Pi calculation smashes records

first_img Bellard, of Paris Telecom Tech, made and checked the calculation by running his own software algorithms for 131 days. The previous record calculation, set by Daisuke Takahashi at the University of Tsukuba in Japan in August 2009, took only 29 hours to complete, but used a super-computer costing millions of dollars, and running 2000 times faster than Bellard’s PC.Pi is the value of the ratio of the circumference of a circle to its diameter, and has been of interest to mathematicians for hundreds of years, since Sir Isaac Newton developed formulae to extend the number of decimal places.Bellard has been following the records for calculating Pi to the maximum number of decimal places since he received his first book about Pi at the age of 14. Computations to find a value to any number of decimal places are part of a branch of mathematics called “arbitrary-precision arithmetic”. For Bellard the calculation was more for fun than because of an obsession with the digits, but he said that arbitrary-precision arithmetic has applications because it can be used for testing algorithms and computers. He claims his method is about 20 times more efficient than previous methods.Bellard said he used the Chudnovsky formula to produce a binary result (a process that took 103 days), which was then checked (which actually took 34 hours on 9 computers, but would have taken 13 days on one PC), and converted to a base-10 result (12 days), which was then verified (3 days).Bellard’s computer cost less than €2000 (roughly $2870 US) and ran Linux’s Red Hat Fedora operating system. It had a Core i7CPU at 2.93 GHz, and had 6 GB of RAM and 7.5 TB of disk storage space in five 1.5 TB hard disks. He wrote all the required software.The world record for memorizing and reciting Pi was set in 2005 by a Chinese graduate student, Lu Chao, who spent a year learning 100,000 digits and was able to recite Pi to the 67,890th decimal place before he made an error. The feat took just over 24 hours. Reciting Bellard’s result of 27 trillion digits would take over 1,284,000 years at the Guinness Book of Records’ required rate of one digit every 15 seconds.M Bellard is perhaps best known as the writer of the open source project FFmpeg and processor emulator QEMU. He said he has no immediate plans to calculate Pi to further digits in the future, but may do, depending on his motivation and the availability of larger and faster storage. He intends to release open-source versions of his software for Linux and Windows to enable anyone who is interested in furthering the calculation to beat him to it. (PhysOrg.com) — A computer scientist in France has broken all previous records for calculating Pi, using only a personal computer. The previous record was approximately 2.6 trillion digits, but the new record, set by Fabrice Bellard, now stands at almost 2.7 trillion decimal places. Explore further A trillion triangles: New computer methods reveal secrets of ancient math problem 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 More information: bellard.org/pi/pi2700e9/ Citation: Pi calculation smashes records (2010, January 7) retrieved 18 August 2019 from https://phys.org/news/2010-01-pi.html © 2010 PhysOrg.comlast_img read more

Physicists propose mechanism that explains the origins of both dark matter and

first_imgThis 3D map shows the large-scale distribution of dark matter, reconstructed from measurements of weak gravitational lensing with the Hubble Space Telescope. The field of view covers about nine times the size of the full moon. Image credit: NASA/ESA/Richard Massey. Citation: Physicists propose mechanism that explains the origins of both dark matter and ‘normal’ matter (2010, December 10) retrieved 18 August 2019 from https://phys.org/news/2010-12-physicists-mechanism-dark.html Copyright 2010 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) — Through precise cosmological measurements, scientists know that about 4.6% of the energy of the Universe is made of baryonic matter (normal atoms), about 23% is made of dark matter, and the remaining 72% or so is dark energy. Scientists also know that almost all the baryonic matter in the observable Universe is matter (with a positive baryon charge) rather than antimatter (with a negative baryon charge). But exactly why this matter and energy came to be this way is still an open question. In a recent study, physicists have proposed a new mechanism that can generate both the baryon asymmetry and the dark matter density of the Universe simultaneously. UBC physicists make atoms and dark matter add up Explore further The scientists, Hooman Davoudiasl from Brookhaven National Laboratory in Upton, New York; David Morrissey and Sean Tulin from TRIUMF in Vancouver, British Columbia; and Kris Sigurdson from the University of British Columbia, also in Vancouver, have published their new proposal in a recent issue of Physical Review Letters. They’ve dubbed the new mechanism “hylogenesis” from the Greek words “hyle,” meaning “primordial matter,” and “genesis,” meaning “origin.” “There are two problems in theoretical physics we are trying to address at once,” Sigurdson said. “The baryon asymmetry (why do we have atoms but not antiatoms in the Universe?) has really been a problem since Paul Dirac proposed antimatter in 1928 and it was discovered in 1932. And what is the dark matter? Hints of dark matter have been around since Fritz Zwicky discovered missing mass in the Coma Cluster in 1933, but its identity is still unknown. This mechanism links the formation of atoms and dark matter and helps resolve the baryon asymmetry mystery, as the total dark plus visible baryon balance of the Universe is restored.”In this matter-formation scenario, a new particle X and its antiparticle X-bar (of equal and opposite charge) are produced in the early Universe. X and X-bar are capable of coupling to quarks (the basic components of baryonic matter, e.g., protons and neutrons) in the visible sector as well as particles in a “hidden” sector (so-called because the particles in it interact only feebly with the visible sector). In this scenario X and X-bar would have been produced when the Universe heated up after inflation, in the first moments after at the start of the big bang.Later, X and X-bar would decay, partly into visible baryons (specifically, a neutron made up of one up quark and two down quarks) and partly into hidden baryons. As the scientists explain, X decays to neutrons more often than X-bar decays to antineutrons. By the same amount, X-bar decays to hidden antiparticles more than X decays to hidden particles. In this scenario, the quarks would be the baryonic matter that makes up almost everything we see, and the hidden antibaryons would be what we know as dark matter. Through this yin-yang decay pattern, the positive baryon number of the visible matter is in balance with the negative baryon number of the dark matter. “The energy densities of visible and dark matter are really close to each other (differing by a factor of five),” Tulin said. “In many scenarios, the processes that generate visible and dark matter are unrelated, occurring during widely separated epochs in the early universe through completely different physics. So, this factor of five seems like either a really big coincidence, or it could be a clue that both kinds of matter had a common origin. I think this is the main reason to take seriously these unified models of visible and dark matter genesis.”The physicists predict that this matter-formation mechanism could provide an entirely new way to look for dark matter, since it would leave a signature that could be experimentally detected. As they explain, once in a while a dark matter antiparticle might collide with and annihilate an ordinary atomic particle, releasing a burst of energy. Although this is very rare, there is a chance that experiments on Earth that look for the spontaneous decay of protons could detect dark matter.“We plan to investigate, in more detail, the prospects for dark matter detection in nucleon decay experiments, as this constitutes a distinct signature of our proposal and can open up a new front in the experimental search for dark matter,” Davoudiasl said. “Other potential signals of hylogenesis can appear in astrophysical observations and perhaps particle accelerator data, and we intend to consider these possibilities in our future work as well.” More information: Hooman Davoudiasl, et al. “Unified Origin for Baryonic Visible Matter and Antibaryonic Dark Matter.” Physical Review Letters 105, 211304 (2010). DOI: 10.1103/PhysRevLett.105.211304 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

Waterpropelled jetpack hits the market for 99500 w video

first_img More information: jetlev-flyer.com and jetlev.comvia: Gizmag (PhysOrg.com) — A water-propelled jetpack called Jetlev R200 is possibly the most fun-looking water activity yet. The Florida-based company Jetlev Technologies, Inc., working with German company MS Watersports GmbH, has recently started limited production in a phased roll-out program. At a cost of $99,500 per jetpack, the target market for the recreational device is holiday resorts. © 2010 PhysOrg.com The Jetlev R200 can reach heights of 28 feet and speeds of 22 mph. Image credit: Jetlev Technologies, Inc. Company to sell ‘world’s first practical jetpack’ for $75,000 (w/ Video) 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 Citation: Water-propelled jetpack hits the market for $99,500 (w/ video) (2011, May 10) retrieved 18 August 2019 from https://phys.org/news/2011-05-water-propelled-jetpack-video.html The Jetlev is lighter (30 pounds [14 kg] when dry) and less bulky than other jetpack designs because its four-stroke, 250-hp engine and fuel are located on a small boat that is tethered to the jetpack by a 33-ft (10-m) hose. As the pilot steers the device, the boat follows along in the water. The boat delivers water to the jetpack through the hose, and thrust is generated by forcing the water downward through the nozzles located on each side of the jetpack.Jetlev Technologies says that this design greatly improves the thrust-to-weight ratio compared to other jetpacks, allowing the Jetlev to propel a 150-lb (68-kg) pilot to speeds of up to 22 mph (35 km/h) at heights of up to 28 ft (8.5 m). The Jetlev can accommodate pilots who are 4.9-6.5 ft (1.5-2 m) tall and weigh 88-330 lb (40-150 kg). With a 26-gallon (100-liter) tank, the Jetlev can operate for about one hour at full throttle or up to three hours at cruising speeds.The company also says that most people can learn how to fly the Jetlev after a few minutes of in-water instruction. Thrust is controlled through grip twist, while lifting the control arms up and down can move the pilot forward or backward by changing the angle of the nozzles. Differential nozzle angles allow the jetpack to be turned left and right. The Jetlev also has several safety features, including a 5-point quick-release harness, protective backrest, head support, and inherent flotation.The ride is not uncomfortable, since the pilot’s weight is supported by the padded unicycle-style saddle and leg trapeze. Although pilots must be at least 18 years old, the company says that “if you are 82, healthy and in good physical condition, there is no reason why you could not fly.”Designed for both fresh and salt water, the Jetlev’s exposed metal pieces are made of either stainless steel or hard coat anodized aluminum with Teflon coating to protect against corrosion and abrasion.last_img read more

