169 years after its discovery, Doppler effect found even at molecular level

But for the first time, scientists have experimentally shown a different version of the Doppler effect at a much, much smaller level– the rotation of an individual molecule. Prior to this such an effect had been theorized, but it took a complex experiment with a synchrotron to prove it's for real.

"Some of us thought of this some time ago, but it's very difficult to show experimentally,"said T. Darrah Thomas, a professor emeritus of chemistry at Oregon State University and part of an international research team that today announced its findings inPhysical Review Letters.

Most illustrations of the Doppler effect are called"translational,"meaning the change in frequency of light or sound when one object moves away from the other in a straight line, like a car passing a radar gun. The basic concept has been understood since an Austrian physicist named Christian Doppler first proposed it in 1842.

But a similar effect can be observed when something rotates as well, scientists say.

"There is plenty of evidence of the rotational Doppler effect in large bodies, such as a spinning planet or galaxy,"Thomas said."When a planet rotates, the light coming from it shifts to higher frequency on the side spinning toward you and a lower frequency on the side spinning away from you. But this same basic force is at work even on the molecular level."

In astrophysics, this rotational Doppler effect has been used to determine the rotational velocity of things such as planets. But in the new study, scientists from Japan, Sweden, France and the United States provided the first experimental proof that the same thing happens even with molecules.

At this tiny level, they found, the rotational Doppler effect can be even more important than the linear motion of the molecules, the study showed.

The findings are expected to have application in a better understanding of molecular spectroscopy, in which the radiation emitted from molecules is used to study their makeup and chemical properties. It is also relevant to the study of high energy electrons, Thomas said.

"There are some studies where a better understanding of this rotational Doppler effect will be important,"Thomas said."Mostly it's just interesting. We've known about the Doppler effect for a very long time but until now have never been able to see the rotationalDoppler effectin molecules."

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Fundamental question on how life started solved?

The researchers published their results in the coming issue of the scientific journalPhysical Review Letters.

"Attempts to calculate the Hoyle state have been unsuccessful since 1954,"said Professor Dr. Ulf-G. Meißner (Helmholtz-Institut für Strahlen- und Kernphysik der Universität Bonn)."But now, we have done it!"The Hoyle state is an energy-rich form of the carbon nucleus. It is the mountain pass over which all roads from one valley to the next lead: From the three nuclei of helium gas to the much larger carbon nucleus. This fusion reaction takes place in the hot interior of heavy stars. If the Hoyle state did not exist, only very little carbon or other higher elements such as oxygen, nitrogen and iron could have formed. Without this type of carbon nucleus, life probably also would not have been possible.

The search for the"slave transmitter"

The Hoyle state had been verified by experiments as early as 1954, but calculating it always failed. For this form of carbon consists of only three, very loosely linked helium nuclei - more of a cloudy diffuse carbon nucleus. And it does not occur individually, only together with other forms of carbon."This is as if you wanted to analyze a radio signal whose main transmitter and several slave transmitters are interfering with each other,"explained Prof. Dr. Evgeny Epelbaum (Institute of Theoretical Physics II at Ruhr-Universität Bochum). The main transmitter is the stable carbon nucleus from which humans - among others - are made."But we are interested in one of the unstable, energy-rich carbon nuclei; so we have to separate the weaker radio transmitter somehow from the dominant signal by means of a noise filter."

What made this possible was a new, improved calculating approach the researchers used that allowed calculating the forces between several nuclear particles more precisely than ever. And in JUGENE, the supercomputer at Forschungszentrum Jülich, a suitable tool was found. It took JUGENE almost a week of calculating. The results matched the experimental data so well that the researchers can be certain that they have indeed calculated the Hoyle state.

More about how the Universe came into existence

"Now we can analyze this exciting and essential form of the carbon nucleus in every detail,"explained Prof. Meißner."We will determine how big it is, and what its structure is. And it also means that we can now take a very close look at the entire chain of how elements are formed."

In future, this may even allow answering philosophical questions using science. For decades, the Hoyle state was a prime example for the theory that natural constants must have precisely their experimentally determined values, and not any different ones, since otherwise we would not be here to observe the Universe (the anthropic principle)."For the Hoyle state this means that it must have exactly the amount of energy it has, or else, we would not exist,"said Prof. Meißner."Now we can calculate whether - in a changed world with other parameters - the Hoyle state would indeed have a different energy when comparing the mass of three helium nuclei."If this is so, this would confirm the anthropic principle.

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Minnesota researcher's findings on dark matter jibe with Italy's DAMA/LIBRA claims

The DAMA/LIBRA team has insisted for 12 years that the data it has found with its detectors backs up the theory that not only does dark matter exist, but that it can be shown to exist by seasonal changes in the amount of recoil hitting in their germaniumdetectors. The idea is that because the Earth moves and supposed clouds of dark matter don’t, there should be times of higher activity when the Earth is moving into or through an area of dense dark matter, and lower activity when it’s not. This is the basis of the argument the DAMA/LIBRA team has had to explain the seasonal changes in the number of hits they see.

The problem with all this though is that there are other teams that have not been able to reproduce the results shown first by the DAMA/LIBRA team, and now by those with the CoGeNT team (most notably the Swiss XENON100 team.) Making the whole argument even more sensational is that the CoGeNT team actually set out to prove to the world that the DAMA/LIBRA team was wrong.

All of the teams are working to prove or disprove the notion that theoretical particles of dark matter, called WIMPS, exist and thus can be used, or not to back up or refute many other theories that serve to explain many of the unexplained phenomena that exist in the universe; such as what holds everything together. Some theories suggest that ifdark matterdoes truly exist, it likely makes up eighty percent of everything there is; if it doesn’t however, a lot ofphysicistswill be going back to the drawing board.

One thing is certain however, and that is much more research will have to be done, both by those that are seeing results and those that aren’t, before anyone can even come close to claiming they understand the invisible forces that make the universe what it is.

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New tool for proton spin

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Nowadays, the most popular theory for subatomic particles is the Standard Model: a menagerie of fundamental particles including quarks, which come in six different types or flavors, and four fundamental forces. These forces include the‘weak’ force that is mediated byparticlescalled W bosons, which are created, albeit only briefly, when protons collide. The researchers discovered that these W bosons are a sensitive probe of the quarks that make up aproton. 

To investigate proton spin, the PHENIX team fired two beams of high-energy protons at one another using the Relativistic Heavy Ion Collider at BNL.“Most of the interactions that take place when the protons collide are‘strong’ interactions,” explains Okada.“But our experiment was sensitive enough to detect‘weak’ interactions too.” The researchers identified two such weak reactions: detection of an electron indicated the decay of a negatively charged W boson (Fig. 1); and detection of a positron—a positively charged electron—indicated the decay of a positively charged W boson. By counting the number of resulting electrons and positrons, the researchers could calculate the probability of each type of interaction.

The PHENIX team then performed two experiments simultaneously. In one, they made protons spin parallel to the axis of the beam; and in the other, they made them spin in the opposite direction. The difference in the rate of weak interactions in each experiment provided information about the spin direction of the quarks in the proton.“The asymmetry of the production rates is connected to the probability that the spin of a particular flavor of quark is aligned to the proton spin direction,” says Okada. This approach could soon be extended to identify the spin contribution of all the proton’s quarks.

Next the team hopes to improve the sensitivity of the experiment.“This time, we only caught electrons and positrons that emerged at 90 degrees to the beam axis,” explains Okada.“We are preparing new detectors to extend this detection region for a more complete analysis.”

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Testing technicolor physics

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TheHiggs bosonis a central component of the"standard model,"a theory that defines the relationships between the forces of the universe. But, what if the Higgs boson is not a fundamental particle, but rather a bound state of new particles that have not yet been seen?

"From the beginning of the standard model, people have been unhappy with the idea that the Higgs boson is a fundamental particle,"said Thomas DeGrand, professor of physics at the University of Colorado.

Scientists who advocate alternative models of particle physics are motivated by the theory of superconductivity. Thesuperconducting state, which is very different from ordinary matter, is not characterized by new particles, but by Cooper pairs--bound states ofelectrons.

The standard model of particle physics suggests that theprotonsandneutronswe're familiar with, that comprise the nuclei of atoms, are made up of combinations of different types of elementary particles called quarks and gluons. We cannot see these particles in isolation because a fundamental force called"the strong interaction"holds them firmly together, but experiments lead physicists to believe these quarks come in three varieties, each with different properties, or"colors".

No one knows why the particle content of the standard model is what it is. A logical possibility exists that there could be more kinds of quarks and gluons with different numbers of colors, strongly interacting with each other. Collectively, these possibilities are known as technicolor theories.

DeGrand spent many years studying the theory behind the interactions of quarks and gluons, known asquantum chromodynamics(QCD), before he turned his attention to technicolor theories. He is the co-author of one of the standard books in the field.

However, QCD does not describe all aspects of the standard model, especially the nature of"final"undiscovered particles. The construction of the LHC, and the sense that new knowledge was waiting around the corner, drew DeGrand to explorations of alternative particle theories.

"I became a little tired of lattice QCD,"DeGrand said."The technicolor theories held more interesting questions."

