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  • richardmitnick 4:46 pm on November 23, 2015 Permalink | Reply
    Tags: Dark Energy/Dark Matter, , ,   

    From JPL: “Earth Might Have Hairy Dark Matter” 


    November 23, 2015
    Elizabeth Landau
    NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

    This illustration shows Earth surrounded by filaments of dark matter called “hairs,” which are proposed in a study in the Astrophysical Journal by Gary Prézeau of NASA’s Jet Propulsion Laboratory, Pasadena, California. A hair is created when a stream of dark matter particles goes through the planet. According to simulations, the hair is densest at a point called the “root.” When particles of a dark matter stream pass through the core of Earth, they form a hair whose root has a particle density about a billion times greater than average. The hairs in this illustration are not to scale. Simulations show that the roots of such hairs can be 600,000 miles (1 million kilometers) from Earth, while Earth’s radius is only about 4,000 miles (6,400 kilometers).

    The solar system might be a lot hairier than we thought.

    A new study publishing this week in the Astrophysical Journal by Gary Prézeau of NASA’s Jet Propulsion Laboratory, Pasadena, California, proposes the existence of long filaments of dark matter, or “hairs.”

    Dark matter is an invisible, mysterious substance that makes up about 27 percent of all matter and energy in the universe. The regular matter, which makes up everything we can see around us, is only 5 percent of the universe. The rest is dark energy, a strange phenomenon associated with the acceleration of our expanding universe.

    Neither dark matter nor dark energy has ever been directly detected, although many experiments are trying to unlock the mysteries of dark matter, whether from deep underground or in space.

    Based on many observations of its gravitational pull in action, scientists are certain that dark matter exists, and have measured how much of it there is in the universe to an accuracy of better than one percent. The leading theory is that dark matter is “cold,” meaning it doesn’t move around much, and it is “dark” insofar as it doesn’t produce or interact with light.

    Galaxies, which contain stars made of ordinary matter, form because of fluctuations in the density of dark matter. Gravity acts as the glue that holds both the ordinary and dark matter together in galaxies.

    According to calculations done in the 1990s and simulations performed in the last decade, dark matter forms “fine-grained streams” of particles that move at the same velocity and orbit galaxies such as ours.

    “A stream can be much larger than the solar system itself, and there are many different streams crisscrossing our galactic neighborhood,” Prézeau said.

    Prézeau likens the formation of fine-grained streams of dark matter to mixing chocolate and vanilla ice cream. Swirl a scoop of each together a few times and you get a mixed pattern, but you can still see the individual colors.

    “When gravity interacts with the cold dark matter gas during galaxy formation, all particles within a stream continue traveling at the same velocity,” Prézeau said.

    But what happens when one of these streams approaches a planet such as Earth? Prézeau used computer simulations to find out.

    His analysis finds that when a dark matter stream goes through a planet, the stream particles focus into an ultra-dense filament, or “hair,” of dark matter. In fact, there should be many such hairs sprouting from Earth.

    A stream of ordinary matter would not go through Earth and out the other side. But from the point of view of dark matter, Earth is no obstacle. According to Prézeau’s simulations, Earth’s gravity would focus and bend the stream of dark matter particles into a narrow, dense hair.

    Hairs emerging from planets have both “roots,” the densest concentration of dark matter particles in the hair, and “tips,” where the hair ends. When particles of a dark matter stream pass through Earth’s core, they focus at the “root” of a hair, where the density of the particles is about a billion times more than average. The root of such a hair should be around 600,000 miles (1 million kilometers) away from the surface, or twice as far as the moon. The stream particles that graze Earth’s surface will form the tip of the hair, about twice as far from Earth as the hair’s root.

    “If we could pinpoint the location of the root of these hairs, we could potentially send a probe there and get a bonanza of data about dark matter,” Prézeau said.

    A stream passing through Jupiter’s core would produce even denser roots: almost 1 trillion times denser than the original stream, according to Prézeau’s simulations.

    “Dark matter has eluded all attempts at direct detection for over 30 years. The roots of dark matter hairs would be an attractive place to look, given how dense they are thought to be,” said Charles Lawrence, chief scientist for JPL’s astronomy, physics and technology directorate.

    Another fascinating finding from these computer simulations is that the changes in density found inside our planet – from the inner core, to the outer core, to the mantle to the crust – would be reflected in the hairs. The hairs would have “kinks” in them that correspond to the transitions between the different layers of Earth.

    Theoretically, if it were possible to obtain this information, scientists could use hairs of cold dark matter to map out the layers of any planetary body, and even infer the depths of oceans on icy moons.

    Further study is needed to support these findings and unlock the mysteries of the nature of dark matter.

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 12:25 pm on November 20, 2015 Permalink | Reply
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    From Scientific American: “Mysterious Glow at Milky Way’s Center Could Be Dark Matter or Hidden Pulsars” 

    Scientific American

    Scientific American

    November 18, 2015
    Clara Moskowitz

    X-ray: NASA/CXC/SAO; Optical: Detlef Hartmann; Infrared: NASA/JPL-Caltech

    The heart of our galaxy is oddly bright. Since 2009 astronomers have suggested that too much gamma-ray light is shining from the Milky Way’s core—more than all the known sources of light can account for. From the beginning scientists have suspected that they were seeing the long-sought signal of dark matter, the invisible form of mass thought to pervade the universe. But two recent studies offer more support for an alternate explanation: The gamma rays come from a group of spinning stars called pulsars that are just slightly too dim to see with current telescopes.

    Part of the confusion stems from uncertainties about the gamma-ray signal, which shows up in data from NASA’s Fermi Gamma-Ray Space Telescope.

    NASA Fermi Telescope

    Many different groups have analyzed Fermi’s publicly available data and claimed to see an unexplained excess of light, but the details of what they find and how they interpret it vary from group to group. Now, for the first time, the Fermi telescope team has confirmed the puzzling excess in a paper submitted to The Astrophysical Journal. The study offers the best description yet of the particularities of the extra light, such as its density and spread in space and its wavelength spectrum as well as all of the contaminating factors, such as systematic errors in the telescope and other sources of gamma-ray light that may muddy the signal. The team’s analysis stokes hopes that scientists may finally be close to making sense of the signal.

    On the trail of dark matter

    The gamma-ray glow has long intrigued theorists who say it uncannily matches predictions for a particular explanation of dark matter. Dark matter must be all around us because the stars and galaxies feel its gravitational pull—but its makeup is unknown. One suggestion is that weakly interacting massive particles, or WIMPs, account for dark matter. These particles would be their own antimatter counterparts, and just as matter and antimatter destroy one another on contact, two WIMPs would annihilate if they collided. At the center of the Milky Way, where dark matter is thought to be extremely dense, WIMPs would often smash together and their explosions would likely give off gamma-ray light—just as Fermi sees.

