Lemma 12.14.12. Notation and assumptions as in Lemma 12.14.10. Let \alpha : A^\bullet \to B^\bullet , \beta : B^\bullet \to C^\bullet be the given morphisms of complexes. Suppose (s')^ n : C^ n \to B^ n and (\pi ')^ n : B^ n \to A^ n is a second choice of splittings. Write (s')^ n = s^ n + \alpha ^ n \circ h^ n and (\pi ')^ n = \pi ^ n + g^ n \circ \beta ^ n for some unique morphisms h^ n : C^ n \to A^ n and g^ n : C^ n \to A^ n. Then
g^ n = - h^ n, and
the family of maps \{ g^ n : C^ n \to A[1]^{n - 1}\} is a homotopy between \delta , \delta ' : C^\bullet \to A[1]^\bullet , more precisely (\delta ')^ n = \delta ^ n + g^{n + 1} \circ d_ C^ n + d_{A[1]}^{n - 1} \circ g^ n.
Comments (3)
Comment #295 by arp on
Comment #5086 by R on
Comment #5297 by Johan on
There are also: