Simon King
David J. Green
Cohomology
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Cohomology of group number 1415 of order 128
General information on the group
- The group has 4 minimal generators and exponent 4.
- It is non-abelian.
- It has p-Rank 4.
- Its center has rank 3.
- It has 2 conjugacy classes of maximal elementary abelian subgroups, which are all of rank 4.
Structure of the cohomology ring
General information
- The cohomology ring is of dimension 4 and depth 3.
- The depth coincides with the Duflot bound.
- The Poincaré series is
t4 − t3 + t2 + 2·t + 1 |
| (t + 1)2 · (t − 1)4 · (t2 + 1) |
- The a-invariants are -∞,-∞,-∞,-5,-4. They were obtained using the filter regular HSOP of the Benson test.
Ring generators
The cohomology ring has 10 minimal generators of maximal degree 4:
- a_1_0, a nilpotent element of degree 1
- a_1_1, a nilpotent element of degree 1
- b_1_2, an element of degree 1
- b_1_3, an element of degree 1
- c_2_7, a Duflot regular element of degree 2
- c_2_8, a Duflot regular element of degree 2
- a_4_9, a nilpotent element of degree 4
- b_4_19, an element of degree 4
- b_4_20, an element of degree 4
- c_4_24, a Duflot regular element of degree 4
Ring relations
There are 18 minimal relations of maximal degree 8:
- a_1_12 + a_1_0·a_1_1 + a_1_02
- b_1_2·b_1_3 + a_1_1·b_1_2
- a_1_1·b_1_3 + a_1_0·b_1_3 + a_1_0·b_1_2 + a_1_12 + a_1_02
- a_1_03
- a_4_9·a_1_1 + c_2_8·a_1_02·b_1_2 + c_2_7·a_1_02·b_1_3 + c_2_7·a_1_02·b_1_2
+ c_2_8·a_1_02·a_1_1
- a_4_9·a_1_0 + c_2_8·a_1_02·b_1_3 + c_2_8·a_1_02·b_1_2 + c_2_7·a_1_02·b_1_3
+ c_2_8·a_1_02·a_1_1 + c_2_7·a_1_02·a_1_1
- b_4_19·b_1_2 + a_4_9·b_1_2 + c_2_7·a_1_1·b_1_22 + c_2_8·a_1_02·b_1_3
+ c_2_8·a_1_02·b_1_2 + c_2_8·a_1_02·a_1_1
- b_4_19·a_1_1 + a_4_9·b_1_3 + c_2_7·a_1_02·b_1_3 + c_2_7·a_1_02·b_1_2
+ c_2_7·a_1_02·a_1_1
- b_4_19·a_1_0 + a_4_9·b_1_3 + c_2_8·a_1_02·b_1_2 + c_2_8·a_1_02·a_1_1
- b_4_20·a_1_1 + a_4_9·b_1_2 + c_2_8·a_1_02·b_1_3 + c_2_8·a_1_02·b_1_2
+ c_2_7·a_1_02·b_1_2
- b_4_20·a_1_0 + c_2_7·a_1_02·b_1_3 + c_2_7·a_1_02·b_1_2 + c_2_7·a_1_02·a_1_1
- b_4_20·b_1_3 + a_1_0·b_1_34 + a_4_9·b_1_3 + a_4_9·b_1_2 + c_2_8·a_1_0·b_1_32
+ c_2_8·a_1_02·a_1_1 + c_2_7·a_1_02·a_1_1
- a_4_92
- a_1_0·b_1_37 + a_4_9·b_1_34 + a_4_9·b_4_19 + c_4_24·a_1_0·b_1_33
+ c_2_7·a_1_0·b_1_35 + c_2_82·a_1_0·b_1_33 + c_2_7·c_2_8·a_1_0·b_1_33 + c_2_72·a_1_0·b_1_33
- b_1_38 + b_4_19·b_1_34 + b_4_192 + c_4_24·b_1_34 + c_2_7·b_1_36
+ c_2_8·a_1_0·b_1_35 + c_2_7·a_1_0·b_1_35 + c_2_82·b_1_34 + c_2_7·c_2_8·b_1_34 + c_2_72·b_1_34
- a_4_9·b_4_20 + c_4_24·a_1_1·b_1_23 + c_2_7·a_1_1·b_1_25
+ c_2_7·c_2_8·a_1_1·b_1_23
- b_4_202 + a_4_9·b_1_24 + c_4_24·b_1_24 + c_2_7·b_1_26 + c_2_7·a_1_1·b_1_25
+ c_2_7·c_2_8·b_1_24
- b_4_19·b_4_20 + a_1_0·b_1_37 + c_4_24·a_1_1·b_1_23 + c_4_24·a_1_0·b_1_33
+ c_2_8·a_4_9·b_1_32 + c_2_7·a_1_1·b_1_25 + c_2_7·a_1_0·b_1_35 + c_2_7·a_4_9·b_1_22 + c_2_82·a_1_0·b_1_33 + c_2_7·c_2_8·a_1_1·b_1_23 + c_2_7·c_2_8·a_1_0·b_1_33 + c_2_72·a_1_0·b_1_33
Data used for Benson′s test
- Benson′s completion test succeeded in degree 8.
