Reverse discrepancy and almost zero-sum stars

Abstract

For $f$ chosen from the $\{-1,1\}$-valued functions on the edges of a hypergraph $\mathcal{H} = (V,E)$ with $\sum_{e \in E} f(e) = 0$, how large can one make $\min_{v \in V} |\sum_{e \ni v} f(e)|$? This question may be viewed as a reverse version of the hypergraph discrepancy problem or as a relaxation of the zero-sum Ramsey problem for stars. We prove exact results when $\mathcal{H}$ is a complete or equipartite hypergraph.