diagonal of a bisimplicial set

**(diagonal)**

For $X_{\bullet,\bullet}$ a bisimplicial set, its **diagonal** is the simplicial set that is the precomposition with $(Id, Id) : \Delta^{op} \to \Delta^{op} \times \Delta^{op}$, i.e. the simplicial set with components.

$d(X)_n = X_{n,n}
\,.$

See also diagonal.

Last revised on April 18, 2013 at 18:50:16. See the history of this page for a list of all contributions to it.