The latest results from the LHC on the 750 GeV "bump" in the data is scheduled to be released at a conference which begins on August 3, 2016, a week from yesterday.
This "bump" which now appears to have been nothing more profound than a statistical fluke, spawned intense interest from the theoretical physics community that resulted in publication of more than five hundred journal article pre-prints in the span of just a few months (see also here in a post at this blog of the same name as this one).
The rumor mill has it that the results will not involve a 5 sigma "discovery" threshold finding and will probably show declining statistical significance. Indeed, the rumor is that the 750 GeV "bump" is basically dead (as I predicted it would be on this blog when the results were first announced). But, of course, we'll have a far more precise answer soon.
The minimal model of the Standard Model together with General Relativity with a cosmological constant continues to reign supreme, explaining pretty much everything except dark matter phenomena. Light sterile neutrinos are essentially ruled out too.
Add to this the failure of direct detection experiments and of satellites trying to detect dark matter annihilation signatures (and a lot of other data) is putting tight constraints on any particle based dark matter solution and ruling out conventional SUSY WIMPS. Not all dark matter particles are ruled out yet, however, and no really wholeheartedly convincing true quantum gravity theory to explain dark matter phenomena is in place either, even though some intriguing efforts has been made on that front.
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Thursday, July 28, 2016
Thursday, July 21, 2016
Ashkenazi Jewish Genetics
Most Jews are either Ashkenazi Jews or Sephardic Jews, and most American Jews are Ashkenazi Jews, typically with origins someplace in Eastern Europe immediately prior to immigration to the United States.
A new paper looks at the genomes of Ashkenazi Jews today in order to determine their population history using computerized tools and a greatly expanded set of Jewish and non-Jewish reference genomes that has accumulated over the last few years.
This is necessary because the historical record provides very little meaningful or reliable insight into the process by which the Jewish diaspora resulted in migrations of Jews from the Middle East to Europe. The gap in the historical record is particularly acute in the several century long gap period after the composition of the Babylonian Talmud and the fall of the Roman Empire, and before the pogroms directed at Jews in Europe which roughly coincided with the Crusades. Yet, this gap period was apparently the period of Ashkenazi Jewish ethnogenesis and the source of the population bottleneck that is a defining feature of Ashkenazi Jewish population genetics.
The quaint term for this time period in historical circles is the "dark ages" and the dearth of historical sources from that era deserve that name, even though we do know a fair amount about that time period now by a variety of means. This time period overlaps with the expansion of the Islamic empire, the Slavic expansion in Eastern Europe, the "migration period" of (mostly) Germanic tribes in Europe, and Anglo-Saxon and Viking raids into and migration of England (which is arguably part of the migration period).
The quaint term for this time period in historical circles is the "dark ages" and the dearth of historical sources from that era deserve that name, even though we do know a fair amount about that time period now by a variety of means. This time period overlaps with the expansion of the Islamic empire, the Slavic expansion in Eastern Europe, the "migration period" of (mostly) Germanic tribes in Europe, and Anglo-Saxon and Viking raids into and migration of England (which is arguably part of the migration period).
The genetic analysis is not straightforward because (1) there are considerable similarities between the genetic profiles of the suspected source populations, (2) there is little ancient DNA to bear on the question very directly, and (3) modern populations are not great proxies of historical populations at the time that the relevant stages of the migrations happened, particularly in the Levant and Slavic Europe. Indeed, the latest results come with considerable acknowledged uncertainty, although the broad outlines of the analysis are probably correct.
The West Hunter blog has a summary of the findings of this open access paper that fairly states the conclusions of the paper at least as well as I could describe them myself:
When they analyze the origins of the European component of Ashkenazi ancestry, they conclude that most is southern – probably Italian, but that smaller amounts originated from (probably) Western Europe and (more certainly) Eastern Europe: and in that temporal order. They conclude that the Italian admixture slightly predated a late medieval founder event. Different methods came up with somewhat different estimates for the total amount of European ancestry: the local ancestry inference (LAI) approach came up with 53% European, while the GLOBETROTTER analysis came up with an estimate of 67% European ancestry (after calibration by simulations). In their best guess, they split the difference and go for 60% European.
To sum up, their model is that a population from the Levant mixed with Italians, and shortly thereafter moved to the Rhineland (the founding bottleneck), perhaps mixing to some degree with the local Europeans there, and certainly mixing some with Slavic types when they moved to the Polish-Lithuanian Commonwealth.
How do their conclusions differ from those in the last report? Previously they were thinking that the bottleneck was around 1350, a product of the Black Death and savage persecution – now they’re talking the original settlement in the Rhineland. Previously they had a somewhat lower estimate of European ancestry (~48%, now 60%). I thought these two conclusions likely a couple of years ago.
The big new point, important if correct, is that the admixture with Italians is relatively recent – too recent to have happened back in Roman times. In their model, this main admixture event is 25-55 generations ago, while the founding bottleneck is 25-35 generations ago. It’s not impossible that the admixture happened at the same time as the founding.
About 15%-25% of Ashkenazi Jewish ancestry, which is a quarter to a almost half or so of the total European ancestry, is Eastern European. I've also seen other sources conclude that the paternal line is more strongly Levantine than Jewish maternal ancestry.
As Razib Khan has noted in comments to his post on the same paper, the Black Plague hypothesis was always suspect as a source of the population bottleneck that is clearly apparent in Ashkenazi Jewish population genetics, because it didn't kill a large enough percentage of the population to be likely to have caused the observed bottleneck effects.
This is also as good a post as any to observe that all Jewish populations in the world from Ashkenazi and Sephardic Jews to Jews in Yemen, India and elsewhere, are significantly admixed with local populations. Endogamy in the founding populations of Jews in the Jewish diaspora has almost always been modest in the founding period, even though these barriers to admixture ossified with time. There are probably far fewer "pure blooded" Jews with exclusively Levantine origins and descended from Jews in their Iron Age kingdoms (I'm not convinced that there are any), than there are "pure blooded" Native Americans who lack European or African admixture, for example.
This is also as good a post as any to observe that all Jewish populations in the world from Ashkenazi and Sephardic Jews to Jews in Yemen, India and elsewhere, are significantly admixed with local populations. Endogamy in the founding populations of Jews in the Jewish diaspora has almost always been modest in the founding period, even though these barriers to admixture ossified with time. There are probably far fewer "pure blooded" Jews with exclusively Levantine origins and descended from Jews in their Iron Age kingdoms (I'm not convinced that there are any), than there are "pure blooded" Native Americans who lack European or African admixture, for example.
Lux Further Constrains Dark Matter Parameter Space By A Factor Of Four
Lux is the gold standard for direct dark matter detection experiments and has further ruled out forms of dark matter that slightly interact with ordinary matter to a much greater degree. Any dark matter particles with masses from 1 GeV to 10,000 GeV that have interactions with ordinary matter that are more than a fraction of the strength of interactions of a neutrino (which is barely any at all) have been ruled out.
The WIMP paradigm (in the narrow sense of dark matter particles that interact via both the weak force and gravity) is well and truly dead.
The WIMP paradigm (in the narrow sense of dark matter particles that interact via both the weak force and gravity) is well and truly dead.
Tuesday, July 19, 2016
From Quantum Mechanics To Gravity
Sean Carroll's latest paper considers (but doesn't really prove) a couple of interesting conjectures:
1. Gravity and space-time geometry are emergent properties of a quantum world that reflect the degree to which particles are entangled with each other (more entanglement implies shorter distances and the mass-energy coupling might emerge more or less naturally and automatically from the formulation).
2. Nature is a quantum system in a finite dimensional Hilbert space, rather than an infinite dimensional Hilbert space as generally assume in quantum mechanics, which would provide a natural (but elegant) cutoff that would insulate the real world from the infinities and singularities found in quantum mechanics and GR done in an infinite dimensional/continuous approximation.
