Citation: Virtual 3D nanorobots could lead to real cancer-fighting technology (2007, December 5) retrieved 18 August 2019 from https://phys.org/news/2007-12-virtual-3d-nanorobots-real-cancer-fighting.html Nanorobots search for organ-inlets demanding protein injection. Image credit: Adriano Cavalcanti, et al. 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. To demonstrate the system, the researchers tested several cases where the nanorobots used different strategies to detect proteins, and in vessels with varying diameters. As expected, their results showed that nanorobots have a better chance of finding a target in smaller vessels. Also, the use of both chemical and thermal biosensors greatly improved the nanorobots’ efficiency compared with random motion.In addition to sensing, the simulation will hopefully provide interactive tools for many challenging aspects of nanorobot design, such as control methods, manufacturing approaches, actuator (motor) design, and more. The researchers are currently using the simulation for tests in laparoscopic surgery, diabetes, cancer, brain aneurysms, cardiology, military biohazard defense, and drug delivery. The development is highly collaborative, with advances depending on future improvements in nanoelectronics, new materials, and genomics research. “One of the major factors for successfully developing nanorobots is to bring together professionals with interdisciplinary views of science and technologies,” Cavalcanti said. “It is necessary to keep your eyes open for chemistry, materials engineering, electronics, computing, physics, mechanics, photonics, pharmaceutics, and medicine technologies. Our work is advancing progressively because we have experts from different backgrounds participating. We all pursue a common interest in working together to build medical nanorobots.”With all these disciplines moving ahead, a precise simulation system can help researchers understand the performance requirements for practical nanorobots, even before the technologies exist.“Some existing components, like sensors, motors, actuators and antennas, are already available as nanodevices,” said Cavalcanti. “Then you have to take the next step: those components should be integrated as embedded parts assembled into a nanorobot.”He explained that the biggest motivator for innovation comes from economic and strategic interests. Due to the wide variety of applications, nanorobots will almost certainly offer economic incentives.“In the case of nanorobots, you have huge potential for commercialization, with enormous chances of profit for the medical and pharmaceutical sectors,” Cavalcanti said. “Among other applications in medicine, nanororobots also represent an important strategic technology for military defense against biohazard contamination, which should help to protect against different sorts of pandemic outbreaks.”Due to these motivations, Cavalcanti hopes that working nanorobots will be here in the not-too-distant future.“If you consider the velocity that miniaturization is moving, from micro to nanoelectronics, then you can easily understand the feasibility to have medical nanorobots integrated as a nanoelectronic molecular machine before 2015,” he predicted, adding that nanorobots, like all medical technologies, would still need to undergo safety testing, which would push back the date for mass production and commercialization.More information: www.nanorobotdesign.comPublication: Cavalcanti, Adriano, Shirinzadeh, Bijan, Freitas, Robert A Jr., and Hogg, Tad. “Nanorobot architecture for medical target identification.” Nanotechnology 19 (2008) 015103 (15pp).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. But there is still a great deal of work to do before tiny “molecular machines” can begin traveling through our arteries for diagnosing or treating our ailments. To try to pick up the pace, a group of researchers has recently developed an innovative approach to help in the research and development of nanorobots – virtual reality. Adriano Cavalcanti, Bijan Shirinzadeh, Robert Freitas, Jr., and Tad Hogg, representing institutions in Melbourne, Australia, and the U.S., have published their simulation procedure in a recent issue of Nanotechnology. Just as 3D simulations previously helped engineers greatly accelerate developmental research in the semiconductor industry, Cavalcanti and colleagues hope that virtual nanorobots, virtual biomolecules and virtual arteries will accelerate the progress of nanorobot development.“The software NCD (nanorobot control design) is a system implemented to serve as a test bed for nanorobot 3D prototyping,” Cavalcanti, CEO of the Center for Automation in Nanobiotech and researcher at Monash University in Melbourne, told PhysOrg.com. “It is an advanced nanomechatronics simulator that provides physical and numerical information for nanorobot task-based modeling. Serving as a fast development platform for medical nanorobots investigation, the NCD simulations show how to interact and control a nanorobot inside the body.”In a demonstration of the real-time simulation, the nanorobots had the task of searching for proteins in a dynamic virtual environment, and identifying and bringing those proteins to a specific “organ-inlet” for drug delivery. The researchers analyzed how the nanorobots used different strategies to achieve this goal. For instance, the nanorobots could employ different sensory capabilities such as chemical and temperature sensors, as well as random movement.For the nanorobots, one of the most difficult parts was maneuvering close enough to a biomolecule to be able to sense that biomolecule, while accounting for many different forces and moving bodies. Unlike on the macroscale, viscosity dominates movement in arteries, affecting the nanorobots’ traveling as it encounters obstacles and proteins moving passively through the fluid. From eliminating the side effects of chemotherapy to treating Alzheimer’s disease, the potential medical applications of nanorobots are vast and ambitious. In the past decade, researchers have made many improvements on the different systems required for developing practical nanorobots, such as sensors, energy supply, and data transmission.
