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.

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.

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 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:

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.

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.

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.

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.

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.

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.

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.

My Genome II

I'd previously discussed my ancestry results from 23 and me which can be summarized as follows:

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 less than 0.1%

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):

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.

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.

[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.

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.

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.

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.

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.

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.

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.

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.

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.

Few European Hunter-Gatherers Survived Last Ice Age

The last ice age peaked at 20,000 years ago.  The people who survived in pockets of survivable territory started to repopulate Europe in the period from 14,000 to 7,000 years ago, called the Mesolithic era.  Several ancient genomes are now available from that era.  They suggest that the effective male population size prior to the repopulation of Europe was just 30 men.

Thus, modern humans only barely hung on through the Ice Age in Europe, and ultimately, their ancestry makes up a fairly modest share of modern European ancestry.

The Latest Combined Higgs Boson Mass Measurement From The LHC

The most up to date available measurement of the Higgs boson mass combining ATLAS and CMS experiment data in two different channels each at the end of the first LHC run to get a single number is:

125.09 +/- 0.237 GeV/c^2.

Analysis

The two sigma range for the Higgs boson mass is now:  124.61 GeV to 125.56 GeV.

This is a material improvement in the margin of error, which had previously hovered around 0.4 GeV.  Some further improvement in the margin of error should come from the second run of the LHC.

This value disfavors the 2H=2W+Z mass formula by 3.7 standard deviations.

There is an argument that the "tree-level" mass of the Higgs boson is 123.114 GeV (half the Higgs vev) but that it is increased by higher order loop corrections that bring it to its experimental value.  The "tree-level" estimate of the mass of the W boson is 78.9 GeV.  If the percentage increase in mass due to higher order loop corrections for the Higgs boson from the tree level value is the same as the higher order loop corrections of the W boson to the experimental value, then the implied Higgs boson mass value would be 125.43 GeV which is consistent at a 1.4 sigma level with the latest combined mass measurement.  No published source actually calculates these higher order loop adjustments, however.  While the actual higher order loop calculation is probably of that order of magnitude, it could easily be higher or lower.  The claim is plausible, but requires further investigation.  If the higher order loop corrections produced a value consistent with 124.65 GeV, that would be remarkable indeed as discussed below.

The hypothesis that the sum of the squares of the Higgs boson mass, W boson mass and Z boson mass equals half of the Higgs vev (using a global fit value of 80.376 GeV for the W boson mass) implies a Higgs boson mass of 124.65 GeV, which is within two sigma of the current measurement.

Using the 80.385 GeV PDG value of the W boson mass and assuming that the sum of squares of boson mass equals one half of the square of the Higgs vev implies a Higgs boson mass of 124.65 GeV as well, so the difference created by that assumption is too small to matter.

This suggests that the quantum corrections to the Higgs boson mass may indeed be very highly fine tuned making supersymmetry unnecessary to address that seemingly unlikely reality.

As discussed below, there is some tension between the best fit Higgs boson mass measurement and the best fit top quark measurement (under the assumption that the sum of the square of all fundamental particle masses equals to the square of the Higgs vev), with the Higgs boson measurement implying a higher than measured top quark measurement.  But, these tensions are within the margins of error in the measurements.  The latest combined best fit value of the top quark mass (i.e. 173.34 GeV) would imply a Higgs boson mass of 125.60 GeV, which is just outside the two sigma band of Higgs boson masses based upon the most recent measurement.

Implications for Top Quark Mass

This also significantly tightens 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.  The uncertainty in the Higgs boson mass had been the second greatest source of uncertainty in that calculation.  The best fit for the top quark mass on that basis (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.

That 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.

How big are the gaps?

The fermion side of the balance sheet could fit a particle as massive as 19 GeV if the fermion sides and boson sides must be equal, and about 16 GeV if they need not be equal, consistent with current particle mass data alone.

But, particles in this mass range would greatly distort the expected cross-sections of Higgs boson decays in ways that would probably already be detectable.  Any such particle has been ruled out by W and Z boson decays to the extent that it can be produced by decays of these particles, and if they were present in Higgs boson decays would dramatically reduce, for example, the expected cross-section of bottom quark pairs from Higgs boson decays (which is the largest single cross-section from Higgs boson decays, making up about two-thirds of them, although this cross-section is hard to measure due to significant backgrounds that also produce bottom quark pairs).  Particles with masses of 10 MeV or less, in contrast, would have only a modest impact on the decay patterns observed in Higgs bosons decays, but would still have to be sterile as to W and Z boson interactions.

Another interesting possibility is that baryons could contribute to the fermion side, and that mesons could contribute to the boson side, rather than just the fundamental particles.  My intuition is that this would not work, but I haven't run the numbers.  Light baryons wouldn't add much, but the heaviest baryons with B quarks would make a significant contribution.  Still, order of magnitude, it isn't impossible.

Another issue is which masses we should be using: pole masses or masses at a single consistent mass scale.  Quark and lepton masses get slightly lower at higher energy scales.  The Higgs boson mass declines more rapidly with higher energy scales.  I think, but don't know, that the W and Z boson masses also decrease faster the quark and lepton masses at higher energy scales.

Since the top quark is the predominant contribution to the fermion side of the equation, only the decline from the top pole mass to some energy scale above the top pole mass is relevant.  But, since the fermion side is already "light" relative to the 50-50 expectation, any decline in the top mass hurts the balance (and would probably be less than 1% in addition to being less than the boson side reduction).  On the boson side, a reduction of 0.185% from the current best fit values would bring the sum of the square of the masses to one half of the Higgs vev.  This may understate the amount of actual renormalization reduction at plausible targets like the top quark mass and the Higgs vev.

The Higgs boson mass runs from 125 GeV at 125 GeV to zero at about 10^15 GeV, on a curve that is concave with respect to a log-linear relationship (i.e. masses are lower at every point except the end points relative to a log-linear relationship of Higgs boson mass and energy scale).  This seems to suggest that the Higgs boson mass at 246 GeV should be more than 13% lower than the pole mass (i.e. about 108.8 GeV), which is far too much of a reduction to fit the formula and would favor using pole masses across the board, as would the Higgs boson mass at 173.35 GeV which should be more than 11% lower than the pole mass of the Higgs boson, if I have the calculations right.  The 0.185% shift required would imply an energy scale of something less than 133.34 GeV (but more than 125.09 GeV), which doesn't make much sense under any theory.

Given how close the experimental masses are to the preferred values using pole masses, however, it isn't obvious that renormalized values are necessary.

But, if the apparent relationship does involve pole masses, then there is very little wiggle room indeed in the predicted values of the Higgs boson mass and top quark mass, although this can be relaxed a little if the sum of the square of the fundamental fermion masses need not be exactly equal to the sum of the square of the fundamental boson masses.

Did Dogs Drive The UP?

A new book entitled "The Invaders" by Pat Shipman, argues that the domestication of dogs was key to the Middle Paleolithic-Upper Paleolithic transition and to the demise of Neanderthals. The theory is reasonably plausible.

The Population Genetics Of The British Isles

A major new study of the whole genomes of the people of the British Isles has been published in the journal Nature.

A few of the "forest" level conclusions:

* The sample size is 2,039 people in the British Isles compared to 6,209 European individuals.  This is pretty much as big a sample as you get in historical population genetics.  The significance of these sample size is magnified by the fact that these are whole genomes, and not just Y-DNA or mtDNA haplogroup data.  Even very small samples of whole genomes can be highly informative, and these samples aren't small.

* All of the peoples of the British Isles are very homogeneous genetically, and the people of Central and Southern Britain (as well as Cornwall), are extremely homogeneous genetically.

This is particularly notable, given that Britain has more than four cultural/linguistic units that are recognized politically as different enough to require autonomy to some extent (Britain, Scotland, Wales, and Northern Ireland, plus some minor dependencies on nearby islands).

There is far more dialect variation in the British Isles than there is in the United States to the extent that one could make a very well informed estimate about someone's origins that is even finer grained than the genetic clusters within the British Isles identified by this study based upon that person's dialect and accent in the English language.

The British Isles are perhaps one of the clearest examples of strong cultural and linguistic substructure in a population that is genetically very homogeneous.  In most areas of the world, the kind of cultural and linguistic substructure seen in the British Isles corresponds to fairly dramatic population genetic differences between the various groups.  In the British Isles, in contrast, populations that are genetically almost identical and not all that far from each other geographically have very distinct cultural identities.

* The fine grained differences between British subpopulations correspond to influences from different parts of the Continental Europe and Scandinavia that largely correspond to population genetic events in the historic era and archaeologically well documented late prehistoric eras, more or less as one would expect with only minor surprises (like Cornwall that one might have expected to be more like  the Welsh people).

For example, as expected from our historical knowledge, the population genetics of Northern Ireland overlap heavily with the population genetics of the area around the western Scottish-English borderlands.

* The Danish Vikings who imposed Danelaw on Britain in the 1st millennium, while they had significant cultural and linguistic impact, had almost no genetic impact outside of the Orkney Islands.  This is analogous to the situation in Hungary, where the people who are the source of Hungary's current language have left almost no genetic trace in the country.

* The Anglo-Saxon contribution to the British gene pool in the 1st millennium is about 10% to 40% of the total (the spread is disappointingly large for such an impressive data set).  This is a significant minority contribution, but not population replacement.  This is reflected mostly in the Central-Southern British cluster that out of 17 clusters makes up about half of the total sample.  Many of the other clusters are in areas that have some level of political autonomy.  Wales, for example, appears to have five different small regional genetic clusters.

* The pre-Anglo-Saxon Celtic substrate in Britain was not uniform; it varied by region.

* There was substantial migration to Britain from Continental Europe in the Neolithic and later eras prior to the arrival of the Romans (and therefore also prior to the arrival of the Danes, the Anglo-Saxons, the Normans, and recent immigration from the 19th century onwards).

* I suspect, but don't know for a fact, that the sample was limited to people who are "ancestrally" British and hence excludes individuals with known recent immigrant ancestry.  Thus, Britain today is probably much more genetically diverse than this sample which was probably picked to be as informative as possible about the ancient and prehistoric genetic history of Britain would indicate.  For example, Britain has a significant South Asian minority population that is largest in greater London, but is found throughout the British Isles, that is not reflected in this data.  These huge genetic chasms, however, are not reflected in Britian's system of regional autonomy and instead is blended into preexisting communities across the British Isles.

Latest Top Quark Mass Measurement From ATLAS

The latest top quark mass measurement from ATLAS (at the LHC) is 172.99 +/- 0.91 GeV.

By comparison the PDG value is 173.21 +/- 0.87 GeV.

A somewhat more recent combined value (because it considers pre-prints and not just published papers) is 173.34 +/- 0.76 GeV.

An extended Koide's rule estimate of the top quark mass using only the electron and muon masses as inputs, predicted a top quark mass of 173.263947 ± 0.000006 GeV.

A prediction that I made in March 2014 which assumed a Higgs bosons mass of about 125.96 GeV and some other assumptions (some of which are just conjectures themselves), predicted a top quark mass of 173.1125 ± 0.0025 GeV.

Of course, the latest experimental value is consistent with all of the other values due to a lack of experimental precision in the top quark mass measurement, which is improving over time, but ever so slowly.

Has ATLAS Seen SUSY?

The ATLAS experiment at the LHC has reported a three sigma excess of events beyond the Standard Model expectation in a particular kind of search for squarks and gluinos, a type of particle predicted by Supersymmetry models.

This is one of the strongest experimental indicators of SUSY phenomena to date amidst an ocean of searches and may simply be an overstated statistical fluke due to look elsewhere effects (i.e. the notion that if you do enough searches, some will come up positive by random chance, undermining the significance of any particular result that is not replicated).  If CMS sees the same thing (and this study failed to reproduce a similar, but slightly weaker excess in the CMS data) then it could very well be real.  If CMS does not see it, it is probably just a fluke.

A five sigma effect is considered necessary to call a finding a "discovery" of a particle.

A summary at the conclusion of the paper states:

This paper presents results of two searches for supersymmetric particles in events with two same-flavour opposite-sign leptons, jets, and E miss T , using 20.3 fb−1 of 8 TeV pp collisions recorded by the ATLAS detector at the LHC. 

The first search targets events with a lepton pair with invariant mass consistent with that of the Z boson and hence probes models in which the lepton pair is produced from the decay Z → ``. In this search 6.4 ± 2.2 (4.2 ± 1.6) events from SM processes are expected in the µµ (ee) SR-Z, as predicted using almost exclusively data-driven methods. The background estimates for the major and most difficult-to-model backgrounds are cross-checked using MC simulation normalised in data control regions, providing further confidence in the SR prediction. Following this assessment of the expected background contribution to the SR the number of events in data is higher than anticipated, with 13 observed in SR-Z µµ and 16 in SR-Z ee. This corresponding significances are 1.7 standard deviations in the muon channel and 3.0 standard deviations in the electron channel. These results are interpreted in a supersymmetric model of general gauge mediation, and probe gluino masses up to 900 GeV. 

The second search targets events with a lepton pair with invariant mass inconsistent with Z boson decay, and probes models with the decay chain χ˜ 0 2 → ` + ` −χ˜ 0 1 . In this case the data are found to be consistent with the expected SM backgrounds. 

No evidence for an excess is observed in the region in which CMS reported a 2.6σ excess [24]. 

The results are interpreted in simplified models with squark- and gluino-pair production, and probe squark (gluino) masses up to about 780 (1170) GeV. 

Lubos Motl offers a cautious but hopeful assessment of the result being really due to SUSY.

UPDATED March 22, 2015: More SUSY exclusions here.

Prehistoric European Quick Hits

* The prehistoric record of tsunamis in Southwest Iberia helps to explain the archaeological record and suggests a possible Iberian tsunami as the source of the Atlantis myth.

* Maju notes the availability of a new collection of papers regarding the early Balkan Neolithic.  The was a launching pad from which much of the process of bringing farming and herding to Europe originated and in turn provides a way to discern its sources in turn.

* Bell Beaker blogger notes a polemic arguing that the Iberian expansion theory of Bell Beaker expansion isn't necessarily as strong, vis-a-vis a central European origin and dispersal in light of the archaeological evidence as has frequently been asserted.  The paper is thin on evidence, looking mostly to dates of Central European cemeteries without detailed discussion, and reinterpreting existing evidence, neither of which are powerful when going up against a prevailing paradigm in the field.  But, it does not mention evidence from the European Y-DNA R1b phylogeny that does tend to support a central European origin and makes the arguments there worth examining more closely.

* Bell Beaker blogger also continues to explore the links between ancient beer brewing and mystical or magic lore in prehistoric Europe, with a linguistic slant.

* Another intriguing Bell Beaker blogger post explores the potential roots of European pottery traditions in the far East and Jomon pottery traditions and links it to Y-DNA R expansion.

* And, Bell Beaker blogger also has a nice post on trade across the Strait of Gibraltar, before and after the Bell Beaker period, in goods like ivory and ostrich egg shells.

* Dienekes' Anthropology blog has picked up on a paper also discussed at Marginal Revolution (where I commented noting various adjustments that could be made to obtain a more accurate measurment) making back of napkin estimates of the potential genetic impact of capital punishment from 1500-1750 CE on the murder rate in Britain.  The murder rate fell tenfold in that period which also experienced many executions.

* Another paper notes at the same blog discusses the arrival of wheat in Britain thousands of years before farming commenced there.

* And, Dienekes comes to some conclusions from his own analysis of Armenian genetics.

* Scandinavian rock art suggests that ancient Swedes may have personally gone all the way to Cyprus to trade copper and tin for amber without a middle man in the Bronze Age.

* Eurogenes notes the important discovery of ancient Y-DNA R1a1 paired with mtDNA H in NW Russian towards Finland in hunter gatherer populations from ca. 4000 BCE.  This is one of several new ancient data points (another being the paper discussed here) that really reinforce the theory that Y-DNA R1a1 paired with mtDNA H in Europe arrived with Indo-Europeans from NW Russia as part of the Corded Ware culture in the Copper Age, and that R1b in Europe paired with mtDNA H might derive in the same period from further South around the Pontic-Caspian Steppe.  The autosomal data from the Pontic-Caspian steppe is a good fit for a major component (perhaps 75% replacement in Central Europe) of Europe's DNA.

* Eurogenes also discusses a new linguistics paper on a European steppe origin for the Indo-European languages.

Prospects For General Relativity A Century Later

Background

A hundred years ago, Albert Einstein came up with the theory of General Relativity that was first presented publicly at a conference in November of 1915, and was published early in 1916 in a series of three papers.

General Relativity basically describes gravity in a way that is subtly different from that of Newton's simply F=GMm/r² law of the 1600s that is perfectly sufficient for most purposes.  But, its formulations allow for a variety of phenomena that Newtonian gravity did not.

One of the most important distinctions is that energy, not just matter, generates and is subject to gravitational fields, and that energy is equivalent to matter for purposes of the conservation of matter-energy, and for gravitational purposes, according to the formula E=mc², where m is mass, E is energy, and c is the speed of light in a vacuum.  For example, since light has energy, it gravitates and is affected by gravity, giving rise to the phenomena of gravitational lensing.

