Physics & Astronomy News
"The strange star discovered by Planet Hunters" by Brad Schaefer
The star KIC 8462852 is reasonably advertised as the most mysterious star in our galaxy. It is by almost all measures a perfectly ordinary F2 main-sequence star, which is to say that it is middle-aged and stable. At a temperature of 6750 K, it’s a bit hotter than our sun, and at 1.43 solar masses, it’s a bit more massive too. Until 2015 the star was unnoticed in the wing of the constellation Cygnus (the Swan), though at a distance of about 1500 light-years and an optical magnitude of about 12, the star is visible with a small telescope. When it was noticed, it created quite a splash.
Learn About the Physics of Superheroes at LSU on March 11
FOR IMMEDIATE RELEASE March 2, 2017 BATON ROUGE - LSU Department of Physics & Astronomy will host author and Professor James Kakalios for a fun and informative talk that will explore the science behind our favorite superheroes and answer these big questions: • Can memory materials explain how The Human Torch and Mr. Fantastic's costumes return to normal even after bursting into flames or stretching like rubber? • Have scientists found the secret to Spider Man's ability to climb walls? • Was it the fall or the webbing that killed Gwen Stacy in the classic /Amazing Spider Man/ #121? • What is the chemical composition of Captain America's shield? Superhero comic books get their science right more often than one would expect! Join Dr. Kakalios on Saturday, March 11 at 11 am on the LSU Campus in room 130 Nicholson Hall, across from the LSU Union on Tower Drive. Kakalios will be available to sign copies of his book, The Physics of Superheroes. James Kakalios is the Taylor Distinguished Professor in the University of Minnesota's School of Physics and Astronomy. His research interests include nanocrystalline and amorphous semiconductors and fluctuation phenomena in neurological systems. He has been reading comic books longer than he has been studying physics. To learn more about Kakalios, visit http://www.physicsofsuperheroes.com
Zhaoliang Liao, Rongying Jin, E. W. Plummer, and Jiandi Zhang, “Delicate Competing Electronic States in Ultrathin Manganite Films”, Phys. Rev. B 95, 085130 (2017)
The coupling between the electrical transport properties of La2/3Sr1/3MnO3 (LSMO) thin films and structural phase transitions of SrTiO3 (STO) substrates at Ts=105K has been investigated. We found that the electrical resistivity of LSMO films exhibit a “cusp” at Ts, which is greatly amplified by tuning films to the verge of metallic and insulating phases, i.e., to the boundary of two delicate competing electronic states. Our results demonstrate that small amounts of strain can tip the subtle balance of competing interactions and tune the electronic properties in correlated electron materials.
Kenneth Matthews Named American Association of Physicists in Medicine Fellow
LSU Department of Physics & Astronomy Associate Professor Kenneth "Kip" Matthews II, has been named a Fellow of the American Association of Physicists in Medicine. A distinct honor among the medical physics profession, an AAPM Fellow honors members who have made significant contributions through service, the advancement of medical physics knowledge based upon independent original research or development, medical physics educational activities, especially in regard to the education and training of medical physicists, medical students, medical residents and allied health personnel, and leadership in the practice of medical physics.
"Primordial tensor modes of the early Universe" by Martínez and Olmedo
We study cosmological tensor perturbations on a quantized background within the hybrid quantization approach. In particular, we consider a flat, homogeneous and isotropic spacetime and small tensor inhomogeneities on it. We truncate the action to second order in the perturbations. The dynamics is ruled by a homogeneous scalar constraint. We carry out a canonical transformation in the system where the Hamiltonian for the tensor perturbations takes a canonical form. The new tensor modes now admit a standard Fock quantization with a unitary dynamics. We then combine this representation with a generic quantum scheme for the homogeneous sector. We adopt a Born-Oppenheimer ansatz for the solutions to the constraint operator, previously employed to study the dynamics of scalar inhomogeneities. We analyze the approximations that allow us to recover, on the one hand, a Schr\"odinger equation similar to the one emerging in the dressed metric approach and, on the other hand, the ones necessary for the effective evolution equations of these primordial tensor modes within the hybrid approach to be valid. Finally, we consider loop quantum cosmology as an example where these quantization techniques can be applied and compare with other approaches.
