Waves & Packets
Jun. 9, 2012

The evolution of interdisciplinarity in physics research
Econophysics Forum
In a paper recently posted on arXiv, a trio of researchers from Finland explore the relationships between the subfields of physics using the Physics and Astronomy Classification Scheme. They observe a clear trend towards increasing interactions between the different subfields. The network of subfields also exhibits core-periphery organization, the nucleus being dominated by condensed matter and general physics. However, over time interdisciplinary physics is steadily increasing its share in the network core, reflecting a shift in the overall trend of physics research.More

There is more hydrogen gas is in the universe than previously thought
Commonwealth Scientific and Industrial Research Organisation
By taking a new look at some archival data, an Australian astronomer has discovered that galaxies around us are hiding about a third more atomic hydrogen gas than previously calculated. The study, which is published in the Astrophysical Journal, also shows that the gas is distributed very differently from how it was in the past, with much less in the galaxies' outer suburbs than billions of years ago. This new finding does not solve the dark matter problem, but it does help explain why stars are forming 20 times more slowly now than in the past.More

What's so important about molecular hydrogen anyway?
Astrobites
Giant dense clouds of molecular hydrogen gas are important because observational evidence tells us that stars form in such clouds. Dense clouds of molecular hydrogen gas self-shield. That is, gas at the periphery of the cloud shields the interior, and that is important in helping the cloud cool into a star forming region. However, should a supernova occur near a cloud of molecular hydrogen gas, two major things happen. First, the molecular hydrogen readily absorbs energy from the explosion, which heats the gas and consequently inhibits star formation. Second, the gas acquires kinetic energy that displaces it to another region of space, which in turn could become a star forming region. These are just two aspects of what is commonly called "supernova feedback," which collectively are important effects to consider in galaxy evolution. A forthcoming paper in the Monthly Notices of the Royal Astronomical Society clearly demonstrates that inclusion of molecular gas in galaxy evolution simulations makes the overall amount of star formation more abundant and more efficient. The results suggest a diagnostic color vs. brightness test to "measure" the molecular gas content of an observed galaxy.More

X-ray 'echoes' map a supermassive black hole's environs
European Space Agency
As matter falls into the accretion disk of a supermassive black hole, internal friction heats the matter, which leads to emissions of UV light and soft X-rays. The outward glow from these emissions makes for a corona outward from the accretion disk and black hole. Light that is emitted inward from the corona towards the accretion disk either causes new soft X-ray emissions, new florescent emissions or gets reflected as hard X-rays from the disc. By measuring the time delays between the corona emission and these "reverberation" events, astronomers are able to map the vicinity of this black hole in unprecedented detail. Astronomers studying the galaxy NGC 4151 with the XMM-Newton space observatory have detected X-rays emitted and then reflected by ionized iron atoms very close to the supermassive black hole at the galaxy's core. This current work is reported in the Monthly Notices of the Royal Astronomical Society and is the first unequivocal evidence of time delay between emission from the corona and different parts of the disc in an AGN, hence confirming that the that the corona is clearly separated from the disc.More

Methane on Mars is not an indication for life
Max Planck Institut für Chemie — Otto Hahn Institut
It was a sensation when scientists discovered methane in Mars' atmosphere nine years ago. Many saw the presence of the gas as a clear indication of life on the inhospitable planet, as on Earth methane is produced predominantly by biological processes. Others assumed geological processes, such as volcanoes, to be the cause. In a Nature paper, a research team of chemists and geoscientists has shown that methane escapes from a meteorite if it is irradiated with UV light under Martian conditions. Since meteorites and interplanetary dust from space, which carry along carbonaceous compounds, continuously impact on the Martian surface, the researchers conclude that high-energy UV radiation triggers the release of methane from the meteorites. The temperature dependence of methane production by the lab samples correlate with spectrographic measurements on Mars itself. But the results do not preclude the possibility that there are in fact methane producing microbes on Mars. Curiosity, the Mars Rover that NASA expects to land at the beginning of August, will provide more details on the formation of methane, and maybe even final clarification as to whether or not there is life on Mars. More

