(91,10,1) block plan

from Wikipedia, the free encyclopedia

The (91,10,1) block diagram is a special symmetrical block diagram . In order to be able to construct it, this combinatorial problem had to be solved: an empty 91 × 91 matrix was filled with ones in such a way that each row of the matrix contains exactly 10 ones and any two rows have exactly 1 one in the same column (not more and not less). That sounds relatively simple, but it is not trivial to solve. There are only certain combinations of parameters (like here v = 91, k = 10, λ = 1) for which such a construction is feasible. The smallest of these (v, k, λ) are listed in this overview .

designation

This symmetrical 2- (91,10,1) block plan is called the 9th order projective plane or Desarguean plane .

properties

This symmetrical block diagram has the parameters v = 91, k = 10, λ = 1 and thus the following properties:

  • It consists of 91 blocks and 91 points.
  • Each block contains exactly 10 points.
  • Every 2 blocks intersect in exactly 1 point.
  • Each point lies on exactly 10 blocks.
  • Each 2 points are connected by exactly 1 block.

Existence and characterization

There are exactly four non-isomorphic 2- (91,10,1) block plans. These solutions are:

  • Solution 1 ( self-duplicated ) with the signature 91 840. It contains 58968 ovals of the 10th order. This is the Desargue's plane
  • Solution 2 ( self-duplicated ) with the signature 91 840. It contains 9720 10th order ovals . This is the Hughes Plain
  • Solution 3 ( dual to solution 4) with the signature 91 · 840. It contains 2808 10th order ovals . This is the first reverb level
  • Solution 4 ( dual to solution 3) with the signature 91 · 840. It contains 2808 10th-order ovals . This is the second reverb level

List of blocks

All the blocks of this block plan are listed here; See this illustration to understand this list

  • Solution 1
  1   2   3   4   5   6   7   8   9  10
  1  11  12  13  14  15  16  17  18  19
  1  20  21  22  23  24  25  26  27  28
  1  29  30  31  32  33  34  35  36  37
  1  38  39  40  41  42  43  44  45  46
  1  47  48  49  50  51  52  53  54  55
  1  56  57  58  59  60  61  62  63  64
  1  65  66  67  68  69  70  71  72  73
  1  74  75  76  77  78  79  80  81  82
  1  83  84  85  86  87  88  89  90  91
  2  11  20  29  38  47  56  65  74  83
  2  12  21  30  39  48  57  66  75  84
  2  13  22  31  40  49  58  67  76  85
  2  14  23  32  41  50  59  68  77  86
  2  15  24  33  42  51  60  69  78  87
  2  16  25  34  43  52  61  70  79  88
  2  17  26  35  44  53  62  71  80  89
  2  18  27  36  45  54  63  72  81  90
  2  19  28  37  46  55  64  73  82  91
  3  11  25  35  45  55  57  67  77  87
  3  12  20  33  44  49  61  68  82  90
  3  13  28  29  43  54  59  71  78  84
  3  14  22  30  38  53  64  69  81  88
  3  15  26  32  40  47  63  66  79  91
  3  16  21  36  42  50  56  73  76  89
  3  17  27  31  46  52  60  65  75  86
  3  18  24  37  41  48  62  70  74  85
  3  19  23  34  39  51  58  72  80  83
  4  11  26  36  46  48  58  68  78  88
  4  12  24  35  40  52  59  73  81  83
  4  13  20  34  45  50  62  69  75  91
  4  14  21  29  44  55  60  72  79  85
  4  15  23  31  38  54  57  70  82  89
  4  16  27  33  41  47  64  67  80  84
  4  17  22  37  43  51  56  66  77  90
  4  18  28  32  39  53  61  65  76  87
  4  19  25  30  42  49  63  71  74  86
  5  11  27  37  39  49  59  69  79  89
  5  12  26  31  43  50  64  72  74  87
  5  13  25  36  41  53  60  66  82  83
  5  14  20  35  46  51  63  70  76  84
  5  15  22  29  45  48  61  73  80  86
  5  16  24  32  38  55  58  71  75  90
  5  17  28  34  42  47  57  68  81  85
  5  18  23  30  44  52  56  67  78  91
  5  19  21  33  40  54  62  65  77  88
  6  11  28  30  40  50  60  70  80  90
  6  12  22  34  41  55  63  65  78  89
  6  13  27  32  44  51  57  73  74  88
  6  14  26  37  42  54  61  67  75  83
  6  15  20  36  39  52  64  71  77  85
  6  16  23  29  46  49  62  66  81  87
  6  17  25  33  38  48  59  72  76  91
  6  18  21  35  43  47  58  69  82  86
  6  19  24  31  45  53  56  68  79  84
  7  11  21  31  41  51  61  71  81  91
  7  12  25  32  46  54  56  69  80  85
  7  13  23  35  42  48  64  65  79  90
  7  14  28  33  45  52  58  66  74  89
  7  15  27  30  43  55  62  68  76  83
  7  16  20  37  40  53  57  72  78  86
  7  17  24  29  39  50  63  67  82  88
  7  18  26  34  38  49  60  73  77  84
  7  19  22  36  44  47  59  70  75  87
  8  11  22  32  42  52  62  72  82  84
  8  12  23  37  45  47  60  71  76  88
  8  13  26  33  39  55  56  70  81  86
  8  14  24  36  43  49  57  65  80  91
  8  15  21  34  46  53  59  67  74  90
  8  16  28  31  44  48  63  69  77  83
  8  17  20  30  41  54  58  73  79  87
  8  18  25  29  40  51  64  68  75  89
  8  19  27  35  38  50  61  66  78  85
  9  11  23  33  43  53  63  73  75  85
  9  12  28  36  38  51  62  67  79  86
  9  13  24  30  46  47  61  72  77  89
  9  14  27  34  40  48  56  71  82  87
  9  15  25  37  44  50  58  65  81  84
  9  16  22  35  39  54  60  68  74  91
  9  17  21  32  45  49  64  70  78  83
  9  18  20  31  42  55  59  66  80  88
  9  19  26  29  41  52  57  69  76  90
 10  11  24  34  44  54  64  66  76  86
 10  12  27  29  42  53  58  70  77  91
 10  13  21  37  38  52  63  68  80  87
 10  14  25  31  39  47  62  73  78  90
 10  15  28  35  41  49  56  72  75  88
 10  16  26  30  45  51  59  65  82  85
 10  17  23  36  40  55  61  69  74  84
 10  18  22  33  46  50  57  71  79  83
 10  19  20  32  43  48  60  67  81  89
  • Solution 2
  1   2   3   4   5   6   7   8   9  10
  1  11  12  13  14  15  16  17  18  19
  1  20  21  22  23  24  25  26  27  28
  1  29  30  31  32  33  34  35  36  37
  1  38  39  40  41  42  43  44  45  46
  1  47  48  49  50  51  52  53  54  55
  1  56  57  58  59  60  61  62  63  64
  1  65  66  67  68  69  70  71  72  73
  1  74  75  76  77  78  79  80  81  82
  1  83  84  85  86  87  88  89  90  91
  2  11  20  29  38  47  56  65  74  83
  2  12  21  30  39  48  57  66  75  84
  2  13  22  31  40  49  58  67  76  85
  2  14  23  32  41  50  59  68  77  86
  2  15  24  33  42  51  60  69  78  87
  2  16  25  34  43  52  61  70  79  88
  2  17  26  35  44  53  62  71  80  89
  2  18  27  36  45  54  63  72  81  90
  2  19  28  37  46  55  64  73  82  91
  3  11  22  30  44  55  63  68  79  87
  3  12  20  31  45  53  64  69  77  88
  3  13  21  29  46  54  62  70  78  86
  3  14  25  33  38  49  57  71  82  90
  3  15  23  34  39  47  58  72  80  91
  3  16  24  32  40  48  56  73  81  89
  3  17  28  36  41  52  60  65  76  84
  3  18  26  37  42  50  61  66  74  85
  3  19  27  35  43  51  59  67  75  83
  4  11  21  31  41  51  61  71  81  91
  4  12  22  29  42  52  59  72  82  89
