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1

Interaction of a weak gravitational wave with a rotating magnetic dipole field  

Microsoft Academic Search

The interaction of a weak gravitational wave of specified frequency with a magnetic-dipole field rotating at a frequency much less than the gravitational-wave frequency is analyzed. The gravitational-wave source is assumed to be situated at the center of the magnetic dipole. It is shown that the interaction results in the production of an electromagnetic wave with the same frequency as

V. I. Denisov

1978-01-01

2

Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

This chapter reviews the data mining methods recently developed to solve standard data problems in weak gravitational lensing. We detail the different steps of the weak lensing data analysis along with the different techniques dedicated to these applications. An overview of the different techniques currently used will be given along with future prospects. Until about 30 years ago, astronomers thought that the Universe was composed almost entirely of ordinary matter: protons, neutrons, electrons, and atoms. The field of weak lensing has been motivated by the observations made in the last decades showing that visible matter represents only about 4-5% of the Universe (see Figure 14.1). Currently, the majority of the Universe is thought to be dark, that is, does not emit electromagnetic radiation. The Universe is thought to be mostly composed of an invisible, pressure less matter - potentially relic from higher energy theories - called "dark matter" (20-21%) and by an even more mysterious term, described in Einstein equations as a vacuum energy density, called "dark energy" (70%). This "dark" Universe is not well described or even understood; its presence is inferred indirectly from its gravitational effects, both on the motions of astronomical objects and on light propagation. So this point could be the next breakthrough in cosmology. Today's cosmology is based on a cosmological model that contains various parameters that need to be determined precisely, such as the matter density parameter Omega_m or the dark energy density parameter Omega_lambda. Weak gravitational lensing is believed to be the most promising tool to understand the nature of dark matter and to constrain the cosmological parameters used to describe the Universe because it provides a method to directly map the distribution of dark matter (see [1,6,60,63,70]). From this dark matter distribution, the nature of dark matter can be better understood and better constraints can be placed on dark energy, which affects the evolution of structures. Gravitational lensing is the process by which light from distant galaxies is bent by the gravity of intervening mass in the Universe as it travels toward us. This bending causes the images of background galaxies to appear slightly distorted, and can be used to extract important cosmological information. In the beginning of the twentieth century, A. Einstein predicted that massive bodies could be seen as gravitational lenses that bend the path of light rays by creating a local curvature in space time. One of the first confirmations of Einstein's new theory was the observation during the 1919 solar eclipse of the deflection of light from distant stars by the sun. Since then, a wide range of lensing phenomena have been detected. The gravitational deflection of light by mass concentrations along light paths produces magnification, multiplication, and distortion of images. These lensing effects are illustrated by Figure 14.2, which shows one of the strongest lenses observed: Abell 2218, a very massive and distant cluster of galaxies in the constellation Draco. The observed gravitational arcs are actually the magnified and strongly distorted images of galaxies that are about 10 times more distant than the cluster itself. These strong gravitational lensing effects are very impressive but they are very rare. Far more prevalent are weak gravitational lensing effects, which we consider in this chapter, and in which the induced distortion in galaxy images is much weaker. These gravitational lensing effects are now widely used, but the amplitude of the weak lensing signal is so weak that its detection relies on the accuracy of the techniques used to analyze the data. Future weak lensing surveys are already planned in order to cover a large fraction of the sky with high accuracy, such as Euclid [68]. However, improving accuracy also places greater demands on the methods used to extract the available information.

Pires, Sandrine; Starck, Jean-Luc; Leonard, Adrienne; Réfrégier, Alexandre

2012-03-01

3

The Generation of Gravitational Waves. 1. Weak-Field Sources: A Plug-in-and-Grind Formalism.  

National Technical Information Service (NTIS)

A plug-in-and-grind formalism is derived for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, then the formalism reduces to standar...

K. S. Thorne S. J. Kovacs

1974-01-01

4

Magnetic field creation by electro-weak interaction in a gravitational field  

Microsoft Academic Search

The possibility of the creation of a magnetic field as a result of vacuum polarization effects in a gravitational field is discussed. It is shown that in the presence of an external static gravitational field, the current of the neutrino field in the vacuum state is nonzero, due to spontaneous neutrino-antineutrino pair formation. The magnitude of the neutrino field current

P. P. Meyer

1981-01-01

5

On slow flows of a weakly stratified relativistic fluid in a static gravitational field  

NASA Astrophysics Data System (ADS)

Simplified equations for slow flows of a weakly stratified (in entropy) fluid inside or near a massive astrophysical object have been derived from the variational formulation of ideal general relativistic hydrodynamics under the conditions that the gravitational field in the leading order is centrosymmetric and static and that the effect of a magnetic field is negligibly small. Internal waves and vortices in such systems are soft modes as compared to sound. This circumstance allows the formulation of a "soundproof" Hamiltonian model. This model is an analog of nonrelativistic hydrodynamic anelastic models, which are widely used in studies of internal waves and/or convection in spatially inhomogeneous compressible media in atmospheric physics, geophysics, and astrophysics.

Ruban, V. P.

2014-04-01

6

The Bianchi identity and weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We consider the Bianchi identity as a field equation for the distortion of the shapes of images produced by weak gravitational lensing. Using the spin coefficient formalism of Newman and Penrose (1962 J. Math. Phys. 3 566 78), we show that certain complex components of the Weyl and Ricci curvature tensors are directly related to fundamental observables in weak gravitational lensing. In the case of weak gravitational fields, we then show that the Bianchi identity provides a field equation for the Ricci tensor assuming a known Weyl tensor. From the Bianchi identity, we derive the integral equation for weak lensing presented by Miralda-Escude (1996 IAU Symp. vol 173 p 131), thus making the Bianchi identity a first principles equation of weak gravitational lensing. This equation is integrated in the important case of an axially symmetric lens and explicitly demonstrated in the case of a point lens and a singular isothermal sphere (SIS) model.

Kling, Thomas P.; Keith, Brian

2005-07-01

7

Flow pattern induced by the plane piston moving in a non-ideal gas with weak gravitational field  

Microsoft Academic Search

A systematic perturbation scheme is used to analyze the flow pattern induced by the motion of a plane piston moving with constant velocity in a non-ideal gas with weak gravitational field. The flow variables are expanded as a series of small parameter ?, which is the ratio of the typical escape velocity to the plasma velocity. The zeroth order solution

L. P. Singh; S. D. Ram; D. B. Singh

2011-01-01

8

The generation of gravitational waves. 1. Weak-field sources: A plug-in-and-grind formalism  

NASA Technical Reports Server (NTRS)

A plug-in-and-grind formalism is derived for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, then the formalism reduces to standard linearized theory. Whether or not gravity affects the motions, if the motions are slow and internal stresses are weak, then the new formalism reduces to the standard quadrupole-moment formalism. In the general case the new formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime, and then breaks the Green's-function integral into five easily understood pieces: direct radiation, produced directly by the motions of the sources; whump radiation, produced by the the gravitational stresses of the source; transition radiation, produced by a time-changing time delay (Shapiro effect) in the propagation of the nonradiative, 1/r field of the source; focussing radiation produced when one portion of the source focusses, in a time-dependent way, the nonradiative field of another portion of the source, and tail radiation, produced by backscatter of the nonradiative field in regions of focussing.

Thorne, K. S.; Kovacs, S. J.

1974-01-01

9

Wave propagation in a weak gravitational field and the validity of the thin lens approximation  

SciTech Connect

Wave effects can be important for the gravitational lensing of gravitational waves. In such a case, wave optics must be used instead of geometric optics. We consider a plane wave entering a lens object and solve numerically the wave equation for three lens models: the uniform density sphere, the singular isothermal sphere, and the Hernquist model. By comparing our numerical solutions with the analytical solutions under the thin lens approximation, we evaluate the error of this approximation. The results show that the relative error of the thin lens approximation is small if the geometrical thickness of the lens is much smaller than the distance between the lens and the observer.

Suyama, Teruaki; Michikoshi, Shugo [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Takahashi, Ryuichi [Division of Theoretical Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

2005-08-15

10

Scattering of weak gravitational waves by a sphere  

Microsoft Academic Search

By considering the gravitational field in the linearized Einstein theory, the scattering of a weak gravitational plane wave by a sphere is studied. The spherical components of the field and the differential scattering cross section are given in terms of the spin-weighted spherical harmonics and the effect on the polarization of the waves is analyzed.

G. F. Torres Del Castillo; L. C. Cortes Cuatli

1996-01-01

11

Scattering of weak gravitational waves by a sphere.  

NASA Astrophysics Data System (ADS)

By considering the gravitational field in the linearized Einstein theory, the scattering of a weak gravitational plane wave by a sphere is studied. The spherical components of the field and the differential scattering cross section are given in terms of the spin-weighted spherical harmonics and the effect on the polarization of the waves is analyzed.

Torres Del Castillo, G. F.; Cortes Cuatli, L. C.

1996-08-01

12

Gravitational anomaly and Hawking radiation near a weakly isolated horizon  

Microsoft Academic Search

Based on the idea of the work by Wilczek and his collaborators, we consider the gravitational anomaly near a weakly isolated horizon. We find that there exists a universal choice of tortoise coordinate for any weakly isolated horizon. Under this coordinate, the leading behavior of a quite arbitrary scalar field near a horizon is a 2-dimensional chiral scalar field. This

Wu Xiaoning; Huang Chaoguang; Sun Jiarui

2008-01-01

13

Weak gravitational lensing of intrinsically aligned galaxies  

NASA Astrophysics Data System (ADS)

Subject of this paper is the weak lensing effect on galaxies that show intrinsically correlated ellipticities. In our model, we investigate the distortion of the ellipticity field if the galaxies experience an apparent shift in their position by weak lensing deflection and compare this effect to the shearing effect induced by tidal fields. Starting with a derivation of intrinsic ellipticity spectra by employing a tidal torquing model generating galactic angular momenta, we model the galaxy ellipticity by assuming that the galactic disc forms perpendicularly to the host halo angular momentum direction and derives intrinsic ellipticity E-mode and B-mode spectra from the angular momentum statistics. The lensing effect on the ellipticity field is modelled by employing the methodology developed in the framework of lensing of the cosmic microwave background polarization. For Euclid, ellipticity correlations are altered by lensing deflection on multipoles ? ? 1000 by ˜5 per cent for the ellipticity E modes and ˜30 per cent for the B modes, while a shallower survey would exhibit larger changes on larger angular scales. In addition to the convolving effect of lensing on the ellipticity spectra, we investigate the E/B-mode conversion and discuss the possibility of measuring correlations between different multipoles, which is evoked by the homogeneity breaking effect of the lensing displacement. Our conclusion is that although shape correlations generated by weak gravitational shear is dominant, the shifting effect due to lensing is shaping the ellipticity spectra on small angular scales and causing a number of interesting phenomena, which might be observable by future surveys.

Giahi-Saravani, Aram; Schäfer, Björn Malte

2014-01-01

14

Titan's Gravitational Field  

NASA Astrophysics Data System (ADS)

Titan's gravitational field is inferred from an analysis of archived radio Doppler data for six Cassini flybys. The analysis considers each flyby separately in contrast to the approach of lumping all the data together in a massive inversion. In this way it is possible to gain an improved understanding of the character of each flyby and its usefulness in constraining the gravitational coefficient C22 . Though our analysis is not yet complete and our final determination of C22 could differ from the result we report here by 1 or 2 sigma, we find a best-fit value of C22 equal to (13.21 × 0.17) × 10-6, significantly larger than the value of 10.0 × 10-6 obtained from an inversion of the lumped Cassini data. We also find no determination of the tidal Love number k2. The larger value of C22 implies a moment of inertia factor equal to 0.3819 × 0.0020 and a less differentiated Titan than is suggested by the smaller value. The larger value of C22 is consistent with an undifferentiated model of the satellite. While it is not possible to rule out either value of C22 , we prefer the larger value because its derivation results from a more hands on analysis of the data that extracts the weak hydrostatic signal while revealing the effects of gravity anomalies and unmodeled spacecraft accelerations on each of the six flybys.

Schubert, G.; Anderson, J. D.

2013-12-01

15

Atomic Inference from Weak Gravitational Lensing Data  

SciTech Connect

We present a novel approach to reconstructing the projected mass distribution from the sparse and noisy weak gravitational lensing shear data. The reconstructions are regularized via the knowledge gained from numerical simulations of clusters, with trial mass distributions constructed from n NFW profile ellipsoidal components. The parameters of these ''atoms'' are distributed a priori as in the simulated clusters. Sampling the mass distributions from the atom parameter probability density function allows estimates of the properties of the mass distribution to be generated, with error bars. The appropriate number of atoms is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reecting the quality of the data. Ensemble average mass maps are found to be robust to the details of the noise realization, and succeed in recovering the demonstration input mass distribution (from a realistic simulated cluster) over a wide range of scales. As an application of such a reliable mapping algorithm, we comment on the residuals of the reconstruction and the implications for predicting convergence and shear at specific points on the sky.

Marshall, Phil; /KIPAC, Menlo Park

2005-12-14

16

Weak cosmic censorship in gravitational collapse with astrophysical parameter values  

NASA Astrophysics Data System (ADS)

The possible violation of the weak cosmic censorship hypothesis in astrophysical phenomena can provide us with information about trans-Planckian physics through observations. We present negative evidence, however, that one should not expect such a possibility at least when the deviation from spherical symmetry is negligible and the parameter values of collapse are astrophysically reasonable. Taking the Lemaître-Tolman-Bondi solution as the model most likely to counter the weak hypothesis, we show that the mass ({? } 1.5 M_? ) and density ({? } 1.5× 10^{15} {g/cm}^3) of the collapsing object produce a gravitational field strong enough to capture any null rays soon after emanating from the singularity.

Miyamoto, Umpei; Jhingan, Sanjay; Harada, Tomohiro

2013-05-01

17

Basal electric and magnetic fields of celestial bodies come from positive-negative charge separation caused by gravitation of quasi-Casimir pressure in weak interaction  

NASA Astrophysics Data System (ADS)

According to f =d(mv)/dt=m(dv/dt)+ v(dm/dt), a same gravitational formula had been de-duced from the variance in physical mass of QFT and from the variance in mass of inductive energy-transfer of GR respectively: f QF T = f GR = -G (mM/r2 )((r/r)+(v/c)) when their interaction-constants are all taken the experimental values (H05-0029-08, E15-0039-08). f QF T is the quasi-Casimir pressure. f GR is equivalent to Einstein's equation, then more easy to solve it. The hypothesis of the equivalent principle is not used in f QF T , but required by f GR . The predictions of f QF T and f GR are identical except that f QF T has quantum effects but f GR has not and f GR has Lense-Thirring effect but f QF T has not. The quantum effects of gravitation had been verified by Nesvizhevsky et al with the ultracold neutrons falling in the earth's gravitational field in 2002. Yet Lense-Thirring effect had not been measured by GP-B. It shows that f QF T is essential but f GR is phenomenological. The macro-f QF T is the statistic average pressure collided by net virtual neutrinos ? 0 flux (after self-offset in opposite directions) and in direct proportion to the mass. But micro-f QF T is in direct proportion to the scattering section. The electric mass (in inverse proportion to de Broglie wavelength ?) far less than nucleonic mass and the electric scattering section (in direct proportion to ?2 ) far large than that of nucleon, then the net ? 0 flux pressure exerted to electron far large than that to nucleon and the electric displacement far large than that of nucleon, it causes the gravitational polarization of positive-negative charge center separation. Because the gravity far less than the electromagnetic binding force, in atoms the gravitational polarization only produces a little separation. But the net ? 0 flux can press a part freedom electrons in plasma of ionosphere into the earth's surface, the static electric force of redundant positive ions prevents electrons from further falling and till reach the equilibrium of stable spatial charge distribution, which is just the cause of the geomagnetic field and the geo-electric field (the observational value on the earth surface is about 120 V/m downward equivalent to 500000 Coulomb negative charges in the earth surface). All celestial bodies are gravitation sources and attract the molecules and ions in space to its circumference by the gravitation of own and other celestial bodies, e.g., all planets in the solar system have their own atmospheres. Therefore, the origin mechanism of geo-electric and geomagnetic fields caused by gravitation is very universal, at least it is appli-cable to all the planets in the solar system. For planets, the joint result of the gravitations of the planets and the sun makes the negative charges and dipolar charges distributed in the surfaces of the celestial bodies. The quicker the rotation is, the larger the angular momentum U is, then larger the accompanying current and magnetic moment P, it accord a experiential law found by subsistent observational data of all celestial bodies in solar system: P = -G 1/2 U cos ? / c (1), ? is the angle between the net ? 0 flux direction (mark by CMB) and the rotational axis of celestial body (Chen Shao-Guang, Chinese Science Bulletin, 26,233,1981). Uranian and Neptunian P predicted with Eq.(1) in 1981 are about -3.4•1028 Gs•cm3 and 1.9•1028 Gs•cm3 respectively (use new rotate speed measured by Voyager 2). The P measured by Voyager 2 in 1986 and 1989 are about -1.9 •1028 Gs•cm3 and 1.5•1028 Gs•cm3 respectively (the contribution of quadrupole P is converted into the contribution of dipole P alone). The neutron star pos-sesses much high density and rotational speed because of the conservation of the mass and the angular momentum during the course of the formation, then has strong gravity and largerU. From Eq.(1) there is a larger P and extremely strong surface magnetic field in neutron star. The origin mechanism of basal electric and magnetic fields of celestial bodies will affect directly all fields refer

Chen, Shao-Guang

18

The Intrinsic Alignment of Galaxies and Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

Galaxy intrinsic alignments (IA) are correlations between intrinsic galaxy shapes and the surrounding density field. These correlations can bias weak gravitational lensing measurements and are the most significant source of astrophysical uncertainty for the next generation of lensing experiments. Despite its importance, IA is poorly understood. The work presented here aims to improve our understanding through both modeling and measuring IA. First, we examine the most frequently employed IA model, the tidal (linear) alignment model, in which galaxy shapes are closely correlated with the surrounding gravitational tidal field. The tidal alignment model provides an accurate description of IA on large scales (r > 10 Mpc/h), as measured for luminous red galaxies in the Sloan Digital Sky Survey (SDSS). The IA amplitude for these objects, as determined in this analysis, will allow predictions for possible contamination in current and future lensing studies. We explore several ways in which the model could be improved and expanded, including how the relationship between galaxies and their host halos can modulate the strength of IA, as well as relevant effects on smaller scales (r < 10 Mpc/h). Second, we develop a method to separate IA from galaxy-galaxy lensing measurements using photometric redshift information. This technique allows the removal of contamination from the desired lensing signal while also providing a probe of IA in different galaxy populations. We employ this method to constrain fractional IA contamination in the SDSS lensing sample to 1-2%, finding that it is a subdominant source of uncertainty at the current level of statistical precision. These developments in both modeling and measurement techniques can be applied in future lensing analyses to mitigate potential contamination from IA. Such considerations will become more important as statistical precision continues to improve.

Blazek, Jonathan

2014-01-01

19

Caution: Strong gravitational field present  

NASA Astrophysics Data System (ADS)

I came up with a new way to introduce the concept of a constant gravitational field near the surface of the Earth. I made "g-field detectors" (see Fig. 1) and suspended them by strings from the ceiling in a regular spacing. The detectors are cardstock arrows with a hole punched out of them and the letter "g" in the center.

Reif, Marc

2014-05-01

20

Particles, Fields, and Gravitation. Proceedings  

SciTech Connect

These proceedings represent papers presented at the Conference on Particles, Fields, and Gravitation held in Lodz, Poland in April, 1998. The topics discussed included quantum deformations and noncommutative geometry, quantum mechanics, quantum and topological field theory, modern gravitation theory and geometrical methods in physics. Solvable and quasisolvable models were also disussed. The talks and the resulting papers provided a comprehensive coverage of the main aspects of contemporary theoretical and mathematical physics. The Conference was attended by more than 100 scientists from all over the world. There were 54 papers presented at the conference,out of which 1 paper has been abstracted for the Energy,Science and Technology database.(AIP)

Rembieli ski, J. [Department of Theoretical Physics, University of Lodz, Lodz 90-236 (Poland)

1998-11-01

21

''Homogeneous'' Gravitational Field in General Relativity ?  

Microsoft Academic Search

The gravitation field of the flat plate was investigated. It have been shown that there exist the internal solution of Einstein equations sewed together with external one, which described a ''homogeneous'' gravitational field.

R. M. Avakyan; E. V. Chubaryan; A. H. Yeranyan

2001-01-01

22

''Homogeneous'' Gravitational Field in General Relativity ?  

Microsoft Academic Search

The gravitation field of the flat plate was investigated. It have been shown\\u000athat there exist the internal solution of Einstein equations sewed together\\u000awith external one, which described a ''homogeneous'' gravitational field.

R. M. Avakyan; E. V. Chubaryan; A. H. Yeranyan

2001-01-01

23

Weak shear study of galaxy clusters by simulated gravitational lensing  

NASA Astrophysics Data System (ADS)

Gravitational lensing has been simulated for numerical galaxy clusters in order to characterize the effects of substructure and shape variations of dark matter halos on the weak lensing properties of clusters. In order to analyze realistic galaxy clusters, 6 high-resolution Adaptive Refinement Tree N-body simulations of clusters with hydrodynamics are used, in addition to a simulation of one group undergoing a merger. For each cluster, the three-dimensional particle distribution is projected perpendicular to three orthogonal lines of sight, providing 21 projected mass density maps. The clusters have representative concentration and mass values for clusters in the concordance cosmology. Two gravitational lensing simulation methods are presented. In the first method, direct integration is used to calculate deflection angles. To overcome computational constraints inherent in this method, a distributed computing project was created for parallel computation. In addition to its use in gravitational lensing simulation, a description of the setup and function of this distributed computing project is presented as an alternative to in-house computing clusters, which has the added benefit of public enrollment in science and low cost. In the second method, shear maps are created using a fast Fourier transform method. From these shear maps, the effects of substructure and shape variation are related to observational gravitational lensing studies. Average shear in regions less than and greater than half of the virial radius demonstrates distinct dispersion, varying by 24% from the mean among the 21 maps. We estimate the numerical error in shear calculations to be of the order of 5%. Therefore, this shear dispersion is a reliable consequence of shape dispersion, correlating most strongly with the ratio of smallest-to-largest principal axis lengths of a cluster isodensity shell. On the other hand, image ellipticities, which are of great importance in mass reconstruction, are shown to have very little variance. However, tangential alignment of average image distortion is quite strong, making mass density peak locations easily resolvable.

Coss, David

24

Development of Gravidynamical Equations for a Weakly Gravitating Body in the Vicinity of Absolute Zero Temperature  

NASA Astrophysics Data System (ADS)

the framework of this model bodies have fuzzy outlines and are represented by means of spheroidal forms. The consistency of the statistical model with the Einstein general relativity3,4,5 has been shown. In the work6, which is a continuation of the paper2, it was investigated a slowly evolving in time process of a gravitational compression (contraction) of a spheroidal body close to an unstable meñhanical equilibrium state (a low mass flow), therefore the process of the gravitational contraction appears slowly developing in time (the case of unobservable velocities of particles composing a spheroidal body). For this case in the work7 it has been shown that the strength and potential of the gravitational field of a slowly contracting spheroidal body satisfy a differential equation of the second order of the parabolic type for the case of unobservable velocities of particles. Therefore gravitational waves of a soliton type are propagated in a weakly gravitating spheroidal body if values of velocities are unobservable. body. In the connection with the above-given statements, in the present paper the following assumptions are used: 1.The spheroidal body under consideration is homogeneous in its chemical structure, i.e. it consists of identical particles with the mass m0. 2.The spheroidal body is not subjected to influence of external fields and bodies. 3.The spheroidal body is isothermal and has temperature close to the absolute zero. 4.The concentration gradient is not too large in the sense that interphase boundaries are absent inside the spheroidal body. 5. In view of low values of the temperature the heat conduction and viscosity processes are not important, which allows to describe the rotation of the spheroidal body as a whole, while movement of flows of particles inside the weakly gravitating spheroidal body is modeled by means of a motion of an ideal medium (the case of observable velocities of particles). 6.Since the process of the gravitational compression (contraction) of the spheroidal body is weak and viscosity is absent, we regard the motion of the continuous medium to be non-turbulent. modeled by means of an ideal liquid. It is determined the connection of this equation with an equation of motion of a particle in a noninertial frame of reference. A gravimagnetic field is introduced in this paper. It is obtained the scalar and vector potentials as well as the Lagrange function of a particle moving in a gravitational and gravimagnetic fields. It is derived the equations of hyperbolic type for the gravitational field of a weakly gravitating spheroidal body under observable values of velocities of particles composing it. 1. A.M.Krot, Achievements in Modern Radioelectronics, special issue "Cosmic Radiophysics", no.8, pp.66- 2. A.M.Krot, Proc. SPIE 13th Symp."AeroSense", Orlando, Florida, April 5-9,1999, vol.3710,pp.1248-1259. 3. L.D.Landau and E.M.Lifshitz, Classical Theory of Fields, Addison-Wesley, 1951. 4. S.Weinberg, Gravitation and Cosmology, John Wiley and Sons, New York, 1972. 5. C.W.Misner, K.S.Thorne, and J.A.Wheeler, Gravitation, W.H.Freeman and Co., San Francisco, 1973. 6. A.M.Krot, Proc. SPIE 14th Symp."AeroSense",Orlando,Florida,April 24-28,2000,vol.4038,pp.1318-1329. 7. A.M.Krot, Proc. SPIE 15th Symp."AeroSense",Orlando,Florida,April 16-20,2001,vol.4394,pp.1271-1282.

Krot, Alexander M.

2002-01-01

25

Primordial magnetic seed field amplification by gravitational waves  

SciTech Connect

Using second-order gauge-invariant perturbation theory, a self-consistent framework describing the nonlinear coupling between gravitational waves and a large-scale homogeneous magnetic field is presented. It is shown how this coupling may be used to amplify seed magnetic fields to strengths needed to support the galactic dynamo. In situations where the gravitational wave background is described by an 'almost' Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology we find that the magnitude of the original magnetic field is amplified by an amount proportional to the magnitude of the gravitational wave induced shear anisotropy and the square of the field's initial comoving scale. We apply this mechanism to the case where the seed field and gravitational wave background are produced during inflation and find that the magnitude of the gravitational boost depends significantly on the manner in which the estimate of the shear anisotropy at the end of inflation is calculated. Assuming a seed field of 10{sup -34} G spanning a comoving scale of about 10 kpc today, the shear anisotropy at the end of inflation must be at least as large as 10{sup -40} in order to obtain a generated magnetic field of the same order of magnitude as the original seed. Moreover, contrasting the weak-field approximation to our gauge-invariant approach, we find that while both methods agree in the limit of high conductivity, their corresponding solutions are otherwise only compatible in the limit of infinitely long-wavelength gravitational waves.

Betschart, Gerold; Zunckel, Caroline [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); Dunsby, Peter K.S. [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa); Marklund, Mattias [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2005-12-15

26

Mars gravitational field estimation error  

NASA Technical Reports Server (NTRS)

The error covariance matrices associated with a weighted least-squares differential correction process have been analyzed for accuracy in determining the gravitational coefficients through degree and order five in the Mars gravitational potential junction. The results are presented in terms of standard deviations for the assumed estimated parameters. The covariance matrices were calculated by assuming Doppler tracking data from a Mars orbiter, a priori statistics for the estimated parameters, and model error uncertainties for tracking-station locations, the Mars ephemeris, the astronomical unit, the Mars gravitational constant (G sub M), and the gravitational coefficients of degrees six and seven. Model errors were treated by using the concept of consider parameters.

Compton, H. R.; Daniels, E. F.

1972-01-01

27

Karhunen-Loeve Analysis for Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the nature of dark energy. This thesis research explores several applications of Karhunen-Loève (KL) analysis to speed and improve the comparison of weak lensing shear catalogs to theory in order to constrain cosmological parameters in current and future lensing surveys. This work addresses three related aspects of weak lensing analysis: Three-dimensional Tomographic Mapping: (Based on work published in Vanderplas et al 2011) We explore a new fast approach to three-dimensional mass mapping in weak lensing surveys. The KL approach uses a KL-based filtering of the shear signal to reconstruct mass structures on the line-of-sight, and provides a unified framework to evaluate the efficacy of linear reconstruction techniques. We find that the KL-based filtering leads to near-optimal angular resolution, and computation times which are faster than previous approaches. We also use the KL formalism to show that linear non-parametric reconstruction methods are fundamentally limited in their ability to resolve lens redshifts. Shear Peak Statistics with Incomplete Data: (Based on work published in Vanderplas et al 2012) We explore the use of KL eigenmodes for interpolation across masked regions in observed shear maps. Mass mapping is an inherently non-local calculation, meaning gaps in the data can have a significant effect on the properties of the derived mass map. Our KL mapping procedure leads to improvements in the recovery of detailed statistics of peaks in the mass map, which holds promise of improved cosmological constraints based on such studies. Two-point parameter estimation with KL modes: The power spectrum of the observed shear can yield powerful cosmological constraints. Incomplete survey sky coverage, however, can lead to mixing of power between Fourier modes, and obfuscate the cosmologically sensitive signal. We show that KL can be used to derive an alternate orthonormal basis for the problem which avoids mode-mixing and allows a convenient formalism for cosmological likelihood computations. Cosmological constraints derived using this method are shown to be competitive with those from the more conventional correlation function approach. We also discuss several aspects of the KL approach which will allow improved handling of correlated errors and redshift information in future surveys.

Vanderplas, Jacob T.

28

Gravitational field maps and navigational errors  

Microsoft Academic Search

It has been proposed to use gravitational field maps to correct navigational errors inherent in some navigational systems presently in use on unmanned underwater vehicles (UUV) and that such a technology might form the basis for a new UUV navigational system. However, the accuracy and usefulness of the navigational solution depends, among other things, on the accuracy of the gravitational

Garner C. Bishop

2000-01-01

29

Classical field approach to quantum weak measurements.  

PubMed

By generalizing the quantum weak measurement protocol to the case of quantum fields, we show that weak measurements probe an effective classical background field that describes the average field configuration in the spacetime region between pre- and postselection boundary conditions. The classical field is itself a weak value of the corresponding quantum field operator and satisfies equations of motion that extremize an effective action. Weak measurements perturb this effective action, producing measurable changes to the classical field dynamics. As such, weakly measured effects always correspond to an effective classical field. This general result explains why these effects appear to be robust for pre- and postselected ensembles, and why they can also be measured using classical field techniques that are not weak for individual excitations of the field. PMID:24702338

Dressel, Justin; Bliokh, Konstantin Y; Nori, Franco

2014-03-21

30

Numerical study of primordial magnetic field amplification by inflation-produced gravitational waves  

SciTech Connect

We numerically study the interaction of inflation-produced magnetic fields with gravitational waves, both of which originate from quantum fluctuations during inflation. The resonance between the magnetic field perturbations and the gravitational waves has been suggested as a possible mechanism for magnetic field amplification. However, some analytical studies suggest that the effect of the inflationary gravitational waves is too small to provide significant amplification. Our numerical study shows more clearly how the interaction affects the magnetic fields and confirms the weakness of the influence of the gravitational waves. We present an investigation based on the magnetohydrodynamic approximation and take into account the differences of the Alfven speed.

Kuroyanagi, Sachiko [Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Tashiro, Hiroyuki [Institut d'Astrophysique Spatiale, Universite Paris-Sud XI and CNR, Orsay, F-91405 (France); Sugiyama, Naoshi [Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute for Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba 277-8582 (Japan)

2010-01-15

31

Weak gravitational lensing systematic errors in the dark energy survey  

NASA Astrophysics Data System (ADS)

Dark energy is one of the most important unsolved problems in modern Physics, and weak gravitational lensing (WL) by mass structures along the line of sight ("cosmic shear") is a promising technique to learn more about its nature. However, WL is subject to numerous systematic errors which induce biases in measured cosmological parameters and prevent the development of its full potential. In this thesis, we advance the understanding of WL systematics in the context of the Dark Energy Survey (DES). We develop a testing suite to assess the performance of the shapelet-based DES WL measurement pipeline. We determine that the measurement bias of the parameters of our Point Spread Function (PSF) model scales as (S/N )-2, implying that a PSF S/N > 75 is needed to satisfy DES requirements. PSF anisotropy suppression also satisfies the requirements for source galaxies with S/N ? 45. For low-noise, marginally-resolved exponential galaxies, the shear calibration errors are up to about 0.06% (for shear values ? 0.075). Galaxies with S/N ? 75 present about 1% errors, sufficient for first-year DES data. However, more work is needed to satisfy full-area DES requirements, especially in the high-noise regime. We then implement tests to validate the high accuracy of the map between pixel coordinates and sky coordinates (astrometric solution), which is crucial to detect the required number of galaxies for WL in stacked images. We also study the effect of atmospheric dispersion on cosmic shear experiments such as DES and the Large Synoptic Survey Telescope (LSST) in the four griz bands. For DES (LSST), we find systematics in the g and r (g, r, and i) bands that are larger than required. We find that a simple linear correction in galaxy color is accurate enough to reduce dispersion shear systematics to insignificant levels in the r ( i) band for DES (LSST). More complex corrections will likely reduce the systematic cosmic-shear errors below statistical errors for LSST r band. However, g-band dispersion effects remain large enough for induced systematics to dominate the statistical error of both surveys, so cosmic-shear measurements should rely on the redder bands.

Plazas, Andres Alejandro

32

The gravitational field and brain function  

NASA Astrophysics Data System (ADS)

The frontal cortex is recognized as the highest adaptive control center of the human brain. The principle of the ``frontalization'' of human brain function offers new possibilities for brain research in space. There is evolutionary and experimental evidence indicating the validity of the principle, including it's role in nervous response to gravitational stimulation. The gravitational field is considered here as one of the more constant and comprehensive factors acting on brain evolution, which has undergone some successive crucial steps: ``encephalization'', ``corticalization'', ``lateralization'' and ``frontalization''. The dominating effects of electrical responses from the frontal cortex have been discovered 1) in experiments under gravitational stimulus; and 2) in processes potentially relating to gravitational adaptation, such as memory and learning, sensory information processing, motor programing, and brain state control. A brain research experiment during space flight is suggested to test the role of the frontal cortex in space adaptation and it's potentiality in brain control.

Mei, Lei; Zhou, Chuan-Dai; Lan, Jing-Quan; Wang, Zhi-Ging; Wu, Wen-Can; Xue, Xin-Min

33

Parametric Instability in Scalar Gravitational Fields  

NASA Astrophysics Data System (ADS)

We present a brief review on a new dynamical mechanism for a strong field effect in scalar-tensor theory. Starting with a summary of the essential features of the theory and subsequent work by several authors, we analytically investigate the parametric excitation of a scalar gravitational field in a spherically symmetric radially pulsating neutron star.

Davies, Trevor B.; Wang, Charles H.-T.; Bingham, Robert; Tito Mendonça, J.

2012-08-01

34

Galilean-invariant scalar fields can strengthen gravitational lensing.  

PubMed

The mystery of dark energy suggests that there is new gravitational physics on long length scales. Yet light degrees of freedom in gravity are strictly limited by Solar System observations. We can resolve this apparent contradiction by adding a Galilean-invariant scalar field to gravity. Called Galileons, these scalars have strong self-interactions near overdensities, like the Solar System, that suppress their dynamical effect. These nonlinearities are weak on cosmological scales, permitting new physics to operate. In this Letter, we point out that a massive-gravity-inspired coupling of Galileons to stress energy can enhance gravitational lensing. Because the enhancement appears at a fixed scaled location for dark matter halos of a wide range of masses, stacked cluster analysis of weak lensing data should be able to detect or constrain this effect. PMID:21668215

Wyman, Mark

2011-05-20

35

Gravitational Field of a Global Monopole in a Modified Gravity  

NASA Astrophysics Data System (ADS)

In this paper we analyze the gravitational field of a global monopole in the context of f(R) gravity. More precisely, we show that the field equations obtained are expressed in terms of F(R) = (df(R))/(dR). Since we are dealing with a spherically symmetric system, we assume that F(R) is a function of the radial coordinate only. Moreover, adopting the weak field approximation, we can provide all components of the metric tensor. A comparison with the corresponding results obtained in General Relativity and in the Brans-Dicke theory is also made.

Caramês, T. R. P.; Bezerra de Mello, E. R.; Guimarães, M. E. X.

2011-06-01

36

Chameleon scalar fields in relativistic gravitational backgrounds  

SciTech Connect

We study the field profile of a scalar field {phi} that couples to a matter fluid (dubbed a chameleon field) in the relativistic gravitational background of a spherically symmetric spacetime. Employing a linear expansion in terms of the gravitational potential {Phi}{sub c} at the surface of a compact object with a constant density, we derive the thin-shell field profile both inside and outside the object, as well as the resulting effective coupling with matter, analytically. We also carry out numerical simulations for the class of inverse power-law potentials V({phi}) = M{sup 4+n}{phi}{sup -n} by employing the information provided by our analytical solutions to set the boundary conditions around the centre of the object and show that thin-shell solutions in fact exist if the gravitational potential {Phi}{sub c} is smaller than 0.3, which marginally covers the case of neutron stars. Thus the chameleon mechanism is present in the relativistic gravitational backgrounds, capable of reducing the effective coupling. Since thin-shell solutions are sensitive to the choice of boundary conditions, our analytic field profile is very helpful to provide appropriate boundary conditions for {Phi}{sub c}{approx}

Tsujikawa, Shinji [Department of Physics, Faculty of Science, Tokyo University of Science, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)] [Department of Physics, Faculty of Science, Tokyo University of Science, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan); Tamaki, Takashi [Department of Physics, Waseda University, Okubo 3-4-1, Tokyo 169-8555 (Japan)] [Department of Physics, Waseda University, Okubo 3-4-1, Tokyo 169-8555 (Japan); Tavakol, Reza, E-mail: shinji@rs.kagu.tus.ac.jp, E-mail: tamaki@gravity.phys.waseda.ac.jp, E-mail: r.tavakol@qmul.ac.uk [Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, London E1 4NS (United Kingdom)] [Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, London E1 4NS (United Kingdom)

2009-05-15

37

Overlap Lattice Fermion in a Gravitational Field  

Microsoft Academic Search

We construct a lattice Dirac operator of overlap type that describes the propagation of a Dirac fermion in an external gravitational field. The local Lorentz symmetry is manifestly realized as a lattice gauge symmetry, while it is believed that the general coordinate invariance is restored only in the continuum limit. Our doubler-free Dirac operator satisfies the conventional Ginsparg-Wilson relation and

Masashi Hayakawa; Hiroto So; Hiroshi Suzuki

2006-01-01

38

Interpretation of the lunar gravitational field  

Microsoft Academic Search

The most significant inference from the gravitational field is that the isostatic compensation of the highlands requires a thorough fractionation of at least one-third of the Moon's mass. The Apollo amples and other recent data make creation of the mascons by surface transfer processes much less plausible, leave their creation by infalling denser bodies speculative, and make more acceptable to

William M. Kaula

1971-01-01

39

Gravitational repulsion in the Schwarzschild field  

SciTech Connect

To the distant observer, who uses measuring instruments not affected by gravity, gravitational repulsion can occur anywhere in the Schwarzschild field. It depends on the relationship between the transverse and radial Schwarzschild velocities. On the other hand, local observers, whose measuring instruments are affected by gravity, can not detect a positive value for the acceleration of gravity.

McGruder, C.H. III

1982-06-15

40

Higgs gravitational interaction, weak boson scattering, and Higgs inflation in Jordan and Einstein frames  

NASA Astrophysics Data System (ADS)

We study gravitational interaction of Higgs boson through the unique dimension-4 operator ?H†HScript R, with H the Higgs doublet and Script R the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling ? on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone equivalence theorem with nonzero ? coupling in both frames, and analyze the unitarity constraints. We study the ?-induced weak boson scattering cross sections at Script O(1?30) TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC (14 TeV) and the next generation pp colliders (50-100 TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data.

Ren, Jing; Xianyu, Zhong-Zhi; He, Hong-Jian

2014-06-01

41

Gravitational radiation from preheating with many fields  

NASA Astrophysics Data System (ADS)

Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple to many other relativistic degrees of freedom present in the early universe. Using simulations in an expanding Friedmann-Lemaître-Robertson-Walker spacetime, in this paper we show how preheating is affected by the addition of multiple fields coupled to the inflaton. We focus our attention on gravitational wave production — an important potential observational signature of the preheating stage. We find that preheating and its gravitational wave signature is robust to the coupling of the inflaton to more matter fields.