    But the light may have a more mundane origin. Pulsars are the remnants of once-large stars that have run out of fuel for nuclear fusion and collapsed. They spin at dizzying speeds—many make a full rotation every millisecond—and shine their light in condensed beams that rotate with them like a lighthouse. Pulsars are known to emit gamma-rays and could conceivably contribute to the surplus if there are enough of them hiding in the galactic center. Two recent studies that came out before the Fermi analysis support this scenario by finding that the extra gamma-ray light looks a bit more clumpy than smooth. Clumps would be expected if the light originated from individual objects—like pulsars—rather than from dark matter particles spread evenly through space. “Having a model based on point sources rather than smooth emission changes your statistics,” says Tracy Slatyer, a physicist at MIT. Together with her collaborators, Mariangela Lisanti and Samuel Lee of Princeton, and Ben Safdi and Wei Xue of MIT, she found a “striking” preference in the data for pulsarlike points of light. A separate study using different statistical methods, led by Christoph Weniger at the University of Amsterdam, came to the same conclusion. “Right now, I think millisecond pulsars are the best bet,” Weniger says. “Although everybody would like to find a dark matter signal, we have to be careful and not to jump to conclusions.”

    The comprehensive information on the gamma-ray light in the new Fermi collaboration study should help clarify the situation. “I think quite highly of the new paper,” Hooper says, adding that it “fills us in about many of the details.” The Fermi team itself is agnostic about the source of the light. “We can conclude that there is an excess on top of the conventional gamma-ray emitters, and there’s certainly an indication that there is something new, but it’s too soon to conclude that there is a dark matter signal,” says Simona Murgia of the University of California, Irvine, one of the primary co-authors of the Fermi paper. As for pulsars, “myself, I would say they are equally plausible.”

    Finding proof

    The good news is that if pulsars are behind the excess, more powerful, telescopes in the future should be able to spot the too-faint spinning stars directly. Pulsars would be prime targets for next-generation radio telescopes such as MeerKAT under construction in South Africa and the Square Kilometer Array (SKA), which encompasses MeerKAT, set to become operational in southern Africa and Australia in 2020.

    SKA MeerKAT Telescope Array

    SKA Meerkat telescope

    “Should we fail to find them in the next five or ten years, a dark matter explanation becomes more likely again,” Weniger says. “This is pretty much a win–win situation. But we have to be patient.”

    Meanwhile support for the dark matter explanation could appear even sooner. If WIMPs are responsible for the invisible matter, they might arise in the particle collisions taking place at the world’s largest atom smasher, the Large Hadron Collider (LHC), which was recently restarted at its highest energies yet.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    So-called direct detection searches are also looking for WIMPs in underground experiments aimed at catching the elusive particles in the rare act of interacting with regular matter. The fact that neither particle accelerators nor direct detectors have yet seen dark matter particles has already put strong constraints on the types of WIMPs that could exist. Astrophysicist Francesca Calore of the University of Amsterdam and her colleagues recently combined the theoretical constraints from all the various searches as well as data from the galactic center. They found many WIMP models are already excluded by the data but some remain plausible. “It came out that there are a few interesting regions that can be probed by the next rounds at the LHC, which can actually be tested in the next year,” Calore says.

    Another check on the dark matter hypothesis comes from dwarf galaxies. After all, if WIMPs are annihilating at the center of the Milky Way, they must also be doing so at the cores of other galaxies. The signal would be too dim to see in neighboring large galaxies but should show up in “dwarf spheroidal” galaxies orbiting the Milky Way, which are thought to be extremely dense with dark matter. “But there’s no signal from dwarfs,” says Kevork Abazajian of U.C. Irvine, noting that only one of the roughly 30 known dwarfs shows a hint of gamma-ray excess. “The story seems to be that the dwarfs are dark and the galactic center is bright.” In fact, the lack of gamma rays in the dwarf galaxies seems to cast significant doubt on the dark matter explanation for the Milky Way glow, Abazajian and a collaborator found in a paper submitted last month to the preprint server arXiv.

    If dwarf galaxies, particle accelerators and direct detection experiments continue to come up empty in future years, the plausibility of the WIMP explanation for dark matter—and for the Milky Way’s excess gamma rays—will get further stretched. The same goes for the search for pulsars in the galactic center. Soon these ideas should either be confirmed or disproved. “It’s always been my fear with this excess that we’d never find a confirming signal in any other dark matter channel but also no good astrophysical observations” such as pulsars, Slatyer says. “That’s a very frustrating situation to be in as a scientist.” Luckily that eventually, she says, is looking less and less likely.

    See the full article here .

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  • richardmitnick 2:54 pm on November 18, 2015 Permalink | Reply
    Tags: Dark Energy/Dark Matter, , ,   

    From Caltech: “Dark Matter Dominates in Nearby Dwarf Galaxy” 

    Caltech Logo

    Lori Dajose

    Dwarf galaxies have few stars but lots of dark matter. This Caltech FIRE (Feedback in Realistic Environments) simulation from shows the predicted distribution of stars (left) and dark matter (right) around a galaxy like the Milky Way. The red circle shows a dwarf galaxy like Triangulum II. Although it has a lot of dark matter, it has very few stars. Dark matter-dominated galaxies like Triangulum II are excellent prospects for detecting the gamma-ray signal from dark matter self-annihilation. Credit: A. Wetzel and P. Hopkins, Caltech

    Dark matter is called “dark” for a good reason. Although they outnumber particles of regular matter by more than a factor of 10, particles of dark matter are elusive. Their existence is inferred by their gravitational influence in galaxies, but no one has ever directly observed signals from dark matter. Now, by measuring the mass of a nearby dwarf galaxy called Triangulum II, Assistant Professor of Astronomy Evan Kirby may have found the highest concentration of dark matter in any known galaxy.

    Triangulum II is a small, faint galaxy at the edge of the Milky Way, made up of only about 1,000 stars. Kirby measured the mass of Triangulum II by examining the velocity of six stars whipping around the galaxy’s center. “The galaxy is challenging to look at,” he says. “Only six of its stars were luminous enough to see with the Keck telescope.”

    Keck Observatory
    Keck Observatory Interior

    By measuring these stars’ velocity, Kirby could infer the gravitational force exerted on the stars and thereby determine the mass of the galaxy.

