- Fischer group
In

mathematics , the term**Fischer groups**usually refers to the three finite groups denoted "Fi"_{22}, "Fi"_{23}, and "Fi"_{24}, all of which aresimple group s. They constitute three of the 26sporadic group s. Sometimes the term encompasses theirautomorphism group s.**3-transposition groups**The Fischer groups are named after

Bernd Fischer who discovered them while investigating 3-transposition groups. These are groups "G" with the following properties:

* "G" is generated by aconjugacy class of elements of order 2, called 'Fischer transpositions'

* The product of any two transpositions has order 1, 2 or 3.The typical example of a 3-transposition group is asymmetric group ,where the Fischer transpositions are genuinely transpositions. Fischer was able to classify 3-transposition groups which satisfy certain extra technical conditions. The groups he found fell into several infinite classes (as well as the symmetric groups, certain classes of symplectic and orthogonal groups fulfilled his conditions) with the exception of the three Fischer groups. These groups are usually referred to as "Fi"_{22}, "Fi"_{23}and "Fi"_{24}. The first two of these are simple groups, and the third contains the simple group "Fi"_{24}' of index 2.**Orders**The "order" of a group is the number of elements in the group.

"Fi"

_{22}has order 2^{17}.3^{9}.5^{2}.7.11.13 = 64561751654400."Fi"

_{23}has order 2^{18}.3^{13}.5^{2}.7.11.13.17.23 = 4089470473293004800."Fi"

_{24}' has order 2^{21}.3^{16}.5^{2}.7^{3}.11.13.17.23.29 = 1255205709190661721292800. It is the 3rd largest of the sporadic groups(after theMonster group andBaby Monster group ).**Notation**There is no uniformly accepted notation for these groups. Some authors use "F" in place of "Fi" ("F"

_{22}, for example).Fischer's notation for the them was "M"(22), "M"(23) and "M"(24)', which emphasised their close relationship with the three largestMathieu group s, "M"_{22}, "M"_{23}and"M"_{24}.One particular source of confusion is that "Fi"

_{24}is sometimes used to refer to the simple group "Fi"_{24}', and is sometimes used to refer to the full 3-transposition group (which is twice the size).**References***Wilson, R. A. "ATLAS of Finite Group Representation."

http://for.mat.bham.ac.uk/atlas/html/contents.html#spo

*(For the factorisations of the orders) Weisstein, Eric W. "Sporadic Group"

http://mathworld.wolfram.com/SporadicGroup.html*"3-Transposition Groups" (Cambridge Tracts in Mathematics) by

Michael Aschbacher . "3-Transposition Groups" contains the first published proof of Fischer's Theorem, written out completely in one place. Publisher: Cambridge University Press (November 28, 1996) ISBN 0-521-57196-0

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