Contents

# Contents

## Definition

###### Definition

(diagonal of a bisimplicial set)

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

$\Delta(X)_n \;\coloneqq\; X_{n,n} \,.$

## References

Last revised on October 24, 2021 at 07:10:53. See the history of this page for a list of all contributions to it.