The hypothesis that the mass of BHs increases with time according to the same law as the volume of the part of the Universe containing it and therefore the population of BHs is similar to dark energy in its action was recently proposed. We demonstrate the reasons why it cannot be accepted, even if all the assumptions on which this hypothesis is based are considered true.
Tuesday, February 28, 2023
Black Holes Are Not A Source Of Dark Energy
Wednesday, February 22, 2023
Homo Erectus Held On Until 100,000 Years Ago In Indonesia
When seafaring modern humans ventured onto the island of Java some 40,000 years ago, they found a rainforest-covered land teeming with life—but they weren’t the first humans to call the island home. Their distant ancestor, Homo erectus, had traveled to Java when it was connected to the mainland via land bridges and lived there for approximately 1.5 million years. These people made their last stand on the island about 100,000 years ago, long after they had gone extinct elsewhere in the world, according a new study assigning reliable dates to previously found H. erectus fossils.
. . .
The newly dated fossils also bookend the existence of a remarkably long-lived human species, says Patrick Roberts, an archaeologist at the Max Planck Institute for the Science of Human History in Jena, Germany, who wasn’t involved with the study.
. . .H. erectus arose in Africa about 1.9 million years ago. These toolmakers with relatively large brains migrated out of Africa and across Asia, crossing into Java by land bridges about 1.6 million years ago, when savanna-like open woodland covered much of the land. Later, sea levels rose, isolating these ancient Javans on an island. Meanwhile, in Africa and mainland Asia, H. erectus disappeared by about 500,000 years ago.
. . .
In 2008 and 2010, [the new study’s lead author, paleoanthropologist Russell] Ciochon’s team re-excavated the site, turning up 867 new fossils belonging to deer, wild cattle, and an extinct, elephantlike animal called a stegodon. Based on photographs and documents from the original excavation, they established that some of the newly found animal fossils came from the same rich bone bed as the H. erectus fossils. The researchers applied five types of radiometric dating, including a new method that provides both minimum and maximum dates, to those animal fossils and the sediments around them. The team concluded that the bones were buried between 117,000 and 108,000 years ago, the researchers report . . . in Nature.
Friday, February 17, 2023
Sabine Hossenfelder On "What's Going Wrong With Particle Physics?"
Married To A Model
This year's Valentine's Day poem from 4 gravitons:
Married to a Model
If you ever face a physics class distracted, Rappers and footballers twinkling on their phones, Then like an awkward youth pastor, interject, “You know who else is married to a Model?” Her name is Standard, you see, Wife of fifty years to Old Man Physics, Known for her beauty, charm, and strangeness too. But Old Man Physics has a wandering eye, and dreams of Models Beyond. Let the old man bend your ear, you’ll hear a litany of Problems. He’ll never understand her, so he starts. Some matters she holds weighty, some feather-light with nary rhyme or reason (which he is owed, he’s sure). She’s unnatural, he says, (echoing Higgins et al.), a set of rules he can’t predict. (But with those rules, all else is possible.) Some regularities she holds to fast, despite room for exception, others breaks, like an ill-lucked bathroom mirror. And then, he says, she’ll just blow up (when taken to extremes), while singing nonsense in the face of Gravity. He’s been keeping a careful eye and noticing anomalies (and each time, confronting them, finds an innocent explanation, but no matter). And he imagines others with yet wilder curves and more sensitive reactions (and nonsense, of course, that he’s lived fifty years without). Old man physics talks, that’s certain. But beyond the talk, beyond the phases and phrases, (conscious uncoupling, non-empirical science), he stays by her side. He knows Truth, in this world, is worth fighting for.
Genius In Action
I went to a conference which was totally about my specialization, and one Ph.D student gave his presentation, sounding very nervous. I could barely follow his talk, and thought I must have forgotten a lot of things, it seemed beyond my knowledge.
