Simon King
David J. Green
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Cohomology of group number 1814 of order 128
General information on the group
- The group has 4 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
t7 − t6 − t4 − t2 − t − 1 |
| (t − 1)3 · (t2 + 1)2 · (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
- b_1_3, an element of degree 1
- a_3_10, a nilpotent element of degree 3
- b_4_12, an element of degree 4
- c_4_13, a Duflot regular element of degree 4
- a_5_13, a nilpotent element of degree 5
- a_6_23, a nilpotent element of degree 6
- a_8_23, a nilpotent element of degree 8
- c_8_31, a Duflot regular element of degree 8
Ring relations
There are 30 minimal relations of maximal degree 16:
- a_1_12 + a_1_0·a_1_1 + a_1_02
- a_1_0·a_1_2
- a_1_03
- a_1_1·b_1_32 + a_1_1·a_1_2·b_1_3 + a_1_02·b_1_3 + a_1_23
- a_1_0·a_3_10
- a_1_23·b_1_32 + a_1_24·b_1_3 + a_1_1·a_1_23·b_1_3 + a_1_25
- b_4_12·a_1_1 + a_1_1·b_1_3·a_3_10 + a_1_22·a_3_10 + a_1_1·a_1_2·a_3_10
- b_1_32·a_3_10 + b_4_12·a_1_2 + a_1_1·b_1_3·a_3_10 + a_1_22·a_3_10 + a_1_25
- a_3_102 + c_4_13·a_1_22
- a_1_2·a_5_13 + b_4_12·a_1_22 + a_1_22·b_1_3·a_3_10 + a_1_1·a_1_2·b_1_3·a_3_10
+ a_1_25·b_1_3
- b_4_12·a_3_10 + a_1_24·a_3_10 + c_4_13·a_1_2·b_1_32 + c_4_13·a_1_1·a_1_2·b_1_3
+ c_4_13·a_1_23
- a_1_02·a_5_13 + b_4_12·a_1_23 + a_1_23·b_1_3·a_3_10
- a_6_23·a_1_1 + b_4_12·a_1_23 + c_4_13·a_1_0·a_1_1·b_1_3 + c_4_13·a_1_02·b_1_3
- a_6_23·a_1_0 + a_1_0·a_1_1·a_5_13 + b_4_12·a_1_23 + a_1_23·b_1_3·a_3_10
+ a_1_1·a_1_22·b_1_3·a_3_10 + c_4_13·a_1_0·a_1_1·b_1_3
- b_4_122 + a_1_25·a_3_10 + c_4_13·b_1_34 + c_4_13·a_1_24
- a_3_10·a_5_13 + a_1_24·b_1_3·a_3_10 + c_4_13·a_1_22·b_1_32 + c_4_13·a_1_23·b_1_3
+ c_4_13·a_1_24
- a_1_0·b_1_32·a_5_13 + a_1_0·a_1_1·b_1_3·a_5_13 + a_6_23·a_1_22
+ a_1_24·b_1_3·a_3_10 + c_4_13·a_1_1·a_1_22·b_1_3
- a_8_23·a_1_1 + a_1_25·b_1_3·a_3_10 + c_4_13·a_1_1·b_1_3·a_3_10
+ c_4_13·a_1_1·a_1_2·a_3_10 + c_4_13·a_1_24·b_1_3 + c_4_13·a_1_1·a_1_23·b_1_3 + c_4_13·a_1_25
- a_8_23·a_1_0 + a_6_23·a_1_22·b_1_3 + c_4_13·a_1_1·a_1_23·b_1_3 + c_4_13·a_1_25
- a_8_23·a_1_2 + a_6_23·a_3_10 + b_4_12·a_1_22·b_1_33 + a_6_23·a_1_22·b_1_3
+ c_4_13·a_1_2·b_1_3·a_3_10 + c_4_13·a_1_1·b_1_3·a_3_10 + c_4_13·a_1_22·a_3_10 + c_4_13·a_1_24·b_1_3 + c_4_13·a_1_1·a_1_23·b_1_3
- b_4_12·a_1_0·a_5_13 + a_6_23·a_1_2·a_3_10 + c_4_13·a_1_1·a_1_2·b_1_3·a_3_10
+ c_4_13·a_1_25·b_1_3
- a_5_132 + c_8_31·a_1_02 + c_4_13·a_1_22·b_1_34 + c_4_13·a_1_1·a_1_22·a_3_10
+ c_4_13·a_1_25·b_1_3
- b_1_35·a_5_13 + a_8_23·b_1_32 + b_4_12·a_6_23 + a_1_22·b_1_38
+ a_6_23·a_1_2·b_1_33 + b_4_12·a_1_22·b_1_34 + a_6_23·a_1_22·b_1_32 + c_4_13·a_1_0·b_1_35 + b_4_12·c_4_13·a_1_2·b_1_3 + c_4_13·a_1_22·b_1_34 + b_4_12·c_4_13·a_1_22 + c_4_13·a_1_23·a_3_10 + c_4_13·a_1_25·b_1_3
