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Decompositions of dual automorphism invariant modules over semiperfect rings
Y. Kuratomi Department of Mathematics, Faculty of Science, Yamaguchi University, Yoshida, Yamaguchi, Japan
Abstract:
A module $M$ is called dual automorphism invariant if whenever $X_1$ and $X_2$ are small submodules of $M$, then each epimorphism $f: M/X_1\to M/X_2$ lifts to an endomorphism $g$ of $M$. A module $M$ is said to be $\mathrm{d}$-square free (dual square free) if whenever some factor module of $M$ is isomorphic to $N^2$ for a module $N$ then $N=0$. We show that each dual automorphism invariant module over a semiperfect ring which is a small epimorphic image of a projective lifting module is a direct sum of cyclic indecomposable $\mathrm{d}$-square free modules. Moreover, we prove that for each module $M$ over a semiperfect ring which is a small epimorphic image of a projective lifting module (e.g., $M$ is a finitely generated module), $M$ is dual automorphism invariant iff $M$ is pseudoprojective. Also, we give the necessary and sufficient conditions for a dual automorphism invariant module over a right perfect ring to be quasiprojective.
Keywords:
dual automorphism invariant module, pseudoprojective module, dual square free module, finite internal exchange property, (semi)perfect ring.
Received: 19.07.2018 Revised: 15.11.2018 Accepted: 19.12.2018
Citation:
Y. Kuratomi, “Decompositions of dual automorphism invariant modules over semiperfect rings”, Sibirsk. Mat. Zh., 60:3 (2019), 630–639; Siberian Math. J., 60:3 (2019), 490–496
Linking options:
https://www.mathnet.ru/eng/smj3099 https://www.mathnet.ru/eng/smj/v60/i3/p630
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Abstract page: | 238 | Full-text PDF : | 33 | References: | 55 | First page: | 4 |
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