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Articles 1 - 30 of 55
Full-Text Articles in Physics
Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan
Funded Research Records
No abstract provided.
Relaxation Of Radiation Effects In Polymers, Alexandra Hughlett Nelson
Relaxation Of Radiation Effects In Polymers, Alexandra Hughlett Nelson
Physics Capstone Projects
Radiation can create atomic-scale defect states in polymers, leading to changes in their optical, electrical and mechanical properties. Recent studies of polymers have shown that these defect states are sensitive to oxygen or water exposure. It is believed that oxygen cause the number of defect states to decrease and the polymers to revert to their original states. However, the time scale of this regression is not known. This experiment quantified the time that it takes five polymers to recover and the extent of said recovery; polypropylene (PP), low density polyethylene (LDPE), fluorinated ethylene propylene (FEP), polymide (PI), and poly ether …
Model‐Based Properties Of The Dayside Open/Closed Boundary: Is There A Ut‐Dependent Variation?, David A. Smith, Jan Josef Sojka
Model‐Based Properties Of The Dayside Open/Closed Boundary: Is There A Ut‐Dependent Variation?, David A. Smith, Jan Josef Sojka
All Physics Faculty Publications
The open‐closed boundary (OCB) defines a region of significant transformation in Earth's protective magnetic shield. Principle among these changes is the transition of magnetic field lines from having two foot points, one in each hemisphere, to one foot point at Earth, the other mapping to the solar wind. Charged particles in the solar wind are able to follow these open field lines into Earth's upper atmosphere. The OCB also defines the polar cap boundary. Being able to identify and track the OCB allows study of several components of the geomagnetic system. Among them are the electrodynamics of the geomagnetic field …
Decomposing The Hamiltonian Of Quantum Circuits Using Machine Learning, Jordan Burns, Yih Sung, Colby Wight
Decomposing The Hamiltonian Of Quantum Circuits Using Machine Learning, Jordan Burns, Yih Sung, Colby Wight
Physics Capstone Projects
Quantum computing is one of the most promising techniques for simulating physical systems that cannot be simulated on classical computers[1]. A significant drawback of this approach is the inherent difficulty in designing circuits that can represent these systems on quantum computers. Every quantum circuit is built out of small components called quantum gates. Each of these gates manipulate the quantum system in a specific way. When used in combination, a finite subset of these gates, the set of universal gates, can be used to construct any possible quantum circuit[2].
Halving Iso(7) Supergravity, Adolfo Guarino, Javier Tarrío, Oscar J. Varela
Halving Iso(7) Supergravity, Adolfo Guarino, Javier Tarrío, Oscar J. Varela
All Physics Faculty Publications
Half-maximal, N = 4, sectors of D = 4 N = 8 supergravity with a dyonic ISO(7) gauging are investigated. We focus on a half-maximal sector including three vector multiplets, that arises as a certain SO(3)R-invariant sector of the full theory. We discuss the embedding of this sector into the largest half-maximal sector of the N = 8 supergravity retaining six vector multiplets. We also provide its canonical N = 4 formulation and show that, from this perspective, our model leads in its own right to a new explicit gauging of N = 4 supergravity. Finally, expressions for …
Melissa: System Description And Spectral Features Of Pre- And Post-Midnight F-Region Echoes, Fabiano S. Rodrigues, Weijia Zhan, Marco A. Milla, B. G. Fejer, Eurico R. De Paula, Acacio C. Neto, Angela M. Santos, Inez S. Batista
Melissa: System Description And Spectral Features Of Pre- And Post-Midnight F-Region Echoes, Fabiano S. Rodrigues, Weijia Zhan, Marco A. Milla, B. G. Fejer, Eurico R. De Paula, Acacio C. Neto, Angela M. Santos, Inez S. Batista
All Physics Faculty Publications
Most of the low‐latitude ionospheric radar observations in South America come from the Jicamarca Radio Observatory, located in the western longitude sector (∼75°W). The deployment of the 30 MHz FAPESP‐Clemson‐INPE (FCI) coherent backscatter radar in the magnetic equatorial site of São Luis, Brazil, in 2001 allowed observations to be made in the eastern sector (∼45°W). However, despite being operational for several years (2001–2012), FCI only made observations during daytime and pre‐midnight hours, with a few exceptions. Here, we describe an upgraded system that replaced the FCI radar and present results of full‐night F‐region observations. This radar is referred to …
