Department of Mathematics Faculty of Science and Technology Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510, Japan

摘要

We give an upper bound of the slope for finite cyclic covering fibrations of an elliptic surface which includes bielliptic fibrations. We also give an upper bound of the slope for triple cyclic covering fibrations of a ruled surface and hyperelliptic fibrations, which provides a new proof of Xiao's upper bound.