ZeroTouch New kind of infrared touch computer interface w video

first_img Explore further Zero-thickness visual hull sensing with ZeroTouch — ecologylab.net/research/zerotouch/index.html– Interface Ecology Lab exhibiting multifinger ZeroTouch sensing at ACM CHI in VancouverCorrection/Update: Jonathan Moeller should have been credited as the inventor of the ZeroTouch, as he was not just a research assistant on the team. Also, according to Moeller, the “ZeroTouch is a full multi-touch sensor, and it tracks 20+ fingers in its current configuration, meaning pinch and spread gestures are entirely possible, as are many other high degree of freedom gestures.” On display at the Computer Human Interaction (CHI) conference this past week, in Vancouver, British Columbia, the ZeroTouch, invented by Jonathan Moeller, was demonstrated by various students working on the team, which was led by Andruid Kerne.In contrast to other touch type screens, such as those on the iPhone or iPad, the ZeroTouch requires no pressure to be exerted, which can mean less muscle fatigue if used over a long period of time; and because it can be used in more than one format, the ZeroTouch is far more versatile; when placed alone on a table for example, it might be used as a drafting device, replacing far more expensive options; and its application as a virtual painting canvas, while unique, is certainly not it’s most engaging feature; that would have to be the ability to place it over a conventional screen, instantly converting it, very cheaply, into a touchscreen device. Play Citation: ZeroTouch: New kind of infrared touch computer interface (w/ video) (2011, May 12) retrieved 18 August 2019 from https://phys.org/news/2011-05-zerotouch-kind-infrared-interface-video.html PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen 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 Mobile devices serve as own mice with optical sensing (w/ Video) To do its magic, the ZeroTouch has LEDs and infrared sensors (similar to the technology used in television remote controls) mounted around the periphery of the frame, which are then connected to a computer that crunches the constant stream of data coming in from the sensors; when a finger or other device is introduced into the invisible plane, the infrared signals sent from LEDs on one part of the frame are blocked from reaching the complementary sensors on the opposite side, which is then interpreted as a touch. More information: © 2010 PhysOrg.com Also, according to Moeller, the “ZeroTouch is a full multi-touch sensor, and it tracks 20+ fingers in its current configuration, meaning pinch and spread gestures are entirely possible, as are many other high degree of freedom gestures.” He also said in a prior interview that he and his team are working on a three-dimensional device where multiple frames are laid atop one another, that he says, should allow for a much higher degree of dexterity. It should also allow for hovering and 3-D hand manipulation of virtual objects, both of which are not currently available with any touchscreen device. (PhysOrg.com) — Students from Texas A&M have unveiled a project they’ve been working on for the past couple of years they call the ZeroTouch; a device that looks like an empty picture frame and uses embedded LEDs and infrared sensors to translate human movement into computer commands. Taking the technology behind the Microsoft Connect a step further, the ZeroTouch can be laid flat on a table, mounted on a computer screen or hung in the air; each for a completely unique purpose. When laid flat, it can be used as a drawing board, when mounted over a regular computer screen it can be used as a touchscreen device, and when hung in the air it can be used as a virtual canvas for painting.last_img read more

There and back again Extending optical storage lifetime by retrieving photon echoes

