Local well-posedness for the fifth-order KdV equations on T

This paper is a continuation of the paper Low regularity Cauchy problem for the fifth-order modified KdV equations on T [7]. In this paper, we consider the fifth-order equation in the Korteweg-de Vries (KdV) hierarchy as following:. (∂tu-∂x5u-30u2∂xu+20∂xu∂x2u+10u∂x3u=0,(t,x)∈R×T,u(0,x)=u0(x)∈Hs(T).We prove the local well-posedness of the fifth-order KdV equation for low regularity Sobolev initial data via the energy method. This paper follows almost same idea and argument as in [7]. Precisely, we use some conservation laws of the KdV Hamiltonians to observe the direction which the nonlinear solution evolves to. Besides, it is essential to use the short time X^s,b spaces to control the nonlinear terms due to high × low ⇒ high interaction component in the non-resonant nonlinear term. We also use the localized version of the modified energy in order to obtain the energy estimate.As an immediate result from a conservation law in the scaling sub-critical problem, we have the global well-posedness result in the energy space H².