0NPL
Proposition 9.20 . The functor V V (9.16 ) inverts Morita equivalences.
0NPM
Proof. It suffices to show that V β‘ ( β ) V(-) sends maps of shape
π β Idem β‘ ( π ) {\mathcal{A}}\mathchoice{\longrightarrow}{\rightarrow}{\rightarrow}{\rightarrow}\Idem({\mathcal{A}}) to isomorphisms. Consider the following diagram
π \textstyle{{\mathcal{A}}\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces} P \scriptstyle{P} β± ΞΊ β ( π ) \textstyle{{\mathcal{F}}_{\kappa}({\mathcal{A}})\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces\ignorespaces} β± ΞΊ β ( P ) \scriptstyle{{\mathcal{F}}_{\kappa}(P)} Ξ£ ΞΊ β ( π ) \textstyle{\Sigma_{\kappa}({\mathcal{A}})\ignorespaces\ignorespaces\ignorespaces\ignorespaces} Ξ£ ΞΊ β ( P ) \scriptstyle{\Sigma_{\kappa}(P)} Idem β‘ ( π ) \textstyle{\Idem({\mathcal{A}})\ignorespaces\ignorespaces\ignorespaces\ignorespaces} β± ΞΊ β ( Idem β‘ ( π ) ) \textstyle{{\mathcal{F}}_{\kappa}(\Idem({\mathcal{A}}))\ignorespaces\ignorespaces\ignorespaces\ignorespaces} Ξ£ ΞΊ β ( Idem β‘ ( π ) ) . \textstyle{\Sigma_{\kappa}(\Idem({\mathcal{A}}))\,.}
PropositionΒ 2.18 implies that β± ΞΊ β ( P ) {\mathcal{F}}_{\kappa}(P) is an
equivalence. Therefore, since both rows are strict-exact sequences and
Ho β‘ ( π ) \Ho({\mathcal{A}}) and Ho β‘ ( Idem β‘ ( π ) ) \Ho(\Idem({\mathcal{A}})) differ by direct summands, we
conclude that Ξ£ ΞΊ β ( P ) \Sigma_{\kappa}(P) is an equivalence. The definition of the
functor V β‘ ( β ) V(-) allow us to conclude the proof.
β