Is dark matter made of axions

first_img Citation: Is dark matter made of axions? (2008, March 3) retrieved 18 August 2019 from https://phys.org/news/2008-03-dark-axions.html Explore further Tevatron experiments report latest results in search for Higgs boson Aaron Chou and William Wester run their Fermilab experiment looking for axions. Photo Credit: Femilab This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.center_img Wester, a scientist at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, worked closely with Aaron Chou, now at New York University, and a group of scientists from Fermilab and the University of Michigan in Ann Arbor, to design an experiment to test the existence of axion-like particles within a certain range. Their results can be found in Physical Review Letters: “Search for Axionlike Particles Using a Variable-Baseline Photon-Regeneration Technique.”Axions are hypothetical particles that have a small mass in the milli-electronvolt (eV) range, making them 500 million times lighter than an electron. Additionally, an axion should have no spin. “Normally,” Chou points out, “we can only detect these kinds of particles with telescopes, looking out into space. And then it is only an indirect detection.” The idea was to create conditions allowing them to detect particles in the milli-eV range during a lab experiment.“For particles that interact strongly enough for us to detect, there are constraints on where they could exist or not,” Chou continues. “For the specific region of our experiment, no one would have thought to look into it without the PVLAS experiment.”Wester explains that the PVLAS collaboration did an experiment in which a signal that could have been an axion was detected. “We wanted to see if we could get the same results,” he says. The PVLAS experimenters eventually ruled out the signal after Wester and Chou started to work with their peers on this experiment. However, there were still some innovations that encouraged the Fermilab group to move forward.“We set things up a little differently,” Wester says. He points out that the Tevatron magnets used in the Fermilab experiment were stronger and better suited for experiments in the milli-eV range than those used in previous experiments. With the magnetic field in place, a laser was aimed down the middle. A “wall” was placed in the middle of the magnetic field as well. The magnetic field would possibly change some of the photons from the laser into axions. The wall would stop the photons, but the axions would emerge on the other side. “There were four different configurations,” Wester continues. “We also had the blocking mechanism placed off to the side to change the effective length of the magnetic field. We also did it with two different polarizations, vertical and horizontal.”Wester says that, unfortunately, the experiment found “no evidence of new particles.” But, he insists, “It turns out we’re able to exclude any possible particle of this type a little more stringently. It extended the region to be excluded.”Chou thinks that maybe, with a stronger magnetic field, it might be worth re-exploring this region. “The effect we are looking for gets stronger as the magnetic field does.”Both scientists are interested in the future possibilities. “There is a proposal out there that involves putting very precisely controlled optical cavities before and after the wall, and using stronger and longer magnets,” Wester explains.Chou also points out that the data from the Fermilab experiment is still being examined. “There is speculation about particles called chameleons, which take on the properties of their environments.” These chameleon particles would have a small mass in low energy density, and large mass in environments of high energy density. “We are continuing analysis to see if maybe we can find a chameleon particle.”In the search for dark matter particles, Wester is optimistic about the role he and his colleagues are playing. “We did a serious measurement and excluded a region,” he says. “If our small experiment helps heighten awareness and leads to more experimental efforts, even using other techniques as well, it will be a huge benefit that we have done this.”Find out more about the Fermi Lab experiment by visiting gammev.fnal.gov .Copyright 2007 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. One of the mysteries of our universe is that of dark energy and matter. Scientists all over the world are attempting to discover what particles make up dark energy and matter. “Axions are one of the particles considered for dark matter,” William Wester tells PhysOrg.com. “We were hoping to get a signal proving that they exist with this experiment.”last_img read more

SingleCrystal Superconductors are a Big Step for the Field

first_img(PhysOrg.com) — In key advances for the field of superconductivity, a research group has created versions of a class of widely studied superconducting compounds that are each one continuous crystal, rather than composed of many crystalline grains. These single-crystal materials are important achievements because they display better properties than polycrystalline types and are easier to study. In a series of four recent papers, three published in Physical Review B and one in Physical Review Letters, the researchers describe the process they developed to “grow” the single-crystal materials. They also lay out the basic but vital measurements they performed on them, including their molecular structures and how they transport charge.The group, which includes scientists from Ames Laboratory in Iowa, Iowa State University (ISU), and San Diego State University, created single-crystal versions of two iron arsenide superconductors, a class of superconductors currently being examined by researchers across the globe. However, most of these researchers are studying polycrystalline varieties, with only recent work coming out on single crystals.The first paper1 describes the barium/iron/arsenic superconductor BaFe2As2 and a compound derived from it that contains a slightly different amount of barium as well as small amounts of potassium (The potassium, in this context, is a “dopant” material that bolsters the material’s properties. Doping is common in superconductivity research.)”Growing single-crystal versions of these materials allows us to study their ‘anisotropic’ superconducting properties—their tendency to display superconductivity along one axis but not others,” said the group’s spokeperson, Ames Lab and ISU scientist Paul Canfield, to PhysOrg.com.The major result published in the first paper is a determination of the highest magnetic field the superconducting state can withstand (called the upper critical field) and an evaluation of how anisotropic it is. Some superconductors are extremely anisotropic, and so fully understanding them requires good measurements of this behavior.Canfield and his group show in their second paper2 that their single-crystal growth method can be applied to another iron arsenide compound, SrFe2As2 (where “Sr” is strontium).And in the third paper3, the researchers discuss a new member of the iron arsenides. The compound is CaFe2As2 (“Ca” is calcium) and it had never before been identified as a member of that particular crystallographic family.”The discovery of CaFe2As2 was very exciting,” said Canfield. “We learned that at a temperature of 170 K [degrees Kelvin, here equal to about -150 degrees Fahrenheit] the material undergoes exceptionally clear changes to its structure and magnetic behavior.”This type of temperature-induced changes are known as “first-order” transitions, and understanding how they occur—a task made easier when the changes are obvious—will aid in scientists’ knowledge of superconducting materials.The fourth paper4 in the series further documents their study of CaFe2As2, detailing exactly why the material can be classified as a superconducting iron arsenide. The researchers found that at modest pressures the structural and magnetic changes that occur at 170 K are suppressed and the material becomes a superconductor.”This means that, from a basic science point of view, CaFe2As2 offers a clean model system that seems to encompass all of the salient features of these compounds (structural, magnetic and superconducting phase transitions) and that its behavior can be tuned with pressure,” Canfield said. “This is a very exciting discovery that may help guide the way to understanding this new family of superconductors.”Citations:1Phys. Rev. B 78, 014507 (2008)2Phys. Rev. B 78, 024516 (2008)3Phys. Rev. Lett. 101, 057006 (2008)4Phys. Rev. B 78, 014523 (2008)Copyright 2008 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Citation: ‘Single-Crystal’ Superconductors are a Big Step for the Field (2008, August 28) retrieved 18 August 2019 from https://phys.org/news/2008-08-single-crystal-superconductors-big-field.html A sample of a potassium-doped iron arsenide superconductor, shown on a millimeter grid. Image courtesy the American Physical Society [N. Ni et al. (10 July 2008). Anisotropic thermodynamic and transport properties of single-crystalline Ba1-xKxFe2As2 (x=0 and 0.45). Physical Review B, Vol 78, p014507, Fig 1] This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Information sharing interferes with wisdom of crowds study