Embedding The Su(3) Sector Of So(8) Supergravity In D = 11, Gabriel Larios, Praxitelis Ntokos, Oscar J. Varela
Embedding The Su(3) Sector Of So(8) Supergravity In D = 11, Gabriel Larios, Praxitelis Ntokos, Oscar J. Varela
All Physics Faculty Publications
The SU(3)-invariant sector of maximal supergravity in four dimensions with an SO(8) gauging is uplifted to D = 11 supergravity. In order to do this, the SU(3)-neutral sector of the tensor and duality hierarchies of the D = 4 �� = 8 supergravity is first worked out. The consistent D = 11 embedding of the full, dynamical SU(3) sector is then expressed at the level of the D = 11 metric and three-form gauge field in terms of these D = 4 tensors. The redundancies introduced by this approach are eliminated at the level of the D = 11 four-form …
The Role Of The Dispersion Parameter In Electrical Properties Of Highly Disordered Insulating Materials, Zachary Gibson
The Role Of The Dispersion Parameter In Electrical Properties Of Highly Disordered Insulating Materials, Zachary Gibson
Physics Student Research
Charge transport in disordered solids can be described with use of a dispersion parameter. The dispersion parameter can be defined simply as either the thermal energy (low electric field regime) or the field energy (high field regime) scaled by the reciprocal of a characteristic energy of the material. A transitionary temperature and electric field are defined when the ratio of thermal or field energy over the characteristic energy is one, respectively. This indicates a transition from dispersive transport to normal transport. Dispersive transport can be described simply by the dispersion parameter for many disordered materials. Models involving the dispersion parameter …
Minimal D = 4 �� = 2 Supergravity From D = 11: An M-Theory Free Lunch, Gabriel Larios, Oscar J. Varela
Minimal D = 4 �� = 2 Supergravity From D = 11: An M-Theory Free Lunch, Gabriel Larios, Oscar J. Varela
All Physics Faculty Publications
We present a new consistent truncation of D = 11 supergravity to D = 4 �� = 2 minimal gauged supergravity, on the seven-dimensional internal Riemannian space corresponding to the most general class of D = 11 solutions with an AdS4 factor and �� = 2 supersymmetry. A truncation ansatz is proposed and its consistency checked at the level of the D = 11 Bianchi identity, bosonic equations of motion, and supersymmetry variations of the gravitino. The general class includes an �� = 2 AdS4 solution dual to the conformal, low energy physics phase corresponding to a mass …
Physics-Driven Dual-Defect Model Fits Of Voltage Step-Up To Breakdown Data In Spacecraft Polymers, Allen Andersen, Jr Dennison
Physics-Driven Dual-Defect Model Fits Of Voltage Step-Up To Breakdown Data In Spacecraft Polymers, Allen Andersen, Jr Dennison
Journal Articles
Overly conservative estimates of breakdown strength can increase the mass and cost of spacecraft electrostatic discharge (ESD) mitigation methods. Improved estimates of ESD likelihood in the space environment require better models of ESD distributions. The purpose of this work is to evaluate our previously proposed dual-defect model of voltage step-up-to-breakdown tests with a case study across four dielectric materials. We predicted that materials best fit by mixed Weibull distributions would exhibit better fits with the dual-defect model compared to a mean field single defect theory. Additional data for biaxially oriented polypropylene (BOPP), polyimide (PI or Kapton) from three sources, and …
Hemispherical Shifted Symmetry In Polar Cap Patch Occurrence: A Survey Of Gps Tec Maps From 2015–2018, Michael David, Jan Josef Sojka, Robert W. Schunk, Anthea J. Coster
Hemispherical Shifted Symmetry In Polar Cap Patch Occurrence: A Survey Of Gps Tec Maps From 2015–2018, Michael David, Jan Josef Sojka, Robert W. Schunk, Anthea J. Coster
All Physics Faculty Presentations
