Category Archives: Science Advance & Theoretical

Prof. Stephen Hawking tells students the universe does not need a God to exist

Prof. Stephen Hawking tells students the universe does not need a God to exist (via Raw Story )

Former Cambridge Professor Stephen Hawking told students at Caltech this week that, contrary to the feelings of many God enthusiasts, the universe did not require a deity to create, nor does it require one to continue existing. Though his speech was supposed to be free of recording devices, some sly…

NASA’s NuSTAR helps solve riddle of black hole spin

This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. (Credit: NASA/JPL-Caltech)

Feb. 27, 2013 — Two X-ray space observatories, NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency’s XMM-Newton, have teamed up to measure definitively, for the first time, the spin rate of a black hole with a mass 2 million times that of our sun.

The supermassive black hole lies at the dust- and gas-filled heart of a galaxy called NGC 1365, and it is spinning almost as fast as Einstein’s theory of gravity will allow. The findings, which appear in a new study in the journal Nature, resolve a long-standing debate about similar measurements in other black holes and will lead to a better understanding of how black holes and galaxies evolve.

“This is hugely important to the field of black hole science,” said Lou Kaluzienski, a NuSTAR program scientist at NASA Headquarters in Washington.

The observations also are a powerful test of Einstein’s theory of general relativity, which says gravity can bend space-time, the fabric that shapes our universe, and the light that travels through it.

“We can trace matter as it swirls into a black hole using X-rays emitted from regions very close to the black hole,” said the coauthor of a new study, NuSTAR principal investigator Fiona Harrison of the California Institute of Technology in Pasadena. “The radiation we see is warped and distorted by the motions of particles and the black hole’s incredibly strong gravity.”

NuSTAR, an Explorer-class mission launched in June 2012, is designed to detect the highest-energy X-ray light in great detail. It complements telescopes that observe lower-energy X-ray light, such as XMM-Newton and NASA’s Chandra X-ray Observatory. Scientists use these and other telescopes to estimate the rates at which black holes spin.

Until now, these measurements were not certain because clouds of gas could have been obscuring the black holes and confusing the results. With help from XMM-Newton, NuSTAR was able to see a broader range of X-ray energies and penetrate deeper into the region around the black hole. The new data demonstrate that X-rays are not being warped by the clouds, but by the tremendous gravity of the black hole. This proves that spin rates of supermassive black holes can be determined conclusively.

“If I could have added one instrument to XMM-Newton, it would have been a telescope like NuSTAR,” said Norbert Schartel, XMM-Newton Project Scientist at the European Space Astronomy Center in Madrid. “The high-energy X-rays provided an essential missing puzzle piece for solving this problem.”

Measuring the spin of a supermassive black hole is fundamental to understanding its past history and that of its host galaxy.

“These monsters, with masses from millions to billions of times that of the sun, are formed as small seeds in the early universe and grow by swallowing stars and gas in their host galaxies, merging with other giant black holes when galaxies collide, or both,” said the study’s lead author, Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and the Italian National Institute for Astrophysics.

Supermassive black holes are surrounded by pancake-like accretion disks, formed as their gravity pulls matter inward. Einstein’s theory predicts the faster a black hole spins, the closer the accretion disk lies to the black hole. The closer the accretion disk is, the more gravity from the black hole will warp X-ray light streaming off the disk.

Astronomers look for these warping effects by analyzing X-ray light emitted by iron circulating in the accretion disk. In the new study, they used both XMM-Newton and NuSTAR to simultaneously observe the black hole in NGC 1365. While XMM-Newton revealed that light from the iron was being warped, NuSTAR proved that this distortion was coming from the gravity of the black hole and not gas clouds in the vicinity. NuSTAR’s higher-energy X-ray data showed that the iron was so close to the black hole that its gravity must be causing the warping effects.

With the possibility of obscuring clouds ruled out, scientists can now use the distortions in the iron signature to measure the black hole’s spin rate. The findings apply to several other black holes as well, removing the uncertainty in the previously measured spin rates.

For more information on NASA’s NuSTAR mission, visit: http://www.nasa.gov/nustar .

For more information on ESA’s XMM-Newton mission, visit: http://go.nasa.gov/YUYpI6 .

