Margarite, a native of the Baton Rouge area, is passionate about physics research. She participated in the National Institute of Standards and Technology (NIST) Summer Undergraduate Research Fellowship (SURF) program and recently presented some of her research "Multiparameter Estimation with Single Photons" at the Japan Society of Applied Physics-Optical Society of America joint symposia in Fukuoka, Japan thanks in part to the LSU Discover Travel Stipend!
China’s President Jinping Xi presented the 2017 International Science and Technology Cooperation Award of the People’s Republic of China to Professor Earl Ward Plummer, a faculty member in the LSU Department of Physics & Astronomy. Plummer was one of seven people to receive this award for his contribution to the development of science and technology in China.
A revolutionary material harbors magnetism and massless electrons that travel near the speed of light—for future ultrasensitive, high-efficiency electronics and sensors.
The Planet Hunters citizen science project announced the serendipitous discovery of KIC 8462852, a peculiar variable star observed by the NASA Kepler mission (Borucki et al. 2010) from 2009 to 2013 (Boyajian et al. 2016). KIC 8462852’s variability manifests itself as asymmetric drops in brightness of up to 22%, many of which last several days (the “dips”). There is little or no sign of periodicity in the four years of Kepler observations (but see Kiefer et al. 2017). Additionally, the duty cycle of the dips is low, occurring for less than 5% of the four-year period Kepler observed it. Subsequent ground-based follow-up observations to better characterize the star revealed nothing other than KIC 8462852 being an ordinary, main-sequence F3 star: no peculiar spectral lines, Doppler shifts indicative of orbiting companions, or signs of youth such as an infrared excess (Lisse et al. 2015; Marengo et al. 2015; Boyajian et al. 2016; Thompson et al. 2016).
We report ground-based spectrophotometry of KIC 8462852, during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour-signature, and are deeper in visual blue wavelengths than in red ones. The flux loss' wavelength dependency can be described with an \AA ngstr\"om absorption coefficient of 2.19±0.45, which is compatible with absorption by optically thin dust with particle sizes on the order of 0.0015 to 0.15 μm. These particles would be smaller than is required to be resistant against blow-out by radiation pressure when close to the star. During occultation events, these particles must be replenished on time-scales of days. If dust is indeed the source of KIC 8462852's dimming events, deeper dimming events should show more neutral colours, as is expected from optically thick absorbers.
A team of more than 100 researchers, led by LSU Department of Physics & Astronomy Assistant Professor Tabetha Boyajian, is one step closer to solving the mystery behind the “most mysterious star in the universe.” KIC 8462852, or “Tabby’s Star,” nicknamed after Boyajian, is otherwise an average star. It is about 50 percent bigger and 1,000 degrees hotter than the Sun. It is more than 1,000 light years away. However, it has been inexplicably dimming and brightening sporadically like no other. Several theories abound to explain the star’s unusual light patterns including an alien megastructure orbiting the star.
Robert F. O'Connell, PhD, LSU Boyd professor, has retired after a distinguished career as a researcher, administrator and mentor. He joined the faculty of the LSU Department of Physics & Astronomy in January 1964 as a tenure-track assistant professor.
A long term program of photoelectric UBVRI photometry has been combined with AAVSO archival data for the hot, R CrB-type hydrogen deficient star MV Sgr. A deep minimum and a trend of decreasing brightness over time at maximum light thereby become evident. Variations seen via monitoring with a CCD detector also are described.
Colleen Fava, program manager of the Louisiana Space Grant Consortium (LaSPACE) / NASA EPSCoR, has been announced as one of the recipients of the 2017 LSU Foundation Staff Outstanding Service Awards. This annual award was established to recognize the superior work performance and outstanding contributions of full-time, non-academic staff employees of the LSU A&M campus and the LSU AgCenter.
This research showed the dramatic dependence of the magnetic state on the size of the crystal lattice and points out the opportunity for exploring the origins of anti-symmetric interactions through a combination of experiment, neutron scattering, and electronic structure calculation.
On Friday December 8, 2017, LSU Board of Supervisors awarded Professor Ward Plummer the rank of Boyd Professor. The Boyd Professorship is the highest professorial rank awarded by the LSU System and is given only to professors who have attained national or international distinction for outstanding teaching and research. Plummer is the 75th Boyd Professor named across LSU, and the 49th from the Flagship campus to be awarded the coveted title since it was established in 1953 to honor brothers David and Thomas Boyd, early faculty members and presidents of LSU. With this appointment, there are now 11 active Boyd Professors at the Flagship University.
On Friday, December 15, LSU Physics & Astronomy welcomed 3 new PhD, 3 MS and 2 BS graduates who conferred their degrees at the Maddox Fieldhouse.
We show that rapid optical flux variations from an accreting Galactic black-hole binary are delayed with respect to X-rays radiated from close to the black hole by about 0.1 seconds, and that this delayed signal appears together with a brightening radio jet. The origin of these subsecond optical variations has hitherto been controversial.
Physics World has announced that the Physics World 2017 Breakthrough of the Year goes to “the international team of astronomers and astrophysicists that ushered in a new era of astronomy by making the first ever multi-messenger observation involving gravitational waves.” The staff of the LIGO Livingston Observatory, together with students and scholars in residence, and including many from LSU, have worked hard for many years to operate and improve the detector, making it capable of participating in this discovery. Another LSU research project was recognized as Physics World announced its top 10 breakthroughs of the year: Ultra-high-energy cosmic rays have extra-galactic origins. LSU Department of Physics & Astronomy Professor Jim Matthews, former co-spokesperson of the Auger Collaboration, works with more than 500 scientists from 17 countries on the world’s leading science project for the exploration of the highest energy cosmic rays to elucidate the origins and properties of the most energetic particles in the universe.
Episode 3 of @LSUExperimental is out featuring @lsuscience
Former LSU PhD student Kaushik Seshadreesan and Assistant Professor Mark M. Wilde, along with their colleague Masahiro Takeoka of NICT Japan, have published their results on quantum key distribution (QKD) in Physical Review Letters. In their paper, they have calculated the maximum transmission rates for any QKD protocol conducted in a broadcast scenario over lossy channels, in which there is a single sender communicating to multiple receivers. They have found a protocol that significantly outperforms a naive time-sharing strategy, which has previously been used in QKD experiments. They have also found a different protocol that comes close to the ultimate limit for this task, and which could be implemented in practical experimental setups.
Assistant Professor Mark M. Wilde, along with colleagues Marco Tomamichel (Univ. Tech. Sydney), Mario Berta (Imperial College), and Seth Lloyd (MIT), have published their findings on quantum illumination in Physical Review Letters. In their work, they derived a formula for the relative entropy variance of quantum Gaussian states. This formula is helpful in characterizing the quantum limits on the distinguishability of quantum Gaussian states, which are states that quantum optics experimentalists can easily create and manipulate in the laboratory. They also applied the formula to quantum illumination, which is the task of determining whether there is a low-reflectivity object embedded in a target region with a bright thermal-noise bath. Wilde and his colleagues found that a quantum illumination transmitter can achieve an error probability exponent stronger than a coherent-state transmitter of the same mean photon number, and furthermore, that it requires far fewer trials to do so. This occurs when the background thermal noise is either low or bright, which means that a quantum advantage over a classical strategy is even easier to witness than in previously considered setups because it occurs for a larger range of parameters. Going forward from here, Wilde et al. expect the formula to have applications in settings well beyond those considered in their paper, especially to quantum communication tasks involving quantum Gaussian channels.
Katherine Nugent, an undergraduate student with an intriguing path into LSU's Physics & Astronomy program. This summer, Katherine helped develop comparison stars for Tabby's Star, a strange star named after LSU researcher Tabby Boyajian that displays odd dips in brightness that may be caused by dust formations. Boyajian's group may learn more about this mysterious star by comparing it's random light dips to other stars nearby.
News article " First cosmic-ray results from CALET on the ISS" about CALET in December issue of CERN Courier, p.9
Jorge Pullin has been appointed to the Advisory Board of the Journal of Universe
The hydrogen atom is the simplest system of atomic and molecular physics, while a two-qubit system is the simplest of quantum information. Remarkably, they share common symmetry aspects which are described in this paper.
Arlo U. Landolt has been elected to a term on the Council of the American Association of Variable Star Observers (AAVSO), 2017-2019.
The CALET Cosmic Ray experiment, led by Professor Shoji Torii from Waseda University in Japan, along with collaborators from LSU and other researchers in the U.S. and abroad, have successfully carried out the high-precision measurement of cosmic-ray electron spectrum up to 3 tera electron volts (TeV) by using the CALorimetric Electron Telescope (CALET) on the Japanese Experimental Module, the Exposed Facility on the International Space Station (ISS). This experiment is the first to make direct measurements of such high energy electrons in space.
More than 100 years after Albert Einstein predicted gravitational waves -- ripples in space-time caused by violent cosmic collisions -- LIGO scientists confirmed their existence using large, extremely precise detectors in Louisiana and Washington. Astrophysicist Gabriela González of the LIGO Scientific Collaboration tells us how this incredible, Nobel-winning discovery happened -- and what it might mean for our understanding of the universe. (In Spanish with English subtitles.)
