Are the coefficients of a polynomial well-conditioned functions of its roots?
For an entire function let be the Newton function associated to . Each zero of is an attractive fixed point of and is contained in an invariant component of the Fatou set of the meromorphic function in which the iterates of converge to . If has an asymptotic representation , in a sector , then there exists an invariant component of the Fatou set where the iterates of tend to infinity. Such a component is called an invariant Baker domain.A question in the opposite direction...
An algorithm for the calculation of a lower bound of the absolute values of the roots of a real algebraic polynomial, of an arbitrary degree, is derived. An example is given to compare the bounds calculated by the method proposed and by other methods.
Newton's method for computation of a square root yields a difference equation which can be solved using the hyperbolic cotangent function. For the computation of the third root Newton's sequence presents a harder problem, which already Cayley was trying to solve. In the present paper two mutually inverse functions are defined in order to solve the difference equation, instead of the hyperbolic cotangent and its inverse. Several coefficients in the expansion around the fixed points are obtained,...