Diagonal subgroup

In the mathematical discipline of group theory, for a given group Template:Math the diagonal subgroup of the n-fold direct product Template:Math is the subgroup

$\{(g,\dots ,g)\in G^n:g\in G\}.$

This subgroup is isomorphic to Template:Math

Properties and applications

• If Template:Math acts on a set Template:Math the n-fold diagonal subgroup has a natural action on the Cartesian product Template:Math induced by the action of Template:Math on Template:Math defined by

$(x_1,\dots ,x_n)\cdot (g,\dots ,g)=(x_1\cdot g,\dots ,x_n\cdot g).$

• If Template:Math acts Template:Math-transitively on Template:Math then the Template:Math-fold diagonal subgroup acts transitively on Template:Math More generally, for an integer Template:Math if Template:Math acts Template:Math-transitively on Template:Math Template:Math acts Template:Math-transitively on Template:Math
• Burnside's lemma can be proved using the action of the twofold diagonal subgroup.

See also

• Diagonalizable group

References

• .

Template:Group-theory-stub