"The Medical Physics Workforce" by Wayne D. Newhauser
The medical physics workforce comprises approximately 24,000 workers worldwide and approximately 8,200 in the United States. The occupation is a recognized, established, and mature profession that is undergoing considerable growth and change, withmany of these changes being driven by scientific, technical, and medical advances. Presently, the medical physics workforce is adequate to meet societal needs. However, data are emerging that suggest potential risks of shortages and other problems that could develop within a few years. Some of the governing factors are well established, such as the increasing number of incident cancers thereby increasing workload, while others, such as the future use of radiation treatments and changes in healthcare economic policies, are uncertain and make the future status of the workforce difficult to forecast beyond the next several years. This review examines some of the major factors that govern supply and demand for medical physicists, discusses published projections and their uncertainties, and presents other information that may help to inform short-and long-term planning of various aspects of the future workforce. It includes a description of the general characteristics of the workforce, including information on its size, educational attainment, certification, age distribution, etc. Because the supply of new workers is governed by educational and training pathways, graduate education, post-doctoral training, and residency training are reviewed, along with trends in state and federal support for research and education. Selected professional aspects of the field also are considered, including professional certification and compensation. We speculate on the future outlook of the workforce and provide recommendations regarding future actions pertaining to the future medical physics workforce.
Mette Gaarde Named Outstanding Referee for Physical Review Journals
Professor Mette Gaarde has been selected by the American Physical Society (APS) as one of the Outstanding Referees for 2017, who has demonstrated exceptional work in the assessment of manuscripts published in the Physical Review journals.
A year later, scientists keep listening to gravitational waves, the soundtrack of the cosmos
LIGO scientists answered by saying that the experiment has already led to technological advances in “vibration isolation” and “laser stabilization,” as well as precision timekeeping. This is also a training ground for scientists moving into other arenas. But no one really sells LIGO on practical grounds. The main selling point: It’s knowledge for its own sake. LIGO probes the darkness, and reveals hidden and universal truths.
"Electron interaction with the spin angular momentum of the electromagnetic field" by R F O'Connell
We give a simple derivation and expansion of a recently proposed new relativistic interaction between the electron and the spin angular momentum of the electromagnetic field in quantum electrodynamics (QED). Our derivation is based on the work of Møller, who pointed out that, in special relativity, a particle with spin must always have a finite extension. After generalizing Møller's classical result to include both rotation and quantum effects, we show that it leads to a new contribution to the energy, which is the special relativistic interaction term. In addition, we show that all relativistic terms involving spin terms arising from the Dirac equation may be obtained by this method.
"What is Physics: The individual and the universal, and seeing past the noise" by A. R. P. Rau
Along with weaving together observations, experiments, and theoretical constructs into a coherent mesh of understanding of the world around us, physics over its past five centuries has continuously refined the base concepts on which the whole framework is built. In quantum physics, first in non-relativistic mechanics and later in quantum field theories, even familiar concepts of position, momentum, wave or particle, are derived constructs from the classical limit in which we live but not intrinsic to the underlying physics. Most crucially, the very idea of the individual, whether an object or an event, distinguished only in a mere label of identity from others identical to it in all the physics, exists only as an approximation, not an element of underlying reality. Failure to recognize this and seeking alternative explanations in many worlds or multiverses leads only to incoherent logic and incorrect physics.
Mark Wilde's Second Edition of his book "Quantum Information Theory" has been published
Developing many of the major, exciting, pre- and post-millennium developments from the ground up, this book is an ideal entry point for graduate students into quantum information theory. Significant attention is given to quantum mechanics for quantum information theory, and careful studies of the important protocols of teleportation, superdense coding, and entanglement distribution are presented. In this new edition, readers can expect to find over 100 pages of new material, including detailed discussions of Bell's theorem, the CHSH game, Tsirelson's theorem, the axiomatic approach to quantum channels, the definition of the diamond norm and its interpretation, and a proof of the Choi-Kraus theorem. Discussion of the importance of the quantum dynamic capacity formula has been completely revised, and many new exercises and references have been added. This new edition will be welcomed by the upcoming generation of quantum information theorists and the already established community of classical information theorists. Contains over 100 pages of new material, including many new exercises and references Offers an extensive overview of classical information theory and recent advances in quantum information theory for the non-expert Provides applications to many example quantum channels of practical interest, including depolarizing, amplitude dampening, and erasure channels
"Milestones of general relativity" by Jorge Pullin
We present a summary for non-specialists of the special issue of the journal Classical and Quantum Gravity on 'Milestones of general relativity', commemorating the 100th anniversary of the theory.
