Tuesday, May 19, 2015
Moffat's MOG Makes A Prediction About Black Hole Shadows
John Moffat's modification of gravity, one version of which is called MOG, is a leading alternative to dark matter theories. A recap at Backreaction of a recent Perimeter Institute talk identifies an experimental test of his theory that may soon be possible to ascertain, namely, the size of a black hole's "shadow" (a name of the extreme lensing effects near its event horizon).
Monday, May 18, 2015
Galactic Cluster Collision Observations Disfavor Heavy Particle Dark Matter
El Gordo is the largest known example of two galaxies colliding. Comparing the X-ray spectrum emissions of hot colliding gas with the visible light from the stars are the cores of the galaxies in the galactic clusters, provides an observational foundation from which the nature of dark matter phenomena in the clusters can be inferred.
The New Result
Scientists who have done this find that a heavy particle model of dark matter is a poor fit to this data.
Wave, Scalar Field and Boson Star Dark Matter
More background on wave dark matter is found here and here. A key point is that "In these wave dark matter mechanisms, the substructure of the dark matter (the perturbations from spherical symmetry) is what drives the substructure in the regular matter (spiral patterns and shells)." The observed texture of luminous matter distributions in elliptical galaxies (which often have "shells") and spiral galaxies (which often have spiral arms rather than being smooth disks) is a major motivation for this theory.
Another notable observation about wave dark matter theories in these links is this one:
A recent analysis of cosmological data in the context of the theory concludes that the right boson mass is actually about 10 orders of magnitude smaller than previously assumed. My own intuition is to note that the bosons of scalar field dark matter are suspiciously close in mass-energy magnitude to the hypothetical graviton. And, indeed, the mass predicted in this recent analysis is precisely the mass a graviton would need to have in order to reproduce the observed cosmology without the cosmological constant. This mass also corresponds to a Compton wave length of approximately the same length of the size of the universe (i.e. about 13 billion light years).
I suspect that a lot of the discussion of the massless graviton confounds particle rest mass, which an infinite range force boson should not have, and mass-energy which is something which gravity couples to and is present even in massless bosons like the photon. It is not at all obvious to me that "massive gravity" theories are in any way distinguishable from "mass-energyful gravity" theories, in which case "massive gravity" is not inconsistent with a graviton that has zero rest mass as expected (but I would seem to be wrong). A hypothetical graviton, while it lacks rest mass, should have mass-energy of some small, finite amount.
Some blog level discussion of massive gravity theories and their history is found here. The criticism is a mass-energyful gravity expressed in the comments is that:
As an aside, an excellent pdf defining the key terms and concepts in GR and the Einstein-Gordon-Klein equation (which describes the gravitational force generated by a scalar field in GR) is found here. The Einstein-Gordon-Klein equation is intimately related to wave dark matter models and scalar field dark matter models.
The New Result
Scientists who have done this find that a heavy particle model of dark matter is a poor fit to this data.
This distinctive configuration has allowed the researchers to establish the relative speed of the collision, which is extreme (~2200km/second), as it puts it at the limit of what is allowed by current theory for dark matter.The underlying study to this interpretative description from a university PR office is here (preprint here). The abstract (with a few mathematical symbols converted to words) states that:
These rare, extreme examples of clusters caught in the act of colliding seem to be challenging the accepted view that dark matter is made up of heavy particles, since no such particles have actually been detected yet, despite the efforts being made to find them by means of the LHC (Large Hadron Particle Collider) accelerator in Geneva and the LUX (Large Underground Xenon Experiment), an underground dark matter detector in the United States. In Tom Broadhurst's opinion, "it's all the more important to find a new model that will enable the mysterious dark matter to be understood better." Broadhurst is one of the authors of a wave-dark-matter model published in Nature Physics last year.
This new piece of research has entailed interpreting the gas observed and the dark matter of El Gordo "hydrodynamically" through the development of an in-house computational model that includes the dark matter, which comprises most of the mass, and which can be observed in the Xray region of the visible spectrum because of its extremely high temperature (100 million kelvin). Dr Broadhurst and Dr Molnar have managed to obtain a unique computational solution for this collision because of the comet-like shape of the hot gas, and the locations and the masses of the two dark matter cores that have passed through each other at an oblique angle at a relative speed of about 2200 km/s. This means that the total energy release is bigger than that of any other known phenomenon, with the exception of the Big Bang.
The distinctive cometary X-ray morphology of the recently discovered massive galaxy cluster "El Gordo" (ACT-CT J0102–4915; z = 0.87) indicates that an unusually high-speed collision is ongoing between two massive galaxy clusters. A bright X-ray "bullet" leads a "twin-tailed" wake, with the Sunyaev-Zel'dovich (SZ) centroid at the end of the northern tail.
We show how the physical properties of this system can be determined using our FLASH-based, N-body/hydrodynamic model, constrained by detailed X-ray, SZ, and Hubble lensing and dynamical data.
The X-ray morphology and the location of the two dark matter components and the SZ peak are accurately described by a simple binary collision viewed about 480 million years after the first core passage. We derive an impact parameter of about 300 kpc, and a relative initial infall velocity of about 2250 km s–1 when separated by the sum of the two virial radii assuming an initial total mass of 2.15 × 1015 M ☉ and a mass ratio of 1.9.
Our model demonstrates that tidally stretched gas accounts for the northern X-ray tail along the collision axis between the mass peaks, and that the southern tail lies off axis, comprising compressed and shock heated gas generated as the less massive component plunges through the main cluster.
The challenge for ΛCDM will be to find out if this physically extreme event can be plausibly accommodated when combined with the similarly massive, high-infall-velocity case of the Bullet cluster and other such cases being uncovered in new SZ based surveys.In the pertinent part of the conclusion the paper states that:
This massive merging cluster with an infall velocity of 2250 km s−1 at the the time the Universe was half of its age (at the redshift of z = 0.87) is apparently very unusual in the standard ΛCDM models, for which extensive simulations have been performed to determine the expected probability distribution of relative velocities (Thompson & Nagamine 2012). At face value, such extreme cases present a challenge to our understanding of structure formation and may lead to a better understanding of dark matter and/or alternative theories of gravity.Basically, then, the example is notable because structure formation of such a huge scale tends to come much later in standard ΛCDM models than is observed. Thompson, Dave & Nagamine 2014, however, finds that the deficit of merging clusters of this type may have simply been an artifact of an inadequate simulation program, and reproduce the observed number of large cluster combinations from the standard ΛCDM models in a simulation using a different methodology.