Much theoretical and observational work has been devoted to studying the occurrence of F region polar cap patches in the Northern Hemisphere; considerably less work has been applied to the Southern Hemisphere. In recent years, the Madrigal database of mappings of total electron content (TEC) has improved in Southern Hemisphere coverage, to the point that we can now carry out a study of patch frequency and occurrence. We find that Southern Hemisphere patch occurrence is very similar to that of the Northern Hemisphere with a half‐year offset, plus an offset in universal time of approximately 12 hr. This is further …
A Unified Description Of The Electrical Properties Of Low-Density Polyethylene Via The Dispersion Parameter, Zack Gibson, Megan Loveland, Jr Dennison
A Unified Description Of The Electrical Properties Of Low-Density Polyethylene Via The Dispersion Parameter, Zack Gibson, Megan Loveland, Jr Dennison
Physics Student Research
Low-density polyethylene is a prototypical highly disordered insulating material. This ubiquitous polymer has a variety of applications from spacecraft charging to high voltage DC power cable insulation. Therefore, the electrical properties are of great interest. The dispersion parameter, which originally appeared in a semi-empirical model to describe anomalies in permittivity data, is central to an understanding of these electrical properties. This parameter depends linearly on either temperature (low field regime) or on electric field (high field regime) and is scaled by the reciprocal of a characteristic energy. When the dispersion parameter reaches one, a transition from dispersive to non-dispersive transport …
Charge Transport In Disordered Materials And The Dispersion Parameter, Zachary Gibson
Charge Transport In Disordered Materials And The Dispersion Parameter, Zachary Gibson
Physics Student Research
Charge transport in disordered solids can be described with use of a dispersion parameter. The dispersion parameter can be defined simply as either the thermal energy (low electric field regime) or the field energy (high field regime) scaled by the reciprocal of a characteristic energy of the material. A transitionary temperature and electric field are defined when the ratio of thermal or field energy over the characteristic energy is one, respectively. This indicates a transition from dispersive transport to normal transport. Dispersive transport can be described simply by the dispersion parameter for many disordered materials. Models involving the dispersion parameter …
Dynamic Secondary Electron Emission In Rough Composite Materials, Leandro Olano, Maria E. Dávila, John R. Dennison, Petronilo Martín-Iglesias, Isabel Montero
Dynamic Secondary Electron Emission In Rough Composite Materials, Leandro Olano, Maria E. Dávila, John R. Dennison, Petronilo Martín-Iglesias, Isabel Montero
All Physics Faculty Publications
The interaction of ionizing radiation with matter is of critical importance in numerous areas of science and technology like space and vacuum technology and even medicine and biotechnology. Secondary electron emission is a consequence of electron irradiation on materials. We achieve extremely low secondary electron emission yield values smaller than 0.2, even up to incident electron energies ~1 keV, due to an undocumented synergy between neighbouring metal and dielectric domains in composite samples. To investigate this experimental discovery, we propose a simple 3D model where the dielectric and metallic domains are arranged in parallel and interleaved. The proposed surface profile …
The Physical Significance Of Α For Electron Transport, Zachary Gibson
The Physical Significance Of Α For Electron Transport, Zachary Gibson
Physics Student Research
Charge transport in crystalline materials can be well understood through the use of Bloch functions, band theory, and extended state transport. Disordered materials do not allow the same luxury, and different methods have to be considered. It turns out that band structures still exist. Although extended state conduction can still occur, localized states within the band gap allow for alternative mechanisms of charge transport in disordered materials. Conduction can be understood through such models as hopping, multiple trapping, and percolation, but all of them can lead to a broad distribution of event times. For example, the hopping-time distribution proposed by …
Stormtime Thermospheric Neutral Winds Obtained From A Data Assimilation Model, Ludger Scherliess
Stormtime Thermospheric Neutral Winds Obtained From A Data Assimilation Model, Ludger Scherliess
Funded Research Records
No abstract provided.
