Simon King
David J. Green
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Cohomology of group number 136 of order 128
General information on the group
- The group has 2 minimal generators and exponent 8.
- It is non-abelian.
- It has p-Rank 3.
- Its center has rank 1.
- It has 2 conjugacy classes of maximal elementary abelian subgroups, which are of rank 2 and 3, respectively.
Structure of the cohomology ring
General information
- The cohomology ring is of dimension 3 and depth 2.
- The depth exceeds the Duflot bound, which is 1.
- The Poincaré series is
(t2 − t + 1) · (t5 + t4 − t2 − t − 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 9 minimal generators of maximal degree 8:
- a_1_0, a nilpotent element of degree 1
- b_1_1, an element of degree 1
- a_2_2, a nilpotent element of degree 2
- b_2_1, an element of degree 2
- b_2_3, an element of degree 2
- b_3_5, an element of degree 3
- a_5_7, a nilpotent element of degree 5
- b_6_10, an element of degree 6
- c_8_14, a Duflot regular element of degree 8
Ring relations
There are 22 minimal relations of maximal degree 12:
- a_1_02
- a_1_0·b_1_1
- a_2_2·a_1_0
- b_2_1·b_1_1
- a_2_2·b_2_1
- a_1_0·b_3_5
- b_1_1·b_3_5 + b_2_3·b_1_12 + a_2_22
- b_2_1·b_2_3·a_1_0
- b_2_32·b_1_1 + b_2_32·a_1_0 + a_2_2·b_2_3·b_1_1 + a_2_22·b_1_1
- a_2_2·b_3_5 + a_2_2·b_2_3·b_1_1
- b_3_52 + b_2_1·b_2_32 + a_2_2·b_2_3·b_1_12 + a_2_2·b_2_32 + a_2_22·b_1_12
+ a_2_22·b_2_3
- a_1_0·a_5_7
- b_1_1·a_5_7 + a_2_2·b_2_3·b_1_12 + a_2_22·b_2_3
- a_2_2·a_5_7 + a_2_22·b_2_3·b_1_1
- b_6_10·a_1_0 + b_2_1·a_5_7
- b_6_10·b_1_1 + a_2_22·b_1_13 + a_2_22·b_2_3·b_1_1
- b_3_5·a_5_7 + a_2_22·b_2_3·b_1_12
- a_2_2·b_6_10
- b_2_1·b_2_3·a_5_7
- a_5_72
- b_6_10·a_5_7 + b_2_13·a_5_7 + b_2_1·c_8_14·a_1_0
- b_6_102 + b_2_12·b_2_3·b_6_10 + b_2_12·b_2_34 + b_2_13·b_6_10 + b_2_13·b_2_33
+ b_2_14·b_2_32 + b_2_12·c_8_14
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_8_14, a Duflot regular element of degree 8
- b_1_12 + b_2_3 + b_2_1, an element of degree 2
- b_3_5, an element of degree 3
- The Raw Filter Degree Type of that HSOP is [-1, -1, 7, 10].
- 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 1
- a_1_0 → 0, an element of degree 1
- b_1_1 → 0, an element of degree 1
- a_2_2 → 0, an element of degree 2
- b_2_1 → 0, an element of degree 2
- b_2_3 → 0, an element of degree 2
- b_3_5 → 0, an element of degree 3
- a_5_7 → 0, an element of degree 5
- b_6_10 → 0, an element of degree 6
- c_8_14 → c_1_08, an element of degree 8
Restriction map to a maximal el. ab. subgp. of rank 2
- a_1_0 → 0, an element of degree 1
- b_1_1 → c_1_1, an element of degree 1
- a_2_2 → 0, an element of degree 2
- b_2_1 → 0, an element of degree 2
- b_2_3 → 0, an element of degree 2
- b_3_5 → 0, an element of degree 3
- a_5_7 → 0, an element of degree 5
- b_6_10 → 0, an element of degree 6
- c_8_14 → c_1_04·c_1_14 + 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
- b_1_1 → 0, an element of degree 1
- a_2_2 → 0, an element of degree 2
- b_2_1 → c_1_12, an element of degree 2
- b_2_3 → c_1_22 + c_1_1·c_1_2, an element of degree 2
- b_3_5 → c_1_1·c_1_22 + c_1_12·c_1_2, an element of degree 3
- a_5_7 → 0, an element of degree 5
- b_6_10 → c_1_14·c_1_22 + c_1_15·c_1_2 + c_1_0·c_1_13·c_1_22 + c_1_0·c_1_14·c_1_2
+ c_1_02·c_1_12·c_1_22 + c_1_02·c_1_13·c_1_2 + c_1_02·c_1_14 + c_1_04·c_1_12, an element of degree 6
- c_8_14 → c_1_28 + c_1_12·c_1_26 + c_1_13·c_1_25 + c_1_14·c_1_24 + c_1_15·c_1_23
+ c_1_17·c_1_2 + c_1_0·c_1_13·c_1_24 + c_1_0·c_1_16·c_1_2 + c_1_02·c_1_16 + c_1_04·c_1_24 + c_1_04·c_1_13·c_1_2 + c_1_08, an element of degree 8
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