Another critical distinction between General Relativity and Newtonian gravity arises in strong gravitational fields, where singularities such as Black Holes and the Big Bang can arise.  Both phenomena are observed.

There are other distinctions: frame dragging, gravitomagnetic effects, and more.  But, they are beyond the scope of this post.

One integration constant in Einstein's formulation of general relativity, known as the cosmological constant full describes to the limits of astronomy data such as the Planck satellite observations, a phenomena know today as "dark energy" when set to the appropriate value.

Einstein's insights come to us virtually unchanged in the leading textbook on the subject, "Gravitation", written by Charles W. Misner, Kip S. Thorne and John Archibald Wheeler in 1973 (called MTW by advanced physics students everywhere).

It is widely asserted that the behavior of a massless spin-2 boson that couple to Standard Model particles and itself with a strength equal in magnitude to the mass-energy of the particle, reproduces general relativity.  There is good reason to believe that this is wrong, and I discuss one of the reasons below.  But, I think that the spin-2 massless graviton model discussed in some of Feynmann's lectures, may be a more accurate description of gravity itself, than it is of General Relativity.

The Problem of Dark Matter Phenomena

But, neither General Relativity nor the Standard Model of Particle Physics, describe a set of phenomena known as "dark matter" which is necessary to model the cosmology of the universe from the Big Bang onward in a way that matches Planck data, and is also necessary to describe, for example, the disconnect between the observed rotation curves of galaxies which do not match the naive predictions of simplified versions of General Relativity applied to the observed luminous matter in those galaxies.

There are two ways to reconcile these effects to General Relativity and the Standard Model.

Dark Matter

One is to hypothesize the existence of "dark matter" that is massive, nearly collisionless with ordinary matter, made up of something other than the protons and neutrons that make up ordinary "baryonic" matter, and makes up the lion's share of matter in the universe.

The simplest model has just a single dark matter fermion particle, but many dark matter theories imagine the existence of dark forces that led to self-interaction of dark matter particles with each other by means other than gravity, or additional kinds of dark matter particles in a complex "dark sector" similar to that of the sector of ordinary matter described by the Standard Model.

At first it was hoped that this problem would be solved by Supersymmetry (SUSY) or string theory models, which would provide dark matter candidates.

Astronomers are no slouches and have worked hard on several fronts to infer the properties of the dark sector from observation.

One approach has been to use analytical and numerical models to determine what the universe should look like if it has a particularly kind and quantity of dark matter and then to compare the predictions of those models to what we actually observe.  The dark matter hypothesis, set forth vaguely, does a very good job of fitting observed cosmic background radiation patterns (which give rise to radio static among other things) to very precise observations, but have proved less successful at predicting the amount of structure observed in the universe (e.g. how many dwarf galaxies surround the Milky Way galaxy and other galaxies of similar size) and halo distribution shape.

One approach has been to infer the distribution and mass of dark matter halos around galaxies from their rotation curves and known luminous matter.  Similar inferences have been made in systems like the Bullet Cluster where a colliding galaxy provides a means by which to discriminate between theories, an in examinations of RAVE stars in the Milky Way galaxy that are outside the galactic plane.  We have some idea regarding what shape dark matter halos must have to fit observations.  Unfortunately, the shape of the halos observed are not a great fit to the NFW dark matter halo shapes we would expect from analytical simulations to see if they universe were made entirely of a single kind of "cold" (i.e. GeV to TeV mass) dark matter particles.  Simulations match experiment between when gravitational interactions between baryons and dark matter are considered, but still show far more scatter in dark halo shapes than is observed.  Simulations also tend to favor "warm dark matter" (in the keV particle mass range) over "cold dark matter" in the GeV to TeV particle mass range that lack self-interactions.

A third approach has been to try to directly detect dark matter particles at high energy colliders.  This has not revealed any evidence of dark matter.  But, they have made clear that dark matter must be made up of one or more types of particles not found in the Standard Model, if it exists, and these effects strongly constrain the parameter space of potential dark matter particles.

A fourth approach has been to in build direct dark matter detection experiments.  So far, these have not revealed any convincing evidence of dark matter.  There have been a few potential "hits" but those have been contradicted by more accurate measurements, or confirmed by experiments of similar accuracy.

A fifth approach has been to look at cosmic rays to see if any could be produced by a hypothetical dark matter annihilation interaction and have no other known source.  Several candidates have been identified as potential signals of dark matter by these means, although there is not a consensus on how to interpret this data.

