EXISTENCE IN SCHWARTZ SPACE AND SOLUTIONS PROPERTIES OF THE HOPF–TYPE EQUATION WITH VARIABLE COEFFICIENTS

The issue of the existence of solutions of the Cauchy problem for a first-order quasi-linear differential equation with partial derivatives and variable coefficients is considered. The studied equation is a generalization of the classic Hopf equation, which is used in the study of many mathematical models of hydrodynamics. This equation arises when constructing approximate (asymptotic) solutions of the Korteweg–de Vries equation and other equations with variable coefficients and a singular perturbation, in particular, when finding their asymptotic step-type soliton-like solutions. For the mentioned differential equation of the first order, the solution of the Cauchy problem is obtained in analytical form, and the statement about sufficient conditions for the existence of solutions of the initial problem in the space of rapidly decreasing functions is proved. A similar problem for a first-order differential equation with partial derivatives with variable coefficients and quadratic nonlinearity is considered.