The California Institute of Technology in Pasadena manages JPL for NASA.

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Cassini sheds light on cosmic particle accelerators

This artist’s impression by the European Space Agency shows NASA’s Cassini spacecraft exploring the magnetic environment of Saturn. (Credit: ESA)

Feb. 19, 2013 — During a chance encounter with what appears to be an unusually strong blast of solar wind at Saturn, NASA’s Cassini spacecraft detected particles being accelerated to ultra-high energies. This is similar to the acceleration that takes place around distant supernovas.

Since we can’t travel out to the far-off stellar explosions right now, the shockwave that forms from the flow of solar wind around Saturn’s magnetic field provides a rare laboratory for scientists with the Cassini mission — a partnership involving NASA, the European Space Agency and the Italian Space Agency — to observe this phenomenon up-close. The findings, published this week in the journal Nature Physics, confirm that certain kinds of shocks can become considerably more effective electron accelerators than previously thought.

Shock waves are commonplace in the universe, for example in the aftermath of a stellar explosion as debris accelerate outward in a supernova remnant, or when the flow of particles from the sun — the solar wind — impinges on the magnetic field of a planet to form a bow shock. Under certain magnetic field orientations and depending on the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. These may be the dominant source of cosmic rays, high-energy particles that pervade our galaxy.

Scientists are particularly interested in “quasi-parallel” shocks, where the magnetic field and the “forward”-facing direction of the shock are almost aligned, as may be found in supernova remnants. The new study, led by Adam Masters of the Institute of Space and Astronautical Science, Sagamihara, Japan, describes the first detection of significant acceleration of electrons in a quasi-parallel shock at Saturn, coinciding with what may be the strongest shock ever encountered at the ringed planet.

“Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own solar system, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely,” said Masters.

The Cassini-Huygens mission is a cooperative project of NASA, ESA and ASI, the Italian space agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington.

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Higgs data indicates our universe is unstable | TG Daily

Posted February 19, 2013 – 04:28 by Kate Taylor

Our universe could one day be wiped out by a new one that bubbles up inside it and replaces it, a Fermilab scientist says.

Through a phenomenon known as vacuum instability, a quantum fluctuation could create a tiny new universe that would then expand at the speed of light.

Whether or not this happens depends on the properties of the Higgs boson, including its precise mass, which would give an indication of just how unstable out universe is. But, physicist Joseph Lykken tells Reuters, “If you use all the physics that we know now and you do what you think is a straightforward calculation, it’s bad news.”

“Many tens of billions of years from now, there’ll be a catastrophe. A little bubble of what you might think of as an ‘alternative’ universe will appear somewhere and then it will expand out and destroy us.”

Ruling this theory in or out depends on the precise mass of the Higgs boson. Frustratingly, the current best measure of the mass of the particle found at the Large Hadron Collider last summer doesn’t resolve the matter.

“Before we knew, the Higgs could have been any mass over a very wide range,” Professor Chris Hill of Ohio State University tells the BBC.

“And what’s amazing to me is that out of all those possible masses from 114 to several hundred GeV, it’s landed at 126-ish where it’s right on the critical line, and now we have to measure it more precisely to find the fate of the universe.”

Unfortunately, that’s not going to happen terribly soon. The LHC is currently shut down to allow for maintenance and repairs, and won’t be back up and running until 2015.

Scientists find weird new property of matter that breaks all the rules | The Verge

Similar eureka moments have brought us maglev trains — what’s next?

By Arikia Millikan on February 18, 2013 06:55 pm Email 156Comments

Don’t miss any stories Follow The Verge

When physicists discover new properties of matter, it usually means better technologies for the rest of us. Superconductors, liquid crystal displays like the ones found in most TVs now, medical imaging technologies that allow doctors to peer inside the human body, and magnetic levitation — which was used to create the Shanghai Maglev train — are all examples of how discoveries of new properties of matter have resulted in revolutionary products.

A quantum dot energy harvester

An array on nano energy harvesters in what the researchers call a “swiss cheese” arrangement. (Credit: Image courtesy of University of Rochester)

Feb. 14, 2013 — A new type of nanoscale engine has been proposed that would use quantum dots to generate electricity from waste heat, potentially making microcircuits more efficient.

