5100 Years Of Ancient DNA From Tibet

There is a new Tibetan ancient DNA paper out with lots of new data. Bernard's blog discusses it at length. I'll discuss it at greater length when I have the time to do so.

A Challenge To A GR Solution To Dark Matter Effects

This is an important paper that deserves a close read and analysis. I have an intense work load this week, so that may take some time, but I'm posting this so that it doesn't get lost in the shuffle.

W. E. V. Barker, M. P. Hobson, A. N. Lasenby "Does gravitational confinement sustain flat galactic rotation curves without dark matter?" arXiv:2303.11094 (March 20, 2023).

The short answer is probably no. Specifically, this paper considers a recent body of work which suggests that general relativity requires neither the support of dark matter halos, nor unconventional baryonic profiles, nor any infrared modification, to be consistent after all with the anomalously rapid orbits observed in many galactic discs. In particular, the gravitoelectric flux is alleged to collapse nonlinearly into regions of enhanced force, in an analogue of the colour-confining chromoelectric flux tube model which has yet to be captured by conventional post-Newtonian methods. However, we show that the scalar gravity model underpinning this proposal is wholly inconsistent with the nonlinear Einstein equations, which themselves appear to prohibit the linear confinement-type potentials which could indicate a disordered gravitational phase. Our findings challenge the fidelity of the previous Euclidean lattice analyses. We confirm by direct calculation using a number of perturbation schemes and gauges that the next-to-leading order gravitoelectric correction to the rotation curve of a reasonable baryonic profile would be imperceptible. The `gravitoelectric flux collapse' programme was also supported by using intragalactic lensing near a specific galactic baryon profile as a field strength heuristic. We recalculate this lensing effect, and conclude that it has been overstated by three orders of magnitude. As a by-product, our analysis suggests fresh approaches to (i) the fluid ball conjecture and (ii) gravitational energy localisation, both to be pursued in future work. In summary, whilst it may be interesting to consider the possibility of confinement-type effects in gravity, we may at least conclude here that confinement-type effects cannot play any significant part in explaining flat or rising galactic rotation curves without dark matter halos.

When Will We Hit Major Neutrinoless Double Beta Decay Thresholds?

We don't have an absolute neutrino mass measurement. 

But due to the observed oscillations between neutrino mass eigenstates, we know that the sum of the three neutrino masses can't be less than about 60 meV if neutrinos have a "normal mass ordering" and can't be less than about 100 meV if neutrinos have an "inverted mass ordering."

The sum of the three neutrino masses could be greater than these minimums. If the sum of the three masses is greater than these minimums, the smallest neutrino mass is equal to a third of the amount by which the relevant minimum is exceeded.

So, for example, if the lightest of the three neutrino masses is 10 meV, then the sum of the three neutrino masses is about 90 meV in a normal mass ordering and about 130 meV in an inverted mass ordering.

If neutrinos have Majorana mass, the Majorana neutrino masses are related to the rate at which neutrinoless double beta decay can occur. The greater the Majorana mass, the more frequent neutrinoless double beta decay should be.

Right now, the non-detection of neutrinoless double beta decay so far puts a cap on the maximum Majorana mass of the neutrinos that is larger than the minimum mass of the inverted neutrino mass ordering. But, it is starting to get close.

As of July of 2022, we could determine with 90% confidence, based upon the non-detection of neutrinoless beta decay in a state of the art experiment establish a minimum half-life for the process of 8.3 * 10^25 years.

As illustrated by the chart below (from this source), an inverted mass hierarchy for neutrinos is ruled out at a half life of about 10^29 years (an improvement by a factor of 1200 in the excluded neutrinoless double beta decay half life over the current state of the art measurement). 

Majorana mass of any kind becomes problematic even in a normal mass hierarchy in about 10^32 or 10^33 years (an improvement by a factor of 1.2 million to 12 million over the current state of the art). 

We aren't there yet, but the likelihood that scientists will have experiments that will either detect neutrinoless double beta decay or rule out Majorana mass neutrinos even if they have a normal Majorana neutrino mass hiearchy, in perhaps 15-30 years, is quite good. 

Ruling out an inverted Majorana neutrino mass hierarchy based upon the non-observation of neutrinoless double beta decay is something that can probably be achieved in half that amount of time, perhaps as soon as the year 2030.