Giblin, John T., Jr.; Price, Larry R.; Siemens, Xavier

2010-08-01

42

Phase shifts in gravitationally evolving density fields  

Microsoft Academic Search

The phases of the Fourier components of an initially Gaussian density field are examined to see how the phases are shifted away from their initial values as the field evolves gravitationally. The analytic expression for the phase shift, in second-order perturbation theory, is presented. To investigate the fully nonlinear regime, 2D N-body simulations were run. The power spectra used were

Barbara S. Ryden; Mirt Gramann

1991-01-01

43

Rotation of the cosmic microwave background polarization from weak gravitational lensing.  

PubMed

When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection. PMID:24580435

Dai, Liang

2014-01-31

44

Lognormal Property of Weak Lensing Fields  

Microsoft Academic Search

The statistical properties of weak-lensing fields are studied quantitatively using ray-tracing simulations. Motivated by an empirical lognormal model that excellently characterizes the probability distribution function of a three-dimensional mass distribution, we critically investigate the validity of the lognormal model in weak-lensing statistics. Assuming that the convergence field kappa is approximately described by the lognormal distribution, we present analytic formulae of

Atsushi Taruya; Masahiro Takada; Takashi Hamana; Issha Kayo; Toshifumi Futamase

2002-01-01

45

Statistical properties of filaments in weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We study the weak lensing properties of filaments that connect clusters of galaxies through large cosmological N-body simulations. We select 4639 halo pairs with masses higher than 1014 h-1 M? from the simulations and investigate dark matter distributions between two haloes with ray-tracing simulations. In order to classify filament candidates, we estimate convergence profiles and perform profile fitting. We find that matter distributions between haloes can be classified in a plane of fitting parameters, which allows us to select straight filaments from the ray-tracing simulations. We also investigate the statistical properties of these filaments, finding them to be consistent with previous studies. We find that 35 per cent of halo pairs possess straight filaments, 4 per cent of which can be detected directly at signal-to-noise ratio S/N ? 2 with weak lensing. Furthermore, we study the statistical properties of haloes at the edges of filaments. We find that haloes are preferentially elongated along filamentary structures and are less massive with increasing filament mass. However, the dependence of these halo properties on the masses of straight filaments is very weak.

Higuchi, Yuichi; Oguri, Masamune; Shirasaki, Masato

2014-06-01

46

GRAVITATIONAL FIELD SHIELDING AND SUPERNOVA EXPLOSIONS  

SciTech Connect

A new mechanism for supernova explosions called gravitational field shielding is proposed, in accord with a five-dimensional fully covariant Kaluza-Klein theory with a scalar field that unifies the four-dimensional Einsteinian general relativity and Maxwellian electromagnetic theory. It is shown that a dense compact collapsing core of a star will suddenly turn off or completely shield its gravitational field when the core collapses to a critical density, which is inversely proportional to the square of mass of the core. As the core suddenly turns off its gravity, the extremely large pressure immediately stops the core collapse and pushes the mantle material of supernova moving outward. The work done by the pressure in the expansion can be the order of energy released in a supernova explosion. The gravity will resume and stop the core from a further expansion when the core density becomes less than the critical density. Therefore, the gravitational field shielding leads a supernova to impulsively explode and form a compact object such as a neutron star as a remnant. It works such that a compressed spring will shoot the oscillator out when the compressed force is suddenly removed.

Zhang, T. X. [Physics Department, Alabama A and M University, Normal, AL 35762 (United States)

2010-12-20

47

Prolate Spheroidal Harmonic Expansion of Gravitational Field  

NASA Astrophysics Data System (ADS)

As a modification of the oblate spheroidal case, a recursive method is developed to compute the point value and a few low-order derivatives of the prolate spheroidal harmonics of the second kind, Qnm (y), namely the unnormalized associated Legendre function (ALF) of the second kind with its argument in the domain, 1 < y < ?. They are required in evaluating the prolate spheroidal harmonic expansion of the gravitational field in addition to the point value and the low-order derivatives of \\overline{P}_{nm}(t), the 4? fully normalized ALF of the first kind with its argument in the domain, |t| <= 1. The new method will be useful in the gravitational field computation of elongated celestial objects.

Fukushima, Toshio

2014-06-01

48

Geometrical structure of gravitation and matter fields  

NASA Astrophysics Data System (ADS)

Einstein's requirement of a unified geometrical description of gravitational fields and their matter sources is shown to become possible (at least for certain matter sources) by relaxing his other requirement of a minimal interaction of gravitation with matter. Arguments are presented to demonstrate that Schrödinger's discovery of pair creation by gravitational fields and the associated effects of virtual pairs make the relaxation of the latter requirement inevitable in order to obtain a complete macroscopic description (which needs no separate insertion to take account of averaged quantum effects). The gravitational field equations in case of a nonminimal interaction need higher derivatives of the metric than the second. The author's gauge theory on the manifold of the anti-de Sitter group SO(3, 2) with the subgroup SO(3, 1) (proper Lorentz group) as gauge group and the factor space of the two group manifolds as space-time manifold gives rise to a Yang-Mills field which can be interpreted to be composed of Riemannian curvature and a tensor formed out of torsion. Einstein's equations with a cosmological member are satisfied by the Cartan-Killing metric on the group manifold so that the generalization to a Kaluza-Klein theory results in a minimal disturbance of the group symmetry. The separation of the Yang-Mills field results in a part of its energy-momentum tensor becoming purely Riemannian; this part may be interpreted to be due to the contribution of virtual matter, whereas the part with torsion is due to real matter and its interaction with curvature. The Yang-Mills field equations have a third-order derivative purely metric part, which is equivalent to the field equations suggested by Yang (in the latter, however, torsion should be inseparably present and has been ignored). The torsion part is the “matter source” of this term and it is tempting to relate it to elementary particle spin. The theory can be regarded as a gauge theory of space-time geometry. It needs generalizations to geometrize matter with an energy-momentum tensor of nonvanishing trace. The equations, however, already considerably modify the problem of gravitational collapse. Further developments should serve to eliminate the “absurdity of relativity”—the collapse to a point (of which Einstein himself never became convinced).

Halpern, Leopold

1994-02-01

49

Components of the gravitational force in the field of a gravitational wave  

Microsoft Academic Search

Gravitational waves bring about the relative motion of free test masses. The detailed knowledge of this motion is important conceptually and practically, because the mirrors of laser interferometric detectors of gravitational waves are essentially free test masses. There exists an analogy between the motion of free masses in the field of a gravitational wave and the motion of free charges

D. Baskaran; L. P. Grishchuk

2004-01-01

50

A Gravitational Experiment Involving Inhomogeneous Electric Fields  

SciTech Connect

Unification of gravitation with other forms of interactions, particularly with electromagnetism, will have tremendous impacts on technology and our understanding of nature. The economic impact of such an achievement will also be unprecedented and far more extensive than the impact experienced in the past century due to the unification of electricity with magnetism and optics. Theoretical unification of gravitation with electromagnetism using classical differential geometry has been pursued since the late nineteen twenties, when Einstein and Cartan used teleparallelism for the task. Recently, Vargas and Torr have followed the same line of research with more powerful mathematics in a more general geometric framework, which allows for the presence of other interactions. Their approach also uses Kaehler generalization of Cartan's exterior calculus, which constitutes a language appropriate for both classical and quantum physics. Given the compelling nature of teleparallelism (path-independent equality of vectors at a distance) and the problems still existing with energy-momentum in general relativity, it is important to seek experimental evidence for such expectations. Such experimental programs are likely to provide quantitative guidance to the further development of current and future theories. We too, have undertaken an experimental search for potential electrically induced gravitational (EIG) effects. This presentation describes some of the practical concerns that relates to our investigation of electrical influences on laboratory size test masses. Preliminary results, appear to indicate a correlation between the application of a spatially inhomogeneous electric field and the appearance of an additional force on the test mass. If confirmed, the presence of such a force will be consistent with the predictions of Vargas-Torr. More importantly, proven results will shed new light and clearer understanding of the interactions between gravitational and electromagnetic effects.

Datta, T. [University of South Carolina, Columbia, SC 29208 (United States); Yin Ming [Benedict College, Columbia, SC 29204 (United States); Vargas, Jose [PST Associates, 600 Westover Rd. Columbia, SC 29210 (United States)

2004-02-04

51

Theory of microemulsions in a gravitational field  

NASA Technical Reports Server (NTRS)

A theory of microemulsions developed previously is extended to include the effect of a gravitational field. It predicts variation with position of drop size, drop volume fraction, and area per molecule in the surfactant films within a microemulsion phase. Variation in volume fraction is greatest and occurs in such a way that oil content increases with increasing elevation, as has been found experimentally. Large composition variations are predicted within a middle phase microemulsion near optimal conditions because inversion from the water-continuous to the oil-continuous arrangement occurs with increasing elevation. Generally speaking, gravity reduces solubilization within microemulsions and promotes separation of excess phases.

Jeng, J. F.; Miller, Clarence A.

1989-01-01

52

Gravitational field of a charged mass point  

PubMed Central

Adopting, with Schwarzschild, the Einstein gauge (???? = -1), a solution of Einstein's field equations for a charged mass point of mass M and charge Q is derived, which differs from the Reissner-Nordstrøm solution only in that the variable r is replaced by R = (r3 + a3)?, where a is a constant. The Newtonian gravitational potential ? ? (2/c2)(1 - g00) obeys exactly the Poisson equation (in the R variable), with the mass density equal to (E2/4?c2), E denoting the electric field. ? also obeys a second linear equation in which the operator on ? is the square root of the Laplacian operator. The electrostatic potential ? (= Q/R), ?, and all the components of the curvature tensor remain finite at the origin of coordinates. The electromagnetic energy of the point charge is finite and equal to (Q2/a). The charge Q defines a pivotal mass M* = (Q/G½). If M < M*, then the whole mass is electromagnetic. If M > M*, the electromagnetic part of the mass Mem equals [M - (M2 - M*2)½], whereas the material part of the mass Mmat equals (M2 - M*2)½. When M > M*, the constant a is determined, following Schwarzschild, by shrinking the “Schwarzschild radius” to zero. When M < M*, a is determined so as to make the gravitational acceleration vanish at the origin.

Pekeris, C. L.

1982-01-01

53

On seasonal variations of Mars' gravitational field  

NASA Technical Reports Server (NTRS)

A great quantity of CO2 is exchanged between the Martian atmosphere and polar caps in the course of a Martian year. This exchange occurs in seasonal cycles: CO2 condenses to form the polar caps in winter and sublimes into the atmosphere in summer. The mass involved is about 25% of the total mass of the Martian atmosphere. This paper studies the effects of the CO2 mass redistribution on the Mars' gravitational field. Two mechanisms are examined: (1) the waxing and waning of solid CO2 in the polar caps, and (2) the geographical distribution of gaseous CO2 in the atmosphere. The maximum changes produced by (1) in the low-degree zonal J sub l harmonics in the Mars gravitational field are found to be as much as 7.5 x 10 to the-9 power for J sub 2 (corresponding to 1.1 cm change in the geoid), and about half as much for J sub 3. The effect of (2) on some most prominent low-degree harmonics (for l =1-3) in the effective topography (defined as the departure of the true topography from the geoid) is also evaluated. Their magnitudes are large by Earth standards. Whether they can be observed by the upcoming Mars Observer is still uncertain.

Chao, B. Fong; Rubincam, David P.

1987-01-01

54

Measuring the galaxy-galaxy-mass three-point correlation function with weak gravitational lensing  

Microsoft Academic Search

We discuss the galaxy-galaxy-mass three-point correlation function and show how to measure it with weak gravitational lensing. The method entails choosing pairs of foreground lens galaxies, rotating them to the common coordinate system defined by the axis connecting them and then constructing a mean shear map by averaging the ellipticities of background source galaxies for a large number of foreground

David E. Johnston

2004-01-01

55

Measuring the Galaxy-Galaxy-Mass Three-point Correlation Function with Weak Gravitational Lensing  

Microsoft Academic Search

We discuss the galaxy-galaxy-mass three-point correlation function and show\\u000ahow to measure it with weak gravitational lensing. The method entails choosing\\u000aa large of pairs of foreground lens galaxies and constructing a mean shear map\\u000awith respect to their axis, by averaging the ellipticities of background source\\u000agalaxies. An average mass map can be reconstructed from this shear map and

David E. Johnston

2005-01-01

56

Symmetries in tetrad theories. [of gravitational fields and general relativity  

NASA Technical Reports Server (NTRS)

The isometry conditions for gravitational fields are given directly at the tetrad level, rather than in terms of the metric. As an illustration, an analysis of the curvature collineations and Killing fields for a twisting type-N vacuum gravitational field is made.

Chinea, F. J.

1988-01-01

57

MOND as the weak-field limit of an extended metric theory of gravity  

NASA Astrophysics Data System (ADS)

We show that the Modified Newtonian Dynamics (MOND) regime can be fully recovered as the weak-field limit of a particular theory of gravity formulated in the metric approach. This is possible when Milgrom's acceleration constant is taken as a fundamental quantity which couples to the theory in a very consistent manner. As a consequence, the scale invariance of the gravitational interaction is naturally broken. In this sense, Newtonian gravity is the weak-field limit of general relativity and MOND is the weak-field limit of that particular extended theory of gravity.

Mendoza, S.; Bernal, T.; Hidalgo, J. C.; Capozziello, S.

2012-07-01

58

Gravitational radiative corrections from effective field theory  

SciTech Connect

In this paper we construct an effective field theory (EFT) that describes long wavelength gravitational radiation from compact systems. To leading order, this EFT consists of the multipole expansion, which we describe in terms of a diffeomorphism invariant point particle Lagrangian. The EFT also systematically captures 'post-Minkowskian' corrections to the multipole expansion due to nonlinear terms in general relativity. Specifically, we compute long distance corrections from the coupling of the (mass) monopole moment to the quadrupole moment, including up to two mass insertions. Along the way, we encounter both logarithmic short distance (UV) and long wavelength (IR) divergences. We show that the UV divergences can be (1) absorbed into a renormalization of the multipole moments and (2) resummed via the renormalization group. The IR singularities are shown to cancel from properly defined physical observables. As a concrete example of the formalism, we use this EFT to reproduce a number of post-Newtonian corrections to the gravitational wave energy flux from nonrelativistic binaries, including long distance effects up to 3 post-Newtonian (v{sup 6}) order. Our results verify that the factorization of scales proposed in the NRGR framework of Goldberger and Rothstein is consistent up to order 3PN.

Goldberger, Walter D.; Ross, Andreas [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2010-06-15

59

Gravitational Descendants in Symplectic Field Theory  

NASA Astrophysics Data System (ADS)

It was pointed out by Y. Eliashberg in his ICM 2006 plenary talk that the rich algebraic formalism of symplectic field theory leads to a natural appearance of quantum and classical integrable systems, at least in the case when the contact manifold is the prequantization space of a symplectic manifold. In this paper we generalize the definition of gravitational descendants in SFT from circle bundles in the Morse-Bott case to general contact manifolds. After we have shown using the ideas in Okounkov and Pandharipande (Ann Math 163(2):517-560, 2006) that for the basic examples of holomorphic curves in SFT, that is, branched covers of cylinders over closed Reeb orbits, the gravitational descendants have a geometric interpretation in terms of branching conditions, we follow the ideas in Cieliebak and Latschev ( http://arixiv.org/abs/0706.3284v2 [math.s6], 2007) to compute the corresponding sequence of Poisson-commuting functions when the contact manifold is the unit cotangent bundle of a Riemannian manifold.

Fabert, Oliver

2011-02-01

60

Consequences of Coupled Electromagnetic-Gravitational Fields  

NASA Technical Reports Server (NTRS)

In the late 1980s there was a flurry of activities involving the newly discovered high Tc superconductors in the development of new devices such as more efficient current transmission, transformers, generators, and motors. One such developmental project by Podkletnov in 1992 noted some small, anomalous gravitational behaviors. A following unpublished paper by Podkletnov 1995 provided data with larger effects using a larger (approx. 25 cm) superconducting disk. Unfortunately this disk was extremely fragile and was broken beyond repair. To date, these experiments have not been successfully repeated because of the difficulties of producing stable, durable (and fired) superconducting disks. This problem with firing these disks has been solved by Li. What remains is to install the disk in "motor", at superconducting temperatures in the presence of appropriately tailored magnetic fields.

Smalley, Larry

2002-01-01

61

Creation of gravitational wave by photon in external electromagnetic field.  

National Technical Information Service (NTIS)

The creation of the gravitational wave by the photon in an electromagnetic field is considered. We show that when the momentum of the photon is perpendicular to the field, the probability of the gravitational wave creation is largest in the direction of t...

N. L. Hoang K. H. Le

1989-01-01

62

Weak equivalence principle for self-gravitating bodies: A sieve for purely metric theories of gravity  

NASA Astrophysics Data System (ADS)

We propose the almost-geodesic motion of self-gravitating test bodies as a possible selection rule among metric theories of gravity. Starting from a heuristic statement, the "gravitational weak equivalence principle," we build a formal operative test able to probe the validity of the principle for any metric theory of gravity in an arbitrary number of spacetime dimensions. We show that, if the theory admits a well-posed variational formulation, this test singles out only the purely metric theories of gravity. This conclusion reproduces known results in the cases of general relativity (as well as with a cosmological constant term) and scalar-tensor theories, but extends also to debated or unknown scenarios, such as the f(R) and Lanczos-Lovelock theories. We thus provide new tools going beyond the standard methods, where the latter turn out to be inconclusive or inapplicable.

Di Casola, Eolo; Liberati, Stefano; Sonego, Sebastiano

2014-04-01

63

Gravitational consequences of modern field theories  

NASA Technical Reports Server (NTRS)

Some gravitational consequences of certain extensions of Einstein's general theory of relativity are discussed. These theories are not alternative theories of gravity in the usual sense. It is assumed that general relativity is the appropriate description of all gravitational phenomena which were observed to date.

Horowitz, Gary T.

1989-01-01

64

Variant of the Bimetric Theory of Gravitation. III. Gravitational Radiation  

Microsoft Academic Search

Gravitational radiation in a variant of the bimetric theory of gravitation is investigated in the case of slow motions and weak fields. Questions of the propagation velocity, polarization, and generation of a weak gravitational wave are considered. The Peters-Matthews coefficients and the dipole emission coefficient are determined.

R. M. Avagyan; A. H. Yeranyan

2000-01-01

65

Variant of the bimetric theory of gravitation. II. Energy-momentum tensor of the gravitational field  

Microsoft Academic Search

Starting from the invariance of action relative to coordinate transformations, differential conservation laws are established\\u000a in the bimetric theory of gravitation with a Lagrangian that is quadratic with respect to “intensities.” Explicit expressions\\u000a are found for the canonical and metric energymomentum tensors of the gravitational field, as well as for the tensor analog\\u000a of the Landau-Lifshitz pseudotensor.

R. M. Avagyan; A. H. Yeranyan

2000-01-01

66

Titan's Gravitational Field Inferred from Six Cassini Flybys  

NASA Astrophysics Data System (ADS)

Titan's gravitational field is inferred from an analysis of archived radio Doppler data for six Cassini flybys. Results are consistent with a differentiated hydrostatic satellite. We find no determination of the tidal Love number k_2.

Anderson, J. D.; Schubert, G.

2014-02-01

67

Energy and angular momentum densities of stationary gravitational fields  

SciTech Connect

We give physical explanations of explicit invariant expressions for the energy and angular momentum densities of gravitational fields in stationary spacetimes. These expressions involve nonlocally defined conformal factors. In certain coordinates these become locally defined in terms of the metric. These results are derived via expressions for total gravitational potential energy from the difference between the total energy and the mechanical energy. The latter involves kinetic energy seen in the frame of static observers. When in the axially symmetric case we consider zero angular momentum observers (who move orthogonally to surfaces of constant time), we find that the angular momentum they attribute to the gravitational field is solely due to their motion.

Lynden-Bell, D.; Bicak, Jiri [Institute of Astronomy, The Observatories, Cambridge CB3 0HA (United Kingdom); Institute of Theoretical Physics, Charles University, 180 00 Prague 8 (Czech Republic); Katz, Joseph [Institute of Astronomy, The Observatories, Cambridge CB3 0HA (United Kingdom); Racah Institute of Physics, Givat Ram, 91904 Jerusalem (Israel); Institute of Theoretical Physics, Charles University, 180 00 Prague 8 (Czech Republic)

2007-01-15

68

An exact Lagrangian integral for the Newtonian gravitational field strength  

NASA Astrophysics Data System (ADS)

An exact expression for the gravitational field strength in a self-gravitating dust continuum is derived within the Lagrangian picture of continuum mechanics. From the Euler Newton system a transport equation for the gravitational field strength is formulated and then integrated along trajectories of continuum elements. The resulting integral solves one of the Lagrangian equations of the corresponding Lagrange Newton system in general. Relations to known exact solutions without symmetry in Newtonian gravity are discussed. The presented integral may be employed to access the nonperturbative regime of structure formation in Newtonian cosmology, and to apply iterative Lagrangian schemes to solve the Lagrange Newton system.

Buchert, Thomas

2006-05-01

69

Components of the gravitational force in the field of a gravitational wave  

NASA Astrophysics Data System (ADS)

Gravitational waves bring about the relative motion of free test masses. The detailed knowledge of this motion is important conceptually and practically, because the mirrors of laser interferometric detectors of gravitational waves are essentially free test masses. There exists an analogy between the motion of free masses in the field of a gravitational wave and the motion of free charges in the field of an electromagnetic wave. In particular, a gravitational wave drives the masses in the plane of the wavefront and also, to a smaller extent, back and forth in the direction of the wave's propagation. To describe this motion, we introduce the notion of 'electric' and 'magnetic' components of the gravitational force. This analogy is not perfect, but it reflects some important features of the phenomenon. Using different methods, we demonstrate the presence and importance of what we call the 'magnetic' component of motion of free masses. It contributes to the variation of distance between a pair of particles. We explicitly derive the full response function of a 2-arm laser interferometer to a gravitational wave of arbitrary polarization. We give a convenient description of the response function in terms of the spin-weighted spherical harmonics. We show that the previously ignored 'magnetic' component may provide a correction of up to 10%, or so, to the usual 'electric' component of the response function. The 'magnetic' contribution must be taken into account in the data analysis, if the parameters of the radiating system are not to be misestimated.

Baskaran, D.; Grishchuk, L. P.

2004-09-01

70

Self-Calibration Techniques for 3-point Intrinsic Alignment Correlations in Weak Gravitational Lensing Surveys  

NASA Astrophysics Data System (ADS)

Weak gravitational lensing due to large scale structure (cosmic shear) has been shown to be contaminated by the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements in planned surveys. To address this contamination, we have extended the 2-point self-calibration techniques to the cosmic shear bispectrum, using information already measured in a weak lensing survey to self-calibrate the IA contamination. The 3-point self-calibration techniques use the redshift separation dependencies of the IA bispectra and the non-linear galaxy bias in order to isolate and remove the impact of the IA correlations on the cosmic shear signal. Using conservative estimates of photo-z accuracy, we find that planned surveys will be able to measure the IA redshift separation dependence over ranges in photo-z of 0.2 in the 3-point ellipticity auto-correlation. For the 3-point cross-correlations, we find that the self-calibration technique allows for reductions in the IA contamination by a factor of 10 or more over most scales and redshift bin choices and in all cases by a factor of 3-5 or more. The 3-point self-calibration techniques thus provide a means to greatly reduce the impact of IA contamination of the bispectrum in future measurements of cosmic shear.

Troxel, Michael A.; Ishak-Boushaki, M. B.

2013-01-01

71

The Born and lens lens corrections to weak gravitational lensing angular power spectra  

NASA Astrophysics Data System (ADS)

We revisit the estimation of higher order corrections to the angular power spectra of weak gravitational lensing. Extending a previous calculation of Cooray and Hu, we find two additional terms to the fourth order in potential perturbations of large-scale structure corresponding to corrections associated with the Born approximation and the neglect of line-of-sight coupling of two foreground lenses in the standard first order result. These terms alter the convergence (??), the lensing shear E-mode (epsiepsi), and their cross-correlation (?epsi) power spectra on large angular scales, but leave the power spectra of the lensing shear B-mode (??) and rotational (??) component unchanged as compared to previous estimates. The new terms complete the calculation of corrections to weak lensing angular power spectra associated with both the Born approximation and the lens lens coupling to an order in which the contributions are most significant. Taking these features together, we find that these corrections are unimportant for any weak lensing survey, including for a full sky survey limited by cosmic variance.

Shapiro, Charles; Cooray, Asantha

2006-03-01

72

Nonlinear superposition of strong gravitational field of compact stars  

NASA Astrophysics Data System (ADS)

According to QFT it is deduced that the gravitation is likely to originate from the polarization effect of Dirac vacuum fluctuation (Chen Shao-Guang, Nuovo Cimento B 104, 611, 1989) . In Dirac vacuum the lowest-energy virtual neutrinos nu possess most number, which exert isotropic colliding pressure to isolated mass-point A (m) , the net force on A is zero. For another mass-point B (M) near A to obstruct nu flux shooting to A, the nu number along the line connecting A and B will decrease and destroy isotropic distribution of nu , which leads to not only the change in momentum P (produces net nu flux and net force Fp) but also the change in energy E or rest mass m (produces net force Fm) because in QFT the rest mass is not the bare mass but the physical mass of renormalization which contains nu with energy. From the definition of force: F ? d (m v) /d t = m ( d v / d t ) + v (d m / d t ) = Fp + Fm (1) , on A (or B) net force (quasi-Casimir pressure of weak interaction) is: F Q = Fp + Fm = - K (m M /r 2 )((r /r ) + (v /c )) (2). According to the change in masses caused by Bondi's inductive transfer of energy in GR (H. Bondi, Proc. R. Soc. London A 427, 249, 1990) and Eq. (1) a new gravitational formula is deduced: F G = Fp +Fm = - G (m M /r 2 )( (r /r ) + (v /c )) (3). F G is equivalent to Einstein's equation. Then we can solve the multi-bodies gravitational problems. K calculated from the weak-electromagnetism unified theory (W-EUT) has the same order of magnitude as experimental gravitational constant G. F G and F Q as a bridge joins QFT and GR. If K ? G, gravitational theory would be merged into W-EUT. The gravitational laws predicted by FG and F Q are identical except that F Q has quantum effects but F G has not, F G has Lense-Thirring effect but F Q has not. The change in masses of A and B caused by the nonlinearity of Einstein's equation or by mass renormalization of QFT will influence their forces on third object C (as self-shielding effect of gravities among objects or each parts of a object): F = - G? m M (1 - q ) r / r 3 = - G (r ) m M r / r 3 (4). Here G (r ) = G? (1 - q ), q = k M / r 2 = k D L S / r 2 . q is a positive shielding coefficient, G? is the gravitational constant when infinite distance between mass-point A and object B (q = 0 ). M / r 2 is the gravitational field strength of B in the place of A, D and L are the density and the thickness respectively, S is the cross section of B. S / r 2 is the solid angle of B subtends to A , k is a constant determined by experiments and called as the section of unit mass. From Stacey et al's experimental results kmu of nucleons to virtual neutrino mu is 4.7×10-19 cm2 g-1 .The section of single nucleon to electronic neutrino obtained by nuclear physics experiments is about 1.1×10-43 cm2 which divided by nucleon-mass is the section of unit mass kmue ?6.6×10-20 cm2 g-1 . For the earth (L ?104 km) as a obstructing layer qmue = 4.6×10-10 ; qmu = 3.3×10-9 . Therefore, the self-shielding effect of gravity can be generally ignored, but can not for the compact stars: A spherical shell of neutron (D large than 1014 g cm-3 ) as obstructing layer, when S / r 2 =1 and L=1 km then qmue =1 and qmu large than 1 (completely obstruct mue and mu ), i.e., the gravity from its inside and exterior will be completely shielded. It makes that a neutron star likes a empty shell then it may rapidly rotating and has not upper limit of masses and radii, which will influence the mechanisms of pulsars, quasars and X-rays generated at the surface of cooling and/or rapidly rotating compact stars.

Chen, Shao-Guang

73

Strong field gravitational lensing in scalar tensor theories  

NASA Astrophysics Data System (ADS)

Strong field gravitational lensing in the Brans Dicke scalar tensor theory has been studied. The deflection angle for photons passing very close to the photon sphere is estimated for the static spherically symmetric spacetime of the theory and the position and magnification of the relativistic images are obtained. Modelling the super massive central object of the galaxy by the Brans Dicke spacetime, numerical values of different strong lensing observables are estimated. It is found that against the expectation there is no significant scalar field effect on the strong field observable lensing parameters. This result raises question on the potentiality of strong field lensing to discriminate different gravitational theories.

Sarkar, Kabita; Bhadra, Arunava

2006-11-01

74

An analytic solution for weak-field Schwarzschild geodesics  

NASA Astrophysics Data System (ADS)

It is well known that the classical gravitational two-body problem can be transformed into a spherical harmonic oscillator by regularization. We find that a modification of the regularization transformation has a similar result to leading order in general relativity. In the resulting harmonic oscillator, the leading-order relativistic perturbation is formally a negative centrifugal force. The net centrifugal force changes sign at 3 Schwarzschild radii, which interestingly mimics the innermost stable circular orbit of the full Schwarzschild problem. Transforming the harmonic-oscillator solution back to spatial coordinates yields, for both time-like and null weak-field Schwarzschild geodesics, a solution for t, r, ? in terms of elementary functions of a variable that can be interpreted as a generalized eccentric anomaly. The textbook expressions for relativistic precession and light deflection are easily recovered. We suggest how this solution could be combined with additional perturbations into numerical methods suitable for applications such as relativistic accretion or dynamics of the Galactic Centre stars.

D'Orazio, Daniel J.; Saha, Prasenjit

2010-08-01

75

Conformal coupling of gravitational wave field to curvature  

SciTech Connect

Conformal properties of the equations for weak gravitational waves in a curved space--time are investigated. The basic equations are derived in the linear approximation from Einstein's equations. They represent, in fact, the equations for the second-rank tensor field h/sub alphabeta/, restricted by the auxiliary conditions h/sub ..cap alpha..//sup ..beta..//sub ;/..cap alpha.. =0, hequivalent..gamma../sub alphabeta/h/sup alphabeta/=0, and embedded into the background space--time with the metric tensor ..gamma../sub alphabeta/. It is shown that the equations for h/sub alphabeta/ are not conformally invariant under the transformations gamma-circumflex/sub alphabeta/ =e/sup 2sigma/..gamma../sub alphabeta/ and h/sub alphabeta/ =e/sup sigma/h/sub alphabeta/, except for those metric rescalings which transform the Ricci scalar R of the original background space--time into e/sup -2sigma/R, where R is the Ricci scalar of the conformally related background space--time. The general form of the equations for h/sub alphabeta/ which are conformally invariant have been deduced. It is shown that these equations cannot be derived in the linear approximation from any tensor equations which generalize the Einstein equations.

Grishchuk, L.P.; Yudin, V.

1980-05-01

76

Equilibrium velocity distribution of low-energy particles in spherically symmetric gravitational field  

Microsoft Academic Search

Based on Einstein's theory of gravitation, we discuss the influence of a spherically symmetric gravitational field on Maxwell's law of velocity distribution. We derive the equilibrium velocity distribution of low-energy particles in the spherically symmetric gravitational field and calculate the escape rate of low-energy particles in a container with a leak placed in the spherically symmetric gravitational field. They can

Jian-Miin Liu

2004-01-01

77

Constraining Horava-Lifshitz gravity by weak and strong gravitational lensing  

SciTech Connect

We discuss gravitational lensing in the Kehagias-Sfetsos space-time emerging in the framework of Horava-Lifshitz gravity. In weak lensing, we show that there are three regimes, depending on the value of {lambda}=1/{omega}d{sup 2}, where {omega} is the Horava-Lifshitz parameter and d characterizes the lensing geometry. When {lambda} is close to zero, light deflection typically produces two images, as in Schwarzschild lensing. For very large {lambda}, the space-time approaches flatness, therefore there is only one undeflected image. In the intermediate range of {lambda}, only the upper focused image is produced due to the existence of a maximal deflection angle {delta}{sub max}, a feature inexistent in the Schwarzschild weak lensing. We also discuss the location of Einstein rings, and determine the range of the Horava-Lifshitz parameter compatible with present-day lensing observations. Finally, we analyze in the strong lensing regime the first two relativistic Einstein rings and determine the constraints on the parameter range to be imposed by forthcoming experiments.

Horvath, Zsolt; Gergely, Laszlo A.; Keresztes, Zoltan; Harko, Tiberiu; Lobo, Francisco S. N. [Departments of Theoretical and Experimental Physics, University of Szeged, Dom ter 9, Szeged 6720 (Hungary); Department of Physics and Center for Theoretical and Computational Physics, University of Hong Kong, Pok Fu Lam Road (Hong Kong); Centro de Astronomia e Astrofisica da Universidade de Lisboa, Campo Grande, Edificio C8 1749-016 Lisboa (Portugal)

2011-10-15

78

Contributions of Spherical Harmonics to Magnetic and Gravitational Fields  

NASA Technical Reports Server (NTRS)

Gravitational forces are of cardinal importance in the dynamics of spacecraft; magnetic attractions sometime play a significant role also, as was the case with the Long Duration Exposure Facility, and as is now true for the first segment of Space Station Freedom. Both satellites depend on gravitational moment and a device known as a magnetic damper to stabilize their orientation. Magnetic fields are mathematically similar to gravitational fields in one important respect: each can be regarded as a gradient of a potential function that, in turn, can be described as an infinite series of spherical harmonics. Consequently, the two fields can be computed, in part, with quantities that need only be evaluated once, resulting in a savings of time when both fields are needed. The objective of this material is to present magnetic field and gravitational force expressions, and point out the terms that belong to both this is accomplished in Section 1 and 2. Section 3 contains the deductive reasoning with which one obtains the expressions of interest. Finally, examples in Section 4 show these equations can be used to reproduce others that arise in connection with special cases such as the magnetic field produced by a tilted dipole, and gravitational force exerted by an oblate spheroid. The mathematics are discussed in the context of terrestrial fields; however, by substituting appropriate constants, the results can be made applicable to fields belonging to other celestial bodies. The expressions presented here share the characteristics of algorithms set forth for computing gravitational force. In particular, computation is performed speedily by means of recursion formulae, and the expressions do not suffer from the shortcoming of a singularity when evaluated at points that lie on the polar axis.

Roithmayr, Carlos M.

2004-01-01

79

Using Gravitational Analogies to Introduce Elementary Electrical Field Theory Concepts  

ERIC Educational Resources Information Center

Since electrical field concepts are usually unfamiliar, abstract, and difficult to visualize, conceptual analogies from familiar gravitational phenomena are valuable for teaching. Such analogies emphasize the underlying continuity of field concepts in physics and support the spiral development of student understanding. We find the following four…

Saeli, Susan; MacIsaac, Dan

2007-01-01

80

Weak and strong field approximations and circular orbits of the Kehagias-Sfetsos space-time  

NASA Astrophysics Data System (ADS)

The Kehagias-Sfetsos asymptotically flat black hole and naked singularity solutions of the Ho?ava-Lifshitz gravity are investigated both in the weak-field and strong-field regimes. In the weak-field limit the gravitational field generated by the Kehagias-Sfetsos spherically symmetric solution is weaker then in the case of the Schwarzschild black hole of general relativity. In the strong-field regime naked singularities with {?0 ? 1} display an unusual distance dependence: gravity becomes weaker when approaching the singularity. The stability of circular orbits is also analyzed. While in the black hole case the square of the angular momentum should be larger than a certain finite, non-zero minimal value, in the naked singularity case there are stable circular orbits for any non-zero value of the angular momentum. In this regime we prove the existence of an infimum of the allowed radii of circular orbits (corresponding to vanishing angular momentum).

Dwornik, M.; Horváth, Zs.; Gergely, L. Á.

2013-11-01

81

Geometric boundary data for the gravitational field  

NASA Astrophysics Data System (ADS)

An outstanding issue in the treatment of boundaries in general relativity is the lack of a local geometric interpretation of the necessary boundary data. For the Cauchy problem, the initial data is supplied by the 3-metric and extrinsic curvature of the initial Cauchy hypersurface, subject to constraints. This Cauchy data determine a solution to Einstein’s equations which is unique up to a diffeomorphism. Here, we show how three pieces of unconstrained boundary data, which are associated locally with the geometry of the boundary, likewise determine a solution of the initial-boundary value problem which is unique, up to a diffeomorphism. Two pieces of this data constitute a conformal class of rank-2 metrics, which represent the two gravitational degrees of freedom. The third piece, constructed from the extrinsic curvature of the boundary, determines the dynamical evolution of the boundary.

Kreiss, H.-O.; Winicour, J.

2014-03-01

82

Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)  

SciTech Connect

SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a separate white paper. The second method is weak gravitational lensing, which relies on the coherent distortions in the shapes of background galaxies by foreground mass structures. The excellent spatial resolution and photometric accuracy afforded by a 2-meter space-based observatory are crucial for achieving the high surface density of resolved galaxies, the tight control of systematic errors in the telescope's Point Spread Function (PSF), and the exquisite redshift accuracy and depth required by this project. These are achieved by the elimination of atmospheric distortion and much of the thermal and gravity loads on the telescope. The SN and WL methods for probing dark energy are highly complementary and the error contours from the two methods are largely orthogonal. The nominal SNAP weak lensing survey covers 1000 square degrees per year of operation in six optical and three near infrared filters (NIR) spanning the range 350 nm to 1.7 {micro}m. This survey will reach a depth of 26.6 AB magnitude in each of the nine filters and allow for approximately 100 resolved galaxies per square arcminute, {approx} 3 times that available from the best ground-based surveys. Photometric redshifts will be measured with statistical accuracy that enables scientific applications for even the faint, high redshift end of the sample. Ongoing work aims to meet the requirements on systematics in galaxy shape measurement, photometric redshift biases, and theoretical predictions.

Albert, J.; Aldering, G.; Allam, S.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Aumeunier, M.; Bailey, S.; Baltay, C.; Barrelet, E.; Basa, S.; Bebek, C.; Bergstom, L.; Bernstein, G.; Bester, M.; Besuner, B.; Bigelow, B.; Blandford, R.; Bohlin, R.; Bonissent, A.; /Caltech /LBL, Berkeley /Fermilab /SLAC /Stockholm U. /Paris, IN2P3 /Marseille, CPPM /Marseille, Lab. Astrophys. /Yale U. /Pennsylvania U. /UC, Berkeley /Michigan U. /Baltimore, Space Telescope Sci. /Indiana U. /Caltech, JPL /Australian Natl. U., Canberra /American Astron. Society /Chicago U. /Cambridge U. /Saclay /Lyon, IPN

2005-08-08

83

Weak gravitation waves in vacuum and in media: Taking nonlinearity into account  

NASA Astrophysics Data System (ADS)

The relevance of the nonlinear nature of gravity waves has been pointed out, in the astrophysical context, in recent publications by Christodoulou and by Thorne, who studied the nonlinear contribution to the memory effect. In the cosmological context, the role of nonlinearity has been discovered by Salopek, who studied the evolution of the primordial cosmological perturbations. In this article, we use the weak-field approximation to derive, in the perturbative approach, the wave equation for pure gravity waves with nonlinear correction terms.

Efroimsky, Michael

1994-06-01

84

Stochastic quantization of the linearized gravitational field  

Microsoft Academic Search

Stochastic field equations for linearized gravity are presented. The theory is compared with the usual quantum field theory and questions of Lorentz covariance are discussed. The classical radiation approximation is also presented.

Mark P. Davidson

1982-01-01

85

Faster than light photons in gravitational fields II  

Microsoft Academic Search

Vacuum polarisation in QED in a background gravitational field induces interactions which effectively violate the strong equivalence principle and affect the propagation of light. In the low frequency limit, Drummond and Hathrell have shown that this mechanism leads to superluminal photon velocities. To confront this phenomenon with causality, however, it is necessary to extend the calculation of the phase velocity

G. M. Shore; Swansea Singleton Park

2002-01-01

86

Tail terms in gravitational radiation reaction via effective field theory  

NASA Astrophysics Data System (ADS)

Gravitational radiation reaction affects the dynamics of gravitationally bound binary systems. Here we focus on the leading “tail” term which modifies binary dynamics at fourth post-Newtonian order, as first computed by Blanchet and Damour. We reproduce this result using effective field theory techniques in the framework of the Lagrangian formalism suitably extended to include dissipation effects. We recover the known logarithmic tail term, consistently with the recent interpretation of the logarithmic tail term in the mass parameter, as a renormalization group effect of the Bondi mass of the system.

Foffa, Stefano; Sturani, Riccardo

2013-02-01

87

Gravitation  

NSDL National Science Digital Library

Known world-wide as "MTW". A classic, graduate level textbook on general relativity. Includes both "math-first" and "physics-first" elements. This text covers material for a graduate level course on gravitation physics and general relativity. Topics include flat spacetime, tools of modern geometry, Einstein's geometric framework for physics, applications such as pulsars and neutron stars, cosmology, gravitational collapse, and gravitational waves. It also includes information on experimental tests of General Relativity, superspace, and quantum geometrodynamics.

Misner, Charles; Thorne, Kip S.; Wheeler, John A.

2004-06-14

88

Why the gravitation of quasi-Casimir pressure in weak interaction is independent of the composition of matter  

NASA Astrophysics Data System (ADS)

According to f =d(mv)/dt=m(dv/dt)+ v(dm/dt), a same gravitational formula had been de-duced from the variance in physical mass of QFT and from the variance in mass of inductive energy-transfer of GR respectively: f QF T = f GR = -G (mM/r2 )((r/r)+(v/c)) when their interaction-constants are all taken the experimental values (H05-0029-08, E15-0039-08). f QF T is the quasi-Casimir pressure of net virtual neutrinos ? 0 flux (after counteract contrary direction ? 0 ). f GR is equivalent to Einstein's equation, then more easy to solve it. The hypothesis of the equivalent principle is not used in f QF T , but required by f GR . The predictions of f QF T and f GR are identical except that f QF T has quantum effects but f GR has not and f GR has Lense-Thirring effect but f QF T has not. The quantum effects of gravitation had been verified by Nesvizhevsky et al with the ultracold neutrons falling in the earth's gravitational field in 2002. Yet Lense-Thirring effect had not been measured by GP-B. It shows that f QF T is essential but f GR is phenomenological. The origin problem of the basis geo-electric and geomagnetic fields can be solved with the positive-negative charge center separation caused by f QF T , but cannot by f GR . The de Broglie wavelength of an electron is longer than that of a nucleon, and the section is larger, so is the net ? 0 flux pressure. The pressures difference between ? 0 flux on the electron and on the nucleon is as an extra pressure solely exerted on the electrons by ? 0 flux, which causes a gravitational polarization of the positive-negative charge center separation and increases the static electric force from the nucleus to the electrons along the opposite direction of ? 0 flux to offset the extra pressure on the electrons. At the same time, there must be a polarized static electric reaction force from the electrons to the nucleus along ? 0 flux direction, just like transferring the extra ? 0 flux pressure of the electrons to the nucleus. Therefore, the extra ? 0 flux pressure exerted on the whole atom is not actually offset by the static electric force from the positive-negative charge separation, i.e., the gravitation will be dependent of the com-position of matter. That is certainly true in the interaction between two isolated mass-points. But nothing can exist without environment. The masses tested in Cavendish's experiment, Eotvos's experiment and other precise gravitational experiments are not isolated mass-points. The electric polarization by ? 0 flux makes the testing mass and around (brackets, walls, houses) become the electric dipoles. In a way of relays the polarization of charge separation will be transported to the edge of the body, and make it become the electric dipole with the positive and negative charge on its two surfaces and the electric neutrality in the center. The interaction between the electric dipoles finally transfers the extra ? 0 flux pressure on the electrons from a body being tested onto the bodies around, i.e., the static electric force from the polarization of the bodies around offsets the extra ? 0 flux pressure on the electrons of testing mass. Because the electromagnetic force is 30 more orders of magnitude stronger than the ? 0 flux weak force, the slightly polarization of the bodies around can completely offset the extra ? 0 flux pressure on the electrons. The compensating action of the static forces between electric dipoles is equiv-alent to the equal section in unit mass of an electron and a nucleon. That is to say, the ? 0 flux pressure gives the same force and displacement to the electron and nucleon just like no positive-negative charge separation. Therefore, for gravitation, the mass of an electron can be converted to a proton, which makes the atom like a particle of absolutely electric neutrality comprising all neutrons, i.e., the macro-gravitation of non-isolated bodies is corresponding to the section only contributed by nucleons in atom. Then no matter how many electrons there are in the atom, the force is always in direct proportion to the

Chen, Shao-Guang

89

Nbody Simulations and Weak Gravitational Lensing using new HPC-Grid resources: the PI2S2 project  

NASA Astrophysics Data System (ADS)

We present the main project of the new grid infrastructure and the researches, that have been already started in Sicily and will be completed by next year. The PI2S2 project of the COMETA consortium is funded by the Italian Ministry of University and Research and will be completed in 2009. Funds are from the European Union Structural Funds for Objective 1 regions. The project, together with a similar project called Trinacria GRID Virtual Laboratory (Trigrid VL), aims to create in Sicily a computational grid for e-science and e-commerce applications with the main goal of increasing the technological innovation of local enterprises and their competition on the global market. PI2S2 project aims to build and develop an e-Infrastructure in Sicily, based on the grid paradigm, mainly for research activity using the grid environment and High Performance Computer systems. As an example we present the first results of a new grid version of FLY a tree Nbody code developed by INAF Astrophysical Observatory of Catania, already published in the CPC program Library, that will be used in the Weak Gravitational Lensing field.

Becciani, U.; Antonuccio-Delogu, V.; Costa, A.; Comparato, M.

2008-08-01

90

Weighing the Giants: Galaxy Cluster Cosmology Anchored by Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

The gas mass fractions and the distribution in mass and redshift of the galaxy cluster population provide powerful probes of cosmology, constraining the cosmic matter density (?m), the amplitude of the matter power spectrum (?8), properties of dark energy, and the mass of neutrinos, among other parameters. Historically, these tests have been limited by the absolute accuracy of cluster mass determinations. Here, mass measurements from weak lensing (made in the right way) have an advantage over estimates based on observations of the intracluster medium (ICM), because the former are nearly unbiased and can be straightforwardly tested against simulations. I will report new cosmological constraints obtained from an analysis of X-ray selected cluster samples, incorporating extensive gravitational lensing data from the Weighing the Giants project -- the first cluster cosmology study to consistently integrate a lensing mass calibration, including a rigorous quantification of all systematic uncertainties. Compared with earlier work, which had to incorporate larger systematic allowances associated with an ICM-based mass calibration, our joint constraints on ?m and ?8 are improved by a factor of 2. Including Cosmic Microwave Background and other cosmological probes in the analysis, we find no evidence for non-zero neutrino mass in the current data. This result is directly dependent on the absolute cluster mass calibration, and conflicts with some recent cluster results using ICM-based masses, highlighting the need for an accurate mass calibration (such as lensing provides). We also obtain tight constraints on dark energy models; for flat models with a constant equation of state (w), the cluster data alone yield w=?0.98±0.15. Our data, and their combination with other leading cosmological data sets, remain consistent with the concordance model of cosmology, with zero global curvature, dark energy as a non-evolving cosmological constant (w=?1), minimal neutrino mass, and gravity described by General Relativity.

Mantz, Adam; Von Der Linden, Anja; Allen, Steven W.; Applegate, Douglas; Kelly, Patrick; Morris, Glenn; Rapetti, David; Schmidt, Robert; Ebeling, Harald

2014-08-01

91

Improving three-dimensional mass mapping with weak gravitational lensing using galaxy clustering  

NASA Astrophysics Data System (ADS)

Context. The weak gravitational lensing distortion of distant galaxy images (defined as sources) probes the projected large-scale matter distribution in the Universe. The availability of redshift information in galaxy surveys also allows us to recover the radial matter distribution to a certain degree. Aims: To improve quality in the mass mapping, we combine the lensing information with the spatial clustering of a population of galaxies (defined as tracers) that trace the matter density with a known galaxy bias. Methods: We construct a minimum-variance estimator for the 3D matter density that incorporates the angular distribution of galaxy tracers, which are coarsely binned in redshift. Merely the second-order bias of the tracers has to be known, which can in principle be self-consistently constrained in the data by lensing techniques. This synergy introduces a new noise component because of the stochasticity in the matter-tracer density relation. We give a description of the stochasticity noise in the Gaussian regime, and we investigate the estimator characteristics analytically. We apply the estimator to a mock survey based on the Millennium Simulation. Results: The estimator linearly mixes the individual lensing mass and tracer number density maps into a combined smoothed mass map. The weighting in the mix depends on the signal-to-noise ratio (S/N) of the individual maps and the correlation, R, between the matter and galaxy density. The weight of the tracers can be reduced by hand. For moderate mixing, the S/N in the mass map improves by a factor ~2-3 for R ? 0.4. Importantly, the systematic offset between a true and apparent mass peak distance (defined as z-shift bias) in a lensing-only map is eliminated, even for weak correlations of R ~ 0.4. Conclusions: If the second-order bias of tracer galaxies can be determined, the synergy technique potentially provides an option to improve redshift accuracy and completeness of the lensing 3D mass map. Herein, the aim is to visualise the spatial distribution of cluster-sized mass peaks. Our noise description of the estimator is accurate in the linear, Gaussian regime. However, its performance on sub-degree scales depends on the details in the galaxy bias mechanism and, hence, on the choice of the tracer population. Nonetheless, we expect that the mapping technique yields qualitatively reasonable results even for arcmin smoothing scales, as observed when this technique is applied to the mock survey with two different tracer populations.

Simon, Patrick

2013-12-01

92

Model of the electro-weak, gravitational and strong interactions in the O-theory  

Microsoft Academic Search

Based on the matrix representation of octonion algebra, supplied with specific multiplication rule, the model of electroweak and gravitational interactions is built up. While electroweak interaction in this model is induced by charged W-bosons, other two forces appear to have slightly more complicated nature. Gravitational interaction coincides in the model with dipole interaction of a pair of charged bosons. The

V. Yu. Dorofeev

2011-01-01

93

Dust Particle Dynamics in a Varying Gravitational Field  

NASA Astrophysics Data System (ADS)

The properties of silica dust suspended in an argon DC glow discharge plasma are analyzed in varying gravitational field. The plasma was created in a 6'' x 1.5'' glass chamber. 340 V was applied to the top of two stainless steel electrodes, placed 4'' apart. In order to trap the dust during microgravity, a floating stainless steel mesh was suspended from the top electrode. The experiment used a current of 1-2 mA and a pressure of 80 to 155 mTorr while gravity ranged from 0 to 1.8g by flying through a series of 30 parabolas. Two CCD cameras recorded the dust cloud illuminated by a 5 mW laser sheet. One camera allowed observation of the interparticle spacing of the dust cloud and individual particle motion. The second camera recorded a wide field view of the overall cloud motion. In hyper-gravity, the dust cloud was 0.26 cm by 1.4 cm. As the gravitational field approached zero, the cloud moved from the center of the chamber, disassembled and reformed on the chamber wall. As gravity increased, the dust particles returned to the center of the chamber and reorganized in their initial formation. During the decrease in the gravitational field, a dust acoustic wave was spontaneously formed as the density of the cloud increased. To better understand the motion of the particles, the electrostatic field was modeled using a particle in cell code.

Merali, Aliya; Zwicker, Andrew

2009-11-01

94

Oriented atoms in weak magnetic fields  

Microsoft Academic Search

This article reviews the early investigations of Series on the resonance absorption and fluorescence of light by samples of oriented atoms dagger subjected to static and oscillatory magnetic fields. These investigations include experiments on optical-radiofrequency double resonance, light beats in double resonance, circulation of coherence in optical pumping, and time-biasing in level-crossing spectroscopy. It then describes some selected laser spectroscopy

Peter Hannaford

1997-01-01

95

Coupling of mirror tilts with earth gravitational field in long-baseline interferometric gravitational-wave detectors  

Microsoft Academic Search

We derive the cavity optical axis length fluctuations induced by tilts of the cavity mirrors in presence of the gravitational field of the earth. By comparison with the typical tilt-induced noises we show that this potential source of noise is negligible for the first operation gravitational wave interferometers. The possibility of utilizing the effect to perform a measurement of the

E. Calloni; L Di Fiore; G Di Sciascio; L. Milano; L. Rosa; C. Stornaiolo

2000-01-01

96

Biological effects due to weak magnetic field on plants  

NASA Astrophysics Data System (ADS)

Throughout the evolution process, Earth's magnetic field (MF, about 50 ?T) was a natural component of the environment for living organisms. Biological objects, flying on planned long-term interplanetary missions, would experience much weaker magnetic fields, since galactic MF is known to be 0.1-1 nT. However, the role of weak magnetic fields and their influence on functioning of biological organisms are still insufficiently understood, and is actively studied. Numerous experiments with seedlings of different plant species placed in weak magnetic field have shown that the growth of their primary roots is inhibited during early germination stages in comparison with control. The proliferative activity and cell reproduction in meristem of plant roots are reduced in weak magnetic field. Cell reproductive cycle slows down due to the expansion of G 1 phase in many plant species (and of G 2 phase in flax and lentil roots), while other phases of cell cycle remain relatively stabile. In plant cells exposed to weak magnetic field, the functional activity of genome at early pre-replicate period is shown to decrease. Weak magnetic field causes intensification of protein synthesis and disintegration in plant roots. At ultrastructural level, changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells were observed in pea roots exposed to weak magnetic field. Mitochondria were found to be very sensitive to weak magnetic field: their size and relative volume in cells increase, matrix becomes electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to weak magnetic field show Ca 2+ over-saturation in all organelles and in cytoplasm unlike the control ones. The data presented suggest that prolonged exposures of plants to weak magnetic field may cause different biological effects at the cellular, tissue and organ levels. They may be functionally related to systems that regulate plant metabolism including the intracellular Ca 2+ homeostasis. However, our understanding of very complex fundamental mechanisms and sites of interactions between weak magnetic fields and biological systems is still incomplete and still deserve strong research efforts.

Belyavskaya, N. A.

2004-01-01

97

[Biological detector of weak cosmic fields].  

PubMed

Possibility of use of biological object as a detector of faint cosmophysical fields is discussed. The signals of free induction and electric echo caused by a short-term effect of light with an intensity of approximately 0.2 mWt/sm2 on biological systems were observed. The experiments with Blatella germanica, Muska domestica were performed in vivo and with red and green seaweeds and yeast cells in vitro. The signals were detected by means of the dielectric permeability measurement in a dynamic regime. Main features of the observed responses are described and assumption on mechanisms of their origin are given. An example of registration of the Lunar eclipse on a detector with in active element of Blatella germanica is given. PMID:1420418

Kopvillem, U Kh; Sharipov, R Z; Zapol'ski?, A M; A?zda?cher, N A

1992-01-01

98

Late-time tails of self-gravitating massless fields  

NASA Astrophysics Data System (ADS)

In this talk I summarize briefly recent results of joint work with P. Bizo?, T. Chmaj and S. Zajaç, on the nonlinear origin of the power-law tails in the long-time evolution of self-gravitating massless fields. We focus on a spherically symmetric massless scalar field and wave map matter coupled to gravity. Using third-order perturbation method we derive explicit expressions for the tail (the decay rate and the amplitude) for solutions starting from small initial data and we verify this prediction via numerical integration of the full system of Einstein field equations. Our results show that the nonlinear effects can dominate the late time asymptotics.

Rostworowski, Andrzej

2010-05-01

99

Generation of magnetic fields and gravitational waves at neutrino decoupling.  

PubMed

We show that an inhomogeneous cosmological lepton number may have produced turbulence in the primordial plasma when neutrinos entered the (almost) free-streaming regime. This effect may be responsible for the origin of cosmic magnetic fields and give rise to a detectable background of gravitational waves. An existence of inhomogeneous lepton asymmetry could be naturally generated by active-sterile neutrino oscillations or by some versions of the Affleck-Dine baryogenesis scenario. PMID:11800930

Dolgov, Alexander D; Grasso, Dario

2002-01-01

100

Electromagnetic waves in the gravitational field of massive dark halos  

NASA Astrophysics Data System (ADS)

The propagation of plane electromagnetic waves in the gravitational field inside a rotating cloud of dark matter is analyzed. Formulas for the deflection and absorption of light and the rotation of the polarization plane are obtained in closed form in terms of the mass density and the angular velocity of the cloud. It is shown that the formulas can be considerably simplified for axisymmetric configurations. As an example, the formalism is applied to a rotating massive cloud described by a Plummer potential.

Hacyan, Shahen

2014-05-01

101

Model of the electro-weak, gravitational and strong interactions in the O-theory  

Microsoft Academic Search

Based on the matrix representation of octonion algebra, supplied with\\u000aspecific multiplication rule, the model of electroweak and gravitational\\u000ainteractions is built up. While electroweak interaction in this model is\\u000ainduced by charged W-bosons, other two forces appear to have slightly more\\u000acomplicated nature. Gravitational interaction coincides in the model with\\u000adipole interaction of a pair of charged bosons. The

V. Yu. Dorofeev

2011-01-01

102

Experimental Data Demonstrating Augmentation of Ambient Gravitational and Geomagnetic Fields  

NASA Astrophysics Data System (ADS)

Despite significant documentation and rigorously controlled conditions, most research involving extraordinary human-generated phenomena (e.g. remote viewing, teleportation, etc.) has focused either upon the observation of the macro-phenomena itself, or cumulative statistical deviation from chance. This paper, however, examines the influences upon and augmentation of ambient gravitational and geomagnetic fields, a previously unobserved and unrecognized concomitant physics phenomenon during activities requiring singular and total concentration. Utilizing simple field measurement instrumentation, original experimental data is presented, discussed, and compared with controlled baselines. Whereas some previous research has examined the influence of ambient fields upon human subjects, published literature is sparse concerning the influence of human subjects specifically upon ambient fields. As well, research that rigorously pursued the study of the effects of indirect human interference on engineering instrumentation did not consider ambient fields for experimental control, perhaps limiting potential theoretical modeling and integration. The presented empirical data demonstrates that gravitational and geomagnetic field augmentation occurring during such all-consuming activity is neither incidental nor subtle and may well be a worthy consideration for modeling frontier scientific theories and expanding current physics paradigms. Insomuch as natural, human-generated phenomena currently stand as the most accessible and repeatable examples of anomalous environmental interactivity, this data and suggested research protocols presented offer exploratory perspectives for observing the underlying scientific principals and physics concepts of ambient field interface as well as potential applications in developing more effective theoretical models for frontier space science.

Graham, Danielle

2006-01-01

103

Non-relativistic Limit of Dirac Equations in Gravitational Field and Quantum Effects of Gravity  

NASA Astrophysics Data System (ADS)

Based on unified theory of electromagnetic interactions and gravitational interactions, the non-relativistic limit of the equation of motion of a charged Dirac particle in gravitational field is studied. From the Schrödinger equation obtained from this non-relativistic limit, we can see that the classical Newtonian gravitational potential appears as a part of the potential in the Schrödinger equation, which can explain the gravitational phase effects found in COW experiments. And because of this Newtonian gravitational potential, a quantum particle in the earth's gravitational field may form a gravitationally bound quantized state, which has already been detected in experiments. Three different kinds of phase effects related to gravitational interactions are studied in this paper, and these phase effects should be observable in some astrophysical processes. Besides, there exists direct coupling between gravitomagnetic field and quantum spin, and radiation caused by this coupling can be used to directly determine the gravitomagnetic field on the surface of a star.

Wu, Ning

2006-03-01

104

Optical strength of weakly absorbing drops in intense light fields  

Microsoft Academic Search

The paper considers possible mechanisms for the destruction (vaporization) of weakly absorbing water drops in intense laser radiation fields. Consideration is given to the effects of such processes as optical breakdown and stimulated Mandelstam-Brillouin scattering on drop vaporization parameters and to the effect of nonuniformity of optical field distribution in drops with radii up to 60 microns. It is shown

A. A. Zemlianov; V. A. Pogodaev; V. N. Pozhidaev; L. K. Chistiakova

1977-01-01

105

Weak ELF Magnetic Field Effects on Hippocampal Rhythmic Slow Activity  

Microsoft Academic Search

Several investigations have revealed that electrical activity within the central nervous system (CNS) can be affected by exposure to weak extremely-low-frequency (ELF) magnetic fields. Many of these studies have implicated CNS structures exhibiting endogenous oscillation and synchrony as optimal sites for field coupling. A particularly well characterized structure in this regard is the rat hippocampus. Under urethane anesthesia, synchronous bursting

K. A. Jenrow; X. Zhang; W. E. Renehan; A. R. Liboff

1998-01-01

106

MOBILITY OF GASEOUS IONS IN WEAK ELECTRIC FIELDS  

Microsoft Academic Search

Kihara's extension of the Chapman-Enskog theory of transport phenomena ; is used to obtain the second order and third order approximations to the mobility ; of gaseous ions in a weak electric field as a function of temperature and field ; strength. In this method it is assumed that there is no charge exchange between ; ions and molecules, there

E. A. Mason; H. W. Jr. Schamp

1958-01-01

107

Detection of weak electric fields by sharks, rays, and skates  

Microsoft Academic Search

The elasmobranchs—sharks, rays, and skates—can detect very weak electric fields in their aqueous environment through a complex sensory system, the ampullae of Lorenzini. The ampullae are conducting tubes that connect the surface of the animal to its interior. In the presence of an electric field, the potential of the surface of the animal will differ from that of the interior

Robert K. Adair; R. Dean Astumian; James C. Weaver

1998-01-01

108

Detection of weak electric fields by sharks, rays, and skates  

Microsoft Academic Search

The elasmobranchs-sharks, rays, and skates-can detect very weak electric fields in their aqueous environment through a complex sensory system, the ampullae of Lorenzini. The ampullae are conducting tubes that connect the surface of the animal to its interior. In the presence of an electric field, the potential of the surface of the animal will differ from that of the interior

Robert K. Adair; R. Dean Astumian; James C. Weaver

1998-01-01

109

The effect of gravitational tidal forces on renormalized quantum fields  

NASA Astrophysics Data System (ADS)

The effect of gravitational tidal forces on renormalized quantum fields propagating in curved spacetime is investigated and a generalisation of the optical theorem to curved spacetime is proved. In the case of QED, the interaction of tidal forces with the vacuum polarization cloud of virtual e + e - pairs dressing the renormalized photon has been shown to produce several novel phenomena. In particular, the photon field amplitude can locally increase as well as decrease, corresponding to a negative imaginary part of the refractive index, in apparent violation of unitarity and the optical theorem. Below threshold decays into e + e - pairs may also occur. In this paper, these issues are studied from the point of view of a non-equilibrium initial-value problem, with the field evolution from an initial null surface being calculated for physically distinct initial conditions and for both scalar field theories and QED. It is shown how a generalised version of the optical theorem, valid in curved spacetime, allows a local increase in amplitude while maintaining consistency with unitarity. The picture emerges of the field being dressed and undressed as it propagates through curved spacetime, with the local gravitational tidal forces determining the degree of dressing and hence the amplitude of the renormalized quantum field. These effects are illustrated with many examples, including a description of the undressing of a photon in the vicinity of a black hole singularity.

Hollowood, Timothy J.; Shore, Graham M.

2012-02-01

110

Two-dimensional colloidal mixtures in magnetic and gravitational fields  

NASA Astrophysics Data System (ADS)

This mini-review is concerned with two-dimensional colloidal mixtures exposed to various kinds of external fields. By a magnetic field perpendicular to the plane, dipole moments are induced in paramagnetic particles which give rise to repulsive interactions leading to complex crystalline alloys in the composition-asymmetry diagram. A quench in the magnetic field induces complex crystal nucleation scenarios. If exposed to a gravitational field, these mixtures exhibit a brazil-nut effect and show a boundary layering which is explained in terms of a depletion bubble picture. The latter persists for time-dependent gravity ("colloidal shaking"). Finally, we summarize crystallization effects when the second species is frozen in a disordered matrix which provides obstacles for the crystallizing component.

Löwen, H.; Horn, T.; Neuhaus, T.; ten Hagen, B.

2013-11-01

111

The construction of gravitational field models on the basis of satellite measurements of gravitational potential derivatives  

NASA Astrophysics Data System (ADS)

In [1] expressions were constructed for the derivatives of all the orders of a planet's gravitational potential with respect to the rectangular coordinates related to the gravity center of a planet. These expressions are series of spherical functions. The coefficients of the series of first-order derivatives depend on two Stokes constants, whereas the coefficients of next-order derivatives are linear combinations of the coefficients of preceding-order derivatives. In the present paper the derived expressions for the first and second potential derivatives are transformed into the form that is most convenient for solving the inverse problem, i.e., evaluating Stokes constants from satellite measurements of these derivatives. Each term of the new series for a derivative depends on a sum of two Stokes constants multiplied by linear combinations of several spherical functions. The new form of the expansions for the potential derivatives makes it possible to calculate Stokes constants by simultaneously applying satellite data either for all three first-order potential derivatives, or for all six second-order derivatives. The constructed series may be applied for modeling the Earth's gravitational field from the satellite data obtained in the international CHAMP, GRACE, and GOCE missions.

Petrovskaya, M. S.; Vershkov, A. N.

2014-03-01

112

Scattering of a plane gravitational wave by a magnetic dipole field in the Schwarzschild metric  

Microsoft Academic Search

The equations governing the propagation of high-frequency coupled gravitational and electromagnetic waves are integrated for the case of a plane gravitational wave impinging onto a Schwarzschild space-time equipped with a magnetic dipole field. The generated electromagnetic wave is focused due to the gravitational lens effect. An expression is derived for the intensity of the electromagnetic wave in the focal region.

T. Elster

1981-01-01

113

Spin in stationary gravitational fields and rotating frames  

SciTech Connect

A spin motion of particles in stationary spacetimes is investigated in the framework of the classical gravity and relativistic quantum mechanics. We bring the Dirac equation for relativistic particles in nonstatic spacetimes to the Hamiltonian form and perform the Foldy-Wouthuysen transformation. We show the importance of the choice of tetrads for description of spin dynamics in the classical gravity. We derive classical and quantum mechanical equations of motion of the spin for relativistic particles in stationary gravitational fields and rotating frames and establish the full agreement between the classical and quantum mechanical approaches.

Obukhov, Yuri N. [Institute for Theoretical Physics, University of Cologne, Koeln 50923 (Germany); Silenko, Alexander J. [Research Institute of Nuclear Problems, Belarusian State University, Minsk 220080 (Belarus); Teryaev, Oleg V. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation)

2010-03-24

114

Saturn's gravitational field, internal rotation, and interior structure.  

PubMed

Saturn's internal rotation period is unknown, though it must be less than 10 hours, 39 minutes, and 22 seconds, as derived from magnetic field plus kilometric radiation data. By using the Cassini spacecraft's gravitational data, along with Pioneer and Voyager radio occultation and wind data, we obtain a rotation period of 10 hours, 32 minutes, and 35 +/- 13 seconds. This more rapid spin implies slower equatorial wind speeds on Saturn than previously assumed, and the winds at higher latitudes flow both east and west, as on Jupiter. Our related Saturn interior model has a molecular-to-metallic hydrogen transition about halfway to the planet's center. PMID:17823351

Anderson, John D; Schubert, Gerald

2007-09-01

115

5th International School on Field Theory and Gravitation  

NASA Astrophysics Data System (ADS)

Following the philosophy that the International School on Field Theory and Gravitation must be held each three years in different Brazilian Universities and, if possible, in different brazilian states, the next meeting will take place at Physics Institute of Universidade Federal do Mato Grosso, UFMT, Cuiabá city on April, 20-24/2009 very close to the beautiful Pantanal and Chapada dos Guimarães area. The goal of the meeting is to promote a greater integration among many physicists from the local university, UFMT, Co-organizing institutions in Brasil and foreign countries such as Canada, USA, Italy, China, England, Swiss, Spain, Brazil and others; to stimulate the organization of scientific events in our physics Institute and thus contributing to local research activities; to exhibit different fields of physics and to stimulate new lines of theoretical research and technological developments in the Universidade Federal do Mato Grosso, UFMT. Finally, we make efforts to promote the development of advanced studies, taking it to the present core of research in a strong process of affirmation of new lines of theoretical studies in our Physics Institute. To this, we invite colleagues, collaborators, researchers, students, and friends to attend this fifth edition of International School on Field Theory and gravitation-2009.

116

Classical effective field theory for weak ultra relativistic scattering  

Microsoft Academic Search

Inspired by the problem of Planckian scattering we describea classical effective field theory for weak ultra relativistic\\u000a scattering in which field propagation is instantaneous and transverse and the particles’ equations of motion localize to the\\u000a instant of passing. An analogy with the non-relativistic (post-Newtonian) approximation is stressed. The small parameter is\\u000a identified and power counting rules are established. The theory

Barak Kol

2011-01-01

117

An experiment to verify that the weak interactions satisfy the strong equivalence principle. [electron capture and gravitational potential  

NASA Technical Reports Server (NTRS)

The construction of a clock based on the beta decay process is proposed to test for any violations by the weak interaction of the strong equivalence principle bu determining whether the weak interaction coupling constant beta is spatially constant or whether it is a function of gravitational potential (U). The clock can be constructed by simply counting the beta disintegrations of some suitable source. The total number of counts are to be taken a measure of elapsed time. The accuracy of the clock is limited by the statistical fluctuations in the number of counts, N, which is equal to the square root of N. Increasing N gives a corresponding increase in accuracy. A source based on the electron capture process can be used so as to avoid low energy electron discrimination problems. Solid state and gaseous detectors are being considered. While the accuracy of this type of beta decay clock is much less than clocks based on the electromagnetic interaction, there is a corresponding lack of knowledge of the behavior of beta as a function of gravitational potential. No predictions from nonmetric theories as to variations in beta are available as yet, but they may occur at the U/sg C level.

Eby, P. B.

1978-01-01

118

Validation of the Weak Equivalence Principle in a Spatially-Vsl Gravitation Model  

NASA Astrophysics Data System (ADS)

The WEP is proven to hold in a scalar-vector gravitation model with spatially variable speed of light and Lorentz-Poincaré type interpretation for the configuration of a non-stationary source.2 In this model the spatially-VSL, c(r) = c'?2 + W, is a coordinate velocity in contrast to the invariant velocity c', which is locally observable due to the application of the gravitationally modified Lorentz Transformations for space and time intervals.4 The Hamiltonian mechanics for particles and photons derived from the corresponding energy and momentum transformations agrees at least till 1-PN with the dynamics of General Relativity Theory.5 Now in a local inertial frame and for a non-stationary source the validity of the WEP is proven by deriving the nil relative acceleration of a locally coincident free-falling particle. This is established by adapting the derivative to incorporate the conventional procedure of localizing its arguments by means of parallel transport. This transport over a free-fall trajectory can be naturally expressed using a composition of gravitationally modified Lorentz transformations.

Broekaert, Jan

2008-09-01

119

Probing high-redshift clusters with HST/ACS gravitational weak-lensing and Chandra x-ray observations  

NASA Astrophysics Data System (ADS)

Clusters of galaxies, the largest gravitationally bound objects in the Universe, are useful tracers of cosmic evolution, and particularly detailed studies of still-forming clusters at high-redshifts can considerably enhance our understanding of the structure formation. We use two powerful methods that have become recently available for the study of these distant clusters: spaced- based gravitational weak-lensing and high-resolution X-ray observations. Detailed analyses of five high-redshift (0.8 < z < 1.3) clusters are presented based on the deep Advanced Camera for Surveys (ACS) and Chandra X-ray images. We show that, when the instrumental characteristics are properly understood, the newly installed ACS on the Hubble Space Telescope (HST) can detect subtle shape distortions of background galaxies down to the limiting magnitudes of the observations, which enables the mapping of the cluster dark matter in unprecedented high-resolution. The cluster masses derived from this HST /ACS weak-lensing study have been compared with those from the re-analyses of the archival Chandra X-ray data. We find that there are interesting offsets between the cluster galaxy, intracluster medium (ICM), and dark matter centroids, and possible scenarios are discussed. If the offset is confirmed to be uniquitous in other clusters, the explanation may necessitate major refinements in our current understanding of the nature of dark matter, as well as the cluster galaxy dynamics. CL0848+4452, the highest-redshift ( z = 1.27) cluster yet detected in weak-lensing, has a significant discrepancy between the weak- lensing and X-ray masses. If this trend is found to be severe and common also for other X-ray weak clusters at redshifts beyond the unity, the conventional X-ray determination of cluster mass functions, often inferred from their immediate X-ray properties such as the X-ray luminosity and temperature via the so-called mass-luminosity (M-L) and mass-temperature (M-T) relations, will become highly unstable in this redshift regime. Therefore, the relatively unbiased weak-lensing measurements of the cluster mass properties can be used to adequately calibrate the scaling relations in future high-redshift cluster investigations.

Jee, Myungkook James

2006-06-01

120

PROTOSTELLAR DISK FORMATION ENABLED BY WEAK, MISALIGNED MAGNETIC FIELDS  

SciTech Connect

The gas from which stars form is magnetized, and strong magnetic fields can efficiently transport angular momentum. Most theoretical models of this phenomenon find that it should prevent formation of large (>100 AU), rotationally supported disks around most protostars, even when non-ideal magnetohydrodynamic (MHD) effects that allow the field and gas to decouple are taken into account. Using recent observations of magnetic field strengths and orientations in protostellar cores, we show that this conclusion is incorrect. The distribution of magnetic field strengths is very broad, and alignments between fields and angular momentum vectors within protostellar cores are essentially random. By combining the field strength and misalignment data with MHD simulations showing that disk formation is expected for both weak and misaligned fields, we show that these observations imply that we should expect disk fractions of {approx}10%-50% even when protostars are still deeply embedded in their parent cores, and even if the gas is governed by ideal MHD.

Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Crutcher, Richard M. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green Street, Urbana, IL 61801 (United States); Hull, Charles L. H., E-mail: mkrumhol@ucsc.edu [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411 (United States)

2013-04-10

121

Cosmological black holes from self-gravitating fields  

NASA Astrophysics Data System (ADS)

Both cosmological expansion and black holes are ubiquitous features of our observable Universe, yet exact solutions connecting the two have remained elusive. To this end, we study self-gravitating classical fields within dynamical spherically symmetric solutions that can describe black holes in an expanding universe. After attempting a perturbative approach of a known black-hole solution with scalar hair, we show by exact methods that the unique scalar field action with first-order derivatives that can source shear-free expansion around a black hole requires noncanonical kinetic terms. The resulting action is an incompressible limit of k-essence, otherwise known as the cuscuton theory, and the spacetime it describes is the McVittie metric. We further show that this solution is an exact solution to the vacuum Ho?ava-Lifshitz gravity with anisotropic Weyl symmetry.

Abdalla, Elcio; Afshordi, Niayesh; Fontanini, Michele; Guariento, Daniel C.; Papantonopoulos, Eleftherios

2014-05-01

122

Pair production in the gravitational field of a cosmic string  

NASA Astrophysics Data System (ADS)

We show that many elementary particle physics processes, such as pair production by a high energy photon, that take place in Minkowski space only if a non-uniform external field provides for momentum non-conservation, do occur in the space-time around a straight cosmic string, even though the space is locally flat and there is no local gravitational potential. We exemplify this mechanism through the evaluation of the cross section per unit length of string for the decay of a massless scalar particle into a pair of massive particles. The cross sections for this kind of processes are typically small. Nevertheless, it is interesting to realize how these reactions occur due to topological properties of space, rather than to the action of a local field. V.S. is grateful to Mario Castagnino for hospitality at the Instituto de Astronomía y Física del Espacio during a visit while this work was done.

Harari, Diego D.; Skarzhinsky, Vladimir D.

1990-04-01

123

Reduced equations of motion of the interface of dielectric liquids in vertical electric and gravitational fields  

NASA Astrophysics Data System (ADS)

The dynamics of the interface between two dielectric fluids in the presence of vertical electric and gravitational fields is studied theoretically. It is shown that, in the particular case where the rate of change of the electric field is proportional to the effective gravitational acceleration, a special flow regime can be realized for which the velocity and electric potentials are linearly dependent functions. This means that there exists a frame of reference in which liquids move along the electric field lines. We derive and analyze the corresponding reduced equations of motion of a liquid-liquid interface. For small density ratio, they turn into the equations describing the Laplacian growth. In the case of two spatial dimensions, we show that these equations determine the asymptotic behavior of the system. For arbitrary density ratios, the Laplacian growth equations adequately describe the initial (weakly nonlinear) stage of the interface instability development. The integrability of these equations makes it possible to investigate the evolution of nonlinear waves at the boundary and, in particular, to demonstrate the tendency to the formation of singularities (cusps).

Kochurin, Evgeny A.; Zubarev, Nikolay M.

2012-07-01

124

Is there a weak mixed polarity background field? Theoretical arguments  

NASA Technical Reports Server (NTRS)

A number of processes associated with the formation of active regions produce 'U-loops': fluxtubes having two ends at the photosphere but otherwise still embedded in the convection zone. The mass trapped on the field lines of such loops makes them behave in a qualitatively different way from the 'omega-loops' that form active regions. It is shown that U-loops will disperse though the convection zone and form a weak (down to a few gauss) field that covers a significant fraction of the solar surface. This field is tentatively identified with the inner-network fields observed at Kitt Peak and Big Bear. The process by which these fields escape through the surface is described; a remarkable property is that it can make active region fields apparently disappear in situ. The mixed polarity moving magnetic features near sunspots are interpreted as a locally intense form of this disappearance by escape of U-loops.

Spruit, H. C.; Title, A. M.; Van Ballegooijen, A. A.

1987-01-01

125

Dynamical mass generation in QED with weak magnetic fields  

SciTech Connect

We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)2.

Ayala, A.; Rojas, E. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, C. U., Apartado Postal 70-543, 04510, Mexico, D. F. (Mexico); Bashir, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, C. U., Apartado Postal 70-543, 04510, Mexico, D. F. (Mexico); Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Apartado Postal 2-82, Morelia, Michoacan 58040 (Mexico); Institute for Particle Physics Phenomenology, University of Durham, Durham DH1 3LE (United Kingdom); Raya, A. [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Apartado Postal 2-82, Morelia, Michoacan 58040 (Mexico); Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Ciurcuito Exterior, C. U., Apartado Postal 70-543, 04510, Mexico, D. F. (Mexico)

2006-09-25

126

Weak gravitational lensing due to large-scale structure of the universe  

NASA Technical Reports Server (NTRS)

The effect of the large-scale structure of the universe on the propagation of light rays is studied. The development of the large-scale density fluctuations in the omega = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 10 to the 6th random light rays between the redshift z = 5 and the observer was followed. It is found that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small. Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In the simulation, the column density was averaged over a comoving area of approximately (1/h Mpc)-squared. No case of a strong gravitational lensing was found, i.e., no 'over-focused' image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.

Jaroszynski, Michal; Park, Changbom; Paczynski, Bohdan; Gott, J. Richard, III

1990-01-01

127

Constants of motion in stationary axisymmetric gravitational fields  

NASA Astrophysics Data System (ADS)

The motion of test particles in stationary axisymmetric gravitational fields is generally non-integrable unless a non-trivial constant of motion, in addition to energy and angular momentum along the symmetry axis, exists. The Carter constant in Kerr-de Sitter space-time is the only example known to date. Proposed astrophysical tests of the black hole no-hair theorem have often involved integrable gravitational fields more general than the Kerr family, but the existence of such fields has been a matter of debate. To elucidate this problem, we treat its Newtonian analogue by systematically searching for non-trivial constants of motion polynomial in the momenta and obtain two theorems. First, solving a set of quadratic integrability conditions, we establish the existence and uniqueness of the family of stationary axisymmetric potentials admitting a quadratic constant. As in Kerr-de Sitter space-time, the mass moments of this class satisfy a `no-hair' recursion relation M2l +2 = a2M2l, and the constant is Noether related to a second-order Killing-Stäckel tensor. Second, solving a new set of quartic integrability conditions, we establish non-existence of quartic constants. Remarkably, a subset of these conditions is satisfied when the mass moments obey a generalized `no-hair' recursion relation M2l +4 = (a2 + b2)M2l +2 - a2b2M2l. The full set of quartic integrability conditions, however, cannot be satisfied non-trivially by any stationary axisymmetric vacuum potential.

