Yes, this is true. Suppose is such a chain complex of free abelian groups.
For each , choose a splitting of the boundary map , so that . (You can do this because , as a subgroup of a free group, is free.) For all , you then have a sub-chain-complex concentrated in degrees and , and is the direct sum of these chain complexes.
Given two such chain complexes and , you get a direct sum decomposition of each, and so it suffices to show that any two complexes , concentrated in degrees and , which are resolutions of the same module are chain homotopy equivalent; but this is some variant of the fundamental theorem of homological algebra.
This is special to abelian groups and is false for modules over a general ring.
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