# nLab enriched (infinity,1)-category

Contents

### Context

#### $(\infty,1)$-Category theory

(∞,1)-category theory

Background

Basic concepts

Universal constructions

Local presentation

Theorems

Extra stuff, structure, properties

Models

#### Enriched category theory

enriched category theory

# Contents

## Idea

The notion of enriched $(\infty,1)$-category is the generalization of the notion of enriched category from category theory to (∞,1)-category theory. For $\mathcal{V}$ a monoidal (∞,1)-category, a $\mathcal{V}$-enriched $(\infty,1)$-category $C$ is

• a set/class of objects $Obj(C)$;

• for every tuple $(a \in C,b \in C)$ an object $C(a,b) \in \mathcal{V}$ “of morphisms” from $a$ to $b$ in $C$;

• for each sequence $(a_i \in C)_{i = 0}^n$ of objects in $C$ an object $C(a_0, \cdots, a_n) \in \mathcal{V}$ “of sequences of composable morphisms and their composites”;

• such that these composites exist essentially uniquely and satisfy associativity in a coherent fashion.

One way to make this precise in a general abstract way should be to define $C$ to be a ∞-algebra over an (∞,1)-operad in $\mathcal{V}^{\otimes}$ over Assoc${}_{Obj(C)}$, the $Obj(C)$-colored version of the associative operad;

$C \in Alg_{Assoc_{Obj(C)}}(\mathcal{V}^\otimes) \,.$

For $\mathcal{V} \in$ ∞Grpd, this should be equivalent to ordinary (∞,1)-categories. This is for instance in (Lurie, def. 4.2.1.12).

A construction that should be a model for this notion in terms of a model category presentation for $\mathcal{V}$ is discussed in (Simpson). For the case that $\mathcal{V} =$ ∞Grpd presented by the standard model structure on simplicial sets this reproduces the notion of Segal categories. (See there for further details and references.) The iteration of this construction yields Segal n-categories, a model for (∞,n)-categories.

Once a model category $V$ for $\mathcal{V}$ has been chosen, one can consider semi-strict $\infty$-enrichments given by ordinary $V$-enriched categories equipped with a notion of weak equivalence that remembers that these are presentations for enriched $(\infty,1)$-categories. See also enriched homotopical category.

## Examples

A stable (∞,1)-category is naturally enriched in the (∞,1)-category of spectra.

More generally, for $R$ an E-∞ ring then an $R$-linear (∞,1)-category is naturally enriched in $R$-∞-modules. (This includes the previous case for $R$ the sphere spectrum.)

A closed monoidal (∞,1)-category is naturally enriched over itself.

## References

Further discussion of (infinity,n)-categories as $\infty$-categories enriched in $(\infty,n-1)$-categories is (via Theta-spaces) in