Abstract. We consider the Cauchy problem of the cubic nonlinear Schrö-dinger equation (NLS) : i∂ t u + Δu = ±|u| 2 u on R d , d ≥ 3, with random initial data and prove almost sure well-posedness results below the scaling-critical regularity. More precisely, given a function on R d , we introduce a randomization adapted to the Wiener decomposition, and, intrinsically, to the so-called modulation spaces. Our goal in this paper is three-fold. (i) We prove almost sure local well-posedness of the cubic NLS below the scalingcritical regularity along with small data global existence and scattering. (ii) We implement a probabilistic perturbation argument and prove 'conditional' almost sure global well-posedness for d = 4 in the defocusing case, assuming an a priori energy bound on the critical Sobolev norm of the nonlinear part of a solution; when d = 4, we show that conditional almost sure global wellposedness in the defocusing case also holds under an additional assumption of global well-posedness of solutions to the defocusing cubic NLS with deterministic initial data in the critical Sobolev regularity. (iii) Lastly, we prove global well-posedness and scattering with a large probability for initial data randomized on dilated cubes.

We consider a randomization of a function on R d that is naturally associated to the Wiener decomposition and, intrinsically, to the modulation spaces. Such randomized functions enjoy better integrability, thus allowing us to improve the Strichartz estimates for the Schrödinger equation. As an example, we also show that the energycritical cubic nonlinear Schrödinger equation on R 4 is almost surely locally well-posed with respect to randomized initial data below the energy space.2010 Mathematics Subject Classification. 42B35, 35Q55.