Nielsen理论中的自符合和根源
Selfcoincidences and roots in Nielsen theory
摘要:
给定两个从球面Sm到一个n-流形N的映射f1和f2,它们什么时候是松散的,也就是说,它们什么时候可以变形而彼此分离?我们研究他们的(通用)重合轨迹的几何形状和Nielsen分解。一方面,由此得到的符合数据的协边性类和相应的Nielsen数是强松弛性障碍。另一方面,这些不变量可能取的值可能满足严格的限制,例如尼尔森数只能取0、1或N的基本群的基数。为了证明这一点,我们比较不同的尼尔森类在根的情况下(其中f1或f2是常数),我们使用的事实,所有,但可能有一个尼尔森类是不必要的自重合的情况下(其中f1 = f2)。同时,我们也得到了强消失的结果。
英文摘要:
Given two maps f1 and f2 from the sphere Sm to an n-manifold N, when are they loose, i.e. when can they be deformed away from one another? We study the geometry of their (generic) coincidence locus and its Nielsen decomposition. On the one hand the resulting bordism class of coincidence data and the corresponding Nielsen numbers are strong looseness obstructions. On the other hand the values which these invariants may possibly assume turn out to satisfy severe restrictions, e.g. the Nielsen numbers can only take the values 0, 1 or the cardinality of the fundamental group of N. In order to show this we compare different Nielsen classes in the root case (where f1 or f2 is constant) and we use the fact that all but possibly one Nielsen class are inessential in the selfcoincidence case (where f1 = f2). Also we deduce strong vanishing results.
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