For a variety of obvious reasons, it’s impossible to reproduce the exact environment in which galaxies form. The lack of direct experimental tests for the models astrophysicists use creates a disconnect between what astronomers observe and theoretical work. However, that barrier is being broken down by a combination of high-powered lasers and a new understanding of how lab-scale experiments can be related to vastly larger systems such as galaxies.

Researchers at the Laboratoire pour l’Utilisation de Lasers Intenses (LULI), along with colleagues at various universities, have successfully simulated the magnetic fields that form in early galaxies. Naively, there seems to be no correspondence between the experiment and the real astrophysical system. The lab set-up is very small, works on a very short time frame, and uses carbon rods and lasers; the real environment for galaxy formation is clouds of gas and dark matter, and the time-scale is hundreds of millions of years. Nevertheless, a magnetic field strength (along with other effects) has been observed in the lab that corresponds to that experienced by early protogalaxies.

(via Bringing galaxy-scale magnetic fields down to size in the lab)

As a quantum theory of gravity, loop quantum gravity could potentially solve one of the biggest problems in physics: reconciling general relativity and quantum mechanics. But like all tentative theories of quantum gravity, loop quantum gravity has never been experimentally tested. Now in a new study, scientists have found that, when black holes evaporate, the radiation they emit could potentially reveal “footprints” of loop quantum gravity, distinct from the usual Hawking radiation that black holes are expected to emit.

In this way, evaporating black holes could enable the first ever experimental test for any theory of quantum gravity. However, the proposed test would not be easy, since scientists have not yet been able to detect any kind of radiation from an evaporating black hole.

The scientists, from institutions in France and the US, have published their study called “Probing Loop Quantum Gravity with Evaporating Black Holes” in a recent issue of Physical Review Letters.

“For decades, Planck-scale physics has been thought to be untestable,” coauthor Aurélien Barrau of the French National Institute of Nuclear and Particle Physics (IN2P3) told PhysOrg.com. “Nowadays, it seems that it might enter the realm of experimental physics! This is very exciting, especially in the appealing framework of loop quantum gravity.”

In their study, the scientists have used algorithms to show that primordial black holes are expected to reveal two distinct loop quantum gravity signatures, while larger black holes are expected to reveal one distinct signature. These signatures refer to features in the black hole’s energy spectrum, such as broad peaks at certain energy levels.

Using Monte Carlo simulations, the scientists estimated the circumstances under which they could discriminate the predicted signatures of loop quantum gravity and those of the Hawking radiation that black holes are expected to emit with or without loop quantum gravity. They found that a discrimination is possible as long as there are enough black holes or a relatively small error on the energy reconstruction.

While the scientists have shown that an analysis of black hole evaporation could possibly serve as a probe for loop quantum gravity, they note that one of the biggest challenges will be simply detecting evaporating black holes.

“We should be honest: this detection will be difficult,” Barrau said. “But it is far from being impossible.”

(via Physicists propose test for loop quantum gravity)

Bats navigate with visual map, additional unknown cues

A number of animal species are capable of astonishing navigational feats. This ability appears to be widespread, with groups as diverse as birds, turtles, insects, and fish all showing navigational skills. Now, we can apparently add bats to the list of species that can manage to find their way, even after researchers have played a variety of tricks on their homing systems. Those tricks weren’t just cruel, however, as the researchers’ work showed that the bats probably use at least two systems to orient themselves and navigate using a three-dimensional representation of their usual surroundings.

The species in question is the Egyptian fruit bat (Rousettus aegyptiacus), which is native to Israel’s Negev Desert and, conveniently, large enough to wear a GPS tracking device. When released near their cave, tagged bats went straight to a small collection of fruit trees about 15km away, typically at speeds of over 35km an hour. And when we say straight, we mean it: the bats passed by other fruit trees on the way, and deviated by less than 3 percent of the total distance traveled. Most bats returned straight to the same trees on consecutive nights. So, from both the consistency and directness perspectives, these bats are superb navigators.