It is probably easier to overestimate how long it will take to achieve this goal than it is to underestimate how long it will take. 

Cosmology bounds on the neutrino mass, and hints from neutrino oscillation studies both favor a normal neutrino mass hierarchy over an inverted neutrino mass hierarchy. So, the discovery of Majorana mass neutrinos, if they do exist, is probably not just around the corner.

For what it is worth, there seem to be deep problems with both of the two main kinds of neutrino mass that have been proposed: Dirac mass and Majorana mass.

The biggest problem with Majorana mass seems to be our ability to clearly distinguish neutrinos and antineutrinos experimentally. 

But, according to the same analysis, the biggest problem with Dirac mass is that it would seem to imply the existence of sterile neutrino counterparts to the three "active" neutrinos and three "active" antineutrinos, even though there is really no evidence to suggest that they exist at all.

I've asked about, and not received a compelling answer to, the question of why these two theoretical proposals are the only possible ways for neutrinos to acquire rest mass. 

But, it seems to me that if your scientific analysis seems to rule (or at least strongly disfavor) both of the theoretical choices that you have considered to explain something, that it is likely that both possibilities are wrong and that the true answer is another approach that is not yet one of the choices.

It is certainly notable that neutrino masses are on the order of a billion (10^9) times smaller than their counterpart charged lepton masses. 

Could that be somehow related to the ratio of the strength of the weak force that dominates the dynamics of neutrinos to the strength of the electromagnetic fore that dominates the dynamics of electrons, muons, and tau leptons, which is about 10^11?

What if every kind of Standard Model fermion had its electroweak self-interaction as one source of rest mass, and the Higgs mechanism as an additional source of rest mass in all charged Standard Model fermions but not in neutrinos?

Could neutrinos have a third kind of mass component, perhaps derived from particle self-interactions, that might exist in every particle, but which would only be measurable in neutrinos?

It is hard to think sensibly about that possibility so it is such untried ground.

Cold Dark Matter Predictions Fail Again At The Center Of The Milky Way

Once again, predictions made about the inferred distribution of cold dark matter in galaxies has turned out to be grossly off the mark now that our astronomy data is better.

MOND which predicts no dark matter phenomena near the galactic center beyond the baseline prediction of general relativity without dark matter, is a much more accurate description of what is observed.

Precise measurements of the stellar orbits around Sagittarius A* have established the existence of a supermassive black hole (SMBH) at the Galactic centre (GC). Due to the interplay between the SMBH and dark matter (DM), the DM density profile in the innermost region of the Galaxy, which is crucial for the DM indirect detection, is still an open question. Among the most popular models in the literature, the theoretical spike profile proposed by Gondolo and Silk (1999; GS hereafter) is well adopted. 

In this work, we investigate the DM spike profile using updated data from the Keck and VLT telescopes considering that the presence of such an extended mass component may affect the orbits of the S-stars in the Galactic center. We examine the radius and slope of the generalized NFW spike profile, analyze the Einasto spike, and discuss the influence of DM annihilation on the results. 

Our findings indicate that an initial slope of γ≳0.92 for the generalized NFW spike profile is ruled out at a 95% confidence level. Additionally, the spike radius R(sp) larger than 21.5 pc is rejected at 95% probability for the Einasto spike with α=0.17, which also contradicts the GS spike model. 

The constraints with the VLT/GRAVITY upper limits are also projected. Although the GS NFW spike is well constrained by the Keck and VLT observation of S2, an NFW spike with a weak annihilation cusp may still be viable, as long as the DM annihilation cross section satisfies ⟨σv⟩≳7.7×10^−27 cm^3s^−1(m(DM)/100 GeV) at 95% level.

Zhao-Qiang Shen, Guan-Wen Yuan, Cheng-Zi Jiang, Yue-Lin Sming Tsai, Qiang Yuan, Yi-Zhong Fan, "Exploring dark matter spike distribution around the Galactic centre with stellar orbits" arXiv:2303.09284 (March 16, 2023) (To be submitted to MNRAS).

