Showing papers on "Field (physics) published in 1992"
TL;DR: An alternative approach using a wave-function treatment to describe the atomic system and it is shown that this treatment is equivalent to the standard density matrix approach leading to the OBE's.
Abstract: A novel treatment of dissipation of energy from a ``small'' quantum system to a reservoir is presented. We replace the usual master equation for the small-system density matrix by a wave-function evolution including a stochastic element. This wave-function approach provides new insight and it allows calculations on problems which would otherwise be exceedingly complicated. The approach is applied here to a two- or three-level atom coupled to a laser field and to the vacuum modes of the quantized electromagnetic field.
1,532 citations
TL;DR: In this article, a generic class of theories where gravity is mediated by one tensor field together with an arbitrary number of scalar fields is considered, and the predictions of these theories are worked out in four different observationally relevant regimes.
Abstract: A generic class of theories where gravity is mediated by one tensor field together with an arbitrary number of scalar fields is considered. The predictions of these theories are worked out in four different observationally relevant regimes: (i) quasi-stationary weak fields (solar system conditions); (ii) rapidly varying weak fields (gravitational wave experiments); (iii) quasi-stationary strong fields (motion of systems of compact bodies, i.e. neutron stars or black holes); and (iv) the mixing of strong and radiative field effects in the gravitational radiation of N-compact-body systems. Moreover, the authors derive several significant relations between the theoretical quantities entering these predictions. They show how strong-field-gravity effects in the motion and gravitational radiation of N-compact-body systems can be parametrized by a set of theory parameters that generalize the usual post-Newtonian parameters ( gamma , beta ,. . .) introduced in the context of quasi-stationary weak gravitational fields. These new parameters ( beta 2, beta ', beta 3, beta ",. . .) provide a chart for the yet essentially unexplored domain of strong-gravitational-field effects, and thereby suggest new directions for testing relativistic gravity. This is illustrated by studying in detail a specific two-parameter tensor-bi-scalar theory T( beta ', beta ") which has the same post-Newtonian limit as general relativity but leads to new nonEinsteinian predictions for the various observables that can be extracted from binary pulsar data.
823 citations
TL;DR: Recent theoretical and experimental advances in the study of homogeneous nucleation are reviewed, with emphasis placed on phase transitions involving single-component liquids (condensation, cavitation, and crystallization from the melt).
Abstract: Recent theoretical and experimental advances in the study of homogeneous nucleation are reviewed, with emphasis placed on phase transitions involving single-component liquids (condensation, cavitation, and crystallization from the melt). Extensions of classical nucleation theory are described and compared with new experiments that now directly measure nucleation rates. Novel methods of statistical mechanics, including density-functional theory and computer simulations, are presented. The recent rapid evolution of this field has opened up many new questions for further research.
603 citations
TL;DR: In this article, it is argued that the observed photospheric field should first be corrected for line-of-sight projection and then matched to the radial component of the potential field.
Abstract: It is shown that the line-of-sight matching procedure involved in potential field models of the solar corona do not make good use of the available data because there is strong evidence that the magnetic field is nearly radial, and therefore nonpotential, at the photosphere. It is argued that the observed photospheric field should first be corrected for line-of-sight projection and then matched to the radial component of the potential field. It is shown that this procedure yields much stronger polar fields than the standard method and produces better agreement with high-latitude coronal holes and with white-light structures in the outer corona. The relationship of both methods to the observed inclination angles of polar plumes is also discussed.
497 citations
TL;DR: The field of high conductivity amorphous solids has been very active during the past two decades, as it has become an increasingly important part of the broader field of solid state ionics as discussed by the authors.