Wave, Scalar Field and Boson Star Dark Matter
More background on wave dark matter is found here and here. A key point is that "In these wave dark matter mechanisms, the substructure of the dark matter (the perturbations from spherical symmetry) is what drives the substructure in the regular matter (spiral patterns and shells)." The observed texture of luminous matter distributions in elliptical galaxies (which often have "shells") and spiral galaxies (which often have spiral arms rather than being smooth disks) is a major motivation for this theory.
Another notable observation about wave dark matter theories in these links is this one:
[T]his is where our discussion intersects with the fascinating works of many others who have studied “scalar field dark matter” and “boson stars.” In the boson star case, the motivation is quantum mechanical, so the above scalar field f is supposed to represent the overall wave function for a very large number of very tiny bosons with masses on the order of 10−23 eV. We relate our constant Υ to the mass of the Klein-Gordon equation by noting that the Compton wavelength in both cases is λ = 2π Υ = h m ≈ 13 light years if we take m ≈ 10−23eV , or equivalently, Υ ≈ 1/(2 light years). These other motivations are interesting as well but should be distinguished from the purely geometric motivations provided in this paper.The related scalar field dark matter theory is also described here and was originally conceived in 1994 by Ji and Sin.
A recent analysis of cosmological data in the context of the theory concludes that the right boson mass is actually about 10 orders of magnitude smaller than previously assumed. My own intuition is to note that the bosons of scalar field dark matter are suspiciously close in mass-energy magnitude to the hypothetical graviton. And, indeed, the mass predicted in this recent analysis is precisely the mass a graviton would need to have in order to reproduce the observed cosmology without the cosmological constant. This mass also corresponds to a Compton wave length of approximately the same length of the size of the universe (i.e. about 13 billion light years).
I suspect that a lot of the discussion of the massless graviton confounds particle rest mass, which an infinite range force boson should not have, and mass-energy which is something which gravity couples to and is present even in massless bosons like the photon. It is not at all obvious to me that "massive gravity" theories are in any way distinguishable from "mass-energyful gravity" theories, in which case "massive gravity" is not inconsistent with a graviton that has zero rest mass as expected (but I would seem to be wrong). A hypothetical graviton, while it lacks rest mass, should have mass-energy of some small, finite amount.
Some blog level discussion of massive gravity theories and their history is found here. The criticism is a mass-energyful gravity expressed in the comments is that:
There is no such thing as the energy density of the curvature. This is an old result from GR --- one cannot define the concept of energy for a gravitational field, locally. It can be done only in a suitable global sense (spacetime with asymptotic global time-translation symmetry).It is indeed an old result, but I continue to think that it is almost certainly wrong and probably the main cause of the deviation between GR and what is observed in Nature. Even if this is true of GR, that may just mean that GR is wrong.
As an aside, an excellent pdf defining the key terms and concepts in GR and the Einstein-Gordon-Klein equation (which describes the gravitational force generated by a scalar field in GR) is found here. The Einstein-Gordon-Klein equation is intimately related to wave dark matter models and scalar field dark matter models.
Oliver Heaviside
Lubos has a wonderful biography of Oliver Heaviside, a self-taught man from a humble condition who was the source of many of the words and much of the modern notation we use to describe classical electromagnetism (e.g. the standard form of Maxwell's equations), in addition to inventing many electromagnetic devices.
He was born on May 18, 1850, succeeding again and again despite the circumstances arrayed against him.
He was born on May 18, 1850, succeeding again and again despite the circumstances arrayed against him.
Sunday, May 17, 2015
Warm Blooded Fish
Opah, a kind of fish also known as Moonfish (scientific name Lampris guttatus), are the first species of warm blooded fish every discovered. Their warm blood gives them an advantage as a predator in deep, cold waters, where other fish, because they are cold blooded, are sluggish.
Sharks and tuna, which are also predators, have a much diminished form of warm bloodedness specific to only a few muscle regions that don't operate at great water depths, but nothing approaching the warm-blooded adaptions of the Opah.
Note that the study reporting the finding does not reach the conclusion that warm bloodedness in the Opah is ancestral to warm bloodedness in mammals and birds. Indeed, this is almost surely not the case, because birds and mammals are descended from cold blooded reptiles (although some dinosaurs were probably also warm blooded). Instead, warm bloodedness in the Opah is an independent case of convergent evolution.
Sharks and tuna, which are also predators, have a much diminished form of warm bloodedness specific to only a few muscle regions that don't operate at great water depths, but nothing approaching the warm-blooded adaptions of the Opah.
Note that the study reporting the finding does not reach the conclusion that warm bloodedness in the Opah is ancestral to warm bloodedness in mammals and birds. Indeed, this is almost surely not the case, because birds and mammals are descended from cold blooded reptiles (although some dinosaurs were probably also warm blooded). Instead, warm bloodedness in the Opah is an independent case of convergent evolution.
Universe Has Disproportionately Left Handed Magnetic Fields
Science Daily reports a new study finding that the universe has disproportionately left handed magnetic fields, rather than equal numbers of left handed and right handed magnetic fields, based upon observations of cosmic gamma rays reaching Earth. The finding could provide a foundation for understanding the matter-antimatter disparity in the universe.
This isn't the first time that a left handed-right handed disparity has been observed in the universe. Another is found in the Standard Model of Particle Physics, in which the weak force acts only on left handed particles and right handed antiparticles.
This isn't the first time that a left handed-right handed disparity has been observed in the universe. Another is found in the Standard Model of Particle Physics, in which the weak force acts only on left handed particles and right handed antiparticles.
Tuesday, May 12, 2015
Happy May 12
Finnish flag image via Wikipedia
Today is the Day of the Finnish Identity, which is celebrated on the birthday of an early Finnish statesman.
How curiously humble to have a day in which you acknowledge that your national identity is something that came into being, or at least, into currency, at a time in historical memory, as opposed to trying to plant the false history that it was eternally in existence since time immemorial.
Sunday, May 3, 2015
The Periodic Table Elements In Chinese
The world's most comprehensive English-Chinese character translation key for the Periodic Table of the elements is now available at the Language Log blog.
There are several instances where the Taiwanese representation and the People's Republic of China representation differ. Mandarin Chinese seeks to represent all of the chemical elements with a single syllable.
There are several instances where the Taiwanese representation and the People's Republic of China representation differ. Mandarin Chinese seeks to represent all of the chemical elements with a single syllable.
Siberian Historical Population Genetics
Siberia has repeatedly swung between being predominantly West Eurasian genetically, and predominantly East Eurasian. One swing, of early Indo-Europeans, peaked around 4000 years ago, and then swung back the other way starting around 1500-2500 years ago (with Turks and then Mongols migrating East to West), only to swing in the West Eurasian direction again with the expansion of the Russian empire starting around 200-300 years ago.
New population genetic studies (open access) reveal that the West Eurasian ancestry in most modern Siberian populations is attributable to the Bronze Age Indo-European wave, rather than the more recent wave of Slavic Russian colonization.
New population genetic studies (open access) reveal that the West Eurasian ancestry in most modern Siberian populations is attributable to the Bronze Age Indo-European wave, rather than the more recent wave of Slavic Russian colonization.
Friday, May 1, 2015
The Genetics of the Kalash People
In an early worldwide survey of this kind, division into five clusters unsurprisingly identified (1) Africans, (2) a widespread group including Europeans, Middle Easterners, and South Asians, (3) East Asians, (4) Oceanians, and (5) Native Americans. However, division into six groups led to a more surprising finding: the sixth group consisted of a single population, the Kalash. The Kalash are an isolated South Asian population of Indo-European speakers residing in the Hindu Kush mountain valleys in northwest Pakistan, near the Afghan frontier. With a reported census size of 5,000 individuals, they represent a religious minority with unique and rich cultural traditions.From a new open access paper in the Journal Cell on their autosomal genetics. This outlier status could, however, be due to sustained genetic isolation and inbreeding in a small population which can create a very unique and uniform autosomal genetic profile with isolated mutations that looks more exotic than it seems.
They are also one of the few populations in the world that are non-Hindu pagans religiously, as opposed to having a revived "neo-pagan" or monotheistic religion.
They are some of the most "white" looking people of South Asia (despite their lack of close genetic affinity to Europeans), which led to historically inaccurate myths that the were descendants of Alexander the Great's troops that marched into the general vicinity in ancient times. As their language illustrates, however, they have had, at least, significant cultural contact with Indo-European people at some point in deep history. They are also lactose tolerant, although due to genes different than those found in Europeans.
Some of the analysis in the paper is controversial and I will update this post to discuss those issues and the detailed conclusions of the genetic analysis if I have time to do so.
One key point that is not particularly controversial is that the Kalash people show closer affinity to ancient DNA from Ma'alta boy, an Upper Paleolithic individual from near the Altai Mountains whose Y-DNA is a very basal version of haplogroup R, than any other extant modern population.
UPDATE May 3, 2015:
For convenience sake, I will reproduce below the pertinent part of a post at Wash Park Prophet on the subject on March 3, 2011:
The Kalash people in a remote part of the Hindu Kush Mountain range are one of the most genetically distinct populations in the world. When one has a computer break the world's autosomal genetics into the most distinct possible seven clusters, the clusters that you get are: African, European, South Asian, East Asian, Papuan, indigenous American and Kalash.
Their Y-DNA haplogroups (from a sample of about 43 people) are as follows:
* L3a 22.7% (most common in Pakistan)
* H1* 20.5% (most common in South Asia)
* R1a 18.2% (most common in Eastern Europe and South Asia)
* G 18.2% (most common in Southern Europe, Anatolia, Druze, Brahui and Pashtuns)
* J2 9.1% (most common in Anatolia and where Indo-Europeans have had an impact)
* R* 6.8% (most common in Thailand, Indonesia, the Phillipines and Australian aborigines)
* R1* 2.3% (most common in indigenous Americans)
* L* 2.3%. (most common in South Asia)
Their mtDNA haplogroups (from a sample of 44 people) are as follows:
* pre-HV 22.7% (most common in Socotri, North Africa, Iran and Arabia)
* HV* 4.5%
* H 4.5% (the modal haplogroup of Europe)
* U2e 15.9% (most common in South Asia)
* U4 34.1% (most common in Central Asia)
* U7 2.3% (most common in South Asia)
* J1 2.3%
* J2 9.1%
* T* 4.5%
They speak a language from the Dardic branch of the Indo-European family (one of the more basal of the Indo-Iranian part of the late language family), and practice a polytheistic religion.
They are between areas that areas typically Central Asian and areas that are typically South Asian in genetic makeup. Their traditions place them as a lost contingent of Alexander the Great's army, but given their uniparental markers, the genetic makeup, their particularly contingent would have had to have picked up members mostly from the area from Anatolia to the Hindu Kush. Their Dardic language is also an anomaly for an isolated community claiming to descend from the Greeks, they lack common distinctively Greek uniparental markers, and their religion is close to Hinduism than it is to Greek pantheistic beliefs. An origin a millennium or two earlier (if not much more ancient) would seem to be a better fit for the facts.
Given their autosomal makeup, any new arrivals in the region from somewhere would have had to either admixed substantially with a relict population that was largely wiped out or overwhelmed genetically elsewhere such as Europe and Central Asia's pre-Neolithic hunter-gatherers, or South Asian hunter-gatherer populations disrupted by Munda, Dravidian, and Indo-Aryan populations respectively. Alternately, they might have undergone significant selectively driven evolution analogous to that found in Tibetans as a result of living at high altitudes. The case for incorporation of a relict Central Asian hunter-gatherer population is most strongly supported by the modal mtDNA haplogroup U4, which was one of the second most common types found in ancient DNA from Central Asian hunter-gatherers.
