Hokkaido University Preprint Series in Mathematics
Let W be a finite irreducible real reflection group, which is a Coxeter roup. We explicitly construct a basis for the module of differential -forms with logarithmic poles along the Coxeter arrangement by sing a primitive derivation. As a consequence, we extend the Hodge iltration, indexed by nonnegative integers, into a filtration indexed by ll integers. This filtration coincides with the filtration by the order f poles. The results are translated into the derivation case.