Small group number 642 of order 128
G is the group 128gp642
G has 3 minimal generators, rank 4 and exponent 8.
The centre has rank 1.
There are 3 conjugacy classes of maximal
elementary abelian subgroups. Their ranks are:
3, 3, 4.
This cohomology ring calculation is complete.
Ring structure
| Completion information
| Koszul information
| Restriction information
| Poincaré series
The cohomology ring has 12 generators:
- y1 in degree 1, a nilpotent element
- y2 in degree 1
- y3 in degree 1
- x1 in degree 2
- x2 in degree 2
- x3 in degree 2
- x4 in degree 2
- w in degree 3
- u1 in degree 5
- u2 in degree 5
- t in degree 6
- r in degree 8, a regular element
There are 32 minimal relations:
- y2.y3 =
y1.y2
- y1.y3 =
0
- y12 =
0
- y3.x4 =
y3.x1
+ y1.x1
- y2.x4 =
y1.x1
- y2.x2 =
y2.x1
+ y1.x3
- y1.x4 =
0
- x42 =
y32.x2
+ y32.x1
- x3.x4 =
x1.x3
+ y2.w
+ y22.x3
- x2.x4 =
x1.x2
+ y22.x1
+ y1.w
- x1.x4 =
y32.x2
+ y32.x1
+ y1.y2.x1
- x12 =
y32.x2
+ y32.x1
+ y22.x1
+ y1.y2.x3
+ y1.y2.x1
- x4.w =
x1.w
- y1.x32 =
y1.x2.x3
+ y1.y2.w
+ y1.y22.x3
- w2 =
x2.x32
+ x22.x3
+ y3.u2
+ y3.x3.w
+ y3.x2.w
+ y32.x22
+ y34.x1
+ y36
+ y22.x32
+ y23.w
+ y24.x3
+ y1.x3.w
+ y1.x2.w
+ y1.y22.w
- x1.x32 =
x1.x2.x3
+ y3.u1
+ y3.x3.w
+ y3.x1.w
+ y32.x32
+ y32.x22
+ y32.x1.x2
+ y33.w
+ y34.x3
+ y36
+ y2.x3.w
+ y22.x32
+ y23.w
+ y24.x3
+ y1.x3.w
+ y1.y22.w
+ y1.y23.x1
- y2.u2 =
y22.x32
+ y23.w
+ y1.x3.w
+ y1.y23.x3
+ y1.y23.x1
- y1.u2 =
y1.x3.w
+ y1.y22.w
- y1.u1 =
y1.x3.w
+ y1.y22.w
+ y1.y23.x1
- x4.u2 =
x1.x3.w
+ y3.t
+ y3.x33
+ y3.x2.x32
+ y3.x1.x2.x3
+ y3.x1.x22
+ y32.u2
+ y32.u1
+ y32.x3.w
+ y32.x2.w
+ y32.x1.w
+ y33.x32
+ y33.x2.x3
+ y33.x1.x3
+ y33.x1.x2
+ y35.x1
+ y1.y23.w
+ y1.y24.x3
+ y1.y24.x1
- x4.u1 =
x1.x3.w
+ y3.x2.x32
+ y3.x22.x3
+ y3.x1.x2.x3
+ y3.x1.x22
+ y32.x2.w
+ y33.x22
+ y33.x1.x3
+ y33.x1.x2
+ y35.x1
- x1.u2 =
x1.x3.w
+ y3.t
+ y3.x33
+ y3.x2.x32
+ y3.x1.x2.x3
+ y3.x1.x22
+ y32.u2
+ y32.u1
+ y32.x3.w
+ y32.x2.w
+ y32.x1.w
+ y33.x32
+ y33.x2.x3
+ y33.x1.x3
+ y33.x1.x2
+ y35.x1
+ y22.x3.w
+ y23.x32
- x1.u1 =
x1.x3.w
+ y3.x2.x32
+ y3.x22.x3
+ y3.x1.x2.x3
+ y3.x1.x22
+ y32.x2.w
+ y33.x22
+ y33.x1.x3
+ y33.x1.x2
+ y35.x1
+ y2.t
+ y2.x33
+ y22.u1
+ y22.x3.w
+ y24.w
+ y1.x22.x3
+ y1.y24.x3
+ y1.y24.x1
- y1.t =
0
- x4.t =
y3.x3.u1
+ y3.x32.w
+ y3.x2.u2
+ y3.x2.x3.w
+ y3.x1.x2.w
+ y32.x33
+ y32.x2.x32
+ y32.x22.x3
+ y32.x23
+ y32.x1.x2.x3
+ y33.u1
+ y34.x2.x3
+ y34.x22
+ y34.x1.x2
+ y35.w
+ y36.x2
+ y38
+ y1.y24.w
+ y1.y25.x3
- x1.t =
y3.x3.u1
+ y3.x32.w
+ y3.x2.u2
+ y3.x2.x3.w
+ y3.x1.x2.w
+ y32.x33
+ y32.x2.x32
+ y32.x22.x3
+ y32.x23
+ y32.x1.x2.x3
+ y33.u1
+ y34.x2.x3
+ y34.x22
+ y34.x1.x2
+ y35.w
+ y36.x2
+ y38
+ y2.x32.w
+ y22.x33
+ y1.x2.x3.w
+ y1.y25.x1
- u22 =
x22.x33
+ x23.x32
+ y3.x2.x3.u2
+ y32.w.u1
+ y32.x3.t
+ y32.x34
+ y32.x2.x33
+ y32.x23.x3
+ y32.x24
+ y32.x1.x22.x3
+ y32.x1.x23
+ y33.x3.u2
+ y33.x32.w
+ y33.x2.u2
+ y33.x2.u1
+ y33.x2.x3.w
+ y33.x1.x3.w
+ y33.x1.x2.w
+ y34.t
+ y34.x33
+ y34.x2.x32
+ y34.x22.x3
+ y34.x1.x2.x3
+ y35.u2
+ y35.u1
+ y35.x2.w
+ y36.x2.x3
+ y36.x22
+ y36.x1.x3
+ y36.x1.x2
+ y37.w
+ y22.x34
+ y23.x32.w
+ y24.x33
+ y26.x32
+ y32.r
- u1.u2 =
x3.w.u2
+ x3.w.u1
+ x32.t
+ x35
+ x2.x3.t
+ x2.x34
+ y3.w.t
+ y3.x32.u2
+ y3.x32.u1
+ y3.x2.x3.u2
+ y3.x2.x32.w
+ y3.x22.u2
+ y3.x22.u1
+ y3.x22.x3.w
+ y32.x34
+ y32.x2.t
+ y32.x2.x33
+ y32.x24
+ y33.x3.u1
+ y33.x32.w
+ y34.x33
+ y34.x22.x3
+ y34.x1.x2.x3
+ y35.x1.w
+ y36.x1.x3
+ y37.w
+ y38.x1
+ y310
+ y2.x32.u1
+ y22.x3.t
+ y22.x34
+ y23.x32.w
+ y25.x3.w
+ y1.x22.x3.w
+ y1.y26.w
+ y1.y27.x3
- u12 =
x22.x33
+ x23.x32
+ y3.x32.u2
+ y3.x32.u1
+ y3.x2.x3.u1
+ y32.w.u1
+ y32.x24
+ y33.x3.u2
+ y33.x32.w
+ y33.x2.u2
+ y33.x2.u1
+ y34.x33
+ y34.x22.x3
+ y34.x23
+ y34.x1.x2.x3
+ y35.u1
+ y35.x2.w
+ y35.x1.w
+ y36.x22
+ y36.x1.x3
+ y2.x33.w
+ y22.x34
+ y23.x32.w
+ y24.x33
+ y26.x32
+ y28.x1
+ y1.x22.x3.w
+ y1.y26.w
+ y1.y27.x1
- u2.t =
x3.w.t
+ x33.u2
+ x34.w
+ x2.x32.u2
+ x2.x32.u1
+ x22.x3.u1
+ x22.x32.w
+ y3.x3.w.u2
+ y3.x2.w.u2
+ y3.x2.w.u1
+ y3.x2.x3.t
+ y3.x22.t
+ y3.x23.x32
+ y3.x24.x3
+ y3.x1.x23.x3
+ y32.x2.x32.w
+ y32.x22.u1
+ y32.x22.x3.w
+ y32.x1.x2.x3.w
+ y33.w.u2
+ y33.x1.x22.x3
+ y33.x1.x23
+ y34.x3.u2
+ y34.x32.w
+ y34.x2.x3.w
+ y34.x1.x3.w
+ y35.x2.x32
+ y35.x23
+ y35.x1.x22
+ y36.x3.w
+ y37.x22
+ y37.x1.x3
+ y37.x1.x2
+ y39.x3
+ y39.x2
+ y39.x1
+ y311
+ y2.x32.t
+ y2.x35
+ y22.x32.u1
+ y23.x34
+ y24.x3.u1
+ y26.x3.w
+ y1.x24.x3
