Simon King
David J. Green
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Cohomology of group number 618 of order 128
General information on the group
- The group has 3 minimal generators and exponent 8.
- It is non-abelian.
- It has p-Rank 3.
- Its center has rank 2.
- It has a unique conjugacy class of maximal elementary abelian subgroups, which is of rank 3.
Structure of the cohomology ring
General information
- The cohomology ring is of dimension 3 and depth 2.
- The depth coincides with the Duflot bound.
- The Poincaré series is
( − 1) · (t2 + t + 1) · (t4 − t3 + t2 + 1) |
| (t + 1) · (t − 1)3 · (t2 + 1) · (t4 + 1) |
- The a-invariants are -∞,-∞,-3,-3. They were obtained using the filter regular HSOP of the Benson test.
Ring generators
The cohomology ring has 11 minimal generators of maximal degree 8:
- a_1_0, a nilpotent element of degree 1
- a_1_1, a nilpotent element of degree 1
- a_1_2, a nilpotent element of degree 1
- a_2_3, a nilpotent element of degree 2
- a_2_4, a nilpotent element of degree 2
- b_2_5, an element of degree 2
- c_2_6, a Duflot regular element of degree 2
- a_5_19, a nilpotent element of degree 5
- b_5_20, an element of degree 5
- a_6_22, a nilpotent element of degree 6
- c_8_39, a Duflot regular element of degree 8
Ring relations
There are 28 minimal relations of maximal degree 12:
- a_1_12 + a_1_02
- a_1_0·a_1_1 + a_1_02
- a_1_0·a_1_2
- a_2_3·a_1_1 + a_2_3·a_1_0
- a_2_4·a_1_1 + a_2_3·a_1_2
- a_2_4·a_1_0
- b_2_5·a_1_1 + b_2_5·a_1_0 + a_1_23 + a_1_1·a_1_22 + a_1_03
- a_2_32 + c_2_6·a_1_02
- a_2_3·a_2_4 + a_2_3·a_1_22
- a_2_42 + a_2_4·a_1_22 + a_2_3·a_1_22 + a_1_24
- b_2_5·a_1_23 + b_2_5·a_1_03
- a_1_1·a_5_19 + a_1_0·a_5_19 + a_2_4·a_1_24
- a_2_4·b_2_52 + a_1_2·a_5_19 + b_2_52·a_1_22 + a_2_4·a_1_24 + c_2_6·a_1_24
- a_1_1·b_5_20 + a_2_3·b_2_52 + b_2_5·c_2_6·a_1_02 + a_2_3·c_2_6·a_1_22
- a_1_0·b_5_20 + a_2_3·b_2_52 + a_2_4·a_1_24 + b_2_5·c_2_6·a_1_02
- a_2_4·a_5_19 + b_2_52·a_1_03 + a_2_4·a_1_25 + a_2_4·c_2_6·a_1_23
+ a_2_3·c_2_6·a_1_03
- a_2_3·b_5_20 + b_2_52·a_1_03 + a_2_4·a_1_25 + b_2_52·c_2_6·a_1_0
+ a_2_3·b_2_5·c_2_6·a_1_0 + a_2_3·c_2_6·a_1_03
- a_6_22·a_1_1 + a_2_3·a_5_19 + a_1_02·a_5_19 + a_2_4·a_1_25 + a_2_3·b_2_5·c_2_6·a_1_0
+ a_2_4·c_2_6·a_1_23 + a_2_3·c_2_6·a_1_03
- a_6_22·a_1_0 + a_2_3·a_5_19 + a_1_02·a_5_19 + a_2_4·a_1_25 + a_2_3·b_2_5·c_2_6·a_1_0
- a_2_4·b_5_20 + a_6_22·a_1_2 + a_2_4·a_1_25 + a_2_4·b_2_5·c_2_6·a_1_2
- a_2_3·a_6_22 + a_2_3·a_1_0·a_5_19 + a_1_03·a_5_19 + c_2_6·a_1_0·a_5_19
+ a_2_4·c_2_6·a_1_24 + b_2_5·c_2_62·a_1_02
- a_2_4·a_6_22 + a_6_22·a_1_22 + a_2_3·b_2_52·a_1_02
- b_5_202 + b_2_54·a_1_02 + b_2_54·c_2_6 + b_2_52·c_2_62·a_1_02
+ a_2_4·c_2_62·a_1_24
- a_5_19·b_5_20 + b_2_52·a_1_2·b_5_20 + b_2_52·a_6_22 + b_2_52·a_1_0·a_5_19
+ a_2_3·b_2_53·a_1_02 + b_2_5·a_1_03·a_5_19 + a_2_3·b_2_53·c_2_6 + b_2_5·c_2_6·a_1_2·a_5_19 + b_2_5·c_2_6·a_1_0·a_5_19 + b_2_53·c_2_6·a_1_22 + c_2_6·a_1_03·a_5_19 + a_2_4·c_2_62·a_1_24