Monday, April 27, 2015
My Genome II
I'd previously discussed my ancestry results from 23 and me which can be summarized as follows:
European 99.9%
*Northern European 95.4% (up 0.6)
**Finnish 43.4% (up 5.3)
**Scandinavian 3.0% (down 13.4)
**British and Irish 9.6% (up 3.3)
**French and German 5.2% (up 4.1)
**Broadly Northern European 34.2% (down 0.7)
*Broadly Southern European 1.9% (down 0.7)
*Broadly European 2.7% (up 0.1)
East Asian - Yakut 0.1%
Middle East & North African - North African less than 0.1% (new)
Unassigned less than 0.1%
Where it comes from
It is also possible to discern that a modest part of the British and Irish component, the about a third the "Southern European" component, and all of the "Yakut" ancestry are from my mother's side of chromosome 6, while the "North African" portion, a modest part of the British and Irish component, and about half of the "Scandinavian" component is from my father's side on chromosome 6.
The remainder of the "Southern European" component, the remainder of the "Scandinavian" component, more of the rest of the British and Irish component, and all of the "French and German" component, are on other chromosomes on my father's side, while a little bit of the British and Irish component is on another chromosome on my mother's side.
Broadly European and Broadly Northern European components are found on every chromosome.
Thus from my mother I receive 43.4% Finnish, perhaps 1.6% British and Irish, and perhaps 0.6% Southern European and 0.1% Yakut, and about 4.3% Broadly Northern European and Broadly European.
Meanwhile from my father, I receive perhaps 8.0% British and Irish, 5.2% French and German, 3.0% Scandinavian, 1.3% Broadly Southern European, less than 0.1% North African, and 32.4% Broadly Northern European and Broadly European.
Analysis
It seems a bit odd that I have one chromosome, number six, that is much more cosmopolitan and well defined than the others.
The rephased results case my mother as even more pure-bloodedly Finnish than she had been before, while my father comes out again as a Northern European mutt.
Neither the trace Yakut on my mother's side, from a region that had trade ties to Finland, nor the trace North African ancestry on my father's side given that I have a Y-DNA haplogroup that is only about three mutations away from a common Berber Y-DNA haplogroup, is much of a surprise. Indeed, I was surprised at the absence of even trace North African ancestry the first time around.
The fact that the British and Irish ancestry is greater than before and mostly on my father's side is unsurprising, given that I have known Irish ancestry on that side. The only surprise about the French and German ancestry on my father's side is that it is so low relative to "Broadly Northern European" ancestry.
Trace Southern European and British and Irish ancestry on my mother's side is a bit of a surprise, but it is small enough in amount to have cryptic origins, although careful examination of my mother's side's well documented genealogy could probably ferret it out.
Y-DNA haplogroup: E1b1b1a2* (E1b1b1 is also known as E-M35, E1b1b1a is E-M78 and my own haplogroup is E-V36/V13).In due course, my children's results came in, and that substantially changed the result for me due to "phasing" associated with the link to a child. It now reads (with changes in bold):
mtDNA haplogroup: H1b
Broad ancestry composition (out of 31 regional groupings including speculative estimates):
European 99.9%
*Northern European 94.8%
**Finnish 38.1%
**Scandinavian 16.4% (Sweden-Norway-Denmark)
**British and Irish 6.3% (UK and Ireland)
**French and German 1.1% (Germany, Netherlands, France, Switzerland, Austria, Belgium)
**Broadly Northern European 32.9%
*Broadly Southern European 2.6%
*Broadly European 2.6%
East Asian - Yakut 0.1%
Unassigned less than 0.1%
European 99.9%
*Northern European 95.4% (up 0.6)
**Finnish 43.4% (up 5.3)
**Scandinavian 3.0% (down 13.4)
**British and Irish 9.6% (up 3.3)
**French and German 5.2% (up 4.1)
**Broadly Northern European 34.2% (down 0.7)
*Broadly Southern European 1.9% (down 0.7)
*Broadly European 2.7% (up 0.1)
East Asian - Yakut 0.1%
Middle East & North African - North African less than 0.1% (new)
Unassigned less than 0.1%
Where it comes from
It is also possible to discern that a modest part of the British and Irish component, the about a third the "Southern European" component, and all of the "Yakut" ancestry are from my mother's side of chromosome 6, while the "North African" portion, a modest part of the British and Irish component, and about half of the "Scandinavian" component is from my father's side on chromosome 6.
The remainder of the "Southern European" component, the remainder of the "Scandinavian" component, more of the rest of the British and Irish component, and all of the "French and German" component, are on other chromosomes on my father's side, while a little bit of the British and Irish component is on another chromosome on my mother's side.
Broadly European and Broadly Northern European components are found on every chromosome.
Thus from my mother I receive 43.4% Finnish, perhaps 1.6% British and Irish, and perhaps 0.6% Southern European and 0.1% Yakut, and about 4.3% Broadly Northern European and Broadly European.
Meanwhile from my father, I receive perhaps 8.0% British and Irish, 5.2% French and German, 3.0% Scandinavian, 1.3% Broadly Southern European, less than 0.1% North African, and 32.4% Broadly Northern European and Broadly European.
Analysis
It seems a bit odd that I have one chromosome, number six, that is much more cosmopolitan and well defined than the others.
The rephased results case my mother as even more pure-bloodedly Finnish than she had been before, while my father comes out again as a Northern European mutt.
Neither the trace Yakut on my mother's side, from a region that had trade ties to Finland, nor the trace North African ancestry on my father's side given that I have a Y-DNA haplogroup that is only about three mutations away from a common Berber Y-DNA haplogroup, is much of a surprise. Indeed, I was surprised at the absence of even trace North African ancestry the first time around.
The fact that the British and Irish ancestry is greater than before and mostly on my father's side is unsurprising, given that I have known Irish ancestry on that side. The only surprise about the French and German ancestry on my father's side is that it is so low relative to "Broadly Northern European" ancestry.
Trace Southern European and British and Irish ancestry on my mother's side is a bit of a surprise, but it is small enough in amount to have cryptic origins, although careful examination of my mother's side's well documented genealogy could probably ferret it out.
Sunday, April 26, 2015
Dark Photon Parameter Space Constrained
The two most viable dark matter models are those with a single keV mass dark matter particle (warm dark matter) and self-interacting dark matter models in which dark matter fermions interact with each other via a "dark photon" that could also potentially mix with ordinary photons. A new study restricts the properties that the dark photon can have in a self-interacting dark matter model.
Jester notes significant restrictions on dark photon parameter space from a variety of recent experiments.
