Simon King
David J. Green
Cohomology
→Theory
→Implementation
Jena:
Faculty
External links:
Singular
Gap
|
Cohomology of group number 1687 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 1.
- It has 3 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) · (t6 + t5 + t2 + t + 1) |
| (t − 1)3 · (t2 + 1) · (t4 + 1) |
- The a-invariants are -∞,-∞,-5,-3. They were obtained using the filter regular HSOP of the Benson test.
Ring generators
The cohomology ring has 8 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_1_3, an element of degree 1
- b_2_8, an element of degree 2
- b_5_26, an element of degree 5
- b_5_27, an element of degree 5
- c_8_57, a Duflot regular element of degree 8
Ring relations
There are 10 minimal relations of maximal degree 10:
- a_1_02
- b_1_1·b_1_2 + a_1_0·b_1_1
- b_1_2·b_1_32 + b_1_22·b_1_3 + b_2_8·b_1_2 + b_2_8·b_1_1 + a_1_0·b_1_32 + b_2_8·a_1_0
- b_2_8·b_1_1·b_1_32
- b_1_1·b_5_26 + b_2_82·b_1_1·b_1_3
- b_1_2·b_5_27 + b_2_8·b_1_23·b_1_3 + b_2_82·b_1_2·b_1_3 + b_2_82·b_1_22
+ a_1_0·b_5_27 + b_2_8·a_1_0·b_1_22·b_1_3 + b_2_82·a_1_0·b_1_3
- b_1_32·b_5_26 + b_1_2·b_1_3·b_5_26 + b_2_8·b_5_27 + b_2_8·b_5_26 + b_2_8·b_1_35
+ b_2_8·b_1_24·b_1_3 + b_2_82·b_1_23 + b_2_83·b_1_2 + a_1_0·b_1_3·b_5_26 + b_2_82·a_1_0·b_1_22 + b_2_83·a_1_0
- b_5_26·b_5_27 + b_2_8·b_1_33·b_5_27 + b_2_8·b_1_22·b_1_3·b_5_26
+ b_2_82·b_1_3·b_5_27 + b_2_82·b_1_3·b_5_26 + b_2_82·b_1_36 + b_2_82·b_1_2·b_5_26 + b_2_83·b_1_23·b_1_3 + b_2_84·b_1_32 + b_2_84·b_1_2·b_1_3 + b_2_84·b_1_22 + b_2_82·a_1_0·b_5_26 + b_2_83·a_1_0·b_1_22·b_1_3 + b_2_84·a_1_0·b_1_3
- b_5_262 + b_2_8·b_1_22·b_1_3·b_5_26 + b_2_82·b_1_36 + b_2_82·b_1_2·b_5_26
+ b_2_82·b_1_26 + b_2_83·b_1_34 + b_2_83·b_1_24 + b_2_84·b_1_32 + b_2_84·b_1_22 + b_2_84·b_1_1·b_1_3 + b_2_82·a_1_0·b_5_26 + c_8_57·b_1_22
- b_5_272 + b_1_1·b_1_34·b_5_27 + b_1_12·b_1_33·b_5_27 + b_1_14·b_1_3·b_5_27
+ b_2_8·b_1_38 + b_2_8·b_1_27·b_1_3 + b_2_82·b_1_25·b_1_3 + b_2_82·b_1_26 + b_2_83·b_1_34 + b_2_83·b_1_23·b_1_3 + b_2_84·b_1_32 + b_2_8·a_1_0·b_1_26·b_1_3 + b_2_82·a_1_0·b_1_24·b_1_3 + b_2_83·a_1_0·b_1_22·b_1_3 + c_8_57·b_1_12
Data used for Benson′s test
- Benson′s completion test succeeded in degree 12.
- However, the last relation was already found in degree 10 and the last generator in degree 8.
- The following is a filter regular homogeneous system of parameters:
- c_8_57, a Duflot regular element of degree 8
- b_1_34 + b_1_23·b_1_3 + b_1_24 + b_1_12·b_1_32 + b_1_14 + b_2_8·b_1_32
+ b_2_8·b_1_2·b_1_3 + b_2_8·b_1_22 + b_2_82, an element of degree 4
- b_1_32, an element of degree 2
- The Raw Filter Degree Type of that HSOP is [-1, -1, 7, 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 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_1_3 → 0, an element of degree 1
- b_2_8 → 0, an element of degree 2
- b_5_26 → 0, an element of degree 5
- b_5_27 → 0, an element of degree 5
- c_8_57 → 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_1_3 → c_1_2, an element of degree 1
- b_2_8 → 0, an element of degree 2
- b_5_26 → 0, an element of degree 5
- b_5_27 → c_1_02·c_1_13 + c_1_04·c_1_1, an element of degree 5
- c_8_57 → c_1_02·c_1_12·c_1_24 + c_1_02·c_1_13·c_1_23 + c_1_02·c_1_15·c_1_2
+ c_1_04·c_1_24 + c_1_04·c_1_1·c_1_23 + c_1_04·c_1_13·c_1_2 + 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 → 0, an element of degree 1
- b_1_3 → c_1_1, an element of degree 1
- b_2_8 → c_1_22, an element of degree 2
- b_5_26 → c_1_1·c_1_24 + c_1_12·c_1_23 + c_1_13·c_1_22, an element of degree 5
- b_5_27 → c_1_1·c_1_24 + c_1_12·c_1_23 + c_1_14·c_1_2, an element of degree 5
- c_8_57 → 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_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_1, an element of degree 1
- b_1_3 → c_1_2 + c_1_1, an element of degree 1
- b_2_8 → c_1_22 + c_1_1·c_1_2, an element of degree 2
- b_5_26 → c_1_25 + c_1_1·c_1_24 + c_1_12·c_1_23 + c_1_14·c_1_2 + c_1_02·c_1_13
+ c_1_04·c_1_1, an element of degree 5
- b_5_27 → c_1_25 + c_1_14·c_1_2, an element of degree 5
- c_8_57 → 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_02·c_1_12·c_1_24 + c_1_02·c_1_13·c_1_23 + c_1_02·c_1_14·c_1_22 + c_1_02·c_1_15·c_1_2 + c_1_04·c_1_24 + c_1_04·c_1_1·c_1_23 + c_1_04·c_1_12·c_1_22 + c_1_04·c_1_13·c_1_2 + c_1_04·c_1_14 + c_1_08, an element of degree 8
|