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diagonal_functor [2014/09/26 15:10] nikolaj |
diagonal_functor [2014/09/26 15:48] nikolaj |
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| @#55CCEE: context | @#55CCEE: ${\bf C},{\bf D}$ ... category | | | @#55CCEE: context | @#55CCEE: ${\bf C},{\bf D}$ ... category | | ||
| @#FFBB00: definiendum | @#FFBB00: $\Delta:{\bf C}\longrightarrow{\bf C}^{\bf D}$ | | | @#FFBB00: definiendum | @#FFBB00: $\Delta:{\bf C}\longrightarrow{\bf C}^{\bf D}$ | | ||
- | | @#FF9944: definition | @#FF9944: $\Delta\,C:=\Delta_C$ | | + | | @#FF9944: definition | @#FF9944: $\Delta C:=\Delta_C$ | |
| @#FF9944: definition | @#FF9944: $\Delta(f):=\mathrm{const}_f$ | | | @#FF9944: definition | @#FF9944: $\Delta(f):=\mathrm{const}_f$ | | ||
==== Discussion ==== | ==== Discussion ==== | ||
+ | === Coherence === | ||
+ | Note that for constant functors $\Delta_A,\Delta_B$, the square in the definition of a natural transformation commutes trivially. Hence any arrow $f:{\bf C}[A,B]$ gives rise to a natural transformation. | ||
+ | |||
=== Reference === | === Reference === | ||
Wikipedia: [[http://en.wikipedia.org/wiki/Diagonal_functor|Diagonal functor]] | Wikipedia: [[http://en.wikipedia.org/wiki/Diagonal_functor|Diagonal functor]] |