But, I would disagree with him that there is no theoretically preferred value for mA' which is the mass of the dark photon (hypothesized as a boson that carries a force by which dark matter interacts with other dark matter). Most studies I have seen have favored a dark photon mass in the MeV range and certainly a mass of less than 10 GeV.
The constraint on mixing between dark photons and ordinary photons is significantly tighter for dark photon masses of under 10 MeV, which is the preferred mass range for dark photons.
The mass of a dark photon impacts the effective range of the force it carries. A dark photon with a mass of 80 Gev-90 GeV would have a range similar to that of the weak force bosons, i.e. on the order of the size of an atomic nucleus. An MeV range dark photon, in contrast, would have a long enough range to produce meaningful interactions of dark matter particles that are near each other sufficiently to tweak the dark matter halo shape in galaxies and galactic clusters.
Thus, this data, collectively, and together with other data attempting to detect dark matter directly, further buttresses the idea that if dark matter exists, that it has almost no interactions with ordinary matter except via gravity.
Interactions between ordinary photons and dark photons aren't important to the overall character of self-interacting dark matter models, but these studies do strictly narrow the classes of self-interacting dark matter models that can be consistent with empirical evidence.
UPDATE: A new study reanalyzes the estimates of the strength of dark matter self-interactions based upon the observations of a galaxy falling into a galactic cluster. The value reached is similar to, but a bit higher than, that estimated from the Bullet Cluster.
Jester notes significant restrictions on dark photon parameter space from a variety of recent experiments.
[T]he mixing angle in the minimal model has to be less than 0.001 as long as the dark photon is lighter than 10 GeV. This is by itself not very revealing, because there is no theoretically preferred value of ε or mA'. However, one interesting consequence the . . . result is that it closes the window where the minimal model can explain the 3σ excess in the muon anomalous magnetic moment.I would agree with Jester that there is no theoretically preferred value for ε, which is the parameter determining the extent to which dark photons and ordinary photons mix.
But, I would disagree with him that there is no theoretically preferred value for mA' which is the mass of the dark photon (hypothesized as a boson that carries a force by which dark matter interacts with other dark matter). Most studies I have seen have favored a dark photon mass in the MeV range and certainly a mass of less than 10 GeV.
The constraint on mixing between dark photons and ordinary photons is significantly tighter for dark photon masses of under 10 MeV, which is the preferred mass range for dark photons.
The mass of a dark photon impacts the effective range of the force it carries. A dark photon with a mass of 80 Gev-90 GeV would have a range similar to that of the weak force bosons, i.e. on the order of the size of an atomic nucleus. An MeV range dark photon, in contrast, would have a long enough range to produce meaningful interactions of dark matter particles that are near each other sufficiently to tweak the dark matter halo shape in galaxies and galactic clusters.
Thus, this data, collectively, and together with other data attempting to detect dark matter directly, further buttresses the idea that if dark matter exists, that it has almost no interactions with ordinary matter except via gravity.
Interactions between ordinary photons and dark photons aren't important to the overall character of self-interacting dark matter models, but these studies do strictly narrow the classes of self-interacting dark matter models that can be consistent with empirical evidence.
UPDATE: A new study reanalyzes the estimates of the strength of dark matter self-interactions based upon the observations of a galaxy falling into a galactic cluster. The value reached is similar to, but a bit higher than, that estimated from the Bullet Cluster.
Ancient DNA Confirms That Proto-Arignacian Was Human Not Neanderthal
An mtDNA sample from the tooth of a Proto-Arignacian individual whom radiocarbon data confirms died 40,170 to 35,650 years before present, was a modern human and not a Neanderthal.
This had been the prevailing opinion regarding the species identity of the Proto-Arignacians and is also consistent with the modern features of the tooth, but this hypothesis had not previously been confirmed with DNA evidence. This mtDNA sample is quite similar to that of the Ust Ishim individual whose 45,000 year old DNA from Siberia was recently announced.
This discovery further advances a narrative in which the Proto-Arignacians, as the first wave of modern humans in Europe, are the proximate cause of the extinction of the Neanderthals.
This had been the prevailing opinion regarding the species identity of the Proto-Arignacians and is also consistent with the modern features of the tooth, but this hypothesis had not previously been confirmed with DNA evidence. This mtDNA sample is quite similar to that of the Ust Ishim individual whose 45,000 year old DNA from Siberia was recently announced.
This discovery further advances a narrative in which the Proto-Arignacians, as the first wave of modern humans in Europe, are the proximate cause of the extinction of the Neanderthals.
Tuesday, April 21, 2015
Two Ho Hum mtDNA Studies
Eurogenes recounts a new study of South Asian mtDNA with a huge sample size. Dienekes reports on a new study of mtDNA lineages in indigenous populations of Arctic North America.
Both studies attempt to frame their results within the existing historical paradigms for the regions. Neither adds much other than some very fine detail to what we already know.
UPDATE May 3, 2015: The main significance of the Arctic North American study is to demonstrate that all post-founding era migrations into the Americas have taken place from West to East, as widely assumed, thereby ruling out (again) the Solutrean hypothesis.
Both studies attempt to frame their results within the existing historical paradigms for the regions. Neither adds much other than some very fine detail to what we already know.
UPDATE May 3, 2015: The main significance of the Arctic North American study is to demonstrate that all post-founding era migrations into the Americas have taken place from West to East, as widely assumed, thereby ruling out (again) the Solutrean hypothesis.
Tuesday, April 14, 2015
A New Study On Y-DNA G1
Map via Wikipedia (not the new study)
Dienekes' has a post on a new paper reviewing that range and phylogeny of Y-DNA haplogroup G1, a Y-DNA clade that seems to play an important role in Iranian population history.
While G1 is found near some proposed homelands for proto-Indo-Europeans, its narrow geographic distribution precludes it as an important component of the proto-Indo-European population.
The abstract notes that (paragraph breaks mine):
Y-chromosomal haplogroup G1 is a minor component of the overall gene pool of South-West and Central Asia but reaches up to 80% frequency in some populations scattered within this area.
We have genotyped the G1-defining marker M285 in 27 Eurasian populations (n= 5,346), analyzed 367 M285-positive samples using 17 Y-STRs, and sequenced ~11 Mb of the Y-chromosome in 20 of these samples to an average coverage of 67X. This allowed detailed phylogenetic reconstruction.
