preimage -- preimage of an ideal under a ring map

Synopsis

• Usage:

  preimage(f,I)

• Inputs:
  • I, an ideal in the target ring of f
  • f
• Outputs:
  • the preimage of I under the map f

Description

i1 : R = QQ[x,y,z]

o1 = R

o1 : PolynomialRing

i2 : S = QQ[t,u]

o2 = S

o2 : PolynomialRing

i3 : f = map(R,S,{x*y,y*z})

o3 = map (R, S, {x*y, y*z})

o3 : RingMap R <--- S

i4 : preimage_f ideal(x^2,y^2)

             2        2
o4 = ideal (u , t*u, t )

o4 : Ideal of S