Small group number 928 of order 128

G is the group 128gp928

G has 3 minimal generators, rank 4 and exponent 8. The centre has rank 1.

The 7 maximal subgroups are: Syl2(M12), 64gp138 (2x), 64gp226, 64gp32 (2x), 64gp34.

There are 5 conjugacy classes of maximal elementary abelian subgroups. Their ranks are: 3, 3, 4, 4, 4.

This cohomology ring calculation is complete.

Ring structure | Completion information | Koszul information | Restriction information | Poincaré series


Ring structure

The cohomology ring has 9 generators:

There are 14 minimal relations:

This minimal generating set constitutes a Gröbner basis for the relations ideal.

Essential ideal: Zero ideal

Nilradical: Zero ideal


Completion information

This cohomology ring was obtained from a calculation out to degree 12. The cohomology ring approximation is stable from degree 6 onwards, and Carlson's tests detect stability from degree 12 onwards.

This cohomology ring has dimension 4 and depth 3. Here is a homogeneous system of parameters:

The first 3 terms h1, h2, h3 form a regular sequence of maximum length. The remaining term h4 is annihilated by the class y3.

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.

The ideal of essential classes is the zero ideal. The essential ideal squares to zero.


Koszul information

A basis for R/(h1, h2, h3, h4) is as follows. Carlson's Koszul condition stipulates that this must be confined to degrees less than 12.

A basis for AnnR/(h1, h2, h3)(h4) is as follows. Carlson's Koszul condition stipulates that this must be confined to degrees less than 8.


Restriction information

Restrictions to maximal subgroups

Restriction to maximal subgroup number 1, which is 64gp226

Restriction to maximal subgroup number 2, which is 64gp138

Restriction to maximal subgroup number 3, which is 64gp32

Restriction to maximal subgroup number 4, which is 64gp138

Restriction to maximal subgroup number 5, which is 64gp32

Restriction to maximal subgroup number 6, which is 64gp134

Restriction to maximal subgroup number 7, which is 64gp34

Restrictions to maximal elementary abelian subgroups

Restriction to maximal elementary abelian number 1, which is V8

Restriction to maximal elementary abelian number 2, which is V8

Restriction to maximal elementary abelian number 3, which is V16

Restriction to maximal elementary abelian number 4, which is V16

Restriction to maximal elementary abelian number 5, which is V16

Restriction to the greatest central elementary abelian subgroup

Restriction to the greatest central elementary abelian, which is C2


Poincaré series

(1 + 3t + 5t2 + 7t3 + 7t4 + 5t5 + 3t6 + t7) / (1 - t2)2 (1 - t4)2


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