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A topological reflection principle equivalent to Shelah's strong hypothesis

Author(s): Assaf Rinot
Journal: Proc. Amer. Math. Soc. 136 (2008), 4413-4416.
MSC (2000): Primary 03E04; Secondary 54G15, 03E65
Posted: July 1, 2008
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Abstract: We notice that Shelah's Strong Hypothesis is equivalent to the following reflection principle:

Suppose $ \langle X,\tau\rangle$ is a first-countable space whose density is a regular cardinal, $ \kappa$. If every separable subspace of $ X$ is of cardinality at most $ \kappa$, then the cardinality of $ X$ is $ \kappa$.


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Additional Information:

Assaf Rinot
Affiliation: School of Mathematical Sciences, Tel Aviv University, Tel Aviv 69978, Israel
Email: assaf@rinot.com

DOI: 10.1090/S0002-9939-08-09411-2
PII: S 0002-9939(08)09411-2
Keywords: Shelah's Strong Hypothesis, first countable, countably tight.
Received by editor(s): September 28, 2007,
Received by editor(s) in revised form: November 3, 2007
Posted: July 1, 2008
Additional Notes: The author would like to thank his Ph.D. advisor, M. Gitik, for his comments and remarks.
Communicated by: Julia Knight
Copyright of article: Copyright 2008, American Mathematical Society
The copyright for this article reverts to public domain after 28 years from publication.


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