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

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.