Thursday, December 28, 2023

The Internal Structure Of A Scalar Meson Finally Understood

The structure of the f0(980) scalar boson has been a mystery for decades. 

A new study, however, appears to show that it is basically a quark-antiquark meson with a valance strange quark and anti-strange quark. In other words, it is strange quark quarkonia. The new study largely rules out tetraquark, meson molecule, and quark-antiquark-gluon hybrid particle alternatives.

Tuesday, December 26, 2023

Newton's Reign

It is sometimes hard to realize how far Issac Newton was ahead of his time. He was born 381 years ago. His scientific contributions were mostly in the time period from 1664, when he was 20 years old, until 1707, when he was 63 years old.

Only 13 of the chemical elements had been discovered at the time (one more would be discovered before his death), and the periodic table of the elements was about two centuries in the future. The germ theory of disease and modern genetics were centuries away. A theory of evolution, even Lamarkian evolution, was more than a century away. The Industrial Revolution was still more than a century away. Electromagnetism and thermodynamics hadn't been worked out in his lifetime. Telescopes (he invented the first practical reflecting telescope) and printing presses were relatively recent inventions. They were still burning witches. Gunpowder had been known in Europe for about four hundred years in his lifetime, but was just starting to become decisive militarily in his lifetime. He lived through the brief interregnum called the Common wealth of England, Scotland and Ireland, during which the British Isles was a republic without a reigning monarch. 

Newtonian mechanics, Newtonian gravity, and Newton's observations about optics went unchallenged and unamended for about 250 years. Scientists and engineers still use them on a daily basis, despite knowing that general relativity, special relativity, and quantum mechanics limit the range of their applicability.

The laws of physics he invented are still taught in high school and freshman college level physics classes. He co-invented calculus, which is still taught in high school and freshman and sophomore level college classes (although the notation of the independent co-inventor of calculus, Leibniz, rather than his own clunky notation, is used today).

Not all parts of Newton's legacy were equally illustrious. He was also a Unitarian theologian and an alchemist, and devoted almost as much time in his life to those ultimately fruitless projects, as he did to science and mathematics. He was also a member of Parliament, ran the Royal Mint for many years, was knighted, and led the Royal Society for twenty-four years. He never married and is not reputed to have had any children.

When Were Elements Discovered?

More than 14 chemical elements have been discovered in my lifetime. That's more than were discovered in the entire history of humanity through the year 1734 CE. The Standard Model of Particle Physics was also developed in my lifetime.


Copper 9000 BCE - Older than agriculture
Lead 7000 BCE
Gold 6000 BCE
Iron 5000 BCE
Silver 5000 BCE
Carbon 3750 BCE
Tin 3500 BCE
Sulfur 2000 BCE - Drought leads to massive spread of Indo-Europeans
Mercury 1500 BCE
Zinc 1000 BCE - After Bronze Age collapse


Antimony 815 CE
Arsenic 815 CE
Bismuth 1000 CE - Lief Erikson reaches North America

Early Modern and Early Industrial Revolution

Phosphorous 1669 CE
Cobalt 1735 CE
Platinum 1735 CE
Nickel 1751 CE
Magnesium 1755 CE
Hydrogen 1766 CE
Oxygen 1771 CE
Nitrogen 1772 CE
Barium 1772 CE
Chlorine 1774 CE
Manganese 1774 CE
Molybdenum 1782 CE
Tellurium 1782 CE
Tungsten 1783 CE
Strontium 1787 CE
Uranium 1789 CE - U.S. Constitution adopted; French Revolution
Zirconium 1789 CE
Titanium 1791 CE - U.S. Bill Of Rights adopted.
Yttrium 1794 CE - First element named after Ytterby, Sweden
Chromium 1794 CE
Beryllium 1798 CE

