Waves & Packets
Apr. 13, 2013

Are there signs of SUSY in Planck data?
Physics World
Evidence of supersymmetry could be lurking in the cosmic microwave background, according to a UK-based physicist who has calculated how the theory could affect fluctuations in the CMB. If these latest calculations are correct, the CMB could offer a window into dark matter and complement the search for SUSY at the Large Hadron Collider when it starts up again in 2015. SUSY postulates that every known particle has an as-yet-unseen partner known as a "superparticle" or "sparticle". Each sparticle has a corresponding field that should have been present in the universe's first moments. A line of reasoning, presented in Physical Review D, suggests that these SUSY fields are responsible for the fluctuations in the CMB, and that the statistical distributions of the fluctuations should be non-Gaussian. There are still significant problems in making a link between SUSY and cosmic inflation because the Planck data showed a Gaussian distribution of the fluctuations. A recent modification of the theory in light of the Planck data, and future cosmology experiments using the Square Kilometer Array may uncover some new physics beyond the Standard Model.More

Interdisciplinary team demonstrates superconducting qualities of topological insulators
University of Illinois
Coupling the surface state of a topological insulator to an s-wave superconductor is predicted to produce the long-sought Majorana quasiparticle excitations. A requisite step in the search for Majorana fermions is to understand the nature and origin of the supercurrent generated between superconducting contacts and a topological insulator. However, superconductivity has not been measured in surface states of a topological insulator when the bulk charge carriers are fully depleted, i.e., in the true topological regime that is relevant for investigating Majorana modes.

Experiments carried out in the laboratory of Illinois physicist and NSBP member, Nadya Mason, measured superconductive surface states in topological insulators where the bulk charge carriers were successfully depleted. Bulk carrier depletions were achieved by doping and employing an electrostatic gate. Theoretical modeling had indicated that superconductivity occurred only at the surface of topological insulators and that this is a unique characteristic of these materials. The experimental results, reported in Nature Communications, confirm the theory. One of the main results indicated that even in cases where there were excess electrons present in the bulk material (via impurities), the superconductivity was mediated through the surface states. This new understanding of how topological insulators behave with regard to superconductivity will assist in the search for the Majorana quasiparticle.More

Physicists create optical analogue to topological insulator
Physics World
Topological insulators have energy differences between their surface states and their bulk states that are so large that an electron moving along the surface cannot scatter into the bulk. Several groups have been pursuing an optical analogue where propagation would persist in edge states without leakage into bulk states. As reported in Nature, a team of physicists has fabricated an array of helical waveguides that behaves completely as a photonic analogue to topological insulators, even in the presence of defects, just like in the case of electronic topological insulators. The group’s idea for such a photonic waveguide follows from the proposition that a topological insulator could be created in a material by subjecting it to time-varying electromagnetic fields. It turns out that the 2-D Schrodinger equation for topological insulators in that case has the same form as the equation that describes the 3-D propagation of light through an array of light guides — if the direction along the waveguides is treated as time rather than the z component of space.More

X-rays reveal coexisting structures in glass
Surprisingly little is known about the interplay between the mechanical properties of glasses and their inner structures. Unlike water, which freezes from a fluid into an ordered solid, the glassy phase retains a fluid-like structure with little order. Nevertheless, the material becomes highly viscous or even hard in the glassy state. Using a unique experimental setup at DESY’s PETRA III X-ray source, physicists have for the first time discovered coexisting structural states in glass and related them shear bands. The researchers established that small structural variations in the colloid glass, too small to have been previously detected, have a large impact on its flow behavior. For the smallest shear rate applied in their experiment, the viscosity of the glass was ten thousand times larger than the viscosity at the largest shear rate. In contrast, the observed structural change over the same range was only less than three percent. The research is published in Scientific Reports, an open access publication of the Nature Publishing Group.More

Experiments uncover rigid triaxial symmetry of germanium-76 nuclei
American Physical Society
Most atomic nuclei are spherical or ellipsoidal. But a much rarer possibility is a triaxial nucleus, which is shaped like a flattened football and was first predicted in 1960. Such nuclei shapes can be either rigid or soft, that is they oscillate between being squashed or unsquashed. Through angular momenta, experimentalist can distinguish between the two. Recent calculations predicted that most of the germanium isotopes have triaxial features in the ground state. In results reported in Physical Review C, a team of experimentalists have found evidence that 76Ge may be a rare example of a nucleus exhibiting rigid triaxial deformation in the low-lying states.More

Superheated Bose-Einstein condensate exists above critical temperature
A team of physicists has demonstrated that Bose-Einstein condensates can exist above the critical temperature. This, they explain in their Nature Physics paper, is just like how distilled water can exist as a superheated liquid above the normal boiling point. The researchers achieved this feat in an optically trapped potassium-39 gas by manipulating the interaction potential between condensed and non-condensed phases. By reducing the interaction potential, the phases become decoupled and they will evolve as two separate systems. This condition makes it possible for the BEC to maintain a higher chemical potential than the non-condensed phase, and thus survive far above its equilibrium transition temperature. If the interaction potential is increased the BEC will boil away, indicating that the lifetime of a BEC can be coherently controlled.More

Do elliptical galaxies have dark matter halos?
Kepler's laws tell us that stars further from the center of their galaxies should have lower rotational velocities. But rotation curves (plots of velocity vs. distance) of stars in spiral galaxies show that the rotational velocities remain constant as distance from the center increases. This tells us that there must be more mass than we can account for based on the light we observe from stars, i.e., that dark matter must exist. Rotation curves of spiral galaxies indicate that the distribution of dark matter extends far beyond the optical edges of the galaxies, i.e., they appear to be embedded in large dark matter "halos". But astronomers cannot measure rotation curves for elliptical galaxies. Instead, they can study the mass-to-light ratio of elliptical galaxies with gravitational lensing. From mass-to-light ratios in Hubble images of elliptical galaxies, two astronomers have found that there is no sign of large amounts of dark matter surrounding these galaxies. The results, submitted to the Astrophysical Journal, suggest that, if dark matter is present in early-type galaxies, its amount does not exceed the amount of luminous matter and its density follows that of luminous matter, in sharp contrast to what is found from rotation curves of spiral galaxies.More

PET scans monitor brain circuits activated by light
Brookhaven National Lab
In research described in the Journal of Neuroscience, scientists at Brookhaven National Lab have exploited light-activated proteins to stimulate particular brain cells. They also used positron emission tomography (PET) scans to trace the effects of that site-specific stimulation throughout the entire brain. The new brain-mapping method combines very recent advances in a field known as "optogenetics" — the use of optics (light activation) and genetics (genetically coded light-sensitive proteins) to control the activity of individual neurons. Using this technique, scientists can specifically follow glucose update by brain cells and associate that with neuro-stimulation and behavior.More

Injectable LEDs shed light on neural processes
The field of optogenetics has provided new insight into complex brain function and has offered some new therapeutic modalities. In research reported in Science, a team of researchers have fabricated ultrathin ribbons with LEDs electrodes and sensors and safely implanted them into the brains of mice to provide insight into the workings of the brain. The complete device platform includes LEDs, temperature and light sensors, microscale heaters and electrodes that can both stimulate and record electrical activity, but they were specifically designed to be minimally invasive. The mice where genetically engineered so that specific neurons in their brains responded to light. Specific neural processes could then be controlled via a wireless signal. The researchers used the devices to activate networks of brain cells that are influenced by dopamine-mediated responses that animals find rewarding. The implants might even be useful in other types of neuroscience studies or may even be applied to different organs. Related devices already are being used to stimulate peripheral nerves for pain management.More

Solar flare indicates Earth-directed coronal mass ejection
The Sun emitted a M6.5 flare on the morning of April 11. It was also associated with an Earth-directed coronal mass ejection that can send billions of tons of solar particles into space and can reach Earth one to three days later. CMEs can trigger geomagnetic storms, and can affect electronic systems in satellites and on the ground. NOAA's Space Weather Prediction Center is official source for space weather forecasts, alerts, watches and warnings in the US. The European Space Agency, the Asia-Pacific Regional Space Agency Forum and the South African National Space Agency fulfill a similar function. Updates will be posted over the next few days on the flare and its associated coronal mass ejection.More

