On totally global solvability of evolutionary Volterra equation of the second kind

A. V. Chernov

Vestnik Udmurtskogo universiteta. Matematika, mehanika, kompʹûternye nauki, Tome 32 (2022) no. 4, pp. 593-614

Résumé

Let $H$ be a Banach space, $T>0$, $\sigma\in[1;\infty]$ and let $W[0;\tau]$, $\tau\in(0;T)$, be the scale of Banach spaces which is induced by restrictions from a space $W=W[0;T]$; $\mathcal{F}\colon L_\sigma(0,T;H)\to W$ be a Volterra operator (an operator with Volterra property); $f[u] \colon W\to L_\sigma(0,T;H)$ be a controlled Volterra operator depending on a control $u\in U$. We consider the equation as follows $$x=\mathcal{F}\bigl( f[u](x)\bigr),\quad x\in W.$$ For this equation we establish signs of totally (with respect to a set of admissible controls) global solvability subject to global solvability of some functional integral inequality in the space $\mathbb{R}$. In many particular cases the above inequality may be realized as the Cauchy problem associated with an ordinary differential equation. In fact, the analogous result which was obtained by the author formerly is developed, this time under other hypotheses, more convenient for practical usage (although in more particular statement). Separately, we consider the cases of compact embedding of spaces and continuity of the operators $\mathcal{F}$, $f[u]$ (such an approach has not been used by the author formerly), from one hand, and of local integral analogue of the Lipschitz condition with respect to that operators, from another hand. In the second case we prove also the uniqueness of solution. In the first case we use Schauder theorem and in the second case we apply the technique of solution continuation along with the time axis (id est continuation along with a Volterra chain). Finally, as an example, we consider a nonlinear wave equation in the space $\mathbb{R}^n$.

Détail

Keywords: nonlinear evolutionary Volterra equation in a Banach space, nonlinear wave equation, totally global solvability, uniqueness of solution.