first_img Is that your final answer? Study suggests method for improving individual decisions More information: How social influence can undermine the wisdom of crowd effect, PNAS, Published online before print May 16, 2011, doi: 10.1073/pnas.1008636108AbstractSocial groups can be remarkably smart and knowledgeable when their averaged judgements are compared with the judgements of individuals. Already Galton [Galton F (1907) Nature 75:7] found evidence that the median estimate of a group can be more accurate than estimates of experts. This wisdom of crowd effect was recently supported by examples from stock markets, political elections, and quiz shows [Surowiecki J (2004) The Wisdom of Crowds]. In contrast, we demonstrate by experimental evidence (N = 144) that even mild social influence can undermine the wisdom of crowd effect in simple estimation tasks. In the experiment, subjects could reconsider their response to factual questions after having received average or full information of the responses of other subjects. We compare subjects’ convergence of estimates and improvements in accuracy over five consecutive estimation periods with a control condition, in which no information about others’ responses was provided. Although groups are initially “wise,” knowledge about estimates of others narrows the diversity of opinions to such an extent that it undermines the wisdom of crowd effect in three different ways. The “social influence effect” diminishes the diversity of the crowd without improvements of its collective error. The “range reduction effect” moves the position of the truth to peripheral regions of the range of estimates so that the crowd becomes less reliable in providing expertise for external observers. The “confidence effect” boosts individuals’ confidence after convergence of their estimates despite lack of improved accuracy. Examples of the revealed mechanism range from misled elites to the recent global financial crisis. Social influence effect: Social influence diminishes group diversity without diminishing the collective error. Typical examples of experimental sessions for three information conditions, displaying five individual responses. Image (c) PNAS, doi: 10.1073/pnas.1008636108 Citation: Information sharing interferes with ‘wisdom of crowds’: study (2011, May 17) retrieved 18 August 2019 from https://phys.org/news/2011-05-wisdom-crowds.html (PhysOrg.com) — A statistical phenomenon, called the Wisdom of Crowds, happens when a group of individuals make guesses and the average of the guesses reveal accurate average answers. However, researchers have discovered that when the individuals are made aware of other participant’s guesses, there is a clear disruption to the accuracy of the guesses. © 2010 PhysOrg.com The study, led by mathematician Jan Lorenz and sociologist Heiko Rahut from Switzerland’s ETH Zurich published their recent findings in Proceedings of the National Academy of Sciences, showing that even a small amount of social influence on a group can interfere with the Wisdom of Crowd effect.For the study, researchers brought in 144 students and placed them in isolated locations and asked them to guess things like how many crimes were committed in 2006 and what the population density of Switzerland was. Based on the accuracy of their answers, participants were given a small monetary award and then the process was repeated for a total of four rounds. The students were broken up into two groups, with one group receiving information on what other peers had guessed and the other remaining isolated.As each round continued, the group with no influence by other peers showed their results becoming more accurate. The individuals that received information on what their peers were guessing however showed less accuracy in their answers.Researchers found that those receiving social input from their peers either led individuals to second guess themselves or, seeing others may have answered the same, become more confident in their incorrect responses. According to the results of the study, the Wisdom of Groups phenomenon appears to only be accurate when the individuals in the group are not aware or influenced by others in the group. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore furtherlast_img read more

