Non-standard realistic models of quantum phenomena and new forms of complementarity

This paper addresses the problem of different complementary interpretations of atomic phenomena. We take complementarity seriously as a meaningful philosophical principle, in the same way that the same principles to which complementarity limits simultaneous recourse, such as realism and causality, are endowed with meaning. We will then discuss the attempts to overcome the complementary relation between waves and particles in a realistic sense by attributing an independent physical reality to both wave-like and particle-like entities, showing the negative results of such attempts, which instead reveal the validity of another formulation of the principle of complementarity: the so-called smooth complementarity, according to which wave and corpuscular representations can mix without a rigid distinction, although one continues to manifest itself at the expense of the other. We will emphasize how a particularly weak realist interpretation of the quantum mechanical wave function conflicts with a (strong) formulation of the causal principle, and show the emergence of another form of classical complementarity between the realist and causal interpretations, which may assume a new smooth form even in this case. Complementarity confirms, in this way, its central role in the foundations of quantum mechanics and indicates at the same time how the philosophical interpretation of this theory, from the point of view of both realism and causality, remains a meaningful open question.