Tuesday, June 18, 2013

Physics Nobel laureate Kenneth Wilson dies | Cornell Chronicle

Physics Nobel laureate Kenneth Wilson dies | Cornell Chronicle:

"Physics visionary Kenneth G. Wilson, winner of the 1982 Nobel Prize in Physics for his research at Cornell, died in Maine June 15 from lymphoma complications. He was 77."

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Kenneth Wilson, Nobel Winner for Physics, Dies - NYTimes.com

Kenneth Wilson, Nobel Winner for Physics, Dies - NYTimes.com:

"SACO, Maine — A physics professor who earned a Nobel prize for pioneering work that changed the way physicists think about phase transitions has died in Maine at age 77."

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21st Century C: C Tips from the New School: Ben Klemens: 9781449327149: Amazon.com: Books

21st Century C: C Tips from the New School: Ben Klemens: 9781449327149: Amazon.com: Books:

 "21st Century C: C Tips from the New School"



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[1306.3503] Constraining Explosion Type of Young Supernova Remnants Using 24 Micron Emission Morphology

[1306.3503] Constraining Explosion Type of Young Supernova Remnants Using 24 Micron Emission 
Morphology:

Determination of the explosion type of supernova remnants (SNRs) can be challenging, as SNRs are hundreds to thousands of years old and supernovae (SNe) are classified based on spectral properties days after explosion. Previous studies of thermal X-ray emission from Milky Way and Large Magellanic Cloud (LMC) SNRs have shown that Type Ia and core-collapse (CC) SNRs have statistically different symmetries, and thus these sources can be typed based on their X-ray morphologies. In this paper, we extend the same technique, a multipole expansion technique using power ratios, to infrared (IR) images of SNRs to test whether they can be typed using the symmetry of their warm dust emission as well. We analyzed archival Spitzer Space Telescope Multiband Imaging Photometer (MIPS) 24 micron observations of the previously used X-ray sample, and we find that the two classes of SNRs separate according to their IR morphologies. The Type Ia SNRs are statistically more circular and mirror symmetric than the CC SNRs, likely due to the different circumstellar environments and explosion geometries of the progenitors. Broadly, our work indicates that the IR emission retains information of the explosive origins of the SNR and offers a new method to type SNRs based on IR morphology.
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Strange, Glowing Night Clouds Continue to Spread | Wired Science | Wired.com

Strange, Glowing Night Clouds Continue to Spread | Wired Science | Wired.com:

 "Just after summer sunsets in northern latitudes, shimmering, wispy clouds appear in the twilight sky. This year, these noctilucent clouds have appeared earlier and farther south than ever before."

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Sunday, June 16, 2013

[1304.7279] Fluctuation-Dissipation Theorem in Isolated Quantum Dipolar Bosons After a Quench

[1304.7279] Fluctuation-Dissipation Theorem in Isolated Quantum Dipolar Bosons After a Quench:

"We examine the validity of fluctuation-dissipation relations in isolated quantum systems taken out of equilibrium by a sudden quench. We focus on the dynamics of trapped hard-core bosons in one-dimensional lattices with dipolar interactions whose strength is changed during the quench. We find that fluctuation-dissipation relations hold if the system is nonintegrable after the quench. They also hold if the system is integrable after the quench if the initial state is an equilibrium state of a nonintegrable Hamiltonian. However, they fail if the system is integrable both before and after quenching"

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[1304.7985] Some Results on Mutual Information of Disjoint Regions in Higher Dimensions

[1304.7985] Some Results on Mutual Information of Disjoint Regions in Higher Dimensions:

We consider the mutual Renyi information I^n(A,B)=S^n_A+S^n_B-S^n_{AUB} of disjoint compact spatial regions A and B in the ground state of a d+1-dimensional conformal field theory (CFT), in the limit when the separation r between A and B is much greater than their sizes R_{A,B}. We show that in general I^n(A,B)\sim C^n_AC^n_B(R_AR_B/r^2)^a, where a the smallest sum of the scaling dimensions of operators whose product has the quantum numbers of the vacuum, and the constants C^n_{A,B} depend only on the shape of the regions and universal data of the CFT. 
For a free massless scalar field, where 2x=d-1, we show that C^2_AR_A^{d-1} is proportional to the capacitance of a thin conducting slab in the shape of A in d+1-dimensional electrostatics, and give explicit formulae for this when A is the interior of a sphere S^{d-1} or an ellipsoid. For spherical regions in d=2 and 3 we obtain explicit results for C^n for all n and hence for the leading term in the mutual information by taking n->1. We also compute a universal logarithmic correction to the area law for the Renyi entropies of a single spherical region for a scalar field theory with a small mass.

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Earthquake Strikes South of Mexican Capital - NYTimes.com

Earthquake Strikes South of Mexican Capital - NYTimes.com:

 "MEXICO CITY — A moderate earthquake hit southern Mexico early Sunday, shaking buildings in the capital of Mexico City and sending frightened people into the streets."

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Saturday, June 15, 2013

[1304.6823] Initial condition from the action principle and its application to cosmology and to false vacuum bubbles

[1304.6823] Initial condition from the action principle and its application to cosmology and to false vacuum bubbles:

"We study models where the gauge coupling constants, masses, etc are functions of some conserved charge in the universe. We first consider the standard Dirac action, but where the mass and the electromagnetic coupling constant are a function of the charge in the universe and afterwards extend this scalar fields. For Dirac field in the flat space formulation, the formalism is not manifestly Lorentz invariant, however Lorentz invariance can be restored by performing a phase transformation of the Dirac field. In the case where scalar field are considered, there is the new feature that an initial condition for the scalar field is derived from the action. In the case of the Higgs field, the initial condition require, that the universe be at the false vacuum state at a certain time slice, which is quite important for inflation scenarios. Also false vacuum branes will be studied in a similar approach. We discuss also the use of "spoiling terms", that violate gauge invariant to introduce these initial condition."

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[1306.2963] Explaining Phenomenologically Observed Space-time Flatness Requires New Fundamental Scale Physics

[1306.2963] Explaining Phenomenologically Observed Space-time Flatness Requires New Fundamental Scale Physics:

"The phenomenologically observed flatness - or near flatness - of spacetime cannot be understood as emerging from continuum Planck (or sub-Planck) scales using known physics. Using dimensional arguments it is demonstrated that any immaginable action will lead to Christoffel symbols that are chaotic. We put forward new physics in the form of fundamental fields that spontaneously break translational invariance. Using these new fields as coordinates we define the metric in such a way that the Riemann tensor vanishes identically as a Bianchi identity. Hence the new fundamental fields define a flat space. General relativity with curvature is recovered as an effective theory at larger scales at which crystal defects in the form of disclinations come into play as the sources of curvature."

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Dennis Ritchie - Wikipedia, the free encyclopedia

Dennis Ritchie - Wikipedia, the free encyclopedia:

"Dennis MacAlistair Ritchie (September 9, 1941 – c. October 12, 2011)[1][2][3][4] was an American computer scientist who "helped shape the digital era."[1] He created the C programming language and, with long-time colleague Ken Thompson, the Unix operating system.[1] Ritchie and Thompson received the Turing Award from the ACM in 1983, the Hamming Medal from the IEEE in 1990 and the National Medal of Technology from President Clinton in 1999. Ritchie was the head of Lucent Technologies System Software Research Department when he retired in 2007. He was the 'R' in K&R C and commonly known by his username dmr."

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Thursday, June 13, 2013

[1304.5266] Stellar variability in open clusters. I. A new class of variable stars in NGC 3766

[1304.5266] Stellar variability in open clusters. I. A new class of variable stars in NGC 3766:

Aims. We analyze the population of periodic variable stars in the open cluster NGC 3766 based on a 7-year multi-band monitoring campaign conducted on the 1.2 m Swiss Euler telescope at La Silla, Chili. 
Methods. The data reduction, light curve cleaning and period search procedures, combined with the long observation time line, allow us to detect variability amplitudes down to the milli-magnitude level. The variability properties are complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. 
Results. We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of delta Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7 d, with amplitudes between 1 and 4 mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our milli-magnitude detection limit. 
The properties of this new group of variable stars are summarized, and arguments set forth in favor of a pulsation origin of the variability, with g-modes sustained by stellar rotation. Potential members of this new class of low-amplitude periodic (most probably pulsating) A and late-B variables in the literature are discussed. 
We additionally identify 16 eclipsing binary, 13 SPB, 14 delta Sct and 12 gamma Dor candidates, as well as 72 fainter periodic variables. All are new discoveries. 
Conclusions. We encourage to search for the existence of this new class of variables in other young open clusters, especially in those hosting a rich population of Be stars.

"We encourage searching for this new class of variables in other young open clusters. That there are so many candidates for this new class in NGC 3766 may be analogous to the large number of Be stars observed in this cluster. This would be understandable if both phenomena are indeed related to high rotational velocities characterizing the stellar population of the cluster. If this is true, then the search would be the most efficient in other clusters that are already known to have rich populations of Be stars as well. Variables of this new class may, for example, already be present in the data of NGC 884 gathered by Saesen et al. (2010) for NGC 884.

Finally, we propose (Sect. 7.4) the name of ‘low amplitude periodic (or pulsating) A and late-B variables’ for this new class of variable stars."

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Monday, June 10, 2013

Scientists Cast Doubt on the Closest Exoplanet

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Cosmic hearts started beating a little faster last fall when a team of European astronomers announced that they had found a planet with a mass comparable to Earth’s orbiting Alpha Centauri B, part of a triple star that is the Sun’s nearest neighbor, only 4.4 light years from here.
ESO
A wide-field view of the sky around Alpha Centauri, 4.4 light-years from Earth, the star system closest to our own.

As Geoffrey W. Marcy, an astronomer at the University of California, Berkeley, said at the time, “This is close enough you can almost spit there.” Close enough, some astronomers said, to send a scientific probe that would get there in our lifetime. The new planet, only four million miles from its home star, would be too hellishly hot for life, but, astronomers said, where there is one planet there are likely to be others, more comfortably situated for life.
Now, however, in a shot across the bow of cosmological optimism, a new analysis of the European data has cast doubt on whether there is actually a “there” there at Alpha Centauri B.
Writing in The Astrophysical Journal last month, Artie P. Hatzes, the director of the Thuringian State Observatory in Tautenburg, Germany, who was not part of the original discovery team, reported that he could not confirm the planet when he went looking for it in the European data on his own. “Sometimes it is there, other times not,” depending on the method he used to reduce the statistical noise, he said in an e-mail.
