Physics Commons^™

Robustness And Mode Selectivity In Parity-Time (Pt) Symmetric Lasers, M. H. Teimourpour, M. Khajavikhan, Demetrios N. Christodoulides, Ramy El-Ganainy

Ramy El-Ganainy

We investigate two important aspects of PT symmetric photonic molecule lasers, namely the robustness of their single longitudinal mode operation against instabilities triggered by spectral hole burning effects, and the possibility of more versatile mode selectivity. Our results, supported by numerically integrating the nonlinear rate equations and performing linear stability analysis, reveals the following: (1) In principle a second threshold exists after which single mode operation becomes unstable, signaling multimode oscillatory dynamics, (2) For a wide range of design parameters, single mode operation of PT lasers having relatively large free spectral range (FSR) can be robust even at higher gain …

Non-Hermitian Matter-Wave Mixing In Bose-Einstein Condensates: Dissipation-Induced Amplification, S. Wuster, Ramy El-Ganainy

Ramy El-Ganainy

We investigate the nonlinear scattering dynamics in interacting atomic Bose-Einstein condensates under non-Hermitian dissipative conditions. We show that, by carefully engineering a momentum-dependent atomic loss profile, one can achieve matter-wave amplification through four-wave mixing in a quasi-one-dimensional nearly-free-space setup—a process that is forbidden in the counterpart Hermitian systems due to energy mismatch. Additionally, we show that similar effects lead to rich nonlinear dynamics in higher dimensions. Finally, we propose a physical realization for selectively tailoring the momentum-dependent atomic dissipation. Our strategy is based on a two-step process: (i) exciting atoms to narrow Rydberg or metastable excited states, and (ii) introducing …

Search For The Neutron Decay N → X + Γ , Where X Is A Dark Matter Particle, Zhoawen Tang, Marie Blatnik, Leah J. Broussard, J. H. Choi, Stephen M. Clayton, Christopher Cude-Woods, Scott Currie, D. E. Fellers, E. M. Fries, Peter Geltenbort, F. Gonzalez, Kevin P. Hickerson, Takeyasu M. Ito, Chen Y. Liu, S. W. T. Macdonald, Mark Makela, Christopher L. Morris, C. M. O'Shaughnessy, Robert W. Pattie Jr., Bradley R. Plaster, D. J. Salvat, Alexander Saunders, Zhehui Wang, Albert R. Young, B. A. Zeck

Robert W. Pattie Jr.

Status Of The Ucnτ Experiment, Robert W. Pattie Jr.

Robert W. Pattie Jr.

Search For Dark Matter Decay Of The Free Neutron From The Ucna Experiment: N → Χ + E^+E^−, Xiaohui Sun, Edith Adamek, Bruno Allgeier, Matthias A. Blatnik, Thomas J. Bowles, Leah J. Broussard, Matthew A. Brown, Richard Carr, Steven M. Clayton, Chris Cude-Woods, Sonja Currie, Eric B. Dees, Xingxing Ding, Bradley W. Filippone, A. Bello García, Peter Geltenbort, Salajeghe Hasan, Kevin P. Hickerson, J. Todd Hoagland, R. Hong, Gary E. Hogan, Anthony T. Holley, Takeyasu M. Ito, Amanda L. Knecht, Chao-Yu Liu, Jingyang Liu, María Makela, Russel Mammei, J. W. Martin, Dan Melconian, Michael P. Mendenhall, Stephen D. Moore, Charles L. Morris, Sushil Nepal, N. Vahedi Nouri, Robert W. Pattie Jr., A. Pérez Galván, David G. Phillips, Richard H. Picker, Margaret L. Pitt, Blakely A. Plaster, Jana C. Ramsey, R. Barreto Rios, Daniel J. Salvat, Andy Saunders, Walter Sondheim, S. Sjue, Steven Slutsky, Charles Swank, Gyani Swift, E. Tatar, R. Bruce Vogelaar, Brittany Vorndick, Z. Wang, Wanchun Wei, J. Wexler, T. Womack, Christopher Wrede, Andrew R. Young, B. A. Zeck

Robert W. Pattie Jr.

