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isCommutative(SimplicialModuleMap) -- whether a simplicial module map commutes with the face/degeneracy maps

Description

For a simplicial module map $f : C \to D$, this method checks whether, for all $i$, we have $dd^D_{i} * f_i = f_{i-1} * dd^C_i$ and, if the source at target are equipped with degeneracy maps, it also checks the equality $ss^D_{i} * f_i = f_{i+1} * ss^C_i$.

We first construct a random simplicial module map which commutes with the face/degeneracy map.

i1 : S = ZZ/101[a,b,c];
i2 : C = simplicialModule(freeResolution coker vars S, Degeneracy => true)

      1      4      10      20
o2 = S  <-- S  <-- S   <-- S  <-- ...
                            
     0      1      2       3

o2 : SimplicialModule
i3 : D = C ** C

      1      16      100      400
o3 = S  <-- S   <-- S    <-- S   <-- ...
                              
     0      1       2        3

o3 : SimplicialModule
i4 : isWellDefined D

o4 = true
i5 : f1 = prune randomSimplicialMap(D, C, Cycle => true, InternalDegree => 1);
i6 : prune normalize f1

          1                       1
o6 = 0 : S  <------------------- S  : 0
               | -14a-6b+26c |

          15                                                      3
     1 : S   <-------------------------------------------------- S  : 1
                {1} | 4a-b-32c     4a+25b+10c   -44a+41b+26c |
                {1} | -20a+28b-27c -23a-14b+13c -22a+28b+34c |
                {1} | -34a+25b-43c -2a-9b+27c   14a-12b-28c  |
                {1} | -40a+43b+17c -31a+48b-12c -35a+16b+29c |
                {1} | -27a-13b+8c  30a+17b-8c   -49a+29b+37c |
                {1} | -39a-5b-23c  -38a-27b-12c -11a+12b+7c  |
                {2} | 22           27           -22          |
                {2} | 15           34           20           |
                {2} | 7            -11          -50          |
                {2} | -16          -27          -6           |
                {2} | -15          -9           44           |
                {2} | 7            10           -2           |
                {2} | 6            -48          -22          |
                {2} | -8           47           26           |
                {2} | -35          -15          47           |

          69                                                      3
     2 : S   <-------------------------------------------------- S  : 2
                {2} | -17a-15b-41c 21a-9b+6c    11a-35b-17c  |
                {2} | -28a-19b+5c  11a+4b-22c   -2a+4b+31c   |
                {2} | 28a+46b+40c  16a-9b-35c   -38a-47b+10c |
                {2} | -31a-31b+25c -35a-47b-17c 9b-48c       |
                {2} | 35a-28b-38c  50a+13b+40c  -29a-5c      |
                {2} | -45a+41b+2c  20a+47b+29c  -10a-27b+2c  |
                {2} | 27a+40b-48c  -22a-14b+13c -28b+5c      |
                {2} | -46a+12b-24c -41a+6b-47c  -22a-30b-25c |
                {2} | 19a-9b+3c    42a+15b+2c   8a-31b-22c   |
                {2} | 13a+27b-33c  -36a-16b-32c -15a+37b-18c |
                {2} | 2a+13b+19c   32a+31c      31a+29b+45c  |
                {2} | 48a-31b-19c  18a+39b+13c  17a+23b+21c  |
                {2} | -9a-47b+12c  -32a-43b+25c 28a+32b-5c   |
                {2} | 27a+15b-31c  -20a+26c     12a+44b-25c  |
                {2} | -28a+42b+27c 28a+36b-12c  -2a+31b-14c  |
                {2} | -30a-38c     -46a-12b+25c -12a-25b+41c |
                {2} | -31a+9b-22c  -28a+44b+26c -2a-36b-25c  |
                {2} | 24a-37b      -25a-42b+23c 7a+46b+12c   |
                {2} | -30a-13b-3c  -48a-38b-36c -40a-2b+24c  |
                {2} | 5a-10b-22c   42a-47b-42c  -14a+27b-38c |
                {2} | -15a+30b     -33a-46b+35c -44a+42b+15c |
                {2} | 12a+20b+49c  28a-47b+50c  45a+48b+48c  |
                {2} | -17a-47b+11c -14a-45b+5c  -23a-15b-5c  |
                {2} | 6a-45b+22c   26a-46b-14c  -15a+14b-32c |
                {3} | -17          -34          39           |
                {3} | 0            -36          0            |
                {3} | -37          23           49           |
                {3} | 34           -33          26           |
                {3} | 4            -48          -44          |
                {3} | 41           -17          -12          |
                {3} | -43          -7           5            |
                {3} | 36           1            15           |
                {3} | 4            24           -35          |
                {3} | -21          -40          22           |
                {3} | -30          9            -8           |
                {3} | 26           36           -8           |
                {3} | 38           -43          38           |
                {3} | 14           20           -9           |
                {3} | -49          -36          -33          |
                {3} | -9           -49          -3           |
                {3} | -3           -30          -24          |
                {3} | -22          -50          9            |
                {3} | 5            -41          -30          |
                {3} | -5           -41          37           |
                {3} | 10           14           18           |
                {3} | -18          26           -28          |
                {3} | 27           6            -50          |
                {3} | 24           -50          11           |
                {3} | 9            49           35           |
                {3} | 8            10           37           |
                {3} | -9           41           -5           |
                {3} | -18          26           40           |
                {3} | -50          33           17           |
                {3} | 3            9            -33          |
                {3} | -25          -40          9            |
                {3} | 41           2            34           |
                {3} | -41          35           45           |
                {3} | -2           -11          -23          |
                {3} | 18           47           -1           |
                {3} | 27           -5           -4           |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |
                {4} | 0            0            0            |

