Souping Up Superfluidity Calculations

first_img Citation: Souping Up Superfluidity Calculations (2006, March 2) retrieved 18 August 2019 from https://phys.org/news/2006-03-souping-superfluidity.html “In quantum mechanics, very seldom do you solve exactly problems involving more than one particle,” explains Massimo Boninsegni, Canada Research Chair at the University of Alberta. Boninsegni and his colleagues, Nikolay Prokof’ev and Boris Svistunov, both at the University of Massachusetts, have found a way to work with quantum systems involving many interacting particles on a scale larger than ever attained before. Their creation, named worm algorithm, is a new approach to path integral Monte Carlo (PIMC) simulations, the only known exact general method in quantum mechanics. Superfluidity is among the most spectacular manifestations regarding the quantum behavior of matter on a macroscopic scale. Superfluids are liquids capable of flowing without resistance, a fascinating phenomenon not yet fully understood. In 2004, another state of particles on the quantum level, supersolids, was discovered. Supersolids act like superfluids (moving without resistance), but maintain the characteristics of crystalline solids. PIMC is the only known method that can afford the theoretical study of superfluidity, by allowing the simulation, on a computer, of realistic models of superfluids, and by providing exact estimates of key physical quantities, such as the superfluid density. This is where Boninsegni, Prokof’ev, and Svistunov come in. In a letter published in Physical Review Letters on February 23, they explain how their worm algorithm overcomes some of the limitations of PIMC, while still making use of its basic ideas. “If you look at what people were doing by PIMC last year, they were working with the same system sizes as 20 years ago,” Boninsegni tells PhysOrg.com. “It seemed impossible to go bigger. The fundamental approach had to be revisited.” Now, he says, it is possible to have results for systems with 100 times more particles, obtaining more accurate predictions for experimentally measurable quantities such as the superfluid transition temperature. Boninsegni continues, “If it was just about getting more accurate numbers, though, I wouldn’t be so excited. We’ve made it possible to do things that seemed out of reach just a year ago.”Some of these things include getting a better understanding of defects in solids or the presences of interfaces between two crystalline samples. In order to do that, it is necessary to have a model of a system large enough to show the complex interactions between many particles, and still have particles left over for the interface. The worm algorithm works by creating entanglement among the particles. This done by “cutting” particles, which Boninsegni explains are “much like strings or polymers that wiggle all over the place.” The polymer-like particles break up and reconnect with other particles in the system. The worm algorithm allows the particle ends to grow and shrink along a fictitious (“imaginary’’) timeline. They connect with and disconnect from other particles, but eventually the two loose ends reconnect. By the time the cut polymer finds itself back together, it has created a large permutation cycle. These cycles are crucial to capture the physics of superfluids. The algorithm was originally applied by Prokof’ev and Svistunov to lattice models of space. But a new set of research possibilities (including discovering a possible “superglass” state, in addition to the supersolid state) has emerged from the fact that this particular project has extended the worm algorithm to continuous space, and not just discrete space.Boninsegni explains that this is not a method of creating a “worm hole,” but rather a mathematical calculation that can better help us understand the underpinnings of our universe. Being able to work with multiple particles and larger, complex systems will open new doors into the possibilities presented by quantum mechanics. By Miranda Marquit, Copyright 2006 PhysOrg.comcenter_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.last_img read more

