Relatively Prime Polynomials and Nonsingular Hankel Matrices over Finite Fields

Relatively Prime Polynomials and Nonsingular Hankel Matrices over Finite Fields


Mario Garcia-Armas

Department of Mathematics,
University of British Columbia
Vancouver, BC V6T 1Z2, Canada

E-Mail: marioga@math.ubc.ca

Sudhir R. Ghorpade

Department of Mathematics
Indian Institute of Technology Bombay
Powai, Mumbai 400076, India

E-Mail: srg@math.iitb.ac.in

and

Samrith Ram

Department of Mathematics
Indian Institute of Technology Bombay
Powai, Mumbai 400076, India

E-Mail: samrith@mgmail.com


Abstract

The probability for two monic polynomials of a positive degree n with coefficients in the finite field Fq to be relatively prime turns out to be identical with the probability for an n x n Hankel matrix over Fq to be nonsingular. Motivated by this, we give an explicit map from pairs of coprime polynomials to nonsingular Hankel matrices that explains this connection. A basic tool used here is the classical notion of Bezoutian of two polynomials. Moreover, we give simpler and direct proofs of the general formulae for the number of m-tuples of relatively prime polynomials over Fq of given degrees and for the number of n x n Hankel matrices over Fq of a given rank.


1 Introduction 1
2 Preliminaries 2
3 An Explicit Surjection 3
4 Relatively Prime Polynomials 5
5 Hankel matrices over Fq 6
References 10


This paper is accepted for publication in the Journal of Combinatorial Theory, Series A. [Preprint Version: arXiv.math/1011.1760v1 (November 2010)]

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