科研之友
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摘要
The notion of an essential map was introduced by Granas [3] and he showed for single valued maps that if a map F is essential and F congruent to G then G is essential. This notion was extended to d-essential maps by Precup [6]. In this paper we discuss d-essential maps for a very large class of maps, namely the class of acyclic maps.
Let X and Z be subsets of Hausdorff topological spaces. We will consider maps F : X -> K(Z); here K(Z) denotes the family of nonempty compact subsets of Z. A nonempty topological space is said to be acyclic if all its reduced Cech homology groups over the rationals are trivial. Now F : X -> K(Z) is acyclic if F is upper semicontinuous with acyclic values.
- 出版日期2013