Seeing through paint

first_img(PhysOrg.com) — When light passes through materials that we consider opaque, such as paint, biological tissue, fabric and paper, it is scattered in such a complex way that an image does not come through. “It is possible to see the light, but not the information,” Sylvain Gigan tells PhysOrg.com. “We wanted to create a way to see the information through opaque media.” Citation: ‘Seeing’ through paint (2010, March 18) retrieved 18 August 2019 from https://phys.org/news/2010-03-seeing-through-paint.html More information: Popff, et. al., “Measuring the Transmission Matrix in Optics: An Approach to the Study and Control of Light Propagation in Disordered Media,” Physical Review Letters (2010). Available online: link.aps.org/doi/10.1103/PhysRevLett.104.100601 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. Schematic of the apparatus. The laser is expanded and reflected off a SLM. The phase-modulated beam is focused on the multiple-scattering sample and the output intensity speckle pattern is imaged by a CCD camera: lens (L), polarizer (P), diaphragm (D). Image (c) 2010 American Physical Society, DOI:10.1103/PhysRevLett.104.100601 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 How to see through opaque materials Gigan is a scientist at the City of Paris Industrial Physics and Chemistry Higher Educational Institute (ESPCI). Gigan worked in a group with Popoff, Lerosey, Carminati, Fink and Boccara to create an experiment that demonstrates that it is possible to construct a transmission matrix that allows them to “see” through some opaque materials. The results of their experiment are described in Physical Review Letters: “Measuring the Transmission Matrix in Optics: An Approach to the Study and Control of Light Propagation in Disordered Media.”“When people try to look into an opaque medium, especially biological material, they use the ballistic light, the light that has not been mixed up by the medium due to scattering. But as you go into the medium, the ballistic light becomes less intense, limited by the scattering process.”Instead of being limited by scattering, though, the group at ESPCI instead looked for ways to use scattering to their advantage. Gigan and his colleagues passed light through zinc oxide, which is common in paint. They observed the way the light of a laser scattered as it passed through, and then created a numerical model to describe the result. “This transmission matrix is a map through the medium,” Gigan explains. “Once we have the transmission matrix, it is possible to analyze whatever pattern goes through.”The process provides the means to put together an image of something on the other side, allowing the researchers to “see” through the zinc oxide layer, even though it is opaque. Reversal is also possible, offering a way to tailor a beam that could pass through opaque material, and then focus. “Such a method could allow for applications in imaging of biological material, among other applications,” Gigan says. “This provides a way to transmit information or focus light in a medium that wouldn’t by any classical means allow that.”There are limitations, however. “This should not be construed to mean that we can see through walls with this technique,” Gigan points out. “Some degree of light has to be able to pass through, and a wall stops light from coming out the other side. You could use white fabric, paint, or paper, though. Even biological tissue, like a chicken breast, could work.”Gigan also admits that so far the process is rather slow. “Getting the matrix is a slow process, taking minutes. We used paint because it is so stable. If you wanted to actually go through biological media, or through liquid, it wouldn’t work with our current set-up, since the light transmission changes as the medium moves.”For now, the group at ESPCI is working on tackling the problems presented by technology. “The main limitation for using this technique in biological microscopy is technical. There are some hints of how to get the transmission matrix faster, but at the moment we’re not really ready.”Despite the limitations, Gigan sees some current applications. “There are implications for nanotechnology, and the propagation of light in this system is interesting. It offers a basis for the idea of manipulating the light wave, and we believe this could be a promising approach to imaging. Perhaps in five years we will have the technology to take this even further.”last_img read more

Basketball shot selection analyzed mathematically

first_img More information: arxiv.org/abs/1107.5793 Source: Wikipedia © 2010 PhysOrg.com Explore further Analyzing Effects Of Hoops Ball Hog In the sport of basketball players are constantly faced with the choice of whether to shoot for the hoop when a shot opportunity arises or to hold on to the ball and hope a better opportunity will arise. Now a theoretical physicist from the University of Minnesota in the US has analyzed the problem mathematically and determined the best strategy. Citation: Basketball shot selection analyzed mathematically (2011, August 5) retrieved 18 August 2019 from https://phys.org/news/2011-08-basketball-shot-mathematically.html Graduate student Brian Skinner decided to analyze basketball shot selection after hearing about traffic flow research that reached the unexpected conclusion that average commuting time could be reduced by road closures that force drivers to travel by routes they would otherwise avoid in order to try to minimize their own commuting time. The traffic flow diagrams reminded Skinner, an enthusiastic fan of basketball, of diagrams of the flow of basketball players in a game. The surprising conclusion also reminded him of a basketball theory named after Patrick Ewing, a high-scoring basketball player. When the games of Ewing’s team were analyzed it was discovered that the team won more games if the big-scoring Ewing was absent.Skinner realized that most of the mathematical equations and variables used in analyzing traffic flow could also be applicable to basketball and the movement of the ball in the game. His analysis, published at arXiv.org, concentrated on the movement of the ball as it approached the hoop.Skinner’s model aimed to find out how likely the shot is to go in before the player should make the shot. Shots more likely to go in were classed as higher quality shots, and the model assumed that the quality of shot opportunities falls randomly. The mathematical model demonstrated the optimal strategy for scoring the maximum points is for the team to take their time and concentrate on making high quality shots as long as there is sufficient time remaining for the shot. The model also concluded that a team playing a faster game and having twice the shot opportunities of its rival should not have double the shooting rate, but taking more time and being more selective about which shots to take would give them the biggest advantage. So, for example, if the slower team shoots at an average rate of 20 seconds, the team playing twice as fast should not shoot every 10 seconds but should take an extra three seconds on average, giving a shooting rate of 13 seconds. 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

Possible new explanation found for sudden demise of Khmer Empire

first_img Explore further Did Climate Influence Angkor’s Collapse? Now, work by a group of scientists indicates it may have been due to drought. The group, led by Mary Beth Day, an earth scientist with the University of Cambridge, is to have the results of their efforts published in a report in the Proceedings of the National Academy of Sciences. The Khmer Empire existed from the period between the 9th and 15th centuries and was centered around the city of Angkor. During that time, it’s very clear that great effort was put into capturing massive amounts of water that came from the skies during the monsoon seasons in the summer, to support drinking and crop growing during the rest of the year. The system apparently worked great for a long time, then suddenly didn’t. The reasons put forth for this sudden change have varied, from disease or warfare, to public strife, to changing environmental conditions. Now, it appears due to this latest research, that at least one of the major factors was indeed environmental.To find out if the problem was a dearth of water due to changes in the weather or the water system, the team took soil samples from one of the largest reservoirs (called barays) built by the Angkor people. Digging down as far as six feet, the team found that prolonged drought and perhaps overuse of the soil for farming may have led to a society unable to feed itself, a sure and straight path to an untimely demise if ever there was one.In studying the soil samples, the team was able to see sediment deposits that had built up on the bottom of the baray over time. During the years leading up to 1431, thinner layers indicted less water became available for storage. They also showed that the rainfall was more erratic. Instead of steady rains during the monsoon seasons, huge storms would erupt flooding farmlands and dumping massive amounts of soil into the baray, which were then followed by periods of no rain at all. The result was much less water available for drinking and growing crops during the drier seasons, and possible destruction of crops that the people were able to grow, due to flooding.This new research doesn’t prove for a fact that it was drought that led to the demise of the Khmer Empire, of course, as there were other factors involved. War with neighbors, the conversion of many of the inhabitants to Buddhism, and natural dispersion due to increasing trade with other countries, all likely had a hand. But it does appear that changing weather patterns might have been the final straw. © 2011 PhysOrg.com (PhysOrg.com) — The Khmer Empire, known to many as the Angkor Civilization, was a society of people that lived for several centuries in Southeast Asia in what is now Cambodia, Thailand, Laos and Viet Nam. What has kept the memory of the empire alive are the huge structures built by the people who lived in the area during that time. Also of note were the roadways, canals and water movement and storage systems that were constructed to support a large population. But like many other lost cultures, what was once a flourishing metropolis, in a very short period of time, gave way to collapse.center_img Map of Southeast Asia circa 900 CE, showing the Khmer Empire in red, Champa in yellow and Haripunjaya in light Green plus additional surrounding states. Image: Wikipedia. Citation: Possible new explanation found for sudden demise of Khmer Empire (2012, January 3) retrieved 18 August 2019 from https://phys.org/news/2012-01-explanation-sudden-demise-khmer-empire.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Study shows nonlinear pattern of migration due to climatic variations

