Simon King
David J. Green
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Cohomology of group number 864 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 1.
- It has 4 conjugacy classes of maximal elementary abelian subgroups, which are all of rank 3.
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
( − 1) · (t5 + t2 + 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 13 minimal generators of maximal degree 8:
- a_1_0, a nilpotent element of degree 1
- b_1_1, an element of degree 1
- b_1_2, an element of degree 1
- b_2_4, an element of degree 2
- b_2_5, an element of degree 2
- b_3_8, an element of degree 3
- b_3_9, an element of degree 3
- b_4_13, an element of degree 4
- b_5_17, an element of degree 5
- b_5_18, an element of degree 5
- b_6_24, an element of degree 6
- b_7_30, an element of degree 7
- c_8_37, a Duflot regular element of degree 8
Ring relations
There are 47 minimal relations of maximal degree 14:
- a_1_02
- a_1_0·b_1_1
- a_1_0·b_1_22 + b_2_4·a_1_0
- b_2_4·b_1_1 + b_2_5·a_1_0
- b_2_5·b_1_1 + b_2_4·b_1_1
- b_1_12·b_1_22
- b_2_52 + b_2_4·b_1_22 + b_2_4·b_2_5 + b_2_42
- a_1_0·b_3_8
- b_2_4·b_1_22 + b_2_42 + a_1_0·b_3_9
- b_1_1·b_3_9 + b_1_1·b_3_8 + b_2_5·b_1_22 + b_2_52 + b_2_4·b_1_22 + b_2_42
- b_1_1·b_1_24 + b_2_5·b_3_8 + b_2_4·b_2_5·a_1_0
- b_2_4·b_3_8
- b_1_22·b_3_9 + b_1_1·b_1_24 + b_2_4·b_3_9 + b_2_4·b_2_5·a_1_0
- b_4_13·a_1_0 + b_2_4·b_2_5·a_1_0
- b_3_8·b_3_9 + b_3_82 + b_1_26 + b_2_5·b_1_24 + b_2_42·b_2_5 + b_2_43
+ b_2_4·a_1_0·b_3_9
- b_3_92 + b_3_82 + b_1_26 + b_2_4·b_4_13 + b_2_42·b_2_5 + b_2_43 + b_2_4·a_1_0·b_3_9
- b_3_82 + b_1_26 + b_4_13·b_1_12 + b_2_43 + b_2_4·a_1_0·b_3_9
- a_1_0·b_5_17
- a_1_0·b_5_18 + b_2_5·a_1_0·b_3_9 + b_2_4·a_1_0·b_3_9
- b_1_1·b_5_18 + b_1_1·b_5_17 + b_1_13·b_3_8 + b_2_5·b_1_24 + b_2_42·b_2_5
- b_4_13·b_1_1·b_1_22 + b_2_5·b_5_17 + b_2_5·b_1_22·b_3_8 + b_2_4·b_5_17
+ b_2_42·b_2_5·a_1_0
- b_4_13·b_1_1·b_1_22 + b_2_5·b_5_18
- b_1_22·b_5_18 + b_1_22·b_5_17 + b_1_24·b_3_8 + b_2_5·b_5_17 + b_2_5·b_1_22·b_3_8
+ b_2_4·b_5_18
- b_6_24·a_1_0
- b_1_22·b_5_17 + b_1_24·b_3_8 + b_1_12·b_5_17 + b_1_14·b_3_8 + b_6_24·b_1_1
+ b_4_13·b_3_8 + b_2_5·b_5_17
- b_3_8·b_5_18 + b_3_8·b_5_17 + b_1_28 + b_4_13·b_1_14 + b_2_5·b_4_13·b_1_22
+ b_2_4·b_2_5·b_4_13 + b_2_44 + b_2_4·b_2_5·a_1_0·b_3_9
- b_3_9·b_5_17 + b_3_8·b_5_17 + b_1_28 + b_4_13·b_1_24 + b_2_5·b_6_24
+ b_2_4·b_2_5·b_4_13 + b_2_42·b_4_13 + b_2_43·b_2_5 + b_2_44 + b_2_42·a_1_0·b_3_9
