CRPC-TR99793-S September 1999 Title: The Sphere of Convergence of Newton's Method on Two Equivalent Systems from Nonlinear Programming Authors: Maria Cristina Villalobos, Richard A. Tapia, and Yin Zhang Submitted November 1999 Abstract: We study a local feature of a Newton logarithmic barrier function method and a Newton primal-dual interior-point method. In particular, we study the radius of the sphere of convergence of Newton's method on two equivalent systems associated with the two aforementioned interior-point methods for nondegenerate problems in inequality contrained optimization problems. Our theoretical and numerical results are clearly in favor of using Newton primal-dual methods for solving the optimization problem. This work is an extension of the authors' earlier work [10] on linear programming problems. ------------------------------------------------------------------------------ Maria Cristina Villalobos cristina@caam.rice.edu Department of Computational and Applied Mathematics Rice University Richard Tapia rat@caam.rice.edu Department of Computational and Applied Mathematics Rice University Yin Zhang zhang@caam.rice.edu Department of Computational and Applied Mathematics Rice Universityz