Simon King
David J. Green
Cohomology
→Theory
→Implementation
Jena:
Faculty
External links:
Singular
Gap
|
Cohomology of group number 480 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 4.
- Its center has rank 3.
- It has a unique conjugacy class of maximal elementary abelian subgroups, which is 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
- The a-invariants are -∞,-∞,-∞,-4,-4. They were obtained using the filter regular HSOP of the Benson test.
Ring generators
The cohomology ring has 7 minimal generators of maximal degree 2:
- a_1_1, a nilpotent element of degree 1
- a_1_0, a nilpotent element of degree 1
- b_1_2, an element of degree 1
- a_2_3, a nilpotent element of degree 2
- c_2_4, a Duflot regular element of degree 2
- c_2_5, a Duflot regular element of degree 2
- c_2_6, a Duflot regular element of degree 2
Ring relations
There are 5 minimal relations of maximal degree 4:
- a_1_12
- a_1_02
- a_1_1·b_1_2 + a_1_1·a_1_0
- a_2_3·a_1_1
- a_2_32
Data used for Benson′s test
- Benson′s completion test succeeded in degree 4.
- 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_4, a Duflot regular element of degree 2
- c_2_5, a Duflot regular element of degree 2
- c_2_6, a Duflot regular element of degree 2
- b_1_22, an element of degree 2
- The Raw Filter Degree Type of that HSOP is [-1, -1, -1, 2, 4].
- 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_1 → 0, an element of degree 1
- a_1_0 → 0, an element of degree 1
- b_1_2 → 0, an element of degree 1
- a_2_3 → 0, an element of degree 2
- c_2_4 → c_1_02, an element of degree 2
- c_2_5 → c_1_12, an element of degree 2
- c_2_6 → c_1_22, an element of degree 2
Restriction map to a maximal el. ab. subgp. of rank 4
- a_1_1 → 0, an element of degree 1
- a_1_0 → 0, an element of degree 1
- b_1_2 → c_1_3, an element of degree 1
- a_2_3 → 0, an element of degree 2
- c_2_4 → c_1_0·c_1_3 + c_1_02, an element of degree 2
- c_2_5 → c_1_32 + c_1_12, an element of degree 2
- c_2_6 → c_1_22, an element of degree 2
|