Solvable group: Difference between revisions
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[[importance rank::2| ]] | |||
==Definition== | ==Definition== | ||
'''Solvable''' is also called '''soluble''' by some people. | |||
===Equivalent definitions in tabular format=== | |||
{| class="sortable" border="1" | |||
! No. !! Shorthand !! A group is termed solvable if ... !! A group <math>G</math> is termed solvable if ... | |||
|- | |||
| 1 || normal series, abelian quotients || there is a [[defining ingredient::normal series]] of finite length starting from the trivial subgroup and ending at the whole group with each successive [[quotient group]] being an [[defining ingredient::abelian group]]. || there exists a series of subgroups <math>\{ e \} = H_0 \le H_1 \le \ldots \le H_n = G</math> such that each <math>H_i</math> is [[normal subgroup|normal]] in <math>G</math> and each <math>H_{i+1}/H_i</math> is [[abelian group|abelian]]. | |||
|- | |||
| 2 || subnormal series, abelian quotients || there is a [[defining ingredient::subnormal series]] of finite length starting from the trivial subgroup and ending at the whole group with each successive [[quotient group]] being an [[abelian group]]. || there exists a series of subgroups:<math>\{ e \}= H_0 \underline{\triangleleft} H_1 \underline{\triangleleft} \dots \underline{\triangleleft} H_n = G</math> such that each <math>H_i</math> is normal in <math>H_{i+1}</math> and each <math>H_{i+1}/H_i</math> is [[abelian group|abelian]]. | |||
|- | |||
| 3 || derived series finite length || the [[defining ingredient::derived series]] reaches the identity in finitely many steps || the [[derived series]] of <math>G</math>, i.e., the series <math>G^{(n)}</math> where <math>G^{(0)} = G</math> and <math>G^{(i+1)} = [G^{(i)}, G^{(i)}]</math> is the [[defining ingredient::derived subgroup]] of its predecessor, reaches the trivial subgroup in finitely many steps. | |||
|- | |||
| 4 || characteristic series, abelian quotients || there is a [[defining ingredient::characteristic series]] of finite length starting from the trivial subgroup and ending at the whole group with each successive [[quotient group]] being an [[defining ingredient::abelian group]]. || there exists a series of subgroups <math>\{ e \} = H_0 \le H_1 \le \ldots \le H_n = G</math> such that each <math>H_i</math> is [[characteristic subgroup|characteristic]] in <math>G</math> and each <math>H_{i+1}/H_i</math> is [[abelian group|abelian]]. | |||
|- | |||
| 5 || fully invariant series, abelian quotients || there is a [[defining ingredient::fully invariant series]] of finite length starting from the trivial subgroup and ending at the whole group with each successive [[quotient group]] being an [[defining ingredient::abelian group]]. || there exists a series of subgroups <math>\{ e \} = H_0 \le H_1 \le \ldots \le H_n = G</math> such that each <math>H_i</math> is [[fully invariant subgroup|fully invariant]] in <math>G</math> and each <math>H_{i+1}/H_i</math> is [[abelian group|abelian]]. | |||
|} | |||
The length of the [[derived series]], and the smallest possible length of a series for any of the other equivalent definitions, is termed the [[derived length]] or solvable length of the group. | |||
{{tabular definition format}} | |||
===Equivalence of definitions=== | |||
{{further|[[Equivalence of definitions of solvable group]], [[equivalence of definitions of derived length]]}} | |||
==Examples== | |||
{{group property see examples}} | |||
===Extreme examples=== | |||
* The [[trivial group]] is solvable. | |||
* [[Symmetric group:S3]] is the smallest solvable non-abelian group. | |||
===Groups satisfying the property=== | |||
{{groups satisfying property by importance rank}} | |||
=== | ===Groups dissatisfying the property=== | ||
{{ | {{groups dissatisfying property sorted by importance rank}} | ||
{{semibasicdef}} | |||
{{pivotal group property}} | |||
{{finite-at|finite solvable group}} | |||
==Metaproperties== | |||
== | |||
{| class="sortable" border="1" | |||
! Metaproperty name !! Satisfied? !! Proof !! Statement with symbols | |||
|- | |||
| [[satisfies metaproperty::pseudovarietal group property]] || Yes || [[solvability is pseudovarietal]] || Solvability is closed under taking subgroups, quotients, and finite direct products (more below). | |||
|- | |||