- b_3_9·b_5_18 + b_3_9·b_5_17 + b_4_13·b_1_14 + b_2_5·b_1_26 + b_2_4·b_6_24
+ b_2_42·b_4_13
- b_1_13·b_5_17 + b_1_15·b_3_8 + b_6_24·b_1_12 + b_4_13·b_1_1·b_3_8
+ b_2_5·b_4_13·b_1_22 + b_2_4·b_2_5·b_4_13 + b_2_4·b_2_5·a_1_0·b_3_9
- a_1_0·b_7_30
- b_3_8·b_5_17 + b_1_28 + b_1_1·b_7_30 + b_1_13·b_5_17 + b_1_15·b_3_8 + b_4_13·b_1_24
+ b_4_13·b_1_1·b_3_8 + b_4_13·b_1_14 + b_2_5·b_1_26 + b_2_42·b_4_13 + b_2_43·b_2_5 + b_2_44 + b_2_4·b_2_5·a_1_0·b_3_9
- b_6_24·b_1_1·b_1_22 + b_2_5·b_7_30 + b_2_5·b_4_13·b_3_9 + b_2_42·b_5_17
+ b_2_42·b_2_5·b_3_9 + b_2_43·b_2_5·a_1_0
- b_1_22·b_7_30 + b_6_24·b_3_9 + b_6_24·b_3_8 + b_4_13·b_5_18 + b_4_13·b_5_17
+ b_4_13·b_1_22·b_3_8 + b_4_13·b_1_12·b_3_8 + b_2_5·b_1_24·b_3_8 + b_2_5·b_4_13·b_3_9 + b_2_5·b_4_13·b_3_8 + b_2_4·b_4_13·b_3_9
- b_2_5·b_4_13·b_3_9 + b_2_4·b_7_30 + b_2_42·b_5_17 + b_2_42·b_2_5·b_3_9
+ b_2_43·b_2_5·a_1_0
- b_1_12·b_7_30 + b_6_24·b_3_9 + b_6_24·b_1_1·b_1_22 + b_6_24·b_1_13 + b_4_13·b_5_18
+ b_4_13·b_5_17 + b_4_13·b_1_22·b_3_8 + b_4_13·b_1_12·b_3_8 + b_4_132·b_1_1 + b_2_4·b_4_13·b_3_9 + b_2_42·b_5_17 + b_2_42·b_2_5·b_3_9
- b_5_182 + b_5_172 + b_1_210 + b_4_13·b_1_16 + b_2_4·b_4_132
+ b_2_42·b_2_5·b_4_13 + b_2_43·b_4_13 + b_2_44·b_2_5 + b_2_45 + b_2_43·a_1_0·b_3_9
- b_5_17·b_5_18 + b_5_172 + b_1_210 + b_6_24·b_1_1·b_3_8 + b_4_13·b_1_26
+ b_4_13·b_1_16 + b_4_132·b_1_12 + b_2_5·b_1_28 + b_2_5·b_4_132 + b_2_43·b_4_13 + b_2_45
- b_5_17·b_5_18 + b_5_172 + b_3_8·b_7_30 + b_1_210 + b_6_24·b_1_24 + b_4_13·b_1_26
+ b_4_13·b_1_1·b_5_17 + b_4_13·b_1_13·b_3_8 + b_4_13·b_1_16 + b_4_132·b_1_12 + b_2_5·b_4_132 + b_2_42·b_6_24 + b_2_43·b_4_13 + b_2_44·b_2_5 + b_2_45
- b_5_17·b_5_18 + b_5_172 + b_3_9·b_7_30 + b_1_210 + b_4_13·b_1_26
+ b_4_13·b_1_1·b_5_17 + b_4_13·b_1_13·b_3_8 + b_4_13·b_1_16 + b_4_132·b_1_12 + b_2_5·b_1_28 + b_2_5·b_4_13·b_1_24 + b_2_4·b_2_5·b_6_24 + b_2_43·b_4_13 + b_2_45
- b_5_17·b_5_18 + b_6_24·b_1_14 + b_4_13·b_1_26 + b_4_13·b_1_1·b_5_17
+ b_4_132·b_1_22 + b_2_5·b_1_28 + b_2_5·b_6_24·b_1_22 + b_2_5·b_4_13·b_1_24 + b_2_4·b_4_132 + b_2_4·b_2_5·b_6_24 + b_2_42·b_2_5·b_4_13 + b_2_43·b_4_13 + b_2_44·b_2_5 + c_8_37·b_1_12
- b_6_24·b_5_18 + b_6_24·b_5_17 + b_6_24·b_1_22·b_3_8 + b_6_24·b_1_12·b_3_8
+ b_4_13·b_1_12·b_5_17 + b_4_13·b_1_14·b_3_8 + b_4_13·b_6_24·b_1_1 + b_4_132·b_3_9 + b_2_5·b_4_13·b_5_17 + b_2_5·b_4_13·b_1_22·b_3_8 + b_2_4·b_4_13·b_5_18 + b_2_42·b_7_30 + b_2_42·b_4_13·b_3_9
