636 research outputs found
Non-integrability of a fifth order equation with integrable two-body dynamics
We consider the fifth order partial differential equation (PDE) u4x,t?5uxxt+4ut+uu5x+2uxu4x?5uu3x?10uxuxx+12uux=0, which is a generalization of the integrable Camassa-Holm equation. The fifth order PDE has exact solutions in terms of an arbitrary number of superposed pulsons, with geodesic Hamiltonian dynamics that is known to be integrable in the two-body case N=2. Numerical simulations show that the pulsons are stable, dominate the initial value problem and scatter elastically. These characteristics are reminiscent of solitons in integrable systems. However, after demonstrating the non-existence of a suitable Lagrangian or bi-Hamiltonian structure, and obtaining negative results from Painlev\'{e} analysis and the Wahlquist-Estabrook method, we assert that the fifth order PDE is not integrable
Analytic solutions and Singularity formation for the Peakon b--Family equations
Using the Abstract Cauchy-Kowalewski Theorem we prove that the -family
equation admits, locally in time, a unique analytic solution. Moreover, if the
initial data is real analytic and it belongs to with , and the
momentum density does not change sign, we prove that the
solution stays analytic globally in time, for . Using pseudospectral
numerical methods, we study, also, the singularity formation for the -family
equations with the singularity tracking method. This method allows us to follow
the process of the singularity formation in the complex plane as the
singularity approaches the real axis, estimating the rate of decay of the
Fourier spectrum
Nonlinear balance and exchange of stability in dynamics of solitons, peakons, ramps/cliffs and leftons in a 1+1 nonlinear evolutionary PDE
We study exchange of stability in the dynamics of solitary wave solutions
under changes in the nonlinear balance in a 1+1 evolutionary partial
differential equation related both to shallow water waves and to turbulence. We
find that solutions of the equation with for fluid velocity change their behavior at the
special values .Comment: 15 pages, 8 figures. For this replacement of the original submission,
we: (1) Introduced key explanations that clarify the differences between Figs
1 and 2, versus 3 and 4. (2) Expanded the introduction to provide added
motivation and precise definitions. (3) Added section and subsection headings
to make the plan of the paper more evident. (4) Added a brief summar
A class of equations with peakon and pulson solutions (with an Appendix by Harry Braden and John Byatt-Smith)
We consider a family of integro-differential equations depending upon a
parameter as well as a symmetric integral kernel . When and
is the peakon kernel (i.e. up to rescaling) the
dispersionless Camassa-Holm equation results, while the Degasperis-Procesi
equation is obtained from the peakon kernel with . Although these two
cases are integrable, generically the corresponding integro-PDE is
non-integrable. However,for the family restricts to the pulson family of
Fringer & Holm, which is Hamiltonian and numerically displays elastic
scattering of pulses. On the other hand, for arbitrary it is still possible
to construct a nonlocal Hamiltonian structure provided that is the peakon
kernel or one of its degenerations: we present a proof of this fact using an
associated functional equation for the skew-symmetric antiderivative of .
The nonlocal bracket reduces to a non-canonical Poisson bracket for the peakon
dynamical system, for any value of .Comment: Contribution to volume of Journal of Nonlinear Mathematical Physics
in honour of Francesco Caloger
Wave Structures and Nonlinear Balances in a Family of 1+1 Evolutionary PDEs
We study the following family of evolutionary 1+1 PDEs that describe the
balance between convection and stretching for small viscosity in the dynamics
of 1D nonlinear waves in fluids: m_t + \underbrace{um_x \}
_{(-2mm)\hbox{convection}(-2mm)} + \underbrace{b u_xm \}
_{(-2mm)\hbox{stretching}(-2mm)} = \underbrace{\nu m_{xx}\
}_{(-2mm)\hbox{viscosity}}, \quad\hbox{with}\quad u=g*m . Here
denotes We study exchanges of
stability in the dynamics of solitons, peakons, ramps/cliffs, leftons,
stationary solutions and other solitary wave solutions associated with this
equation under changes in the nonlinear balance parameter .Comment: 69 pages, 26 figure
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