(via Ars Technica)

Micro Machinist Takes on Bug Brains

Wired: What is it that you do?

Gus Lott: I think of it as reverse robotics. We’re dealing with organisms that have evolved circuits and adaptive-learning algorithms—mostly worms, fruit flies, and rodents—and we’re trying to develop tools that reverse-engineer how these natural machines work. We’re trying to figure out how nature built its own algorithm.

(via Wired Magazine)

The laser is a very special light source: the spatial, temporal, and frequency aspects of laser light can be exquisitely controlled. This control has enabled much of modern life, and it has had a major impact on research itself. But even the smallest laser is rather large. And many of the things we like to do with light, like imaging, are limited by the fact that normal optical elements can only focus light to a spot with a diameter that is something like the wavelength of light.

To compensate for this shortcoming, researchers have turned to the world of surface plasmon polaritons. The nice thing about plasmons is that they involve an interaction between electrons in a metal and a light field that leads to the wavelength becoming much shorter. The result is that plasmon optics are much smaller and can focus light to much smaller spot sizes. 

The dirty little secret of plasmons is that they decay away very quickly, making them tough to work with. To overcome this, researchers are working on plasmonic laser sources, called spasers.

If you’re thinking, “I’ve been here before,” you’re not wrong. In 2009, a group of researchers published the first results on a spaser. In that work, the researcher took what might be considered the chocolate-coated nut approach. Take a small gold ball and coat it in a plastic material that lases. To make the spaser go, you simply put millions of them in water and shoot a enormous laser pulse into the water—voilà, a small number of the plastic-coated gold balls will start to lase. Of course, the light goes in every direction and it isn’t much use unless you were looking for a weakly glowing cell of cloudy water. More work was certainly required.

The latest work is a natural extension of that previous effort. Instead of spheres, the researchers used gold and silver wires. These were also coated in a plastic material that could lase. Like the previous work, the researchers used another laser to excite the plastic. 

In this case, however, the details of the laser action are a little different. The plastic material absorbs light and emits photons at a lower frequency. Some of this light is captured by the wire, exciting a surface plasmon polariton that travels around the circumference of the wire. The field of the plasmon passes through the plastic material, stimulating more emission into the plasmon, increasing its intensity.

(via Ars Technica)

Reducing the signal-to-noise ratio to get a lock on quantum signals

There is an art to making good measurements. In the ideal case, you want a really sensitive measuring device so that you can measure the smallest of changes to the signal you are interested in. But what you find is that most of the sensitivity is wasted, because in addition to signal, there is always noise. And for most “on the bleeding edge” experiments, the noise is huge compared to the signal.

In classical physics, there is a seemingly magical machine, called a lock-in amplifier, that extracts signal from the deepest and darkest pits of noise. But it seemed that the way quantum mechanics worked would make a quantum lock-in relatively useless. It turns out that, with a bit of clever thinking, you can make a quantum lock-in, and the resulting measurements have even more exquisite sensitivity.

So what is this lock-in amplifier that you speak of? Basically, if you already know something about the signal that you want to extract, then you can use that to get the rest. Imagine that I have a very weak light emitter sitting in a very bright room and I want to know how bright it is. The bright light in the room is the noise and I want to see my very weak emitter. There are several possibilities that are, on the surface, very different, but they’re actually all the same thing.

In this first case, I know what color to look for. Say it emits a very pure form of blue light—I design a filter that only passes that specific color of blue and look into the room through that filter. I will, with any luck, see my signal. That’s because, for any given signal, the total amount of noise is nearly always much greater than the signal, but the amount of noise just in the region of interest around the signal is usually smaller than the signal. So any filter that is specific enough will allow you to see the signal.

How do you filter the signal? Typically, it’s very small and changes slowly, putting it right in the worst of the noise. The first step is to shift the signal to a higher frequency, which we do by multiplying it with some pure oscillating source. Now we are looking for very small changes on a high frequency signal, where it is still drowned in the surrounding noise. 

