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Nonlinear dispersion equations: Smooth deformations,compactions, and extensions to higher orders
Authors:V A Galaktionov
Institution:(1) Department of Mathematical Sciences, University of Bath, Math, BA2 7AY, UK
Abstract:The third-order nonlinear dispersion PDE, as the key model,
$$
u_t  = (uu_x )_{xx} in\mathbb{R} \times \mathbb{R}_ +  
$$ ((0.1))
is studied. Two Riemann’s problems for (0.1) with the initial data S (x) = ∓ sgn.x create shock (u(x, t) ≡ S (x)) and smooth rarefaction (for the data S +) waves (see 16]). The concept of “δ-entropy” solutions and others are developed for establishing the existence and uniqueness for (0.1) by using stable smooth δ-deformations of shock-type solutions. These are analogous to entropy theory for scalar conservation laws such as u t + uu x = 0, which were developed by Oleinik and Kruzhkov (in x ∊ ℝ N ) in the 1950s–1960s. The Rosenau-Hyman K(2, 2) (compacton) equation
$$
u_t  = (uu_x )_{xx}  + 4uu_x ,
$$
which has a special importance for applications, is studied. Compactons as compactly supported travelling wave solutions are shown to be δ-entropy. Shock and rarefaction waves are discussed for other NDEs such as
$$
u_t  = (u^2 u_x )_{xx} ,u_{tt}  = (uu_x )_{xx} ,u_{tt}  = uu_x ,u_{ttt}  = (uu_x )_{xx} ,u_t  = (uu_x )_{xxxxx} ,etc.
$$
. This article was submitted by the author in English. Dedicated to the memory of Professors O.A. Oleinik and S.N. Kruzhkov
Keywords:Odd-order quasi-linear PDE  shock and rarefaction waves  entropy solutions  self-similar patterns
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