The Referents of a Physical Theory

Mario Bunge

A semantical and methodological analysis of physical theories is performed in order to find out their relation to reality and to human experience. It is shown that every physical theory refers immediately to an idealized model of waht is supposed to be a piece of reality-the mediate referent of the theory. Two kinds of physical interpretation of physical symbols are distinguished : objective and operational, and the difference between reference and evidence is stressed. It is claimed that for a theory to be physically meaningful it is necessary that it includes rules of objective reference. In some cases a theory contains, in addition, evidential reference rules, i.e. correspondences between some of its concepts and empirical items. But the test. of any theory requires, rather than operational rules, further theories that can bridge the gap between what the theory refers to (e.g., the passage of a cosmic ray) and its remote symptom (e.g., the click of a counter). The conditions for the semantical consistency are sketched and it is argued that there does not exist a semantically consistency inter-pretation of any of the formalisms of quantum theory. From this analysis arguments in favor of critical realism are drawn.

Tiago Martinelli, Diogo O. Soares-Pinto

The Page-Wootters mechanism questioned the fundamental nature of time in quantum physics. The mechanism explored the notion that a given physical quantity is always defined and measured relative to a reference frame, in general, not explained in the theoretical description of quantum physical experiments. Recently, the resource theory of asymmetry deals explicitly with the physical conditions necessary for a quantum system to serve as a good reference frame. Nonetheless, to quantify a quantum reference frame in relation to another one, it is important to establish an internal description of quantum theory, i.e., without the need for a classical reference frame. In this work, we address this issue with the concept of mutual asymmetry and use this machinery in the Page-Wootters mechanism by identifying the concept of mutual asymmetry as mutual or internal coherence. To do so, the notion of quantum coherence in relation to a quantum reference frame is revisited and a quantifier is proposed in this scenario. Also, this opens space to investigate the link of internal coherence and correlations, as proposed by Page and Wootters, under a resource theory approach.

P. A. M. Dirac

Hans Primas

Nijalingappa Umakantha

A new approach to probability theory is presented with reference to statistics and statistical physics. At the outset, it is recognized that the “average man” of a population and the “average particle” of a gas are only objects of thought, and not real entities which exist in nature. The concept of average (man) is generalized as a new concept of represental (man) whose epistemological status is intermediate between those of the particular (the man) and the universal (a man). This new concept has become necessary as a result of emergence of statistics as a new branch of human knowledge at the beginning of the nineteenth century. Probability is defined with reference to the represental. The concept of probability is the same in probability theory and in physics. But whereas in statistics the probabilities are estimated using random sequences, in statistical physics they are determined either by the laws of physics alone or by making use of the laws of probability also. Thus in physics we deal with probability at a more basic level than in statistics. This approach is free from most of the controversies we face at present in interpreting probability theory and quantum mechanics.