At the any questions stage, someone stood up, and suggested one part was wrong, with an alternative explanation, which seemed convincing - lots of people nodding, as he said what would have happened if the student speaker had been right.
Then instantly a second person stood up and said the first critic was right about the error, but his explanation was wrong, and explained why it was wrong and gave a second alternative explanation. Wow, criticizing an explanation and alternative explanation on a complex subject he had just heard 10 seconds ago. Lots of people nodding and ooing "oh yes."
Then a third person stood up, gave his name and was immediately recognized as a Nobel prize winner, (who just happened to be in town visiting an friend), but not a specialist in the topics of the conference. He told the original presenter what their error was, then told the first critic what was really wrong with his alternative explanation, told the second critic that he was wrong in each alternative he had offered (including his wrong explanation of what was wrong) and then explained what was really really going on.Silence. Every one sat going through what this not a specialist had said about everything, and slowly we all started nodding in agreement. We were all wiped out by how he could correct things outside of his own specialism and also how we all took so long to work out he was right. Genius is truly impressive when it swings into action.
From here (with minor spelling and punctuation edits and paragraph breaks added).
Wednesday, February 15, 2023
The Únětice Culture
Haak et al. 2015 examined the remains of 8 individuals of the Unetice culture buried in modern-day Germany c. 2200–1800 BC. The 3 samples of Y-DNA extracted belonged to Y-haplogroups I2a2, I2c2 and I2, while the 8 samples of mtDNA extracted were determined to belong to haplogroup I3a (2 samples), U5a1, W3a1, U5b2a1b, H4a1a1, H3 and V. The examined Unetice individuals were found to be very closely related to peoples of the earlier Yamnaya culture, Bell Beaker culture and Corded Ware culture. Their amount of steppe-related ancestry is comparable to that of some modern Europeans.Allentoft et al. 2015 examined the remains of 7 individuals of the Unetice culture buried in modern-day Poland and Czech Republic from c. 2300–1800 BC. The 7 samples of mtDNA extracted were determined to belong to haplogroup U4, U2e1f1, H6a1b, U5a1b1, K1a4a1, T2b and K1b1a. An additional male from the late Corded Ware culture or early Unetice culture in Łęki Małe, Poland of c. 2300–2000 BC was found to be a carrier of the paternal haplogroup R1b1a and the maternal haplogroup T2e. It was found that the people of the Corded Ware culture, Bell Beaker culture, Unetice culture and Nordic Bronze Age were genetically very similar to one another, and displayed a significant amount of genetic affinity with the Yamnaya culture.
The Únětice culture, named for a type-site cemetery in the village of Únětice, was a Bronze Age culture that first emerged around 2300–1600 BC. The culture is distinguished by its characteristic metal objects, including ingot torcs, flat axes, flat triangular daggers, bracelets with spiral ends, disk- and paddle-headed pins, and curl rings, which are distributed over a wide area of Central Europe and beyond. One of the most important discoveries attributed to the Únětice Culture is the Nebra sky disc, found buried on the Mittelberg hill near Nebra in Germany. The Nebra sky disc is made from bronze and has a blue-green patina inlaid with gold symbols, that archaeologists have interpreted to represent the Sun or full moon, a lunar crescent, and the stars.Archaeologists from the Adam Mickiewicz University have discovered a fortified Únětice Culture settlement, located near the town of Śmigiel, in the Kościan County of Poland. The settlement was situated on an island promontory, where 4,000-years-ago there was a lake on the edge of the Samica Kościańska valley, which today is a flowering meadow. The promontory was cut off from the mainland by a deep moat or ditch, with at least two rows of wooden palisades creating a fortified enclosure. The settlement occupied an area of 3.7 acres and supported a population of up to 100 people, which the researchers suggest was a metallurgical centre and a stronghold of power in the northern reaches of the Únětice Culture.The results of the study, published in the “Journal of Archaeological Science: Reports” reveals that the settlement was discovered after a geoarchaeological analysis of the former lake which was formed when a glacier retreated around 18,000-years-ago. Based on core samples obtained by drilling, the lake started to shrink around 800 BC, eventually turning into a large bog at the turn of the era.