| [[satisfies metaproperty::extension-closed group property]] || Yes || [[solvability is extension-closed]] || Suppose <math>H</math> is a [[normal subgroup]] of <math>G</math> such that both <math>H</math> and the [[quotient group]] <math>G/H</math> are [[solvable group]]s. Then <math>G</math> is a [[solvable group]]. | |||
|- | |||
| [[satisfies metaproperty::subgroup-closed group property]] || Yes || [[solvability is subgroup-closed]] || If <math>G</math> is solvable, and <math>H \le G</math> is a [[subgroup]], then <math>H</math> is solvable. | |||
|- | |||
| [[satisfies metaproperty::quotient-closed group property]] || Yes || [[solvability is quotient-closed]] || If <math>G</math> is solvable, and <math>H</math> is a [[normal subgroup]] of <math>G</math>, the [[quotient group]] <math>G/H</math> is solvable. | |||
|- | |||
| [[satisfies metaproperty::finite direct product-closed group property]] || Yes || [[solvability is finite direct product-closed]] || If <math>G_1, G_2, \dots, G_n</math> are solvable, the [[external direct product]] <math>G_1 \times G_2 \times \dots \times G_n</math> is also solvable. | |||
|- | |||
| [[satisfies metaproperty::finite normal join-closed group property]] || Yes || [[solvability is finite normal join-closed]] || If <math>G</math> is a group and <math>N_1,N_2,\dots,N_r</math> are all [[solvable normal subgroup]]s of <math>G</math>, the [[join of subgroups]] (in this case also the [[product of subgroups]]) <math>N_1N_2\dots N_r</math> is also solvable. | |||
|- | |||
| [[satisfies metaproperty::isoclinism-invariant group property]] || Yes || [[isoclinic groups have same derived length]] || If <math>G_1</math> and <math>G_2</math> are [[isoclinic groups]], then <math>G_1</math> is solvable if and only if <math>G_2</math> is. Moreover, if so, the derived length of <math>G_1</math> equals the derived length of <math>G_2</math>, unless one of the groups is trivial and the other is nontrivial abelian. | |||
|} | |||
==Relation with other properties== | ==Relation with other properties== | ||
| Line 70: | Line 72: | ||
===Stronger properties=== | ===Stronger properties=== | ||
{| class="sortable" border="1" | |||
! Property !! Meaning !! Proof of implication !! Proof of strictness (reverse implication failure) !! Intermediate notions !! Comparison | |||
|- | |||
| [[Weaker than::abelian group]] || [[derived subgroup]] is trivial || [[abelian implies solvable]] || [[solvable not implies abelian]] {{strictness examples|solvable group|abelian group}} || {{intermediate notions short|solvable group|abelian group}} || | |||
|- | |||
| [[Weaker than::cyclic group]] || || || {{strictness examples|solvable group|cyclic group}} || {{intermediate notions short|solvable group|cyclic group}} || | |||
|- | |||
| [[Weaker than::nilpotent group]] || [[lower central series]] reaches the identity || [[nilpotent implies solvable]] || [[solvable not implies nilpotent]] {{strictness examples|solvable group|nilpotent group}} || {{intermediate notions short|solvable group|nilpotent group}} || [[nilpotent versus solvable]] | |||
|- | |||
| [[Weaker than::metabelian group]] || [[abelian normal subgroup]] with abelian quotient; derived length two || || {{strictness examples|solvable group|metabelian group}} || {{intermediate notions short|metabelian group|solvable group}} || | |||
|- | |||
| [[Weaker than::supersolvable group]] || [[normal series]] with cyclic factor groups|| [[supersolvable implies solvable]] || [[solvable not implies supersolvable]] {{strictness examples|solvable group|supersolvable group}} || {{intermediate notions short|solvable group|supersolvable group}} || | |||
|- | |||
| [[Weaker than::polycyclic group]] || [[subnormal series]] with cyclic factor groups<br>equivalent to solvable in the [[finite solvable group|finite case]] || [[polycyclic implies solvable]] || [[solvable not implies polycyclic]] {{strictness examples|solvable group|polycyclic group}} || {{intermediate notions short|solvable group|polycyclic group}} || | |||
|- | |||
| [[Weaker than::metacyclic group]] || [[cyclic normal subgroup]] with cyclic quotient group || || {{strictness examples|solvable group|metacyclic group}} || {{intermediate notions|solvable group|metacyclic group}} || | |||
|} | |||
===Weaker properties=== | ===Weaker properties=== | ||
{| class="sortable" border="1" | |||
! Property !! Meaning !! Proof of implication !! Proof of strictness (reverse implication failure) !! Intermediate notions !! Comparison | |||
|- | |||