first_img © 2014 Phys.org , Physical Review Letters “For this reason, research on quantum optical memories attracted a lot of attention,” Akimov told Phys.org. “Current investigations of photon echoes have concentrated primarily on atomic vapors and rare earth crystals with long storage times, which are crucial for implementation of robust light-matter interfaces. However,” he noted, “light-matter coupling is weaker in these systems, so operation speed is not as fast as it could be in semiconductors. For example,” he illustrated, “efficient optical excitation in atomic systems is possible with optical pulses longer than one nanosecond, which slow down the operation speed by three orders of magnitude as compared to our protocol – and for rare earth crystals the pulse duration should be even longer.”In contrast to classical storage, quantum memory forbids measurement of the optical field during saving and retrieving processes. “In other words,” Akimov said, “storage of non-classical quantum light – such as squeezed light or a single photon – should occur without knowing which optical fields have been stored and retrieved, because otherwise the quantum state would be irreversibly destroyed during the measurement procedure. However, our protocol allows quantum storage since transfer between optical excitation and spin excitation does not require state measurement.” In other words, the new protocol transfers a quantum superposition between optically coupled states (optical excitation) and the other pair of states coupled by a magnetic field (spin excitation). In this process no measurement takes place – just the transformation between different excitations.Regarding the quantum well, the researchers specifically concentrated on an n-doped CdTe/(Cd,Mg)Te quantum well where storage time increased from picoseconds to tens of nanoseconds. The structures were grown by Prof. Grzegorz Karczewski and Prof. Tomasz Wojtowiczin the Institute of Physics, Polish Academy of Sciences in Warsaw using molecular beam epitaxy. (CdTe/(Cd,Mg)Te is a cadmium telluride compound in which some of the cadmium is replaced by magnesium.) “The cadmium telluride semiconductor quantum well structure is a model proof-of-principle system for extending the photon echo delay,” Akimov told Phys.org. “In such two-dimensional structures, the carriers are confined in one direction; this results in well-defined spin-level system and clean selection rules for optical transitions. Secondly, n-type doping of barriers with donors provides excess electrons in the quantum well which, again, are responsible for long-lived spin excitations.”That said, while using cadmium telluride quantum wells enabled very clean experiments on the ensemble of trions to be performed because their optical transitions are well isolated spectrally, the researchers had to maintain weak optical pulse intensity to prevent interactions between weakly localized trions. “In order to increase the efficiency and to achieve longer delays for photon echoes it is necessary to try different type of semiconductor nanostructures which can be also based on other compounds.,’ Akimov explained. “One of such candidates is the ensemble of quantum dots where the electrons and holes are localized much more strongly in all three dimensions. This is in contrast to quantum wells where strong confinement is present only along one direction.”Finally, Akimov noted that in semiconductors there are two types of fundamental optical excitations: excitons (electron-hole pairs bound by Coulomb interactions) and trions – charged excitons consisting of an exciton bound with an excess electron or hole. “A trion is a three-particle complex, and after its decay there’s always an excess carrier left,” he explained. “In our case, we deal with excess electrons which possess spin 1/2. Therefore, in contrast to excitons, it is possible to save information about optical excitation in the spin of the excess electrons left after trion recombination. This transformation is only possible when an external magnetic field is applied, since it allows us to mix the electronic states in the proper way.” The most salient advantage of quantum well structures is that exciton and trion resonances are spectrally well separated – meaning that picosecond laser pulses let the researchers address only the optical transition from excess electron to trion.For all of these seemingly daunting challenges, the researchers’ key insight was to study photon echoes emitted by trions in semiconductor nanostructures subject to an external magnetic field – and by then using a transient four-wave mixing (FWM) technique to measure magnetic-field-induced long-term photon echoes, they were able to show that photon echoes can be retrieved from excess electron spin ensembles. (Transient four-wave mixing belongs to time-resolved coherent spectroscopy based on non-linear optics, whereby interactions between two or three optical pulses in medium produce fourth optical field in the signal) “We used ultrashort optical pulses with duration of about one picosecond,” Akimov explained, “because efficient optical excitation in semiconductors is possible on the order of 0.1-1ps.” In addition, he said, the experiments had to be performed at extremely low temperatures – about two degrees above absolute zero – in order to keep the system robust against interactions with phonons (collective excitations, similar to quasiparticles, in a periodic, elastic arrangement of atoms or molecules in condensed matter, such as solids and some liquids), as well as to suppress other relaxation mechanisms which could lead to irreversible dephasing of optical and spin excitations and thereby loss of coherence. “From an experimental point of view,” he added, “our primary challenge was combining four-wave mixing with ultrashort picosecond pulses and external magnetic fields at low temperatures.”The current study demonstrates that photon echoes can be retrieved from the spin system on the timescale of 10-100 ns. “However,” Akimov said, “this time delay is still too short for practical applications. In order to solve this problem we need to extend the decay time of spin excitations.” There are two possible reasons for decay of spin excitations: dephasing of spins and irreversible spin relaxation through decoherence – that is, due to interaction with the environment. “The first point can be addressed by means of spin resonance techniques using dynamic decoupling,” he explained, “which is an approach largely the same as photon echo but based on periodic excitation of the spin ensemble with microwave pulses which lead to spin echoes. In that way it will be possible to keep the spin ensemble of excess electrons free of dephasing, and timescales up to tens or even hundreds of microseconds may be achieved. However, irreversible spin relaxation is more difficult to solve – but there are several attempts to reduce hyperfine interaction between nuclear and electron spins. One of the solutions would be to use compounds with isotopes carrying zero nuclear spin. In this case storage times in the milliseconds can be available.”In fact, Akimov added that the scientists plan to investigate extending the timescale of photon echoes further into the microsecond and millisecond range. “We’ll test other nanostructures, such as quantum dots with strong trion localization, and will search for new materials with suppressed spin excitation decay. In addition,” he said, “we’ll use spin resonance techniques in order to eliminate spin dephasing in the ensemble of excess electrons.”Akimov also mentioned applications beyond optical memory. “While most applications are related to optical memories where the optical information should be saved and released on demand,” he said, “there’s another fundamental aspect: Our studies combine optical and spin phenomena, and in this sense it’s very interesting to explore our approach for monitoring the time evolution of combined optical and spin excitations.”A unique feature of photon echo experiments is the dephasing which already occurs at the initial stage directly after excitation with the first pulse, where the sequence of two linearly polarized pulses create comprehensive spin distribution for excess electrons without net spin polarization. While each of the electrons has a certain well-defined spin, the ensemble spin polarization, or average spin, is zero – and the information about the optical pulses, such as polarization and interpulse delay, is encoded in the spins of excess electrons. “This differs from conventional techniques,” Akimov pointed out. “For example, in well-established pump-probe experiments the non-zero spin polarization in the system is first induced by a circularly polarized pump pulse, and then the evolution of the spin in time is probed.” The scientists therefore believe that their approach based on photon echoes in a magnetic field constitutes an interesting platform for fundamental spin studies.Along these exploratory lines, Phys.org asked Akimov if, given that storage times of seconds or longer might be possible by further exploiting the hyperfine interaction between electrons and nuclei in quantum dots, quantum wells and self-assembling quantum dots might at some point be combined in a single quantum system that emulates human short- and long-term memory. “I think we are still far from that,” he replied. “In order to achieve this goal it would be necessary to establish a net of such quantum dot ensembles, analogous to cells, which would communicate between each other.” He added that while he does not exclude such possibility, he emphasizes that such a quantum system would very complex and would contain and integrate far more than a simple set of quantum nanostructures. “Several challenging issues such as communication between different ensembles have to be addressed, and for that it is necessary to accomplish directed and selective coupling of light at the nanoscale in and out of the cells. Accordingly, realization of such a network would need integration of photonic crystals or waveguide layers which can be based on semiconductors. Nevertheless,” he concluded, “this is a special area of research which deserves a lot of attention.” 