自然科学版
陕西师范大学学报(自然科学版)
数学与计算机科学
拓扑空间上连续自映射的拓扑熵的不变性
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来阿龙, 赵虎, 李生刚*
(陕西师范大学 数学与信息科学学院, 陕西 西安 710062)
来阿龙,女,硕士研究生,研究方向为格上拓扑与拟阵理论.E-mail:lal880320@126.com.*通信作者:李生刚,男,教授,博士研究生导师.E-mail:shenggangli@yahoo.com.cn.
摘要:
研究了拓扑空间上连续自映射的拓扑熵在空间变小或拓扑变弱时是否不变的问题.运用开覆盖、不变子集和非游荡集的理论讨论了拓扑空间上连续自映射的拓扑熵的相关性质.利用这些性质证明了:若拓扑空间上的连续自映射f的非游荡集是紧集,则f的拓扑熵等于f在它的非游荡集上的限制映射的拓扑熵;一个强θ-紧Hausdorff空间(X,T)上的连续自映射的拓扑熵等于这一映射在(X,θ(T))上的拓扑熵,这里θ(T)表示(X,T)中的θ-开集的全体.
关键词:
拓扑熵; 非游荡集; θ-开集; θ-连续映射
收稿日期:
2012-01-05
中图分类号:
O189.1
文献标识码:
A
文章编号:
1672-4291(2012)04-0011-05
基金项目:
国家自然科学基金资助项目(11071151); 陕西省自然科学基金资助项目(2010JM1005);陕西师范大学研究生培养创新基金资助项目(2012CXS038).
Doi:
The invariance of topological entropies of continuousself-mappings on topological spaces
LAI A-long, ZHAO Hu, LI Sheng-gang*
(College of Mathematics and Information Science, Shaanxi Normal University, Xi′an 710062, Shaanxi, China)
Abstract:
The problem whether the topological entropy of a continuous self-mapping on a topological space is invariant when the space becomes smaller or its topology becomes weaker is studied.Relevant properties of the topological entropy of a continuous self-mapping on a topological space are discussed by applying the theory of open cover, invariant subset and non-wandering set. Based on this, it is proved that if non-wandering set of the continuous self-mapping f on a topological space is compact, then the topological entropy of f is the same as that of the restriction of f to its non-wandering set, and the topological entropy of a continuous self-mapping on a strong θ-compact Hausdorff space (X,T) is the same as that of the mapping on (X,θ(T)),where θ(T) is the set of all θ-open sets in (X,T).
KeyWords:
topological entropy; non-wandering set; θ-open set; θ-continuous mapping