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10 votes
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Applications of sheaf theory to the computation of invariants of LS-category type

I would like to know if sheaf theory can be applied to a particular class of questions in topology. The Schwarz genus (also known as sectional category) of a continuous map $p\colon\thinspace E\to ...
Mark Grant's user avatar
  • 35.9k
9 votes
0 answers
369 views

Topologies (and sheaves) on Cat and CAT

I've been wondering lately what sort of Grothendieck (pre)topologies there are on $Cat$ (the category of small categories) and $CAT$ (the v. large category of large categories - to forestall criticism ...
David Roberts's user avatar
  • 35.5k
7 votes
0 answers
362 views

What is a morphism of ∞-sites?

Recall that a morphism of sites is a covering-flat functor that preserves covering families. Morphisms of sites can be identified with those geometric morphisms of induced toposes for which the ...
Dmitri Pavlov's user avatar
7 votes
0 answers
160 views

Is it always possible to write a derived manifold (in the sense of Spivak) as a homotopy colimit of principal derived manifolds?

Is it always possible to write a derived manifold as a homotopy colimit of principal derived manifolds (i.e. zero sets of smooth functions)? This is true for schemes and derived schemes, so it seems ...
John Rached's user avatar
7 votes
0 answers
407 views

Generalities on sheaves - Where can I find the technology that can make this "proof" of Atiyah duality precise?

Fix $R$ an $E_{\infty}$ ring spectrum which admits a "six functor formalism" over a suitable class of spaces (by which I mean a context in which what I'm about to say can be made correct). Let $X$ ...
Saal Hardali's user avatar
  • 7,789
5 votes
0 answers
113 views

How "commutative" are Cech cochains of a sheaf of commutative (dg) algebras?

Let $X$ be a topological space and $\mathcal{F}$ be a sheaf of commutative dg-algebras over $X$. Let $\mathfrak{U}$ be a fixed open covering of $X$ and $C^\bullet(\mathfrak{U},\mathcal{F})$ be the ...
algebrachallenged's user avatar
5 votes
0 answers
380 views

Does the de Rham complex induce a functorial soft resolution of the category of cochain complexes of sheaves of vector spaces on a smooth manifold?

I apologize in advance if this is pretty straightforward; I'm a differential geometer and physicist by training so my homological algebra and homotopy theory are a bit weak. Question: Let $M$ be a ...
ಠ_ಠ's user avatar
  • 6,025
5 votes
0 answers
377 views

Push forward of the constant sheaf for a Serre's fibration

Let $f\colon X\to Y$ be a proper continuous map of topological spaces which is a Serre's fibration. $X$ and $Y$ may be assumed to be locally compact, $Y$ is connected topological manifold of finite ...
asv's user avatar
  • 21.8k
2 votes
0 answers
65 views

Coequalizers and pullbacks in $\infty$-topoi

In an $\infty$-topos, suppose we have two cartesian diagrams of the form $$ \require{AMScd} \begin{CD} \overline{A} @>>> \overline{B} \\ @VVV @VVV \\ A @>>> B . \end{CD} $$ Let $$ \...
grass man's user avatar
1 vote
0 answers
78 views

Homotopy limits indexed by a covering

We all know that the homotopy fiber of a continuous function $f: A \to B$ has a simple expression in terms of points and paths connecting them, that is $$ \textrm{hofib}_y(f) = \{ (x,\gamma) \in A \...
Andrea Marino's user avatar