Talk:Functor
![]() | This ![]() It is of interest to the following WikiProjects: | ||||||||||
|
|
|
"Too technical for most readers to understand"
I removed this banner. It's a formal mathematical definition of an object in category theory. Things are bound to get technical, that is the nature of the topic. Nothing is lost if a layperson with no background in mathematics does not understand it. — Preceding unsigned comment added by Spacebusdriver (talk • contribs) 21:37, 9 March 2025 (UTC)
Covariance and contravariance in a coordinate co/basis
I'm having trouble with the paragraph beginning "There is a convention which refers to "vectors"...
I think it's easily shown to be wrong with a scalar example. Suppose the change of basis is . Then the dual transformation is . And in higher dimensions, a change of basis induces the dual transformation . (Note: this verifies the invariance of the contraction under a change of basis) This correction can remediate the third sentence of the paragraph, as well.
The fourth/final sentence is correct, although the terminological confusion might be explained by the fact that, while the pull-back of the cobasis transforms contravariantly, the components of a covector (with respect to its cobasis) transform covariantly, and vice versa for the basis and components of a vector.--ScriboErgoSum (talk) 08:17, 21 November 2021 (UTC)