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	<title>Comments on: My Favorite Random Fact About Abelian Categories</title>
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	<link>http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/</link>
	<description>Geometry, Topology, Categories, Groups, Physics, . . . Everything</description>
	<pubDate>Sat, 19 Jul 2008 10:31:44 +0000</pubDate>
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		<title>By: icecube</title>
		<link>http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/#comment-81</link>
		<dc:creator>icecube</dc:creator>
		<pubDate>Mon, 23 Jul 2007 16:34:40 +0000</pubDate>
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		<description>Oh that's also my favourite fact about abelian categories!  I don't, however, know much more personally about them.</description>
		<content:encoded><![CDATA[<p>Oh that&#8217;s also my favourite fact about abelian categories!  I don&#8217;t, however, know much more personally about them.</p>
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		<title>By: Ars Mathematica &#187; Blog Archive &#187; Secret of Blogging about Everything</title>
		<link>http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/#comment-72</link>
		<dc:creator>Ars Mathematica &#187; Blog Archive &#187; Secret of Blogging about Everything</dc:creator>
		<pubDate>Sun, 22 Jul 2007 05:59:08 +0000</pubDate>
		<guid isPermaLink="false">http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/#comment-72</guid>
		<description>[...] both cover a broad range of advanced topics. Enjoy them while you can &#8212; as you can see here open hostilities between the two are about to break [...]</description>
		<content:encoded><![CDATA[<p>[...] both cover a broad range of advanced topics. Enjoy them while you can &mdash; as you can see here open hostilities between the two are about to break [...]</p>
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		<title>By: John Armstrong</title>
		<link>http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/#comment-70</link>
		<dc:creator>John Armstrong</dc:creator>
		<pubDate>Sat, 21 Jul 2007 02:12:35 +0000</pubDate>
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		<description>I'm not so sure this is really "secret".  There are a lot of these sorts of enriched categories.

Let's say you have a category with "zero morphisms".  That is, for every pair of objects $latex A$ and $latex B$ there's a morphism $latex 0:A\rightarrow B$ so that $latex 0\circ f$ and $latex g\circ0$ are the appropriate zero morphisms.  This is "secretly" the same thing as a category enriched over $latex \mathbf{pSet}$ -- the category of pointed sets.  We can slip back and forth between seeing it as a category that satisfies certain properties or an enriched category.</description>
		<content:encoded><![CDATA[<p>I&#8217;m not so sure this is really &#8220;secret&#8221;.  There are a lot of these sorts of enriched categories.</p>
<p>Let&#8217;s say you have a category with &#8220;zero morphisms&#8221;.  That is, for every pair of objects <img src='http://l.wordpress.com/latex.php?latex=A&amp;bg=ffffff&amp;fg=000000&amp;s=0' alt='A' title='A' class='latex' /> and <img src='http://l.wordpress.com/latex.php?latex=B&amp;bg=ffffff&amp;fg=000000&amp;s=0' alt='B' title='B' class='latex' /> there&#8217;s a morphism <img src='http://l.wordpress.com/latex.php?latex=0%3AA%5Crightarrow+B&amp;bg=ffffff&amp;fg=000000&amp;s=0' alt='0:A\rightarrow B' title='0:A\rightarrow B' class='latex' /> so that <img src='http://l.wordpress.com/latex.php?latex=0%5Ccirc+f&amp;bg=ffffff&amp;fg=000000&amp;s=0' alt='0\circ f' title='0\circ f' class='latex' /> and <img src='http://l.wordpress.com/latex.php?latex=g%5Ccirc0&amp;bg=ffffff&amp;fg=000000&amp;s=0' alt='g\circ0' title='g\circ0' class='latex' /> are the appropriate zero morphisms.  This is &#8220;secretly&#8221; the same thing as a category enriched over <img src='http://l.wordpress.com/latex.php?latex=%5Cmathbf%7BpSet%7D&amp;bg=ffffff&amp;fg=000000&amp;s=0' alt='\mathbf{pSet}' title='\mathbf{pSet}' class='latex' /> &#8212; the category of pointed sets.  We can slip back and forth between seeing it as a category that satisfies certain properties or an enriched category.</p>
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		<title>By: A.J. Tolland</title>
		<link>http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/#comment-69</link>
		<dc:creator>A.J. Tolland</dc:creator>
		<pubDate>Sat, 21 Jul 2007 01:26:36 +0000</pubDate>
		<guid isPermaLink="false">http://cornellmath.wordpress.com/2007/07/20/my-favorite-random-fact-about-abelian-categories/#comment-69</guid>
		<description>Coincidentally, I'll be keeping an eye on you^H^H^H^H visiting the library at MSRI next week.</description>
		<content:encoded><![CDATA[<p>Coincidentally, I&#8217;ll be keeping an eye on you^H^H^H^H visiting the library at MSRI next week.</p>
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