19th Century

Niobium 1801 CE
Vanadium 1801 CE
Palladium 1802 CE
Tantalum 1802 CE
Iridium 1803 CE
Osmium 1803 CE
Cerium 1803 CE
Rhodium 1804 CE
Potassium 1807 CE
Sodium 1807 CE
Calcium 1808 CE
Boron 1808 CE
Fluorine 1810 CE
Iodine 1811 CE
Selenium 1817 CE
Cadmium 1817 CE
Lithium 1817 CE
Silicon 1818 CE
Aluminum 1824 CE - a.k.a. Aluminium
Bromine 1825 CE
Thorium 1829 CE
Lanthanum 1838 CE
Terbium 1843 CE
Erbium 1843 CE - Second element named after Ytterby
Ruthenium 1844 CE
Cesium 1860 CE
Thallium 1861 CE - U.S. Civil War starts
Rubidium 1861 CE
Indium 1863 CE
Helium 1868 CE - 14th Amendment to U.S. Constitution adopted
Holmium 1878 CE
Ytterbium 1878 CE - Third element named after Ytterby
Samarium 1879 CE
Thulium 1879 CE
Scandium 1879 CE
Gadolinium 1880 CE
Neodymium 1885 CE
Praseodymium 1885 CE
Dysprosium 1886 CE
Germanium 1886 CE
Argon 1894 CE
Europium 1896 CE
Neon 1898 CE
Xenon 1898 CE
Krypton 1898 CE
Radium 1898 CE
Polonium 1898 CE
Radon 1899 CE

20th Century

Actinium 1901 CE
Lutetium 1906 CE
Protactinium 1913 CE
Hafnium 1922 CE
Rhenium 1925 CE
Technetium 1937 CE - First artificially produced element
Francium 1939 CE - World War II begins
Neptunium 1940 CE
Astatine 1940 CE
Plutonium 1940 CE
Curium 1944 CE
Americium 1944 CE
Promethium 1945 CE - World War II ends
Berkelium 1949 CE
Californium 1950 CE
Fermium 1952 CE
Einsteinium 1952 CE
Mendelevium 1955 CE
Lawrencium 1961 CE
Nobelium 1966 CE
Rutherfordium 1969 CE
Dubnium 1970 CE - I am born
Seaborgium 1974 CE
Bohrium 1981 CE
Meitnerium 1982 CE
Hassium 1984 CE
Roentgenium 1994 CE - I get married
Darmstadtium 1994 CE
Copernicium 1996 CE
Flerovium 1998 CE
Livermorium 2000 CE

21st Century

Oganesson 2002 CE
Moscovium 2003 CE
Nihonium 2003 CE
Tennessine 2009 CE


Thursday, December 21, 2023

Improving Our Understanding Of The Bantu Expansion

A new paper confirms and more specifically describes the paradigmatic understanding of Bantu expansion.

a,b, Putative migration routes of BSP inferred using pairwise FST values (a) and after removing the Zambian Lozi population from the analyses (b). Arrow colours correspond to north-western Bantu speakers 2 (NW-BSP 2; brown; one arrow between Cameroon and CAR), west-western Bantu speakers (WW-BSP; green), south-western Bantu speakers (SW-BSP; dark blue) and eastern Bantu speakers (E-BSP; red). c, Spatial visualization of effective migration rates (EEMS software) estimated with the masked Only-BSP dataset. log(m) denotes the effective migration rate on a log10 scale, relative to the overall migration rate across the habitat. Populations are coloured according to each Bantu-speaking linguistic group (brown, green, dark blue and red dots). d, GenGrad analysis using FST as the genetic distance for the admixture-masked BSP dataset. Hexagons of the grid were plotted with a colour scale representing the FST gradient (key).
The expansion of people speaking Bantu languages is the most dramatic demographic event in Late Holocene Africa and fundamentally reshaped the linguistic, cultural and biological landscape of the continent. 
With a comprehensive genomic dataset, including newly generated data of modern-day and ancient DNA from previously unsampled regions in Africa, we contribute insights into this expansion that started 6,000–4,000 years ago in western Africa. We genotyped 1,763 participants, including 1,526 Bantu speakers from 147 populations across 14 African countries, and generated whole-genome sequences from 12 Late Iron Age individuals. 
We show that genetic diversity amongst Bantu-speaking populations declines with distance from western Africa, with current-day Zambia and the Democratic Republic of Congo as possible crossroads of interaction
Using spatially explicit methods and correlating genetic, linguistic and geographical data, we provide cross-disciplinary support for a serial-founder migration model. We further show that Bantu speakers received significant gene flow from local groups in regions they expanded into
Our genetic dataset provides an exhaustive modern-day African comparative dataset for ancient DNA studies and will be important to a wide range of disciplines from science and humanities, as well as to the medical sector studying human genetic variation and health in African and African-descendant populations.
Cesar A. Fortes-Lima, et al., "The genetic legacy of the expansion of Bantu-speaking peoples in Africa" Nature (November 29, 2023).

