# nLab smooth E-infinity-groupoid

Contents

under construction

# Contents

## Idea

For $\mathbf{B} = Sh_\infty(CRing_\infty^{op}, et)$ the (∞,1)-topos of E-∞ geometry, let

$\mathbf{H} \coloneqq Sh_\infty(SmoothMfd, \mathbf{B})$

be the (∞,1)-category of (∞,1)-sheaves on the site of smooth manifolds with values in $\mathbf{B}$.

An object in this $\mathbf{H}$ combines the properties of a smooth ∞-groupoid and an object in E-∞ geometry, hence might be called a “smooth $E_\infty$-groupoid”.

It is useful to regard this as a cohesive (∞,1)-topos over $\mathbf{B}$

$\mathbf{H} \stackrel{\overset{\Pi}{\longrightarrow}}{\stackrel{\overset{Disc}{\leftarrow}}{\stackrel{\overset{\Gamma}{\longrightarrow}}{\underset{coDisc}{\leftarrow}}}} \mathbf{B} \,.$

As such this appears for instance in the discussion at

## Constructions

### Multiplicative group

Write

$\mathbb{G}_m \in \mathbf{B}$

for the sheaf which sends each ring to its ∞-group of units

$\mathbb{G}_m \;\colon\; R \mapsto R^\times \,.$

This is the canonical group object in $\mathbf{B}$. The mapping stacks into it are the Picard ∞-stacks.

(…)

For E-∞ rings over the complex numbers, hence E-∞ algebras over $\mathbb{C}$, the multiplicative group

$\mathbb{G}_m = \mathbb{C}^\times$

naturally carries both the structure of an object in smooth ∞-groupoids and in E-∞ geometry, which may be combined to the structure of a smooth $E_\infty$-groupoid.

For $U \in SmthMfd$ and $A \in CRing_\infty(\mathbb{C})$ let $\mathbb{G}_m \in \mathbf{H}$ be given by

$\mathbb{G}_m \;\colon\; (U,A) \mapsto GL_1(A)\otimes C^\infty(U,\mathbb{C}^\times) \,,$

where on the right we have the ∞-groupoid underlying the abelian ∞-group which is the tensor product of the ∞-group of units of $A$ with the abelian group of non-vanishing complex-valued smooth functions on $X$.

Last revised on May 21, 2014 at 12:50:22. See the history of this page for a list of all contributions to it.