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On Non-split Abelian Extensions
Bulletin of the Iranian Mathematical Society ( IF 0.7 ) Pub Date : 2020-06-15 , DOI: 10.1007/s41980-020-00410-9
Noureddine Snanou , Mohammed Elhassani Charkani

Let \(G_{2}\) be a group which acts trivially on an abelian group \(G_{1}\). According to the Schreier’s Theorem, each 2-cocycle \(\varepsilon \in Z^{2}(G_{2},G_{1})\) determines a group \(G_{\varepsilon }\) which is a central extension of \(G_{1}\) by \(G_{2}\), and we will denote this group by \(G_{1}\underset{\varepsilon }{\times }G_{2} \) and call it the perturbed direct product of \(G_{1}\) by \(G_{2}\) under \(\varepsilon \). The aim of this paper is to study properties of the perturbed direct products. For two distinct 2-cocycles \(\varepsilon _{1}\) and \(\varepsilon _{2}\), we find necessary and sufficient conditions for \(G_{1}\underset{\varepsilon _{1}}{\times }G_{2} \) to be isomorphic to \(G_{1}\underset{\varepsilon _{2}}{\times }G_{2}\). Furthermore, we obtain some results about decompositions for a given perturbed direct product \(G_{1}\underset{ \varepsilon }{\times }G_{2}\) when \(G_{1}\) or \(G_{2}\) is a nontrivial direct product.



中文翻译:

关于非拆分阿贝尔扩展

假设\(G_ {2} \)是对阿贝尔群\(G_ {1} \)起作用的一个组。根据施赖埃尔定理,每个2上闭链\(\ varepsilon \沿Z ^ {2}(G_ {2},G_ {1})\)确定一组\(G _ {\ varepsilon} \) ,其是中心的扩展\(G_ {1} \)\(G_ {2} \),我们将表示该组由\(G_ {1} \底流{\ varepsilon} {\倍} G_ {2} \)和称其为\(\ varepsilon \)\(G_ {1} \)\(G_ {2} \)的摄动直接积。本文的目的是研究被摄动的直接产品的性质。对于两个不同的2-cocycles \(\ varepsilon _ {1} \)\(\ varepsilon _ {2} \),我们发现\(G_ {1} \ underset {\ varepsilon _ {1}} {\ times} G_ {2} \)同构为\的必要和充分条件(G_ {1} \ underset {\ varepsilon _ {2}} {\ times} G_ {2} \)。此外,对于给定的摄动直接积\(G_ {1} \ underset {\ varepsilon} {\ times} G_ {2} \),\(G_ {1} \)\(G_ { 2} \)是非平凡的直接产品。

更新日期:2020-06-18
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