Talk:Inverse image functor

some of the -1's have come out as 1's I don't know how to fix this 129.215.104.170 (talk) 17:35, 12 October 2009 (UTC)

Contravariant is Confusing in this Context
The first sentence of the article is confusing. I think it should be rewritten as "In mathematics, the inverse image functor is a contravariant construction on topological spaces that induces a covariant functor on sheaves".

To explain, I believe the author is trying to say that if we have continuous maps $$f\colon X\to Y$$ and $$g\colon Y\to Z$$ then $$(g\circ f)^{-1}=f^{-1}\circ g^{-1}$$. However, for a fixed ringed space morphism $$f\colon X\to Y$$, $$f^{-1}:\operatorname{Ab}(Y)\to\operatorname{Ab}(X)$$ is actually a covariant functor. This difference makes the first sentence confusing. Nrekuski (talk) 01:49, 6 December 2019 (UTC)


 * An inverse image functor is a *covariant* functor while the formation of an inverse image functor is contravariant. I agree the first sentence is confusing; I have added a clarification but the first sentence should be rewritten, though I’m not completely sure how. — Taku (talk) 23:12, 12 December 2019 (UTC)