Plasmons, the collective excitations of electrons in the bulk or at the surface, play an important role in the properties of materials, and have generated the field of “plasmonics.” We report the observation of a highly unusual acoustic plasmon mode on the surface of a three-dimensional topological insulator (TI) Bi2Se3, using momentum resolved inelastic electron scattering. In sharp contrast to ordinary plasmon modes, this mode exhibits almost linear dispersion into the second Brillouin zone and remains prominent with remarkably weak damping not seen in any other systems. This behavior must be associated with the inherent robustness of the electrons in the TI surface state, so that not only the surface Dirac states but also their collective excitations are topologically protected. On the other hand, this mode has much smaller energy dispersion than expected from a continuous media excitation picture, which can be attributed to the strong coupling with surface phonons.
We have studied La2/3Sr1/3MnO3 thin films grown on (3×1)-reconstructed SrTiO3 (110) substrates. Films with thicknesses less than the critical thickness of θc≅8 unit cells are insulating in the measured temperature (T) range (2–400 K). However, films with thicknesses slightly over θc exhibit reentrant nonmetallic behavior at low temperatures in addition to the normally observed metal-insulator transition at higher temperatures. In contrast, the magnetization does not show signs of low-T transitions. Such reentrance of a low-T nonmetallic phase is affected by the film thickness as well as the density of oxygen vacancies. The electrical resistivity analysis reveals that localization effects are responsible for the reentrant nonmetallic behavior, which is enhanced with reduced film thickness. Reentrance of low-temperature nonmetallic phase of L a 2 / 3 S r 1 / 3 Mn O 3 (110) thin films. Available from: https://www.researchgate.net/publication/319241498_Reentrance_of_low-temperature_nonmetallic_phase_of_L_a_2_3_S_r_1_3_Mn_O_3_110_thin_films [accessed Oct 20 2017].
Discovery made at LIGO Livingston by LSU physicists marks first cosmic event observed in both gravitational waves and light - For the first time, scientists have directly detected gravitational waves — ripples in space and time — in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light. The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory, or LIGO; the Europe-based Virgo detector; and some 70 ground- and space-based observatories.
The Gravitational Wave Astrophysics conference sponsored by the International Astronomical Union will livestream the LIGO Laboratory, LIGO Scientific Collaboration, National Science Foundation and Virgo Collaboration press conference. Journalists are invited to watch the livestream of the press conference on Monday, Oct. 16, at 9 a.m. (CDT) from the National Press Club in Washington, D.C. The livestreamed press conference will begin with an overview of new findings from LIGO, Virgo and partners that span the globe, followed by details from telescopes that work with the LIGO and Virgo Collaboration to study extreme events in the cosmos.
The invention will enhance protection of radiation workers, such as radiologists. Those who work in radiation fields are at increased risk to develop cataracts, cancer, and other radiation effects. Our device accurately measures, records, and reports exposure to the user in real time, thereby providing the information needed to limit exposures to safe levels.
oday the 2017 Nobel Prize in Physics was awarded to the pioneering leaders of the Laser Interferometer Gravitational-wave Observatory, or LIGO, for the first detection of gravitational waves. The detection confirmed a major prediction of Albert Einstein's 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
The National Science Foundation, or NSF, announced new awards for non-tenured researchers through their Established Program to Stimulate Competitive Research, or EPSCoR, Research Infrastructure Improvement Track-4 fellowship program. Kristina Launey, LSU Ph.D. ('03) alumna and assistant professor in the Department of Physics & Astronomy, is one of 30 to receive the NSF Research Fellowship. These fellowships partner researchers with premier research centers, enhancing their ability to work at the frontiers of science and engineering.
- In a paper published in the journal Science, the Pierre Auger Collaboration reports observational evidence demonstrating that cosmic rays with energies a million times greater than that of the protons accelerated in the Large Hadron Collider come from much further away than from our galaxy. LSU Department of Physics & Astronomy Professor Jim Matthews, former co-spokesperson of the Auger Collaboration, works with more than 500 scientists from 17 countries on the world's leading science project for the exploration of the highest energy cosmic rays to elucidate the origins and properties of the most energetic particles in the Universe. The collaboration is reconstructing the path of the Universe's most energetic cosmic rays, bringing new insights into the origin and nature of this intergalactic phenomenon.