CERN offers UN advice on bringing women into science
Symmetry Magazine
CERN dedicated its first act as an observer to the United Nations General Assembly to addressing the disparity between the number of men and women who build careers in science. Amongst the recommendations are the following: fight gender stereotypes at all levels, help young people build a strong physics identity, implement equitable parental leaves, and have broad discussions about gender issues at large scientific meetings. More

Letter to the editor
Waves and Packets
Dear editor,

I would like to draw your attention to another PRL article, published four years ago, which offers a simple quantitative explanation of the cosmic ray positron excess (Waves and Packets, Vol IV No 12), based on a series of publications from mostly 1993, PL Beirman, et al., Cosmic Ray Electrons and Positrons from Supernova Explosions of Massive Stars, Physical Review Letters, 103, 061101 (2009). The key is to consider the properties of the stars which explode. The analysis is really quite simple, and it explains the excess found by AMS and other experiments quantitatively, twenty years after the original series of papers was published.

Peter L. Bierman
Max Planck Institut für Radioastronomie, Bonn

Dear editor,

Referring to your story on the US Brain Initiative (Waves and Packets, Vol IV No 12), both the European Union and China are actively pursuing their own “brain initiatives”. European scientists have a 10-year, $1.5 billion Human Brain Project with support from the European Commission and 80 international research institutions. China's Brainnetome initiative has been producing a steady flow of research findings since 2004.

Kofi Berhane
University of Yaoundé, Cameroon More

National Society of Black Physicists jobs board postings
Assistant Editor, Physical Review D
Summer Internship
MIT Physics Lecturer/Sr. Lecturer
Martin and Michele Cohen Dean of Science
Visiting Assistant Professor
Instructor of Physics - North Carolina School of Science and Mathematics
Wiess Instructorship in Physics and Astronomy
Upper School Physics Teacher
Full-time Lecturer in Experimental Physics
Summer Intern
Postdoctoral Fellowship - Stanford Molecular Imaging Scholars Program
Postdoctoral Fellowship - Stanford Molecular Imaging Scholars Program
Summer Undergraduate Researcher

Experiments uncover rigid triaxial symmetry of germanium-76 nuclei
American Physical Society
Most atomic nuclei are spherical or ellipsoidal. But a much rarer possibility is a triaxial nucleus, which is shaped like a flattened football and was first predicted in 1960.More

DARPA, NIH and NSF embark on Brain Initiative
Medical News Today
President Barak Obama announced recently that he will ask for $100 million in his fiscal 2014 budget next week to sponsor the first year of the "BRAIN Initiative", a bold, new 10-year research effort to advance our understanding of the human brain and uncover new ways to treat, prevent and cure brain disorders like autism, epilepsy, traumatic brain injury, schizophrenia and Alzheimer's.More

Eagerly anticipated survey of cosmic-ray positrons reported in Physical Review Letters
American Physical Society
Via Physical Review Letters, the AMS Collaboration has reported its first results on the precision measurement of the positron fraction in primary cosmic rays for 0.5-350 GeV.More

Latest research from Physical Biology
IOP Publishing
Multi-ion conduction bands in a simple model of calcium ion channels

Physics of the immune system

Physical model of the immune response of bacteria against bacteriophage through the adaptive CRISPR-Cas immune system

Effect of deformability difference between two erythrocytes on their aggregation

Multiscale model for the effects of adaptive immunity suppression on the viral therapy of cancer More

Latest research from Physics of the Dark Universe
Gamma ray signals from dark matter: Concepts, status and prospects

Exploring the role of axions and other WISPs in the dark universe

Multi-component dark matter with magnetic moments for Fermi-LAT gamma-ray line

From gamma ray line signals of dark matter to the LHC

The empirical case for 10-GeV dark matter

SU(1,1) Lie algebraic approach for the evolution of the quantum inflationary universe More