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

This paper is a continuation of the paper Low regularity Cauchy problem for the fifth-order modified KdV equations on  TT[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 Xs,bXs,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 H2H2.