laurent series ring induced homomorphism

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No, you can!

The posted question comes with no special situation, so i will try to generate one with a non-obvious homomorphism of base ring(s). The rings will be R and S, we define some morphism f between them, then the line Lf = LR.Hom(LS)(f)is the answer to the question, it constructs the induced morphism between the Laurent polynomial rings

• LR of R, and respectively
• LS of S.

(There is some issue with the right names for the generators.)

Details in a concrete situation. So let us declare in sage $$R=\mathbb Z[x] / (\ x^2 + 6x + 3 \ )\longrightarrow\mathbb F_{49}=S\ ,$$ as follows:

R0.<x> = PolynomialRing(ZZ)
R.<a> = R0.quotient( x^2 + 6*x + 3 )
S.<b> = GF( 7**2, modulus = x^2 + 6*x + 3 )
f = R.Hom(S)( [ b^7, ] )

Here, the generator $a$ of $R$ goes to $b^7$. For instance:

sage: f( 1+a )
6*b + 2
sage: 1+b^7
6*b + 2

We then introduce the Laurent polynomial rings LR, LS over $R,S$, and we have the induced morphism Lf. Sample code:

sage: LR.<s,t> = LaurentPolynomialRing( R )
sage: LS.<s,t> = LaurentPolynomialRing( S )
sage: sR,tR = LR.gens()
sage: Lf = LR.Hom(LS)(f)
sage: Lf
Ring morphism:
  From: Multivariate Laurent Polynomial Ring in s, t
        over Univariate Quotient Polynomial Ring in a
        over Integer Ring with modulus x^2 + 6*x + 3
  To:   Multivariate Laurent Polynomial Ring in s, t
        over Finite Field in b of size 7^2
  Defn: Induced from base ring by
        Ring morphism:
          From: Univariate Quotient Polynomial Ring in a
                over Integer Ring with modulus x^2 + 6*x + 3
          To:   Finite Field in b of size 7^2
          Defn: a |--> 6*b + 1
sage: Lf( (1+a)*sR + 8*tR )
(6*b + 2)*s + t

The information on Lf was manually arranged.

Note: In such cases please always give the concrete mathematical example of interest. (And of course, code initializing the objects in sage is welcome!) Things become simpler if the