Reedy category

In mathematics, especially category theory, a Reedy category is a category R that has a structure so that the functor category from R to a model category M would also get the induced model category structure. A prototypical example is the simplex category or its opposite. It was introduced by Christopher Reedy in his unpublished manuscript. ^[1]

Definition

A Reedy category consists of the following data: a category R, two wide (lluf) subcategories ${\displaystyle R_{-},R_{+}}$ and a functorial factorization of each map into a map in ${\displaystyle R_{-}}$ followed by a map in ${\displaystyle R_{+}}$ that are subject to the condition: for some total ordering (degree), the nonidentity maps in ${\displaystyle R_{-},R_{+}}$ lower or raise degrees. ^[2]

Note some authors such as nlab require each factorization to be unique. ^{[3] [4]}

Eilenberg–Zilber category

An Eilenberg–Zilber category is a variant of a Reedy category.

References

1. Reedy’s manuscript can be found at https://math.mit.edu/~psh/
2. Barwic 2007 , Definition 1.6. harvnb error: no target: CITEREFBarwic2007 (help)
3. nlab, https://ncatlab.org/nlab/show/Reedy+category
4. https://mathoverflow.net/questions/176983/the-definition-of-reedy-category

• Clark Barwick, On Reedy Model Categories (arXiv:0708.2832)
• Cisinski, Denis-Charles (2023). Higher Categories and Homotopical Algebra (PDF). Cambridge University Press. ISBN   978-1108473200.
• Clemens Berger, Ieke Moerdijk, On an extension of the notion of Reedy category, Mathematische Zeitschrift, 269, 2011 (arXiv:0809.3341, doi:10.1007/s00209-010-0770-x)
• Tim Campion, Cubical sites as Eilenberg-Zilber categories, 2023, arXiv:2303.06206

Further reading

• https://ncatlab.org/nlab/show/Eilenberg-Zilber+category
• https://ncatlab.org/nlab/show/generalized+Reedy+category
• http://pantodon.jp/index.rb?body=Reedy_category in Japanese