Large sum-free sets in \(\mathbb Z/p\mathbb Z\) (Q2472718)

Let \(A\subseteq\mathbb Z/p\mathbb Z\) with \(p\) a prime. Suppose that \(A\) is sum-free (i.e., \(x+y=z\) for no \(x,y,z\in A\)). The author proves that if \(n=| A| >0.33p\) then there is an integer \(d\) such that \(A\subseteq\{dm\bmod p: n\leq m\leq p-n\}\). The author remarks that 0.33 cannot be replaced by a positive integer smaller than 0.2. The proof of the main result involves character sums and combinatorial arguments. The paper is well-written and quite readable.