  4  13  20  30  43  50  60  73  80  90
  4  14  24  34  44  54  64  65  75  85
  4  15  25  32  45  55  62  66  76  83
  4  16  23  33  46  53  63  67  74  84
  4  17  27  37  38  48  58  68  78  88
  4  18  28  35  39  49  56  69  79  86
  4  19  26  36  40  47  57  70  77  87
  5  11  26  32  39  54  60  67  82  88
  5  12  27  33  40  55  61  65  80  86
  5  13  28  34  38  53  59  66  81  87
  5  14  20  35  42  48  63  70  76  91
  5  15  21  36  43  49  64  68  74  89
  5  16  22  37  41  47  62  69  75  90
  5  17  23  29  45  51  57  73  79  85
  5  18  24  30  46  52  58  71  77  83
  5  19  25  31  44  50  56  72  78  84
  6  11  28  33  43  48  62  72  77  85
  6  12  26  34  41  49  63  73  78  83
  6  13  27  32  42  47  64  71  79  84
  6  14  22  36  46  51  56  66  80  88
  6  15  20  37  44  52  57  67  81  86
  6  16  21  35  45  50  58  65  82  87
  6  17  25  30  40  54  59  69  74  91
  6  18  23  31  38  55  60  70  75  89
  6  19  24  29  39  53  61  68  76  90
  7  11  27  34  46  50  57  69  76  89
  7  12  28  32  44  51  58  70  74  90
  7  13  26  33  45  52  56  68  75  91
  7  14  21  37  40  53  60  72  79  83
  7  15  22  35  38  54  61  73  77  84
  7  16  20  36  39  55  59  71  78  85
  7  17  24  31  43  47  63  66  82  86
  7  18  25  29  41  48  64  67  80  87
  7  19  23  30  42  49  62  65  81  88
  8  11  23  35  40  52  64  66  78  90
  8  12  24  36  38  50  62  67  79  91
  8  13  25  37  39  51  63  65  77  89
  8  14  26  29  43  55  58  69  81  84
  8  15  27  30  41  53  56  70  82  85
  8  16  28  31  42  54  57  68  80  83
  8  17  20  32  46  49  61  72  75  87
  8  18  21  33  44  47  59  73  76  88
  8  19  22  34  45  48  60  71  74  86
  9  11  25  36  42  53  58  73  75  86
  9  12  23  37  43  54  56  71  76  87
  9  13  24  35  41  55  57  72  74  88
  9  14  28  30  45  47  61  67  78  89
  9  15  26  31  46  48  59  65  79  90
  9  16  27  29  44  49  60  66  77  91
  9  17  22  33  39  50  64  70  81  83
  9  18  20  34  40  51  62  68  82  84
  9  19  21  32  38  52  63  69  80  85
 10  11  24  37  45  49  59  70  80  84
 10  12  25  35  46  47  60  68  81  85
 10  13  23  36  44  48  61  69  82  83
 10  14  27  31  39  52  62  73  74  87
 10  15  28  29  40  50  63  71  75  88
 10  16  26  30  38  51  64  72  76  86
 10  17  21  34  42  55  56  67  77  90
 10  18  22  32  43  53  57  65  78  91
 10  19  20  33  41  54  58  66  79  89
  • Solution 3
  1   2   3   4   5   6   7   8   9  10
  1  11  12  13  14  15  16  17  18  19
  1  20  21  22  23  24  25  26  27  28
  1  29  30  31  32  33  34  35  36  37
  1  38  39  40  41  42  43  44  45  46
  1  47  48  49  50  51  52  53  54  55
  1  56  57  58  59  60  61  62  63  64
  1  65  66  67  68  69  70  71  72  73
  1  74  75  76  77  78  79  80  81  82
  1  83  84  85  86  87  88  89  90  91
  2  11  20  29  38  47  56  65  74  83
  2  12  21  30  39  48  57  66  75  84
  2  13  22  31  40  49  58  67  76  85
  2  14  23  32  41  50  59  68  77  86
  2  15  24  33  42  51  60  69  78  87
  2  16  25  34  43  52  61  70  79  88
  2  17  26  35  44  53  62  71  80  89
  2  18  27  36  45  54  63  72  81  90
  2  19  28  37  46  55  64  73  82  91
  3  11  22  30  44  55  63  68  79  87
  3  12  20  31  45  53  64  69  77  88
  3  13  21  29  46  54  62  70  78  86
  3  14  25  33  38  49  57  71  82  90
  3  15  23  34  39  47  58  72  80  91
  3  16  24  32  40  48  56  73  81  89
  3  17  28  36  41  52  60  65  76  84
  3  18  26  37  42  50  61  66  74  85
  3  19  27  35  43  51  59  67  75  83
  4  11  21  31  41  51  61  71  81  91
  4  12  22  29  42  52  59  72  82  89
  4  13  20  30  43  50  60  73  80  90
  4  14  24  34  44  54  64  65  75  85
  4  15  25  32  45  55  62  66  76  83
  4  16  23  33  46  53  63  67  74  84
  4  17  27  37  38  48  58  68  78  88
  4  18  28  35  39  49  56  69  79  86
  4  19  26  36  40  47  57  70  77  87
  5  11  26  32  39  52  64  67  78  90
  5  12  27  33  40  50  62  65  79  91
  5  13  28  34  38  51  63  66  77  89
  5  14  20  35  46  48  61  72  76  87
  5  15  21  36  44  49  59  73  74  88
  5  16  22  37  45  47  60  71  75  86
  5  17  23  29  43  55  57  69  81  85
  5  18  24  30  41  53  58  70  82  83
  5  19  25  31  42  54  56  68  80  84
  6  11  28  33  45  48  59  70  80  85
  6  12  26  34  46  49  60  68  81  83
  6  13  27  32  44  47  61  69  82  84
  6  14  22  36  43  53  56  66  78  91
  6  15  20  37  41  54  57  67  79  89
  6  16  21  35  42  55  58  65  77  90
  6  17  25  30  40  51  64  72  74  86
  6  18  23  31  38  52  62  73  75  87
  6  19  24  29  39  50  63  71  76  88
  7  11  27  34  42  53  57  73  76  86
  7  12  28  32  43  54  58  71  74  87
  7  13  26  33  41  55  56  72  75  88
  7  14  21  37  40  52  63  69  80  83
  7  15  22  35  38  50  64  70  81  84
  7  16  20  36  39  51  62  68  82  85
