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  • richardmitnick 3:36 pm on February 16, 2018 Permalink | Reply
    Tags: , , , , , , , Dark Matter, European backed missions,   

    From CERN Courier: “Europe defines astroparticle strategy” 


    CERN Courier

    Feb 16, 2018

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    Multi-messenger astronomy, neutrino physics and dark matter are among several topics in astroparticle physics set to take priority in Europe in the coming years, according to a report by the Astroparticle Physics European Consortium (APPEC).

    The APPEC strategy for 2017–2026, launched at an event in Brussels on 9 January, is the culmination of two years of consultation with the astroparticle and related communities. It involved some 20 agencies in 16 countries and includes representation from the European Committee for Future Accelerators, CERN and the European Southern Observatory (ESO).

    Lying at the intersection of astronomy, particle physics and cosmology, astroparticle physics is well placed to search for signs of physics beyond the standard models of particle physics and cosmology. As a relatively new field, however, European astroparticle physics does not have dedicated intergovernmental organisations such as CERN or ESO to help drive it. In 2001, European scientific agencies founded APPEC to promote cooperation and coordination, and specifically to formulate a strategy for the field.

    Building on earlier strategies released in 2008 and 2011, APPEC’s latest roadmap presents 21 recommendations spanning scientific issues, organisational aspects and societal factors such as education and industry, helping Europe to exploit tantalising potential for new discoveries in the field.

    The recent detection of gravitational waves from the merger of two neutron stars (CERN Courier December 2017 p16) opens a new line of exploration based on the complementary power of charged cosmic rays, electromagnetic waves, neutrinos and gravitational waves for the study of extreme events such as supernovae, black-hole mergers and the Big Bang itself. “We need to look at cross-fertilisation between these modes to maximise the investment in facilities,” says APPEC chair Antonio Masiero of the INFN and the University of Padova. “This is really going to become big.”

    APPEC strongly supports Europe’s next-generation ground-based gravitational interferometer, the Einstein Telescope, and the space-based LISA detector.

    ASPERA Einstein Telescope

    ESA/NASA eLISA space based the future of gravitational wave research

    In the neutrino sector, KM3NeT is being completed for high-energy cosmic neutrinos at its site in Sicily, as well as for precision studies of atmospheric neutrinos at its French site near Toulon.

    Artist’s expression of the KM3NeT neutrino telescope

    Europe is also heavily involved in the upgrade of the leading cosmic-ray facility the Pierre Auger Observatory in Argentina.

    Pierre Auger Observatory in the western Mendoza Province, Argentina, near the Andes, at an altitude of 1330 m–1620 m, average ~1400 m

    Significant R&D work is taking place at CERN’s neutrino platform for the benefit of long- and short-baseline neutrino experiments in Japan and the US (CERN Courier July/August 2016 p21), and Europe is host to several important neutrino experiments. Among them are KATRIN at KIT in Germany, which is about to begin measurements of the neutrino absolute mass scale, and experiments searching for neutrinoless double-beta decay (NDBD) such as GERDA and CUORE at INFN’s Gran Sasso National Laboratory (CERN Courier December 2017 p8).


    KIT Katrin experiment

    CUORE experiment UC Berkeley, experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS), a search for neutrinoless double beta decay

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    There are plans to join forces with experiments in the US to build the next generation of NDBD detectors. APPEC has a similar vision for dark matter, aiming to converge next year on plans for an “ultimate” 100-tonne scale detector based on xenon and argon via the DARWIN and Argo projects.

    DARWIN Dark Matter experiment

    APPEC also supports ESA’s Euclid mission, which will establish European leadership in dark-energy research, and encourages continued European participation in the US-led DES and LSST ground-based projects.

    Dark Energy Camera [DECam], built at FNAL


    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    Following from ESA’s successful Planck mission, APPEC strongly endorses a European-led satellite mission, such as COrE, to map the cosmic-microwave background and the consortium plans to enhance its interactions with its present observers ESO and CERN in areas of mutual interest.

    ESA/Planck

    “It is important at this time to put together the human forces,” says Masiero. “APPEC will exercise influence in the European Strategy for Particle Physics, and has a significant role to play in the next European Commission Framework Project, FP9.”

    A substantial investment is needed to build the next generation of astroparticle-physics research, the report concedes. According to Masiero, European agencies within APPEC currently invest around €80 million per year in astroparticle-related activities, in addition to funding large research infrastructures. A major effort in Europe is necessary for it to keep its leading position. “Many young people are drawn into science by challenges like dark matter and, together with Europe’s existing research infrastructures in the field, we have a high technological level and are pushing industries to develop new technologies,” continues Masiero. “There are great opportunities ahead in European astroparticle physics.”

    See the full article here .

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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
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    CERN LHC particles

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  • richardmitnick 8:29 am on February 9, 2018 Permalink | Reply
    Tags: , , , , Dark Matter,   

    From Rutgers va COSMOS: “Do massive dark matter “nuggets” lurk in our galaxy?” 

    Rutgers University
    Rutgers University

    1

    COSMOS

    09 February 2018
    Richard A Lovett

    1
    If dark matter particles can cool down sufficiently, they could coalesce into dark planets many times larger than the sun. VICTOR HABBICK VISIONS/SCIENCE PHOTO LIBRARY/Getty Images.

    When astrophysicists talk about dark matter – a mysterious substance that comprises 80% of the universe’s total mass – they are generally thinking in terms of vast clouds of particles extending like halos from the normal matter concentrated at the heart of galaxies.

    But does dark matter exist solely in this tenuous form, or can it condense into denser structures, analogous to those formed by normal matter?