“The system is really a simple one, which exploits certain properties of quantum dots to harvest heat,” Professor Andrew Jordan of the University of Rochester said. “Despite this simplicity, the power it could generate is still larger than any other nanoengine that has been considered until now.”

The engines would be microscopic in size, and have no moving parts. Each would only produce a tiny amount of power — a millionth or less of what a light bulb uses. But by combining millions of the engines in a layered structure, Jordan says a device that was a square inch in area could produce about a watt of power for every one degree difference in temperature. Enough of them could make a notable difference in the energy consumption of a computer.

A paper describing the new work is being published in Physical Review B by Jordan, a theoretical physics professor, and his collaborators, Björn Sothmann and Markus Buttiker from the University of Geneva, and Rafael Sánchez from the Material Sciences Institute in Madrid.

Jordan explained that each of the proposed nanoengines is based on two adjacent quantum dots, with current flowing through one and then the other. Quantum dots are manufactured systems that due to their small size act as quantum mechanical objects, or artificial atoms.

The path the electrons have to take across both quantum dots can be adjusted to have an uphill slope. To make it up this (electrical) hill, electrons need energy. They take the energy from the middle of the region, which is kept hot, and use this energy to come out the other side, higher up the hill. This removes heat from where it is being generated and converts it into electrical power with a high efficiency.

To do this, the system makes use of a quantum mechanical effect called resonant tunneling, which means the quantum dots act as perfect energy filters. When the system is in the resonant tunneling mode, electrons can only pass through the quantum dots when they have a specific energy that can be adjusted. All other electrons that do not have this energy are blocked.

Quantum dots can be grown in a self-assembling way out of semiconductor materials. This allows for a practical way to produce many of these tiny engines as part of a larger array, and in multiple layers, which the authors refer to as the Swiss Cheese Sandwich configuration (see image).

How much electrical power is produced depends on the temperature difference across the energy harvester — the higher the temperature difference, the higher the power that will be generated. This requires good insulation between the hot and cold regions, Jordan says.

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New-found prime number is 17 million digits long | TG Daily

Posted February 6, 2013 – 09:17 by Emma Woollacott

Mathematicians have discovered the largest prime number yet – two to the power of 257,885,161, minus one.

The number has 17,425,170 digits, and was found using the Great Internet Mersenne Prime Search (GIMPS) project – the longest-evercontinuously-running global ‘grassroots supercomputing’ project, involving 360,000 CPUs peaking at 150 trillion calculations per second.

The new prime number is a member of a special class of extremely rare prime numbers known as Mersenne primes, and is only the 48th of these to be discovered.

Mersenne primes were named for the French monk Marin Mersenne, who studied these numbers more than 350 years ago. All take the form 2 to the power of p – 1, where p is also a prime number – although not all numbers that take that form are prime.

Mathematicians suspect that there may be an infinite number of Mersenne primes. GIMPS, founded in 1996, has discovered all 14 of the largest known Mersenne primes – with this latest one taking 39 days of non-stop computing to establish.

To prove there were no errors in the prime discovery process, the latest one was independently verified using different programs running on different hardware.

This is the third record prime for Dr Curtis Cooper and the University of Central Missouri, the others having been discovered in 2005 and2006. Computers at UCLA broke that record in 2008 with a 12,978,189 digit prime number that was the longest until now.
Work to find more will continue – especially given the $150,000 reward promised by the Electronic Frontier Foundation to the first person to find a 100 million-digit prime.

Anyone with a reasonably powerful PC can join GIMPS and have a shot themselves, with the necessary software available free at www.mersenne.org/freesoft.htm.

New order found in quantum electronic material: May lead to new materials, magnets and superconductors

High-speed train. Two Rutgers physics professors have proposed an explanation for a new type of order, or symmetry, in an exotic material made with uranium — a theory that may one day lead to enhanced computer displays and data storage systems and more powerful superconducting magnets for medical imaging and levitating high-speed trains. (Credit: © Daniel Loncarevic / Fotolia)

Jan. 30, 2013 — Two Rutgers physics professors have proposed an explanation for a new type of order, or symmetry, in an exotic material made with uranium — a theory that may one day lead to enhanced computer displays and data storage systems and more powerful superconducting magnets for medical imaging and levitating high-speed trains.