Tuesday, February 14, 2023
What Drives The Hubble Tension?
Stacy McGaugh suggests in his latest blog post that the Hubble tension is probably due to the estimate of Hubble's constant from the cosmic microwave background (CMB) which has gotten lower as greater precision measurements of it have been made, rather than from errors in recent time Hubble constant measurements as it is more common to suppose.
He argues that observed early galaxy formation, which is contrary to the LambdaCDM model and thus not accounted for by it when calculating the early time Hubble constant from the CMB, is likely to be a big part of the discrepancy.
Friday, February 10, 2023
Many of the "notable links" in the sidebar are dead or go to defunct blogs. I am purging them from the sidebar, but saving the names of the linked sites and the links that aren't dead for dormant blogs here for future reference to access the existing posts at those links, and also, in case the links are restored or the blogs are revived. I've also resorted the sidebar links alphabetically. The links removed were:
- Arcadian Gravity (author deceased)
- Archaeobotany and Domestication (deactivated account)
- Dienekes' Anthropology Blog (last activity January 1, 2021)
- Ethio Helix (last activity July 31, 2015)
- For What They Were . . . We Are (last activity December 21, 2018, closure announced in last post)
- Gauge Connection (last activity August 13, 2019)
- Linear Population Model (open to invited readers only)
- NJ's arya blog (last activity May 26, 2018)
- A Replicated Typo (last activity May 26, 2021)
Tuesday, February 7, 2023
A New Top Quark Mass Measurement
The mass of the top quark is measured in 36.3 fb−1 of LHC proton-proton collision data collected with the CMS detector at s√ = 13 TeV. The measurement uses a sample of top quark pair candidate events containing one isolated electron or muon and at least four jets in the final state. For each event, the mass is reconstructed from a kinematic fit of the decay products to a top quark pair hypothesis. A profile likelihood method is applied using up to five observables to extract the top quark mass. The top quark mass is measured to be 171.77 ± 0.37 GeV. This approach significantly improves the precision over previous measurements.
Monday, February 6, 2023
Dark Matter Still Has Nothing On MOND In The Milky Way
We use data from the Gaia DR3 dataset to estimate the mass of the Milky Way (MW) by analyzing the rotation curve in the range of distances 5 kpc to 28 kpc.
We consider three mass models: the first model adds a spherical dark matter (DM) halo, following the Navarro-Frenk-White (NFW) profile, to the known stellar components. The second model assumes that DM is confined to the Galactic disk, following the idea that the observed density of gas in the Galaxy is related to the presence of more massive DM disk (DMD), similar to the observed correlation between DM and gas in other galaxies. The third model only uses the known stellar mass components and is based on the Modified Newton Dynamics (MOND) theory.
Our results indicate that the DMD model is comparable in accuracy to the NFW and MOND models and fits the data better at large radii where the rotation curve declines but has the largest errors. For the NFW model we obtain a virial mass M(vir)=(6.5±0.3)×10^11M⊙ with concentration parameter c=14.5, that is lower than what is typically reported. In the DMD case we find that the MW mass is M(d)=(1.6±0.5)×10^11M⊙ with a disk's characteristic radius of Rd=17 kpc.
Friday, February 3, 2023
Physics Needs Better Literature Reviews
Mirror Cosmology Recapped
Here is a recap, all in one place, of work on mirror cosmology with an anti-matter universe before the Big Bang that is a mirror of our own and our own matter dominated universe that I've previously blogged, stripped of (probably wrong) speculations about dark matter and right handed neutrinos:
We argue that the Big Bang can be understood as a type of mirror. We show how reflecting boundary conditions for spinors and higher spin fields are fixed by local Lorentz and gauge symmetry, and how a temporal mirror (like the Bang) differs from a spatial mirror (like the AdS boundary), providing a possible explanation for the observed pattern of left- and right-handed fermions. By regarding the Standard Model as the limit of a minimal left-right symmetric theory, we obtain a new, cosmological solution of the strong CP problem, without an axion.
