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Small Inductive Dimension of Topological Spaces. Part II

Authors :
Karol Pąk
Source :
Formalized Mathematics, Vol 17, Iss 3, Pp 219-222 (2009)
Publication Year :
2009
Publisher :
Walter de Gruyter GmbH, 2009.

Abstract

In this paper n denotes a natural number, X denotes a set, and F1, G1 denote families of subsets of X. Let us consider X, F1. We say that F1 is finite-order if and only if: (Def. 1) There exists n such that for every G1 such that G1 ⊆ F1 and n ∈ CardG1 holds ⋂ G1 is empty. Let us consider X. Observe that there exists a family of subsets of X which is finite-order and every family of subsets of X which is finite is also finite-order. Let us considerX, F1. The functor orderF1 yielding an extended real number is defined as follows: (Def. 2)(i) For everyG1 such that orderF1+1 ∈ CardG1 andG1 ⊆ F1 holds ⋂ G1 is empty and there exists G1 such that G1 ⊆ F1 but CardG1 = orderF1+1 but ⋂ G1 is non empty or G1 is empty if F1 is finite-order, (ii) orderF1 = +∞, otherwise.

Details

ISSN :
18989934 and 14262630
Volume :
17
Database :
OpenAIRE
Journal :
Formalized Mathematics
Accession number :
edsair.doi.dedup.....8266bc7226872fcd630433ae97df5898