Waves & Packets
Aug. 25, 2012

Committee recommends ending NSF funding for some astronomy facilities
Physics World
Last week the astronomy division at the U.S. National Science Foundation released the report of its portfolio review committee that recommended defunding, but not necessarily closing, the Green Bank Telescope, the Very Long Baseline Array the Mayall Telescope, the Wisconsin-Indiana-Yale-National Optical Astronomy Observatory, 2.1 meter optical/infrared telescopes at Kitt Peak, and the McMath-Pierce Solar Telescope. The portfolio review was brought on by fiscal realities and the desire to keep the land-based astronomy program balanced in terms of support for investigators and operation of facilities.

Some astronomers have responded with alarm. Michael Kramer of the Max Planck Institute for Radio Astronomy has called the Green Bank Telescope "...one of the most important radio telescopes in the world." Tony Beasley, Director of the U.S. National Radio Astronomy Observatory, also responded to the report and commented more broadly on the process and the budget for astronomy in an interview with Waves and Packets.

Caltech astronomy professor and NSBP member, John Johnson commented to Waves and Packets, "While it is painful to see facilities cut, there exists enough archival data and existing facilities to do a lot of good research over the next decade. But if the salaries aren't there, then the research can't be done, even with the best facilities available."More

Physicists demonstrate 1st time reversal of water waves
Researchers in France have reported via Physical Review Letters that water waves in a small laboratory tank can still exhibit time reversal in spite of the strong damping. In spite of its name, the time reversal of a wave does not involve sending the wave back in time. What is actually happening is that after a source generates a wave, the wave propagates through a medium and is recorded at a few points in its surroundings by an optical method. Then, the wave is re-emitted in a way so that its energy focuses back at the initial source position, as though the wave were being played backwards. Because the wave precisely retraces its original path as it travels back to its source, its mathematical description is reversed in time but is otherwise exactly the same. More

1-molecule-thick material has big advantages
A whole family of two-dimensional materials may open up even broader possibilities for applications that could change many aspects of modern life. Results published in Nano Letters demonstrate that fabricating circuits with two-dimensional molybdenum disulfide is much easier than using graphene. Moreover MoS2 comes with a natural bandgap, which graphene does not. That means a graphene switch, for instance, can be turned on but cannot be turned off, i.e., you cannot do digital logic with graphene switches. That problem goes away with MoS2. MoS2 is already used in bulk form in many industrial applications. In its two-dimensional form it can be deposited on virtually any other material, and researchers at MIT already have used it to make some basic electronic logic elements. More

Fractal calculus may help explain superconductivity
Purdue University
A research team at Purdue University and University of Illinois has introduced a new set of methods based on fractal geometry to analyze strongly correlated electronic systems such as cuprate superconductors. The team noticed that in cuprate superconductors there were seemingly random, four-atom-wide dark lines of electrons on the crystal surface crystals. When they identified a pattern in these lines, which were separate from the expected structure of the material, they discovered that the lines exist throughout the crystal, and the suggestion was that they could play a role in the material's superconductivity. Applying universal cluster properties, they found that the electron nematic, i.e., the ordering and symmetry breaking, is fractal in nature, and that it extends throughout the bulk of the material. Whether or not important electronic properties are related directly to a particular fractal dimension remains to be seen, but this new result that leads to new methods of analysis is published in Nature Communications.More

Observing the dynamics of supermassive black hole binaries with pulsar timing arrays
American Physical Society
Massive astrophysical objects are believed to produce ripples in spacetime called gravitational waves. Proposed or ongoing pulsar timing experiments offer the chance to detect these gravitational waves and use them to study the behavior of the objects that create them. In a paper appearing in Physical Review Letters, a team of astrophysicists analyze the potential and limitations of using data from groups of pulsars for this kind of research. Using calculations for gravitational waves produced by a pair of supermassive black holes orbiting each other, the authors suggest a plan for how experimental detection of gravitational waves might shed light on the details of black hole masses, spins, formation and evolution. More

Pulsar timekeepers measure up to atomic clocks
Physics World
An international team of astronomers has come up with a new way of keeping track of time by observing a collection of pulsars. Pulsar timing can be used to create timescales that rival those generated by atomic or optical clocks, which operate using the frequencies of certain atomic transitions. Using the Parkes radio telescope in Australia, the team compared timescales generated from a set of 19 pulsars in different parts of the Milky Way to two different atomic-clock based timescales. They were able to find a known deficiency in a well-used atomic clock timescale, and furthermore demonstrate that pulsar-timing is indeed a reliable standard for timekeeping. The research will be published in Monthly Notices of the Royal Astronomical Society. More

Negative frequency photons: The impact of something we thought could not exist has now been detected
Ars Technica
A team of physicists has shown in a paper recently published in Physical Review Letters that light with a negative frequency (thought to be a quirk of the Maxwell equations) actually, in some sense, exists. The Maxwell equations have solutions that have positive and negative frequencies. If we just consider the positive frequency component, then there are four solutions to the equation. Negative frequency solutions are at first glance unphysical. But it turns out that the negative frequency solutions are sometimes useful, especially in cases of strong fields in materials where the electrons do not follow exactly the oscillations of the a pulse of light. So-called negative resonant radiation originates from the coupling of the input pulse to the negative-frequency branch of the dispersion relation. The research team proved that a resonant response due to a negative frequency is real and can be measured as positive frequency radiation. More

Neutrinos alter physics of exploding stars
Science Daily
In a so-called core-collapse supernova, as material falls inwards towards the stellar core, the core actually responds by sending streams of neutrinos outward in the opposite direction. A small number of neutrinos actually scatter and cross trajectories of other neutrinos. Previously it was thought that the number of scattering neutrinos is so small that their effects can be ignored. But a University of California, San Diego, graduate student has shown in a paper in Physical Review Letters that the neutrino interactions in these instances lead to significant flavor changes amongst the neutrinos in the halo around the core. Chemical elements produced in these supernovas are dramatically impacted by changes in the neutrino flavor distribution. And many other important things about the resulting neutron star are determined by neutrino flavor.More

Elusive conditions for nickel oxide conductivity discovered
Carnegie Institute of Science
Carnegie scientists are the first to discover the conditions under which nickel oxide can turn into an electricity-conducting metal. Nickel oxide is one of the first compounds to be studied for its electronic properties, but until now scientists have not been able to induce a metallic state. Despite its partially filled outer shell of electrons, nickel oxide remains an insulator. With a sample in a diamond anvil cell the researchers were able to see conductivity in the material at ultrahigh pressure (1.3 million atmospheres). At 2.4 million atmospheres there was a dramatic, three-order-of-magnitude increase in conductivity indicating a change from a semiconducting to a metallic state. The finding is published in Physical Review Letters, and is an important result with implications in condensed matter physics, planetary science and in the astrophysics of stars. More

National Society of Black Physicists jobs board postings
Tenure-Track Faculty Position, Department of Physics, Emory University
Assistant Professor of Science, Technology, and Society and Physics
NASA Postdoctoral Fellowships
Assistant or Associate Professor — Gravitational wave and particle astrophysics / elementary particle physics
Assistant Professor
Faculty position in LCLS Science
Chamberlain Fellowship
Assistant Professor of Physics, tenure track
Faculty Positions in Science, Technology, and Innovation
Project Leader: Nanoscale Measurements for Energy Storage Technologies
LBNL Divisional Fellow — Theoretical Particle Physics
2-Year Full-Time Postdoctoral Fellowship in Acoustics
Divisional Fellow — Experimental Particle Physics
IceCube Computing Facilities Manager
JWST Mission System Engineer
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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