1. Gravity and space-time geometry are emergent properties of a quantum world that reflect the degree to which particles are entangled with each other (more entanglement implies shorter distances and the mass-energy coupling might emerge more or less naturally and automatically from the formulation).
2. Nature is a quantum system in a finite dimensional Hilbert space, rather than an infinite dimensional Hilbert space as generally assume in quantum mechanics, which would provide a natural (but elegant) cutoff that would insulate the real world from the infinities and singularities found in quantum mechanics and GR done in an infinite dimensional/continuous approximation.
Tuesday, July 12, 2016
More On Madagascar's Genetic Origins
The biggest surprises of a new paper on the genetic origins of the people of Madagascar are the roughly 2/3rds African origin demonstrated when some previous estimates had been closer to 35%-50%, and more surprisingly, that the affinity of that African component to Southern African Bantu, when previous data had rejected that hypothesis in favor of an affinity to East African Bantu populations (less some recent Nilo-Saharan admixture).
Southern African Bantu have a substrate of pre-Bantu Mozambique people which is very distinctive from any extant African population to the extent that it basically constitutes a "lost race" of Africans that coincides with linguistic substrates of Bantu languages in that region indicating that the pre-Bantu people of Mozambique spoke a click language. There are also uniparental markers private to Mozambique that are largely absent from Madagascar. So, there are strong reasons to be skeptical of a Southern African as opposed to East African source for the African genetic contribution to Madagascar.
The lack of a strong historical connection between Mozambique across the strait from Madagascar and that island is likewise demonstrated by a lack of archaeological support for those kinds of trade ties and a lack of Southeast Asian genetic traces in mainland Africa (anywhere).
The conclusions on the Asian genetic origins side of the analysis, on the other hand, are plausible and very consistent with previous research on the topic, although the analysis does not identify indications from previous studies that the migration was probably along the Indian Ocean's coast with stops in South Asia and East Africa, rather than directly across the Indian Ocean as a graphic in the new paper misleadingly suggests.
I'll need to look more closely at the various papers involved to see if these new results can be reconciled with the prior research, and if not, to determine the likely source of the disparity. The two-thirds percentage is probably right, but the South African Bantu affinity seems suspect. The fact that only the Asian conclusions and not the controversial African ones end up in the abstract of the paper is also notable.
The pertinent portion of the paper addressing this point states:
The Supplemental Materials indicate that the African samples other than South African Bantu come from International HapMap, et al. (2010) (i.e. Integrating common and rare genetic variation in diverse human populations. Nature 467: 52-58. doi: 10.1038/nature09298) and Pagani, et al. (2012) (i.e. Ethiopian genetic diversity reveals linguistic stratification and complex influences on the Ethiopian gene pool. Am J Hum Genet 91: 83-96. doi: 10.1016/j.ajhg.2012.05.015). The South African Bantu sample comes from May, et al. (2013) (Genetic diversity in black South Africans from Soweto. BMC Genomics 14: 644. doi: 10.1186/1471-2164-14-644).
Another data set of Southeastern Bantu speakers referenced in May, et al. (2013) seems to overlap with the Soweto sample and derives from Schlebusch, et al., "Genomic variation in seven Khoe-San groups reveals adaptation and complex African history." Science. 2012, 338: 374-379.
It is also possible that Soweto Bantus are very genetically distinct from Mozambique Bantus and may be more similar to ancestral East African Bantus than modern East African Bantus, because they may lack subsequent Nilo-Saharan Ancestry and may, in general have less of a substrate influence.
