Computing selected solutions of polynomial equations

Abstract

We present efficient and accurate algorithms to compute solutions of zero-dimensional multivariate polynomial equations in a given domain. Earlier methods for solving polynomial equations are based on iterative methods, homotopy methods or symbolic elimination. The total number of solutions correspond to the Bezout bound for dense polynomial systems or the BKK bound for sparse systems. In most applications the actual number of solutions in the domain of interest is much lower than the Bezout or BKK bound. Our approach is based on global formulation of the problem using resultants and matrix computations and localizing it to find selected solutions only. The problem of finding roots is reduced to computing eigenvalues of a generalized companion matrix and we use the structure of the matrix to compute the solutions in the domain of interest only. The resulting algorithm is iterative in nature and we discuss its performance on a number of applications.