Liquid Battery Offers Promising Solar Energy Storage Technique The new Metal-Air Ionic Liquid battery is being designed by Cody Friesen, a professor of materials science at Arizona State and founder of Fluidic Energy, along with other researchers. The key to the new battery is that it uses ionic liquids as its electrolyte, which could help it overcome some significant problems faced by previous metal-air batteries. In the past, metal-air batteries have usually used water-based electrolytes, but due to water evaporation, the batteries tended to fail prematurely. The advantage of ionic liquids, like those used in Fluidic Energy’s new battery, is that they don’t evaporate. Ionic liquids are salts that are a liquid at room temperature. Compared to water, ionic liquids are much more viscous, and they also conduct electricity fairly well. The challenge will be finding an inexpensive ionic liquid that works well in the new batteries, although Friesen has not yet discussed the specific ionic liquids his company has been investigating. A metal-air battery that uses ionic liquids as its electrolyte could have several advantages. For one thing, it can function for a longer period time since its electrolyte doesn’t evaporate. Also, the batteries could offer better electrochemical stability, which means they could use materials that have a greater energy density than zinc. Friesen and his research team hope to achieve energy densities of anywhere from 900 to 1,600 watt-hours per kilogram. This density could lead to electric vehicles that could travel 400 to 500 miles on a single charge, Friesen said.Finally, Fluidic Energy is tackling another problem facing rechargeable batteries: the growth of dendrites that occurs on the electrodes during charging. Dendrites limit the number of charging cycles and decrease the lifetime of the battery. To combat this problem, Fluidic Energy has designed a porous electrode scaffold that prevents dendrite formation. “I’m not claiming we have it yet, but if we do succeed, it really does change the way we think about storage,” Friesen said.via: Technology Review© 2009 PhysOrg.com Citation: Metal-Air Battery Could Store 11 Times More Energy than Lithium-Ion (2009, November 5) retrieved 18 August 2019 from https://phys.org/news/2009-11-metal-air-battery-energy-lithium-ion.html Explore further Ionic liquids (in blue) in a beaker of mineral oil. Image credit: John Wilkes. (PhysOrg.com) — A spinoff company from Arizona State University plans to build a new battery with an energy density 11 times greater than that of lithium-ion batteries for just one-third the cost. With a $5.13 million research grant from the US Department of Energy awarded last week, Fluidic Energy hopes to turn its ultra-dense energy storage technology into a reality. 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.
Citation: Bright lights, small systems: Molecular differentiation using free-electron lasers (2011, October 28) retrieved 18 August 2019 from https://phys.org/news/2011-10-bright-small-molecular-differentiation-free-electron.html Explore further How not to blow up a molecule More information: Double-core-hole spectroscopy for chemical analysis with an intense X-ray femtosecond laser, Published online before print October 3, 2011, PNAS October 11, 2011 vol. 108 no. 41 16912-16915, doi:10.1073/pnas.1111380108 Lead author Nora Berrah, working with her Western Michigan University research teams, as well as with those at Tohoku University, University of Turku, Stockholm University, Uppsala University, Sincrotrone Trieste, Stanford Linear Accelerator Center, Hiroshima University, and Institute for Molecular Science, faced several challenges in conducting the investigation. In performing direct observation of double-core holes, Berrah cites double-core-hole ionization as a powerful and useful process which can be achieved effectively with multi-photon ionization using a free-electron laser. “The challenge for us was to isolate the multi-photon effect of interest, the two-sites double core hole (tsDCH), from other multi-photon effects or from the many single photon effects, because the instrument and technique we used detected and displayed all electrons coming from any ionization and decay process.” Moreover, Berrah adds, “The main challenge to observing direct double-core holes in a molecule is to have enough photons in the FEL pulse to displace the two innermost electrons from each of the atoms that form the molecule. This effect needs to be achieved very fast – within a few femtoseconds (fs), or quadrillionths of a second – and certainly before the holes have a chance to refill via the Auger process, with the outer electrons of the atoms that form the molecule.” The ultra-short pulse duration is what allowed them to bypass the Auger effect. Berrah notes that it was rather straightforward to compare their measurements with theoretical