first_img © 2014 Phys.org Citation: Study shows nonlinear pattern of migration due to climatic variations (2014, June 24) retrieved 18 August 2019 from https://phys.org/news/2014-06-nonlinear-pattern-migration-due-climatic.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. Indonesia is the fourth most populous country in the world with its people scattered over many islands. It’s also a place with frequent earthquakes and volcanic eruptions—approximately 40 percent of the people in that country make their living from agriculture, generally near the coasts. Taken together, these factors will likely mean major disruptions for the country as global warming causes temperatures to rise, rainfall to change and sea levels to rise. In their study, the researchers sought to learn how temperature and rainfall changes impacted permanent migration in the country, from one region or island to another.The researchers used data from the Rand Corporation’s, The Indonesia Family Life Survey, which has been running since 1993/94. Among other things, the survey tracks the movement of 7,185 people living in that country. The researchers compared the migratory data from the survey with weather data from the same period to see if any patterns might emerge. They found that if the average temperature for any given place was below, 25 °C, small increases in temperature did not give rise to permanent migrations. In places where the average temperature was above 25 °C, however, temperature increases did cause permanent migration to occur. And the more temperature increased, the more people moved away. As an example, they noted that a one degree rise, from 26 to 27 degrees raised the probability of migration by 0.8 percent, but the probability jumped to 1.4 percent if the temperature rose from 27 to 28 degrees. They noted that changes in rainfall had a similar impact, but was not as pronounced.The team conducted similar studies on natural disasters in the area to see if they had a similar impact and found migration from such events tended to be short term as people generally moved back when able to do so.The researchers suggest their results indicate that Indonesia is likely to see large permanent migration as global warming causes rising temperatures, with people moving away from some of the most heavily populated provinces, such as Jakarta. They note also that such migration trends are likely to occur in other countries as well. Journal information: Proceedings of the National Academy of Sciences (Phys.org) —A team of researchers in the U.S. has found that local temperature increases only caused permanent migration in Indonesia when such increases occurred above 25 °C, providing hints of possible migration patterns as global warming continues in the future. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they used data from another study to track migration over a multi-year period as a means of predicting migration patterns due to global warming.center_img Nonlinear effects of temperature and precipitation on annual migration probability. Credit: Pratikshya Bohra-Mishra, PNAS, doi: 10.1073/pnas.1317166111 Explore further Research duo quantify global human migration numbers More information: Nonlinear permanent migration response to climatic variations but minimal response to disasters, Pratikshya Bohra-Mishra, PNAS, DOI: 10.1073/pnas.1317166111AbstractWe present a microlevel study to simultaneously investigate the effects of variations in temperature and precipitation along with sudden natural disasters to infer their relative influence on migration that is likely permanent. The study is made possible by the availability of household panel data from Indonesia with an exceptional tracking rate combined with frequent occurrence of natural disasters and significant climatic variations, thus providing a quasi-experiment to examine the influence of environment on migration. Using data on 7,185 households followed over 15 y, we analyze whole-household, province-to-province migration, which allows us to understand the effects of environmental factors on permanent moves that may differ from temporary migration. The results suggest that permanent migration is influenced by climatic variations, whereas episodic disasters tend to have much smaller or no impact on such migration. In particular, temperature has a nonlinear effect on migration such that above 25 °C, a rise in temperature is related to an increase in outmigration, potentially through its impact on economic conditions. We use these results to estimate the impact of projected temperature increases on future permanent migration. Though precipitation also has a similar nonlinear effect on migration, the effect is smaller than that of temperature, underscoring the importance of using an expanded set of climatic factors as predictors of migration. These findings on the minimal influence of natural disasters and precipitation on permanent moves supplement previous findings on the significant role of these variables in promoting temporary migration.Press releaselast_img read more

Foodies affair

first_imgTreat yourself with some exotic food brought  to you by The Imperial this month. Enjoy a lavish Sunday brunch at 1911 with 7 Wonders of the World, featuring specialties from the regions of seven wonders across the globe on 17, 24 and 31 August. Nostalgia at 1911 Brasserie presents Coffee, Chocolate and Cognac from 21 to 31 August. It gives you relaxing cup of coffee, finest cognacs and flavoured white and dark chocolates that calls for an unrivalled dining experience. To top it all superb wine list accompanied by sinful deserts is designed to cast a spell, making your evening with us an affair to remember. Daneill’s Tavern host the Home Style Food from 25 August to 7 September. Savour comforting recipes to summon memories of cosy meals at home with family. The Chefs have put together some all time favourite home-style specialties this season that will surely remind you of your grandma’s kitchen. So hurry up and book your table.last_img read more

