Physics Commons^™

Boosted Top Production: Factorization And Resummation For Single-Particle Inclusive Distributions, Andrea Ferroglia, Simone Marzani, Ben D. Pecjak, Li Lin Yang

Publications and Research

We study single-particle inclusive (1PI) distributions in top-quark pair production at hadron colliders, working in the highly boosted regime where the top-quarkpTis much larger than its mass. In particular, we derive a novel factorization formula validin the small-mass and soft limits of the differential partonic cross section. This providesa framework for the simultaneous resummation of soft gluon corrections and small-mass logarithms, and also an efficient means of obtaining higher-order corrections to the differential cross section in this limit. The result involves five distinct one-scale functions, three of which arise through the subfactorization of soft real radiation in the small-mass limit. …

Spin Density Waves In Periodically Strained Graphene Nanoribbons, Nabil M. Al-Aqtash, Renat F. Sabirianov

Nebraska Center for Materials and Nanoscience: Faculty Publications

Zigzag graphene nanoribbons (ZGNRs) are antiferromagnetic in the ground state with zero net magnetization due to the compensation of contributions from opposite edges. Uniform deformations (both shear and axial) do not produce magnetization due to symmetry restrictions. However, we report the results of first-principles calculations that predict the induction of spin density waves (SDWs) in ZGNRs under non-uniform periodic strain. Using the density functional theory (DFT) method, we show that a sinusoidal magnetization variation along the axis of the ribbon occurs under a sinusoidal transversal shear strain. SDWs appear due to the presence of a strain gradient that induced asymmetry …

Investigation Of The Structure Of The Few Body Kaonic Nuclei Using The Method Of Hyperspherical Functions In Momentum Space, Roman Ya. Kezerashvili, Shalva M. Tsiklauri

Publications and Research

The kaonic clusters KNN and KNNN are studied within the method of hyperspherical functions in the momentum representation. Binding energies and widths of three- and four-body nuclear quasibound states are calculated by employing realistic NN potentials and the energy dependent chiral KN interaction, as well as a phenomenological KN potential. The comparison of the results of calculations obtained in the framework of the variational method, Faddeev, Faddeev-Yakubovsky equations, and method of hyperspherical functions in configuration space are discussed.

Low Mach Number Fluctuating Hydrodynamics Of Diffusively Mixing Fluids, Aleksandar Donev, Andy J. Nonaka, Yifei Sun, Thomas Fai, Alejandro Garcia, John B. Bell

Faculty Publications

We formulate low Mach number fluctuating hydrodynamic equations appropriate for modeling diffusive mixing in isothermal mixtures of fluids with different density and transport coefficients. These equations eliminate the fast isentropic fluctuations in pressure associated with the propagation of sound waves by replacing the equation of state with a local thermodynamic constraint. We demonstrate that the low Mach number model preserves the spatio-temporal spectrum of the slower diffusive fluctuations. We develop a strictly conservative finite-volume spatial discretization of the low Mach number fluctuating equations in both two and three dimensions. We construct several explicit Runge-Kutta temporal integrators that strictly maintain the …

Normal Modes Of A Small Gamelan Gong, Robert Perrin, Daniel Elford, Luke Chambers, Gerry M. Swallowe, Thomas R. Moore, Sinin Hamdan, Benjamin J. Halkon

Faculty Publications

Studies have been made of the normal modes of a 20.7 cm diameter steel gamelan gong. A finite-element model has been constructed and its predictions for normal modes compared with experimental results obtained using electronic speckle pattern interferometry. Agreement was reasonable in view of the lack of precision in the manufacture of the instrument. The results agree with expectations for an axially symmetric system subject to small symmetry breaking. The extent to which the results obey Chladni's law is discussed. Comparison with vibrational and acoustical spectra enabled the identification of the small number of modes responsible for the sound output …

Radiographic Image Quality Enhancement By The Use Of Copper Filters, Timothy T. Sakogawa, Bernice Mills

STAR Program Research Presentations

In x-radiography, filters are often used in order to improve the overall image quality. Filters achieve this by making the x-ray beam have less energy spread, resulting in a cleaner image. Step wedges of different materials were used to compare radiographic density with and without a copper filter to identify the effect of the copper filter at different energies and exposure times. The step wedges used were CRS 1018 (cold rolled steel), Stainless Steel 304L, Al 1100, Al 6061 T6, titanium, copper, PTFE (polytetrafluoroethylene or Teflon), brass, carbon, magnesium, phenolic, tungsten, and tantalum. Out of the 14 step wedges tested, …

Chirally Sensitive Electron-Induced Molecular Breakup And The Vester-Ulbricht Hypothesis, J. M. Dreiling, Timothy J. Gay

Timothy J. Gay Publications

We have studied dissociative electron attachment in sub-eV collisions between longitudinally polarized electrons and chiral bromocamphor molecules. For a given target enantiomer, the dissociative Br anion production depends on the helicity of the incident electrons, with an asymmetry that depends on the electron energy and is of order 3 × 10⁻⁴. The existence of chiral sensitivity in a well-defined molecular breakup reaction demonstrates the viability of the Vester-Ulbrict hypothesis, namely, that the longitudinal polarization of cosmic beta radiation was responsible for the origins of biological homochirality.

The Spin State Of A Molecular Adsorbate Driven By The Ferroelectric Substrate Polarization†, Xin Zhang, Tatiana Palamarciuc, Jean-François Létard, Patrick Rosa, Eduardo Vega Lozada, Fernand Torres, Luis G. Rosa, Bernard Doudin, Peter A. Dowben

Peter Dowben Publications

The spin state of [Fe(H₂B(pz)₂)₂(bipy)] thin films is mediated by changes in the electric field at the interface of organic ferroelectric polyvinylidene fluoride with trifluoroethylene (PVDF–TrFE). Signatures of the molecular crossover transition are evident in changes in the unoccupied states and the related shift from diamagnetic to paramagnetic characteristics. This may point the way to the molecular magneto-electric effect on devices.

Positive Exchange Bias In Epitaxial Permalloy/Mgo Integrated With Si (100), S. S. Rao, J. T. Prater, Fan Wu, S. Nori, D. Kumar, Lanping Yue, Sy_Hwang Liou, Jagdish Narayan

Sy-Hwang Liou Publications

In magnetic random access memory (MRAM) devices, soft magnetic thin film elements such as permalloy (Py) are used as unit cells of information. The epitaxial integration of these elements with the technologically important substrate Si (100) and a thorough understanding of their magnetic properties are critical for CMOS-based magnetic devices. We report on the epitaxial growth of Ni_82.5Fe_17.5 (permalloy, Py) on Si (100) using a TiN/MgO buffer layer. Initial stages of growth are characterized by the formation of discrete islands that gradually merge into a continuous film as deposition times are extended. Interestingly, we find that the …

“Spaghetti” Design For Gravitational Wave Superconducting Antenna, Armen Gulian, J Foreman, Vahan Nikoghosyan, Shmuel Nussinov, Louis Sica, Jeff Tollaksen

Mathematics, Physics, and Computer Science Faculty Articles and Research

A new concept for detectors of gravitational wave radiation is discussed. Estimates suggest that strain sensitivity essentially better than that of the existing devices can be achieved in the wide frequency range. Such sensitivity could be obtained with devices about one meter long. Suggested device consists of multi-billion bimetallic superconducting wires ("spaghettis") and requires cryogenic operational temperatures (~0.3K in the case considered).

Quantum Harmonic Oscillator With Superoscillating Initial Datum, Roman V. Buniy, Fabrizio Colombo, Irene Sabadini, Daniele C. Struppa

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this paper, we study the evolution of superoscillating initial data for the quantum driven harmonic oscillator. Our main result shows that superoscillations are amplified by the harmonic potential and that the analytic solution develops a singularity in finite time. We also show that for a large class of solutions of the Schrodinger equation, superoscillating behavior at any given time implies superoscillating behavior at any other time.

Three‐Dimensional Brain Mri For Dbs Patients Within Ultra‐Low Radiofrequency Power Limits, Subhendra N. Sarkar, Efstathios Papavassiliou, David Hackney, David Alsop, Ananth Madhuranthakam, Ludy Shih, Reed Busse, Susan Laruche, Rafeeque Bhadelia

Publications and Research

Background: For patients with deep brain stimulators (DBS), local absorbed radiofrequency (RF) power is unknown and is much higher than what the system estimates. We developed a comprehensive, highquality brain magnetic resonance imaging (MRI) protocol for DBS patients utilizing three-dimensional (3D) magnetic resonance sequences at very low RF power. Methods: Six patients with DBS were imaged (10 sessions) using a transmit/receive head coil at 1.5 Tesla with modified 3D sequences within ultra-low specific absorption rate (SAR) limits (0.1 W/kg) using T2, fast fluid-attenuated inversion recovery (FLAIR) and T1- weighted image contrast. Tissue signal and tissue contrast from the low-SAR images …