Within the last five years, scientists realized that many of the computational techniques that had been invented for QCD could be applied technicolor theories as well. In 2008, two colleagues from Tel Aviv University, Yigal Shamir and Benjamin Svetitsky, invited DeGrand to join their research team. Applying the same methodology DeGrand helped perfect for QCD, the team began simulating technicolor candidate theories and drawing conclusions from the odd outcomes of these simulated worlds.

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Above is a map of technicolor particle theories that Thomas DeGrand studies. The axes represent (horizontal) the number of colors and (vertical) the number of flavors of quarks. The different colors describe different kinds of color structure for the quarks. The shaded bands are where theorists (D. Dietrich and F. Sannino) predict that there are"unparticle"theories. Credit: Physical Review D75, 085018 (2007)

To calculate the interactions of new kinds of quarks and gluons in various configurations on lattices of giant grids, the team used the National Science Foundation (NSF)-funded Ranger supercomputer--one of the largest in the world--located at the Texas Advanced Computing Center. In the numerical simulations, the grids are housed (virtually) in boxes of various sizes and the reaction of the particles to the box size provides information about the energy characteristics of the system.

"This is not something an experimentalist can do,"DeGrand said."But as theorists, we can invent these fake worlds where the system sits in a specific sized box, and we can measure the strength of the quark-gluon interactions in large boxes, medium boxes and small boxes to see how it changes. Changing the energy or momentum scales is related to changing the physical size of the system."

Supercomputing plays a pivotal role in this process, which involves solving complex quantum equations for a large number of particles. Over the last two years, DeGrand and his colleagues have used nearly three million processing hours on Ranger (the equivalent of 340 years on a single processor) to simulate new particles comprised of quarks with two colors and three colors, respectively. The simulations help characterize the new particles and determine whether they are candidates for beyond-the-standard-model physics.

The Ranger simulations revealed that the simplest technicolor models, with two colors, have properties that are very different from a conventional particle system. Professor H. Georgi of Harvard University coined the name"unparticle theory"to describe such systems.

The three-color system was a bit more mysterious. The researchers couldn't tell if it was a particle theory or an unparticle theory. However, the simulations clearly didn't represent a viable real-world scenario. For a technicolor theory to be a feasible candidate for new physics, it must exhibit unusual behavior to avoid conflict with the constraints defined by present-day experimental knowledge. The three-color system didn't satisfy these criteria. The researchers are currently continuing their map of possible particle models by simulating four-color quark systems.

"The idea that the Higgs mechanism could be caused by the strong interactions of still-to-be-discoveredelementary particleshas been with us for some time, but until recently, it has been difficult to test this idea for lack of adequate computing resources,"said Carlton DeTar, a longtime collaborator from the University of Utah not involved in the current research."DeGrand and his collaborators are among the foremost groups in the world using powerful numerical simulations to investigate this exciting alternative. The results could have profound implications for the search for the Higgs particle at the Large Hadron Collider in Europe."

Just as Salvador Dali's surreal paintings reveal taken-for-granted aspects of our material world, the alternative technicolor theories have intellectual value. They teach us about particle theories by placing them in a larger context.

For DeGrand, the stretching of the mind is what matters most--that, and the adventure of discovering something truly novel.

"It's high-risk, high-reward research,"DeGrand said.

But, if he and his colleagues find a viable alternative to thestandard model, it could drive the next theory of everything.

The work was also supported by the U.S. Department of Energy. Additional computations were done on facilities of the USQCD Collaboration at Fermilab, which are funded by the Office of Science of the U.S. Department of Energy.

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Forecast calls for nanoflowers to help return eyesight

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These flowers are not roses, tulips or columbines. They will be nanoflowers seeded from nano-sized particles of metals that grow, or self assemble, in a natural process -- diffusion limited aggregation. They will be fractals that mimic and communicate efficiently with neurons.

Fractals are"a trademark building block of nature,"Taylor says. Fractals are objects with irregular curves or shapes, of which any one component seen under magnification is also the same shape. In math, that property is self-similarity. Trees, clouds, rivers, galaxies, lungs and neurons are fractals, Taylor says. Today's commercialelectronic chipsare not fractals, he adds.

Eye surgeons would implant these fractal devices within the eyes of blind patients, providing interface circuitry that would collect light captured by the retina and guide it with almost 100 percent efficiency to neurons for relay to theoptic nerveto process vision.

In an article titled"Vision of beauty"forPhysics World, Taylor, a physicist and director of the UO Materials Science Institute, describes his envisioned approach and how it might overcome the problems occurring with current efforts to insert photodiodes behind the eyes. Current chip technology is limited, because it doesn't allow sufficient connections with neurons.

"The wiring -- the neurons -- in the retina is fractal, but the chips are not fractal,"Taylor says."They are just little squares of electrodes that provide too little overlap with the neurons."

