A note on Harris Morrison sweeping families

作者:Beorchia Valentina*; Zucconi Francesco
来源:Collectanea Mathematica, 2015, 66(2): 191-202.
DOI:10.1007/s13348-014-0128-5

摘要

Harris and Morrison (Invent. Math. 99:321-355, 1990, Theorem 2.5), constructed certain semistable fibrations in -gonal curves of genus , such that for every the corresponding modular curves give a sweeping family in the -gonal locus . Their construction depends on the choice of a smooth curve . We show that if the genus is sufficiently high with respect to , then the ratio is asymptotically with respect to . Moreover, if the conjectured estimates given in Harris and Morrison (Invent. Math. 99:321-355, 1990, pp. 351-352) hold, we show that if is big enough, then is a surface of positive index.

  • 出版日期2015-5

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