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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | brgic 18401 | The relation "is isomorphic to" for groups. (Contributed by Stefan O'Rear, 25-Jan-2015.) |
⊢ (𝑅 ≃𝑔 𝑆 ↔ (𝑅 GrpIso 𝑆) ≠ ∅) | ||
Theorem | brgici 18402 | Prove isomorphic by an explicit isomorphism. (Contributed by Stefan O'Rear, 25-Jan-2015.) |
⊢ (𝐹 ∈ (𝑅 GrpIso 𝑆) → 𝑅 ≃𝑔 𝑆) | ||
Theorem | gicref 18403 | Isomorphism is reflexive. (Contributed by Mario Carneiro, 21-Apr-2016.) |
⊢ (𝑅 ∈ Grp → 𝑅 ≃𝑔 𝑅) | ||
Theorem | giclcl 18404 | Isomorphism implies the left side is a group. (Contributed by Stefan O'Rear, 25-Jan-2015.) |
⊢ (𝑅 ≃𝑔 𝑆 → 𝑅 ∈ Grp) | ||
Theorem | gicrcl 18405 | Isomorphism implies the right side is a group. (Contributed by Mario Carneiro, 6-May-2015.) |
⊢ (𝑅 ≃𝑔 𝑆 → 𝑆 ∈ Grp) | ||
Theorem | gicsym 18406 | Isomorphism is symmetric. (Contributed by Mario Carneiro, 21-Apr-2016.) |
⊢ (𝑅 ≃𝑔 𝑆 → 𝑆 ≃𝑔 𝑅) | ||
Theorem | gictr 18407 | Isomorphism is transitive. (Contributed by Mario Carneiro, 21-Apr-2016.) |
⊢ ((𝑅 ≃𝑔 𝑆 ∧ 𝑆 ≃𝑔 𝑇) → 𝑅 ≃𝑔 𝑇) | ||
Theorem | gicer 18408 | Isomorphism is an equivalence relation on groups. (Contributed by Mario Carneiro, 21-Apr-2016.) (Proof shortened by AV, 1-May-2021.) |
⊢ ≃𝑔 Er Grp | ||
Theorem | gicen 18409 | Isomorphic groups have equinumerous base sets. (Contributed by Stefan O'Rear, 25-Jan-2015.) |
⊢ 𝐵 = (Base‘𝑅) & ⊢ 𝐶 = (Base‘𝑆) ⇒ ⊢ (𝑅 ≃𝑔 𝑆 → 𝐵 ≈ 𝐶) | ||
Theorem | gicsubgen 18410 | A less trivial example of a group invariant: cardinality of the subgroup lattice. (Contributed by Stefan O'Rear, 25-Jan-2015.) |
⊢ (𝑅 ≃𝑔 𝑆 → (SubGrp‘𝑅) ≈ (SubGrp‘𝑆)) | ||
Syntax | cga 18411 | Extend class definition to include the class of group actions. |
class GrpAct | ||
Definition | df-ga 18412* | Define the class of all group actions. A group 𝐺 acts on a set 𝑆 if a permutation on 𝑆 is associated with every element of 𝐺 in such a way that the identity permutation on 𝑆 is associated with the neutral element of 𝐺, and the composition of the permutations associated with two elements of 𝐺 is identical with the permutation associated with the composition of these two elements (in the same order) in the group 𝐺. (Contributed by Jeff Hankins, 10-Aug-2009.) |
⊢ GrpAct = (𝑔 ∈ Grp, 𝑠 ∈ V ↦ ⦋(Base‘𝑔) / 𝑏⦌{𝑚 ∈ (𝑠 ↑m (𝑏 × 𝑠)) ∣ ∀𝑥 ∈ 𝑠 (((0g‘𝑔)𝑚𝑥) = 𝑥 ∧ ∀𝑦 ∈ 𝑏 ∀𝑧 ∈ 𝑏 ((𝑦(+g‘𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))}) | ||
Theorem | isga 18413* | The predicate "is a (left) group action." The group 𝐺 is said to act on the base set 𝑌 of the action, which is not assumed to have any special properties. There is a related notion of right group action, but as the Wikipedia article explains, it is not mathematically interesting. The way actions are usually thought of is that each element 𝑔 of 𝐺 is a permutation of the elements of 𝑌 (see gapm 18428). Since group theory was classically about symmetry groups, it is therefore likely that the notion of group action was useful even in early group theory. (Contributed by Jeff Hankins, 10-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ( ⊕ ∈ (𝐺 GrpAct 𝑌) ↔ ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) ∧ ( ⊕ :(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑥 ∈ 𝑌 (( 0 ⊕ 𝑥) = 𝑥 ∧ ∀𝑦 ∈ 𝑋 ∀𝑧 ∈ 𝑋 ((𝑦 + 𝑧) ⊕ 𝑥) = (𝑦 ⊕ (𝑧 ⊕ 𝑥)))))) | ||