    Matthew Buckley, a theoretical astrophysicist at Rutgers University in New Brunswick, New Jersey, US, thinks such structures are theoretically possible. Within the next few years, he suggests, it might even be possible to detect them in our own galaxy via their gravitational effects.

    Not that he’s going so far as to say there might be dark-matter planets, suns, or even people – fascinating as that might be to a science fiction fan. What he’s looking for are larger structures, with masses of one million to 100 million times that of the sun. (Since our galaxy contains about a trillion suns worth of dark matter, there could easily be many of these objects around … if they exist at all.)

    On first impression, it seems an obvious idea. After all, if normal matter can condense into the gas and dust clouds that eventually form into planets, moons, suns, rocks, poodles, and people, why can’t dark matter do the same?

    It turns out not to be as simple as that, Buckley says. For dark matter to condense in this manner, he says, there has to be a way for the particles to lose energy, or “cool”, as they fall toward each other. Otherwise, they just whizz past too quickly to clump together and head off on their own ways again, like ships in the night.

    For ordinary matter, Buckley says, the thing that slows them down is the emission of electromagnetic radiation. This bleeds off energy, gradually slowing the particles’ motion by enough to allow them to clump together.

    Initially, Buckley says, he thought this was impossible for dark matter, but in a 2009 paper in the journal Physical Review D, he was part of team that calculated the theoretical feasibility of “dark radiation” that would serve the same function for dark matter.

    But scientists know that the giant dark matter halos surrounding large galaxies can’t collapse in this matter. If they could, they would have done so long ago and would no longer exist.

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Buckley’s newest realisation, described in a paper currently posted on the pre-print server arXiv, [Phys. Rev. Lett] was that this didn’t mean smaller blobs of dark matter couldn’t condense. “If you fiddle with the parameters,” he says, “you can make it so smaller halos cool and big ones don’t.”

    What this means is that there might be “nuggets” of dark matter floating through a haze of dark matter – not just in the dark matter halo, but within the portions of the galaxy where we live.

    How large these “nuggets” might be is an open question, based on such key factors as the masses of the dark-matter equivalents of electrons and protons, and the strength of their interaction with dark radiation. But by fiddling with these parameters, Buckley says, it’s possible to create a model in which million-stellar-mass blobs of dark matter condense, while the sprawling trillion-solar-mass halo of the entire galaxy does not.

    Buckley notes that to date, his dark matter model is very simple – far less complex than our understanding of normal matter’s sub-atomic world.

    “It’s fun to build really complicated models,” he says, “but until I have a hint that this is how dark matter works, then spending time writing increasingly baroque models for it is maybe not the best use of my time.”

    He also chose parameters to produce objects in the size range of 100 million solar masses to one million solar masses. In this case, the reason is simple: that’s a size range in which their gravitational effects should soon be detectable with the European Space Agency’s Gaia space telescope.

    ESA/GAIA satellite

    That telescope is currently in the process of a five to nine year mission to monitor the movements of a billion stars. Once the data is in, one of the things it should be able to show are loosely paired binary stars: pairs that orbit each other but are so far apart that the gravitational forces between them are barely strong enough to hold them together.

    If dark matter objects of the size Buckley is looking for exist, they would have enough gravity that chance encounters with them should long ago have yanked apart most of these loose binaries. Thus, by looking at how many loose binary pairs exist, he says, it should be possible to put an upper bound on the number of dark matter objects roaming the galaxy.

    Even if such objects prove not to exist, he says, it would be a useful find because it would rule out one form that dark matter could take.

    “We’ve known about dark matter for a long time,” Buckley says, but “we still don’t really know what it is.

    “I wrote down this model. I don’t know whether it’s true or false, but I believe I will be able to answer that question in the near future.”

    Brad Tucker, an astrophysicist-cosmologist at Australian National University who was not part of Buckley’s study team, is impressed.

    “I like this paper,” he says. “It’s particularly interesting that this was done with a ‘vanilla/basic’ model of dark matter particle physics.”

    With a more complex model, he says, “you can get even smaller or different effects.”

    He also agrees that Gaia is a perfect instrument for testing the theory. The best way to detect such dark matter objects he says, “is to see how they gravitationally influence small-scale objects such clusters, stars, and so on”.

    “The precision of Gaia means now this is possible,” he adds.

    See the full article here .

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  • richardmitnick 6:56 am on January 30, 2018 Permalink | Reply
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    From SciNews: “Clumps of dark matter could be lurking undetected in our galaxy” 


    ScienceNews

    January 26, 2018
    Emily Conover

    A hypothetical ‘dark’ force could allow clouds of invisible particles to collapse into small structures.

    1
    ESO/ L. Calçada (CC BY 4.0)

    Clumps of dark matter may be sailing through the Milky Way and other galaxies.

    Typically thought to form featureless blobs surrounding entire galaxies, dark matter could also collapse into smaller clumps — similar to normal matter condensing into stars and planets — a new study proposes. Thousands of collapsed dark clumps could constitute 10 percent of the Milky Way’s dark matter, researchers from Rutgers University in Piscataway, N.J., report in a paper accepted in Physical Review Letters.

    Dark matter is necessary to explain the motions of stars in galaxies. Without an extra source of mass, astronomers can’t explain why stars move at the speeds they do. Such observations suggest that a spherical “halo” of invisible, unidentified massive particles surrounds each galaxy.

    But the halo might be only part of the story. “We don’t really know what dark matter at smaller scales is doing,” says theoretical physicist Matthew Buckley, who coauthored the study with physicist Anthony DiFranzo. More complex structures might be hiding within the halo.

