2016/03/09 by Terence Tao, Van Vu, Tao, Terence +1 · 1 citation
Engineering · Mathematics · #11B30 #Combinatorics (math.CO) #FOS: Mathematics #Finite Group Theory Research #Limits and Structures in Graph Theory #graph theory and CDMA systems
paper · pdf · doi:10.48550/arxiv.1603.03071
openalex publication_date 2016/03/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We discuss several questions concerning sum-free sets in groups, raised by Erdős in his survey "Extremal problems in number theory" (Proceedings of the Symp. Pure Math. VIII AMS) published in 1965. Among other things, we give a characterization for large sets A in an abelian group G which do not contain a subset B of fixed size k such that the sum of any two different elements of B do not belong to A (in other words, B is sum-free with respect to A). Erdős, in the above mentioned survey, conjectured that if |A| is sufficiently large compared to k, then A contains two elements that add up to zero. This is known to be true for k ≤ 3. We give counterexamples for all k ≥ 4. On the other hand, using the new characterization result, we are able to prove a positive result in the case when |G| is not divisible by small primes.