On the inverse Goldbach problem

Abstract

We establish two quantitative results concerning additive decompositions of the set $\mathbb{P}$ of primes. First, we prove that, if $A,B\subseteq\mathbb N$ have at least two elements and $A+B$ differs from the primes by only finitely many elements, then $$ \frac{\sqrt{x}}{\log x}\ll A(x),B(x) \ll \sqrt{x}. $$ Second, we show that, if $A,B,C\subseteq\mathbb N$ have at least two elements each, then $$ ((A+B+C)\mathbin{\bigtriangleup}\mathbb P)(x) \gg \frac{\sqrt{x}}{(\log x)^2}. $$ An analogous estimate is obtained for sumsets of $k\ge 3$ sets. The proofs use Montgomery's large sieve, Gallagher's larger sieve, a mean-value argument for a certain multiplicative function, and a submultiplicative sumset inequality.