Cosmological dynamics of Higgs potential fine tuning
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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Results for “wave fields”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Accelerating particle-in-cell kinetic plasma simulations via reduced-order modeling of space-charge dynamics using dynamic mode decomposition
We present a data-driven reduced-order modeling of the space-charge dynamics for electromagnetic particle-in-cell (EMPIC) plasma simulations based on dynamic mode decomposition (DMD). The dynamics of the charged particles in kinetic plasma simulations such as EMPIC is manifested through the plasma current density defined along the edges of the spatial mesh. We showcase the efficacy of DMD in modeling the time evolution of current density through a low-dimensional feature space. Not only do such DMD based predictive reduced-order models help accelerate EMPIC simulations, they also have the potential to facilitate investigative analysis and control applications. Here, we demonstrate the proposed DMD-EMPIC scheme for reduced-order modeling of current density and speedup in EMPIC simulations involving electron beam under the influence of magnetic field, virtual cathode oscillations, and backward wave oscillator.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Generation and Evolution of High-Mach-Number Laser-Driven Magnetized Collisionless Shocks in the Laboratory
Here, we present the first laboratory generation of high-Mach-number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient plasma. Time-resolved, two-dimensional imaging of plasma density and magnetic fields shows the formation and evolution of a supercritical shock propagating at magnetosonic Mach number M ms ≈ 12. Particle-in-cell simulations constrained by experimental data further detail the shock formation and separate dynamics of the multi-ion-species ambient plasma. The results show that the shocks form on time scales as fast as one gyroperiod, aided by the efficient coupling of energy, and the generation of a magnetic barrier between the piston and ambient ions. The development of this experimental platform complements present remote sensing and spacecraft observations, and opens the way for controlled laboratory investigations of high-Mach number collisionless shocks, including the mechanisms and efficiency of particle acceleration.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Three-Dimensional Chiral Lattice Fermion in Floquet Systems
Here, we show that the Nielsen-Ninomiya no-go theorem still holds on a Floquet lattice: there is an equal number of right-handed and left-handed Weyl points in a three-dimensional Floquet lattice. However, in the adiabatic limit, where the time evolution of the low-energy subspace is decoupled from the high-energy subspace, we show that the bulk dynamics in the low-energy subspace can be described by Floquet bands with extra left- or right-handed Weyl points, despite the no-go theorem. Assuming adiabatic evolution of two bands, we show that the difference of the number of right-handed and left-handed Weyl points equals twice the winding number of the adiabatic Floquet operator over the Brillouin zone. Based on these findings, we propose a realization of purely left- or right-handed Weyl particles on a 3D lattice using a Hamiltonian obtained through dimensional reduction of a four-dimensional quantum Hall system. We argue that the breakdown of the adiabatic approximation on the surface facilitates unusual closed orbits of wave packets in an applied magnetic field, which traverse alternatively through the low-energy and high-energy sector of the spectrum.
