Class-determining field: Difference between revisions
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{{termrelatedto|linear representation theory}} | {{termrelatedto|linear representation theory}} | ||
{{group-parametrized field property}} | |||
==Definition== | ==Definition== | ||
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===Symbol-free definition=== | ===Symbol-free definition=== | ||
A [[field]] is said to be a '''class-determining field''' for a [[group]] if any representation is determined by the conjugacy classes in which the images of the conjugacy classes of the group lie under that representation. | A [[field]] is said to be a '''class-determining field''' for a [[group]] if any [[finite-dimensional linear representation]] is determined by the conjugacy classes in which the images of the conjugacy classes of the group lie under that representation. | ||
In other words, for any two distinct (i.e. inequivalent) linear representations, there exists a conjugacy class whose image under the two representations does not lie in the same conjugacy class in the [[general linear group]]. | In other words, for any two distinct (i.e. [[fact about::equivalent linear representations|inequivalent]]) linear representations, there exists a conjugacy class whose image under the two representations does not lie in the same conjugacy class in the [[general linear group]]. | ||
Equivalently, no two inequivalent linear representations are [[locally conjugate representation|locally conjugate]]. | Equivalently, no two inequivalent linear representations are [[locally conjugate representation|locally conjugate]]. | ||
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===Definition with symbols=== | ===Definition with symbols=== | ||
A [[field]] <math>k</math> is termed a '''class-determining field''' for a [[group]] <math>G</math> if for any two finite-dimensional linear | A [[field]] <math>k</math> is termed a '''class-determining field''' for a [[group]] <math>G</math> if for any two [[fact about::equivalent linear representations|inequivalent]] [[finite-dimensional linear representation]]s <math>\rho_1,\rho_2:G \to GL(V)</math>, there exists <math>g \in G</math> such that <math>\rho_1(g)</math> and <math>\rho_2(g)</math> are not conjugate. | ||
==Facts== | ==Facts== | ||
For a finite group, any field of | * [[Non-modular implies class-determining]]: For a [[finite group]], any field whose characteristic does not divide the order of the group is a class-determining field. | ||
* [[Cyclic implies every field is class-determining]] | |||
* [[Elementary abelian of prime-square order implies corresponding prime field is not class-determining]] | |||
Latest revision as of 13:56, 21 July 2011
This term is related to: linear representation theory
View other terms related to linear representation theory | View facts related to linear representation theory
This term associates to every group, a corresponding field property. In other words, given a field, every field either has the property with respect to that group or does not have the property with respect to that group
Definition
Symbol-free definition
A field is said to be a class-determining field for a group if any finite-dimensional linear representation is determined by the conjugacy classes in which the images of the conjugacy classes of the group lie under that representation.
In other words, for any two distinct (i.e. inequivalent) linear representations, there exists a conjugacy class whose image under the two representations does not lie in the same conjugacy class in the general linear group.
Equivalently, no two inequivalent linear representations are locally conjugate.
Definition with symbols
A field is termed a class-determining field for a group if for any two inequivalent finite-dimensional linear representations , there exists such that and are not conjugate.
Facts
- Non-modular implies class-determining: For a finite group, any field whose characteristic does not divide the order of the group is a class-determining field.
- Cyclic implies every field is class-determining
- Elementary abelian of prime-square order implies corresponding prime field is not class-determining