Stable Regularity for Relational Structures

We generalize the stable graph regularity lemma of Malliaris and Shelah to the case of finite structures in finite relational languages, e.g., finite hypergraphs. We show that under the model-theoretic assumption of stability, such a structure has an equitable regularity partition of size polynomial in the reciprocal of the desired accuracy, and such that for each k-ary relation and k-tuple of parts of the partition, the density is close to either 0 or 1. In addition, we provide regularity results for finite and Borel structures that satisfy a weaker notion that we call almost stability.