The ΛCDM model v. F(R) Gravity

Once again, the ΛCDM model disappoints.

Over the last decades, tests on the standard model of cosmology, the so-called ΛCDM model, have been widely analysed and compared with many different models for describing dark energy. Modified gravities have played an important role in this sense as an alternative to ΛCDM model. Previous observational data has been always favouring ΛCDM model in comparison to any other model. While statistically speaking, alternative models have shown their power, fitting in some cases the observational data slightly better than ΛCDM, the significance and goodness of the fits were not significantly relevant to exclude the standard model of cosmology. 

In this paper, a generalisation of exponential F(R) gravity is considered and compared with ΛCDM model by using the latest observational data. Also some well-known model independent parameterisations for the equation of state (EoS) of dark energy are explored. 

These scenarios are confronted with the renewed observational data involving the Pantheon plus datasets of supernovae type Ia, the Hubble parameter estimations, data from the cosmic microwave background and baryon acoustic oscillations, where the latter includes the data provided by Dark Energy Spectroscopic Instrument collaboration. 

Results of this analysis suggest that standard exponential F(R) models provide much better fits than ΛCDM model, which is excluded at 4σ. Moreover, the parameterisations of the equation of state suggest a non-constant EoS parameter for dark energy, where ΛCDM model is also excluded at 4σ.

Sergei D. Odintsov, Diego Sáez-Chillón Gómez, German S. Sharov, "Modified gravity/Dynamical Dark Energy vs ΛCDM: is the game over?" arXiv:2412.09409 (December 12, 2024).

Another Notable Attempt To Capture Galaxy Dynamics Without DM From GR

The highly robust Tully-Fischer relation is the strongest evidence for MOND or some other gravitational explanation for dark matter phenomena. 

Multiple attempts to use gravitomagnetism as the cause of this from conventional GR have failed, because this GR effect is too small. But this is not the only possible GR effect that is ignored in the Newtonian approximation so often used in the weak-field, slow-motion regime of astronomy and cosmology. This paper looks at a different neglected GR effect and finds that it is significant and can explain the Tully-Fischer relation without dark matter.

We study the low-energy limit of General Relativity in the presence of stationarity and axial symmetry, coupled to dust. Specifically, we demonstrate that differences between the dynamics of General Relativity and those of Newtonian gravity persist even in the weak-field and slow-motion regime. Notably, these differences are driven by dragging terms that are not necessarily small, as is typically the case in the well-known gravitomagnetic limit. To highlight this distinction, we introduce the concept of strong gravitomagnetism. We provide a pedagogical discussion of how these discrepancies arise and outline a systematic procedure to solve the equations of motion for such systems. Furthermore, we present analytical results for specific cases and also give the general solution for the vacuum case. A particularly notable result is our demonstration of how General Relativity can naturally account for a Tully-Fisher-like relation.

Davide Astesiano, Matteo Luca Ruggiero, "On the low-energy limit of stationary and axisymmetric solutions in General Relativity" arXiv:2412.08598 (December 11, 2024).

Tiny Black Holes And Some Related Conjectures

The Schwarzschild radius is the size of the event horizon of a black hole and is a linear function of mass. Specifically, the Schwarzschild radius is calculated using the formula: R = 2GM/c² where G is the gravitational constant, M is the mass of the object, and c is the speed of light. (Spin and charge in a black hole tweak this value.)

Galaxies

The Schwarzschild radius of a typical galaxy is about 10^15 meters (i.e. about 10^12 km or 0.1 light years). In fact, however, this is about 10 times larger than the most massive theoretically possible black holes.

Supermassive Black Holes

The supermassive black hole at the center of the Milky Way has a Schwarzschild radius of around 12 million kilometers (i.e. 1.2 * 10^13 meters a.k.a. about 0.001 light years, which is about 4 light days) due to its mass of about 4.1 million solar masses. The supermassive black holes at the center of galaxies have densities comparable to that of water. The theoretical limit for the mass of a black hole with typical properties is only 5×10^10 M☉, but can reach 2.7×10^11 M☉ at maximal prograde spin (a = 1).

Stellar Black Holes

The Schwarzschild radius of the smallest possible stellar black hole is approximately 10^4 meters (i.e. about 10 km to 12 km), which means that the mass per event horizon volume (i.e. density) of a small stellar black hole is on the order of the same as an atomic nucleus (which is part of why the most dense macroscopic object that is not a black hole is called a neutron star). These are the highest density objects known in nature, and it may be that there is some theoretical maximum density of anything in this vicinity (which would render primordial black holes of sub-stellar mass theoretically impossible).

Black holes should not be able to form from the gravitational collapse of a star below this mass.

The Sun

The Schwarzschild radius of our Sun is 2.9 * 10^3 meters (i.e. 2.9 km).

