pushFwd(Module,RingMap) -- push forward of a module

Synopsis

Given a (not necessarily finite) ring map f:A → B and a B-module N which is finite over A, the function returns a presentation of N as an A-module.

i1 : kk = QQ

o1 = QQ

o1 : Ring

i2 : A = kk[t]

o2 = A

o2 : PolynomialRing

i3 : B = kk[x,y]/(x*y)

o3 = B

o3 : QuotientRing

i4 : use B

o4 = B

o4 : QuotientRing

i5 : i = ideal(x)

o5 = ideal(x)

o5 : Ideal of B

i6 : f = map(B,A,{x})

o6 = map(B,A,{x})

o6 : RingMap B <--- A

i7 : pushFwd(module i,f)

      1
o7 = A

o7 : A-module, free, degrees {1}