Giraud's theorem for Segal topoi

From papers

Let AA be a V\mathbb{V}-small Segal category. A U\mathbb{U}-Segal topos is a Segal category satisfying the conditions in the claim below; a coproduct is disjoint when its canonical squares with the initial object are cartesian, and a groupoid object is a simplicial object satisfying the Segal and invertibility conditions. For a groupoid object XX_{*}, write X|X_{*}| for the colimit of its simplicial diagram and N(X0X)N(X_{0} \rightarrow |X_{*}|) for the nerve of the natural morphism.

Giraud's theorem for Segal topoi. AA is a U\mathbb{U}-Segal topos if and only if:

  1. The simplicial sets of morphisms in AA are essentially U\mathbb{U}-small.
  2. AA has all U\mathbb{U}-small colimits, and coproducts in AA are disjoint.
  3. For every groupoid object XX_{*} in AA, the natural morphism
XN(X0X)X_{*} \longrightarrow N(X_{0} \rightarrow |X_{*}|)

is an equivalence of simplicial objects in AA. 4. Colimits in AA are stable by pullbacks: for every U\mathbb{U}-small category II, every II-diagram xx_{*} in AA, and morphisms from ColimiIxi\operatorname{Colim}_{i\in I}x_{i} to zz and from yy to zz, the natural morphism

ColimiI(xi×zy)(ColimiIxi)×zy\operatorname{Colim}_{i\in I}\left(x_{i}\times_{z}y\right) \longrightarrow \left(\operatorname{Colim}_{i\in I}x_{i}\right)\times_{z}y

is an equivalence. 5. AA has a U\mathbb{U}-small set of strong generators.

This is presented as the Segal-category analogue of Giraud's theorem, characterizing Segal topoi by smallness, colimits, disjoint coproducts, effective groupoid objects, pullback-stable colimits, and strong generators. The parser supplies no evidence that the claim has been resolved; its status is therefore open.

Progress summary

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Sources & referencesView supporting material

Primary source

Bertrand Toen and Gabriele Vezzosi, “Segal topoi and stacks over Segal categories”, arXiv:math/0212330 (2003).

Solutions 0

No solutions have been posted yet.