摘要
本文讨论了Ponomarev系统中的一个逆问题.对于Ponomarev系统(f,M,X,P)(或(f,M,X,{P_n})),证明了f是2序列覆盖映射当且仅当P是X的sof网(或每一P_n是X的so覆盖).作为一个推论,本文得到了空间X是度量空间的2序列覆盖映射像(或2序列覆盖π映射像)当且仅当X有sof网(或so覆盖组成的点星网).
This paper investigates an inverse problem in Ponomarev-systems. For a Ponomarev-system （f,M,X,7a） （resp. （f,M,X,{Tan}））, we prove that f is a 2-sequence- covering mapping iff P is an sol-network of X （resp. every Pn is an so-cover of X）. By these results, we obtain that a space X is a 2-sequence-covering （resp. 2-sequence-covering π-） image of a metric space iff X has an sol-network （resp. a point-star network consisting of so-covers）.
出处
《数学进展》
CSCD
北大核心
2015年第5期752-756,共5页
Advances in Mathematics（China）
基金
supported by NSFC(No.11301367,No.11471153,No.61472469,No.11461005)
Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20123201120001,No.2014T70537)
China Postdoctoral Science Foundation(No.2013M541710)
Jiangsu Province Natural Science Foundation(No.BK20140583)
Jiangsu Province Postdoctoral Science Foundation(No.1302156C)
