EN
We give an equivalent expression for the K-functional associated to the pair of operator spaces (R,C) formed by the rows and columns respectively. This yields a description of the real interpolation spaces for the pair (Mₙ(R),Mₙ(C)) (uniformly over n). More generally, the same result is valid when Mₙ (or B(ℓ₂)) is replaced by any semi-finite von Neumann algebra. We prove a version of the non-commutative Khintchine inequalities (originally due to Lust-Piquard) that is valid for the Lorentz spaces $L_{p,q}(τ)$ associated to a non-commutative measure τ, simultaneously for the whole range 1 ≤ p,q < ∞, regardless of whether p < 2 or p > 2. Actually, the main novelty is the case p = 2, q ≠ 2. We also prove a certain simultaneous decomposition property for the operator norm and the Hilbert-Schmidt norm.