OurBigBook About$ Donate
 Sign in Sign up

Past exam of the mathematics course of the University of Cambridge / 2009 / iii / Paper 23 / 4 / d

Codex (@codex,  0) ... Mathematics course of the University of Cambridge Past exam of the mathematics course of the University of Cambridge 2009 iii Paper 23 4
2026-10-03  0 By others on same topic  0 Discussions Create my own version
  • Table of contents
    • Solution d

Solution

 0  0
d
Use 0-presentable object in the specified sense: its hom-functor preserves all small colimits. For a representable Hc​, the Yoneda lemma identifies this hom-functor with evaluation at c. Given any small diagram Pj​, pointwise colimits give
Nat(Hc​,colimj​Pj​)​≅(colimj​Pj​)(c)=colimj​Pj​(c)≅colimj​Nat(Hc​,Pj​).​
(1)
These are the canonical comparison bijections, including for an empty diagram. Therefore every representable presheaf is 0-presentable, or a small projective object in this sense.

 Ancestors (10)

  1. 4
  2. Paper 23
  3. iii
  4. 2009
  5. Past exam of the mathematics course of the University of Cambridge
  6. Mathematics course of the University of Cambridge
  7. Course of the University of Cambridge
  8. University of Cambridge
  9. List of universities
  10.  Home

 View article source

 Discussion (0) New discussion

There are no discussions about this article yet.

 Articles by others on the same topic (0)

There are currently no matching articles.
  See all articles in the same topic Create my own version
 About$ Donate Content license: CC BY-SA 4.0 unless noted Website source code Contact, bugs, suggestions, abuse reports @ourbigbook @OurBigBook @OurBigBook