    To collapse, dark matter would need a way to lose energy, slowing particles as gravity pulls them into the center of the clump, so they can glom on to one another rather than zipping right through. In normal matter, this energy loss occurs via electromagnetic interactions. But the most commonly proposed type of dark matter particles, weakly interacting massive particles, or WIMPs, have no such way to lose energy.

    Buckley and DiFranzo imagined what might happen if an analogous “dark electromagnetism” allowed dark matter particles to interact and radiate energy. The researchers considered how dark matter would behave if it were like a pared-down version of normal matter, composed of two types of charged particles — a dark proton and a dark electron. Those particles could interact — forming dark atoms, for example — and radiate energy in the form of dark photons, a dark matter analog to particles of light.

    The researchers found that small clouds of such dark matter could collapse, but larger clouds, the mass of the Milky Way, for example, couldn’t — they have too much energy to get rid of. This finding means that the Milky Way could harbor a vast halo, with a sprinkling of dark matter clumps within. By picking particular masses for the hypothetical particles, the researchers were able to calculate the number and sizes of clumps that could be floating through the Milky Way. Varying the choice of masses led to different levels of clumpiness.

    In Buckley and DiFranzo’s scenario, the dark matter can’t squish down to the size of a star. Before the clumps get that small, they reach a point where they can’t lose any more energy. So a single clump might be hundreds of light-years across.

    The result, says theoretical astrophysicist Dan Hooper of Fermilab in Batavia, Ill., is “interesting and novel … but it also leaves a lot of open questions.” Without knowing more about dark matter, it’s hard to predict what kind of clumps it might actually form.

    Scientists have looked for the gravitational effects of unidentified, star-sized objects, which could be made either of normal matter or dark matter, known as massive compact halo objects, or MACHOs. But such objects turned out to be too rare to make up a significant fraction of dark matter. On the other hand, says Hooper, “what if these things collapse to solar system‒sized objects?” Such larger clumps haven’t have been ruled out yet.

    By looking for the effects of unexplained gravitational tugs on stars, scientists may be able to determine whether galaxies are littered with dark matter clumps. “Because we didn’t think these things were a possibility, I don’t think people have looked,” Buckley says. “It was a blind spot.”

    Up until now, most scientists have focused on WIMPs. But after decades of searching in sophisticated detectors, there’s no sign of the particles (SN: 11/12/16, p. 14). As a result, says theoretical physicist Hai-Bo Yu of the University of California, Riverside, “there’s a movement in the community.” Scientists are now exploring new ideas for what dark matter might be.

    See the full article here .

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  • richardmitnick 3:41 pm on January 22, 2018 Permalink | Reply
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    From CfA: “A New Bound on Axions” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    January 19, 2018

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    A composite image of M87 in the X-ray from Chandra (blue) and in radio emission from the Very Large Array (red-orange). Astronomers used the X-ray emission from M87 to constrain the properties of axions, putative particles suggested as dark matter candidates. X-ray NASA/CXC/KIPAC/N. Werner, E. Million et al.; Radio NRAO/AUI/NSF/F. Owen.

    NASA/Chandra Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    An axion is a hypothetical elementary particle whose existence was postulated in order to explain why certain subatomic reactions appear to violate basic symmetry constraints, in particular symmetry in time. The 1980 Nobel Prize in Physics went for the discovery of time-asymmetric reactions. Meanwhile, during the following decades, astronomers studying the motions of galaxies and the character of the cosmic microwave background [CMB] radiation came to realize that most of the matter in the universe was not visible.

    CMB per ESA/Planck

    Cosmic Background Radiation per Planck

    ESA/Planck

    It was dubbed dark matter, and today’s best measurements find that about 84% of matter in the cosmos is dark. This component is dark not only because it does not emit light — it is not composed of atoms or their usual constituents, like electrons and protons, and its nature is mysterious. Axions have been suggested as one possible solution. Particle physicists, however, have so far not been able to detect directly axions, leaving their existence in doubt and reinvigorating the puzzles they were supposed to resolve.

    CfA astronomer Paul Nulsen and his colleagues used a novel method to investigate the nature of axions. Quantum mechanics constrain axions, if they exist, to interact with light in the presence of a magnetic field. As they propagate along a strong field, axions and photons should transmute from one to the other other in an oscillatory manner. Because the strength of any possible effect depends in part on the energy of the photons, the astronomers used the Chandra X-ray Observatory to monitor bright X-ray emission from galaxies. They observed X-rays from the nucleus of the galaxy Messier 87, which is known to have strong magnetic fields, and which (at a distance of only fifty-three million light-years) is close enough to enable precise measurements of variations in the X-ray flux. Moreover, Me3ssier 87 lies in a cluster of galaxies, the Virgo cluster, which should insure the magnetic fields extend over very large scales and also facilitate the interpretation. Not least, Messier 87 has been carefully studied for decades and its properties are relatively well known.

    The search did not find the signature of axions. It does, however, set an important new limit on the strength of the coupling between axions and photons, and is able to rule out a substantial fraction of the possible future experiments that might be undertaken to detect axions. The scientists note that their research highlights the power of X-ray astronomy to probe some basic issues in particle physics, and point to complementary research activities that can be undertaken on other bright X-ray emitting galaxies.

    Science paper:
    A New Bound on Axion-Like Particles, Journal of Cosmology and Astroparticle Physics.

    See the full article here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 9:41 am on January 17, 2018 Permalink | Reply
    Tags: , , , , Dark Matter, , Newsweek, ,   

    From Interactions.org via Newsweek: “What Is Dark Matter Day? Scientists Launch First-Ever Event Celebrating Universe’s Biggest Mystery” 

    Interactions.org

    1

    Newsweek

    10/30/17 [Well hidden]
    Hannah Osborne

    As the rest of the world marks Halloween, scientists from across the globe will be celebrating something far more eerie—dark matter.

