文摘
Let be a reduced plane curve of degree 6k, with only nodes and ordinary cusps as singularities. Let I be the ideal of the points where C has a cusp. Let be a minimal resolution of I. We show that . From this we obtain that the Mordell-Weil rank of the elliptic threefold equals . Using this we find an upper bound for the Mordell-Weil rank of W, which is and we find an upper bound for the exponent of in the Alexander polynomial of C, which is . This improves a recent bound of Cogolludo and Libgober almost by a factor 2.