    “The total mass I measured was much, much greater than the mass of the total number of stars—implying that there’s a ton of densely packed dark matter contributing to the total mass,” Kirby says. “The ratio of dark matter to luminous matter is the highest of any galaxy we know. After I had made my measurements, I was just thinking—wow.”

    Triangulum II could thus become a leading candidate for efforts to directly detect the signatures of dark matter. Certain particles of dark matter, called supersymmetric WIMPs (weakly interacting massive particles), will annihilate one another upon colliding and produce gamma rays that can then be detected from Earth.

    While current theories predict that dark matter is producing gamma rays almost everywhere in the universe, detecting these particular signals among other galactic noises, like gamma rays emitted from pulsars, is a challenge. Triangulum II, on the other hand, is a very quiet galaxy. It lacks the gas and other material necessary to form stars, so it isn’t forming new stars—astronomers call it “dead.” Any gamma ray signals coming from colliding dark matter particles would theoretically be clearly visible.

    It hasn’t been definitively confirmed, though, that what Kirby measured is actually the total mass of the galaxy. Another group, led by researchers from the University of Strasbourg in France, measured the velocities of stars just outside Triangulum II and found that they are actually moving faster than the stars closer into the galaxy’s center—the opposite of what’s expected. This could suggest that the little galaxy is being pulled apart, or “tidally disrupted,” by the Milky Way’s gravity.

    “My next steps are to make measurements to confirm that other group’s findings,” Kirby says. “If it turns out that those outer stars aren’t actually moving faster than the inner ones, then the galaxy could be in what’s called dynamic equilibrium. That would make it the most excellent candidate for detecting dark matter with gamma rays.”

    A paper describing this research appears in the November 17 issue of the Astrophysical Journal Letters. Judith Cohen (PhD ’71), the Kate Van Nuys Page Professor of Astronomy, is a Caltech coauthor.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 11:40 am on November 12, 2015 Permalink | Reply
    Tags: Dark Energy/Dark Matter, , , ,   

    From physicsworld.com: “Gran Sasso steps up the hunt for missing particles” 


    Nov 11, 2015
    Edwin Cartlidge


    Physicists working at the Gran Sasso National Laboratory in central Italy, located 1400 m under the mountain of the same name, are soon to start taking data from two new experiments.

    INFN Gran Sasso ICARUS
    Gran Sasso

    Each facility will target a different kind of missing matter: one will search for dark matter while the other will try and detect absent neutrinos to prove that neutrinos are their own antiparticle.

    Dark flash

    The hunt for dark matter – the mysterious substance believed to make up about 80% of all matter in the universe but not yet detected directly – will be carried out using XENON1T. This experiment, which was inaugurated at an event at Gran Sasso today, consists of 3.5 tonnes of liquid xenon. It is designed to measure very faint flashes of light that are given off whenever particles from the dark matter halo of the Milky Way collide with the xenon nuclei. The xenon will be stored at a temperature of about –100 °C in a cryostat and surrounded by a tank containing some 700 tonnes of purified water to minimize background radioactivity.

    Run by an international collaboration of 120 students and scientists from more than 2 institutions, XENON1T is expected to be about 100 times more sensitive than its 160 kg predecessor experiment and around 40 times better than the world’s current leading dark-matter detector – the 370 kg Large Underground Xenon experiment in South Dakota, US.

    LUX Dark matter

    Due to start taking data by the end of March next year, XENON1T will either detect dark matter or place severe constraints on the properties of theoretically-favoured weakly interacting massive particles (WIMPs), says collaboration spokesperson Elena Aprile of Columbia University in New York.

    Dark heart

    The other new experiment at Gran Sasso is the Cryogenic Underground Observatory for Rare Events (CUORE), which will look for an extremely rare nuclear process known as neutrinoless double beta decay.

    CUORE experiment

    That decay, if it exists, would involve two neutrons in certain nuclei decaying simultaneously into two protons while emitting two electrons but no antineutrinos (unlike normal beta decay), implying that the neutrino is its own antiparticle. Due to turn on early next year, CUORE will measure the energy spectrum of electrons emitted by 741 kg of tellurium dioxide surrounded by radioactively inert lead blocks recovered from a Roman ship that sank 2000 years ago.

    Meanwhile, towards the end of 2016 another group of scientists at Gran Sasso should take delivery of about a kilogram of cerium oxide powder, which they will place several metres below the Borexino neutrino detector.

    Borexino Solar Neutrino detector

    The Short Distance Neutrino Oscillations with BoreXino (SOX) experiment will look for a sinusoidal-like variation in the number of interactions generated within the detector by neutrinos from the radioactive cerium. SOX leader Marco Pallavicini of the University of Genoa says that such a variation would be a sure sign of “sterile” neutrinos – hypothetical particles outside the Standard Model of particle physics that would “oscillate” into ordinary neutrinos but would not interact with any other kind of matter.

    See the full article here .

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  • richardmitnick 1:29 pm on November 11, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter, , XENON1T experiment   

    From Symmetry: “Dark matter’s newest pursuer” 


    Mike Ross

    Scientists have inaugurated the new XENON1T experiment at Gran Sasso National Laboratory in Italy.


    Researchers at a laboratory deep underneath the tallest mountain in central Italy have inaugurated XENON1T, the world’s largest and most sensitive device designed to detect a popular dark matter candidate.

    Gran Sasso XENON1T
    XENON1T tank

    “We will be the biggest game in town,” says Columbia University physicist Elena Aprile, spokesperson for the XENON collaboration, which has over the past decade designed, built and operated a succession of ever-larger experiments that use liquid xenon to look for evidence of weakly interacting massive dark matter particles or WIMPs, at the Gran Sasso National Laboratory.

    Gran Sasso National Laboratory

    Interactions with these dark matter particles are expected to be rare: Just one a year for every 1000 kilograms of xenon. As a result, larger experiments have a better chance of intercepting a WIMP as it passes through the Earth.

    XENON1T’s predecessors—XENON 10 (2006 to 2009) and XENON 100 (2010 to the present)—held 25 and 160 kilograms of xenon, respectively. The new XENON11 experiment’s detector measures 1 meter high and 1 meter in diameter and contains 3500 kilograms of liquid xenon, nearly 10 times as much as the next-biggest xenon-filled dark matter experiment, the Large Underground Xenon [LUX] experiment.