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. Scheme of photon echo experiment and optical properties of investigated structure. (A) The CdTe/(Cd,Mg)Te quantum well (QW) is optically excited with a sequence of three laser pulses with variable delays t12and t23 relative to each other. The resulting four-wave mixing transients |EFWM(t)| are detected in 2k2-k1 direction using heterodyne detection. All measurements are performed at temperature of 2 K. (B) Top: schematic presentation of exciton (X) and trion (T-) complexes in QW. The QW potential of conduction (CB) and valence (VB) bands leads to spatial trapping of electrons and holes. Bottom: Photoluminescence (PL) spectrum (solid line) measured for above-barrier excitation with photon energy 2.33 eV, demonstrating X and T- emission. The laser spectrum (dashed line) used in photon echo experiment is tuned to the low energy flank of T- emission line. (C) Four-wave mixing transients for t12 = 23 ps and t23 = 39 ps. Spontaneous (PE) and stimulated (SPE) photon echo signals appear at tref =2t12 and tref =2t12 +t23, respectively. (D) Decay of PE and SPE peak amplitudes. From exponential fits (dashed lines) we evaluate T2=72 ps and T1 = 45 ps. Credit: Ilya A. Akimov. Journal information: Nature Photonics Explore further Schematic presentation of the main mechanisms responsible for magnetic-field-induced stimulated photon echoes (SPE). The whole process comprises three steps: 1. pulse 1 creates the optical excitation (initialization—conversion of the optical field into a material excitation); 2. pulse 2 performs a transformation of the optical excitation into the spin system (storage); 3. pulse 3 stimulates the photon echo (readout). Optical pulses are circularly polarized. (A) Transfer of optical coherence into electron spin coherence (Sx and Sy components). The efficiency is maximum for t12=p/wL. (B) Creation of spectral spin fringes for electrons and trions (Sz and Jz components). This mechanism is most efficient for t12=2p/wL. The spectral spin gratings for electrons and trions are shown in (C) at the moment of creation by the second pulse (t=t12=2p/wL) and in (D) after trion recombination and before arrival of pulse 3 (t>>t12+T1). Credit: Ilya A. Akimov.center_img More information: Access to long-term optical memories using photon echoes retrieved from semiconductor spins, Nature Photonics (Published online 28 September 2014), doi:10.1038/nphoton.2014.219Related:1Magnetic-Field Control of Photon Echo from the Electron-Trion System in a CdTe Quantum Well: Shuffling Coherence between Optically Accessible and Inaccessible States, Physical Review Letters 109, 157403 (2 October 2012), doi:10.1103/PhysRevLett.109.157403 In their study, the researchers found that picosecond optical pulses and an applied weak transverse magnetic field led to the transfer of a short-lived optical excitation into a long-lived electron spin state. In turn, this induced stimulated photon echoes with high bandwidth on submicrosecond timescales that exceeded optical excitation lifetime by a factor exceeding three orders of magnitude. Moreover, the scientists state that the ability to address all three spin components –parallel and perpendicular to applied magnetic field – as well as the energy level structure of localized trions being identical in quantum wells and self-assembled quantum dots make their approach “highly appealing” for future memory device applications and may lead to the fabrication of semiconductor nanostructure-based optical memories.Dr. Ilya Akimov discussed the paper that he, Doctoral Student Lukas Langer and their co-authors from Dortmund, St-Petersburg and Warsaw published in Nature Photonics, starting with the main challenges in devising a new experimental approach to stimulated photon echoes by transferring the information contained in the optical field into a spin system, where it is decoupled from the optical vacuum field. “A photon echo can be considered as a flash of light initiated in a medium after a sequence of two or more optical pulses,” Akimov told Phys.org. “Properties of the photon echo pulse – that is, intensity, optical coherence and phase – are identical to the properties of the initial pulse; therefore this phenomenon can be used to store information in all-optical systems.” Photon echoes because they occur in structures which rapidly dephase optical excitation in response to the first pulse, but with the second pulse reverse the dephasing process. Akimov pointed out that the timescale at which photon echoes can be observed is determined by the period during which optical excitation coherence is preserved. “This is why photon echoes are coherent,” he explained. “If scattering processes are suppressed, optical excitation coherence is limited by its lifetime as governed by intrinsic properties of the materials. Nevertheless there is a general rule that the more efficient light-matter interaction, the faster decay into the ground state will be observed – for example, faster spontaneous emission due to the optical vacuum field. Here we have a dilemma,” he noted. “On the one hand, we’d like to excite the medium quickly with the shortest possible pulse, which requires strong light-matter interaction. However, this limits the timescale at which the photon echoes can be observed.” The opposite is also true: To observe long-lived photon echoes, materials with weak light-matter coupling are needed – and although semiconductor systems belong to materials with strong light-matter interaction, it’s possible to extend photon echo decay if the optical excitation is transferred into the spin excitation and then recovered back to the optical excitation – that is precisely what Akimov and co-authors have accomplished. Quantum holograms as atomic scale memory keepsake “In order to achieve this goal,” he said, “we’ve used semiconductor quantum wells with excess electrons.” (A quantum well is a thin layer which can confine quasiparticles – emergent phenomena that occur when a microscopically complicated system, such as a solid, behaves as if it contains weakly interacting particles in free space – in the dimension perpendicular to the layer surface.) What’s key is that the spin excitation coherence time of such electrons decays three orders of magnitude more slowly than the lifetime of optical excitations. “In our protocol the first pulse leads to optical excitation in semiconductor quantum well; next, after dephasing of the optical excitation the second pulse transfers optical excitation into the electron spin excitation; and finally – even after a long delay, which can be 1,000 times longer than the delay between the first and second pulses – we apply the third pulse.” This third pulse transforms spin excitation back to optical excitation and initiates rephasing, so that resulting photon echoes are retrieved from the spin ensemble – and therefore the third pulse can be associated with the readout of optical information previously saved by the optical-to-spin transformation induced by the second pulse.”The unique feature of photon echoes is that they contain the information about the first optical pulse,” Akimov pointed out. “Therefore, photon echoes can be used for information technology optical memory applications. Moreover, it’s possible to perform not only classical light storage but to use photon echoes for realization of quantum optical memories.” This is essential, he stresses, for the development of quantum information and communication systems which use the laws of quantum mechanics to significantly enhance the speed and capacity of future computers. Citation: There and back again: Extending optical storage lifetime by retrieving photon echoes from semiconductor spin excitations (2014, October 31) retrieved 18 August 2019 from https://phys.org/news/2014-10-optical-storage-lifetime-photon-echoes.html (Phys.org) —For all of their differences, classical and quantum communication have at least one thing in common: the importance of being able to store optical information. That being said, optical storage is a complex process that depends largely on the material being used to convert, store and retrieve this information in a controllable, consistent manner – a process especially prone to short optimal memory times when implemented in certain semiconductor quantum structures. Recently, however, scientists at Technische Universität Dortmund, Germany in collaboration with Saint Petersburg State University, Russia and Institute of Physics in Warsaw, Poland demonstrated magnetic-field-induced long-lived stimulated photon echoes1 – coherent optical phenomena in which resonant excitation of a medium by short optical pulses results in a delayed coherent optical flash response – in the electron–trion system, allowed the bidirectional coherent transfer of quantum information in a semiconductor between optical and spin excitations. (Trions are excitations comprising three charged quasiparticles – emergent phenomena that occur when a microscopically complex system, such as a solid, behaves as if it contained different weakly interacting particles in free space.)last_img read more

Xray point source discovered at the center of a distant dwarf galaxy

first_img 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. HST image of Henize 2-10. The inset shows the new 160 ks Chandra observation with VLA radio contours from Reines et al. (2011) and has dimensions 600 × 400 (∼ 265 pc × 175 pc). Credit: Reines et al., 2016. Located some 34 million light years away in the constellation of Pyxis, Henize 2-10 is the first dwarf galaxy found to have a supermassive black hole at its center. With a mass of less than 10 billion solar masses, it is a compact starburst galaxy hosting numerous young “super star clusters” and a candidate low-luminosity active galactic nucleus (AGN).The presence of an AGN in Henize 2-10 offers an excellent opportunity to study massive black hole accretion and star formation. This is due to the fact that active nuclei in dwarf galaxies undergoing a burst of star formation reveal essential astronomical processes. They could offer crucial insights on the interplay between a massive black hole and the stars of the galaxy in which it forms.Last year, in February 2015, a team of astronomers led by Amy Reines of the University of Michigan conducted new Chandra observations of Henize 2-10 complementary to those performed in 2001. The new data obtained by the researchers allowed them to uncover the presence of a previously unidentified X-ray point source, spatially coincident with the known nuclear radio source in this dwarf galaxy.”Chandra clearly resolved the nuclear emission in Henize 2-10 and revealed the varying hard X-ray source to be due to a nearby X-ray binary, where a black hole, or a neutron star, eats material from a nearby typical star,” Mark Reynolds of the University of Michigan, co-author of the paper, told Phys.org.The fact that the new source is so bright allows the researchers to assume that the X-ray binary contains a “hungry” stellar-mass black hole that is eating very rapidly. They added that only very few X-ray binaries in our galaxy consume as much material as this source. However, the scientists still need to determine the cause of the variability observed from that source.”For example, it might be due to changes in the structure of the material it is eating. Another idea is that the variability could be driven by the time it takes the nearby star to orbit the stellar-mass black hole,” Reynolds said.This black hole in Henize 2-10 is potentially of great importance for astronomers, as it is the best-known example of a supermassive black hole in a dwarf galaxy. It is believed that early in the universe, relatively low-mass black holes grew in the initial galaxies that were small and gas-rich, such as Henize 2-10.”Thus, this provides critical insight into the early stages of galaxy and black hole evolution. Our new observations have shed light on the X-rays emitted from the nucleus of Henize 2-10. The massive black hole in this galaxy appears to be eating material in a similar manner to, for example, the supermassive black hole at the center of our Galaxy,” Reynolds concluded.The team plans to focus their future observations of Henize 2-10 on studying its supermassive black hole emission by observing when the X-ray binary is eating relatively slowly and is not bright. This could provide new information on the relationship between how this supermassive black hole eats material and the “burps” it gives off, and to determine how this influences star formation in this galaxy. © 2016 Phys.org (Phys.org)—NASA’s Chandra X-ray Observatory has helped astronomers to uncover a previously unidentified X-ray point source at the massive black hole in the center of a distant compact starburst galaxy known as Henize 2-10. The findings are available in a paper published Oct. 5 on the arXiv pre-print server. Citation: X-ray point source discovered at the center of a distant dwarf galaxy Henize 2-10 (2016, October 19) retrieved 18 August 2019 from https://phys.org/news/2016-10-x-ray-source-center-distant-dwarf.html Black hole hunters tackle a cosmic conundrum More information: Deep Chandra Observations of the Compact Starburst Galaxy Henize 2-10: X-rays from the Massive Black Hole, arXiv:1610.01598 [astro-ph.HE] arxiv.org/abs/1610.01598AbstractWe present follow-up X-ray observations of the candidate massive black hole (BH) in the nucleus of the low-mass, compact starburst galaxy Henize 2-10. Using new high-resolution observations from the Chandra X-ray Observatory totaling 200 ks in duration, as well as archival Chandra observations from 2001, we demonstrate the presence of a previously unidentified X-ray point source that is spatially coincident with the known nuclear radio source in Henize 2-10 (i.e., the massive BH). We show that the hard X-ray emission previously identified in the 2001 observation is dominated by a source that is distinct from the nucleus, with the properties expected for a high-mass X-ray binary. The X-ray luminosity of the nuclear source suggests the massive BH is radiating significantly below its Eddington limit (~10^-6 L_Edd), and the soft spectrum resembles other weakly accreting massive BHs including Sagittarius A*. Analysis of the X-ray light curve of the nucleus reveals the tentative detection of a ~9-hour periodicity, although additional observations are required to confirm this result. Our study highlights the need for sensitive high-resolution X-ray observations to probe low-level accretion, which is the dominant mode of BH activity throughout the Universe.last_img read more

