Cohomology of group number 857 of order 128

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General information on the group

  • The group has 3 minimal generators and exponent 4.
  • It is non-abelian.
  • It has p-Rank 4.
  • Its center has rank 2.
  • 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 2.
  • The depth coincides with the Duflot bound.
  • The Poincaré series is
    ( − 1) · (t7  −  t6  −  t5  +  t3  −  t2  −  1)
    (t  +  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.

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Ring generators

The cohomology ring has 13 minimal generators of maximal degree 8:

  1. a_1_0, a nilpotent element of degree 1
  2. a_1_1, a nilpotent element of degree 1
  3. c_1_2, a Duflot regular element of degree 1
  4. b_2_4, an element of degree 2
  5. b_2_5, an element of degree 2
  6. b_2_6, an element of degree 2
  7. b_3_11, an element of degree 3
  8. a_5_21, a nilpotent element of degree 5
  9. b_5_25, an element of degree 5
  10. b_6_34, an element of degree 6
  11. b_6_36, an element of degree 6
  12. b_7_49, an element of degree 7
  13. c_8_65, a Duflot regular element of degree 8

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Ring relations

There are 44 minimal relations of maximal degree 14:

  1. a_1_02
  2. a_1_0·a_1_1
  3. b_2_5·a_1_1 + b_2_4·a_1_1
  4. b_2_5·a_1_0 + b_2_4·a_1_1
  5. b_2_6·a_1_0 + a_1_13
  6. b_2_52 + b_2_4·b_2_5
  7. a_1_1·b_3_11
  8. a_1_0·b_3_11
  9. b_2_6·a_1_13
  10. b_3_112 + b_2_4·b_2_62
  11. a_1_1·a_5_21 + b_2_62·a_1_12
  12. a_1_0·a_5_21
  13. a_1_0·b_5_25
  14. b_2_6·a_5_21 + b_2_63·a_1_1 + a_1_12·b_5_25
  15. b_2_5·b_5_25 + b_2_4·b_2_5·b_3_11 + b_2_5·a_5_21 + b_2_43·a_1_1
  16. b_2_5·b_2_6·b_3_11 + b_2_4·b_5_25 + b_2_4·b_2_6·b_3_11 + b_2_4·b_2_5·b_3_11
       + b_2_5·a_5_21 + b_2_43·a_1_1
  17. b_6_34·a_1_1 + b_2_6·a_5_21 + b_2_63·a_1_1 + b_2_5·a_5_21 + b_2_43·a_1_1
  18. b_6_34·a_1_0 + b_2_4·a_5_21 + b_2_43·a_1_1
  19. b_6_36·a_1_1 + b_2_63·a_1_1 + b_2_5·a_5_21 + b_2_43·a_1_1
  20. b_6_36·a_1_0 + b_2_5·a_5_21 + b_2_43·a_1_1
  21. b_3_11·a_5_21
  22. b_3_11·b_5_25 + b_2_5·b_2_63 + b_2_4·b_2_63 + b_2_4·b_2_5·b_2_62
  23. b_2_5·b_6_36 + b_2_5·b_6_34 + b_2_5·b_2_63
  24. b_2_5·b_6_34 + b_2_4·b_6_36 + b_2_4·b_2_63
  25. a_1_1·b_7_49 + b_2_6·a_1_1·b_5_25 + b_2_63·a_1_12
  26. a_1_0·b_7_49
  27. b_6_36·b_3_11 + b_2_63·b_3_11 + b_2_5·b_7_49 + b_2_4·b_2_6·b_5_25
       + b_2_4·b_2_62·b_3_11 + b_2_42·b_5_25 + b_2_42·b_2_6·b_3_11 + b_2_4·b_2_5·a_5_21
       + b_2_44·a_1_1
  28. b_6_34·b_3_11 + b_2_4·b_7_49 + b_2_4·b_2_6·b_5_25 + b_2_4·b_2_62·b_3_11
       + b_2_42·b_2_6·b_3_11 + b_2_43·b_3_11 + b_2_4·b_2_5·a_5_21 + b_2_42·a_5_21
  29. a_5_212 + b_2_64·a_1_12
  30. a_5_21·b_5_25 + b_2_62·a_1_1·b_5_25
  31. b_3_11·b_7_49 + b_2_62·b_6_34 + b_2_5·b_2_64 + b_2_4·b_2_5·b_2_63
       + b_2_42·b_2_63 + b_2_43·b_2_62 + b_2_62·a_1_1·b_5_25 + b_2_64·a_1_12
  32. b_5_252 + b_2_5·b_2_64 + b_2_4·b_2_64 + b_2_42·b_2_5·b_2_62
       + b_2_62·a_1_1·b_5_25 + c_8_65·a_1_12
  33. b_6_36·b_5_25 + b_2_63·b_5_25 + b_2_4·b_2_5·b_7_49 + b_2_42·b_2_6·b_5_25
       + b_2_42·b_2_62·b_3_11 + b_2_43·b_5_25 + b_2_43·b_2_6·b_3_11 + b_6_36·a_5_21
       + b_2_65·a_1_1
  34. b_6_36·b_5_25 + b_6_34·b_5_25 + b_2_63·b_5_25 + b_2_5·b_2_6·b_7_49 + b_2_4·b_2_6·b_7_49
       + b_2_42·b_2_6·b_5_25 + b_2_43·b_2_6·b_3_11 + b_2_62·a_1_12·b_5_25
       + c_8_65·a_1_13
  35. b_6_36·a_5_21 + b_2_65·a_1_1 + b_2_42·b_2_5·a_5_21 + b_2_62·a_1_12·b_5_25
       + b_2_4·c_8_65·a_1_1
  36. b_6_34·a_5_21 + b_2_43·a_5_21 + b_2_62·a_1_12·b_5_25 + b_2_4·c_8_65·a_1_0
  37. b_6_362 + b_6_34·b_6_36 + b_2_63·b_6_34 + b_2_66
  38. a_5_21·b_7_49 + b_2_63·a_1_1·b_5_25 + b_2_65·a_1_12
  39. b_6_362 + b_2_66 + b_2_42·b_2_6·b_6_36 + b_2_42·b_2_64 + b_2_42·b_2_5·b_2_63
       + b_2_43·b_2_5·b_2_62 + b_2_45·b_2_5 + b_2_4·b_2_5·c_8_65
  40. b_6_342 + b_2_42·b_2_6·b_6_34 + b_2_42·b_2_5·b_2_63 + b_2_43·b_6_36
       + b_2_43·b_6_34 + b_2_43·b_2_63 + b_2_43·b_2_5·b_2_62 + b_2_44·b_2_5·b_2_6
       + b_2_45·b_2_6 + b_2_45·b_2_5 + b_2_42·c_8_65
  41. b_5_25·b_7_49 + b_2_63·b_6_36 + b_2_63·b_6_34 + b_2_66 + b_2_4·b_2_62·b_6_36
       + b_2_4·b_2_65 + b_2_42·b_2_64 + b_2_42·b_2_5·b_2_63 + b_2_43·b_2_63
       + b_2_43·b_2_5·b_2_62 + b_2_63·a_1_1·b_5_25 + b_2_6·c_8_65·a_1_12
  42. b_6_36·b_7_49 + b_2_63·b_7_49 + b_2_5·b_2_62·b_7_49 + b_2_4·b_2_63·b_5_25
       + b_2_4·b_2_64·b_3_11 + b_2_4·b_2_5·b_2_6·b_7_49 + b_2_42·b_2_62·b_5_25
       + b_2_42·b_2_63·b_3_11 + b_2_42·b_2_5·b_7_49 + b_2_44·b_5_25 + b_2_44·b_2_6·b_3_11
       + b_2_44·b_2_5·b_3_11 + b_2_43·b_2_5·a_5_21 + b_2_46·a_1_1 + b_2_63·a_1_12·b_5_25
       + b_2_5·c_8_65·b_3_11
  43. b_6_34·b_7_49 + b_2_5·b_2_62·b_7_49 + b_2_4·b_2_63·b_5_25 + b_2_4·b_2_64·b_3_11
       + b_2_4·b_2_5·b_2_6·b_7_49 + b_2_42·b_2_62·b_5_25 + b_2_42·b_2_63·b_3_11
       + b_2_42·b_2_5·b_7_49 + b_2_44·b_2_6·b_3_11 + b_2_43·b_2_5·a_5_21 + b_2_44·a_5_21
       + b_2_63·a_1_12·b_5_25 + b_2_4·c_8_65·b_3_11 + b_2_42·c_8_65·a_1_1
       + b_2_42·c_8_65·a_1_0
  44. b_7_492 + b_2_5·b_2_66 + b_2_4·b_2_63·b_6_34 + b_2_4·b_2_5·b_2_65
       + b_2_42·b_2_62·b_6_36 + b_2_42·b_2_62·b_6_34 + b_2_42·b_2_65 + b_2_43·b_2_64
       + b_2_43·b_2_5·b_2_63 + b_2_44·b_2_63 + b_2_44·b_2_5·b_2_62 + b_2_45·b_2_62
       + b_2_64·a_1_1·b_5_25 + b_2_66·a_1_12 + b_2_4·b_2_62·c_8_65
       + b_2_62·c_8_65·a_1_12