Earth

The Schwarzschild radius of the Earth is 0.88 * 10^-2 meters (i.e. 0.88 cm).

Asteroids 

The Schwarzschild radius of a typical asteroid is approximately 10^-3 meters (i.e. it is about one millimeter). This density is about 10^21 times greater than an atomic nucleus or in the lightest possible stellar black hole. This is roughly the size of primordial dark matter candidates that have not been ruled out due to either evaporation due to Hawking radiation over the life of the universe so far, or due to astronomy efforts to detect micro-lensing.

Planck Length

The Planck length is 1.616255(18) × 10^−35 meters. 

All distances smaller than this may be ill-defined or limited by the discreteness of space-time if space-time is not continuous.

Top Quark

The Schwarzschild radius of a top quark is approximately 10^-52 meters. This radius is about 10^37 times smaller than the actual size of a proton or neutron, and the volume is about 10^111 times smaller than a proton or neutron. The density of a top quark mass black hole would be about 10^113 times greater than a proton or neutron.

The formula for the Compton wavelength, which is "λ = h/(mc)" where h is Planck's constant, m is the mass of the particle, and c is the speed of light. The Compton radius of a top quark is about 1.1 * 10^-18 meters. 

The mean lifetime of the top quark is slightly longer than that of the W boson by which it decays, which could also be a fundamental floor on the mean lifetime of a particle and as a result on the maximum mass of a fundamental particle, which would explain why there are only three generations of fundamental fermions.

Gauge Bosons

The Schwarzschild radius of a W boson, Z boson, or Higgs boson is approximately 10^-52 to 10^-53 meters.

Bottom Quark

The Schwarzschild radius of a bottom quark is about 10^-53 meters.

Tau Leptons

The Schwarzschild radius of a tau lepton is a little less than twice the Schwarzschild radius of a proton, and a little less than half the Schwarzschild radius of a bottom quark.

Atoms and Nucleons

A proton or neutron has a radius on the order of 10^-15 meters, while an atomic nucleus of the largest possible atom has a radius that is 6-7 times larger. An entire atom, including its associated electrons, has a radius on the order of 10^-10 meters. All atomic nuclei have densities roughly the same as the density of a proton or neutron.

The Schwarzschild radius of a proton or neutron is 2.4 * 10^-54 meters. 

Up and Down Quarks

The Schwarzschild radius of an up quark or down quark is about 10^-56 meters.

Electrons

The Schwarzschild radius of an electron is 1.35 x 10^-57 meters. The Compton radius of an electron (a.k.a. its Compton wavelength) is 2.43 * 10^-12 meters.

Neutrinos

Assuming the neutrinos have masses on the order of 0.6 meV to 60 meV, the Schwarzschild radius of an neutrino is about 10^-66 to 10^-64 meters. The Compton radius of a neutrino (a.k.a. its Compton wavelength) about 10^-6 to 10^-8 meters. A neutrino cross-section is around 10^-38 cm^2 (about 10^-42 meters squared). The Planck area is about 10^-66 cm^2 (about 10^-70 meters squared).

Primordial Black Holes And Renormalization Considerations

As a footnote, when it comes the primordial black hole formation, it also bears noting that the temperature of the universe was vastly higher, and the volume of the universe was vastly larger, in the time frame when this would have happened. 

This means that the Standard Model constants would run to their higher energy scale values, most notably, with the weakening of the Higgs field at high energy scales which reduces the rest masses of Standard Model particles. It isn't clear how that would impact general relativity considerations. 

Energy and not just mass gravitates, and pressure also impacts the E=mc^2 conversion, but energy is generally more diffuse in space than rest mass. Intuitively, while the smaller volume of the universe would tend to favor primordial black hole formation, the higher temperatures of the very early universe would tend to disfavor it, and it isn't clear how these factors would balance out. 

It could also be the case that clumps of matter that weren't initially sufficient to form a black hole due to the weak Higgs field could suddenly flip over into one as the Higgs field strengthened at lower temperatures.

Slavery and Bride Migration In Bronze Age Germany

Germany had slavery and imported brides from outside their communities in social structure that lasted at least 700 years in one community that was studied.

High status families in late Neolithic and Bronze Age Germany kept slaves, genetic analysis reveals.

The finding, reported in the journal Science, provides fresh insight into ancient life in Europe, showing that complex slave-owning societies were well established long before those of classical Greece and Rome.

The research, centred on genome-wide data gathered from 104 individuals buried in Germany’s Lech Valley between about 2500 BCE and 1700 BCE, was conducted by researchers led by archaeo-geneticist Alissa Mittnik from the Max Planck Institute for the Science of Human History, in Jena, Germany.

The scientists gathered nuclear and mitochondrial DNA from each individual and compared it to genetic databases covering ancient and modern humans. They also looked at how the graves were arranged and examined the relationship between the number and type of artefacts buried in each.

The picture that emerged was of a surprisingly stable and enduring society that depended on the import of fertile women and menial underlings. The Lech Valley hosted a farming community, Mittnik and colleagues concluded, that persisted for about 700 years.

The people of the valley were a mixture of Western Hunter-Gatherers, Anatolian Neolithic farmers and Steppe pastoralists, with the farmers’ genetic heritage becoming more dominant as the centuries passed.

Analysis of strontium and oxygen deposits in bone revealed that the men remained in the community across multiple generations – a condition known as patrilocality. The women, in contrast, were largely born outside the area – some, indeed, hailed from a region more than 350 kilometres away, on the other side of the Alps.

The absence of women genetically related to the males strongly indicates that they left the community to join other groups.

Mittnik and colleagues also looked at grave goods as signifiers of social importance.

“Certain types of grave goods, especially weapons – daggers, axes, chisels and arrow heads – in male graves and elaborate body adornments in female graves – large headdresses, massive leg rings – as well as pins in graves of both sexes are likely status-associated,” they write.

Among the cohort of corpses examined, they found examples of children and adolescents who were genetically related to adult males and who had been interred with significant artefacts. This suggests that social standing was inherited rather than earned.

From here. Further analysis at the Old European Culture blog.

Clovis People Used Bones Of Small Predators For Needles

The Clovis people (who are not the first indigenous American culture, although they are derived from the Founding population of the Americas whose main wave of expansion came about fifteen hundred years earlier) are known for the spears that they used to hunt big game in North America before the Younger Dryas event wiped out their culture. But to survive in North America, they also needed needles to make clothing so they could function in this relatively cool region.

Tiny artifacts unearthed at a Wyoming site where a mammoth was butchered 13,000 years ago are revealing intriguing details about how the earliest Americans survived the last ice age.

Archaeologists found 32 needle fragments made from animal bone buried almost 15 feet (nearly 5 meters) underground at the La Prele site in Converse County. They are not the earliest eyed needles in the archaeological record, but for the first time scientists have been able to identify what the needles were made of by analyzing protein information contained in the bone collagen. The results were not what they expected.

“We had assumed they would be made out of bison or mammoth bone, which comprise most of the animal bones found at La Prele and other sites of its age in the High Plains and Rocky Mountains of North America,” said Wyoming state archaeologist Spencer Pelton, lead author of a new study on the needles published November 27 in the scientific journal PLOS ONE.

Instead, the needles were created from the bones of red foxes, bobcats, mountain lions, lynx, the now-extinct American cheetah, and hares or rabbits, the study found.

“It was extremely surprising that these needles were made out of small carnivores,” Pelton said.

From CNN. 

Ancient DNA Prefers Deep Linguistic Divide Between Western & Eastern Europe

Image via Razib Khan.

A new ancient DNA study, Fulya Eylem Yediay et al., Ancient genomics support deep divergence between Eastern and Western Mediterranean Indo-European languages, bioRxiv (December 2, 2024), shows a deep rooted divide between the Western Mediterranean in Iberia, Southern France and Italy, and the Eastern Mediterranean in Greece, with a jumble in the Balkans. 

The abstract of the preprint is as follows:

The Indo-European languages are among the most widely spoken in the world, yet their early diversification remains contentious. It is widely accepted that the spread of this language family across Europe from the 5th millennium BP correlates with the expansion and diversification of steppe-related genetic ancestry from the onset of the Bronze Age. However, multiple steppe-derived populations co-existed in Europe during this period, and it remains unclear how these populations diverged and which provided the demographic channels for the ancestral forms of the Italic, Celtic, Greek, and Armenian languages. 

To investigate the ancestral histories of Indo-European-speaking groups in Southern Europe, we sequenced genomes from 314 ancient individuals from the Mediterranean and surrounding regions, spanning from 5,200 BP to 2,100 BP, and co-analysed these with published genome data. We additionally conducted strontium isotope analyses on 224 of these individuals. 

We find a deep east-west divide of steppe ancestry in Southern Europe during the Bronze Age. Specifically, we show that the arrival of steppe ancestry in Spain, France, and Italy was mediated by Bell Beaker (BB) populations of Western Europe, likely contributing to the emergence of the Italic and Celtic languages. In contrast, Armenian and Greek populations acquired steppe ancestry directly from Yamnaya groups of Eastern Europe. These results are consistent with the linguistic Italo-Celtic and Graeco-Armenian hypotheses accounting for the origins of most Mediterranean Indo-European languages of Classical Antiquity. Our findings thus align with specific linguistic divergence models for the Indo-European language family while contradicting others. This underlines the power of ancient DNA in uncovering prehistoric diversifications of human populations and language communities.

While genes do not necessarily match languages, and pots are not people, the correlations between population genetics, language, and material culture tends to be strong, especially in more ancient times.

