52 research outputs found
Similarity Analysis of Nonlinear Equations and Bases of Finite Wavelength Solitons
We introduce a generalized similarity analysis which grants a qualitative
description of the localised solutions of any nonlinear differential equation.
This procedure provides relations between amplitude, width, and velocity of the
solutions, and it is shown to be useful in analysing nonlinear structures like
solitons, dublets, triplets, compact supported solitons and other patterns. We
also introduce kink-antikink compact solutions for a nonlinear-nonlinear
dispersion equation, and we construct a basis of finite wavelength functions
having self-similar properties.Comment: 18 pages Latex, 6 figures ep
Scaling analyses based on wavelet transforms for the Talbot effect
The fractal properties of the transverse Talbot images are analysed with two
well-known scaling methods, the wavelet transform modulus maxima (WTMM) and the
wavelet transform multifractal detrended fluctuation analysis (WT-MFDFA). We
use the widths of the singularity spectra, Delta alpha=alpha_H-alpha_min, as a
characteristic feature of these Talbot images. The tau scaling exponents of the
q moments are linear in q within the two methods, which proves the
monofractality of the transverse diffractive paraxial field in the case of
these imagesComment: 9 pages, 6 figures, version accepted at Physica
Nonlinear Modes of Liquid Drops as Solitary Waves
The nolinear hydrodynamic equations of the surface of a liquid drop are shown to be directly connected to Korteweg de Vries (KdV, MKdV) systems, giving traveling solutions that are cnoidal waves. They generate multiscale patterns ranging from small harmonic oscillations (linearized model), to nonlinear oscillations, up through solitary waves. These non-axis-symmetric localized shapes are also described by a KdV Hamiltonian system. Recently such ``rotons'' were observed experimentally when the shape oscillations of a droplet became nonlinear. The results apply to drop-like systems from cluster formation to stellar models, including hyperdeformed nuclei and fission
Wavelets and Quantum Algebras
Wavelets, known to be useful in non-linear multi-scale processes and in
multi-resolution analysis, are shown to have a q-deformed algebraic structure.
The translation and dilation operators of the theory associate with any scaling
equation a non-linear, two parameter algebra. This structure can be mapped onto
the quantum group in one limit, and approaches a Fourier series
generating algebra, in another limit. A duality between any scaling function
and its corresponding non-linear algebra is obtained. Examples for the Haar and
B-wavelets are worked out in detail.Comment: 27 pages Latex, 3 figure p
A New Nonlinear Liquid Drop Model. Clusters as Solitons on The Nuclear Surface
By introducing in the hydrodynamic model, i.e. in the hydrodynamic equations
and the corresponding boundary conditions, the higher order terms in the
deviation of the shape, we obtain in the second order the Korteweg de Vries
equation (KdV). The same equation is obtained by introducing in the liquid drop
model (LDM), i.e. in the kinetic, surface and Coulomb terms, the higher terms
in the second order. The KdV equation has the cnoidal waves as steady-state
solutions. These waves could describe the small anharmonic vibrations of
spherical nuclei up to the solitary waves. The solitons could describe the
preformation of clusters on the nuclear surface. We apply this nonlinear liquid
drop model to the alpha formation in heavy nuclei. We find an additional
minimum in the total energy of such systems, corresponding to the solitons as
clusters on the nuclear surface. By introducing the shell effects we choose
this minimum to be degenerated with the ground state. The spectroscopic factor
is given by the ratio of the square amplitudes in the two minima.Comment: 27 pages, LateX, 8 figures, Submitted J. Phys. G: Nucl. Part. Phys.,
PACS: 23.60.+e, 21.60.Gx, 24.30.-v, 25.70.e
Generalized KdV Equation for Fluid Dynamics and Quantum Algebras
We generalize the non-linear one-dimensional equation of a fluid layer for
any depth and length as an infinite order differential equation for the steady
waves. This equation can be written as a q-differential one, with its general
solution written as a power series expansion with coefficients satisfying a
nonlinear recurrence relation. In the limit of long and shallow water (shallow
channels) we reobtain the well known Korteweg-de-Vries equation together with
its single-soliton solution.Comment: 17 pages, Latex, PACS: 47.20.Ky, 43.25.Rq, 47.35.+i, 03.40.Kf,
43.25.Fe, 02.20.Tw, MSC: 16W30, 17B37, 81R50, 35Q51, 34B15, 34L30, 76E3
Analysis and classification of nonlinear dispersive evolution equations in the potential representation
A potential representation for the subset of travelling solutions of nonlinear dispersive evolution equations is introduced. The procedure involves reduction of a third-order partial differential equation to a first-order ordinary differential equation. The potential representation allows us to deduce certain properties of the solutions without the actual need to solve the underlying evolution equation. In particular, the paper deals with the so-called K(n, m) equations. Starting from their respective potential representations it is shown that these equations can be classified according to a simple point transformation. As a result, e.g., all equations with linear dispersion join the same equivalence class with the Korteweg-deVries equation being its representative, and all soliton solutions of higher order nonlinear equations are thus equivalent to the KdV soliton. Certain equations with both linear and quadratic dispersions can also be treated within this equivalence class
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