considerable genetic continuity from her to modern populations that were until recently hunter-gathers in the region over the last 14,000 years.

She shows an even greater autosomal genetic affinity to contemporaneous Northeast Asians on the brink of the Bering land bridge and to the oldest Native American ancient genomes, than she does with mainland Southeast Asian Hoabinhians.

Her autosomal DNA reflected most strongly an ancestral DNA component now associated with Southeast Asia with a significant minority of ancestry that was distinctively Northeast Asian, in addition to trace ancestry components that were distinctive African, specifically Native American, European or Papuan (and she has no distinctive South Asian ancestry component).

This indicates that 14,000 years ago, there was already differentiation and population structure between Northeast Asia and mainland Southeast Asia that had formed, and then produced admixed populations again, of which she was a member.

Archaic Hominin Ancestry

Her percentages of Neanderthal (1.27%) and Denisovan (1.29%) autosomal DNA admixture is similar to that other modern humans of that era and does not show enhanced or recent archaic admixture. Her Neanderthal and Denisovan ancestry percentages are broadly similar to modern Asian people from this region today.

This is what the paradigm would expect since there are no really definitive examples of archaic hominins in mainland Southeast Asia or China more recent than about 100,000 years ago. 

Evidence of a Neanderthal presence has never been found east of South Asia in places south of the Altai. 

The History Of Two Asian Genetic Variants

She lacks a derived genetic variant associated with light skin in modern East Asians that an analysis of many ancient and modern DNA samples in the papers concludes arose only in the early Holocene era (i.e. in the last 10,000 years) with the oldest isolated example from 7,500 years ago and some examples in the las 5,000 years and predominance in the last hundred years.

The paper also analyzes the emergence of the derived EDAR variant which is the source of some of the distinctively "Asian" phenotype. This arises many thousands of years earlier than the light skin genetic variant, but apparently the ancient DNA sample from this woman was missing the part of her genome that would have contains the EDAR variant, so we don't know if she had it or not. The oldest example of the derived EDAR variant is from the Amur region in Northeast Asia from about 19,000 years ago (although mutation rate estimates suggest it originated 30,000 years ago), and it is fairly widespread in East Asia, Northeast Asia, and the Americas from 11,600 years ago onward, becoming predominant in Southeast Asia, East Asia, Northeast Asia and the Americas by 4,900 years ago.

Both of these derived genetic variants that are distinguishing features of modern Southeast and East Asians post-dated the Last Glacial Maximum which led to essentially total population replacement in Northern Asia (and preceded any significant modern human population that left lasting traces in the Americas).

