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Results for “STRONG COUPLING”

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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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Stability of spin-0 graviton and strong coupling in Horava-Lifshitz theory of gravity

In this paper, we consider two different issues, stability and strong coupling, which have been raised recently in the newly proposed Horava-Lifshitz theory of quantum gravity with the projectability condition. We find that all the scalar modes are stable in the de Sitter background, due to two different kinds of effects, one from high-order derivatives of the spacetime curvature and the other from the exponential expansion of the de Sitter space. Combining these effects properly, one can make the instability found in the Minkowski background never appear even for small-scale modes, provided that the IR limit is sufficiently close to the relativistic fixed point. At the fixed point, all the modes become stabilized. We also show that the instability of Minkowski spacetime can be cured by introducing mass to the spin-0 graviton. The strong coupling problem is investigated following the effective field theory approach, and we find that it cannot be cured by the Blas-Pujolas-Sibiryakov mechanism, initially designed for the case without the projectability condition, but might be circumvented by the Vainshtein mechanism, due to the nonlinear effects. In fact, we construct a class of exact solutions, and show explicitly that they reduce smoothly to the de Sitter spacetime in the relativistic limit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Nonlinear ion modes in a dense plasma with strongly coupled ions and degenerate electron fluids

The properties of solitary and shock structures associated with nonlinear ion modes in a dense plasma with strongly coupled nondegenerate ions and degenerate electron fluids are presented. For this purpose, we have used the viscoelastic fluid model for the ions, the inertialess electron momentum equation with weakly and ultrarelativistic pressure laws for the degenerate electron fluids, and Poisson's equation to derive the Burgers and Kortweg-de Vries equations. Possible stationary solutions of the latter are the shock and solitary structures, respectively. It is found that the speed, amplitude, and width of the shock and solitary waves critically depend on the strong coupling between ions and electron degeneracy effects. The relevance of our investigation to the role of localized excitations in dense astrophysical objects is briefly discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Strong D*{yields}D{pi} and B*{yields}B{pi} couplings

We compute g{sub D}{sup *}{sub D{pi}} and g{sub B}{sup *}{sub B{pi}} using a framework in which all elements are constrained by Dyson-Schwinger equation studies of QCD and therefore incorporates a consistent, direct, and simultaneous description of light and heavy quarks and the states they may constitute. We link these couplings with the heavy-light-meson leptonic decay constants and thereby obtain g{sub D}{sup *}{sub D{pi}}=15.9{sub -1.0}{sup +2.1} and g{sub B}{sup *}{sub B{pi}}=30.0{sub -1.4}{sup +3.2}. From the latter, we infer g{sub B}=0.37{sub -0.02}{sup +0.04}. A comparison between g{sub D}{sup *}{sub D{pi}} and g{sub B}{sup *}{sub B{pi}} indicates that when the c quark is a system's heaviest constituent, {Lambda}{sub QCD}/m{sub c}-corrections are not under good control.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Parametrizations of coupled betatron motion for strongly coupled lattices

The coupling of transverse motion is a natural occurrence in particle accelerators, either in the form of a residual coupling arising from imperfections or originating by design from strong systematic coupling fields. While the first can be treated perturbatively, the latter requires a robust approach adapted to strongly coupled optics, and a parametrization of the linear optics must be performed to explore beam dynamics in such peculiar lattices. This work highlights the key physical interpretations of the main parametrization formalisms to describe linear coupled optics, along with explicit links and comparisons of these parametrizations. Concepts rarely illustrated in other works, such as forced mode flips and local coupling, are explored in detail, clarifying some anomalies that can arise in lattice functions. The analytical methods have been implemented in a reference Python package and connected with ray-tracing and integration codes to explore examples of strongly coupled lattices, which are discussed in detail to highlight the key physical interpretations of the parametrizations and characteristics of the lattices.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

QCD and Strongly Coupled Gauge Theories: Challenges and Perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to stongly-coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Second harmonic generation from metamaterials strongly coupled to intersubband transitions in quantum wells

