Weak solutions to the Navier-Stokes initial boundary value problem in exterior domains with initial data in L(3,∞)

(Lorentz space). Apart from its own analytical interest, the research is connected with questions related to the space-time asymptotic properties of solutions to the NS-IBVP. However these questions are not discussed. The assumption on the initial data in L(3,∞) cuts the L2-theory out, which is the unique known for weak solutions. We find a simple strategy to bypass the difficulties of an initial data /∈ L2, and we take care to perform the same “regularity properties” of Leary’s weak solutions, hence to furnish a structure theorem of a weak solution.