A Near Horizon Extreme Binary Black Hole Geometry, Jacob Ciafre, Maria J. Rodriguez
A Near Horizon Extreme Binary Black Hole Geometry, Jacob Ciafre, Maria J. Rodriguez
All Physics Faculty Presentations
A new solution of four-dimensional vacuum General Relativity is presented. It describes the near horizon region of the extreme (maximally spinning) binary black hole system with two identical extreme Kerr black holes held in equilibrium by a massless strut. This is the first example of a non-supersymmetric, near horizon extreme binary black hole geometry of two uncharged black holes. The black holes are co-rotating, their relative distance is fixed, and the solution is uniquely specified by the mass. Asymptotically, the geometry corresponds to the near horizon extreme Kerr (NHEK) black hole. The binary extreme system has finite entropy.
Large‐Amplitude Mountain Waves In The Mesosphere Observed On 21 June 2014 During Deepwave: 2. Nonlinear Dynamics, Wave Breaking, And Instabilities, David C. Fritts, Ling Wang, Michael J. Taylor, Pierre-Dominique Pautet, Neal R. Criddle, Bernd Kaifler, Stephen D. Eckermann, Ben Liley
Large‐Amplitude Mountain Waves In The Mesosphere Observed On 21 June 2014 During Deepwave: 2. Nonlinear Dynamics, Wave Breaking, And Instabilities, David C. Fritts, Ling Wang, Michael J. Taylor, Pierre-Dominique Pautet, Neal R. Criddle, Bernd Kaifler, Stephen D. Eckermann, Ben Liley
Publications
Weak cross‐mountain flow over the New Zealand South Island on 21 June 2014 during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) led to large‐amplitude mountain waves in the mesosphere and lower thermosphere. The mesosphere and lower thermosphere responses were observed by ground‐based instruments in the lee of the Southern Alps supporting DEEPWAVE, including an Advanced Mesosphere Temperature Mapper, a Rayleigh lidar, an All‐Sky Imager, and a Fabry‐Perot Interferometer. The character of the mountain wave responses at horizontal scales of ~30–90 km reveals strong “sawtooth” variations in the temperature field suggesting large vertical and horizontal displacements leading to mountain wave overturning. …
Generalized Near Horizon Extreme Binary Black Hole Geometry, Jacob Ciafre, Shahar Hadar, Erin Rickenbach, Maria J. Rodriguez
Generalized Near Horizon Extreme Binary Black Hole Geometry, Jacob Ciafre, Shahar Hadar, Erin Rickenbach, Maria J. Rodriguez
All Physics Faculty Publications
We present a new vacuum solution of Einstein’s equations describing the near horizon region of two neutral, extreme (zero-temperature), corotating, nonidentical Kerr black holes. The metric is stationary, asymptotically near horizon extremal Kerr (NHEK), and contains a localized massless strut along the symmetry axis between the black holes. In the deep infrared, it flows to two separate throats which we call “pierced-NHEK” geometries: each throat is NHEK pierced by a conical singularity. We find that in spite of the presence of the strut for the pierced-NHEK geometries the isometry group SL(2,R)×U(1) is restored. We find the physical parameters and entropy.
Yang-Mills Sources For Biconformal Gravity, Walter Davis Muhwezi
Yang-Mills Sources For Biconformal Gravity, Walter Davis Muhwezi
Physics Capstone Projects
We present a gauge formulation of Yang-Mills matter sources for Biconformal gravity. Biconformal gravity is a 2n-dimensional conformal gauge theory with a curvature linear action that has been shown to reproduce scale invariant general relativity on the cotangent bundle of n-dimensional space time. We present a generalization of Yang-Mills theories in biconformal space and show that the field equations with sources reduce the Yang-Mills sector to n-dimensional Yang-Mills theory in curved spacetime. We compute the restrictive conditions on the energy-momentum tensor required by the gravitational field equations.