modeling. “Plotting our experimental data against the theory demonstrates clearly the agreement,” she notes, “which is very good concerning the structures we observed. However, there are discrepancies regarding the intensity of the structures, which may be due to effects not included in the calculations. That being said, the calculations guided us very well.”The key innovation the team developed to address these challenges, says Berrah, was demonstrating that two-sites double core holes can be measured to fingerprint molecules that are similar enough. ”Other spectroscopic techniques can’t resolve the spectral lines from similar molecules using single-core-hole ionization. We believe that this is a rebirth of electron spectroscopy for chemical analysis, or ESCA, which earned Kai Siegbahn a Nobel Prize.” Schematic illustration of (A) the electronic structure of the CO molecule, (B) the SCH ionization at the C K-edge (SCH_C) and the SCH ionization at the O K-edge (SCH_O), and (C) the ssDCH ionization at the C K-edge (ssDCH_C), the ssDCH ionization of the O K-edge (ssDCH_O) and the tsDCH ionization. Copyright ©PNAS, doi:10.1073/pnas.1111380108 Other innovations are also possible. “The current experimental design, known as simple time-of-flight detection,” says Berrah, “has in fact already been improved by our group and used in recent experiments carried out this summer and fall at the LCLS X-FEL with an electron magnetic bottle (built at Uppsala University) which improves significantly the detection efficiency of the process. Furthermore, this new technique allows what we call covariance mapping which is similar to measuring coincidence events among many different electrons. This technique allows us to delineate every physical process cleanly and will allow us to spot new physical processes not known to us.”Furthermore, the group’s findings have implications for future X-ray control of physical inner-shell processes. “One could achieve X-ray control in the future by deciding and choosing certain electronic decay patterns that are desirable by selecting specific ionization stage,” Berrah explains. “Right now, when we ionize matter, all electrons are emitted if the frequency and intensity are sufficient. However, with FELs, if we decided for example to only make hollow matter, then choosing very short pulse duration – that is, shorter than the Auger decay of the atoms of interest in the molecule – and very intense pulses, would allow us to ionize only the two-K shell, or innermost shell, electrons.” This hollow matter has benefits, in addition to demonstrating the existence of new exotic matter. Hollow matter is transparent to X-rays since after the ionization of the two innermost electrons, the pulse is over and no ionization is possible. This effect can be used in scattering of biological matter, which allows taking a snapshot of proteins or viruses whose structure is unknown (and can’t be obtained using synchrotrons because they can’t crystallize) without distorting or destroying them before their image is obtained. Moving forward, Berrah states that they need to analyze the data taken with the new electron magnetic bottle to know what new physical or chemical processes could be determined with their new methodology. In addition, Berrah concludes, a United States (Western Michigan University- Linac Coherent Light Source, Stanford Linear Accelerator Center) / German (Max Planck Society) collaboration is building sophisticated instrumentation to use fully the X-FEL. “One of the instruments will allow us to conduct X-ray pump-X-ray probe experiments on matter to understand how bonds are broken and how they are formed in real time. These time-resolved experiments with either optical lasers or the X-FEL are the next most powerful means to understand, in real time, how matter responds to X-ray radiation.” Copyright 2011 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. (PhysOrg.com) — Double-core-hole (DCH) states – in which two electrons are ejected from their positions, creating vacancies – occurring at different atomic sites are very sensitive to the chemical environment of the two holes. While differentiating between similar chemical systems using double-core-hole spectroscopy has historically been examined only theoretically, and so far there is no published work on two-site DCH states using conventional X-ray photoelectron spectroscopy based on single-photon ionization. However, a study led by Western Michigan University researchers has recently reported direct observation of double-core holes with single vacancies on two different sites produced using short, intense X-ray pulses from the Linac Coherent Light Source (LCLS) free-electron laser (FEL). Their results compare favorably with theoretical modeling, which the scientists say proves the feasibility of their approach. 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.