To extract the signal, we multiply it again, this time with a second oscillator with the same frequency. This has two effects. First, the oscillator can be very strong, so it acts as a sort of amplifier, making the signal stronger. The second is that we can now just look at the part of the signal that’s changing very slowly. All the noise, apart from the tiny component that happened to have the same frequency and phase as the oscillator, gets eliminated.

(via Ars Technica)

Moving mirrors make light from nothing

A team of physicists is claiming to have coaxed sparks from the vacuum of empty space¹. If verified, the finding would be one of the most unusual experimental proofs of quantum mechanics in recent years and “a significant milestone”, says John Pendry, a theoretical physicist at Imperial College London who was not involved in the study.

…At the heart of the experiment is one of the weirdest, and most important, tenets of quantum mechanics: the principle that empty space is anything but. Quantum theory predicts that a vacuum is actually a writhing foam of particles flitting in and out of existence.

The existence of these particles is so fleeting that they are often described as virtual, yet they can have tangible effects. For example, if two mirrors are placed extremely close together, the kinds of virtual light particles, or photons, that can exist between them can be limited. The limit means that more virtual photons exist outside the mirrors than between them, creating a force that pushes the plates together. This ‘Casimir force’ is strong enough at short distances for scientists to physically measure it.

…For decades, theorists have predicted that a similar effect can be produced in a single mirror that is moving very quickly. According to theory, a mirror can absorb energy from virtual photons onto its surface and then re-emit that energy as real photons. The effect only works when the mirror is moving through a vacuum at nearly the speed of light — which is almost impossible for everyday mechanical devices.

Per Delsing, a physicist at the Chalmers University of Technology, and his colleagues circumvented this problem using a piece of quantum electronics known as a superconducting quantum interference device (SQUID), which is extraordinarily sensitive to magnetic fields.

The team fashioned a superconducting circuit in which the SQUID effectively acted as a mirror. Passing a magnetic field through the SQUID moved the mirror slightly, and switching the direction of magnetic field several billion times per second caused it to ‘wiggle’ at around 5% the speed of light, a speed great enough to see the effect.

The result was a shower of microwave photons shaken loose from the vacuum, the team claims. The group’s analysis shows that the frequency of the photons was roughly half the frequency at which they wiggled the mirror — as was predicted by quantum theory.

(via Nature News h/t to fuckyeahquantummechanics)

(IMAGE: Figure 2. An example of a smoothed ROSAT frame rejected due to uneven exposure/ high X-ray background variation. Seven such frames containing eleven filaments in total were rejected for this reason. [Still in the paper, though.])

Monash student finds Universe’s missing mass

A Monash student has made a breakthrough in the field of astrophysics, discovering what has until now been described as the Universe’s ‘missing mass’. Amelia Fraser-McKelvie, working within a team at the Monash School of Physics, conducted a targeted X-ray search for the matter and within just three months found it – or at least some of it.

What makes the discovery all the more noteworthy is the fact that Ms Fraser-McKelvie is not a career researcher, or even studying at a postgraduate level. She is a 22-year-old undergraduate Aerospace Engineering/Science student who pinpointed the missing mass during a summer scholarship, working with two astrophysicists at the School of Physics, Dr Kevin Pimbblet and Dr Jasmina Lazendic-Galloway.

The School of Physics put out a call for students interested in a six-week paid astrophysics research internship during a recent vacation period, and chose Ms Fraser-McKelvie from a large number of applicants. Dr Pimbblet, lecturer in the School of Physics put the magnitude of the discovery in context by explaining that scientists had been hunting for the Universe’s missing mass for decades.

“It was thought from a theoretical viewpoint that there should be about double the amount of matter in the local Universe compared to what was observed.  It was predicted that the majority of this missing mass should be located in large-scale cosmic structures called filaments - a bit like thick shoelaces,” said Dr Pimbblet.  

Astrophysicists also predicted that the mass would be low in density, but high in temperature - approximately one million degrees Celsius. This meant that, in theory, the matter should have been observable at X-ray wavelengths. Amelia Fraser-McKelvie’s discovery has proved that prediction correct.