Markakis, C.

2014-07-01

128

Search for the Effects of Inhomogenous Electric Fields on Gravitation  

NASA Astrophysics Data System (ADS)

The effect of inhomogenous electric fields on the weight of test masses is being investigated. Inhomogenous field is produced by applying dc bias between a horizontal flat electrode and the tip of a conical bottom electrode of an electrostatic capacitor. The equipotentials and the electric field distribution has been numerically calculated using “MATLAB” software. The test masses are gold-coated metal spheres, electrically isolated and suspended between the electrodes of the capacitor. The test masses are spheres of equal sizes but different density hence different masses. The sample mass and the capacitor are placed inside a measurement cell filled with high purity nitrogen gas. The whole apparatus is setup in an underground chamber below a large climate controlled laboratory. With the electric field on, off and reversed the weight of the masses is measured by an analytical balance. Quantitative data, such as, baseline weight and the response to the electric field will be presented. Initial analyses favor a direct correlation between the sample masses and the differential signals. Such a scaling of the signal with mass may be indicative of a gravitational signature.

Yin, Ming; Bleiweiss, Michael; Prozorov, Ruslan; Datta, Timir

2002-04-01

129

Gravitational waves from neutron stars with large toroidal B fields  

NASA Astrophysics Data System (ADS)

We show that NS's with large toroidal B fields tend naturally to evolve into potent gravitational-wave (GW) emitters. The toroidal field Bt tends to distort the NS into a prolate shape, and this magnetic distortion dominates over the oblateness ``frozen into'' the NS crust for Bt>~3.4×1012 G (?s/300 Hz)2. An elastic NS with frozen-in B field of this magnitude is clearly secularly unstable: the wobble angle between the NS's angular momentum Ji and the star's magnetic axis niB grows on a dissipation time scale until Ji and niB are orthogonal. This final orientation is clearly the optimal one for GW emission. The basic cause of the instability is quite general, so we conjecture that the same final state is reached for a realistic NS, with superfluid core. Assuming this, we show that for LMXB's with Bt~2×1012-2×1014 G, the spindown from GW's is sufficient to balance the accretion torque-supporting a suggestion by Bildsten. The spindown rates of most millisecond pulsars can also be attributed to GW emission sourced by toroidal B fields, and both these sources could be observed by LIGO II. While the first-year spindown of a newborn NS is most likely dominated by electromagnetic processes, reasonable values of Bt and the (external) dipolar field Bd can lead to detectable levels of GW emission, for a newborn NS in our own Galaxy.

Cutler, Curt

2002-10-01

130

CHARGED TORI IN SPHERICAL GRAVITATIONAL AND DIPOLAR MAGNETIC FIELDS  

SciTech Connect

A Newtonian model of non-conductive, charged, perfect fluid tori orbiting in combined spherical gravitational and dipolar magnetic fields is presented and stationary, axisymmetric toroidal structures are analyzed. Matter in such tori exhibits a purely circulatory motion and the resulting convection carries charges into permanent rotation around the symmetry axis. As a main result, we demonstrate the possible existence of off-equatorial charged tori and equatorial tori with cusps that also enable outflows of matter from the torus in the Newtonian regime. These phenomena qualitatively represent a new consequence of the interplay between gravity and electromagnetism. From an astrophysical point of view, our investigation can provide insight into processes that determine the vertical structure of dusty tori surrounding accretion disks.

Slany, P.; Kovar, J.; Stuchlik, Z. [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava Bezrucovo nam. 13, CZ-746 01 Opava (Czech Republic)] [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava Bezrucovo nam. 13, CZ-746 01 Opava (Czech Republic); Karas, V., E-mail: petr.slany@fpf.slu.cz [Astronomical Institute, Academy of Sciences, Bocni II, Prague CZ-141 31 (Czech Republic)

2013-03-01

131

Comment on 'Primordial magnetic seed field amplification by gravitational waves'  

SciTech Connect

We consider the amplification of cosmological magnetic fields by gravitational waves as it was recently presented by Betschart et al. That study confined to infinitely conductive environments, arguing that on spatially flat Friedmann backgrounds the gravito-magnetic interaction proceeds always as if the Universe were a perfect conductor. We explain why this claim is not correct and then reexamine the Maxwell-Weyl coupling at the limit of ideal magnetohydrodynamics. We find that the scales of the main results of Betschart et al. were not properly assessed and that the incorrect scale assessment has compromised both the physical and the numerical results of the paper. This comment aims to clarify these issues on the one hand, while on the other it takes a closer look at the gauge invariance and the nonlinearity of the formalism proposed by Betschart et al.

Tsagas, Christos G. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

2007-04-15

132

Optimized formulas for the gravitational field of a tesseroid  

NASA Astrophysics Data System (ADS)

Various tasks in geodesy, geophysics, and related geosciences require precise information on the impact of mass distributions on gravity field-related quantities, such as the gravitational potential and its partial derivatives. Using forward modeling based on Newton's integral, mass distributions are generally decomposed into regular elementary bodies. In classical approaches, prisms or point mass approximations are mostly utilized. Considering the effect of the sphericity of the Earth, alternative mass modeling methods based on tesseroid bodies (spherical prisms) should be taken into account, particularly in regional and global applications. Expressions for the gravitational field of a point mass are relatively simple when formulated in Cartesian coordinates. In the case of integrating over a tesseroid volume bounded by geocentric spherical coordinates, it will be shown that it is also beneficial to represent the integral kernel in terms of Cartesian coordinates. This considerably simplifies the determination of the tesseroid's potential derivatives in comparison with previously published methodologies that make use of integral kernels expressed in spherical coordinates. Based on this idea, optimized formulas for the gravitational potential of a homogeneous tesseroid and its derivatives up to second-order are elaborated in this paper. These new formulas do not suffer from the polar singularity of the spherical coordinate system and can, therefore, be evaluated for any position on the globe. Since integrals over tesseroid volumes cannot be solved analytically, the numerical evaluation is achieved by means of expanding the integral kernel in a Taylor series with fourth-order error in the spatial coordinates of the integration point. As the structure of the Cartesian integral kernel is substantially simplified, Taylor coefficients can be represented in a compact and computationally attractive form. Thus, the use of the optimized tesseroid formulas particularly benefits from a significant decrease in computation time by about 45 % compared to previously used algorithms. In order to show the computational efficiency and to validate the mathematical derivations, the new tesseroid formulas are applied to two realistic numerical experiments and are compared to previously published tesseroid methods and the conventional prism approach.

Grombein, Thomas; Seitz, Kurt; Heck, Bernhard

2013-07-01

133

Gravitational perturbation of the BTZ black hole induced by test particles and weak cosmic censorship in AdS spacetime  

NASA Astrophysics Data System (ADS)

We analyze the gravitational perturbations induced by particles falling into a three dimensional, asymptotically AdS black hole geometry. More specifically, we solve the linearized perturbation equations obtained from the geodesic motion of a ringlike distribution of test particles in the BTZ background. This setup ensures that the U(1) symmetry of the background is preserved. The nonasymptotic flatness of the background raises difficulties in attributing the significance of energy and angular momentum to the conserved quantities of the test particles. This issue is well known but, to the best of our knowledge, has never been addressed in the literature. We confirm that the naive expressions for energy and angular momentum are the correct definitions. Finally, we put an asymptotically AdS version of the weak cosmic censorship to a test: by attempting to overspin the BTZ black hole with test particles it is found that the black hole cannot be spun-up past its extremal limit.

Rocha, Jorge V.; Cardoso, Vitor

2011-05-01

134

Effects of very weak magnetic fields on radical pair reformation.  

PubMed

We can expect that biological responses to very weak ELF electromagnetic fields will be masked by thermal noise. However, the spin of electrons bound to biologically important molecules is not strongly coupled to the thermal bath, and the effects of the precession of those spins by external magnetic fields is not bounded by thermal noise. Hence, the known role of spin orientation in the recombination of radical pairs (RP) may constitute a mechanism for the biological effects of very weak fields. That recombination will generally take place only if the valence electrons in the two radicals are in a singlet state and the effect of the magnetic field is manifest through differential spin precessions that affect the occupation of that state. Because the spin relaxation times are of the order of microseconds, any effects must be largely independent of frequency up to values of a few megahertz. Using exact calculations on an appropriately general model system, we show that one can expect small, but significant, modifications of the recombination rate by a 50 microT field only under a narrow range of circumstances: the cage time during which the two elements are together must be exceptionally long--of the order of 50 ns or longer; the hyperfine field of either radical must not be so great as to generate a precession period greater than the cage containment time; and the characteristic recombination time of the radical pair in the singlet state must be about equal to the containment time. Thus, even under such singularly favorable conditions, fields as small as 5 microT (50 milligauss) cannot change the recombination rate by as much as 1%. Hence, we conclude that environmental magnetic fields much weaker than the earth's field cannot be expected to affect biology significantly by modifying radical pair recombination probabilities. PMID:10230939

Adair, R K

1999-01-01

135

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation  

NASA Astrophysics Data System (ADS)

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation is studied on the basis of kinetic theory. We consider the situation in which the Knudsen number (the mean free path divided by the characteristic length of the cross section) is small and the dimensionless gravity (the characteristic length divided by the ascent height of the molecules against gravity) is of the order of the square of the Knudsen number. The behavior of the gas is studied analytically on the basis of the fluid-dynamic-type equation and the slip-type boundary condition derived from the Boltzmann equation for small Knudsen numbers. Extending the analysis of the two-dimensional channel problem, the solution for a pipe with an arbitrary cross section is obtained in a semianalytical form. When the temperature gradient is imposed along the pipe, the pressure gradient is produced not only in the vertical direction but also in the horizontal direction due to the effect of gravity. Although this pressure gradient is of the order of the square of the Knudsen number, it induces a flow of the order of the Knudsen number. As a result, the apparently higher order effect of gravity produces a relatively finite effect on thermal transpiration. This phenomenon, first observed in plane thermal transpiration, is clarified for a pipe with a general cross section. The explicit solution is obtained for the pipe with the cross section of an annulus between eccentric circular cylinders. Based on the solution, the effect of weak gravitation on the mass flow rate of the gas, as well as on the flow velocity, is clarified over a wide range of the radii ratio and the eccentricity of the cylinders.

Doi, Toshiyuki

2013-10-01

136

NUMERICAL TESTS OF FAST RECONNECTION IN WEAKLY STOCHASTIC MAGNETIC FIELDS  

SciTech Connect

We study the effects of turbulence on magnetic reconnection using three-dimensional direct numerical simulations. This is the first attempt to test a model of fast magnetic reconnection in the presence of weak turbulence proposed by Lazarian and Vishniac. This model predicts that weak turbulence, which is generically present in most astrophysical systems, enhances the rate of reconnection by reducing the transverse scale for reconnection events and by allowing many independent flux reconnection events to occur simultaneously. As a result, the reconnection speed becomes independent of Ohmic resistivity and is determined by the magnetic field wandering induced by turbulence. We test the dependence of the reconnection speed on turbulent power, the energy injection scale, and resistivity. We apply the open and experiment with the outflow boundary conditions in our numerical model and discuss the advantages and drawbacks of various setups. To test our results, we also perform simulations of turbulence with the same outflow boundaries but without a large-scale field reversal, thus without large-scale reconnection. To quantify the reconnection speed we use both an intuitive definition, i.e., the speed of the reconnected flux inflow, and a more sophisticated definition based on a formally derived analytical expression. Our results confirm the predictions of the Lazarian and Vishniac model. In particular, we find that the reconnection speed is proportional to the square root of the injected power, as predicted by the model. The dependence on the injection scale for some of our models is a bit weaker than expected, i.e., l{sup 3/4}{sub inj}, compared to the predicted linear dependence on the injection scale, which may require some refinement of the model or may be due to effects such as the finite size of the excitation region, which are not a part of the model. The reconnection speed was found to depend on the expected rate of magnetic field wandering and not on the magnitude of the guide field. In our models, we see no dependence on the guide field when its strength is comparable to the reconnected component. More importantly, while in the absence of turbulence we successfully reproduce the Sweet-Parker scaling of reconnection, in the presence of turbulence we do not observe any dependence on Ohmic resistivity, confirming that the reconnection of the weakly stochastic field is fast. We also do not observe a dependence on anomalous resistivity, which suggests that the presence of anomalous effects, e.g., Hall MHD effects, may be irrelevant for astrophysical systems with weakly stochastic magnetic fields.

Kowal, Grzegorz; Lazarian, A. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Vishniac, E. T. [Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1 (Canada); Otmianowska-Mazur, K. [Astronomical Observatory, Jagiellonian University, Orla 171, 30-244 Krakow (Poland)], E-mail: kowal@astro.wisc.edu, E-mail: lazarian@astro.wisc.edu, E-mail: otmian@astro.wisc.edu, E-mail: ethan@mcmaster.ca

2009-07-20

137

THE IMPACT OF THERMODYNAMICS ON GRAVITATIONAL COLLAPSE: FILAMENT FORMATION AND MAGNETIC FIELD AMPLIFICATION  

SciTech Connect

Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k{rho}{sup {Gamma}}, with both sub-isothermal exponents {Gamma} < 1 and super-isothermal exponents {Gamma} > 1. We find significant differences between these two cases. For {Gamma} > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For {Gamma} < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.

Peters, Thomas; Klessen, Ralf S.; Federrath, Christoph; Smith, Rowan J. [Zentrum fuer Astronomie, Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Schleicher, Dominik R. G. [Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Banerjee, Robi [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Sur, Sharanya, E-mail: tpeters@physik.uzh.ch [Raman Research Institute, C. V. Raman Avenue, Sadashivnagar, Bangalore 560080 (India)

2012-12-01

138

Seasonal Variations of the Earth's Gravitational Field: An Analysis of Atmospheric and Ocean Tidal Excitation  

NASA Technical Reports Server (NTRS)

Laser ranging measurements to single satellite are sensitive to the Earth's gravitational field and its temporal variations. Using 13 years (1980-1992) of LAGEOS I laser ranging data, we have recovered monthly mean linear combinations of even and odd degree zonal spherical harmonic coefficients of the Earth's gravitational field.

Dong, D.; Gross, R. S.; Dickey, J. O.

1994-01-01

139

Model for the optimization of escape from two pursuers in a gravitational field  

NASA Astrophysics Data System (ADS)

A solution is obtained to the simplifed game-theoretic problem of determining the optimal encounter of three players in a gravitational field, assuming that two of the players form a coalition while the third is performing evasive maneuvers. The problem is one of determining coplanar impulse transfer in the gravitational field.

Novoselov, V. S.

140

Atmospheric Gravitational Torque Variations Based on Various Gravity Fields  

NASA Technical Reports Server (NTRS)

Advancements in the study of the Earth's variable rate of rotation and the motion of its rotation axis have given impetus to the analysis of the torques between the atmosphere, oceans and solid Earth. The output from global general circulation models of the atmosphere (pressure, surface stress) is being used as input to the torque computations. Gravitational torque between the atmosphere, oceans and solid Earth is an important component of the torque budget. Computation of the gravitational torque involves the adoption of a gravitational model from a wide variety available. The purpose of this investigation is to ascertain to what extent this choice might influence the results of gravitational torque computations.

Sanchez, Braulio V.; Rowlands, David; Smith, David E. (Technical Monitor)

2001-01-01

141

Presence of dark energy and dark matter: does cosmic acceleration signifies a weak gravitational collapse?  

NASA Astrophysics Data System (ADS)

In this work the collapsing process of a spherically symmetric star, made of dust cloud, in the background of dark energy is studied for two different gravity theories separately, i.e., DGP Brane gravity and Loop Quantum gravity. Two types of dark energy fluids, namely, Modified Chaplygin gas and Generalised Cosmic Chaplygin gas are considered for each model. Graphs are drawn to characterize the nature and the probable outcome of gravitational collapse. A comparative study is done between the collapsing process in the two different gravity theories. It is found that in case of dark matter, there is a great possibility of collapse and consequent formation of Black hole. In case of dark energy possibility of collapse is far lesser compared to the other cases, due to the large negative pressure of dark energy component. There is an increase in mass of the cloud in case of dark matter collapse due to matter accumulation. The mass decreases considerably in case of dark energy due to dark energy accretion on the cloud. In case of collapse with a combination of dark energy and dark matter, it is found that in the absence of interaction there is a far better possibility of formation of black hole in DGP brane model compared to Loop quantum cosmology model.

Rudra, Prabir; Biswas, Ritabrata; Debnath, Ujjal

2012-12-01

142

Jet Deflection by Very Weak Guide Fields during Magnetic Reconnection  

SciTech Connect

Previous 2D simulations of reconnection using a standard model of initially antiparallel magnetic fields have detected electron jets outflowing from the x point into the ion outflow exhausts. Associated with these jets are extended ''outer electron diffusion regions.'' New PIC simulations with an ion to electron mass ratio as large as 1836 (an H{sup +} plasma) now show that the jets are strongly deflected and the outer electron diffusion region is broken up by a very weak out-of-plane magnetic guide field, even though the diffusion rate itself is unchanged. Jet outflow and deflection are interpreted in terms of electron dynamics and are compared to recent measurements of jets in the presence of a small guide field in Earth's magnetosheath.

Goldman, M. V.; Newman, D. L.; Che, H. [Department of Physics and CIPS, University of Colorado, Boulder, Colorado 80309 (United States); Lapenta, G.; Markidis, S. [Centrum voor Plasma-Astrofysica, Katholieke Universiteit, Leuven (Belgium)

2011-09-23

143

Detection of weak electric fields by sharks, rays, and skates  

NASA Astrophysics Data System (ADS)

The elasmobranchs-sharks, rays, and skates-can detect very weak electric fields in their aqueous environment through a complex sensory system, the ampullae of Lorenzini. The ampullae are conducting tubes that connect the surface of the animal to its interior. In the presence of an electric field, the potential of the surface of the animal will differ from that of the interior and that potential is applied across the apical membrane of the special sensory cells that line the ampullae. The firing rate of the afferent neurons that transmit signals from the ampullae has been shown to vary with that potential. We show that those firing rates can be described quantitatively in terms of synchronous firing of the sensory cells that feed the neurons. We demonstrate that such synchronism follows naturally from a hypothetical weak cell-to-cell interaction that results in a self-organization of the sensory cells. Moreover, the pulse rates of those cells-and the neurons that service the cells-can be expected to vary with the imposed electric fields in accord with measured values through actions of voltage gated transmembrane proteins in the apical sector of the cell membranes that admit Ca++ ions. We also present a more conjectural model of signal processing at the neuron level that could exploit small differences in firing rates of nerve fibers servicing different ampullae to send an unambiguous signal to the central nervous system of the animal.

Adair, Robert K.; Astumian, R. Dean; Weaver, James C.

1998-09-01

144

Mass and concentration estimates from weak and strong gravitational lensing: a systematic study  

NASA Astrophysics Data System (ADS)

We study how well halo properties of galaxy clusters, such as mass and concentration, are recovered using lensing data. In order to generate a large sample of systems at different redshifts, we use the code MOKA. We measure halo mass and concentration using weak lensing data alone (WL), fitting to a Navarro, Frenk & White (NFW) profile the reduced tangential shear profile, or by combining weak and strong lensing data, by adding information about the size of the Einstein radius (WL+SL). For different redshifts, we measure the mass and the concentration biases and find that these are mainly caused by the random orientation of the halo ellipsoid with respect to the line of sight. Since our simulations account for the presence of a bright central galaxy, we perform mass and concentration measurements using a generalized NFW profile which allows for a free inner slope. This reduces both the mass and the concentration biases. We discuss how the mass function and the concentration-mass relation change when using WL and WL+SL estimates. We investigate how selection effects impact the measured concentration-mass relation showing that strong lens clusters may have a concentration 20-30 per cent higher than the average, at fixed mass, considering also the particular case of strong lensing selected samples of relaxed clusters. Finally, we notice that selecting a sample of relaxed galaxy clusters, as is done in some cluster surveys, explains the concentration-mass relation biases.

Giocoli, Carlo; Meneghetti, Massimo; Metcalf, R. Benton; Ettori, Stefano; Moscardini, Lauro

2014-05-01

145

Wide-field weak lensing by RXJ1347-1145  

NASA Astrophysics Data System (ADS)

We present an analysis of weak lensing observations for RXJ1347--1145 over a 43 ' × 43 ' field taken in B and R filters on the Blanco 4m telescope at CTIO. RXJ1347--1145 is a massive cluster at redshift z=0.45. Using a population of galaxies with 20weak lensing signal at the p<0.0005 level, finding best-fit parameters of ?_v=1400^+130_-140 km s-1 for a singular isothermal sphere model and r_200 = 3.53 Mpc for a NFW model in an ?m = 0.3, ?_? = 0.7 cosmology. These values are consistent with the previous weak lensing study of RXJ1347--1145 by Fischer and Tyson, 1997, as well as recent X-ray studies by Allen et al, 2002 and Ettori et al 2001. However, these best-fit parameters are not consistent with recent optical velocity dispersion measurements by Cohen and Kneib, 2002.

Kling, Thomas P.; dell'Antonio, Ian; Wittman, David; Tyson, J. Anthony

2004-05-01

146

Free-fall in a uniform gravitational field in noncommutative quantum mechanics  

SciTech Connect

We study the free-fall of a quantum particle in the context of noncommutative quantum mechanics (NCQM). Assuming noncommutativity of the canonical type between the coordinates of a two-dimensional configuration space, we consider a neutral particle trapped in a gravitational well and exactly solve the energy eigenvalue problem. By resorting to experimental data from the GRANIT experiment, in which the first energy levels of freely falling quantum ultracold neutrons were determined, we impose an upper-bound on the noncommutativity parameter. We also investigate the time of flight of a quantum particle moving in a uniform gravitational field in NCQM. This is related to the weak equivalence principle. As we consider stationary, energy eigenstates, i.e., delocalized states, the time of flight must be measured by a quantum clock, suitably coupled to the particle. By considering the clock as a small perturbation, we solve the (stationary) scattering problem associated and show that the time of flight is equal to the classical result, when the measurement is made far from the turning point. This result is interpreted as an extension of the equivalence principle to the realm of NCQM.

Castello-Branco, K. H. C. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao-Carlense, 400, Sao Carlos, Sao Paulo 13560-970 (Brazil); Martins, A. G. [Departamento de Ciencias Naturais, Universidade do Estado do Para, Av. Djalma Dutra, s/n, Belem, Para 66113-200 (Brazil)

2010-10-15

147

Unified equation of motion of a test charge in electromagnetic and gravitational fields  

NASA Astrophysics Data System (ADS)

This work starts by generalizing in a gravitational field the fundamental quantum mechanical commutation relations between the coordinates of a charged test particle and its momentum. Assuming that the components of the momentum of this test charge obey a noncommutative algebra in the presence of an electromagnetic field, it is proved that the commutator can be identified with the electromagnetic field tensor. Using these results, the equation of motion of this charged object in the presence of both the electromagnetic and gravitational fields is derived from their field equations. In this work, the laws of motion of a particle in the electromagnetic and gravitational fields has been unified with the field equations. Although the field equations themselves are not directly unified, this work strongly suggests that the scheme may act as a possible framework for the unification of at least gravitational and electromagnetic interactions.

Bandyopadhyay, Akash

1993-09-01

148

Weak-field limit of Kaluza-Klein models with spherical compactification: Experimental constraints  

NASA Astrophysics Data System (ADS)

We investigate the classical gravitational tests for the six-dimensional Kaluza-Klein model with spherical (of a radius a) compactification of the internal space. The model contains also a bare multidimensional cosmological constant ?6. The matter, which corresponds to this ansatz, can be simulated by a perfect fluid with the vacuum equation of state in the external space and an arbitrary equation of state with the parameter ?1 in the internal space. For example, ?1=1 and ?1=2 correspond to the monopole two-forms and the Casimir effect, respectively. In the particular case ?6=0, the parameter ?1 is also absent: ?1=0. In the weak-field approximation, we perturb the background ansatz by a pointlike mass. We demonstrate that in the case ?1>0 the perturbed metric coefficients have the Yukawa-type corrections with respect to the usual Newtonian gravitational potential. The inverse square law experiments restrict the parameters of the model: a/?1?6×10-3cm. Therefore, in the Solar System the parameterized post-Newtonian parameter ? is equal to 1 with very high accuracy. Thus, our model satisfies the gravitational experiments (the deflection of light and the time delay of radar echoes) at the same level of accuracy as general relativity. We demonstrate also that our background matter provides the stable compactification of the internal space in the case ?1>0. However, if ?1=0, then the parameterized post-Newtonian parameter ?=1/3, which strongly contradicts the observations.

Chopovsky, Alexey; Eingorn, Maxim; Zhuk, Alexander

2012-03-01

149

The HST Frontier Fields: Gravitational Lensing Models Release  

NASA Astrophysics Data System (ADS)

The Hubble Frontier Fields (HFF) is a Director's Discretionary Time (DDT) program to deeply observe up to six massive strong-lensing galaxy clusters and six "blank" fields in parallel. These complementary observations will yield magnified and direct images of some of the most distant galaxies yet observed. The strongly lensed images will be our deepest views of our universe to date. Interpretation of some (but not all) observed properties of the strongly lensed galaxies requires gravitational lens modeling. In order to maximize the value of this public dataset to the extragalactic community, STScI commissioned five teams funded by NASA to derive the best possible lens models from existing data. After coordinating to share observational constraints, including measured redshifts of strongly lensed galaxies, the teams independently derived lens models using robust, established methodologies. STScI released these models to the community in October before HFF observations of the first cluster, Abell 2744. Here we describe these models as well as a web tool which allows users to extract magnification estimates with uncertainties from all models for any galaxy strongly lensed by a HFF cluster. Inputs are the galaxy's coordinates (RA and Dec), redshift, and (optionally) observed radius. We also discuss ongoing work to study lens model uncertainties by modeling simulated clusters.

Coe, Dan A.; Lotz, J.; Natarajan, P.; Richard, J.; Zitrin, A.; Kneib, J.; Ebeling, H.; Sharon, K.; Johnson, T.; Limousin, M.; Bradac, M.; Hoag, A.; Cain, B.; Merten, J.; Williams, L. L.; Sebesta, K.; Meneghetti, M.; Koekemoer, A. M.; Barker, E. A.

2014-01-01

150

The MOG weak field approximation - II. Observational test of Chandra X-ray clusters  

NASA Astrophysics Data System (ADS)

We apply the weak field approximation limit of the covariant scalar-tensor-vector gravity theory, so-called MOdified gravity (MOG), to the dynamics of clusters of galaxies by using only baryonic matter. The MOG effective gravitational potential in the weak field approximation is composed of an attractive Newtonian term and a repulsive Yukawa term with two parameters ? and ?. The numerical values of these parameters have been obtained by fitting the predicted rotation curves of galaxies to observational data, yielding the best-fitting result: ? = 8.89 ± 0.34 and ? = 0.042 ± 0.004 kpc-1. We extend the observational test of this theory to clusters of galaxies, using data for the ionized gas and the temperature profile of nearby clusters obtained by the Chandra X-ray telescope. Using the MOG virial theorem for clusters, we compare the mass profiles of clusters from observation and theory for 11 clusters. The theoretical mass profiles for the inner parts of clusters exceed the observational data. However, the observational data for the inner parts of clusters (i.e. r < 0.1r500) is scattered, but at distances larger than ˜300 kpc, the observed and predicted mass profiles converge. Our results indicate that MOG as a theory of modified gravity is compatible with the observational data from the Solar system to megaparsec scales without invoking dark matter.

Moffat, J. W.; Rahvar, S.

2014-07-01

151

Reversible absorption of weak fields revealed in coherent transients  

NASA Astrophysics Data System (ADS)

It is shown that the absorbtion of a weak field in a thick resonant absorber is a reversible process even in the case of the homogeneous broadening of the absorption line. As an example, the propagation of a long rectangular pulse with sharp edges in an optically dense resonant medium is studied theoretically in the linear response approximation. Transient nutation (TN), free induction decay (FID), and transients, induced by the phase switch of the incident pulse, are considered. It is shown that in exact resonance the amplitude of FID increases with the length of the medium. FID arises due to the scattered radiation field (dipoles ringing). In a thick medium the scattered field is almost of the same amplitude but opposite in phase with the incident radiation field. Both fields interfere destructively to produce what is seen as radiation damping at the output of the medium. The scattered field needs time to develop. Therefore, the leading edge of the pulse is not absorbed, demonstrating temporal transparency followed by TN. Phase shift (180?) of the pulse brings the incident pulse in phase with the scattered radiation. Constructive interference of the pulse with the scattered radiation field produces a short pulse with an amplitude that is two times larger than the amplitude of the incident pulse. If the input pulse is detuned from resonance, for a particular detuning and optical thickness of the medium the amplitude of the transient pulse, induced by the phase shift, is nearly three times larger than the amplitude of the incident pulse. This is explained by the interference of the scattered field, the phase-shifted input field, and the slowly propagating part of the pulse, developed before the phase shift.

Shakhmuratov, R. N.

2012-02-01

152

Bound states of Dirac particles in gravitational fields  

SciTech Connect

We investigate the quantum motion of a neutral Dirac particle bouncing on a mirror in curved spacetime. We consider different geometries: Rindler, Kasner-Taub, and Schwarzschild, and show how to solve the Dirac equation by using geometrical methods. We discuss, in a first-quantized framework, the implementation of appropriate boundary conditions. This leads us to consider a Robin boundary condition that gives the quantization of the energy, the existence of bound states and of critical heights at which the Dirac particle bounces, extending the well-known results established from the Schroedinger equation. We also allow for a nonminimal coupling to a weak magnetic field. The problem is solved in an analytical way on the Rindler spacetime. In the other cases, we compute the energy spectrum up to the first relativistic corrections, exhibiting the contributions brought by both the geometry and the spin. These calculations are done in two different ways. On the one hand, using a relativistic expansion and, on the other hand, with Foldy-Wouthuysen transformations. Contrary to what is sometimes claimed in the literature, both methods are in agreement, as expected. Finally, we make contact with the GRANIT experiment. Relativistic effects and effects that go beyond the equivalence principle escape the sensitivity of such an experiment. However, we show that the influence of a weak magnetic field could lead to observable phenomena.

Boulanger, Nicolas; Spindel, Philippe; Buisseret, Fabien [Service de Mecanique et Gravitation, Universite de Mons-Hainaut, Academie universitaire Wallonie-Bruxelles, Place du Parc 20, BE-7000 Mons (Belgium); Groupe de Physique Nucleaire Theorique, Universite de Mons-Hainaut, Academie universitaire Wallonie-Bruxelles, Place du Parc 20, BE-7000 Mons (Belgium)

2006-12-15

153

Shapes and gravitational fields of rotating two-layer Maclaurin ellipsoids: Application to planets and satellites  

Microsoft Academic Search

The exact solution for the shape and gravitational field of a rotating two-layer Maclaurin ellipsoid of revolution is compared with predictions of the theory of figures up to third order in the small rotational parameter of the theory of figures. An explicit formula is derived for the external gravitational coefficient J2 of the exact solution. A new approach to the

Gerald Schubert; John Anderson; Keke Zhang; D. Kong; Ravit Helled

2011-01-01

154

Monopoles for gravitation and for higher spin fields  

SciTech Connect

We consider massless higher spin gauge theories with both electric and magnetic sources, with a special emphasis on the spin two case. We write the equations of motion at the linear level (with conserved external sources) and introduce Dirac strings so as to derive the equations from a variational principle. We then derive a quantization condition that generalizes the familiar Dirac quantization condition, and which involves the conserved charges associated with the asymptotic symmetries for higher spins. Next we discuss briefly how the result extends to the nonlinear theory. This is done in the context of gravitation, where the Taub-NUT solution provides the exact solution of the field equations with both types of sources. We rederive, in analogy with electromagnetism, the quantization condition from the quantization of the angular momentum. We also observe that the Taub-NUT metric is asymptotically flat at spatial infinity in the sense of Regge and Teitelboim (including their parity conditions). It follows, in particular, that one can consistently consider in the variational principle configurations with different electric and magnetic masses.

Bunster, Claudio; Portugues, Ruben [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Cnockaert, Sandrine [Physique Theorique et Mathematique, Universite Libre de Bruxelles and International Solvay Institutes, ULB Campus Plaine C.P. 231, B-1050 Brussels (Belgium); Henneaux, Marc [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Physique Theorique et Mathematique, Universite Libre de Bruxelles and International Solvay Institutes, ULB Campus Plaine C.P. 231, B-1050 Brussels (Belgium)

2006-05-15

155

Gravitational field models for the earth (GEM 1 and 2)  

NASA Technical Reports Server (NTRS)

Two models of the earth's gravitational field have been computed at Goddard Space Flight Center. The first, Goddard Earth Model 1 (GEM 1), has been derived from satellite tracking data. The second, Goddard Earth Model 2 (GEM 2), has been derived from a combination of satellite tracking and surface gravimetric data. The geopotential models are represented in spherical harmonics complete to degree and order 16 for the combined solution and complete to degree and order 12 for the satellite solution. Both solutions include zonal terms to degree 21 and related satellite resonant coefficients to degree 22. The satellite data consisted primarily of optical data processed on 300 weekly orbital arcs for 25 close earth satellites. Surface gravity data were employed in the form of 5 deg x 5 deg mean free-air gravity anomalies providing about 70% world coverage. Station locations were obtained for 46 tracking sites by combining electronic, laser, and additional optical tracking data with the above satellite data. Analysis of the radial positions of these stations and a value of mean gravity on the geoid indicated a mean equatorial radius for the earth of about 6378145 meters. Results of geopotential tests on satellite data not used in the solution show that better agreement was obtained with the GEM 1 and GEM 2 models than with the 1969 Smithsonian Standard Earth 2 model.

Lerch, F. J.; Wagner, C. A.; Smith, D. E.; Andson, M. L.; Brownd, J. E.; Richardson, J. A.

1972-01-01

156

Scalar-Tensor Theory and Gravitational Waves  

Microsoft Academic Search

An analysis of general scalar-tensor gravitation theory, containing two arbitrary functions of the scalar field, is presented. The weak-field limit is considered in detail, and predictions for the classical tests of gravitation theory are derived. A definite relationship between the light propagation and perihelion shift effects is found to hold under very general conditions. The theory of the detection of

Robert V. Wagoner

1970-01-01

157

CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We present a study of the relation between dark matter halo mass and the baryonic content of their host galaxies, quantified through galaxy luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. To interpret the weak lensing signal around our galaxies, we employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction. Our analysis is limited to lenses at redshifts between 0.2 and 0.4, split into a red and a blue sample. We express the relationship between dark matter halo mass and baryonic observable as a power law with pivot points of 10^{11} h_{70}^{-2} L_{{?}} and 2× 10^{11} h_{70}^{-2} M_{{?}} for luminosity and stellar mass, respectively. For the luminosity-halo mass relation, we find a slope of 1.32 ± 0.06 and a normalization of 1.19^{+0.06}_{-0.07}× 10^{13} h_{70}^{-1} M_{{?}} for red galaxies, while for blue galaxies the best-fitting slope is 1.09^{+0.20}_{-0.13} and the normalization is 0.18^{+0.04}_{-0.05}× 10^{13} h_{70}^{-1} M_{{?}}. Similarly, we find a best-fitting slope of 1.36^{+0.06}_{-0.07} and a normalization of 1.43^{+0.11}_{-0.08}× 10^{13} h_{70}^{-1} M_{{?}} for the stellar mass-halo mass relation of red galaxies, while for blue galaxies the corresponding values are 0.98^{+0.08}_{-0.07} and 0.84^{+0.20}_{-0.16}× 10^{13} h_{70}^{-1} M_{{? }}. All numbers convey the 68 per cent confidence limit. For red lenses, the fraction which are satellites inside a larger halo tends to decrease with luminosity and stellar mass, with the sample being nearly all satellites for a stellar mass of 2× 109 h_{70}^{-2} M_{{?}}. The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity or stellar mass. This, together with the shallower relation between halo mass and baryonic tracer, is a direct confirmation from galaxy-galaxy lensing that blue galaxies reside in less clustered environments than red galaxies. We also find that the halo model, while matching the lensing signal around red lenses well, is prone to overpredicting the large-scale signal for faint and less massive blue lenses. This could be a further indication that these galaxies tend to be more isolated than assumed.

Velander, Malin; van Uitert, Edo; Hoekstra, Henk; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Giodini, Stefania; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta

2014-01-01

158

MEASURING THE GEOMETRY OF THE UNIVERSE FROM WEAK GRAVITATIONAL LENSING BEHIND GALAXY GROUPS IN THE HST COSMOS SURVEY  

SciTech Connect

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component {Omega}{sub X} at greater than 99% confidence for an equation-of-state parameter -2.5 {<=} w {<=} -0.1. For the case w = -1, we find a value for the cosmological constant density parameter {Omega}{sub {Lambda}} = 0.85{sup +0.044}{sub -}0{sub .19} (68% CL) and detect cosmic acceleration (q{sub 0} < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.

Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Massey, Richard J. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rhodes, Jason; Ellis, Richard; Scoville, Nick [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kitching, Thomas D. [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Ilbert, Olivier; Kneib, Jean-Paul [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Jullo, Eric [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Koekemoer, Anton M., E-mail: taylor@uwaterloo.ca [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-04-20

159

Gravitational Waves from Rotating and Precessing Rigid Bodies. 2: General Solutions and Computationally Useful Formulae.  

National Technical Information Service (NTIS)

The classical mechanics results for free precession which are needed in order to calculate the weak field, slow-motion, quadrupole-moment gravitational waves are reviewed. Within that formalism, algorithms are given for computing the exact gravitational p...

M. Zimmerman

1979-01-01

160

Gravitational waves from Abelian gauge fields and cosmic strings at preheating  

NASA Astrophysics Data System (ADS)

Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space. We show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearance of new peaks at characteristic frequencies that are related to the mass scales in the problem. We also show how these new features in the spectra correlate with stringlike spatial configurations in both the Higgs and gauge fields that arise due to the appearance of topological winding numbers of the Higgs around Nielsen-Olesen strings. We study in detail the time evolution of the spectrum of gauge fields and gravitational waves as these strings evolve and decay before entering a turbulent regime where the gravitational wave energy density saturates.

Dufaux, Jean-François; Figueroa, Daniel G.; García-Bellido, Juan

2010-10-01

161

Test of Gravity on Large Scales with Weak Gravitational Lensing and Clustering Measurements of SDSS Luminous Red Galaxies  

NASA Astrophysics Data System (ADS)

We perform a test of gravity on large scales (5-50 Mpc/h) using 70,000 luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) DR7 with redshifts 0.16weak gravitational lensing, galaxy peculiar velocities, and galaxy clustering-- that can discriminate between different theories of gravity and is largely independent of galaxy bias and sigma_8. In particular, E_G is sensitive to the relation between the spatial and temporal scalar perturbations in the space-time metric. While these two potentials are equivalent in concordance cosmology (GR+LCDM) in the absence of anisotropic stress, they are not equivalent in alternative theories of gravity in general, so that different models make different predictions for E_G. We find E_G=0.37±0.05 averaged over scales 5

Reyes, Reinabelle; Mandelbaum, R.; Seljak, U.; Gunn, J.; Lombriser, L.

2009-01-01

162

Strong versus weak wave-turbulence in relativistic field theory  

NASA Astrophysics Data System (ADS)

Nonthermal scaling phenomena can exhibit a characteristic dependence on the dimensionality d of space. For d=3 and 4 we simulate a relativistic scalar field theory on a lattice and compute turbulent scaling exponents. We recover Kolmogorov or weak wave-turbulence in the perturbative high-momentum regime, where it exhibits the scaling exponent ?w=d-3/2. In the nonperturbative infrared regime, we find a different scaling exponent ?s=4(5) for d=3(4), which is in agreement with the recently predicted anomalously large values ?s=d+1 of strong turbulence. We show how the latter can be seen to characterize stationary transport of a conserved effective particle number.

Berges, Jürgen; Sexty, Dénes

2011-04-01

163

Singularity analysis of potential fields to enhance weak anomalies  

NASA Astrophysics Data System (ADS)

Geoanomalies generally are nonlinear, non-stationary and weak, especially in the land cover areas, however, the traditional methods of geoanomaly identification are usually based on linear theory. In past two decades, many power-law function models have been developed based on fractal concept in mineral exploration and mineral resource assessment, such that the density-area (C-A) model and spectrum-area model (S-A) suggested by Qiuming Cheng have played important roles in extracting geophysical and geochemical anomalies. Several power-law relationships are evident in geophysical potential fields, such as field value-distance, power spectrum-wave number as well as density-area models. The singularity index based on density-area model involves the first derivative transformation of the measure. Hence, we introduce the singularity analysis to develop a novel high-pass filter for extracting gravity and magnetic anomalies with the advantage of scale invariance. Furthermore, we suggest that the statistics of singularity indices can provide a new edge detection scheme for the gravity or magnetic source bodies. Meanwhile, theoretical magnetic anomalies are established to verify these assertions. In the case study from Nanling mineral district in south China and Qikou Depression in east China, compared with traditional geophysical filtering methods including multiscale wavelet analysis and total horizontal gradient methods, the singularity method enhances and extracts the weak anomalies caused by buried magmatic rocks more effectively, and provides more distinct boundary information of rocks. Moreover, the singularity mapping results have good correspondence relationship with both the outcropping rocks and known mineral deposits to support future mineral resource exploration. The singularity method based on fractal analysis has potential to be a new useful theory and technique for processing gravity and magnetic anomaly data.

Chen, G.; Cheng, Q.; Liu, T.

2013-12-01

164

Student Understanding Of Gravitational Potential Energy And The Motion Of Bodies In A Gravitational Field  

NSDL National Science Digital Library

We have been investigating student understanding of energy concepts in the context of introductory courses for non-science majors as well as those for science and engineering majors. We have found that many students develop incomplete and incorrect understandings of the concept of gravitational potential energy. Moreover, students often have incorrect notions about the motion of bodies under the influence of gravity. These incorrect beliefs may prevent the development of a coherent understanding of energy as a conserved quantity.

Loverude, Michael E.

2010-01-18

165

Gravitational quantum effects in an isotropic universe  

NASA Astrophysics Data System (ADS)

The effects of polarization of a vacuum by an external gravitational field in a system of spinor, scalar, and vector mass-particles are analyzed within the framework of a model of a conformally planar space-time. Expressions for radiative corrections to the Einstein equations are derived, both of the second- and third-order. The role of these corrections in gravitational theory, in asymptotic regions of weak and strong gravitational fields are discussed.

Beilin, V. A.; Vereshkov, G. M.; Grishkan, Iu. S.; Ivanov, N. M.; Nesterenko, V. A.; Poltavtsev, A. N.

1980-06-01

166

Modeling the electric field of weakly electric fish.  

PubMed

Weakly electric fish characterize the environment in which they live by sensing distortions in their self-generated electric field. These distortions result in electric images forming across their skin. In order to better understand electric field generation and image formation in one particular species of electric fish, Apteronotus leptorhynchus, we have developed three different numerical models of a two-dimensional cross-section of the fish's body and its surroundings. One of these models mimics the real contour of the fish; two other geometrically simple models allow for an independent study of the effects of the fish's body geometry and conductivity on electric field and image formation. Using these models, we show that the fish's tapered body shape is mainly responsible for the smooth, uniform field in the rostral region, where most electroreceptors are located. The fish's narrowing body geometry is also responsible for the relatively large electric potential in the caudal region. Numerical tests also confirm the previous hypothesis that the electric fish body acts approximately like an ideal voltage divider; this is true especially for the tail region. Next, we calculate electric images produced by simple objects and find they vary according to the current density profile assigned to the fish's electric organ. This explains some of the qualitative differences previously reported for different modeling approaches. The variation of the electric image's shape as a function of different object locations is explained in terms of the fish's geometrical and electrical parameters. Lastly, we discuss novel cues for determining an object's rostro-caudal location and lateral distance using these electric images. PMID:16943504

Babineau, David; Longtin, André; Lewis, John E

2006-09-01

167

Kinetic simulation of rarefied and weakly ionized hypersonic flow fields  

NASA Astrophysics Data System (ADS)

When a vehicle enters the Earth's atmosphere at the very large velocities associated with Lunar and Mars return, a strong bow shock is formed in front of the vehicle. The shock heats the air to very high temperatures, causing collisions that are sufficiently energetic to produce ionized particles. As a result, a weakly ionized plasma is formed in the region between the bow shock and the vehicle surface. The presence of this plasma impedes the transport of radio frequency waves to the vehicle, causing the phenomenon known as "communications black out". The plasma also interacts with the neutral particles in the flow field, and contributes to the heat flux at the vehicle surface. Since it is difficult to characterize these flow fields using flight or ground based experiments, computational tools play an important role in the design of reentry vehicles. It is important to include the physical phenomena associated with the presence of the plasma in the computational analysis of the flow fields about these vehicles. Physical models for the plasma phenomena are investigated using a state of the art, Direct Simulation Monte Carlo (DSMC) code. Models for collisions between charged particles, plasma chemistry, and the self-induced electric field that currently exist in the literature are implemented. Using these baseline models, steady state flow field solutions are computed for the FIRE II reentry vehicle at two different trajectory points. The accuracy of each baseline plasma model is assessed in a systematic fashion, using one flight condition of the FIRE II vehicle as the test case. Experimental collision cross section data is implemented to model collisions of electrons with neutral particles. Theoretical and experimental reaction cross section data are implemented to model chemical reactions that involve electron impact, and an associative ionization reaction. One-dimensional Particle-In-Cell (PIC) routines are developed and coupled to the DSMC code, to assess the limitations of the baseline electric field model. Interpretation of the DSMC-PIC results leads to the development of an improved electric field model that does not require the substantial computational resources needed to obtain DSMC-PIC solutions.

Farbar, Erin D.

168

Gravitational field of a spinning sigma-model cosmic string  

SciTech Connect

We study the effect of internal space rotation on the gravitational properties of infinite straight and stationary cosmic strings. From the approximate solution of Einstein equations for the spinning Q-lump string, we obtain long-range gravitational acceleration resembling that of a rotating massive cylindrical shell. We also compute the angular velocity of the inertial frame dragging and the angle of light deflection by the Q-lump string. Matter accretion onto spinning strings can play a role in galaxy formation when the angular velocity times the string width is comparable to the speed of light.

Simanek, E. [Department of Physics, University of California, Riverside, California 92521 (United States)

2008-08-15

169

Weak-Field Magnetoresistance in p-Type Lead Telluride at Room Temperature and 77°K  

Microsoft Academic Search

The weak-field magnetoresistance of six single crystals of p-type PbTe was measured at room temperature and 77°K. The general predictions of weak-field theory were precisely obeyed in the range of magnetic-field intensities for which the theory should apply. In stronger fields at 77°K, deviations from weak-field behavior of three types were observed which agree with the Gold-Roth theory of magnetoresistance

Robert S. Allgaier

1960-01-01

170

Nonlinear gravitational-field equations in the special theory of relativity  

NASA Astrophysics Data System (ADS)

A method is proposed for the consideration of field nonlinearity which is based on the fact that the structure of the Lagrangian expressed through the potential of the field and its derivatives is not prescribed beforehand but is derived as a result of the solution in phase space of the self-action equation whose unknown is the field Lagrangian. It is shown that this equation has a solution and that the Lagrangian is nonpolynomial with respect to the field potential. The gravitational-field equations which follow from the variational principle are found to be structurally similar to the general-relativity equations and coincide with them in the linear approximation. Equations of other fields with allowance for gravitation are constructed along with the equation of motion of a test particle in a gravitational field.

Razgovorov, N. N.

1983-08-01

171

On the gravitational potential and field anomalies due to thin mass layers  

NASA Technical Reports Server (NTRS)

The gravitational potential and field anomalies for thin mass layers are derived using the technique of matched asymptotic expansions. An inner solution is obtained using an expansion in powers of the thickness and it is shown that the outer solution is given by a surface distribution of mass sources and dipoles. Coefficients are evaluated by matching the inner expansion of the outer solution with the outer expansion of the inner solution. The leading term in the inner expansion for the normal gravitational field gives the Bouguer formula. The leading term in the expansion for the gravitational potential gives an expression for the perturbation to the geoid. The predictions given by this term are compared with measurements by satellite altimetry. The second-order terms in the expansion for the gravitational field are required to predict the gravity anomaly at a continental margin. The results are compared with observations.

Ockendon, J. R.; Turcotte, D. L.

1977-01-01

172

Phase conjugation of nonclassical fields and weak optical signals  

NASA Astrophysics Data System (ADS)

This thesis describes work that has been published as articles in the scientific literature, as well as work that is in preparation for submission for publication. Chapter 1 is a general introduction to optical phase conjugation at the level of a researcher new to the field. In the two theoretical chapters, Chapters 2 and 3, I investigate optical phase conjugation via the technique of four-wave mixing of signal fields that can be in nonclassical states, the quadrature-squeezed state and the amplitude-squeezed state. In Chapter 4, I describe a high-reflectivity (up to 670%) wide-bandwidth (up to 230 MHz) phase-conjugate mirror (PCM) that I have built in the laboratory. The PCM bandwidths are ten times greater than are theoretical predictions, and the reflectivity-bandwidth product of the PCM is over an order of magnitude improvement over those achieved by other continuous-wave PCMs. In Chapter 5, I present measurements of phase conjugation and aberration correction of 250 femtowatt continuous- wave optical signals with a signal-to-noise ratio of 18:1. These measurements show that our PCM can perform phase conjugation with near-unity reflectivity of signals with very weak power levels (i.e., 250 fW with a signal- to-noise ratio of 18:1). Clearly, the potential for phase conjugating weak optical signals is relevant for potential applications in optical communications and in optical signal processing. In addition, the results are in qualitative agreement with theory and show that the conditions under which the minimum signal can be phase conjugated are similar to the conditions under which the PCM can be operated near its quantum-noise limit. In Chapter 6, I describe the results of a comprehensive investigation of the quantum-noise properties of our PCM. I discuss the the quantum-noise properties of the PCM as functions of several experimental parameters and compare the measurements of the PCM noise figure with the noise figure predicted for an ideal quantum-noise-limited PCM. The experimental results are also in qualitative agreement with the results of quantum theory. In Chapter 7, I discuss my conclusions and propose ideas for future research.

Lanzerotti, Mary Yvonne

1997-06-01

173

Electromagnetic Waves in a Uniform Gravitational Field and Planck's Postulate  

ERIC Educational Resources Information Center

The gravitational redshift forms the central part of the majority of the classical tests for the general theory of relativity. It could be successfully checked even in laboratory experiments on the earth's surface. The standard derivation of this effect is based on the distortion of the local structure of spacetime induced by large masses. The…

Acedo, Luis; Tung, Michael M.

2012-01-01

174

Measuring the Geometry of the Universe from Weak Gravitational Lensing behind Galaxy Groups in the HST COSMOS Survey  

NASA Astrophysics Data System (ADS)

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component ? X at greater than 99% confidence for an equation-of-state parameter -2.5 <= w <= -0.1. For the case w = -1, we find a value for the cosmological constant density parameter ?? = 0.85+0.044 -0.19 (68% CL) and detect cosmic acceleration (q 0 < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA Inc. under the NASA contract NAS 5-26555; the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the European Southern Observatory under the Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

Taylor, James E.; Massey, Richard J.; Leauthaud, Alexie; George, Matthew R.; Rhodes, Jason; Kitching, Thomas D.; Capak, Peter; Ellis, Richard; Finoguenov, Alexis; Ilbert, Olivier; Jullo, Eric; Kneib, Jean-Paul; Koekemoer, Anton M.; Scoville, Nick; Tanaka, Masayuki

2012-04-01

175

Nonlinear equations of the gravitational field in the special theory of relativity  

NASA Astrophysics Data System (ADS)

It is proposed that the nonlinearity of the field be taken into account with the help of a method which essentially consists of the fact that the structure of the Lagrangian, expressed in terms of the potential of the field and its derivatives, is not known a priori, but is obtained from a solution of the self-action equation in phase space in which the Lagrangian is the unknown. This equation has a solution and the Lagrangian turns out to be a nonpolynomial function with respect to the field potential. The gravitational field equations following from the variational principle have a similar structure to the equations of general relativity and coincide with them in the linear approximation. The equations of other fields taking into account gravitation, as well as the equation of motion of a test particle in a gravitational field, are constructed.

Razgovorov, N. N.

1983-08-01

176

Deep HST imaging of distant weak radio and field galaxies  

NASA Technical Reports Server (NTRS)

We present deep Hubble Space Telescope (HST) Wide-Field Camera (WFC) V- and I-band images of three distant weak radio galaxies with z = 0.311-2.390 and seven field galaxies with z = 0.131-0.58. The images were deconvolved with both the Lucy and multiresolution CLEAN methods, which yield a restoring Full Width at Half Maximum (FWHM) of less than or equal to 0.2 sec, (nearly) preserve photons and signal-to-noise ratio at low spatial frequencies, and produce consistent light profiles down to our 2 sigma surface brightness sensitivity limit of V approximately 27.2 and I approximately 25.9 mag/sq arcsec. Multi-component image modeling was used to provide deconvolution-independent estimates of structural parameters for symmetric galaxies. We present 12-band (m(sub 2750) UBVRIgriJHK) photometry for a subset of the galaxies and bootstrap the unknown FOC/48 zero point at 2750 A in three independent ways (yielding m(sub 2750) = 21.34 +/- 0.09 mag for 1.0 e(-)/s). Two radio galaxies with z = 0.311 and 0.528, as well as one field galaxy with z = 0.58, have the colors and spectra of early-type galaxies, and a(exp 1/4)-like light profiles in the HST images. The two at z greater than 0.5 have little or no color gradients in V - I and are likely giant ellipticals, while the z = 0.311 radio galaxy has a dim exponential disk and is likely an S0. Six of the seven field galaxies have light profiles that indicate (small) inner bulges following a(exp 1/4) laws and outer exponential disks, both with little or no color gradients. These are (early-type) spiral galaxies with z = 0.131-0.528. About half have faint companions or bars. One shows lumpy structure, possibly a merger. The compact narrow-line galaxy 53W002 at z = 2.390 has less than or = 30% +/- 10% of its HST V and I flux in the central kiloparsec (due to its weak Active Galactic Nucleus (AGN)). Most of its light (V approximately equal to 23.3) occurs in a symmetric envelope with a regular a(exp 1/4)-like profile of effective radius a approximately equal to 1.1 sec (approximately equal to 12 kpc for H(sub 0) = 50, q(sub 0) = 0.1. Its (HST) V - I color varies at most from approximately 0.3 mag at a approximately equal to 0.2 sec to approximately 1.2 mag at a approximately greater than 0.4 sec, and possibly to approximately greater than 2.2 mag at a approximately greater than 1.2 sec. Together with its I - K color (approximately equal to 2.5 mag for a approximately greater than 1.0 sec-2.0 sec), this is consistent with an aging stellar population approximately 0.3-0.5 Gyr old in the galaxy center (a approx. less than 2 kpc radius), and possibly approximately 0.5-1.0 Gyr old at a approximately greater than 10 kpc radius. While its outer part may thus have started to collapse at z = 2.5-4, its inner part still is aligned with its redshifted Ly(alpha) cloud and its radio axis, possibly caused by star formation associated with the radio jet, or by reflection from its AGN cone.

Windhorst, R. A.; Gordon, J. M.; Pascarelle, S. M.; Schmidtke, P. C.; Keel, W. C.; Burkey, J. M.; Dunlop, J. S.

1994-01-01

177

A spherically symmetric electro-vacuum solution of the Poincaré gauge field theory of gravitation  

Microsoft Academic Search

We consider the Poincaré gauge field theory of gravitation with a purely quadratic lagrangian in the case coupled with the electromagnetic field. We solve the field equations to obtain a static spherically symmetric electro-vacuum solution. This solution reduces to Baekler's vacuum solution in the limit beta --> 0, and the metric in this solution reduces to the Reissner-Nordström metric in

Chul H. Lee

1983-01-01

178

Probing strong-field scalar-tensor gravity with gravitational wave asteroseismology  

SciTech Connect

We present an alternative way of tracing the existence of a scalar field based on the analysis of the gravitational wave spectrum of a vibrating neutron star. Scalar-tensor theories in strong-field gravity can potentially introduce much greater differences in the parameters of a neutron star than the uncertainties introduced by the various equations of state. The detection of gravitational waves from neutron stars can set constraints on the existence and the strength of scalar fields. We show that the oscillation spectrum is dramatically affected by the presence of a scalar field, and can provide unique confirmation of its existence.

Sotani, Hajime; Kokkotas, Kostas D. [Research Institute for Science and Engineering, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan); Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Center for Gravitational Wave Physics, 104 Davey Laboratory, University Park, Pennsylvania 16802 (United States)

2004-10-15

179

Biological effects due to weak magnetic fields on plants  

NASA Astrophysics Data System (ADS)

In the evolution process, living organisms have experienced the action of the Earth's magnetic field (MF) that is a natural component of our environment. It is known that a galactic MF induction does not exceed 0.1 nT, since investigations of weak magnetic field (WMF) effects on biological systems have attracted attention of biologists due to planning long-term space flights to other planets where the magnetizing force is near 10-5 Oe. However, the role of WMF and its influence on organisms' functioning are still insufficiently investigated. A large number of experiments with seedlings of different plant species placed in WMF has found that the growth of their primary roots is inhibited during the early terms of germination in comparison with control. The proliferation activity and cell reproduction are reduced in meristem of plant roots under WMF application. The prolongation of total cell reproductive cycle is registered due to the expansion of G phase in1 different plant species as well as of G phase in flax and lentil roots along with2 relative stability of time parameters of other phases of cell cycle. In plant cells exposed to WMF, the decrease in functional activity of genome at early prereplicate period is shown. WMF causes the intensification in the processes of proteins' synthesis and break-up in plant roots. Qualitative and quantitative changes in protein spectrum in growing and differentiated cells of plant roots exposed to WMF are revealed. At ultrastructural level, there are observed such ultrastructural peculiarities as changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells of pea roots exposed to WMF. Mitochondria are the most sensitive organelle to WMF application: their size and relative volume in cells increase, matrix is electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to WMF show the Ca2 + oversaturation both in all organelles and in a hyaloplasm of the cells unlike the control ones. The data presented suggest that prolonged plant exposures to WMF may cause different biological effects at the cellular, tissue and organ level. They may be functionally related to systems that regulate plant metabolism including the intracellular Ca 2 + homeostasis. The understanding of the fundamental mechanisms and sites of interactions between WMF and biological systems are complex and still deserve strong efforts, particular addressed to basic principles of coupling between field energy and biomolecules.

Belyavskaya, N.

180

Effect of a uniform sea-level change on the earth's rotation and gravitational field  

Microsoft Academic Search

Global water redistriburtion between the oceans, atmosphere and continents causes changes in the earth's rotation and gravitational field. To conserve water mass, the effect of the small uniform change in sea-level must be considered. Explicit formulas are provided for these sea-level corrections to the gravitational Stokes coefficients, polar motion and length of day. In two recent publications, this sea-level correction

B. Fong Chao; William P. O'Connor

1988-01-01

181

Dynamics of self-gravitating shells driven by radiation pressure from the field stars  

NASA Astrophysics Data System (ADS)

It is shown that self-gravitating shells can be accelerated only when the energy density of the stellar radiation exceeds the critical value of 3.6 x 10 to the -13th J/cu m. It is thus concluded that the acceleration mechanism for self-gravitating shells connected with radiation pressure from the field stars is not effective for systems with Galaxy parameters.

Pas'ko, V. P.; Silich, S. A.

1988-04-01

182

Generalized crossing states in the interacting case: The uniform gravitational field  

SciTech Connect

We reconsider Baute et al.'s free crossing states [Phys. Rev. A 61, 022118 (2000)] and show that if we require a generalization in the interacting case that goes in complete parallel with the free-particle case, then this generalized crossing state cannot be arbitrary but is determined by the null space of the particle's quantum time-of-arrival operator. Nonetheless, the free crossing states appear as the leading term in the asymptotic expansion of our generalized crossing state in the limit of large momentum. We then examine the quantum time-of-arrival problem of a spinless particle in a uniform gravitational field. Mass-dependent time-of-arrival probability distributions emerge, signifying quantum departures from the weak equivalence principle. However, in the classical limit of large mass and vanishing uncertainty in position, the mass dependence of the quantum time-of-arrival distribution becomes exponentially small and the mean quantum time of arrival reduces to the classical time of arrival.

Villanueva, Anthony D.; Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman Quezon City, 1101 Philippines (Philippines)

2010-11-15

183

Effects of a helical magnetic field on the stability of a gravitating cylinder. II  

NASA Astrophysics Data System (ADS)

The generation of axisymmetric perturbations by the effect of an external magnetic field on an infinite gravitating cylinder is studied, and it is found that a destabilization of the system occurs, due to the external field, at very high values of field pitch. The calculations of this study extend the recent work of Karnik and Talwar (1981) to the case where the form of the external, twisted magnetic field is in agreement with boundary conditions requiring magnetic field continuity at the boundary.

Karnik, A. M.

1982-03-01

184

Understanding possible electromagnetic counterparts to loud gravitational wave events: Binary black hole effects on electromagnetic fields  

SciTech Connect

In addition to producing loud gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as an enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.

Palenzuela, Carlos [Canadian Institute for Theoretical Astrophysics (CITA), Toronto, Ontario M5S 3H8 (Canada); Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Berlin, D-14476 Golm (Germany); Lehner, Luis [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Canadian Institute For Advanced Research (CIFAR), Cosmology and Gravity Program (Canada); Yoshida, Shin [Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo, Meguro, Tokyo 153-8902 (Japan)

2010-04-15

185

Extremely low frequency, weak electric fields affect schedule-controlled behaviour of monkeys  

Microsoft Academic Search

THE effect of weak electric fields on behaviour of orgasnims has potentially important implications for basic neurophysiology and evaluation of environmental hazards (chronic exposure to weak 60-Hz electric fields has become a way of life). We have demonstrated1 that weak (approximately 7 V m-1 p-p), extremely low frequency (7 Hz) electric fields could modify a lever-press response in monkeys. We

R. Gavalas-Medici; S. R. Day-Magdaleno

1976-01-01

186

Rhea's Gravitational Field and Interior Structure Inferred from Archival Data Files of the 2005 Cassini Flyby  

Microsoft Academic Search

There are three published gravitational fields for Rhea, and they all differ significantly. We conclude that this difference is caused by systematic error in the Cassini radio Doppler data used in the analysis. All three published fields fit the systematically corrupted data equally well. However, by restricting the data in the fit to a shorter interval surrounding the closest approach

John D. Anderson; G. Schubert

2008-01-01

187

Gravitational field and radiation in general relativity and cosmology  

SciTech Connect

Properties of specific particle-like and cosmological solutions of general relativity are studied. In the first part, solution for the NUT geodesics was studied to help understand the physical interpretation of the NUT parameter. It is shown that the properties of the NUT geodesics are similar to the properties of the trajectories of a charged particle in a potential created by a magnetic monopole. The properties of the NUT geodesics are summarized. The second part of this dissertation is the study of an inhomogeneous generalization of the Bianchi I cosmological solution which contains gravitational waves. This model considers the interaction of the initial inhomogeneities with the evolution of the background geometry, electromagnetic radiation, gravity waves, and matter. In this model the initial inhomogeneities evolve at late times into gravitational waves, which are propagating through a smooth Bianchi I background. As the wave evolves it interacts with the global shear and different forms of energy. Around the origin the propagation of the wave is governed by the shear, where as, at later times the influence of the shear decreases and the radiation density dominates the solution.

Yaghoubi-Shahir, B.

1987-01-01

188

Short guide to direct gravitational field modelling with Hotine's equations  

NASA Astrophysics Data System (ADS)

This paper presents a unified approach to the least squares spherical harmonic analysis of the acceleration vector and Eötvös tensor (gravitational gradients) in an arbitrary orientation. The Jacobian matrices are based on Hotine's equations that hold in the Earth-fixed Cartesian frame and do not need any derivatives of the associated Legendre functions. The implementation was confirmed through closed-loop tests in which the simulated input is inverted in the least square sense using the rotated Hotine's equations. The precision achieved is at the level of rounding error with RMS about 10^{-12}{-}10^{-14} m in terms of the height anomaly. The second validation of the linear model is done with help from the standard ellipsoidal correction for the gravity disturbance that can be computed with an analytic expression as well as with the rotated equations. Although the analytic expression for this correction is only of a limited accuracy at the submillimeter level, it was used for an independent validation. Finally, the equivalent of the ellipsoidal correction, called the effect of the normal, has been numerically obtained also for other gravitational functionals and some of their combinations. Most of the numerical investigations are provided up to spherical harmonic degree 70, with degree 80 for the computation time comparison using real GRACE data. The relevant Matlab source codes for the design matrices are provided.

Sebera, Josef; Wagner, Carl A.; Bezd?k, Aleš; Kloko?ník, Jaroslav

2013-03-01

189

Field of a charged particle in Brans-Dicke theory of gravitation  

NASA Astrophysics Data System (ADS)

Field equations in the Brans-Dicke scalar-tensor theory of gravitation are obtained for a static charged point mass with the aid of a spherically symmetric, conformally flat metric. A closed-form exact solution of the field equations is presented, and may be considered as describing the field due to a charged mass point at the origin surrounded by a scalar-tensor field in a conformally flat space.

Reddy, D. R. K.; Rao, V. U. M.

1981-08-01

190

Responsiveness of Elasmobranch Fishes to Weak Electric Fields.  

National Technical Information Service (NTIS)

Determination of the threshold field strength that produces effects in cell membranes of living organisms exposed to electromagnetic (EM) fields is of prime importance in the establishment of safe levels of exposure to EM fields. For most organisms the tr...

H. M. Fishman

1987-01-01

191

Magnetic field of a long wire in a static background gravitational field: A classroom exercise in general relativity  

SciTech Connect

A general expression is found for the magnetic field generated by a long rectilinear current placed in a static background gravitational field. Then it is applied to the case of uniform, Schwarzschild, general Reissner--Nordstrom and ''charge-equal-to-mass'' Reissner--Nordstrom background metrics. All the calculations are very simple and can easily be done in the classroom.

De Fatima A. Da Silva, M.; Da Silveira Filho, O. T.; Souza, J. A.

1989-08-01

192

Physical interpretation of cylindrically symmetric static gravitational fields  

NASA Astrophysics Data System (ADS)

An explicit relationship is determined between the interior properties of a static cylindrical matter distribution and the metric of the exterior space-time according to Einstein gravity for space-time dimensionality larger than or equal to four. This is achieved through use of a coordinate system isotropic in the transverse coordinates. As a corollary, similar results are obtained for a spherical matter distribution in Brans-Dicke gravity for dimensions larger than or equal to three. The approach used here leads to consistency conditions for those parameters characterizing the exterior metric. It is shown that these conditions are equivalent to the requirement of hydrostatic equilibrium of the matter distribution (generalized Oppenheimer-Volkoff equations). These conditions lead to a consistent Newtonian limit where pressures and the gravitational constant go to zero at the same rate.

Colding, J.; Nielsen, N. K.; Verbin, Y.

1997-09-01

193

Influence of the gravitational field on the quantum-nondemolition measurement of atomic momentum in the dispersive Jaynes Cummings model  

NASA Astrophysics Data System (ADS)

We present a theoretical scheme based on an su(2) dynamical algebraic structure to investigate the influence of a homogeneous gravitational field on the quantum-nondemolition measurement of atomic momentum in the dispersive Jaynes-Cummings model. In the dispersive Jaynes-Cummings model, when detuning is large and the atomic motion is in a propagating light wave, we consider a two-level atom interacting with the quantized cavity field in the presence of a homogeneous gravitational field. We derive an effective Hamiltonian describing the dispersive atom-field interaction in the presence of the gravitational field. We investigate the influence of the gravitational field on both the momentum filter and momentum distribution. Particularly, we find that the gravitational field decreases both the tooth spacing of momentum and the tooth width of momentum.

Mohammadi, M.; Naderi, M. H.; Soltanolkotabi, M.

2006-09-01

194

Multipole expansions of the general-relativistic gravitational field of the external universe  

SciTech Connect

The generic, vacuum, dynamical gravitational field in the vicinity of a freely falling observer is expanded in powers of distance away from the observer's spatial origin (i.e., in distance away from his timelike-geodesic world line). The expansion is determined fully, aside from coordinate freedom, by two families of time-dependent multipole moments: ''electric-type moments'' and ''magnetic-type moments'': which characterize the gravitational influence of the external universe. These ''external multipole moments'' are defined covariantly in terms of the Riemann curvature tensor and its spatial derivatives, evaluated on the observer's world line. The properties of these moments are discussed, and an analysis is given of the structure of the gravitational field's multipole expansion for the special case of de Donder coordinates. In de Donder coordinates the expansion involves only integral powers of distance from the origin; no logarithmic terms occur in this multiparameter expansion.

Zhang, X.

1986-08-15

195

Direct electro - gravitational couplings and the behaviour of primordial large-scale magnetic fields  

Microsoft Academic Search

A comprehensive approach is suggested for describing the origin and evolution of large-scale magnetic fields. Vorticity-dependent fluctuations acting on a primordial charged plasma account for field generation, and the properties of gauge-invariant (but conformally non-invariant) couplings of electromagnetic and gravitational fields in a FRW background are applied in order to supply a source-independent, gravity-driven mechanism of conductance induction in the

M. Novello; L. A. R. Oliveira; J. M. Salim

1996-01-01

196

General solutions for the field of a charged particle in Brans-Dicke theory of gravitation  

NASA Astrophysics Data System (ADS)

The field equations in the Brans-Dicke (BD) scalar-tensor theory of gravitation are solved for a spherically symmetric metric. The solutions generalise earlier conformally flat results and may all be considered as describing the field of a charged mass point surrounded by a scalar-tensor field. The conformally flat solutions are shown to be not physically meaningful for 'standard' BD theory with 2(omega) + 3 greater than zero.

van den Bergh, N.

1983-07-01

197

Gravitational lenses  

SciTech Connect

For several years astronomers have devoted considerable effort to finding and studying a class of celestial phenomena whose very existence depends on rare cosmic accidents. These are gravitational-lens events, which occur when two or more objects at different distances from the earth happen to lie along the same line of sight and so coincide in the sky. The radiation from the more distant object, typically a quasar, is bent by the gravitational field of the foreground object. The bending creates a cosmic mirage: distorted or multiple images of the background object. Such phenomena may reveal many otherwise undetectable features of the image source, of the foreground object and of the space lying between them. Such observations could help to resolve several fundamental questions in cosmology. In the past decade theoretical and observational research on gravitational lenses has grown rapidly and steadily. At this writing at least 17 candidate lens systems have been discussed in the literature. Of the 17 lens candidates reported so far in professional literature, only five are considered to have been reliably established by subsequent observations. Another three are generally regarded as weak or speculative cases with less than 50 percent chance of actually being lens systems. In the remaining nine cases the evidence is mixed or is sparse enough so that the final judgment could swing either way. As might be concluded, little of the scientific promise of gravitational lenses has yet been realized. The work has not yielded a clear value for the proportionality constant or any of the other fundamental cosmological parameter. 7 figs.

Turner, E.L.

1988-07-01

198

Gravitational field of the quantized electromagnetic plane wave  

Microsoft Academic Search

The quantum and classical descriptions of an electro-magnetic field are connected by the correspondence principle. We consider the electromagntic field as a source for gravity and compare the metrics due to a classical and quantized electromagnetic field. The quantization of the source demands the quantization of gravity. We also show that (i) the conformal degree of the freedom isnot an

T. Padmanabhan

1987-01-01

199

Search for the Effects of Inhomogenous Electric Fields on Gravitation  

Microsoft Academic Search

The effect of inhomogenous electric fields on the weight of test masses is being investigated. Inhomogenous field is produced by applying dc bias between a horizontal flat electrode and the tip of a conical bottom electrode of an electrostatic capacitor. The equipotentials and the electric field distribution has been numerically calculated using ``MATLAB'' software. The test masses are gold-coated metal

Ming Yin; Michael Bleiweiss; Ruslan Prozorov; Timir Datta

2002-01-01

200

Heat Transfer Control in Quiescent Air with Thermal Gradient by Magnetizing Force Under both Gravitational and Nongravitational Fields  

Microsoft Academic Search

Two-dimensional numerical computations were carried out to clarify the influence of magnetizing force on quiescent air with thermal gradient in a vertical cylindrical container under both gravitational and nongravitational fields. Several sizes and axial positions of a circular electric coil were tested so that the magnetizing force depended on the magnetic gradient. Under both gravitational and nongravitational fields, the convection

Masato Akamatsu; Mitsuo Higano; Yoshio Takahashi; Hiroyuki Ozoe

2005-01-01

201

Unsymmetrical magnetization switching in Fe/Si(001) single crystalline film induced by weak bias field  

NASA Astrophysics Data System (ADS)

The weak bias field applied on perpendicular direction of the external field provides an excellent opportunity to investigate the in-plane magnetization reversal process of Fe/Si(001) film. In this work, we present the magneto-optical Kerr effect test of Fe single crystal film grown on Si(001) substrate with ultrathin p(2 × 2) iron silicide as buffer layer. Owing to the weak bias field, both 180° and 90° domain wall displacements were observed in one hysteresis loop between the easy axis and hard axis of iron film. Furthermore, both the 180° and 90° domain wall pinning energies can be derived from one hysteresis loop with weak bias field.

Ye, Jun; He, Wei; Wu, Qiong; Hu, Bo; Tang, Jin; Zhang, Xiang-Qun; Chen, Zi-Yu; Cheng, Zhao-Hua

2014-03-01

202

Decomposition Covariante et Energie du Champ Gravitationnel (Covariant Decomposition and Energy of the Gravitational Field).  

National Technical Information Service (NTIS)

The covariant decomposition of a symmetric tensor leads, for systems with a moment of time symmetry, to a transparent derivation of the result that the energy of the gravitational field is positive definite. More precisely, we show that the energy, as a f...

S. Deser

1967-01-01

203

Where Else Is Null the Gravitational Field between Two Massive Spheres?  

ERIC Educational Resources Information Center

To find the point between two massive spherical bodies at which their gravitational fields cancel is an apparently simple problem usually found in introductory physics textbooks. However, by noting that such a point does not exist when the distance between the spheres is small and one of the masses is much smaller than the other--e.g., between the…

Lima, F. M. S.

2009-01-01

204

Anomalies of an external and internal gravitational field of upper Earth layers in square law approximation  

Microsoft Academic Search

The explicit form for the quadratic contribution to the gravitational field from the dipole distributed anomalous masses is found. The anomalous masses are represented in the form of layers of variable height, arranged relative to the reference ellipsoid. The solution is reduced to the mathematical problem of finding an expression for the coefficients of expansion in terms of spherical harmonics

L. P. Nasonova; N. A. Chujkova

2007-01-01

205

Dynamics of multibody systems in planar motion in a central gravitational field  

Microsoft Academic Search

Multibody systems in planar motion are modelled as two or more rigid components that are connected and can move relative to each other. The dynamics of such multibody systems in planar motion in a central gravitational force field is analysed. The equations of motion of the system include the equations for the orbital motion of the bodies, the orientation (attitude)

Amit K. Sanyal; Anthony Bloch; N. Harris McClamroch

2004-01-01

206

Zonal Harmonics of the Earth's Gravitational Field and the Basic Hypothesis of Geodesy  

Microsoft Academic Search

The basic hypothesis of geodesy as stated by Vening Meinesz and Heiskanen calls for an extremely smooth gravitational field for the earth as a whole, apart from local irregu- larities. From satellite measurements of zonal harmonics of orders 2, 3, and 4 it is shown that the actual roughness is about an order of magnitude greater than that demanded by

John A. O'Keefe

1959-01-01

207

Variations of the gravitational field as a motive power for rhythmics of biochemical processes  

NASA Astrophysics Data System (ADS)

Variations of the gravitational field affected by the Sun and the Moon while the Earth's moving along the orbit seem to be a powerful source of many rhythmical processes typical of biochemical processes. Studies carried out in AARI revealed the obvious relationships between the dynamics of some biochemical reactions and ?D- function describing the regular variations of the gravitational field under combined influence of the Sun and the Moon. The following of them are examined as examples: the rate of the unithiol oxidation in vitro, concentration of the thiol compounds in human urine, some hematological indicators (rate of the erythrocytes sedimentation, hemoglobin content). Compatibility of run of the biochemical indicators and ?D-function is indicative of essential influence of the regular variations of the gravitational field on rhythmics of the biochemical processes. As this takes place, the solar activity acts like to the instability factor. Balance of the solar activity effects and the varying gravitational field effect alter in time depending on location in the solar activity cycle.

Troshichev, O. A.; Gorshkov, E. S.; Shapovalov, S. N.; Sokolovskii, V. V.; Ivanov, V. V.; Vorobeitchikov, V. M.

2004-01-01

208

Illustrating Some Principles of Separation Science through Gravitational Field-Flow Fractionation  

ERIC Educational Resources Information Center

Particle separation is an important but often neglected topic in undergraduate curricula. This article discusses how the method of gravitational field-flow fractionation (GrFFF) can be used to illustrate many principles of separation science and some fundamental concepts of physical chemistry. GrFFF separates particles during their elution through…

Beckett, Ronald; Sharma, Reshmi; Andric, Goja; Chantiwas, Rattikan; Jakmunee, Jaroon; Grudpan, Kate

2007-01-01

209

Reply to 'Comment on 'Primordial magnetic seed field amplification by gravitational waves''  

SciTech Connect

Here we respond to the comment by Tsagas on our earlier paper. We show that the results in that comment are flawed and cannot be used for drawing conclusions about the nature of magnetic field amplification by gravitational waves and give further support that the results of our earlier paper are correct.

Betschart, Gerold [Racah Institute of Physics, Hebrew University of Jerusalem, Givat Ram, 91904 Jerusalem (Israel); Zunckel, Caroline [Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Dunsby, Peter K S [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa); Marklund, Mattias [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2007-04-15

210

Variations of the gravitational field as a motive power for rhythmics of biochemical processes.  

PubMed

Variations of the gravitational field affected by the Sun and the Moon while the Earth's moving along the orbit seem to be a powerful source of many rhythmical processes typical of biochemical processes. Studies carried out in AARI revealed the obvious relationships between the dynamics of some biochemical reactions and lambda(D)-function describing the regular variations of the gravitational field under combined influence of the Sun and the Moon. The following of them are examined as examples: the rate of the unithiol oxidation in vitro, concentration of the thiol compounds in human urine, some hematological indicators (rate of the erythrocytes sedimentation, hemoglobin content). Compatibility of run of the biochemical indicators and lambda(D)-function is indicative of essential influence of the regular variations of the gravitational field on rhythmics of the biochemical processes. As this takes place, the solar activity acts like to the instability factor. Balance of the solar activity effects and the varying gravitational field effect alter in time depending on location in the solar activity cycle. PMID:15880902

Troshichev, O A; Gorshkov, E S; Shapovalov, S N; Sokolovskii, V V; Ivanov, V V; Vorobeitchikov, V M

2004-01-01

211

Magnetohydrodynamic channel flows with weak transverse magnetic fields.  

PubMed

Magnetohydrodynamic flow of an incompressible fluid through a plane channel with slowly varying walls and a magnetic field applied transverse to the channel is investigated in the high Reynolds number limit. It is found that the magnetic field can first influence the hydrodynamic flow when the Hartmann number reaches a sufficiently large value. The magnetic field is found to suppress the steady and unsteady viscous flow near the channel walls unless the wall shapes become large. PMID:24936018

Rothmayer, A P

2014-07-28

212

Existence of two-solar-mass neutron star constrains gravitational constant GN at strong field  

NASA Astrophysics Data System (ADS)

In general relativity, there is a maximum mass allowed for neutron stars that, if exceeded, entails collapse into a black hole. Its precise value depends on details of the nuclear matter equation of state, a subject where much progress has been accomplished thanks to low energy effective theories. The discovery of a two-solar-mass neutron star, near that maximum mass, when analyzed with modern equations of state, implies that Newton's gravitational constant in the star cannot exceed its value on Earth by more than 12% at the 95% confidence level. This significantly extends the gravitational field intensity at which the constant has been constrained at the 10% level.

Dobado, Antonio; Llanes-Estrada, Felipe J.; Oller, Jose Antonio

2012-01-01

213

Magnetic field decay in neutron stars: from soft gamma repeaters to 'weak-field magnetars'  

NASA Astrophysics Data System (ADS)

The recent discovery of the 'weak-field, old magnetar' soft gamma repeater (SGR) J0418+5729, whose dipole magnetic field, Bdip, is less than 7.5 × 1012 G, has raised perplexing questions: how can the neutron star produce SGR-like bursts with such a low magnetic field? What powers the observed X-ray emission when neither the rotational energy nor the magnetic dipole energy is sufficient? These observations, which suggest either a much larger energy reservoir or a much younger true age (or both), have renewed the interest in the evolutionary sequence of magnetars. We examine here a phenomenological model for the magnetic field decay: ? and compare its predictions with the observed period, P, the period derivative, ?, and the X-ray luminosity, LX, of magnetar candidates. We find a strong evidence for a dipole field decay on a time-scale of ˜103 yr for the strongest (Bdip˜ 1015 G) field objects, with a decay index within the range 1 ?? < 2 and more likely within 1.5 ??? 1.8. The decaying field implies a younger age than what is implied by ?. Surprisingly, even with the younger age, the energy released in the dipole field decay is insufficient to power the X-ray emission, suggesting the existence of a stronger internal field, Bint. Examining several models for the internal magnetic field decay, we find that it must have a very large (? 1016 G) initial value. Our findings suggest two clear distinct evolutionary tracks - the SGR/anomalous X-ray pulsar branch and the transient branch, with a possible third branch involving high-field radio pulsars that age into low-luminosity X-ray dim isolated neutron stars.

Dall'Osso, S.; Granot, J.; Piran, T.

2012-06-01

214

Dynamics of plasma bunch in weakly inhomogeneous magnetic field  

Microsoft Academic Search

Summary form only given. The initially confined plasma bunch in vacuum in the absence of magnetic field unlimitedly expands and cools with time. It occurs that a certain configuration of external magnetic field allows the bunch to accelerate and compress as a whole. Using the exact solution of a system of two 3D Vlasov kinetic equations with a self-consistent electric

D. S. Dorozhkina; V. E. Semenov

1999-01-01

215

Temporal variations of the earth's gravitational field from satellite laser ranging to LAGEOS  

NASA Technical Reports Server (NTRS)

Monthly values of the J2 and J3 earth gravitational coefficients were estimated using LAGEOS satellite laser ranging data collected between 1980 and 1989. Monthly variations in gravitational coefficients caused by atmospheric mass redistribution were calculated using measurements of variations in surface atmospheric pressure. Results for correlation studies of the two time series are presented. The LAGEOS and atmospheric J2 time series agree well and it appears that variations in J2 can be attributed to the redistribution of atmospheric mass. Atmospheric and LAGEOS estimates for J3 show poorer agreement, J3 estimates appear to be very sensitive to unmodeled forces acting on the satellite. Results indicate that the LAGEOS data can be used to detect small variations in the gravitational field.

Nerem, R. S.; Chao, B. F.; Au, A. Y.; Chan, J. C.; Klosko, S. M.; Pavlis, N. K.; Williamson, R. G.

1993-01-01

216

Quantum fields on manifolds: PCT and gravitationally induced thermal states  

Microsoft Academic Search

We formulate an axiomatic scheme, designed to provide a framework for a general, rigorous theory of relativistic quantum fields on a class of manifolds, that includes Kruskal's extension of Schwarzchild space-time, as well as Minkowski space-time. The scheme is an adaptation of Wightman's to this class of manifolds. We infer from it that, given an arbitrary field (in general, interacting)

G SEWELL

1982-01-01

217

Gravitational research. Gravitational waves  

NASA Astrophysics Data System (ADS)

Gravitational wave research is reviewed. Gravitational theory, relativity theory, experiments in general relativity, sources of gravitational waves, the Rome gravitational experiment, quantic limits of gravitational waves measurements and how to avoid those limits are discussed.

Amaldi, E.; Pizzella, G.

1985-04-01

218

Streamer Initiation from Hydrometeors in Weak Thundercloud Electric Fields  

NASA Astrophysics Data System (ADS)

How atmospheric lightning initiates in thunderclouds has been a scientific puzzle for decades. One theory of air electrical breakdown that has been applied to explaining the initiation of lightning discharges is the conventional breakdown theory [e.g., MacGorman and Rust, p. 86, 1998; Rakov and Uman, p. 121, 2003]. A critical component of this theory is to demonstrate that streamers are able to form and propagate in the field with a magnitude similar to the observed thundercloud electric fields. The observed maximum value of this field varies from 0.13-0.3E_k [Stolzenburg et al., 2007], where E_k is the conventional breakdown threshold field. This value fails to provide a sufficient condition for the initiation of electron avalanches and then the electrical breakdown process. To overcome this obstacle, the theory of streamer initiation from thundercloud hydrometeors (water drops, ice crystals, etc.) was brought forward [e.g., Dawson, JGR, 74 (28), 6859, 1969; Griffiths and Latham, Quart. J. Roy. Meteorol. Soc., 100, 163, 1974; Griffiths and Phelps, Quart. J. Roy. Meteorol. Soc., 102, 4019, 1976]. Hydrometeors are abundant in thunderclouds and they can cause significant field enhancement in their vicinity. For this study, the streamer discharge model reported by Liu and Pasko [JGR, 109, A04301, 2004] is utilized and modified to investigate whether streamers can successfully originate from isolated hydrometeors in the thundercloud electric field. The thundercloud hydrometeors are modeled using a neutral plasma column. Our simulation results show successful formation of streamers from model hydrometeors in a uniform applied electric field below the conventional breakdown threshold field. We report detailed modeling results at thundercloud altitude for the applied electric fields close to the observed maximum thundercloud field. It is demonstrated that the dimensions, i.e., length and radius, of the plasma column have a critical effect on the initiation of streamers. The results also show that at lower applied electric fields for certain initial conditions, branching structures easily appear at the tip of the hydrometeor. To reduce the effects of branching, we investigate the possibility of using other geometries, specifically an ellipsoid, for the initial ionization column. So far, the minimum electric field value required for the stable formation of streamers from hydrometeors without the occurrence of branching structures has been observed to be 0.3E_k at 7 km from our modeling results.

Sadighi, S.; Liu, N.; Dwyer, J. R.; Rassoul, H. K.

2011-12-01

219

Critical turbulent energy reductions in plasmas using weak magnetic fields  

SciTech Connect

With an arc-driven shock tube, laser induced fluorescence, and a multipoint density diagnostic technique, we study the turbulence behind an ionizing shock wave in the presence of a magnetic field. The magnetic field is directed either parallel to or antiparallel to the direction of the shock wave's propagation, and is configured in such a way as to couple with turbulent velocity fluctuations in the plane perpendicular to the direction of flow. We find that the magnetic field can be used to reduce the turbulent energy in a plasma system. Further, when the evolution to turbulence is treated as a second-order phase transformation, the critical turbulent energy decreases with increasing magnetic field.

Raynor, Chavis T.; Mezonlin, Ephrem D.; Johnson, Joseph A. III [Center for Plasma Science and Technology, Florida A and M University, Tallahassee, Florida 32310 (United States)

2009-02-15

220

Studies on Weak Electromagnetic Fields Effects in Chick Embryos.  

National Technical Information Service (NTIS)

This research was directed to test some experimental conditions of the Henhouse project and to enforce a previous study on VLF electromagnetic fields effects on chick embryos. Henhouse Project: We studied the response of White Leghorn Hisex embryos to fie...

J. Leal

1986-01-01

221

Ramsey's method of separated oscillating fields and its application to gravitationally induced quantum phase shifts  

SciTech Connect

We propose to apply Ramsey's method of separated oscillating fields to the spectroscopy of the quantum states in the gravity potential above a horizontal mirror. This method allows a precise measurement of quantum mechanical phaseshifts of a Schroedinger wave packet bouncing off a hard surface in the gravitational field of the Earth. Measurements with ultracold neutrons will offer a sensitivity to Newton's law or hypothetical short-ranged interactions, which is about 21 orders of magnitude below the energy scale of electromagnetism.

Abele, H.; Jenke, T.; Leeb, H.; Schmiedmayer, J. [Technische Universitaet Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria)

2010-03-15

222

Evolution of the gravitational fields and figures of Jupiter and Saturn  

SciTech Connect

The gravitational fields and figures of Jupiter and Saturn at different times in their evolutionary contraction are found through a numerical solution of the system of integrodifferential figure equations. The time variation of their angular velocity and radial density distribution is taken into account. Time dependences are obtained for the flattening of the planetary figures and the field harmonics of numbers 2, 4, and 6.

Bobrov, A.M.; Vasil'ev, P.P.; Trubitsyn, V.P.

1983-03-01

223

Ion Collection by a Cylindrical Probe in a Weak Magnetic Field  

Microsoft Academic Search

The structure of a plasma-sheath transition region surrounding a negatively biased cylindrical probe in a weak axial magnetic field is systematically studied on the basis of the moment equations. A weakly ionized plasma is treated, and it is assumed that the mean free path is long but finite, and that the collision frequency is constant. Since the mean free path

Yasutomo Ohguchi; Shigeki Miyajima; Kenzo Yamamoto

1969-01-01

224

[Influence of weak magnetic fields on fish retina photoreceptors].  

PubMed

It has been shown for the first time that retina photoreceptors of the salmon Oncorhynchus masou (masu salmon) fry exposed to a constant magnetic field (80 Gs) in conditions of twilight illumination demonstrated not a twilight reaction, as in the control, but a darkness (scotopic) reaction. The pigment epithelium in this case reacted as to bright light. Under the influence of long wavelength red light, the retinomotor reaction corresponded to partial light adaptation. After the indemnification of the horizontal component (0.1 Gs) of the geomagnetic field, fish retina adapted to complete darkness demonstrated changes that could not be attributed to one of standard conditions of light exposure. Thus, the rods and cones demonstrated a reaction similar to that to twilight, double cones reacted as to complete darkness ("correct" reaction), and PE borrowed a position as at twilight. Apparently, the basic stimuli of the retina reactions were not light but changes of the magnetic field. Based on these results and the results available in literature, the authors offer a new variant of the hypothesis of light-dependent magnetoreception, which is based on the assumption that the liquid crystals of retina pigments are very sensitive receptors of magnetic field and do not require the presence of magnetite crystals. We assume that the layer of retina pigment epithelium participates in the complex process of transformation of a light signal, which takes into account the influence of magnetic field but not simply absorbs light superfluous for photoreceptors. The changes in magnetic field cause a distortion of the liquid crystal line structure of the pigment, which results in the transformation of the light signal acting on the photoreceptors. Monochromatic red light in the same way deforms the response to the native magnetic signal. PMID:17969928

Maksimovich, A A; Zagal'skaia, E O

2007-01-01

225

Weak gravity conjecture for effective field theories with N species  

NASA Astrophysics Data System (ADS)

We conjecture an intrinsic UV cutoff for the validity of the effective field theory with a large number of species coupled to gravity. In four dimensions such an UV cutoff takes the form ?=?/NMp for N scalar fields with the same potential ??i4, i=1,…,N. This conjecture implies that the assisted chaotic inflation or N-flation might be in the swampland, not in the landscape. Similarly an UV cutoff ?=gMp/N is conjectured for the U(1) gauge theory with N species.

Huang, Qing-Guo

2008-05-01

226

A Global Gravitational Field Model from GOCE Gradiometer Observations  

NASA Astrophysics Data System (ADS)

In this contribution, the focus is set on the global gravity field determination from GOCE gradiometer observations using a spherical harmonic representation. The key characteristic of the processing strategy is the use of short arcs of the satellite orbit. The gradiometer observations within each arc are decorrelated using an empirical co variance function. By introducing additional empirical parameters into the functional model, the long-periodic gradiometer error behaviour is taken into account. An ad equate separation of the gravity signal from the observation noise is crucial in order to exploit the strength of the satellite mission GOCE in recovering the static Earth's gravity field with unprecedented accuracy and resolution. The developed gradiometry gravity field model is validated by comparison with the official ESA models. The validation results are highly encouraging.

Schall, J.; Mayer-Gürr, T.; Eicker, A.; Kusche, J.

2011-07-01

227

Gravitational field models for study of Earth mantle dynamics  

NASA Technical Reports Server (NTRS)

The tectonic forces or stresses due to the small scale mantle flow under the South American plate are detected and determined by utilizing the harmonics of the geopotential field model. The high degree harmonics are assumed to describe the small scale mantle convection patterns. The input data used in the derivation of this model is made up of 840,000 optical, electronic, and laser observations and 1,656 5 deg x 5 deg mean free air anomalies. Although there remain some statistically questionable aspects of the high degree harmonics, it seems appropriate now to explore their implications for the tectonic forces or stress field under the crust.

1979-01-01

228

Cartographic generalization of urban street networks based on gravitational field theory  

NASA Astrophysics Data System (ADS)

The automatic generalization of urban street networks is a constant and important aspect of geographical information science. Previous studies show that the dual graph for street-street relationships more accurately reflects the overall morphological properties and importance of streets than do other methods. In this study, we construct a dual graph to represent street-street relationship and propose an approach to generalize street networks based on gravitational field theory. We retain the global structural properties and topological connectivity of an original street network and borrow from gravitational field theory to define the gravitational force between nodes. The concept of multi-order neighbors is introduced and the gravitational force is taken as the measure of the importance contribution between nodes. The importance of a node is defined as the result of the interaction between a given node and its multi-order neighbors. Degree distribution is used to evaluate the level of maintaining the global structure and topological characteristics of a street network and to illustrate the efficiency of the suggested method. Experimental results indicate that the proposed approach can be used in generalizing street networks and retaining their density characteristics, connectivity and global structure.

Liu, Gang; Li, Yongshu; Li, Zheng; Guo, Jiawei

2014-05-01

229

Phase conjugation of nonclassical fields and weak optical signals  

Microsoft Academic Search

This thesis describes work that has been published as articles in the scientific literature, as well as work that is in preparation for submission for publication. Chapter 1 is a general introduction to optical phase conjugation at the level of a researcher new to the field. In the two theoretical chapters, Chapters 2 and 3, I investigate optical phase conjugation

Mary Yvonne Lanzerotti

1997-01-01

230

Gravitational radiation from collapsing magnetized dust  

SciTech Connect

In this article we study the influence of magnetic fields on the axial gravitational waves emitted during the collapse of a homogeneous dust sphere. We found that while the energy emitted depends weakly on the initial matter perturbations it has strong dependence on the strength and the distribution of the magnetic field perturbations. The gravitational wave output of such a collapse can be up to an order of magnitude larger or smaller calling for detailed numerical 3D studies of collapsing magnetized configurations.

Sotani, Hajime [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Yoshida, Shijun [Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kokkotas, Kostas D. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Theoretical Astrophysics, University of Tuebingen, Auf der Morgenstelle 10, 72076, Tuebingen (Germany)

2007-04-15

231

Resonant amplification of magnetic seed fields by gravitational waves in the early universe  

SciTech Connect

Inflation is known to produce both gravitational waves and seed magnetic fields on scales well beyond the size of the horizon. The general relativistic study of the interaction between these two sources after the end of inflation, showed a significant amplification of the initial magnetic seed which brought the latter within the currently accepted dynamo limits. In the present article we revisit this gravitomagnetic interaction and argue that the observed strong growth of the field is the result of resonance. More specifically, we show that the maximum magnetic boost always occurs when the wavelength of the inducing gravitational radiation and the scale of the original seed field coincide. We also look closer at the physics of the proposed Maxwell-Weyl coupling, consider the implications of finite electrical conductivity for the efficiency of the amplification mechanism and clarify further the mathematics of the analysis.

Tsagas, Christos G. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2005-12-15

232

Horizon thermodynamics and gravitational field equations in Horava-Lifshitz gravity  

SciTech Connect

We explore the relationship between the first law of thermodynamics and gravitational field equation at a static, spherically symmetric black hole horizon in Horava-Lifshitz theory with/without detailed balance. It turns out that as in the cases of Einstein gravity and Lovelock gravity, the gravitational field equation can be cast to a form of the first law of thermodynamics at the black hole horizon. This way we obtain the expressions for entropy and mass in terms of black hole horizon, consistent with those from other approaches. We also define a generalized Misner-Sharp energy for static, spherically symmetric spacetimes in Horava-Lifshitz theory. The generalized Misner-Sharp energy is conserved in the case without matter field, and its variation gives the first law of black hole thermodynamics at the black hole horizon.

Cai Ronggen [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China); Department of Physics, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan); Ohta, Nobuyoshi [Department of Physics, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan)

2010-04-15

233

Energy contribution of the quadrupole perturbation of central gravitational field.  

National Technical Information Service (NTIS)

The solution of Einstein equations with the Minkowski space condition for the central field with a quadrupole perturbation is calculated as an 1/r-expansion up to terms quadratic in the first quadrupole constant. It is shown that the perturbation is shown...

S. N. Sokolov

1990-01-01

234

Dynamical mass generation in strongly coupled quantum electrodynamics with weak magnetic fields  

SciTech Connect

We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of weak magnetic fields using Schwinger-Dyson equations. Contrary to the case where the magnetic field is strong, in the weak field limit the coupling should exceed certain critical value in order for the generation of masses to take place, just as in the case where no magnetic field is present. The weak field limit is defined as eB<field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB){sup 2}.

Ayala, Alejandro; Raya, Alfredo; Rojas, Eduardo [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico Distrito Federal 04510 (Mexico); Bashir, Adnan [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico Distrito Federal 04510 (Mexico); Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Apartado Postal 2-82, Morelia, Michoacan 58040 (Mexico); IPPP, Durham University, Durham, DH1 3LE (United Kingdom)

2006-05-15

235

Direct electro - gravitational couplings and the behaviour of primordial large-scale magnetic fields  

NASA Astrophysics Data System (ADS)

A comprehensive approach is suggested for describing the origin and evolution of large-scale magnetic fields. Vorticity-dependent fluctuations acting on a primordial charged plasma account for field generation, and the properties of gauge-invariant (but conformally non-invariant) couplings of electromagnetic and gravitational fields in a FRW background are applied in order to supply a source-independent, gravity-driven mechanism of conductance induction in the course of the reheating phase of inflationary cosmic scenarios. In consequence, the description of the behaviour of large-scale primordial magnetic fields is complemented so as to cover the whole post-inflationary history of the universe.

Novello, M.; Oliveira, L. A. R.; Salim, J. M.

1996-05-01

236

[Geomagnetic and artificial weak magnetic fields of superlow frequency as factors changing the body radiosensitivity].  

PubMed

Geomagnetic disturbances and experimentally generated weak variable superlow-frequency magnetic fields have either a radioprotecting or radiosensitizing effect on the mouse body depending on the time, intensity, and mode of influence. PMID:11605401

Stashkov, A M; Kopylov, A N; Gorokhov, I E

2001-01-01

237

Affecting weak light localization by strong magnetic fields  

NASA Astrophysics Data System (ADS)

We report an experimental study of the magneto-optical Faraday effect in strongly multiple scattering media using magnetic fields up to 23 Tesla. Faraday rotation of the polarization of laser light, diffusing through samples consisting of colloidal particles embedded in a Faraday-active glass matrix, is found to destroy coherent backscattering. The angular shape of the coherent backscattering cone varies as a function of the applied field B in agreement with a simple model and with numerical simulations. In particular, the intensity at backscattering is found to decrease with B like the intensity with scattering angle at B = 0, as predicted. The multiple scattering Faraday effect provides a unique experimental way to destroy constructive interferences between time reversed optical scattering paths. It is thus expected to affect light localization and may be used to prove (or disprove) its existence.

Lenke, R.; Maret, G.

1993-01-01

238

Detection of weak electric fields by sharks, rays, and skates  

Microsoft Academic Search

The elasmobranchs—sharks, rays, and skates—can de- tect electric fields as small as 0.5 mV\\/m in the saltwater in which they live by placing the potential difference be- tween the center of their body and the outer skin across the membranes of sensory cells lining sensory organs, the ampullae of Lorenzini. We show that this sensitivity, and the results of measurements

Robert K. Adair; James C. Weaver

239

The Effect of Weak Combined Magnetic Field on Root Gravitropism and a Role of Ca2+ Ions Therein  

NASA Astrophysics Data System (ADS)

At present, magnetic fields of different types are widely used to study gravity sensing in plants. For instance, magnetic levitation of amyloplasts caused by high gradient magnetic field enables us to alter the effective gravity sensed by plant cells. For the first time we showed that a weak combined magnetic field (CMF), that is the sum of collinear permanent and alternating magnetic fields ( 0.5 gauss, 0-100 Hz), changes a cress and pea root positive gravitropic reaction on a negative one. This effect has the form of resonance and occurs at the frequency of cyclotron resonance of calcium ions. What is especially interesting is that under gravistimulation in the CMF, the displacement of amylopasts in the root cap statocytes is directed to the upper wall of a cell, i.e. in the direction opposite to the gravitational vector. The displacement of amyloplasts, which contain the abundance of free Ca2+ ions in the stroma, is accompanied by Ca2+ redistribution in the same direction, and increasing in the cytosol around amyloplasts near ten times in the CMF in comparison with the state magnetic field. Earlier, we also observed the Ca2+ accumulation in the upper site of a root curvature in the elongation zone in the CMF unlike a positive gravitropic reaction. Thus, it should be stressed that a root is bending in the same direction in which amyloplasts are displacing: downwards when gravitropism is positive and upwards when gravitropism is negative. The obtained data confirm the amyloplast statolithic function and give another striking demonstration of a leading role of Ca2+ ions in root gravitropism. But these data bring the question: what forces can promote amyloplast displacement against gravity? The possible explanation of the effect found is discussed. It is based on the ion cyclotron resonance in biosystems proposed by Liboff.. The original approach based on the use of a weak CMF may be helpful for understanding the mechanisms of plant gravisensing

Kordyum, Elizabeth; Bogatina, Nina; Kondrachuk, A.

240

Non-Linear Stability of a Weakly Ionized Plasma with a Nonuniform Magnetic Field  

Microsoft Academic Search

Using vector eignfunction expansion, an asymptotic nonlinear theory of a weakly ionized plasma in a strong magnetic field is presented. When the external field H is slightly larger than the critical magnetic field Hc, an instability exists. For slightly unstable plasma motions, a precise form on Landau's equation is obtained. The inclusion of nonlinearities gives rise to amplitude saturation. It

S. K. Malik; M. Singh

1978-01-01

241

Analysis of biological effects and limits of exposure to weak magnetic fields  

Microsoft Academic Search

Adverse biological outcomes due to thermal effects of exposure to high power magnetic fields are well understood and are the basis for standards for limiting human exposure to such fields. Over the past few decades a controversy has arisen over possible adverse biological effects due to exposure to weak, low frequency magnetic fields. This paper involves a critical analysis of

D. A. Chathurika; M. F. Peter; N. H. Malka

2010-01-01

242

Thermodynamics and orientational order in systems of extended gravitating objects: A mean-field theory approach. I. Basic formalism  

SciTech Connect

A mean-field-theory approach, in which the orientation of an extended gravitating object is approximately determined by the mean gravitational field of all the other objects in the system, is presented. It is shown that the mean field is characterized by an effective single-body potential called the 'pseudopotential' which is obtained from the full two-body gravitational potential by means of a certain averaging procedure. The possible occurrence of an 'orientational phase transition' whereby large-scale orientational order may develop in the system is discussed. 59 refs.

Bhattacharjee, P.; Ghosh, P.; Cowsik, R.

1989-04-01

243

Reversal of alexia in multiple sclerosis by weak electromagnetic fields.  

PubMed

The occurrence of cognitive deficits in patients with multiple sclerosis (MS) has been recognized since 1877 when Charcot first observed "enfeeblement of memory" in his patients. Cognitive deficits have been reported in almost 50% of patients with a relapsing-remitting course and in a significantly higher percentage of patients with a chronic progressive course leading to intellectual disability which is often severe enough to preclude employment. MS is considered a form of subcortical dementia and the occurrence of classical cortical disorders such as aphasia, agnosia and apraxia is reported to be rare in the disease. However, in my experience alexia, a reading impairment unrelated to visual acuity or visual field defects, is common in patients with MS. Recently, I reported that treatment with picotesla range electromagnetic fields (EMFs) is an efficacious modality in the management of both the motor and cognitive symptoms of MS. Three patients with MS who developed alexia as a manifestation of the disease are presented. In all patients the alexia was reversed several months after they began treatment with EMFs. Since alexia usually reflects a disconnection syndrome whereby lesions involving the left visual cortex and the splenium of the corpus callosum disconnect language association areas from visual association areas, it is suggested that reversal of the alexia in these patients by EMFs was related to improved interhemispheric transcallosal transmission of visual information. In addition, it is conceivable that changes in the metabolism of monoamines, which are involved in visual information processing and reading comprehension, may have been important in causing reversal of the alexia. This report further supports the unique efficacy of this treatment modality in reversing specific cognitive deficits in MS. PMID:8746750

Sandyk, R

1995-11-01

244

Quantum electrodynamics in the gravitational field of a cosmic string  

NASA Astrophysics Data System (ADS)

We evaluate the cross section for electron-positron pair production by a single high energy photon in the space-time of a static, straight cosmic string. Energy and momentum conservation precludes this process in empty Minkowski space. It happens around a cosmic string, in spite of the local flatness of the metric, as a consequence of the conical structure of space. Previous results based on a simplified model with scalar fields are here extended to the realistic QED case. Analytic expressions are found in three different regimes: near the threshold, at energies much larger than the electron rest mass M, and at ultrahigh energies, much larger than M/?, with ? the string mass per unit length in Planck units.

Skarzhinsky, Vladimir D.; Harari, Diego D.; Jasper, Ulf

1994-01-01

245

Einstein's Theory of Gravitation as a Lagrangian Theory for Tensor Fields  

NASA Astrophysics Data System (ADS)

Einstein's theory of gravitation (ETG) is considered as a Lagrangian theory of tensor fields over (pseudo) Riemannian spaces without torsion (Vn spaces, n=4) by means of the method of Lagrangians with covariant derivarives (MLCD). In a trivial manner Euler-Lagrange's equations as Einstein's equations are obtained. The corresponding energy-momentum tensors (EMT's) are found for the standard for the ETG Lagrangian invariant on the basis of the covariant Noether identities. The symmetric energy-momentum tensor of Hilbert appears as an element irrelevant to the whole scheme of the considered Lagrangian thoery of tensor fields over Vn spaces despite of the fact that it has some elements of the structure of the variational EMT of Euler-Lagrange. The notion of the active gravitational rest mast density is related to the variational EMT of Euler-Lagrange and on this basis to a certain extent to the EMT of Hilbert.

Manoff, S.

246

General Relativistic Theory of the VLBI Time Delay in the Gravitational Field of Moving Bodies  

NASA Technical Reports Server (NTRS)

The general relativistic theory of the gravitational VLBI experiment conducted on September 8, 2002 by Fomalont and Kopeikin is explained. Equations of radio waves (light) propagating from the quasar to the observer are integrated in the time-dependent gravitational field of the solar system by making use of either retarded or advanced solutions of the Einstein field equations. This mathematical technique separates explicitly the effects associated with the propagation of gravity from those associated with light in the integral expression for the relativistic VLBI time delay of light. We prove that the relativistic correction to the Shapiro time delay, discovered by Kopeikin (ApJ, 556, L1, 2001), changes sign if one retains direction of the light propagation but replaces the retarded for the advanced solution of the Einstein equations. Hence, this correction is associated with the propagation of gravity. The VLBI observation measured its speed, and that the retarded solution is the correct one.

Kopeikin, Sergei

2003-01-01

247

The forthcoming Radioastron Mission as a tool for GR tests in the strong gravitational field limit  

NASA Astrophysics Data System (ADS)

In 2007 the Radioastron satellite will be launched As a result 10-meter radio telescope will be located at a high orbit around the Earth Actually it will be a generalization of VLBI technique using space -- ground base The interferometer will have extraordinary angular resolution namely at the shortest wavelengths angular resolution is about 10 -5 -10 -6 as These angular sizes are comparable with angular sizes of shadows mirages around nearest supermassive black holes For example the size of the shadow around the black hole in the Galactic Centre is about 50 mu as it means that in principle such a tool like the Radioastron interferometer could resolve the shadow Analyzing the shapes of shadows mirages one could evaluate parameters of a black hole such as spin a inclination angle theta and a black hole charge or magnetic monopole and test GR in the strong gravitational field limit corresponding gravitational fields near black hole horizons

Zakharov, A.; De Paolis, F.; Nucita, A.; Ingrosso, G.

248

Anomalous character of the axion-photon coupling in a magnetic field distorted by a pp-wave gravitational background  

NASA Astrophysics Data System (ADS)

We study the problem of axion-photon coupling in the magnetic field influenced by gravitational radiation. We focus on exact solutions to the equations for axion electrodynamics in the pp-wave gravitational background for two models with initially constant magnetic field. The first model describes the response of an initially constant magnetic field in a gravitational-wave vacuum with unit refraction index; the second model is characterized by a non-unit refraction index prescribed to the presence of ordinary and/or dark matter. We show that both models demonstrate anomalous behavior of the electromagnetic field generated by the axion-photon coupling in the presence of magnetic field, evolving in the gravitational wave background. The role of axionic dark matter in the formation of the anomalous response of this electrodynamic system is discussed.

Balakin, Alexander B.; Ni, Wei-Tou

2014-05-01

249

Changes in the earth's rotation and low-degree gravitational field induced by earthquakes  

Microsoft Academic Search

Analytical formulas based on the normal-mode theory are used together with a spherically symmetric earth model and the centroid-moment tensor solutions for earthquake sources to compute the earthquake-induced changes in the earth's rotation and low-degree harmonics of the gravitational field for the period 1977-1985. Spectral and statistical analyses are conducted on these changes. It is found that the earthquake-induced changes

B. Fong Chao; Richard S. Gross

1987-01-01

250

Changes in the Earth's rotation and low-degree gravitational field induced by earthquakes  

Microsoft Academic Search

The change in the Earth's density distribution caused by an earthquake dislocation will change the Earth's rotation and gravitational field. In this paper the authors first develop the analytical formulae based on the normal-mode theory. Equipped with these formulae and using a spherically symmetric earth model (1066B) and the centroid-moment tensor solutions for earthquake sources, they then compute the earthquake-induced

B. F. Chao; R. S. Gross

1987-01-01

251

Separation of Polystyrene Microbeads Using Dielectrophoretic\\/Gravitational Field-Flow-Fractionation  

Microsoft Academic Search

The characterization of a dielectrophoretic\\/gravitational field-flow-fractionation (DEP\\/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15?m in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and

Xiao-Bo Wang; Jody Vykoukal; Frederick F. Becker; Peter R. C. Gascoyne

1998-01-01

252

Weak magnetic fields of intermediate-mass stars  

NASA Astrophysics Data System (ADS)

We present the result of a highly sensitive spectropolarimetric study dedicated to intermediate-mass stars. We report the detection of sub-gauss surface magnetic fields on the normal, rapidly-rotating A-type star Vega and on the moderately-rotating Am star Sirius A. These magnetic detections constitute the first evidence that tepid stars that do not belong to the class of Ap/Bp stars can also host magnetized photospheres, suggesting that a significant fraction of stars in this mass regime are magnetic. We present here the observational clues gathered so far to progress towards understanding the physical processes at the origin of this newly identified Vega-like magnetism. Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l�nivers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Petit, P.; Lignières, F.; Wade, G. A.; Aurière, M.; Alina, D.; Böhm, T.; Oza, A.

2011-12-01

253

Testing the gravitational field in elliptical galaxies - NGC 5077  

SciTech Connect

The intrinsic shape and the mass distribution of the underlying galaxy of NGC 5077, a southern elliptical galaxy with a disk of ionized gas along its minor axis, are investigated on the basis of observations of the structure and kinematics of this gas disk. It is shown that it is possible to construct realistic triaxial mass models for early-type galaxies. These models suggest that NGC 5077 has a constant M/L of about 4-5 in solar units throughout the central 5-10 kpc. The velocity fields of the triaxial models offer three advantages: they can explain the observed position angle differnce of 23 degrees between the gas rotation axis and the apparent major axis of the stars as being due to a projection effect; they provide a natural explanation for the observed increase in the gas velocity dispersion in the central 2-3 arcsec; and the associated density distributions have small cores, so they do not require M/L to drop to low values in the center. Equilibrium and polar ring models and other galaxies are discussed as well. 71 refs.

Bertola, F.; Bettoni, D.; Danziger, J.; Sadler, E.; Sparke, L. (Padova, Universita, Padua (Italy) Padova, Osservatorio Astronomico, Padua (Italy) European Southern Observatory, Garching (Federal Republic of Germany) Anglo-Australian Observatory, Epping (Australia) Kapteyn Laboratorium, Groningen (Netherlands))

1991-06-01

254

ON THE EFFECT OF A WEAK INTERPLANETARY MAGNETIC FIELD ON THE INTERACTION BETWEEN THE SOLAR WIND AND THE GEOMAGNETIC FIELD  

Microsoft Academic Search

the presence of a weak interplanetary magnetic field may lead to the ; formation of a collision-free shock wave upstream from the boundary of the ; geomagnetic field and to a transition region characterized by an irregular ; magnetic field in the intervening space. Previous calculations of the ; coordinates of the shock wave are improved upon by application of

John R. Spreiter; Wm. Prichard Jones

1963-01-01

255

The electro-weak and color bundles for the Standard Model in a gravitation field  

Microsoft Academic Search

It is known that the Standard Model describing all of the currently known elementary particles is based on the $U(1)\\\\times SU(2)\\\\times SU(3)$ symmetry. In order to implement this symmetry on the ground of a non-flat space-time manifold one should introduce three special bundles. Some aspects of the mathematical theory of these bundles are studied in this paper.

Ruslan Sharipov

2006-01-01

256

The theory of equilibrium and gravitational field of the Galilean satellite Io. The second approximation  

NASA Astrophysics Data System (ADS)

There have been constructed the theory of figures and gravitational field of the Galilean satellite Io to within terms of second orders in the small parameter ?=?^2s_1^3/Gm_0, where ?, s_1, G and m_0 are the angular velocity, the radius of a sphere of equivalent volume (the average radius), the gravitational constant and mass of Io, respectively. In a second approximation of the theory of figurs the radius r is represented as the sum of the following figure functions: s_2(s), s22(s), s31(s), s33(s), s_4(s), s42(s) and s44(s), multiplied by corresponding spherical harmonics. Integrodifferential equations, the solutions of which determine the values of figure parameters and gravitational moments of equilibrium Io have been derived. Figure parameters (at s=s_1) and gravitational moments for s_2, s22, J_2 and C22 are determined by Love numbers h_2 and ?; for s31, s33, C31 and C33 (J_3=s31=s32=s33=C32=0) are determined by Love numbers h_3 and the small parameter ?_1=(s_1/R)?, where R is the radius of Io's orbit. For the uniform model of Io the values of figure parameters and gravitational moments of the forth order are the following: s_4=885/224 ?^2, s42=-75/224 ?^2, s44=15/896 ?^2, J_4=-885/224?^2, C42=-75/224?^2, C44=15/896?^2.

Zharkov, V. N.

257

On the separation of gravitation and inertia and the determination of the relativistic gravity field in the case of free motion  

Microsoft Academic Search

The authors explored the possibility of separating gravitation from inertia in the frame of general relativity. The Riemann tensor is intimately related with gravitational fields and has nothing to do with inertial effects. One can judge the existence or nonexistence of a gravitational field according as the Riemann tensor does not vanish or vanishes. In the free fall case, by

Wenbin Shen; Helmut Moritz

1996-01-01

258

Manipulation of Persistent Spin Helix States by Weak External Magnetic Fields  

NASA Astrophysics Data System (ADS)

We study theoretically the effect of weak external magnetic fields on persistent spin helix states in semiconductor two-dimensional electron gases with both Rashba and linear-in-momentum Dresselhaus spin-orbit coupling. We show that in the presence of weak external magnetic fields, some basic properties of a persistent spin helix state, including the dispersion relation between the decay time and the magnitude of the wavevector, the maximum decay time and the value of the characteristic magnitude of the wavevector at which the maximum decay time occurs, will all depend sensitively on the directions of applied external magnetic fields.

Hu, Mao-Jin; Chai, Zheng; Hu, Liang-Bin

2014-03-01

259

Dynamics of positive and negative streamers in air in weak uniform electric fields  

Microsoft Academic Search

The results of two-dimensional numerical simulation of single positive and negative streamer development in atmospheric air in weak uniform electric fields are presented. It is shown that the form of streamer channel and the rate of growth of streamer velocity with its length are determined by the magnitude and polarity of the applied field E0. The difference between the parameters

N. Yu. Babaeva; G. V. Naidis

1997-01-01

260

Evidence of deflected super-Alfvénic electron jet in a reconnection region with weak guide field  

NASA Astrophysics Data System (ADS)

numerical simulations demonstrated that electron diffusion region develops into two-scale structure, i.e., the inner electron diffusion region and the outer electron diffusion region. The outer diffusion region is manifested as super-Alfvénic electron jet embedded in central current sheet. However, the electron jets are deflected from neutral sheet with a weak guide field. In this paper we present the in situ evidence of deflected super-Alfvénic electron jet in a reconnection region with a weak guide field in the Earth's magnetotail. The electron-scale jet was detected at about 37 ion inertial lengths from the X line. There was a strong electric field at the jet. The strong electric field at the jet was primarily balanced by Hall electric field, as the intense current was mainly carried by magnetized electrons. Another event in the magnetosheath also supports our conclusion that guide field deflects the electron jet away the neutral sheet.

Zhou, Meng; Deng, Xiaohua; Tang, Rongxin; Pang, Ye; Xu, Xiaojun; Yuan, Zhigang; Huang, Shiyong

2014-03-01

261

Gravitational lensing by 3-d matter distributions  

NASA Astrophysics Data System (ADS)

Gravitational lensing studies have become an important tool for studying galactic structure and cluster morphology because the methods do not rely heavily on specific knowledge of cosmological parameters. To date, lensing studies use a weak- field, thin lens approximation where the lensing action is assumed to occur in a two-dimensional lens plane. We compare this approximation with the results of integrating the null geodesic equations for weak field metrics with ``standard'' three dimensional mass distributions.

Kling, Thomas

2006-04-01

262

Controllable surfaces of path interference in the multiphoton ionization of atoms by a weak trichromatic field  

NASA Astrophysics Data System (ADS)

Multiphoton detachment rates for the H- 1S ground state irradiated by a weak trichromatic ac field consisting of the fundamental frequency ? = 0.272 eV and its second, third or fourth higher harmonics were computed from first principles. The weak intensities are in the range of 107-108 W cm-2. The calculations incorporated systematically electronic structure and electron correlation effects. They were done by implementing a time-independent, nonperturbative many-electron, many-photon theory (MEMPT) which obtains cycle-averaged complex eigenvalues, whose real part gives the field-induced energy shift, ?, and the imaginary part is the multiphoton ionization rate, ?. Through analysis, plausible arguments and computation, we show that when the intensities are weak the dependence of ? on phase differences is simple. Specifically, ?s are depicted in the form of plane surfaces, with minor ripples due to higher order ionization paths, in terms of trigonometric functions of the phase differences. This dependence is likely to be applicable to other atomic systems as well, and to provide a definition of the weak field regime in the trichromatic case. When the field intensities are such that higher order ionization paths become important, these dependences break down and we reach the strong field regime.

Mercouris, Theodoros; Nicolaides, Cleanthes A.

2005-10-01

263

Traveling-wave tubes and backward-wave oscillators with weak external magnetic fields  

SciTech Connect

Recent development of plasma-assisted slow-wave oscillators [Goebel IEEE Trans. Plasma Sci. >22, 547 (1994)], microwave sources that operate without guiding magnetic fields, has stimulated interest in the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields, due to the space charge forces and the radial electric field of the wave, the electrons may propagate radially outward which increases electron coupling to the slow wave whose field is localized near the slow-wave structure (SWS). This increases the wave growth rate and efficiency, and hence allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it does not lead to interception of electrons by the SWS. To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on the operation of traveling-wave tubes and backward-wave oscillators with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting the SWS from electron bombardment at different power levels. Theoretical predictions of the efficiency enhancement due to the weak magnetic field are confirmed in experiments.

Abu-elfadl, T. M.; Nusinovich, G. S.; Shkvarunets, A. G.; Carmel, Y.; Antonsen, T. M.; Goebel, D.

