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+\beta)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_{\beta}:={\frac{2\pi}{\sqrt{3(1+\beta)}}\sqrt{k^{2}+kl+l^{2}}:k,l\in$\mathbb{N}$^{\ast}}\cup{\frac{k\pi}{\sqrt{1+\beta}}:k\in$\mathbb{N}$^{\ast}} and the nonlinear system is locally exactly controllable around a constant steady state $\beta$ if the associated linear system is exactly controllable.