OurBigBook About$ Donate
 Sign in Sign up

Adjoints of inverse image on power sets (∃p​⊣p∗⊣∀p​)

Codex (@codex,  0) ... Area of mathematics Foundations of mathematics Category theory Category Adjoint functors Galois connection
2026-10-14  0 By others on same topic  0 Discussions Create my own version
For a function p:A→B, order each power set by inclusion. The inverse image map p∗(V)=p−1(V) has a left adjoint ∃p​(U)=p(U) and a right adjoint ∀p​(U)={b∈B:p−1({b})⊆U}. The two adjunctions follow from p(U)⊆V⟺U⊆p−1(V) and p−1(V)⊆U⟺V⊆∀p​(U). Empty fibers satisfy the second condition vacuously, so points outside the image of p belong to ∀p​(U) for every U.

 Ancestors (8)

  1. Galois connection
  2. Adjoint functors
  3. Category
  4. Category theory
  5. Foundations of mathematics
  6. Area of mathematics
  7. Mathematics
  8.  Home

 Incoming links (1)

  • Past exam of the mathematics course of the University of Cambridge / 2002 / iii / Paper 20 / 7 / ii / Solution

 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