Brun 1915 / Selberg 1947 / Iwaniec 1980s sieves: combinatorial-analytic estimates on primes in sets; Brun proved sum 1/p_twin converges; Goldston-Pintz-Yildirim 2005 small gaps; Zhang 2013 bounded gaps.
Brun 1915 / Selberg 1947 / Iwaniec 1980s sieves: combinatorial-analytic estimates on primes in sets; Brun proved sum 1/p_twin converges; Goldston-Pintz-Yildirim 2005 small gaps; Zhang 2013 bounded gaps.