@@ -4,17 +4,17 @@ \chapter{Finite group theory}
44the \C {fingroup} and \C {solvable} directories. It covers a substantial
55part of~\cite {gorenstein2007finite } and~\cite {9781139175319 } ranging from
66basic notions like morphisms, quotients, actions, cyclic and p-groups to more
7- substantial topics as Sylow and Hall groups, the Abelian
8- structure theorem and the Jordan Holder theorem.
7+ substantial topics as Sylow and Hall groups, the abelian
8+ structure theorem and the Jordan-H \" older theorem.
99The paper~\cite {DBLP:conf /mkm /Mahboubi13 }
1010describes the constructions and formalization techniques
11- needed in order to prove the Jordan Holder theorem.
11+ needed in order to prove the Jordan-H \" older theorem.
1212
1313\paragraph {contents }
1414
1515\lib {..}
1616
17- \paragraph {Basic formalization choices } To ease the study of sub-groups ,
17+ \paragraph {Basic formalization choices } To ease the study of subgroups ,
1818the type of groups is indexed over a container group called
1919\C {finGroupType}, fixing the group law and imposing finiteness by
2020inheriting from \C {finType}.
@@ -25,24 +25,24 @@ \chapter{Finite group theory}
2525Concepts already existing on sets are kept there and not redefined.
2626Type inference is programmed to infer the group structure whenever possible.
2727For example the type of \C {(G :&: H)} is \C {\{ set gT\} } but such expression
28- is automatically promoted to a group when needed, similarly to what
28+ is automatically promoted to a group when needed, similarly to what
2929was done in section~\ref {sec:tupleinvariant } for tuples.
3030
31- group concepts usually here defined on sets, but then
32- possibly using the generated group operation to fulfill
33- stricter requirements. This generalized the math concept and
34- ease the integration with set stuff . This is possible because
35- the container is a group and we can always generate from a set.
31+ Group concepts are usually defined on sets, but then
32+ possibly use the generated group operation to fulfill
33+ stricter requirements. This generalizes the math concept and
34+ eases the integration with set theory . This is possible because
35+ the container is a group and we can always generate one from a set.
3636
37- morphisms carry domain set in type.
37+ Morphisms carry their domain set in their type.
3838
3939\paragraph {Notations } The same infix \C {*} notation can be used to
4040multiply both sets (or groups) and their points. For example
4141\C {(g * h \\ in G * H)} is a valid writing, meaning that
4242$ g\cdot h \in \{ x\cdot y | x \in G, y \in H\} $ . Given the \C {finGroupType}
4343container many open notations are also supported, for example the normalizer
4444of \C {A}, written \C {'N(A)} for \C {A} being a \C {\{ set gT\} }, is a sensible
45- writing. Another bonus from the container.
45+ writing, another bonus from the container.
4646
4747\begin {coq }{}{}
4848Definition normaliser A := [set x | A :^ x \subset A].
@@ -63,7 +63,7 @@ \chapter{Finite group theory}
6363
6464notations for actions acts-on, transitive, Fix, 'N(A|P) and co.
6565
66- \paragraph {Formalization trick: totality of operations } In standard math one
66+ \paragraph {Formalization trick: totality of operations } In standard mathematics, one
6767can write \C {A/H} only if the normality condition \C {(H <| A)} holds.
6868Such construction is made total by defining \C {A/H} as
6969\C {(('N(H) :&: A) * H) / H)}, i.e. \C {A} is intersected with
@@ -76,7 +76,7 @@ \chapter{Finite group theory}
7676Lemma quotientMl A B : A \subset 'N(H) -> A * B / H = (A / H) * (B / H).
7777\end {coq }
7878Remark that the equational form lets you require only one precondition:
79- if \C {B} exceeds the \C {'N(H)} then the equation still holds, since
79+ if \C {B} exceeds \C {'N(H)}, then the equation still holds, since
8080the intersection with the normalizer of \C {H} occurs on both sides.
8181
8282A similar choice is used for the (semi) direct and central product.
@@ -98,15 +98,15 @@ \chapter{Finite group theory}
9898the trivial group.
9999
100100\paragraph {Formalization trick: presentations } One cannot decide if a group
101- presented via generators and relations is finite, hence the integration of such
101+ presented via generators and relations is finite, hence the integration of such a
102102concept in a library of finite groups is tricky. The notation
103103\C {(G \\ homg Grp (x : (x ^+ n)))} states that the finite group \C {G}
104104is generated by a single point \C {x} of order \C {n} (as in the standard
105105mathematical notation, \C {(x ^+ n)} really means \C {(x ^+ n = 1)}).
106106The shrewdness is that the notation hides an existential quantification
107107postulating the existence of a finite tuple of generators satisfying
108108the equations and building \C {G}: the potentially infinite object is never
109- built as well the \C {\\ homg} relation, standing for homomorphic image,
109+ built, and the \C {\\ homg} relation ( standing for homomorphic image)
110110suggests the fact that \C {G} is the image of the presented group, not the
111111group itself. Notation
112112\C {(G \\ homg Grp (x_1 : .. x_n : (s_1 = t_1, .., s_m = t_m))}
@@ -118,7 +118,7 @@ \chapter{Finite group theory}
118118 == (G, (t_1, .. (t_m-1, t_m) ..))]
119119\end {coq }
120120Such formula is generated reflexively, i.e. by a \Coq {} program that
121- takes in input the syntax of the presentation and produces that statement.
121+ takes as input the syntax of the presentation and produces that statement.
122122Remark the $ m+1 $ components compared by \C {(_ == _)}. It first compares
123123the group generated by the generators \C {x_1 .. x_n} with \C {G}; then
124124it compares all the expressions being related.
@@ -145,6 +145,6 @@ \chapter{Representation and Character theory}
145145
146146\cite {isaacs1976character }
147147
148- As an example of application, in particular of the linear algebra
148+ As an example of application of the library , in particular of the linear algebra
149149theory.
150150
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