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On topological Kadec norms
Authors:Mohammad?Abry  author-information"  >  author-information__contact u-icon-before"  >  mailto:mabry@cs.vu.nl"   title="  mabry@cs.vu.nl"   itemprop="  email"   data-track="  click"   data-track-action="  Email author"   data-track-label="  "  >Email author,Jan J.?Dijkstra
Affiliation:(1) Faculteit der Exacte Wetenschappen/Afdeling Wiskunde, Vrije Universiteit, De Boelelaan 1081 a, 1081, HV, Amsterdam, The Netherlands
Abstract:We present a topological analogue of the classic Kadec Renorming Theorem, as follows. Let MediaObjects/s00208-005-0651-5flb1.gif be two separable metric topologies on the same set X. We prove that every point in X has an MediaObjects/s00208-005-0651-5flb2.gif-neighbourhood basis consisting of sets that are MediaObjects/s00208-005-0651-5flb3.gif-closed if and only if there exists a function φ: X→ℝ that is MediaObjects/s00208-005-0651-5flb3.gif-lower semi-continuous and such that MediaObjects/s00208-005-0651-5flb2.gif is the weakest topology on X that contains MediaObjects/s00208-005-0651-5flb3.gif and that makes φ continuous. An immediate corollary is that the class of almost n-dimensional spaces consists precisely of the graphs of lower semi-continuous functions with at most n-dimensional domains.
Keywords:54C08  46B03  54F45  54E55
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