Existence of a Sidon set for the distinct distance constant

Abstract: We highlight a certain compactness of Sidon sets and $B_2[g]$-sets and provide several applications. Notably, we prove the existence of such sets that maximize certain functions. In particular, we show the existence of a Sidon set whose reciprocal sum is equal to the distinct distance constant, which answers a question from Guy and Zhang. We also improve the best known upper bound for this constant.