Quantum Non-Locality Vs. Quasi-Local Measurement In The Conditions Of The Aharonov-Bohm Effect, Armen Gulian

Mathematics, Physics, and Computer Science Faculty Articles and Research

Theoretical explanation of the Meissner effect involves proportionality between current density and vector potential, which has many deep consequences. As noticed by de Gennes, superconductors in a magnetic field "find an equilibrium state where the sum of kinetic and magnetic energies is minimum" and this state "corresponds to the expulsion of the magnetic field". This statement still leaves an open question: from which source is the superconducting current acquiring its kinetic energy? A naïve answer, perhaps, is from the energy of the magnetic field. However, one can consider situations (Aharonov-Bohm effect), where the classical magnetic field is locally absent in …

Observation Of A Quantum Cheshire Cat In A Matter-Wave Interferometer Experiment, Tobias Denkmayr, Hermann Geppert, Stephan Sponar, Hartmut Lemmel, Alexandre Matzkin, Jeff Tollaksen, Yuji Hasegawa

Mathematics, Physics, and Computer Science Faculty Articles and Research

From its very beginning, quantum theory has been revealing extraordinary and counter-intuitive phenomena, such as wave-particle duality, Schrodinger cats and quantum non-locality. Another paradoxical phenomenon found within the framework of quantum mechanics is the 'quantum Cheshire Cat': if a quantum system is subject to a certain pre- and postselection, it can behave as if a particle and its property are spatially separated. It has been suggested to employ weak measurements in order to explore the Cheshire Cat's nature. Here we report an experiment in which we send neutrons through a perfect silicon crystal interferometer and perform weak measurements to probe …

Directed Ratchet Transport In Granular Crystals, Vincent Berardi, J. Lydon, P. G. Kevrekidis, C. Daraio, R. Carretero-González

Psychology Faculty Articles and Research

Directed-ratchet transport (DRT) in a one-dimensional lattice of spherical beads, which serves as a prototype for granular chains, is investigated. We consider a system where the trajectory of the central bead is prescribed by a biharmonic forcing function with broken time-reversal symmetry. By comparing the mean integrated force of beads equidistant from the forcing bead, two distinct types of directed transport can be observed—spatial and temporal DRT. Based on the value of the frequency of the forcing function relative to the cutoff frequency, the system can be categorized by the presence and magnitude of each type of DRT. Furthermore, we …

Global Fossil Energy Markets And Climate Change Mitigation: An Analysis With Remind, Nico Bauer, Ioanna Mouratiadou, Gunnar Luderer, Lavinia Baumstark, Robert J. Brecha, Ottmar Edenhofer, Elmar Kriegler

Physics Faculty Publications

We analyze the dynamics of global fossil resource markets under different assumptions for the supply of fossil fuel resources, development pathways for energy demand, and climate policy settings. Resource markets, in particular the oil market, are characterized by a large discrepancy between costs of resource extraction and commodity prices on international markets. We explain this observation in terms of (a) the intertemporal scarcity rent, (b) regional price differentials arising from trade and transport costs, (c) heterogeneity and inertia in the extraction sector. These effects are captured by the REMIND model. We use the model to explore economic effects of changes …

The Carbon Rent Economics Of Climate Policy, Matthias Kalkuhl, Robert J. Brecha

Physics Faculty Publications

By reducing the demand for fossil fuels, climate policy can reduce scarcity rents for fossil resource owners. As mitigation policies ultimately aim to limit emissions, a new scarcity for “space” in the atmosphere to deposit emissions is created. The associated scarcity rent, or climate rent (that is, for example, directly visible in permit prices under an emission trading scheme) can be higher or lower than the original fossil resource rent. In this paper, we analyze analytically and numerically the impact of mitigation targets, resource availability, backstop costs, discount rates and demand parameters on fossil resource rents and the climate rent. …

Use Of Zwitterionic Molecules For Forming A Hole Or Electron Transport Layer, Bernard Doudin, Pierre Braunstein, Lucie Routaboul, Guillaume Dalmas, Zhengzheng Zhang, Peter Dowben

Peter Dowben Publications

The invention relates to the use of zwitterionic molecules for forming a hole or electron transport layer. The preferred zwitterionic molecules of the invention are derivatives of p-benzoquinonemonoimines. The invention is useful in the field of electronic devices in particular.