This work tested the feasibility of a silicon-on-insulator microdosimeter, which mimics the size and shape of specific cells within the human body, to determine dose equivalent from neutron irradiation. The microdosimeters were analyzed in terms of their basic diode characteristics, i.e., leakage current as a function of bias voltage. Lineal energy spectra were acquired using two different converter layers placed atop the microdosimeter: a tissue-substitute converter made from high-density polyethylene, and a boron converter consisting of epoxy coated with boron powder. The spectra were then converted into absorbed dose and dose equivalent. Experimental results were compared to Monte Carlo simulations of the neutron irradiations, revealing good agreement. Uncertainty in the dose equivalent determinations was 7.5% when using the cell-shaped microdosimeter with the tissue-substitute converter and 13.1% when using the boron converter. This work confirmed that the SOI approach to cell-mimicking microdosimetry is feasible.
Homoepitaxial SrTiO3(110) film is grown by molecular beam epitaxy in ultra-high vacuum with oxygen diffusing from substrate as the only oxidant. The resulted oxygen vacancies (VOs) are found to be spatially confined within few subsurface layers only, forming a quasi-two-dimensional doped region with a tunable high concentration. Such a δ-function distribution of VOs is essentially determined by the thermodynamics associated with the surface reconstruction, and facilitated by the relatively high growth temperature. Our results demonstrate that it is feasible to tune VOs distribution at the atomic scale by controlling the lattice structure of oxide surfaces.
The purpose of this study was to evaluate the impact of selected configuration parameters that govern multileaf collimator (MLC) transmission and rounded leaf offset in a commercial treatment planning system (TPS) (Pinnacle3, Philips Medical Systems, Andover, MA, USA) on the accuracy of intensity-modulated radiation therapy (IMRT) dose calculation. The MLC leaf transmission factor was modified based on measurements made with ionization chambers. The table of parameters containing rounded-leaf-end offset values was modified by measuring the radiation field edge as a function of leaf bank position with an ionization chamber in a scanning water-tank dosimetry system and comparing the locations to those predicted by the TPS. The modified parameter values were validated by performing IMRT quality assurance (QA) measurements on 19 gantry-static IMRT plans. Planar dose measurements were performed with radiographic film and a diode array (MapCHECK2) and compared to TPS calculated dose distributions using default and modified configuration parameters. Based on measurements, the leaf transmission factor was changed from a default value of 0.001 to 0.005. Surprisingly, this modification resulted in a small but statistically significant worsening of IMRT QA gamma-index passing rate, which revealed that the overall dosimetric accuracy of the TPS depends on multiple configuration parameters in a manner that is coupled and not intuitive because of the commissioning protocol used in our clinic. The rounded leaf offset table had little room for improvement, with the average difference between the default and modified offset values being −0.2 ± 0.7 mm. While our results depend on the current clinical protocols, treatment unit and TPS used, the methodology used in this study is generally applicable. Different clinics could potentially obtain different results and improve their dosimetric accuracy using our approach.
Since its discovery two years ago, a star that resides around 1,300 light years from Earth has gained a reputation as the most bizarre in the galaxy. Named KIC 8462852, the star gained worldwide attention when scientists suggested its weird behaviour could be explained by the presence of a huge shield built by an advanced alien civilization. Back then Tabetha Boyajian, from Louisiana State University, and her colleagues discovered that KIC 8462852 exhibited huge dips in its brightness at regular intervals using data from the Kepler Space Telescope—sometimes by as much as 20 percent.
Imagine taking a prediction made a hundred years ago by one of the greatest minds of the 20th century and finding the evidence to prove it to be true today. That’s what an Argentine-born female physicist did as part of a team of scientists in Louisiana. By validating Albert Einstein’s theory of relativity, they are being showered with worldwide acclaim, and the near certainty of a Nobel Prize. John Zarrella spent time with Dr. Gabriela Gonzalez, who insists there is more to come.
In 2010, there were 24 proton therapy centers operating around the world. During the past 6 years, 33 new centers have opened, 32 are under construction, and 17 are in the planning phase (1).
A pilot project this summer at Oak Ridge Associated Universities, or ORAU, hearkens back to the organization’s roots ...... A near-certain outcome is that the students will finish their internships with a head start on a project that could become their master’s thesis or doctoral dissertation. Such is the case for Daniel DiMarco from Marrero, La.
On August 21, 2017, more than a thousand astronomy enthusiasts gathered on the LSU Parade Ground to view the Great American Eclipse. Physics & Astronomy Department Chair John DiTusa and WAFB chief meteorologist Jay Grymes emceed the event on the first day of class for the fall semester. While students, faculty and staff shared solar viewing glasses to look at the partial eclipse, faculty talked about the science and history of the eclipse, including Manos Chatzopoulos, Gabriela Gonzalez and Rob Parks. Attendees also experienced alternative ways to view the eclipse with a sun spotter, solar filter disk, pinhole cameras, and even viewing the eclipse on the ground through the oak trees.
