Not signed in

Want to take part in these discussions? Sign in if you have an account, or apply for one below

• Username
• Password
• Remember me

• Sign in using OpenID
• Remember me

• Forgot your password?
• Apply for membership

(0 1)-category-theory 2-category 2-category-theory 2-monad abelian-categories accessible adjoint algebra algebraic algebraic-geometry analysis arithmetic beauty book bundle categories category category-theory chern-simons-theory cohesion cohesive-homotopy-type-theory cohomology combinatorics complex-geometry conference connection constructive constructive-mathematics cosmology deformation-theory descent differential differential-cohomology differential-geometry duality enriched enriched-category-theory enrichment examples factorization-system fibration forms foundations functional-analysis functor galois-theory gauge-theory gebra general topology geometric geometric-quantization geometry gravity group-theory higher higher-algebra higher-category-theory higher-geometry higher-topos-theory history homological homological-algebra homology homotopy homotopy-theory homotopy-type-theory homtopy-type-theory index-theory infinity-groupoid integration-theory internal-categories internalization kan lie lie-algebras lie-theory limit limits linear linear-algebra locale localization localization-theory logic manifolds mathematics measure measure-theory mechanics meta modal-logic model model-category-theory monad monoidal-category monoidal-category-theory morphism motivic-cohomology n-groups newpage noncommutative noncommutative-geometry operator operator-algebra order-theory particle-physics phenomenology philosophy physics pretopology pro-object probability-theory quantum quantum-field-theory quantum-mechanics quantum-physics quantum-theory question relative representation representation-theory riemannian-geometry scheme set set-theory sheaf simplicial space stable-homotopy-theory stack string string-theory subobject supergeometry symplectic-geometry tannaka tensor terminology theory topologica-quantum-field-theory topology topos topos-theory torsor tqft type type-theory universal weighted-limit

1. • CommentRowNumber1.
   • CommentAuthorChris SchommerPries
   • CommentTimeApr 11th 2012
   • PermaLink
   Author: Chris SchommerPries
   Format: MarkdownItexThis is basically a reference request. What is a good source which describes the theory of colimits in the 2-category Cat? Here I mean colimits in the 2-categorical pseudo snese, but not necessarily the lax sense. In usually category theory we know that if you have all coequalizers and all coproducts, then you have all colimits. Is there a similar statement here? Is there an explicit way to understand the colimit of a diagram of categories, maybe for certain fundamental sorts of colimits? What if I restrict myself to diagrams which are just ordinary 1-categories? I am really interested in the case where we replace Cat be the 2-category of Abelian categories and additive functors. Where should I look to find these sorts of colimits? Thanks in advance!

   This is basically a reference request.

   What is a good source which describes the theory of colimits in the 2-category Cat? Here I mean colimits in the 2-categorical pseudo snese, but not necessarily the lax sense.

   In usually category theory we know that if you have all coequalizers and all coproducts, then you have all colimits. Is there a similar statement here? Is there an explicit way to understand the colimit of a diagram of categories, maybe for certain fundamental sorts of colimits? What if I restrict myself to diagrams which are just ordinary 1-categories?

   I am really interested in the case where we replace Cat be the 2-category of Abelian categories and additive functors. Where should I look to find these sorts of colimits?

   Thanks in advance!

2. • CommentRowNumber2.
   • CommentAuthorDavidRoberts
   • CommentTimeApr 12th 2012
   • PermaLink
   Author: DavidRoberts
   Format: MarkdownItexPresumably there are 'co-' analogues of [[PIE-limits]] and an analogous theorem about pseudocolimits. I don't know the situation for either of the examples you mention, though.

   Presumably there are ’co-’ analogues of PIE-limits and an analogous theorem about pseudocolimits. I don’t know the situation for either of the examples you mention, though.

3. • CommentRowNumber3.
   • CommentAuthorTim_Porter
   • CommentTimeApr 12th 2012
   • (edited Apr 12th 2012)
   • PermaLink
   Author: Tim_Porter
   Format: MarkdownItexChris, have you looked at Chapter 4 of Tom Fiore's book. [Memoirs of the American Mathematical Society 182 (2006), no. 860.](http://arxiv.org/abs/math.CT/0408298)

   Chris, have you looked at Chapter 4 of Tom Fiore’s book. Memoirs of the American Mathematical Society 182 (2006), no. 860.

4. • CommentRowNumber4.
   • CommentAuthorMike Shulman
   • CommentTimeApr 12th 2012
   • PermaLink
   Author: Mike Shulman
   Format: MarkdownItexThe nLab has a section on [2-colimits in Cat](http://ncatlab.org/nlab/show/2-limit#2ColimitsInCat) constructed via the Grothendieck construction, which presumably can be identified with Tom's version. For the construction of (co)limits out of (co)products and (co)equalizers in an arbitrary bicategory, see the Correction to Ross Street's paper "Fibrations in bicategories". (The paper itself gave an incorrect construction; the correction fixed it.)

   The nLab has a section on 2-colimits in Cat constructed via the Grothendieck construction, which presumably can be identified with Tom’s version.

   For the construction of (co)limits out of (co)products and (co)equalizers in an arbitrary bicategory, see the Correction to Ross Street’s paper “Fibrations in bicategories”. (The paper itself gave an incorrect construction; the correction fixed it.)

5. • CommentRowNumber5.
   • CommentAuthorChris SchommerPries
   • CommentTimeApr 16th 2012
   • PermaLink
   Author: Chris SchommerPries
   Format: MarkdownItexThanks everyone. This is quite helpful and will at least get me looking in the right places. Thanks again.

   Thanks everyone. This is quite helpful and will at least get me looking in the right places. Thanks again.