Thursday, June 29, 2023

IceCube Proves Its Neutrino Telescope Works

The IceCube Neutrino Observatory's latest improvements have brought it to the point where it has started to function as a genuine neutrino telescope as intended. A new paper to be released tomorrow documents its successful test run.
[T]he IceCube Neutrino Observatory has produced an image of the Milky Way using neutrinos—tiny, ghostlike astronomical messengers. In an article to be published tomorrow, June 30, in the journal Science, the IceCube Collaboration, an international group of over 350 scientists, presents evidence of high-energy neutrino emission from the Milky Way. 
The high-energy neutrinos, with energies millions to billions of times higher than those produced by the fusion reactions that power stars, were detected by the IceCube Neutrino Observatory, a gigaton detector operating at the Amundsen-Scott South Pole Station. . . . 
[U]nlike the case for light of any wavelength, in neutrinos, the universe outshines the nearby sources in our own galaxy. . . . Interactions between cosmic rays—high-energy protons and heavier nuclei, also produced in our galaxy–and galactic gas and dust inevitably produce both gamma rays and neutrinos. 
Given the observation of gamma rays from the galactic plane, the Milky Way was expected to be a source of high-energy neutrinos. “A neutrino counterpart has now been measured, thus confirming what we know about our galaxy and cosmic ray sources. . . 
“The improved methods allowed us to retain over an order of magnitude more neutrino events with better angular reconstruction, resulting in an analysis that is three times more sensitive than the previous search,” . . . . The dataset used in the study included 60,000 neutrinos spanning 10 years of IceCube data, 30 times as many events as the selection used in a previous analysis of the galactic plane using cascade events. These neutrinos were compared to previously published prediction maps of locations in the sky where the galaxy was expected to shine in neutrinos.

The Gravitational Wave Background Per NANOGrav

By carefully observing ultra-precise pulsar timing data over fifteen years and correlating irregularities from different sources, they have observed a shared random background gravitational wave signal that follows a power law. The signal seen is what would be expected from the gravitational waves created by multiple supermassive binary black hole systems.
We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. 
The correlations follow the Hellings–Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 10^14, and this same model is favored over an uncorrelated common power-law spectrum model with Bayes factors of 200–1000, depending on spectral modeling choices. 
We have built a statistical background distribution for the latter Bayes factors using a method that removes interpulsar correlations from our data set, finding p = 10^−3 (≈3σ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of interpulsar correlations yields p = 5 × 10^−5 to 1.9 × 10^−4 (≈3.5σ–4σ). 
Assuming a fiducial f−2/3 characteristic strain spectrum, as appropriate for an ensemble of binary supermassive black hole inspirals, the strain amplitude is (median + 90% credible interval) at a reference frequency of 1 yr^−1. The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings–Downs correlations points to the gravitational-wave origin of this signal.
Gabriella Agazie, et al., "The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background" 951(1) The Astrophysical Journal Letters L8 (June 29, 2023) DOI 10.3847/2041-8213/acdac6

Cold Dark Matter Still Doesn't Work, MOND Moves Forward

Stacy McGaugh at Triton Station recaps a long list of problems with cold dark matter (CDM) theories from a decade old review article that are almost all still there and in some cases worse. But these issues for CDM aren't troublesome for MOND for the most part. I have a list of 33 CDM theory problems, but I'm sure that I'm missing some of them from this list (like the far lower than expected number of galaxies in large scale structure voids, which is natural in MOND).

Why the discipline stands by a LambdaCDM theory that is dying from a thousand cuts is beyond me.

Toy-model MOND may not be the final solution, which either is, or looks something like, Deur's gravitational field self-interaction approach (that relies on the non-perturbative behavior of the General Relativity Lagrangian and mimics MOND closing in its domain of applicability). 

The strong tendency of Deur's theory and reality to favor disk-like matter distributions over sphere-like matter distributions (noted at several points in the recap), and the apparently weaker MOND effects outside the galactic plane, both support this approach, as does the relationship between the ellipticity of elliptical galaxies and their apparent dark matter fraction.  

Dark matter phenomena just has to have a gravity-type solution that reproduces MOND in the basic behavior of most galaxies. Dark matter phenomena are wave-like, not particle-like. The evidence of this is overwhelming.

The biggest issue within the MOND community, which was front and center at its 40th anniversary conference, is what the wide binary star system tests show. These tests, potentially, are powerful discriminants between different variants of modified gravity theories. Analyzing the data in a way that can show which properties wide binary stars really have is hard. But it is not an insurmountable problem. The firehose of new, better quality data from a variety of "telescopes" continues to flow and computer processing power to make sense of it continues to improve, so we will get our answers soon enough. 

Some of the problems not on my existing list:

The local void challenge.
Peebles has been pointing out for a long time that voids are more empty than they should be, and do not contain the population of galaxies expected in LCDM. They’re too normal, too big, and gee it would help if structure formed faster. In our review, we pointed out that the “Local Void” hosts only 3 galaxies, which is much less than the expected ∼ 20 for a typical similar void in ΛCDM.