Abstract: Mobile ions in amorphous solids are interesting from both academic and practical perspectives. They are of academic interest, because of the challenge to explain how the structures of a wide variety of liquids can change during cooling so as to permit truly enormous differences in their particle mobilities (up to factors of 1014) to develop. In the fluid states of most nonpolymeric fast ion glass-forming liquids, the time scales for electrical relaxation (by the most mobile species) and mechanical relaxation (by the least mobile species) are within an order of magnitude ( 1 , 2). They are of practical interest, because these materials may serve as the solid electrolyte in a wide variety of electrical devices, such as primary and secondary batteries, sensors, and electro chromic displays. The field of high conductivity amorphous solids has been very active during the past two decades, as it has become an increasingly important part of the broader field of solid state ionics. With the urgent societal need for nonpolluting vehicle power sources now being a subject of legislation in many states, the importance of this subject area is destined to grow considerably. The amorphous solid conductor field comprises two important subfields and shares a further subfield with the crystalline branch of the su bject. The subfields referred to are, respectively, fast ion-conducting ("superionic") glasses and salt-in-solvating-polymer solutions. The shared subfield is that of rotator phases and certain other highly disordered crystals that obey the Vogel-Tammann Fulcher (VTF) equation and show glass transitions.
476 citations
TL;DR: In this article, the structure of QCD Green functions with one external nucleon, treated as a very massive field, was analyzed and the matching conditions and relations of various nucleon matrix elements of quark currents to the relativistic approach were discussed.
439 citations
TL;DR: In this paper, the fluctuation spectrum that must arise in a mean field dynamo generation of galactic fields if the initial field is weak is considered and a kinetic equation for its evolution is derived and solved.
Abstract: The fluctuation spectrum that must arise in a mean field dynamo generation of galactic fields if the initial field is weak is considered. A kinetic equation for its evolution is derived and solved. The spectrum evolves by transfer of energy from one magnetic mode to another by interaction with turbulent velocity modes. This kinetic equation is valid in the limit that the rate of evolution of the magnetic modes is slower than the reciprocal decorrelation time of the turbulent modes. This turns out to be the case by a factor greater than 3. Most of the fluctuation energy concentrates on small scales, shorter than the hydrodynamic turbulent scales. The fluctuation energy builds up to equipartition with the turbulent energy in times that are short compared to the e-folding time of the mean field. The turbulence becomes strongly modified before the dynamo amplification starts. Thus, the kinematic assumption of the mean dynamo theory is invalid. Thus, the galactic field must have a primordial origin, although it may subsequently be modified by dynamo action.
417 citations
Journal Article•
381 citations
TL;DR: In this paper, the existence of a non-renormalizable infinity in the two-loop effective action of perturbative quantum gravity by means of an explicit calculation was proved, and the background-field method in coordinate space, combined with dimensional regularization and a heat kernel representation for the propagators, was used.
327 citations
TL;DR: This paper derives the leading nonlinear hereditary effects in the generation of gravitational radiation, i.e., the terms in the wave form which depend in an irreducible manner on the entire past history of the source.
Abstract: This paper derives the leading nonlinear hereditary effects in the generation of gravitational radiation, i.e., the terms in the wave form which depend in an irreducible manner on the entire past history of the source. At the quadratically nonlinear order there are two types of hereditary contributions. The first ones are due to the readiation of gravitational waves by the stress-energy distribution of (linear) gravitational waves, and give rise to a net cumulative change in the wave form of bursts ("memory effect"). The second ones come from the backscattering of (linear) gravitational waves emitted in the past onto the constant curvature associated with the total mass of the source ("gravitational-wave tails"). An extension of a previously proposed multipole-moment wave generation formalism allows us to compute explicitly the wave form, including hereditary contributions, up to terms of fractional order ${(\frac{v}{c})}^{4}$. Our results are derived for slow-moving systems of bodies, independently of the strength of their internal gravity. The tail contribution to the far wave-zone field is found to be fully consistent with a corresponding hereditary contribution to the gravitational radiation damping previously derived from a study of the near-zone field.
321 citations
TL;DR: In this paper, the problem of constructing a time-dependent map of the magnetic field at the core-mantle boundary was considered and the smoothest solution compatible with the observations was proposed.
Abstract: We consider the problem of constructing a time-dependent map of the magnetic field at the core-mantle boundary. We use almost all the available data from the last 300 years to produce two maps, one for the period 1690-1840 and the other for 1840-1990. We represent the spatial dependency of the field using spherical harmonics, the time dependency using a cubic B-spline basis, and seek the smoothest solutions compatible with the observations. We argue that, for observations from permanent magnetic observatories, the most efficient strategy is to use the first differences of annual means; for satellite data, the most efficient strategy is simply to limit the number of data used so as to minimize any tendency to map the crustal field into the core field. The resulting model fits the observatory data better than any previous model. The resulting time-dependent field map exhibits much of the same structure in the field and its secular variation identified in earlier studies.
TL;DR: A model which attempts to account for the necessary primordial primordial magnetism by invoking a pseudo-Goldstone boson coupled to electro-magnetism is discussed.
Abstract: The existence of large-scale magnetic fields in galaxies is well established, but there is no accepted mechanism for generating a primordial field which could grow into what is observed today. We discuss a model which attempts to account for the necessary primordial field by invoking a pseudo Goldstone boson coupled to electromagnetism. The evolution of this boson during inflation generates a magnetic field; however, it seems difficult on rather general grounds to obtain fields of sufficient strength on astrophysically interesting scales.
TL;DR: An algorithm for automated evaluation of single static threshold visual field test results in glaucoma, which uses empirically determined limits of normality for up-down differences in the Statpac probability maps of the Humphrey Field Analyzer to detect localized visual field loss.
Abstract: We have developed an algorithm, the Glaucoma Hemifield Test (GHT), for automated evaluation of single static threshold visual field test results in glaucoma. The GHT uses empirically determined limits of normality for up-down differences in the Statpac probability maps of the Humphrey Field Analyzer to detect localized visual field loss. It is also constructed to detect field loss that is symmetric around the horizontal meridian. Analysis is done in five corresponding pairs of sectors that are based on the normal anatomy of the retinal nerve fiber layer. Deviations from the age-corrected normal threshold in the most sensitive portions of the visual field are used to detect general reductions of sensitivity or abnormally high sensitivities. The GHT provides brief visual field evaluations printed on the field chart as plain text. The aim of this article is to describe the fundamentals of the analysis program and to provide clinical examples.
TL;DR: In this paper, the spectral and bidirectional reflectance of 26 soils was measured in the laboratory both with a field spectroradiometer (1000 narrow wavebands from 450 nm to 2450 nm) and a radiometer simulating TM channels (the five TM2, TM3, TM4, TM5, and TM7 broad bands).
TL;DR: In this article, an algorithm for evolving collisionless stellar systems with density profiles like the R exp 1/4 law is described, using only a few terms in the expansions, and a good fit is obtained for a truncated isothermal distribution, which renders the method appropriate for galaxies with flat rotation curves.
Abstract: The present study describes an algorithm for evolving collisionless stellar systems in order to investigate the evolution of systems with density profiles like the R exp 1/4 law, using only a few terms in the expansions. A good fit is obtained for a truncated isothermal distribution, which renders the method appropriate for galaxies with flat rotation curves. Calculations employing N of about 10 exp 6-7 are straightforward on existing supercomputers, making possible simulations having significantly smoother fields than with direct methods such as tree-codes. Orbits are found in a given static or time-dependent gravitational field; the potential, phi(r, t) is revised from the resultant density, rho(r, t). Possible scientific uses of this technique are discussed, including tidal perturbations of dwarf galaxies, the adiabatic growth of central masses in spheroidal galaxies, instabilities in realistic galaxy models, and secular processes in galactic evolution.
TL;DR: It is shown that far-infrared radiation can be generated in the depletion field near semiconductor surfaces via the inverse Franz-Keldysh effect or electric-field-induced optical rectification.
Abstract: We show that far-infrared radiation can be generated in the depletion field near semiconductor surfaces via the inverse Franz-Keldysh effect or electric-field-induced optical rectification. This mechanism is conceptually different from those previously proposed and accounts for many recent experimental observations
TL;DR: The electric field at the amino terminus of an alpha helix in water has been determined by measuring the shift in the absorption band for a covalently attached, neutral probe molecule with an electric dipole moment difference between the ground and excited electronic states.
Abstract: The strengths of electrostatic interactions in biological molecules are difficult to calculate or predict because they occur in complicated, inhomogeneous environments. The electric field at the amino terminus of an alpha helix in water has been determined by measuring the shift in the absorption band for a covalently attached, neutral probe molecule with an electric dipole moment difference between the ground and excited electronic states (an internal Stark effect). The field at the interface between the helix and the solvent is found to be an order of magnitude stronger than expected from the dielectric properties of bulk water. Furthermore, although the total electric dipole moment of the helix increases with length, the electric field at the amino terminus does not.
