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A theorem about hyperspaces

  • J. L. Hursch (a1)
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Recently Isbell(4) and Ward (6) have given examples of pairs of uniformities inducing the same topology on the hyperspace of subsets of a uniform space. Smith (5) has shown that, if two uniformities induce the same topology on the hyperspace, they must be equal in proximity. The author, in (2), has introduced a relation, ‘height’, between uniformities which is in a sense dual to proximity. It is the purpose of this paper to show that, if two uniformities are equal in proximity and height, then they induce the same topology on the hyperspace. Although Ward's uniformities are not equal in height, an example of two distinct uniformities equal in proximity and height is given in (3). In fact, a slight modification of that example will give an example of a countably infinite number of distinct uniformities, all of which are equal in proximity and height.

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(1)Bourbaki, N.Topologie générale, Chaps. 1–2, Act. Sci. Ind. no. 858, 1940; 3rd ed., Act. Sci. Ind. no. 1142 (Hermann; Paris, 1960).
(2)Hursch, J. L. JrProximity and height. Math. Scand. 17 (1965), 150160.
(3)Hursch, J. L. Jr An example of two uniformities equal in proximity and height. To appear in Proc. Amer. Math. Soc.
(4)Isbell, J. R. Insufficiency of the hyperspace. To appear in Proc. Cambridge Philos. Soc.
(5)Smith, D. H.Hyperspaces of a uniformizable space. Proc. Cambridge Philos. Soc. 62 (1966), 2528.
(6)Ward, A. J.A counter-example in uniformity theory. Proc. Cambridge Philos. Soc. 62 (1966), 207208.
(7)Ward, A. J. On H-equivalence of uniformities. To appear in Pacific J. Math.
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Mathematical Proceedings of the Cambridge Philosophical Society
  • ISSN: 0305-0041
  • EISSN: 1469-8064
  • URL: /core/journals/mathematical-proceedings-of-the-cambridge-philosophical-society
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