    This October 31 marks the inaugural Dark Matter Day, an event launched by Interactions Collaboration, a group of particle physics communication specialists hoping to raise awareness about the elusive substance and the experiments currently taking place to find and understand it.

    Scientific institutions around the world, including CERN, the European Organization for Nuclear Research, London’s Royal Astronomical Society, as well as institutions across the U.S., are holding events in honor of the day.

    What is dark matter?

    2
    The Milky Way galaxy. NASA/ESA Hubble

    Normal matter—the stuff that makes up everything we can see in the universe, like stars and planets, makes up just 5 percent of the universe. Most of the universe—about 68 percent—is dark energy, the unseen force thought to be driving the expansion of the universe. The rest, around 27 percent, is dark matter.

    Our knowledge of dark matter dates back to the 19th century, when astronomers started noticing inconsistences in what they were seeing versus what should be there. Dutch astronomer Joacobus Kapteyn first suggested the existence of “dark matter” in the 1920s, and in the decades that followed more scientists began to give weight to the idea of the universe’s unseen matter.

    We now know that dark matter exists because of the gravitational influence it has on galaxies. Galaxies, including our own Milky Way, rotate. Dark matter slows this rotation—if it wasn’t there, they would spin themselves into oblivion.

    However, attempts to observe dark matter have proven futile. It is, by nature, dark, meaning we cannot see it—it does not absorb, reflect or emit light. Understanding what dark matter is made of would help scientists answer fundamental questions about the universe.

    What are scientists doing to find dark matter?


    One half hour

    Experiments are currently underway in locations across the globe to try to trace dark matter. These normally involve detectors buried deep underground, where interactions from outside influences are limited.

    This includes the IceCube Neutrino Observatory in Antarctica, where scientists look for dark matter by detecting neutrinos—cosmic particles that only interact with weak subatomic force and gravity.


    IceCube Gen-2 DeepCore


    U Wisconsin ICECUBE neutrino detector at the South Pole

    One of the main hypotheses in the hunt for dark matter is that it is made of weakly interacting massive particles (WIMPs). These hypothetical particles interact via gravity and forces that are not currently part of the standard model of particle physics. Scientists think that with a high enough density, WIMPs would annihilate each other and decay into neutrinos. Evidence of this is yet to be found, however.

    What would discovering dark matter mean?

    3
    Artist impression of a black hole. NASA/SOFIA/Lynette Cook

    Understanding the nature of dark matter would help scientists fill out the standard model—it would provide a major piece of the jigsaw puzzle that is the universe we live in. By getting a handle on dark matter, we would be able to start answering other unanswered questions, like what happened just after the Big Bang, and how the universe came to be as it is today. One controversial theory has even linked dark matter to black holes.

    As the organizers at Interactions Collaboration explain: “Dark matter is the glue that holds galaxies together, but we don’t know what it is. Understanding its true nature could explain its origins, evolution, and overall structure in the universe.”

    See the full article here .

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  • richardmitnick 2:52 pm on January 16, 2018 Permalink | Reply
    Tags: , , Dark Matter, , , , , , The Dark Sector   

    From Symmetry: “Voyage into the dark sector” 

    Symmetry Mag

    Symmetry

    01/16/18
    Sarah Charley

    1
    Artwork by Sandbox Studio, Chicago with Ana Kova

    A hidden world of particles awaits. [We hope!]

    We don’t need extra dimensions or parallel universes to have an alternate reality superimposed right on top of our own. Invisible matter is everywhere.

    For example, take neutrinos generated by the sun, says Jessie Shelton, a theorist at the University of Illinois at Urbana-Champaign who works on dark sector physics. “We are constantly bombarded with neutrinos, but they pass right through us. They share the same space as our atoms but almost never interact.”

    As far as scientists can tell, neutrinos are solitary particles. But what if there is a whole world of particles that interact with one another but not with ordinary atoms? This is the idea behind the dark sector: a theoretical world of matter existing alongside our own but invisible to the detectors we use to study the particles we know.

    “Dark sectors are, by their very definition, built out of particles that don’t interact strongly with the Standard Model,” Shelton says.

    The Standard Model is a physicist’s field guide to the 17 particles and forces that make up all visible matter.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Standard Model of Particle Physics from Symmetry Magazine

    It explains how atoms can form and why the sun shines. But it cannot explain gravity, the cosmic imbalance of matter and antimatter, or the disparate strengths of nature’s four forces.

    CERN ALPHA Antimatter Factory

    On its own, an invisible world of dark sector particles cannot solve all these problems. But it certainly helps.

    2
    Artwork by Sandbox Studio, Chicago with Ana Kova

    The main selling point for the dark sector is that the theories comprehensively confront the problem of dark matter. Dark matter is a term physicists coined to explain bizarre gravitational effects they observe in the cosmos. Distant starlight appears to bend around invisible objects as it traverses the cosmos, and galaxies spin as if they had five times more mass than their visible matter can explain. Even the ancient light preserved in cosmic microwave background seems to suggest that there is an invisible scaffolding on which galaxies are formed.

    Some theories suggest that dark matter is simple cosmic debris that adds mass—but little else—to the complexity of our cosmos. But after decades of searching, physicists have yet to find dark matter in a laboratory experiment. Maybe the reason scientists haven’t been able to detect it is that they’ve been underestimating it.