Ms Fraser-McKelvie said the ‘Eureka moment’ came when Dr Lazendic-Galloway closely examined the data they had collected.

“Using her expert knowledge in the X-ray astronomy field, Jasmina reanalysed our results to find that we had in fact detected the filaments in our data, where previously we believed we had not.”

X-ray observations provide important information about physical properties of large-scale structures, which can help astrophysicists better understand their true nature. Until now, they had been making deductions based only on numerical models, so the discovery is a huge step forward in determining what amount of mass is actually contained within filaments.

The paper can be found on the Cornell University website.

TOBA is a-swingin’, looking for gravity waves

A few months ago, we reported on a theoretical paper that discussed the potential advantages of a gravity wave detector based on a torsion bar, which the creators called TOBA. In the intervening time, the team has not been idle, as they have a small-scale test bar up and running. Deep in the night of August 15, 2009, they performed a test run to look for gravity waves—not gravity induced pressure fluctuations in Earth’s atmospheric pressure, but stretching space-time.

The good thing about the TOBA experiment is that it fills an important spectral gap in the current generation of gravity wave detectors. Cosmological and astronomical observations can be used to look for extremely low frequency (10^-6Hz) gravitational waves, while the laser interferometer detector (LIGO), and other Earth-bound instruments are used to look for gravity waves with frequencies in the 100Hz plus range. TOBA is designed to operate in the 0.1-1Hz range.

This is important because of something called the cosmic gravitational wave background. You may have heard of cosmic background radiation. This radiation is the oldest in the Universe. It originates in that time interval when the hot dense Universe went through a phase transition from a plasma (consisting of unbound electrons and ions) to neutral atomic species. Before this time, radiation was scattered an awful lot, meaning that its history was rapidly lost. After the Universe became neutral, the scattering was very much reduced, allowing this light to retain its history. The remnant that we measure is the unscattered light from that transition but, optically, that moment in time is like a wall that we simply cannot see through.

So, all the physics of the Universe from times before the transition must be tested rather indirectly, based on what the physics implies about the phase transition. That doesn’t mean it’s all guesswork, but more direct observational data would always be welcome.

This is where gravitational waves can play an important role. Gravity waves don’t care about electromagnetic charge, so this phase transition is unimportant as far as they are concerned. Furthermore, the early Universe is thought to have rung like a bell, with space-time stretching and contracting rhythmically. The frequency and directionality of these waves will tell us about the symmetry properties and, as a result, the physics of the early Universe. These waves are spread across the low frequency end of the gravity wave spectrum, including the range covered by TOBA.

(via Ars Technica)

1932: Dr. J A Purves of Taunton, Somerset, UK, assisted by his son, invents, designs and tests out the Dynasphere, a monowheeled car, on Brean Sands, near Weston-super-Mare.

Eyewitness account:

As a lad I lived in Weston. One day in the 1930s I went to the beach and saw a man trying to drive a huge wheel across the sands. It wasn’t very successful and wobbled about. I have always wondered what it was or whether I imagined it.

Dr. Purves’s “Dynasphere” Monowheel, c. 1932

(via WesleyTreat)

Those plucky quadrotors at UPenn’s GRASP laboratory never cease to amaze. In this latest video, watch them autonomously build a structure. In the future, construction workers will be a buzzing, mildly disturbing haze of mechanical diligence.

(via io9.com)

(Source: grasp.upenn.edu)

New State of Matter Seen in Clay - ScienceNOW

Researchers have observed a new kind of extremely light and stable gel in a suspension of clay at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The so-called equilibrium gel, predicted 4 years ago by physicists, could lead to improved drug-delivery systems and other novel microscopic devices.

A gel is a liquid that is rendered solid by a more or less rigid but disordered network of microscopic particles dispersed throughout its volume. These jellylike materials are extremely common and are used in everything from foods and pharmaceuticals to paints and cosmetics. However, many gels are made by “phase separating” a liquid suspension, which means cooling the liquid down until it splits into two distinct components, the more dense of which is the gel. Unfortunately, this is an unstable process that makes it difficult to control certain properties of the gel, including its density.

In the latest research, carried out over 7 years, physicist Barbara Ruzicka of the University of Rome “La Sapienza” and colleagues have shown how an existing material—the synthetic clay Laponite, which is used as a thickener in many household products—can form a stable gel. The researchers suspended Laponite in water and used the powerful x-ray beams of ESRF to study how the structure of the suspension changes over time and how this evolution depends on the amount of clay present.

At concentrations of up to 1% Laponite by weight, the initial fluid transformed into a gel after a few months, the researchers found. Then about 3 years later, it separated into two phases: one clay-rich and the other clay-poor. However, no such phase separation occurred at concentrations above 1%. Unlike at the lower concentrations, at which the arrangement of the clay particles was continually in flux, at concentrations above 1% the structure eventually stopped changing, indicating that the particles had locked into a stable structure: the equilibrium gel.

According to Ruzicka and co-workers, the clay particles reach an equilibrium because of the way they interact with one another. Typical particles dispersed in a liquid have charges distributed symmetrically across their surfaces and will interact with all of their nearest neighbors when they form a gel. The relatively high density of particles needed to do this will not generally exist in the liquid state, but they can exist if the liquid undergoes phase separation.

Clay particles, in contrast, are disc-shaped and have an asymmetric charge distribution—a net negative charge on their faces and a net positive charge along their edges. So they do not interact with all of their nearest neighbors, allowing them to lock together at lower densities. As such, say the researchers, the material will be able to form a gel without the help of a phase transition. Ruzicka explains that the suspension will change reversibly and continuously from the liquid state into the gel state, a process confirmed by computer simulations developed by the group.

This finding has lots of potential applications, says Ruzicka. One is batteries containing a gel electrolyte, which would produce a relatively high power for a given weight of battery and which could be incorporated into microscopic devices if the gel could be made at a low enough density. Alternatively, equilibrium gels could be used as coatings to deliver drugs into the body. These coatings are needed to protect against the body’s immune system and dissolve when the drug reaches its target, so making the coatings lighter would reduce the amount of material that ultimately ends up in the body.

Tom McLeish, a soft condensed matter physicist at Durham University in the United Kingdom, who was not involved with the research, says that the work is important because it provides an experimental demonstration of a new state of matter. And he agrees that the work could also have “applications aplenty.” He argues that the scope for applications could be enhanced enormously by fabricating equilibrium gels artificially—in other words, by making gels that contain particles with specific charge distributions rather than using preexisting materials, as was the case in the current work. 

Acoustic superlens a very cool proof-of-principle

“… I love me some sub-diffraction-limited imaging. But even though I hate to admit it, light is not the only thing we use for imaging. You might imagine that I am thinking of electrons or neutrons or something more exotic. But, no, I’m talking about acoustic imaging. It’s an oft-forgotten workhorse of the medical and engineering world, not to mention the Earth Sciences. So I would be remiss in not talking about a recent Nature Physics paper that describes sub-diffraction-limited acoustic imaging.

What the authors have published is an acoustic superlens made of metamaterials. In this case, the lens consists of 1600 square brass tubes in a 40x40 array, all clamped in an aluminum tube and held together by that standby of elephant removal men: superglue. The experimental geometry was pretty simple. Place the lens just in front of an object to be imaged and place a loudspeaker on the other side. 

In this case, the object was a brass plate with some holes and other shapes milled into it and the sound frequency was around 2kHz. This low frequency, long wavelength sound made it easy to make both the superlens (which required subwavelength structuring) and objects that couldn’t be resolved without it—that is objects with features that are closer spaced than the sound wavelength.

Using this setup, they showed that they could image features at something like 50 times smaller than the wavelength.”

Maps: How Mankind Remade Nature

As scientists get used to the idea that Earth is in a new geological age, that the Holocene — the last geological age — has been replaced by Anthropocene, they’re figuring out how it got to be that way.