The Paper's Analysis

The discussion section of the paper generally sums up these themes and adds some additional cross-disciplinary speculation, most of which is plausible, although the bold underlined conjecture really has no solid support.
Southern East Asia harbors rich archaeo-anthropological sites with rich morphological diversities, including the ∼100 kya Zhiren Cave and ∼120–80 kya Fuyan Cave in southern China (although a recent study suggested much younger dates for these two sites), the ∼190–50 kya H. floresiensis, and the 67 kya H. luzonensis in Southeast Asia.  
Indeed, based on the published mitochondrial genome data, the matrilineal lineage diversity of the Late Pleistocene hominins in eastern Eurasia is quite high, including the reported Ust’-Ishim (45.0 kya, novel N), Salkhit (34.0 kya, independent novel N), Tianyuan (40.0 kya, basal B), Yana-old (32.0 kya, U), MA-1 (24.3 kya, novel U), LLR (11.0 kya, M27d), and MZR (14.0 kya, basal M9) in this study, many of which were lost during the post Pleistocene (<11.7 kya) human evolutionary histories. 
In addition, the hominin fossils from these archaeological sites, such as MZR and LLR, all exhibit rich physical anthropological diversities, some of which were thought to overlap with the morphological characteristics of archaic hominins and triggered proposals of different scenarios of human evolution in this area.
In this study, we provide compelling evidence that the Late Pleistocene MZR from Malu Dong in Southwest China is an AMH. The nuclear genome data indicate that MZR represents an early diversified AMH lineage in East Asia. The mtDNA of MZR belongs to one of the root matrilineal lineages of AMHs in southern East Asia. Identified as a novel basal M9 lineage, MZR may represent one of the extinct pioneer hunter-gatherers ancestral to millet and rice farmers in China who emerged in the Yellow River and Yangtze River valley during the Early Neolithic period. Additionally, we observe obvious stratification and substructure of ancient human populations between southern China and mainland Southeast Asia, an indication of already diversified genetic backgrounds of the Late Pleistocene populations in southern East Asia. . . .
It should be noted that the MZR morphological data are indeed informative in reconstructing human morphological diversity during the Late Pleistocene in southern East Asia. However, due to the limited human remains as well as the limited number of morphological traits, it would be hard to confidently reveal the identity of the studied subject. To this end, genome sequence data are critical for unequivocal species identification, quantification of genetic introgression, and reconstruction of population history.
Spatiotemporal tracing of mutations related to phenotypic changes in human populations can help reconstruct the prehistoric patterns of how natural selection has shaped these adaptive events. We observed that the OCA2-HiS615Arg (rs1800414) variant, a key adaptive mutation causing skin lightening in East Asians, initially emerged in the southern coastal region of China during the early Neolithic (Liangdao2-7.5kya). The rapid dispersal of this variant during the past 4,000 years in East Asia is consistent with the proposed Darwinian positive selection on the adaptive allele (OCA2-615Arg), leading to skin lightening in East Asians to cope with the relatively low UV radiation in high-latitude areas. Interestingly, the rapid explosion of OCA2-615Arg coincides with the known major population expansion in China during the Late Holocene epoch. It should be noted that due to the limited aDNA data in East Asia, the inferred time of selection onset for OCA2-HiS615Arg is a rough estimation. With more aDNA data available in the future, we expect more accurate time estimation and high-resolution spatial-temporal tracking of adaptive genetic variants in East Asia.
Consistent with the dating of MZR (14.0 kya), following the end of the LGM (26.5–19.0 kya) and the earliest securely dated sites in Beringia (15–14 kya), we demonstrate that MZR has a higher affinity to First Americans than to Tianyuan (40 kya) and all the pre-LGM Late Pleistocene Siberians. MZR, Amur-19K, and UKY are cladal with respect to First Americans, while Amur-14kya and UKY exhibit a higher affinity to the Americans compared to MZR. Thus, MZR is linked deeply and indirectly to the ancestry that contributed to First Americans. We speculate that during the Late Pleistocene, there was an express northward expansion of AMHs starting in southern East Asia through the coastal line of China, possibly by way of the Japanese Islands, and eventually crossing the Bering Strait and reaching the Americas. However, the scenario that MZR shows a higher affinity to Americans compared to Jomon likely reflects that the 2.6 kya Jomon population does not represent the early post-LGM humans who settled in the Japanese archipelago. 
The proposed migratory route along the east coast of East Asia by way of the Japanese Islands is supported by a recent finding of a Paleolithic site (∼16 kya) at Cooper’s Ferry of western Idaho, USA, where they found the use of unfluted stemmed projectile point technologies before the appearance of the Clovis Paleoindian tradition. Notably, it exhibits early cultural connections with Paleolithic nonfluted projectile point traditions in Japan. The bifacial point and backed blade technologies (∼22–16 kya) in Honshu, Japan, lend technological correlates to the shared ecological and geographical factors with the Americas.
This scenario is also supported by the current distribution pattern of the ancient Y-chromosome lineage Hg C in coastal East Asia, Siberia, and North America. Approximately 40 kya, stemming from southern East Asia, the Hg C carriers started a northward expansion along the coastal regions of mainland China, the Korean Peninsula, and the Japanese archipelago, reaching Siberia ∼15 kya, and finally made their way to the Americas.  
In addition, unlike all other East Asian populations, the indigenous Ainu people in northern Japan and Sakhalin Island, Russia, show a closer genetic affinity with northeastern Siberians than with central Siberians. Hence, the Japanese Islands may serve as the midway station along the proposed migratory route, and aDNA data of Late Pleistocene human remains from Japan will be highly informative in testing the proposed coastal route. 
Finally, the spatial-temporal distribution of the East Asian-specific EDAR-V370A variant, as well as its early presence in the LosRieles-12.0kya sample from coastal Chile of South America, supported a clear contribution of the Late Pleistocene East Asians to the first Americans.
In summary, we generated ancient genome sequences of MZR, a Late Pleistocene female who lived in Southwest China, one of the global biodiversity hotspots and the ice age refuge region. The aDNA data confirm that she possesses diverse genetic components and represents an early diversified population, suggesting the scenario of more diverse AMH lineages than previously thought during the Late Pleistocene in southern East Asia. Our study paves the way to explore genetic explanations of morphological complexities of early hominins. MZR also shows a deep and indirect link to the ancestry that contributed to First Americans, which may help reconstruct the earliest migratory route from East Asia to the Americas.