+ y1.y27.w
+ y1.y28.x3
+ y3.x1.r
+ y33.r
+ y1.x1.r
- u1.t =
x3.w.t
+ x33.u1
+ x34.w
+ x2.x32.u2
+ x2.x32.u1
+ x22.x3.u2
+ x22.x32.w
+ y3.x3.w.u1
+ y3.x32.t
+ y3.x35
+ y3.x2.w.u2
+ y3.x2.w.u1
+ y3.x2.x34
+ y3.x22.t
+ y3.x22.x33
+ y3.x24.x3
+ y32.w.t
+ y32.x32.u2
+ y32.x32.u1
+ y32.x2.x3.u1
+ y32.x2.x32.w
+ y32.x22.u2
+ y33.w.u1
+ y33.x3.t
+ y33.x2.x33
+ y33.x22.x32
+ y33.x24
+ y34.x32.w
+ y34.x2.u2
+ y35.t
+ y35.x22.x3
+ y35.x23
+ y35.x1.x2.x3
+ y36.u2
+ y36.u1
+ y36.x2.w
+ y36.x1.w
+ y37.x32
+ y37.x2.x3
+ y37.x22
+ y39.x3
+ y39.x2
+ y39.x1
+ y2.x32.t
+ y2.x35
+ y22.x32.u1
+ y22.x33.w
+ y23.x3.t
+ y25.x33
+ y1.x24.x3
+ y1.y27.w
+ y1.y28.x3
+ y1.y28.x1
- t2 =
x36
+ x24.x32
+ y3.x2.x32.u2
+ y3.x2.x32.u1
+ y3.x22.x3.u2
+ y3.x22.x3.u1
+ y32.x32.t
+ y32.x35
+ y32.x2.x34
+ y32.x22.x33
+ y32.x23.x32
+ y32.x24.x3
+ y32.x1.x24
+ y33.x32.u2
+ y33.x2.x3.u2
+ y33.x2.x32.w
+ y33.x22.x3.w
+ y33.x1.x22.w
+ y34.x3.t
+ y34.x34
+ y34.x2.t
+ y34.x23.x3
+ y34.x24
+ y34.x1.x22.x3
+ y34.x1.x23
+ y35.x2.u2
+ y35.x1.x3.w
+ y35.x1.x2.w
+ y36.t
+ y36.x2.x32
+ y36.x22.x3
+ y36.x23
+ y37.u2
+ y38.x32
+ y38.x2.x3
+ y38.x22
+ y38.x1.x2
+ y39.w
+ y310.x2
+ y23.x33.w
+ y27.x3.w
+ y28.x32
+ y1.y28.w
+ y1.y29.x3
+ y32.x2.r
+ y32.x1.r
+ y34.r
A minimal Gröbner basis for the relations ideal
consists of this minimal generating set, together with the
following redundant relations:
- y2.x1.x3 =
y22.w
+ y23.x3
+ y1.y2.w
+ y1.y22.x3
- y1.x1.x3 =
y1.y2.w
+ y1.y22.x3
- y1.x1.x2 =
y1.y22.x1
- y2.x1.w =
0
- y1.x1.w =
0
- y1.y2.x3.w =
0
- y2.w.u1 =
y2.x3.t
+ y2.x34
+ y22.x32.w
+ y24.x3.w
+ y1.x23.x3
- y2.w.t =
y2.x33.w
+ y22.x3.t
+ y22.x34
+ y1.x22.x3.w
+ y1.y26.w
+ y1.y27.x3
This cohomology ring was obtained from a calculation
out to degree 13. The cohomology ring approximation
is stable from degree 12 onwards, and
Benson's tests detect stability from degree 13
onwards.
This cohomology ring has dimension 4 and depth 2.
Here is a homogeneous system of parameters:
- h1 =
r
in degree 8
- h2 =
x32
+ x2.x3
+ x22
+ y34
+ y2.w
+ y22.x3
+ y22.x1
+ y24
+ y1.y2.x3
+ y1.y2.x1
in degree 4
- h3 =
x3
+ y32
in degree 2
- h4 =
y3
in degree 1
The first
2 terms h1, h2 form
a regular sequence of maximum length.
