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pureWeyman -- first Betti number of specific exact complex

Synopsis

Description

pureWeyman corresponds to the construction in math.AC/0709.1529v3 "The Existence of Pure Free Resolutions", Section 4.
i1 : L = {0,2,3,9}

o1 = {0, 2, 3, 9}

o1 : List
i2 : B = pureBettiDiagram L

            0  1  2 3
o2 = total: 7 27 21 1
         0: 7  .  . .
         1: . 27 21 .
         2: .  .  . .
         3: .  .  . .
         4: .  .  . .
         5: .  .  . .
         6: .  .  . 1

o2 : BettiTally
i3 : pureWeyman L

o3 = 21
i4 : L1 = {0,3,5,6}

o4 = {0, 3, 5, 6}

o4 : List
i5 : B1 = pureBettiDiagram L1

            0 1 2 3
o5 = total: 1 5 9 5
         0: 1 . . .
         1: . . . .
         2: . 5 . .
         3: . . 9 5

o5 : BettiTally
i6 : pureWeyman L1

o6 = 3
Thus, for large enough multiples m, m*B occurs as the Betti diagram of a module in the Weyman construction

However, B itself occurs for some modules:
i7 : betti res randomSocleModule(L,1)

            0  1  2 3
o7 = total: 7 27 21 1
         0: 7  .  . .
         1: . 27 21 .
         2: .  .  . .
         3: .  .  . .
         4: .  .  . .
         5: .  .  . .
         6: .  .  . 1

o7 : BettiTally
i8 : betti res randomModule(L,1)

            0  1  2  3
o8 = total: 7 27 35 15
         0: 7  .  .  .
         1: . 27 11  .
         2: .  . 24 15

o8 : BettiTally
i9 : betti res randomModule({0,6,7,9},1)

            0  1  2 3
o9 = total: 1 21 27 7
         0: 1  .  . .
         1: .  .  . .
         2: .  .  . .
         3: .  .  . .
         4: .  .  . .
         5: . 21 27 .
         6: .  .  . 7

o9 : BettiTally
i10 : betti res randomSocleModule(L1,1)

             0 1 2 3
o10 = total: 1 5 9 5
          0: 1 . . .
          1: . . . .
          2: . 5 . .
          3: . . 9 5

o10 : BettiTally
i11 : betti res randomModule(L1,1)

             0 1 2 3
o11 = total: 1 5 9 5
          0: 1 . . .
          1: . . . .
          2: . 5 . .
          3: . . 9 5

o11 : BettiTally
i12 : betti res randomModule({0,1,3,6},1)

             0 1 2 3
o12 = total: 5 9 7 3
          0: 5 9 . .
          1: . . 4 .
          2: . . 3 3

o12 : BettiTally
i13 : betti res randomSocleModule({0,1,3,6},1)     	  

             0 1 2 3
o13 = total: 5 9 5 1
          0: 5 9 . .
          1: . . 5 .
          2: . . . .
          3: . . . 1

o13 : BettiTally

See also

Ways to use pureWeyman :

For the programmer

The object pureWeyman is a method function.