Germany sets weekend record for solar power

first_img Citation: Germany sets weekend record for solar power (2012, May 30) retrieved 18 August 2019 from https://phys.org/news/2012-05-germany-weekend-solar-power.html Explore further Image: Array Technologies That comparison is significant because, in the wake of the Fukushima nuclear disaster in Japan, Germany abandoned nuclear energy endeavors. They shut down eight plants in favor of safer options and instead shouldered the task of further developing renewable energy sources. Allnoch said the data is based on information from the European Energy Exchange (EEX), based in Leipzig.Germany aggressively supports alternative energy sources and, by the year 2022, Germany expects to shutter its remaining nine nuclear power plants. The lack of these nuclear power facilities will create a gap in the country’s energy infrastructure, however. Germany is looking toward sources such as solar, wind and biomass.That support and commitment have come at a price. A 2012 Environment Ministry report showed that German taxpayers pay an extra four billion euros per year on top of their electricity bills to support solar power.Allnoch and his supporters would prefer to look at the “price” context in another way. “Even with all the safety precautions”, he said, there is still a risk at nuclear plants. “A global phaseout would be ideal but is not likely to happen soon.”As for costs, he said that while everyone worries about costs, the markets are shifting. He said once the uncertainty calms down, “we will see that we can do without nuclear power.”In relegating nuclear energy to the past, the road to replace it may be rocky, he added, but it is do-able. “We need to rise to this challenge.”The new record-breaking figures from Germany, however, do not quiet some energy experts who stress that without good storage strategies for excess power, such record-breaking numbers are not meaningful. They say the real point is to get consistently large percentages of power from renewable sources. German cabinet passes nuclear exit billcenter_img © 2012 Phys.Org (Phys.org) — Solar power plants in Germany have set a new record. “Never before anywhere has a country produced as much photovoltaic electricity,” said Norbert Allnoch, Germany’s director of the Institute of the Renewable Energy Industry in Muenster. The plants peaked at 22 gigawatts of output for a few hours over the weekend, on Friday and Saturday. The numbers are important in that they yielded almost half the country’s energy mid-day electricity needs. The 22 gigawatts is up from 14 GW a year ago. Also, this 22 gigawatts of output is equal to about 20 nuclear plants. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

MYO armband to muscle into computer control w video

first_imgMYO armbands The next interface: Electrical fields, MGC3130, and your hand (w/ Video) © 2013 Phys.org More information: getmyo.com/ Explore further (Phys.org) —”Wave goodbye to camera-based gesture control.” That is the confident directive coming from a one-year-old Waterloo, Ontario, startup called Thalmic Labs. The company is prepared to ship its next batch of wearable-computing armbands for device controls early next year. The $149 armbands called MYO do not require cameras in order to track hand or arm movements. The armbands can wirelessly control and interact with computers and other digital consumer products by recognizing the electric impulses in users’ muscles.center_img “We work day and night,” said one team member, and their steadfastness is fed by a notion that the MYO could revolutionize the way people interact with technology. Thalmic Labs said they are accepting pre-orders for the second shipment of MYOs shipping early 2014. The MYO is worn around the forearm; its purpose is to control computers, phones, and other devices, sending the data via Bluetooth. Windows and Mac operating systems are supported and APIs will be available for iOS and Android.Bluetooth 4.0 Low Energy (BLE) is used for the MYO to communicate with the paired devices. (Bluetooth version 4.0 is the most recent version of Bluetooth wireless technology. It includes a low-energy feature promoted as good news for developers and manufacturers of Bluetooth devices and applications—enabling markets for devices that are low-cost and operate with low-power wireless connectivity.)The MYO specs include on-board, rechargeable lithium-ion batteries and an ARM processor. Also part of the mix are the company’s proprietary muscle-activity sensors and a six-axis inertial measurement unit.A user’s gestures and movements are actually detected in two ways: muscle activity and motion sensing. The Thalmic team says that when sensing the muscle movements of the user, the MYO can detect changes down to each individual finger. Also, when tracking arm and hand positions, the MYO picks up subtle movements and rotations in all directions.Right now, as indicated in their newly released video of the company, Thalmic Labs hopes for greater things for MYO via a developer community. They expect an official developer program to be up and running in the next few months. They pride themselves in groundbreaking technology, as a team with specialties from electrical engineering to embedded system design. Nonetheless, they are looking to developers for innovative ideas in applications. Citation: MYO armband to muscle into computer control (w/ video) (2013, April 28) retrieved 18 August 2019 from https://phys.org/news/2013-04-myo-armband-muscle-video.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Global warming may be causing surge in numbers of pink salmon