We identified five branches, all with high geographical specificity: G1-L1323 in Kazakhs, the closely related G1-GG1 in Mongols, G1-GG265 in Armenians and its distant brother clade G1-GG162 in Bashkirs, and G1-GG362 in West Indians.
The haplotype diversity, which decreased from West Iran to Central Asia, allows us to hypothesize that this rare haplogroup could have been carried by the expansion of Iranic speakers northwards to the Eurasian steppe and via founder effects became a predominant genetic component of some populations, including the Argyn tribe of the Kazakhs.The study is also notable for its "clan" level genetic analysis, which is midway between geneology based studies and studies looking at large national or ethnic populations, and for its use of that method to more precisely pin down Y-DNA mutation rates in human populations.
Y-DNA G was the plurality haplogroup for men in the first wave of the Neolithic revolution, but then faded to a minor component of the European gene pool in most areas outside Sardinia, Tuscany, the Caucasus and West Asia. But, G2 played a larger role than G1 in the Neolithic and in European populations traceable to that migration.
The geography of G1 and G2 respectively, suggest an origin for the most basal branch of Y-DNA haplogroup G in central to Western Iran.
Monday, April 13, 2015
Major Systematic Error In Dark Energy Estimates Discovered
It turns out that there are two different subtypes of type 1a supernovas, with one more common in the early universe, and the other more common recently. They are very hard to distinguish in the visible light spectrum, but have clear differences in the UV spectrum. As a result, the rate at which the universe is expanding, if indeed it is expanding, and the amount of dark energy in the universe, are systemically overestimated by a significant amount.
Less dark energy may, however, mean that another cosmology mystery is more profound. This could bring the relative amounts of dark matter and dark energy in the universe closer together, something that is already called the cosmic coincidence problem because there is no obvious theoretical reason for the two dark components of cosmology to be so similar in aggregate amount.
Less dark energy may, however, mean that another cosmology mystery is more profound. This could bring the relative amounts of dark matter and dark energy in the universe closer together, something that is already called the cosmic coincidence problem because there is no obvious theoretical reason for the two dark components of cosmology to be so similar in aggregate amount.
A (Probably) Final Tevatron Top Quark Mass Measurement
The final Tevatron mass measurement for the top quark is 174.34±0.64 GeV. This is the most accurate single measurement of this fundamental standard model mass parameter to date.
This compares to the latest top quark mass estimate from ATLAS of 172.99 +/- 0.91 GeV. The latest combined mass estimate of the top quark (excluding the latest top quark mass measurement estimate from ATLAS) is 173.34 +/- 0.76 GeV.
The Tevatron measurement pulls the LHC estimates to a higher value, which is a good fit for some theoretical expectations for it. The overlap of the combined one sigma experimentally measured ranges for the top quark mass at Tevatron and the LHC is 173.70 to 174.10 GeV with an average of 173.90 GeV. Weighting the Tevatron results slightly more heavily than the LHC combined result since it has a smaller margin of error, only slightly increases the average since the margins of error are still quite similar.
The expected value of the top mass from the formula that the sum of the square of each of the fundamental particle masses equals the square of the Higgs vaccum expectation value, given the state of the art Higgs boson mass measurement (using a global fit value of 80.376 GeV for the W boson rather than the PDG value) is 173.73 GeV (173.39 to 174.07 GeV within the plus or minus one sigma band of the current Higgs boson measurement).
If the the sum of the square of the boson masses equals the sum of the square of the fermion masses the implied top quark mass is 174.03 GeV if pole masses of the quarks are used, and 174.05 GeV if MS masses at typical scales are used.
The experimental measurements are perfectly consistent with any of these theoretical expectations.
This compares to the latest top quark mass estimate from ATLAS of 172.99 +/- 0.91 GeV. The latest combined mass estimate of the top quark (excluding the latest top quark mass measurement estimate from ATLAS) is 173.34 +/- 0.76 GeV.
The Tevatron measurement pulls the LHC estimates to a higher value, which is a good fit for some theoretical expectations for it. The overlap of the combined one sigma experimentally measured ranges for the top quark mass at Tevatron and the LHC is 173.70 to 174.10 GeV with an average of 173.90 GeV. Weighting the Tevatron results slightly more heavily than the LHC combined result since it has a smaller margin of error, only slightly increases the average since the margins of error are still quite similar.
The expected value of the top mass from the formula that the sum of the square of each of the fundamental particle masses equals the square of the Higgs vaccum expectation value, given the state of the art Higgs boson mass measurement (using a global fit value of 80.376 GeV for the W boson rather than the PDG value) is 173.73 GeV (173.39 to 174.07 GeV within the plus or minus one sigma band of the current Higgs boson measurement).
If the the sum of the square of the boson masses equals the sum of the square of the fermion masses the implied top quark mass is 174.03 GeV if pole masses of the quarks are used, and 174.05 GeV if MS masses at typical scales are used.
The experimental measurements are perfectly consistent with any of these theoretical expectations.
Tuesday, April 7, 2015
Planck Data Bounds On Dark Matter
A new preprint sets bounds on the minimum dark matter mean lifetime of 3.57*10^24 seconds, and also establishes a minimum value for cross-section of interaction divided by dark matter mass, based on the Planck data. This is roughly 10^17 years.
By comparison the age of the universe is roughly 1.38 * 10^9 years. This means that dark matter (if it exists) is at least as stable as anything other than a proton, which has an experimentally determined mean lifetime of at least 10^33 years.
By comparison the age of the universe is roughly 1.38 * 10^9 years. This means that dark matter (if it exists) is at least as stable as anything other than a proton, which has an experimentally determined mean lifetime of at least 10^33 years.
Genealogy v Genetics
Genealogy still towers over genetics in establishing family relationships. 23andMe located just under a thousand second and more distant cousins and relatives. But, a genealogy website used in Finland has located approximately 350,000 of my closest relatives on my mother's side! The Finns love their family histories, apparently.
Seriously, more than 6% of the population of Finland has a publicly documented family relationship to me.
I've met about half a dozen of my Finnish relatives and one stayed with my family for a summer after I had left for college. The most illustrious of them was awarded a knighthood for his service to Finland by revolutionizing their waste treatment system, banishing diseases that would have otherwise afflicted Finland's people.
Seriously, more than 6% of the population of Finland has a publicly documented family relationship to me.