- b_6_24·b_5_18 + b_6_24·b_1_12·b_3_8 + b_6_24·b_1_15 + b_4_13·b_7_30
+ b_4_13·b_1_14·b_3_8 + b_4_132·b_3_9 + b_4_132·b_1_13 + b_2_5·b_1_26·b_3_8 + b_2_5·b_6_24·b_3_8 + b_2_5·b_4_13·b_5_17 + b_2_4·b_4_13·b_5_18 + b_2_42·b_4_13·b_3_9 + c_8_37·b_1_1·b_1_22 + c_8_37·b_1_13 + b_2_5·c_8_37·a_1_0
- b_5_18·b_7_30 + b_5_17·b_7_30 + b_6_24·b_1_26 + b_6_24·b_1_13·b_3_8
+ b_4_13·b_6_24·b_1_12 + b_4_132·b_1_1·b_3_8 + b_2_5·b_1_210 + b_2_5·b_6_24·b_1_24 + b_2_5·b_4_13·b_1_26 + b_2_5·b_4_13·b_6_24 + b_2_43·b_6_24 + b_2_43·b_2_5·b_4_13 + b_2_45·b_2_5
- b_1_212 + b_6_24·b_1_13·b_3_8 + b_6_24·b_1_16 + b_6_242 + b_4_13·b_1_15·b_3_8
+ b_4_13·b_6_24·b_1_22 + b_4_13·b_6_24·b_1_12 + b_4_132·b_1_24 + b_4_132·b_1_1·b_3_8 + b_4_132·b_1_14 + b_4_133 + b_2_5·b_1_210 + b_2_5·b_4_132·b_1_22 + b_2_4·b_4_13·b_6_24 + b_2_4·b_2_5·b_4_132 + b_2_42·b_4_132 + b_2_43·b_2_5·b_4_13 + b_2_45·b_2_5 + b_2_46 + b_2_43·b_2_5·a_1_0·b_3_9 + c_8_37·b_1_24 + c_8_37·b_1_14 + b_2_42·c_8_37
- b_5_18·b_7_30 + b_6_24·b_1_16 + b_4_13·b_1_15·b_3_8 + b_4_13·b_6_24·b_1_22
+ b_2_5·b_1_210 + b_2_5·b_6_24·b_1_24 + b_2_5·b_4_13·b_1_26 + b_2_4·b_4_13·b_6_24 + b_2_42·b_2_5·b_6_24 + b_2_43·b_2_5·b_4_13 + b_2_45·b_2_5 + c_8_37·b_1_1·b_3_8 + c_8_37·b_1_14
- b_1_210·b_3_8 + b_6_24·b_7_30 + b_6_24·b_1_17 + b_4_13·b_1_16·b_3_8
+ b_4_13·b_6_24·b_3_8 + b_4_132·b_5_17 + b_4_132·b_1_12·b_3_8 + b_2_5·b_6_24·b_1_22·b_3_8 + b_2_42·b_4_13·b_5_17 + c_8_37·b_1_22·b_3_8 + c_8_37·b_1_12·b_3_8 + c_8_37·b_1_15 + b_2_5·c_8_37·b_3_8
- b_7_302 + b_6_242·b_1_22 + b_6_242·b_1_12 + b_4_13·b_6_24·b_1_1·b_3_8
+ b_4_13·b_6_24·b_1_14 + b_4_132·b_1_1·b_5_17 + b_4_133·b_1_12 + b_2_5·b_4_13·b_6_24·b_1_22 + b_2_5·b_4_132·b_1_24 + b_2_5·b_4_133 + b_2_4·b_4_133 + b_2_4·b_2_5·b_4_13·b_6_24 + b_2_42·b_2_5·b_4_132 + b_2_44·b_2_5·a_1_0·b_3_9 + b_4_13·c_8_37·b_1_12
Data used for Benson′s test
- Benson′s completion test succeeded in degree 14.
- 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_37, a Duflot regular element of degree 8
- b_1_14 + b_4_13 + b_2_4·b_2_5 + b_2_42, an element of degree 4
- b_1_26 + b_4_13·b_1_22 + b_4_13·b_1_12 + b_2_42·b_2_5 + b_2_43, an element of degree 6
- The Raw Filter Degree Type of that HSOP is [-1, -1, 9, 15].
- The filter degree type of any filter regular HSOP is [-1, -2, -3, -3].
- We found that there exists some filter regular HSOP formed by the first term of the above HSOP, together with 2 elements of degree 4.