Theorem | gagrp 18414 | The left argument of a group action is a group. (Contributed by Jeff Hankins, 11-Aug-2009.) (Revised by Mario Carneiro, 30-Apr-2015.) |
⊢ ( ⊕ ∈ (𝐺 GrpAct 𝑌) → 𝐺 ∈ Grp) | ||
Theorem | gaset 18415 | The right argument of a group action is a set. (Contributed by Mario Carneiro, 30-Apr-2015.) |
⊢ ( ⊕ ∈ (𝐺 GrpAct 𝑌) → 𝑌 ∈ V) | ||
Theorem | gagrpid 18416 | The identity of the group does not alter the base set. (Contributed by Jeff Hankins, 11-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 0 = (0g‘𝐺) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) → ( 0 ⊕ 𝐴) = 𝐴) | ||
Theorem | gaf 18417 | The mapping of the group action operation. (Contributed by Jeff Hankins, 11-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) ⇒ ⊢ ( ⊕ ∈ (𝐺 GrpAct 𝑌) → ⊕ :(𝑋 × 𝑌)⟶𝑌) | ||
Theorem | gafo 18418 | A group action is onto its base set. (Contributed by Jeff Hankins, 10-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) ⇒ ⊢ ( ⊕ ∈ (𝐺 GrpAct 𝑌) → ⊕ :(𝑋 × 𝑌)–onto→𝑌) | ||
Theorem | gaass 18419 | An "associative" property for group actions. (Contributed by Jeff Hankins, 11-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ (𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋 ∧ 𝐶 ∈ 𝑌)) → ((𝐴 + 𝐵) ⊕ 𝐶) = (𝐴 ⊕ (𝐵 ⊕ 𝐶))) | ||
Theorem | ga0 18420 | The action of a group on the empty set. (Contributed by Jeff Hankins, 11-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ (𝐺 ∈ Grp → ∅ ∈ (𝐺 GrpAct ∅)) | ||
Theorem | gaid 18421 | The trivial action of a group on any set. Each group element corresponds to the identity permutation. (Contributed by Jeff Hankins, 11-Aug-2009.) (Proof shortened by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑆 ∈ 𝑉) → (2nd ↾ (𝑋 × 𝑆)) ∈ (𝐺 GrpAct 𝑆)) | ||
Theorem | subgga 18422* | A subgroup acts on its parent group. (Contributed by Jeff Hankins, 13-Aug-2009.) (Proof shortened by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 𝐻 = (𝐺 ↾s 𝑌) & ⊢ 𝐹 = (𝑥 ∈ 𝑌, 𝑦 ∈ 𝑋 ↦ (𝑥 + 𝑦)) ⇒ ⊢ (𝑌 ∈ (SubGrp‘𝐺) → 𝐹 ∈ (𝐻 GrpAct 𝑋)) | ||
Theorem | gass 18423* | A subset of a group action is a group action iff it is closed under the group action operation. (Contributed by Mario Carneiro, 17-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝑍 ⊆ 𝑌) → (( ⊕ ↾ (𝑋 × 𝑍)) ∈ (𝐺 GrpAct 𝑍) ↔ ∀𝑥 ∈ 𝑋 ∀𝑦 ∈ 𝑍 (𝑥 ⊕ 𝑦) ∈ 𝑍)) | ||
Theorem | gasubg 18424 | The restriction of a group action to a subgroup is a group action. (Contributed by Mario Carneiro, 17-Jan-2015.) |
⊢ 𝐻 = (𝐺 ↾s 𝑆) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝑆 ∈ (SubGrp‘𝐺)) → ( ⊕ ↾ (𝑆 × 𝑌)) ∈ (𝐻 GrpAct 𝑌)) | ||
Theorem | gaid2 18425* | A group operation is a left group action of the group on itself. (Contributed by FL, 17-May-2010.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 𝐹 = (𝑥 ∈ 𝑋, 𝑦 ∈ 𝑋 ↦ (𝑥 + 𝑦)) ⇒ ⊢ (𝐺 ∈ Grp → 𝐹 ∈ (𝐺 GrpAct 𝑋)) | ||