  7  17  24  31  46  47  59  66  79  90
  7  18  25  29  44  48  60  67  77  91
  7  19  23  30  45  49  61  65  78  89
  8  11  23  35  40  54  60  66  82  88
  8  12  24  36  38  55  61  67  80  86
  8  13  25  37  39  53  59  65  81  87
  8  14  26  29  45  51  58  73  79  84
  8  15  27  30  46  52  56  71  77  85
  8  16  28  31  44  50  57  72  78  83
  8  17  20  32  42  49  63  70  75  91
  8  18  21  33  43  47  64  68  76  89
  8  19  22  34  41  48  62  69  74  90
  9  11  25  36  46  50  58  69  75  89
  9  12  23  37  44  51  56  70  76  90
  9  13  24  35  45  52  57  68  74  91
  9  14  28  30  42  47  62  67  81  88
  9  15  26  31  43  48  63  65  82  86
  9  16  27  29  41  49  64  66  80  87
  9  17  22  33  39  54  61  73  77  83
  9  18  20  34  40  55  59  71  78  84
  9  19  21  32  38  53  60  72  79  85
 10  11  24  37  43  49  62  72  77  84
 10  12  25  35  41  47  63  73  78  85
 10  13  23  36  42  48  64  71  79  83
 10  14  27  31  39  55  60  70  74  89
 10  15  28  29  40  53  61  68  75  90
 10  16  26  30  38  54  59  69  76  91
 10  17  21  34  45  50  56  67  82  87
 10  18  22  32  46  51  57  65  80  88
 10  19  20  33  44  52  58  66  81  86
  • Solution 4
  1   2   3   4   5   6   7   8   9  10
  1  11  12  13  14  15  16  17  18  19
  1  20  21  22  23  24  25  26  27  28
  1  29  30  31  32  33  34  35  36  37
  1  38  39  40  41  42  43  44  45  46
  1  47  48  49  50  51  52  53  54  55
  1  56  57  58  59  60  61  62  63  64
  1  65  66  67  68  69  70  71  72  73
  1  74  75  76  77  78  79  80  81  82
  1  83  84  85  86  87  88  89  90  91
  2  11  20  29  38  47  56  65  74  83
  2  12  21  30  39  48  57  66  75  84
  2  13  22  31  40  49  58  67  76  85
  2  14  23  32  41  50  59  68  77  86
  2  15  24  33  42  51  60  69  78  87
  2  16  25  34  43  52  61  70  79  88
  2  17  26  35  44  53  62  71  80  89
  2  18  27  36  45  54  63  72  81  90
  2  19  28  37  46  55  64  73  82  91
  3  11  21  31  41  51  61  71  81  91
  3  12  22  29  42  52  59  72  82  89
  3  13  20  30  43  50  60  73  80  90
  3  14  24  34  44  54  64  65  75  85
  3  15  25  32  45  55  62  66  76  83
  3  16  23  33  46  53  63  67  74  84
  3  17  27  37  38  48  58  68  78  88
  3  18  28  35  39  49  56  69  79  86
  3  19  26  36  40  47  57  70  77  87
  4  11  22  30  44  55  63  68  79  87
  4  12  20  31  45  53  64  69  77  88
  4  13  21  29  46  54  62  70  78  86
  4  14  25  33  38  49  57  71  82  90
  4  15  23  34  39  47  58  72  80  91
  4  16  24  32  40  48  56  73  81  89
  4  17  28  36  41  52  60  65  76  84
  4  18  26  37  42  50  61  66  74  85
  4  19  27  35  43  51  59  67  75  83
  5  11  23  35  40  54  60  66  82  88
  5  12  24  36  38  55  61  67  80  86
  5  13  25  37  39  53  59  65  81  87
  5  14  26  29  45  51  58  73  79  84
  5  15  27  30  46  52  56  71  77  85
  5  16  28  31  44  50  57  72  78  83
  5  17  20  32  42  49  63  70  75  91
  5  18  21  33  43  47  64  68  76  89
  5  19  22  34  41  48  62  69  74  90
  6  11  24  37  43  49  62  72  77  84
  6  12  25  35  41  47  63  73  78  85
  6  13  23  36  42  48  64  71  79  83
  6  14  27  31  39  55  60  70  74  89
  6  15  28  29  40  53  61  68  75  90
  6  16  26  30  38  54  59  69  76  91
  6  17  21  34  45  50  56  67  82  87
  6  18  22  32  46  51  57  65  80  88
  6  19  20  33  44  52  58  66  81  86
  7  11  25  36  46  50  58  69  75  89
  7  12  23  37  44  51  56  70  76  90
  7  13  24  35  45  52  57  68  74  91
  7  14  28  30  42  47  62  67  81  88
  7  15  26  31  43  48  63  65  82  86
  7  16  27  29  41  49  64  66  80  87
  7  17  22  33  39  54  61  73  77  83
  7  18  20  34  40  55  59  71  78  84
  7  19  21  32  38  53  60  72  79  85
  8  11  26  32  39  52  64  67  78  90
  8  12  27  33  40  50  62  65  79  91
  8  13  28  34  38  51  63  66  77  89
  8  14  20  35  46  48  61  72  76  87
  8  15  21  36  44  49  59  73  74  88
  8  16  22  37  45  47  60  71  75  86
  8  17  23  29  43  55  57  69  81  85
  8  18  24  30  41  53  58  70  82  83
  8  19  25  31  42  54  56  68  80  84
  9  11  27  34  42  53  57  73  76  86
  9  12  28  32  43  54  58  71  74  87
  9  13  26  33  41  55  56  72  75  88
  9  14  21  37  40  52  63  69  80  83
  9  15  22  35  38  50  64  70  81  84
  9  16  20  36  39  51  62  68  82  85
  9  17  24  31  46  47  59  66  79  90
  9  18  25  29  44  48  60  67  77  91
  9  19  23  30  45  49  61  65  78  89
 10  11  28  33  45  48  59  70  80  85
 10  12  26  34  46  49  60  68  81  83
 10  13  27  32  44  47  61  69  82  84
 10  14  22  36  43  53  56  66  78  91
 10  15  20  37  41  54  57  67  79  89
 10  16  21  35  42  55  58  65  77  90
 10  17  25  30  40  51  64  72  74  86
 10  18  23  31  38  52  62  73  75  87
 10  19  24  29  39  50  63  71  76  88

