Cohomological Support and the Geometric Join
Let $M,N$ be finitely generated modules over a local complete intersection $R$. Assume that all the modules $\torRi(M,N)$ are zero for $i>0$. We prove that the cohomological support of $M\otimesR N$ (in the sense of Avramov-Buchweitz) is equal to the geometric join of the cohomological supports of $M,N$. This result gives a new connection between two active areas or research, and immediately produces several interesting corollaries. Naturally, it also raises many intriguing new questions about the homological properties of modules over a complete intersection, some of which are investigated in this work. 2010 MSC Classification: 13D07
2010 Mathematics Subject Classification:
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