text
stringlengths 9
78.2k
|
|---|
There are reports of rain in the southern parts of the las Vegas valley. Here is the latest from Chief Meteorologist Bryan Scofield.
|
There is a Severe Thunderstorm Warning in effect for northwestern Arizona and central Clark County until 1:30 p.m. The storm could bring heavy rain and hail to the area.
|
The storm is currently moving into the Boulder City area.
|
Can culture shifts, open architecture prod defense acquisition reform?
|
Deloitte's Elizabeth McGrath, the Defense Department's former deputy chief management officer, was among the witnesses at a June 24 House Armed Services Committee hearing.
|
Improving and streamlining defense acquisition is a perennial topic of congressional hearings. But reform doesn't mean the same thing to everyone. The occasionally conflicting demands of legislators, as well as cultural factors inside the Department of Defense, may be what make acquisition reform such a tough nut to crack.
|
At a June 24 hearing of the House Armed Services Committee, a panel of former Defense officials and policy experts heard from members who were worried that acquisition was too bogged down in red tape, too slow, too expensive, too friendly to longtime incumbent contractors and inimical to small business participation, but also occasionally rushed at the expense of an enterprise-wide approach.
|
"I believe the causes for our discontent with the performance of the acquisition system do not lie in the laws and regulation," said retired Navy Vice-Admiral David Venlet. "It's underlying decisions that are made that try to respond for the years of acquisition reform pressures. ... do this faster, do this cheaper. That pressure has an unintended consequence of suppressing the practice of good sound fundamentals and realism."
|
Elizabeth McGrath, the recently retired former deputy chief management officer at DOD, and a leader in enterprise-wide IT acquisition policy, said her tenure taught her that rapid prototyping and revision, strong program management, and contract flexibility to account for changes in requirements that occur in an agile development process are key elements to effective technology acquisition.
|
But having a strategy and executing it are two different things.
|
McGrath, who is now with Deloitte Consulting LLP, noted that, culturally, the department is still in the midst of a generational shift, from maintaining a staff of dedicated coders to grooming program managers with expertise in acquiring and implementing commercial off-off-the-shelf products for use in DOD business systems. Staffing and culture have "not kept up with the way the technology evolved," McGrath said.
|
"The workforce needs to be trained on how do you acquire and configure commercial capabilities as opposed to what we do today in the acquisition process. The training isn't focused, I don't think, enough on how to enable a better implementation," McGrath said.
|
The latest iteration of the DoD Directive 5000, the acquisitions bible used in defense procurement, embeds new guidance that differentiates the acquisition of commercial IT products for business use from procurement of weapons systems. McGrath said that earlier efforts to create a separate rulebook for IT "confused people." At the same time, McGrath said that IT is different, and requires different training and processes. "It has the opportunity to move faster than perhaps some of the other aspects of acquisition," she said.
|
Software for weapons, ships, aircraft, and other complex hardware systems poses a separate problem, said Ronald O'Rourke, a naval specialist at the Congressional Research Service. The Navy is trying to contain costs and problems of interoperability by "moving to more open architecture approaches to the integration of software in weapons system platforms," O'Rourke said. He cited the Acoustic Rapid COTS Insertion program, an open architecture program for swapping in the latest signal-processing computers in Navy submarines. The ARCI program can be viewed as an early example of 'walking the walk' on open architecture," O'Rourke said in his prepared testimony. One key benefit of open architecture, he said, is that it lowers barriers to small business participation.
|
Data transparency is another area for possible reform, said Christopher Lamb of the National Defense University. Currently analytic resources are concentrated in the individual services. "They own the data, the models, and the trained personnel for evaluating tradeoffs," Lamb said. They are fierce defenders of their own programs and prerogatives, and can supply data and arguments to support their decisions. "They do not want to reopen the evaluation process to reconsider performance parameters that would challenge their programs in a joint venue." As a result, "the large amounts of resources used for analysis in the Pentagon often obscure rather than illuminate choices." Fixing the problem isn't a matter of rewriting acquisition rules, he cautioned, but a deep, structural change in the way military leadership is organized.