Monitoring Ambient Laboratory Conditions With A Raspberry Pi, Joshua Boman
Monitoring Ambient Laboratory Conditions With A Raspberry Pi, Joshua Boman
Physics Capstone Projects
Precise experimental devices and measurements can be sensitive to changing physical conditions in the lab. The purpose of this research was to develop a standardized computer automated package to monitor and record changes in laboratory conditions, including ambient temperature, atmospheric pressure, relative humidity, light intensity, motion, and power outages. The computer-interfaced device was based around an inexpensive Raspberry Pi microcomputer and commercially available sensors. The Raspberry Pi uploads the sensor data to a file used by LabVIEW to further analyze, plot and display the calibrated sensor data in real time and trigger alarms. This capability allows the Material Physics Research …
Secondary Electron Yield Measurements Of Carbon Nanotube Forests: Dependence On Morphology And Substrate, Brian Wood, Jordan Lee, Gregory Wilson, T. -C. Shen, Jr Dennison
Secondary Electron Yield Measurements Of Carbon Nanotube Forests: Dependence On Morphology And Substrate, Brian Wood, Jordan Lee, Gregory Wilson, T. -C. Shen, Jr Dennison
Journal Articles
Total, secondary, and backscatter electron yield data were taken with beam energies between 15 eV and 30 keV, in conjunction with energy emission data, to determine the extent of suppression of yield caused by carbon nanotube (CNT) forest coatings on substrates. CNT forests can potentially lower substrate yield due to both its inherently low-yield, low-atomic number (Z) carbon composition, and its bundled, high-aspect ratio structure. Rough surfaces, and in particular, surfaces with deep high-aspect-ratio voids, can suppress yields, as the electrons emitted from lower lying surfaces are recaptured by surface protrusions rather than escaping the near-surface region. Yields of multilayered …
Wireless Antenna Detection Of Electrostatic Discharge Events, Allen Andersen, Jr Dennison
Wireless Antenna Detection Of Electrostatic Discharge Events, Allen Andersen, Jr Dennison
Journal Articles
Wireless intraspacecraft communication technology is being developed for signal transfer on space missions to save weight and simplify the design. One consideration for this new technology is its interaction with space environmentinduced electrostatic discharges (ESDs). The short time scales of spacecraft ESD events result in broad frequency band signals that can interact with high-frequency wireless antennas. These interactions present a source of signal noise. However, they also present a possibility of in-flight wireless ESD monitoring. We present laboratory measurements of arcing on common spacecraft insulators using commercially available single-band 2.4-GHz and dual-band 2.4-/5.8-GHz Wi-Fi antennas. These wireless detections are shown …
Classification Of Isometry Algebras Of Solutions Of Einstein's Field Equations, Eugene Hwang
Classification Of Isometry Algebras Of Solutions Of Einstein's Field Equations, Eugene Hwang
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Since Schwarzschild found the first solution of the Einstein’s equations, more than 800 solutions were found. Solutions of Einstein’s equations are classified according to their Lie algebras of isometries and their isotropy subalgebras. Solutions were taken from the USU electronic library of solutions of Einstein’s field equations and the classification used Maple code developed at USU. This classification adds to the data contained in the library of solutions and provides additional tools for addressing the equivalence problem for solutions to the Einstein field equations. In this thesis, homogeneous spacetimes, hypersurface-homogeneous spacetimes, Robinson-Trautman solutions, and some famous black hole solutions have …
Solar Response And Long‐Term Trend Of Midlatitude Mesopause Region Temperature Based On 28 Years (1990–2017) Of Na Lidar Observations, Chiao-Yao She, Uwe Berger, Zhao-Ai Yan, Tao Yuan, F.-J. Lübken, David A. Krueger, Xiong Hu
Solar Response And Long‐Term Trend Of Midlatitude Mesopause Region Temperature Based On 28 Years (1990–2017) Of Na Lidar Observations, Chiao-Yao She, Uwe Berger, Zhao-Ai Yan, Tao Yuan, F.-J. Lübken, David A. Krueger, Xiong Hu
All Physics Faculty Publications