Refracted Gravity And Superfluid Dark Matter

By audience demand and for ease of reference purposes. Refracted gravity is a newish gravity based approach to explaining dark matter phenomena.  Fuller analysis will come later. Some first impressions: 

(1) the shape of the matter distribution doesn't seem to be important and it doesn't seem to have a source of isotropy violation, which are both problematic; 

(2) like GR with a cosmological constant and many other gravity modifications, it is a scalar-tensor theory (Deur's GR-SI is a pure tensor theory as is GR without a cosmological constant) - an important downside of a scalar-tensor v. a tensor theory is that it makes generalization to a quantum gravity theory harder; 

(3) unlike Deur's approach, it doesn't appear to resolve the conservation of energy issues associated with the lion's share of gravity theories with a dark energy component, but this calls for closer inspection and isn't entirely clear from the abstract; 

(4) further inspection of the permittivity-mass density relationship proposed is necessary for me to really understand it; 

(5) it appears to have one more experimentally fixed parameter than GR with a cosmological constant, similar to relativistic MOND with a cosmological constant; 

(6) there are lots of key areas (early galaxy formation, CMB peaks, cluster dynamics, Bullet cluster, cluster collision rate expectations, tendency of satellite galaxies to line up in planes, Hubble tension) where it isn't clear what is predicted although other papers may develop the theory more fully;

(7) all development of gravity based solutions to dark matter and dark energy phenomena are a welcome change, even though I'm skeptical that this will get the job done and the core assumption about permittivity isn't very well motivated (at least in the abstract).

We propose a covariant formulation of refracted gravity (RG), a classical theory of gravity based on the introduction of the gravitational permittivity -- a monotonic function of the local mass density -- in the standard Poisson equation. 

The gravitational permittivity mimics the dark matter phenomenology. Our covariant formulation of RG (CRG) belongs to the class of scalar-tensor theories, where the scalar field φ has a self-interaction potential (φ)=−Ξφ, with Ξ a normalization constant. We show that the scalar field is twice the gravitational permittivity in the weak-field limit. 

Far from a spherical source of density ρs(r), the transition between the Newtonian and the RG regime appears below the acceleration scale aΞ=(2Ξ−8πGρ/φ)1/2, with ρ=ρs+ρbg and ρbg an isotropic and homogeneous background. 

In the limit 2Ξ≫8πGρ/φ, we obtain aΞ∼10−10~m~s−2. This acceleration is comparable to the acceleration a0 originally introduced in Modified Newtonian Dynamics (MOND). 

From CRG, we also derive the modified Friedmann equations for an expanding, homogeneous, and isotropic universe. We find that the same scalar field that mimics dark matter also drives the accelerated expansion of the Universe. Since Ξ plays a role roughly similar to the cosmological constant Λ in the standard model and has a comparable value, CRG suggests a natural explanation of the known relation a0∼Λ1/2. 

CRG thus appears to describe both the dynamics of cosmic structure and the expanding Universe with a single scalar field, and falls within the family of models that unify the two dark sectors, highlighting a possible deep connection between phenomena currently attributed to dark matter and dark energy separately.

Andrea Pierfrancesco Sanna, Titos Matsakos, Antonaldo Diaferio, "Covariant Formulation of refracted gravity" arXiv:2109.11217 (September 25, 2021) (submitted to Physical Review D).

A new paper on a superfluid dark matter theory with two of my favorite physicists as authors, which is betwixt and between a gravitational and a dark matter particle approach, finds that SFDM falls short. Again, any work on gravitational or MOND-replicating theories is a good thing, even if individual theory failures point the way to the true solution.

We investigate superfluid dark matter (SFDM), a model that promises to reproduce the successes of both particle dark matter on cosmological scales and those of Modified Newtonian Dynamics (MOND) on galactic scales. 

But SFDM reproduces MOND only up to a certain distance from the galactic center and only for kinematic observables. Most importantly, it does not affect trajectories of light. We test whether or not this is in conflict with a recent analysis of weak gravitational lensing which has probed accelerations around galaxies at unprecedentedly large radii. This analysis found the data to be close to the prediction of MOND, suggesting they might be difficult to fit with SFDM. 

To investigate this matter, we solved the equations of motion of the model and compared the result to observational data. Our results show that the SFDM model is incompatible with the weak-lensing observations, at least in its current form.