Theorem | galcan 18426 | The action of a particular group element is left-cancelable. (Contributed by FL, 17-May-2010.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ (𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑌 ∧ 𝐶 ∈ 𝑌)) → ((𝐴 ⊕ 𝐵) = (𝐴 ⊕ 𝐶) ↔ 𝐵 = 𝐶)) | ||
Theorem | gacan 18427 | Group inverses cancel in a group action. (Contributed by Jeff Hankins, 11-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ (𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑌 ∧ 𝐶 ∈ 𝑌)) → ((𝐴 ⊕ 𝐵) = 𝐶 ↔ ((𝑁‘𝐴) ⊕ 𝐶) = 𝐵)) | ||
Theorem | gapm 18428* | The action of a particular group element is a permutation of the base set. (Contributed by Jeff Hankins, 11-Aug-2009.) (Proof shortened by Mario Carneiro, 13-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐹 = (𝑥 ∈ 𝑌 ↦ (𝐴 ⊕ 𝑥)) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑋) → 𝐹:𝑌–1-1-onto→𝑌) | ||
Theorem | gaorb 18429* | The orbit equivalence relation puts two points in the group action in the same equivalence class iff there is a group element that takes one element to the other. (Contributed by Mario Carneiro, 14-Jan-2015.) |
⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ({𝑥, 𝑦} ⊆ 𝑌 ∧ ∃𝑔 ∈ 𝑋 (𝑔 ⊕ 𝑥) = 𝑦)} ⇒ ⊢ (𝐴 ∼ 𝐵 ↔ (𝐴 ∈ 𝑌 ∧ 𝐵 ∈ 𝑌 ∧ ∃ℎ ∈ 𝑋 (ℎ ⊕ 𝐴) = 𝐵)) | ||
Theorem | gaorber 18430* | The orbit equivalence relation is an equivalence relation on the target set of the group action. (Contributed by NM, 11-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.) |
⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ({𝑥, 𝑦} ⊆ 𝑌 ∧ ∃𝑔 ∈ 𝑋 (𝑔 ⊕ 𝑥) = 𝑦)} & ⊢ 𝑋 = (Base‘𝐺) ⇒ ⊢ ( ⊕ ∈ (𝐺 GrpAct 𝑌) → ∼ Er 𝑌) | ||
Theorem | gastacl 18431* | The stabilizer subgroup in a group action. (Contributed by Mario Carneiro, 15-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐻 = {𝑢 ∈ 𝑋 ∣ (𝑢 ⊕ 𝐴) = 𝐴} ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) → 𝐻 ∈ (SubGrp‘𝐺)) | ||
Theorem | gastacos 18432* | Write the coset relation for the stabilizer subgroup. (Contributed by Mario Carneiro, 15-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐻 = {𝑢 ∈ 𝑋 ∣ (𝑢 ⊕ 𝐴) = 𝐴} & ⊢ ∼ = (𝐺 ~QG 𝐻) ⇒ ⊢ ((( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) ∧ (𝐵 ∈ 𝑋 ∧ 𝐶 ∈ 𝑋)) → (𝐵 ∼ 𝐶 ↔ (𝐵 ⊕ 𝐴) = (𝐶 ⊕ 𝐴))) | ||
Theorem | orbstafun 18433* | Existence and uniqueness for the function of orbsta 18435. (Contributed by Mario Carneiro, 15-Jan-2015.) (Proof shortened by Mario Carneiro, 23-Dec-2016.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐻 = {𝑢 ∈ 𝑋 ∣ (𝑢 ⊕ 𝐴) = 𝐴} & ⊢ ∼ = (𝐺 ~QG 𝐻) & ⊢ 𝐹 = ran (𝑘 ∈ 𝑋 ↦ 〈[𝑘] ∼ , (𝑘 ⊕ 𝐴)〉) ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) → Fun 𝐹) | ||
Theorem | orbstaval 18434* | Value of the function at a given equivalence class element. (Contributed by Mario Carneiro, 15-Jan-2015.) (Proof shortened by Mario Carneiro, 23-Dec-2016.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐻 = {𝑢 ∈ 𝑋 ∣ (𝑢 ⊕ 𝐴) = 𝐴} & ⊢ ∼ = (𝐺 ~QG 𝐻) & ⊢ 𝐹 = ran (𝑘 ∈ 𝑋 ↦ 〈[𝑘] ∼ , (𝑘 ⊕ 𝐴)〉) ⇒ ⊢ ((( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) ∧ 𝐵 ∈ 𝑋) → (𝐹‘[𝐵] ∼ ) = (𝐵 ⊕ 𝐴)) | ||
Theorem | orbsta 18435* | The Orbit-Stabilizer theorem. The mapping 𝐹 is a bijection from the cosets of the stabilizer subgroup of 𝐴 to the orbit of 𝐴. (Contributed by Mario Carneiro, 15-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐻 = {𝑢 ∈ 𝑋 ∣ (𝑢 ⊕ 𝐴) = 𝐴} & ⊢ ∼ = (𝐺 ~QG 𝐻) & ⊢ 𝐹 = ran (𝑘 ∈ 𝑋 ↦ 〈[𝑘] ∼ , (𝑘 ⊕ 𝐴)〉) & ⊢ 𝑂 = {〈𝑥, 𝑦〉 ∣ ({𝑥, 𝑦} ⊆ 𝑌 ∧ ∃𝑔 ∈ 𝑋 (𝑔 ⊕ 𝑥) = 𝑦)} ⇒ ⊢ (( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) → 𝐹:(𝑋 / ∼ )–1-1-onto→[𝐴]𝑂) | ||
Theorem | orbsta2 18436* | Relation between the size of the orbit and the size of the stabilizer of a point in a finite group action. (Contributed by Mario Carneiro, 16-Jan-2015.) |
⊢ 𝑋 = (Base‘𝐺) & ⊢ 𝐻 = {𝑢 ∈ 𝑋 ∣ (𝑢 ⊕ 𝐴) = 𝐴} & ⊢ ∼ = (𝐺 ~QG 𝐻) & ⊢ 𝑂 = {〈𝑥, 𝑦〉 ∣ ({𝑥, 𝑦} ⊆ 𝑌 ∧ ∃𝑔 ∈ 𝑋 (𝑔 ⊕ 𝑥) = 𝑦)} ⇒ ⊢ ((( ⊕ ∈ (𝐺 GrpAct 𝑌) ∧ 𝐴 ∈ 𝑌) ∧ 𝑋 ∈ Fin) → (♯‘𝑋) = ((♯‘[𝐴]𝑂) · (♯‘𝐻))) | ||
Syntax | ccntz 18437 | Syntax for the centralizer of a set in a monoid. |
class Cntz | ||
Syntax | ccntr 18438 | Syntax for the centralizer of a monoid. |
class Cntr | ||
Definition | df-cntz 18439* | Define the centralizer of a subset of a magma, which is the set of elements each of which commutes with each element of the given subset. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ Cntz = (𝑚 ∈ V ↦ (𝑠 ∈ 𝒫 (Base‘𝑚) ↦ {𝑥 ∈ (Base‘𝑚) ∣ ∀𝑦 ∈ 𝑠 (𝑥(+g‘𝑚)𝑦) = (𝑦(+g‘𝑚)𝑥)})) | ||
Definition | df-cntr 18440 | Define the center of a magma, which is the elements that commute with all others. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ Cntr = (𝑚 ∈ V ↦ ((Cntz‘𝑚)‘(Base‘𝑚))) | ||
Theorem | cntrval 18441 | Substitute definition of the center. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑍‘𝐵) = (Cntr‘𝑀) | ||
Theorem | cntzfval 18442* | First level substitution for a centralizer. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑀 ∈ 𝑉 → 𝑍 = (𝑠 ∈ 𝒫 𝐵 ↦ {𝑥 ∈ 𝐵 ∣ ∀𝑦 ∈ 𝑠 (𝑥 + 𝑦) = (𝑦 + 𝑥)})) | ||
Theorem | cntzval 18443* | Definition substitution for a centralizer. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑆 ⊆ 𝐵 → (𝑍‘𝑆) = {𝑥 ∈ 𝐵 ∣ ∀𝑦 ∈ 𝑆 (𝑥 + 𝑦) = (𝑦 + 𝑥)}) | ||
Theorem | elcntz 18444* | Elementhood in the centralizer. (Contributed by Mario Carneiro, 22-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑆 ⊆ 𝐵 → (𝐴 ∈ (𝑍‘𝑆) ↔ (𝐴 ∈ 𝐵 ∧ ∀𝑦 ∈ 𝑆 (𝐴 + 𝑦) = (𝑦 + 𝐴)))) | ||
Theorem | cntzel 18445* | Membership in a centralizer. (Contributed by Stefan O'Rear, 6-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑆 ⊆ 𝐵 ∧ 𝑋 ∈ 𝐵) → (𝑋 ∈ (𝑍‘𝑆) ↔ ∀𝑦 ∈ 𝑆 (𝑋 + 𝑦) = (𝑦 + 𝑋))) | ||
Theorem | cntzsnval 18446* | Special substitution for the centralizer of a singleton. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑌 ∈ 𝐵 → (𝑍‘{𝑌}) = {𝑥 ∈ 𝐵 ∣ (𝑥 + 𝑌) = (𝑌 + 𝑥)}) | ||
Theorem | elcntzsn 18447 | Value of the centralizer of a singleton. (Contributed by Mario Carneiro, 25-Apr-2016.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑌 ∈ 𝐵 → (𝑋 ∈ (𝑍‘{𝑌}) ↔ (𝑋 ∈ 𝐵 ∧ (𝑋 + 𝑌) = (𝑌 + 𝑋)))) | ||