Citation: Leap Motion targets May for pre-orders and store sales (2013, March 9) retrieved 18 August 2019 from https://phys.org/news/2013-03-motion-pre-orders-sales.html This is 3-D gesture-control where a user controls the screen in three dimensions using hands and fingers. It is capable of imaging all ten fingers and the entire hand and it actually tracks hands and fingers as well as chopsticks. © 2013 Phys.org (Phys.org) —Leap Motion will start shipping its 3-D motion controllers on pre-order basis in mid-May. Big news? For a growing Leap Motion fan base, it’s great news. Leap Motion launched its sensing controller last year, and developers began working with this advanced motion sensing technology for human computer interactions. Thousands of developers have since worked with Leap Motion’s device. According to the company, the device will cost $79.99 on pre-order and will ship from May 13. Following that, the device will be sold at Best Buy from May 19 at $80. Leap Motion creates finger-happy gesture control (w/ Video) Explore further 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. The hardware will be supported in Windows 7 or 8 and Mac OS 10.7 or 10.8. The process begins when the user plugs the Leap Motion controller into a USB port, loads Leap Motion software, and waves to calibrate. The company’s claim is that its technology is 200 times more accurate than anything else on the market. Leap Motion sees its controller as potentially entering numerous applications beyond gaming. For digital art, the art work could more readily feature 3-D images; in business, the user would create signatures; in medicine, surgeons could control 3-D medical data on the screen with hand waves and without having to remove their gloves. While Microsoft Kinect for Windows features hand and finger control, the Leap Motion device is not the same as it commands a smaller observation space, where Kinect works in an entire living room space. Technology watchers believe Leap Motion will play its own role in how future computer users interact with screens beyond mouse and touchpad. Last year’s headlines alone reflected a high level of interest in the company’s technology. Wired in May headlined “Why the Leap is the Best Gesture Control System We’ve Ever Tested.” Technology Review a month later told its readers, “Forget pinch-to-zoom,” and instead imagine rotating a hand to control the orientation of an object with six degrees of freedom, or using both hands at once to control either end of a surface, in sculpting, as part of an object destined for a 3-D printer.Recently, Leap Motion’s tendency to unleash imaginations was in evidence when Robbie Tilton reported on his blog that he used a Leap Motion for working on an image projected on to a prism. The display he designed created the illusion of depth. His use of Leap Motion helped to create a visually arresting gesture-controllable display that looked like a spinning globe floating in mid-air; a computer monitor was laid flat on a table and aimed up at the prism.
More information: Yijiang Chen, et al. “Active laser ranging over planetary distances with millimeter accuracy.” Applied Physics Letters 102, 241107 (2013). DOI: 10.1063/1.4810906 (Phys.org) —Currently, precision laser ranging is limited to the Earth-Moon distance. These systems are based on passive laser ranging, so that the signal deteriorates as 1/R4 over distance R. In a new study, physicists have designed a system that has a range thousands of times this distance due to the fact that it is based on active laser ranging, where the signal deteriorates as only 1/R2. The new system also has the potential to achieve sub-millimeter accuracy, yielding an overall performance improvement that is more than three orders of magnitude better than today’s state-of-the-art space ranging systems. Explore further Birnbaum explained that the laser itself is not any more powerful than those in use today.”The lasers themselves do not need to be very powerful,” he said. “Commercially available lasers have enough pulse energy, and the light intensity as it leaves the transmitter can be low enough that it is even eye-safe. The key is to have a very sensitive receiver and a method to pick out the ‘signal’ photons from all the background light.”The scientists tested the approach with lab experiments and field testing on Earth. They measured deviations in actual distance of no more than 0.14 mm, well below the goal of 1 mm precision. Although fluctuations due to atmospheric turbulence in Earth’s atmosphere will add a small amount of error, the scientists think that this error can be limited to less than 1 mm.The biggest challenges to realizing the long-range, high-precision laser include synchronizing the transceivers and overcoming a background of stray light. The researchers plan to overcome these challenges by using a new synchronization scheme involving interplanetary laser communications, along with using short pulses with a low repetition rate. In the future, they’d like to test the system on a somewhat larger scale.”Having demonstrated this technique in the lab and between two terminals in the field, we’d like to next perform ranging between a transceiver mounted on an airplane and one on the ground,” Birnbaum said. “Then we could move on to ranging between a ground terminal and a spacecraft.”This giant leap in laser ranging could have many applications. One of the first may be to solve the puzzle of the composition of Mars’ interior. Since the 1970s, scientists have been trying to find out if the interior is liquid or solid, but their attempts have been thwarted due to limitations of RF ranging precision. If the new laser ranging approach were applied to a future mission to Mars, particularly Mars Landers, it has the potential to resolve this open question.Interplanetary precision laser ranging could also enable new tests of fundamental physics, including tests of the equivalence principle, the apparent acceleration of the expanding universe, and the possible existence of extra dimensions. The laser system could also enable tests of gravity, which could lead to the discovery of a violation or extension of general relativity, or the presence of an additional long-range interaction. Finally, the laser system could enable various tests to be performed on the planets and other solar system bodies, which could shed light on their evolution, atmospheres, oceans, and ring material. These measurements are currently based on RF ranging techniques, which have limited precision. © 2013 Phys.org. All rights reserved. Journal information: Applied Physics Letters Citation: Interplanetary precision laser could reach to Mars and beyond (2013, July 12) retrieved 18 August 2019 from https://phys.org/news/2013-07-interplanetary-precision-laser-mars.html The scientists, Yijiang Chen, Kevin M. Birnbaum, and Hamid Hemmati at the California Institute of Technology’s Jet Propulsion Laboratory in Pasadena, California, have published their paper on the long-range, high-precision laser system in a recent issue of Applied Physics Letters.”In principle, this approach could be scaled up to any interplanetary distance by increasing the size of the telescopes,” Birnbaum told Phys.org. “We calculated that ranging from Earth to Mars or Jupiter should be achievable with quite modest telescopes of 1 m in diameter on Earth and 15 cm on the spacecraft.”In the new laser ranging scheme, there is one transceiver at each end of the distance to be measured. Each transceiver transmits and receives laser pulses. The pulses are time tagged when transmitted and when received, and the time it takes the pulses to travel between transceivers is used to measure the distance between the transceivers. As the scientists explain, having these “active transceivers” is key to the long-distance range.”Radio frequency (RF) techniques are limited by uncertainties in the intervening medium that can slow down the radio wave by a variable amount,” Birnbaum said. “The effects of the medium—that the gap between the spacecraft and the ground terminal is not a completely empty vacuum—are smaller at optical frequencies.”Compared to current optical technologies, the key is that we use an active transceiver. Currently, optical ranging is done by bouncing light off of a passive target, a reflector. This is very effective for ranges up to the Earth-Moon distance, but it is simply not reasonable for interplanetary distances because the planets are thousands of times farther than the Moon. The amount of light falls as 1/R4, so the signal would get trillions of times weaker if you tried to use the same passive system to measure the range of the planets. We use active transceivers with lasers at both ends, so each end can see a much brighter signal.” Space-time diagram of active laser ranging between the Earth and a planet. In order to achieve long-distance laser ranging, the system uses active transceivers with lasers at both ends, so each end can see a much brighter signal than with passive transceivers. Credit: Chen, et al. ©2013 AIP Publishing LLC Developing a new laser to detect methane leaks 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.
Journal information: Nature Citation: Computer simulations suggest aridification of Sahara occurred longer ago than thought (2014, September 18) retrieved 18 August 2019 from https://phys.org/news/2014-09-simulations-aridification-sahara-longer-thought.html Explore further Credit: Luca Galuzzi / Wikipedia Computer simulation suggests early Earth bombarded by asteroids and comets (Phys.org) —A team of researchers with members from China, Norway and France has built a computer simulation that shows that the Sahara desert came about far earlier than conventional thinking suggests. In their paper published in the journal Nature, the team explains how they gathered data from several sources to create their simulation and why it shows an older Sahara. Most planetary scientists believe that the Sahara desert came to exist sometime between two and three million years ago (during the most recent glaciation cycling)—geological data has supported this notion. Recently, however, studies of dune deposits have suggested the area became drier farther back in time than that. The problem was, there wasn’t a smoking gun that might explain the relatively sudden changes in rainfall. Intrigued by the seeming conundrum, the researchers with this new effort, sought to build a computer simulation that might shed more light on the history of Northern Africa and the conditions that led to the creation of the largest (non-polar) desert in the world.To create their simulation, the researchers input data that described the geology of the area over the past 30 millions of years, including tectonic plate shifting. They also input atmospheric conditions and changes in the Earth’s orbital position over the same time-span.In running the simulation, the researchers watched as what was once the Tethys Sea—a massive body of water that separated the supercontinents—was largely drained when the African plate collided with the Eurasian plate, giving rise to the Himalayas and Alps and leaving behind the Mediterranean, Caspian and Black Seas and a suddenly exposed Arabian Peninsula. That left less reflective surface area in the region, the simulation showed, which led to less rainfall (approximately half as much) over North Africa. Less rainfall during subsequent times of changes to Earth’s tilt, led eventually to desertification—all approximately 7 million years ago.More research will have to be done of course, but if the simulation is eventually excepted as depicting the actual history of the area, that could have major implications for scientists who study human ancestry—our forbearers are believed to have got their start, after all, just south of the area in question. © 2014 Phys.org More information: Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene, Nature 513, 401–404 (18 September 2014) DOI: 10.1038/nature13705AbstractIt is widely believed that the Sahara desert is no more than ~2–3 million years (Myr) old1, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages2, 3, 4. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth’s orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial–interglacial cycles2. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ~2–3 Myr ago. The later discovery, however, of aeolian dune deposits ~7 Myr old suggested a much older age, although this interpretation is hotly challenged1 and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (~7–11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa. 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.
