# Prime gaps

If [math]p_n[/math] denotes the n^th prime, then [math]p_{n+1}-p_n[/math] is the n^th prime gap.

On average, the prime number theorem tells us that [math]p_{n+1}-p_n[/math] has size [math]O(\log p_n)[/math].

A recent result of Goldston-Pintz-Yildirim shows that there exist infinitely many n for which the gap is as small as [math]o(\log p_n)[/math] (in fact more precise bounds are known). But the set of small gaps established by this method is sparse.

Cramer's conjecture asserts that the prime gap never exceeds [math]O(\log^2 p_n)[/math] in size. If so, this resolves the finding primes project positively. However, the best upper bound on the prime gap is [math]O( p_n^{1/2} \log p_n )[/math] assuming the Riemann hypothesis, and [math]O( p_n^{0.525} )[/math] otherwise (a result of Baker, Harman, and Pintz; an earlier bound of [math]O(p_n^{0.535})[/math] was obtained by Baker and Harman.).

Rankin showed that the prime gap can be as large as [math]\log p_n \frac{\log \log p_n \log \log \log \log p_n}{(\log \log \log p_n)^3}[/math].

- R. C. Baker and G. Harman, “The difference between consecutive primes,” Proc. Lond. Math. Soc., series 3, 72 (1996) 261–280. MR 96k:11111
- K. Soundararajan, Small gaps between prime numbers: The work of Goldston-Pintz-Yildirim
- The Wikipedia entry on prime gaps