Beginning this summer, Taylor's doctoral student Rick Montgomery will begin a yearlong collaboration with Simon Brown at the University of Canterbury in New Zealand to experiment with various metals to grow the fractal flowers on implantable chips.

The idea for the project emerged as Taylor was working under a Cottrell Scholar Award he received in 2003 from the Research Corporation for Science Advancement. His vision is now beginning to blossom under grants from the Office of Naval Research (ONR), the U.S. Air Force and the National Science Foundation.

Taylor's theoretical concept for fractal-based photodiodes also is the focus of a U.S. patent application filed by the UO's Office of Technology Transfer under Taylor's and Brown's names, the UO and University of Canterbury.

The project, he writes in thePhysics Worldarticle, is based on"the striking similarities between the eye and the digital camera."

"The front end of both systems,"he writes,"consists of an adjustable aperture within a compound lens, and advances bring these similarities closer each year."Digital cameras, he adds, are approaching the capacity to capture the 127 megapixels of the human eye, but current chip-based implants, because of their interface, are only providing about 50 pixels of resolution.

Among the challenges, Taylor says, is determining which metals can best go into body without toxicity problems."We're right at the start of this amazing voyage,"Taylor says."The ultimate thrill for me will be to go to a blind person and say, we're developing a chip that one day will help you see again. For me, that is very different from my previous research, where I've been looking at electronics to go into computers, to actually help somebody ... if I can pull that off that will be a tremendous thrill for me."

Taylor also is working under a Research Corp. grant to pursue fractal-based solar cells.

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Model shows how scientific paradigms rise and fall

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The researchers, Stefan Bornholdt from the University of Bremen in Bremen, Germany, and Mogens Høgh Jensen and Kim Sneppen from the Niels Bohr Institute in Copenhagen, Denmark, have published their study called“Emergence and Decline of Scientific Paradigms” in a recent issue ofPhysical Review Letters.

“Our model addresses the interplay between a new idea and the difficulty it has in displacing old ideas in a world where alignment of interests is dominating,” Bornholdt toldPhysOrg.com.

Several models of opinion formation already exist, but the new model differs from earlier models in a few important ways. Unlike previous models, the new model allows for an infinite variety of ideas, although each idea has a small probability of being initiated. Also, each idea can appear only once, and an agent (or individual) cannot return to any of the ideas that they have previously held, reflecting scientists’ ongoing hunt for new ideas.

In the model, which is defined on a 2D square lattice, ideas spread in two possible ways. In the first way, an agent adopts a new idea held by its neighbors, with a probability proportional to how many agents already hold this particular idea. In the second way, an agent randomly gets a new idea that does not appear anywhere else in the system with a probability that depends on the“innovation rate.” The first way represents cooperative effects in social systems, while the second way represents innovation.

The model shows how a system with one dominating scientific paradigm transitions into a system with small clusters of ideas, some of which continue to grow until one dominates, and the process repeats with new ideas. The dynamics of the rise and fall of scientific paradigms depends on the system’s innovation rate. Systems with high innovation rates tend to contain a high degree of noise, along with many small domains of ideas that are constantly generated and replaced. In contrast, systems with low innovation rates tend to have low noise and a state that remains dominant for a long time until a single event replaces it.

In addition to providing a theoretical understanding of how scientific paradigms rise and fall, the model also provides insight that helps explain some observations in real life. For instance, the model shows how small systems have the potential to be more dynamic than large systems, which explains why large companies sometimes acquire small start-up firms as a source of innovation.

“Our model indicates that social cooperation makes it more difficult for new ideas to nucleate because of social pressure,” Bornholdt said.“Accordingly, our model finds a‘winner take all’ dynamic, suggesting a fashion-like dynamic for the prevailing focus of contemporary science.

“Even though our model is extremely simplified and does not deal with right and wrong, it explores the effect of herd mentality in the propagation of ideas,” he added.“Our model suggests that herd mentality makes a larger system less innovative than several smaller ones. In short, for innovation it’s better to listen to yourself than to others.”

Overall, the model shows how new paradigms have a tendency to quickly rise to dominance, to decline slowly, and to quickly be replaced by other paradigms. When theinnovationrate is high, the takeover process is chaotic, with many new ideas competing for dominance. Regardless of the idea itself, the model shows that the pattern of paradigm shifts remains fairly consistent over time.

The results could have implications for science philosophy and science policy, as the model suggests that scientific diversity may need special attention. In addition, the researchers are applying the model to the study of the spread of epidemics.

“We are currently studying the ideas of‘new’ and‘old’ in epidemics modeling,” Bornholdt said,“where the‘never-return-policy’ of ideas in the abovemodelis associated with immunity of infected hosts: A host that has been infected by a particular virus in the past will be immune to this virus in the future and, thus, will never acquire the same infection twice.”

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