    LUX Dark matter

    Looking for WIMPs

    Should a WIMP collide with a xenon atom, kicking its nucleus or knocking out one of its electrons, the result is a burst of fast ultraviolet light and a bunch of free electrons. Scientists built a strong electric field in the XENON1T detector to direct these freed particles to the top of the chamber, where they will create a second burst of light. The relative timing and brightness of the two flashes will help the scientists determine the type of particle that created them.

    “Since our detectors can detect even a single electron or photon, XENON1T will be sensitive to even the most feeble particle interactions,” says Rafael Lang, a Purdue University physicist on the XENON collaboration.

    Scientists cool the xenon to minus 163 degrees Fahrenheit to turn it into a liquid three times denser than water. One oddity of xenon is that its boiling temperature is only 7 degrees Fahrenheit above its melting temperature. So “we have to control our temperature and pressure precisely,” Aprile says.

    The experiment is shielded from other particles such as cosmic rays by separate layers of water, lead, polyethylene and copper—not to mention 1400 meters of Apennine rock that lie above the Gran Sasso lab’s underground tunnels.

    Keeping the xenon free of contaminants is essential to the detector’s sensitivity. Oxygen, for example, can trap electrons. And the decay of some radioactive krypton isotopes, which are difficult to separate from xenon, can obscure a WIMP signal. The XENON collaboration’s solution is to continuously circulate and filter 100 liters of xenon gas every minute from the top of the detector through a filtering system before chilling it and returning it to service.
    A matter of scale

    XENON researchers hope that their new experiment will finally be the one to see definitive evidence of WIMPs. But just in case, XENON1T was designed to accommodate a swift upgrade to 7000 kilograms of xenon in its next iteration. (At the same time, the LUX and UK-based Zeplin groups joined forces to design a similar-scale xenon detector, LZ.)

    “If we see nothing with XENON1T, it will still be worth it to move up to the 7000-kilogram device, since it will be relatively easy to do that,” Aprile says. “If we do see a few events with XENON1T—and we’re sure they are from the dark matter particle—then the best way to prove that it’s real is to confirm that result with a larger, more sensitive experiment.

    “In any case,” Aprile says, “we should know whether the WIMP is real or not before 2020.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 2:16 pm on November 9, 2015 Permalink | Reply
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    From ars technica: “Finally some answers on dark energy, the mysterious master of the Universe” 

    Ars Technica
    ars technica

    Nov 5, 2015
    Eric Berger

    U Texas McDonald Observatory Hobby-Eberle 9.1 meter Telescope
    U Texas McDonald Observatory Hobby Eberle 9.1 meter Telescope Interior
    U Texas McDonald Observatory Hobby-Eberle 9.1 meter Telescope

    Unless you’re an astrophysicist, you probably don’t sit around thinking about dark energy all that often. That’s understandable, as dark energy doesn’t really affect anyone’s life. But when you stop to ponder dark energy, it’s really rather remarkable. This mysterious force, which makes up the bulk of the Universe but was only discovered 17 years ago, somehow is blasting the vast cosmos apart at ever-increasing rates.

    Astrophysicists do sit around and think about dark energy a lot. And they’re desperate for more information about it as, right now, they have essentially two data points. One shows the Universe in its infancy, at 380,000 years old, thanks to observations of the cosmic microwave background radiation. And by pointing their telescopes into the sky and looking about, they can measure the present expansion rate of the Universe.

    But astronomers would desperately like to know what happened in between the Big Bang and now. Is dark energy constant, or is it accelerating? Or, more crazily still, might it be about to undergo some kind of phase change and turn everything into ice, as ice-nine did in Kurt Vonnegut’s novel Cat’s Cradle? Probably not, but really, no one knows.

    The Plan

    Fortunately astronomers in West Texas have a $42 million plan to use the world’s fourth largest optical telescope to get some answers. Until now, the 9-meter Hobby-Eberly telescope at McDonald Observatory has excelled at observing very distant objects, but this has necessitated a narrow field of view. However, with a clever new optical system, astronomers have expanded the telescope’s field of view by a factor of 120, to nearly the size of a full Moon. The next step is to build a suite of spectrographs and, using 34,000 optical fibers, wire them into the focal plane of the telescope.

    “We’re going to make this 3-D map of the Universe,” Karl Gebhardt, a professor of astronomy at the University of Texas at Austin, told Ars. “On this giant map, for every image that we take, we’ll get that many spectra. No other telescope can touch this kind of information.”

    With this detailed information about the location and age of objects in the sky, astronomers hope to gain an understanding of how dark energy affected the expansion rate of the Universe 5 billion to 10 billion years ago. There are many theories about what dark energy might be and how the expansion rate has changed over time. Those theories make predictions that can now be tested with actual data.

    In Texas, there’s a fierce sporting rivalry between the Longhorns in Austin and Texas A&M Aggies in College Station. But in the field of astronomy and astrophysics the two universities have worked closely together. And perhaps no one is more excited than A&M’s Nick Suntzeff about the new data that will come down over the next four years from the Hobby-Eberly telescope.

    Suntzeff is most well known for co-founding the High-Z Supernova Search Team along with Brian Schmidt, one of two research groups that discovered dark energy in 1998. This startling observation that the expansion rate of the Universe was in fact accelerating upended physicists’ understanding of the cosmos. They continue to grapple with understanding the mysterious force—hence the enigmatic appellation dark energy—that could be causing this acceleration.

    Dawn of the cosmos

    When scientists observe quantum mechanics, they see tiny energy fluctuations. They think these same fluctuations occurred at the very dawn of the Universe, Suntzeff explained to Ars. And as the early Universe expanded, so did these fluctuations. Then, at about 1 second, when the temperature of the Universe was about 10 billion degrees Kelvin, these fluctuations were essentially imprinted onto dark matter. From then on, this dark matter (whatever it actually is) responded only to the force of gravity.

    Meanwhile, normal matter and light were also filling the Universe, and they were more strongly affected by electromagnetism than gravity. As the Universe expanded, this light and matter rippled outward at the speed of sound. Then, at 380,000 years, Suntzeff said these sound waves “froze,” leaving the cosmic microwave background.

    These ripples, frozen with respect to one another, expanded outward as the Universe likewise grew. They can still be faintly seen today—many galaxies are spaced apart by about 500 million light years, the size of the largest ripples. But what happened between this freezing long ago, and what astronomers see today, is a mystery.

    The Texas experiment will allow astronomers to fill in some of that gap. They should be able to tease apart the two forces acting upon the expansion of the Universe. There’s the gravitational clumping, due to dark matter, which is holding back expansion. Then there’s the acceleration due to dark energy. Because the Universe’s expansion rate is now accelerating, dark energy appears to be dominating now. But is it constant? And when did it overtake dark matter’s gravitational pull?

