On the two differences l(I^*/R)-l(R/I) and rl(R/I)-l(I^*/R)

Abstract

Let R be a one-dimensional local Noetherian domain, which is supposed analytically irreducible and residually rational, and let I be a proper ideal of R. Our purpose is to study the two numbers l(I^*/R)-l(R/I) and rl(R/I)-l(I^*/R) (l denotes the length, r the Cohen-Macaulay type) already considered in the literature under various points of view. The basic idea is the expression of these invariants in terms of the type sequence.