Yoneda product
In algebra, the Yoneda product (named after Nobuo Yoneda) is the pairing between Ext groups of modules:
induced by
Specifically, for an element , thought of as an extension
- ,
and similarly
- ,
we form the Yoneda (cup) product
- .
Note that the middle map factors through the given maps to .
We extend this definition to include using the usual functoriality of the groups.
References
- May, Notes on Tor and Ext
External links
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