$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$



The simplicial set $\operatorname{\mathcal{QC}}_{\ast }^{\operatorname{lax}}$ is an $\infty $-category.


The projection map $U: \operatorname{ \pmb {\mathcal{QC}} }_{\ast } = \operatorname{ \pmb {\mathcal{QC}} }_{\Delta ^{0} / } \rightarrow \operatorname{ \pmb {\mathcal{QC}} }$ restricts to a functor

\[ U_0: \operatorname{\mathcal{QC}}_{\ast }^{\operatorname{lax}} = \operatorname{Pith}( \operatorname{ \pmb {\mathcal{QC}} }_{\ast }^{\operatorname{lax}} ) \rightarrow \operatorname{Pith}(\operatorname{ \pmb {\mathcal{QC}} }) = \operatorname{\mathcal{QC}}. \]

The diagram

\[ \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{QC}}_{\ast }^{\operatorname{lax}} \ar [r] \ar [d]^-{U_0} & \operatorname{ \pmb {\mathcal{QC}} }_{\ast }^{\operatorname{lax}} \ar [d]^-{U} \\ \operatorname{\mathcal{QC}}\ar [r] & \operatorname{ \pmb {\mathcal{QC}} }} \]

is a pullback square of simplicial sets.


The functor $U_0$ is a cocartesian fibration of $\infty $-categories.

Proof. Assertion $(1)$ follows from Proposition Since $U$ is an interior fibration (Proposition, assertions $(2)$ and $(3)$ follow from Proposition Assertion $(4)$ is a special case of Corollary $\square$