Theorem | sscntz 18448* | A centralizer expression for two sets elementwise commuting. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑆 ⊆ 𝐵 ∧ 𝑇 ⊆ 𝐵) → (𝑆 ⊆ (𝑍‘𝑇) ↔ ∀𝑥 ∈ 𝑆 ∀𝑦 ∈ 𝑇 (𝑥 + 𝑦) = (𝑦 + 𝑥))) | ||
Theorem | cntzrcl 18449 | Reverse closure for elements of the centralizer. (Contributed by Stefan O'Rear, 6-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑋 ∈ (𝑍‘𝑆) → (𝑀 ∈ V ∧ 𝑆 ⊆ 𝐵)) | ||
Theorem | cntzssv 18450 | The centralizer is unconditionally a subset. (Contributed by Stefan O'Rear, 6-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑍‘𝑆) ⊆ 𝐵 | ||
Theorem | cntzi 18451 | Membership in a centralizer (inference). (Contributed by Stefan O'Rear, 6-Sep-2015.) (Revised by Mario Carneiro, 22-Sep-2015.) |
⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑋 ∈ (𝑍‘𝑆) ∧ 𝑌 ∈ 𝑆) → (𝑋 + 𝑌) = (𝑌 + 𝑋)) | ||
Theorem | cntrss 18452 | The center is a subset of the base field. (Contributed by Thierry Arnoux, 21-Aug-2023.) |
⊢ 𝐵 = (Base‘𝑀) ⇒ ⊢ (Cntr‘𝑀) ⊆ 𝐵 | ||
Theorem | cntri 18453 | Defining property of the center of a group. (Contributed by Mario Carneiro, 22-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) & ⊢ 𝑍 = (Cntr‘𝑀) ⇒ ⊢ ((𝑋 ∈ 𝑍 ∧ 𝑌 ∈ 𝐵) → (𝑋 + 𝑌) = (𝑌 + 𝑋)) | ||
Theorem | resscntz 18454 | Centralizer in a substructure. (Contributed by Mario Carneiro, 3-Oct-2015.) |
⊢ 𝐻 = (𝐺 ↾s 𝐴) & ⊢ 𝑍 = (Cntz‘𝐺) & ⊢ 𝑌 = (Cntz‘𝐻) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝑆 ⊆ 𝐴) → (𝑌‘𝑆) = ((𝑍‘𝑆) ∩ 𝐴)) | ||
Theorem | cntz2ss 18455 | Centralizers reverse the subset relation. (Contributed by Mario Carneiro, 3-Oct-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑆 ⊆ 𝐵 ∧ 𝑇 ⊆ 𝑆) → (𝑍‘𝑆) ⊆ (𝑍‘𝑇)) | ||
Theorem | cntzrec 18456 | Reciprocity relationship for centralizers. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑆 ⊆ 𝐵 ∧ 𝑇 ⊆ 𝐵) → (𝑆 ⊆ (𝑍‘𝑇) ↔ 𝑇 ⊆ (𝑍‘𝑆))) | ||
Theorem | cntziinsn 18457* | Express any centralizer as an intersection of singleton centralizers. (Contributed by Stefan O'Rear, 5-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ (𝑆 ⊆ 𝐵 → (𝑍‘𝑆) = (𝐵 ∩ ∩ 𝑥 ∈ 𝑆 (𝑍‘{𝑥}))) | ||
Theorem | cntzsubm 18458 | Centralizers in a monoid are submonoids. (Contributed by Stefan O'Rear, 6-Sep-2015.) (Revised by Mario Carneiro, 19-Apr-2016.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑀 ∈ Mnd ∧ 𝑆 ⊆ 𝐵) → (𝑍‘𝑆) ∈ (SubMnd‘𝑀)) | ||
Theorem | cntzsubg 18459 | Centralizers in a group are subgroups. (Contributed by Stefan O'Rear, 6-Sep-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑍 = (Cntz‘𝑀) ⇒ ⊢ ((𝑀 ∈ Grp ∧ 𝑆 ⊆ 𝐵) → (𝑍‘𝑆) ∈ (SubGrp‘𝑀)) | ||
Theorem | cntzidss 18460 | If the elements of 𝑆 commute, the elements of a subset 𝑇 also commute. (Contributed by Mario Carneiro, 25-Apr-2016.) |
⊢ 𝑍 = (Cntz‘𝐺) ⇒ ⊢ ((𝑆 ⊆ (𝑍‘𝑆) ∧ 𝑇 ⊆ 𝑆) → 𝑇 ⊆ (𝑍‘𝑇)) | ||
Theorem | cntzmhm 18461 | Centralizers in a monoid are preserved by monoid homomorphisms. (Contributed by Mario Carneiro, 24-Apr-2016.) |
⊢ 𝑍 = (Cntz‘𝐺) & ⊢ 𝑌 = (Cntz‘𝐻) ⇒ ⊢ ((𝐹 ∈ (𝐺 MndHom 𝐻) ∧ 𝐴 ∈ (𝑍‘𝑆)) → (𝐹‘𝐴) ∈ (𝑌‘(𝐹 “ 𝑆))) | ||
Theorem | cntzmhm2 18462 | Centralizers in a monoid are preserved by monoid homomorphisms. (Contributed by Mario Carneiro, 24-Apr-2016.) |
⊢ 𝑍 = (Cntz‘𝐺) & ⊢ 𝑌 = (Cntz‘𝐻) ⇒ ⊢ ((𝐹 ∈ (𝐺 MndHom 𝐻) ∧ 𝑆 ⊆ (𝑍‘𝑇)) → (𝐹 “ 𝑆) ⊆ (𝑌‘(𝐹 “ 𝑇))) | ||
Theorem | cntrsubgnsg 18463 | A central subgroup is normal. (Contributed by Stefan O'Rear, 6-Sep-2015.) |
⊢ 𝑍 = (Cntr‘𝑀) ⇒ ⊢ ((𝑋 ∈ (SubGrp‘𝑀) ∧ 𝑋 ⊆ 𝑍) → 𝑋 ∈ (NrmSGrp‘𝑀)) | ||
Theorem | cntrnsg 18464 | The center of a group is a normal subgroup. (Contributed by Stefan O'Rear, 6-Sep-2015.) |
⊢ 𝑍 = (Cntr‘𝑀) ⇒ ⊢ (𝑀 ∈ Grp → 𝑍 ∈ (NrmSGrp‘𝑀)) | ||
Syntax | coppg 18465 | The opposite group operation. |
class oppg | ||
Definition | df-oppg 18466 | Define an opposite group, which is the same as the original group but with addition written the other way around. df-oppr 19369 does the same thing for multiplication. (Contributed by Stefan O'Rear, 25-Aug-2015.) |
⊢ oppg = (𝑤 ∈ V ↦ (𝑤 sSet 〈(+g‘ndx), tpos (+g‘𝑤)〉)) | ||
Theorem | oppgval 18467 | Value of the opposite group. (Contributed by Stefan O'Rear, 25-Aug-2015.) (Revised by Mario Carneiro, 16-Sep-2015.) (Revised by Fan Zheng, 26-Jun-2016.) |
⊢ + = (+g‘𝑅) & ⊢ 𝑂 = (oppg‘𝑅) ⇒ ⊢ 𝑂 = (𝑅 sSet 〈(+g‘ndx), tpos + 〉) | ||
Theorem | oppgplusfval 18468 | Value of the addition operation of an opposite group. (Contributed by Stefan O'Rear, 26-Aug-2015.) (Revised by Fan Zheng, 26-Jun-2016.) |
⊢ + = (+g‘𝑅) & ⊢ 𝑂 = (oppg‘𝑅) & ⊢ ✚ = (+g‘𝑂) ⇒ ⊢ ✚ = tpos + | ||
Theorem | oppgplus 18469 | Value of the addition operation of an opposite ring. (Contributed by Stefan O'Rear, 26-Aug-2015.) (Revised by Fan Zheng, 26-Jun-2016.) |
⊢ + = (+g‘𝑅) & ⊢ 𝑂 = (oppg‘𝑅) & ⊢ ✚ = (+g‘𝑂) ⇒ ⊢ (𝑋 ✚ 𝑌) = (𝑌 + 𝑋) | ||
Theorem | oppglem 18470 | Lemma for oppgbas 18471. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝑅) & ⊢ 𝐸 = Slot 𝑁 & ⊢ 𝑁 ∈ ℕ & ⊢ 𝑁 ≠ 2 ⇒ ⊢ (𝐸‘𝑅) = (𝐸‘𝑂) | ||
Theorem | oppgbas 18471 | Base set of an opposite group. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝑅) & ⊢ 𝐵 = (Base‘𝑅) ⇒ ⊢ 𝐵 = (Base‘𝑂) | ||
Theorem | oppgtset 18472 | Topology of an opposite group. (Contributed by Mario Carneiro, 17-Sep-2015.) |
⊢ 𝑂 = (oppg‘𝑅) & ⊢ 𝐽 = (TopSet‘𝑅) ⇒ ⊢ 𝐽 = (TopSet‘𝑂) | ||
Theorem | oppgtopn 18473 | Topology of an opposite group. (Contributed by Mario Carneiro, 17-Sep-2015.) |
⊢ 𝑂 = (oppg‘𝑅) & ⊢ 𝐽 = (TopOpen‘𝑅) ⇒ ⊢ 𝐽 = (TopOpen‘𝑂) | ||
Theorem | oppgmnd 18474 | The opposite of a monoid is a monoid. (Contributed by Stefan O'Rear, 26-Aug-2015.) (Revised by Mario Carneiro, 16-Sep-2015.) |
⊢ 𝑂 = (oppg‘𝑅) ⇒ ⊢ (𝑅 ∈ Mnd → 𝑂 ∈ Mnd) | ||
Theorem | oppgmndb 18475 | Bidirectional form of oppgmnd 18474. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝑅) ⇒ ⊢ (𝑅 ∈ Mnd ↔ 𝑂 ∈ Mnd) | ||
Theorem | oppgid 18476 | Zero in a monoid is a symmetric notion. (Contributed by Stefan O'Rear, 26-Aug-2015.) (Revised by Mario Carneiro, 16-Sep-2015.) |
⊢ 𝑂 = (oppg‘𝑅) & ⊢ 0 = (0g‘𝑅) ⇒ ⊢ 0 = (0g‘𝑂) | ||
Theorem | oppggrp 18477 | The opposite of a group is a group. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝑅) ⇒ ⊢ (𝑅 ∈ Grp → 𝑂 ∈ Grp) | ||