2001-06-01

264

Traveling-wave tubes and backward-wave oscillators with weak external magnetic fields.  

PubMed

Recent development of plasma-assisted slow-wave oscillators [Goebel et al. IEEE Trans. Plasma Sci. 22, 547 (1994)], microwave sources that operate without guiding magnetic fields, has stimulated interest in the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields, due to the space charge forces and the radial electric field of the wave, the electrons may propagate radially outward which increases electron coupling to the slow wave whose field is localized near the slow-wave structure (SWS). This increases the wave growth rate and efficiency, and hence allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it does not lead to interception of electrons by the SWS. To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on the operation of traveling-wave tubes and backward-wave oscillators with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting the SWS from electron bombardment at different power levels. Theoretical predictions of the efficiency enhancement due to the weak magnetic field are confirmed in experiments. PMID:11415235

Abu-elfadl, T M; Nusinovich, G S; Shkvarunets, A G; Carmel, Y; Antonsen, T M; Goebel, D

2001-06-01

265

The Earth-Moon-Sun natural laboratory for testing of gravitational and electromagnetic fields coupling  

NASA Astrophysics Data System (ADS)

Experimental investigations of electromagnetic fields in the atmosphere boundary layer are done at the distance spaced stations, situated on VSU test ground, at Main Geophysical Observa-tory(St. Petersburg), on Kamchatka pen., on Lake Baikal. The distance spaced reception of electrical and magnetic fields will allow to analyze more widely the nature of the investigated interactions. Monitoring of electromagnetic fields in the ELF range is being realized. The work is connected with search of interconnection of the electromagnetic field of the atmosphere boundary layer with the gravitational Compact Binaries wave fields. For analyzing Compact Binaries were taken with ELF of GW-radiation: J 0700+6418, J 1012+5307, J 1537+1155, J 1959+2048, J 2130+1210, J 1915+1606, J 1910+0004, J 1910+0004, J 1748-2446A.For analyz-ing the spectrum of the magnetic fields there was used the information of VSU station and the monitoring information of Japanese geomagnetic stations Kakioka and Mambetsu. The aim of such investigations is connected with displaying tide processes (the Moon tides) and gravita-tional wave influence of Compact Binaries in the electromagnetic fields.On the first stage of the investigations a correlative spectral analysis of the experimental data was being carried out. There was factually extracted the influence of the atmosphere lower layer electromagnetic field of the thermogravitational solar tides and a number of gravitational: M1, M2, N2. It was ob-tained that astrophysical sources GV-6, GV-3,GV-4, GV-8, GV-9 have the most probability of non-casual of events. The subsequent investigations are connected with search of main features accompanying such influences. They are signal modulations by diurnal and year's rotation of the Earth. Such modulations are peculiar to sources of non-terrestrial origin. We are planning an extraction of the radiation frequency change of the source because of energy loss for the radiation of GW. Such investigations turned out to be possible after developing the method of scanning experimental signal of electromagnetic field into non-correlated components. There is shown efficiency of using latent vectors of covariance matrixes to expose complex periodical component of time series, including the ease when such components don't have energetic dom-inate in time series.The work was carried out with supporting of grants RFBR 09-05-08176, Program DSPHS 2.1.1/5660.

Grunskaya, Lubov; Isakevich, Valiriy; Efimov, Vladislav; Zakirov, Alexander

266

Separation of polystyrene microbeads using dielectrophoretic/gravitational field-flow-fractionation.  

PubMed Central

The characterization of a dielectrophoretic/gravitational field-flow-fractionation (DEP/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15 microm in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and applied field frequency and voltage. Experimental data were analyzed using a previously reported theoretical model and good agreement between theory and experiment was found. It was shown that separation of PS beads was based on the differences in their effective dielectric properties. Particles possessing different dielectric properties were positioned at different heights in a fluid-flow profile in a thin chamber by the balance of DEP and gravitational forces, transported at different velocities under the influence of the fluid flow, and thereby separated. To explore hydrodynamic (HD) lift effects, velocities of PS beads were determined as a function of fluid flow rate in the separation chamber when no DEP field was applied. In this case, particle equilibrium height positions were governed solely by the balance of HD lift and gravitational forces. It was concluded that under the experimental conditions reported here, the DEP force was the dominant factor in controlling particle equilibrium height and that HD lift force played little role in DEP/G-FFF operation. Finally, the influence of various experimental parameters on separation performance was discussed for the optimization of DEP/G-FFF.

Wang, X B; Vykoukal, J; Becker, F F; Gascoyne, P R

1998-01-01

267

Global surface-water-induced seasonal variations in the earth's rotation and gravitational field  

NASA Technical Reports Server (NTRS)

The effects of seasonal changes in continental surface-water storage on the low-degree gravitational-field coefficients (J), the annual wobble excitation (Psi), and the seasonal length-of-day (LOD) variations are investigated by means of numerical simulations based on compiled meteorological data (Willmott et al., 1985) and satellite snow-load estimates (Chao et al., 1987). The formulation of the model equations and the overall characteristics of the data sets are discussed in detail, and the computation results are presented in tables and graphs. The effect on Psi is found to be relatively small due to longitudinal cancellation, but those on LOD and J are considered significant.

Chao, B. F.; O'Connor, William P.

1988-01-01

268

Multifractal analysis of the electronic states in the Fibonacci superlattice under weak electric fields  

NASA Astrophysics Data System (ADS)

Influence of the weak electric field on the electronic structure of the Fibonacci superlattice is considered. The electric field produces a nonlinear dynamics of the energy spectrum of the aperiodic superlattice. Mechanism of the nonlinearity is explained in terms of energy levels anticrossings. The multifractal formalism is applied to investigate the effect of weak electric field on the statistical properties of electronic eigenfunctions. It is shown that the applied electric field does not remove the multifractal character of the electronic eigenfunctions, and that the singularity spectrum remains non-parabolic, however with a modified shape. Changes of the distances between energy levels of neighbouring eigenstates lead to the changes of the inverse participation ratio of the corresponding eigenfunctions in the weak electric field. It is demonstrated, that the local minima of the inverse participation ratio in the vicinity of the anticrossings correspond to discontinuity of the first derivative of the difference between marginal values of the singularity strength. Analysis of the generalized dimension as a function of the electric field shows that the electric field correlates spatial fluctuations of the neighbouring electronic eigenfunction amplitudes in the vicinity of anticrossings, and the nonlinear character of the scaling exponent confirms multifractality of the corresponding electronic eigenfunctions.

Wo?oszyn, M.; Spisak, B. J.

2012-01-01

269

On Gravitational Waves  

Microsoft Academic Search

The rigorous solution for cylindrical gravitational waves is given. For the convenience of the reader the theory of gravitational waves and their production, already known in principle, is given in the first part of this paper.After encountering relationships which cast doubt on the existence of rigorous solutions for undulatory gravitational fields, we investigate rigorously the case of cylindrical gravitational waves.

A. Einstein; N. Rosen

1937-01-01

270

Stellar explosion in the weak field approximation of the Brans–Dicke theory  

Microsoft Academic Search

We treat a very crude model of an exploding star, in the weak field approximation of the Brans–Dicke theory, in a scenario that resembles some characteristic data of a type Ia supernova. The most noticeable feature, in the electromagnetic component, is the relationship between the absolute magnitude at maximum brightness of the star and the decline rate in one magnitude

Victor H. Hamity; Daniel E. Barraco

2005-01-01

271

Stellar explosion in the weak field approximation of the Brans Dicke theory  

Microsoft Academic Search

We treat a very crude model of an exploding star, in the weak field approximation of the Brans Dicke theory, in a scenario that resembles some characteristic data of a type Ia supernova. The most noticeable feature, in the electromagnetic component, is the relationship between the absolute magnitude at maximum brightness of the star and the decline rate in one

Victor H. Hamity; Daniel E. Barraco

2005-01-01

272

New Method for Computing the Weak-Field Hall Coefficient. Ii. Some Extensions and Modifications.  

National Technical Information Service (NTIS)

An earlier paper described a simple method for computing the weak-field Hall coefficient through the use of a Fermi surface composed entirely of planar faces. That paper developed a set of rules which linked the general behavior of the Hall coefficient to...

R. S. Allgaier

1970-01-01

273

The reflected pressure field in the interaction of weak shock waves with a compressible foam  

Microsoft Academic Search

This paper deals with the waves that are reflected from slabs of porous compressible foam attached to a rigid wall when impacted by a weak shock wave. The interest is in establishing possible attenuation of the pressure field after a shock or blast wave has struck the surface. Foam densities from 14 to 38 kg\\/m3 were tested over a range

B. W. Skews

1991-01-01

274

Effects of a Weak Planetary Field on a Model Venus Ionosphere  

NASA Astrophysics Data System (ADS)

There are a number of attributes of the near-Venus space environment and upper atmosphere that remain mysterious, including occasional large polar magnetic field stuctures seen on VEX and nightside ionospheric holes seen on PVO. We have been exploring the consequences of a weak global dipole magnetic field of Venus using results of BATS-R-US MHD simulations. An advantage of these models is that they include the effects on a realistic ionosphere. We compare some of the weak magnetosphere's ionospheric properties with the typical unmagnetized ionsphere case. The results show the differences can be quite subtle for dipole fields less than ~10 nT at the equator, as might be expected. Nevertheless the dipole fields do produce distinctive details, especially in the upper regions.

Luhmann, Janet G.; Ma, Yingjuan; Villarreal, Michaela

2014-05-01

275

Zeeman resonances for radical-pair reactions in weak static magnetic fields  

NASA Astrophysics Data System (ADS)

Recent reaction-yield-detected magnetic resonance experiments in weak static magnetic fields and the observation of resonance effects in animal orientation experiments provide the motivation for renewed studies of magnetic field effects on radical-pair reactions. Here, we investigate theoretically resonance patterns for weak static magnetic fields. We focus on the question: for which radical pairs can one expect Zeeman resonances to occur if the static field is weaker than typical hyperfine interactions? Using analytical approaches, we rationalize the occurrence of Zeeman resonances for simple radical pairs. Numerical solutions are presented for a wide range of radical pairs with up to seven hyperfine interactions employing the rotating-frame transformation. The results suggest that resonances occur close to either the Larmor frequency or half the Larmor frequency for a wide variety of radical pairs for spin Hamiltonians with a high degree of symmetry. For larger numbers of hyperfine interactions, Zeeman resonances decrease in size.

Wang, Kefei; Ritz, Thorsten

2006-05-01

276

On observation of neutron quantum states in the Earth's gravitational field  

NASA Astrophysics Data System (ADS)

Observation of neutron gravitational quantum states En=mgzn in the peV energy range (z1 is about 10?m in the vertical direction) in the experiment conducted at Laue-Langevin Institute, Grenoble, with ultracold neutrons was recently reported in a series of publications. The purpose of the present work is to analyze the experiment. The experimental apparatus is designed to measure a transmission function T(za), namely, a horizontal flux of relatively fast neutrons (k?kz in wavelength terms) passing through a slit of variable height za of upper absorbing wall. The quantum states in question are defined by the so-called Airy functions, which are solutions to the stationary 1D equation for a neutron “bouncing” above the perfect mirror in a linear potential field. The Airy functions describe the quantum bouncer (QB), the concept of which is subject to theoretical study of toy 1D models of gravitationally bound particles in nonrelativistic quantum mechanics (QM). This is essentially different from the 3D nonstationary QM object, “the running QB,” investigated in the experiment. The authors assume that there is a connection between T(za) and the probability density distribution P(z,za) for QB states. They devised the “phenomenological model,” in which the quantum pattern should be visible in the transmission curve. We argue, however, that the measured curve T(za) is not sensitive to QB states. Instead, it is sensitive to dynamics of neutron horizontal transport inside the absorbing slit for neutrons of energy values about 105 times greater than eigenvalues En. The latter are related to the neutron transverse mode kz and cannot be termed “energies of neutron gravitational quantum states.” We conclude that the experiment setup and real conditions are not adequate to the claimed objective, and the methodology of measured data treatment is flawed. The authors’ claim that “neutron gravitational quantum states are observed” is neither theoretically nor experimentally substantiated. Final, statistically significant results of the experiment are consistent with our physical reasoning that the experiment is not sensitive to “neutron gravitational quantum states” (in terms of Airy mode) and does not prove even their existence in rigorous quantum-mechanical terms.

Vankov, Anatoli Andrei

2010-03-01

277

On observation of neutron quantum states in the Earth's gravitational field  

SciTech Connect

Observation of neutron gravitational quantum states E{sub n}=mgz{sub n} in the peV energy range (z{sub 1} is about 10 {mu}m in the vertical direction) in the experiment conducted at Laue-Langevin Institute, Grenoble, with ultracold neutrons was recently reported in a series of publications. The purpose of the present work is to analyze the experiment. The experimental apparatus is designed to measure a transmission function T(z{sub a}), namely, a horizontal flux of relatively fast neutrons (k>>k{sub z} in wavelength terms) passing through a slit of variable height z{sub a} of upper absorbing wall. The quantum states in question are defined by the so-called Airy functions, which are solutions to the stationary 1D equation for a neutron 'bouncing' above the perfect mirror in a linear potential field. The Airy functions describe the quantum bouncer (QB), the concept of which is subject to theoretical study of toy 1D models of gravitationally bound particles in nonrelativistic quantum mechanics (QM). This is essentially different from the 3D nonstationary QM object, 'the running QB', investigated in the experiment. The authors assume that there is a connection between T(z{sub a}) and the probability density distribution P(z,z{sub a}) for QB states. They devised the 'phenomenological model', in which the quantum pattern should be visible in the transmission curve. We argue, however, that the measured curve T(z{sub a}) is not sensitive to QB states. Instead, it is sensitive to dynamics of neutron horizontal transport inside the absorbing slit for neutrons of energy values about 10{sup 5} times greater than eigenvalues E{sub n}. The latter are related to the neutron transverse mode k{sub z} and cannot be termed ''energies of neutron gravitational quantum states.'' We conclude that the experiment setup and real conditions are not adequate to the claimed objective, and the methodology of measured data treatment is flawed. The authors' claim that 'neutron gravitational quantum states are observed' is neither theoretically nor experimentally substantiated. Final, statistically significant results of the experiment are consistent with our physical reasoning that the experiment is not sensitive to 'neutron gravitational quantum states' (in terms of Airy mode) and does not prove even their existence in rigorous quantum-mechanical terms.

Vankov, Anatoli Andrei [Institute of Physics and Power Engineering, 1 Bondarenko Square, Obninsk, Kaluga Region, 249020 (Russian Federation); Bethany College, 335 E. Swensson Street, Lindsborg, Kansas 67456 (United States)

2010-03-01

278

Inhomogeneous magnetic seed fields and gravitational waves within the magnetohydrodynamic limit  

SciTech Connect

In this paper we apply second-order gauge-invariant perturbation theory to investigate the possibility that the coupling between gravitational waves (GWs) and a large-scale inhomogeneous magnetic field acts as an amplification mechanism in an 'almost' Friedmann-Lemaitre-Robertson-Walker Universe. The spatial inhomogeneities in the magnetic field are consistently implemented using the magnetohydrodynamic (MHD) approximation, which yields an additional source term due to the interaction of the magnetic field with velocity perturbations in the plasma. Comparing the solutions with the corresponding results in our previous work indicates that, on superhorizon scales, the interaction with the spatially inhomogeneous field in the dust regime induces the same boost as the case of a homogeneous field, at least in the ideal MHD approximation. This is attributed to the observation that the MHD induced part of the generated field effectively only contributes on scales where the coherence length of the initial field is less than the Hubble scale. At subhorizon scales, the GW induced magnetic field is completely negligible in relation to the MHD induced field. Moreover, there is no amplification found in the long-wavelength limit.

Zunckel, Caroline [Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); Betschart, Gerold [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); Racah Institute of Physics, Hebrew University of Jerusalem, Givat Ram, 91904 Jerusalem (Israel); Dunsby, Peter K.S. [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa); Marklund, Mattias [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2006-05-15

279

A weak magnetic field measurement system using micro-fluxgate sensors and delta-sigma interface  

Microsoft Academic Search

This paper presents a weak magnetic field measurement system using micro-fluxgate (FG) sensors and a sensor signal processing technique using the delta-sigma modulation in the negative feedback loop. The feedback of the lowpass filtered bitstream output of a delta-sigma modulator to the magnetic field improves system linearity, hysteresis, and stability. In spite of the fact that the second-order delta-sigma modulator

Shoji Kawahito; Ales Cerman; Keita Aramaki; Yoshiaki Tadokoro

2003-01-01

280

SELF-GRAVITATING BODY WITH AN INTERNAL MAGNETIC FIELD. I. NEW ANALYTICAL EQUILIBRIA  

SciTech Connect

We construct exact analytical solutions of the equations describing the equilibrium of a self-gravitating magnetized fluid body, possibly rigidly rotating, by superposing two solutions of finite energy defined in the whole space, one describing a non-magnetized gravitating equilibrium (ST1) and the other describing a magnetized non-gravitating equilibrium (ST2). A large number of ST1s can be found in the literature and directly used for our constructions, and we thus concentrate on ST2s, which are difficult to obtain. We derive some of their general properties and exhibit two explicit classes of axisymmetric 'elementary' such equilibria. The first one is extracted from the stellar models proposed by Prendergast and by Kutvitskii and Solov'ev, respectively. The second one is constructed by using Palumbo's theory of isodynamic equilibria, for which the magnetic pressure is constant on each flux surface. Both types of ST2s have their magnetic field confined within a bounded region, respectively, of spherical and toroidal shapes. A much more general ST2 can be obtained by juxtaposing n+q elementary ST2s, with n of the first type and q of the second type, in such a way that the magnetic regions do not pairwise overlap. The specific equilibria we obtain by superposition thus have no external field extending to infinity, and may be three dimensional (3D), which invalidates a recent nonexistence conjecture. Moreover, they may be arranged to contain force-free regions. Our superposition method can be considered as a 3D generalization of the axisymmetric splitting method previously developed by Kutvitskii and Solov'ev.

Aly, J.-J. [AIM-Unite Mixte de Recherche CEA-CNRS-Universite Paris VII-UMR no. 7158, Centre d'Etudes de Saclay, F-91191 Gif sur Yvette Cedex (France); Amari, T., E-mail: jean-jacques.aly@cea.fr [CNRS, Centre de Physique Theorique de l'Ecole Polytechnique, F-91128 Palaiseau Cedex (France)

2012-05-01

281

First-order correction terms in the weak-field asymptotic theory of tunneling ionization  

NASA Astrophysics Data System (ADS)

The weak-field asymptotic theory (WFAT) of tunneling ionization in a static electric field is developed to the next order in field. The first-order corrections to the ionization rate and transverse momentum distribution of the ionized electrons are derived. This extends the region of applicability of the WFAT at the quantitative level toward stronger fields, practically up to the boundary between tunneling and over-the-barrier regimes of ionization. The results apply to any atom or molecule treated in the single-active-electron and frozen-nuclei approximations. The theory is illustrated by calculations for hydrogen and noble-gas atoms.

Trinh, Vinh H.; Tolstikhin, Oleg I.; Madsen, Lars Bojer; Morishita, Toru

2013-04-01

282

Levitation of delocalized states at weak magnetic field: Critical exponents and phase diagram  

NASA Astrophysics Data System (ADS)

We study numerically the form of the critical line in the disorder-magnetic field phase diagram of the p-q network model, constructed to study the levitation of extended states at weak magnetic fields. We use one-parameter scaling, keeping either q (related to magnetic field) or p (related to energy) constant, to calculate two critical exponents, describing the divergence of the localization length in each case. The ratio of those two exponents defines the form of the critical line close to zero magnetic field.

Kagalovsky, V.

2013-01-01

283

Progressive Muscle Atrophy and Weakness After Treatment by Mantle Field Radiotherapy in Hodgkin Lymphoma Survivors  

SciTech Connect

Purpose: To describe the damage to the muscles and propose a pathophysiologic mechanism for muscle atrophy and weakness after mantle field radiotherapy in Hodgkin lymphoma (HL) survivors. Methods and Materials: We examined 12 patients treated by mantle field radiotherapy between 1969 and 1998. Besides evaluation of their symptoms, the following tests were performed: dynamometry; ultrasound of the sternocleidomastoid, biceps, and antebrachial flexor muscles; and needle electromyography of the neck, deltoid, and ultrasonographically affected arm muscles. Results: Ten patients (83%) experienced neck complaints, mostly pain and muscle weakness. On clinical examination, neck flexors were more often affected than neck extensors. On ultrasound, the sternocleidomastoid was severely atrophic in 8 patients, but abnormal echo intensity was seen in only 3 patients. Electromyography of the neck muscles showed mostly myogenic changes, whereas the deltoid, biceps, and antebrachial flexor muscles seemed to have mostly neurogenic damage. Conclusions: Many patients previously treated by mantle field radiotherapy develop severe atrophy and weakness of the neck muscles. Neck muscles within the radiation field show mostly myogenic damage, and muscles outside the mantle field show mostly neurogenic damage. The discrepancy between echo intensity and atrophy suggests that muscle damage is most likely caused by an extrinsic factor such as progressive microvascular fibrosis. This is also presumed to cause damage to nerves within the radiated field, resulting in neurogenic damage of the deltoid and arm muscles.

Leeuwen-Segarceanu, Elena M. van, E-mail: e.segarceanu@antoniusziekenhuis.nl [Department of Internal Medicine, St. Antonius Hospital, Nieuwegein (Netherlands); Dorresteijn, Lucille D.A. [Department of Neurology, Medisch Spectrum Twente, Enschede (Netherlands); Pillen, Sigrid [Department of Neurology and Clinical Neurophysiology, Donders Center for Neuroscience, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands); Biesma, Douwe H. [Department of Internal Medicine, University Medical Center Utrecht (Netherlands); Vogels, Oscar J.M. [Department of Neurology and Clinical Neurophysiology, St. Antonius Hospital, Nieuwegein (Netherlands); Alfen, Nens van [Department of Neurology and Clinical Neurophysiology, Donders Center for Neuroscience, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands)

2012-02-01

284

Where else is null the gravitational field between two massive spheres?  

NASA Astrophysics Data System (ADS)

To find the point between two massive spherical bodies at which their gravitational fields cancel is an apparently simple problem usually found in introductory physics textbooks. However, by noting that such a point does not exist when the distance between the spheres is small and one of the masses is much smaller than the other—e.g., between the Earth and a billiard ball near the ground—I develop here a simple analysis for establishing existence conditions for this point. Unexpectedly, I have found that the net gravitational field can be null also in certain points inside each sphere. The position of these 'inner' points can be determined by solving a cubic equation via the standard method, known as Cardan's solution. However, when the discriminant of this equation is negative one has the irreducible case, for which Cardan's solution 'fails', but a trigonometric method proposed recently yields exact closed-form expressions. Interestingly, it is shown that these 'inner points' do occur in the Earth-Moon system, in which they are determined just by solving irreducible cubic equations.

Lima, F. M. S.

2009-07-01

285

Gas-Phase Influence on Quasisteady "Liquid Flames" in Gravitational Fields  

NASA Technical Reports Server (NTRS)

We consider the SHS (self-propagating high-temperature synthesis) process for synthesizing materials. In this process a powder mixture of reactants is cold pressed into a sample, which is ignited at one end. A high temperature combustion wave then propagates through the sample converting reactants to the desired product material. In this process, melting of some or all the components is often observed. Therefore, we study combustion waves propagating through a high caloricity inorganic powder mixture whose combustion temperature exceeds the melting temperatures of many components. The solid matrix is thus destroyed by the propagating combustion wave due to melting ahead of the reaction zone, and a liquid bath is formed which contains gaseous bubbles. The waves propagate in the presence of a gravitational field. Due to the effect of gravity, there is relative motion between the rising bubbles and the descending bath, which affects the composition of the medium, its thermophysical properties, the 'liquid flame' structure, and the propagation velocity. To enhance our understanding of phenomena associated with the interaction of the relative motion with the propagating combustion wave we formulate and analyze a relatively simple mathematical model of liquid flames in a gravitational field. We describe the wave structure and combustion characteristics including the combustion velocity. We compare our results to existing experimental observations and suggest new experiments to be performed. We consider the effects of gravity and, in particular, examine both microgravity and large gravity conditions.

Shkadinsky, K. G.; Shkadinskaya, G. V.; Matkowsky, B. J.; Gokoglu, S. (Technical Monitor)

2000-01-01

286

Super-ferrimagnetism of magnetite nanoparticles in a weak magnetic field  

NASA Astrophysics Data System (ADS)

Film composites based on the magnetite Fe3O4 nanoparticles in the polyvinyl alcohol matrix were studied by means of the Mössbauer spectroscopy in a weak magnetic field, mainly at room temperature. The Mössbauer spectra in the absence of a magnetic field show a superposition of minor (poor-resolved) magnetic hyperfine structure and major collapsed spectrum typical for superparamagnetic particles. Such a pattern evidences for the mean particles size ( approx 4 nm) being close to the 'blocking' size for this material at a given temperature. The spectra taken in a weak (0.34 T) magnetic field show almost complete restoration of the magnetic hyperfine structure characteristic for the nanoparticles of the kind. The experimental Mössbauer spectra have been analyzed within the recently developed three-level relaxation model of magnetic dynamics in an ensemble of single-domain particles. This model takes into account the precession and diffusion of particle's uniform magnetization as well as the particles size distribution.

Polikarpov, M. A.; Cherepanov, V. M.; Chuev, M. A.; Shishkov, S. Yu; Yakimov, S. S.

2010-03-01

287

Simulation of the flyby anomaly by means of an empirical asymmetric gravitational field with definite spatial orientation  

Microsoft Academic Search

All anomalous velocity increases until now observed during the Earth flybys of the spacecrafts Galileo, NEAR, Rosetta, Cassini and Messenger have been correctly calculated by computer simulation using an asymmetric field term in addition to the Newtonian gravitational field. The specific characteristic of this term is the lack of coupling to the rotation of the Earth or to the direction

Hans-Juergen Busack; Wulfsdorfer Weg

2007-01-01

288

Orbit determination and gravitational field accuracy for a Mercury transponder satellite  

NASA Technical Reports Server (NTRS)

Covariance studies were performed to investigate the orbit determination problem for a small transponder satellite in a nearly circular polar orbit with 4-hour period around Mercury. With X band and Ka band Doppler and range measurements, the analysis indicates that the gravitational field through degree and order 10 can be solved for from as few as 40 separate 8-hour arcs of tracking data. In addition, the earth-Mercury distance can be determined during each ranging period with about 6-cm accuracy. The expected geoid accuracy is 10 cm up through degree 5, and 1 m through degree 8. The main error sources were the geocentric range measurement error, the uncertainties in higher degree gravity field terms, which were not solved for, and the solar radiation pressure uncertainty.

Vincent, Mark A.; Bender, Pater L.

1990-01-01

289

Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian Dugesia tigrina.  

PubMed

We recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. We report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 microT. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 microV/m. The addition of either 51.1 or 78.4 microT DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas our previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling. These results together with those reported previously point to two distinct physiological effects produced in regenerating planaria by exposure to weak extremely-low-frequency (ELF) magnetic fields. They further suggest that the planarian, which has recently been identified elsewhere as an excellent system for use in teratogenic investigations involving chemical teratogens, might be used similarly in teratogenic investigations involving ELF magnetic fields. PMID:8986364

Jenrow, K A; Smith, C H; Liboff, A R

1996-01-01

290

Magnetoconvection in an inclined magnetic field: linear and weakly non-linear models  

NASA Astrophysics Data System (ADS)

Recent observations of sunspots have revealed a rich range of behaviour and a complicated magnetic field structure; magnetoconvection is the key physical process underlying these phenomena. Traditional studies of magnetoconvection have considered vertical, or sometimes horizontal, imposed fields. Tilted fields have received less attention, and yet these are crucial to sunspot dynamics, particularly in the penumbra where field lines are inclined at a variety of angles to the vertical. Tilting the field is also interesting from a purely theoretical viewpoint since it breaks many of the symmetries usually associated with convection problems. In this paper we study the linear stability of a layer permeated by an inclined magnetic field and go on to set up model equations in order to study the patterns formed in the weakly non-linear regime. Possible applications of the results to sunspots are discussed.

Thompson, S. D.

2005-07-01

291

Classical and quantum decay of oscillations: Oscillating self-gravitating real scalar field solitons  

NASA Astrophysics Data System (ADS)

The oscillating gravitational field of an oscillaton of finite mass M causes it to lose energy by emitting classical scalar field waves, but at a rate that is nonperturbatively tiny for small ??GMm/?c, where m is the scalar field mass: dM/dt?-3 797 437.776(c3/G)?-2e-39.433 795 197/?[1+O(?)]. Oscillatons also decay by the quantum process of the annihilation of scalarons into gravitons, which is only perturbatively small in ?, giving by itself dM/dt?-0.008 513 223 935(m2c2/?)?5[1+O(?2)]. Thus the quantum decay is faster than the classical one for ??39.4338/[ln(?c/Gm2)+7 ln(1/?)+19.9160]. The time for an oscillaton to decay away completely into free scalarons and gravitons is tdecay˜2?6c3/G5m11˜10324 yr(1 meV/mc2)11. Oscillatons of more than one real scalar field of the same mass generically asymptotically approach a static-geometry U(1) boson star configuration with ?=?0, at the rate d(GM/c3)/dt?[(C/?4)e-?/?+Q(m/mPl)2?3](?2-?20), with ?0 depending on the magnitudes and relative phases of the oscillating fields, and with the same constants C, ?, and Q given numerically above for the single-field case that is equivalent to ?0=0.

Page, Don N.

2004-07-01

292

An experiment to test the gravitational Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

The gravitational Aharonov-Bohm (AB) effect is examined in the weak-field approximation to general relativity. In analogy with the electromagnetic AB effect, we find that a gravitoelectromagnetic 4-vector potential gives rise to interference effects. A matter wave interferometry experiment, based on a modification of the gravity-induced quantum interference experiment of Colella, Overhauser and Werner (COW), is proposed to explicitly test the gravitoelectric version of the AB effect in a uniform gravitational field.

Ho, Vu B.; Morgan, Michael J.

293

Searching For Weak Solar Magnetic Fields. What Can We Learn From the Hanle Effect?  

NASA Astrophysics Data System (ADS)

Many dynamical phenomena taking place in the solar atmosphere, such as flares and coronal mass ejections, are driven by the interplay between the magnetic field and the turbulent solar plasma. Long standing questions on the physical origin of coronal heating and solar wind acceleration are also probably related to magnetic mechanisms. So the issue of how to measure magnetic fields in the solar atmosphere, from the photosphere up to the corona, is of crucial importance in solar physics. Because of the high value of the Reynolds magnetic number in the solar atmosphere, magnetic structures may develop from large to very small spatial scales, typically ranging from the scale of the solar diameter down to few tens of kilometers. The magnetic field strength also shows a broad dispersion from several thousands of Gauss in active regions like sunspots, down to a few Gauss in the quiet Sun. The amount of magnetic energy stored in magnetic structures is still unkown, and, according to recent numerical simulations, a significant fraction may be stored in weak, small scale fields, which cover a large fraction of the solar surface. However these field are hardly detectable in magnetograms based on the Zeeman effect because of their limited performances both in terms of polarimetric sensitivity and of spatial resolution. The Hanle effect is a valuable alternative for the diagnostics of weak fields with mixed polarity at small scales. It affects the linear polarization of spectral lines formed by scattering of photons in the solar atmosphere. I will present how weak magnetic fields investigations have changed our vision of the solar magnetism and discuss future research directions, in the context of solar polarimetry projects with ground based or space based intruments.

Faurobert, M.

2012-12-01

294

Weak Antilocalization in Open Quantum Dots and the Effect of Parallel Magnetic Fields  

Microsoft Academic Search

We present measurements of weak antilocalization due to spin-orbit coupling in open GaAs\\/AlGaAs quantum dots. Average and variance of conductance through the dot as a function of perpendicular and parallel magnetic field and temperature (0.3 to 4K) are discussed and compared to theory. Dot sizes varying from 1 mu m^2 to 8 mu m^2 were investigated, spaning dimensions smaller than

D. M. Zumbühl; J. B. Miller; C. M. Marcus; A. C. Gossard

2002-01-01

295

Effects of the weak alternating electric field on Na + concentration inside human red blood cells  

Microsoft Academic Search

In the present experiment, the NMR technique was employed to detect the sodium ion concentration, using the shift reagent Dy(ppp), to differentiate the chemical shifts of the Na+ outside\\/inside the cells. Sodium ion concentration inside the human red blood cells ([Na+]i) could be remarkably reduced when the cells were exposed to weak alternating electric fields (WEF) of different frequencies. The

Gang Chen; Guoping Cai; Riqing Zhang; Pingguan Tu; Nanming Zhao

1998-01-01

296

Theory of Traveling-wave Tubes with Weak External Magnetic Field  

NASA Astrophysics Data System (ADS)

Recent development of PASOTRONs [1], microwave sources which operate without guiding magnetic fields, stimulated an interest to the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields the electrons may propagate radially outward which increases electrons coupling to the slow wave whose field is localized near circuit wall. This increases the wave growth rate and efficiency and allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it doesn't lead to interception of electrons with the slow-wave structure (SWS). To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on operation of traveling-wave tubes with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting SWS walls from electron bombardment at different power levels. [1] D. G. Goebel, J. M. Butler, R. W. Schumacher, J. Santoru, and R. L. Eisenhart. IEEE Plasma Science, vol. 22, p. 547, October 1994.

Abuelfadl, Tamer; Nusinovich, Gregory; Carmel, Yuval

2000-10-01

297

Biological effects due to weak electric and magnetic fields: the temperature variation threshold.  

PubMed Central

A large number of epidemiological and experimental studies suggest that prolonged (>100 s) weak 50-60-Hz electric and magnetic field (EMF) exposures may cause biological effects(NIEHS Working Group, NIH, 1998; Bersani, 1999). We show, however, that for typical temperature sensitivities of biochemical processes, realistic temperature variations during long exposures raise the threshold exposure by two to three orders of magnitude over a fundamental value, independent of the biophysical coupling mechanism. Temperature variations have been omitted in previous theoretical analyses of possible weak field effects, particularly stochastic resonance (Bezrukov and Vodyanoy 1997a. Nature. 385:319-321; Astumian et al., 1997 Nature. 338:632-633; Bezrukov and Vodyanoy, 1997b. Nature. 338:663; Dykman and McClintock, 1998. Nature. 391:344; McClintock, 1998;. Gammaitoni et al., 1998. Rev. Mod. Phys. 70:223-287). Although sensory systems usually respond to much shorter (approximately 1 s) exposures and can approach fundamental limits (Bialek, 1987 Annu. Rev. Biophys. Biophys. Chem. 16:455-468; Adair et al, 1998. Chaos. 8:576-587), our results significantly decrease the plausibility of effects for nonsensory biological systems due to prolonged, weak-field exposures.

Weaver, J C; Vaughan, T E; Martin, G T

1999-01-01

298

On the Effect of Weak Magnetic Field on Solutions of Glutamic Acid: the Function of Water  

NASA Astrophysics Data System (ADS)

Even though a wide literature is available on the effects of weak Extremely Low Frequency ElectroMagnetic Fields (ELF-EMF) on the biochemical reactions, nevertheless the physical nature of these effects is largely unknown. The main challenge is the mismatch between the infinitesimal amount of the energy carried by the perturbation and the entity of the response of the system. More than 10 years ago, it was claimed that a weak current can be induced in a aqueous solution of Glutamic acid exposed to a weak magnetic field having a certain frequency. We have checked the influence of ELF-EMF on Glutamic acid using the FTIR-ATR spectroscopy in order to observe structural changes induced by the exposure. Samples have been exposed for 10, 20 or 30 minutes to a magnetic field generated by Helmoltz coils and then placed into the spectrometer. After the exposure solutions having different pH values always shown a shift toward the de-protonated species. The effect lasts for minutes after the exposure before the native configuration is restored.

De Ninno, A.; Congiu Castellano, A.

2011-12-01

299

General equations for the motions of ice crystals and water drops in gravitational and electric fields  

NASA Technical Reports Server (NTRS)

General equations for the Reynolds number of a variety of types of ice crystals and water drops are given in terms of the Davies, Bond, and Knudsen numbers. The equations are in terms of the basic physical parameters of the system and are valid for calculating velocities in gravitational and electric fields over a very wide range of sizes and atmospheric conditions. The equations are asymptotically matched at the bottom and top of the size spectrum, useful when checking large computer codes. A numerical system for specifying the dimensional properties of ice crystals is introduced. Within the limits imposed by such variables as particle density, which have large deviations, the accuracy of velocities appears to be within 10 percent over the entire range of sizes of interest.

Nisbet, John S.

1989-01-01

300

Improved model of the Earth's gravitational field: GEM-T1  

SciTech Connect

Goddard Earth Model T1 (GEM-T1), which was developed from an analysis of direct satellite tracking observations, is the first in a new series of such models. GEM-T1 is complete to degree and order 36. It was developed using consistent reference parameters and extensive earth and ocean tidal models. It was simultaneously solved for gravitational and tidal terms, earth orientation parameters, and the orbital parameters of 580 individual satellite arcs. The solution used only satellite tracking data acquired on 17 different satellites and is predominantly based upon the precise laser data taken by third generation systems. In all, 800,000 observations were used. A major improvement in field accuracy was obtained. For marine geodetic applications, long wavelength geoidal modeling is twice as good as in earlier satellite-only GEM models. Orbit determination accuracy has also been substantially advanced over a wide range of satellites that have been tested.

Marsh, J.G.; Lerch, F.J.; Christodoulidis, D.C.; Putney, B.H.; Felsentreger, T.L.; Sanchez, B.V.; Smith, D.E.; Klosko, S.M.; Martin, T.V.; Pavlis, E.C.

1987-07-01

301

On the local standard of rest. [comoving with young objects in gravitational field of spiral galaxies  

NASA Technical Reports Server (NTRS)

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a spiral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars. Previously announced in STAR as N83-24443

Yuan, C.

1983-01-01

302

Orbital dynamics of the gravitational field in Bardeen space-time  

NASA Astrophysics Data System (ADS)

In this paper, the orbital dynamics of the gravitational field in Bardeen space-time are investigated. The equations of the particle's orbital motion are given by solving the Lagrangian equation, and the stability and types of orbits are studied by means of analysing the effective potential of particles. Also, with the help of phase-plane method, the closed and non-closed orbits of test particle are analysed. We find that the stability and types of orbits in the Bardeen space-time are determined not only by the particles' energy but also by the angular momentum. And for q=0.5 M and b<3.3731 M, absorbed by the black hole is the only fate of the test particle. We also find that the position of the innermost stable circular orbit of Bardeen black hole occurs at r min =5.5722 M.

Zhang, Yu; Li, EnKun; Geng, JinLing

2014-06-01

303

An improved model of the Earth's gravitational field: GEM-T1  

NASA Technical Reports Server (NTRS)

Goddard Earth Model T1 (GEM-T1), which was developed from an analysis of direct satellite tracking observations, is the first in a new series of such models. GEM-T1 is complete to degree and order 36. It was developed using consistent reference parameters and extensive earth and ocean tidal models. It was simultaneously solved for gravitational and tidal terms, earth orientation parameters, and the orbital parameters of 580 individual satellite arcs. The solution used only satellite tracking data acquired on 17 different satellites and is predominantly based upon the precise laser data taken by third generation systems. In all, 800,000 observations were used. A major improvement in field accuracy was obtained. For marine geodetic applications, long wavelength geoidal modeling is twice as good as in earlier satellite-only GEM models. Orbit determination accuracy has also been substantially advanced over a wide range of satellites that have been tested.

Marsh, J. G.; Lerch, F. J.; Christodoulidis, D. C.; Putney, B. H.; Felsentreger, T. L.; Sanchez, B. V.; Smith, D. E.; Klosko, S. M.; Martin, T. V.; Pavlis, E. C.

1987-01-01

304

Classical-field approximation for cold weakly interacting bosons without free parameters  

NASA Astrophysics Data System (ADS)

The classical-field approximation to cold weakly interacting bosons allows for a unified treatment of condensed and uncondensed parts of the system. Until now, however, the quantitative predictions were limited by a dependence of the results on a grid chosen for numerical implementation of the method. In this paper, we propose replacing this unphysical ambiguity by an additional postulate: the temperature of the gas at thermal equilibrium should be the same as that of an ideal Bose gas with the same fraction of condensed atoms. As it turns out, with this additional assumption, nearly all atoms are within the classical fields, thus the method applies to the whole system.

