Additivity of the two-dimensional Miller ideal

Let J (M) denote the σ-ideal associated with two-dimensional Miller forcing. We show that it is relatively consistent with ZFC that the additivity of J (M) is bigger than the covering number of the ideal of the meager subsets of ω. We also show that Martin’s Axiom implies that the additivity of J (M) is 2. Finally we prove that there are no analytic infinite maximal antichains in any finite product of P(ω)/fin.