On Fifth Order KdV-Type Equation

The dynamics of the highly nonlinear fifth order $KdV$-type equation is discussed in the framework of the Lagrangian and Hamiltonian formalisms. The symmetries of the Lagrangian produce three commuting conserved quantities that are found to be recursively related to one-another for a certain specific value of the power of nonlinearity. The above cited recursion relations are obeyed with a second Poisson bracket which sheds light on the integrability properties of the above nonlinear equation. It is shown that a Miura-type transformation can be made to obtain the fifth order $mKdV$-type equation from the fifth order $KdV$-type equation. The spatial dependence of the fields involved is, however, not physically interesting from the point of view of the solitonic solutions. As a consequence, it seems that the fifth order $KdV$- and $mKdV$-type equations are completely independent nonlinear evolution equations in their own right.