Beyond Pioneer Quantum Mechanics

The new era of quantum theory began around 1932, and witnessed a maturation, many extensive developments, and a striking turn to an abstract structural approach. Important results of modern quantum theory, although easily accessible, are as yet not very well known. In spite of its urgency, the conceptual recasting of pioneer quantum mechanics has been slow. Even slower is the transference of successful reformulations into our textbooks which are still full of archaisms and inconsistencies; they hardly reflect the important progress made in the last two decades. In this chapter we shall attempt to give a brief outline of the main trends in the development of quantum theory since 1932. In this period, the new results have been so voluminous that it is necessary to limit our discussion and to select a few topics which are of special importance for the theory of molecular matter. Naturally the selection is in part guided by my prejudices, so my apologies are due to all those whose work has been ignored or insufficiently discussed.