期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1971
卷号：68
期号：5
页码：894-896
DOI：10.1073/pnas.68.5.894
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The circle group G is said to act pseudofreely if it is not free and if every orbit is one-dimensional and if the isotropy group is the identity except on isolated exceptional orbits where the isotropy group is the finite cyclic group Zk, k > 1. We consider differentiable actions of this kind on homotopy seven spheres and classify all such actions. As a corollary, it follows that there can be any finite number of exceptional orbits, in contrast to the linear case where there can be at most four.