74 ATOMIC AND MOLECULAR PHYSICS↗
From Scattering Amplitudes to Classical Potentials in the Post-Minkowskian Expansion
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Quantum Mechanics of Gravitational Waves
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71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Radiated Angular Momentum and Dissipative Effects in Classical Scattering
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79 ASTRONOMY AND ASTROPHYSICS↗
Binary Dynamics through the Fifth Power of Spin at O ( G 2 )
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79 ASTRONOMY AND ASTROPHYSICS↗
Effective Field Theory for Extreme Mass Ratio Binaries
We derive an effective field theory describing a pair of gravitationally interacting point particles in an expansion in their mass ratio, also known as the self-force (SF) expansion. The 0SF dynamics are trivially obtained to all orders in Newton’s constant by the geodesic motion of the light body in a Schwarzschild background encoding the gravitational field of the heavy body. The corrections at 1SF and higher are generated by perturbations about this configuration—that is, the geodesic deviation of the light body and the fluctuation graviton—but crucially supplemented by an operator describing the recoil of the heavy body as it interacts with the smaller companion. Using this formalism we compute new results at third post-Minkowskian order for the conservative dynamics of a system of gravitationally interacting massive particles coupled to a set of additional scalar and vector fields.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Peculiarities in the Formation of X-Ray Fluxes by Waveguide–Resonators of Different Construction
The phenomenon of total external reflection (TER) of quasi-monochromatic X-ray radiation fluxes on a material interface and the effect of waveguide–resonator propagation of these fluxes in nanosize extended slit clearance, as well as a device operating on the basis of this effect—a planar X-ray waveguide–resonator—are briefly described. Experimental data on the formation of an X-ray flux by a composite X-ray waveguide–resonator are presented, and a model describing the decrease in the angular divergence of the formed flux without a decrease in the integral intensity is proposed. The model is based on the conception of partial angular tunneling of the radiation flux in the gap between two consequently mounted and mutually adjusted waveguide–resonators; the tunneling is implemented due to the interaction between interference fields of standing X-ray waves excited by the radiation transported by the slit clearance of these waveguide–resonators.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Electron energy balance and ionization in the channel of a stationary plasma thruster
The paper presents results of numerical simulations of the electron dynamics in the field of the azimuthal and longitudinal waves excited in the channel of a stationary plasma thruster (SPT). The simulations are based on the experimentally determined wave characteristics. The simulation results show that the azimuthal wave displayed as ionization instability enhances electron transport along the thruster channel. It is established that the electron transport rate in the azimuthal wave increases as compared to the rate of diffusion caused by electron scattering from neutral atoms in proportion to the ratio between the times of electron− neutral collisions responsible for ionization and elastic electron scattering, respectively. An expression governing the plasma conductivity is derived with allowance for electron interaction with the azimuthal wave. The Hall parameter, the electron component of the discharge current, and the electron heating power in the thruster channel are calculated for two model SPTs operating with krypton and xenon. The simulation results agree well with the results of experimental studies of these two SPTs.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Modulational instabilities in relativistic pair plasmas
We study the modulational instability of an intense photon beam in a relativistic pair plasma. We use the wave-kinetic description of the photon field and relativistic fluid equations for electrons and positrons. This allows us to consider the influence of the photon spectral distribution and photon recoil effects on the instability threshold and growth rates. The case of very low frequencies modulations, well below plasma frequency, is compared to that of high-frequency modulations corresponding to the plasmon decay instability.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Filtration of Surface Magnetostatic Waves in Yttrium Iron Garnet Films of Variable Width Excited by Focusing Transducers
We have studied the filtration of surface spin waves in yttrium iron garnet (YIG) films of variable width excited by focusing transducers integrated with the film.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Observation of EHO in NSTX and theoretical study of its active control using HHFW antenna
Two important topics in the tokamak ELM control, using the non-axisymmetric (3D) magnetic perturbations, are studied in NSTX and combined envisioning ELM control in the future NSTX-U operation: Experimental observations of the edge harmonic oscillation in NSTX (not necessarily the same as EHOs in DIII-D), and theoretical study of its external drive using the high harmonic fast wave (HHFW) antenna as a 3D field coil. Edge harmonic oscillations were observed particularly well in NSTX ELM-free operation with low n core modes, with various diagnostics confirming n = 4 ~ 6 edge-localized and coherent oscillations in 2 ~ 8kHz frequency range. These oscillations seem to have a favored operational window in rotational shear, similarly to EHOs in DIII-D QH modes. However, in NSTX, they are not observed to provide particle or impurity control, possibly due to their weak amplitudes, of a few mm displacements, as measured by reflectometry. The external drive of these modes has been proposed in NSTX, by utilizing audio-frequency currents in the HHFW antenna straps. Analysis shows that the HHFW straps can be optimized to maximize n = 4 ~ 6 while minimizing n = 1 ~ 3. Also, IPEC calculations show that the optimized configuration with only 1kAt current can produce comparable or larger displacements than the observed internal modes. If this optimized external drive can be constructively combined, or further resonated with the internal modes, the edge harmonic oscillations in NSTX may be able to produce sufficient particle control to modify ELMs.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Theoretical Formulation of an Ambient Stress State in Isotropic Elastic Media
Due to the weight of overburden and tectonic forces, the solid earth is subject to an ambient stress state. This stress state is quasi-static in that it is generally in a state of equilibrium. Typically, seismology assumes this ambient stress field has a negligible effect on wave propagation. However, two basic theories have been put forward to describe the effects of ambient stress on wave propagation. Dahlen and Tromp (2002) expound a theory based on perturbation analysis that largely supports the traditional seismological view that ambient stress is negligible for wave propagation. The second theory, espoused by Korneev and Glubokovskikh (2013) and supported by some experimental work, states that perturbation analysis is inappropriate since the elastic modulus is very sensitive to the ambient stress states. This brief report reformulates the equations given by Korneev and Glubokovskikh (2013) into a more compact form that makes it amenable to statement in terms of a pre-stress form of Hooke's Law. Furthermore, this report demonstrates the symmetries of the pre-stress modulus tensor and discusses the reciprocity relationship implied by the symmetry conditions.