The abstract of the paper and its citation data are as follows:The pertinent portion of the paper addressing this point states:
The admixture profile of our dataset (2183 individuals from 61 populations genotyped for 40,272 SNPs; Supplementary figures S2 and S3, Supplementary Material online), based on ADMIXTURE analyses (Alexander, et al. 2009), shows that the Malagasy genetic diversity is best described as a mixture of 68% African genomic components and 32% Asian components, corresponding well with the results of previous studies (Capredon, et al. 2013; Pierron et al. 2014). While the African ancestry component in Malagasy appears to be broadly similar to that still present today in South African Bantu, the Asian ancestry presents a more complex pattern. . . . to more specifically identify the Asian ancestry of the Malagasy genome, we performed a Local Ancestry analysis with PCAdmix (Brisbin, et al. 2012) using two proxy parental meta-populations comprising 100 individuals with African ancestry (randomly selected from Yoruba, South African Bantu, Kenyan Luhya and Somali groups) and Asian ancestry (randomly selected from Chinese, Philippine Igorot, Bornean Ma’anyan and Malay groups). . . . To expand on this, however, we inferred the population sources of the Malagasy, their relative ratios and the dates of potential admixture events with GLOBETROTTER (Hellenthal, et al. 2014), defining each population in our dataset as a donor/surrogate group and the Malagasy as the recipient, using the haplotype ‘painting’ data obtained with Chromopainter (Lawson, et al. 2012). The best fit outcome for the Malagasy was obtained under a model of a single admixture event between two sources: the Banjar representing 37% of modern Malagasy and the South African Bantu population representing the other 63% (r2 =0.99, P<0.01; Figure 2 and Supplementary table S5, Supplementary Material online). The admixture event was dated to 675 years BP (95% CI: 625-725 years BP, Supplementary table S5, Supplementary Material online), which is similar to the dates of admixture estimated by ALDER (550-750 years BP) using Banjar population in combination with the South African Bantu (Supplementary table S6, Supplementary Material online)(Loh, et al. 2013). When each Malagasy ethnic group is analysed separately, similar parental populations, admixture proportions and dates are obtained with the noticeable older by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from estimated dates towards the east coast of Madagascar (Supplementary table S5, Supplementary Material online). Crucially, these dates of genetic admixture, in agreement with a previous study (Pierron et al. 2014), reflect the midpoint or end of noticeable admixture between groups of Asian and African ancestry in Madagascar, rather than the start of this contact. Therefore they could correspond to the end of the period of the main Austronesian presence in Madagascar that started around the first millennium CE (Dahl 1951, 1991; Dewar and Wright 1993; Adelaar 1995; Cox et al. 2012; Adelaar forthcoming). On the other hand, around 1100-700 years BP, climatic changes in the South of Africa forced Bantu populations to move to more hospitable places (Huffman 2000). This South Bantu migration has previously been suggested as an explanation for the higher density of populations observed in the South of Madagascar (Beaujard 2012a). As all of our sampled groups live in the South of Madagascar, and considering that the estimated dates of admixture are more recent on the west coast (Supplementary tables S5 and S6, Supplementary Material online), it is tempting to interpret our admixture date as marking the last significant Bantu migration to Madagascar, perhaps initiated by climatic changes in Africa.Suffice it to say that the analysis of the African side of the genetic contribution is shallow and does not rigorously compare competing hypotheses of African contributions.
The Supplemental Materials indicate that the African samples other than South African Bantu come from International HapMap, et al. (2010) (i.e. Integrating common and rare genetic variation in diverse human populations. Nature 467: 52-58. doi: 10.1038/nature09298) and Pagani, et al. (2012) (i.e. Ethiopian genetic diversity reveals linguistic stratification and complex influences on the Ethiopian gene pool. Am J Hum Genet 91: 83-96. doi: 10.1016/j.ajhg.2012.05.015). The South African Bantu sample comes from May, et al. (2013) (Genetic diversity in black South Africans from Soweto. BMC Genomics 14: 644. doi: 10.1186/1471-2164-14-644).
Another data set of Southeastern Bantu speakers referenced in May, et al. (2013) seems to overlap with the Soweto sample and derives from Schlebusch, et al., "Genomic variation in seven Khoe-San groups reveals adaptation and complex African history." Science. 2012, 338: 374-379.
It is also possible that Soweto Bantus are very genetically distinct from Mozambique Bantus and may be more similar to ancestral East African Bantus than modern East African Bantus, because they may lack subsequent Nilo-Saharan Ancestry and may, in general have less of a substrate influence.