first_img(Phys.org) —A pair of researchers, one with the University of Alaska, the other with Independent, Auke Bay are suggesting in a paper they’ve had printed in Proceedings of the National Academy of Sciences, that global warming is partially responsible for large increases in pink salmon populations in North America and Asia. Alan Springer and Gus van Vliet claim that rising ocean temperatures are at least partly to blame for increased pink salmon populations due to an increase in the amount of available food. Explore further Citation: Global warming may be causing surge in numbers of pink salmon (2014, April 1) retrieved 18 August 2019 from https://phys.org/news/2014-04-global-surge-pink-salmon.html Scientists have blamed global warming for smaller numbers of many fish species—a recent Intergovernmental Panel on Climate Change, for example, claimed that rising ocean temperatures (due to global warming) is causing a reduction in numbers of tuna and cod populations in the Atlantic Ocean. Now it appears that global warming may actually cause some fish populations to increase.Springer and Vliet suggest that pink salmon swimming in warmer water during their formative years are exposed to more food (zooplankton, small fish and squid, etc.) which allows them to eat more, and then later, to produce more offspring. It leads to more fish in the sea, they say, which in turn might have a negative impact on other sea life that feed on the same prey. They focused their study on sea life in the Aleutian Islands and the Bering Sea, looking to find out if burgeoning fish populations are causing a decrease in bird populations. In sampling both populations, they noted that second year salmon were more numerous and that bird populations sank as salmon surged, due to less egg laying and lowered survival rate of chicks—signs of nutritional stress.Whatever the cause, what is undeniable is that pink salmon are thriving and are beginning to take over ecosystems previously dominated by other types of salmon or even other types of animals altogether. Complicating the situation is the fact that many of the salmon swimming freely in the ocean came to be there after being released by fish hatcheries in an effort to boost harvests.Pink salmon populations have been rising since the 1970’s, roughly the same time frame as global warming—so much so that some have begun suggesting that it’s a problem easily solved by allowing fishermen to catch more. While that may help solve the problem of too many fish, it doesn’t really answer the question of whether global warming is truly to blame, and if it is, what other changes it may be causing in poorly understood ocean ecosystems. Oncorhynchus gorbuscha. Credit: Timothy Knepp/U.S. Fish and Wildlife Service Journal information: Proceedings of the National Academy of Sciencescenter_img Researchers uncover some good news for BC’s troubled salmon populations More information: Climate change, pink salmon, and the nexus between bottom-up and top-down forcing in the subarctic Pacific Ocean and Bering Sea, PNAS, Alan M. Springer, DOI: 10.1073/pnas.1319089111AbstractClimate change in the last century was associated with spectacular growth of many wild Pacific salmon stocks in the North Pacific Ocean and Bering Sea, apparently through bottom-up forcing linking meteorology to ocean physics, water temperature, and plankton production. One species in particular, pink salmon, became so numerous by the 1990s that they began to dominate other species of salmon for prey resources and to exert top-down control in the open ocean ecosystem. Information from long-term monitoring of seabirds in the Aleutian Islands and Bering Sea reveals that the sphere of influence of pink salmon is much larger than previously known. Seabirds, pink salmon, other species of salmon, and by extension other higher-order predators, are tightly linked ecologically and must be included in international management and conservation policies for sustaining all species that compete for common, finite resource pools. These data further emphasize that the unique 2-y cycle in abundance of pink salmon drives interannual shifts between two alternate states of a complex marine ecosystem. © 2014 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Study indicates Spanish conquest of Peru may have resulted in changes to