|
There are moves inside the DOD and in Congress to make changes to military procurement, with Frank Kendall, undersecretary of Defense for acquisition, technology and logistics, leading efforts at the Pentagon, and Rep. Mac Thornberry (R-Texas), vice chairman of the House Armed Services Committee, exploring options in the House. But if history is any guide, a lasting solution will prove elusive.
|
"This is something we've done over and over. But I'm confident that this time it's going to be perfect," joked committee Chairman Buck McKeon (R-Calif.).
|
Defense minister says he made decision so he could oversee developments in the South.
|
Ahead of an additional Israeli response to Wednesday's bomb attack along the border with the Gaza Strip, Defense Minister Ehud Barak on Wednesday cancelled a planned visit to Washington, where he was scheduled to meet Defense Secretary Robert Gates. Barak said he canceled his trip so he could monitor the developments in Gaza. The IDF was prepared for every possible eventuality, he said. On Tuesday night, the Israel Air Force bombed three tunnels along the Philadelphi Corridor in response to the bombing attack earlier in the day, which killed an IDF Beduin tracker and wounded three other soldiers. Defense officials said that a radical Palestinian terror group affiliated with global jihad elements was behind the attack but that it could not have been perpetrated without Hamas's consent. "We will continue with our response to the attack even though it was carried out by a group that is not Hamas," Barak said in a speech before students at the Herzliya Interdisciplinary Center. "We hold Hamas responsible for everything that happens in Gaza." Barak said it was possible that there would be more attacks before a cease-fire was implemented by Hamas and Israel. Barak was supposed to spend one day in Washington for talks with Gates and National Security Advisor James Jones. Barak told US Mideast envoy George Mitchell on Wednesday that Israel would not tolerate harm to its civilians or its sovereignty. Speaking during a meeting at the King David Hotel in Jerusalem, Barak said Israel would act decisively in responding to every attempt by Hamas and other Gaza terror groups to attack.
|
The war in the construction industry opened up new fronts today, Wednesday.
|
Protests on construction sites across Britain turned into mass stay-aways.
|
For the second time this week groups of construction workers have united with electricians to walk off the job.
|
At the Ratcliffe-on-Soar power station in Nottinghamshire, electricians, scaffolders and welders all stayed out of work.
|
More than 200 electricians picketed both gates at SSI steel works (formerly Corus), in Redcar on Teeside with the scaffolders and electricians refusing to work.
|
A student delegation from Teesside University unfurled a banner with “students and workers unite and fight” on it.
|
One electrician spoke of the solidarity they have received from students while another spoke about the importance of unity between public and private sector workers.
|
There was a short meeting that concluded in electricians blocking the Redcar entrance of the site with traffic backed up around the roundabout.
|
Workers also stayed off the job at the Pembroke power station in Wales. At Ferrybridge power station in West Yorkshire scaffolders, welders and electricians all refused to work.
|
In Saltend workers on one project protested and in Liverpool 20 workers from the John Moores University site refused to work and joined the protest there.
|
In London, up to 200 workers protested at the Farringdon Crossrail construction site.
|
The contractor, Crown House, says it wants to replace teams of electricians with teams made up of only one electrician and eight semi-skilled workers—who will earn a third less.
|
Two Unite union stewards were recently elected on the site—but management refused to recognise them. After today’s protest they agreed to recognise one of the stewards.
|
At the site the main delivery gate had mysteriously been locked with what one worker called a “rank and file” padlock so preventing lorries getting in or out.
|
This produced a flurry of activity from management. But electricians from the site refused to go into work—despite a company photographer trying to photograph protesters.
|
Other grades that went into work remained in the canteen and refused to work.
|
On the picket line workers held an impromptu meeting and discussed where to take the campaign. Many were keen on taking the protests to the offices of the companies and to those of the clients.