Theorem | oppggrpb 18478 | Bidirectional form of oppggrp 18477. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝑅) ⇒ ⊢ (𝑅 ∈ Grp ↔ 𝑂 ∈ Grp) | ||
Theorem | oppginv 18479 | Inverses in a group are a symmetric notion. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝑅) & ⊢ 𝐼 = (invg‘𝑅) ⇒ ⊢ (𝑅 ∈ Grp → 𝐼 = (invg‘𝑂)) | ||
Theorem | invoppggim 18480 | The inverse is an antiautomorphism on any group. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝐺) & ⊢ 𝐼 = (invg‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 𝐼 ∈ (𝐺 GrpIso 𝑂)) | ||
Theorem | oppggic 18481 | Every group is (naturally) isomorphic to its opposite. (Contributed by Stefan O'Rear, 26-Aug-2015.) |
⊢ 𝑂 = (oppg‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 𝐺 ≃𝑔 𝑂) | ||
Theorem | oppgsubm 18482 | Being a submonoid is a symmetric property. (Contributed by Mario Carneiro, 17-Sep-2015.) |
⊢ 𝑂 = (oppg‘𝐺) ⇒ ⊢ (SubMnd‘𝐺) = (SubMnd‘𝑂) | ||
Theorem | oppgsubg 18483 | Being a subgroup is a symmetric property. (Contributed by Mario Carneiro, 17-Sep-2015.) |
⊢ 𝑂 = (oppg‘𝐺) ⇒ ⊢ (SubGrp‘𝐺) = (SubGrp‘𝑂) | ||
Theorem | oppgcntz 18484 | A centralizer in a group is the same as the centralizer in the opposite group. (Contributed by Mario Carneiro, 21-Apr-2016.) |
⊢ 𝑂 = (oppg‘𝐺) & ⊢ 𝑍 = (Cntz‘𝐺) ⇒ ⊢ (𝑍‘𝐴) = ((Cntz‘𝑂)‘𝐴) | ||
Theorem | oppgcntr 18485 | The center of a group is the same as the center of the opposite group. (Contributed by Mario Carneiro, 21-Apr-2016.) |
⊢ 𝑂 = (oppg‘𝐺) & ⊢ 𝑍 = (Cntr‘𝐺) ⇒ ⊢ 𝑍 = (Cntr‘𝑂) | ||
Theorem | gsumwrev 18486 | A sum in an opposite monoid is the regular sum of a reversed word. (Contributed by Stefan O'Rear, 27-Aug-2015.) (Proof shortened by Mario Carneiro, 28-Feb-2016.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝑂 = (oppg‘𝑀) ⇒ ⊢ ((𝑀 ∈ Mnd ∧ 𝑊 ∈ Word 𝐵) → (𝑂 Σg 𝑊) = (𝑀 Σg (reverse‘𝑊))) | ||
According to Wikipedia ("Symmetric group", 09-Mar-2019,
https://en.wikipedia.org/wiki/symmetric_group) "In abstract algebra, the
symmetric group defined over any set is the group whose elements are all the
bijections from the set to itself, and whose group operation is the composition
of functions." and according to Encyclopedia of Mathematics ("Symmetric group",
09-Mar-2019, https://www.encyclopediaofmath.org/index.php/Symmetric_group)
"The group of all permutations (self-bijections) of a set with the operation of
composition (see Permutation group).". In [Rotman] p. 27 "If X is a nonempty
set, a permutation of X is a function a : X -> X that is a one-to-one
correspondence." and "If X is a nonempty set, the symmetric group on X, denoted
SX, is the group whose elements are the permutations of X and whose
binary operation is composition of functions.". Therefore, we define the
symmetric group on a set 𝐴 as the set of one-to-one onto functions
from 𝐴 to itself under function composition, see df-symg 18488. However, the
set is allowed to be empty, see symgbas0 18509. Hint: The symmetric groups
should not be confused with "symmetry groups" which is a different topic in
group theory.