The angular momentum challenge 

During galaxy formation, the baryons sink to the centers of their dark matter halos. A persistent idea is that they spin up as they do so (like a figure skater pulling her arms in), ultimately establishing a rotationally supported equilibrium in which the galaxy disk is around ten or twenty times smaller than the dark matter halo that birthed it, depending on the initial spin of the halo. This is a seductively simple picture that still has many adherents despite never having really worked. In live simulations, in which baryonic and dark matter particles interact, there is a net transfer of angular momentum from the baryonic disk to the dark halo. This results in simulated disks being much too small.

This problem is solved by invoking just-so feedback again. Whether the feedback one needs to solve this problem is consistent with the feedback one needs to solve the cusp-core problem is unclear, in large part because different groups have different implementations of feedback that all do different things. At most one of them can be right. Given familiarity with the approximations involved, a more likely number is Zero.

The pure disk challenge 

Structure forms hierarchically in CDM: small galaxies merge into larger ones. This process is hostile to the existence of dynamically cold, rotating disks, preferring instead to construct dynamically hot, spheroidal galaxies. All the merging destroys disks. Yet spiral galaxies are ubiquitous, and many late type galaxies have no central bulge component at all. At some point it was recognized that the existence of quiescent disks didn’t make a whole lot of sense in LCDM. To form such things, one needs to let gas dissipate and settle into a plane without getting torqued and bombarded by lots of lumps falling onto it from random directions. Indeed, it proved difficult to form large, bulgeless, thin disk galaxies in simulations.

The solution seems to be just-so feedback again, though I don’t see how that can preclude the dynamical chaos caused by merging dark matter halos regardless of what the baryons do.

The stability challenge 

One of the early indications of the need for spiral galaxies to be embedded in dark matter halos was the stability of disks. Thin, dynamically cold spiral disks are everywhere around us, yet Newton can’t hold them together by himself: simulated spirals self destruct on a short timescale (a few orbits). A dark matter halo precludes this from happening by counterbalancing the self-gravity of the disk. This is a somewhat fine-tuned situation: too little halo, and a disk goes unstable; too much and disk self-gravity is suppressed – and spiral arms and bars along with it.

I recognized this as a potential test early on. Dark matter halos tend to over-stabilize low surface density disks against the formation of bars and spirals. You need a lot of dark matter to explain the rotation curve, but not too much so as to allow for spiral structure. These tensions can be contradictory, and the tension I anticipated long ago has been realized in subsequent analyses.

I’m not aware of this problem being addressed in the context of cold dark matter models, much less solved. The problem is very much present in modern hydrodynamical simulations, as illustrated by this figure from the enormous review by Banik & Zhao:

The missing baryons challenge

The cosmic fraction of baryons – the ratio of normal matter to dark matter – is well known (16 ± 1%). One might reasonably expect individual CDM halos to be in in possession of this universal baryon fraction: the sum of the stars and gas in a galaxy should be 16% of the total, mostly dark mass. However, most objects fall well short of this mark, with the only exception being the most massive clusters of galaxies. So where are all the baryons? 

All told this adds about four or five problems to my existing 33 problems with Lambda CDM.

Ancient Giant Sharks Were Warm-Blooded

Being warm-blooded can support larger body size and ancient giant sharks called megalodons were among them. Most fish and reptiles are cold blooded.

Otodus megalodon (center in this illustration, preying on a seal) was warmer-blooded than the great white shark (top left). That warm-bloodedness may have helped it grow so large, but also ultimately spelled its doom as food sources dwindled.
Massive, megatoothed Otodus megalodon ran hot — the ancient shark was at least somewhat warm-blooded, new evidence shows.

Chemical measurements from fossil O. megalodon teeth suggest the sharks had higher body temperatures than their surrounding waters, researchers report June 26 in Proceedings of the National Academy of Sciences. Analyses of carbon and oxygen in the teeth of these and other sharks, both living and extinct, revealed that the giant shark’s body temperature was about 7 degrees Celsius warmer than estimated seawater temperatures at the time.
From Science News citing three papers:

* M. Griffiths et al., Endothermic physiology of extinct megatooth sharks. Proceedings of the National Academy of Sciences (June 26, 2023). doi: 10.1073/pnas.2218153120.

* J. A. Cooper et al. The extinct shark Otodus megalodon was a transoceanic superpredator: Inferences from 3D modeling. Science Advances (August 17, 2022). doi: 10.1126/sciadv.abm9424.

* H. Ferrón. Regional endothermy as a trigger for gigantism in some extinct macropredatory sharks. PLOS ONE (September 22, 2017). doi: 10.1371/journal.pone.0185185.

