In dimension 1 and 2 and over an algebraically closed field of characteristic 0, unirationality implies rationality (hence a fortiori stable rationality). In the surface case, this follows from the Castenuovo characterization of smooth projective rational surfaces as those smooth projective surfaces X satisfying q(X) = p2(X) = 0 (see [5]). Starting from dimension 3, the answer to the Lüroth pro...