Quake kills at least 36 in India PM takes stock

first_imgAt least 36 people were killed and more than 100 injured in India on Saturday due to the massive earthquake that had its epicentre in Nepal. Prime Minister Narendra Modi held a high-level meeting on the situation and spoke with the chief ministers of the affected states. Though Nepal was the worst affected with over 900 dead, India was not spared, as 25 people were killed in Bihar, 8 in Uttar Pradesh and 3 in West Bengal.President Pranab Mukherjee wrote to the governors of Bihar, Uttar Pradesh, West Bengal and Sikkim, condoling the loss of lives. Modi held a high-level meeting with senior ministers and officials and spoke with the chief ministers of Uttar Pradesh, Bihar, West Bengal, Sikkim and Madhya Pradesh.  Also Read – Need to understand why law graduate’s natural choice is not legal profession: CJI“The prime minister was briefed on the inputs regarding the extent of damage to life and property received so far from various places in India and Nepal,” said a statement issued by the Prime Minister’s Office (PMO).Defence Minister Manohar Parrikar said he has directed all army units to carry out rescue operations and extend full cooperation to local authorities. In order to deal with the situation in the affected states, five teams of the National Disaster Response Force (NDRF) have already been sent – one to Gorakhpur in Uttar Pradesh and one each to Darbhanga, Supaul, Motihari and Gopalganj in Bihar. Also Read – Health remains key challenge in India’s development: KovindHome Secretary L.C. Goyal said the impact of the earthquake was felt in many states in India, particularly in Bihar, Uttar Pradesh, Sikkim and West Bengal. The ministry has been in constant touch with all the affected states to assess the situation. Each team of the NDRF consists of 45 personnel who are fully equipped with modern equipment to deal with search and rescue operations, he said.The team also includes medical and paramedic personnel. The teams have equipment such as live detector machines, cutters which can cut steel, concrete and wood.last_img read more

Madhyamik results to be out today

first_imgKolkata: The West Bengal Board of Secondary Education (WBBSE) will announce the results of Madhyamik examination 2018 on Wednesday. The results will be declared in a Press conference at the Board office in Salt Lake at 9 am. A senior official of WBBSE informed that the results can be accessed from as many as eleven websites, including www.webresults.in/wbbse.org, examresults.net/wb, westbengal.indiaresults and exametc.com, from 10 am onwards. Apart from this, candidates can also type WB 10, followed by their roll number and send it to 54242 or 5888 to receive their marks.It may be mentioned that a total of 11,21,921 candidates had appeared for Madhyamik examination this year, which is 31,075 higher than 2017. Among the examinees, 6,21,366 were girls, while 4,81,555 were boys. There were 2,811 centres in which the examination was held from 12 to 21 March.The results are being declared within 77 days of the completion of the examination.last_img read more

South Dinajpur conducts drives against prenatal sex determination

first_imgBalurghat: Initiative to conduct massive awareness drive in order to stop the illegal practice of prenatal determination of sex has been taken up in South Dinajpur.The step has been taken up following a decrease in male-female ratio in South Dinajpur and the awareness drive will be carried out to check the illegal practice. According to the source, different NGOs will take part actively in the awareness campaigning.Sukumar Dey, Chief Medical Officer of Health (CMOH) of South Dinajpur, said the state government wants to curb the menace of sex determination at any cost. Also Read – Heavy rain hits traffic, flightsAccording to him, the move follows statistics that the number of girls in this district in respect to the number of boys is plummeting.Notably, the district has a district hospital in headquarter, Balurghat, along with eight block hospitals located in each block, where the birth rate of girls is decreasing compared to that of boys.As per 2011 census report in aspect to South Dinajpur, the average sex ratio stands at 956 girls to every 1000 boys. There were also reports of flouting the law against sex determination in private health care facilities and nursing homes.”We are determined to stop the illegal practice of fetus determination. We will organise workshops in different parts of the district to make people aware through NGOs. Private facilities and nursing homes will also take part in it,” Dey said.last_img read more

Switzerland grants final special stripper visas

first_imgMore than 700 foreign strippers received a special Swiss work permit in 2015, the last issued in a controversial programme that expires on January 1, the immigration office said today.Switzerland began awarding eight-month permits in 1995 to women from outside the European Union who wanted to come to the country to work as strippers and cabaret dancers.The programme was meant to protect people who may have otherwise been vulnerable to sex traffickers, and dancers from Russia, the Dominican Republic and Thailand were among the top recipients.But following a prolonged investigation, Swiss authorities in 2014 announced that the programme was no longer serving a protective role, with some permit holders subjected to forced prostitution after arrival in the country.Migration office spokeswoman Lea Wertheimer confirmed that the programme will formally be cancelled as of the new year.last_img read more