Cohomology of group number 17 of order 128

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

General information on the group

  • The group has 2 minimal generators and exponent 8.
  • It is non-abelian.
  • It has p-Rank 3.
  • Its center has rank 2.
  • It has a unique conjugacy class of maximal elementary abelian subgroups, which is of rank 3.

Structure of the cohomology ring

General information

  • The cohomology ring is of dimension 3 and depth 2.
  • The depth coincides with the Duflot bound.
  • The Poincaré series is
    ( − 1) · (t4  +  t3  +  t2  +  1)
    (t  +  1) · (t  −  1)3 · (t2  +  1)2
  • The a-invariants are -∞,-∞,-3,-3. They were obtained using the filter regular HSOP of the Benson test.

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Ring generators

The cohomology ring has 18 minimal generators of maximal degree 6:

  1. a_1_0, a nilpotent element of degree 1
  2. a_1_1, a nilpotent element of degree 1
  3. a_2_0, a nilpotent element of degree 2
  4. a_2_1, a nilpotent element of degree 2
  5. b_2_2, an element of degree 2
  6. a_3_1, a nilpotent element of degree 3
  7. a_3_2, a nilpotent element of degree 3
  8. a_3_3, a nilpotent element of degree 3
  9. a_3_4, a nilpotent element of degree 3
  10. a_4_2, a nilpotent element of degree 4
  11. a_4_3, a nilpotent element of degree 4
  12. a_4_4, a nilpotent element of degree 4
  13. b_4_6, an element of degree 4
  14. c_4_7, a Duflot regular element of degree 4
  15. c_4_8, a Duflot regular element of degree 4
  16. a_5_10, a nilpotent element of degree 5
  17. a_5_11, a nilpotent element of degree 5
  18. a_6_9, a nilpotent element of degree 6

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

Ring relations

There are 119 minimal relations of maximal degree 12:

  1. a_1_02
  2. a_1_12
  3. a_1_0·a_1_1
  4. a_2_0·a_1_1
  5. a_2_0·a_1_0
  6. a_2_1·a_1_1
  7. a_2_1·a_1_0
  8. b_2_2·a_1_0
  9. a_2_02
  10. a_2_0·a_2_1
  11. a_2_12
  12. a_1_1·a_3_1
  13. a_1_0·a_3_1
  14. a_1_1·a_3_2
  15. a_1_0·a_3_2
  16. a_2_0·b_2_2 + a_1_1·a_3_3
  17. a_1_0·a_3_3
  18. a_2_1·b_2_2 + a_2_0·b_2_2 + a_1_1·a_3_4
  19. a_1_0·a_3_4
  20. a_2_0·a_3_1
  21. a_2_1·a_3_1 + a_2_0·a_3_2
  22. a_2_1·a_3_2
  23. a_2_0·a_3_3
  24. b_2_2·a_3_1 + a_2_1·a_3_3
  25. b_2_2·a_3_1 + a_2_0·a_3_4
  26. b_2_2·a_3_1 + a_2_1·a_3_4
  27. a_4_2·a_1_1 + a_2_1·a_3_1
  28. a_4_2·a_1_0
  29. a_4_3·a_1_1
  30. a_4_3·a_1_0 + a_2_1·a_3_1
  31. b_2_2·a_3_1 + a_4_4·a_1_1
  32. a_4_4·a_1_0 + a_2_1·a_3_1
  33. b_4_6·a_1_1 + b_2_2·a_3_2 + b_2_2·a_3_1 + a_2_1·a_3_1
  34. b_4_6·a_1_0
  35. a_3_12
  36. a_3_22
  37. a_3_1·a_3_2
  38. a_3_1·a_3_3
  39. a_3_32 + b_2_2·a_1_1·a_3_3
  40. a_3_1·a_3_4
  41. a_3_42 + a_3_32
  42. b_2_2·a_4_2 + a_3_2·a_3_3 + b_2_2·a_1_1·a_3_4
  43. a_2_0·a_4_2
  44. a_2_1·a_4_2
  45. b_2_2·a_4_3 + a_3_2·a_3_4 + b_2_2·a_1_1·a_3_4
  46. a_2_0·a_4_3
  47. a_2_1·a_4_3
  48. b_2_2·a_4_4 + a_3_3·a_3_4 + a_3_32 + a_3_2·a_3_4
  49. a_2_0·a_4_4
  50. a_2_1·a_4_4
  51. a_2_0·b_4_6 + a_3_2·a_3_3
  52. a_2_1·b_4_6 + a_3_2·a_3_4 + a_3_2·a_3_3
  53. a_3_2·a_3_3 + a_1_1·a_5_10 + b_2_2·a_1_1·a_3_4
  54. a_1_0·a_5_10
  55. a_3_2·a_3_4 + a_1_1·a_5_11
  56. a_1_0·a_5_11
  57. a_4_2·a_3_3 + a_1_1·a_3_3·a_3_4
  58. a_4_2·a_3_2
  59. a_4_2·a_3_1
  60. a_4_3·a_3_3 + a_4_2·a_3_4 + a_1_1·a_3_3·a_3_4
  61. a_4_3·a_3_2
  62. a_4_3·a_3_1
  63. a_4_3·a_3_4
  64. a_4_4·a_3_3 + a_4_2·a_3_4 + a_1_1·a_3_3·a_3_4
  65. a_4_4·a_3_2 + a_4_2·a_3_4
  66. a_4_4·a_3_1
  67. a_4_4·a_3_4 + a_1_1·a_3_3·a_3_4
  68. b_4_6·a_3_2 + b_2_22·a_3_2 + a_4_2·a_3_4 + a_1_1·a_3_3·a_3_4 + b_2_2·c_4_7·a_1_1
  69. b_4_6·a_3_1 + a_4_2·a_3_4
  70. b_4_6·a_3_3 + b_2_2·a_5_10 + b_2_22·a_3_4 + b_2_22·a_3_2 + a_1_1·a_3_3·a_3_4
       + b_2_2·c_4_7·a_1_1
  71. a_2_0·a_5_10 + a_1_1·a_3_3·a_3_4
  72. a_4_2·a_3_4 + a_2_1·a_5_10 + a_1_1·a_3_3·a_3_4
  73. b_4_6·a_3_4 + b_2_2·a_5_11 + b_2_22·a_3_2 + a_4_2·a_3_4 + b_2_2·c_4_8·a_1_1
  74. a_4_2·a_3_4 + a_2_0·a_5_11
  75. a_4_2·a_3_4 + a_2_1·a_5_11
  76. a_6_9·a_1_1 + a_4_2·a_3_4 + a_1_1·a_3_3·a_3_4
  77. a_6_9·a_1_0
  78. a_4_22
  79. a_4_32
  80. a_4_2·a_4_3
  81. a_4_3·a_4_4
  82. a_4_42
  83. a_4_2·a_4_4
  84. a_4_3·b_4_6 + c_4_7·a_1_1·a_3_4
  85. a_3_3·a_5_10 + b_2_2·a_3_3·a_3_4 + c_4_7·a_1_1·a_3_3
  86. a_4_2·b_4_6 + a_3_2·a_5_10
  87. a_3_1·a_5_10
  88. b_4_62 + b_2_22·b_4_6 + b_2_2·a_1_1·a_5_10 + b_2_22·a_1_1·a_3_4
       + b_2_22·a_1_1·a_3_3 + b_2_22·c_4_7
  89. b_4_62 + b_2_22·b_4_6 + a_4_4·b_4_6 + a_3_4·a_5_10 + b_2_22·c_4_7
