  In this work we prove the existence of an autonomous Hamiltonian vector field
in W^{1,r}(T^d;R^d) with r< d-1and d>=4 for which the associated transport
equation has non-unique positive solutions. As a consequence of Ambrosio
superposition principle, we show that this vector field has non-unique integral
curves with a positive Lebesgue measure set of initial data and moreover we
show that the Hamiltonian is not constant along these integral curves.
