Very weak solutions and large uniqueness classes of stationary Navier–Stokes equations in bounded domains of R2

Extending the notion of very weak solutions, developed recently in the three-dimensional case, to bounded domains Ω⊂R2 we obtain a new class of unique solutions u in Lq(Ω), q>2, to the stationary Navier–Stokes system −Δu+u⋅∇u+∇p=f, divu=k, u|∂Ω=g with data f,k,g of low regularity. As a main consequence we obtain a new uniqueness class also for classical weak or strong solutions. Indeed, such a solution is unique if its Lq-norm is sufficiently small or the data satisfy the uniqueness condition of a very weak solution.