13.2.6 Morphisms Corepresentably Fully Faithful on Cores

    Let $\mathcal{C}$ be a bicategory.

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

    1. 1.

      The $1$-morphism $f$ is corepresentably full on cores (Definition 13.2.5.1.1) and corepresentably faithful on cores (Definition 13.2.1.1.1).

  • 2.

    For each $X\in \operatorname {\mathrm{Obj}}\webleft (\mathcal{C}\webright )$, the functor

    \[ f^{*}\colon \mathsf{Core}\webleft (\mathsf{Hom}_{\mathcal{C}}\webleft (B,X\webright )\webright )\to \mathsf{Core}\webleft (\mathsf{Hom}_{\mathcal{C}}\webleft (A,X\webright )\webright ) \]

    given by precomposition by $f$ is fully faithful.

  • In detail, $f$ is corepresentably fully faithful on cores if the conditions in Remark 13.2.4.1.2 and Remark 13.2.5.1.2 hold:

    1. 1.

      For all diagrams in $\mathcal{C}$ of the form

      if $\alpha $ and $\beta $ are $2$-isomorphisms and we have

      \[ \alpha \mathbin {\star }\operatorname {\mathrm{id}}_{f}=\beta \mathbin {\star }\operatorname {\mathrm{id}}_{f}, \]

      then $\alpha =\beta $.

    2. 2.

      For each $X\in \operatorname {\mathrm{Obj}}\webleft (\mathcal{C}\webright )$ and each $2$-isomorphism

      of $\mathcal{C}$, there exists a $2$-isomorphism
      of $\mathcal{C}$ such that we have an equality
      of pasting diagrams in $\mathcal{C}$, i.e. such that we have

      \[ \beta =\alpha \mathbin {\star }\operatorname {\mathrm{id}}_{f}. \]


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