About the group Ring generators Ring relations Completion information Restriction maps Back to groups of order 128

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:
    1. c_1_2, a Duflot regular element of degree 1
    2. c_8_65, a Duflot regular element of degree 8
    3. b_2_6 + b_2_4, an element of degree 2
    4. b_3_11, an element of degree 3
  • The Raw Filter Degree Type of that HSOP is [-1, -1, 3, 7, 10].
  • The filter degree type of any filter regular HSOP is [-1, -2, -3, -4, -4].

About the group Ring generators Ring relations Completion information Restriction maps Back to groups of order 128

Restriction maps

Restriction map to the greatest central el. ab. subgp., which is of rank 2

  1. a_1_0 → 0, an element of degree 1
  2. a_1_1 → 0, an element of degree 1
  3. c_1_2 → c_1_0, an element of degree 1
  4. b_2_4 → 0, an element of degree 2
  5. b_2_5 → 0, an element of degree 2
  6. b_2_6 → 0, an element of degree 2
  7. b_3_11 → 0, an element of degree 3
  8. a_5_21 → 0, an element of degree 5
  9. b_5_25 → 0, an element of degree 5
  10. b_6_34 → 0, an element of degree 6
  11. b_6_36 → 0, an element of degree 6
  12. b_7_49 → 0, an element of degree 7
  13. c_8_65 → c_1_18, an element of degree 8

Restriction map to a maximal el. ab. subgp. of rank 4

  1. a_1_0 → 0, an element of degree 1
  2. a_1_1 → 0, an element of degree 1
  3. c_1_2 → c_1_0, an element of degree 1
  4. b_2_4 → c_1_22, an element of degree 2
  5. b_2_5 → 0, an element of degree 2
  6. b_2_6 → c_1_32 + c_1_2·c_1_3, an element of degree 2
  7. b_3_11 → c_1_2·c_1_32 + c_1_22·c_1_3, an element of degree 3
  8. a_5_21 → 0, an element of degree 5
  9. b_5_25 → c_1_2·c_1_34 + c_1_23·c_1_32, an element of degree 5
  10. b_6_34 → c_1_22·c_1_34 + c_1_25·c_1_3 + c_1_1·c_1_23·c_1_32 + c_1_1·c_1_24·c_1_3
       + c_1_12·c_1_22·c_1_32 + c_1_12·c_1_23·c_1_3 + c_1_12·c_1_24
       + c_1_14·c_1_22, an element of degree 6
  11. b_6_36 → c_1_36 + c_1_2·c_1_35 + c_1_22·c_1_34 + c_1_23·c_1_33, an element of degree 6
  12. b_7_49 → c_1_2·c_1_36 + c_1_22·c_1_35 + c_1_23·c_1_34 + c_1_24·c_1_33
       + c_1_25·c_1_32 + c_1_26·c_1_3 + c_1_1·c_1_22·c_1_34 + c_1_1·c_1_24·c_1_32
       + c_1_12·c_1_2·c_1_34 + c_1_12·c_1_24·c_1_3 + c_1_14·c_1_2·c_1_32
       + c_1_14·c_1_22·c_1_3, an element of degree 7
  13. c_8_65 → c_1_38 + c_1_22·c_1_36 + c_1_23·c_1_35 + c_1_24·c_1_34 + c_1_25·c_1_33
       + c_1_26·c_1_32 + c_1_1·c_1_23·c_1_34 + c_1_1·c_1_26·c_1_3 + c_1_12·c_1_26
       + c_1_14·c_1_34 + c_1_14·c_1_23·c_1_3 + c_1_18, an element of degree 8

