Published online by Cambridge University Press: 22 January 2016
Let X ⊆ Pr be a reduced, irreducible and non-degenerate projective variety over an algebraically closed field K of characteristic 0. Let reg(x) be the Castelnuovo-Mumford regularity of the sheaf of ideals associated to X.
Then it is an open problem—due to D. Eisenbud (see e.g. [E-Go])—whether
(0.1) reg(X) ≤ deg(x) - codim (x) + 1,
where deg(x) denotes the degree of X and codim(x) denotes the codimension of X. In many cases, this inequality has been proven to hold true.