We theoretically analyze the second harmonic generation capacity of two-dimensional periodic metamaterials comprising sub-wavelength resonators strongly coupled to intersubband transitions in quantum wells (QWs) at mid-infrared frequencies. The metamaterial is designed to support a fundamental resonance at ∼30 THz and an orthogonally polarized resonance at the second harmonic frequency (∼60 THz), while the asymmetric quantum well structure is designed to provide a large second order susceptibility. Upon continuous wave illumination at the fundamental frequency we observe second harmonic signals in both the forward and backward directions, with the forward efficiency being larger. We calculate the overall second harmonic conversion efficiency of the forward wave to be ∼1.3 × 10{sup −2} W/W{sup 2}—a remarkably large value, given the deep sub-wavelength dimensions of the QW structure (about 1/15th of the free space wavelength of 10 μm). The results shown in this Letter provide a strategy for designing easily fabricated sources across the entire infrared spectrum through proper choice of QW and resonator designs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Towards the gravity dual of quarkonium in the strongly coupled QCD plasma

We build a 'bottom-up' holographic model of charmonium by matching the essential spectral data. We argue that these data must include not only the masses but also the decay constants of the J/{psi} and {psi}{sup '} mesons. Relative to the 'soft-wall' models for light mesons, such a matching requires two new features in the holographic potential: an overall upward shift as well as a narrow 'dip' near the holographic boundary. We calculate the spectral function as well as the position of the complex singularities (quasinormal frequencies) of the retarded correlator of the charm current at finite temperatures. We further extend this analysis by showing that the residue associated with such a singularity is given by the boundary derivative of the appropriately normalized quasinormal mode. We find that the 'melting' of the J/{psi} spectral peak occurs at a temperature T{approx_equal}540 MeV, or 2.8T{sub c}, in good agreement with lattice results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Coherent Spin Pumping in a Strongly Coupled Magnon-Magnon Hybrid System

Here, we experimentally identify coherent spin pumping in the magnon-magnon hybrid modes of yttrium iron garnet/permalloy (YIG/Py) bilayers. By reducing the YIG and Py thicknesses, the strong interfacial exchange coupling leads to large avoided crossings between the uniform mode of Py and the spin wave modes of YIG enabling accurate determination of modification of the linewidths due to the dampinglike torque. We identify additional linewidth suppression and enhancement for the in-phase and out-of-phase hybrid modes, respectively, which can be interpreted as concerted dampinglike torque from spin pumping. Furthermore, varying the Py thickness shows that both the fieldlike and dampinglike couplings vary like 1/$\sqrt{𝑡_{Py}}$, verifying the prediction by the coupled Landau-Lifshitz equations.

ferromagnetic resonance↗
DOE OSTI2019

Orientational Dependence of Cofacial Porphyrin–Quinone Electronic Interactions within the Strong Coupling Regime

We examine the relative magnitudes of electronic coupling HDA in two face-to-face rigid and diastereomeric (porphinato)zinc(II)–quinone (PZn–Q) as-semblies, 1β-ZnA and 1β-ZnB, in which the six quinonyl carbon atoms lie in virtually identical arrangements relative to the PZn plane at sub-van der Waals donor–acceptor (D–A) interplanar separations. Steady-state and time-resolved transient optical data and computational studies show that minor differences in relative D–A cofacial orientation give rise to disparate H DA magnitudes for both photoinduced charge separation (CS) and thermal charge recombination (CR). Here, time-dependent density functional theory (TDDFT) computations illuminate the nature of direct charge transfer states and the electronic structural factors that give rise to these differential H DA s. These data show more extensive mixing of locally excited (LE) and CS states in 1β-ZnA relative to 1β-ZnB and that these H DA differences track the magnitudes of electronic coupling matrix elements determined from steady-state electronic spectral data and thermal CR rate constants measured via pump–probe spectroscopy. Collectively, this work shows that electron transfer dynamics may be manipulated in cofacial D–A systems, even at sub-van der Waals contact, provided that conformational rigidity precludes structural fluctuations that modulate D–A interactions on the charge transfer time scale.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