Search results for "Water waves"
showing 10 items of 55 documents
Dispersive evaluation of the D-term form factor in deeply virtual Compton scattering
2014
We present a dispersive representation of the D-term form factor for hard exclusive reactions, using unsubtracted $t$-channel dispersion relations. The $t$-channel unitarity relation is saturated with the contribution of two-pion intermediate states, using the two-pion distributions amplitude for the $\gamma^*\gamma\rightarrow \pi\pi$ subprocess and reconstructing the $\pi\pi\rightarrow N\bar N$ subprocess from available information on pion-nucleon partial-wave helicity amplitudes. Results for the D-term form factor as function of $t$ as well as at $t=0$ are discussed in comparison with available model predictions and phenomenological parametrizations.
Conditions for achieving invisibility of hyperbolic multilayered nanotubes
2016
Invisibility of nanotubes has recently been demonstrated in highly anisotropic metamaterials in the transition regime from hyperbolic to elliptic dispersion [Sci. Rep. 5 (2015) 16027]. In such study, the characterization of a realistic multilayered metamaterial was carried out by means of an effective medium approach providing average components of the permittivity tensor and wave fields. Here, the edge effects of the metal-dielectric stratified nanotube for different combinations were thoroughly analyzed. We show how the boundary layers, which in principle remain fully irrelevant in the estimation of the effective permittivity of the nanotube, however play a critical role in the scattering…
Effects of nonlinearity and substrate’s deformability on modulation instability in NKG equation
2017
International audience; This article investigates combined effects of nonlinearities and substrate's deformability on modulational instability. For that, we consider a lattice model based on the nonlinear Klein-Gordon equation with an on-site potential of deformable shape. Such a consideration enables to broaden the description of energy-localization mechanisms in various physical systems. We consider the strong-coupling limit and employ semi-discrete approximation to show that nonlinear wave modulations can be described by an extended nonlinear Schrodinger equation containing a fourth-order dispersion component. The stability of modulation of carrier waves is scrutinized and the following …
Experimental observations of topologically guided water waves within non-hexagonal structures
2020
International audience; We investigate symmetry-protected topological water waves within a strategically engineered square lattice system. Thus far, symmetry protected topological modes in hexagonal systems have primarily been studied in electromagnetism and acoustics, i.e., dispersionless media. Herein, we show experimentally how crucial geometrical properties of square structures allow for topological transport that is ordinarily forbidden within conventional hexagonal structures. We perform numerical simulations that take into account the inherent dispersion within water waves and devise a topological insulator that supports symmetry-protected transport along the domain walls. Our measur…
A perfect Fresnel acoustic reflector implemented by a Fano-resonant metascreen
2018
We propose a perfectly reflecting acoustic metasurface which is designed by replacing the curved segments of the traditional Fresnel reflector by flat Fano-resonant sub-wavelength unit cells. To preserve the original Fresnel focusing mechanism, the unit cell phase follows a specific phase profile which is obtained by applying the generalized Snell's law and Fermat's principle. The reflected curved phase fronts are thus created at the air-metasurface boundary by tailoring the metasurface dispersion as dictated by Huygens' principle. Since the unit cells are implemented by sub-wavelength double slit-shaped cavity resonators, the impinging sound waves are perfectly reflected producing acoustic…
On the effect of damping on dispersion curves in plates
2013
AbstractThis paper presents a study on quantitative prediction and understanding of time-harmonic wave characteristics in damped plates. Material dissipation is modelled by using complex-valued velocities of free dilatation and shear waves in an unbounded volume. As a numerical example, solution of the classical Rayleigh–Lamb problem for a viscoelastic plate is presented to illustrate and discuss the role of dissipation in the cut-off phenomenon and in the phenomenon of veering for dispersion curves. These phenomena are explained in more detail considering a simple model, which allows accurate asymptotic analysis of the perturbation of dispersion curves in the regions of cut-off and veering.
Quasiparticle interference of spin momentum locked surface states at step edges on Re(0001)
2020
Quasiparticle interference patterns formed by a surface state on the Re(0001) surface were investigated using scanning tunneling spectroscopy. The energy dispersion is inferred from Fourier-transformed differential conductivity maps for occupied and unoccupied states. The band dispersion for occupied states agrees with earlier published results obtained by angle-resolved photoemission spectroscopy. An analysis of the phase of interference patterns at step edges reveals a drastic change in the effective energy barrier for backscattering above and below the Fermi level. The attenuation of the interference pattern with increasing distance indicates interband scattering is the dominant scatteri…
Thermalization of the dispersive three-wave interaction
2007
We investigate the role of dispersion effects on the long-term evolution of the nonlinear three-wave interaction. We show that the three waves exhibit, as a general rule, an irreversible evolution towards a thermodynamic equilibrium state in which they propagate with identical velocities. As a result of this thermalization process, the three-wave system is driven away from spatio-temporal resonance, so that the equilibrium state does not satisfy the (phase-matching) resonant conditions of energy and momentum conservation for the averaged frequencies. Moreover, we show that the interplay between temporal dispersion and spatial diffraction leads to the emergence of a peculiar equilibrium stat…
Notice of Removal: Stochastic generation of the phononic band structure of lossy and infinite crystals
2017
The concept of the band structure is central to the field of phononic crystals. Indeed, capturing the dispersion of Bloch waves — the eigenmodes of propagation in periodic media — gives invaluable information on allowed propagation modes, their phase and group velocities, local resonances, and band gaps. Band structures are usually obtained by solving an eigenvalue problem defined on a closed and bounded domain, which results in a discrete spectrum. There are at least two cases, however, that cannot be reduced to a simple eigenvalue problem: first, when materials showing dispersive loss are present and second, when the unit-cell extends beyond any bound, as in the case of phononic crystal o…
Numerical study of a multiscale expansion of the Korteweg de Vries equation and Painlev\'e-II equation
2007
The Cauchy problem for the Korteweg de Vries (KdV) equation with small dispersion of order $\e^2$, $\e\ll 1$, is characterized by the appearance of a zone of rapid modulated oscillations. These oscillations are approximately described by the elliptic solution of KdV where the amplitude, wave-number and frequency are not constant but evolve according to the Whitham equations. Whereas the difference between the KdV and the asymptotic solution decreases as $\epsilon$ in the interior of the Whitham oscillatory zone, it is known to be only of order $\epsilon^{1/3}$ near the leading edge of this zone. To obtain a more accurate description near the leading edge of the oscillatory zone we present a…