In a series of recent papers, we have argued that the Big Bang can be described as a mirror separating two sheets of spacetime. Let us briefly recap some of the observational and theoretical motivations for this idea.Observations indicate that the early Universe was strikingly simple: a fraction of a second after the Big Bang, the Universe was radiation-dominated, almost perfectly homogeneous, isotropic, and spatially flat; with tiny (around 10^−5) deviations from perfect symmetry also taking a highly economical form: random, statistically gaussian, nearly scale-invariant, adiabatic, growing mode density perturbations. Although we cannot see all the way back to the bang, we have this essential observational hint: the further back we look (all the way back to a fraction of a second), the simpler and more regular the Universe gets. This is the central clue in early Universe cosmology: the question is what it is trying to tell us.In the standard (inflationary) theory of the early Universe one regards this observed trend as illusory: one imagines that, if one could look back even further, one would find a messy, disordered state, requiring a period of inflation to transform it into the cosmos we observe.An alternative approach is to take the fundamental clue at face value and imagine that, as we follow it back to the bang, the Universe really does approach the ultra-simple radiation-dominated state described above (as all observations so far seem to indicate).Then, although we have a singularity in our past, it is extremely special. Denoting the conformal time by τ , the scale factor a(τ) is ∝ τ at small τ so the metric g^(µν) ∼ a(τ)^(2ηµν) has an analytic, conformal zero through which it may be extended to a “mirror-reflected” universe at negative τ.[W]e point out that, by taking seriously the symmetries and complex analytic properties of this extended two-sheeted spacetime, we are led to elegant and testable new explanations for many of the observed features of our Universe including: . . . (ii) the absence of primordial gravitational waves, vorticity, or decaying mode density perturbations; (iii) the thermodynamic arrow of time (i.e. the fact that entropy increases away from the bang); and (iv) the homogeneity, isotropy and flatness of the Universe, among others.In a forthcoming paper, we show that, with our new mechanism for ensuring conformal symmetry at the bang, this picture can also explain the observed primordial density perturbations.In this Letter, we show that: (i) there is a crucial distinction, for spinors, between spatial and temporal mirrors; (ii) the reflecting boundary conditions (b.c.’s) at the bang for spinors and higher spin fields are fixed by local Lorentz invariance and gauge invariance; (iii) they explain an observed pattern in the Standard Model (SM) relating left- and right-handed spinors; and (iv) they provide a new solution of the strong CP problem. . . .In this paper, we have seen how the requirement that the Big Bang is a surface of quantum CT symmetry yields a new solution to the strong CP problem. It also gives rise to classical solutions that are symmetric under time reversal, and satisfy appropriate reflecting boundary conditions at the bang.The classical solutions we describe are stationary points of the action and are analytic in the conformal time τ. Hence they are natural saddle points to a path integral over fields and four-geometries. The full quantum theory is presumably based on a path integral between boundary conditions at future and past infinity that are related by CT-symmetry. The cosmologically relevant classical saddles inherit their analytic, time-reversal symmetry from this path integral, although the individual paths are not required to be time-symmetric in the same sense (and, moreover may, in general, be highly jagged and non-analytic).We will describe in more detail the quantum CT-symmetric ensemble which implements (12), including the question of whether all of the analytic saddles are necessarily time-symmetric, and the calculation of the associated gravitational entanglement entropy, elsewhere.