Restriction map to a maximal el. ab. subgp. of rank 4

  1. a_1_0 → 0, an element of degree 1
  2. a_1_1 → 0, an element of degree 1
  3. c_1_2 → c_1_0, an element of degree 1
  4. b_2_4 → c_1_32, an element of degree 2
  5. b_2_5 → c_1_32, an element of degree 2
  6. b_2_6 → c_1_2·c_1_3 + c_1_22, an element of degree 2
  7. b_3_11 → c_1_2·c_1_32 + c_1_22·c_1_3, an element of degree 3
  8. a_5_21 → 0, an element of degree 5
  9. b_5_25 → c_1_2·c_1_34 + c_1_22·c_1_33, an element of degree 5
  10. b_6_34 → c_1_2·c_1_35 + c_1_24·c_1_32 + c_1_1·c_1_2·c_1_34 + c_1_1·c_1_22·c_1_33
       + c_1_12·c_1_34 + c_1_12·c_1_2·c_1_33 + c_1_12·c_1_22·c_1_32
       + c_1_14·c_1_32, an element of degree 6
  11. b_6_36 → c_1_2·c_1_35 + c_1_23·c_1_33 + c_1_25·c_1_3 + c_1_26 + c_1_1·c_1_2·c_1_34
       + c_1_1·c_1_22·c_1_33 + c_1_12·c_1_34 + c_1_12·c_1_2·c_1_33
       + c_1_12·c_1_22·c_1_32 + c_1_14·c_1_32, an element of degree 6
  12. b_7_49 → c_1_2·c_1_36 + c_1_24·c_1_33 + c_1_1·c_1_22·c_1_34 + c_1_1·c_1_24·c_1_32
       + c_1_12·c_1_2·c_1_34 + c_1_12·c_1_24·c_1_3 + c_1_14·c_1_2·c_1_32
       + c_1_14·c_1_22·c_1_3, an element of degree 7
  13. c_8_65 → c_1_38 + c_1_22·c_1_36 + c_1_28 + c_1_1·c_1_22·c_1_35 + c_1_1·c_1_24·c_1_33
       + c_1_12·c_1_2·c_1_35 + c_1_12·c_1_22·c_1_34 + c_1_14·c_1_34
       + c_1_14·c_1_2·c_1_33 + c_1_14·c_1_24 + c_1_18, an element of degree 8

About the group Ring generators Ring relations Completion information Restriction maps Back to groups of order 128


Simon A. King David J. Green
Fakultät für Mathematik und Informatik Fakultät für Mathematik und Informatik
Friedrich-Schiller-Universität Jena Friedrich-Schiller-Universität Jena
Ernst-Abbe-Platz 2 Ernst-Abbe-Platz 2
D-07743 Jena D-07743 Jena
Germany Germany
E-mail: simon dot king at uni hyphen jena dot de
Tel: +49 (0)3641 9-46184
Fax: +49 (0)3641 9-46162
Office: Zi. 3524, Ernst-Abbe-Platz 2
E-mail: david dot green at uni hyphen jena dot de
Tel: +49 3641 9-46166
Fax: +49 3641 9-46162
Office: Zi 3512, Ernst-Abbe-Platz 2

Last change: 25.08.2009