The first
term h1 forms
a complete Duflot regular sequence.
That is, its restriction to the greatest central elementary abelian
subgroup forms a regular sequence of maximal length.
Data for Benson's test:
-
Raw filter degree type:
-1, -1, 8, 10, 11.
-
Filter degree type:
-1, -2, -3, -4, -4.
-
α = 0
-
The system of parameters is very strongly quasi-regular.
-
The regularity conjecture is satisfied.
A basis for R/(h1, h2, h3, h4) is as follows.
-
1
in degree 0
-
y2
in degree 1
-
y1
in degree 1
-
x4
in degree 2
-
x2
in degree 2
-
x1
in degree 2
-
y22
in degree 2
-
w
in degree 3
-
y2.x1
in degree 3
-
y23
in degree 3
-
y1.x2
in degree 3
-
x1.x2
in degree 4
-
y22.x1
in degree 4
-
y24
in degree 4
-
y1.w
in degree 4
-
u2
in degree 5
-
u1
in degree 5
-
x2.w
in degree 5
-
x1.w
in degree 5
-
y23.x1
in degree 5
-
t
in degree 6
-
y2.u1
in degree 6
-
y1.x2.w
in degree 6
-
x2.u2
in degree 7
-
x2.u1
in degree 7
-
x1.x2.w
in degree 7
-
y2.t
in degree 7
-
y22.u1
in degree 7
-
w.u2
in degree 8
-
w.u1
in degree 8
-
x2.t
in degree 8
-
y22.t
in degree 8
-
y23.u1
in degree 8
-
w.t
in degree 9
-
y23.t
in degree 9
-
y24.u1
in degree 9
-
x2.w.u2
in degree 10
-
x2.w.u1
in degree 10
-
y24.t
in degree 10
-
x2.w.t
in degree 11
A basis for AnnR/(h1, h2, h3)(h4) is as follows.
-
y1
in degree 1
-
y2.h
in degree 2
-
y1.x2
in degree 3
-
x4.h
+ x1.h
in degree 3
-
y22.h
in degree 3
-
y1.w
in degree 4
-
y2.x1.h
in degree 4
-
y23.h
in degree 4
-
u1
+ x1.w
+ y23.x1
+ x2.h3
+ x1.h3
+ h5
in degree 5
-
y22.x1.h
in degree 5
-
y24.h
in degree 5
-
y2.u1
+ y2.x1.w
+ y24.x1
+ y2.x2.h3
+ y2.x1.h3
+ y2.h5
in degree 6
-
y1.x2.w
in degree 6
-
y23.x1.h
in degree 6
-
x2.u1
+ x1.x2.w
+ y23.x1.x2
+ x22.h3
+ x1.x2.h3
+ x2.h5
in degree 7
-
y2.t
in degree 7
-
y22.u1
+ y22.x1.w
+ y25.x1
+ y22.x2.h3
+ y22.x1.h3
+ y22.h5
in degree 7
-
w.u1
+ x1.w2
+ y23.x1.w
+ x2.w.h3
+ x1.w.h3
+ w.h5
in degree 8
-
y22.t
in degree 8
-
y23.u1
+ y23.x1.w
+ y26.x1
+ y23.x2.h3
+ y23.x1.h3
+ y23.h5
in degree 8
-
y23.t
in degree 9
-
y24.u1
+ y24.x1.w
+ y27.x1
+ y24.x2.h3
+ y24.x1.h3
+ y24.h5
in degree 9
-
x2.w.u1
+ x1.x2.w2
+ y23.x1.x2.w
+ x22.w.h3
+ x1.x2.w.h3
+ x2.w.h5
in degree 10
-
y24.t
in degree 10
A basis for AnnR/(h1, h2)(h3) is as follows.
-
y1.x2
+ y1.x1
+ y1.h
in degree 3
-
y1.y2.h
in degree 4
-
y1.y24
+ y1.h2
in degree 5
-
y1.x1.h
in degree 5
-
y1.y22.h
in degree 5
-
y1.x2.w
+ y1.x1.w
+ y1.w.h
in degree 6
-
y1.y2.x1.h
in degree 6
-
y1.y23.h
in degree 6
-
y1.y22.x1.h
in degree 7
-
y1.h3
in degree 7
-
y1.y23.x1.h
in degree 8
-
y1.w.h2
in degree 8