Abstract:
We study a version of the classical problem on the convergence of formal solutions of systems of partial differential equations. A necessary and sufficient condition for the convergence of a given formal solution (found by any method) is proved. This convergence criterion applies to systems of partial differential equations (possibly, nonlinear) solved for the highest-order derivatives or, which is most important, “almost solved for the highest-order derivatives.”
Keywords:systems of partial differential equations, convergence of formal solutions, ordered semigroup $\mathbb{Z}^n_{\geqslant 0}$, system of partial differential equations solved for the highest-order
derivatives, system of partial differential equations “almost solved for the highest-order derivatives”.