یوسف محمدی

‎In this paper‎, ‎in order to develop a mathematical model underlying uncertainty and fuzziness in a dynamical system‎, ‎which is called relative mathematical modeling‎, ‎we are going to apply the notion of observer‎. ‎First‎, ‎by using a mathematical model of a one dimensional observer‎, ‎the notion of‎ ‎relative entropy for a relative dynamical system having countably many atoms is considered‎. ‎Also‎, ‎some ergodic properties of relative dynamical systems are investigated‎. ‎At the end‎, ‎a new version of Kolmogorov-Sinai theorem for a relative dynamical system having countably many atoms is given‎.