Diagonal subgroup

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In the mathematical discipline of group theory, for a given group G,Script error: No such module "Check for unknown parameters". the diagonal subgroup of the n-fold direct product G  nScript error: No such module "Check for unknown parameters". is the subgroup

{(g,,g)Gn:gG}.

This subgroup is isomorphic to G.Script error: No such module "Check for unknown parameters".

Properties and applications

  • If GScript error: No such module "Check for unknown parameters". acts on a set X,Script error: No such module "Check for unknown parameters". the n-fold diagonal subgroup has a natural action on the Cartesian product XnScript error: No such module "Check for unknown parameters". induced by the action of GScript error: No such module "Check for unknown parameters". on X,Script error: No such module "Check for unknown parameters". defined by
(x1,,xn)(g,,g)=(x1g,,xng).
  • If GScript error: No such module "Check for unknown parameters". acts nScript error: No such module "Check for unknown parameters".-transitively on X,Script error: No such module "Check for unknown parameters". then the nScript error: No such module "Check for unknown parameters".-fold diagonal subgroup acts transitively on Xn.Script error: No such module "Check for unknown parameters". More generally, for an integer k,Script error: No such module "Check for unknown parameters". if GScript error: No such module "Check for unknown parameters". acts knScript error: No such module "Check for unknown parameters".-transitively on X,Script error: No such module "Check for unknown parameters". GScript error: No such module "Check for unknown parameters". acts kScript error: No such module "Check for unknown parameters".-transitively on Xn.Script error: No such module "Check for unknown parameters".
  • Burnside's lemma can be proved using the action of the twofold diagonal subgroup.

See also

References

  • Script error: No such module "citation/CS1"..


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