Abstract:In the presented paper known (up to the beginning of 2008) Lie-and non-Lie exact solutions of different (1 + 1)-dimensional diffusion-convection equations of form f (x)u t = (g(x)A(u)u x ) x + h(x)B(u)u x are collected.
“…There are a lot of handbooks and manuscripts devoted to demonstration, construction and analysis of the exact solutions of various nonlinear partial differential equations (see, e.g., [17][18][19]). A collection of exact solutions (1+1)-dimensional diffusion-convection equations is presented in [20]. To give a physical interpretation of these solutions is not a purpose of that work.…”
“…There are a lot of handbooks and manuscripts devoted to demonstration, construction and analysis of the exact solutions of various nonlinear partial differential equations (see, e.g., [17][18][19]). A collection of exact solutions (1+1)-dimensional diffusion-convection equations is presented in [20]. To give a physical interpretation of these solutions is not a purpose of that work.…”
“…Also equations in the entries 3b and 7b are linear equations. The lists of known exact solutions of these equations can be found, e.g., in [11,18]. Table 4 Subalgebras Δ i , similarity variables, similarity solutions and reduced equations for (3)…”
Section: One-dimensional Subalgebrasmentioning
confidence: 99%
“…Equivalence group G ∼ 3 of class (2) consists of the 11-parameter group of point transformations: t = ε 6 t + ε 1 ,x = ε 7 x + ε 11 t + ε 2 ,ỹ = ε 8 y + ε 3 ,z = ε 9 z + ε 4 ,ũ = ε 10 u + ε 5 , 11 , where ε 1 , . .…”
Section: Group Classification Of (3 + 1)-dimensional Equationsmentioning
We perform the complete Lie group classification of a (2 + 1)-and a (3 + 1)-dimensional classes of non-linear diffusion-convection equations. This classification generalizes and completes existing results in the literature. The derived Lie symmetries are used for construction of similarity reductions and exact solutions of certain equations from both classes.
“…In what follows all spaces are of dimension n 2. The case n = 1 although relatively trivial for our approach in general it is not so and has been studied for example in [18,19].…”
Section: Lie Point Symmetries and Collineations In Riemannian Spacesmentioning
We study the reduction of the heat equation in Riemannian spaces which admit a gradient Killing vector, a gradient homothetic vector and in Petrov Type D,N,II and Type III space-times. In each reduction we identify the source of the Type II hidden symmetries. More specifically we find that a) If we reduce the heat equation by the symmetries generated by the gradient KV the reduced equation is a linear heat equation in the nondecomposable space. b) If we reduce the heat equation via the symmetries generated by the gradient HV the reduced equation is a Laplace equation for an appropriate metric. In this case the Type II hidden symmetries are generated from the proper CKVs. c) In the Petrov spacetimes the reduction of the heat equation by the symmetry generated from the nongradient HV gives PDEs which inherit the Lie symmetries hence no Type II hidden symmetries appear. We apply the general results to cases in which the initial metric is specified. We consider the case that the irreducible part of the decomposed space is a space of constant nonvanishing curvature and the case of the spatially flat Friedmann-Robertson-Walker space time used in Cosmology. In each case we give explicitly the Type II hidden symmetries provided they exist.
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