Characterization Of The Drilling Via The Vibration Augmenter Of Rotary-Drills And Sound Signal Processing Of Impacted Pipe As A Potential Water Height Assessment Tool, Nicholas Morris

STAR Program Research Presentations

The focus of the internship has been on two topics: a) Characterize the drilling performance of a novel percussive augmenter – this drill was developed by the JPL’s Advanced Technologies Group and its performance was characterized; and b) Examine the feasibility of striking a pipe as a means of assessing the water height inside the pipe. The purpose of this investigation is to examine the possibility of using a simple method of applying impacts to a pipe wall and determining the water height from the sonic characteristic differences including damping, resonance frequencies, etc. Due to multiple variables that are relevant …

Adaptive Wiener Filter Super-Resolution Of Color Filter Array Images, Barry K. Karch, Russell C. Hardie

Electrical and Computer Engineering Faculty Publications

Digital color cameras using a single detector array with a Bayer color filter array (CFA) require interpolation or demosaicing to estimate missing color information and provide full-color images. However, demosaicing does not specifically address fundamental undersampling and aliasing inherent in typical camera designs. Fast non-uniform interpolation based super-resolution (SR) is an attractive approach to reduce or eliminate aliasing and its relatively low computational load is amenable to real-time applications. The adaptive Wiener filter (AWF) SR algorithm was initially developed for grayscale imaging and has not previously been applied to color SR demosaicing. Here, we develop a novel fast SR method …

An Ethnographic Study: Becoming A Physics Expert In A Biophysics Research Group, Idaykis Rodriguez

FIU Electronic Theses and Dissertations

Expertise in physics has been traditionally studied in cognitive science, where physics expertise is understood through the difference between novice and expert problem solving skills. The cognitive perspective of physics experts only create a partial model of physics expertise and does not take into account the development of physics experts in the natural context of research. This dissertation takes a social and cultural perspective of learning through apprenticeship to model the development of physics expertise of physics graduate students in a research group. I use a qualitative methodological approach of an ethnographic case study to observe and video record the …

Relations Between Distorted And Original Angles In Str, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

Using the Oblique-Length Contraction Factor, which is a generalization of Lorentz Contraction Factor, one shows several trigonometric relations between distorted and original angles of a moving object lengths in the Special Theory of Relativity.

Development Without Energy? Assessing Future Scenarios Of Energy Consumption In Developing Countries, Jan Christof Steckel, Robert J. Brecha, Michael Jakob, Jessica Strefler, Gunnar Luderer

Physics Faculty Publications

We analyze the relationship between economic development and energy consumption in the context of greenhouse gas mitigation. The main contribution of this work is to compare estimates of energy thresholds in the form of minimum energy requirements to reach high levels of development with output projections of per capita final energy supply from a group of integrated assessment models (IAMs). Scenarios project that reductions of carbon emissions in developing countries will be achieved not only by means of decreasing the carbon intensity, but also by making a significant break with the historically observed relationship between energy use and economic growth. …

Testing The Well-Posedness Of Characteristic Evolution Of Scalar Waves, Maria Babiuc-Hamilton, Heinz Otto Kreiss, Jeffrey Winicour

Physics Faculty Research

Recent results have revealed a critical way in which lower order terms affect the well-posedness of the characteristic initial value problem for the scalar wave equation. The proper choice of such terms can make the Cauchy problem for scalar waves well posed even on a background spacetime with closed lightlike curves. These results provide new guidance for developing stable characteristic evolution algorithms. In this regard, we present here the finite difference version of these recent results and implement them in a stable evolution code. We describe test results which validate the code and exhibit some of the interesting features due …

Information-Based Physics: An Intelligent Embedded Agent's Guide To The Universe, Kevin H. Knuth

Physics Faculty Scholarship

In this talk, I propose an approach to understanding the foundations of physics by considering the optimal inferences an intelligent agent can make about the universe in which he or she is embedded. Information acts to constrain an agent’s beliefs. However, at a fundamental level, any information is obtained from interactions where something influences something else. Given this, the laws of physics must be constrained by both the nature of such influences and the rules by which we can make inferences based on information about these influences. I will review the recent progress we have made in this direction. This …

Study Of The Growth And Switching Kinetics On Ferroelectric Nanocrystals Of Copolymer Vinylidene Fluoride And Trifluoroethylene On An Atomic Force Microscope, R. V. Gaynutdinov, O. A. Lysova, A. L. Tolstikhina, V. M. Fridkin, S. G. Yudin, Stephen Ducharme

Stephen Ducharme Publications

The growth of nanocrystals obtained from Langmuir-Blodgett films of ferroelectric copolymer consisting of 70% vinylidene fluoride and 30% trifluoroethylene has been investigated by atomic force microscopy (AFM). The radius and concentration of nanocrystals are found to depend on the annealing time of the film. A model for nanocrystal growth is proposed which yields adequate time dependences for nanocrystal size parameters. The switching kinetics of individual ferroelectric nanocrystals with an average diameter of 100–200 nm and a height of 15–20 nm has been investigated in the piezoelectric response mode. It is shown that the switching of nanocrystals has an activation character.

Strain-Mediated Elastic Coupling In Magnetoelectric Nickel/Barium-Titanate Heterostructures, Robert Streubel, Denny Köhler, Rudolf Schäfer, Lukas M. Eng

Robert Streubel Papers

Multiferroic nanomaterials bear the potential for assembling a manifold of novel and smart devices. For room temperature (RT) applications, however, only the BiFeO3 single-phase perovskites are potential candidates to date. Nevertheless, vertical heterostructures separating magnetic and ferroelectric functionality into different layers are now widely proposed to circumvent this lack in materials' availability. We show here that the second approach is very profitable as illustrated by the strain-mediated coupling between such two layers, i.e., a ferroelectric barium titanate single-crystal (BTO) and a magnetostrictive nickel (Ni) thin film. Applying an electric field across the BTO substrate forces the magnetic easy axis in …

Adherent Cells Avoid Polarization Gradients On Periodically Poled Litao3 Ferroelectrics, Christof Christophis, Elisabetta Ada Cavalcanti-Adam, Maximilian Hanke, Kenji Kitamura, Alexei Gruverman, Michael Grunze, Peter A. Dowben, Axel Rosenhahn

Peter Dowben Publications

The response of fibroblast cells to periodically poled LiTaO₃ ferroelectric crystals has been studied. While fibroblast cells do not show morphological differences on the two polarization directions, they show a tendency to avoid the field gradients that occur between polarization domains of the ferroelectric. The response to the field gradients is fully established after one hour, a time at which fibroblasts form their first focal contacts. If suspension cells, with a lower tendency to establish strong surface contacts are used, no influence of the field gradients is observed.

Optically Pumped Spin-Exchange Polarized-Electron Source, Munir Pirbhai, J. Knepper, E. T. Litaker, D. Tupa, Timothy J. Gay

Timothy J. Gay Publications

We describe the operation of a prototype polarized-electron source. Rubidium vapor, contained in a cell, is optically pumped in the presence of a buffer gas. Unpolarized electrons from a tungsten filament are injected into the cell and extracted after undergoing spin exchange with the Rb atoms. We compare the performance of the source when different buffer gases are used. We measure a decrease in electron polarization as their injection energy increases, but find an unexpected regime at higher injection energies yielding increased electron polarization accompanied by a 40-fold increase in current, suggesting the production of slow secondary electrons in the …

Rose: Roadmaps Towards Sustainable Energy Futures And Climate Protection: A Synthesis Of Results From The Rose Project, Elmar Kriegler, Ioanna Mouratiadou, Gunnar Luderer, Nico Bauer, Katherine Calvin, Enrica Decian, Robert J. Brecha, Wenying Chen, Aleh Cherp, Jae Edmonds, Kejun Jiang, Shonali Pachauri, Fabio Sferra, Massimo Tavoni, Ottmar Edenhofer

Physics Faculty Publications

EXECUTIVE SUMMARY

Exploring energy demand and supply uncertainty: An exploration of uncertainty on drivers of energy demand and supply is indispensable for better understanding the prospects of long-tern climate stabilization. The RoSE study is the first of its kind to systematically explore the impact of economic growth, population and fossil fuel scarcity, in scenarios with and without climate policy, using a model ensemble. A feature of RoSE is the participation of five established integrated assessment modelling teams from three important regions in international climate policy negotiations: the EU, the USA and China.

Economic growth: Neither slow nor rapid economic growth …