John Archibald Wheeler

Quantum Theory and Measurement

The forty-nine papers collected here illuminate the meaning of quantum theory as it is disclosed in the measurement process. Together with an introduction and a supplemental annotated bibliography, they discuss issues that make quantum theory, overarching principle of twentieth-century physics, appear to many to prefigure a new revolution in science.Originally published in 1983.The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

Classical physics as geometry

If classical physics be regarded as comprising gravitation, source free electromagnetism, unquantized charge, and unquantized mass of concentrations of electromagnetic field energy (geons), then classical physics can be described in terms of curved empty space, and nothing more. No changes are made in existing theory. The electromagnetic field is given by the Maxwell square root of the contracted curvature tensor of Ricci and Einstein. Maxwells equations then reduce, as shown thirty years ago by Rainich, to a simple statement connecting the Ricci curvature and its rate of change. In contrast to unified field theories, one then secures from the standard theory of Maxwell and Einstein an already unified field theory. This purely geometrical description of electromagnetism is traced out in detail. Charge receives a natural interpretation in terms of source-free electromagnetic fields that (1) are everywhere subject to Maxwells equations for free space but (2) are trapped in the worm holes of a space with a multiply-connected topology. Electromagnetism in such a space receives a detailed description in terms of the existing beautiful and highly developed mathematics of topology and harmonic vector fields. Elementary particles and real masses are completely excluded from discussion as belonging to the world of quantum physics.

SEMICLASSICAL DESCRIPTION OF SCATTERING

Abstract The quantum-mechanical scattering amplitude can be simply related to the classical deflection function when the conditions for a semiclassical analysis of the quantum-mechanical scattering are met. Various interesting characteristic features of the scattering are related to special features of the classical deflection function. The characteristic types of scattering discussed are: interference, when the deflection function possesses more than one branch at a given angle; rainbow scattering, when the deflection function has a relative maximum or minimum; glory scattering, when the deflection function passes smoothly through 0° or through an integral multiple of ± π; and orbiting, when the deflection function possesses a singularity. The consideration of the characteristic features of semiclassical scattering makes possible the analysis of an observed differential cross section to yield the classical deflection function, which in turn may be used to construct the potential.

On the Nature of quantum geometrodynamics

Abstract Classical gravitation, electromagnetism, charge, and mass are described in a preceding article in terms of curved empty space and nothing more. In advance of the detailed quantization of this pure Einstein-Maxwell geometrodynamics, an attempt is made here (1) to bring to light some of the most important properties to be expected for quantized geometrodynamics and (2) to assess whether this theory, without addition of any inventive elements, can contribute anything to the understanding of the elementary particle problem. Gravitational field fluctuations are concluded to have qualitatively new consequences at distances of the order of ( h G c 3 ) 1 2 = 1.6 × 10 −33 cm . They lead one to expect the virtual creation and annihilation throughout all space of pairs with electric charges of the order ∼( h c) 1 2 and energies of the order ( h c 5 G ) 1 2 = (2.18 × 10 −5 g )c 2 = 2.4 × 10 22 mc 2 . The problem is discussed, to what extent these charges can be identified with the unrenormalized or “undressed” charges of electron theory. Decisive for the future usefulness of quantum geometroydnamics is the question whether spin shows itself as an inevitable geometrical concomitant of quantization, or whether it and other ideas have to superposed on this purely geometrical description of nature.

Quantum effects near a barrier maximum

Abstract A potential barrier is considered which is parabolic over an appreciable region near its maximum. When the motion is unbounded to both left and right, the barrier penetrability is the quantity of interest. It dose not follow the Gamow value near the summit, but instead shows a transition behavior previously derived by two of us and here related to other phenomena. When the motion is symmetrically bounded on both left and right, energy levels below the barrier maximum are known to be associated in pairs of even and odd states, and are generally tacitly assumed to be unpaired above the barrier. The present analysis leads to a transition formula which shows that the pairing effect never vanishes but falls off smoothly with increase of the energy across the barrier maximum. When the motion is bounded to the left of the barrier and unbounded on the right, the quantity of interest is the phase shift. A “mixing formula” is derived which combines the semiclassical JWKB phase integrals to the left and right of the barrier to give a phase shift that varies smoothly through the barrier. In the analysis appears the function Γ( 1 2 + iϵ) , for which a simple optional approximation formula is presented. Typical curves are presented for the phase shift as a function of energy in the transition region. The analysis is used in an accompanying paper as the basis of a discussion of the special case of scattering which is known as orbiting, where classically a particle spirals near a potential maximum.

Application of semiclassical scattering analysis

Abstract Several different examples of scattering processes are analyzed, and for each, semiclassical approximations are discussed. The scattering of magnetic monopoles by charged particles is an illustrative example demonstrating rainbow and glory effects. In this example, exact classical and quantum results are also obtained and comparison made with semiclassical results. For the scattering of alpha particles by nuclei, the influence of absorption and of the phenomenon of orbiting on the cross section are studied semiclassically, and comparison with experiment is made. For the scattering of atoms by atoms, rainbow, glory, and orbiting effects may all exist, and one example is worked out semiclassically in detail. The scattering of electrons or muons by nuclei is discussed briefly and the semiclassical analysis shown not to be valid at any energy.

Iterative Solution Methods for Modeling Multiphase Flow in Porous Media Fully Implicitly

We discuss several fully implicit techniques for solving the nonlinear algebraic system arising in an expanded mixed finite element or cell-centered finite difference discretization of two- and three-phase porous media flow. Every outer nonlinear Newton iteration requires solution of a nonsymmetric Jacobian linear system. Two major types of preconditioners, supercoarsening multigrid (SCMG) and two-stage, are developed for the GMRES iteration applied to the solution of the Jacobian system. The SCMG reduces the three-dimensional system to two dimensions using a vertical aggregation followed by a two-dimensional multigrid. The two-stage preconditioners are based on decoupling the system into a pressure and concentration equations. Several pressure preconditioners of different types are described. Extensive numerical results are presented using the integrated parallel reservoir simulator (IPARS) and indicate that these methods have low arithmetical complexity per iteration and good convergence rates.

From Relativity to Mutability

From Relativity to Gravitational Collapse; and from the Consequences of Collapse to the Principle that Nature Conserves Nothing

The computer and the universe

The reasons are briefly recalled why (1) time cannot be a primordial category in the description of nature, but secondary, approximate and derived, and (2) the laws of physics could not have been engraved for all time upon a tablet of granite, but had to come into being by a higgledy-piggledy mechanism. It is difficult to defend the view that existence is built at bottom upon particles, fields of force or space and time. Attention is called to the “elementary quantum phenomenon” as potential building element for all that is. The task of construction of physics from such elements is compared and contrasted with the problem of constructing a computer out of “yes, no” devices.

A New Generation EOS Compositional Reservoir Simulator: Part II - Framework and Multiprocessing

This paper describes the design and implementation of a Problem Solving Environment (PSE) for developing parallel reservoir simulators that use multiple fault blocks, multiple physical models and dynamic locally adaptive meshrefinements. The objective of the PSE is to reduce the complexity of building flexible and efficient parallel reservoir simulators through the use of a high-level programming interface for problem specification and model composition, object-oriented programming abstractions that implement application objects, and distributed dynamic data-management that efficiently supports adaptation and parallelism. This work is presented in two parts. In Part I (SPE 37979), we describe the mathematical formulation and discuss numerical solution techniques, while this Part II paper we address framework and multiprocessing issues.