Space-time in a simple model of a physical system

A model of space-time is worked out starting from the two primitive concepts of preparticle and of membership relation of set theory. We obtain as derivative concepts those of space-time and inertial reference frame, also those of energy, frequency, momentum, and wavelength of a physical system in a given reference frame. Proportionality relations between energy and frequency, and between momentum and (wavelength)^–1 are shown to be satisfied in our model. The same constant of proportionality intervenes in these two relations, and we interpret it as the Planck constant expressed in a particular system of units. Energy and momentum are conserved in the usual sense, provided we consider sufficiently large regions of the space-time diagram associated to the reference frame under consideration. Lorentz transformations and Heisenberg's inequalities are discussed within the framework of our model.