first_img The sand dune ridges along the northern coast of Peru came about, the researchers claim, due to earthquakes loosening sand deposits in the Chira valley. That sand was eventually swept into rivers which carried it to the sea. Currents then carried it north eventually depositing it along the shoreline, building up over time into large ridges. Radiocarbon dating of charcoal remnants from fire pits atop some of the ridges has shown them to have formed from over 5000 years ago to as recently as 400 years ago. Excavating one of the existing ridges, the two researchers report, revealed mollusk shells which because there were so many of them, served as a shield against the wind, which would have blown the sand off the ridges long ago, had not the shells been there to offer protection.The Inca, the researchers report, lived along the shorelines of northwest South America for thousands of years, catching, cooking and eating mollusks and tossing the shells aside as they sat atop a ridge. The result was millions of shells littering the surface of the ridges, forming armor of sorts, which allowed the ridges to remain intact far longer than they would have otherwise. But, then, the Spanish arrived, conquering the Incas and forcing them to move inland. After that, the shell littering ceased—without a constantly rejuvenated suit of armor, many of the ridges succumbed to the winds and vanished. Thus, the coast was altered in a way that neither the Inca nor their conquerors could have possibly imagined. Space image: Aorounga Crater, Chad (Phys.org) —A study by a pair of researchers with the University of Maine suggests that the northern coast of Peru may have been altered due to population shifts as a result of the Spanish conquest in the 1500’s. In their paper published in Proceedings of the National Academy of Sciences, Daniel Belknap and Daniel Sandweiss describe a field study they conducted in the area that suggested that Inca living on the coast prior to the Spanish conquest, may have inadvertently been supporting the existence of sand ridges by discarding mollusk shells. After they left, it appears, some of the sand ridges were blown away by the wind. Citation: Study indicates Spanish conquest of Peru may have resulted in changes to coastal shoreline (2014, May 20) retrieved 18 August 2019 from https://phys.org/news/2014-05-spanish-conquest-peru-resulted-coastal.html Journal information: Proceedings of the National Academy of Sciences Surface of ridge J and test pit surface test pit-Chira-1997-number 4: STP-C-97-4. Credit: PNAS, doi: 10.1073/pnas.1404568111center_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further © 2014 Phys.org More information: Effect of the Spanish Conquest on coastal change in Northwestern Peru, Daniel F. Belknap, PNAS, DOI: 10.1073/pnas.1404568111AbstractWhen Francisco Pizarro and his small band of Spanish conquistadores landed in northern Peru in A.D. 1532 to begin their conquest of the vast Inca Empire, they initiated profound changes in the culture, language, technology, economics, and demography of western South America. They also altered anthropogenically modulated processes of shoreline change that had functioned for millennia. Beginning with the extirpation of local cultures as a result of the Spanish Conquest, and continuing through today, the intersection of demography, economy, and El Niño-driven beach-ridge formation on the Chira beach-ridge plain of Northwestern Peru has changed the nature of coastal evolution in this region. A similar event may have occurred at about 2800 calibrated y B.P. in association with increased El Niño frequency.last_img read more

Bridgmanite sample found to remain stable at lower mantle conditions

first_imgSchematic picture of the Earth’s interior. On the right side is the example of the part of the two-dimensional wide scan of x-ray diffraction image of Fe, Al-bearing bridgmanite, on the left side is the crystal structure of pure Fe-bridgmanite. Credit: Leyla Ismailova/University of Bayreuth More information: L. Ismailova et al. Stability of Fe,Al-bearing bridgmanite in the lower mantle and synthesis of pure Fe-bridgmanite, Science Advances (2016). DOI: 10.1126/sciadv.1600427AbstractThe physical and chemical properties of Earth’s mantle, as well as its dynamics and evolution, heavily depend on the phase composition of the region. On the basis of experiments in laser-heated diamond anvil cells, we demonstrate that Fe,Al-bearing bridgmanite (magnesium silicate perovskite) is stable to pressures over 120 GPa and temperatures above 3000 K. Ferric iron stabilizes Fe-rich bridgmanite such that we were able to synthesize pure iron bridgmanite at pressures between ~45 and 110 GPa. The compressibility of ferric iron–bearing bridgmanite is significantly different from any known bridgmanite, which has direct implications for the interpretation of seismic tomography data. Journal information: Science Advances (Phys.org)—A diverse team of researchers with members from Germany, France, Russia and the U.S. has subjected a sample of bridgmanite to conditions believed to be present at Earth’s lower mantle and has found that it remained stable. In their paper published in the journal Science Advances, the team describes the testing they conducted, what they found and their theory regarding the dynamo effect that is, perhaps, the source of the planet’s magnetic field Citation: Bridgmanite sample found to remain stable at lower mantle conditions (2016, July 18) retrieved 18 August 2019 from https://phys.org/news/2016-07-bridgmanite-sample-stable-mantle-conditions.html Developing a picture of the Earth’s mantlecenter_img Explore further Studying the interior of planet Earth is difficult due to the huge scale involved—researchers cannot simply drill a hole all the way to the core to grab samples of material. For that reason, they have developed and used other tools such as seismic monitors to learn more. Though the have learned much, there is still a lot that is unknown or uncertain. One of these uncertainties is the makeup of the planet’s lower mantle—the part just next to the core. Prior research has indicated that it is likely a mineral called bridgmanite. Other researchers have suggested that bridgmanite would not be stable under the very high temperature and pressure that would exist in the lower mantle. In this new effort, the researchers sought to settle this debate by bringing samples of bridgmanite into their lab and testing it.To exert very high pressure on the sample similar to that believed to exist in the lower mantle, the researchers used laser-heated diamond anvil cells—creating a vice-like grip by squeezing a very small sample between two diamonds and focusing a laser on them. The team ran several such experiments at different temperatures and pressures, maxing out at 23 gigapascals and 1,800 Kelvin. They then used X-rays to examine the samples to see how they held. The team reports that the samples held up very well and concluded that bridgmanite is stable under the conditions believed to exist at the lower mantle.The team found that when samples contained different amounts of iron, there were differing levels of stability. Those differences, they suggest, could offer an explanation for seismic activity deep in the planet which could play a role in establishing the dynamo that is responsible for the planet’s magnetic field. © 2016 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Physicists extend stochastic thermodynamics deeper into quantum territory

first_img The physicists, Anthony Bartolotta, a graduate student at Caltech, and Sebastian Deffner, Physics Professor at the University of Maryland Baltimore County, have written a paper on the Jarzynski equality for quantum field theories that will be published in an upcoming issue of Physical Review X.The work address one of the biggest challenges in fundamental physics, which is to determine how the laws of classical thermodynamics can be extended to the quantum scale. Understanding work and heat flow at the level of subatomic particles would benefit a wide range of areas, from designing nanoscale materials to understanding the evolution of the early universe.As Bartolotta and Deffner explain in their paper, in contrast to the large leaps made in the “microscopic theories” of classical and quantum mechanics during the past century, the development of thermodynamics has been rather stagnant over that time. Although thermodynamics was originally developed to describe the relation between energy and work, the theory traditionally applies only to systems that change infinitely slowly. In 1997, physicist Christopher Jarzynski at the University of Maryland College Park introduced a way to extend thermodynamics to systems in which heat and energy transfer processes occur at any rate. The fluctuation theorems, the most prominent of which is now called the Jarzynski equality, have made it possible to understand the thermodynamics of a wider range of smaller, yet still classical, systems.”Thermodynamics is a phenomenological theory to describe the average behavior of heat and work,” Deffner told Phys.org. “Originally designed to improve big, stinky heat engines, it was not capable of describing small systems and systems that operate far from equilibrium. The Jarzynski equality dramatically broadened the scope of thermodynamics and laid the groundwork for stochastic thermodynamics, which is a new and very active branch of research.” Thermodynamic laws that describe heat and energy are being extended to the quantum scale. Source: Pexels. Photograph by Paweł Kadysz Stochastic thermodynamics deals with classical thermodynamic concepts such as work, heat, and entropy, but on the level of fluctuating trajectories of atoms and molecules. This more detailed picture is particularly important for understanding thermodynamics in small-scale systems, which is also the realm of various emerging applications.It wasn’t for another decade, however, until the Jarzynski equality and other fluctuation theorems were extended to the quantum scale, at least up to a point. In 2007, researchers determined how quantum effects modify the usual interpretation of work. However, many questions still remain and overall, the area of quantum stochastic thermodynamics is still incomplete. Against this backdrop, the results of the new study represent a significant advance.”Now, in 2018 we have taken the next big step forward,” Deffner said. “We have generalized stochastic thermodynamics to quantum field theories (QFT). In a certain sense we have extended stochastic thermodynamics to its ultimate range of validity, since QFT is designed to be the most fundamental theory in physics.”One of the keys to the achievement was to develop a completely novel graph theoretic approach, which allowed the researchers to classify and combine the Feynman diagrams used to describe particle behavior in a new way. More specifically, the approach makes it possible to precisely calculate infinite sums of all the possible permutations (or arrangements) of disconnected subdiagrams describing the particle trajectories.”The quantity we were interested in, the work, is different than the quantities usually calculated by particle theorists and thus required a different approach,” Bartolotta said.The physicists expect that the results will allow other scientists to apply the fluctuation theorems to a wide variety of problems at the forefront of physics, such as in particle physics, cosmology, and condensed matter physics. This includes studying things like quantum engines, the thermodynamic properties of graphene, and the quark gluon plasma produced in heavy ion colliders—some of the most extreme conditions found in nature.In the future, the physicists plan to generalize their approach to a wider variety of quantum field theories, which will open up even further possibilities. What is quantum in quantum thermodynamics? More information: Anthony Bartolotta and Sebastian Deffner. “Jarzynski Equality for Driven Quantum Field Theories.” Physical Review X. DOI: 10.1103/PhysRevX.8.011033. Also at arXiv:1710.00829 [cond-mat.stat-mech] Citation: Physicists extend stochastic thermodynamics deeper into quantum territory (2018, February 13) retrieved 18 August 2019 from https://phys.org/news/2018-02-physicists-stochastic-thermodynamics-deeper-quantum.html © 2018 Phys.org Journal information: Physical Review X This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Physicists have extended one of the most prominent fluctuation theorems of classical stochastic thermodynamics, the Jarzynski equality, to quantum field theory. As quantum field theory is considered to be the most fundamental theory in physics, the results allow the knowledge of stochastic thermodynamics to be applied, for the first time, across the full range of energy and length scales. Explore furtherlast_img read more

