finite Finite is the opposite of infinite. It may refer to: * Finite number (disambiguation) * Finite set, a set whose cardinality (number of elements) is some natural number * Finite verb, a verb form that has a subject, usually being inflected or marked ...

group theory In abstract algebra, group theory studies the algebraic structures known as group (mathematics), groups. The concept of a group is central to abstract algebra: other well-known algebraic structures, such as ring (mathematics), rings, field ...

, a branch of

mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

, a group is said to be of characteristic 2 type or even type or of even characteristic if it resembles a group of Lie type over a

field Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grass ...

characteristic 2 In mathematics, the characteristic of a ring , often denoted , is defined to be the smallest number of times one must use the ring's multiplicative identity (1) in a sum to get the additive identity (0). If this sum never reaches the additive id ...

. In the

classification of finite simple groups In mathematics, the classification of the finite simple groups is a result of group theory stating that every finite simple group is either cyclic, or alternating, or it belongs to a broad infinite class called the groups of Lie type, or else it ...

, there is a major division between group of characteristic 2 type, where involutions resemble unipotent elements, and other groups, where involutions resemble semisimple elements. Groups of characteristic 2 type and rank at least 3 are classified by the

trichotomy theorem In group theory, the trichotomy theorem divides the finite simple groups of characteristic 2 type and rank at least 3 into three classes. It was proved by for rank 3 and by for rank at least 4. The three classes are groups of GF(2) ...

Definitions

A group is said to be of even characteristic if :

C_M(O_2(M)) \le O_2(M)

for all maximal 2-local subgroups ''M'' that contain a Sylow 2-subgroup of ''G''. If this condition holds for all maximal 2-local subgroups ''M'' then ''G'' is said to be of characteristic 2 type. use a modified version of this called even type.

References

* *{{Citation , last1=Gorenstein , first1=D. , author1-link=Daniel Gorenstein , last2=Lyons , first2=Richard , last3=Solomon , first3=Ronald , title=The classification of the finite simple groups , url=https://www.ams.org/online_bks/surv401 , publisher=

American Mathematical Society The American Mathematical Society (AMS) is an association of professional mathematicians dedicated to the interests of mathematical research and scholarship, and serves the national and international community through its publications, meetings, ...

, location=Providence, R.I. , series=Mathematical Surveys and Monographs , isbn=978-0-8218-0334-9 , mr=1303592 , year=1994 , volume=40 Finite groups