Their discovery, published in this week’s issue of the journal Nature, has piqued the interest of scientists worldwide. It is one of the rare theory-only papers that this selective publication accepts.

Collaborating with the Rutgers professors was a postdoctoral researcher at Massachusetts Institute of Technology (MIT) who earned her doctorate at Rutgers.

“Scientists have seen this behavior for 25 years, but it has eluded explanation.” said Piers Coleman, professor in the Department of Physics and Astronomy in the School of Arts and Sciences. When cooled to 17.5 degrees above absolute zero or lower (a bone-chilling minus 428 degrees Fahrenheit), the flow of electricity through this material changes subtly.

The material essentially acts like an electronic version of polarized sunglasses, he explains. Electrons behave like tiny magnets, and normally these magnets can point in any direction. But when they flow through this cooled material, they come out with their magnetic fields aligned with the material’s main crystal axis.

This effect, claims Coleman, comes from a new type of hidden order, or symmetry, in this material’s magnetic and electronic properties. Changes in order are what make liquid crystals, magnetic materials and superconductors work and perform useful functions.

“Our quest to understand new types of order is a vital part of understanding how materials can be developed to benefit the world around us,” he said.

Similar discoveries have led to technologies such as liquid crystal displays, which are now ubiquitous in flat-screen TVs, computers and smart phones, although the scientists are quick to acknowledge that their theoretical discovery won’t transform high-tech products overnight.

Coleman, along with Rutgers colleague Premala Chandra and MIT collaborator Rebecca Flint, describe what they call a “hidden order” in this compound of uranium, ruthenium and silicon. Uranium is commonly known for being nuclear reactor fuel or weapons material, but in this case physicists value it as a heavy metal with electrons that behave differently than those in common metals.

Recent experiments on the material at the National High Magnetic Field Laboratory at Los Alamos National Laboratory in New Mexico provided the three physicists with data to refine their discovery.

“We’ve dubbed our fundamental new order ‘hastatic’ order, named after the Greek word for spear,” said Chandra, also a professor in the Department of Physics and Astronomy. The name reflects the highly ordered properties of the material and its effect on aligning electrons that flow through it.

“This new category of order may open the world to new kinds of materials, magnets, superconductors and states of matter with properties yet unknown,” she said. The scientists have predicted other instances where hastatic order may show up, and physicists are beginning to test for it.

The scientists’ work was funded by the National Science Foundation and the Simons Foundation. Flint is a Simons Postdoctoral Fellow in physics at MIT.

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Chinese Physicists Build “Ghost” Cloaking Device | MIT Technology Review

A working invisibility cloak that makes one object look like ghostly versions of another has been built in China

Illusion cloaks that make one object look like another are a fascinating type of invisibility device. The general idea is that such a device would make an apple look like a banana or a fighter plane look like an airliner. Clearly this would have important applications.

But while materials scientists have made great strides in building ordinary invisibility cloaks that work in the microwave, infrared and optical parts of the spectrum, making illusion cloaks is much harder. That’s because the bespoke materials they rely on require manufacturing techniques that seem like a distant dream.

Today, Tie Jun Cui and buddies at Southeast University in Nanjing, China, say they’ve designed and built a practical alternative to illusion cloaks, which they call a “ghost cloak”.

Conventional illusion cloaks rely on a two stage process. The first is a kind of invisibility stage which distorts incoming light to remove the scattering effect of the cloaked object, an apple for example. The second stage then distorts the scattered light to make it look as if it has been scattered off another object, a banana, for example. The result is that the apple ends up looking like a banana.

But materials that can perform this two-stage process are too demanding to make with current techniques.

So Tie Jun Cui and co have developed a single stage process that achieves a slightly different effect. Their idea is to do away with the first stage that makes the apple invisible.

Instead, their device takes the light scattered from the apple and distorts it to look like something else such as a banana. The symmetry of the effect–light is scattered on both sides of the apple–mean that this approach produces two “ghost” bananas, one on each side of the apple. The technique does not remove the apple entirely but distorts it, making it appear much smaller.