High Consequence Scenarios For North Korean Atmospheric Nuclear Tests With Policy Recommendations For The U.S. Government, Thomas S. Popik, Jordan T. Kearns, George H. Baker Iii, Henry F. Cooper, William R. Harris

George H Baker

The government of North Korea has declared high-altitude EMP-capability to be a “strategic goal” and has also threatened an atmospheric test of a hydrogen bomb. Atmospheric nuclear tests have the potential to cripple satellites and the undersea cable networks critical to communication, and navigation necessary for trans-Pacific trade among the U.S., China, and other nations. When a nuclear warhead is detonated at high altitude, a series of electromagnetic pulses radiate downward within the line of sight of the blast. These pulses can disable equipment with miniature electronics and long conductors. Electric grid controls and transmission systems are especially vulnerable. Intense …

Measurement Of The Neutron Lifetime Using A Magneto-Gravitational Trap And In Situ Detection, Robert W. Pattie Jr., Nathan B. Callahan, Chris Cude-Woods, Edith R. Adamek, Leah J. Broussard, Stephen M. Clayton, Scott A. Currie, Eric B. Dees, Xiaoping Ding, Egbert M. Engel, D. E. Fellers, William Fox, Peter Geltenbort, Kevin P. Hickerson, Mark A. Hoffbauer, Anthony T. Holley, A. Komives, Chen Liu, S. W. T. Macdonald, Mark Makela, Christopher L. Morris, Joseph D. Ortiz, John C. Ramsey, Daniel J. Salvat, Alexander Saunders, Susan J. Seestrom, E. I. Sharapov, S. K. Sjue, Zebo Tang, J. Vanderwerp, Bruce Vogelaar, P. L. Walstrom, Zhehui Wang, Wei Wei, H. L. Weaver, Judith W. Wexler, Tanner L. Womack, Andrew R. Young, B. A. Zeck

Robert W. Pattie Jr.

Power-Law Scaling Of Extreme Dynamics Near Higher-Order Exceptional Points, Q. Zhong, Demetrios N. Christodoulides, M. Khajavikhan, K. G. Makris, Ramy El-Ganainy

Ramy El-Ganainy

We investigate the extreme dynamics of non-Hermitian systems near higher-order exceptional points in photonic networks constructed using the bosonic algebra method. We show that strong power oscillations for certain initial conditions can occur as a result of the peculiar eigenspace geometry and its dimensionality collapse near these singularities. By using complementary numerical and analytical approaches, we show that, in the parity-time (PT) phase near exceptional points, the logarithm of the maximum optical power amplification scales linearly with the order of the exceptional point. We focus in our discussion on photonic systems, but we note that our results apply to other …

Topological Hybrid Silicon Microlasers, Han Zhao, Pei Mao University Of Pennsylvania, Mohammad H. Teimourpour, Simon Malzard, Ramy El-Ganainy, Henning Schomerus, Liang Feng

Ramy El-Ganainy

Topological physics provides a robust framework for strategically controlling wave confinement and propagation dynamics. However, current implementations have been restricted to the limited design parameter space defined by passive topological structures. Active systems provide a more general framework where different fundamental symmetry paradigms, such as those arising from non-Hermiticity and nonlinear interaction, can generate a new landscape for topological physics and its applications. Here, we bridge this gap and present an experimental investigation of an active topological photonic system, demonstrating a topological hybrid silicon microlaser array respecting the charge-conjugation symmetry. The created new symmetry features favour the lasing of a …

The Subject Librarian Newsletter, Physics, Spring 2017, Sandy Avila

Sandy Avila

No abstract provided.

The Subject Librarian Newsletter, Physics, Fall 2016, Sandy Avila

Sandy Avila

No abstract provided.

