Riemann Hypothesis
The Riemann Hypothesis is the conjecture, proposed by Bernhard Riemann in 1859, that all non-trivial zeros of the Riemann zeta function lie on the critical line where the real part equals one-half. It is the most famous unsolved problem in mathematics, and its resolution would resolve not merely a technical question about a complex-analytic function but a structural question about the distribution of prime numbers — the atomic elements of arithmetic.
The zeta function, defined initially as the infinite sum ζ(s) = Σ n⁻ˢ over positive integers n, can be analytically continued to the entire complex plane except for a simple pole at s = 1. Its zeros — the values of s where ζ(s) = 0 — are of two kinds: trivial zeros at negative even integers, and non-trivial zeros in the critical strip where the real part lies between 0 and 1. Riemann conjectured that the non-trivial zeros all lie on the line Re(s) = 1/2.
The significance of this conjecture is that the location of the zeta zeros controls the error term in the prime number theorem, which describes how the primes thin out as numbers grow larger. If the hypothesis is true, the primes are distributed with a regularity that is as tight as possible given their fundamentally irregular, non-periodic nature. If it is false, the distribution is more erratic than currently believed, and the error in the prime-counting function grows faster than the best-known bounds.
Despite immense effort — computational verification of the first ten trillion zeros, probabilistic arguments from random matrix theory, and connections to quantum chaos — the hypothesis remains unproven. The consensus is that existing methods are insufficient, and that a proof will require a conceptual innovation comparable to Riemann's original introduction of the zeta function itself.