Researchers suggest coal ash and tailings dam disasters could be prevented

first_img © 2019 Science X Network More information: J. Carlos Santamarina et al. Why coal ash and tailings dam disasters occur, Science (2019). DOI: 10.1126/science.aax1927 Iron mining produces a waste product known as tailings. Tailings are typically dumped into man-made ponds, which are more often than not dammed up to prevent them from oozing downhill when it rains. Similar ponds are constructed to contain coal ash waste produced by coal power plants. Besides representing a pollution problem, the ponds are also mudslide hazards. The researchers point out that thousands of people around the world have been killed by such mudslides over the past century. They suggest it is time that governments engage more fully with those building and maintaining such ponds.The researchers note that mudslides from tailings or coal ash occur when the dam holding the material gives way. Many people believe that the reason such dams give way is because of the pond contents and what happens to them. Evidence of liquefaction of pond materials is almost always in evidence along mudslide routes. But prior study has shown that liquefaction almost always happens after the dam gives way, not before. Instead, the researchers suggest that the major reason for most of the disasters is failure to follow best engineering practices in building and maintaining the dams.One of the biggest problems, the researchers point out, is that proper action is not taken during heavy rain causing overflow, which puts excess stress on the dam. Another problem is layering on the bottom of such ponds that result in deposits with different hydromechanical properties—this usually leads to weaknesses in the system. Also, cementation can loosen sediment structures, which can also weaken the system. And problems can also develop when material is compressed near the dam. They note also that preexisting weaknesses in the foundation of the dam can lead to failure later, and so can piping erosion or mineral buildup.The researchers conclude by suggesting more attention to such ponds, because the mudslides that can result when they fail appear to be far more preventable than many in the field have suggested. How bacteria can prevent coal ash spills Explore further Credit: CC0 Public Domaincenter_img A trio of researchers from the King Abdullah University of Science and Technology, the University of the Witwatersrand and Geosyntec has published a Perspectives piece in the journal Science. Carlos Santamarina, Luis Torres-Cruz and Robert Bachus note in the article that many lives are lost each year when coal ash or tailings dams fail, causing mudslides. Many such failures are preventable. Citation: Researchers suggest coal ash and tailings dam disasters could be prevented (2019, May 10) retrieved 18 August 2019 from https://phys.org/news/2019-05-coal-ash-tailings-disasters.html Journal information: Science 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

Four new hot Jupiters discovered

first_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. More information: C. Hellier, et al. WASP-South hot Jupiters: WASP-178b, WASP-184b, WASP-185b & WASP-192b arXiv:1907.11667v1 [astro-ph.EP]: arxiv.org/abs/1907.11667 Image credit: WASP-178b discovery data: (Top) The WASP data folded on the transit period. (Second panel) The EulerCAM transit lightcurve together with the fitted MCMC model. (Third panel) The CORALIE RV data and fitted model. (Bottom) The bisector spans of the CORALIE data (which provide a check against transit mimics). Credit: Hellier et al., 2019. Eight new ‘hot Jupiters’ discovered by astronomers Citation: Four new ‘hot Jupiters’ discovered (2019, August 5) retrieved 18 August 2019 from https://phys.org/news/2019-08-hot-jupiters.html Astronomers report the detection of four new “hot Jupiter” exoplanets as part of the WASP-south survey. The newfound alien worlds received designations: WASP-178b, WASP-184b, WASP-185b and WASP-192b. The discovery is detailed in a paper published July 26 on arXiv.org. © 2019 Science X Network Explore further The detection was made by a team of researchers led by Coel Hellier of the Keele University, U.K. They used the WASP-South telescope at the South African Astronomical Observatory (SAAO) in South Africa. WASP (Wide Angle Search for Planets) is an international consortium conducting an ultra-wide angle search for exoplanets using the transit photometry method.The astronomers identified transit signals in the light curves of four stars during an observational campaign taking place between 2006 and 2014. The planetary nature of these signals was later confirmed by follow-up observations at the Euler-Swiss telescope and the TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST), both located in Chile.”We report on four new transiting hot Jupiters discovered by the WASP-South survey. (…) The WASP-South photometry was accumulated into multi-year lightcurves for every cataloged star, which were then searched for transits using automated routines followed by human vetting of the search outputs. Planet candidates were then listed for follow-up observations by the TRAPPIST-South 0.6-m robotic photometer and the Euler/CORALIE spectrograph,” the astronomers wrote in the paper.All four newly identified alien worlds were classified as “hot Jupiters,” as they are similar in characteristics to the solar system’s biggest planet, with orbital periods of less than 10 days. Such exoplanets have high surface temperatures, as they orbit their parent stars very closely.Located about 1,360 light years away from the Earth, WASP-178b was even classified as an “ultra-hot Jupiter,” given that its day-side temperature exceeds 2,200 K. In the case of this planet, this parameter was calculated to be around 2,470 K, what makes it one of the hottest exoplanets of this type known to date. Observations show that WASP-178b has a radius approximately 81 percent larger than that of Jupiter, while its mass is around 1.66 Jupiter masses. It takes the planet about 3.34 days to fully orbit its host, WASP-178b (a star of spectral type A1V, around twice as massive as the sun, with an effective temperature of 9,350 K), at a distance of some 0.056 AU from it. The parent star turns out to be the second-hottest transit host so far identified.WASP-184b is the least massive planet out of the newly discovered quartet—with a mass of only 0.57 Jupiter masses, however, around 33 larger than Jupiter. The alien world was found to be transiting a G0 host, every 5.18 days, separated by approximately 0.063 from the star. The planet’s temperature was calculated to be around 1,480 K. The host is about 65 percent larger and 23 percent more massive than the sun, located nearly 2,100 light years away.WASP-185b has a radius of about 1.25 Jupiter radii and is approximately as massive as Jupiter. However, although its mass and radius are typical for “hot Jupiters,” it’s orbital parameters are rare among such planets. The observations indicate that this extrasolar world has an eccentric orbit (with an eccentricity of about 0.24) and a relatively long orbital period of about 9.4 days. The planet’s mean distance to the host is around 0.09 AU and its temperature was calculated to be 1,160 K. With an effective temperature of 5,900 K, the parent star is of spectral type G0 and has a mass of approximately 1.12 solar masses. The system is located about 900 light years away.WASP-192b is the most massive exoplanet reported in the paper. With a radius of about 1.23 Jupiter radii, it is around 2.3 times more massive than Jupiter. The planet orbits WASP-192 (a moderately evolved G0 star with a mass of approximately 1.09 solar masses and an effective temperature of 5,900 K) every 2.88 days, at a distance of some 0.04 AU from it. The planet’s temperature was measured to be about 1,620 K. The planetary system is approximately 1,600 light years away from the Earth.last_img read more

