A polynomial regularity lemma for semi-algebraic hypergraphs and its applications in geometry and property testing

TL;DR

This paper improves a regularity lemma for semi-algebraic hypergraphs by showing the number of parts can be polynomial in 1/epsilon, enabling efficient property testing and applications in geometry.

Contribution

It proves a polynomial bound on the number of parts in the regularity lemma for semi-algebraic hypergraphs, enhancing applications in geometry and property testing.

Findings

Number of parts in the regularity lemma is polynomial in 1/epsilon.

Regularity lemma applies to geometric problems and property testing.

Efficient polynomial-query algorithms for hereditary property testing.

Abstract

Fox, Gromov, Lafforgue, Naor, and Pach proved a regularity lemma for semi-algebraic $k$-uniform hypergraphs of bounded complexity, showing that for each $\epsilon>0$ the vertex set can be equitably partitioned into a bounded number of parts (in terms of $\epsilon$ and the complexity) so that all but an $\epsilon$-fraction of the $k$-tuples of parts are homogeneous. We prove that the number of parts can be taken to be polynomial in $1/\epsilon$. Our improved regularity lemma can be applied to geometric problems and to the following general question on property testing: is it possible to decide, with query complexity polynomial in the reciprocal of the approximation parameter, whether a hypergraph has a given hereditary property? We give an affirmative answer for testing typical hereditary properties for semi-algebraic hypergraphs of bounded complexity.