# Contents

## Idea

A derived $\infty$-Lie algebroid is an ∞-Lie algebroid whose underlying space is a derived space , for instance a derived smooth manifold.

More precisely, let $T$ be any abelian Lawvere theory and $T \hookrightarrow C \hookrightarrow T Alg^{op}$ a small full subcategory of geometric test objects formally dual to T-algebras. Then by the theory of function algebras on ∞-stacks over $C$ one identifies $\infty LieAlgd$ with the subcategory

$(T Alg^\Delta)^{op} \stackrel{\overset{\mathcal{O}}{\leftarrow}}{\to} [C^{op}, sSet]$

of the (∞,1)-category of (∞,1)-sheaves on $C$ modeled by cosimplicial T-algebras. Under the Dold-Kan correspondence applied to the underlying cosimplicial ordinary algbra, this identifies with non-negatively graded dg-algebras: the Chevalley-Eilenberg algebras of the corresponding dual $\infty$-Lie algebroids.

But in full derived geometry this setup is further generalized: instead of considering ∞-stacks on just a category of duals of $T$-algebras, one considers derived ∞-stacks over an (∞,1)-site of simplicial algebras. Let $T \hookrightarrow C^{\Delta^{op}} \hookrightarrow T Alg^{\Delta^{op}}$ be accordingly a small subcategory of simplicial $T$-algebra, then the above adjunction generalizes to

$((T Alg^{\Delta^{op}})^\Delta)^{op} \stackrel{\overset{\mathcal{O}}{\leftarrow}}{\to} [C^{op}, sSet] \,,$

where now on the left we have cosimplicial simplicial algebras . Under the Dold-Kan correspondence these now identify with unbounded dg-algebras $CE(\mathfrak{a})$. We have that

• the categorical degree $k$ coming from k-morphisms of the $\infty$-sheaves contributes to positive degrees in $CE(\mathfrak{a})$;

• the derived degree $l$ coming from $l$-morphisms in the $\infty$-function algebras ontribute to negative degree.

This category $(T Alg^{\Delta^{op} \times \Delta})^{op}$ we identify with that of derived $\infty$-Lie algebroids.

## Examples

### BV-BRST complex

In the literature the most familiar example of a derived $\infty$-Lie algebroids – even if not under this name – are the BV-BRST complexes. These are action Lie algebroids for actions of ∞-Lie algebras on derived smooth manifolds.