Wednesday, June 28, 2023

Pion Decays Rule Out Vector X17 Bosons

In advance of more targeted tests, data from pion decays rule out a vector X17 boson and strongly constrain an axial-vector X17 boson. In the end, the ATOMKI claim will be discredited.
We derive constraints on the couplings of light vector particles to all first-generation Standard Model fermions using leptonic decays of the charged pion, π+→e+νeXμ. In models where the net charge to which Xμ couples to is not conserved, no lepton helicity flip is required for the decay to happen, enhancing the decay rate by factors of O(m4π/m2em2X). A past search at the SINDRUM-I spectrometer severely constrains this possibility. In the context of the hypothesized 17 MeV particle proposed to explain anomalous 8Be, 4He, and 12C nuclear transitions claimed by the ATOMKI experiment, this limit rules out vector-boson explanations and poses strong limits on axial-vector ones.
Matheus Hostert, Maxim Pospelov, "Pion decay constraints on exotic 17 MeV vector bosons" arXiv:2306.15077 (June 26, 2023).

Tuesday, June 20, 2023

Calculations Of Quark Masses And The Strong Coupling Constant

The New Parameter Determinations

A pair of new papers (here and here) make precision determinations of the quark masses and the strong force coupling constant using the renormalization group summed perturbation theory (RGSPT). For comparison purposes, I have followed each value with the Particle Data Group (PDG) value, and then the 2021 Flavor Lattice Averaging Group (FLAG) value.

α(s)(n(f)=5)(M(Z)) = 0.1171(7)
<----> 0.1179(9) <----> 0.1184(8). 

m_b(MS mass pole mass) = 4174.3(9.5) MeV 
<----> 4180-20+30 MeV <----> 4203(11) MeV

m_c(MS mass pole mass) = 1281.1(3.8) MeV 
<----> 1270(20) MeV <----> 1278(13) MeV

m_s(2 GeV) = 104.34-4.21+4.23 MeV
<----> 93.4-3.4+8.6 MeV <----> 93.44(68) MeV

m_d(2 GeV) = 4.21-0.45+0.48 MeV
<----> 4.67-0.17+0.48 MeV <----> 4.70(5) MeV

m_u(2 GeV) = 2.00-0.40+0.33 MeV
<----> 2.16-0.26+0.49 MeV <----> 2.14(8) MeV


All of the RGSPT values are consistent at the two sigma level with the Particle Data Group global average measurements, although there is more tension between the strange quark mass estimates (1.14 sigma) than between the other parameter determinations, which are consistent at the sub-one sigma level. 

Some of the tensions between the RGSPT values and the FLAG values are more significant: the bottom quark mass discrepancy is just under two sigma. The strange quark discrepancy is 2.56 sigma. The strong force coupling constant tension is 1.22 sigma.

The FLAG values and Particle Data Group global averages are all consistent with each other at the one sigma or less level.


The uncertainties in the RGSPT values are smaller than in the Particle Data Group global averages, except for the down quark. The up quark uncertainties are roughly comparable overall between the RGSPT values and the Particle Data Group global averages.

The FLAG values have less uncertainty for the light quarks than the RGSPT values, slightly more uncertainty than the RGSPT values for the charm quark mass, the bottom quark mass, and the strong force coupling constant. 

The FLAG values all have less uncertainty than the corresponding Particle Data Group global averages.

Why Are These Values Hard To Determine?

The difficulties involved in measuring these parameters almost entirely come down to calculation issues. Quarks other than the top quark always appear either confined in composite hadron particles, or in a quark-gluon plasma which makes localization of free quark masses impossible as a practical matter. Likewise, there are no clean isolated measurements of the strong force coupling constant. 

All of these parameters have to be inferred from the properties of hadrons which have been measured directly to vastly greater precision, and then converted with wickedly difficult quantum chromodynamics (QCD) calculations (sometimes with electromagnetic and weak force adjustments), to determine the fundamental parameter values.

Monday, June 19, 2023

Albanian Origins

A new article explores the genetic and linguistic origins of the Albanian people in the context of know historical events and ancient DNA.
The origins of the Albanian people have vexed linguists and historians for centuries, as Albanians first appear in the historical record in the 11th century CE, while their language is one of the most enigmatic branches of the Indo-European family. 
To identify the populations that contributed to the ancestry of Albanians, we undertake a genomic transect of the Balkans over the last 8000 years, where we analyse more than 6000 previously published ancient genomes using state-of-the-art bioinformatics tools and algorithms that quantify spatiotemporal human mobility. 
We find that modern Albanians descend from Roman era western Balkan populations, with additional admixture from Slavic-related groups. Remarkably, Albanian paternal ancestry shows continuity from Bronze Age Balkan populations, including those known as Illyrians. Our results provide an unprecedented understanding of the historical and demographic processes that led to the formation of modern Albanians and help locate the area where the Albanian language developed.
Leonidas-Romanos Davranoglou, Aris Aristodemou, David Wesolowski, Alexandros Heraclides, "Ancient DNA reveals the origins of the Albanians" bioRxiv (June 7, 2023).

