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1. • CommentRowNumber1.
   • CommentAuthorDavid_Corfield
   • CommentTimeNov 30th 2009
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   Author: David_Corfield
   Format: HtmlStarted <a href="http://ncatlab.org/nlab/show/injective+hull">injective hull</a>.

   Started injective hull.
2. • CommentRowNumber2.
   • CommentAuthorDavid_Corfield
   • CommentTimeNov 30th 2009
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   Author: David_Corfield
   Format: HtmlThere's a lot of terminology being used by the authors. I'm wary of starting up pages for 'extension' a kind of 'embedding', and 'injective' and 'essential embedding'. Do these only apply to concrete categories?

   There's a lot of terminology being used by the authors. I'm wary of starting up pages for 'extension' a kind of 'embedding', and 'injective' and 'essential embedding'. Do these only apply to concrete categories?
3. • CommentRowNumber3.
   • CommentAuthorDavid_Corfield
   • CommentTimeDec 1st 2009
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   Author: David_Corfield
   Format: HtmlAdded the fact that assigning an object its injective hull is not natural. Does this tell us something interesting?

   Added the fact that assigning an object its injective hull is not natural. Does this tell us something interesting?
4. • CommentRowNumber4.
   • CommentAuthorTobyBartels
   • CommentTimeDec 4th 2009
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   Author: TobyBartels
   Format: MarkdownThis has always been a strange thing to beginning category theorists (and maybe still for the rest of us). The usual example seems to be the algebraic closure of a field (although that's an injective hull only in a slightly unobvious category, now noted on our page). Any two algebraic closures are isomorphic, but not canonically so, and this applies to injective hulls in general. It should tell us something, but I don't know what.

   This has always been a strange thing to beginning category theorists (and maybe still for the rest of us). The usual example seems to be the algebraic closure of a field (although that's an injective hull only in a slightly unobvious category, now noted on our page). Any two algebraic closures are isomorphic, but not canonically so, and this applies to injective hulls in general.

   It should tell us something, but I don't know what.