So the result is that the apple is changed into a much more complex picture that is significantly different from the original.

The big advantage of this approach is that it can be achieved now with existing technology. Tie Jun Cui and co first simulate the effect of their ghost cloak on a computer model.

They then go on to build a working prototype using concentric cylinders of split ring resonators that operates in 2 dimensions. They say that the results of their tests on this device closely match the results of the simulation.

That’s an interesting advance. The ability to distort and camouflage objects is clearly useful. However, an important question is whether the distortion that this device offers is good enough for any practical applications. Tie Jun Cui and co mention “security enhancement” but just how effective this would be when the original object is still visible, albeit in shrunken form, is debatable.

It may be that there are ways of improving the performance so it’ll be interesting to see what this team comes out with next.

Ref: arxiv.org/abs/1301.3710 : Creation of Ghost Illusions Using Metamaterials in Wave Dynamics

Teleportation gets a theoretical breakthrough | TG Daily

Posted January 17, 2013 – 09:43 by Thomas Anderson

For the last decade, theoretical physicists have hypothesized that the intense connections generated between particles as established in the quantum law of “entanglement” may hold the key to eventual teleportation of quantum information.

Recently, physicists from Cambridge, University College London and the University of Gdansk claim to have determined just how entanglement could be “recycled” to increase the efficiency of these connections.

The result, says scientists, could conceivably take us a step closer to sci-fi style teleportation in the future, although they freely admit the research is purely theoretical in nature, at least at this stage.

Interestingly, the team also managed to devise a generalized form of teleportation, which allows for a wide variety of potential applications in quantum physics. Once considered impossible, in 1993 a team of scientists calculated that teleportation could work in principle using quantum laws. As noted above, quantum teleportation harnesses the “entanglement” law to transmit particle-sized bites of information across potentially vast distances in an instant.

Entanglement involves a pair of quantum particles such as electrons or protons that are intrinsically bound together, retaining synchronisation between the two that holds whether the particles are next to each other or on opposing sides of a galaxy. Through this connection, quantum bits of information – qubits – can be relayed using only traditional forms of classical communication.

Previous teleportation protocols, have fallen into one of two primary camps: those that could only send scrambled information requiring correction by the receiver, or more recently, “port-based” teleportation that doesn’t require a correction, but required an impractical amount of entanglement – as each object sent would destroy the entangled state.

However, the above-mentioned team of physicists managed to develop a protocol that provides an optimal solution in which the entangled state is essentially “recycled.” Meaning, the gateway between particles holds for the teleportation of multiple objects. Indeed, they have even devised a protocol in which multiple qubits can be teleported simultaneously, although the entangled state degrades proportionally to the amount of qubits sent in both cases.

“The first protocol consists of sequentially teleporting states, and the second teleports them in a bulk,” said Sergii Strelchuck from Cambridge’s Department of Applied Mathematics and Theoretical Physics, who led the research with colleagues Jonathan Oppenheim of Cambridge and UCL and Michal Horodecki of the University of Gdansk.

“We have also found a generalised teleportation technique which we hope will find applications in areas such as quantum computation.”

Einstein famously loathed the theory of quantum entanglement, dismissing it as “spooky action at a distance.” Nevertheless, entanglement has since been proven to be a very real feature of our universe, and one that offers extraordinary potential.

“There is a close connection between teleportation and quantum computers, which are devices which exploit quantum mechanics to perform computations which would not be feasible on a classical computer,” Strelchuck explained.

“Building a quantum computer is one of the great challenges of modern physics, and it is hoped that the new teleportation protocol will lead to advances in this area.”

While the Cambridge physicists’ protocol is completely theoretical, last year a team of Chinese scientists reported teleporting photons over 143km, breaking previous records, and quantum entanglement is increasingly seen as an important area of scientific investment.

Teleportation of information carried by single atoms is certainly feasible with current technologies. Sadly, the teleportation of large objects – such as Captain Kirk and his Enterprise crew – remains in the realm of science fiction.

“[Basically], entanglement can be thought of as the fuel, which powers teleportation. Our protocol is more fuel efficient, able to use entanglement thriftily while eliminating the need for error correction,” Strelchuck added.