Simon King
David J. Green
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Cohomology of group number 1786 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 4.
- Its center has rank 2.
- It has 3 conjugacy classes of maximal elementary abelian subgroups, which are of rank 3, 3 and 4, respectively.
Structure of the cohomology ring
General information
- The cohomology ring is of dimension 4 and depth 2.
- The depth coincides with the Duflot bound.
- The Poincaré series is
( − 1) · (t6 − t5 − t4 + t3 − 1) |
| (t − 1)4 · (t2 + 1) · (t4 + 1) |
- The a-invariants are -∞,-∞,-6,-4,-4. 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:
- b_1_0, an element of degree 1
- b_1_1, an element of degree 1
- b_1_2, an element of degree 1
- b_1_3, an element of degree 1
- c_2_8, a Duflot regular element of degree 2
- a_4_8, a nilpotent element of degree 4
- b_5_29, an element of degree 5
- b_5_30, an element of degree 5
- b_5_31, an element of degree 5
- a_8_41, a nilpotent element of degree 8
- c_8_77, a Duflot regular element of degree 8
Ring relations
There are 29 minimal relations of maximal degree 16:
- b_1_12 + b_1_0·b_1_1
- b_1_0·b_1_2
- b_1_1·b_1_22 + b_1_0·b_1_32 + b_1_02·b_1_1
- b_1_0·b_1_34 + b_1_04·b_1_1
- a_4_8·b_1_0
- a_4_8·b_1_1
- b_1_2·b_5_29
- b_1_1·b_5_29 + b_1_0·b_5_30 + b_1_05·b_1_1
- b_1_1·b_5_30 + b_1_1·b_5_29 + b_1_05·b_1_1
- b_1_1·b_5_29 + b_1_0·b_5_31 + b_1_05·b_1_1
- b_1_2·b_5_30 + b_1_23·b_1_33 + b_1_1·b_5_31 + b_1_1·b_5_29 + b_1_05·b_1_1
+ a_4_8·b_1_32 + c_2_8·b_1_1·b_1_2·b_1_32
- b_1_32·b_5_29 + b_1_1·b_1_2·b_5_31 + b_1_02·b_5_30 + b_1_06·b_1_1
- a_4_82
- a_4_8·b_5_29
- a_4_8·b_5_30 + a_4_8·b_1_22·b_1_33
- b_1_1·b_1_33·b_5_31 + b_1_1·b_1_2·b_1_32·b_5_31 + b_1_03·b_1_3·b_5_30
+ a_8_41·b_1_2 + a_4_8·b_5_31 + a_4_8·b_1_35 + a_4_8·b_1_2·b_1_34 + a_4_8·b_1_24·b_1_3 + c_2_8·b_1_1·b_1_3·b_5_31 + c_2_8·b_1_1·b_1_36 + c_2_8·b_1_1·b_1_2·b_1_35 + c_2_8·b_1_0·b_1_3·b_5_30 + c_2_8·b_1_06·b_1_1 + c_2_8·a_4_8·b_1_33 + c_2_8·a_4_8·b_1_22·b_1_3 + c_2_82·a_4_8·b_1_2
- a_8_41·b_1_0 + c_2_8·b_1_0·b_1_3·b_5_30 + c_2_8·b_1_0·b_1_3·b_5_29
+ c_2_8·b_1_05·b_1_1·b_1_3 + c_2_82·b_1_03·b_1_1·b_1_3 + c_2_82·b_1_04·b_1_1
- a_8_41·b_1_1 + c_2_82·b_1_03·b_1_1·b_1_3 + c_2_82·b_1_04·b_1_1
- b_5_302 + b_5_29·b_5_30 + b_1_24·b_1_36 + b_1_05·b_5_30
- b_5_302 + b_5_29·b_5_31 + b_1_24·b_1_36 + b_1_05·b_5_30
+ c_2_8·b_1_1·b_1_2·b_1_36
- b_5_292 + b_1_09·b_1_1 + c_8_77·b_1_02 + c_2_8·b_1_03·b_5_29
+ c_2_82·b_1_05·b_1_1 + c_2_83·b_1_03·b_1_1
- b_5_302 + b_1_24·b_1_36 + c_8_77·b_1_0·b_1_1 + c_2_8·b_1_03·b_5_30
+ c_2_8·b_1_07·b_1_1 + c_2_82·b_1_05·b_1_1 + c_2_83·b_1_03·b_1_1
- b_5_312 + b_5_302 + b_1_2·b_1_34·b_5_31 + b_1_23·b_1_32·b_5_31 + b_1_23·b_1_37
