Generating cofibrations for nonnegative chain complexes
= Generating cofibrations for nonnegative chain complexes
{title2=$I=\{0\to S^0(R)\}\cup\{S^{n-1}(R)\to D^n(R):n\geq1\}$}
The <sphere chain complex> inclusions into <disk chain complexes>, together with the separate degree-zero cell, generate the <model cofibrations> by cell attachment and retracts. Their right-injective class is exactly the <acyclic fibration in the projective chain-complex model structure>.