Numerically stable conditions on rational and essential singularities

Abstract

This paper demonstrates some connections between the coefficients of a Taylor series $f(z)=\ds\sum_{n=0}^\infty a_n z^n$ and singularities of the function. There are many known results of this type, for example, counting the number of poles on the circle of convergence, and doing convergence or overconvergence for $f$ on any arc of holomorphy. A new approach proposed here is that these kinds of results are extended by relaxing the classical conditions for singularities and convergence theorems. This is done by allowing the coefficients to be sufficiently small instead of being zero.