+ b_1_24·b_1_36 + b_1_25·b_5_31 + b_1_25·b_1_35 + b_1_26·b_1_34 + b_1_27·b_1_33 + b_1_29·b_1_3 + a_8_41·b_1_2·b_1_3 + a_8_41·b_1_22 + a_4_8·b_1_3·b_5_31 + a_4_8·b_1_2·b_5_31 + a_4_8·b_1_25·b_1_3 + a_4_8·b_1_26 + c_8_77·b_1_22 + c_2_8·b_1_38 + c_2_8·b_1_22·b_1_36 + c_2_8·b_1_23·b_5_31 + c_2_8·b_1_24·b_1_34 + c_2_8·b_1_25·b_1_33 + c_2_8·b_1_26·b_1_32 + c_2_8·b_1_1·b_1_32·b_5_31 + c_2_8·b_1_1·b_1_37 + c_2_8·b_1_1·b_1_2·b_1_3·b_5_31 + c_2_8·b_1_1·b_1_2·b_1_36 + c_2_8·b_1_03·b_5_30 + c_2_8·b_1_06·b_1_1·b_1_3 + c_2_8·b_1_07·b_1_1 + c_2_8·a_4_8·b_1_34 + c_2_8·a_4_8·b_1_2·b_1_33 + c_2_8·a_4_8·b_1_23·b_1_3 + c_2_82·a_4_8·b_1_2·b_1_3 + c_2_82·a_4_8·b_1_22 + c_2_83·b_1_22·b_1_32
- b_5_30·b_5_31 + b_5_302 + b_1_35·b_5_30 + b_1_22·b_1_33·b_5_31 + b_1_22·b_1_38
+ b_1_24·b_1_36 + b_1_04·b_1_3·b_5_30 + a_8_41·b_1_32 + a_4_8·b_1_36 + a_4_8·b_1_23·b_1_33 + c_8_77·b_1_1·b_1_2 + c_2_8·b_1_33·b_5_30 + c_2_8·b_1_22·b_1_36 + c_2_8·b_1_1·b_1_32·b_5_31 + c_2_8·b_1_1·b_1_2·b_1_3·b_5_31 + c_2_8·b_1_1·b_1_2·b_1_36 + c_2_8·b_1_02·b_1_3·b_5_30 + c_2_8·b_1_03·b_5_30 + c_2_8·a_4_8·b_1_2·b_1_33 + c_2_82·b_1_1·b_1_35 + c_2_82·b_1_05·b_1_1 + c_2_82·a_4_8·b_1_32 + c_2_83·b_1_1·b_1_2·b_1_32
- a_4_8·a_8_41
- a_8_41·b_5_30 + a_8_41·b_1_22·b_1_33 + c_2_82·b_1_03·b_1_3·b_5_30
+ c_2_82·b_1_04·b_5_30
- a_8_41·b_5_29 + c_2_8·c_8_77·b_1_0·b_1_1·b_1_3 + c_2_8·c_8_77·b_1_02·b_1_3
+ c_2_82·b_1_03·b_1_3·b_5_29 + c_2_82·b_1_04·b_5_30 + c_2_82·b_1_08·b_1_1
- b_1_38·b_5_30 + b_1_22·b_1_311 + b_1_08·b_5_30 + a_8_41·b_5_31 + a_8_41·b_5_30
+ a_8_41·b_1_35 + a_4_8·b_1_39 + a_4_8·b_1_2·b_1_33·b_5_31 + a_4_8·b_1_2·b_1_38 + a_4_8·b_1_22·b_1_32·b_5_31 + a_4_8·b_1_23·b_1_3·b_5_31 + a_4_8·b_1_23·b_1_36 + a_4_8·b_1_24·b_5_31 + a_4_8·b_1_24·b_1_35 + a_4_8·b_1_26·b_1_33 + a_4_8·b_1_28·b_1_3 + c_8_77·b_1_1·b_1_2·b_1_33 + c_2_8·b_1_36·b_5_30 + c_2_8·b_1_22·b_1_39 + c_2_8·b_1_1·b_1_310 + c_2_8·b_1_06·b_5_30 + c_2_8·b_1_010·b_1_1 + a_4_8·c_8_77·b_1_2 + c_2_8·a_8_41·b_1_33 + c_2_8·a_8_41·b_1_2·b_1_32 + c_2_8·a_8_41·b_1_22·b_1_3 + c_2_8·a_4_8·b_1_32·b_5_31 + c_2_8·a_4_8·b_1_2·b_1_36 + c_2_8·a_4_8·b_1_22·b_5_31 + c_2_8·a_4_8·b_1_22·b_1_35 + c_2_8·a_4_8·b_1_23·b_1_34 + c_2_8·c_8_77·b_1_1·b_1_2·b_1_3 + c_2_82·b_1_34·b_5_30 + c_2_82·b_1_22·b_1_37 + c_2_82·b_1_1·b_1_38 + c_2_82·b_1_1·b_1_2·b_1_32·b_5_31 + c_2_82·b_1_04·b_5_30 + c_2_82·b_1_07·b_1_1·b_1_3 + c_2_82·a_8_41·b_1_2 + c_2_82·a_4_8·b_1_35 + c_2_82·a_4_8·b_1_2·b_1_34 + c_2_82·a_4_8·b_1_23·b_1_32 + c_2_82·a_4_8·b_1_24·b_1_3 + c_2_83·b_1_1·b_1_3·b_5_31 + c_2_83·b_1_0·b_1_3·b_5_30 + c_2_83·b_1_05·b_1_1·b_1_3 + c_2_83·b_1_06·b_1_1 + c_2_84·b_1_1·b_1_2·b_1_33 + c_2_84·a_4_8·b_1_2
- a_8_412
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_2_8, a Duflot regular element of degree 2
- c_8_77, a Duflot regular element of degree 8
- b_1_32 + b_1_2·b_1_3 + b_1_22 + b_1_1·b_1_3 + b_1_02, an element of degree 2
- b_1_2·b_1_32 + b_1_22·b_1_3 + b_1_0·b_1_32 + b_1_02·b_1_1, an element of degree 3
- The Raw Filter Degree Type of that HSOP is [-1, -1, 4, 8, 11].
