Space whose product with paracompact space is paracompact - MathOverflow most recent 30 from http://mathoverflow.net 2013-06-19T20:19:27Z http://mathoverflow.net/feeds/question/11153 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/11153/space-whose-product-with-paracompact-space-is-paracompact Space whose product with paracompact space is paracompact Vipul Naik 2010-01-08T15:02:46Z 2011-06-23T13:15:26Z <p>Is there a nice characterization of topological spaces with the property that the product with any paracompact space is paracompact?</p> <p>All compact spaces have this property (this can be shown from the tube lemma). But somebody once gave me an example (that I cannot locate) of a non-compact space with the property. I didn't check the example carefully, so I cannot vouch for its accuracy.</p> <p>If a characterization is too hard, an example of a non-compact space would also be great.</p> <p>[NOTE: I don't assume Hausdorffness in my definitions of compact and paracompact, though it would be nice if the example were a Hausdorff space.]</p> <p>ADDED LATER: I forgot to mention this, but a product of paracompact spaces need not be paracompact. The standard example is the Sorgenfrey line (the real line with the lower limit topology), which is paracompact, whose product with itself, the Sorgenfrey plane, is not paracompact.</p> http://mathoverflow.net/questions/11153/space-whose-product-with-paracompact-space-is-paracompact/18334#18334 Answer by François G. Dorais for Space whose product with paracompact space is paracompact François G. Dorais 2010-03-16T02:48:26Z 2010-03-16T04:38:10Z <p>One interesting conjectured characterization is due to Rastislav Telgársky. In <a href="http://matwbn.icm.edu.pl/ksiazki/fm/fm88/fm88120.pdf" rel="nofollow"><em>Spaces defined by topological games</em></a> (Fund. Math. 88, 1975), Telgársky coined several games and provided partial results regarding this class of paracompact spaces (among other things). In <em>Some remarks on a Telgarsky’s conjecture concerning products of paracompact spaces</em> (Topology Appl. 156, 2009, <a href="http://www.ams.org/mathscinet-getitem?mr=2512606" rel="nofollow">MR2512606</a>), Kazimierz Alster made some significant progress in showing that one of Telgársky's games completely characterizes the class of spaces whose product with every paracompact space is paracompact.</p> <p>Looking at MathSciNet, it looks like Alster is getting close to answering this question (<a href="http://www.ams.org/mathscinet-getitem?mr=2243730" rel="nofollow">MR2243730</a> and <a href="http://www.ams.org/mathscinet-getitem?mr=2502008" rel="nofollow">MR2502008</a>).</p> http://mathoverflow.net/questions/11153/space-whose-product-with-paracompact-space-is-paracompact/19253#19253 Answer by David Carchedi for Space whose product with paracompact space is paracompact David Carchedi 2010-03-25T00:07:12Z 2010-03-25T00:07:12Z <p>The product of a CW-complex with a paracompact-Hausdorff space is again paracompact Hausdorff. I'm not sure what happens if you remove the word Hausdorff.</p>