13.1.10 Pseudomonic Morphisms

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

A $1$-morphism $f\colon A\to B$ of $\mathcal{C}$ is pseudomonic if, for each $X\in \operatorname {\mathrm{Obj}}\webleft (\mathcal{C}\webright )$, the functor

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

given by postcomposition by $f$ is pseudomonic.

In detail, a $1$-morphism $f\colon A\to B$ of $\mathcal{C}$ is pseudomonic if it satisfies the following conditions:

  1. 1.

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

    if we have

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

    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

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

Let $f\colon A\to B$ be a $1$-morphism of $\mathcal{C}$.

  1. 1.

    Characterisations. The following conditions are equivalent:

    1. (a)

      The morphism $f$ is pseudomonic.

    2. (b)

      The morphism $f$ is representably full on cores and representably faithful.

    3. (c)

      We have an isocomma square of the form

      in $\mathcal{C}$ up to equivalence.

  2. 2.

    Interaction With Cotensors. If $\mathcal{C}$ has cotensors with $\mathbb {1}$, then the following conditions are equivalent:

    1. (a)

      The morphism $f$ is pseudomonic.

    2. (b)

      We have an isocomma square of the form

      in $\mathcal{C}$ up to equivalence.

Item 1: Characterisations
Omitted.

Item 2: Interaction With Cotensors
Omitted.


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