MOND Has Predicted Early Galaxies For A Long Time

Triton Station reviews the fact that MOND has predicted very early galaxies for a long time, which the James Webb Space Telescope (JWST) is now confirming even more firmly than earlier telescopes had. This is contrary to very solid predicts of the LambdaCDM "Standard Model of Cosmology." 

The "impossible early galaxy problem" isn't new, but JWST underlines even more strongly that it is not an artifact of methodological issues, now having seen a galaxy at z=13 (the bigger the z the closer a galaxy is to the Big Bang) after just a few weeks of looking for one.

Image from Wikipedia

Indeed, as in the case of galaxy clusters, MOND makes corrections that are substantial, and in the right direction between reality and what is predicted, but not quite strong enough, even though it does much better than LambdaCDM does when it comes to galaxy formation time. This is probably for the same or similar reasons, since the environment in the Universe in which the first galaxies emerged probably was fairly similar to that of galaxy clusters in which active star and galaxy formation are going on today.

In particular, I have in mind the dimensional reduction flux tube kind of considerations raised in A. Deur, “Implications of Graviton-Graviton Interaction to Dark Matter” (May 6, 2009) (published at 676 Phys. Lett. B 21 (2009) the effectively strength the dark matter phenomena effects in galaxy clusters due to the geometry of the mass distributions. 

These considerations are explored on a statistical many particle basis in Alexandre Deur, "Effect of gravitational field self-interaction on large structure formation" arXiv: 2018:04649 (July 9, 2021) (Accepted for publication in Phys. Lett. B) DOI: 10.1016/j.physletb.2021.136510; and in  A. Deur, "Effect of the field self-interaction of General Relativity on the Cosmic Microwave Background Anisotropies" arXiv:2203.02350 (March 4, 2022).
The 1998 October conference was titled “After the dark ages, when galaxies were young (the universe at 2 < z < 5).” That right there tells you what we were expecting. Redshift 5 was high – when the universe was a mere billion years old. Before that, not much going on (dark ages).

This was when the now famous SN Ia results corroborating the acceleration of the expansion rate predicted by concordance LCDM were shiny and new. Many of us already strongly suspected we needed to put the Lambda back in cosmology; the SN results sealed the deal.

One of the many lines of evidence leading to the rehabilitation of Lambda – previously anathema – was that we needed a bit more time to get observed structures to form. One wants the universe to be older than its contents, an off and on problem with globular clusters for forever. . . .

Famed simulator Carlos Frenk was there, and assured us not to worry. He had already done LCDM simulations, and knew the timing.

“There is nothing above redshift 7.” . . . 

[F]igure adapted from the thesis Jay Franck wrote here 5 years ago using Spitzer data (round points). It shows the characteristic brightness (Schechter M*) of galaxies as a function of redshift. The data diverge from the LCDM prediction (squares) as redshift increases.
The divergence happens because real galaxies are brighter (more stellar mass has assembled into a single object) than predicted by the hierarchical timeline expected in LCDM.
Remarkably, the data roughly follow the green line, which is an L* galaxy magically put in place at the inconceivably high redshift of z=10. Galaxies seem to have gotten big impossibly early. This is why you see us astronomers flipping our lids at the JWST results. Can’t happen.

Except that it can, and was predicted to do so by Bob Sanders a quarter century ago: “Objects of galaxy mass are the first virialized objects to form (by z=10) and larger structure develops rapidly.”

The reason is MOND. After decoupling, the baryons find themselves bereft of radiation support and suddenly deep in the low acceleration regime. Structure grows fast and becomes nonlinear almost immediately. It’s as if there is tons more dark matter than we infer nowadays.

Monday, July 18, 2022

There Are No WIMPs

Weakly interacting massive particles, a dark matter hypothesis inspired by supersymmetry theories, has long ago been falsified. 

The failure of direct detection experiments (in mass  ranges from 250 MeV to more than 10 TeV) shown  below is matched by lack of any signs of such particles in particle accelerators up to hundreds and thousands of GeV, and by the dynamics of inferred dark matter in galaxies.

Image from here. The dotted blue line labeled Z portal Cx=1 in the chart below is basically equivalent to the cross-section of interaction with nucleons of ordinary Standard Model neutrinos. A femtobarn (fb) is 10^-39 cm^2. An attobarn (ab) is 10^-42 cm^2. A zeptobarn (zb) is 10^-45 cm^2. A yoctobarn (yb) is 10^-48 cm^2.
The latest experimental limits on WIMP dark matter from LZ (arXiv:2207.03764). The parameter space above the line is excluded. Note the scale on the y-axis bearing in mind that the original expectation was for a cross section around 10-39 cm2, well above the top edge of this graph.
LZ is a merger of two previous experiments compelled to grow still bigger in the never-ending search for dark matter. It contains “seven active tonnes of liquid xenon,” which is an absurd amount, being a substantial fraction of the entire terrestrial supply. It all has to be super-cooled to near absolute zero and filtered of all contaminants that might include naturally radioactive isotopes that might mimic the sought-after signal of dark matter scattering off of xenon nuclei. It is a technological tour de force.
The technology is really fantastic. The experimentalists have accomplished amazing things in building these detectors. They have accomplished the target sensitivity, and then some. If WIMPs existed, they should have found them by now.

WIMPs have not been discovered. As the experiments have improved, the theorists have been obliged to repeatedly move the goalposts. The original (1980s) expectation for the interaction cross-section was 10^-39 cm^2. That was quickly excluded, but more careful (1990s) calculation suggested perhaps more like 10^-42 cm^2. This was also excluded experimentally. By the late 2000s, the “prediction” had migrated to 10^-46 cm^2. This has also now been excluded, so the goalposts have been moved to 10^-48 cm^2. This migration has been driven entirely by the data; there is nothing miraculous about a WIMP with this cross section.

From Triton Station

Still No Sign Of Neutrinoless Double Beta Decay

From here (arXiv 2207.07638).

Of course, we have good reason (from cosmology data and from the pattern of the neutrino mass differences in oscillation data) to think that the neutrino masses are smaller than the masses at which neutrinoless double beta decay ought to be possible to detect with existing experiments in any case, so the null result doesn't necessarily do much to shake the Majorana neutrino mass hypothesis yet.

Friday, July 15, 2022

Happy Friday!


Kroupa On Dark Matter v. MOND

Pavel Kroupa, a leading MOND researcher, published an article in the IAI news, directed at a broader audience on July 12, 2022 forthrightly titled "Dark Matter Doesn't Exist" that makes some less commonly discussed arguments for this position. It states in some notable parts:
This dark-matter-based model (for each gram of normal matter there are 25 grams of the exotic dark matter) is about 20 years old, but the strong belief in the scientific community that dark matter exists goes back 30 years. . . .

The many searches worldwide for evidence of dark matter particles, going on since at least 30 years, have come up empty handed. . . .

there is a simple test that these scientists are ignoring and which has already been applied and it tells us that dark matter does not exist. This test goes back to Subrahmanyan Chandrasekhar who, in 1943, showed that a massive body (e.g. a dwarf galaxy) that moves through a background of comparatively low mass particles (e.g. dark matter particles), will slow down. This process of "Chandrasekhar dynamical friction" is exceedingly well understood. . . .With my collaborators and students, we have applied a number of observed galaxy systems to the calculations of Chandrasekhar dynamical friction we would expect to see if dark matter existed, and in all and every case it turns out that the slow-down is not in the data. . . . Rather than observing the slow down of galaxies through Chandrasekhar dynamical friction, we observed a speed-up as the galaxies fall towards each other. This is the same as two stars that fall towards each other in a star cluster. They get faster until they pass each other and then they recede again from each other. . . .

satellite galaxies are typically orbiting their host galaxies in vast disks of satellites, much like the planets orbit the Sun in one plane, while according to the dark matter models, they should be orbiting in all possible directions. . . .

the research community has largely ignored these falsifications

Three other very major tests of the dark-matter based models have been published recently:

(A) One test relies on how rapidly a dark-matter-filled universe can form extremely massive clusters of galaxies that also penetrate each other. The El Gordo galaxy cluster is immensely heavy, weighing a thousand times the mass of the Milky Way and Andromeda together. This cluster is actually composed of two such clusters which have formed and transgressed through each other at a time when the Universe was only half its present age. It turns out that the dark-matter-based models cannot, under any circumstances, grow such massive clusters and also have them falling through each other by that time, falsifying the dark-matter based models rigorously.