“Historically, the concept of symmetry has played important roles in physics, both in identifying and formulating fundamental laws of nature, and in using these laws to understand and predict natural phenomena such as dynamics and phases of matters,” Hirosi Ooguri, one of the researchers who carried out the study, told Phys.org. “However, there has been theoretical evidence to suggest that, once we combine gravity and quantum mechanics (the two fundamental ideas in modern physics), all global symmetries are gone.”In physics, symmetries can be of two kinds: gauge and global. For several decades, researchers have proposed the idea that global symmetries should not be possible in quantum gravity, as the unified theory of gravity and quantum mechanics would not allow for any symmetry. This is a profound claim with important consequences. For instance, it predicts that a proton would not be stable against decaying into other particles. “The standard model of particle physics has both kinds of symmetries, so we are predicting that the global ones must only be approximate,” Daniel Harlow, the other researcher involved in the study, told Phys.org. “So far, this idea has had some circumstantial support, but there was no convincing argument. In our paper, we gave what we think is a rather convincing argument in the special case of the AdS/CFT correspondence. This correspondence gives our best-understood theories of quantum gravity, and we were able to show that it does not allow global symmetries.”Prior to Ooguri and Harlow’s paper, other researchers made arguments supporting the claim that quantum gravity (the unification of quantum mechanics and gravity) cannot have any symmetry. Nonetheless, these arguments often presented logical gaps or loopholes, for instance failing to address some important cases (e.g. discrete symmetry). “Our new paper provides a rigorous proof of this claim in the context of the AdS/CFT correspondence, where quantum gravity is defined in a mathematically precise way, and we have done so in the most general way, excluding all possible global symmetries from quantum gravity,” Ooguri said. Journal information: Physical Review Letters Explore further More information: Daniel Harlow et al. Constraints on Symmetries from Holography, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.122.191601Daniel Harlow, Hirosi Ooguri. Symmetries in quantum field theory and quantum gravity. arXiv:1810.05338 [hep-th]. arxiv.org/abs/1810.05338G. ‘t Hooft. Dimensional reduction in quantum gravity. arXiv:gr-qc/9310026. arxiv.org/abs/gr-qc/9310026L. Susskind. The world as a hologram. arXiv:hep-th/9409089. arxiv.org/abs/hep-th/9409089Juan M. Maldacena. The large N limit of superconformal field theories and supergravity. arXiv:hep-th/9711200. arxiv.org/abs/hep-th/9711200 How spacetime is built by quantum entanglement A pair of researchers, one at the Massachusetts Institute of Technology (MIT) and another at California Institute of Technology (Caltech) and the University of Tokyo, have recently investigated a set of old conjectures about symmetries in quantum gravity. The specific conjectures of focus: (1) Quantum gravity does not allow for global symmetries; (2) For gauge symmetry, all possible charges must be realized; (3) Internal gauge groups must be compact. Their paper, published in Physical Review Letters, shows that these old assumptions hold within the anti-de Sitter/conformal field theory (AdS-CFT) correspondence. The proof presented by Ooguri and Harlow is based on two important ideas: the holographic principle of quantum gravity and quantum error correcting codes. The holographic principle was first introduced by Gerard ‘t Hooft and Leonard Susskind in the early ’90s, yet it has since been widely built upon. One of its most crucial developments was the discovery of the AdS/CFT correspondence by Juan Maldacena in 1997. Ooguri and Harlow wished to prove a mathematical theorem on quantum gravity, so they required a precise definition of the holographic principle. They decided to adopt the AdS/CFT correspondence, as this was the only way they felt they could achieve their goal. “Our basic tools are quantum error correction, the AdS/CFT correspondence, and quantum field theory,” Harlow said. “Probably the most important point to convey