Waves & Packets
Sep. 8, 2012

Quasicrystals, meet topological insulators and maybe string theory
American Physical Society
In a paper appearing in Physical Review Letters, two researchers from Weizmann Institute of Science reveal an unexpected mathematical connection between quasicrystals and topological insulators. Furthermore they show a practical example of this connection via an optical waveguide device that creates a quasiperiodic potential for light. In this device the waveguides are not exactly parallel but have a slowly varying separation between them along the length of the device. As light moves along the length of the waveguide, the evanescent part of the light field can tunnel into adjacent waveguides. This slow variation in separation between the guides leads to "adiabatic pumping" of light from one edge of the device to the other, under what turns out to be a quasiperiodic potential. This result, which would not be possible for a periodic potential, establishes the connection between quasiperiodicity in one dimension and the integer quantum Hall effect in two dimensions.

In a synopsis of the work, Alexander Quant of the DST/NRF Centre of Excellence in Strong Materials in Witwatersrand, South Africa comments that finding of a connection between two seemingly different kinds of materials may deeply influence the way theorists design models to explore the physics of quasicrystals. Noting that this result may hold for higher-dimensional quasicrystals that are described by higher-dimensional Hamiltonians, he wonders if this line of research might draw in other fields, such as string theory, into the realm of quasicrystals research. More

Ultracold fermions simulate spin-orbit coupling
Physics World
Two independent research teams are the first to use ultracold fermionic atoms to simulate spin–orbit coupling. Both experiments were done by firing laser beams at the atoms, which caused their momentum to change by an amount that depends on their intrinsic spin. In one set of experiments potassium-40 atoms in an optical trap were exposed to two laser beams from opposing directions that were resonant with the transition between two spin states. In the other experiment lithium-6 atoms were exposed to radio waves to drive them into spin-orbit coupling states. These two new experimental approaches using the precision of photonic control and relatively simple atomic systems could shed further light on a range of physical phenomena, including magnetism, superconductivity, conductance in topological insulators and the presence of Majorana fermions. And they could profoundly impact the development of spintronic devices.More

Mathematicians offer unified theory of dark matter, dark energy, altering Einstein field equations
Indiana University
A pair of mathematicians has proposed a unified theory of dark matter and dark energy that alters Einstein's equations describing the fundamentals of gravity. In a paper posted on arXiv, the researchers employ the same metric of curved spacetime that Einstein used in his field equations, the researchers argue the presence of dark matter and dark energy requires a new set of gravitational field equations that take into account a new type of energy caused by the nonuniform distribution of matter in the universe. This new energy can be both positive and negative, and the total over spacetime is conserved. It is curved spacetime, along with a new scalar potential field representing the new energy density, and the interactions between the two that form the foundation for the new gravitational field equations. More

67-attosecond extreme ultraviolet laser pulse is the world's shortest
University of Central Florida
A team of physicists has generated a 67-attosecond pulse of extreme ultraviolet radiation, setting a world record. The previous record was an 80-attosecond pulse, set in 2008 by a team at the Max Planck Institute in Garching, Germany. Previously Chang's group created a technique called Double Optical Grating that allows extreme ultraviolet radiation to be cut off in a manner that concentrates the maximum amount of energy in the shortest possible pulse. The current work is described in a paper accepted for publication in Optics Letters. More

Stellar makeup impacts habitable zone evolution
Arizona State University
Astrobiologists and planetary scientists agree that a planet's distance from its parent star is of paramount importance in its habitabilty. As a star evolves, it becomes brighter, causing the habitable zone to move outwards through its solar system. A new study suggests that the host star's chemical makeup can also impact conditions of habitability of planets that orbit it. In a paper published in Astrophysical Journal Letters, researchers indicate that a star's abundance of oxygen, carbon, sodium, magnesium and silicon should be a plus for an inner solar system's long-term habitability because the abundance of these elements makes the star cooler and cause it to evolve more slowly. This gives planets in its habitable zone more time to develop life as we know it. The chemical dynamics in stars are extremely complicated, depending on temperature, composition, pressure, etc. And the very definition of habitability is an imprecise concept. But this new study identifies at least one simple connection between stellar chemistry and planetary life. More

Where is all the lithium-7?
Cosmologists have been stumped by an observation first made some 30 years ago. They noted that in studying the halos of older stars, that there should be more lithium-7 than there appeared to be in the universe. Since that time many studies have been conducted in trying to explain this apparent anomaly, but thus far no one has been able to come up with a reasonable explanation.

