ScalingStacks

[0042]

Lemma 3.2.9.

The following hold.

  1. Let \(\mathcal C\in \mathrm{Pr}^{\mathrm{L},\mathrm{cp}}\) and \(S\) a small set of compact-projective generators. Then the set \(S\subseteq \mathcal C^{\mathrm{cp}}\) generates the full subcategory \(\mathcal C^{\mathrm{cp}}\) under retracts and finite coproducts. In particular, every compact-projective object in \(\mathcal C\) is a retract of a finite coproduct of objects in \(S\).

  2. Let \(\mathcal C\in \mathrm{Pr}^{\mathrm{L},\mathrm{c}}\) and \(S\) a small set of compact generators. Then the set \(S\subseteq \mathcal C^{c}\) generates the full subcategory \(\mathcal C^{c}\) under retracts and finite colimits. In particular, every compact object in \(\mathcal C\) is a retract of an iterated finite colimit of objects in \(S\).

[0045]

Proof.

The first statement is [Lur09, Prop. 5.5.8.25.(2).(iii)], the proof of the second statement is analogous. ◻

Original mathematics by the credited authors. Source collection and HTML conversion remain in progress.

Yu Leon Liu, Aaron Mazel-Gee, David Reutter, Catharina Stroppel, Paul Wedrich

Original source: arXiv:2401.02956v2

Original source · 2401.02956v2