    “There is no particular reason to expect that whatever is going on in the dark sector has to be as simple as our most minimal models,” Shelton says. “After all, we know that our visible world has a lot of rich physics: Photons, electrons, protons, nuclei and neutrinos are all critically important for understanding the cosmology of how we got here. The dark sector could be a busy place as well.”

    According to Shelton, dark matter could be the only surviving particle out of a similarly complicated set of dark particles.

    “It could even be something like the proton, a bound state of particles interacting via a very strong dark force. Or it could even be something like a hydrogen atom, a bound state of particles interacting via a weaker dark force,” she says.

    Even if terrestrial experiments cannot see these stable dark matter particles directly, they might be sensitive to other kinds of dark particles, such as dark photons or short-lived dark particles that interact strongly with the Higgs boson.

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

    “The Higgs is one of the easiest ways for the Standard Model particles to talk to the dark sector,” Shelton says.

    As far as scientists know, the Higgs boson is not picky. It may very well interact will all sorts of massive particles, including those invisible to ordinary atoms. If the Higgs boson interacts with massive dark sector particles, scientists should find that its properties deviate slightly from the Standard Model’s predictions. Scientists at the Large Hadron Collider are precisely measuring the properties of the Higgs boson to search for unexpected quirks that could open a gateway to new physics.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    At the same time, scientists are also using the LHC to search for dark sector particles directly. One theory is that at extremely high temperatures, dark matter and ordinary matter are not so different and can transform into one another through a dark force. In the hot and dense early universe, this would have been quite common.

    “But as the universe expanded and cooled, this interaction froze out, leaving some relic dark matter behind,” Shelton says.

    The energetic particle collisions generated by the LHC imitate the conditions that existed in the early universe and could unlock dark sector particles. If scientists are lucky, they might even catch dark sector particles metamorphosing into ordinary matter, an event that could materialize in the experimental data as particle tracks that suddenly appear from no apparent source.

    But there are also several feasible scenarios in which any interactions between the dark sector and our Standard Model particles are so tiny that they are out of reach of modern experiments, according to Shelton.

    “These ‘nightmare’ scenarios are completely logical possibilities, and in this case, we will have to think very carefully about astrophysical and cosmological ways to look for the footprints of dark particle physics,” she says.

    Even if the dark sector is inaccessible to particle detectors, dark matter will always be visible through the gravitational fingerprint it leaves on the cosmos.

    “Gravity tells us a lot about how much dark matter is in the universe and the kinds of particle interactions dark sector particles can and cannot have,” Shelton says. “For instance, more sensitive gravitational-wave experiments will give us the possibility to look back in time and see what our universe looked like at extremely high energies, and could maybe reveal more about this invisible matter living in our cosmos.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:43 pm on December 27, 2017 Permalink | Reply
    Tags: , , , , , Dark Matter, , , , Toothbrush Cluster   

    From CfA: “The Toothbrush Cluster” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    A multiwavelength false-color image of the “Toothbrush” cluster of galaxies, 1RXS J0603.3+4214. The intensity in red shows the radio emission, blue is X -ray, and the background color composite is optical emission. Astronomers studying the cluster with new radio observations combined with other wavelengths have been able to confirm the galaxy merger scenario and estimate the magnetic field strength in the shocks. van Weeren et al.

    Most galaxies lie in clusters containing from a few to thousands of objects. Our Milky Way, for example, belongs to a cluster of about fifty galaxies called the Local Group whose other large member is the Andromeda galaxy about 2.3 million light-years away.

    Local Group. Andrew Z. Colvin 3 March 2011

    Andromeda Galaxy Adam Evans

    Clusters are the most massive gravitationally bound objects in the universe and form (according to current ideas) in a “bottoms-up” fashion with smaller structures developing first and larger groupings assembling later in cosmic history. Dark matter plays an important role in this growth process.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Dark matter halo Image credit: Virgo consortium / A. Amblard / ESA

    Exactly how they grow, however, appears to depend on several competing physical processes including the behavior of the intracluster gas. There is more mass in this gas than there is in all the stars of a cluster’s galaxies, and the gas can have a temperature of ten million kelvin or even higher. As a result, the gas plays an important role in the cluster’s evolution. The hot intracluster gas contains rapidly moving charged particles that radiate strongly at radio wavelengths, sometimes revealing long filamentary structures.

    The “Toothbrush” galaxy cluster, 1RXS J0603.3+4214, hosts three of these radio structures as well as a large halo. The most prominent radio feature extends over more than six million light years, with three distinct components that resemble the brush and handle of a toothbrush. The handle is particularly enigmatic because, besides being large and very straight, it is off center from the axis of the cluster. The halo is thought to result from turbulence produced by the merger of galaxies, although some other possibilities have been suggested.

    CfA astronomers Reinout van Weeren, Bill Forman, Felipe Andrade-Santos, Ralph Kraft, and Christine Jones and their colleagues used the Very Large Array (VLA) facility to observe the relativistic particles in the cluster with precise, sensitive radio imaging, which they compared with Chandra X-ray and other datasets.

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    NASA/Chandra Telescope

    In the radio, the Toothbrush has a very narrow ridge, created by a huge shock resulting from the merger, and at least thirty-two previously undetected compact sources. The halo’s radio and X-ray morphologies are very similar and lend support to the merger scenario. Astronomers are also able to estimate the strength of the magnetic field, and combined with other results, use it to conclude that the merger scenario is most suitable.