- a_6_23·a_5_13 + b_4_12·a_6_23·a_1_2 + c_4_13·a_1_1·b_1_3·a_5_13 + c_8_31·a_1_02·a_1_1
+ c_4_13·a_1_23·b_1_3·a_3_10 + c_4_13·a_1_24·a_3_10
- a_8_23·a_3_10 + a_6_23·a_1_2·b_1_3·a_3_10 + c_4_13·a_1_22·b_1_35
+ c_4_13·a_6_23·a_1_2 + b_4_12·c_4_13·a_1_23 + c_4_13·a_1_1·a_1_22·b_1_3·a_3_10 + c_4_132·a_1_22·b_1_3 + c_4_132·a_1_1·a_1_2·b_1_3 + c_4_132·a_1_23
- a_6_232 + b_4_12·a_1_22·b_1_36 + c_4_13·a_1_22·b_1_36
+ c_4_132·a_1_02·a_1_1·b_1_3 + c_4_132·a_1_1·a_1_23
- b_4_12·b_1_33·a_5_13 + b_4_12·a_8_23 + b_4_12·a_1_22·b_1_36
+ b_4_12·a_6_23·a_1_2·b_1_3 + b_4_12·a_6_23·a_1_22 + c_4_13·a_6_23·b_1_32 + b_4_12·c_4_13·a_1_0·b_1_33 + c_4_13·a_1_22·b_1_36 + b_4_12·c_4_13·a_1_22·b_1_32 + c_4_13·a_1_0·a_1_1·b_1_3·a_5_13 + b_4_12·c_4_13·a_1_23·b_1_3 + c_4_132·a_1_2·b_1_33 + c_4_132·a_1_22·b_1_32 + c_4_132·a_1_1·a_1_22·b_1_3 + c_4_132·a_1_02·a_1_1·b_1_3 + c_4_132·a_1_24 + c_4_132·a_1_1·a_1_23
- a_8_23·a_5_13 + b_4_12·a_6_23·a_1_22·b_1_3 + c_4_13·a_1_22·b_1_37
+ c_4_13·a_6_23·a_1_2·b_1_32 + c_4_13·a_6_23·a_1_22·b_1_3 + c_8_31·a_1_1·a_1_23·b_1_3 + c_4_132·a_1_22·b_1_33 + c_4_132·a_1_24·b_1_3 + c_4_132·a_1_25
- a_6_23·a_8_23 + b_4_12·a_6_23·a_1_2·b_1_33 + a_6_23·a_1_22·b_1_36
+ b_4_12·a_6_23·a_1_22·b_1_32 + c_4_13·a_1_22·b_1_38 + c_4_13·a_6_23·b_1_3·a_3_10 + b_4_12·c_4_13·a_1_22·b_1_34 + c_4_13·a_6_23·a_1_2·a_3_10 + c_4_13·a_6_23·a_1_22·b_1_32 + c_4_132·a_1_25·b_1_3
- a_8_232 + c_4_13·a_1_22·b_1_310 + b_4_12·c_4_13·a_1_22·b_1_36
+ c_4_132·a_1_22·b_1_36 + c_4_133·a_1_22·b_1_32 + c_4_133·a_1_24
Data used for Benson′s test
- Benson′s completion test succeeded in degree 16.
- 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_4_13, a Duflot regular element of degree 4
- c_8_31, a Duflot regular element of degree 8
- b_1_32, an element of degree 2
- The Raw Filter Degree Type of that HSOP is [-1, -1, 9, 11].
- 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
- b_1_3 → 0, an element of degree 1
- a_3_10 → 0, an element of degree 3
- b_4_12 → 0, an element of degree 4
- c_4_13 → c_1_04, an element of degree 4
- a_5_13 → 0, an element of degree 5
- a_6_23 → 0, an element of degree 6
- a_8_23 → 0, an element of degree 8
- c_8_31 → c_1_18, 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
- b_1_3 → c_1_2, an element of degree 1
- a_3_10 → 0, an element of degree 3
- b_4_12 → c_1_02·c_1_22, an element of degree 4
- c_4_13 → c_1_04, an element of degree 4
- a_5_13 → 0, an element of degree 5
- a_6_23 → 0, an element of degree 6
- a_8_23 → 0, an element of degree 8
- c_8_31 → c_1_14·c_1_24 + c_1_18 + c_1_06·c_1_22, an element of degree 8
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