|
An official strike ballot of Balfour Beatty electricians is underway and the result is due on 30 November. A number of speakers spoke about how that should be the spark to walking off sites and joining the public sector strikes that day.
|
The electricians are campaigning to stop building bosses tearing up their national JIB agreement and cutting wages by up to 35 percent.
|
The contractors attacking the agreement are Bailey Building Services, Balfour Beatty Engineering Services, Tommy Clarke, Crown House Technologies, SES and Spie Matthew Hall.
|
In reality, agencies are already recruiting the new grade of “installers” in preparation for the introduction of the new contracts.
|
Members of the Ucatt construction workers’ union have voted overwhelmingly to join the 30 November public sector strikes.
|
Building workers in local government, NHS, the prison service and the civil service voted by a margin of more than four to one in favour of strikes. In total 83 percent voted to strike on a 27 percent turnout.
|
It was an exciting morning at Legoland Florida Resort as officials held a media event to unveil Heartlake City, the latest themed section. Heartlake City is based on the Lego Friends line of products, which have storylin es based on a group of young women, Mia, Emma, Stephanie, Olivia and Andrea.
|
Legoland Florida does an excellent job of incorporating local children into its media events, and Thursday was no exception. The park collaborated with The Wright Step School of Dance Winter Haven, headed by Amy Wright. The school brought a large group of kids, mostly girls, who performed a choreographed dance during the unveiling ceremony. The children were rewarded with invitations to test out Mia’s Riding Adventure and attend a performance of “Friends To the Rescue,” the live show in Heartlake Hall.
|
Heartlake City introduces what is likely to be one of the most popular photo opportunities in the park, a pink bench near the entrance surrounded by life-sized figures of the five Lego Friends.
|
The Chelsea High boys basketball team improved to 4-0 in the Commonwealth Athletic Conference with a 68-53 triumph over Greater Lowell Tuesday evening.
|
The Red Devils led all the way, grabbing a 16-4 lead after one period and never allowing Greater Lowell to bring the margin under double figures. Chelsea featured a balanced scoring attack as Sammy Mojica led the Red Devils in the scoring column with 16 points, followed by Jordan Virella with 14, Joseph Rivera with 12, and Felix Crespo with nine.
|
Chelsea head coach Jay Seigal also utilized a pressing defense that kept Greater Lowell off balance and resulted in a large number of turnovers. “We’re at our best when our defense creates offensive opportunities and we can maintain an up-tempo pace,” said Seigal.
|
The victory snapped a three game losing streak for Chelsea, all of which came against non league rivals. The Red Devils lost both games in their Christmas tournament last week, falling to Masconomet in the preliminary round, 50-38, and then to Triton in the consolation game, 59-57.
|
The latter contest saw Chelsea almost pull off a miraculous comeback victory as the Red Devils overcame a 14 point deficit with 2:35 to play and knotted matters at 57-57 with 19 seconds on the clock.
|
Chelsea played excellent defense as Triton tried for a final shot. The game seemed to be headed into overtime, but Triton caught a break when a loose ball was picked up by one if its players, who then threw up a shot at the buzzer which went through the hoop to win the game.
|
Mojica pumped in 23 points, including 13 in the final frame, as he and Virella led the charge in the final minutes that almost led to a victory.
|
Chelsea held a 28-17 lead midway through the second quarter and had some chances to expand the lead, but couldn’t get the ball to fall. Peabody then rallied for a nine point run before the half to make it a 28-26 affair at the intermission. The teams played nip and tuck through the third frame until Peabody pulled away in the final eight mutes.
|
Crespo hit for 17 points and Rivera popped in 16 against the Tanners, the Red Devils’ former Greater Boston League rival which now is in the Northeastern Conference.
|
Seigal and crew now will take on two of their toughest CAC foes when they travel to Greater Lawrence Friday and then journey to Lynn Tech Tuesday.
