===== Automorphism group =====
==== Set ====
| @#55CCEE: context     | @#55CCEE: $\bf C$ ... concrete category |
| @#55CCEE: context     | @#55CCEE: $X:\mathrm{Ob}_{\bf C}$ |
| @#FFBB00: definiendum | @#FFBB00: $\mathrm{Aut}(X)\equiv\langle\!\langle X\cong X,\circ\rangle\!\rangle$ |

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=== Elaboration ===
Obviously, $\circ$ denotes the concatentaion of arrows in $\bf C$ here.

=== Theorems ===
The automorphisms (which for concrete $\bf C$ can always be viewed as functions) equipped with $\circ$ indeed form a group. 

=== Reference ===
Wikipedia: [[http://en.wikipedia.org/wiki/Automorphism|Automorphism]]

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=== Context ===
[[Concrete category]]
=== Subset of ===
[[Group]]
=== Requirements ===
[[Automorphism]]