The Line in the Complex Plane on which the Riemann Hypothesis asserts that all nontrivial (Complex) Roots of the Riemann Zeta Function lie. Although it is known that an Infinite number of zeros lie on the critical line and that these comprise at least 40% of all zeros, the Riemann Hypothesis is still unproven.
See also Riemann Hypothesis, Riemann Zeta Function
Vardi, I. Computational Recreations in Mathematica. Reading, MA: Addison-Wesley, p. 142, 1991.