D = 1 Supergravity and Quantum Cosmology

Using a D = 1 supergravity framework I construct a super-Friedmann equation for an isotropic and homogenous universe including dynamical scalar fields. In the context of quantum theory this becomes an equation for a wave function of the universe of spinorial type, the Wheeler–DeWitt–Dirac equation. It is argued that a cosmological constant breaks a certain chiral symmetry of this equation, a symmetry in the Hilbert space of universe states, which could protect a small cosmological constant from being affected by large quantum corrections.

     

Can Quantum Gravity be Exposed in the Laboratory?

I propose an experiment that may be performed, with present low temperature and cryogenic technology, to reveal Wheeler’s quantum foam. It involves coupling an optical photon’s momentum to the center of mass motion of a macroscopic transparent block with parameters such that the latter is displaced in space by approximately a Planck length. I argue that such displacement is sensitive to quantum foam and will react back on the photon’s probability of transiting the block. This might allow determination of the precise scale at which quantum fluctuations of space–time become large, and so differentiate between the brane-world and the traditional scenarios of spacetime.     

Wheeler complexes in crystals

The basic properties of Wheeler complexes have been estimated for crystals that include positrons, positronium, electrons, holes, and excitons. Two basic forms of such quasiparticle states in crystals are considered: a) delocalized states, and b) states localized at defects. It is possible to observe Wheeler complexes by examining the annihilation characteristics of positrons in the presence of external fields such as static magnetic fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 10–14, April, 1981.     

Quantum geometrodynamics: whence,whither?

Quantum geometrodynamics is canonical quantum gravity with the three-metric as the configuration variable. Its central equation is the Wheeler–DeWitt equation. Here I give an overview of the status of this approach. The issues discussed include the problem of time, the relation to the covariant theory, the semiclassical approximation as well as applications to black holes and cosmology. I conclude that quantum geometrodynamics is still a viable approach and provides insights into both the conceptual and technical aspects of quantum gravity.

These considerations reveal that the concepts of spacetime and time itself are not primary but secondary ideas in the structure of physical theory. These concepts are valid in the classical approximation. However, they have neither meaning nor application under circumstances when quantum-geometrodynamical effects become important. ...There is no spacetime, there is no time, there is no before, there is no after. The question what happens “next” is without meaning [1].

Dedicated to the memory of John Archibald Wheeler.     

A Quantum Cosmological Bianchi I Model with Interacting Spinor and Scalar Fields

A Bianchi I model of the Universe filled with interacting nonlinear spinor and scalar fields is studied within quantum geometrodynamics. Three types of interaction are considered: gradient, Yukawa, and axion ones. For massless fermion fields, the variables in the Wheeler – de Witt equation will separate. The solution can be interpreted using a two-component perfect liquid. One component corresponds to a massless scalar field, while the other – to a nonlinear spinor field. The interaction between the spinor and scalar fields can lead to elimination of singularity of the wave function. There is a possibility of existence of a discrete spectrum of the quantum Universe, as well as tunneling from the region with a rigorous equation of state to the region of the de Sitter vacuum.     

“It’s better to forget physics”: The Idea of the Tactical Nuclear Weapon in the Early Cold War

Physics in Perspective - The American physicist John Wheeler once told his colleague Richard Feynman that, in case of war, “it’s better to forget physics and tell the admirals and...     

An extension to the Wheeler phase-field model to allow decoupling of the capillary and kinetic anisotropies

The formulation of the phase-field problem due to Wheeler et al. [Physica D 66, 243 (1993)] has been adopted and extended as a tool for solidification research by many groups around the World. However, an intrinsic problem of this model is that it couples two physically distinct anisotropies, those associated with the surface energy of the solid-liquid interface and attachment kinetics, into a single anisotropy parameter. In this paper we present a simple extension to the Wheeler model in which we show that introducing a complex form of the anisotropy function allows these two physical parameters to be decoupled.Received: 16 June 2004, Published online: 21 October 2004PACS: 81.10.-h Methods of crystal growth; physics of crystal growth - 81.30.Fb Solidification - 64.70.Dv Solid-liquid transitions     

Large N-wormhole approach to spacetime foam

A simple model of spacetime foam, made by N wormholes in a semiclassical approximation, is taken under examination. We show that the qualitative behaviour of the fluctuation of the metric conjectured by Wheeler is here reproduced.     

Geometry in a manifold with projective structure

Parallel transport of line elements, surface elements etc. along geodesics and more general curves in a projectively connected manifold is investigated analytically and in terms of geometrical constructions. Projective curvature is characterized geometrically by a projective analogue of the geodesic deviation equation and by a geometrical construction. The results are interpreted physically as statements about free fall world lines in space-time.This paper is dedicated to our friend John Archibald Wheeler, geometer and physicist, who celebrated his sixtieth birthday on July 9, 1971.This work was supported in part by the National Science Foundation (Grant No. GP-34639X). One of the authors (A.S.) did much of this work while visiting the Université Libre de Bruxelles (summer, 1968), Cambridge University (summer, 1970), and the Nordic Institute for Theoretical Atomic Physics (1970-71); he wishes to thank these institutions and Drs. I. Prigogine, D. Sciama, and C. Møller for their kind hospitality.     

