scholarly journals Maxwell wave packets in de Sitter expanding universe

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Ion I. Cotăescu ◽  
Ion Cotăescu
Keyword(s):  
Wave Packet ◽  
Wave Packets ◽  
Plane Waves ◽  
Null Geodesic ◽  
Free Field ◽  
Graphical Analysis ◽  
Expanding Universe ◽  
De Sitter ◽  
First Time ◽  
Gaussian Packet

AbstractWe study for the first time the propagation of the packets of plane waves of the Maxwell free field in the de Sitter expanding universe as detected by an observer staying at rest in his proper frame with physical de Sitter–Painlevé coordinates. This observes an accelerate propagation of the wave packet along to a null geodesic, laying out a severe exponential decay and a moderate dispersion, increasing exponentially in time during propagation. The example we give is the usual anisotropic Gaussian packet for which we present a short graphical analysis pointing out the accelerated propagation, decay and dispersion. Moreover, we show that the observer perceives his horizon as a mirror stopping the wave packets prepared on it and reflecting those prepared beyond it.

scholarly journals Light from Reissner–Nordstrom–de Sitter black holes

2021 ◽  
pp. 2150162
Author(s):  
Ion I. Cotăescu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Expanding Universe ◽  
De Sitter ◽  
Principal Parameter ◽  
Null Geodesics ◽  
Charged Black Holes ◽  
Peculiar Velocities ◽  
First Time

We derive for the first time the form of the spiral null geodesics around the photon sphere of the Reissner–Nordstrom black hole in the de Sitter expanding universe. Moreover, we obtain the principal parameter we need for deriving, according to our method [I. I. Cotăescu, Eur. Phys. J. C 81, 32 (2021)], the black hole shadow and the related redshift as measured by a remote observer situated in the asymptotic zone. We obtain thus a criterion of detecting charged black holes without peculiar velocities when one knows the mass, redshift and the black hole shadow.

scholarly journals Quantum theory of redshift in de Sitter expanding universe

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Ion I. Cotăescu
Keyword(s):  
Quantum Theory ◽  
Projection Operator ◽  
Free Field ◽  
Quantum Corrections ◽  
Uncertainty Relations ◽  
Expanding Universe ◽  
De Sitter ◽  
Expectation Values ◽  
Hubble’S Law ◽  
Coherent Quantum

AbstractThe quantum theory of the Maxwell free field in Coulomb gauge on the de Sitter expanding universe is completed with the technical elements needed for building a coherent quantum theory of redshift. Paying special attention to the conserved observables and defining the projection operator selecting the detected momenta it is shown that the expectation values of the energies of the emitted and detected photons comply with the Lemaître rule of Hubble’s law. Moreover, the quantum corrections to the dispersions of the principal observables and new uncertainty relations are derived.

scholarly journals The Stationary Frontal Wave Packet Spontaneously Generated in Mesoscale Dipoles

2008 ◽  
Vol 38 (1) ◽  
pp. 243-256 ◽  
Author(s):  
Álvaro Viúdez
Keyword(s):  
Wave Packet ◽  
Wave Packets ◽  
Plane Waves ◽  
Three Dimensional ◽  
Vertical Shear ◽  
Vertical Column ◽  
Vortical Structures ◽  
Frontal Wave ◽  
Fluid Particles ◽  
Balanced Flow

Abstract Three-dimensional numerical simulations of rotating, statically and inertially stable, mesoscale flows show that wave packets, with vertical velocity comparable to that of the balanced flow, can be spontaneously generated and amplified in the frontal part of translating vortical structures. These frontal wave packets remain stationary relative to the vortical structure (e.g., in the baroclinic dipole, tripole, and quadrupole) and are due to inertia–gravity oscillations, near the inertial frequency, experienced by the fluid particles as they decelerate when leaving the large speed regions. The ratio between the horizontal and vertical wavenumbers depends on the ratio between the horizontal and vertical shears of the background velocity. Theoretical solutions of plane waves with varying wavenumbers in background flow confirm these results. Using the material description of the fields it is shown that, among the particles simultaneously located in the vertical column in the dipole’s center, the first ones to experience the inertia–gravity oscillations are those in the upper layer, in the region of the maximum vertical shear. The wave packet propagates afterward to the fluid particles located below.

scholarly journals On quantum corrections to geodesics in de-Sitter spacetime

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Viacheslav A. Emelyanov
Keyword(s):  
Wave Packet ◽  
Gordon Equation ◽  
Plane Waves ◽  
Hubble Constant ◽  
De Sitter ◽  
Field Mass ◽  
Sitter Spacetime ◽  
Klein Gordon ◽  
De Sitter Universe ◽  
Positive Frequency

AbstractWe find a coordinate-independent wave-packet solution of the massive Klein–Gordon equation with the conformal coupling to gravity in the de-Sitter universe. This solution can locally be represented through the superposition of positive-frequency plane waves at any space-time point, assuming that the scalar-field mass M is much bigger than the de-Sitter Hubble constant H. The solution is also shown to be related to the two-point function in the de-Sitter quantum vacuum. Moreover, we study the wave-packet propagation over cosmological times, depending on the ratio of M and H. In doing so, we find that this wave packet propagates like a point-like particle of the same mass if $$M \ggg H$$ M ⋙ H , but, if otherwise, the wave packet behaves highly non-classically.