Tobias Mistele, Stacy McGaugh, Sabine Hossenfelder, "Superfluid dark matter in tension with weak gravitational lensing data" arXiv:2303.08560 (March 15, 2023).

Stone Tools: Monkeys Or Humans?

It turns out the stone tools of old world monkeys and the stone tools of early humans are hard to distinguish from each other (citing Tomos Proffitt, et al., "Wild macaques challenge the origin of intentional tool production." Science Advances (2023) DOI: 10.1126/sciadv.ade8159).

There Are Multiple Possible Boring Explanations Of The Gallium Anomaly

An anomaly in neutrino physics has several plausible explanations that don't require new physics. I would rate each of the beyond the Standard Model explanations in their paper lower than they do in plausibility by at least two stars.

A series of experiments studying neutrinos from intense radioactive sources have reported a deficit in the measured event rate which, in combination, has reached a statistical significance of ∼5σ. 

In this paper, we explore avenues for explaining this anomaly, both within the Standard Model and beyond. 

First, we discuss possible biases in the predicted cross section for the detection reaction νe+71Ga→e−+71Ge, which could arise from mismeasurement of the inverse process, 71Ge decay, or from the presence of as yet unknown low-lying excited states of 71Ga. The latter would imply that not all 71Ge decays go to the ground state of 71Ga, so the extraction of the ground state-to-ground state matrix element relevant for neutrino capture on gallium would be incorrect. 

Second, we scrutinize the measurement of the source intensity in gallium experiments, and we point out that a ∼2% error in the branching ratios for 51Cr decay would be enough to explain the anomaly. 

Third, we investigate the calibration of the radiochemical germanium extraction efficiency as a possible origin of anomaly.

From here.

Gravitomagnetism Doesn't Explain Galaxy Rotation Curves

There are a variety of general relativistic effects that could explain dark matter phenomena. There seems to be a very solid analysis, however, concluding that gravitomagnetic effects in linearised general relativity are not among them.

We investigate recent claims that gravitomagnetic effects in linearised general relativity can explain flat and rising rotation curves, such as those observed in galaxies, without the need for dark matter. 

If one models a galaxy as an axisymmetric, stationary, rotating, non-relativistic and pressureless 'dust' of stars in the gravitoelectromagnetic (GEM) formalism, we show that GEM effects on the circular velocity v of a star are O(10^−6) smaller than the standard Newtonian (gravitoelectric) effects. 

Moreover, we find that gravitomagnetic effects are O(10^−6) too small to provide the vertical support necessary to maintain the dynamical equilibrium assumed. 

These issues are obscured if one constructs a single equation for v, as considered previously. We nevertheless solve this equation for a galaxy having a Miyamoto--Nagai density profile. We show that for the values of the mass, M, and semi-major and semi-minor axes, a and b, typical for a dwarf galaxy, the rotation curve depends only very weakly on M. Moreover, for aspect ratios a/b>2, the rotation curves are concave over their entire range, which does not match observations in any galaxy. 

Most importantly, we show that for the poloidal gravitomagnetic flux ψ to provide the necessary vertical support, it must become singular at the origin. This originates from the unwitting, but forbidden, inclusion of free-space solutions of the Poisson-like equation that determines ψ, hence ruling out the methodology as a means of explaining flat galaxy rotation curves. 

We further show that recent deliberate attempts to leverage such free-space solutions against the rotation curve problem yield no deterministic modification outside the thin disk approximation, and that, in any case, the homogeneous contributions to ψ are ruled out by the boundary value problem posed by any physical axisymmetric galaxy.

A. N. Lasenby, M. P. Hobson, W. E. V. Barker, "Gravitomagnetism and galaxy rotation curves: a cautionary tale" arXiv:2303.06115 (March 10, 2023).

Free Floating Planets And Other Astronomy Quick Hits

* There are vast numbers of free floating planets out there, ripped from the stars around which the formed. The James Webb Space Telescope (JWST) will soon reveal many more of them.

While these are ultimately just cold rocks, there are also isolated stars outside any galaxy out there. What if life developed in a place like that?

The possibilities found in the universe are awe inspiring.

* In other astronomy observations, "general relativistic contributions" reduce "the probability that the solar system destabilizes within 5 Gyr by a factor of 60."