| [[Stronger than::hypoabelian group]] || transfinite derived series reaches identity;<br>equivalent to solvable in the [[finite solvable group|finite case]] || [[solvable implies hypoabelian]] || [[hypoabelian not implies solvable]] || {{intermediate notions short|hypoabelian group|solvable group}} || | |||
|- | |||
| [[Stronger than::imperfect group]] || no nontrivial perfect quotient group || [[solvable implies imperfect]] || [[imperfect not implies solvable]] || {{intermediate notions short|imperfect group|solvable group}} || | |||
|- | |||
| [[Stronger than::locally solvable group]] || every finitely generated subgroup is solvable<br>equivalent to solvable in the [[finite solvable group|finite case]] || || || || | |||
|- | |||
| [[Stronger than::residually solvable group]] || every non-identity element has a non-identity image in some solvable quotient<br>equivalent to solvable in the [[finite solvable group|finite case]] || || || || | |||
|} | |||
===Conjunction with other properties=== | ===Conjunction with other properties=== | ||
{| class="sortable" border="1" | |||
! Conjunction !! Other component of conjunction !! Additional comments | |||
|- | |||
| [[finite solvable group]] || [[finite group]] || For finite groups, being solvable is equivalent to being polycyclic, and has many other alternative characterizations. | |||
|- | |||
| [[solvable T-group]] || [[T-group]] || | |||
|- | |||
| [[solvable HN-group]] || [[HN-group]] || | |||
|} | |||
== | ==Formalisms== | ||
{{ | {{group extension operator}} | ||
The group property of being solvable can be obtained in either of these equivalent ways: | |||
* By applying the [[poly operator]] to the group property of being [[abelian group|abelian]] | |||
* By applying the [[finite normal series operator]] to the group property of being [[abelian group|abelian]] | |||
* By applying the [[finite characteristic series operator]] to the group property of being [[abelian group|abelian]] | |||
Note that all these three operators have the same effect in the case of abelian groups, though in general they may not have. | |||
==Testing== | ==Testing== | ||
| Line 125: | Line 135: | ||
The problem of testing whether a group is solvable or not reduces to the problem of computing its [[derived series]]. This can be done when the group is described by means of a generating set, if the [[normal closure]] algorithm can be implemented. | The problem of testing whether a group is solvable or not reduces to the problem of computing its [[derived series]]. This can be done when the group is described by means of a generating set, if the [[normal closure]] algorithm can be implemented. | ||
{{GAP command for gp| | {{GAP command for gp| | ||
test = IsSolvableGroup}} | |||
To determine whether a group is solvable or not, we cna use the following GAP command: | To determine whether a group is solvable or not, we cna use the following GAP command: | ||
<pre> | <pre>IsSolvableGroup(group);</pre> | ||
where <tt>group</tt> may be a definition of the group or a name for a group previously defined. | |||
==Study of this notion== | ==Study of this notion== | ||
| Line 140: | Line 152: | ||
Also closely related is 20F19: Generalizations of nilpotent and solvable groups. | Also closely related is 20F19: Generalizations of nilpotent and solvable groups. | ||
== | ==References== | ||
===Textbook references=== | |||
=== | |||
{| class="sortable" border="1" | |||
! Book !! Page number !! Chapter and section !! Contextual information !! View | |||
|- | |||
| {{booklink-defined-tabular|DummitFoote|105||formal definition}} || | |||
|- | |||
| {{booklink-defined-tabular|Herstein|116||formal definition, introduced between exercises}} || | |||
|- | |||
| {{booklink-defined-tabular|Lang|18||definition in paragraph}} || | |||
|- | |||
| {{booklink-defined-tabular|RobinsonGT|121||formal definition}} || | |||
|- | |||
| {{booklink-defined-tabular|AlperinBell|95||definition in paragraph}} || | |||
|- | |||
| {{booklink-defined-tabular|RobinsonAA|171||definition in paragraph}} || | |||
|- | |||
| {{booklink-defined-tabular|Fraleigh|194|Definition 3.4.16|formal definition}} || | |||
|- | |||
| {{booklink-defined-tabular|Hungerford|102|Definition 7.9|formal definition}} || | |||
|- | |||
| {{booklink-defined-tabular|Gallian|563||}} || | |||
|- | |||
| {{booklink-defined-tabular|Herstein|116||formal definition, introduced between exercises}} || | |||
|} | |||
Latest revision as of 07:16, 3 August 2024
Definition
Solvable is also called soluble by some people.
