“…A special case of great interest is when f is a product of linear forms, and then V is a hyperplane arrangement A, and the corresponding complement is traditionally denoted by M(A). A lot of efforts were made, in the case of hyperplane arrangements most of the time, to determine the eigenvalues of the monodromy operators (1.1) h m : H m (F, C) → H m (F, C) with 1 ≤ m ≤ n, see for instance [1,2,3,4,8,9,10,12,21,22,32,33,36,45,47]. However, in most of these papers, either only the monodromy action on H 1 (F, C) is considered, or the results are just sufficient conditions for the vanishing of some eigenspaces H m (F, C) λ .…”