Two years ago, ecologists Erle Ellis and Navin Ramankutty at the University of Maryland, Baltimore County, released a map of the world’s biological areas, traditionally known as biomes. Similar maps were found on science classroom walls across the land, but theirs was different in one very fundamental way: They updated the definition of biome to reflect how human beings used the land.

Ellis and Ramankutty said this was much more relevant to the 21st century, with more than six billion people using more of Earth’s water, energy and matter than any other species, than classical biomes that didn’t account for humanity’s influence. They called their newly-defined areas “anthromes,” short for anthropological biomes. It was a map for the anthropocene.

During a subsequent presentation, someone asked the researchers for details on how the anthropocene evolved. To answer that question, Ellis and Ramankutty have come out with a new set of maps that show how anthromes have changed since the beginning of the Industrial Revolution.

“You now have a biosphere that’s completely transformed by people. Biology goes on in the human context, not the natural,” he said. “And given the idea that most of ecosystem form and process is created by and ruled by human activity, how did it get to be that way?”

(click photo for rest of article)

[Via: WIRED]

Cornell researchers made a thin film of europium titanate ferromagnetic and ferroelectric by “stretching” it. They did it by depositing the material on an underlying substrate with a larger spacing between its atoms.

Researchers ‘stretch’ a lackluster material into a possible electronics revolution

It’s the Clark Kent of oxide compounds, and - on its own - it is pretty boring. But slice europium titanate nanometers thin and physically stretch it, and then it takes on super hero-like properties that could revolutionize electronics, according to new Cornell research. (Nature, Aug. 19, 2010.)

Researchers report that thin films of europium titanate become both ferroelectric (electrically polarized) and ferromagnetic (exhibiting a permanent magnetic field) when stretched across a substrate of dysprosium scandate, another type of oxide. The best simultaneously ferroelectric, ferromagnetic material to date pales in comparison by a factor of 1,000.

Simultaneous ferroelectricity and ferromagnetism is rare in nature and coveted by electronics visionaries. A material with this magical combination could form the basis for low-power, highly sensitive magnetic memory, magnetic sensors or highly tunable microwave devices.

The search for ferromagnetic ferroelectrics dates back to 1966, when the first such compound - a nickel boracite - was discovered. Since then, scientists have found a few additional ferromagnetic ferroelectrics, but none stronger than the nickel compound - that is, until now.

“Previous researchers were searching directly for a ferromagnetic ferroelectric - an extremely rare form of matter,” said Darrell Schlom, Cornell professor of materials science and engineering, and an author on the paper.

“Our strategy is to use first-principles theory to look among materials that are neither ferromagnetic nor ferroelectric, of which there are many, and to identify candidates that, when squeezed or stretched, will take on these properties,” said Craig Fennie, assistant professor of applied and engineering physics, and another author on the paper.

This fresh strategy, demonstrated using the europium titanate, opens the door to other ferromagnetic ferroelectrics that may work at even higher temperatures using the same materials-by-design strategy, the researchers said.

Other authors include David A. Muller, Cornell professor of applied and engineering physics; and first author June Hyuk Lee, a graduate student in Schlom’s lab.

The researchers took an ultra-thin layer of the oxide and “stretched” it by placing it on top of the disprosium compound. The crystal structure of the europium titanate became strained because of its tendency to align itself with the underlying arrangement of atoms in the substrate.

Fennie’s previous theoretical work had indicated that a different kind of material strain - more akin to squishing by compression - would also produce ferromagnetism and ferroelectricity. But the team discovered that the stretched europium compound displayed electrical properties 1,000 times better than the best-known ferroelectric/ferromagnetic material thus far, translating to thicker, higher-quality films.

This new approach to ferromagnetic ferroelectrics could prove a key step toward the development of next-generation memory storage, superb magnetic field sensors and many other applications long dreamed about. But commercial devices are a long way off; no devices have yet been made using this material. The Cornell experiment was conducted at an extremely cold temperature - about 4 degrees Kelvin (-452 Fahrenheit). The team is already working on materials that are predicted to show such properties at much higher temperatures.

Provided by Cornell University (news : web)

[Source: Phys.org]