    “I like to think of it sort of as a flag,” Suntzeff said. “We don’t see the wind, but we know the strength of the wind by the way the flag ripples in the breeze. The same with the ripples. We don’t see dark energy and dark matter, but we see how they push and pull the ripples over time, and therefore we can measure their strengths over time.”
    The universe’s end?

    Funding for the $42 million experiment at McDonald Observatory, called HETDEX for Hobby-Eberly Telescope Dark Energy Experiment, will come from three different sources: one-third from the state of Texas, one-third from the federal government, and a third from private foundations.

    The telescope is in the Davis Mountains of West Texas, which provide some of the darkest and clearest skies in the continental United States. The upgraded version took its first image on July 29. Completing the experiment will take three or four years, but astronomers expect to have a pretty good idea about their findings within the first year.

    If dark energy is constant, then our Universe has a dark, lonely future, as most of what we can now observe will eventually disappear over the horizon at speeds faster than that of light. But if dark energy changes over time, then it is hard to know what will happen, Suntzeff said. One unlikely scenario—among many, he said—is a phase transition. Dark energy might go through some kind of catalytic change that would propagate through the Universe. Then it might be game over, which would be a nice thing to know about in advance.

    Or perhaps not.

    See the full article here .

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    Ars Technica was founded in 1998 when Founder & Editor-in-Chief Ken Fisher announced his plans for starting a publication devoted to technology that would cater to what he called “alpha geeks”: technologists and IT professionals. Ken’s vision was to build a publication with a simple editorial mission: be “technically savvy, up-to-date, and more fun” than what was currently popular in the space. In the ensuing years, with formidable contributions by a unique editorial staff, Ars Technica became a trusted source for technology news, tech policy analysis, breakdowns of the latest scientific advancements, gadget reviews, software, hardware, and nearly everything else found in between layers of silicon.

    Ars Technica innovates by listening to its core readership. Readers have come to demand devotedness to accuracy and integrity, flanked by a willingness to leave each day’s meaningless, click-bait fodder by the wayside. The result is something unique: the unparalleled marriage of breadth and depth in technology journalism. By 2001, Ars Technica was regularly producing news reports, op-eds, and the like, but the company stood out from the competition by regularly providing long thought-pieces and in-depth explainers.

    And thanks to its readership, Ars Technica also accomplished a number of industry leading moves. In 2001, Ars launched a digital subscription service when such things were non-existent for digital media. Ars was also the first IT publication to begin covering the resurgence of Apple, and the first to draw analytical and cultural ties between the world of high technology and gaming. Ars was also first to begin selling its long form content in digitally distributable forms, such as PDFs and eventually eBooks (again, starting in 2001).

  • richardmitnick 9:12 am on November 9, 2015 Permalink | Reply
    Tags: , , , Dark Energy/Dark Matter   

    From COSMOS: “Dark matter uncovered” 

    Cosmos Magazine bloc


    9 Nov 2015

    Temp 1

    Most of the matter in the Universe consists of stuff we can’t see. It is dubbed dark matter and we know it must be out there. Without dark matter rapidly spinning galaxies (such as those circled, above) would not have sufficient gravitational glue to hold their stars and gas clouds together. These elements would fly off into space instead, like rain drops on a spinning bicycle wheel. What might this ghostly, galaxy glue be made of? Nobody knows. But in 2006 astronomers got a new clue.

    Temp 1
    Credit: NASA, ESA, J. Jee (University of California, Davis), J. Hughes (Rutgers Univ.), F. Menanteau (Rutgers University & University of Illinois, Urbana-Champaign), C. Sifon (Leiden Obs.), R. Mandelbum (Carnegie Mellon University), L. Barrientos (University Catolica de Chile), and K. Ng (University of California, Davis)

    X-rays of a bullet cluster

    In 2006, NASA astronomers aimed their orbiting Chandra X-ray Observatory at the galaxy cluster shown on the previous image, 1E 0657-56.

    NASA Chandra Telescope

    It captured a very different picture.

    Chandra picks up the X-rays given off by hot clouds of gas (shown above in red, overlaid on a Hubble snapshot). The striking shape of the newly revealed gas clouds earned them an instant nickname: the bullet cluster.

    But the bullet cluster had a bigger secret to reveal.

    Temp 1
    Credit: NASA / CXC / M. Weiss

    When galaxies collide

    Astronomers think the bullet cluster began to form around 100 million years ago, when one small cluster of galaxies barrelled right through the middle of a larger cluster, and out the other side. The four-step artist’s illustration above depicts the sequence of events.

    The colliding gas particles in each galaxy are shown in red. As the little gas cloud elbowed its way past its bigger partner it acquired its dramatic bullet shape.

    Temp 1
    Credit: NASA / CXC / CfA /M. Markevitch et al.; Optical: NASA / STScI; Magellan / U. Arizona / D. Clowe et al.; Lensing Map: NASA / STScI; ESO WFI; Magellan / U. Arizona / D. Clowe et al.

    Dark matter revealed

    What about the dark matter?

    Astronomers can track the location of dark matter because its gravity bends the light of stars behind it. The technique is called gravitational lensing. Using the Hubble Space Telescope, they were able to see where the dark matter was located in the bullet cluster (violet shading).

    NASA Hubble Telescope
    NASA/ESA Hubble

    While the gas particles jostled and elbowed their way past each other, the dark matter particles slipped right past unnoticed – just what you’d expect from ghosts.

    Temp 1
    Credit: NASA / ESA / R. Massey (California Institute of Technology)

    Ghost map

    It may be ghostly but the Hubble telescope can detect dark matter because of the way it bends light from stars. Using this information, in 2007 astronomers mapped its location in the Universe and how it has changed over billions of years (pictured).

    In the early days of the Universe (far right), dark matter was spread out quite evenly. But over time, gravity collapsed this structure into dense clumps (far left).

    Some astronomers think these dark matter clumps created an essential scaffold. Ordinary matter was drawn to it and started forming stars, galaxies and ultimately, ourselves.

    See the full article here .

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  • richardmitnick 6:35 am on November 8, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter,   

    From Symmetry: “The light side of dark matter” 


    Glenn Roberts Jr.

    New technology and new thinking are pushing the dark matter hunt to lower and lower masses.


    It’s a seemingly paradoxical but important question in particle physics: Can dark matter be light?