(B) Astronomers have also discovered that the local Universe expands more rapidly than the distant Universe. This problem, known as the "Hubble Tension", has triggered many concurrent conferences and hugely long texts written by hundreds of scientists in which all possible solutions are being discussed and explained. Very exotic dark-matter-based models are being developed, with additional processes being speculated to act on dark matter (e.g. dark matter could be decaying, there could be dark photons) or that dark energy has some complex time behaviour or multiple dark forms. Impressive is that this vast expert community, that includes or is driven by major-prize-winning scientists, is entirely ignoring the obvious solution to the Hubble Tension: we are in a region spanning more than a billion lightyears across which contains fewer galaxies by about a factor of two than should be there. Galaxies in this void fall towards its sides (like apples falling to the ground) which is why we witness an apparently faster expanding Local Universe. While this "KBC Void" naturally accounts for the Hubble Tension, the KBC Void is entirely incompatible with the dark-matter-based models because these constitute a model universe which is homogeneous and isotropic on scales larger than a few dozen million lightyears.

(C) Another test of the dark matter models is to compare the thickness of galaxies with those observed in the real Universe in which more than 90 per cent of all galaxies are very thin spiral, or disk, galaxies. In the dark matter models galaxies grow over time mostly by merging with other galaxies. These galaxy-crashes typically destroy the thin disks. Our sophisticated analysis of thousands of observed galaxies show the dark matter based models to be totally incompatible with the real Universe, as the model produces galaxies that are typically too roundish compared to the profusive thin disk galaxies in the real Universe. 

Other problems between the real Universe and the dark-matter models include massive galaxies to have been observed at an early time at which they should not yet exist, 
that modern observations tell us there to be dust between galaxies which challenges the interpretation of the cosmic microwave back ground as being the photosphere of the Hot Big Bang and that the cosmic microwave background has features in it that are incompatible with an inflationary origin, suggest that the Universe is structured on all scales (like a fractal perhaps) such that it may be understandable in terms of dust emission rather than a Hot Big Bang.

Three implications arise from the above:

(a) Modern cosmological theory is totally wrong and we need to develop a new theory based on MOND. MOND is a modern non-relativistic theory of gravitation which extends that of Newton by incorporating data from galaxies which were neither available to Newton nor to Einstein, both of whom had to base their deductions on data limited to the Solar System only. All predictions made 40 years ago by Mordehai Milgrom in the foundation papers have been verified, and in Prague and Bonn we (with Nils Wittenburg and Nick Samaras) are now performing the first ever full cosmological calculations with star formation of a MOND universe. 
MOND comes from a simple space-time scale symmetry and may be a consequence of the quantum vacuum, opening a possible path towards unifying gravitation with standard-model particle physics. A major recent review for further in-depth reading has just been published.
Some of the criticisms are familiar, but a few are less commonly discussed. 

The case against dark matter from a lack of evidence of "Chandrasekhar dynamical friction"is a rarely raised by solid and fairly global and robust challenge of a wide variety of dark matter paradigms.

The argument that too many galaxies are thin disks for a LambdaCDM galaxy assembly history to make sense is also a good and rarely raised argument.

The Hubble tension argument is less compelling, because there are so many competing and plausible explanations for it from systemic measurement biases, to overlooked GR effects, to various forms of new physics and it needs to be sorted out and lots of researchers are working in good faith to do that.

The other criticisms are long standing and familiar (and his list omits some of my favorites).

Kroupa's article lacks a bit in not recognizing the importance of having a fundamental foundation for MOND which is a non-relativistic toy model in its original form and which needs to be generalized into a relativistic theory that can be integrated more easily with existing Standard Model and GR physics (which may not even require modification of GR). In truth, there are many ways to create models that largely recreate MOND's results.

It also lacks a bit for failing to recognize that dark matter particle theories are evolving to address their short fallings with more elaborate models, setting up something of a straw man argument.

Greater clarity on what exactly is being falsified would be helpful and is possible to do.

Still, on the merits, for reasons that extend beyond those in the article itself, I do think that he is right that there is no dark matter and the scientific community is too locked into the dark matter paradigm, even though I would make some of those arguments more tightly and would focus on somewhat different conflicts that he does.

I'll close this post by recapping his references, highlighting the most critical ones, such as those that support the stronger points above:
[1] "Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation" Kroupa, P., 2015CaJPh..93..169K

[2] "Fast galaxy bars continue to challenge standard cosmology" Roshan, M. et al., 2021MNRAS.508..926R

[3] "The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology" Kroupa, P., 2012PASA...29..395K

[4] "Phase-Space Correlations among Systems of Satellite Galaxies" Pawlowski, M., 2021Galax...9...66P

[5] "Are Disks of Satellites Comprised of Tidal Dwarf Galaxies?" Bilek, M., et al., 2021Galax...9..100B

[6] "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

[7] "The KBC void and Hubble tension contradict ΛCDM on a Gpc scale - Milgromian dynamics as a possible solution" Haslbauer, M. et al., 2020MNRAS.499.2845H

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

[9] "The Impossibly Early Galaxy Problem" Steinhardt, C.L., et al., 2016ApJ...824...21S

[10] "Universe opacity and CMB" Vavrycuk, V., 2018MNRAS.478..283V

[11] "CMB anomalies after Planck" Schwarz, D., et al., 2016CQGra..33r4001S

[12] "A modification of the Newtonian dynamics as a possible alternative to the hidden mass hypothesis." Milgrom, M., 1983ApJ...270..365M

[13] "A modification of the Newtonian dynamics - Implications for galaxies." Milgrom, M., 1983ApJ...270..371M

[14] "A modification of the newtonian dynamics : implications for galaxy systems." Milgrom, M., 1983ApJ...270..384M

[15] "The Mond Limit from Spacetime Scale Invariance" Milgrom, M., 2009ApJ...698.1630M

[16] "The modified dynamics as a vacuum effect" Milgrom, M., 1999PhLA..253..273M

[17] "From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity" Banik, I. and Zhao, H.S., 2022Symm...14.1331B

[18] "A Philosophical Approach to MOND: Assessing the Milgromian Research Program in Cosmology" Merritt, D., 2020, Cambridge University Press, ISBN: 9781108492690, 2020

Wednesday, July 13, 2022

What Does The Latest Cosmology Data Say About Neutrinos?

Cosmology data combined with neutrino oscillation data favors a sum of three neutrino masses between 0.06 and 0.087 eV (nominally ruling out an inverted mass hierarchy at the 95% confidence interval level, which oscillation data alone favor at a 2-2.7σ level), implying a lightest neutrino mass eigenstate of about 0.007 eV or less (compared to an upper bound on the lightest neutrino mass of 0.8 eV potentially reducible to 0.2 eV within a few years from direct measurements). 

These combined data sources also imply that there are exactly three neutrino types with masses low enough to count as neutrinos in the ΛCDM model at the five sigma level, which would include any light sterile neutrinos if they existed. The predicted value of N(eff) in this scenario is 3.045 which is within 0.2 sigma of the observed value.


We present robust, model-marginalized limits on both the total neutrino mass (mν) and abundance (Neff) to minimize the role of parameterizations, priors and models when extracting neutrino properties from cosmology. The cosmological observations we consider are CMB temperature fluctuation and polarization measurements, Supernovae Ia luminosity distances, BAO observations and determinations of the growth rate parameter from the Data Release 16 of the Sloan Digital Sky Survey IV. 
The degenerate neutrino mass spectrum (which implies mν>0) is weakly (moderately) preferred over the normal and inverted hierarchy possibilities, which imply the priors mν>0.06 and mν>0.1 eV respectively. Concerning the underlying cosmological model, the ΛCDM minimal scenario is almost always strongly preferred over the possible extensions explored here. The most constraining 95% CL bound on the total neutrino mass in the ΛCDM+mν picture is mν<0.087 eV. The parameter Neff is restricted to 3.08±0.17 (68% CL) in the ΛCDM+Neff model. These limits barely change when considering the ΛCDM+mν+Neff scenario. 
Given the robustness and the strong constraining power of the cosmological measurements employed here, the model-marginalized posteriors obtained considering a large spectra of non-minimal cosmologies are very close to the previous bounds, obtained within the ΛCDM framework in the degenerate neutrino mass spectrum. Future cosmological measurements may improve the current Bayesian evidence favouring the degenerate neutrino mass spectra, challenging therefore the consistency between cosmological neutrino mass bounds and oscillation neutrino measurements, and potentially suggesting a more complicated cosmological model and/or neutrino sector.
Eleonora di Valentino, Stefano Gariazzo, Olga Mena, "Model marginalized constraints on neutrino properties from cosmology" arXiv:2207.05167 (July 11, 2022).