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2-category 2-category-theory abelian-categories adjoint algebra algebraic algebraic-geometry algebraic-topology analysis analytic-geometry arithmetic arithmetic-geometry book bundles calculus categorical categories category category-theory chern-weil-theory cohesion cohesive-homotopy-type-theory cohomology colimits combinatorics complex complex-geometry computable-mathematics computer-science constructive cosmology deformation-theory descent diagrams differential differential-cohomology differential-equations differential-geometry digraphs duality elliptic-cohomology enriched fibration foundation foundations functional-analysis functor galois-theory gauge-theory gebra geometric-quantization geometry graph graphs gravity grothendieck group group-theory harmonic-analysis higher higher-algebra higher-category-theory higher-differential-geometry higher-geometry higher-lie-theory higher-topos-theory homological homological-algebra homotopy homotopy-theory homotopy-type-theory index-theory integration integration-theory k-theory lie-theory limits linear linear-algebra locale localization logic mathematics measure-theory modal modal-logic model model-category-theory monad monads monoidal monoidal-category-theory morphism motives motivic-cohomology nlab noncommutative noncommutative-geometry number-theory of operads operator operator-algebra order-theory pages pasting philosophy physics planar pro-object probability probability-theory quantization quantum quantum-field quantum-field-theory quantum-mechanics quantum-physics quantum-theory question representation representation-theory riemannian-geometry scheme schemes set set-theory sheaf simplicial space spin-geometry stable-homotopy-theory stack string string-theory superalgebra supergeometry svg symplectic-geometry synthetic-differential-geometry terminology theory topology topos topos-theory tqft type type-theory universal variational-calculus

1. • CommentRowNumber1.
   • CommentAuthorUrs
   • CommentTimeJun 25th 2021
   • PermaLink
   Author: Urs
   Format: MarkdownItexFinally noticed that this entry here was a stub without TOC, without references and without cross-links. Have touched it a little. <a href="https://ncatlab.org/nlab/revision/diff/groupoid+object/4">diff</a>, <a href="https://ncatlab.org/nlab/revision/groupoid+object/4">v4</a>, <a href="https://ncatlab.org/nlab/show/groupoid+object">current</a>

   Finally noticed that this entry here was a stub without TOC, without references and without cross-links. Have touched it a little.

   diff, v4, current

2. • CommentRowNumber2.
   • CommentAuthorBryceClarke
   • CommentTime6 days ago
   • PermaLink
   Author: BryceClarke
   Format: MarkdownItexAdded a reference: * [[Nelson Martins-Ferreira]], _Internal groupoids as involutive-2-links_, 2023. [[arXiv:2305.13537](https://arxiv.org/abs/2305.13537)] <a href="https://ncatlab.org/nlab/revision/diff/groupoid+object/7">diff</a>, <a href="https://ncatlab.org/nlab/revision/groupoid+object/7">v7</a>, <a href="https://ncatlab.org/nlab/show/groupoid+object">current</a>

   Added a reference:

   • Nelson Martins-Ferreira, Internal groupoids as involutive-2-links, 2023. [arXiv:2305.13537]

   diff, v7, current

3. • CommentRowNumber3.
   • CommentAuthorzskoda
   • CommentTime6 days ago
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   Author: zskoda
   Format: MarkdownItexI guess in the definition we need to define it as a contravariant functor.

   I guess in the definition we need to define it as a contravariant functor.

4. • CommentRowNumber4.
   • CommentAuthorzskoda
   • CommentTime6 days ago
   • PermaLink
   Author: zskoda
   Format: MarkdownItexCorrected.

   Corrected.