"Brief review on black hole loop quantization" by Javier Olmedo
Here, we present a review about the quantization of spherically-symmetric spacetimes adopting loop quantum gravity techniques. Several models that have been studied so far share similar properties: the resolution of the classical singularity and some of them an intrinsic discretization of the geometry. We also explain the extension to Reissner---Nordstr\"om black holes. Besides, we review how quantum test fields on these quantum geometries allow us to study phenomena, like the Casimir effect or Hawking radiation. Finally, we briefly describe a recent proposal that incorporates spherically-symmetric matter, discussing its relevance for the understanding of black hole evolution.
LSU Announces New CAMD Director Richard Kurtz
BATON ROUGE –LSU Department of Physics & Astronomy Professor Richard L. Kurtz has been named director of the Center for Advanced Microstructures and Devices, or CAMD.
Chinese Academy of Sciences Awards LSU Physicist for International Scientific Contributions
LSU Department of Physics & Astronomy Professor E. Ward Plummer has been honored with the Award for International Scientific Cooperation from the Chinese Academy of Sciences, or CAS. He is one of three international experts to receive this award in 2016. He is the only physicist from the US to have ever received this award. Plummer received the award for his contributions to build a talent pool of professionals with international vision. For more than 16 years, Plummer has actively promoted substantive collaboration in science and technology as well as talent cultivation between CAS and LSU. With his support, the Institute of Physics worked with LSU to develop a dual degree program in physics, where students spend at least two years at each institution, taking their core courses at the home institution and doing their research and advanced courses at the host institution.
Param Singh and Sahil Saini discuss research discovering framework to guarantee resolution of singularities
A research paper by graduate student Sahil Saini and Prof. Param Singh has been highlighted by Classical and Quantum Gravity journal. The paper proves genericness of singularity resolution for spacetimes closely related to black hole spacetimes. Based on these results, Classical and Quantum Gravity requested Dr. Singh to write a popular science insight on this research direction for their website. For the popular science article on how to destroy a singularity, see below: https://cqgplus.com/2017/01/23/want-to-crush-a-singularity-first-make-it-strong-and-then/
National Academy of Sciences Honors Gaby Gonzalez & LIGO Researchers
The National Academy of Sciences announced today that LSU Professor of Physics and Astronomy Gabriela González is one of the recipients of the academy’s 2017 Award for Scientific Discovery.
Top High-Energy Astrophysics Prize Awarded to LSU Physicist and LIGO Scientist Gabriela González
The 2017 Rossi Prize has been awarded to Gabriela González and the LIGO Scientific Collaboration for the first direct detections of gravitational waves, for the discovery of merging black hole binaries and for beginning the new era of gravitational-wave astronomy.
Tabby's Star: The Most Mysterious Star in the Universe
Tabetha Boyajian, an assistant professor of Physics and Astronomy at LSU and a new addition to LSU College of Science faculty as of fall 2016, has a star in her name. But Tabby’s Star, or more officially KIC 8462852, isn’t just any old star. It’s been called the most mysterious star in the universe.
"Evolution in totally constrained models: Schrödinger vs. Heisenberg pictures" by Javier Olmedo
We study the relation between two evolution pictures that are currently considered for totally constrained theories. Both descriptions are based on Rovelli's evolving constants approach, where one identifies a (possibly local) degree of freedom of the system as an internal time. This method is well understood classically in several situations. The purpose of this paper is to further analyze this approach at the quantum level. Concretely, we will compare the (Schr\"odinger-like) picture where the physical states evolve in time with the (Heisenberg-like) picture in which one defines parametrized observables (or evolving constants of the motion). We will show that in the particular situations considered in this manuscript (the parametrized relativistic particle and a spatially flat homogeneous and isotropic spacetime coupled to a massless scalar field) both descriptions are equivalent. We will finally comment on possible issues and on the genericness of the equivalence between both pictures.