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Yoneda lemma for (infinity,1)-categories

Yoneda lemma

Ingredients

Incarnations

Properties

Universal aspects

Applications

In higher category theory

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(∞,1)-category theory

Background

Basic concepts

Universal constructions

Local presentation

Theorems

Extra stuff, structure, properties

Models

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Yoneda lemma for (,1)-categories

Idea

The statement of the Yoneda lemma has a straightforward generalization from categories to (∞,1)-categories.

Details

Theorem

(,1)-Yoneda embedding

Let C be an (∞,1)-category and PSh(C):=Func(C op,Grpd) be the corresponding (∞,1)-category of (∞,1)-presheaves. Then the canonical (∞,1)-functor

Y:CPSh(C)Y : C \to PSh(C)

is a full and faithful (∞,1)-functor.

Proof

In terms of quasi-categories, this is proposition 5.1.3.1 in

Theorem

(,1)-Yoneda theorem

For C a small (,1)-category and F:C opGrpd an (,1)-functor, the composite

C opPSh (,1)(C) opHom(,F)GrpdC^{op} \to PSh_{(\infty,1)}(C)^{op} \stackrel{Hom(-,F)}{\to} \infty Grpd

is equivalent to F.

Proof

This appears as HTT Lemma 5.5.2.1.

The statement is a direct consequence of the sSet-enriched Yoneda lemma by using the fact that the (infinity,1)-category of (infinity,1)-presheaves PSh (,1)(C) is modeled by the enriched functor category [C op,sSet] proj with C regarded as a simplicially enriched category and using the global model structure on simplicial presheaves.

References

Published statements appear in

as indicated above.

See also the discussion on MathOverflow.