Double module

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A synonym for bimodule.

A pair of subgroups of a group which are members of the decomposition of into double cosets, i.e. in the decomposition of into non-intersecting subsets of the type , where is an element of . A subset is said to be a coset of the group modulo or a double coset of the group modulo . Thus, the decomposition of a group of order 24 into double cosets modulo , where and are its Sylow - and -subgroups, consists of a single coset modulo . Any double coset consists of cosets of by and, at the same time, of cosets of by , where denotes the index of a subgroup in a group .


[1] P. Hall, "The theory of groups" , Macmillan (1959)


The phrase "double module" in the setting of 2) is obsolete. One uses instead the phrase "double cosetdouble coset" . The double cosets of modulo coincide with the orbits of the direct product in , acting by , , , . (See also Orbit). The set of these double cosets is denoted by .

How to Cite This Entry:
Double module. V.D. Mazurov (originator), Encyclopedia of Mathematics. URL:
This text originally appeared in Encyclopedia of Mathematics - ISBN 1402006098