* Power laws continue to be fascinating and make random phenomena, while still random, far more ordered than they seem, while also suggesting the kind of processes that give rise to them.

Many astronomical phenomena, including Fast Radio Bursts and Soft Gamma Repeaters, consist of brief distinct aperiodic events. The intervals between these events vary randomly, but there are periods of greater activity, with shorter mean intervals, and of lesser activity, with longer mean intervals. A single dimensionless parameter, the width of a log-normal function fitted to the distribution of waiting times between events, quantifies the variability of the activity. This parameter describes its dynamics in analogy to the critical exponents and universality classes of renormalization group theory. If the distribution of event strengths is a power law, the width of the log-normal fit is independent of the detection threshold and is a robust measure of the dynamics of the phenomenon.

J. I. Katz, "Log-Normal Waiting Time Widths Characterize Dynamics" arXiv:2303.05578 (March 9, 2023) (3 pages).

* Organic molecules that seeded life may have had a head start in interstellar space according to a new preprint: "Protoplanetary disk around a just born young star contains a lot of cosmic dust. especially polycyclic-aromatic-hydrocarbon (PAH), which would become basic component to create biological organics. "

A New 146 GeV LHC Anomaly?

Sabine Hossenfelder has noted a new anomaly at 146 GeV identified by a new paper from the CMS experiment at the Large Hadron Collider (LHC).

I am not holding my breath that it will amount to anything. 

It has a local significance of 3.8 sigma, but a global significance of just 2.8 sigma if there was a particle that decayed into an electron and a muon, for example, which is a pretty weak tension with the Standard Model. 

After all, a deviation of 2 sigma or less from the Standard Model is considered to be "consistent" with the Standard Model, while a 5 sigma deviation is required for new physics to be considered "discovered."

A Novel Analysis Constrains The Dark Matter Parameter Space

Considering the impact that dark matter particles, if the existed, would have on the rate at which neutron star masses grow (potentially tipping neutron stars into black holes), place quite tight and general boundaries on masses of hypothetical dark matter particles for a fairly broad class of potential dark matter particles that aren't completely "sterile" (i.e. not having any non-gravitational interactions).

For reference purposes, the cross-section of interaction between neutrinos and nucleons (i.e. protons and neutrons) is about σnv = 10^−40 cm^2. 

The exclusions in this study for a broad range of dark matter particle masses from 100 MeV (which is less than the mass of a pion, which is the least massive particle containing quarks, or the mass of a muon which is a second generation electron) to 1 TeV (about the mass of six top quarks) requires that dark matter particles have interactions with ordinary baryonic matter that are at least a hundred thousand times weaker than the interactions between neutrinos and ordinary baryonic matter (which is basically the entire WIMP mass range).

The Size Of The Exclusion Range Explained

The only Standard Model particles that can exist outside hadrons (i.e. Standard Model particles that don't have quarks or gluons), which have masses below that mass range are electrons, all three kinds of Standard Model neutrinos, and photons (and free up and down quarks in an extremely high temperature gluon quark plasma which is inconsistent with cold or warm dark matter). 

This mass range includes muons, tau leptons, free top quarks (up to five of them), as well as high energy free charm and bottom quarks in a gluon-quark plasma. It comes just barely short of including free strange quarks in a high energy gluon quark plasma, which would still have to have an almost hundred thousand times weaker interaction with ordinary baryonic matter than neutrinos.

All observed hadrons, all predicted hadrons and glueballs, all candidates for "meson molecules" and "baryon molecules" and simple "hadron molecules" with both mesons and baryons bound by residual binding forces are also in that range. Even a hypothetical and unthinkably short lived and improbable top quark meson or baryon or tetraquark or pentaquark would be in that mass range. This mass range even includes all isotopes of all observed or predicted atoms are also in that mass ranges. The mass of the heaviest known element (Tennessine which is element 117) is about 273 GeV, which is less than a third of one TeV.

The only composite particles with a single particle mass in excess of 1 TeV each (1074 atomic mass units) are large molecules (for example, a hydrocarbon with a single chain of 76 carbon atoms), and crystals with many atoms. 

