Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$

Corollary 7.3.9.7. Let $U: \operatorname{\mathcal{D}}\rightarrow \operatorname{\mathcal{E}}$ be a cocartesian fibration of $\infty $-categories, let $\operatorname{\mathcal{C}}$ be an $\infty $-category, and let $\operatorname{\mathcal{C}}^{0} \subseteq \operatorname{\mathcal{C}}$ be a full subcategory. Suppose that the following conditions are satisfied:

  • For every object $C \in \operatorname{\mathcal{C}}$ and every object $E \in \operatorname{\mathcal{E}}$, the $\infty $-category $\operatorname{\mathcal{D}}_{E} = \{ E\} \times _{\operatorname{\mathcal{E}}} \operatorname{\mathcal{D}}$ admits $\operatorname{\mathcal{C}}^{0}_{/C}$-indexed colimits.

  • For every object $C \in \operatorname{\mathcal{C}}$ and every morphism $e: E \rightarrow E'$ in $\operatorname{\mathcal{E}}$, the covariant transport functor $e_{!}: \operatorname{\mathcal{D}}_{E} \rightarrow \operatorname{\mathcal{D}}_{E'}$ preserves $\operatorname{\mathcal{C}}^{0}_{/C}$-indexed colimits.

Then every lifting problem

\[ \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}^{0} \ar [r]^-{ F } \ar [d] & \operatorname{\mathcal{D}}\ar [d]^{U} \\ \operatorname{\mathcal{C}}\ar [r] \ar@ {-->}[ur]^{\overline{F}} & \operatorname{\mathcal{E}}} \]

admits a solution $\overline{F}: \operatorname{\mathcal{C}}\rightarrow \operatorname{\mathcal{D}}$ which is $U$-left Kan extended from $\operatorname{\mathcal{C}}^{0}$.

Proof. Combine Proposition 7.3.5.5 with Corollary 7.3.9.6. $\square$