| ||
Syntax | csymg 18487 | Extend class notation to include the class of symmetric groups. |
class SymGrp | ||
Definition | df-symg 18488* | Define the symmetric group on set 𝑥. We represent the group as the set of one-to-one onto functions from 𝑥 to itself under function composition, and topologize it as a function space assuming the set is discrete. This definition is based on the fact that a symmetric group is a restriction of the monoid of endofunctions. (Contributed by Paul Chapman, 25-Feb-2008.) (Revised by AV, 28-Mar-2024.) |
⊢ SymGrp = (𝑥 ∈ V ↦ ((EndoFMnd‘𝑥) ↾s {ℎ ∣ ℎ:𝑥–1-1-onto→𝑥})) | ||
Theorem | symgval 18489* | The value of the symmetric group function at 𝐴. (Contributed by Paul Chapman, 25-Feb-2008.) (Revised by Mario Carneiro, 12-Jan-2015.) (Revised by AV, 28-Mar-2024.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = {𝑥 ∣ 𝑥:𝐴–1-1-onto→𝐴} ⇒ ⊢ 𝐺 = ((EndoFMnd‘𝐴) ↾s 𝐵) | ||
Theorem | permsetex 18490* | The set of permutations of a set 𝐴 exists. (Contributed by AV, 30-Mar-2024.) |
⊢ (𝐴 ∈ 𝑉 → {𝑓 ∣ 𝑓:𝐴–1-1-onto→𝐴} ∈ V) | ||
Theorem | symgbas 18491* | The base set of the symmetric group. (Contributed by Mario Carneiro, 12-Jan-2015.) (Proof shortened by AV, 29-Mar-2024.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ 𝐵 = {𝑥 ∣ 𝑥:𝐴–1-1-onto→𝐴} | ||
Theorem | symgbasex 18492 | The base set of the symmetric group over a set 𝐴 exists. (Contributed by AV, 30-Mar-2024.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐴 ∈ 𝑉 → 𝐵 ∈ V) | ||
Theorem | elsymgbas2 18493 | Two ways of saying a function is a 1-1-onto mapping of A to itself. (Contributed by Mario Carneiro, 28-Jan-2015.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐹 ∈ 𝑉 → (𝐹 ∈ 𝐵 ↔ 𝐹:𝐴–1-1-onto→𝐴)) | ||
Theorem | elsymgbas 18494 | Two ways of saying a function is a 1-1-onto mapping of A to itself. (Contributed by Paul Chapman, 25-Feb-2008.) (Revised by Mario Carneiro, 28-Jan-2015.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐴 ∈ 𝑉 → (𝐹 ∈ 𝐵 ↔ 𝐹:𝐴–1-1-onto→𝐴)) | ||
Theorem | symgbasf1o 18495 | Elements in the symmetric group are 1-1 onto functions. (Contributed by SO, 9-Jul-2018.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐹 ∈ 𝐵 → 𝐹:𝐴–1-1-onto→𝐴) | ||
Theorem | symgbasf 18496 | A permutation (element of the symmetric group) is a function from a set into itself. (Contributed by AV, 1-Jan-2019.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐹 ∈ 𝐵 → 𝐹:𝐴⟶𝐴) | ||
Theorem | symgbasmap 18497 | A permutation (element of the symmetric group) is a mapping (or set exponentiation) from a set into itself. (Contributed by AV, 30-Mar-2024.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐹 ∈ 𝐵 → 𝐹 ∈ (𝐴 ↑m 𝐴)) | ||
Theorem | symghash 18498 | The symmetric group on 𝑛 objects has cardinality 𝑛!. (Contributed by Mario Carneiro, 22-Jan-2015.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐴 ∈ Fin → (♯‘𝐵) = (!‘(♯‘𝐴))) | ||
Theorem | symgbasfi 18499 | The symmetric group on a finite index set is finite. (Contributed by SO, 9-Jul-2018.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐴 ∈ Fin → 𝐵 ∈ Fin) | ||
Theorem | symgfv 18500 | The function value of a permutation. (Contributed by AV, 1-Jan-2019.) |
⊢ 𝐺 = (SymGrp‘𝐴) & ⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ ((𝐹 ∈ 𝐵 ∧ 𝑋 ∈ 𝐴) → (𝐹‘𝑋) ∈ 𝐴) |
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