Definition 15.117.1. Let $R$ be a ring. An $R$-module $M$ is invertible if the functor
\[ \text{Mod}_ R \longrightarrow \text{Mod}_ R,\quad N \longmapsto M \otimes _ R N \]
is an equivalence of categories. An invertible $R$-module is said to be trivial if it is isomorphic to $R$ as an $R$-module.
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Comment #6341 by Yuto Masamura on
Comment #6442 by Johan on