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» Disjoint Unions of Topological Spaces and Choice
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MLQ
1998
74views more  MLQ 1998»
13 years 4 months ago
Disjoint Unions of Topological Spaces and Choice
We find properties of topological spaces which are not shared by disjoint unions in the absence of some form of the Axiom of Choice.
Paul E. Howard, Kyriakos Keremedis, Herman Rubin, ...
MLQ
1998
103views more  MLQ 1998»
13 years 4 months ago
Versions of Normality and Some Weak Forms of the Axiom of Choice
Abstract. We investigate the set theoretical strength of some properties of normality, including Urysohn’s Lemma, Tietze-Urysohn Extension Theorem, normality of disjoint unions o...
Paul E. Howard, Kyriakos Keremedis, Herman Rubin, ...
CCA
2009
Springer
13 years 11 months ago
Weihrauch Degrees, Omniscience Principles and Weak Computability
Abstract. In this paper we study a reducibility that has been introduced by Klaus Weihrauch or, more precisely, a natural extension of this reducibility for multi-valued functions ...
Vasco Brattka, Guido Gherardi