58 GEOSCIENCES↗
Theoretical Formulation of an Ambient Stress State in Isotropic Elastic Media
Due to the weight of overburden and tectonic forces, the solid earth is subject to an ambient stress state. This stress state is quasi-static in that it is generally in a state of equilibrium. Typically, seismology assumes this ambient stress field has a negligible effect on wave propagation. However, two basic theories have been put forward to describe the effects of ambient stress on wave propagation. Dahlen and Tromp (2002) expound a theory based on perturbation analysis that largely supports the traditional seismological view that ambient stress is negligible for wave propagation. The second theory, espoused by Korneev and Glubokovskikh (2013) and supported by some experimental work, states that perturbation analysis is inappropriate since the elastic modulus is very sensitive to the ambient stress states. This brief report reformulates the equations given by Korneev and Glubokovskikh (2013) into a more compact form that makes it amenable to statement in terms of a pre-stress form of Hooke's Law. Furthermore, this report demonstrates the symmetries of the pre-stress modulus tensor and discusses the reciprocity relationship implied by the symmetry conditions.
58 GEOSCIENCES↗
Characterizing Interference in a Wave-Powered Buoy
Oceanographic measurement buoys are power constrained by the capacity of their batteries and the available solar power. Many buoys are in locations with abundant wave energy, but wave energy converters are not being used to power them. One reason wave energy converters may not have not been developed for wave measurement buoys is that many buoys measure waves by precisely following the wave motion. Wave energy converters may inhibit this wave-following ability by altering a buoy's response to incoming waves. In this report, we present the results of field tests that measured the extent to which buoy motion was changed by modifications to the buoy for wave energy harvesting. The motion of the buoy was significantly modified by the addition of the hardware components necessary for harvesting wave energy. The ratio of the mass of the wave energy converter to the mass of the buoy was high for the system tested, which strongly affected buoy motion. A lower value for this ratio would decrease the effect of the wave energy converter on the motion of the buoy, thereby decreasing the impact on the buoy's ability to measure waves but also decreasing the power production capabilities. Therefore, the use of wave energy converters to power wave measurement buoys may be feasible for large buoys that measure low-frequency waves and have low power requirements.
16 TIDAL AND WAVE POWER↗
Magnetic field amplification by collisionless shocks in partially ionized plasmas
In this paper, we study the shock structures of collisionless shocks in partially ionized plasmas by means of two-dimensional hybrid simulations, where the shock is a perpendicular shock with shock velocity v{sub sh}≈40 v{sub A}≈1333 km s{sup −1} and the upstream ionization fraction is 0.5. We find that large density fluctuations and large magnetic field fluctuations are generated both in the upstream and downstream regions. In addition, we find that the velocity distribution of downstream hydrogen atoms has three components. The observed shock structures suggest that diffusive shock acceleration can operate at perpendicular shocks propagating into partially ionized plasmas in real three-dimensional systems.
79 ASTRONOMY AND ASTROPHYSICS↗