#We find all primitive subgroups of $GL(18,5)$ with parameters $e=9$, $a=2$. In this case $b=2$ divides $a$, so we use item (i) of Lemma 5.5. We start with #primitive solvable subgroups in $GL(9,5^b)=GL(9,25)$ and then produce primitive subgroups in $GL(18,5)$. #In the notations of Theorem 5.1, if $H$ is a primitive solvable subgroup, then it possesses a series #$$1 e:=9;; p:=5;; d:=18;; a:=2;; #Since 5-1 is not divisible by 3, we take generators of primitive subgroups in $GL(9,25)$ from the file generators-GL(9,25).txt as a list gens for every matrix #g in gens we substitute each entry $g_{i,j}\in GF(5^2)$ by a 2\times2-matrix over $GF(5)$ gap> bas:= Basis( AsVectorSpace( GF(p),GF(p^a) ) );; gap> genS:=[];; gap> for i in [1..Size(gens)] do > genS[i]:=[];; > for j in gens[i]do > Append(genS[i],[BlownUpMat(bas,j)]);; > od; > od; #Now we produce Singer cycle in $GL(2,5)$ that agrees with generators obtained above and element from normalizer inducing the field automorphism of order $2$. #We find a central element in subgroup H with generators genS[44], its center is cyclic of order $24$. gap> H:=Subgroup(GL(18,5),genS[44]);; gap> Zz:=Center(H); gap> Order(Zz); 24 gap> gn:=GeneratorsOfGroup(Zz); [ < immutable compressed matrix 18x18 over GF(5) >, < immutable compressed matrix 18x18 over GF(5) >, < immutable compressed matrix 18x18 over GF(5) >, < immutable compressed matrix 18x18 over GF(5) > ] gap> Order(gn[1]); 12 gap> Order(gn[2]); 8 gap> Order(gn[3]); 12 gap> Order(gn[4]); 8 gap> x:=gn[1]^4*gn[2];; gap> Order(x); 24 gap> Display(x); 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . 2 3 . . . . . . . . . . . . . . . . 4 . #Now we produce t so that $I_9\otimes t=x$ and find $s$ such that $t^s=t^5$ gap> z:=Z(5);; gap> t:=[[z,z^(-1)],[z^2,0*z]];; gap> Display(t); 2 3 4 . gap> s:=RepresentativeAction(GL(a,p),t,t^p);; gap> s18:=KroneckerProduct(IdentityMat(9,Z(5)),s);; gap> Display(s18); 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 4 3 . . . . . . . . . . . . . . . . . 1 #We check, that s18 normalizes Fitting subgroup of H gap> F:=FittingSubgroup(H); gap> Order(F); 1944 gap> F^s18=F; true #Now we find the full normalizer of $F$ in $GL(18,5)$ isomorphic to $((24\circ 3^{1+4}).Sp(4,3)).2$ and has order #$(p^a-1)*e^2*|Sp(4,3)|*2=(5^2-1)*9^2*3^4*(3^2-1)*(3^4-1)*2$ gap> gen:=Concatenation(genS[44],[s18]);; gap> N:=Subgroup(GL(18,5),gen);; gap> n:=Size(N); 201553920 gap> n=(5^2-1)*9*9*3^4*(3^2-1)*(3^4-1)*2; true #Now we run the following loop. Each entry of the list result has three items: the first is the #number of the group in the list genS, the second is the order of the group, and the third is the order of the stabilizer of v in H. #If the order of the stabilizer is 1, then |v^H=|H| and Corollary 2.5 can be applied. gap> v:=[z,z^2,z^3,0*z,z^3,z,z,z^2,z^3,z^2,0*z,z,z^3,z^0,z^2,z^3,z,z^2];; gap> result:=[]; gap> for k in [1..Size(genS)] do > L:=Subgroup(GL(18,5),genS[k]);; > H:=Normalizer(N,L); > n:=Size(H);; > m:=Size(v^H); > result[k]:=[k,n,n/m]; > Display(result[k]); > od; [ 1, 155520, 1 ] [ 2, 155520, 1 ] [ 3, 746496, 1 ] [ 4, 497664, 1 ] [ 5, 155520, 1 ] [ 6, 1492992, 1 ] [ 7, 1492992, 1 ] [ 8, 746496, 1 ] [ 9, 497664, 1 ] [ 10, 248832, 1 ] [ 11, 248832, 1 ] [ 12, 124416, 1 ] [ 13, 746496, 1 ] [ 14, 155520, 1 ] [ 15, 7464960, 1 ] [ 16, 746496, 1 ] [ 17, 497664, 1 ] [ 18, 497664, 1 ] [ 19, 248832, 1 ] [ 20, 248832, 1 ] [ 21, 746496, 1 ] [ 22, 373248, 1 ] [ 23, 373248, 1 ] [ 24, 373248, 1 ] [ 25, 373248, 1 ] [ 26, 4478976, 1 ] [ 27, 497664, 1 ] [ 28, 497664, 1 ] [ 29, 746496, 1 ] [ 30, 746496, 1 ] [ 31, 746496, 1 ] [ 32, 746496, 1 ] [ 33, 373248, 1 ] [ 34, 1244160, 1 ] [ 35, 1492992, 1 ] [ 36, 4478976, 1 ] [ 37, 4478976, 1 ] [ 38, 2239488, 1 ] [ 39, 746496, 1 ] [ 40, 1244160, 1 ] [ 41, 4478976, 1 ] [ 42, 1492992, 1 ] [ 43, 4478976, 1 ] [ 44, 4478976, 1 ]