We present midlatitude solar response and linear trend from Colorado State University/Utah State University Na lidar nocturnal temperature observations between 1990 and 2017. Along with the nightly mean temperatures (_Ngt), we also use the corresponding 2‐hr means centered at midnight (_2MN), resulting in vertical trend profiles similar in shapes as those previously published. The 28‐year trend from _Ngt (_2MN) data set starts from a small warming at 85 km, to cooling at 87 (88) km, reaching a maximum of 1.85 ± 0.53 (1.09 ± 0.74) at 92 (93) km and turns positive again at 102 (100) km. The 6‐month winter …
On The Balance Between Plasma And Magnetic Pressure Across Equatorial Plasma Depletions, J. Rodríguez-Zuluaga, C. Stolle, Y. Yamazaki, H. Lühr, J. Park, Ludger Scherliess, J. L. Chau
On The Balance Between Plasma And Magnetic Pressure Across Equatorial Plasma Depletions, J. Rodríguez-Zuluaga, C. Stolle, Y. Yamazaki, H. Lühr, J. Park, Ludger Scherliess, J. L. Chau
All Physics Faculty Publications
In magnetized plasmas such as the ionosphere, electric currents develop in regions of strong density gradients to balance the resulting plasma pressure gradients. These currents, usually known as diamagnetic currents decrease the magnetic pressure where the plasma pressure increases, and vice versa. In the low‐latitude ionosphere, equatorial plasma depletions (EPDs) are well known for their steep plasma density gradients and adverse effect on radio wave propagation. In this paper, we use continuous measurements of the magnetic field and electron density from the European Space Agency's Swarm constellation mission to assess the balance between plasma and magnetic pressure across large‐scale EPDs. …
Equatorial Disturbance Dynamo Vertical Plasma Drifts Over Jicamarca: Bi‐Monthly And Solar Cycle Dependence, Luis A. Navarro Dominguez, B. G. Fejer, Ludger Scherliess
Equatorial Disturbance Dynamo Vertical Plasma Drifts Over Jicamarca: Bi‐Monthly And Solar Cycle Dependence, Luis A. Navarro Dominguez, B. G. Fejer, Ludger Scherliess
All Physics Faculty Publications
We use extensive incoherent scatter radar observations from the Jicamarca Radio Observatory to study the local time and bi‐monthly dependence of the equatorial disturbance dynamo vertical plasma drifts on solar flux and geomagnetic activity. We show that the daytime disturbance drifts have generally small magnitudes with largest values before noon and an apparent annual variation. Near dusk, they are downward throughout the year with largest values during the equinoxes and smallest during June solstice. These downward drifts increase strongly with solar flux, and shift to later local times. They also increase with increasing geomagnetically active conditions with no apparent local …
Blandford-Znajek Process In Vacuo And Its Holographic Dual, Ted Jacobson, Maria J. Rodriguez
Blandford-Znajek Process In Vacuo And Its Holographic Dual, Ted Jacobson, Maria J. Rodriguez
All Physics Faculty Presentations
Blandford and Znajek discovered a process by which a spinning black hole can transfer rotational energy to a plasma, offering a mechanism for energy and jet emissions from quasars. Here we describe a version of this mechanism that operates with only vacuum electromagnetic fields outside the black hole. The setting, which is not astrophysically realistic, involves either a cylindrical black hole or one that lives in 2+1 spacetime dimensions, and the field is given in simple, closed form for a wide class of metrics. For asymptotically anti–de Sitter black holes in 2+1 dimensions, the holographic dual of this mechanism is …
Usu Materials Physics Group Nasa Missions, Jr Dennison
The Long‐Term Trends Of Nocturnal Mesopause Temperature And Altitude Revealed By Na Lidar Observations Between 1990 And 2018 At Midlatitude, Tao Yuan, Stanley C. Solomon, Chiao -Y. She, D. A. Krueger, Han-Li Liu
The Long‐Term Trends Of Nocturnal Mesopause Temperature And Altitude Revealed By Na Lidar Observations Between 1990 And 2018 At Midlatitude, Tao Yuan, Stanley C. Solomon, Chiao -Y. She, D. A. Krueger, Han-Li Liu
All Physics Faculty Publications
The mesopause, a boundary between mesosphere and thermosphere with the coldest atmospheric temperature, is formed mainly by the combining effects of radiative cooling of CO2, and the vertical adiabatic flow in the upper atmosphere. A continuous multidecade (1990‐2018) nocturnal temperature data base of an advanced Na lidar, obtained at Fort Collins, CO (41°N, 105°W), and at Logan, UT (42°N, 112°W), provides an unprecedented opportunity to study the long‐term variations of this important atmospheric boundary. In this study, we categorize the lidar‐observed mesopause into two categories: the “high mesopause” (HM) above 97 km during nonsummer months, mainly formed through the radiative …