Cyclical representation

There is a cyclical representation ( Singer cycle ) for solution 1 of this block diagram, it is isomorphic to the above list of blocks. Starting from the block shown, the remaining blocks of the block plan are obtained by cyclic permutation of the points it contains.

  • Solution 1
  1   2   7  11  24  27  35  42  54  56

Orthogonal Latin Squares (MOLS)

This order 9 projective plane is equivalent to these 8 MOLS of order 9:

  • Solution 1



  • Solution 2



  • Solution 3



  • Solution 4


oval

An oval of the block plan is a set of its points, no three of which are on a block. Here is an example of a maximum order oval for each solution to this block diagram:

  • Solution 1
  1   2  11  21  32  55  63  69  76  88
  • Solution 2
  1   2  11  21  32  49  62  73  79  90
  • Solution 3
  1   2  11  21  42  50  64  72  80  88
  • Solution 4
  1   2  11  21  42  50  64  72  80  88

literature

Individual evidence

  1. Zvonimir Janko , Tran van Trung : The Classification of Projective Planes of Order 9 Which Possess an Involution. In: Journal of Combinatorial Theory, Series A. Vol. 33, No. 1, 1982, pp. 65-75, doi : 10.1016 / 0097-3165 (82) 90079-6 .
  2. ^ Rudolf Mathon, Alexander Rosa : 2- (ν, κ, λ) Designs of Small Order. In: Charles J. Colbourn , Jeffrey H. Dinitz (Eds.): Handbook of Combinatorial Designs. 2nd edition. Chapman and Hall / CRC, Boca Raton FL et al. 2007, ISBN 978-1-4200-1054-1 , pp. 25-57.
  3. ^ Clement WH Lam , Galina Kolesova, Larry Thiel: A computer search for finite projective planes of order 9. In: Discrete Mathematics. Vol. 92, No. 1/3, 1991, pp. 187-195, doi : 10.1016 / 0012-365X (91) 90280-F .