Algorithms for Function Fields
Jürgen Klüners · Experimental Mathematics · 2002
Let K/Q(t) be a finite extension. We describe algorithms for computingsubfields and automorphisms of K/Q(t). As an application we give an algorithm for finding decompositions of rational functions in Q(α). We also present an algorithm which decides if an extension L/Q(t) is a subfield of K. In case [K: Q(t)] = [L: Q(t)] we obtain a Q(t)-isomorphism test. Furthermore, we describe an algorithm which computes subfields of the normal closure of K/Q(t).