The body text of the paper explains that:
During the Iron Age (1100 BCE–150 CE), the Balkans were characterised by remarkable cultural, linguistic, and genetic heterogeneity. In the western Balkans, “Celtic” cultures such as Hallstatt and La Tène, interacted for centuries with local groups referred to as the “Illyrians” and “Dalmatians”. Deep in the Balkan heartland, heterogenous populations named by classical authors as “Dacians”, “Dardanians”, “Moesians”, and “Paeonians” bordered nomadic cultures from the Pontic-Caspian steppe known as the “Scythians”, while the southeastern part of the peninsula was inhabited by “Thracians” and “Greeks”. Balkan peoples also expanded beyond the confines of the peninsula, with “Messapians” migrating to southeast Italy at least since 600 BCE. 
The linguistic and cultural diversity of the Balkans was considerably homogenised during the Hellenistic, Roman, and especially the Migration Period, when Germanic and Slavic-speaking groups massively settled in the region. These events ultimately led to the extinction of all palaeo-Balkan languages except Greek and Albanian. The latter is one of the most enigmatic branches of the Indo-European language family, having vexed linguists for more than two centuries.

Tracing the origins of Albanians and their language is challenging for several reasons. Only a handful of historical sources comment on the ethnic and linguistic composition of the southwest Balkans during the transition from classical antiquity to Medieval times (500-1000 CE), and none of them mention an Albanian-speaking population from the territory of modern Albania. Speakers of Slavic languages are reported to have inhabited what is now southern Albania in the 8th century CE, where the frequency of Slavic toponyms also peaks, while the same region is characterised by the presence of Greek-speakers at least since the Medieval period. The urbanised Medieval populations of the northwest, referred to by contemporary historians as the Romani/Ῥωμᾶνοι, are thought to have spoken a variant of vulgar Latin known as West Balkan Romance that persisted at least until the 13th century CE. The demographic and linguistic situation in the mountainous interior is unknown, and it is only in the 11th century CE that Albanians appear in the historical record, while the earliest surviving written document of their language dates to 1462 CE.

A number of linguistic hypotheses have attempted to identify the affinities of the Albanian language and to locate the region where it developed, yet no definitive conclusions have been drawn. The most prominent, mutually exclusive hypotheses can be divided into those arguing for a local west Balkan origin from an Illyrian or Messapic background [which may or may not have been distinct languages], and those proposing a non-local origin from a Daco-Moesian-Thracian background or an unattested Balkan language, whose speakers entered Albania from the central-east Balkans sometime after 400 CE. 
The validity of these hypotheses, although hotly debated, is hard to test, as these ancient languages are poorly recorded, being known only from fragmentary inscriptions, toponyms, and a handful of historical sources. 
Furthermore, all of the ethnonyms of ancient Balkan peoples, such as “Illyrian” and “Thracian”, are likely artificial labels that were coined by ancient and modern authors, and may include several related languages with largely obscure geographical limits, intelligibility, and emic identities of their speakers. The most recent linguistic hypotheses propose a sister-group relationship of Albanian to Greek or to the Greek-Armenian clade, which firmly places the origin of the language in the Balkans but does not pinpoint the location of the proto-Albanian homeland within the peninsula and its potential affiliation to historically attested populations.

Archaeological data on Albania’s Medieval cultures are also inconclusive, especially for the Komani-Kruja complex (ca. 600-800 CE), which has been interpreted as the cultural expression of either a Romanised population (local or intrusive) or an indigenous Albanian-speaking group.

Due to the challenges associated with linking archaeological, literary, and linguistic evidence, an archaeogenetic approach may offer novel insights into the origin of the Albanians, their biological relationships to ancient people, and the affinities of their language. Although gene flow is not always accompanied by language shifts [as in the case of Basque and Etruscan], migration is one of the primary vectors of cultural change, of which language dissemination is a frequent outcome. Recent years have witnessed a surge in the palaeogenomic sampling of the Balkan peninsula, yet the resulting datasets have not been mined to help us understand how migration led to the emergence and spread of new material cultures, communities, and languages in the territory of modern Albania. . . . 
Our genomic transect of the population of Albania from the Neolithic to the modern era reveals fluctuations in genetic ancestry over a period of 8000 years. In contrast to the southeastern Balkans, where the arrival of Pontic-Caspian steppe ancestry and the associated Indo-European cultural package during the EBA did not lead to a lasting genetic turnover, we show that contemporary populations in Albania were genetically transformed both in autosomal and paternal ancestry. We find that more than a millennium later, BA-IA Balkan populations with high levels of steppe ancestry (30-40%) formed a distinct genetic cluster that extended from northwestern Greece, North Macedonia and the Adriatic coast (including Albania) and transcended archaeological and linguistic boundaries. This genetic continuum was broken down across the Balkans during the Roman and Migration period, due to mass settlement of Germanic and Slavic-speaking groups in the region.

However, in agreement with linguistic studies, we find that Albanians likely descend from a surviving West palaeo-Balkan population that experienced significant demographic increase approximately between 500-800 CE, perhaps after a population bottleneck. We show that in contrast to the rest of the Balkans, the Medieval samples from both North and South Albania experienced little to no contribution from surrounding Slavic populations and maintained high levels of BA-IA West Balkan ancestry. 
Remarkably, the same genetic profile persisted 500-800 years later in most of the post-Medieval samples from Bardhoc, as shown both by the PCA, qpAdm analyses, and IBD data, which indicate significant genetic continuity from the Medieval populations of Albania. However, qpAdm models cannot exclude the possibility of additional admixture with currently unsampled neighbouring late Roman-early Medieval palaeo-Balkan groups with a similar ancestry profile. Based on linguistic data, the area of modern Kosovo and southeastern Serbia may have been such a source.

Despite being largely unaffected by the demographic changes that took place during the Migration period, the historical Albanians did not emerge in isolation. At the peak of the Migration Period, the Medieval population of Albania displayed genetic links as far as Pannonia, while in post-Medieval times we detected the presence of individuals likely related to modern Roma people. Furthermore, two of the post-Medieval samples exhibit significant admixture with South Slavic populations, and modern Albanians display highly variable levels of Slavic ancestry. This indicates complex historical interactions with South Slavic populations, as suggested by toponymy and linguistics.

We reveal that a significant proportion of the paternal ancestry of modern Albanians derives from groups ultimately descending from the BA-IA West Balkans, including those traditionally known as “Illyrians”, which reflects our findings on autosomal ancestry. However, inferring the language spoken by the Medieval samples from Albania is challenging, as Greek, South Slavic and West Balkan Romance are the only recorded languages of the region, while there is no indication of the survival of “Illyrian” following the first centuries of Roman rule. Furthermore, Albanian displays Latin loans from both the Western and Eastern Balkans, which attests to linguistic influences beyond the confines of modern Albania. Testing the Messapic hypothesis for Albanian was not possible due to the low coverage of said samples. Although the presence of haplogroups J2b-L283, I-M223, and R1b-Z2103 among the Messapians suggests a West Balkan origin, whether a related language persisted in the Balkans during Medieval times is unknown.

Even though Eastern Roman historians were unfamiliar with Albanians, we cannot exclude the possibility that proto-Albanians interacted with populations speaking Greek, Aromanian, or Slavic in what is now southern Albania during Medieval times. Given that genetic data strongly suggest a predominantly local origin for Albanians, their Medieval ancestors may have inhabited a geographically restricted area [possibly the region of Mat in central Albania], only occasionally venturing towards the south. These movements may have increased in scale over time, finally attracting the attention of Greek-speaking historians in the 11th century.

While the quest for the origins of the Albanian language will certainly continue, we expect that the present study will shape these debates and provide the necessary framework for more extensive research on the genetic ancestry of the ancient and modern inhabitants of Albania.

Thursday, June 15, 2023

Brain Size v. Body Size In Mammals

It turns out that the relationship between brain size and body size in mammals is pretty simple and universal if you don't insist on linear relationships.
Despite decades of comparative studies, fundamental questions remain about how brain and body size co-evolved. Divergent explanations exist concurrently in the literature for phenomena such as variation in brain relative to body size, variability in the scaling relationship across taxonomic levels and between taxonomic groups, and purported evolutionary trends. Here we resolve these issues using a comprehensive dataset of brain and body masses across the mammal radiation, and a method enabling us to study brain relative to body mass evolution while estimating their evolutionary rates along the branches of a phylogeny. 
Contrary to the rarely questioned assumption of a log-linear relationship, we find that a curvilinear model best describes the evolutionary relationship between log brain mass and log body mass. This model greatly simplifies our understanding of mammalian brain-body co-evolution: it can simultaneously explain both the much-discussed taxon-level effect and variation in slopes and intercepts previously attributed to complex scaling patterns. 
We also document substantial variation in rates of relative brain mass evolution, with bursts of change scattered through the tree. General trends for increasing relative brain size over time are found in only three mammalian orders, with the most extreme case being primates, setting the stage for the uniquely rapid directional increase that ultimately produced the computational powers of the human brain.
Chris Venditti, Joanna Baker, Robert A. Barton, "Co-evolutionary dynamics of mammalian brain and body size" bioRxiv (June 9, 2023)

Chemistry Is Awesome!


Tuesday, June 13, 2023

New Find Documents Earliest Modern Humans In Southeast Asia

While it is close, this find is still consistent with a modern human migration through Southeast Asia made possible by the Toba eruption.
The timing of the first arrival of Homo sapiens in East Asia from Africa and the degree to which they interbred with or replaced local archaic populations is controversial. Previous discoveries from Tam Pà Ling cave (Laos) identified H. sapiens in Southeast Asia by at least 46 kyr. We report on a recently discovered frontal bone (TPL 6) and tibial fragment (TPL 7) found in the deepest layers of TPL. 
Bayesian modeling of luminescence dating of sediments and U-series and combined U-series-ESR dating of mammalian teeth reveals a depositional sequence spanning ~86 kyr. TPL 6 confirms the presence of H. sapiens by 70 ± 3 kyr, and TPL 7 extends this range to 77 ± 9 kyr, supporting an early dispersal of H. sapiens into Southeast Asia. Geometric morphometric analyses of TPL 6 suggest descent from a gracile immigrant population rather than evolution from or admixture with local archaic populations.
Sarah E. Freidline, et al., "Early presence of Homo sapiens in Southeast Asia by 86–68 kyr at Tam Pà Ling, Northern Laos" 14 Nature Communications 3193 (June 13, 2023).

Thursday, June 8, 2023

BMW Estimate Of Muon g-2 Continues To Be Corroborated

The body text of a new paper quoted below sums up the myriad discrepancies between the "official" estimate of muon g-2 (a 4.2 sigma difference from the actual measurement) and data including the lattice QCD estimate by the BMW group which is consistent with the measurement at the 1.5 sigma level.

The bottom line is that the 2020 White Paper calculation of the Standard Model prediction for muon g-2 is wrong, and the BMW calculation is correct and confirms the experimentally measured value of muon g-2. There is not, in fact, a muon g-2 anomaly, just as there is also not, in fact, a W boson mass anomaly (a discrepancy arising from recent a misanalysis of old Tevatron data). 

It isn't entirely clear if the problem with the 2020 White Paper arises from flaws in the e+e- data upon which its calculation relies. This was the problem in the case of the muonic hydrogen proton radius puzzle. But the problem could also be with the way that the e+e- data was incorporated into an otherwise first principles based calculation was incorrect in some way.

An unambiguous interpretation of the new measurement of the muon g−2 by the E989 experiment at Fermilab is impeded by several tensions that have been exposed since the publication of the 2020 White Paper: (1) There is a tension of 2.1σ between a single lattice calculation and the WP-recommended value for aµhvp,LO, based on e+e− cross section data published prior to 2023; (2) There is a tension of almost 4σ between several lattice calculations and the corresponding dispersive estimate based on the same e+e− data; (3) There is a tension of 2−3σ in the hadronic running of α, as estimated by two lattice calculations and e+e− data; (4) There is a slight tension of1−2σ in the Adler function determined from lattice and perturbative QCD on the one hand, and e+e−data on the other; (5) Finally, there is a tension of 2.7σ in the dominant π+π−channel between BaBar and KLOE, as well as a tension of about 4σ between CMD-3 and all other experiments.
In this context, it is important to realise that a larger SM prediction for aµ is not in contradiction with global electroweak constraints, at least at the current level of precision. 
Obviously, an independent cross-check of the BMW lattice result for aµhvp,LO, with sub-percent precision is badly needed. Furthermore, the tension among e+e−data must be elucidated, a task for which the alternative determination of the R-ratio from τ decays could be useful. These activities are currently in progress. The Muon g−2 Theory Initiative is preparing an update of the original WP, which will thoroughly address the issues that have come to the fore since 2020.

The Larger Implications Of The Muon g-2 Results

The fact that the muon g-2 experiments confirm the Standard Model prediction, correctly calculated, to extreme precision, is an excellent global test of the completeness and correctness of the Standard Model up to a few orders of magnitude of energy scale above the electroweak scale. New physics at very high energies, however, effectively decouple from the lower energy physics involved in the muon g-2 observable and can't be detected even at the ultrahigh precision of these measurements and calculations.

Standing alone, the lack of a discrepancy between the muon g-2 measurement and the Standard Model prediction for it doesn't rule out all new physics in the experimentally testable energy range. But it does mean that any new physics in that energy range must either be tiny tweaks to the Standard Model (e.g. tweaks of the size involved in considering quantum gravity effects on the calculation) or must be tweaks that cancel out in the calculation of muon g-2, a calculation that involves all three of the Standard Model forces (the electromagnetic force, the weak force, and the strong force). 

Ultimately, one can never rule out experimentally the possibility that beyond the Standard Model physics with effects smaller than the most precise experiments that are possible at any given time. 

But one can rule out many possible beyond the Standard Model theories that would cancel out in a muon g-2 calculation at energy scales up to a few orders of magnitude above the electroweak scale with other experimental tests, direct and indirect.

Probably the most important class of new physics that wouldn't impact the muon g-2 calculation would be new "sterile" particles that interact via gravity but not via any of the three Standard Model forces, such as many dark matter particle candidates and the right handed neutrinos proposed in see-saw models of neutrino mass generation. Sterile dark matter candidates are disfavored by the tightness of the fit between inferred dark matter distributions and distributions of ordinary baryonic matter. 

The neutrino physics experiments necessary to distinguish between right hand neutrinos in see-saw models of neutrino mass generation and alternative models of neutrino mass generation are a work in progress. Observing neutrinoless double beta decay would destroy the justification of these models, but if we determine from the non-observation of neutrinoless double beta decay that neutrinos do not have Majorana mass (and my educated guess is that this is precisely what will happen in the next decade or two), there isn't a clear agenda for experiments that would establish how neutrinos do get their mass. 