    Light in this case refers to the mass of the as-yet undiscovered particle or group of particles that may make up dark matter, the unseen stuff that accounts for about 85 percent of all matter in the universe.

    Ever-more-sensitive particle detectors, experimental hints and evolving theories about the makeup of dark matter are driving this expanding search for lighter and lighter particles—even below the mass of a single proton—with several experiments giving chase.

    An alternative to WIMPs?

    Theorized weakly interacting massive particles, or WIMPs, are counted among the leading candidates for dark matter particles. They most tidily fit some of the leading models.

    Many scientists expected WIMPs might have a mass of around 100 billion electronvolts—about 100 times the mass of a proton. The fact that they haven’t definitively showed up in searches covering a range from about 10 billion electronvolts to 1 trillion electronvolts has cracked the door to alternative theories about WIMPs and other candidate dark matter particles.

    Possible low-energy signals measured at underground dark matter experiments CoGeNT in Minnesota and DAMA/LIBRA in Italy, along with earlier hints of dark matter particles in space observations of our galaxy’s center by the Fermi Gamma-ray Space Telescope, excited interest in a mass range below about 11 billion electronvolts—roughly 11 times the mass of a proton.

    CoGeNT experiment

    DAMA LIBRA Dark Matter Experiment

    NASA Fermi Telescope

    Such low-energy particles could be thought of as lighter, “wimpier” WIMPs, or they could be a different kind of particles: light dark matter.

    SuperCDMS, an WIMP-hunting experiment in the Soudan Underground Laboratory in Minnesota, created a special search mode, called CDMSlite, to make its detectors sensitive to particles with mass reaching below 5 billion electronvolts. With planned upgrades, CDMSlite should eventually be able to stretch down to detect particles with a mass about 50 times less than this.


    In September, the CDMS collaboration released results that narrow the parameters used to search for light WIMPs in a mass range of 1.6 billion to 5.5 billion electronvolts.

    Also in September, collaborators with the CRESST experiment (pictured above) at Gran Sasso laboratory in Italy released results that explored for the first time masses down to 0.5 billion electronvolts.

    Other underground experiments, such as LUX at the Sanford Underground Research Facility in South Dakota, Edelweiss at Modane Underground Laboratory in France, and DAMIC at SNOLAB in Canada, are also working to detect light dark matter particles. Many more experiments, including Earth- and space-based telescopes and CERN’s Large Hadron Collider, are playing a role in the dark matter hunt as well.

    LUX Dark matter


    Edelweiss Dark Matter Experiment

    This hunt has broadened in many directions, says David Kaplan, a physics professor at Johns Hopkins University.

    “Incredible progress has been made—scientists literally gained over 10 orders of magnitude in sensitivity from the beginning of really dedicated WIMP experiments until now,” he says. “In a sense, the WIMP is the most boring possibility. And if the WIMP is ruled out, it’s an extremely interesting time.”

    Peter Graham, an assistant professor of physics at Stanford University, says the light dark matter search is especially intriguing because any discovery in the light dark matter range would fly in the face of classical physics theories. “If we find it, it won’t be in the Standard Model,” he says.

    Coming attractions

    The experiments searching for light dark matter are working together to see through the background particles that can obscure their searches, says Dan Bauer, spokesman for the SuperCDMS collaboration and group leader for the effort at Fermilab..

    “In this whole field, it’s competitive but it’s also collaborative,” he says. “We all share information.”

    The next few months will bring new results from the CDMSlite experiment and for CRESST.

    An upgrade, now in progress, will push the lower limits of the CRESST detectors to about 0.1 billion to 0.2 billion electronvolts, says Federica Petricca, a researcher at the Max Planck Institute for Physics and spokesperson for the CRESST experiment.

    “The community has learned to be a bit more open and not to focus on a specific region of the mass range of the dark matter particle,” Petricca says. “I think this is interesting simply because there are motivated theories behind this, and there is no reason to limit the search to some specific model.”

    Researchers are also looking out for future results from an experiment called DAMIC. DAMIC searches for signs of dark matter using an array of specialized charge-coupled devices, similar to the light-sensitive sensors found in today’s smartphone cameras.

    DAMIC already can search for particles with a mass below 6 billion electronvolts. The experiment’s next iteration, known as DAMIC100, should be able to take measurements below 0.3 billion electronvolts after it starts up in 2016, says DAMIC spokesperson Juan Estrada of Fermilab.

    “I think it is very valuable to have several experiments that are looking in the same region,” Estrada says, “because it doesn’t look like any single experiment will be able to confirm a dark matter signal—we will need to have many experiments.

    “There is still a lot of room for innovation.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 7:37 am on October 28, 2015 Permalink | Reply
    Tags: Dark Energy/Dark Matter, , , ,   

    From AMS-02- “Studying Dark Matter In Space: It Matters!” 

    AMS-02 Bloc

    AMS 02 schematic

    Alpha Magnetic Spectrometer

    Oct. 27, 2015
    Editor: Kristine Rainey


    See the full article here .

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    AMS-02 Mission Control at CERN
    AMS-02 Mission Control at CERN in Prevessin, France

    The Alpha Magnetic Spectrometer (AMS-02) is a state-of-the-art particle physics detector designed to operate as an external module on the International Space Station. It will use the unique environment of space to study the universe and its origin by searching for antimatter, dark matter while performing precision measurements of cosmic rays composition and flux. The AMS-02 observations will help answer fundamental questions, such as “What makes up the universe’s invisible mass?” or “What happened to the primordial antimatter?”

    Background of AMS

    AMS was assembled and tested at the European Organization for Nuclear Research, CERN, Geneva, Switzerland. Detector components were constructed at universities and research institutes around the world. Fifteen countries from Europe, Asia, and America participated in the construction of AMS (Finland, France, Germany, Netherlands, Italy, Portugal, Spain, Switzerland, Turkey, China, Korea, Taiwan, Russia, Mexico and the United States). The Principal Investigator of AMS is Prof. Samuel Ting of MIT and CERN. AMS is a U.S. Department of Energy sponsored particle physics experiment on the ISS under a DOE-NASA Implementing Arrangement. The Collaboration works closely with the NASA AMS Project Management team from Johnson Space Center as it has throughout the entire process. AMS was launched by NASA to the ISS as the primary payload onboard the final mission of space shuttle Endeavour (STS-134) on May 16, 2011. Once installed on the ISS, AMS was powered up and immediately began collecting data from primary sources in space and these were transmitted to the AMS Payload Operations Control Center (POCC). The POCC is located at CERN, Geneva, Switzerland.

