SEMINARIO

We point out that there exists a class of nonlocal operators which can be consistently added to the Yang-Mills action. Albeit nonlocal, these operators can be localized by means of the introduction of auxiliary fields. The resulting local theory turns out to be renormalizable. The examples of Zwanziger's horizon term and of the gauge invariant nonlocal mass term, F 1/D2 F, will be analysed in detail. The potential relevance of these operators for gluon confinement is outlined.