Neumann boundary controllability of the Korteweg-de Vries equation on a bounded domain
In this paper we study boundary controllability of the Korteweg-de Vries (KdV) equation posed on a finite domain $(0,L)$ with the Neumann boundary conditions: u_t+u_x+uu_x+u_{xxx}=0 in (0,L)x(0,T), u_{xx}(0,t)=0, u_x(L,t)=h(t), u_{xx}(L,t)=0 in (0,T), u(x,0)=u_0(x) in (0,L). We show that the associated linearized system u_t+(1+β)u_x+u_{xxx}=0 in (0,L)x(0,T), u_{xx}(0,t)=0, u_x(L,t)=h(t), u_{xx}(L,t)=0 in (0,T), u(x,0)=u_0(x) in (0,L) is exactly controllable if and only if the length $L$ of the spatial domain $(0,L)$ does not equal to $-1$ or does not belong to set R_β:={\frac{2π}{\sqrt{3(1+β)}}\sqrt{k^{2}+kl+l^{2}}:k,l\in\mathbb{N}^{\ast}}\cup{\frac{kπ}{\sqrt{1+β}}:k\in\mathbb{N}^{\ast}} and the nonlinear system is locally exactly controllable around a constant steady state $β$ if the associated linear system is exactly controllable.