- 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_7, a Duflot regular element of degree 2
- c_2_8, a Duflot regular element of degree 2
- c_4_24, a Duflot regular element of degree 4
- b_1_32 + b_1_22, an element of degree 2
- The Raw Filter Degree Type of that HSOP is [-1, -1, -1, 3, 6].
- The filter degree type of any filter regular HSOP is [-1, -2, -3, -4, -4].
Restriction maps
Restriction map to the greatest central el. ab. subgp., which is of rank 3
- a_1_0 → 0, an element of degree 1
- a_1_1 → 0, an element of degree 1
- b_1_2 → 0, an element of degree 1
- b_1_3 → 0, an element of degree 1
- c_2_7 → c_1_12, an element of degree 2
- c_2_8 → c_1_22, an element of degree 2
- a_4_9 → 0, an element of degree 4
- b_4_19 → 0, an element of degree 4
- b_4_20 → 0, an element of degree 4
- c_4_24 → c_1_12·c_1_22 + c_1_04, an element of degree 4
Restriction map to a maximal el. ab. subgp. of rank 4
- a_1_0 → 0, an element of degree 1
- a_1_1 → 0, an element of degree 1
- b_1_2 → c_1_3, an element of degree 1
- b_1_3 → 0, an element of degree 1
- c_2_7 → c_1_1·c_1_3 + c_1_12, an element of degree 2
- c_2_8 → c_1_2·c_1_3 + c_1_22, an element of degree 2
- a_4_9 → 0, an element of degree 4
- b_4_19 → 0, an element of degree 4
- b_4_20 → c_1_02·c_1_32, an element of degree 4
- c_4_24 → c_1_1·c_1_33 + c_1_1·c_1_2·c_1_32 + c_1_1·c_1_22·c_1_3 + c_1_12·c_1_32
+ c_1_12·c_1_2·c_1_3 + c_1_12·c_1_22 + c_1_04, an element of degree 4
Restriction map to a maximal el. ab. subgp. of rank 4
- a_1_0 → 0, an element of degree 1
- a_1_1 → 0, an element of degree 1
- b_1_2 → 0, an element of degree 1
- b_1_3 → c_1_3, an element of degree 1
- c_2_7 → c_1_1·c_1_3 + c_1_12, an element of degree 2
- c_2_8 → c_1_2·c_1_3 + c_1_22, an element of degree 2
- a_4_9 → 0, an element of degree 4
- b_4_19 → c_1_34 + c_1_2·c_1_33 + c_1_22·c_1_32 + c_1_1·c_1_33 + c_1_12·c_1_32
+ c_1_02·c_1_32, an element of degree 4
- b_4_20 → 0, an element of degree 4
- c_4_24 → c_1_34 + c_1_2·c_1_33 + c_1_22·c_1_32 + c_1_1·c_1_2·c_1_32
+ c_1_1·c_1_22·c_1_3 + c_1_12·c_1_2·c_1_3 + c_1_12·c_1_22 + c_1_02·c_1_32 + c_1_04, an element of degree 4
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