New research published in Nature has deepened the mystery further by finding that the amount of lithium-7 in the path between us and a very young star aligns with would have been expected shortly after the Big Bang, but doesn't take into account the creation of new amounts since that time. The authors suggest the discrepancy is troubling because it cannot be explained with normal astrophysics models.More

X-rays reveal spin waves in 2-Dimensional high-temperature superconductors
Brookhaven National Lab
Using a technique called resonant inelastic X-ray scattering, scientists examined the magnetic spins of atomically thin layers of copper oxide materials. The technique uses very intense, tunable, X-ray beams on very well-defined two-dimensional samples of superconducting materials. It allowed the team to detect the very small signals resulting from just a few atoms spin-flipping to create a coherent spin wave. Such spin waves, at least the coherent coupling of two spins, may play a role in superconductivity. In a surprising discovery published in Nature Materials, researchers found that the spin waves present in complete, three-dimensional samples survived all the way down to the atomic level. Furthermore they found that quantum spins behave very similarly to classical magnets, and that other predicted quantum effects were not present in the two-dimensional samples.More

Charting a course for heliophysics
Sky and Telescope
A new report, titled "Solar and Space Physics: A Science for a Technological Society," provides a vision and recommendations for U.S. research in solar and space physics in the coming decade. It is the third major "decadal survey" dealing with space science to be released in the past couple of years, the other two having delved into astrophysics and planetary exploration. The study emphasizes completing projects already under way. For NASA, this means spacecraft such as the just-launched Radiation Belt Storm Probes and the forthcoming Interface Region Imaging Spectrograph (2013) and Magnetospheric Multiscale mission (2014). For the National Science Foundation, the top jobs will be completing the 4-meter-aperture Advanced Technology Solar Telescope (the world's largest) and the Advanced Modular Incoherent Scatter Radar, a mobile observatory for studying the upper atmosphere and space-weather events. The report also calls for better coordination between NASA and NSF, with supporting roles from the National Oceanic and Atmospheric Administration and the Defense Department. More

National Society of Black Physicists jobs board postings
Tenure Track Assistant Professor — Denison University
Assistant Professor Position in Experimental Nuclear Physics at Duke University
Assistant Professor in Experimental Condensed Matter Magnetism — Miami University of Ohio
Tenure Track Assistant Professor in Evolution
Faculty Opening Carnegie Mellon University McWilliams Center for Cosmology
Tenure-Track Faculty Position, Department of Physics, Emory University
Assistant Professor of Science, Technology, and Society and Physics
NASA Postdoctoral Fellowships
Assistant Professor
Assistant or Associate Professor — Gravitational wave and particle astrophysics / elementary particle physics
Faculty position in LCLS Science
Chamberlain Fellowship
Assistant Professor of Physics, tenure track
2-Year Full-Time Postdoctoral Fellowship in Acoustics
Assistant Professor — Experimental Condensed Matter and Materials Physics — Ohio State University
National Astrophysics and Space Science Program
Postdoctoral Research Associate PositionsMore

Increase your options for graduate or REU program admissions
The NSBP GradApps and REUApps services are open to all students and allows them to upload all the elements of an admissions application, including academic and work history, transcripts, letters of recommendation and a personal statement. Graduate and REU programs can subscribe to these databases to increase the programs' applicant pool, while at the same time allowing students can put their credentials in front of more programs than to which they would otherwise apply. More

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IOP Publishing
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