most recent 30 from http://mathoverflow.net 2013-05-21T21:08:58Z http://mathoverflow.net/feeds/question/53094 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/53094/on-tensor-product tensorproductgogogle 2011-01-24T17:39:28Z 2011-01-24T17:39:28Z

<p>Let $\alpha\colon G\to H$ be a group homomorphism and $R$ be a commutative ring. Regard $R$ as $RN$-module with trivial $N$-action.</p> <p>Further, we denote $N=\operatorname{Ker}\alpha$.</p> <p>Is it true that $\mathbb{Z}G\otimes_{\mathbb{Z}}R\otimes_{RN}R=RH$ even $\alpha$ is not onto? </p>