Natural transformation

Revision as of 20:55, 2 September 2008 by Jam (talk | contribs) (New page: A natural transformation is a way of turning one functor into another functor while 'preserving' the structure of the categories. Natural transformations...)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

A natural transformation is a way of turning one functor into another functor while 'preserving' the structure of the categories. Natural transformations can be thought of a 'morphisms between functors,' and indeed they are precisely the morphisms in functor categories.

More precisely, given two categories $\mathcal{C}$ and $\mathcal{D}$, and two functors $F,G:\mathcal{C}\to \mathcal{D}$, then a natural transformation $\varphi:F\to G$ is a mapping which assigns to each object $X\in \text{Ob}(\mathcal{C})$ a morphism $\varphi_X:F(X)\to G(X)$ in $\mathcal{D}$ such that for every morphism $f:X\to Y$ of $\mathcal{C}$, we have:\[\varphi_Y\circ F(f) = G(f)\circ \varphi_X.\]

This article is a stub. Help us out by expanding it.