The exclusion of the dark matter particle parameter space from neutron star masses is strongest for a 10 GeV dark matter particle. This has about the mass of a carbon atom, or the heaviest observed hadrons, such as a bottomonium meson, or a baryon with two bottom quarks and a light quark. For a 10 GeV dark matter particle, the neutron star data imply that any  interactions between this dark matter particle candidate and ordinary baryonic matter are at least a billion times weaker than interactions between neutrinos and ordinary baryonic matter.

The paper and its abstract are as follows:

Neutron stars (NSs) can be used to constrain dark matter (DM) since a NS can transform into a black hole (BH) if it captures sufficient DM particles and exceeds the Chandrasekhar limit. We extend earlier work and for the first time take into account the Galactic motion of individual NSs, which changes the amount of the captured DM by as large as one to two orders of magnitude. We systematically apply the analysis to 414 NSs in the Milky Way, and constrain the DM particle mass and its interaction with nucleon simultaneously. We find that the most stringent bound is placed by a few NSs and the bound becomes stronger after considering the Galactic motion. 

The survival of observed NSs already excludes a cross section σnX ≳ 10^−45 cm^2 for DM particles with mass from 100 MeV to 10^3 GeV. Especially for a mass around 10 GeV, the constraint on the cross section is as stringent as σnX ≲ 10^−49 cm^2.

Dicong Liang, Lijing Shao, "Improved bounds on the bosonic dark matter with pulsars in the Milky Way" arXiv:2303.05107 (March 9, 2023).

Leveraging This New Information Into Broader Dark Matter Parameter Space Exclusions

Sterile Dark Matter Doesn't Work

What gives this conclusion extra punch is that we can pretty much rule out, based upon observations of inferred dark matter halo shapes and based upon the tight correlation between inferred dark matter halos and ordinary matter distributions in galaxies, completely sterile dark matter particle candidates. 

The exclusion for completely sterile dark matter particle candidates can even be extended down to, for example, of keV mass "warm dark matter" particles. 

Sterile dark matter particle candidates which are "thermal freeze out" dark matter candidates below the warm dark matter mass scale in the single digit keV masses are likewise ruled out because this would be "hot dark matter" which is inconsistent with the amount of structure observed in the universe, for example, in galaxies and galaxy clusters.

Simple Self-Interacting But Otherwise Sterile Dark Matter Doesn't Work

It also appears that mere self-interaction between dark matter particles doesn't solve the problems of purely sterile dark matter particles either. 

There has to be some kind of interaction between dark matter particles an ordinary baryonic matter to explain the way that dark matter is inferred to be distributed in a dark matter particle paradigm.

Bottom Line

So, on one hand, you actually need dark matter to have some kind of not entirely negligible interaction with ordinary matter to reproduce what we observe. 

But, on the other hand, a variety of tests have ruled out any kind of interactions with ordinary matter for a large class of potential dark matter particle candidates.

Decaying Or Meaningfully Annihilating Dark Matter Doesn't Work

Model dependent observational constraints require dark matter particles to be either stable or to have a mean lifetime significantly greater than the age of the universe which is about 13.7 billion years old.

Observational data also largely ruling out dark matter candidates that annihilate with other dark matter particles into any products that can be detected with "telescopes" broadly defined at any meaningful rate - effectively ruling out another kind of self-interacting dark matter.

Gaps In The Efforts To Rule Out Dark Matter Particle Candidates That Are Not Sterile Or Nearly So.

There are still a few gaps in the dark matter parameter space.

Gaps For Heavy Dark Matter Candidates

There is another gap between the 1 TeV mass range and MACHO mass object sized dark matter particle candidates (e.g. with medium sized asteroid mass) that are stable over long time periods. 

But all forms of baryonic dark matter are ruled out, and a hypothetical stable exotic hadrons made of ordinary matter such as "quark nuggets" and hexaquarks, are likewise ruled out (because there is no plausible argument that they can't be stable).

The main dark matter candidate in this mass range, primordial black holes (PBHs), which were already ruled out except at asteroid mass due to evaporation via Hawking radiation at the low end and a lack of weak lensing at the high end, have now basically been completely ruled out. This last remaining range of masses where PBHs weren't ruled out have been excluded, for example, by the lack of perturbations in the asteroid belts of the solar system basically ruling out the few corners of parameter space that had remained for PBHs with masses with magnitudes similar to asteroid masses. 

This doesn't entirely and rigorously rule out some non-baryonic beyond the Standard Model particle in the more than 1 TeV particle mass range up to asteroid mass. But that approach isn't well motivated.

Gaps For Light Dark Matter Candidates

Today's preprint places a quite general upper bound on non-sterile dark matter that does not have a mass under 100 MeV.

There is also an upper bound on the mass of sterile dark matter particles of anything above 10 keV as recounted in warm dark matter papers. 

By comparison, an electron has a mass of 511 keV.

More generally, light dark matter particle candidates have to be non-thermal freeze out dark matter candidates in order to keep the mean velocities of these light dark matter candidates low enough to keep them out of the experimentally excluded "hot dark matter" category.

Another gap does not rule out some kinds of axion like particle (ALP) dark matter candidates or other ultralight dark matter candidates (i.e. far below 1 keV) although the ALP exclusion space is full of tiny rule out zones in its parameter space that don't obviously overlap to form a larger exclusion. 

Quote Of The Day

CERN buildings not only have evacuation instructions for the building in case of a fire, but also evacuation instructions for the whole site.

From 4gravitons.

The Easter Island Statues Have Bodies

Via this news story (which has many more photos of Easter Island statue bodies).

The fact that the Easter Island (a.k.a. Rapa Nui) statues (which are known as "moai" from the Spanish word for statue) have bodies is old news. 

But the statues shown with their full bodies are still striking to actually see, and are a nice image to brighten your day. Why these statutes ended up getting so deeply buried also appears to be a still open question in anthropology.

What are they?

Moai or moʻai (/ˈmoʊ.aɪ/ (listen) MOH-eye; Spanish: moái; Rapa Nui: moʻai, lit. 'statue') are monolithic human figures carved by the Rapa Nui people on Rapa Nui (Easter Island) in eastern Polynesia between the years 1250 and 1500. Nearly half are still at Rano Raraku, the main moai quarry, but hundreds were transported from there and set on stone platforms called ahu around the island's perimeter. 

Almost all moai have overly large heads, which comprise three-eighths the size of the whole statue and they have no legs. The moai are chiefly the living faces (aringa ora) of deified ancestors (aringa ora ata tepuna). The statues still gazed inland across their clan lands when Europeans first visited the island in 1722, but all of them had fallen by the latter part of the 19th century. The moai were toppled in the late 18th and early 19th centuries, possibly as a result of European contact or internecine tribal wars. . . .

Though moai are whole-body statues, they are often referred to as "Easter Island heads" in some popular literature. This is partly because of the disproportionate size of most moai heads, and partly because many of the iconic images for the island showing upright moai are the statues on the slopes of Rano Raraku, many of which are buried to their shoulders. Some of the "heads" at Rano Raraku have been excavated and their bodies seen, and observed to have markings that had been protected from erosion by their burial.

The average height of the moai is about 4 m (13 ft), with the average width at the base around 1.6 m (5.2 ft). These massive creations usually weigh around 12.5 tonnes (13.8 tons) each. . . . 

It is thought that the moai with carved eye sockets were probably allocated to the ahu and ceremonial sites, suggesting that a selective Rapa Nui hierarchy was attributed to the moai design until its demise with the advent of the religion revolving around the tangata manu. 

. . .

Archaeologists believe that the statues were a representation of the ancient Polynesians' ancestors. The moai statues face away from the ocean and towards the villages as if to watch over the people. The exception is the seven Ahu Akivi which face out to sea to help travelers find the island. There is a legend that says there were seven men who waited for their king to arrive. A study in 2019 concluded that ancient people believed that quarrying of the moai might be related to improving soil fertility and thereby critical food supplies.

. . .

Those moai that are less eroded typically have designs carved on their backs and posteriors. The Routledge expedition of 1914 established a cultural link between these designs and the island's traditional tattooing, which had been repressed by missionaries a half-century earlier. . . .

The statues were carved by the Polynesian colonizers of the island, mostly between 1250 and 1500 [CE]. In addition to representing deceased ancestors, the moai, once they were erected on ahu, may also have been regarded as the embodiment of powerful living or former chiefs and important lineage status symbols. Each moai presented a status: "The larger the statue placed upon an ahu, the more mana the chief who commissioned it had." The competition for grandest statue was ever prevalent in the culture of the Easter Islanders. The proof stems from the varying sizes of moai.

Completed statues were moved to ahu mostly on the coast, then erected, sometimes with pukao, red stone cylinders, on their heads. Moai must have been extremely expensive to craft and transport; not only would the actual carving of each statue require effort and resources, but the finished product was then hauled to its final location and erected.

The quarries in Rano Raraku appear to have been abandoned abruptly, with a litter of stone tools and many completed moai outside the quarry awaiting transport and almost as many incomplete statues still in situ as were installed on ahu. In the nineteenth century, this led to conjecture that the island was the remnant of a sunken continent and that most completed moai were under the sea. That idea has long been debunked, and now it is understood that: 

• Some statues were rock carvings and never intended to be completed. 
• Some were incomplete because, when inclusions were encountered, the carvers would abandon a partial statue and start a new one. Tuff is a soft rock with occasional lumps of much harder rock included in it.
• Some completed statues at Rano Raraku were placed there permanently and not parked temporarily awaiting removal.
• Some were indeed incomplete when the statue-building era came to an end.

. . .

Since the island was largely treeless by the time the Europeans first visited, the movement of the statues was a mystery for a long time; pollen analysis has now established that the island was almost totally forested until 1200 CE. The tree pollen disappeared from the record by 1650. 

. . . 

Originally, Easter Islanders had a paramount chief or single leader. Through the years the power levels veered from sole chiefs to a warrior class known as matatoʻa. The therianthropic figure of a half bird and half-man was the symbol of the matatoʻa; the distinct character connected the sacred site of Orongo. The new cult prompted battles of tribes over worship of ancestry. Creating the moai was one way the islanders would honor their ancestors; during the height of the birdman cult there is evidence which suggests that the construction of moai stopped.

New T2K Measurements Of Neutrino Oscillation Parameters

The T2K experiment has used to brute force of running lots of collisions and new clever analysis techniques to come up with its latest measurement of neutrino oscillation parameters. 

Jester retweets physicist Peter Denton who notes in commenting on this paper that:

Their weak evidence for CP violation has decreased somewhat. Was just under 3sigma, now just under 2sigma (depending on the choice of prior).

The bottom line is as follows:

Frequentist and Bayesian analyses are presented, including results on sin2θ13 and the impact of priors on the δCP measurement. Both analyses prefer the normal mass ordering and upper octant of sin2θ23 with a nearly maximally CP-violating phase. 

Assuming the normal ordering and using the constraint on sin2θ13 from reactors, sin2θ23=0.561+0.021−0.032 using Feldman--Cousins corrected intervals, and Δm232=2.494+0.041−0.058×10−3 eV2 using constant Δχ2 intervals. The CP-violating phase is constrained to δCP=−1.97+0.97−0.70 using Feldman--Cousins corrected intervals, and δCP=0,π is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than 2σ credible level using a flat prior in δCP, and just below 2σ using a flat prior in sinδCP. 

When the external constraint on sin2θ13 is removed, sin2θ13=28.0+2.8−6.5×10−3, in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.

From the body text:

The analysis with (without) the reactor constraint sees a Bayes factor (BF) of 3.35 (1.43) for the upper over the lower θ23 octant; 4.21 (1.83) for the normal over inverted mass ordering; and a combined factor of 1.58 (0.63) for upper θ23 octant and normal ordering. 

When calculating the BFs, the alternate hypothesis is any other combination of octant and mass ordering. Interpreting the largest BFs with the Jeffreys’ scale, there is substantial evidence for the normal ordering when marginalising over the octant, and substantial evidence for the upper octant when marginalising over the mass ordering. In the more recent interpretation of BFs by Kass and Raftery, these both correspond to positive evidence. Importantly, the Jeffreys and Kass–Raftery definitions of “evidence” do not equate to the criteria often used in particle physics. For instance, a probability of 95.4% (“2σ”) is equivalent to a BF of 20.7, which is deemed as “decisive” on the Jeffreys’ scale, and as “strong” on the Kass–Raftery scale.