Equivalent definitions in tabular format
| No. | Shorthand | A group is termed solvable if ... | A group is termed solvable if ... |
|---|---|---|---|
| 1 | normal series, abelian quotients | there is a normal series of finite length starting from the trivial subgroup and ending at the whole group with each successive quotient group being an abelian group. | there exists a series of subgroups such that each is normal in and each is abelian. |
| 2 | subnormal series, abelian quotients | there is a subnormal series of finite length starting from the trivial subgroup and ending at the whole group with each successive quotient group being an abelian group. | there exists a series of subgroups: such that each is normal in and each is abelian. |
| 3 | derived series finite length | the derived series reaches the identity in finitely many steps | the derived series of , i.e., the series where and is the derived subgroup of its predecessor, reaches the trivial subgroup in finitely many steps. |
| 4 | characteristic series, abelian quotients | there is a characteristic series of finite length starting from the trivial subgroup and ending at the whole group with each successive quotient group being an abelian group. | there exists a series of subgroups such that each is characteristic in and each is abelian. |
| 5 | fully invariant series, abelian quotients | there is a fully invariant series of finite length starting from the trivial subgroup and ending at the whole group with each successive quotient group being an abelian group. | there exists a series of subgroups such that each is fully invariant in and each is abelian. |
The length of the derived series, and the smallest possible length of a series for any of the other equivalent definitions, is termed the derived length or solvable length of the group.
This definition is presented using a tabular format. |View all pages with definitions in tabular format
Equivalence of definitions
Further information: Equivalence of definitions of solvable group, equivalence of definitions of derived length
Examples
VIEW: groups satisfying this property | groups dissatisfying this property
VIEW: Related group property satisfactions | Related group property dissatisfactions
Extreme examples
- The trivial group is solvable.
- Symmetric group:S3 is the smallest solvable non-abelian group.
