How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
- Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
- AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
- AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.
These labels describe origin, not correctness: citations and verification chips remain separate evidence.
Preservation, reflection, and creation of limits and colimits; continuous and cocontinuous functors
Definition
Let be a functor (Covariant functor, identity functor, composite functor, and contravariant functor) and fix an indexing category .
- preserves -limits if the image under of every limiting cone over is limiting over .
- reflects -limits if a cone over is limiting whenever its image is limiting.
- In the ordinary isomorphism-invariant sense used here, creates -limits if every limiting cone over is isomorphic as a cone (Natural isomorphism) to the image of a cone over , that source cone is limiting, and any source cone whose image is limiting is limiting. This does not require an on-the-nose lift of the target apex.
- The functor strictly creates -limits if every limiting cone over has a unique lift with exactly the same apex and legs under , and that lifted cone is limiting. Strict creation therefore contains data not demanded by ordinary isomorphism-invariant creation.
The terms preserves, reflects, and creates colimits use cocones and colimits (Limits and colimits as terminal cones and initial cocones, with existence and uniqueness in their universal properties). A functor is continuous if it preserves all small limits and cocontinuous if it preserves all small colimits.
Depends on
Used by
- Hom(X,−) is continuous, while Hom(−,X) sends every existing small colimit to a limit of sets Corollary
- FALSE: a functor preserving binary products and equalizers must preserve all finite limits False statement
- FALSE: the underlying-set functor Top→Set fails to preserve some small limit False statement
- A functor preserves a chosen limit exactly when its canonical comparison to the chosen target limit is an isomorphism, and dually for colimits Lemma
- A functor that creates limits of a given shape lifts their existence and preserves the created limits, and dually for colimits Proposition
- Equivalences preserve, reflect, and create limits and colimits in the isomorphism-invariant sense Proposition
- Fully faithful functors reflect limits and colimits Proposition
- Top is complete and cocomplete, and its underlying-set functor preserves all small limits and colimits Theorem
Dependency tree · next 3 levels
Direct dependencies and their dependencies through the next three levels: 16 results over 9 levels. An arrow runs from a result to what uses it, and this result sits at the bottom with a heavier outline. Click the chart to enlarge it.
Sources
- E. Riehl, Category Theory in Context, Definition 3.4.1 and Remark 3.4.2 (standard reference, not scraped)