|
New Study Shows A Grave Lack Of Gender Diversity In The Music Industry Among other findings, more than 90 percent of Grammy nominees in the past six years have been men.
|
Lorde, seen here at the 2014 Grammy Awards, is the only woman nominated in this year's album of the year category.
|
Ahead of Sunday night's 60th Grammy Awards ceremony, a new study published by University of Southern California's Annenberg Inclusion Initiative finds that more than 90 percent of Grammy nominees in the past six years have been male. Stacey Smith, co-author of the study — titled Inclusion in the Recording Studio? -- says there is an "epidemic of invisibility" in the music industry, particularly in songwriting and producing.
|
"When it comes to songwriters, only 12 percent are female, and perhaps most egregiously, only 2 percent of 651 producers were women," Smith says. "And only two of those producers were women of color."
|
The study wasn't only about the Grammys: Researchers also looked at the 600 most popular songs since 2012. The evidence suggests a heavily male-dominated industry overall — and when you consider that the music industry tends to favor the songwriters with a pedigree for churning out hits, that pool becomes even more shallow.
|
"There are nine male songwriters that are setting the agenda for popular culture across a fifth of the most popular songs over the last six years," Smith says. "Nine men! I think consumers should know this, and I think there should be concern that such a narrow slice of humanity is responsible for and driving our ideas in music."
|
Heba Kadry is a mastering engineer based in Brooklyn. She says she doesn't believe the Grammys are the best indication of what's actually going on in the music industry right now, and that some advances in diversity have been made — but that even so, she is a still a minority in her field and faces uphill battles in getting work.
|
"Any time you're in a room with a bunch of people who are considering hiring you, there is this immediate assumption, like, 'Who do you manage?' or 'Whose girlfriend are you?' ... They don't think of you as potentially a person who knows what they're doing," Kadry says. "And so you feel like you kind of have to prove yourself twice as much as males."
|
Kadry says that the major labels, the hitmakers, rarely go outside their comfort zones in her experience — but sometimes their hands can be forced.
|
"They usually go for their rolodex of the same dudes," she says. "I think when the artist has enough clout to be like, 'You know what? No. I want to work with this person,' then can the tides really change."
|
The Intergovernmental Panel on Climate Change (IPCC) is widely regarded in the media as the ultimate authority on climate change. Created by two divisions of the United Nations, and recipient of the 2007 Nobel Peace Prize, its pronouncements are received as if they come down from Mount Olympus or Mount Sinai. The common presumption is that the IPCC has assembled the best scientific knowledge. Let’s take a closer look at this organization to see whether it merits such uncritical deference.
|
Clearly, the IPCC does not speak as one voice when leading scientists on its panel contradict its official position. The solution to this apparent riddle lies in the structure of the IPCC itself. What the media report are the policymakers’ summaries, not the far lengthier reports prepared by scientists. The policymakers’ summaries are produced by a committee of 51 government appointees, many of whom are not scientists.
|
The policymakers’ summaries are presented as the “consensus” of 2,500 scientists who have contributed input to the IPCC’s scientific reports. “Consensus” does NOT mean that all of the scientists endorse the policymakers’ summaries. In fact, some of the 2,500 scientists have resigned in protest against those summaries. Other contributing scientists, such as the individuals quoted above, publicly contradict the assertions of the policymakers’ summaries.
|
To better understand the “consensus” presented in the policymakers’ summaries, it is helpful to be aware of the structure of the IPCC. Those who compose the summaries are given considerable latitude to modify the scientific reports. Page four of Appendix A to the Principles Governing IPCC Work states: “Changes (other than grammatical or minor editorial changes) made after acceptance by the Working Group of the Panel shall be those necessary to ensure consistency with the Summary for Policymakers or the Overview Chapter.” In other words, when there is a discrepancy between what the scientists say and what the authors of the policymakers’ summaries want to say, the latter prevails.
