Mann's theorem is a theorem widely circulated as the " conjecture" that was subsequently proven by
Mann (1942). It states that if
and
are sets of integers each containing 0, then
Here,
denotes the direct sum, i.e.,
, and
is the Schnirelmann
density.
Mann's theorem is optimal in the sense that satisfies
.
Mann's theorem implies Schnirelmann's theorem as follows. Let ,
then Mann's theorem proves that
, so as more and more copies of
the primes are included, the Schnirelmann density
increases at least linearly, and so reaches 1 with at most
copies of the primes. Since the only sets
with Schnirelmann density 1 are the sets
containing all positive integers, Schnirelmann's
theorem follows.