Questions of method in the consistency problem of quantum mechanics

Robert S. Cohen, John J. Stachel

K. Tamvakis

This collection of solved problems corresponds to the standard topics covered in established undergraduate and graduate courses in Quantum Mechanics. Problems are also included on topics of interest which are often absent in the existing literature. Solutions are presented in considerable detail, to enable students to follow each step. The emphasis is on stressing the principles and methods used, allowing students to master new ways of thinking and problem-solving techniques. The problems themselves are longer than those usually encountered in textbooks and consist of a number of questions based around a central theme, highlighting properties and concepts of interest. For undergraduate and graduate students, as well as those involved in teaching Quantum Mechanics, the book can be used as a supplementary text or as an independent self-study tool.

Elias Okon, Daniel Sudarsky

Emilio d’Emilio, Luigi E. Picasso

Bernard d’Espagnat

The problem of retrodiction is associated with basic questions, but for this very reason it is, unfortunately, quite difficult, even in classical physics. In quantum physics it is even more subtle. In quantum mechanics, a consistent definition of what is called a "system" leads to problems that do not exist in classical physics, and correspondingly the answers to the questions raised are less straightforward. This chapter discusses the conditions under which it is possible to speak of an "independent time evolution" of a system S and to study what kinds of predictions can legitimately be made when these conditions are fulfilled. It describes retroactive computation to investigate whether or not the assumed knowledge in question is really consistent with the standard quantum mechanical formalism. The concept of retrodiction is related to the notions of time reversal and of irreversibility. Both these notions play a central role in physics.

Vladimir K. Ignatovich

The book contains four chapters. The first one deals with elementary problems of one dimensional quantum mechanics of scalar particles, and their solution is given by much more simpler method than in standard textbooks. Attention should be paid to problems with periodic potentials. In the second chapter methods of one-dimensional quantum mechanics are applied to three-dimensional scattering problems. Here a new approach to the dynamic diffraction theory based on multiple wave scattering method is proposed. Diffraction on a crystalline plane is solved exactly, and is shown to vanish in contradiction with experimental observations. In the third chapter, all the problems of the first one are generalized to spinor particles. The most interesting questions are related to polarization of particles and rotation of polarization by means of radio-frequency fields, which create superpositions of states with different energies and speeds. The fourth chapter is devoted to fundamental questions of quantum mechanics. The theory of weak measurements is criticized. Some experiments related to wave packets and to determination of quantization axis of non polarized neutron beams are proposed.