# Start a new discussion

## Not signed in

Want to take part in these discussions? Sign in if you have an account, or apply for one below

## Discussion Tag Cloud

Vanilla 1.1.10 is a product of Lussumo. More Information: Documentation, Community Support.

• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeSep 2nd 2012
• (edited Sep 24th 2012)

thought we’d need an entry homotopy category of chain complexes

• CommentRowNumber2.
• CommentAuthorjim_stasheff
• CommentTimeSep 3rd 2012
perhaps with a distinction from and/or link to higher homotopies
• CommentRowNumber3.
• CommentAuthorUrs
• CommentTimeSep 24th 2012
• (edited Sep 24th 2012)

I have expanded homotopy category of chain complexes by adding a few basics.

In the course of this I have also touched the formatting of the following entries:

Will be further working on derived category now.

• CommentRowNumber4.
• CommentAuthorUrs
• CommentTimeSep 24th 2012
• (edited Sep 24th 2012)

I needed to spell out somewhere a very basic expositional example of what goes wrong in $\mathcal{K}(\mathcal{A})$ that is rectified in the derived category such that the example roughly motivates the idea of projective resolutions. I ended up putting it here into a new section Examples - Chain homotopies that ought to exist but do not. It could probably go elsewhere just as well.

• Please log in or leave your comment as a "guest post". If commenting as a "guest", please include your name in the message as a courtesy. Note: only certain categories allow guest posts.
• To produce a hyperlink to an nLab entry, simply put double square brackets around its name, e.g. [[category]]. To use (La)TeX mathematics in your post, make sure Markdown+Itex is selected below and put your mathematics between dollar signs as usual. Only a subset of the usual TeX math commands are accepted: see here for a list.

• (Help)