The Spectrum Segmentation Algorithm of Multimode Vibration Signal Based on Spectral Clustering

2011 ◽  
Vol 121-126 ◽  
pp. 2372-2376
Author(s):  
Dan Dan Wang ◽  
Yu Zhou ◽  
Qing Wei Ye ◽  
Xiao Dong Wang
Keyword(s):  
Wave Packet ◽  
Frequency Domain ◽  
Spectral Clustering ◽  
Clustering Algorithm ◽  
Wave Packets ◽  
Vibration Signal ◽  
Segmentation Algorithm ◽  
Frequency Curve ◽  
Macroscopic Observation ◽  
Spectral Clustering Algorithm

The mode peaks in frequency domain of vibration signal are strongly interfered by strong noise, causing the inaccuracy mode parameters. According to this situation, this paper comes up with the thought of mode-peak segmentation based on the spectral clustering algorithm. First, according to the concept of wave packet, the amplitude-frequency of vibration signal is divided into wave packets. Taking each wave packet as a sample of clustering algorithm, the spectral clustering algorithm is used to classify these wave packets. The amplitude-frequency curve of a mode peak becomes a big wave packet in macroscopic. The experiment to simulation signals indicates that this spectral clustering algorithm could accord with the macroscopic observation of mode segmentation effectively, and has outstanding performance especially in strong noise.

scholarly journals Spin-Orbit Entanglement in Time Evolution of Radial Wave Packets in Hydrogenic Systems

2004 ◽  
Vol 11 (04) ◽  
pp. 401-409
Author(s):  
Marcin Turek ◽  
Piotr Rozmej
Keyword(s):  
Wave Packet ◽  
Time Evolution ◽  
Time Scale ◽  
Degrees Of Freedom ◽  
Wave Packets ◽  
Characteristic Time Scale ◽  
Radial Wave ◽  
Mean Values ◽  
Breathing Motion ◽  
Wave Packet Revival

Time evolution of radial wave packets built from the eigenstates of Dirac equation for a hydrogenic system is considered. Radial wave packets are constructed from the states of different n quantum numbers and the same lowest angular momentum. In general they exhibit a kind of breathing motion with dispersion and (partial) revivals. Calculations show that for some particular preparations of the wave packet one can observe interesting effects in spin motion, coming from inherent entanglement of spin and orbital degrees of freedom. These effects manifest themselves through some oscillations in the mean values of spin operators and through changes of spatial probability density carried by upper and lower components of the wave function. It is also shown that the characteristic time scale of predicted effects (called T ls ) is much smaller for radial wave packets than in other cases, reaching values comparable to (or even less than) the time scale for the wave packet revival.

scholarly journals Dynamics of scalar potentials in theory of gravity

2019 ◽  
Vol 97 (8) ◽  
pp. 880-894
Author(s):  
M. Zubair ◽  
Farzana Kousar ◽  
Saira Waheed
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Graphical Analysis ◽  
Chaplygin Gas ◽  
Field Potentials ◽  
De Sitter ◽  
Field Equations ◽  
Barotropic Fluid ◽  
First Case ◽  
De Sitter Universe

In this paper, we explore the nature of scalar field potential in [Formula: see text] gravity using a well-motivated reconstruction scheme for flat Friedmann–Robertson–Walker (FRW) geometry. The beauty of this scheme lies in the assumption that the Hubble parameter can be expressed in terms of scalar field and vice versa. Firstly, we develop field equations in this gravity and present some general explicit forms of scalar field potential via this technique. In the first case, we take the de Sitter universe model and construct some field potentials by taking different cases for the coupling function. In the second case, we derive some field potentials using the power law model in the presence of different matter sources like barotropic fluid, cosmological constant, and Chaplygin gas for some coupling functions. From graphical analysis, it is concluded that using some specific values of the involved parameters, the reconstructed scalar field potentials are cosmologically viable in both cases.

scholarly journals Local and electronic structure around Ga in CdTe: evidence of DX- and A-centers

2012 ◽  
Vol 20 (1) ◽  
pp. 166-171
Author(s):  
Vasil Koteski ◽  
Jelena Belošević-Čavor ◽  
Petro Fochuk ◽  
Heinz-Eberhard Mahnke
Keyword(s):  
Density Functional ◽  
Plane Waves ◽  
Lattice Relaxation ◽  
Defect Structures ◽  
Functional Theory ◽  
Edge Structure ◽  
X Ray ◽  
First Time ◽  
X Ray Absorption ◽  
Good Agreement

The lattice relaxation around Ga in CdTe is investigated by means of extended X-ray absorption spectroscopy (EXAFS) and density functional theory (DFT) calculations using the linear augmented plane waves plus local orbitals (LAPW+lo) method. In addition to the substitutional position, the calculations are performed for DX- and A-centers of Ga in CdTe. The results of the calculations are in good agreement with the experimental data, as obtained from EXAFS and X-ray absorption near-edge structure (XANES). They allow the experimental identification of several defect structures in CdTe. In particular, direct experimental evidence for the existence of DX-centers in CdTe is provided, and for the first time the local bond lengths of this defect are measured directly.

scholarly journals ACCELERATION OF PARTICLES BY THE FIELDS OF WAVE PACKETS

2019 ◽  
pp. 43-46
Author(s):  
V.А. Buts ◽  
V.V. Kuzmin ◽  
A.P. Tolstoluzhsky
Keyword(s):  
Wave Packet ◽  
Wave Packets ◽  
Dynamic Chaos ◽  
Acceleration Of Particles ◽  
Nonlinear Resonances ◽  
Dynamics Of Particles

The dynamics of particles in the field of a wave packet excited in a plasma is considered. The conditions are found under which such dynamics is regular, and when it becomes chaotic. It was found that the well-known (phenomenological) criterion for the emergence of dynamic chaos − the criterion for overlapping Chirikov nonlinear resonances − requires careful use.

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