TL;DR: Under conditions of strong dipole coupling an optical cavity containing one atom behaves as a two-state system when excited near one of the ``vacuum'' Rabi resonances.
Abstract: Under conditions of strong dipole coupling an optical cavity containing one atom behaves as a two-state system when excited near one of the ``vacuum'' Rabi resonances. A coherent driving field induces a dynamic Stark splitting of the ``vacuum'' Rabi resonance. We demonstrate this two-state behavior in computer experiments based on quantum trajectory simulations.
TL;DR: In this article, it was shown that cellulose microcrystals in aqueous solution can be strongly oriented by strong homogeneous magnetic fields so that their long axes became perpendicular to the field direction.
Abstract: It is shown that cellulose microcrystals in aqueous solution can be strongly oriented by strong homogeneous magnetic fields so that their long axes became perpendicular to the field direction. In addition, fthe dried cellulose films displayed a uniplanar-axial orientation
TL;DR: The nature of the pure-field-state superposition generated at such times as revival time and asymptotically disentangled is investigated.
Abstract: The Jaynes-Cummings model of optical resonance describes the simplest fully quantized interaction between two quantum systems of different nature: a two-level atom (fermionic system) and a quantized field mode (bosonic system). This interaction leads to extreme quantum entanglement of the atom and field. However, the model also predicts that, at precisely half of the revival time, the atom and field become asymptotically disentangled. This disentanglement becomes more exact as the coherent-state amplitude increases. In this paper we investigate the nature of the pure-field-state superposition generated at such times
TL;DR: The analysis of the problem of phase measurement leads to the conclusion that the appropriate dynamical variables for the measured sine and cosine depend on the measurement scheme, and that different schemes correspond to different operators.
Abstract: We examine the problem of determining the phase difference between two optical fields, first for classical and later for quantum fields, by reference to two simple measurement schemes that yield the sine and/or cosine of the phase difference between classical fields. We show that certain difficulties exist even within the framework of semiclassical radiation theory when the field is very weak, and particularly when amplitude and phase fluctuations are correlated. We find that a clear distinction has to be made between the measured values of the sine or cosine and the values that can be inferred from a series of repeated measurements. A corresponding distinction can be made also for a quantum field, although the interpretation is not the same. The dynamical variables chosen to represent the cosine and sine that emerge from the discussion of the measurement schemes commute when the sine and cosine are obtained together, but not when the measurement yields one or the other. These sine and cosine operators have well-defined values only when there is a large dispersion of the photon number. We arrive at expressions for the moments of the measured and of the inferred sines and cosines that differ from most previous treatments. The expressions are applied to optical fields in several different quantum states. Only for the Fock state and for the so-called phase state, which was treated recently at some length by Pegg and Barnett [Phys. Rev. A 39, 1665 (1989)], do the measured and the inferred moments coincide. Our analysis of the problem of phase measurement leads to the conclusion that the appropriate dynamical variables for the measured sine and cosine depend on the measurement scheme, and that different schemes correspond to different operators.
TL;DR: In this article, the authors show that extending an electric dipole can reduce the static effect due to confined resistivity anomalies smaller than a dipole length, which is a modification of the sensor characteristics that involves a spatial filtering process.
Abstract: Electromagnetic Array Profiling (EMAP) is an adaptation of magnetotellurics to overcome spatial aliasing effects associated with the sampling of the surface electric field. Undersampling lateral electric field variations can result in misleading geoelectric interpretations of the subsurface, particularly under the common presence of static distortion. In the EMAP field procedure, electric dipoles are positioned end‐to‐end along a continuous survey path; this configuration, in addition to reducing aliasing effects, lends itself to low‐pass filtering of the lateral electric field variations. We show that lengthening an electric dipole can reduce the static effect due to confined resistivity anomalies smaller than a dipole length. This modification of the sensor characteristics involves a spatial filtering process in which the cutoff wavenumber is inversely proportional to the length of the dipole. However, excessively long dipoles may not prove appropriate at high frequencies where the objective is to sense...