Modifications of Gravity

The other is to tweak General Relativity in weak gravitational fields of large objects such as galaxy and galactic clusters, in a way that reproduces phenomena attributed to dark matter.  There are about half a dozen to a dozen ways of doing this in a way that reproduces the dark matter phenomena seen in galaxies with a fair degree of accuracy that have been published and compared to the data, the most famous of which is MOND, a toy model theory proposed in 1983 by Mordehai (Moti) Milgrom.

MOND itself is not the best of those theories.  It is strictly a phenomenological relationship, it underestimates dark matter effects in galactic clusters, and it isn't great at predicting galactic dynamics outside the plane of a galaxy.  But, it also has an impressive record of making firm predictions about unobserved phenomena that were later confirmed by observation, with only one new experimentally measured physical constant, and has a general relativistic generalization, TeVeS, devised by one of Milgrom's colleagues, Jacob D. Bekenstein.

MOG and similar theories proposed by John M. Moffat as the University of Toronto, has the distinction of having a broader range of applicability that describes phenomena in galactic clusters as well as galaxies.

A number of theories known as F(R) theories, which add a term that is a function of the Ricci scalar to the equations of general relativity, have also had some success in describing dark matter, dark energy and cosmological inflation.

If General Relativity Is Wrong, In What Way Is It Wrong?

General Relativity is a very tightly formulated set of equations based on a handful of mathematical first principles.  But, perhaps quantum gravity or simply an omitted term in General Relativity could do what modified gravity theories that account for dark matter do.

To go beyond purely phenomenological models like MOND to a full fledged competitor to General Relativity, however, one needs a good theoretical justification for the modifications to the equations of General Relativity.

Deur has been at the forefront of demonstrating that the real key problem could be that conventional general relativity theory is wrong about the real world effects of gravitational self-interactions.

Section 20.4 of MTW at 467 is emphatic about this question:

To ask for the amount of electromagnetic energy and momen tum in an element of 3-volume make sense.  First, there is one and only one forula for this quantity.  Second, and more important, this energy-momentum in principle "has weight."  It curves space.  It serves as a source term on the righthand side of Einstein's field equations.  It produces a relative geodesic deviation of two nearby world lines that pass through the region of space in question.  It is observable.  Not one of these properties does "local gravitational energy-momentum" possess.  There is no unique formula for it, but a multitude of quite distinct formulas.  The two cited are only two among an infinity.  Moreover, "local gravitational energy-momentum" has no weight.  It does not curve space.  It does not serve as a source term on the righthand side of Einstein's equations.  It does not produce any relative geodesic deviation of two nearby world lines that pass through the region of space in question.  It is not observable. 

Anybody who looks for a magic formula for "local gravitational energy-momentum" is looking forthe right answer to the wrong question.  unhappily, enormous time and effort were devoted in the past to trying to "answer this question" before investigators realized the futility of the enterprise.  Toward the end, above all mathematical arguments, one came to appreciate the quiet but rock-like strength of Einstein's equivalence principle.  One can always find in any given locality a frame of reference in which all local gravitational fields" (all Christoffel symbols . . .) disappear.  No [Christoffel symbols] means no "gravitational field" and no local gravitational field means no "local gravitational energy-momentum." 

Nobody can deny or wants to deny that gravitational forces make a contribution to the mass-energy of a gravitationally interacting system.  The mass-energy of the Earth-moon system is less than the mass-energy that system would have if the two objects were at infinite separation.  The mass-energy of a neutron star is less than the mass-energy of the same number of baryons at infinite separation.  Surround a region of empty space where there is a concentration of gravitational waves, there is a net attraction, betokening a positive net mass-energy in that region of space (see Chapter 35).  At issue is not the existence of gravitational energy, but the localizability of gravitational energy.  It is not localizable.  The equivalence principle forbids it.

Of course, in 1915, and even in 1973, the analogy of QCD, in which a force is carried by particles that are self-interacting (gluons in that case) was not known.  But, QCD without self-interacting gluons would produce a very different effect.

A graviton, of course, is the very epitome of localized gravitational energy, which is why conventional General Relativity as espoused in MTW is fundamentally inconsistent with quantum gravity theories.

