RegularChains[ConstructibleSetTools]
RationalMapImage
compute the image of a variety or a constructible set under a rational map
Calling Sequence
Parameters
Description
Examples
RationalMapImage(F, RM, R, S)
RationalMapImage(F, H, RM, R, S)
RationalMapImage(CS, RM, R, S)
F
-
list of polynomials
RM
a list of rational functions in R
R
a polynomial ring (source)
S
a polynomial ring (target)
H
CS
constructible set
The command RationalMapImage(F, RM, R, S) returns a constructible set cs which is the image of the variety V⁡F under the rational map RM.
If H is specified, let W be the variety defined by the product of polynomials in H. The command RationalMapImage(F, H, RM, R, S) returns the image of the constructible set V-W under the rational map RM.
The command RationalMapImage(CS, RM, R, S) returns the image of the constructible set CS under the rational map RM.
Both rings R and S should be over the same ground field.
The variable sets of R and S should be disjoint.
The number of polynomials in RM is equal to the number of variables of ring S.
with⁡RegularChains:
with⁡ConstructibleSetTools:
The following example is related to the tacnode curve.
S≔PolynomialRing⁡t
S≔polynomial_ring
T≔PolynomialRing⁡x,y
T≔polynomial_ring
F≔
RM≔t3−6⁢t2+9⁢t−22⁢t4−16⁢t3+40⁢t2−32⁢t+9,t2−4⁢t+42⁢t4−16⁢t3+40⁢t2−32⁢t+9
cs≔RationalMapImage⁡F,RM,S,T
cs≔constructible_set
Info⁡cs,T
2⁢x4−3⁢y⁢x2+y4−2⁢y3+y2,y,10⁢y+2⁢x2+2⁢y3−y2−y,964⁢y6−480⁢y5−6858⁢y4−4328⁢y3−888⁢y2−72⁢y−2⁢x2−88⁢y8+2104⁢y7−2316⁢y6−943⁢y5+892⁢y4+318⁢y3+32⁢y2+y,x,y−1,1,x,y,1
See Also
ConstructibleSet
Difference
MakePairwiseDisjoint
Projection
RegularChains
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