TL;DR: In this article, it is argued that the effective action theory may be regarded as a phenomenological theory describing a certain class of measurements irrespective of the nature of fundamental quantum objects, and a connection between the effective field and observables is established.
Abstract: It is argued that the effective action theory may be regarded as a phenomenological theory describing a certain class of measurements irrespective of the nature of fundamental quantum objects. The effective action in quantum field theory is discussed in detail and used as a guide. A connection between the effective field and observables is established. The approach is applied to the gravitational collapse problem. A procedure for building a basis of non-local gravitational invariants is described and a result for the vacuum radiation in a spherically symmetric in-state is presented. A conclusion about breakdown of measurements at the Planck scale is revised.
TL;DR: In this paper, the authors present in a concise analytical form two asymptotically flat metrics describing the superposition of the Kerr solution with an arbitrary static vacuum Weyl field which differ in their angular momentum distributions.
Abstract: The authors present in a concise analytical form two asymptotically flat metrics describing the superposition of the Kerr solution with an arbitrary static vacuum Weyl field which differ in their angular momentum distributions. They are then used for the construction of two asymptotically flat generalizations of the Kerr-Newman spacetime possessing the full set of mass-multipole moments able to describe the exterior gravitational field of a charged rotating arbitrary axisymmetric mass.
TL;DR: Calculations exhibiting the nature of these pendular states for a linear molecule and characteristic features of infrared and microwave spectra which become observable in strong fields are presented.
Abstract: Recent experiments have demonstrated the feasibility of orienting rotationally cooled polar molecules in an electric field. The anisotropy of the Stark effect allows molecules in low rotational states to be trapped in ``pendular states,'' confined to librate over a limited angular range about the field direction. We present calculations exhibiting the nature of these pendular states for a linear molecule and characteristic features of infrared and microwave spectra which become observable in strong fields.
TL;DR: The results indicate that signal transduction involving calcium is an important biological constraint which operates to mediate this field interaction, and is consistent with a proposed parametric resonance theory of interaction of low intensity magnetic fields with biological systems.
TL;DR: The model consists of Skyrme-type interactions in four-, six-, and eight-fermion point couplings in a manifestly nonrenormalizable Lagrangian, which also contains derivative terms to simulate the finite ranges of the mesonic interactions.
Abstract: We present initial results in the calculation of nuclear ground state properties in a relativistic Hartree approximation. Our model consists of Skyrme-type interactions in four-, six-, and eight-fermion point couplings in a manifestly nonrenormalizable Lagrangian, which also contains derivative terms to simulate the finite ranges of the mesonic interactions. A self-consistent procedure has been developed to solve the model equations for several nuclei simultaneously by use of a generalized nonlinear least-squares adjustment algorithm. With this procedure we determine the nine coupling constants of our model so as to reproduce measured ground state binding energies, rms charge radii, and spin-orbit splittings of selected closed major shell and closed subshell nuclei in nondeformed regions. The coupling constants obtained in this way predict these same observables for a much larger set of closed shell spherical nuclei to good accuracy and also predict these quantities for similar nuclei far outside the valley of beta stability. Finally, they yield properties of saturated nuclear matter in agreement with recent relativistic mean meson field approaches.
Book•
01 Jan 1992
TL;DR: To the best of our knowledge, the only known fractional statistics in the Chern-Simons field theory is the fractional statistic in the Anyon field theory of as discussed by the authors.
Abstract: to Fractional Statistics in Two Dimensions.- Fractional Statistics in the Chern-Simons Gauge.- Fractional Statistics in the Anyon Gauge.- Non-relativistic Chern-Simons Field Theory.- Anyons in a Magnetic Field.- Statistical Mechanics of Anyons.- Anyons and the Fractional Quantum Hall Effect.- Anyons and Conformal Field Theories.
TL;DR: Results of a precise calculation of the Coulomb self-energy for states with n=1 and 2 for nuclear charge Z in the range 5-110 in increments of 5 are given, providing improved accuracy over previous calculations.
Abstract: Results of a precise calculation of the Coulomb self-energy for states with n=1 and 2 for nuclear charge Z in the range 5--110 in increments of 5 are given. Results are also given for some elements that are of particular experimental interest. These values provide improved accuracy over previous calculations.