We show that in a dilute gas the wave function’s spreading is limited by scattering off other particles. This shows that quantum mechanics can be consistent with the kinetic theory of gases.

The “special state” understanding of the measurement process is presented, namely there is no “measurement process,” only unitary time evolution. However, in contrast to the many worlds interpretation, there is only one world. How this can be accomplished and how statistical mechanics is changed as a result are also discussed. The focus though is on experimental tests of this theory and the in-principle realization that this can give rise to feasible experimental tests. Those tests rely on the particular feature of (...) having only one world, so that any change in the wave function must have a proximate cause, and it is the detection of that cause that constitutes the test. In a companion article there is further exploration concerning the details of the test. In addition, in the present article, the special state theory is extended theoretically through evidence of the uniqueness of the Cauchy distribution as well as explicit recognition of the role of entanglement. (shrink)

The emergence of macroscopic variables can be effected through coarse graining. Despite practical and fundamental benefits conveyed by this partitioning of state space, the apparently subjective nature of the selection of coarse grains has been considered problematic. We provide objective selection methods, deriving from the existence of relatively slow dynamical time scales. Using a framework for nonequilibrium statistical mechanics developed by us, we show the emergence of both spatial variables and order parameters. Although significant objective criteria are introduced in the (...) coarse graining, we do not provide a unique prescription. Most significantly, the grains, and by implication entropy, are only defined modulo a characteristic time scale of observation. (shrink)

In most theories of the quantum measurement process changes in an observer’s perception of a state can take place without forces, as for example if a state is prepared in an eigenstate of \ but \ is measured. In the “special state” theory any change in wave function requires forces. This allows experimental tests to distinguish these ideas and in the present article two examples of such tests are considered. The first is a kind of double Stern–Gerlach experiment, the second (...) a check for angular momentum changes in a polarizer. (shrink)

In most theories of the quantum measurement process changes in an observer’s perception of a state can take place without forces, as for example if a state is prepared in an eigenstate of \ but \ is measured. In the “special state” theory any change in wave function requires forces. This allows experimental tests to distinguish these ideas and in the present article two examples of such tests are considered. The first is a kind of double Stern–Gerlach experiment, the second (...) a check for angular momentum changes in a polarizer. (shrink)

A pair of harmonic oscillators come in contact and then separate. This could be a model of an atom encountering an electromagnetic field. We explore the coherence properties of the resulting state as a function of the sort of initial condition used. A surprising result is that if one imagines a large collection of these objects repeatedly coming in contact and separating, the asymptotic distribution functions are not Boltzmann distributions, but rather exponentials with the same rate of dropoff.

The “absorber theory” of Wheeler and Feynman is supposed to justify the use of retarded potentials in ordinary electromagnetic calculations despite a fundamentally time symmetric interaction. We restate the thesis of absorber theory as follows: here exist causal solutions of time symmetric electrodynamics. In our formulation, absorption need only take place in one direction of time (the future) rather than both, as seems to be required by Wheeler and Feynman. Even with complete absorption, however, the effects of advanced interactions are (...) not entirely eliminated and a residual field may introduce a degree of indeterminacy into particle trajectories obtained using retarded potentials alone. (shrink)

In a recently proposed quantum measurement theory the definiteness of quantum measurements is achieved by means of “special” states. The recovery of the usual quantum probabilities is related to the relative abundance of particular classes of “special” states. In the present article we consider two-state discrimination, and model the apparatus modes that could provide the “special” states. We find that there are structural features which, if generally present in apparatus, will provide universal recovery of standard probabilities. These structural features relate (...) to the distribution of certain Hamiltonian matrix elements or interaction times. In particular, those quantities must be asymptotically (x → ∞) distributed according to the Cauchy law, Ca(x)=a/π(x 2 +a 2 ). (shrink)

The quantum Zeno effect (QZE) is often associated with the ironic maxim, “a watched pot never boils”, although the notion of “watching” suggests a continuous activity at odds with the usual (pulsed measurement) presentation of the QZE. We show how continuous watching can provide the same halting of decay as the usual QZE, and, for incomplete hindrance, we provide a precise connection between the interval between projections and the response time of the continuous observer. Thus, watching closely, but not so (...) closely as to halt the “boiling”, is equivalent to—gives the same degree of partial hindrance as—pulsed measurements with a particular pulsing rate. Our demonstration is accomplished by treating the apparatus for the continuous watching as a fully quantum object. This in turn allows us a second perspective on the QZE, in which it is the modified level structure of the combined system/apparatus Hamiltonian that slows the decay. This and other considerations favor the characterization “dominated time evolution” for the QZE. (shrink)