Background from the introductory part of the body text:
African populations speaking Bantu languages (Bantu-speaking populations (BSP)) constitute about 30% of Africa’s total population, of which about 350 million people across 9 million km2 speak more than 500 Bantu languages. Archaeological, linguistic, historical and anthropological sources attest to the complex history of the expansion of BSP across subequatorial Africa, which fundamentally reshaped the linguistic, cultural and biological landscape of the continent. There is a broad interdisciplinary consensus that the initial spread of Bantu languages was a demic expansion and ancestral BSP migrated first through the Congo rainforest and later to the savannas further east and south. However, debates persist on the pathways and modes of the expansion.

Whereas most recent human expansions involved latitudinal movements through regions with similar climatic conditions, the expansion of the BSP is notable for its primarily longitudinal trajectory, traversing regions with highly diverse climates and biomes, including the highlands of Cameroon, central African rainforests, African savannas and arid south-western Africa

Tuesday, December 12, 2023

Notable New Papers About Gravity

One new paper finds a new form of significant tension between astronomy observations and the ΛCDM model.
We present the first measurement of the Weyl potential at four redshifts bins using data from the first three years of observations of the Dark Energy Survey (DES). The Weyl potential, which is the sum of the spatial and temporal distortions of the Universe's geometry, provides a direct way of testing the theory of gravity and the validity of the ΛCDM model. We find that the measured Weyl potential is 2.3σ, respectively 3.1σ, below the ΛCDM predictions in the two lowest redshift bins. We show that these low values of the Weyl potential are at the origin of the σ8 tension between Cosmic Microwave Background (CMB) measurements and weak lensing measurements. Interestingly, we find that the tension remains if no information from the CMB is used. DES data on their own prefer a high value of the primordial fluctuations, followed by a slow evolution of the Weyl potential. A remarkable feature of our method is that the measurements of the Weyl potential are model-independent and can therefore be confronted with any theory of gravity, allowing efficient tests of models beyond General Relativity.
Isaac Tutusaus, Camille Bonvin, Nastassia Grimm, "First measurement of the Weyl potential evolution from the Year 3 Dark Energy Survey data: Localising the σ8 tension" arXiv:2312.06434 (December 11, 2023).

The other new paper proposes a new gravitational theory to explain dark matter phenomena, by emphasizing Mach's principle, which is the idea that inertia is due to the cumulative gravitational pull of everything in the universe on massive objects.
The general theory of relativity (GR) has excelled in explaining gravitational phenomena at the scale of the solar system with remarkable precision. However, when extended to the galactic or cosmological scale, it requires dark matter and dark energy to explain observations. In our previous article arXiv:2308.04503, we've formulated a gravity theory based in Mach's principle, known as Machian gravity. We demonstrated that the theory successfully explains galactic velocity profiles without requiring additional dark matter components. In previous studies, for a selected set of galaxy clusters, we also showed its ability to explain the velocity dispersion in the clusters without extra unseen matter components. This paper primarily explores the mass profiles of galaxy clusters. We test the Machian Gravity acceleration law on two distinct sets comprising approximately 150 galaxy clusters sourced from various studies. We fitted the dynamic mass profiles using the Machian gravity model. The outcomes of our study show exceptional agreement between the theory and observational results.
Santanu Das, "Aspects of Machian Gravity (III): Testing Theory against Galaxy Cluster mass" arXiv:2312.06312 (December 11, 2023).