    Reference(s):

    Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range 1-2 GHz, K. Rajpurohit, M. Hoeft, R. J. van Weeren, L. Rudnick, H. J. A. R ottgering, W. R. Forman, M. Bruggen, J. H. Croston, F. Andrade-Santos, W. A. Dawson, H. T. Intema, R. P. Kraft, C. Jones, and M. James Jee, http://lanl.arxiv.org/abs/1712.01327

    See the full article here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 2:56 pm on December 23, 2017 Permalink | Reply
    Tags: ADMX Axion Dark Matter Experiment at the University of Washington, , , Cosmic Axion Spin-Precession Experiment (CASPEr), Dark Matter, International Linear Collider in Japan, Large Underground Xenon (LUX) dark matter experiment, LBNL LZ project at SURF Lead SD USA, MACHOs, SIMPs, ,   

    From UC Berkeley: “MACHOs are Dead. WIMPs are a No-Show. Say Hello to SIMPs” 

    UC Berkeley

    UC Berkeley

    December 4, 2017
    Robert Sanders
    rlsanders@berkeley.edu

    The intensive, worldwide search for dark matter, the missing mass in the universe, has so far failed to find an abundance of dark, massive stars or scads of strange new weakly interacting particles, but a new candidate is slowly gaining followers and observational support.

    1
    Fundamental structures of a pion (left) and a proposed SIMP (strongly interacting massive particle). Pions are composed of an up quark and a down antiquark, with a gluon (g) holding them together. A SIMP would be composed of a quark and an antiquark held together by an unknown type of gluon (G). (Kavli IPMU graphic)

    Called SIMPs – strongly interacting massive particles – they were proposed three years ago by UC Berkeley theoretical physicist Hitoshi Murayama, a professor of physics and director of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, and former UC Berkeley postdoc Yonit Hochberg, now at Hebrew University in Israel.

    Murayama says that recent observations of a nearby galactic pile-up [Nature] could be evidence for the existence of SIMPs, and he anticipates that future particle physics experiments will discover one of them.

    Murayama discussed his latest theoretical ideas about SIMPs and how the colliding galaxies support the theory in an invited talk Dec. 4 at the 29th Texas Symposium on Relativistic Astrophysics in Cape Town, South Africa.

    Astronomers have calculated that dark matter, while invisible, makes up about 85 percent of the mass of the universe. The solidest evidence for its existence is the motion of stars inside galaxies: Without an unseen blob of dark matter, galaxies would fly apart. In some galaxies, the visible stars are so rare that dark matter makes up 99.9 percent of the mass of the galaxy.

    Theorists first thought that this invisible matter was just normal matter too dim to see: failed stars called brown dwarfs, burned-out stars or black holes. Yet so-called massive compact halo objects – MACHOs – eluded discovery, and earlier this year a survey of the Andromeda galaxy by the Subaru Telescope basically ruled out any significant undiscovered population of black holes.


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    The researchers searched for black holes left over from the very early universe, so-called primordial black holes, by looking for sudden brightenings produced when they pass in front of background stars and act like a weak lens. They found exactly one – too few to contribute significantly to the mass of the galaxy.

    3
    This Hubble Space Telescope image of the galaxy cluster Abell 3827 shows the ongoing collision of four bright galaxies and one faint central galaxy, as well as foreground stars in our Milky Way galaxy and galaxies behind the cluster (Arc B and Lensed image A) that are distorted because of normal and dark matter within the cluster. SIMPs could explain why the dark matter, unseen but detectable because of the lensing, lags behind the normal matter in the collision.

    “That study pretty much eliminated the possibility of MACHOs; I would say it is pretty much gone,” Murayama said.

    WIMPs — weakly interacting massive particles — have fared no better, despite being the focus of researchers’ attention for several decades. They should be relatively large – about 100 times heavier than the proton – and interact so rarely with one another that they are termed “weakly” interacting. They were thought to interact more frequently with normal matter through gravity, helping to attract normal matter into clumps that grow into galaxies and eventually spawn stars.

    SIMPs interact with themselves, but not others.

    SIMPs, like WIMPs and MACHOs, theoretically would have been produced in large quantities early in the history of the universe and since have cooled to the average cosmic temperature. But unlike WIMPs, SIMPs are theorized to interact strongly with themselves via gravity but very weakly with normal matter. One possibility proposed by Murayama is that a SIMP is a new combination of quarks, which are the fundamental components of particles like the proton and neutron, called baryons. Whereas protons and neutrons are composed of three quarks, a SIMP would be more like a pion in containing only two: a quark and an antiquark.

    4
    Conventional WIMP theories predict that dark matter particles rarely interact. Murayama and Hochberg predict that dark matter SIMPs, comprised of a quark and an antiquark, would collide and interact, producing noticeable effects when the dark matter in galaxies collide. (Kavli IPMU graphic)

    The SIMP would be smaller than a WIMP, with a size or cross section like that of an atomic nucleus, which implies there are more of them than there would be WIMPs. Larger numbers would mean that, despite their weak interaction with normal matter – primarily by scattering off of it, as opposed to merging with or decaying into normal matter – they would still leave a fingerprint on normal matter, Murayama said.

    He sees such a fingerprint in four colliding galaxies within the Abell 3827 cluster, where, surprisingly, the dark matter appears to lag behind the visible matter. This could be explained, he said, by interactions between the dark matter in each galaxy that slows down the merger of dark matter but not that of normal matter, basically stars.

    “One way to understand why the dark matter is lagging behind the luminous matter is that the dark matter particles actually have finite size, they scatter against each other, so when they want to move toward the rest of the system they get pushed back,” Murayama said. “This would explain the observation. That is the kind of thing predicted by my theory of dark matter being a bound state of new kind of quarks.”

    SIMPs also overcome a major failing of WIMP theory: the ability to explain the distribution of dark matter in small galaxies.