  90. b_4_62 + b_2_22·b_4_6 + a_4_4·b_4_6 + a_4_2·b_4_6 + a_3_3·a_5_11 + b_2_22·a_1_1·a_3_3
       + b_2_22·c_4_7 + c_4_8·a_1_1·a_3_3 + c_4_7·a_1_1·a_3_4 + c_4_7·a_1_1·a_3_3
  91. b_4_62 + b_2_22·b_4_6 + a_4_2·b_4_6 + a_3_2·a_5_11 + b_2_22·a_1_1·a_3_3
       + b_2_22·c_4_7 + c_4_7·a_1_1·a_3_4 + c_4_7·a_1_1·a_3_3
  92. a_3_1·a_5_11
  93. b_4_62 + b_2_22·b_4_6 + a_4_2·b_4_6 + b_2_2·a_1_1·a_5_11 + b_2_22·a_1_1·a_3_3
       + b_2_22·c_4_7 + c_4_7·a_1_1·a_3_3
  94. a_4_2·b_4_6 + a_3_4·a_5_11 + c_4_8·a_1_1·a_3_4 + c_4_7·a_1_1·a_3_3
  95. a_4_4·b_4_6 + a_4_2·b_4_6 + b_2_2·a_6_9 + b_2_2·a_3_3·a_3_4 + b_2_22·a_1_1·a_3_4
       + c_4_8·a_1_1·a_3_4 + c_4_7·a_1_1·a_3_4
  96. a_2_0·a_6_9
  97. a_2_1·a_6_9
  98. a_4_3·a_5_10 + a_2_0·c_4_8·a_3_2 + a_2_0·c_4_7·a_3_4
  99. a_4_2·a_5_10 + a_2_0·c_4_7·a_3_2
  100. a_4_3·a_5_11
  101. a_4_4·a_5_10 + a_1_1·a_3_3·a_5_11 + b_2_2·a_1_1·a_3_3·a_3_4 + a_2_0·c_4_8·a_3_2
  102. b_4_6·a_5_10 + b_2_22·a_5_11 + b_2_22·a_5_10 + b_2_23·a_3_4 + b_2_23·a_3_2
       + a_4_4·a_5_10 + b_2_2·a_1_1·a_3_3·a_3_4 + b_2_2·c_4_7·a_3_3 + b_2_2·c_4_7·a_3_2
       + b_2_22·c_4_8·a_1_1 + a_2_0·c_4_7·a_3_4 + a_2_0·c_4_7·a_3_2
  103. a_4_4·a_5_11 + a_2_0·c_4_8·a_3_4 + a_2_0·c_4_8·a_3_2
  104. b_4_6·a_5_11 + b_4_6·a_5_10 + b_2_22·a_5_10 + b_2_23·a_3_4 + b_2_23·a_3_2
       + a_4_4·a_5_10 + b_2_2·a_1_1·a_3_3·a_3_4 + b_2_2·c_4_8·a_3_2 + b_2_2·c_4_7·a_3_4
       + b_2_2·c_4_7·a_3_3 + b_2_2·c_4_7·a_3_2 + b_2_22·c_4_7·a_1_1 + a_2_0·c_4_8·a_3_4
       + a_2_0·c_4_8·a_3_2 + a_2_0·c_4_7·a_3_2
  105. a_4_4·a_5_10 + a_4_2·a_5_11 + b_2_2·a_1_1·a_3_3·a_3_4 + a_2_0·c_4_7·a_3_4
  106. a_6_9·a_3_3 + a_4_4·a_5_10 + b_2_2·a_1_1·a_3_3·a_3_4 + a_2_0·c_4_8·a_3_4
       + a_2_0·c_4_8·a_3_2
  107. a_6_9·a_3_2 + a_2_0·c_4_8·a_3_2 + a_2_0·c_4_7·a_3_4 + a_2_0·c_4_7·a_3_2
  108. a_6_9·a_3_1 + a_2_0·c_4_8·a_3_2
  109. a_6_9·a_3_4 + a_2_0·c_4_8·a_3_2 + a_2_0·c_4_7·a_3_4
  110. a_5_102 + b_2_22·a_1_1·a_5_10 + b_2_23·a_1_1·a_3_4 + b_2_23·a_1_1·a_3_3
       + b_2_2·c_4_7·a_1_1·a_3_3
  111. a_5_112 + b_2_22·a_1_1·a_5_10 + b_2_23·a_1_1·a_3_4 + b_2_2·c_4_7·a_1_1·a_3_3
  112. a_5_10·a_5_11 + b_2_2·a_3_3·a_5_11 + b_2_22·a_1_1·a_5_10 + b_2_23·a_1_1·a_3_4
       + c_4_8·a_1_1·a_5_10 + c_4_7·a_3_3·a_3_4 + c_4_7·a_1_1·a_5_11 + b_2_2·c_4_8·a_1_1·a_3_3
       + b_2_2·c_4_7·a_1_1·a_3_4 + b_2_2·c_4_7·a_1_1·a_3_3
  113. a_4_3·a_6_9
  114. a_4_4·a_6_9
  115. b_4_6·a_6_9 + b_2_22·a_1_1·a_5_11 + c_4_8·a_1_1·a_5_11 + c_4_7·a_3_3·a_3_4
       + c_4_7·a_1_1·a_5_10 + b_2_2·c_4_7·a_1_1·a_3_4
  116. a_4_2·a_6_9
  117. a_6_9·a_5_10 + b_2_2·a_1_1·a_3_3·a_5_11 + a_2_0·c_4_8·a_5_11 + a_2_0·c_4_7·a_5_11
  118. a_6_9·a_5_11 + a_2_0·c_4_8·a_5_11 + a_2_0·c_4_7·a_5_11 + c_4_8·a_1_1·a_3_3·a_3_4
       + c_4_7·a_1_1·a_3_3·a_3_4
  119. a_6_92

