Abstract. This paper considers the initial value problem for a class of fifth order dispersive models containing the fifth order KdV equationThe main results show that regularity or polynomial decay of the data on the positive half-line yields regularity in the solution for positive times.
IntroductionIn this work we study propagation of regularity and persistence of decay results for a class of fifth order dispersive models. For concreteness, the main theorems are stated for initial value problems of the formwhere c j are real constants, u : R × R → R is an unknown function and u 0 : R → R is a given function. Eq. (1.1) contains the specific equationwhich is the third equation in the sequence of nonlinear dispersive equationsknown as the KdV hierarchy. Here the polynomials Q j are chosen so that equation (1.3) has the Lax pair formulationThe first two equations in the hierarchy areand the KdV equationWith only slight modifications concerning the hypothesis on the initial data, the techniques in this paper apply to a large class of fifth order equations including the following models arising from mathematical physics: