Approximate Controllability Problems for the Heat Equation in a Half-Plane Controlled by the Dirichlet Boundary Condition with a Bounded Control

Abstract: In the paper, the problems of approximate controllability are studied for the control system $w_t=\Delta w$, $w(0,x_2,t)=u(x_2,t)$, $x_1\in\mathbb R_+=(0,+\infty)$, $x_2\in\mathbb R$, $t\in(0,T)$, where $u$ is a control belonging to a special subset of $L^\infty(\mathbb R\times (0,T))\cap L^2(\mathbb R\times (0,T))$. It is proved that each initial state belonging to $L^2(\mathbb R_+\times\mathbb R)$ is approximately controllable to an arbitrary end state belonging to $L^2(\mathbb R_+\times\mathbb R)$ by applying these controls. A numerical algorithm of solving the approximate controllability problem for this system is given. The results are illustrated by an example.