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.
Faithful, full, fully faithful, essentially surjective, and split essentially surjective functors
Definition
Let be a functor (Covariant functor, identity functor, composite functor, and contravariant functor). For each , it induces
The functor is faithful when every is injective, full when every is surjective, and fully faithful when every is bijective (Injection, surjection, bijection).
It is essentially surjective when every object of is isomorphic to some (Isomorphism, groupoid, and connected category). It is split essentially surjective when the data include, for every , a specified object and specified isomorphism . The word split records these witnesses and is strictly stronger as data than their mere existence.
Depends on
Used by
- The inclusion of one object into a discrete two-object category is fully faithful but not essentially surjective Counterexample
- Embedding and full embedding of categories Definition
- Chosen bases exhibit Mat_F as equivalent to finite-dimensional vector spaces Example
- Under the Axiom of Choice, essential surjectivity onto a small category admits a splitting Lemma
- Every fully faithful functor reflects isomorphisms Proposition
- A functor is an equivalence exactly when it is fully faithful and split essentially surjective, without Choice Theorem
Dependency tree · next 3 levels
Direct dependencies and their dependencies through the next three levels: 15 results over 7 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
- Emily Riehl, Category Theory in Context, Chapter 1 (standard reference, not scraped)
- Ahrens, Kapulkin and Shulman, Univalent categories and the Rezk completion, section 6 (standard reference, not scraped)