This analysis places the question of the baseline model into which controversy over the answer to the origins of the now extinct Anatolian languages must be fit on a more sturdy footing.

This new paper is analyzed at Bernard's blog (quoted below in English per Google translate with some obvious translation errors corrected, all images from the new article except as noted):

Bronze Age individuals from Italy are grouped into three distinct clusters. The first is the group linked to the Bell Beaker common to individuals from France and Spain. It includes all the ancient individuals from Corsica and central Italy. A second group is more linked to the [first] farmers of Europe. It includes the ancient individuals from the Olmo site in northern Italy. The third group is linked to the Yamnaya group and includes the ancient individuals from the Adriatic coast.

The Adriatic coast group is probably an early precursor of maritime Magna Graecia colonization. The people with first farmer genetics are probably the ancestors of the Etruscans and kindred non-Indo-European ethnicities of the region. These genetics generally support the Italo-Celtic grouping of Indo-European languages.

Map from Wikipedia

The spread of the Neolithic to the Caucasus and Iran contributed to the diffusion of Anatolian farmer ancestry into this region, which mixed with local hunter-gatherer ancestry from the Caucasus CHG. In addition, the expansion of the Kuro-Araxes culture during the third millennium BC connected the Caucasus with the Levant and Mesopotamia through trade networks. Interaction between Anatolia and the Caucasus increased during the Chalcolithic and Bronze Ages, leading to the expansion of the CHG component into these regions and beyond into the Mediterranean. 

In this study, the authors analyzed the genomes of 25 Bronze and Iron Age individuals from Anatolia. They all originate from a genetic mixture between a local Anatolian farmer component, a Caucasian hunter-gatherer component and a small proportion of the Iranian farmer component. In addition, some individuals have a small proportion of Eastern European hunter-gatherer (EHG) ancestry. Both CHG and EHG components are higher in the Iron Age than in the Bronze Age. Thus, in the Iron Age, the authors observed the arrival of a steppe ancestry in central Anatolia identical to that present in the Balkans and Greece, suggesting a migration from the latter region to Anatolia. The authors hypothesize that this migration is linked to the emergence of the Phrygian state in the second millennium BC.

This suggests Indo-European migration into Anatolia from the west via Greece, rather than the East, via the Caucuses.

The ancient individuals from Cyprus suggest that this island and especially the coastal cities were a genetic melting pot during the Bronze Age. They have a genetic profile close to those of ancient individuals from Lebanon and eastern Anatolia. However, one individual is genetically close to the early farmers of Anatolia, another has a genetic profile close to ancient individuals from the Balkans and Greece. 

An ancient individual with the genetic profile of ancient individuals from Scandinavia is also found at this time in a rock-cut tomb at the Vounous Bellapais site dated between 2000 and 1800 BC. Interestingly, this man is also of the Y chromosome haplogroup: I1 typical of Scandinavia. His strontium isotope analysis confirms his foreign origin consistent with Scandinavia. This result suggests very long-distance interactions on the island of Cyprus during the Bronze Age. 

In the following period, during the Iron Age, the population of Cyprus has a more homogeneous genetic profile containing a small proportion of Yamnaya ancestry. . . .

In conclusion, this study shows that the results of paleogenetics support the Italo-Celtic and Greco-Armenian linguistic models and disqualify the Indo-Greek and Italo-Germanic models. 

Thus, the oldest occurrence of steppe ancestry in Italy comes from two individuals from Latium dated 2100 BC, linked to the Bell Beaker group and not to the Yamnaya group, similarly to the Celtic populations of western Europe. 

In Greece, the oldest occurrence of steppe ancestry is dated 2200 BC in individuals directly linked to the Yamnaya group. They do not have a component from the globular amphora culture. This arrival precedes the emergence of the Greek language in the form of Linear B writing.

Greek is thus, more basal, within the Indo-European linguistic family, deriving directly from the Yamnaya people, rather than being mediated through intermediate Corded Ware and Bell Beaker people. 

The Armenian language has been attested for about 1550 years in the southern Caucasus and eastern Anatolia. At the end of the Iron Age this region was under the control of the Urartian kingdom . This state was culturally diverse and contained Armenian linguistic elements suggested by borrowings between the two languages ​​Urartian and Armenian. Steppe ancestry has been detected in several individuals from this region in the Bronze Age at the end of the third millennium BC coinciding with the fall of the Kuro-Araxes culture. These individuals with steppe ancestry are related to the Yamnaya group, like the ancient Greeks.

Armenian is probably hard to classify because it is a boundary of deeply linguistically divided branches of the Indo-European language family as well as non-Indo-European substrate languages. But the genetics of ancient Armenians suggest an ancestral Greek origin as a start point for its ultimate linguistic mix.

Turtle

 

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