Non-distributive Lattices, Stable Matchings, and Linear Optimization

We show that all finite lattices, including non-distributive lattices, arise as stable matching lattices under standard assumptions on choice functions. In the process, we introduce new tools to reason on general lattices for optimization purposes: the partial representation of a lattice, which partially extends Birkhoff's representation theorem to non-distributive lattices; the distributive closure of a lattice, which gives such a partial representation; and join constraints, which can be added to the distributive closure to obtain a representation for the original lattice. Then, we use these techniques to show that the minimum cost stable matching problem under the same standard assumptions on choice functions is NP-hard, by establishing a connection with antimatroid theory.