Tuesday, June 6, 2023

Story Of Human Evolution Not Actually Rewritten

Deep inside a South African cave, researchers say they have discovered graves dug by our ancient, small-brained relatives more than 100,000 years before the oldest known human burials, a claim that would revise the story of our evolution.
From the Washington Post.

Yes, this story about Homo naledi is cool.

Does it revise our story of evolution? 


Does it spark debate among people who knew the existing story prior to this discovery? 

Not really, beyond the fine details of interpretation of the site.

This is a side story about a dead end hominin species that existed contemporaneously in Africa with the most direct ancestors of modern humans. It is basically a story from The Silmarillion of hominin evolution. It is entertaining, especially for hard core human evolution fans, but it doesn't really advance the plot.

Meanwhile, John Hawks discusses another recent paper he has co-authored on Homo Naledi from ten years after the original find about H. Naledi teeth.
More than 150 hominin teeth, dated to ∼330–241 thousand years ago, were recovered during the 2013–2015 excavations of the Dinaledi Chamber of the Rising Star cave system, South Africa. These fossils comprise the first large single-site sample of hominin teeth from the Middle Pleistocene of Africa. Though scattered remains attributable to Homo sapiens, or their possible lineal ancestors, are known from older and younger sites across the continent, the distinctive morphological feature set of the Dinaledi teeth supports the recognition of a novel hominin species, Homo naledi. This material provides evidence of African Homo lineage diversity that lasts until at least the Middle Pleistocene. Here, a catalog, anatomical descriptions, and details of preservation and taphonomic alteration are provided for the Dinaledi teeth. Where possible, provisional associations among teeth are also proposed. To facilitate future research, we also provide access to a catalog of surface files of the Rising Star jaws and teeth.
Delezene, L. K., Skinner, M. M., Bailey, S. E., Brophy, J. K., Elliott, M. C., Gurtov, A., Irish, J. D., Moggi-Cecchi, J., de Ruiter, D. J., Hawks, J., & Berger, L. R., "Descriptive catalog of Homo naledi dental remains from the 2013 to 2015 excavations of the Dinaledi Chamber, site U.W. 101, within the Rising Star cave system, South Africa." 180  Journal of Human Evolution 103372 (2023) 

Monday, June 5, 2023

The Plague Was In Britain In 2000 BCE

We know that the plague was in Britain around 2000 BCE (the earliest known cases in Britain) based upon ancient plague DNA from that time period, according to the press release for the journal article: Pooja Swali, et al., "Yersinia pestis genomes reveal plague in Britain 4000 years ago." 14(1) Nature Communications (2023) DOI: 10.1038/s41467-023-38393-w

Deur Responds To Critical Preprint

It isn't clear why the arXiv posting was delayed so long. But, the response is in line with previous discussions in Deur's papers.
We comment on the methods and the conclusion of Ref. [1], "Does gravitational confinement sustain flat galactic rotation curves without dark matter?" The article employs two methods to investigate whether non-perturbative corrections from General Relativity are important for galactic rotation curves, and concludes that they are not. This contradicts a series of articles [2-4] that had determined that such corrections are large. We comment here that Ref. [1] use approximations known to exclude the specific mechanism studied in [2-4] and therefore is not testing the finding of Refs. [2-4].
A. Deur, "Comment on "Does gravitational confinement sustain flat galactic rotation curves without dark matter?'' arXiv:2306.00992 (May 13, 2023).