WAFB Chanel 9 interviewed Dr. Chatopoulos's for Solar Eclipse event in LSU.
On August 21, a solar eclipse will pass across the United States, first darkening Oregon and creating a path of totality all the way to South Carolina over the course of a few hours. Everyone along this path will experience a few minutes of complete darkness along with the spectacular features of a total solar eclipse. The rest of the nation will experience a partial solar eclipse. Those not along the path of totality may feel like they are missing out, but NASA’s Eclipse Balloon Project has a solution for that!
August 21, 12-2pm lsu parade ground rain location: union
On Friday, August 4, LSU Physics & Astronomy welcomed 4 new PhD, 3 MS and 4 BS graduates who conferred their degrees at the Marvavich Assembly Center.
Advances in modern electronics has demanded the requisite hardware, transistors, to be smaller in each new iteration. Recent progress in nanotechnology has reduced the size of silicon transistors down to the order of 10 nanometers. However, for such small transistors, other physical effects set in, which limit their functionality. For example, the power consumption and heat production in these devices is creating significant problems for device design. Therefore, novel quantum materials and device concepts are required to develop a new generation of energy-saving information technology. The recent discoveries of topological materials — a new class of relativistic quantum materials — hold great promise for use in energy saving electronics. Researchers in the Louisiana Consortium for Neutron Scattering, or LaCNS, led by LSU Department of Physics & Astronomy Chair and Professor John F. DiTusa and Tulane University Professor Zhiqiang Mao, with collaborators at Oak Ridge National Lab, the National High Magnetic Field Laboratory, Florida State University, and the University of New Orleans, recently reported the first observation of this topological behavior in a magnet, Sr1-yMn1-zSb2 (y, z < 0.1). These results were published this week in Nature Materials (doi:10.1038/nmat4953).
BATON ROUGE - On August 21, 2017, a solar eclipse will be visible across North America, passing through the U.S. from Oregon to South Carolina. A solar eclipse occurs when the Moon's shadow passes over the Earth's surface, temporarily blocking the view of the Sun from the Earth. The last time a total solar eclipse occurred in the continental U.S. was 1979. This year, on Aug. 21, the eclipse will pass over the country again, with an 80% partial eclipse visible in Louisiana. With a grant from the Louisiana Space Grant Consortium (LaSPACE), Dr. Dana Browne, Professor and Associate Chair of the LSU Department of Physics & Astronomy, led a small team of K-12 teachers to develop a website toolkit for educators to teach students about the solar eclipse.
Charge density wave (CDW) is an important concept in condensed matter physics, germane to a number of physical phenomena. But the origin of CDW is still under debate, partly because the origin and properties of CDW are highly material-dependent. The concept of a CDW has been applied to many materials without a clear definition of the fundamental nature of CDW. As a result, misconceptions about CDW can be seen in literature. In this review, we will try to describe and explain the possible existing misconceptions associated with the origin of CDWs.
A team of students and faculty from the Louisiana Space Grant Consortium, LaSPACE, led by LSU and including Delgado Community College, or DCC; Louisiana Tech University, or LaTech; and McNeese State University, or MSU, will launch two high-altitude balloons on Aug. 21 as part of a NASA-sponsored project to live-stream aerial video footage of the “Great American Eclipse.”
Among topological materials, experimental study of topological semimetals that host Dirac/Weyl fermions has just begun, even though these topological concepts were proposed nearly a century ago by Dirac and Weyl. Our work shows magnetic-semimetal BaMnSb2 exhibits nearly zero-mass fermions with high mobility and a non-trivial Berry phase. What is unique is the magnetic ordering, indicating the system is Weyl type due to time-reversal symmetry breaking. Theory shows that the spin order is very fragile, so it is expected that the application of magnetic field or uniaxial pressure could drive the material to be a type-II Weyl semimetal.
Developments in synthesis and characterization of artificially structured materials has greatly advanced the possibility to explore new states of matter in material science. Recent discoveries show that new quantum states can be achieved at hetero-interfaces with various electromagnetic and mechanical boundary conditions. It remains an open question on how to design ultrathin layers with properties inaccessible in bulk phases, which is amenable to technological applications. In this work, we grow heterostructures with extremely high quality interfaces, characterized by state-of-the-art atomically resolved electron microscopy and spectroscopy. This combination allows us to identify an interface-induced structure that stabilizes ferromagnetism. Coupled with theory, we provide conceptually useful recipe to design low-dimensional materials with novel functionalities, in line with the loop of “make, measure, model”.