Extracting Vibration Characteristics Of A Guitar Using Finite Element, Modal Analysis, And Digital Image Correlation Techniques, Kiran Patil, Javad Baqersad, Daniel Ludwigsen, Yaomin Dong

Daniel Ludwigsen

The sound quality generated by the guitar depends on the vibration characteristics (i.e. natural frequencies and mode shapes) of this instrument. Thus, it is of particular interest to the guitar manufacturers to be able to obtain global information about the characteristics of the guitar. Traditional sensors can only measure at discrete locations. However, digital image correlation (DIC) can measure full-field data on the surface of the structure. In the current paper, a finite element (FE) model of a guitar with free boundary configurations was developed using quadratic solid elements. An eigensolution was performed on the FE model to determine its …

Hyperpolarization Of Silicon Nanoparticles With Tempo Radicals, Jingzhe Hu, Nicholas Whiting, Pratip Bhattacharya

Nicholas Whiting

Analysis Of Regolith Simulant Stratification And Migration In An Asteroid-Like Environment, Gillian Gomer, Michael Fraser, Adrienne Dove, Seamus Anderson, Akbar Whizin, Kristen John, Marc Fries

Gillian Gomer

No abstract provided.

New Result For The Neutron Β -Asymmetry Parameter A 0 From Ucna, Michael Brown, E. B. Dees, E. Adamek, B. Allgeier, M. Blatnik, Thomas J. Bowles, L. J. Broussard, Richard Carr, Stephen M. Clayton, C. Cude-Woods, S. A. Currie, Xiaoping Ding, B. W. Filippone, A. Garcia, Peter Geltenbort, Siraj S. Hasan, Kevin P. Hickerson, J. Hoagland, R. Hong, Gary E. Hogan, A. T. Holley, Takeyasu M. Ito, A. Knecht, C.-Y. Liu, J. Liu, M. Makela, J. W. Martin, Daniel G. Melconian, M. P. Mendenhall, S. D. Moore, Sandhya Nepal, N. Nouri, Robert W. Pattie Jr., A. Pérez Galván, David G. Phillips, Richard H. Picker, Margaret L. Pitt, Bradley R. Plaster, J. C. Ramsey, R. Rios, Daniel J. Salvat, Andy Saunders, Walter E. Sondheim, S.J. Seestrom, Sky Sjue, Steven Slutsky, Xiaohui Sun, Charles Swank, Gyani Swift, E. Tatar, R. Bruce Vogelaar, Brittany Vorndick, Z. Wang, J. Wexler, Tanner Womack, Christopher Wrede, Albert Young, B.A. Zeck

Robert W. Pattie Jr.

Optically Controlled Laser-Plasma Electron Acceleration For Compact Gamma-Ray Sources, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick

Serge Youri Kalmykov

Damage Analysis Modified Trac Computer Program (Damtrac), George H. Baker Iii, Alan D. Mcnutt, G. Bradford Shea, David M. Rubenstein

George H Baker

A computer program tailored for EMP damage analysis of solid-state circuitry has been developed by modifying the existing TRAC network analysis program. Modification of the TRAC diode and transistor models to include breakdown parameters and the addition of a semiconductor device parameter library have greatly simplified the analyst's task. An added feature is a subroutine that automatically calculates the amplitude and duration of transient power dissipated in electronic circuit components.

Optically Controlled Laser-Plasma Electron Accelerator For Compact Gamma-Ray Sources, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick

Serge Youri Kalmykov

Multi-Color, Femtosecond Gamma-Ray Pulse Trains Driven By Comb-Like Electron Beams, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick

Serge Youri Kalmykov

Performance Of The Upgraded Ultracold Neutron Source At Los Alamos National Laboratory And Its Implication For A Possible Neutron Electric Dipole Moment Experiment, Takeyasu M. Ito, Evan R. Adamek, Nathan B. Callahan, J. H. Choi, Stephen M. Clayton, Chris Cude-Woods, Scott Currie, Xinjian Ding, D. E. Fellers, Peter Geltenbort, Steve K. Lamoreaux, C. Y. Liu, S. Macdonald, Mark Makela, Charles L. Morris, Robert W. Pattie Jr., John Clinton Ramsey, Daniel J. Salvat, Andy Saunders, Edward I. Sharapov, S. Sjue, A. P. Sprow, Zebo Tang, H. L. Weaver, Wanchun Wei, Andrew R. Young

Robert W. Pattie Jr.

