Search results for "plane wave"

Plane-Wave Density Functional Theory

2016

Breathing solitary waves in a Sine-Gordon two-dimensional lattice.

1995

We study theoretically and numerically the dynamical behavior of a two-dimensional sine-Gordon lattice. We show that, via modulational instability, an initial-low-amplitude plane wave can evolve spontaneously into moving localized modes with large amplitude. These nonlinear modes, with dimensions depending on the characteristic wavelengths of the instability, behave like breathing solitary waves and present particlelike properties.

The fixed angle scattering problem with a first order perturbation

2021

We study the inverse scattering problem of determining a magnetic field and electric potential from scattering measurements corresponding to finitely many plane waves. The main result shows that the coefficients are uniquely determined by $2n$ measurements up to a natural gauge. We also show that one can recover the full first order term for a related equation having no gauge invariance, and that it is possible to reduce the number of measurements if the coefficients have certain symmetries. This work extends the fixed angle scattering results of Rakesh and M. Salo to Hamiltonians with first order perturbations, and it is based on wave equation methods and Carleman estimates.

Measurement of the ExclusiveH3e(e,e′p)Reaction Below the Quasielastic Peak

2004

New, high-precision measurements of the 3He(e,ep) reaction using the A1 Collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasielastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on the plane wave impulse approximation were observed in both the two- and three-body breakup channels. Full Faddeev-ty…

Stabilizing and controlling domain walls and dark-ring cavity solitons.

2009

We demonstrate two alternative techniques for controlling and stabilizing domain walls (DW) in phase-sensitive, nonlinear optical resonators. The first of them uses input pumps with spatially modulated phase and can be applied also to dark-ring cavity solitons. An optical memory based on the latter is demonstrated. Here the physical mechanism of control relies on the advection caused to any feature by the phase gradients. The second technique uses a plane wave input pump with holes of null intensity across its transverse plane, which are able to capture DWs. Here the physical mechanism of control is of topological nature. When distributed as a regular array, these holes delimit spatial opti…

Thermodynamic properties of neutral and charged oxygen vacancies in BaZrO3 based on first principles phonon calculations.

2015

The structural, electronic and thermodynamic properties of neutral and positively doubly charged oxygen vacancies in BaZrO3 are addressed by first principles phonon calculations. The calculations are performed using two complementary first principles approaches and functionals; the linear combination of atomic orbitals (LCAO) within the hybrid Hartree–Fock and density functional theory formalism (HF-DFT), and the projector augmented plane wave approach (PAW) within DFT. Phonons are shown to contribute significantly to the formation energy of the charged oxygen vacancy at high temperatures (∼1 eV at 1000 K), due to both its large distortion of the local structure, and its large negative form…

Two-dimensional temporal coherence coding for super resolved imaging

2009

In this paper, we present an approach that can be used for transmission of 2D spatial information through space-limited systems capable of transmitting even only a single spatial pixel. The input 2D object is illuminated with temporally incoherent illumination. The axial coherence length is very short and it equals only a few microns. Attached to the input object spatial random phase mask generates different axial shift for every pixel of the input. The temporal delays of the encoding (axial shifts) of every pixel are longer than the coherence length of the illuminating source. Therefore no temporal correlation exists between the various pixels of the input. A lens combines all spatial pixe…

Solitons and modulational instability

1996

We introduce the localized nonlinear waves called solitons which can occur in nature with different profiles such as kink, pulse, and envelope solitons. The envelope-soliton is important because without modulation the wave carry no information. It is a solution of the so-called nonlinear Schrodinger equation which describes the evolution of dispersive and weakly nonlinear waves. The generation of envelope soliton trains can result from the modulational instability phenomenon that leads to self induced modulations, with respect to small perturbations, such as noise, of input plane wave.

Nonlinear Schrödinger models and modulational instability in real electrical lattices

1995

International audience; In nonlinear dispersive media, the propagation of modulated waves, such as envelope (bright) solitons or hole (dark) solitons, has been the subject of considerable interest for many years, as for example in nonlinear optics [A.C. Newell and J.V. Moloney, Nonlinear Optics (Addison-Presley, 1991)]. On the other hand, discrete electrical transmission lines are very convenient tools to study the wave propagation in 1D nonlinear dispersive media [A.C. Scott (Wiley-Interscience, 1970)]. In the present paper, we study the generation of nonlinear modulated waves in real electrical lattices. In the continuum limit, our theoretical analysis based on the Nonlinear Schrodinger e…

Variation of physical constants and electron–positron oscillations: Zitterbewegung in a plane wave

2021

The space and time dependence of physical constants is currently a debated issue for experimental findings, and theoretical reasons seem to indicate that this is not a mere speculative possibility. The paper provides a relativistic description of a free fermion evolving under the assumption of temporal variation of the physical constants. The assumed generalisation of the Dirac equation is particularly simple and permits a grouping of the constants in one single parameter and a consequent agile treatment of the problem. The form of the equations suggests a rescaling of the temporal coordinate $$x^0=ct$$ which allows a plane wave solution. Two are the main results of the treatment. First, th…