I've met about half a dozen of my Finnish relatives and one stayed with my family for a summer after I had left for college. The most illustrious of them was awarded a knighthood for his service to Finland by revolutionizing their waste treatment system, banishing diseases that would have otherwise afflicted Finland's people.
Monday, April 6, 2015
My Genome (An Executive Summary)
My 23 and Me personal genome testing preliminary results are in (much more promptly than advertised, for what it is worth):
Highlights
Y-DNA haplogroup: E1b1b1a2* (E1b1b1 is also known as E-M35, E1b1b1a is E-M78 and my own haplogroup is E-V36/V13).
mtDNA haplogroup: H1b
Broad ancestry composition (out of 31 regional groupings including speculative estimates):
European 99.9%
*Northern European 94.8%
**Finnish 38.1%
**Scandinavian 16.4% (Sweden-Norway-Denmark)
**British and Irish 6.3% (UK and Ireland)
**French and German 1.1% (Germany, Netherlands, France, Switzerland, Austria, Belgium)
**Broadly Northern European 32.9%
*Broadly Southern European 2.6%
*Broadly European 2.6%
East Asian - Yakut 0.1%
Unassigned < 0.1%
Neanderthal Ancestry 2.9% (79th percentile; 82nd percentile for Europeans).
Feel-Good Gene: AC (mixed ancestral "C" and feel-good "A" type)
Analysis
My Y-DNA haplogroup, which is most common in Greece and Albania, is surprising as it is rare in the places that are home to my ancestors (Protestant Germany near the former West German-East German border), but not shocking. It could have been a part of either a first wave early European farmer migration, or a Bronze Age migration, to the north and west from the Balkans. The source of this Y-DNA was probably not recent as my genome lacks any East European and only a very modest amount of Southern European ancestry, and no Near Eastern ancestry.
My combined Y-DNA and mtDNA haplogroups, while not terribly remarkable for someone of my ancestry, would also be quite normal for a man of Berber origin, until one gets to the very last couple of mutations in the Y-DNA haplogroup that are European specific.
I was surprised to be more Finnish than Scandinavian. My Finnish ancestors are Swedish language speaking Finns and I'd expected the Scandinavian component to be half or more of the total. But, apparently, Swede-Finns absorbed more native Finnish ancestry than I'd expected, although the possibility that Swedish ancestry which due to founder's effects is most common in Finland counts as Finnish could also be a factor.
The trace Yakut ancestry isn't too surprising given my substantial Finnish heritage, with a presumed cryptic circumpolar migration producing an ancestor hundreds of years ago. This trace, which appears only on one of my chromosomes in a single bunch, also highlights the fact that you can have ancestry which is not reflected in either of your uniparental haplogroups.
The higher than average Neanderthal ancestry was also expected as Finns have above average hunter-gatherer ancestry in Europe and European hunter-gathers had higher levels of Neanderthal ancestry than post-Last Glacial Maximum migrants from the Near East.
There is less specifically British and Irish ancestry than I'd expected and less German ancestry than I'd expected, and I hadn't expected any Southern European ancestry. But, as most of my father's ancestry is ascribed to "Broadly Northern European", it is fair to say that he's pretty much a Northern European mutt.
The "Feel-Good Gene" is one where I'd thought it was likely that I'd have a mixed or completely derived type, as this gene is particularly common in Finns and is associated with phenotypes that fit my personality.
Some spot checking has revealed that there are a not insignificant number of SNPs for which no result was obtained, although they are clearly a small minority and I don't expect 100% reads on everything in a mailed in spit test analyzed for an average price of less than $99 per genome.
Ethics and Motivation
I'm aware that by posting this information, I am also posting without their consent, by inference, information about the uniparental genetics of my father, one my two children, my brother, my uncle, my male paternal first cousin, two maternal uncles, a maternal aunt, four maternal first cousins, and two children of one of my maternal first cousins, for a total of at least fourteen people, in addition to large numbers of deceased people (e.g. my grandparents and mother) and many more distant relatives.
On the other hand, the information is intrinsically a part of me and hence morally belongs to me to use as I see fit, anyone using it has to tease out the family relationships to do so, and there is not strong stereotypes attached to Y-DNA and mtDNA haplogroups at this point, although there is arguably mild anti-Neanderthal stigma that this post my help to dissolve (or enhance, depending upon what you think about me). And, I think it is worthwhile for someone who blogs a great deal about genetics to disclose his own, after benefiting so much from the disclosures of others.
Moreover, the kind of information that I have disclosed already really provides very little information that couldn't be inferred from publicly available information on my family tree, ancestry, appearance, and demeanor. I would think twice before posting my whole genome, or portions of it with greater medical significance.
I also think it is important for the public to put a face on genetic information, and make my own contribution here.
Also, knowledge of your own genes inevitably colors your interest in our research, something which I should disclose to my readers.
For example, Maju just blogged on mtDNA H1 in Cantabria from 19,000 years ago, something that it had previously not been clear existed. This area in Northern Spain was a refuge in which modern humans survived the deepest part of the last Ice Age, with glaciers that reached their greatest extent around 20,000 years ago. So, this find disproves the hypothesis that everyone in Europe who survived the last Ice Age was mtDNA U with all other haplogroups arriving more recently from the Near East, which had been the prevailing paradigm based upon ancient DNA findings to date, before this discovery.
Knowing that I bear this mtDNA haplogroup makes that discovery one of more personal significance than it otherwise would have been, although it was surely noteworthy in any case.
Highlights
Y-DNA haplogroup: E1b1b1a2* (E1b1b1 is also known as E-M35, E1b1b1a is E-M78 and my own haplogroup is E-V36/V13).
mtDNA haplogroup: H1b
Broad ancestry composition (out of 31 regional groupings including speculative estimates):
European 99.9%
*Northern European 94.8%
**Finnish 38.1%
**Scandinavian 16.4% (Sweden-Norway-Denmark)
**British and Irish 6.3% (UK and Ireland)
**French and German 1.1% (Germany, Netherlands, France, Switzerland, Austria, Belgium)
**Broadly Northern European 32.9%
*Broadly Southern European 2.6%
*Broadly European 2.6%
East Asian - Yakut 0.1%
Unassigned < 0.1%
Neanderthal Ancestry 2.9% (79th percentile; 82nd percentile for Europeans).
