Yoneda and representing objects
Research context
postgraduate concept · established · As of 2026-10-10
For a locally small category C, a functor F:C→Set and object c, natural transformations from Hom(c,−) to F correspond bijectively to elements of F(c), by evaluating at the identity of c.
Key knowledge
For a locally small category C, a functor F:C→Set and object c, natural transformations from Hom(c,−) to F correspond bijectively to elements of F(c), by evaluating at the identity of c. Consequently objects are determined up to isomorphism by their represented functors. This describes a universal characterization, not an algorithm for reconstructing arbitrary objects from finitely sampled observations.
Values and equations
Nat(Hom(c,−),F) ≅ F(c)
- c
- Object of a locally small category C
- F
- Covariant Set-valued functor
- Nat
- Natural transformations
Conditions and scope
- Hom-sets are sets and F is covariant in the displayed version.
- The inverse sends x in F(c) to the transformation f↦F(f)(x).
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: §§1.1–1.4 categories/functors/naturality, §2.2 Yoneda, chapter 4 adjunctions. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
Entry details
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- research-math-yoneda-representability
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- Postgraduate & research reference