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.
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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
- Absolute colimits Definition
- Finitary functors and finitary monads Definition
- Left exact and right exact functors Definition
- U-split pairs and ordinary or strict creation of their coequalizers Definition
- FALSE: A continuous functor on a complete category necessarily has a left adjoint False statement
- FALSE: a functor preserving binary products and equalizers must preserve all finite limits False statement
- FALSE: A reflective inclusion creates colimits False statement
- FALSE: every functor preserves the ends that exist in its domain False statement
- FALSE: the underlying-set functor Top→Set fails to preserve some small limit False statement
- A comma-category projection strictly creates the limits preserved by the functor Lemma
- 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
- A functor preserving twisted-arrow limits preserves ends, and dually for coends Theorem
- A reflective inclusion creates every ambient limit in the ordinary isomorphism-invariant sense Theorem
- General adjoint functor theorem, objectwise initial-object form Theorem
- Right adjoints preserve every limit that exists Theorem
- Special adjoint functor theorem, objectwise form with explicit intersection smallness or preservation data Theorem
- The Eilenberg–Moore forgetful functor creates every colimit in the base that the monad and its square preserve Theorem
- The Eilenberg–Moore forgetful functor strictly creates every limit that exists in the base Theorem
- Top is complete and cocomplete, and its underlying-set functor preserves all small limits and colimits Theorem
Dependency tree · two levels
11 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on 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)