here is that although AdS/CFT is a beautiful theory of quantum gravity, it is not the theory of quantum gravity in our world. It is a toy model of the type that physicists like to study (such as the famous spherical cow). We believe, however, that lessons we learn in this toy model should carry over to our world provided that we are careful.”A few years ago, a different research group that also included Harlow showed that holography works in quantum gravity in a similar way to how quantum error correction works in quantum computing. In the AdS/CFT correspondence, spacetime geometry in the anti-de Sitter Space emerges from quantum entanglement in the conformal field theory. Harlow and his colleagues showed that the emergent geometric data is, in fact, quantum error correcting codes, from a CFT standpoint. The insight from this previous research was essential to prove the theorem in the researchers’ recent study. In their new study, Ooguri and Harlow found that the way quantum error correction works is not compatible with any symmetry. Thus, once quantum mechanics and gravity are merged, no symmetry is exact. “It has generally been believed that symmetry is a fundamental concept in nature,” Ooguri said. “Many physicists believe that there must be a beautiful set of laws in nature, and that one way to quantify beauty is by symmetry. Some of the symmetry may be hidden in our world (or ‘spontaneously broken,” in physics terms), but they may manifest themselves if we look at nature at a more fundamental level. We showed that the belief expressed in the above is wrong. The laws of nature at the most fundamental level, where quantum mechanics and gravity is unified, have no global symmetry.”The study carried out by Ooguri and Harlow brings key insight to the physics field, ruling out the possibility of global symmetries in a wide class of quantum gravity theories. Their findings have implications for numerous areas of study, for instance predicting the instability of protons. “Our findings predict that the proton should not be stable,” Harlow said. “It isn’t obvious, but it also predicts the existence of magnetic monopoles: isolated objects which carry magnetic charge. So far, we have never seen such an object, but people are still searching for them. Unfortunately, our results are not strong enough to say how many monopoles should exist, where they should be, or how long we have to wait to see a proton decay.”In their future work, Harlow and Ooguri would like to quantify how symmetry is broken. So far, they have merely proved that quantum gravity cannot have any symmetry without clarifying how it is taken apart. For instance, their findings suggest that the proton should decay, yet they do not clarify how it decays or how long it can live for before it does. These are very important questions, which the researchers hope to address in their future research. “The Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo, of which I am the director, is involved in the Hyper-Kamiokande project to be built in the Kamioka zinc mine in the central mountain area in Japan,” Ooguri added. “One of the aims of the project is to see whether the proton decays and to do this experimenters will build a large water tank in the mine. According to our theorem, the protons should decay. But, we cannot tell experimenters how big the water tanks should be for them to be able to see the protons decay within a reasonable period of time. This is one example of why quantifying how symmetry is broken would be crucial. Daniel and I have some idea on how to quantify the way symmetry is broken and we are now continuing our investigation in this direction.” The figure shows the essence of the researchers’ argument against global symmetries. They assume that a global symmetry exists and also that the object in the center of the diagram is charged under the symmetry, and then show that this would require the object to be in the shaded grey regions, which it isn’t; this is proof by contradiction! Credit: Harlow & Ooguri. © 2019 Science X Network Citation: Researchers demonstrate constraints on symmetries from holography (2019, May 28) retrieved 18 August 2019 from https://phys.org/news/2019-05-constraints-symmetries-holography.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.
Panneerselvam, who also holds the Finance portfolio, announced exemption of VAT on fishing accessories like fishing ropes and floats, fish net twine, fishing lamps and fishing swivel, apparently to appease the vast fishermen community. Besides, the government reduced VAT on mobile phones from 14.5 per cent to five per cent.Presenting the Budget, Panneerselvam said the state has to rely more on its own strength, besides slow growth in States’ Own Tax Revenue (SOTR), even as devolution and grants in aid of the Centre are expected to go down. Also Read – Need to understand why law graduate’s natural choice is not legal profession: CJI”Notwithstanding this increased financial burden and the slow growth in SOTR, our government has decided not to impose any new tax,” he said. The opposition DMK boycotted the proceedings and staged a walkout after its floor leader M K Stalin was denied permission by Speaker P Dhanapal to raise some issues.Among tax sops offered by the government, which Panneerselvam termed as ‘critical concessions’ to boost the manufacturing sector, were withdrawal of electricity tax on plants using biomass, Also Read – Health remains key challenge in India’s development: Kovindexcluding bagasse.He said the government proposes to raise net borrowings to Rs 30,446.68 crore and overall outstanding debt would be in excess of Rs 2.11 lakh crore by end of March 2016.However, the fiscal deficit would remain at 2.89 per cent of Gross State Domestic Product as against the norm of three per cent.O Panneerselvam, who presented the four-year-old AIADMK government’s first Budget in the absence of party supremo and former Chief Minister J Jayalalithaa, waging a legal battle over her conviction in a disproportionate assets case, heaped encomiums on her, saying she has “unfailing courage, benevolence, wisdom and zeal.” Talking on resources for financing the Budget, he said SOTR growth remains a serious challenge even as “sluggish economic environment” in the country has significantly affected the growth in collection of commercial taxes.Besides, due to the fall in international crude oil prices and the consequent decline in retail rates of petroleum products, commercial tax revenue has been further “dented” to an extent of Rs 1,000 crore in the current year.
Interior Minister Bernard Cazeneuve said security forces had staged dawn raids on Monday to take into custody four people, aged between 16 and 23, who were “planning to commit a terrorist act against French military installations.” A source close to the investigation into the thwarted attack, who asked to remain anonymous, said the four arrested had been planning to film the decapitation of a member of the military based in southern France. One of the four people arrested had served in the navy, Cazeneuve said. Also Read – Pro-Govt supporters rally as Hong Kong’s divisions deepenThe youngest suspect was later freed, a judicial source told AFP. The mastermind of the foiled attack had been planning to travel to jihadist-controlled areas of war-torn Syria, Cazeneuve said. The news of the arrests followed a statement from President Francois Hollande, who said attacks had been thwarted in recent days.“This week, we stopped terrorist attacks which could have taken place,” Hollande said on a visit to the southern city of Marseille. France remains on high alert more than six months after jihadist attacks in January that claimed 17 lives and started with shootings at satirical magazine Charlie Hebdo. At traditional July 14 celebrations, Hollande said: “Every week, we are arresting, preventing … terrorist acts.” Also Read – Pak Army ‘fully prepared’ to face any challenge: Army spokesmanThe suspected plotters are now in the custody of France’s intelligence services, the DGSI, and anti-terrorist prosecutors in Paris have opened a probe, Cazeneuve said.“I want to congratulate our security services for this new blow to the terrorists and for again foiling an attack,” said the minister. There are 1,850 French citizens or people living in France who are “implicated” in jihadist networks, with around 500 in Syria or Iraq, authorities said.
Kolkata: The state School Education department is planning to introduce Mahatma Gandhi’s life and his contribution to the freedom movement as part of the syllabus right from the primary level.”Students of Class IV and V will now have to study Gandhi. Some aspects of his life and his contribution to India’s freedom movement will be incorporated in three subjects – Bengali, English as well as Environment Studies. If everything goes as per plan, we will introduce this from the next academic year itself,” a senior official of the department said. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedThe syllabus restructure committee will finalise the modalities on how the study on Gandhiji can be included in the syllabus of Class IV and V. “We are now in the initial stage and are discussing with experts,” said Avik Majumdar, chairman of the syllabus restructure committee. It may be mentioned that the state government has made plans to celebrate the 150th birth anniversary of Gandhiji in a befitting manner. Chief Minister Mamata Banerjee has formed a high-powered committee, consisting of 46 members, including prominent academicians and intel- Also Read – Naihati: 10 councillors return to TMC from BJPlectuals. As part of the celebrations leading up to Gandhiji’s 150th birth anniversary in 2019, the committee will hold elocution tests, essay competitions for children and distribute booklets with Gandhiji’s views on untouchability and patriotism among the city people. The idea of introducing the study about Mahatma Gandhi was floated by Banerjee herself in one of the meetings. “We have plans to celebrate the birthday of the Father of the Nation in all schools and colleges in the state on October 2 this year,” an official of the state Education department said. It may be mentioned that under the present curriculum students study in detail about Mahatma’s life, ideology and his contribution to the Indian freedom struggle in classes IX, X and also in Higher Secondary. “The committee is of the opinion that students in the primary level need to have some idea about Mahatma Gandhi right from an early age, as he is the role model of many in the state and the country as well,” the official maintained. The committee has already decided to renovate Gandhi Bhavan in Beleghata area of the city, where the visionary had stayed and fasted in 1946.