|
To its credit, the IPCC debunks many of the alarmist exaggerations of radical greens. However, its scientific authority remains irreparably compromised by political tampering. When a U.S. State Department official writes to the co-chair of the IPCC that “it is essential that … chapter authors be prevailed upon to modify their text in an appropriate manner,” the political character of IPCC is plain.
|
The sponsors of the IPCC, the United Nations, and liberal American politicians all share the goal of reducing Americans’ wealth by capping our consumption of energy with a binding international climate change treaty. They are willing to resort to scientific fraud to further their goal. In the words of Al Gore’s ally, former Under-Secretary of State Tim Wirth, “Even if the theory of global warming is wrong, we will be doing the right thing” by reducing Americans’ consumption of fossil fuels. Keep that in mind whenever the IPCC is cited in support of a climate treaty.
|
The declassified images are a treasure trove for scientists who study the empires of antiquity.
|
Michelangelo Antonioni’s 1966 film Blow-Up features a wayward London fashion photographer called Thomas who unwittingly documents a murder. Hidden in the blurred background of one of his most recent photographs is a detail so obscured by shadows and foliage that, at first, Thomas does not even see it. Only after he repeatedly blows up the image, zooming in over and over again on this otherwise minor feature, is the disturbing truth revealed: a terrible crime has been committed and this photograph has made Thomas an unexpected witness. The most important thing in the photo had been concealed in the background all along.
|
It was revealed earlier this month that declassified U.S. spy satellite photographs taken above the Antarctic have inadvertently also documented how that continent has been affected by climate change. In this case, deep in the archives of national intelligence agencies are satellite photos half a century old in which scientifically useful data has been hiding in plain sight. These now-outdated spy photographs have thus found an unexpected second life as important tools of planetary science—and, like Thomas’s photo in Blow-Up, their background details have proved at least as, if not far more, valuable than their original purpose.
|
A group of researchers, led by Shujie Wang at the University of Cincinnati, explained that classified photographs taken by the CIA’s ARGON satellite platform in the early 1960s have, upon reevaluation, added decades’ worth of visual evidence through which glaciologists can track the melting of Antarctica’s ice sheets. Building on earlier analyses of these same satellite photos performed by teams at other institutions, Wang’s group demonstrated that the images have pushed back the start date for large-scale Antarctic melting by at least three decades. In other words, these seemingly featureless expanses of ice captured merely as an incidental detail during Cold War surveillance missions now offer significant new insights into how Earth’s polar regions are responding to climate change.
|
While Wang’s work focuses specifically on precursor evidence for the 2002 collapse of the Larsen B ice shelf, the larger takeaway of her team’s approach is that it can be remarkably easy to overlook unusual data sets simply because of their original context. How can you find something if you don’t even know you’re supposed to be looking for it? As this work shows, however, a satellite photograph taken for reasons of international espionage is technically identical to a satellite photo taken for reasons of glaciology. In a very real sense, the only difference comes from what a viewer chooses to focus on.
|
Archaeologist Jesse Casana describes arriving at this realization in his own field by using the metaphor of turning swords into ploughshares—that is, transforming what is essentially a weapon of the Cold War into a tool of civilian research. Casana spoke to me about the CORONA satellite program, in particular. The CORONA photographs are the earliest available spy satellite images, taken for roughly a decade beginning in the late 1950s. When they were declassified by the Clinton Administration in 1995, nearly 900,000 previously top secret satellite images became available for public research with the stroke of a pen.
|
Archaeologists were amongst the first to pounce.
|
Casana described the CORONA imagery with undisguised enthusiasm. “CORONA is an amazing tool for archaeological discovery, in general,” he said—but the engineering feats that made the photographs possible in the first place are equally awe-inspiring. The satellites’ camera systems, for example, relied on special, high-definition film developed in secret by Kodak. An exposed roll of this ultra-sensitive film would then need to be physically recovered from its satellite in order to be processed. This meant that individual film canisters would be jettisoned from orbit; as the film fell back to Earth, a tiny parachute would pop open, usually somewhere over the Pacific, and the canister would then drift back down through the atmosphere. A U.S. military airplane armed with a skyhook would then grab the film during descent and bring it back to the ground for processing. These complex aerial acrobatics are almost laughably archaic by today’s standards, but they also reveal how much effort the U.S. exerted in keeping tabs on Soviet arms buildups and on the internal activities of other nation-states.
