Not signed in (Sign In)

Not signed in

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

  • Sign in using OpenID

Site Tag Cloud

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 definitions deformation-theory descent diagrams differential differential-cohomology differential-equations differential-geometry digraphs duality elliptic-cohomology enriched fibration foundation foundations functional-analysis functor 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 nforum nlab noncommutative noncommutative-geometry number-theory of operads operator operator-algebra order-theory pages pasting philosophy physics 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

Vanilla 1.1.10 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to nForum
If you want to take part in these discussions either sign in now (if you have an account), apply for one now (if you don't).
    • CommentRowNumber1.
    • CommentAuthorDavid_Corfield
    • CommentTimeApr 9th 2024

    Put this page into regular format.

    diff, v2, current

    • CommentRowNumber2.
    • CommentAuthorDavid_Corfield
    • CommentTimeApr 9th 2024

    I see that Connes and Consani in the article listed there define a Γ\Gamma-set as a pointed functor from Fin *Fin_{\ast} to Set *Set_{\ast} rather than functors to SetSet as we have here.

    The latter would seem to sit better with Gamma-space.

    • CommentRowNumber3.
    • CommentAuthorDavid_Corfield
    • CommentTimeApr 9th 2024

    I added something on Connes and Consani’s different definition.

    diff, v3, current

    • CommentRowNumber4.
    • CommentAuthorDmitri Pavlov
    • CommentTimeApr 9th 2024

    The category of Γ-sets in this sense is no longer a topos

    Why is it not a topos? Set_* is a slice topos, presheaves valued in a topos again form a topos.

    • CommentRowNumber5.
    • CommentAuthorUrs
    • CommentTimeApr 9th 2024

    Rather a co-slice, no?

    • CommentRowNumber6.
    • CommentAuthorDmitri Pavlov
    • CommentTimeApr 9th 2024

    Re #5: I confused slice and co-slice, I guess.

    But this does raise a question: what kind of category does the co-slice category of a topos form?

    • CommentRowNumber7.
    • CommentAuthorRodMcGuire
    • CommentTimeApr 10th 2024

    But this does raise a question: what kind of category does the co-slice category of a topos form?

    in this case it is not just a coslice but one from the global point (terminal object) which makes it have a sub object classifier I think. If that is worth anything.

    • CommentRowNumber8.
    • CommentAuthorUrs
    • CommentTimeApr 10th 2024

    There is a comment by Vladimir Sotirov in MO:a/4765697 on pointed sets having a subobject classifier but not being an elementary topos.