    5
    Conventional WIMP theories predict a highly peaked distribution, or cusp, of dark matter in a small area in the center of every galaxy. SIMP theory predicts a spread of dark matter in the center, which is more typical of dwarf galaxies. (Kavli IPMU graphic based on NASA, STScI images)

    “There has been this longstanding puzzle: If you look at dwarf galaxies, which are very small with rather few stars, they are really dominated by dark matter. And if you go through numerical simulations of how dark matter clumps together, they always predict that there is a huge concentration towards the center. A cusp,” Murayama said. “But observations seem to suggest that concentration is flatter: a core instead of a cusp. The core/cusp problem has been considered one of the major issues with dark matter that doesn’t interact other than by gravity. But if dark matter has a finite size, like a SIMP, the particles can go ‘clink’ and disperse themselves, and that would actually flatten out the mass profile toward the center. That is another piece of ‘evidence’ for this kind of theoretical idea.”

    Ongoing searches for WIMPs and axions

    Ground-based experiments to look for SIMPs are being planned, mostly at accelerators like the Large Hadron Collider at CERN in Geneva, where physicists are always looking for unknown particles that fit new predictions.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Another experiment at the planned International Linear Collider in Japan could also be used to look for SIMPs.

    ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan

    As Murayama and his colleagues refine the theory of SIMPs and look for ways to find them, the search for WIMPs continues. The Large Underground Xenon (LUX) dark matter experiment in an underground mine in South Dakota has set stringent limits on what a WIMP can look like, and an upgraded experiment called LZ will push those limits further. Daniel McKinsey, a UC Berkeley professor of physics, is one of the co-spokespersons for this experiment, working closely with Lawrence Berkeley National Laboratory, where Murayama is a faculty senior scientist.

    Lux Dark Matter 2 at SURF, Lead, SD, USA

    LBNL LZ project at SURF, Lead, SD, USA

    Physicists are also seeking other dark matter candidates that are not WIMPs. UC Berkeley faculty are involved in two experiments looking for a hypothetical particle called an axion, which may fit the requirements for dark matter. The Cosmic Axion Spin-Precession Experiment (CASPEr), led by Dmitry Budker, a professor emeritus of physics who is now at the University of Mainz in Germany, and theoretician Surjeet Rajendran, a UC Berkeley professor of physics, is planning to look for perturbations in nuclear spin caused by an axion field. Karl van Bibber, a professor of nuclear engineering, plays a key role in the (ADMX-HF), which seeks to detect axions inside a microwave cavity within a strong magnetic field as they convert to photons.

    ADMX Axion Dark Matter Experiment at the University of Washington

    “Of course we shouldn’t abandon looking for WIMPs,” Murayama said, “but the experimental limits are getting really, really important. Once you get to the level of measurement, where we will be in the near future, even neutrinos end up being the background to the experiment, which is unimaginable.”

    Neutrinos interact so rarely with normal matter that an estimated 100 trillion fly through our bodies every second without our noticing, something that makes them extremely difficult to detect.

    “The community consensus is kind of, we don’t know how far we need to go, but at least we need to get down to this level,” he added. “But because there are definitely no signs of WIMPs appearing, people are starting to think more broadly these days. Let’s stop and think about it again.”

    Murayama’s research is supported by the U.S. Department of Energy, National Science Foundation and Japanese Ministry of Education, Culture, Sports, Science and Technology. Murayama is also collaborating with Eric Kuflik of Hebrew University, Tomer Volansky of Tel Aviv University and Jay Wacker of Quora Inc. in Mountain View, California, and Stanford University.

    See the full article here .

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  • richardmitnick 1:51 pm on December 19, 2017 Permalink | Reply
    Tags: A specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster, Dark Matter, In 2014 astronomers reported the detection of an unusual emission line in X-ray light from the Perseus and other galaxy clusters, , , , Perseus Cluster: A New Twist in the Dark Matter Tale   

    From Chandra: “Perseus Cluster: A New Twist in the Dark Matter Tale” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    December 19, 2017

    1
    Composite

    2
    X-ray

    3
    Optical/Radio
    Credit X-ray: NASA/CXO/Oxford University/J. Conlon et al. Radio: NRAO/AUI/NSF/Univ. of Montreal/Gendron-Marsolais et al. Optical: NASA/ESA/IoA/A. Fabian et al.; DSS

    Dark matter is a mysterious invisible substance that makes up about 85% of matter in the Universe.

    In 2014, astronomers reported the detection of an unusual emission line in X-ray light from the Perseus and other galaxy clusters.

    A new interpretation of this detection and follow up observations may provide an explanation of this signal.

    If confirmed with future observations, this result could help resolve the nature of dark matter.

    An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter, as described in our latest press release [written by Megan Watzke, Chandra X-ray Center, Cambridge, Mass. 617-496-7998 mwatzke@cfa.harvard.edu]. The finding involves a new explanation for a set of results made with NASA’s Chandra X-ray Observatory, ESA’s XMM-Newton and Hitomi, a Japanese-led X-ray telescope.

    ESA/XMM Newton X-ray telescope

    JAXA/Hitomi telescope lost

    If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the Universe.

    The image shown here contains X-ray data from Chandra (blue) of the Perseus galaxy cluster, which has been combined with optical data from the Hubble Space Telescope (pink) and radio emission from the Very Large Array (red).

    NASA/ESA Hubble Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    In 2014, researchers detected an unusual spike of intensity, known as an emission line, at a specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster. They also reported the presence of this same emission line in a study of 73 other galaxy clusters.

    In the subsequent months and years, astronomers have tried to confirm the existence of this 3.5 keV line. They are eager to do so because it may give us important clues about the nature of dark matter. However, it has been debated in the astronomical community exactly what the original and follow-up observations have revealed.

    4
    Credit: NASA/CXC/M. Weiss

    A new analysis of Chandra data by a team from Oxford University, however, is providing a fresh take on this debate. The latest work shows that absorption of X-rays at an energy of 3.5 keV is detected when observing the region surrounding the supermassive black hole at the center of Perseus. This suggests that dark matter particles in the cluster are both absorbing and emitting X-rays (see our artist’s impression above for a diagram helping to explain this behavior, where 3.5 keV X-rays are shown). If the new model turns out to be correct, it could provide a path for scientists to one day identify the true nature of dark matter. For next steps, astronomers will need further observations of the Perseus cluster and others like it with current X-ray telescopes and those being planned for the next decade and beyond.

    A paper describing these results was published in Physical Review D on December 19, 2017 and a preprint is available online. The authors of the paper are Joseph Conlon, Francesca Day, Nicolas Jennings, Sven Krippendorf and Markus Rummel, all from Oxford University in the UK. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

    From the Press Release

    Other materials about the findings are available at:
    http://chandra.si.edu/photo/2017/dark/

    For more Chandra images, multimedia and related materials, visit:
    http://www.nasa.gov/chandra

    See the full article here .

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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 3:29 pm on December 1, 2017 Permalink | Reply
    Tags: André Maeder, , , , Dark Matter, , Katie Mack, , The strongest evidence for dark matter comes not from the motions of stars and galaxies “but from the behavior of matter on cosmological scales as measured by signatures in the cosmic microwave back   

    From COSMOS: “Radical dark matter theory prompts robust rebuttals” 

    Cosmos Magazine bloc

    COSMOS Magazine

    01 December 2017
    Richard A Lovett

    1
    Most cosmologists invoke dark energy to explain the accelerating expansion of the universe. A few are not so certain. Mina De La O / Getty
    Images

    In 1887, physicists Alfred Michelson and Edward Morley set up an array of prisms and mirrors in an elegant attempt to measure the passage of the Earth through what was then known as “luminiferous ether” – a mysterious substance through which light waves were believed to propagate, like sound waves through air.

    The experiment should have worked, but in one of the most famous results of Nineteenth Century physics no ether movement was detected. That was a head-scratcher until 1905, when Albert Einstein took the results at face value and used them as a cornerstone in developing his theory of relativity.

    Today, physicists are hunting for two equally mysterious commodities: dark matter and dark energy. And maybe, suggests a recent line of research from astrophysicist André Maeder at the University of Geneva, Switzerland, they too don’t exist, and scientists need to again revise their theories, this time to look for ways to explain the universe without the need for either of them.

    Dark matter was first proposed all the way back in 1933, when astrophysicists realised there wasn’t enough visible matter to explain the motions of stars and galaxies. Instead, there appeared to be a hidden component contributing to the gravitational forces affecting their motion. It is now believed that even though we still have not successfully observed it, dark matter is five times more prevalent in the universe than normal matter.

    Dark energy came into the picture more recently, when astrophysicists realised that the expansion of the universe could not be explained without the existence of some kind of energy that provides a repulsive force that steadily accelerates the rate at which galaxies are flying away from each other. Dark energy is believed to be even more prevalent than dark matter, comprising a full 70% of the universe’s total mass-energy.

    Maeder’s argument, published in a series of papers this year in The Astrophysical Journal is that maybe we don’t need dark matter and dark energy to explain these effects. Maybe it’s our concept of Einsteinian space-time that’s wrong.

    His argument begins with the conventional cosmological understanding that the universe started with a Big Bang, about 13.8 billion years ago, followed by continual expansion. But in this mode, there is a possibility that hasn’t been taken into account, he says: “By that I mean the scale invariance of empty space; in other words the empty space and its properties do not change following a dilation or contraction.”

    If so, that would affect our entire understanding of gravity and the evolution of the universe.

    Based on this hypothesis, Maeder found that with the right parameters he could explain the expansion of the universe without dark energy. He could also explain the motion of stars and galaxies without the need for dark matter.

    To say that Maeder’s ideas are controversial is an understatement. Katie Mack, an astrophysicist at the University of Melbourne on Australia, calls them “massively overhyped.” And physicist and blogger Sabine Hossenfelder of the Frankfurt Institute for Advanced Studies, Germany, wrote that while Maeder “clearly knows his stuff,” he does not yet have “a consistent theory.”

    Specifically, Mack notes that the strongest evidence for dark matter comes not from the motions of stars and galaxies, “but from the behavior of matter on cosmological scales, as measured by signatures in the cosmic microwave background [CMB] and the distribution of galaxies.” Gravitational lensing of distant objects by nearer galaxies also reveals the existence of dark matter, she says.

    CMB per ESA/Planck

    ESA/Planck

    Gravitational Lensing NASA/ESA

    Also, she notes that while there are a “whole heap” of ways to modify Einstein’s theories, these are “nothing new and not especially interesting.”

    The challenge, she says, is to reproduce everything, including “dark matter and dark energy’s biggest successes.” Until a new theory can produce “precise agreement” with measurements of a wide range of cosmic variables, she says, there’s no reason “at all” to throw out the existing theory.

    Dark matter researcher Benjamin Roberts, at the University of Reno, Nevada, US, agrees. “The evidence for dark matter is very substantial and comes from a large number of sources,” he says. “Until a single theory can explain all of these observations, there is no reason to doubt the existence of dark matter.”

    That said, this doesn’t mean that “new physics” theories such as Maeder’s should be ignored. “They should be, and are, taken seriously,” he says.

    Or as Maeder puts it, “Nothing can ever be taken for granted.”

    See the full article here .

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