|
As Casana pointed out, the declassification order came after heavy lobbying from Robert McCormick Adams, an archaeologist and, at the time, Secretary of the Smithsonian Institution. Adams knew the historical value of these photographs, but he also knew that, in the 1990s, with the Soviet Union no longer in existence, they no longer played any real strategic role for U.S. intelligence. Best of all, Casana pointed out, the CORONA photos also captured landscapes throughout the Middle East in a primarily pre-industrial state, before surface ruins or subsurface remnants had been permanently destroyed by 20th-century urbanization, agriculture, or even acts of war. “The old satellite imagery from the 1960s or earlier often preserves a picture of these sites and features that, in many cases, no longer exist today,” Casana told me. The photographs, in other words, are often the only physical record archaeologists now possess.
|
Casana is director of the CORONA Atlas Project, an attempt to methodically and systematically identify all sites of archaeological interest in the backgrounds of these images. Archaeologists are poring over each image, looking for anomalous landscape features, such as unusual lines or odd patterns. The numbers so far have been astonishing. Together with other recently declassified U.S. satellite photos—from the ARGON, HEXAGON, GAMBIT, and LANYARD programs—the images include shots of roughly 4,200 previously known sites. However, archaeologists have now identified as many as 12,000 new sites of potential historic interest. Satellite photos originally taken for international espionage have truly been “a bonanza for archaeology,” in Casana’s words.
|
Mining this resource for its archaeological riches is, however, a time-consuming affair. In theory, archaeologists could follow the lead of firms such as Orbital Insight and program a machine-vision algorithm to help identify unknown historic sites in these photos. Analyzing hundreds, if not thousands, of photographs at a time, archaeologists of the future could then work side by side with AI.
|
Casana is not alone in his approach, hoping to rediscover a lost ancient past by way of the sky. Articles about remote sensing appear regularly in academic publications, and, in 2013, Springer published two hefty compilations exploring Archaeology from Historical Aerial and Satellite Archives and Mapping Archaeological Landscapes from Space, respectively. Many other archaeologists today, including Sarah Parcak, have also helped pioneer space-based landscape research, primarily using state-of-the-art satellite imaging. Parcak, for example, has used satellite data to help find the likely site of buried Egyptian pyramids, and she was also part of a team that detected new evidence of an urban site near Petra, deploying both modern satellite imaging and drones. Further afield, Parcak also helped to discover a previously unknown Viking settlement in southwest Newfoundland, a find greatly assisted by having access to a modern eye in the sky.
|
“The kinds of features that survive for us to find, however, are often the products of very powerful, centralized governments from the earliest empires,” he explained. “They built large walled cities; they excavated elaborate irrigation systems that ran dozens of kilometers; they built roads.” The traces left by minor paths, seasonal campsites, and other ephemeral terrains generated by everyday human movement frequently fall outside the imaging capabilities of satellites. Space-based archaeology can thus inadvertently be biased toward an analysis of empires, not pastoralists, of centers, not peripheries.
|
While the CORONA images are undeniably valuable, they will not necessarily reveal subtle landscape effects on the remote edges of these once-great empires. Like Thomas in Blow-Up, archaeologists can pore over endless archives of photographs, zooming in to ever-more extreme levels of resolution to find traces of walls, foundations, and lost cities, but the other cultures Jason Ur told me about—the pastoral nomads, the marsh-dwellers—won’t necessarily show up on film. To learn more about them, archaeologists must still rely on good, old-fashioned digging.
|
Could it be the students who attend HBCUs today have no business in college at all? I suspect most of these students should not have graduated high school.
