In this paper we will take a careful look at the well-known fact that a complete 2 rotation in three dimensional space, while leaving vectors, tensors and generally the integral representations of the rotation group unchanged, causes a sign change in the half-integral spinor representations of the rotation group. First, in a brief introduction, we review the origin of the sign change of spinors by a 2 rotation. Next, we analyze Aharonov and Susskind's (hereafter referred to as A. & S.) (...) (1967) original proposal for detecting such a sign change and compare it with a later proposal1 for detecting the sign change using neutron beams that are coherently split and recombined. While the A. & S. experiment is, we think, conceptually more interesting, the neutron beam experiment has actually been carried out. And finally, we discuss the philosophical significance of the rotationally induced spinor sign change. (shrink)

The Einstein-Podolsky-Rosen (EPR) paradox and the correlated states it introduced comprise one of the central interpretive problems of quantum mechanics. Because of the apparent nonlocal character of this paradox, it should be given a relativistic treatment. The purpose of this paper is to provide such a treatment.

In this note a recently developed quantum oscillating finite space cosmological model is described. The principle novelty of the model is that there is a quantum blurring of the classical singularity between cycles, instead of a singularity free bounce. Recently, Quentin Smith (1988) has argued that present theoretical and observational evidence justifies the belief that the past history of the universe is finite. The relevance of this cosmological model to Smith's arguments is discussed.

The equivalence principle as well as the spin-two character of the weak gravitational field lead to difficulties in the measurability analysis of this field which are not encountered in Bohr and Rosenfeld's corresponding inquiry into the electromagnetic field. To meet these difficulties, atomic elastic structures are proposed as gravitational field detectors whose parameters (masses, total volumes, lattice and elastic constants) are adjustable. The limitations imposed by the uncertainty principle and by the radiation reaction of the detectors on the determination of (...) the amplitude, frequency, and direction of the field are then exhibited. Finally, the relevance of the present work to the investigation of DeWitt and to Einstein's full theory of gravitation is briefly considered. (shrink)

Foundations of Space-Time Theories, by Michael Friedman, falls naturally into two parts. In the first, he presents the general framework within which he will characterize and discuss space-time theories, and then he devotes a chapter each to Newtonian physics, special relativity, and general relativity. Although there is some rich philosophical discussion along the way, these chapters are, of necessity, somewhat technical expositions of the general framework in action. It is in the second part, consisting of two substantial chapters, one on (...) relationalism, the other on conventionalism, that more general philosophical issues are addressed. (shrink)