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1. • CommentRowNumber1.
   • CommentAuthorDmitri Pavlov
   • CommentTimeJun 22nd 2023
   • PermaLink
   Author: Dmitri Pavlov
   Format: MarkdownItexA stub recording a reference: ## Idea In a [[double category]] $C$ with [[companions]], a __retrocell__ is … ## Example In the [[double category]] of [[spans]], a retrocell boils down to a morphism of spans, where the source span is the [[pullback]] of the original source span along the corresponding horizontal arrow. (Paré, §5.) ## References * [[Robert Paré]], _Retrocells_, [arXiv:2306.06436](https://arxiv.org/abs/2306.06436). <a href="https://ncatlab.org/nlab/revision/retrocell/1">v1</a>, <a href="https://ncatlab.org/nlab/show/retrocell">current</a>

   A stub recording a reference:

   Idea

   In a double category $C$ with companions, a retrocell is …

   Example

   In the double category of spans, a retrocell boils down to a morphism of spans, where the source span is the pullback of the original source span along the corresponding horizontal arrow. (Paré, §5.)

   References

   • Robert Paré, Retrocells, arXiv:2306.06436.

   v1, current

2. • CommentRowNumber2.
   • CommentAuthorBryceClarke
   • CommentTime6 days ago
   • PermaLink
   Author: BryceClarke
   Format: MarkdownItexCompleted the definition of retrocell with diagrams, and added more details for the example of a retrocell in the double category of spans. <a href="https://ncatlab.org/nlab/revision/diff/retrocell/3">diff</a>, <a href="https://ncatlab.org/nlab/revision/retrocell/3">v3</a>, <a href="https://ncatlab.org/nlab/show/retrocell">current</a>

   Completed the definition of retrocell with diagrams, and added more details for the example of a retrocell in the double category of spans.

   diff, v3, current