Deur argues, by analogy to QCD, that self-interacting gravitons do indeed have observable effects and gravitons curve space just like any other carrier boson would.  To the extent that Einstein's equations do not reflect this fact, they are wrong.  This, he argues with back of napkin estimates, produces dark matter phenomena of approximately the right amount in galaxies and galactic clusters, and accurately reflects the pattern seen in which more spherically symmetric systems have less apparent dark matter than those that have (in the original sense of the word) more pretzelosity.

Gravity is weak, and so, the gravitational self-interactions of gravity in low mass systems are modest.  but, gravity is also cumulative, because it is always attractive, so in immense systems, gravitational self-interactions have material observable effects that probably give rise to substantially all dark matter phenomena, and by weakening gravitational fields in directions from which gravitons are diverted to give rise to dark matter phenomena effects elsewhere, also some or all dark energy phenomena.

Future Prospects

I am quite convinced that the failure of the Einstein equations to reflect a contribution of gravitational self-energy is the most likely by far reason for dark matter phenomena that we observe and most of the dark energy phenomena that we observe, and that correcting this error will cause theory and observation to match exquisitely without the need for any beyond the Standard Model particles other than the massless spin-2 graviton that couples with a strength equal to the mass-energy of a particle.

I am confident that sooner or later, probably within ten to forty years, such a theory will be well articulated and tested against the data and will become the scientific consensus, and that dark matter theories will be discarded.

Thus, we will be left with the Standard Model and a very simple quantum gravity, with no dark matter or dark energy.  Thus, the six quarks, three charged leptons, three neutrinos, photon, three weak force bosons, eight gluons and Higgs boson of the Standard Model, plus the graviton and their interactions according to four coupling constants, will prove to be the only particles needed to account for everything in the universe.  All other proposed theories of fundamental physics will end up on the scrap heap of intellectual history.  Maybe somebody will come up with a way to unify these pieces and explain the source of all of their constants, and maybe they won't.  But, for practical purposes, it doesn't really matter one way or the other.  The results will be the same.

Trying 23andMe

I have ordered 23andMe personal genome kits for the whole family.  The price is right and the technology seems to be mature for the near future.  Honestly, as much as anything, the reason for doing so is not to learn anything new about my ancestry as it is to confirm my confidence in the testing system.

I know a great deal more about my ancestry than most people.  I've met numerous third and fourth cousins, have met relatives from Finland (whom my parents and brother visited in person), and I am familiar with the time and exact place from which my German ancestors emigrated (my father was finally able to meet some of my relatives there when West Germany and East Germany merged), and I have a fair amount of familiarity with my Irish ancestors (although no one in my family has made contact with my Irish relations).

We also know quite a bit about my wife's Korean ancestors and could probably trace their ancestry for hundreds of years with a visit to Korea if I spoke Korean and the relevant records weren't destroyed or placed beyond reach in North Korea during the Korean War.

We've been close enough to family that we also have a reasonably complete medical history, and genetics is still enough in its infancy that even if 23andMe were allowed to make medical commentary of the raw genome data (for the foreseeable future it is prohibited by the FDA from doing that), the predictions from our medical history would probably be more accurate.

We also know at least some of our relatives are in the system and might pop up as related.  And, of course, we have actual phenotype knowledge about ourselves that can be matched against those genes for which phenotype-genotype relationships have been established (e.g. eye and hair and skin pigmentation, ear wax type, etc.).

Still, it will be fun to see the results, and to see the strong predictions that I can make about them fulfilled (or contradicted) in detail.

Neutrino Physics Update

The 16th Neutrino Telescope Conference is underway.

One notable early result puts the sum of the three neutrino masses between the 0.056 eV lower bound from oscillation experiments, and an upper bound of 0.14 eV at a 95% confidence interval.  This is almost, but not quite, tight enough to distinguish between a "normal" and an "inverted" neutrino mass hierarchy.  This means that the absolute masses of the neutrinos are now known with a precision rivaling that of the up quark.

State of the art direct measurements of absolute neutrino masses which are in the process of being carried out would place only a 0.4 eV cap on the mass of the electron neutrino, which we know from cosmology must actually be less than about 0.05 eV, and in a normal hierarchy is likely to be about 0.001 eV or less.

UPDATED March 5, 2015:

The lastest neutrinoless double beta decay exclusion from GERDA at a 90% confidence interval is now a low limit on the half-life of neutrinoless double beta decay of 2.1*10^25 years.  This is unchanged since last summer.

God, Country, Yale or . . .

I would lay down my life for two brothers or eight cousins.

- J.B.S. Haldane, from here.