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improveFamily -- Find a 1-parameter smoothing family with perhaps smaller number of terms and coefficients

Description

We first compute the flat family of ideals which uses the same terms as J using getParameterFamily. We then choose a point in a smoothing component of the base which uses hopefully fewer terms and smaller coefficients by using getOneParameterFamily

i1 : R=QQ[x_0..x_1, x_3, x_5..x_6, z, Degrees => {7..8, 17, 19..20, 1}]

o1 = R

o1 : PolynomialRing
i2 : J=ideal(x_1^3-x_0*x_3+x_1*z^16+x_0*z^17,x_1*x_5-x_0*x_6+x_0^2*z^13+x_1*z^19-x_0*z^20,x_0^4-x_1*x_6+x_0*x_1*z^13
   +x_0^2*z^14-x_1*z^20,x_1^2*x_3-x_0^2*x_5-x_5*z^14+x_3*z^16+x_1^2*z^17+x_0*x_1*z^18+x_0^2*z^19,x_3^2-x_0^2*x_6
   +x_0^3*z^13-x_6*z^14+x_1^2*z^18+2*x_0*x_1*z^19-x_0^2*z^20+x_0*z^27-2*z^34,x_3*x_5-x_1^2*x_6+x_0*x_1^2*z^13-x_
   6*z^16-x_5*z^17+x_3*z^19-x_1^2*z^20+x_0*z^29-2*z^36,x_0^3*x_1^2-x_3*x_6+x_0*x_3*z^13+x_0*x_1^2*z^14+x_0^3*z^
   16+x_6*z^17-x_3*z^20+z^37,x_0^3*x_3-x_5^2+x_0^2*x_1*z^16+x_0^3*z^17+x_6*z^18-x_0*z^31+2*z^38,x_0^2*x_1*x_3-x_
   5*x_6+x_0*x_5*z^13+x_0*x_1^2*z^16+x_0^2*x_1*z^17+x_0^3*z^18+x_6*z^19-x_5*z^20+z^39,x_0^3*x_5-x_6^2+2*x_0*x_6*
   z^13+x_0*x_5*z^14+x_0^3*z^19-2*x_6*z^20-x_0^2*z^26+3*x_0*z^33-z^40)

             3             16      17                 2 13      19      20
o2 = ideal (x  - x x  + x z   + x z  , x x  - x x  + x z   + x z   - x z  ,
             1    0 3    1       0      1 5    0 6    0       1       0
  4               13    2 14      20   2      2        14      16    2 17
 x  - x x  + x x z   + x z   - x z  , x x  - x x  - x z   + x z   + x z
  0    1 6    0 1       0       1      1 3    0 5    5       3       1
        18    2 19   2    2      3 13      14    2 18         19    2 20
 + x x z   + x z  , x  - x x  + x z   - x z   + x z   + 2x x z   - x z
    0 1       0      3    0 6    0       6       1        0 1       0
      27     34          2        2 13      16      17      19    2 20
 + x z   - 2z  , x x  - x x  + x x z   - x z   - x z   + x z   - x z   +
    0             3 5    1 6    0 1       6       5       3       1
    29     36   3 2               13      2 14    3 16      17      20
 x z   - 2z  , x x  - x x  + x x z   + x x z   + x z   + x z   - x z   +
  0             0 1    3 6    0 3       0 1       0       6       3
  37   3      2    2   16    3 17      18      31     38   2
 z  , x x  - x  + x x z   + x z   + x z   - x z   + 2z  , x x x  - x x  +
       0 3    5    0 1       0       6       0             0 1 3    5 6
      13      2 16    2   17    3 18      19      20    39   3      2
 x x z   + x x z   + x x z   + x z   + x z   - x z   + z  , x x  - x  +
  0 5       0 1       0 1       0       6       5            0 5    6
       13        14    3 19       20    2 26       33    40
 2x x z   + x x z   + x z   - 2x z   - x z   + 3x z   - z  )
   0 6       0 5       0        6       0        0

o2 : Ideal of R
i3 : L=flatten drop(degrees R,-1)

o3 = {7, 8, 17, 19, 20}

o3 : List
i4 : J1=improveFamily(J)

#pos = 1, #posa = 1
#pos = 2, #posa = 2

             3             16      17                 2 13      19   4
o4 = ideal (x  - x x  + x z   + x z  , x x  - x x  + x z   + x z  , x  - x x
              1    0 3    1       0      1 5    0 6    0       1      0    1 6
        13    2 14   2      2        14      16    2 17        18
 + x x z   + x z  , x x  - x x  - x z   + x z   + x z   + x x z   +
    0 1       0      1 3    0 5    5       3       1       0 1
  2 19   2    2      3 13      14    2 18         19      27    34
 x z  , x  - x x  + x z   - x z   + x z   + 2x x z   + x z   - z  , x x
  0      3    0 6    0       6       1        0 1       0            3 5
    2        2 13      16      17      19      29    36   3 2
 - x x  + x x z   - x z   - x z   + x z   + x z   - z  , x x  - x x  +
    1 6    0 1       6       5       3       0            0 1    3 6
      13      2 14    3 16      17   3      2    2   16    3 17      18
 x x z   + x x z   + x z   + x z  , x x  - x  + x x z   + x z   + x z   -
  0 3       0 1       0       6      0 3    5    0 1       0       6
    31    38   2                   13      2 16    2   17    3 18
 x z   + z  , x x x  - x x  + x x z   + x x z   + x x z   + x z   +
  0            0 1 3    5 6    0 5       0 1       0 1       0
    19   3      2         13        14    3 19    2 26      33
 x z  , x x  - x  + 2x x z   + x x z   + x z   - x z   + x z  )
  6      0 5    6     0 6       0 5       0       0       0

o4 : Ideal of R
i5 : J_*/size

o5 = {4, 5, 5, 7, 9, 9, 8, 7, 9, 9}

o5 : List
i6 : J1_*/size

o6 = {4, 4, 4, 7, 8, 8, 6, 7, 7, 7}

o6 : List
i7 : (M,C)=coefficients gens J;
i8 : unique (entries flatten C)_0

o8 = {0, 1, -1, 2, -2, 3}

o8 : List
i9 : (M1,C1)=coefficients gens J1;
i10 : unique (entries flatten C1)_0

o10 = {0, 1, -1, 2}

o10 : List

Caveat

It is possible that the function does not find a smooth fiber, which results in a message that these example needs to be repeated.

See also

Ways to use improveFamily:

  • improveFamily(Ideal)

For the programmer

The object improveFamily is a method function with options.


The source of this document is in /build/reproducible-path/macaulay2-1.26.06+ds/M2/Macaulay2/packages/WeierstrassSemigroups.m2:1983:0.