That doesn’t mean the planet does not exist, Dr. Hatzes wrote, but “in my years of experience in extracting planet signals, this simply does not ‘smell’ like a real planet.”
Dr. Hatzes’s skepticism proved catching. Suzanne Aigrain of Oxford University quoted Carl Sagan’s dictum that extraordinary claims require extraordinary evidence, saying that Dr. Hatzes’s paper “certainly casts doubt on the original evidence.”
Xavier Dumusque of the University of Geneva, who led the original discovery effort, said that Dr. Hatzes’s challenge was healthy for science. “Calling to question a detection is always something fruitful,” Dr. Dumusque wrote in an e-mail. But he added that it was clear in his team’s paper that “the signal we are searching for is at the limit of the data precision.”
More data, everyone agrees, is essential, and luckily there will be more data, according to Debra Fischer, a Yale astronomer who has studied the Alpha Centauri system. Both her group and the Geneva team of which Dr. Dumusque is a member obtained more observations in May.
May was a bad time for exoplanet astronomers. NASA’s planet-hunting Kepler satellite lost its pointing capability.
Quoting Jeff Lebowski, the hero of the Coen brothers movie “The Big Lebowski,” Dr. Hatzes said, “Life is indeed ‘gutters and strikes,’ and this week were some gutters.”
The Alpha Centauri B planet is hardly the first promising world to slip into the shadows of uncertainty. Astronomers are still arguing about the existence of Gliese 581g, a “Goldilocks” planet said to be almost a sure bet for life when it was discovered in 2010.
It all goes to show just how devilish the details have become as astronomers close in on the goal of finding Earth-like planets.
Dr. Dumusque and his colleagues first found the planet by the so-called wobble method — perfected over the years by Michel Mayor and his colleagues at the Geneva Observatory — which measures planets’ masses by how much they tug their host star to and fro as they orbit it.
The group uses a specially built spectrograph called Harps on a 140-inch-diameter telescope at the European Southern Observatory in La Silla, Chile, to measure those wobbles, which show up as slight rhythmic shifts in the wavelength of starlight.
The Earth imparts a kick of about four inches a second to the Sun as it orbits around, but that is much smaller than the jitter caused by sunspots and magnetic activity.
The result is that success in detecting low-mass planets depends more and more on digging a small signal out of a much larger background of noise in a reliable manner.
Kepler, which uses the blink method to find planets when they cross in front of their stars, is running up against limits of time.
On the grounds that three blinks were needed to verify an orbit, Kepler’s astronomers once thought they would need three years to verify the existence of planets in comfortable orbits like our own.
But the stars turned out to be noisier than predicted; a year ago, Kepler’s mission was extended so that more blinks could be collected, but the failure of a reaction wheel that allows the telescope to point precisely has probably brought an end to that.
There is still an enormous amount of data in Kepler’s pipeline, including 132 confirmed planets and, as of last week, 3,216 planet candidates.
Waiting in the wings for a 2017 launching is the Transiting Exoplanet Survey Satellite, TESS, which will monitor about two million nearby stars for exoplanets. “In fact,” the project’s leader, George R. Ricker of the Massachusetts Institute of Technology, said during a talk at Google a few years ago, “when starships transporting colonists first depart the solar system, they may well be headed toward a TESS-discovered planet as their new home.”
It might even be in Alpha Centauri.

Rock samples suggest meteor caused Tunguska blast : Nature News & Comment

Rock samples suggest meteor caused Tunguska blast : Nature News & Comment:

 "Grains from Siberian peat bog may be remnants of the biggest Earth impact in recorded history."

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Midwest Rains

Steve Hebert for The New York Times
“This is the worst spring I can remember,” said Rob Korff of Missouri, who planted his corn a month late because of the weather.
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NORBORNE, Mo. — About this time last year, farmers were looking to the heavens, pleading for rain. Now, they are praying for the rain to stop.
Multimedia
One of the worst droughts in this nation’s history, a dry spell that persisted through the early part of this year, has ended with torrential rains this spring that have overwhelmed vast stretches of the country, including much of the farm belt. One result has been flooded acres that have drowned corn and soybean plants, stunted their growth or prevented them from being planted at all.
With fields, dusty and dry one moment, muddy and saturated the next, farmers face a familiar fear — that their crops will not make it.
“This is the worst spring I can remember in my 30 years farming,” said Rob Korff, who plants 3,500 acres of corn and soybeans here in northwestern Missouri. “Just continuous rain, not having an opportunity to plant. It can still be a decent crop, but as far as a good crop or a great crop, that’s not going to happen.”
As farmers go through the ritual of examining every weather map and every tick on the futures boards, trying to divine if and how their pocketbooks can survive another curveball from nature, they are also keeping an eye on Washington, where Congress is still bickering over the farm bill. Farmers are hoping that lawmakers will maintain taxpayer-subsidized crop insurance and other support programs that will help them get through disasters like floods and drought.
Another year of mediocre crop yields could well trickle down to consumers, though agriculture experts insist that it is too early to rule out a robust harvest of corn and soybeans for this year.
“If there’s a shortage of corn and soybeans, and feed costs are higher,” said Bill Northey, the Iowa agriculture secretary, “there’s certainly a possibility that well down the road — six months or a year after that harvest — that you end up seeing higher meat prices than you would have if you’d had a full supply.”
Still, last year’s poor production had only a minor effect on food prices, analysts say, and even with the early planting problems, they expect better yields this year.
Since the beginning of the year, parts of the Mississippi River basin, from eastern Minnesota down through Illinois and Missouri, have received up to three times their normal precipitation. Storm systems also brought flooding to parts of Montana and the Dakotas, and into Nebraska, Iowa and Oklahoma. Iowa, the nation’s top corn producer, had a record 17.66 inches of precipitation this spring.
Just over 44 percent of the country remains in drought, down more than 9 percentage points from the beginning of March.
Ideally, farmers need the top two to four inches of soil to be dry when they are planting so that when they drive their tractors in the field they do not pack down the mud, which prevents the roots from getting oxygen. Oversaturated earth also means that pockets where oxygen can filter through to help the roots breathe will instead be filled with water. Ideally, the moisture should be in the soil directly below the seed.
With rain falling day after day, farmers have been hard pressed to find windows of time when they have dry topsoil to get into their fields to plant. The task has been made harder by lower temperatures and cloudy skies that prevent the land from drying even when it is not raining. Many farmers find themselves more than a month behind in their planting, and some have even given up on planting all their seeds. Late planting could stunt the growth of crops, decreasing production once harvest rolls around.
On May 12, 28 percent of the nation’s corn crop had been planted, compared with 85 percent on the same day last year. As of the United States Department of Agriculture’slatest report, released last week, 91 percent of corn had been planted by June 2, compared with 100 percent a year earlier.
This year, the Agriculture Department had estimated that 97.3 million acres of corn, the most since 1936, would be planted, and that a record 14.14 billion bushels would result from them.
Now, there is concern that “not as much corn was planted as had been indicated,” Joseph W. Glauber, the department’s chief economist, wrote in an e-mail, and “that yields will be adversely affected because plantings were less.”
Mr. Korff, 44, planted all his corn in the middle of May, about a month later than usual, and he has yet to plant any of his soybeans because there has not been a long enough break in the weather, he said. This area about an hour east of Kansas City has already gotten 23.6 inches of rain this year, four inches shy of the total for all of last year.
By this time, three weeks after planting, Mr. Korff said, his corn should be waist high. But instead, his crop looks like rows of small blades of grass, with the plants popping about only four inches out of the ground. The leaves are a pale yellow with brown lesions. Some patches of the field are bald, washed away by the rains. The earth is mucky and chocolate brown in some spots. A narrow stream of water slices through it.
“It doesn’t have the appearance I like to see,” Mr. Korff said.
But on an optimistic note, he said all it would take would be about a week of temperatures in the 80s or 90s and the corn could shoot up.
The rain has benefited some farm operations, however.
“This has been a great spring for cattlemen — just absolutely perfect,” said Kyle Kirby, who has a herd of 2,500 cattle in Liberal, Mo., which has had 29.13 inches of precipitation this year, about a foot more than in the same period last year.
The rain has replenished the pasture grass that cattle eat and has filled the ponds and streams where they drink. During last year’s drought, pastures were a charred brown, and evaporated ponds became nothing more than divots of parched earth. The refreshed pastures will also mean an abundance of hay to feed cattle. Hay was in such short supply last year that prices skyrocketed. Mr. Kirby said he was paying as much as $250 for a ton of hay last year, about two and a half times the normal price.
Still, Mr. Kirby is tempering his excitement. This spring has taught him that the whim that brought moisture could just as cruelly take it back.
“It doesn’t matter how wet it is today,” he said. “We’re just two weeks away from a drought.”
NYT

Sunday, June 09, 2013

[1305.7381] Mind and Matter

[1305.7381] Mind and Matter:

"It is argued that the problem of interpreting quantum mechanics, and the philosophical problem of consciousness, both have their roots in the same set of misguided Cartesian assumptions. The confusions underlying those assumptions are analyzed in detail. It is sometimes suggested that quantum mechanics might explain consciousness. That is not the suggestion here. Rather it is suggested that an adequate non-Cartesian philosophy would transform our understanding of both quantum mechanics and consciousness. Consequently, it would change our ideas as to just what it is that we are trying to explain."

"There is no mathematical description in the sky. The only descriptions around are the ones we humanly construct and which, being human, are necessarily partial."

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