Recursive constructions of k-normal polynomials using some rational transformations over finite fields

Some results on the [Formula: see text]-normal elements and [Formula: see text]-normal polynomials over finite fields are given in the recent literature. In this paper, we show that a transformation [Formula: see text] can be used to produce an infinite sequence of irreducible polynomials over a finite field [Formula: see text] of characteristic [Formula: see text]. By iteration of this transformation, we construct the [Formula: see text]-normal polynomials of degree [Formula: see text] in [Formula: see text] starting from a suitable initial [Formula: see text]-normal polynomial of degree [Formula: see text]. We also construct an infinite sequence of [Formula: see text]-normal polynomials using a certain quadratic transformation over [Formula: see text].

A FIRST APPROACH TOWARDS NORMAL PARAMETRIZATIONS OF ALGEBRAIC SURFACES

In this paper we analyze the problem of deciding the normality (i.e. the surjectivity) of a rational parametrization of a surface [Formula: see text]. The problem can be approached by means of elimination theory techniques, providing a proper close subset [Formula: see text] where surjectivity needs to be analyzed. In general, these direct approaches are unfeasible because [Formula: see text] is very complicated and its elements computationally hard to manipulate. Motivated by this fact, we study ad hoc computational alternative methods that simplifies [Formula: see text]. For this goal, we introduce the notion of pseudo-normality, a concept that provides necessary conditions for a parametrization for being normal. Also, we provide an algorithm for deciding the pseudo-normality. Finally, we state necessary and sufficient conditions on a pseudo-normal parametrization to be normal. As a consequence, certain types of parametrizations are shown to be always normal. For instance, pseudo-normal polynomial parametrizations are normal. Moreover, for certain class of parametrizations, we derive an algorithm for deciding the normality.