Quantum mechanics stands as one of the most remarkable achievements of the twentieth century: at once a new and startling insight into the nature of matter and a spectacularly successful predictive theory. However, while the predictive abilty of the quantum theory has been rigorously tested time and time again, so that it now satisfies any criterion of reliability as a tool of scientific inquiry, surprisingly fundamental difficulties remain with its interpretation. This book introduces the general reader to the philosophical issues (...) raised by the success of the quantum theory. What exactly is the wavefunction, the mathematical device that resides at the heart of the theory? In what sense does this device represent reality? The wavefunction is believed to describe the probability of a system's behaving in a particular way, yet the equations which describe the wave function are totally deterministic: what then is the relationship between determinism and ramdomness in the microworld? Does this tell us anything about the freedom of will in a world governed by the immutable world of physics? Do these laws rely for their existence on the presence of concious observers? Euan Squires explains to a non-specialised readership how these profound difficulties arise in the simplest of experimental arrangements. He outlines with great clarity the different points of view adopted by various schools of physicists who are striving to understand the meaning underlying the theories they use every day. The reader is encouraged to see how this most successful of physical theories is relevant to issues outside physics - even to the existence of God. other_titles. (shrink)

Interference phenomena are a well-known and crucial feature of quantum mechanics, the two-slit experiment providing a standard example. There are situations, however, in which interference effects are (artificially or spontaneously) suppressed. We shall need to make precise what this means, but the theory of decoherence is the study of (spontaneous) interactions between a system and its environment that lead to such suppression of interference. This study includes detailed modelling of system-environment interactions, derivation of equations (‘master equations’) for the (reduced) state (...) of the system, discussion of time-scales etc. A discussion of the concept of suppression of interference and a simplified survey of the theory is given in Section 2, emphasising features that will be relevant to the following discussion (and restricted to standard non-relativistic particle quantum mechanics.[1] A partially overlapping field is that of decoherent histories, which proceeds from an abstract definition of loss of interference, but which we shall not be considering in any detail. (shrink)

A new version of quantum theory is proposed, according to which probabilistic events occur whenever new statioinary or bound states are created as a result of inelastic collisions. The new theory recovers the experimental success of orthodox quantum theory, but differs form the orthodox theory for as yet unperformed experiments.