          147                            1
     3 : S    <------------------------ S  : 3
                 {3} | 24a-36b-30c  |
                 {3} | 39a+8b+15c   |
                 {3} | 23b-47c      |
                 {3} | 37a-39b+5c   |
                 {3} | -49a+33b-23c |
                 {3} | -19a-33b-29c |
                 {3} | -16a+17b+4c  |
                 {3} | -39a+44b-20c |
                 {3} | -39a+9b+36c  |
                 {3} | 47a+13b+4c   |
                 {3} | -29a+19b+19c |
                 {3} | -10a-29b-8c  |
                 {3} | -22a-29b-24c |
                 {3} | 22a-26b-18c  |
                 {3} | -8a-11b-49c  |
                 {3} | -35a-31b-48c |
                 {3} | -38a-16b+39c |
                 {3} | 21a+34b+19c  |
                 {3} | -47a-39b-18c |
                 {3} | 3a+43b-22c   |
                 {3} | 20a+33b-29c  |
                 {3} | 10a+36b-8c   |
                 {3} | -13a-43b-15c |
                 {3} | -28a-47b+38c |
                 {3} | 2a+16b+22c   |
                 {3} | -33a-45b-26c |
                 {3} | -5a-11b-3c   |
                 {3} | -35a+9b-22c  |
                 {3} | 45a-34b-48c  |
                 {3} | -47a+47b+19c |
                 {3} | -16a+7b+15c  |
                 {3} | -30a-28b-49c |
                 {3} | 5a+41b-40c   |
                 {3} | -13a+15b-48c |
                 {3} | -28a+16b+46c |
                 {3} | 9a-6b+10c    |
                 {3} | -26a+16b+30c |
                 {3} | -23a+39b+43c |
                 {3} | -17a-11b+48c |
                 {3} | 36a+35b+11c  |
                 {3} | 35a-49b+8c   |
                 {3} | 21a-4b-44c   |
                 {3} | -4a-32b-9c   |
                 {3} | 40a+6b-35c   |
                 {3} | -42a+18b+28c |
                 {3} | -16a+8b+3c   |
                 {3} | -38a+33b+40c |
                 {3} | 11a+46b-28c  |
                 {3} | a-3b+22c     |
                 {3} | 25a-31b-45c  |
                 {3} | -2a-2b+24c   |
                 {3} | 7a-18b-41c   |
                 {3} | 4a-13b-49c   |
                 {3} | -28a-47b+30c |
                 {3} | 49a-7b+27c   |
                 {3} | -47a-23b-7c  |
                 {4} | -38          |
                 {4} | -27          |
                 {4} | -42          |
                 {4} | 12           |
                 {4} | 20           |
                 {4} | -23          |
                 {4} | 27           |
                 {4} | -48          |
                 {4} | 17           |
                 {4} | -26          |
                 {4} | -25          |
                 {4} | -16          |
                 {4} | 44           |
                 {4} | -47          |
                 {4} | 42           |
                 {4} | -37          |
                 {4} | -33          |
                 {4} | -37          |
                 {4} | 27           |
                 {4} | -33          |
                 {4} | 40           |
                 {4} | 35           |
                 {4} | -29          |
                 {4} | 5            |
                 {4} | 15           |
                 {4} | -34          |
                 {4} | 35           |
                 {4} | 30           |
                 {4} | -19          |
                 {4} | 27           |
                 {4} | 29           |
                 {4} | -9           |
                 {4} | 5            |
                 {4} | -7           |
                 {4} | -43          |
                 {4} | 41           |
                 {4} | 32           |
                 {4} | 31           |
                 {4} | -29          |
                 {4} | 42           |
                 {4} | 37           |
                 {4} | 34           |
                 {4} | 0            |
                 {4} | 0            |
                 {4} | 0            |
                 {4} | 16           |
                 {4} | -1           |
                 {4} | 49           |
                 {4} | -42          |
                 {4} | -17          |
                 {4} | -23          |
                 {4} | 0            |
                 {4} | 0            |
                 {4} | 0            |
                 {4} | 30           |
                 {4} | -20          |
                 {4} | -17          |
                 {4} | -24          |
                 {4} | -47          |
                 {4} | 12           |
                 {4} | 0            |
                 {4} | 0            |
                 {4} | 0            |
                 {4} | -31          |
                 {4} | -33          |
                 {4} | 41           |
                 {4} | -16          |
                 {4} | 6            |
                 {4} | -43          |
                 {4} | -27          |
                 {4} | -50          |
                 {4} | -6           |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {5} | 0            |
                 {6} | 0            |

o6 : ComplexMap
i7 : isCommutative oo

o7 = true
i8 : isCommutative f1

o8 = true
i9 : assert(degree f1 == 0)

We next generate a simplicial module map that is commutative and (likely) induces a nontrivial map on homology.

i10 : f2 = randomSimplicialMap(D, C, Cycle => true);
i11 : isCommutative f2

o11 = true
i12 : assert(degree f2 == 0)
i13 : assert isSimplicialMorphism f2

If the debugLevel is greater than zero, then the location of the first failure of commutativity is displayed.

See also

Ways to use this method:


The source of this document is in /build/reproducible-path/macaulay2-1.26.05+ds/M2/Macaulay2/packages/SimplicialModules/SimplicialModuleDOC.m2:2134:0.