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EMBEDDING FLOWS OF DIFFEOMORPHISMS
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作者 Yangyou Pan Xiang Zhang 《Annals of Differential Equations》 2014年第2期166-173,共8页
In this paper we first survey the results on the embedding flow problem of dif-feomorphisms in higher dimensional spaces. Next we present some new results on the characterization of semi-unipotent diffeomorphisms in R... In this paper we first survey the results on the embedding flow problem of dif-feomorphisms in higher dimensional spaces. Next we present some new results on the characterization of semi-unipotent diffeomorphisms in R3, which have a formal embedding flows. 展开更多
关键词 DIFFEOMORPHISMS embedding vector field normal form
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Local integrable differential systems and their normal forms
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作者 Shiliang Weng Xiang Zhang 《上海师范大学学报(自然科学版)》 2014年第5期476-485,共10页
In this paper we first summarize our results published in recent years and their sketch proofs on local integrability,which are on the characterization of local integrability and on the existence of analytic normaliza... In this paper we first summarize our results published in recent years and their sketch proofs on local integrability,which are on the characterization of local integrability and on the existence of analytic normalization of analytically integrable differential systems. Then we present a new result on the equivalent characterization of the existence of the first integrals of an analytic differential systems near a nonhyperbolic singularity. Finally we pose some open problems on this subject. 展开更多
关键词 formal diffeomorphism embedding vector field normal form
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乘积流形的嵌入拉回度量与Killing向量场
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作者 卢卫君 黄浩 卢若飞 《中国科学:数学》 CSCD 北大核心 2020年第11期1579-1596,共18页
在四维乘积流形M4=S2×S2上如何赋予一般的Riemann度量并考虑其相关截曲率能否保持不变号是非常有趣的几何拓扑问题,吸引了不少几何学者的极大关注和探索.本文将从以下三个角度来讨论M4的截曲率:(1)嵌入R6至R9的拉回度量;(2)作极小... 在四维乘积流形M4=S2×S2上如何赋予一般的Riemann度量并考虑其相关截曲率能否保持不变号是非常有趣的几何拓扑问题,吸引了不少几何学者的极大关注和探索.本文将从以下三个角度来讨论M4的截曲率:(1)嵌入R6至R9的拉回度量;(2)作极小嵌入F:Σ?R4→S5(2)?R6得到Clifford环面;(3)偶数维紧致Riemann流形的正截曲率度量与Killing向量场的奇异点之间的关系.本文得出在这些情形之下, M4不可回避零截曲率的出现从而支持Hopf猜想. 展开更多
关键词 四维乘积流形 嵌入拉回度量 Hopf猜想 截曲率 KILLING向量场
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