    After 40 months of operations in space, AMS has collected 54 billion cosmic ray events. To date 41 billion have been analyzed. The data is analyzed at the AMS Science Operations Center (SOC) located at CERN as well as AMS universities around the world. Over the lifetime of the Space Station, AMS is expected to measure hundreds of billions of primary cosmic rays. Among the physics objectives of AMS is the search for antimatter, dark matter, and the origin of cosmic rays. The Collaboration will also conduct precision measurements on topics such as the boron to carbon ratio, nuclei and antimatter nuclei, and antiprotons, precision measurements of helium flux, proton flux and photons as well as the search for new physics and astrophysics phenomena such as strangelets.

    It is important to note that, in the search for an understanding of dark matter, there are three distinct approaches:

    Production experiments, such as those being carried at the LHC with the ATLAS and CMS experiments, use particle collisions to produce dark matter particles and detect their decay products. This is similar to experiments at the Brookhaven, Fermilab, CERN-SPS and CERN-LHC which led to the discovery of CP violation, the J particle, Z and W bosons, the b and t quarks, and the Higgs boson.

    Scattering experiments utilize the fact that dark matter can penetrate deep underground and that it can be detected by recoil nuclei from the scattering of dark matter with pure liquid or solid targets. This is similar to electron-proton scattering experiments performed at SLAC leading to the discovery of partons and the electro-weak effects.

    Annihilation experiments for dark matter are done in space and are based on the fact that dark matter collisions can produce excesses of positrons and anti-protons. These are the main goals of AMS. On the ground, annihilation experiments are done in electron-positron colliders (SPEAR, PETRA, LEP, BaBar, TRISTAN) leading to the discovery of the psi particle, the heavy electron (tau) and gluons, precision measurements of CP violation effects and the properties of Z and W bosons.

    The scattering experiments, the production experiments, and the annihilation experiments each produce unique physics discoveries. The absence of a dark matter signal from one of these three ways does not exclude its discovery by the other two.

    The U.S. participation in AMS involves MIT, Yale (Professor Jack Sandweiss), the University of Hawaii (Professors Veronica Bindi and Philip von Doetinchem), the University of Maryland (Professor Roald Sagdeev and Professor Eun Suk SEO) and NASA’s Johnson Space Center (Mr. Trent Martin and Mr. Ken Bollweg). The AMS project is coordinated by the Laboratory for Nuclear Science at MIT under the leadership of Professor Richard Milner. The major responsibility for space operations and data analysis is carried by Drs. U. J. Becker, J. Burger, X.D. Cai, M. Capell, V. Choutko, F.J. Eppling, P. Fisher, A. Kounine,V. Koutsenko, A. Lebedev, Z.Weng, and P. Zuccon of MIT.

    Germany made a major contribution to the detector construction and data analysis under the leadership of Professors Dr. Stefan Schael, Henning Gast, and Iris Gebauer. Germany’s participation is supported by DLR and RWTH Aachen.

    Italy made a major contribution to the detector construction and presently to the data analysis, under the leadership of Professors Roberto Battiston, Deputy PI and currently President of ASI, Bruna Bertucci, Italian Coordinator, Franco Cervelli, Andrea Contin, Giovanni Ambrosi, Marco Incagli, Giuliano Laurenti, Federico Palmonari, and Pier-Giorgio Rancoita. Italy’s participation is supported by ASI and INFN.

    Spain made a major contribution to the detector construction and presently to the data analysis under the leadership of Manuel Aguilar, Javier Berdugo, Jorge Casaus, Carlos Delgado and Carlos Mana. Spain’s participation is supported by CIEMAT and CDTI.

    France has made major contributions to the detector construction and to the data analysis both from LPSC, Grenoble and LAPP, Annecy under the leadership of Professors Laurent Derome, Sylvie Rosier-Lees, and Jean-Pierre Vialle. France’s participation is supported by IN2P3 and CNES.

    Taiwan made a major contribution to the detector construction and presently to the data analysis, under the leadership of Academician Shih-Chang Lee and Profs. Y.H. Chang and S. Haino. Taiwan’s participation is supported by Academia Sinica, National Science Council and CSIST. Taiwan also maintains the AMS Asia POCC.

    From China, Shandong University made a major contribution to the detector construction and to the data analysis under the leadership of Professor Cheng Lin. The Institute of High Energy Physics in Beijing has made major contributions to the detector construction and data analysis under the leadership of Academician Hesheng Chen. Southeast University in Nanjing has made major contributions to the detector construction and data analysis under the leadership of Professor Hong Yi and J. Z. Luo. Beihang University under the leadership of Academician Wei Li, Professor Zhi-Ming Zheng and Dr. Baosong Shan made important contributions to the data analysis. Sun Yat-Sen University in Guangzhou has made major contributions to the detector construction and data analysis under the leadership of Professor N.S. Xu. Shanghai Jiaotong University in Shanghai has made important contributions to the detector construction. The Institute of Electrical Engineering under Q. L. Wang and the Chinese Academy of Launch Vehicle Technology were responsible for the AMS permanent magnet.

    Switzerland has made a major contribution to the detector construction and the data analysis, both from ETH/Zurich and the University of Geneva under the leadership of Professors Maurice Bourquin, Catherine Leluc, and Martin Pohl of the University of Geneva.

    Collaborating Insititutes on the two Physical Review Letters:

    I. Physics Institute and JARA-FAME, RWTH Aachen University, D-52056 Aachen, Germany

    Department of Physics, Middle East Technical University, METU, 06800 Ankara, Turkey

    Laboratoire d’Annecy-Le-Vieux de Physique des Particules, LAPP, IN2P3/CNRS and Universite de Savoie, F-74941 Annecy-le-Vieux, France

    Beihang University, BUAA, Beijing, 100191, China

    Institute of Electrical Engineering, IEE, Chinese Academy of Sciences, Beijing, 100080, China

    Institute of High Energy Physics, IHEP, Chinese Academy of Sciences, Beijing, 100039, China

    INFN-Sezione di Bologna, I-40126 Bologna, Italy

    Universita di Bologna, I-40126 Bologna, Italy

    Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA

    National Central University, NCU, Chung-Li, Tao Yuan 32054, Taiwan

    East-West Center for Space Science, University of Maryland, College Park, Maryland 20742, USA

    IPST, University of Maryland, College Park, Maryland 20742, USA

    CHEP, Kyungpook National University, 702-701 Daegu, Korea

    CNR-IROE, I-50125 Firenze, Italy

    European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland

    DPNC, Universite de Geneve, CH-1211 Geneve 4, Switzerland

    Laboratoire de Physique subatomique et de cosmologie, LPSC, Universite Grenoble-Alpes, CNRS/IN2P3, F-38026 Grenoble, France

    Sun Yat-Sen University, SYSU, Guangzhou, 510275, China

    University of Hawaii, Physics and Astronomy Department, 2505 Correa Road, WAT 432; Honolulu, Hawaii 96822, USA

    Julich Supercomputing Centre and JARA-FAME, Research Centre Julich, D-52425 Julich, Germany

    NASA, National Aeronautics and Space Administration, Johnson Space Center, JSC, and Jacobs-Sverdrup, Houston, TX 77058, USA

    Institut fur Experimentelle Kernphysik, Karlsruhe Institute of Technology, KIT, D-76128 Karlsruhe, Germany

    Instituto de Astrofisica de Canarias, IAC, E-38205, La Laguna, Tenerife, Spain

    Laboratorio de Instrumentacao e Fisica Experimental de Particulas, LIP, P-1000 Lisboa, Portugal

    National Chung-Shan Institute of Science and Technology, NCSIST, Longtan, Tao Yuan 325, Taiwan

    Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, CIEMAT, E-28040 Madrid, Spain

    Instituto de Fisica, Universidad Nacional Autonoma de Mexico, UNAM, Mexico, D. F., 01000 Mexico

    INFN-Sezione di Milano and Universita di Milano, I-20090 Milano, Italy

    INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy

    Universita di Milano-Bicocca, I-20126 Milano, Italy

    Laboratoire Univers et Particules de Montpellier, LUPM, IN2P3/CNRS and Universite de Montpellier II, F-34095 Montpellier, France

    Southeast University, SEU, Nanjing, 210096, China

    Physics Department, Yale University, New Haven, Connecticut 06520, USA

    INFN-Sezione di Perugia, I-06100 Perugia, Italy

    Universita di Perugia, I-06100 Perugia, Italy

    INFN-Sezione di Pisa, I-56100 Pisa, Italy

    Universita di Pisa, I-56100 Pisa, Italy

    INFN-TIFPA and Universita di Trento, I-38123 Povo, Trento, Italy

    INFN-Sezione di Roma 1, I-00185 Roma, Italy

    Universita di Roma La Sapienza, I-00185 Roma, Italy

    Department of Physics, Ewha Womans University, Seoul, 120-750, Korea

    Shandong University, SDU, Jinan, Shandong, 250100, China

    Shanghai Jiaotong University, SJTU, Shanghai, 200030, China

    Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan

    Space Research Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland

  • richardmitnick 2:14 pm on October 19, 2015 Permalink | Reply
    Tags: Dark Energy/Dark Matter, , ,   

    From Science Node: “How did the universe get here?” 

    Science Node bloc
    Science Node

    09 Oct, 2015
    Lance Farrell

    Courtesy DEUS-FUR; V Reverdy.

    The big bang model explains the history of the universe, but scientists are looking to an unseen force called dark energy to explain the universe’s accelerating expansion. To find dark energy’s cosmic fingerprints, scientists simulated the entire expansion of the universe on the Curie supercomputer.

    Curie supercomputer designed by Bull for GENCI

    To answer the world’s oldest question, researchers at the Dark Energy Universe Simulation: Full Universe Runs (DEUS-FUR) project did something new. Using the Curie supercomputer they were the first to simulate the unfolding of the entire universe to see how dark energy might lie hidden in plain sight.

    Using 50 million hours of supercomputing time (3,500 years if performed on a single computer), the DEUS group was able to calculate the trajectory of about 550 billion dark matter particles, each the size of our galaxy. Courtesy DEUS Consortium.

    Explaining the evolution of our universe is a timeless task. One hundred years ago, the theory of general relativity launched a scientific method to model the cosmos. From this revolution in thought came the notion of the big bang — a singularity of infinite density that expanded about 14 billion years ago, creating the known universe in its wake. With the discovery of an accelerating universe, the big bang model has grown complicated; dark energy is one of the prevailing models to account for the speeding expansion.

    But simulating the unfolding of the whole universe is a tremendous computational feat, taxing even the most powerful computers. DEUS scientists ran full universe models on 4,752 nodes and 300 TB of memory on Curie, one of Europe’s first petascale supercomputers. To highlight the numerical challenge behind the simulations, the team updated their findings last month in the International Journal of High Performance Computing Applications.

    “In our domain, high-performance computing is our only way to build universes, let them evolve to explore theoretical hypotheses, connect them to observations, and understand how observed phenomena emerge from fundamental laws,” says Vincent Reverdy, numerical cosmologist in the Department of Astronomy at the University of Illinois at Urbana-Champaign and co-author of the DEUS-FUR study.

    To reveal the hidden imprint of dark energy and chart the historical development of cosmic structures (clusters and superclusters of galaxies), the DEUS project contrasted three competing dark energy models, each suggesting a different history of structure formation.

    Map of voids and superclusters within 500 million light years from Milky Way
    Date 08/11/09
    Source http://www.atlasoftheuniverse.com/nearsc.html
    Author Richard Powell

    By simulating the path of photons through star clusters, the DEUS group learned that even slight deviations between models can change the way observers perceive the universe — not to mention the results they obtain while measuring cosmological distances.

    The simulations are a first in numerical cosmology, but the technical effort to achieve them points to applicability for compilers, geo-localization software, and artificial intelligence, Reverdy says. As satisfying as the applications might be, for Reverdy, the real prize is found in discovery.

    “For me, the goal of research is, before anything else, cultural and philosophical,” he says, cautious of appearing pompous. “Physics tell us something fundamental about what Nature is, or more exactly about what Nature is not. This project is a very small piece in the large puzzle of understanding gravity and the accelerating expansion of the universe.”

    download the mp4 video here.
    Curie. When added to others run by the DEUS group, scientists now have simulations scaling from less than 1/100 the size of the Milky Way up to the entirety of the observable universe — the first simulation to achieve this size. To do the job, DEUS looked to Curie, one of Europe’s first petascale supercomputers. Courtesy DEUS-FUR; V Reverdy.

    See the full article here .

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    Science Node is an international weekly online publication that covers distributed computing and the research it enables.

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

    In its current incarnation, Science Node is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

    You can read Science Node via our homepage, RSS, or email. For the complete iSGTW experience, sign up for an account or log in with OpenID and manage your email subscription from your account preferences. If you do not wish to access the website’s features, you can just subscribe to the weekly email.”

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