Tuesday, December 5, 2023

The Pre-History Of California

A new study looks at genetics, archeology, and linguistics to explain linguistic diversity in pre-Columbian California. 

Before the colonial period, California harboured more language variation than all of Europe, and linguistic and archaeological analyses have led to many hypotheses to explain this diversity. 
We report genome-wide data from 79 ancient individuals from California and 40 ancient individuals from Northern Mexico dating to 7,400–200 years before present (BP). Our analyses document long-term genetic continuity between people living on the Northern Channel Islands of California and the adjacent Santa Barbara mainland coast from 7,400 years BP to modern Chumash groups represented by individuals who lived around 200 years BP. 
The distinctive genetic lineages that characterize present-day and ancient people from Northwest Mexico increased in frequency in Southern and Central California by 5,200 years BP, providing evidence for northward migrations that are candidates for spreading Uto-Aztecan languages before the dispersal of maize agriculture from Mexico. 
Individuals from Baja California share more alleles with the earliest individual from Central California in the dataset than with later individuals from Central California, potentially reflecting an earlier linguistic substrate, whose impact on local ancestry was diluted by later migrations from inland regions. 
After 1,600 years BP, ancient individuals from the Channel Islands lived in communities with effective sizes similar to those in pre-agricultural Caribbean and Patagonia, and smaller than those on the California mainland and in sampled regions of Mexico.

Two Quantum Gravity Papers For Future Reference

I haven't read either of them, but the papers seem to make pretty big claims. If I get I chance, I'll blog them and write more.
The effort to discover a quantum theory of gravity is motivated by the need to reconcile the incompatibility between quantum theory and general relativity. 
Here, we present an alternative approach by constructing a consistent theory of classical gravity coupled to quantum field theory. The dynamics is linear in the density matrix, completely positive and trace preserving, and reduces to Einstein's theory of general relativity in the classical limit. Consequently, the dynamics doesn't suffer from the pathologies of the semiclassical theory based on expectation values. 
The assumption that general relativity is classical necessarily modifies the dynamical laws of quantum mechanics -- the theory must be fundamentally stochastic in both the metric degrees of freedom and in the quantum matter fields. This allows it to evade several no-go theorems purporting to forbid classical-quantum interactions. 
The measurement postulate of quantum mechanics is not needed -- the interaction of the quantum degrees of freedom with classical space-time necessarily causes decoherence in the quantum system. 
We first derive the general form of classical-quantum dynamics and consider realisations which have as its limit deterministic classical Hamiltonian evolution. The formalism is then applied to quantum field theory interacting with the classical space-time metric. 
One can view the classical-quantum theory as fundamental or as an effective theory useful for computing the back-reaction of quantum fields on geometry. We discuss a number of open questions from the perspective of both viewpoints.
Jonathan Oppenheim, "A postquantum theory of classical gravity?", Physical Review X (2023). … 584bc2567e68f9f76c1e. On arXiv: DOI: 10.48550/arxiv.1811.03116 (Comments: "It's very difficult to find a black cat in a dark room, especially if there is no cat.")
We consider two interacting systems when one is treated classically while the other system remains quantum. Consistent dynamics of this coupling has been shown to exist, and explored in the context of treating space-time classically. 
Here, we prove that any such hybrid dynamics necessarily results in decoherence of the quantum system, and a breakdown in predictability in the classical phase space. We further prove that a trade-off between the rate of this decoherence and the degree of diffusion induced in the classical system is a general feature of all classical quantum dynamics; long coherence times require strong diffusion in phase-space relative to the strength of the coupling. 
Applying the trade-off relation to gravity, we find a relationship between the strength of gravitationally-induced decoherence versus diffusion of the metric and its conjugate momenta. This provides an experimental signature of theories in which gravity is fundamentally classical. 
Bounds on decoherence rates arising from current interferometry experiments, combined with precision measurements of mass, place significant restrictions on theories where Einstein’s classical theory of gravity interacts with quantum matter. We find that part of the parameter space of such theories are already squeezed out, and provide figures of merit which can be used in future mass measurements and interference experiments.
Jonathan Oppenheim et al, "Gravitationally induced decoherence vs space-time diffusion: testing the quantum nature of gravity", Nature Communications (2023). DOI: 10.1038/s41467-023-43348-2 (open access).