- 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 2
- b_1_0 → 0, an element of degree 1
- b_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_8 → c_1_02, an element of degree 2
- a_4_8 → 0, an element of degree 4
- b_5_29 → 0, an element of degree 5
- b_5_30 → 0, an element of degree 5
- b_5_31 → 0, an element of degree 5
- a_8_41 → 0, an element of degree 8
- c_8_77 → c_1_18, an element of degree 8
Restriction map to a maximal el. ab. subgp. of rank 3
- b_1_0 → c_1_2, an element of degree 1
- b_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_8 → c_1_0·c_1_2 + c_1_02, an element of degree 2
- a_4_8 → 0, an element of degree 4
- b_5_29 → c_1_12·c_1_23 + c_1_14·c_1_2, an element of degree 5
- b_5_30 → 0, an element of degree 5
- b_5_31 → 0, an element of degree 5
- a_8_41 → 0, an element of degree 8
- c_8_77 → c_1_14·c_1_24 + c_1_18 + c_1_0·c_1_12·c_1_25 + c_1_0·c_1_14·c_1_23
+ c_1_02·c_1_12·c_1_24 + c_1_02·c_1_14·c_1_22, an element of degree 8
Restriction map to a maximal el. ab. subgp. of rank 3
- b_1_0 → c_1_2, an element of degree 1
- b_1_1 → c_1_2, an element of degree 1
- b_1_2 → 0, an element of degree 1
- b_1_3 → c_1_2, an element of degree 1
- c_2_8 → c_1_0·c_1_2 + c_1_02, an element of degree 2
- a_4_8 → 0, an element of degree 4
- b_5_29 → c_1_25 + c_1_12·c_1_23 + c_1_14·c_1_2 + c_1_0·c_1_24 + c_1_02·c_1_23, an element of degree 5
- b_5_30 → c_1_12·c_1_23 + c_1_14·c_1_2 + c_1_0·c_1_24 + c_1_02·c_1_23, an element of degree 5
- b_5_31 → c_1_12·c_1_23 + c_1_14·c_1_2 + c_1_0·c_1_24 + c_1_02·c_1_23, an element of degree 5
- a_8_41 → 0, an element of degree 8
- c_8_77 → c_1_14·c_1_24 + c_1_18 + c_1_0·c_1_27 + c_1_0·c_1_12·c_1_25
+ c_1_0·c_1_14·c_1_23 + c_1_02·c_1_12·c_1_24 + c_1_02·c_1_14·c_1_22 + c_1_03·c_1_25 + c_1_05·c_1_23 + c_1_06·c_1_22, an element of degree 8
Restriction map to a maximal el. ab. subgp. of rank 4
- b_1_0 → 0, an element of degree 1
- b_1_1 → 0, an element of degree 1
- b_1_2 → c_1_2, an element of degree 1
- b_1_3 → c_1_3, an element of degree 1
- c_2_8 → c_1_0·c_1_2 + c_1_02, an element of degree 2
- a_4_8 → 0, an element of degree 4
- b_5_29 → 0, an element of degree 5
- b_5_30 → c_1_22·c_1_33, an element of degree 5
- b_5_31 → c_1_2·c_1_34 + c_1_22·c_1_33 + c_1_24·c_1_3 + c_1_12·c_1_23 + c_1_14·c_1_2
+ c_1_0·c_1_34 + c_1_02·c_1_2·c_1_32, an element of degree 5
- a_8_41 → 0, an element of degree 8
- c_8_77 → c_1_23·c_1_35 + c_1_25·c_1_33 + c_1_26·c_1_32 + c_1_12·c_1_22·c_1_34
+ c_1_12·c_1_24·c_1_32 + c_1_12·c_1_26 + c_1_14·c_1_34 + c_1_14·c_1_22·c_1_32 + c_1_18 + c_1_0·c_1_23·c_1_34 + c_1_0·c_1_25·c_1_32 + c_1_0·c_1_26·c_1_3 + c_1_0·c_1_12·c_1_25 + c_1_0·c_1_14·c_1_23 + c_1_02·c_1_25·c_1_3 + c_1_02·c_1_12·c_1_24 + c_1_02·c_1_14·c_1_22 + c_1_03·c_1_2·c_1_34 + c_1_04·c_1_34 + c_1_05·c_1_2·c_1_32 + c_1_06·c_1_32, an element of degree 8
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