A new proof of Fitzgerald's characterization of primitive polynomials

We give a new proof of Fitzgerald's criterion for primitive polynomials over a finite field. Existing proofs essentially use the theory of linear recurrences over finite fields. Here, we give a much shorter and self-contained proof which does not use the theory of linear recurrences.     

The number of irreducible polynomials over finite fields of characteristic 2 with given trace and subtrace

In this paper we obtained the formula for the number of irreducible polynomials with degree n over finite fields of characteristic two with given trace and subtrace. This formula is a generalization of the result of Cattell et al. (2003) [2].     

The coefficients of primitive polynomials over finite fields

For , we prove that there always exists a primitive polynomial of degree over a finite field with the first and second coefficients prescribed in advance.

     

Primitive normal polynomials with the specified last two coefficients

We get that for any element a∈F_q and any primitive element , there exists a primitive normal polynomial f(x)=xⁿ−σ₁xⁿ⁻¹+?+(−1)ⁿ⁻¹σ_n−1x+(−1)ⁿσ_n with σ_n−1=a, σ_n=b for n≥5. The estimates of hybrid extended Kloostermann sums over finite fields and some new variations of Cohen’s sieve techniques help to get the above result.     

Bivariate identities related to Chebyshev and Dickson polynomials over Fq

Let ${\mathbb{F}}_q$ be a field of q elements, where q is a power of an odd prime p. The polynomial $f(y)\in {\mathbb{F}}_q[y]$ defined by$f(y):={(1+\sqrt{y})}^{(q+1)/2}+{(1-\sqrt{y})}^{(q+1)/2}$ has the property that$f(1-y)=\rho (2)f(y),$ where ρ is the quadratic character on ${\mathbb{F}}_q$. This univariate identity was applied to prove a recent theorem of N. Katz. We formulate and prove a bivariate extension, and give an application to quadratic residuacity.     

The parity of the number of irreducible factors for some pentanomials

It is well known that the Stickelberger–Swan theorem is very important for determining the reducibility of polynomials over a binary field. Using this theorem the parity of the number of irreducible factors for some kinds of polynomials over a binary field, for instance, trinomials, tetranomials, self-reciprocal polynomials and so on was determined. We discuss this problem for Type II pentanomials, namely x^m+xⁿ⁺²+xⁿ⁺¹+xⁿ+1F₂[x] for even m. Such pentanomials can be used for the efficient implementation of multiplication in finite fields of characteristic two. Based on the computation of the discriminant of these pentanomials with integer coefficients, we will characterize the parity of the number of irreducible factors over F₂ and establish necessary conditions for the existence of this kind of irreducible pentanomials.Our results have been obtained in an experimental way by computing a significant number of values with Mathematica and extracting the relevant properties.     

Fibre products of supersingular curves and the enumeration of irreducible polynomials with prescribed coefficients

For any positive integers $n\ge 3$, $r\ge 1$ we present formulae for the number of irreducible polynomials of degree n over the finite field ${\mathbb{F}}_{2^r}$ where the coefficients of $x^{n-1}$, $x^{n-2}$ and $x^{n-3}$ are zero. Our proofs involve counting the number of points on certain algebraic curves over finite fields, a technique which arose from Fourier-analysing the known formulae for the ${\mathbb{F}}_2$ base field cases, reverse-engineering an economical new proof and then extending it. This approach gives rise to fibre products of supersingular curves and makes explicit why the formulae have period 24 in n.     

Complete permutation polynomials with the form (xpm−x+δ)s+axpm+bx over Fpn

In this paper, several classes of complete permutation polynomials with the form ${(x^{p^m}-x+\delta )}^s+a{x}^{p^m}+bx$ over ${\mathbb{F}}_{p^n}$ are proposed by the AGW criterion and determining the number of solutions of some equations. Our results also enrich constructions of known permutation polynomials.     

Using the theory of cyclotomy to factor cyclotomic polynomials over finite fields

We examine the problem of factoring the th cyclotomic polynomial, over , and distinct primes. Given the traces of the roots of we construct the coefficients of in time . We demonstrate a deterministic algorithm for factoring in time when has precisely two irreducible factors. Finally, we present a deterministic algorithm for computing the sum of the irreducible factors of in time .

     

On the enumeration of polynomials with prescribed factorization pattern

We use generating functions over group rings to count polynomials over finite fields with the first few coefficients and a factorization pattern prescribed. In particular, we obtain different exact formulas for the number of monic n-smooth polynomials of degree m over a finite field, as well as the number of monic n-smooth polynomials of degree m with the prescribed trace coefficient.