Feel-Good Gene: AC (mixed ancestral "C" and feel-good "A" type)
Analysis
My Y-DNA haplogroup, which is most common in Greece and Albania, is surprising as it is rare in the places that are home to my ancestors (Protestant Germany near the former West German-East German border), but not shocking. It could have been a part of either a first wave early European farmer migration, or a Bronze Age migration, to the north and west from the Balkans. The source of this Y-DNA was probably not recent as my genome lacks any East European and only a very modest amount of Southern European ancestry, and no Near Eastern ancestry.
My combined Y-DNA and mtDNA haplogroups, while not terribly remarkable for someone of my ancestry, would also be quite normal for a man of Berber origin, until one gets to the very last couple of mutations in the Y-DNA haplogroup that are European specific.
I was surprised to be more Finnish than Scandinavian. My Finnish ancestors are Swedish language speaking Finns and I'd expected the Scandinavian component to be half or more of the total. But, apparently, Swede-Finns absorbed more native Finnish ancestry than I'd expected, although the possibility that Swedish ancestry which due to founder's effects is most common in Finland counts as Finnish could also be a factor.
The trace Yakut ancestry isn't too surprising given my substantial Finnish heritage, with a presumed cryptic circumpolar migration producing an ancestor hundreds of years ago. This trace, which appears only on one of my chromosomes in a single bunch, also highlights the fact that you can have ancestry which is not reflected in either of your uniparental haplogroups.
The higher than average Neanderthal ancestry was also expected as Finns have above average hunter-gatherer ancestry in Europe and European hunter-gathers had higher levels of Neanderthal ancestry than post-Last Glacial Maximum migrants from the Near East.
There is less specifically British and Irish ancestry than I'd expected and less German ancestry than I'd expected, and I hadn't expected any Southern European ancestry. But, as most of my father's ancestry is ascribed to "Broadly Northern European", it is fair to say that he's pretty much a Northern European mutt.
The "Feel-Good Gene" is one where I'd thought it was likely that I'd have a mixed or completely derived type, as this gene is particularly common in Finns and is associated with phenotypes that fit my personality.
Some spot checking has revealed that there are a not insignificant number of SNPs for which no result was obtained, although they are clearly a small minority and I don't expect 100% reads on everything in a mailed in spit test analyzed for an average price of less than $99 per genome.
Ethics and Motivation
I'm aware that by posting this information, I am also posting without their consent, by inference, information about the uniparental genetics of my father, one my two children, my brother, my uncle, my male paternal first cousin, two maternal uncles, a maternal aunt, four maternal first cousins, and two children of one of my maternal first cousins, for a total of at least fourteen people, in addition to large numbers of deceased people (e.g. my grandparents and mother) and many more distant relatives.
On the other hand, the information is intrinsically a part of me and hence morally belongs to me to use as I see fit, anyone using it has to tease out the family relationships to do so, and there is not strong stereotypes attached to Y-DNA and mtDNA haplogroups at this point, although there is arguably mild anti-Neanderthal stigma that this post my help to dissolve (or enhance, depending upon what you think about me). And, I think it is worthwhile for someone who blogs a great deal about genetics to disclose his own, after benefiting so much from the disclosures of others.
Moreover, the kind of information that I have disclosed already really provides very little information that couldn't be inferred from publicly available information on my family tree, ancestry, appearance, and demeanor. I would think twice before posting my whole genome, or portions of it with greater medical significance.
I also think it is important for the public to put a face on genetic information, and make my own contribution here.
Also, knowledge of your own genes inevitably colors your interest in our research, something which I should disclose to my readers.
For example, Maju just blogged on mtDNA H1 in Cantabria from 19,000 years ago, something that it had previously not been clear existed. This area in Northern Spain was a refuge in which modern humans survived the deepest part of the last Ice Age, with glaciers that reached their greatest extent around 20,000 years ago. So, this find disproves the hypothesis that everyone in Europe who survived the last Ice Age was mtDNA U with all other haplogroups arriving more recently from the Near East, which had been the prevailing paradigm based upon ancient DNA findings to date, before this discovery.
Knowing that I bear this mtDNA haplogroup makes that discovery one of more personal significance than it otherwise would have been, although it was surely noteworthy in any case.
Wednesday, April 1, 2015
Blue Police Box Found In Precolumbian Peruvian Tomb
This morning, a police box resembling the one above was found in a tomb of the pre-Columbian Peruvian pyramid from the Norte Chico civilization shown below.
The artifact was apparently constructed on site near the Huaynaputina volcano, as it is much larger than any of the entrances to the chamber where it was found, which appears to have been hewn from solid bedrock by hand with stone chisels. Radioactive isotype and material composition tests to determine if the materials in the artifact were locally sourced or obtained through trade have not yet been completed. Researchers noted that the color of the artifact shows some similarity to Maya Blue which originates in the Yucatan Peninsula of Mexico.
Experts argue that this artifact demonstrates the high level of civility demonstrated by a people whose prehistoric culture is often demeaned merely because they sacrificed live (but humanely drugged) children to a volcano God from the Underworld (Uku Pacha) in order to further the greater good of the society, a practice that Jeremy Bentham himself surely would have approved of, if asked.
In fact, these signs of respect for authority merely show that the Incas were among the most civilized prehistoric peoples of the Americas. While the barbaric and rebellious United States of America was founded on the right to Life, Liberty and the Pursuit of Happiness, apparently the Incas, like the people of Australia, Canada, New Zealand, and South Africa, favored a society based upon Peace, Order and Good Government.
Some researchers have suggested that the inscription on the artifact found in the tomb may indicate that there were pre-Columbian links between the English government and Peru, although Scotland Yard adamantly denies any such connection and claims that this is a case of a pure chance similarity between languages. Other researchers at the London School of Economics, cognizant of the long standing immigration history linking the two countries and London, in particular, whose immigrant narratives dating back to ancient times and before that into European prehistory are not always well known to non-specialists in the field, however, were not so quick to dismiss this hypothesis.
While pre-Columbian contacts between South America and the Old World were extremely rare, they are not entirely without precedent, although not all such claims are plausible.
Lead investigator Dr. Who from the Perimeter Institute of Waterloo, Canada, was not available for comment on this report.
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