REAL NUMBER COMPUTATIONS - ON THE USE OF INFORMATION

When comparing complexity theory over the ring Z (Turing machine) on o ne hand and over the ring R (Blum-Shub-Smale machine) on the other han d, it will be important to study how methods and ideas of the first ca n be transformed to the second one. In this sense the present paper is concerned with the relation between a characterization of the P = N P ? - question for the Z-case (given by Krentel) and a special class of quadratic - programming problems which are important in the real model .