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arXiv math/0408251math.RA
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关于Galois余模

On Galois comodules

Robert Wisbauer

摘要:

推广伽罗瓦核环的概念,伽罗瓦余模被引入为在$A$上的余模$P$-核$\cC$,其中$P_A$是逆生成的和投射的,并且评估图$μ_\cC:\Hom^\cC(P,\cC)\ot_SP\to \cC$是(核环的)同构,其中$S=\End^\cC(P)$。我们发现,对于这样的余模,从右$A$ -模范畴到右$\cC$ -余模范畴的函子$\Hom_A(P,-)\ot_SP$和$-\ot_A\cC$是同构的.在本注记中,我们称具有此性质的模为{$P$ Galois余模},而不要求$P_A$是可逆生成的和投射的。这概括了这个名字的旧概念,但我们表明,基本属性和关系保持。这些余模接近于生成元,并且与倾斜(余)模有一些共同的性质。我们的一些结果也适用于广义Hopf伽罗瓦(余代数伽罗瓦)扩展。

英文摘要:

Generalising the notion of Galois corings, Galois comodules were introduced as comodules $P$ over an $A$-coring $\cC$ for which $P_A$ is finitely generated and projective and the evaluation map $μ_\cC:\Hom^\cC(P,\cC)\ot_SP\to \cC$ is an isomorphism (of corings) where $S=\End^\cC(P)$. It was observed that for such comodules the functors $\Hom_A(P,-)\ot_SP$ and $-\ot_A\cC$ from the category of right $A$-modules to the category of right $\cC$-comodules are isomorphic. In this note we call modules $P$ with this property {\em Galois comodules} without requiring $P_A$ to be finitely generated and projective. This generalises the old notion with this name but we show that essential properties and relationships are maintained. These comodules are close to being generators and have some common properties with tilting (co)modules. Some of our results also apply to generalised Hopf Galois (coalgebra Galois) extensions.

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