Constructing small-bias sets from algebraic-geometric codes

We give an explicit construction of an ∈-biased set over k bits of size O (k/∈²log(1/∈))^5/4. This improves upon previous explicit constructions when ∈ is roughly (ignoring logarithmic factors) in the range [k^-1.5, k^-0.5]. The construction builds on an algebraic-geometric code. However, unlike previous constructions we use low-degree divisors whose degree is significantly smaller than the genus. Studying the limits of our technique, we arrive at a hypothesis that if true implies the existence of ∈-biased sets with parameters nearly matching the lower bound, and in particular giving binary error correcting codes beating the Gilbert-Varshamov bound.