Brucatol, et al., "Malagasy genetic ancestry comes from an historical Malay trading post in Southeast Borneo." 33 (7) Molecular Biology and Evolution (July 5, 2016).Malagasy genetic diversity results from an exceptional proto-globalisation process that took place over a thousand years ago across the Indian Ocean. Previous efforts to locate the Asian origin of Malagasy highlighted Borneo broadly as a potential source, but so far no firm source populations were identified. Here, we have generated genome-wide data from two Southeast Borneo populations, the Banjar and the Ngaju, together with published data from populations across the Indian Ocean region. We find strong support for an origin of the Asian ancestry of Malagasy among the Banjar. This group emerged from the long-standing presence of a Malay Empire trading post in Southeast Borneo, which favoured admixture between the Malay and an autochthonous Borneo group, the Ma’anyan. Reconciling genetic, historical and linguistic data, we show that the Banjar, in Malay-led voyages, were the most probable Asian source among the analysed groups in the founding of the Malagasy gene pool.
The literature cited is as follows (and admittedly includes some other papers I haven't yet seen):
* Adelaar A. 2009a. Towards an Integrated Theory about the lndonesian Migrations to Madagascar. In. Ancient human migrations: a multidisciplinary approach.: University of Utah Press
* Adelaar KA. 1995. Borneo as a cross-roads for comparative Austronesian linguistics. In: Canberra AAEP, editor. The Austronesians: historical and comparative perspectives. p. 81–102.
* Adelaar KA. 2009b. Loanwords in Malagasy. In: Haspelmath M, Tadmor U, editors. Loanwords in the world’s languages: a comparative handbook. Berlin, Germany: De Gruyter Mouton. p. 717-746.
* Adelaar KA 1989. Malay influence on Malagasy: linguistic and culture-historical implications. Oceanic Linguistics 28: 1-46. doi: 10.2307/3622973
* Adelaar KA. forthcoming. Who were the first Malagasy, and what did they speak? In: Acri A, Landmann A, editors. Cultural Transfer in Early Monsoon Asia. Singapore: Institute of Southeast Asian Studies.
* Alexander DH, Novembre J, Lange K 2009. Fast model-based estimation of ancestry in unrelated individuals. Genome Research 19: 1655-1664. doi: 10.1101/gr.094052.109 by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from Beaujard P. 2012a. Les mondes de l’ocean indien. Vol. 2 : L’océan Indien, au cœur des globalisations de l'Ancien Monde (7e-15e siècles). Paris, France: Armand Collin. Beaujard P. 2012b. Les mondes de l’océan Indien. Vol. 1 : De la formation de l’État au premier système-monde afro-eurasien (4e millénaire av. J.-C.-6e siècle apr. J.-C.). Paris, France:
* Armand Collin. Brisbin A, Bryc K, Byrnes J, Zakharia F, Omberg L, Degenhardt J, Reynolds A, Ostrer H, Mezey JG, Bustamante CD 2012. PCAdmix: Principal componentsbased assignment of ancestry along each chromosome in individuals with admixed ancestry from two or more populations. Human Biology 84: 343-364. doi: 10.3378/027.084.0401
* Capredon M, Brucato N, Tonasso L, Choesmel-Cadamuro V, Ricaut F-X, Razafindrazaka H, Rakotondrabe AB, Ratolojanahary MA, Randriamarolaza L-P, Champion B, Dugoujon J-M 2013. Tracing arab-islamic inheritance in Madagascar: Study of the Y-chromosome and mitochondrial DNA in the Antemoro. PLoS One 8: e80932. doi: 10.1371/journal.pone.0080932
* Cox MP, Nelson MG, Tumonggor MK, Ricaut F-X, Sudoyo H 2012. A small cohort of Island Southeast Asian women founded Madagascar. Proceedings of the Royal Society B: Biological Sciences 279: 2761-2768. doi: 10.1098/rspb.2012.0012
* Dahl OC 1951. Malgache et maanjan: une comparaison linguistique. Oslo, Norway: Edege-Intituttet.
* Dahl OC 1991. Migration from Kalimantan to Madagascar. Oslo, Norway: Norwegian University Press : Institute for Comparative Research in Human Culture.
* Dewar RE, Wright HT 1993. The culture history of Madagascar. Journal of World Prehistory 7: 417-466. doi: 10.1007/BF00997802 by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from Fourquet R, Sarthou J, Roux J, Aori K 1974. Hemoglobine S et origines du peuplement de Madagascar: nouvelle hypothese sur son introduction en Afrique [Hemoglobin S and origins for the settlement of Madagascar: new hypothesis on its introduction to Africa]. Arch. Inst. Pasteur Madagascar 43: 185–220.
* Fuller DQ, Boivin N, Hoogervorst T, Allaby R 2011. Across the Indian Ocean: the prehistoric movement of plants and animals. Antiquity 85: 544-558.
* Hellenthal G, Busby GB, Band G, Wilson JF, Capelli C, Falush D, Myers S 2014. A genetic atlas of human admixture history. Science 343: 747-751. doi: 10.1126/science.1243518
* Hewitt R, Krause A, Goldman A, Campbell G, Jenkins T 1996. beta-globin haplotype analysis suggests that a major source of Malagasy ancestry is derived from Bantu-speaking Negroids. Am. J. Hum. Genet. 58: 1303–1308.
* Huffman TN. 2000. Mapungubwe and the origins of the Zimbabwe culture. In: Leslie M, Maggs T, editors. African naissance: The Limpopo valley 1000 years ago. Cape Town, South Africa: South African Archaeological Society. p. 14-29.
* Hurles ME, Sykes BC, Jobling MA, Forster P 2005. The dual origin of the Malagasy in Island Southeast Asia and East Africa: evidence from maternal and paternal lineages. Am J Hum Genet 76: 894-901.
* Kusuma P, Brucato N, Cox MP, Pierron D, Razafindrazaka H, Adelaar A, Sudoyo H, Letellier T, Ricaut F-X 2016. Contrasting Linguistic and Genetic Influences during the Austronesian Settlement of Madagascar. Scientific Reports 6:26066. doi: doi: 10.1038/srep26066
* Kusuma P, Cox MP, Pierron D, Razafindrazaka H, Brucato N, Tonasso L, Suryadi HL, Letellier T, Sudoyo H, Ricaut F-X 2015. Mitochondrial DNA and the Y by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from chromosome suggest the settlement of Madagascar by Indonesian sea nomad populations. BMC Genomics 16: 191. doi: 10.1186/s12864-015-1394-7
* Lawler A 2014. Sailing Sinbad's seas. Science 344: 1440-1445. doi: 10.1126/science.344.6191.1440
* Lawson DJ, Hellenthal G, Myers S, Falush D 2012. Inference of population structure using dense haplotype data. PLoS Genet 8: e1002453. doi: 10.1371/journal.pgen.1002453
* Loh PR, Lipson M, Patterson N, Moorjani P, Pickrell JK, Reich D, Berger B 2013. Inferring admixture histories of human populations using linkage disequilibrium. Genetics 193: 1233-1254. doi: 10.1534/genetics.112.147330
* Patterson N, Price AL, Reich D 2006. Population structure and eigenanalysis. PLoS Genet 2: e190. doi: 10.1371/journal.pgen.0020190
* Patterson NJ, Moorjani P, Luo Y, Mallick S, Rohland N, Zhan Y, Genschoreck T, Webster T, Reich D 2012. Ancient admixture in human history. Genetics 192: 1065-1093. doi: 10.1534/genetics.112.145037
* Pickrell JK, Pritchard JK 2012. Inference of population splits and mixtures from genome-wide allele frequency data. PLoS Genet 8: e1002967. doi: 10.1371/journal.pgen.1002967
* Pierron D, Razafindrazaka H, Pagani L, Ricaut F-X, Antao T, Capredon M, Sambo C, Radimilahy C, Rakotoarisoa J-A, Blench RM, Letellier T, Kivisild T 2014. Genome-wide evidence of Austronesian–Bantu admixture and cultural reversion in a hunter-gatherer group of Madagascar. Proceedings of the National Academy of Sciences 111: 936-941. doi: 10.1073/pnas.1321860111
* Ras JJ. 1968. Hikajat Banjar: a study in Malay historiography. The Hague: Martinus Nijhoff. by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from Serva M, Petroni F, Volchenkov D, Wichmann Sr 2012. Malagasy dialects and the peopling of Madagascar. Journal of the Royal Society Interface 9: 54-67. doi: 10.1098/rsif.2011.0228
* Soodyall H, Jenkins T, Hewitt R, Krause A, Stoneking M. 1996. The peopling of Madagascar. In: Boyce A, Mascie-Taylor C, editors. Molecular biology and human diversity. Cambridge, UK: Cambridge University Press. p. 156–170.
* Tofanelli S, Bertoncini S, Castri L, Luiselli D, Calafell F, Donati G, Paoli G 2009. On the origins and admixture of Malagasy: new evidence from high-resolution analyses of paternal and maternal lineages. Mol Biol Evol 26: 2109-2124.
Thursday, July 7, 2016
Evidence Increasingly Rules Out Light Sterile Neutrino Hypothesis
The Standard Model of Particle Physics includes three flavors of neutrinos - electron neutrinos, muon neutrinos and tau neutrinos, so named because particle physicists weren't feeling particularly creative when they were hypothesized (and ultimately discovered).
There needs to be a neutrino counterpart to each charged lepton to preserve the approximate lepton flavor conservation symmetry of the theory (neutrino oscillation prevents it from being a perfectly conserved symmetry), and weak force boson decays have long confirmed that there are three flavors of weakly interacting neutrinos, so three flavors of neutrinos are necessary to make electroweak theory conform to observation.
Anomalies in reactor neutrino data had suggested the possibility of a fourth light neutrino that oscillates with the three ordinary neutrinos, but do not interact via the weak force.
The cosmologically measured constant Neff (effective N) for the number of neutrino flavors increasingly disfavors a fourth type of neutrino that the existing three flavors oscillate with (but which does not interact via the weak force). So do new cosmological data bounds on the sum of the mass of all neutrino flavors because the difference between the maximum value of the sum of the masses of the three neutrino flavors and the minimum value derived from the differences in mass between the three primary neutrino mass states is increasingly small, placing an upper bound on the mass of any fourth sterile neutrino.
(Note, however, that the cosmology purposes, a neutrino with a mass far in excess of 1 eV/c^2 such as a sterile neutrino with a mass on the order of a keV, which has been proposed as a dark matter candidate, is outside the cosmology definition of a neutrino. The cosmology definition is largely synonymous with the definition of "hot dark matter", rather than using the usual Standard Model definition.)
This year's Neutrino 2016 Conference has produced three papers all documenting new experimental findings the strongly disfavor the kind of sterile neutrino that is light enough and mixed enough with the other three neutrino flavors to explain the apparent reactor neutrino anomalies that had prompted the light sterile neutrino hypothesis. One of the papers setting for the new experimental limits is based on data from the Daya Bay experiment, one is based on MINOS data, and one combines data from the Daya Bay, MINOS and Bugey-3 experiments to obtain a global exclusion based upon the latest data.
Taken together, the cosmology and earth based experimental exclusions provide a strong and robust exclusion of the light sterile neutrino hypothesis in all circumstances in which any other evidence might have suggested it in the first place (and the reactor anomaly itself have also grown less acute as more data and analysis have examined it).
Also, the titles and abstracts of the papers on neutrinoless double beta decay this year make clear that nobody has credibly observed neutrinoless double beta decay yet experimentally, so the experimental minimum bound on the potential mean time frame of neutrinoless double beta decay continues to get incrementally longer from the last time this data was reported. No instances of lepton number violation have been observed in any other context either.
There needs to be a neutrino counterpart to each charged lepton to preserve the approximate lepton flavor conservation symmetry of the theory (neutrino oscillation prevents it from being a perfectly conserved symmetry), and weak force boson decays have long confirmed that there are three flavors of weakly interacting neutrinos, so three flavors of neutrinos are necessary to make electroweak theory conform to observation.
Anomalies in reactor neutrino data had suggested the possibility of a fourth light neutrino that oscillates with the three ordinary neutrinos, but do not interact via the weak force.
The cosmologically measured constant Neff (effective N) for the number of neutrino flavors increasingly disfavors a fourth type of neutrino that the existing three flavors oscillate with (but which does not interact via the weak force). So do new cosmological data bounds on the sum of the mass of all neutrino flavors because the difference between the maximum value of the sum of the masses of the three neutrino flavors and the minimum value derived from the differences in mass between the three primary neutrino mass states is increasingly small, placing an upper bound on the mass of any fourth sterile neutrino.
(Note, however, that the cosmology purposes, a neutrino with a mass far in excess of 1 eV/c^2 such as a sterile neutrino with a mass on the order of a keV, which has been proposed as a dark matter candidate, is outside the cosmology definition of a neutrino. The cosmology definition is largely synonymous with the definition of "hot dark matter", rather than using the usual Standard Model definition.)
This year's Neutrino 2016 Conference has produced three papers all documenting new experimental findings the strongly disfavor the kind of sterile neutrino that is light enough and mixed enough with the other three neutrino flavors to explain the apparent reactor neutrino anomalies that had prompted the light sterile neutrino hypothesis. One of the papers setting for the new experimental limits is based on data from the Daya Bay experiment, one is based on MINOS data, and one combines data from the Daya Bay, MINOS and Bugey-3 experiments to obtain a global exclusion based upon the latest data.
Taken together, the cosmology and earth based experimental exclusions provide a strong and robust exclusion of the light sterile neutrino hypothesis in all circumstances in which any other evidence might have suggested it in the first place (and the reactor anomaly itself have also grown less acute as more data and analysis have examined it).
Also, the titles and abstracts of the papers on neutrinoless double beta decay this year make clear that nobody has credibly observed neutrinoless double beta decay yet experimentally, so the experimental minimum bound on the potential mean time frame of neutrinoless double beta decay continues to get incrementally longer from the last time this data was reported. No instances of lepton number violation have been observed in any other context either.
Gravitationally Bound Composite Neutrino Structures?
The following abstract describes a poster presentation at the Neutrino 2016 Conference that is currently in progress (July 4-9) in South Kensington, England:
Boya and Rivera have reviewed a number of similar theories.
Poster session 3 – Wednesday 6 July
P3.037 Gravitationally confined relativistic neutrinos
C Vayenas1,2, A Fokas3,4 and D Grigoriou1
1University of Patras, Greece, 2Division of Natural Sciences, Greece, 3University of Cambridge, UK, 4University of Southern California, USA
Combining special relativity, the equivalence principle and Newton’s universal gravitational law with gravitational rather than rest masses, one computes that gravitational interactions between relativistic neutrinos with kinetic energies above 10 MeV are very strong and can lead to formation of gravitationally confined composite structures. One may model the formation of such composite structures by considering three neutrinos moving symmetrically on a circular orbit under the influence of their gravitational attraction, and by assuming quantization of their angular momentum, as in the Bohr model of the H atom. The model contains no adjustable parameters and its solution leads to composite state radii close to 1 fm and neutrino velocities so close to c, that the corresponding Lorentz factor, gamma, values are of the order of 5*109.
It is thus found that when the neutrino rest masses are of the order of 0.05 eV/c2, then the mass, 3(gamma)mo, of such three rotating neutrinos structures is very similar to that of hadrons (~ 1 GeV/c2). The thermodynamics of the phase condensation of neutrinos to form such structures are compared with QCD calculations for the quark-gluon condensation temperature.The W boson coincidence is particularly interesting. Another interesting poster considers a possible gravitational source for neutrino mass.
Using the same approach we find that the mass of relativistic rotating Ve – e+/- pairs is 81 GeV/c2, close to that of W+/-bosons.
Boya and Rivera have reviewed a number of similar theories.