- a_5_192 + b_2_52·a_1_2·a_5_19 + b_2_52·a_1_0·a_5_19 + b_2_54·a_1_22
+ b_2_54·a_1_02 + a_2_3·b_2_5·a_1_0·a_5_19 + a_2_3·b_2_53·a_1_02 + c_8_39·a_1_02 + b_2_53·c_2_6·a_1_02 + a_2_3·c_2_6·a_1_0·a_5_19 + a_2_3·b_2_52·c_2_6·a_1_02 + b_2_52·c_2_62·a_1_02
- a_6_22·b_5_20 + a_2_3·b_2_52·a_5_19 + b_2_52·a_1_02·a_5_19
+ a_2_3·b_2_5·a_1_02·a_5_19 + b_2_52·c_2_6·a_5_19 + b_2_54·c_2_6·a_1_2 + b_2_5·c_2_6·a_6_22·a_1_2 + a_2_3·b_2_5·c_2_6·a_5_19 + b_2_5·c_2_6·a_1_02·a_5_19 + a_2_3·c_2_6·a_1_02·a_5_19 + b_2_53·c_2_62·a_1_0 + a_2_3·b_2_52·c_2_62·a_1_0 + c_2_62·a_1_22·a_5_19 + b_2_52·c_2_62·a_1_03 + a_2_4·c_2_62·a_1_25 + c_2_63·a_1_25
- a_6_22·a_5_19 + b_2_52·a_1_22·b_5_20 + a_2_3·b_2_52·a_5_19 + a_2_3·b_2_54·a_1_0
+ b_2_52·a_1_02·a_5_19 + b_2_54·a_1_03 + a_2_3·c_8_39·a_1_0 + a_2_3·b_2_5·c_2_6·a_5_19 + a_2_3·b_2_53·c_2_6·a_1_0 + c_8_39·a_1_03 + b_2_5·c_2_6·a_1_02·a_5_19 + b_2_53·c_2_6·a_1_03 + a_2_3·c_2_6·a_1_02·a_5_19 + a_2_3·b_2_52·c_2_62·a_1_0 + c_2_62·a_1_02·a_5_19
- a_6_222 + b_2_52·c_2_6·a_1_2·a_5_19 + b_2_52·c_2_6·a_1_0·a_5_19
+ b_2_54·c_2_6·a_1_02 + a_2_3·b_2_5·c_2_6·a_1_0·a_5_19 + a_2_3·b_2_53·c_2_6·a_1_02 + c_2_6·c_8_39·a_1_02 + b_2_53·c_2_62·a_1_02 + a_2_3·c_2_62·a_1_0·a_5_19 + a_2_3·b_2_52·c_2_62·a_1_02 + c_2_62·a_1_03·a_5_19
Data used for Benson′s test
- Benson′s completion test succeeded in degree 12.
- The completion test was perfect: It applied in the last degree in which a generator or relation was found.
- The following is a filter regular homogeneous system of parameters:
- c_2_6, a Duflot regular element of degree 2
- c_8_39, a Duflot regular element of degree 8
- b_2_5, an element of degree 2
- The Raw Filter Degree Type of that HSOP is [-1, -1, 7, 9].
- The filter degree type of any filter regular HSOP is [-1, -2, -3, -3].
Restriction maps
Restriction map to the greatest central el. ab. subgp., which is of rank 2
- a_1_0 → 0, an element of degree 1
- a_1_1 → 0, an element of degree 1
- a_1_2 → 0, an element of degree 1
- a_2_3 → 0, an element of degree 2
- a_2_4 → 0, an element of degree 2
- b_2_5 → 0, an element of degree 2
- c_2_6 → c_1_12, an element of degree 2
- a_5_19 → 0, an element of degree 5
- b_5_20 → 0, an element of degree 5
- a_6_22 → 0, an element of degree 6
- c_8_39 → c_1_08, an element of degree 8
Restriction map to a maximal el. ab. subgp. of rank 3
- a_1_0 → 0, an element of degree 1
- a_1_1 → 0, an element of degree 1
- a_1_2 → 0, an element of degree 1
- a_2_3 → 0, an element of degree 2
- a_2_4 → 0, an element of degree 2
- b_2_5 → c_1_22, an element of degree 2
- c_2_6 → c_1_12, an element of degree 2
- a_5_19 → 0, an element of degree 5
- b_5_20 → c_1_1·c_1_24, an element of degree 5
- a_6_22 → 0, an element of degree 6
- c_8_39 → c_1_12·c_1_26 + c_1_14·c_1_24 + c_1_04·c_1_24 + c_1_08, an element of degree 8
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