Tangelo in the town

first_imgThe year has begun well for the Faculty of Engineering and Technology, Jamia Millia Islamia. The Faculty organised Tangelo Town’13, the annual techno-cultural fest which commenced on Friday.The theme is globalisation, model United Nations, international conference on sustainable technologies and tangelo sports league are the flagship events among 50 events to roll out in the next three days. ‘For the first time, the students council of Faculty of Engineering and Technology, Jamia has taken an initiative to move towards an international festival which has been named Tangelo Town. This festival will be a combined cultural, technical, sports, literary and arts festival. Spread over a span of three days, it’s expected to recieve a footfall of over 45,000 people,’ said Hammad, event coordinator. Also Read – ‘Playing Jojo was emotionally exhausting’The list of popular events to be held at the fest includes Pro Nite, Model United Nations, Photography Exhibit, Overnight Hackathon, Junk Yard Wars, Stage Play Competition, Tangelo Sports League 2013, Reflections, Altercatio and Nukkadh Natak. There will also be a photo exhibition called 50 States 50 Days which will be held in the MF Husain Art Gallery. Cricketer, Virender Sehwag, an alumnus of Jamia, will be the chief guest at the festival.While Tangelo Sports League started on 14 January, it had colleges and universities competing in football, tennis, badminton, basketball and cricket. Stunt Arena, Tech Fiesta and Management Fest are other events rolling in from today. If you are the management geek kinds and have an inclination towards money involved in economy, this is the place for you. Also Read – Leslie doing new comedy special with NetflixThe most sought after Pro Nite will see singer Angaraag Mahanta (Papon), of Jiye Kyu and Tere Naam fame performing on the last day of the festival . ‘I am happy and take pride in the ability of my students to organise such a wide scale celebration  which is already beginning to make its mark,’ said Najeeb Jung, Vice Chancellor, Jamia.So be there.DETAILAt: Jamia University campusOn Till: 20 JanuaryTimings: 11 am to 5 pmlast_img read more

Reading the way the French do

first_imgIt was an evening of Francophone literary experience with three authors having diverse style of strokes at the Swiss Embassy. Soiree Litteraire 2013, with an aim to build audiences for contemporary writing in French. The event involved readings from the original text by the authors followed by conversations.The guests of the event were three Francophone authors, Nicolas Ancion from Belgium, David Collin from Switzerland and Chowra Makaremi from France and Classical guitarist Shyamant Behal. Also Read – ‘Playing Jojo was emotionally exhausting’Nicolas Ancion, a lover of literary challenges and performances, who had written a novel in 24 hours in public during Brussels Book Fair in 2010, read out excerpts from his The 35 billion Euro Man, a novel which describes the abduction of multi billionaire Lakshmi Mittal. The author said, ‘It is fun to write and I love writing the way I see the world. Through this book I wanted to tell the story of my birth city Liege.’ The author has a knack for humor and writes fiction for adults and children. His session was moderated by Professor Vijaya Rao of JNU. Also Read – Leslie doing new comedy special with NetflixSwiss David Collin, read pericopes from his novel Memorial Circles and was moderated by Annie Mathews, a journalist cum film production Manager. The author’s variegated expertise includes performing arts projects, organizing literary events, producing cultural programs and writing short stories and essays.Iranian born Chowra Makaremi, got hold of a few excerpts from her novel Aziz’s Notebook based on the memoirs of her grandfather, in which he had narrated the event of execution of his two daughters during the Iranian Revolution in 1979 including the author’s mother. The author said, ‘It is a pleasure to write, what you are committed to’ in her discussion with the moderator Renuka George, a documentary film maker.’ Classical guitarist Shyamant Behal wooed the listeners by reciting short notes from traditional latin genres.last_img read more