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
- b_1_2 → 0, an element of degree 1
- b_2_4 → 0, an element of degree 2
- b_2_5 → 0, an element of degree 2
- b_3_8 → 0, an element of degree 3
- b_3_9 → 0, an element of degree 3
- b_4_13 → 0, an element of degree 4
- b_5_17 → 0, an element of degree 5
- b_5_18 → 0, an element of degree 5
- b_6_24 → 0, an element of degree 6
- b_7_30 → 0, an element of degree 7
- c_8_37 → 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 → c_1_1, an element of degree 1
- b_1_2 → 0, an element of degree 1
- b_2_4 → 0, an element of degree 2
- b_2_5 → 0, an element of degree 2
- b_3_8 → c_1_1·c_1_22 + c_1_12·c_1_2, an element of degree 3
- b_3_9 → c_1_1·c_1_22 + c_1_12·c_1_2, an element of degree 3
- b_4_13 → c_1_24 + c_1_12·c_1_22, an element of degree 4
- b_5_17 → c_1_02·c_1_13 + c_1_04·c_1_1, an element of degree 5
- b_5_18 → c_1_13·c_1_22 + c_1_14·c_1_2 + c_1_02·c_1_13 + c_1_04·c_1_1, an element of degree 5
- b_6_24 → c_1_26 + c_1_1·c_1_25 + c_1_12·c_1_24 + c_1_13·c_1_23 + c_1_14·c_1_22
+ c_1_15·c_1_2 + c_1_02·c_1_14 + c_1_04·c_1_12, an element of degree 6
- b_7_30 → c_1_1·c_1_26 + c_1_12·c_1_25 + c_1_14·c_1_23 + c_1_16·c_1_2
+ c_1_02·c_1_13·c_1_22 + c_1_02·c_1_14·c_1_2 + c_1_02·c_1_15 + c_1_04·c_1_1·c_1_22 + c_1_04·c_1_12·c_1_2 + c_1_04·c_1_13, an element of degree 7
- c_8_37 → 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_16·c_1_22 + c_1_17·c_1_2 + c_1_02·c_1_12·c_1_24 + c_1_02·c_1_15·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
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
- b_1_2 → c_1_2, an element of degree 1
- b_2_4 → 0, an element of degree 2
- b_2_5 → 0, an element of degree 2
- b_3_8 → c_1_23, an element of degree 3
- b_3_9 → 0, an element of degree 3
- b_4_13 → c_1_24 + c_1_12·c_1_22 + c_1_14, an element of degree 4
- b_5_17 → c_1_12·c_1_23 + c_1_14·c_1_2, an element of degree 5
- b_5_18 → c_1_25 + c_1_12·c_1_23 + c_1_14·c_1_2, an element of degree 5
- b_6_24 → c_1_12·c_1_24 + c_1_16 + c_1_02·c_1_24 + c_1_04·c_1_22, an element of degree 6
- b_7_30 → c_1_12·c_1_25 + c_1_16·c_1_2 + c_1_02·c_1_25 + c_1_04·c_1_23, an element of degree 7
- c_8_37 → c_1_28 + c_1_14·c_1_24 + c_1_16·c_1_22 + c_1_02·c_1_26
+ c_1_02·c_1_12·c_1_24 + c_1_02·c_1_14·c_1_22 + c_1_04·c_1_12·c_1_22 + 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
- b_1_2 → c_1_2, an element of degree 1
- b_2_4 → c_1_22, an element of degree 2
- b_2_5 → 0, an element of degree 2
- b_3_8 → 0, an element of degree 3
- b_3_9 → c_1_1·c_1_22 + c_1_12·c_1_2, an element of degree 3
- b_4_13 → c_1_12·c_1_22 + c_1_14, an element of degree 4
- b_5_17 → 0, an element of degree 5
- b_5_18 → c_1_1·c_1_24 + c_1_14·c_1_2, an element of degree 5
- b_6_24 → c_1_13·c_1_23 + c_1_14·c_1_22 + c_1_15·c_1_2 + c_1_16, an element of degree 6
- b_7_30 → 0, an element of degree 7
- c_8_37 → c_1_12·c_1_26 + c_1_14·c_1_24 + c_1_02·c_1_12·c_1_24
+ c_1_02·c_1_14·c_1_22 + c_1_04·c_1_24 + c_1_04·c_1_12·c_1_22 + 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
- b_1_2 → c_1_2, an element of degree 1
- b_2_4 → c_1_22, an element of degree 2
- b_2_5 → c_1_22, an element of degree 2
- b_3_8 → 0, an element of degree 3
- b_3_9 → c_1_1·c_1_22 + c_1_12·c_1_2, an element of degree 3
- b_4_13 → c_1_24 + c_1_12·c_1_22 + c_1_14, an element of degree 4
- b_5_17 → c_1_12·c_1_23 + c_1_14·c_1_2, an element of degree 5
- b_5_18 → 0, an element of degree 5
- b_6_24 → c_1_12·c_1_24 + c_1_13·c_1_23 + c_1_15·c_1_2 + c_1_16, an element of degree 6
- b_7_30 → c_1_12·c_1_25 + c_1_13·c_1_24 + c_1_15·c_1_22 + c_1_16·c_1_2, an element of degree 7
- c_8_37 → c_1_12·c_1_26 + c_1_13·c_1_25 + c_1_15·c_1_23 + c_1_16·c_1_22
+ c_1_02·c_1_12·c_1_24 + c_1_02·c_1_14·c_1_22 + c_1_04·c_1_24 + c_1_04·c_1_12·c_1_22 + c_1_04·c_1_14 + c_1_08, an element of degree 8
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