Giant black hole kicked out of home galaxy
Harvard-Smithsonian Center for Astrophysics
Astronomers at the Harvard-Smithsonian Center for Astrophysics have made new observations using NASA's Chandra X-ray Observatory that at least pinpoints which of the two previously observed compact optical sources in the distant galaxy CID-42 is also an X-ray source. X-ray emission is telltale sign of AGNs, like supermassive black holes, and this new result suggests that just one of the optical sources is black hole, and the other is perhaps a region of intense star formation. Researchers have previously studied CID-42 using Hubble, the Magellan and Very Large Telescope in Chile, and the existence of the two compact optical sources indicated that it might harbor two active galactic nuclei, or a single recoiling AGN. Despite these new X-ray observations, they do not allow either the recoiling or the dual AGN scenario for CID-42 to be excluded. Spatially-resolved and higher-quality optical spectra, radio imaging, and CO or 21 cm observations will be necessary to further understand CID-24.More

Black holes can change regimes when returning mass and energy to the universe
Royal Astronomical Society
Black holes consume matter from a relatively two-dimensional accretion disk. They return a great deal of matter and energy to the universe, usually through X-ray emission and outflows of matter in powerful collimated jets. Many observations over several years have made clear that there is connection between the X-ray emission from a black hole and its jet outflow, and that the connection can be reflected in relative X-ray, radio and optical luminosities. There seems to be two different types of black holes based on this connection, and it was once thought that black holes were all the time of one type or the other. But through Chandra X-ray observations, and contemporaneous radio observations from the Expanded Very Large Array in New Mexico, as well as optical observations, a team of Dutch astronomers has determined that black holes can actually switch between the two types. The team's findings are published in two papers in the Monthly Notices of the Royal Astronomical Society.More

OPERA observes 2nd tau neutrino
Symmetry magazine
At the Neutrino 2012 conference in Japan, the OPERA collaboration announced its second observation of a tau neutrino, a particle that is extremely difficult to detect. The experiment, which made its first such observation in 2010, searches for evidence of neutrino oscillation, the process in which neutrinos transform from one type to another. Several other experiments have shown that neutrinos can spontaneously oscillate as they travel long distances, but OPERA is the first to catch a muon neutrino changing into a tau neutrino. More

Moon's tidal forces cause differences in proton orbits at LHC
Quantum Diaries
The next time you want to know if the moon is full, just check the luminosity plot from the LHC. It turns out that given the 27-km circumference of the accelerator, the gravitational force exerted by the moon on one side is not the same as the one felt at the opposite side, creating a small distortion of the tunnel. Since the moon's effect is very small, only large bodies like oceans feel its effect in the form of tides. But the LHC is such a sensitive apparatus, it can detect the minute deformations created by the small differences in the gravitational force across its diameter. The effect is of course largest when the moon is full. So, on full moon nights, the LHC beam controller has to periodically adjust the proton beam orbits.More

The gravitational Aharonov-Bohm effect
American Physical Society
The celebrated Aharonov-Bohm experiment showed that the electromagnetic potential — not just the fields — could have measurable effects on quantum particles. In a Physical Review Letters paper, an international team has proposed a gravitational equivalent of this experiment that they claim would demonstrate that particles need not experience any gravitational force in order to experience measurable effects from the gravitational potential. The experiment, they argue, would show that the potential is the true fundamental quantity, not the force. They would use an optical lattice to move ultracold atoms along a line in such a way that they would feel zero gravitational force. Splitting the atoms into matter waves and recombining them could show an interference pattern that could only result from the gravitational potential. In addition to the Aharonov-Bohm effect, the result would also constitute the first demonstration of a force-free gravitational redshift, where the two atomic matter waves serve as clocks experiencing different gravitational potentials. More

High-temperature superconductivity starts with nanoscale electronic islands
Cornell University
Using extremely precise scanning tunneling microscopes, physicists have shown for the first time that superconductivity in a material starts out in discrete islands or domains. These isolated nanoscale patches gradually expand as the amount of doping (electron sources) increases, eventually filling up the entire physical space. This new result, reported in Nature Physics, provides new views of Mottness, i.e., a material’s behavior as an insulator even though its band structure suggests it should be a conductor; as well as the so-called pseudogap region of superconductors, i.e., the missing electronic states between the insulating state near the Fermi energy and the superconducting state.More

Colloidal particles exhibit phasons in laser potential
PhysOrg
"Phasons" are low-energy collective atomic motions in quasicrystals that propagate throughout the structure. They are one of many properties of quasicrystals that do not exist in conventional crystals. Phasons can be modeled by two independent descriptions, either via continuum mechanics as hydrodynamic displacement of density waves, or via discrete excitation dynamics where atomic positions "flip" or "hop" through the quasicrystal. A research team in Germany has constructed a new model of phasons that links these two pictures. Using a colloidal model system where the particle motions are biased by external potential provided by a five-laser array, the researchers were able to force particles into a quasicrystal structure. By tuning the lasers, they could create a phasonic drift that causes atomic displacement, and could then use those to explore phasonic flips in the colloidal model. This new physical model is described in Physical Review Letters.More

Physicists use ultrafast lasers to create first tabletop X-ray device
University of Colorado-Bolder
An international research team led by the University of Colorado Boulder has generated the first laser-like beams of X-rays from a tabletop device. In work described in Science, the team showed that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5,000. The resulting beam emerges as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to more than 1.6 kilo–electron volts. The system exhibits high spatial coherence; and in principle allows the generation of pulses as short as 2.5 attoseconds. More

NASA cancels mission to study effects of black holes and neutron stars
Science Insider
NASA has cancelled Gravity and Extreme Magnetism Small Explorer, an X-ray telescope designed to indirectly measure the regions of distorted space around spinning black holes and neutron stars. It was scheduled to be launched in 2014. By systematically measuring the polarization of cosmic X-ray sources, the fundamental questions scientists hoped GEMS would answer included, Where is the energy released near black holes? Where do the X-ray emissions from pulsars and neutron stars originate? What is the structure of the magnetic fields in supernova remnants? The mission was supposed to cost no more than $119 million. But independent external reviews of the project found that the final costs were likely to exceed that cap by 20-30 percent. More

National Society of Black Physicists jobs board postings
NSBP
Accelerator Physicist/Engineer (Research Associate)
Advanced Topics in Astrostatistics
Biophotonic Solutions 2012 MIIPS Ultrafast Pulse Shaping Workshop
Faculty Positions in Science, Technology and Innovation
Research Datacenter and Computing Infrastructure Manager
SKA Project Scientist
Women's Business Enterprise National Council Student Program
3x Senior Astronomers — SKA Africa
Nanoscale Measurements For Soft Matter Systems
NASA Postdoctoral Fellowships
National Astrophysics and Space Science Program
Postdoctoral Research Associate PositionsMore

Latest reseach from Journal of Physics B: Atomic, Molecular and Optical Physics
IOP Journal
Atomic frequency comb memory with spin-wave storage in 153Eu3 +:Y2SiO5

The effect of frequency-mismatched spontaneous emission on atom-field entanglement

Quantum memory

Rephasing processes and quantum memory for light: reversibility issues and how to fix them

In situ determination of Zeeman content of collective atomic memoriesMore

Latest research from Annals of Physics
Elsevier
Graphene and the Zermelo optical metric of the BTZ black hole

Magnetic rogue wave in a perpendicular anisotropic ferromagnetic nanowire with spin-transfer torque

Quasi-coherent states for photon in time varying dielectric media

Unitary cocycle representations of the Galilean line group: Quantum mechanical principle of equivalence

Gauge anomaly cancellation in chiral gauge theoriesMore