Groups satisfying the property
Here are some basic/important groups satisfying the property:
| GAP ID | |
|---|---|
| Cyclic group:Z2 | 2 (1) |
| Cyclic group:Z3 | 3 (1) |
| Symmetric group:S3 | 6 (1) |
Here are some relatively less basic/important groups satisfying the property:
| GAP ID | |
|---|---|
| Alternating group:A4 | 12 (3) |
| Dihedral group:D8 | 8 (3) |
| Quaternion group | 8 (4) |
Here are some even more complicated/less basic groups satisfying the property:
Groups dissatisfying the property
Here are some basic/important groups that do not satisfy the property:
Here are some relatively less basic/important groups that do not satisfy the property:
| GAP ID | |
|---|---|
| Alternating group:A6 | 360 (118) |
| Projective special linear group:PSL(3,2) | 168 (42) |
Here are some even more complicated/less basic groups that do not satisfy the property:
This article is about a standard (though not very rudimentary) definition in group theory. The article text may, however, contain more than just the basic definition
VIEW: Definitions built on this | Facts about this: (facts closely related to Solvable group, all facts related to Solvable group) |Survey articles about this | Survey articles about definitions built on this
VIEW RELATED: Analogues of this | Variations of this | Opposites of this |
View a complete list of semi-basic definitions on this wiki
This article defines a group property that is pivotal (i.e., important) among existing group properties
View a list of pivotal group properties | View a complete list of group properties [SHOW MORE]
The version of this for finite groups is at: finite solvable group
Metaproperties
Relation with other properties
Stronger properties
Weaker properties
| Property | Meaning | Proof of implication | Proof of strictness (reverse implication failure) | Intermediate notions | Comparison |
|---|---|---|---|---|---|
| hypoabelian group | transfinite derived series reaches identity; equivalent to solvable in the finite case |
solvable implies hypoabelian | hypoabelian not implies solvable | |FULL LIST, MORE INFO | |
| imperfect group | no nontrivial perfect quotient group | solvable implies imperfect | imperfect not implies solvable | |FULL LIST, MORE INFO | |
| locally solvable group | every finitely generated subgroup is solvable equivalent to solvable in the finite case |
||||
| residually solvable group | every non-identity element has a non-identity image in some solvable quotient equivalent to solvable in the finite case |
Conjunction with other properties
| Conjunction | Other component of conjunction | Additional comments |
|---|---|---|
| finite solvable group | finite group | For finite groups, being solvable is equivalent to being polycyclic, and has many other alternative characterizations. |
| solvable T-group | T-group | |
| solvable HN-group | HN-group |
Formalisms
In terms of the group extension operator
This group property can be expressed in terms of the group extension operator and/or group property modifiers that arise from this operator The group property of being solvable can be obtained in either of these equivalent ways:
- By applying the poly operator to the group property of being abelian
- By applying the finite normal series operator to the group property of being abelian
- By applying the finite characteristic series operator to the group property of being abelian
Note that all these three operators have the same effect in the case of abelian groups, though in general they may not have.
Testing
The testing problem
Further information: Solvability testing problem
The problem of testing whether a group is solvable or not reduces to the problem of computing its derived series. This can be done when the group is described by means of a generating set, if the normal closure algorithm can be implemented.
GAP command
This group property can be tested using built-in functionality of Groups, Algorithms, Programming (GAP).
The GAP command for this group property is:IsSolvableGroup
View GAP-testable group properties
To determine whether a group is solvable or not, we cna use the following GAP command:
IsSolvableGroup(group);
where group may be a definition of the group or a name for a group previously defined.
Study of this notion
Mathematical subject classification
Under the Mathematical subject classification, the study of this notion comes under the class: 20F16
The class 20F16 is used for the general theory of solvable groups, while the class 20D10 (coming under 20D which is for finite groups) focusses on finite solvable groups.
Also closely related is 20F19: Generalizations of nilpotent and solvable groups.
References
Textbook references
| Book | Page number | Chapter and section | Contextual information | View |
|---|---|---|---|---|
| Abstract Algebra by David S. Dummit and Richard M. Foote, 10-digit ISBN 0471433349, 13-digit ISBN 978-0471433347More info | 105 | formal definition | ||
| Topics in Algebra by I. N. HersteinMore info | 116 | formal definition, introduced between exercises | ||
| Algebra by Serge Lang, ISBN 038795385XMore info | 18 | definition in paragraph | ||
| A Course in the Theory of Groups by Derek J. S. Robinson, ISBN 0387944613More info | 121 | formal definition | ||
| Groups and representations by Jonathan Lazare Alperin and Rowen B. Bell, ISBN 0387945261More info | 95 | definition in paragraph | ||
| An Introduction to Abstract Algebra by Derek J. S. Robinson, ISBN 3110175444More info | 171 | definition in paragraph | ||
| A First Course in Abstract Algebra (6th Edition) by John B. Fraleigh, ISBN 0201763907More info | 194 | Definition 3.4.16 | formal definition | |
| Algebra (Graduate Texts in Mathematics) by Thomas W. Hungerford, ISBN 0387905189More info | 102 | Definition 7.9 | formal definition | |
| Contemporary Abstract Algeba by Joseph Gallian, ISBN 0618514716More info | 563 | |||
| Topics in Algebra by I. N. HersteinMore info | 116 | formal definition, introduced between exercises |