Simulation Of Charge Transport In Multi-Island Tunneling Devices: Application To Disordered One-Dimensional Systems At Low And High Biases, Madhusudan A. Savaikar, Douglas R. Banyai, Paul Bergstrom, John A. Jaszczak

John Jaszczak

Although devices have been fabricated displaying interesting single-electron transport characteristics, there has been limited progress in the development of tools that can simulate such devices based on their physical geometry over a range of bias conditions up to a few volts per junction. In this work, we present the development of a multi-island transport simulator, MITS, a simulator of tunneling transport in multi-island devices that takes into account geometrical and material parameters, and can span low and high source-drain biases. First, the capabilities of MITS are demonstrated by modeling experimentaldevices described in the literature, and showing that the simulated device …

Roughening And Preroughening Of Diamond-Cubic {111} Surfaces, Donald L. Woodraska, John A. Jaszczak

John Jaszczak

A solid-on-solid model for {111} surfaces of diamond-cubic materials that correctly takes into account the diamond-cubic crystal structure has been developed for Monte Carlo simulation. In addition to a roughening transition at temperature TR, a distinct preroughening transition at TPR≈0.43TR is indicated by divergences in the surface specific heat and order-parameter susceptibility. Preroughening appears to arise naturally in our nearest-neighbor bond model from the entropic freedom available in the nontrivial crystal structure. Preroughening is shown to dramatically lower the nucleation barrier for growth and etching at low driving forces.

Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak

John Jaszczak

Inspired by experimental observations of spatially ordered growth hillocks on the (001) surfaces of natural graphite crystals, a mechanism for spatial organization in quantum dotself-assembly is proposed. The regular arrangement of steps from a screw dislocation-generated growth spiral provides the overall template for such ordering. An ordered array of quantum dots may be formed or nucleated from impurities driven to the step corners by diffusion and by their interactions with the spiral’s steps and kinks. Kinetic Monte Carlo simulation of a solid-on-solid model supports the feasibility of such a mechanism.

Giant Intrinsic Carrier Mobilities In Graphene And Its Bilayer, S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, D. C. Elias, John A. Jaszczak, A. K. Geim

John Jaszczak

We have studied temperature dependences of electron transport in graphene and its bilayer and found extremely low electron-phonon scattering rates that set the fundamental limit on possible charge carrier mobilities at room temperature. Our measurements show that mobilities higher than 200,000 cm2/V s are achievable, if extrinsic disorder is eliminated. A sharp (threshold-like) increase in resistivity observed above ∼200K is unexpected but can qualitatively be understood within a model of a rippled graphene sheet in which scattering occurs on intraripple flexural phonons.

Hyperpolarized Porous Silicon Nanoparticles: Potential Theragnostic Material For 29si Magnetic Resonance Imaging, Hyeonglim Seo, Ikjang Choi, Nicholas Whiting, Jingzhe Hu, Quy S. Luu, Shivanand Pudakalakatti, Caitlin Mccowan, Yaewon Kim, Niki Zacharias Millward, Seunghyun Lee, Pratip Bhattacharya, Youngbok Lee

Nicholas Whiting

Black Holes, Wormholes, And Extra Dimensions, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

No abstract provided.

New Numerical Code For Black Hole Initial Data, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

There are no exact solutions of Einstein Equations that describes a bound system radiating gravitational waves. One needs to resort to numerical simulations, or analytical approximation methods. Current methods to constrained initial data exhibit junk radiation and ambiguities about constrained and free data. It was mathematically proved that given the correct initial data, Einstein equation will yield the expected solution.

Undergraduate Research In Gravitational Waves Astronomy At Marshall University, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

This is a presentation of undergraduate student research into gravitational waves at Marshall University.

Dawn Of Gravitational Wave Astronomy, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

This presentation chronicles the discovery of gravity waves.

Learning To Teach And Teaching To Learn, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

New studies show that students do better in science classes that are taught interactively. We compare two different pedagogical approaches in teaching introductory physics: the lecture-based method, the active learning laboratories. We present the data on student performance on exams, homework, lab activities and tests, from 126 students taking the 200-level introductory physics courses at Marshall University, in Huntington, WV. We discuss the efficiency of each method in fostering the success of students in the introductory physics courses. We find that subtle differentiations can be implicitly detected in students’ exam grades, homework, participation, and choice of major.