|
The racists who run: Princeton, Harvard, Stanford, Yale, Dartmouth, et. al., can fix this gap. How? Admit fewer black students. I suspect 85-90% of the blacks at these colleges would not have been admitted if they were white. When the Sheila Jackson Lees, Michelle and Barack Obamas and their like no longer fill the Ivy League, this newest "Gap" will be reduced.
|
Elite colleges admission procedures are racist. We know this because they damage the HBCUs.
|
Home » dvd buzz » question of the day: What’s up with this apparently but nonsensically homophobic DVD cover?
|
question of the day: What’s up with this apparently but nonsensically homophobic DVD cover?
|
Is it me, or is there something a little hinky in the difference between these two DVD covers for the same movie?
|
On the left is the Region 2 DVD cover art for Make the Yuletide Gay. On the right is the Region 1 DVD cover art for the same film.
|
Now, actually, I don’t think the homophobia explanation makes sense: This title was never going to be showing up on the shelves of Wal-Mart where it might scare the locals, and it should in fact be designed to appeal to gays and gay-friendlies on sites like Amazon, where the DVD cover is the first thing you notice. But I can’t figure out what other explanation there could be.
|
What’s up with this apparently but nonsensically homophobic DVD cover?
|
One of the most interesting and challenging problems in physics is understanding strongly correlated many-body systems, where strong interactions can yield many remarkable phenomena such as superfluidity in 4He, high-temperature superconductivity, etc. In order to attack these problems, we often need to reduce the complexity of the systems to simple models in hopes of getting better insights into the properties of the systems. The Hubbard model, the focus of this dissertation, is one of the most famous examples of such model, which describes a tunneling of electrons between nearest neighbor sites of a lattice with on-site interactions. This simple model is an important concept in condensed matter physics and provides rich understandings of electronic and magnetic properties of materials. Despite its simplicity, there is no general analytical solution to the Hubbard model beyond 1D.;The discovery of ultracold atoms and optical lattices opens up the possibility of emulating the Hubbard model in experiments. Optical lattices provide an ideal realization of the Hubbard model where relevant parameters can be tuned systematically. It makes theoretical studies of the Hubbard model increasingly attractive since a direct comparison between theoretical calculations and experimental results becomes more and more possible.;In this dissertation, the ground-state properties of the repulsive Hubbard model for weak to intermediate interaction strengths in two, three dimensions and their dimensional crossover are studied within the mean field theory. We show that the system exhibits unidirectional spin-density wave (SDW) order with antiferromagnetic correlations and a long wavelength modulation. The modulating wave is along the [0011-direction at low interaction strength U/t and along the [1111-direction at higher U/t. The evolution of the wavelength of the SDW is determined as a function of U/t, the density, and t⊥/t. With an analysis of the pairing of spins based on nesting and deformation of the Fermi surface, we discuss how these results can be rationalized and how a simple, predictive model can be constructed for the properties of the SDW states.
|
Xu, Jie, "Magnetic Order and Dimensional Crossover in Optical Lattices with Repulsive Interaction" (2013). Dissertations, Theses, and Masters Projects. Paper 1539623610.
|
NEW YORK (ForexNewsNow) – “A statesman of value must have two essential qualities: cautiousness and imprudence,” Ruggiero Bonghi once said.
|
This quote is perfect for the current predicament US Federal Reserve Chairman Ben Bernanke presently finds himself in since he decided to postpone any quantitative easing (QE3) for now. The problem is that the Harvard graduate seems to only trust prudence, and it could come back to haunt the US economy in a few months.
|
“Who will believe that commitment to cut spending can survive a lengthy stagnation with high prolonged unemployment and social dissatisfaction?” she asked.
|
According to both Bernanke and Lagarde, the ball is in Washington’s hands. In other words, it is the fiscal policy of the United States which is at stake here. Is Barack Obama too cautious or are the Republicans in Congress preventing him from being too imprudent?
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.