forceImage -- declare which is the image of a rational map

Synopsis

• Usage:

  forceImage(Phi,I)

• Inputs:
  • Phi, a rational map
  • I, an ideal
• Outputs:
  • null

Description

This method allows to inform the system about the image of a given rational map without performing any computation. In particular, this can be used to declare that a rational map is dominant.

i1 : P6 = QQ[t_0..t_6]; X = minors(3,matrix{{t_0..t_4},{t_1..t_5},{t_2..t_6}});

o2 : Ideal of P6

i3 : Phi = rationalMap(X,Dominant=>2);

o3 : RationalMap (cubic rational map from PP^6 to 6-dimensional subvariety of PP^9)

i4 : time forceImage(Phi,ideal 0_(target Phi))
 -- used 0.00100037s (cpu); 0.000497656s (thread); 0s (gc)

i5 : Phi;

o5 : RationalMap (cubic dominant rational map from PP^6 to 6-dimensional subvariety of PP^9)

Caveat

See also

• image(RationalMap) -- closure of the image of a rational map
• forceInverseMap -- declare that two rational maps are one the inverse of the other