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 12.
  • 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_4_7, a Duflot regular element of degree 4
    2. c_4_8, a Duflot regular element of degree 4
    3. b_2_2, an element of degree 2
  • The Raw Filter Degree Type of that HSOP is [-1, -1, 5, 7].
  • The filter degree type of any filter regular HSOP is [-1, -2, -3, -3].

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. a_2_0 → 0, an element of degree 2
  4. a_2_1 → 0, an element of degree 2
  5. b_2_2 → 0, an element of degree 2
  6. a_3_1 → 0, an element of degree 3
  7. a_3_2 → 0, an element of degree 3
  8. a_3_3 → 0, an element of degree 3
  9. a_3_4 → 0, an element of degree 3
  10. a_4_2 → 0, an element of degree 4
  11. a_4_3 → 0, an element of degree 4
  12. a_4_4 → 0, an element of degree 4
  13. b_4_6 → 0, an element of degree 4
  14. c_4_7 → c_1_14 + c_1_04, an element of degree 4
  15. c_4_8 → c_1_04, an element of degree 4
  16. a_5_10 → 0, an element of degree 5
  17. a_5_11 → 0, an element of degree 5
  18. a_6_9 → 0, an element of degree 6

Restriction map to a maximal el. ab. subgp. of rank 3

  1. a_1_0 → 0, an element of degree 1
  2. a_1_1 → 0, an element of degree 1
  3. a_2_0 → 0, an element of degree 2
  4. a_2_1 → 0, an element of degree 2
  5. b_2_2 → c_1_22, an element of degree 2
  6. a_3_1 → 0, an element of degree 3
  7. a_3_2 → 0, an element of degree 3
  8. a_3_3 → 0, an element of degree 3
  9. a_3_4 → 0, an element of degree 3
  10. a_4_2 → 0, an element of degree 4
  11. a_4_3 → 0, an element of degree 4
  12. a_4_4 → 0, an element of degree 4
  13. b_4_6 → c_1_12·c_1_22 + c_1_02·c_1_22, an element of degree 4
  14. c_4_7 → c_1_12·c_1_22 + c_1_14 + c_1_02·c_1_22 + c_1_04, an element of degree 4
  15. c_4_8 → c_1_12·c_1_22 + c_1_04, an element of degree 4
  16. a_5_10 → 0, an element of degree 5
  17. a_5_11 → 0, an element of degree 5
  18. a_6_9 → 0, an element of degree 6

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