In a recent work, Turok, Boyle and Finn hypothesized a model of universe that does not violate the CPT-symmetry as alternative for inflation. With this approach they described the birth of the Universe from a pair of universes, one the CPT image of the other, living in pre- and post-big bang epochs. The CPT-invariance strictly constrains the vacuum states of the quantized fields, with notable consequences on the cosmological scenarios.Here we examine the validity of this proposal by adopting the point of view of archaic cosmology, based on de Sitter projective relativity, with an event-based reading of quantum mechanics, which is a consequence of the relationship between the universal information reservoir of the archaic universe and its out-of-equilibrium state through quantum jumps. In this scenario, the big bang is caused by the instability of the original (pre)vacuum with respect to the nucleation of micro-events that represent the actual creation of particles.Finally, we compare our results with those by Turok et al., including the analytic continuation across the big bang investigated by Volovik and show that many aspects of these cosmological scenarios find a clear physical interpretation by using our approach. Moreover, in the archaic universe framework we do not have to assume a priori the CPT-invariance like in the other models of universe, it is instead a necessary consequence of the archaic vacuum structure and the nucleation process, divided into two specular universes.
The universe before the Big Bang is the CPT reflection of the universe after the bang, so that the state of the universe does not spontaneously violate CPT. The universe before the bang and the universe after the bang may be viewed as a universe/anti-universe pair, created from nothing. The early universe is radiation dominated and inflationary energy is not required. We show how CPT selects a preferred vacuum state for quantum fields on such a cosmological spacetime. This, in turn, leads to a new view of the cosmological matter/anti-matter asymmetry[.]
In the multiverse, the universes can be created in entangled pairs with spacetimes that are both expanding in terms of the time variables experienced by internal observers in their particle physics experiments. The time variables of the two universes are related by an antipodal-like symmetry that might explain why there is no antimatter in our universe: at the origin, antimatter is created, by definition and for any observer, in the observer's partner universe. The Euclidean region of the spacetime that separates the two universes acts as a quantum barrier that prevents matter-antimatter from collapse.
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10^−36 seconds after the conjectured Big Bang singularity to some time between 10^−33 and 10^−32 seconds after the singularity. Following the inflationary period, the universe continued to expand, but at a slower rate. The acceleration of this expansion due to dark energy began after the universe was already over 7.7 billion years old (5.4 billion years ago). . . . It was developed further in the early 1980s. It explains the origin of the large-scale structure of the cosmos. Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the Universe. Many physicists also believe that inflation explains why the universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the universe is flat, and why no magnetic monopoles have been observed.
Thursday, February 2, 2023
Galaxies Ten Billion Years Ago Look A Lot Like Galaxies Today
We study the dynamics of cold molecular gas in two main-sequence galaxies at cosmic noon (zC-488879 at z≃1.47 and zC-400569 at z≃2.24) using new high-resolution ALMA observations of multiple 12CO transitions. For zC-400569 we also re-analyze high-quality Hα data from the SINS/zC-SINF survey.
We find that (1) Both galaxies have regularly rotating CO disks and their rotation curves are flat out to ∼8 kpc contrary to previous results pointing to outer declines in the rotation speed Vrot; (2) The intrinsic velocity dispersions are low (σCO≲15 km/s for CO and σHα≲37 km/s for Hα) and imply Vrot/σCO≳17−22 yielding no significant pressure support; (3) Mass models using HST images display a severe disk-halo degeneracy: models with inner baryon dominance and models with "cuspy" dark matter halos can fit the rotation curves equally well due to the uncertainties on stellar and gas masses; (4) Milgromian dynamics (MOND) can successfully fit the rotation curves with the same acceleration scale a0 measured at z≃0.
The question of the amount and distribution of dark matter in high-z galaxies remains unsettled due to the limited spatial extent of the available kinematic data; we discuss the suitability of various emission lines to trace extended rotation curves at high z. Nevertheless, the properties of these two high-z galaxies (high Vrot/σV ratios, inner rotation curve shapes, bulge-to-total mass ratios) are remarkably similar to those of massive spirals at z≃0, suggesting weak dynamical evolution over more than 10 Gyr of the Universe's lifetime.