A $1$-morphism $f\colon A\to B$ of $\mathcal{C}$ is corepresentably fully faithful[1] if the following equivalent conditions are satisfied:

  1. The $1$-morphism $f$ is corepresentably full (Definition 9.2.2.1.1) and corepresentably faithful (Definition 9.2.1.1.1).
  2. For each $X\in \text{Obj}\webleft (\mathcal{C}\webright )$, the functor
    \[ f^{*}\colon \mathsf{Hom}_{\mathcal{C}}\webleft (B,X\webright )\to \mathsf{Hom}_{\mathcal{C}}\webleft (A,X\webright ) \]

    given by precomposition by $f$ is fully faithful.


Footnotes

[1] Further Terminology: Corepresentably fully faithful morphisms have also been called lax epimorphisms in the literature (e.g. in [Adámek–Bashir–Sobral–Velebil, On Functors Which Are Lax Epimorphisms]), though we will always use the name “corepresentably fully faithful morphism” instead in this work.

Noticed something off, or have any comments? Feel free to reach out!


You can also use the contact form below: