ON THE APPLICATION OF THE SOLUTION OF THE DEGENERATE NONLINEAR BURGERS EQUATION WITH A SMALL PARAMETER AND THE THEORY OF p-REGULARITY

The article discusses various modifications of the nonlinear Burgers equation with small parameter and degenerate in solution of the form

\(F(u,\varepsilon ) = {{u}_{t}} - {{u}_{{xx}}} + u{{u}_{x}} + \varepsilon {{u}^{2}} - f(x,t) = 0,\)            (1)

where \(F:\Omega \to C([0,\pi ] \times [0,T])\), \(T > 0\), \(\Omega = {{C}^{2}}([0,\pi ] \times [0,T]\,)\,\mathbb{R}\) and \(u(0,t) = u(\pi ,t) = 0\), \(u(x,0) = \varphi (x)\), \(f(x,t) \in C([0,\pi ] \times [0,T])\), \(\varphi (x) \in C[0,\pi ]\). We will be interested in the most important in applications case of a small parameter ε with oscillating initial conditions of the form \(\varphi (x) = k\sin x\), where k –some, generally speaking, constant depending on ε, and study the question of the existence of a solution in neighborhood of the trivial \((u{\kern 1pt} *,\varepsilon {\kern 1pt} *) = (0,0)\), which corresponds to \(k = k{\kern 1pt} * = 0\) and at what initial Under certain conditions on the values of k, it is possible to construct an analytical approximation of this solution for small ε.

We will look for a solution in the traditional way of separation of variables on a subspace of functions of the form \(u(x,t) = v(t)u(x)\), where \(v(t) = c{{e}^{{ - t}}}\), \(u(x) \in {{\mathcal{C}}^{2}}([0,\pi ])\). In this case, the problem under consideration is degenerate at the point \((u{\kern 1pt} *,\varepsilon {\kern 1pt} *) = (0,0)\), since \({\text{Im}}F_{u}^{'}(u{\kern 1pt} *,\varepsilon {\kern 1pt} *) \ne Z = \mathcal{C}([0,\pi ] \times [0,T])\). This follows from the Sturm-Liouville theory. To achieve our goals, we apply the apparatus of p-regularity theory [6, 7, 15, 16] and show that the mapping \(F(u,\varepsilon )\) is 3-regular at the point \((u{\kern 1pt} *,\varepsilon {\kern 1pt} *) = (0,0)\), т.е. p = 3.