GroupMultiplicationTable
GroupMultiplicationTable[group]
gives the multiplication table of group as an array.
Details
- For a group of order n, GroupMultiplicationTable returns an n×n matrix mat of integers such that element matij gives the result of the multiplication of elements i and j in the group. Positions i, j, and matij are computed with the function GroupElementPosition.
Examples
open allclose allBasic Examples (1)
These are the multiplications of all pairs of elements, numbered as returned by GroupElementPosition:
Generate all eight permutations of the group:
The product of permutations 5 and 2 is permutation 7 in the list:
Applications (1)
In permutation-group algebra the basic elements are linear combinations of the permutations of a group. It is possible to avoid recomputation of products of permutations by using a multiplication table. Denoting elements of the group algebra as lists of coefficients, it is possible to multiply them:
Properties & Relations (7)
Every row and every column of the multiplication table of a group contains every permutation once, but in different order. Hence, the table is a Latin square (note that not every Latin square corresponds to a group, because associativity is not guaranteed):
Multiplication table of the trivial group:
The Cayley theorem states that every finite group is isomorphic to a subgroup of some symmetric group of permutations. Hence every multiplication table is a subtable of the table of a symmetric group, perhaps after renumbering of permutations.
This is the multiplication table of a subgroup of :
Therefore it can be extracted as a subtable of the table of :
A group is Abelian if and only if its multiplication table is symmetric under transposition. Take the symmetric group of degree 3:
When all elements of a group are involutions, the group is Abelian. That is, if the multiplication table has only 1s in the diagonal, then it is symmetric:
The multiplication table can be obtained by direct use of PermutationProduct and GroupElementPosition:
Two groups are isomorphic as abstract groups if they have the same group multiplication table, modulo reordering of their elements:
However, those two groups are not isomorphic as permutation groups, because their permutations have different cyclic structures:
Possible Issues (1)
Text
Wolfram Research (2010), GroupMultiplicationTable, Wolfram Language function, https://reference.wolfram.com/language/ref/GroupMultiplicationTable.html.
CMS
Wolfram Language. 2010. "GroupMultiplicationTable." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/GroupMultiplicationTable.html.
APA
Wolfram Language. (2010). GroupMultiplicationTable. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/GroupMultiplicationTable.html