The introduction ends by stating:
To reach the conclusion that FSI is important for galactic rotation curves, Refs. [2, 3] performed static lattice calculations of the GR potential, and Ref. [4] computed that potential within a lensing model based on mean-field technique. The approximations of the former and the modeling of the latter break some of the tenets of GR. In contrast, the authors of [1] strive to be analytical and to preserve GR’s basic principles. Consequently, they employ different methods from Refs. [2, 3] and Ref. [4], whose results they could not reproduce. This lead the authors of [1] to refute the validity of [2–4, 7–11] and the basic connection of GEFC to GR. 
In what follows, we expand (Section II) on why perturbative methods like the one used in [1] miss the non-perturbative effects of FSI of GR. Next, (Section III) we discuss the lensing-based model initially developed in [4] and signals two reasons why the calculation in Ref. [1] miss the FSI effects. Then, (Section IV) we argue that GEFC is in fact based on GR. We then summarize and conclude.
The conclusion states:
Disproving the non-perturbative, non-analytical results cannot be done by using the perturbative PPN framework as done in Ref. [1]. That GEFC is unrelated to GR is rebutted by showing that GEFC’s approximations preserve the relevant features of its starting point, viz GR. This is achieved by applying GEFC’s method to known cases, which was done for 7 distinct potentials (free-field in 1, 2 and 3 dimensions, Yukawa force, leading order PPN, φ 4 theory, and QCD). Lets consider the following five facts: (i) FSI, a feature of GR, provides naturally and without invoking DM and DE a unified explanation of the phenomena otherwise requiring DM and DE when analyzed in frameworks where FSI is absent (Newtonian gravity) or cancels (cosmological principle); (ii) FSI makes predictions of novel phenomena that have been subsequently observed; (iii) Intriguing parallels exist between GR and QCD, both for the theories and the phenomena they control;<7> (iv) FSI provides an innate framework for observations not explained naturally in ΛCDM<8>; and (v) solving the equivalent QCD problem of determining the increase of the force magnitude due to FSI has been notoriously difficult and its resolution remains a leading problem in physics. 
These facts suggest that, even if a calculation yields too small FSI, it more likely points to an insufficiency of the method, as the PPN in [1], rather than a failure of GEFC.  
In the worst case scenario that approximations used in lead incorrectly to conclude that GR’s FSI are significant enough, then the facts (i-v) would be pointing to GEFC missing the right mechanism rather than being wrong. In fact, even if the proposed mechanism (FSI) has been misidentified, it would only put GEFC on the same footing as ΛCDM and alternatives, e.g., MOND, that are not supported by a verified theory. It would not affect GEFC’s demonstration that alternatives to DM/DE-based models are possible even in the era of precision cosmology: contrary to oft-stated, high-precision observations, e.g., that of the CMB, do not establish the existence of DM/DE. 
Another example is the claim that the Bullet Cluster observation proves DM (this article is titled “A direct empirical proof of the existence of dark matter”). This is disproved by the fact that the observation is naturally expected by GEFC, immaterial to whether or not the FSI mechanism is relevant. 
That the numerous parallels between cosmology and hadronic physics are purely fortuitous coincidences is unlikely, especially because of the similar theoretical structure of GR and QCD. It is injudicious to ignore these leads only because exact calculations are impossible and approximations can be contested. This is especially true in light of the issues presently faced by ΛCDM and the ability of GEFC to explain astronomical and cosmological observations. 
As GEFC’s claims are outstanding and far-reaching, they must be rigorously scrutinized. This is what Ref. [1] undertook but with a method not adapted to the problem. The way forward is to test GEFC with numerical non-perturbative methods and remember that 50 years of trying to solve the similar, but simpler QCD problem has checked many methods.
Footnote 7: Specifically, these parallels are between (a) the GR Lagrangian, (b) the observations interpreted as evidence of dark matter, (c) those for dark energy, (d) the cosmic coincidence problem, (e) the Tully-Fisher relation, (f) galactic matter density profiles on the GR side, and (A) the QCD Lagrangian, (B) the magnitude of hadron masses, (C & D) the confinement of QCD forces in hadrons, (E) hadron’s Regge trajectories, (F) hadronic density profiles on the QCD side, respectively. 
Footnote 8: Inter alia, the Tully-Fisher and RAR correlations, Renzo’s rule, cosmic coincidence, Hubble tension, dwarf galaxies overcounting, absence of direct detection of dark matter particle and absence of natural candidates within particle physics. 

Thursday, June 1, 2023

Cold Dark Matter Still Gets Galaxies Wrong

MOND or another theory giving rise to a comparable effect is necessary and sufficient to explain galaxy dynamics. This is hard to do with dark matter particle theories.
to explain statistically late-type galaxy dynamics within the disk it is necessary and sufficient to explain the RAR and lack of any significant, partially independent correlation. While simple in some modified dynamics models, this poses a challenge to standard cosmology.
From here.

It basically can't be done in a cold dark matter theory.
Before halo compression, high-mass galaxies approximately lie on the observed RAR whereas low-mass galaxies display up-bending "hooks" at small radii due to DM cusps, making them deviate systematically from the observed relation. After halo compression, the initial NFW halos become more concentrated at small radii, making larger contributions to rotation curves. This increases the total accelerations, moving all model galaxies away from the observed relation. These systematic deviations suggest that the CDM model with abundance matching alone cannot explain the observed RAR. Further effects (e.g., feedback) would need to counteract the compression with precisely the right amount of halo expansion, even in high mass galaxies with deep potential wells where such effects are generally predicted to be negligible.
From here and recapitulated here and here.

Cosmology also continue to be a problem for the LambdaCDM model.
We establish a new and cosmological-model-independent method to explore the cosmic background dynamics in this work. Utilizing the latest Pantheon+ type Ia supernova sample and the Hubble parameter measurements, we obtain the values of the Hubble parameter and the deceleration parameter at five different redshift points ranging from 0.2 to 0.6, and find that they can deviate from the predictions of the ΛCDM model at more than 2σ. We further probe the equation of state of dark energy and obtain that a slightly oscillating equation of state of dark energy around the −1 line is favored.
From here.

Milgrom, meanwhile, considers a version of MOND that is matter distribution shape dependent, which was critical to Deur's generalization of the gravitational approach to dark matter to a wider range of applicability.