模空间与二次曲面双复盖的辫单值型
Moduli spaces and braid monodromy types of bidouble covers of the quadric
摘要：
二次曲面Q的双复盖$π: S \mapsto Q$由依赖于四个正整数a，b，c，d的连通族参数化.在b=d的特殊情况下，我们称它们为abc-曲面。这样的Galois覆盖$π$允许一个小的扰动产生一个一般的4元组覆盖的Q与分支曲线$\De$，和一个自然的Lefschetz纤维化从一个小扰动的组成$ π$与第一个投影。我们证明了一个更一般的结果，这意味着对应于$\De$的辫子单值分解确定了abc-曲面的三个整数a，b，c。我们引入了一种新的方法，以区分不稳定等价的分解。这一结果与第一和第三作者以前的结果形成鲜明对比，表明对应于相应自然Lefschetz束的映射类群分解对于具有相同a+c，b值的abc-曲面是等价的。这个结果暗示了具有固定值a+c，b的abc-曲面，尽管是复纯的但不是形变等价的，可能不是正则辛同构的。
英文摘要：
Bidouble covers $π: S \mapsto Q$ of the quadric Q are parametrized by connected families depending on four positive integers a,b,c,d. In the special case where b=d we call them abc-surfaces. Such a Galois covering $π$ admits a small perturbation yielding a general 4-tuple covering of Q with branch curve $\De$, and a natural Lefschetz fibration obtained from a small perturbation of the composition of $ π$ with the first projection. We prove a more general result implying that the braid monodromy factorization corresponding to $\De$ determines the three integers a,b,c in the case of abc-surfaces. We introduce a new method in order to distinguish factorizations which are not stably equivalent. This result is in sharp contrast with a previous result of the first and third author, showing that the mapping class group factorizations corresponding to the respective natural Lefschetz pencils are equivalent for abc-surfaces with the same values of a+c, b. This result hints at the possibility that abc-surfaces with fixed values of a+c, b, although diffeomorphic but not deformation equivalent, might be not canonically symplectomorphic.
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