Marvels of cinema on stage

first_imgRaising the issue of gender equality in cinema, Arth made an extraordinary impact back in 1980s. This semi-autobiographical film directed by Mahesh Bhatt in 1982 changed the face of Indian cinema forever and is back with a bang as a theatrical production. After the recent success of   his plays The Last Salute and Trial of Errors which also launched his latest protégé Imran Zahid, the duo are now pairing up again for the dramatic adaptation of Arth Also Read – ‘Playing Jojo was emotionally exhausting’.Bhatt feels that Arth was a classic film that raised the issue of gender equality way back in the 80’s. ‘The film looked at the issue of women emancipation like no Indian dramatic work ever has. No one has been able to better what Arth highlighted in the world of movies or in theatre. I think the 21st century India needs to be experience the theme of Arth through theatre’ says the filmmaker ahead of translating the screenplay for the stage. Arth was way ahead of its time and Bhatt feels that subject will strike a chord even with today’s generation. It looked at the bold subject of extra marital relationships was also remembered for its memorable soundtrack. Also Read – Leslie doing new comedy special with NetflixBelieving that the fabric of society has not gone under a complete change over the yearsm the director adds, ‘The issues with regards to our society that were raised in Arth are relevant in even in todays times. Theater has given me an entirely new outlet and after staging two successful plays The Last Salute and Trial of Errors I took this decision.I think adapting such a piece of art into a theatrical adaptation will not be an easy task but I am ready for this test.  I feel this medium has help connecting with audience in all together different way,’ he adds.Delhi-based actor Imran Zahid , who earlier essayed the role of Muntadar Al Zaidiin The Last Salute and of journalist Rehan in Trial of Errors is all gearing up for this new assignment.‘Mahesh Bhatt is all set to recreate magic of film in a theatrical play. It’ll be a big challenge for me to play the lead but I am up for it,’ says Imran.last_img read more