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VersalDeformations :: DefParam

DefParam -- deformation parameter

Description

DefParam is the name of an optional arguemt. Its value is a symbol, which specifies the name of the deformation parameter. Its default value is determined by the loadtime configuration Option DefaultDefParam, which has default value t.

For example, we may use the deformation parameter s:

i1 : S=QQ[x_0..x_4];
i2 : I=minors(2,matrix {{x_0,x_1,x_2,x_3},{x_1,x_2,x_3,x_4}});

o2 : Ideal of S
i3 : F0=gens I

o3 = | -x_1^2+x_0x_2 -x_1x_2+x_0x_3 -x_2^2+x_1x_3 -x_1x_3+x_0x_4
     ------------------------------------------------------------------------
     -x_2x_3+x_1x_4 -x_3^2+x_2x_4 |

             1       6
o3 : Matrix S  <--- S
i4 : (F,R,G,C)=versalDeformation(F0,DefParam=>s);
i5 : sum F

o5 = | x_1s_1+x_0s_2-x_1^2+x_0x_2 -s_1s_3+x_0s_4-x_1x_2+x_0x_3
     ------------------------------------------------------------------------
     -s_2s_3+s_3^2-s_1s_4-x_3s_1-x_2s_2+x_1s_4-x_2^2+x_1x_3
     ------------------------------------------------------------------------
     s_2s_3-s_3^2+x_2s_3-x_1x_3+x_0x_4 -x_4s_1-x_3s_2+x_3s_3-x_2x_3+x_1x_4
     ------------------------------------------------------------------------
     x_4s_3-x_3s_4-x_3^2+x_2x_4 |

                       1                 6
o5 : Matrix (S[s ..s ])  <--- (S[s ..s ])
                1   4             1   4

See also

Functions with optional argument named DefParam :

For the programmer

The object DefParam is a symbol.