Monday, December 4, 2023

The Imperial Chinese Harem System

The Imperial Chinese Harem System persisted with only brief interruptions over almost all of China's dynasties (when there were splits, most or all of the factions had them) from 220 BCE to 1908 CE, about 2128 years! 

This is a longer period of time, for example, than the entire history of Christianity, and the institution changed far more modestly during that time period than Christianity did.

During last days of China's final Qing Dynasty, which formally ended in 1912 with an Emperor's abdication (with a brief restoration that was not widely recognized later in the nineteen teens), however, it had already started to peter out:
The Kangxi Emperor (r. 1661–1722) holds the record for having the most imperial consorts [in the Qing Dynasty] with 79, while the Guangxu Emperor (r. 1875–1908) holds the record for having the fewest, with one empress and two consorts—a total of just three imperial consorts.

Functionally, this system, somewhat like the Saudi Arabian monarchy's succession system, insured that the hereditary emperorship would not end for lack of an heir. It also provided a pool of potential heirs from which a worthy successor could be chosen, mitigating, although not entirely eliminating, the harm caused by the occasional "mad king". 

Graviton-Sized Dark Matter Particle Theories

Generally speaking, gravity modification theories are better explanations of dark matter phenomena than dark matter particle theories. In gravity modification theories (which sometimes have scalar and/or vector gravitons or massive gravitons in addition to massless tensor gravitons), gravitons are what give rise to dark matter phenomena.

The theories discussed in the pre-print below involve dark matter particles, nominally unrelated to gravity, that have wave-like behavior and per particle mass-energies reasonable close to those of gravitons in a vanilla quantum gravity realization of General Relativity or a modest modification of it. The convergence of dark matter particle theories on this class of dark matter particles, as astronomy observations increasingly rule out or disfavor the alternatives, is itself interesting.
The Scalar Field Dark Matter model has been known in various ways throughout its history; Fuzzy, BEC, Wave, Ultralight, Axion-like Dark Matter, etc. 
All of them consist in proposing that the dark matter of the universe is a spinless field Φ that follows the Klein-Gordon (KG) equation of motion ◻Φ−dV/dΦ=0, for a given scalar field potential V. The difference between different models is sometimes the choice of the scalar field potential V. 
In the literature we find that people usually work in the nonrelativistic, weak-field limit of the KG equation where it transforms into the Schrödinger equation and the Einstein equations into the Poisson equation, reducing the KG-Einstein system, to the Schrödinger-Poisson system. 
In this paper, we review some of the most interesting achievements of this model from the historical point of view and its comparison with observations, showing that this model could be the last answer to the question about the nature of dark matter in the universe.
Tonatiuh Matos, Luis A. Ureña-López, Jae-Weon Lee, "Short Review of the main achievements of the Scalar Field, Fuzzy, Ultralight, Wave, BEC Dark Matter model" arXiv:2312.00254 (November 30, 2023).