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Exact sequences are a well known notion in homological algebra. We investigate here the more vague properties of `homotopical exactness', appearing for instance in the fibre or cofibre sequence of a map. Such notions of exactness can be given for very general `categories with homotopies' having homotopy kernels and cokernels, but become more interesting under suitable `stability' hypotheses, satisfied - in particular - by chain complexes. It is then possible to measure the default of homotopical exactness of a sequence by the homotopy type of a certain object, a sort of `homotopical homology'.
@article{TAC_2001_9_a1, author = {Marco Grandis}, title = {A note on exactness and stability in homotopical algebra}, journal = {Theory and applications of categories}, pages = {17--42}, publisher = {mathdoc}, volume = {9}, year = {2001}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2001_9_a1/} }
Marco Grandis. A note on exactness and stability in homotopical algebra. Theory and applications of categories, CT2000, Tome 9 (2001), pp. 17-42. http://geodesic.mathdoc.fr/item/TAC_2001_9_a1/