A High Precision Estimate Of The Strong Force Coupling Constant

A new pre-print uses novel methods to make a high precision determination of the strong force coupling constant, at greater precision than all previous determinations combined, which is:

αs(mZ) = 0.11873(56)

The relative uncertainty is one part per 212.

This is important because all strong force (i.e. QCD) calculations rely upon this experimentally determined physical constant.

The Particle Data Group value is 0.1180(9) which is a relative uncertainty of one part per 131 using an error weighted average of all strong force coupling constant measurements.

Radial Migration Of Stars In MOND v. DM

Testable predictions to distinguish between MOND and dark matter theories are valuable.

Multiple studies on radial migration in disc galaxies have proven the importance of the effect of resonances with non-axisymmetric components on the evolution of galactic discs. However, the dynamical effects of classic Newtonian dynamics with dark matter (DM) differ from MOdified Newtonian Dynamics (MOND) and might trigger different radial migration. A thorough analysis of radial migration considering these two gravitational regimes might shed some light on different predictions of DM and MOND theories. We aim to quantitatively and qualitatively compare the effects of resonances and stellar radial migration (churning) in a Milky Way-like (MW-like) galaxy in the DM and MOND regimes. We performed simulations of a MW-like galaxy to analyse the effect of non-axisymmetric structures (galactic bar and spiral arms) considering various parameters of the spiral structure. We conducted a two-dimensional numerical simulation consisting of the integration of 2⋅10^6 stars in a static rotating galactic potential for 6 Gyr. We analysed the change in the star's position, the guiding radius, as well as the frequency phase space. We investigated DM and MOND approaches. The outcome of the simulation shows that the radial migration is much more pronounced in the MOND regime compared to the DM one. Compared to the DM approach, in the MOND regime, we observe up to five times as many stars with a maximum change in the guiding radius of more than 1.5 kpc during the time interval from 2−6 Gyr. Analysis of the frequency phase space reveals that the most prominent resonances in all DM and MOND configurations are the co-rotation resonance with the spiral arms (m=p=1), outer Lindblad resonance with the galactic bar and spiral arms, and the co-rotation resonance (m=2, p=1) with the superposition of the galactic bar and spiral arms, 2Ω=Ωb+Ωsp.

R. Nagy, F. Janák, M. Šturc, M. Jurčík, E. Puha, "Comparing radial migration in dark matter and MOND regimes" arXiv:2501.05924 (January 10, 2025).

No Wonder Astrophysics Papers Aren't Popular

 

From Questionable Content.

Human Sacrifice In Northern Peru Ca. 500 CE

A new study analyzed the remains of six people at an elite burial in northern coastal Peru in the Moche culture. One boy and one girl were human sacrifices. They were strangled to death which was the norm for human sacrifices in this region. Unexpectedly, the sacrificed children were themselves part of this royal family. The boy was sacrificed with his father. The girl who was sacrificed was the niece of the woman whom she was sacrificed with, who was the highest ranking figure, probably a queen. The graves were the subject of a memorial fire for at least 166 years.

Non-Perturbative GR Strikes Again

Non-perturbative general relativity, which has conventionally been ignored in many circumstances where it is actually relevant, including in modeling ordinary stars.

The general theory of relativity is currently established as the most precise theory of gravity supported by observations, and its application is diverse ranging from astronomy to cosmology, while its application to astrophysics has been restricted only to compact stars due to the assumption that the Newtonian approximation is sufficient for celestial bodies with medium density such as the sun. Surprisingly, the recent research of the author has implied that this long-held assumption is not valid, and that non-perturbative effects significantly change relevant results obtained by Newtonian gravity. In particular, local physical quantities inside the sun are newly predicted to exhibit power law differently from the so-called standard solar model. This surprising result is reviewed including brief discussion of physics behind the discrepancy and a new application of the new mass formula to gas planets.

Shuichi Yokoyama, "Stellar Physics and General Relativity" arXiv:2501.01442 (December 27, 2024) (published in Astronomische Nachrichte).

Quote Of The Day

They say that science progresses one funeral at a time. But it’s no longer true. Because the first generation of string theorists has raised their students who are now continuing the same stuff. And why would they not, these are cozy jobs, and there is nothing and no one that could stop them. So yeah, Siegfried is right. String theory is not dead. It’s undead, and now walks around like a zombie eating people’s brains.

From Sabine Hossenfelder's Youtube video String Theory Isn’t Dead about the article that Peter Woit discussed here.

Ancient DNA From Siberia As A Source For Modern Populations

Different strains of Siberian ancestry spread east to the New World and west to Scandinavia.

Human populations across a vast area in northern Eurasia, from Fennoscandia to Chukotka, share a distinct genetic component often referred to as the Siberian ancestry. Most enriched in present-day Samoyedic-speaking populations such as Nganasans, its origins and history still remain elusive despite the growing list of ancient and present-day genomes from Siberia. 

Here, we reanalyze published ancient and present-day Siberian genomes focusing on the Baikal and Yakutia, resolving key questions regarding their genetic history. First, we show a long-term presence of a unique genetic profile in southern Siberia, up to 6,000 yr ago, which distinctly shares a deep ancestral connection with Native Americans. Second, we provide plausible historical models tracing genetic changes in West Baikal and Yakutia in fine resolution. Third, the Middle Neolithic individual from Yakutia, belonging to the Belkachi culture, serves as the best source so far available for the spread of the Siberian ancestry into Fennoscandia and Greenland. These findings shed light on the genetic legacy of the Siberian ancestry and provide insights into the complex interplay between different populations in northern Eurasia throughout history.

Haechan Gill, Juhyeon Lee, Choongwon Jeon, "Reconstructing the Genetic Relationship between Ancient and Present-Day Siberian Populations" 16(4) Genome Biology and Evolution evae063 (March 25, 2024) https://doi.org/10.1093/gbe/evae063

Shifts In IQ Over Time

The chart, via Razib Khan, is based upon polygenetic scores calculated based upon ancient DNA.