Formulation and justification of the Wheeler-Feynman absorber theory

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.     

Phase space distributions from variation of information measures

As a part of the so-called Wheeler program, we present an information theoretic treatment for phase space distributions.     

Thermodynamics of the λ line in binary fluid mixtures

Thermodynamics of the λ line, variations on a theme by Wheeler and Griffiths, have been presented.     

Existence of “free will” as a problem of physics

The proof of Bell's inequality is based on the assumption that distant observers can freely and independently choose their experiments. As Bell's inequality isexperimentally violated, it appears that distant physical systems may behave as a single, nonlocal, indivisible entity. This apparent contradiction is resolved. It is shown that the free will assumption is, under usual circumstances, an excellent approximation.I have set before you life and death, blessing and cursing: therefore choose life....

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The cosmological constant as an eigenvalue of the Hamiltonian constraint in a varying speed of light theory

In the framework of a Varying Speed of Light theory, we study the eigenvalues associated with the Wheeler‐DeWitt equation representing the vacuum expectation values associated with the cosmological constant. We find that the Wheeler‐DeWitt equation for the Friedmann‐Lemaître‐Robertson‐Walker metric is completely equivalent to a Sturm‐Liouville problem provided that the related eigenvalue and the cosmological constant be identified. The explicit calculation is performed with the help of a variational procedure with trial wave functionals related to the Bessel function of the second kind . After having verified that in ordinary General Relativity no eigenvalue appears, we find that in a Varying Speed of Light theory this is not the case. Nevertheless, instead of a single eigenvalue, we discover the existence of a family of eigenvalues associated to a negative power of the scale. A brief comment on what happens at the inflationary scale is also included.     

The Wheeler-Feynman absorber theory: A reinterpretation?

The “reinterpretation” of the Wheeler-Feynman absorber theory of radiation, as presented by H. Price in Refs. 1 and 2, is shown not to be a reinterpretation of the mathematical framework of the theory, but an alteration of the theory, which renders it asymmetric. It is shown that Price is mistaken in accusing Wheeler and Feynman of presenting flawed arguments as to whether the advanced and retarded components are distinct; and about the reasons for excluding the time-reversed version of the absorber theory.     

An inhomogeneous toy model of the quantum gravity with the explicitly evolvable observables

An inhomogeneous (1? $+$ ?1)-dimensional model of the quantum gravity is considered. It is found, that this model corresponds to a string propagating in some curved background space. The quantization scheme including the Wheeler–DeWitt equation and the “particle on a sphere” type of the gauge condition is suggested. In the quantization scheme considered, the “problem of time” is resolved by building of the quasi-Heisenberg operators acting in a space of solutions of the Wheeler–DeWitt equation, and the normalization of the wave function corresponds to the Klein–Gordon type. To analyze the physical consequences of the scheme, a (1? $+$ ?1)-dimensional background space is considered for which a classical solution is found and quantized. The obtained estimations show the way to solution of the cosmological constant problem for this model. Such a solution consists in compensation of the zero-point oscillations of the matter fields by the quantum oscillations of the scale factor. Along with such a compensation, a slow global evolution of a background exists that corresponds to an universe expansion.     

An orifice-string in the standard Kaluza-Klein theory

In the standard Kaluza-Klein theory an orifice solution is proposed which can be spliced into a four-dimensional Reissner-Nordstrom space-time. From the point of view of a four-dimensional observer, the obtained orifice solution can be treated as a string moving in a Wheeler superspace of four geometries.Kyrgyz State University, Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 78–81, June, 1993.     

Objective reality,causality and the aspect experiment

It is argued that, in the framework of Wheeler—Feynman electrodynamics objective reality and causality in the strict sense are consistent with the outcome of atomic cascade photon correlation experiments, provided this outcome is not altered by the Aspect experimental modification.     

Wheeler–DeWitt Equation with a Screened-Coulomb Dilation Potential

Wheeler–DeWitt equation for anisotropically expanding homogeneous high-dimension spaces is approximately solved under a screened-coulomb dilation potential via an appropriate approximation. The wave function is reported in terms of the Jacobi polynomials and eigenvalues and eigenfunctions are reported via the Nikiforov–Uvarov technique.     

Dilaton Quantum Cosmology with a Schrödinger-like Equation

A quantum cosmological model with radiation and a dilaton scalar field is analyzed. The Wheeler–DeWitt equation in the minisuperspace induces a Schrödinger equation, which can be solved. An explicit wavepacket is constructed for a particular choice of the ordering factor. A consistent solution is possible only when the scalar field is a phantom field. Moreover, although the wavepacket is time-dependent, a Bohmian analysis allows to extract a bouncing behavior for the scale factor.