Zawitkowski, ?ukasz; Brewczyk, Miros?aw; Gajda, Mariusz; Rz??ewski, Kazimierz

2004-09-01

305

Vortex states in rotating 3A in a weak magnetic field  

NASA Astrophysics Data System (ADS)

We study theoretically the phase diagram of vortex states in 3A in a weak magnetic field H~H0(30 Oe). We find that the lattice of 2? analytic vortices proposed by Fujita et al. has the lowest free energy for H<>H0 the lattice of vortex pairs (Seppälä-Volovik vortices) is more favorable. In the vicinity of the transition temperature (T>0.8Tc) the lattice of dipole-locked vortex pairs appears between the above two configurations in a magnetic field H~0.5H0 and for a rotation speed ?<~0.04 rad/sec.

Zotos, Xenophon; Maki, Kazumi

1985-06-01

306

Transient effect of weak electromagnetic fields on calcium ion concentration in Arabidopsis thaliana  

PubMed Central

Background Weak magnetic and electromagnetic fields can influence physiological processes in animals, plants and microorganisms, but the underlying way of perception is poorly understood. The ion cyclotron resonance is one of the discussed mechanisms, predicting biological effects for definite frequencies and intensities of electromagnetic fields possibly by affecting the physiological availability of small ions. Above all an influence on Calcium, which is crucial for many life processes, is in the focus of interest. We show that in Arabidopsis thaliana, changes in Ca2+-concentrations can be induced by combinations of magnetic and electromagnetic fields that match Ca2+-ion cyclotron resonance conditions. Results An aequorin expressing Arabidopsis thaliana mutant (Col0-1 Aeq Cy+) was subjected to a magnetic field around 65 microtesla (0.65 Gauss) and an electromagnetic field with the corresponding Ca2+ cyclotron frequency of 50 Hz. The resulting changes in free Ca2+ were monitored by aequorin bioluminescence, using a high sensitive photomultiplier unit. The experiments were referenced by the additional use of wild type plants. Transient increases of cytosolic Ca2+ were observed both after switching the electromagnetic field on and off, with the latter effect decreasing with increasing duration of the electromagnetic impact. Compared with this the uninfluenced long-term loss of bioluminescence activity without any exogenic impact was negligible. The magnetic field effect rapidly decreased if ion cyclotron resonance conditions were mismatched by varying the magnetic fieldstrength, also a dependence on the amplitude of the electromagnetic component was seen. Conclusion Considering the various functions of Ca2+ as a second messenger in plants, this mechanism may be relevant for perception of these combined fields. The applicability of recently hypothesized mechanisms for the ion cyclotron resonance effect in biological systems is discussed considering it's operating at magnetic field strengths weak enough, to occur occasionally in our all day environment.

Pazur, Alexander; Rassadina, Valentina

2009-01-01

307

A 660 D&O Gravitational Field of the Moon from the GRAIL Primary Mission  

NASA Astrophysics Data System (ADS)

The Gravity Recovery and Interior Laboratory (GRAIL) mission has completed its primary three-month tour that resulted in a gravitational field of 660 degree-and-order or equivalent surface resolution of 8 km. The primary measurement for the gravity field is the inter-spacecraft K-Band Range Rate (KBRR) measurement derived from dual spacecraft one-way range. Direct Doppler tracking at X-band from the Deep Space Network for Ebb and Flow supplemented The KBRR. Advanced system calibrations and measurement timing have resulted in unprecedented data quality of better than 0.1 microns/sec. The gravity field solution shows an error spectrum with several orders of magnitude improvement for all wavelengths when compared to previous missions. Nearly uniform correlations with topography exist through higher harmonic degrees and are a good measure of field integrity. The results of the mission satisfy the scientific objectives of determining the structure of the lunar interior from crust to core and advancing the understanding of the thermal evolution of the Moon. They also directly address the mission's investigations that include mapping the structure of the crust and lithosphere, understanding the Moon's asymmetric thermal evolution, determining the subsurface structure of impact basins and the origin of mascons, ascertaining the temporal evolution of the crustal brecciation and magmatism, constrain deep interior structure from tides, and place limits on the size of a possible solid inner core.

Yuan, Dah-Ning; Konopliv, Alex; Asmar, Sami; Park, Ryan; Williams, James; Watkins, Michael; Fahnestock, Eugene; Kruizinga, Gerhard; Paik, Meegyeong; Strekalov, Dmitry; Harvey, Nate; Zuber, Maria; Smith, David

2013-04-01

308

Rectification and signal averaging of weak electric fields by biological cells.  

PubMed Central

Oscillating electric fields can be rectified by proteins in cell membranes to give rise to a dc transport of a substance across the membrane or a net conversion of a substrate to a product. This provides a basis for signal averaging and may be important for understanding the effects of weak extremely low frequency (ELF) electric fields on cellular systems. We consider the limits imposed by thermal and "excess" biological noise on the magnitude and exposure duration of such electric field-induced membrane activity. Under certain circumstances, the excess noise leads to an increase in the signal-to-noise ratio in a manner similar to processes labeled "stochastic resonance." Numerical results indicate that it is difficult to reconcile biological effects with low field strengths.

Astumian, R D; Weaver, J C; Adair, R K

1995-01-01

309

Wide-Field Weak Lensing by RX J1347-1145  

NASA Astrophysics Data System (ADS)

We present an analysis of weak-lensing observations for RX J1347-1145 over a 43'×43' field taken in B and R filters on the Blanco 4 m telescope at CTIO. RX J1347-1145 is a massive cluster at redshift z=0.45. Using a population of galaxies with 20weak-lensing signal at the p<0.0005 level, finding best-fit parameters of ?v=1400+130-140 km s-1 for a singular isothermal sphere model and r200=3.5+0.8-0.2 Mpc with c=15+64-10 for an NFW model in an ?m=0.3, ??=0.7 cosmology. In addition, a mass-to-light ratio M/LR=90+/-20 Msolar/LRsolar was determined. These values are consistent with the previous weak-lensing study of RX J1347-1145 by Fischer & Tyson, giving strong evidence that systemic bias was not introduced by the relatively small field of view in that study. Our best-fit parameter values are also consistent with recent X-ray studies by Allen et al. and Ettori et al. but are not consistent with recent optical velocity dispersion measurements by Cohen & Kneib.

Kling, Thomas P.; Dell'Antonio, Ian; Wittman, David; Tyson, J. Anthony

2005-06-01

310

Principles of gravitational biology  

NASA Technical Reports Server (NTRS)

Physical principles of gravitation are enumerated, including gravitational and inertial forces, weight and mass, weightlessness, size and scale effects, scale limits of gravitational effects, and gravity as biogenic factor. Statocysts, otolithic organs of vertebrates, gravity reception in plants, and clinostat studies for gravitation orientation are reviewed. Chronic acceleration is also studied, as well as physiology of hyper and hypodynamic fields. Responses of animals to a decreased acceleration field are examined, considering postural changes, work capacity, growth, and physiologic deadaptation.

Smith, A. H.

1975-01-01

311

Investigation of the regular motion of bodies of variable mass in a gravitational field with allowance for relativistic effects  

Microsoft Academic Search

The motion of many material points with variable masses that are analytic functions of time in a post-Newtonian gravitational field is investigated, taking into account general-relativistic effects. A solution to the relevant system of differential equations of regular motion relative to some absolute coordinate system is obtained as a series expansion in powers of time that converges on a certain

N. G. Magnaradze

1978-01-01

312

Transpiration of Upper and Lower Surfaces of a Leaf at Various Orientations in the Earth'S Gravitational Field.  

National Technical Information Service (NTIS)

Changes were noted in the transpiration of the upper and lower surfaces of a leaf rotated so the surfaces are 180 degrees from their natural orientation with respect to the earth's gravitational field. Undetached sugar beet leaves were used in the study. ...

V. Z. Kotlyar M. A. Lyubynskyi

1969-01-01

313

Weak interactions from 1950-1960: a quantitative bibliometric study of the formation of a field  

SciTech Connect

A quantitative technique is illustrated which uses publication statistics from a bibliography of citations in the area of weak interactions to provide a view of trends and patterns in the development of the field during the period from 1950 to 1960. An overview is given of what the physicists working in weak interactions during this period were doing as indicated by an analysis of the subjects of their papers. The dominant problems and concerns are discussed. Focus is then turned to the events surrounding the emergence of the tau/theta particle puzzle, the discovery of parity nonconservation, and the resolution offered by the V-A theory. Displaying the data from the citation index in unusual ways highlights dominant issues of the period, especially the close relationship between theory and experiment in the latter half of the decade. 64 refs., 14 figs. (LEW)

White, D.H.; Sullivan, D.

1986-01-01

314

Field electron emission from carbon nanotubes in the presence of a weak high-frequency electric field  

NASA Astrophysics Data System (ADS)

Series of narrow peaks in the frequency range of f ? 50-1200 MHz have been revealed in the frequency responses of the emission current from carbon nanotubes in the presence of a weak high-frequency electric field. The analysis makes it possible to attribute these peaks to resonance of the first and second harmonics of forced mechanical vibrations of carbon nanotubes in a high-frequency electric field. The determined Q factor of nanotubes is in the range of 100-300.

Musatov, A. L.; Izrael'yants, K. R.; Blagov, E. V.

2014-04-01

315

Weak Bipolar Fields in the Solar Wind and Cusp: A Theoretical Interpretation*  

NASA Astrophysics Data System (ADS)

Localized bipolar electrostatic field structures have now been measured in Earth's auroral ionosphere,1 in conjunction with magnetic reconnection in the magnetotail,2 in the vicinity of the magnetopause and cusp,3 and in the solar wind.4 In most of these venues the associated measured potentials, ?, often have extremely low amplitudes with ?m? e?max/Te? 1 (sometimes with ?m 10-3 or less). A systematic analytic theory of stationary bipolar fields (i.e., as viewed in their co-moving frame) is developed based on the smallness parameter ?m. The theory appears to explain a number of features of measured weak bipolar structures in terms of electron phase space holes, and predicts relatively simple relationships between bipolar waveforms and the corresponding distributions of passing and trapped electrons. The analytic potential obtained from theory takes the form of a hyperbolic secant raised to the fourth power for the simplest trapped electron distribution. This potential yields a good fit to bipolar waveforms measured in the solar wind and Earth's cusp region. For measurements of hundreds of weak bipolar field events in the cusp,3 the theory is shown to be consistent with the most frequently observed half-width (defined as half the distance between bipolar field peaks, which is ~2 Debye lengths). The theory is also consistent with various other features of the measured distribution of hole velocities vs hole half-widths. It is demonstrated using Vlasov simulations that a variety of the weak bipolar structures are stable over long times in one dimension, provided that they moving sufficiently fast relative to the mean velocity of the ions. * Research supported by NSF, NASA, and DOE. 1 Ergun, R.E., et al., Phys. Rev. Lett., 81, 826 (1998). 2 Cattell, C., et al., J. Geophys. Res., 110, A01211 (2005). 3 Franz, J.R., et al., J. Geophys. Res., 110, A09212 (2005). 4 Mangeney, A., private communication.

Goldman, M. V.; Newman, D. L.; Mangeney, A.

2007-05-01

316

The R.I. Pimenov unified gravitation and electromagnetism field theory as semi-Riemannian geometry  

SciTech Connect

More than forty years ago R.I. Pimenov introduced a new geometry-semi-Riemannian one-as a set of geometrical objects consistent with a fibering pr: M{sub n} {yields} M{sub m}. He suggested the heuristic principle according to which the physically different quantities (meter, second, Coulomb, etc.) are geometrically modelled as space coordinates that are not superposed by automorphisms. As there is only one type of coordinates in Riemannian geometry and only three types of coordinates in pseudo-Riemannian one, a multiple-fibered semi-Riemannian geometry is the most appropriate one for the treatment of more than three different physical quantities as unified geometrical field theory. Semi-Euclidean geometry {sup 3}R{sub 5}{sup 4} with 1-dimensional fiber x{sup 5} and 4-dimensional Minkowski space-time as a base is naturally interpreted as classical electrodynamics. Semi-Riemannian geometry {sup 3}V{sub 5}{sup 4} with the general relativity pseudo-Riemannian space-time {sup 3}V{sub 4}, and 1-dimensional fiber x{sup 5}, responsible for the electromagnetism, provides the unified field theory of gravitation and electromagnetism. Unlike Kaluza-Klein theories, where the fifth coordinate appears in nondegenerate Riemannian or pseudo-Riemannian geometry, the theory based on semi-Riemannian geometry is free from defects of the former. In particular, scalar field does not arise.

Gromov, N. A., E-mail: gromov@dm.komisc.r [Komi Science Center UrD RAS, Department of Mathematics (Russian Federation)

2009-05-15

317

The Optical Gravitational Lensing Experiment. Gaia South Ecliptic Pole Field as Seen by OGLE-IV  

NASA Astrophysics Data System (ADS)

We present a comprehensive analysis of the Gaia South Ecliptic Pole (GSEP) field, 5.3 square degrees area around the South Ecliptic Pole on the outskirts of the LMC, based on the data collected during the fourth phase of the Optical Gravitational Lensing Experiment, OGLE-IV. The GSEP field will be observed during the commissioning phase of the ESA Gaia space mission for testing and calibrating the Gaia instruments. We provide the photometric maps of the GSEP region containing the mean VI photometry of all detected stellar objects and their equatorial coordinates. We show the quality and completeness of the OGLE-IV photometry and color-magnitude diagrams of this region. We conducted an extensive search for variable stars in the GSEP field leading to the discovery of 6789 variable stars. In this sample we found 132 classical Cepheids, 686 RR Lyr type stars, 2819 long-period, and 1377 eclipsing variables. Several objects deserving special attention were also selected, including a new classical Cepheid in a binary eclipsing system. To provide empirical data for the Gaia Science Alert system we also conducted a search for optical transients. We discovered two firm type Ia supernovae and nine additional supernova candidates. To facilitate future Gaia supernovae detections we prepared a list of more than 1900 galaxies to redshift about 0.1 located in the GSEP field. Finally, we present the results of astrometric study of the GSEP field. With the 26 months time base of the presented here OGLE-IV data, proper motions of stars could be detected with the accuracy reaching 2 mas/yr. Astrometry allowed to distinguish galactic foreground variable stars detected in the GSEP field from LMC objects and to discover about 50 high proper motion stars (proper motion ? 100 mas/yr). Among them three new nearby white dwarfs were found. All data presented in this paper are available to the astronomical community from the OGLE Internet archive.

Soszy?ski, I.; Udalski, A.; Poleski, R.; Koz?owski, S.; Wyrzykowski, ?.; Pietrukowicz, P.; Szyma?ski, M. K.; Kubiak, M.; Pietrzy?ski, G.; Ulaczyk, K.; Skowron, J.

2012-09-01

318

Gravitation physics at BGPL  

NASA Astrophysics Data System (ADS)

We report progress on a program of gravitational physics experiments using cryogenic torsion pendula undergoing large-amplitude torsion oscillation. This program includes tests of the gravitational inverse square law and of the weak equivalence principle. Here, we describe our ongoing search for inverse-square-law violation at a strength down to 10 -5 of standard gravity. The low-vibration environment provided by the Battelle Gravitation Physics Laboratory (BGPL) is uniquely suited to this study.

Boynton, P. E.; Bonicalzi, R. M.; Kalet, A. M.; Kleczewski, A. M.; Lingwood, J. K.; McKenney, K. J.; Moore, M. W.; Steffen, J. H.; Berg, E. C.; Cross, W. D.; Newman, R. D.; Gephart, R. E.

2007-03-01

319

Effects of thermal-solutal convection on temperature and solutal fields under various gravitational orientations  

NASA Technical Reports Server (NTRS)

Semiconductor crystals such as Hg(1-x)CD(x)Te grown by unidirectional solidification Bridgmann method have shown compositional segregations in both the axial and radial directions. Due to the wide separation between the liquidus and the solidus of its pseudobinary phase diagram, there is a diffusion layer of higher HgTe content built up in the melt near the melt-solid interface which gives a solute concentration gradient in the axial direction. The value of effective diffusion coefficient calculated from fitting of the data to 1D model varies with Hg(1-x)Cd(x)Te growth conditions. This indicates that the growth condition of the Hg(1-x)Cd(x)Te is not purely diffusion controlled. Because of the higher thermal conductivity in the melt than that in the crystal in the growth system, there is a thermal leakage through the fused silica crucible wall near the melt-solid interface. This gives a thermal gradient in the radial direction. Hart, and Thorpe, Hutt and Soulsby have shown that under such conditon a fluid will become convectively unstable as a result of different diffusitivities of temperature and solute. It is quite important to understand the effects of this thermosolute convection on the compositonal segregation in both axial and radial directions in the unidirectionally solidified crystals under various gravitational directions. To reach this goal, we start with a simplified problem to study the effects of thermal-solutal convection on the temperature and solutal fields under various gravitional orientations. We begin by reviewing model governing equations.

Wang, Jai-Ching

1993-01-01

320

Application of the weak-field asymptotic theory to tunneling ionization of H2O  

NASA Astrophysics Data System (ADS)

The weak-field asymptotic theory of tunneling ionization in a static electric field is applied to H2O. The orientation dependence of the ionization rate is studied. The use of polarization-consistent basis sets with up to heptuble-zeta accuracy and variationally optimized exponents improves the asymptotic form of the wave function and allows for an accurate extraction of the structure factor defining the ionization rate. The results are presented based on Hartree-Fock wave functions and density functional theory. The density functional theory reproduces closely the experimental vertical ionization potential. We find that the rate peaks at an angle of 81? between the field and molecular principal inertial axis through the O atom. The predictions for the orientation dependence of the rate are compared to available theoretical results.

Madsen, Lars Bojer; Jensen, Frank; Tolstikhin, Oleg I.; Morishita, Toru

2014-03-01

321

Force field parametrization by weak coupling. Re-engineering SPC water  

NASA Astrophysics Data System (ADS)

A recently developed scheme for the automatic adjustment of force field parameters to experimentally observed properties is applied to the simple-point-charge (SPC) water model. The refinement procedure is based on a first-order coupling of a force-field parameter (say, an atomic charge) to the deviation of a calculated bulk liquid property (e.g. the heat of vaporization) from its ideal value. I.e. the method is very similar in spirit to the weak-coupling scheme used to implement constant-temperature or constant-pressure molecular dynamics. With the method we have refined the charges and the Lennard-Jones diameter of the SPC water model at several state points of high temperature and high pressure. We also have studied how these force-field parameters have to be reoptimized as the cutoff distance is varied.

Berweger, Christian D.; van Gunsteren, Wilfred F.; Müller-Plathe, Florian

1995-01-01

322

Symmetric reflection band broadening of weakly polymer stabilized cholesteric thin films using low DC electric fields  

NASA Astrophysics Data System (ADS)

We report on a new, low field electro-optical effect in weakly polymer stabilized cholesteric liquid crystals with negative dielectric anisotropy. By applying low DC electric fields (<3V/?m), a symmetric broadening of the cholesteric reflection band can be seen, resulting in band width increases by factors of two or more. An intensive study of the various experimental parameters combined with numerical calculations of the transmission spectra, indicate that the polymer interacts with the electric fields resulting in an approximately constant pitch gradient across the cell thickness. Our results show that the maximum pitch distortions reach values of approximately 15% the zero voltage value for notches in the visible range (pitches of 300-400nm), but increase along with the pitch. Possible physical mechanisms will be explored and discussed that might explain this interesting electro-optical effect.

Dunning, Madeline; Bailey, Christopher; Voevodin, Anastasia; Tondiglia, Vincent; Natarajan, Lalgudi; White, Timothy; Bunning, Timothy

2011-03-01

323

Non-Langevin high-temperature magnetization of nanoparticles in a weak magnetic field  

SciTech Connect

Experimental evidence and theoretical substantiation are presented for the asymptotic behavior of high-temperature magnetization of an ensemble of nanoparticles in a weak magnetic field, which was predicted earlier and which differs qualitatively from the 'Langevin' limit for ideal superparamagnetic particles. It is shown that the physical reason for the new asymptotic behavior is the temperature-independent 'positive' tilt of the uniform magnetization vector at local energy minima in the direction of the field; this asymptotic behavior is associated with the nonstandard thermodynamics of single-domain particles, which depends on the ratio of characteristic frequencies of regular precession and random diffusion of this vector. An alternative approach is proposed for describing the magnetic dynamics of an ensemble of nanoparticles in a magnetic field, and the precession orbits of the magnetization vector are considered as stochastic states of each particle, whereas each state is characterized by the trajectory-averaged value of magnetization.

Chuev, M. A. [Russian Academy of Sciences, Institute of Physics and Technology (Russian Federation)], E-mail: m_a_chuev@mail.ru

2009-02-15

324

Robust ground state and artificial gauge in DQW exciton condensates under weak magnetic field  

NASA Astrophysics Data System (ADS)

An exciton condensate is a vast playground in studying a number of symmetries that are of high interest in the recent developments in topological condensed matter physics. In double quantum wells (DQWs) they pose highly nonconventional properties due to the pairing of non-identical fermions with a spin dependent order parameter. Here, we demonstrate a new feature in these systems: the robustness of the ground state to weak external magnetic field and the appearance of the artificial spinor gauge fields beyond a critical field strength where negative energy pair-breaking quasi particle excitations, i.e. de-excitation pockets (DX-pockets), are created in certain k regions. The DX-pockets are the Kramers symmetry broken analogs of the negative energy pockets examined in the 1960s by Sarma. They respect a disk or a shell-topology in k-space or a mixture between them depending on the magnetic field strength and the electron-hole density mismatch. The Berry connection between the artificial spinor gauge field and the TKNN number is made. This field describes a collection of pure spin vortices in real space when the magnetic field has only inplane components.

Hakio?lu, T.; Özgün, Ege; Günay, Mehmet

2014-08-01

325

Lipid utilization in radish seedlings as affected by weak horizontal extremely low frequency magnetic field.  

PubMed

Composition and content of lipids were studied in 5-day-old radish seedlings (Raphanus sativus L. var. radicula DC.) grown in lowlight and darkness in an extremely low frequency (ELF) magnetic field characterized by 50?Hz frequency and ?500?µT flux density. The control seedlings were grown under the same conditions, but without exposure to the magnetic field. The products of lipid metabolism were compared with lipid composition in seeds. In control seedlings, reserve neutral lipids, mostly triacylglycerides, were utilized for the formation of polar lipids (PL). As a result, the amount of the latter doubled, particularly due to glycolipids (GL) and phospholipids (PhL) compared to their content in seeds. At 20-22?°C in light, magnetic field exposure increased the production of PL by threefold specifically, GL content increased fourfold and PhL content rose 2.5 times, compared to seeds. In darkness, the effect of magnetic field on lipids was weaker. At the lower temperature of 13-16?°C in light, the effect of the magnetic field was weak, but in the darkness, no magnetic field action was recorded. It is concluded that ELF magnetic field stimulated lipid synthesis in chloroplast, mitochondrial, and other cell membranes in radish seedlings grown in light at 20-22?°C and 13-16?°C. PMID:24123065

Novitskii, Yurii I; Novitskaya, Galina V; Serdyukov, Yurii A

2014-02-01

326

Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian, Dugesia tigrina  

SciTech Connect

The authors recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. The authors report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 {micro}T. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 {micro} V/m. The addition of either 51.1 or 78.4 {micro}T DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas the previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling.

Jenrow, K.A.; Smith, C.H.; Liboff, A.R. [Oakland Univ., Rochester, MI (United States). Dept. of Physics] [Oakland Univ., Rochester, MI (United States). Dept. of Physics

1996-12-31

327

Dynamics of neutrino-driven winds: inclusion of accurate weak interaction rates in strong magnetic fields  

NASA Astrophysics Data System (ADS)

Solving Newtonian steady-state wind equations while considering the accurate weak interaction rates and magnetic fields (MFs) of young neutron stars, we study the dynamics and nucleosynthesis of neutrino-driven winds (NDWs) from proto neutron stars (PNSs). For a typical 1.4 Msolar PNS model, we find that the nucleosynthesis products are closely related to the luminosity of neutrinos and anti-neutrinos. The lower the luminosity is, the larger is the effect on the NDWs caused by weak interactions and MFs. At a high anti-neutrino luminosity of typically 8 × 1051 erg s-1, neutrinos and anti-neutrinos dominate the processes in an NDW and the MFs hardly change the wind's properties. But at a low anti-neutrino luminosity of 1051 erg s-1 at the late stage of an NDW the mass of the product and process of nucleosynthesis are changed significantly in strong MFs. Therefore, in most of the models considered for the NDWs from PNSs, based on our calculations, the influences of MFs and the net weak interactions on the nucleosynthesis are not significant.

Liu, Men-Quan; Wang, Zhong-Xiang

2013-02-01

328

Incommensurate Filling of Ultracold Spin-1 Atoms in Optical Superlattice with a Weak Magnetic Field  

NASA Astrophysics Data System (ADS)

The ground states of ultracold spin-1 atoms trapped in an optical superlattice in a weak magnetic field with incommensurate filling of three atoms in one double-well are obtained. It is shown that the ground-state diagrams of the reduced double-well model are remarkably different for the antiferromagnetic and ferromagnetic atoms. These novel spin-states can be controlled easily and exactly by modulating the tunneling parameter and the quadratic Zeeman energy, which may be a tool for the study of spin-entanglement.

Zheng, Gong-Ping; Qin, Shuai-Feng; Jian, Wen-Tian; Wang, Shou-Yang

2013-08-01

329

Weakly nonlinear study of normal-field instability in confined ferrofluids.  

PubMed

Similar to the classic three-dimensional Rosensweig instability, a ferrofluid confined in a vertical Hele-Shaw cell subjected to an in-plane normal magnetic field develops a periodic array of peaked interfacial structures. We perform a weakly nonlinear analysis that is able to reproduce the morphology of such pattern formation phenomenon at lowest nonlinear order. A mode-coupling theory is applied to compare the early nonlinear evolution of the interface with static shapes obtained when relevant forces equilibrate. Our nonlinear results indicate that the time-evolving shapes tend to approach stable stationary solutions. PMID:21867300

Lira, Sérgio A; Miranda, José A

2011-07-01

330

Random fields and the weakly first-order phase transition in superconductors  

SciTech Connect

We study the influence of random fields with short-range and long-range correlations on the weakly first-order phase transition in superconductors. Renormalization-group (RG) analysis near the upper critical dimensionality d/sub u/ = 6 (short-range correlations) reveals a new critical behavior which holds if the number of the order-parameter components is n>10. In the long-range case, the RG transformation is self-consistent only if the parameter theta of the long-range correlations is assumed of order epsilon, epsilon = 6-d.

Busiello, G.; De Cesare, L.; Uzunov, D.I.

1986-10-01

331

Ultra-cold anti-neutrons (UC overlineN) . (II). Production probability under magnetic and gravitational fields  

NASA Astrophysics Data System (ADS)

The effects of wall collisions on an oscillating ultra-cold neutron-anti-neutron system can be partially compensated by an applied magnetic field. In this work we investigate this system in some detail based on the facts described in part I of this article using available overlinen-nucleus potentials. We integrate over the UCN phase space including the effects of the earth's gravitational field.

Yoshiki, H.; Golub, R.

1992-01-01

332

Exact and analytic solutions of the Ernst equation governing axially symmetric stationary vacuum gravitational fields  

NASA Astrophysics Data System (ADS)

We obtain solutions to a transformation of the axially symmetric Ernst equation, which governs a class of exact solutions of Einstein's field equations. Physically, the equation serves as a model of axially symmetric stationary vacuum gravitational fields. By an application of the method of homotopy analysis, we are able to construct approximate analytic solutions to the relevant boundary value problem in the case where exact solutions are not possible. The results presented constitute a solution for a complicated nonlinear and singular initial value problem. Through appropriate selection of the auxiliary linear operator and convergence control parameter, we are able to obtain low order approximations which minimize residual error over the problem domain. The benefit to such approach is that we obtain very accurate approximations after computing very few terms, hence the computational efficiency is high. Finally, an exact solution is provided in a special case, and this corresponds to the analytical solutions obtained in the more general case. The approximate solutions agree qualitatively with the exact solutions.

Baxter, Mathew; Van Gorder, Robert A.

2013-03-01

333

Gravitational collapse of a homogeneous scalar field in deformed phase space  

NASA Astrophysics Data System (ADS)

We study the gravitational collapse of a homogeneous scalar field, minimally coupled to gravity, in the presence of a particular type of dynamical deformation between the canonical momenta of the scale factor and of the scalar field. In the absence of such a deformation, a class of solutions can be found in the literature [R. Goswami and P. S. Joshi], whereby a curvature singularity occurs at the collapse end state, which can be either hidden behind a horizon or be visible to external observers. However, when the phase space is deformed, as implemented herein this paper, we find that the singularity may be either removed or instead, attained faster. More precisely, for negative values of the deformation parameter, we identify the emergence of a negative pressure term, which slows down the collapse so that the singularity is replaced with a bounce. In this respect, the formation of a dynamical horizon can be avoided depending on the suitable choice of the boundary surface of the star. Whereas for positive values, the pressure that originates from the deformation effects assists the collapse toward the singularity formation. In this case, since the collapse speed is unbounded, the condition on the horizon formation is always satisfied and furthermore the dynamical horizon develops earlier than when the phase-space deformations are absent. These results are obtained by means of a thoroughly numerical discussion.

Rasouli, S. M. M.; Ziaie, A. H.; Marto, J.; Moniz, P. V.

2014-02-01

334

New Estimates of Hydrological and Oceanic Excitations of Variations of Earth's Rotation, Geocenter and Gravitational Field  

NASA Technical Reports Server (NTRS)

Hydrological mass transport in the geophysical fluids of the atmosphere-hydrosphere-solid Earth surface system can excite Earth's rotational variations in both length-of-day and polar motion. These effects can be computed in terms of the hydrological angular momentum by proper integration of global meteorological data. We do so using the 40-year NCEP data and the 18-year NASA GEOS-1 data, where the precipitation and evapotranspiration budgets are computed via the water mass balance of the atmosphere based on Oki et al.'s (1995) algorithm. This hydrological mass redistribution will also cause geocenter motion and changes in Earth's gravitational field, which are similarly computed using the same data sets. Corresponding geodynamic effects due to the oceanic mass transports (i.e. oceanic angular momentum and ocean-induced geocenter/gravity changes) have also been computed in a similar manner. We here compare two independent sets of the result from: (1) non-steric ocean surface topography observations based on Topex/Poseidon, and (2) the model output of the mass field by the Parallel Ocean Climate Model. Finally, the hydrological and the oceanic time series are combined in an effort to better explain the observed non-atmospheric effects. The latter are obtained by subtracting the atmospheric angular momentum from Earth rotation observations, and the atmosphere- induced geocenter/gravity effects from corresponding geodetic observations, both using the above-mentioned atmospheric data sets.

Chao, Benjamin F.; Chen, J. L.; Johnson, T.; Au, A. Y.

1998-01-01

335

Golden Binary Gravitational-Wave Sources: Robust Probes of Strong-Field Gravity  

Microsoft Academic Search

Space-borne gravitational-wave interferometers such as LISA will detect the gravitational wave (GW) signal from the inspiral, plunge, and ringdown phases of massive black hole binary mergers at cosmological distances. From the inspiral waves, we will be able to measure the masses of the binaries' members; from the ringdown waves, we will be able to measure the mass of the final

Scott A. Hughes; Kristen Menou

2005-01-01

336

Theory of tunneling ionization of molecules: Weak-field asymptotics including dipole effects  

SciTech Connect

The formulation of the parabolic adiabatic expansion approach to the problem of ionization of atomic systems in a static electric field, originally developed for the axially symmetric case [Phys. Rev. A 82, 023416 (2010)], is generalized to arbitrary potentials. This approach is used to rederive the asymptotic theory of tunneling ionization in the weak-field limit. In the atomic case, the resulting formulas for the ionization rate coincide with previously known results. In addition, the present theory accounts for the possible existence of a permanent dipole moment of the unperturbed system and, hence, applies to polar molecules. Accounting for dipole effects constitutes an important difference of the present theory from the so-called molecular Ammosov-Delone-Krainov theory. The theory is illustrated by comparing exact and asymptotic results for a set of model polar molecules and a realistic molecular ion HeH{sup 2+} in the 2p{sigma} state.

Tolstikhin, Oleg I. [National Research Center ''Kurchatov Institute'', Kurchatov Square 1, Moscow 123182 (Russian Federation); Morishita, Toru [Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofu-ga-oka, Chofu-shi, Tokyo 182-8585 (Japan); Madsen, Lars Bojer [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University (Denmark)

2011-11-15

337

Motion of the Three Viscoelastic Planets in Gravitational Field of the Mutual Attraction  

NASA Astrophysics Data System (ADS)

The translational-rotational motion of the three viscoelastic planets in gravitational field of the mutual attraction is studied. We model the planets by the homogeneous isotropic viscoelastic bodies, which in the natural non-deformed state occupy the spherical regions in the three-dimensional Eucliden space. The problem is being solved within the framework of the linear model of the theory of elasticity. The functional of the inner dissipative forces corresponds to the Kelvin-Voigt model. Each of the planets deforms due to its rotation around its mass center and its movement relative to the system's mass centre: the planet is being compressed endwise its axis of rotation and tidal humps appear aloud the lines binding the planet's mass centers. The changes in the planet's shape in their turn alter its translational-rotational movement. The system of equations of motion of the considered mechanical system is deduced from the D'Alembert-Lagrange variational principle and represents a complicated integro-differential system of equations in the banach space. The method of separation of motions is applied to the obtained system of equations and an approximate system of ordinary differential equations is deduced witch describes the translational-rotational motion of the planets, taking into account the perturbations caused by elasticity and dissipation. Unperturbed system of equations corresponds to the problem of the motion of the three rigid spheres interacting under the law of universal gravitation. Boundary problem of finding the vector of elastic displacement, describing forced oscillation of the planet under the influence of external forces and inertial forces of the translational motion is solved for each of the planets. Due to the planets' sphericity in their natural non-deformed state, the solutions of the boundary problems can be represented analytically as a sum of finite number of spherical functions. The solutions of the boundary problems are used to form the perturbing additives to the equations of motion. As a result of this procedure we get a vectorial perturbated system of ordinary differential equations on the radius of the planets' mass centers and the vectors of the planets' angular momentums. The stationary motion of the system of the three viscoelastic planets when the dissipative functional is equal to zero (the analogue of the triangular libration points in the classical three-body problem) is founded. According to this movement, the spheres move as one solid body with constant angular velocity, and the spheres' mass centers lie on a plan, orthogonal to the vector of angular velocity. If in unperturbed problem the mass centers of the planets form an equilateral triangle, the presence of perturbations leads to the emergence of the additives to stationary values of the triangle's side lengths, as the result of which the triangular in general case becomes inequilaterally. Due to the presence of dissipation of the system, the stationary triangular configuration is unsteady. This work is an extension of the series of articles [1-4] devoted to the problem of the viscoelastic spheres motion in gravitational field, the model problem for investigating the tidal evolution of the planets motion. The work is supported by RFBR, project 08-02-00367. References 1) Vilke V.G. The Motion of a Spherical Viscoelastic Body in the Central Newtonian Field of Forces // Appl. Math. Mech., 1980, Vol. 44, No 3, pp. 395-402. 2) Vilke V.G. Analytical and qualitative methods in the dynamics of the systems with infinite number of degrees of freedom. Moscow: Moscow State University, 1986. 3) Shatina A.V. Evolution of the Motion of a Viscoelastic Sphere in a Central Newtonian Field // Cosmic Research, 2001, Vol. 39, No 3, pp. 282-294. 4) Vilke V.G., Shatina A.V. Translational-Rotational Motion of a Viscoelastic Sphere in Gravitational Field of an Attracting Center and a Satellite // Cosmic Research, 2004, Vol. 42, No 1, pp. 95-106.

Vilke, V. G.; Shatina, A. V.; Shatina, L. S.

2009-04-01

338

The effects of weak extremely low frequency magnetic fields on calcium/calmodulin interactions.  

PubMed Central

Mechanisms by which weak electromagnetic fields may affect biological systems are of current interest because of their potential health effects. Lednev has proposed an ion parametric resonance hypothesis (Lednev, 1991, Bioelectromagnetics, 12:71-75), which predicts that when the ac, frequency of a combined dc-ac magnetic field equals the cyclotron frequency of calcium, the affinity of calcium for calcium-binding proteins such as calmodulin will be markedly affected. The present study evaluated Lednev's theory using two independent systems, each sensitive to changes in the affinity of calcium for calmodulin. One of the systems used was the calcium/calmodulin-dependent activation of myosin light chain kinase, a system similar to that previously used by Lednev. The other system monitored optical changes in the binding of a fluorescent peptide to the calcium/calmodulin complex. Each system was exposed to a 20.9 microT static field superimposed on a 20.9 microT sinusoidal field over a narrow frequency range centered at 16 Hz, the cyclotron frequency of the unhydrated calcium ion. In contrast to Lednev's predictions, no significant effect of combined dc-ac magnetic fields on calcium/calmodulin interactions was indicated in either experimental system.

Hendee, S P; Faour, F A; Christensen, D A; Patrick, B; Durney, C H; Blumenthal, D K

1996-01-01

339

Postnewtonian Quantum effects of motion in gravitational fields. Fine and Hyperfine structure of mass particles levels in Kerr-Newman fields  

Microsoft Academic Search

The fine and hyperfine structure of levels of scalar mass particles and electrons (electrically charged fermions) is examined in Schwarzschild, Reissner-Nordstrom and Kerr gravitational and electromagnetic fields. The Klein-Gordon and Dirac equations are solved by variables separation. The bound states, responding to energies E

A. B. Gaina; G. Chizhov

1980-01-01

340

Models of magnetic field evolution and effective viscosity in weakly collisional extragalactic plasmas  

NASA Astrophysics Data System (ADS)

In weakly collisional plasmas such as the intracluster medium (ICM), the viscous stress and the rate of change of the magnetic energy are proportional to the local pressure anisotropy, so subject to constraints imposed by the pressure-anisotropy-driven microinstabilities (mirror and firehose) and controlled by the local instantaneous plasma ?. The dynamics of such plasmas can be dramatically different from a conventional magnetohydrodynamic fluid. The plasma is expected to stay locally marginal with respect to the instabilities, but how it does this remains an open question. Two models of magnetic field evolution are investigated. In the first, marginality is achieved via suppression of the rate of change of the field. In the second, the instabilities give rise to anomalous collisionality, reducing pressure anisotropy to marginal - at the same time decreasing viscosity and so increasing the turbulent rate of strain. Implications of these two models are studied in a simplified zero-dimensional setting. In the first model, the field grows explosively but on a time-scale that scales with the initial ?, while in the second, dynamical field strength can be reached in one large-scale turbulence turnover time regardless of the initial seed. Both models produce very intermittent fields. Both also suffer from fairly strong constraints on their applicability: for typical cluster-core conditions, scale separation between the fluid motions (with account of suppressed viscous stress) and the miscoscale fluctuations break down at ? ˜ 104-105. At larger ? (weaker fields), a fully collisionless plasma dynamo theory is needed to justify field growth from a tiny primordial seed. However, the models discussed here are appropriate for studying the structure of the currently observed field as well as large-scale dynamics and thermodynamics of the magnetized ICM or similarly dilute astrophysical plasmas.

Mogavero, Federico; Schekochihin, Alexander A.

2014-06-01

341

The transient nature of biological effects induced by weak extremely low-frequency electromagnetic fields  

SciTech Connect

It has been shown that exposure of bio-systems to weak extremely low frequency (elf) electromagnetic fields (EMFs) results in a transient biological response in those systems. The observed results suggest a complex relation between the bio-effects and the exposure parameters. Windows -- ranges in which the system exhibits enhanced sensitivity -- have been reported for field amplitude (or power), as well as field frequency and exposure time duration. This research explores the dose-response relationships in terms of a multi-step chemical model and possible field-cell interaction mechanisms. The multi-step chemical model is presented to quantify the transient behavior of the elf field-induced bio-response as revealed by changes in the mRNA concentration from its equilibrium level. It is assumed that the direct effect of exposure to EMFs is to enhance the rates of production and degradation of mRNA. The mRNA concentration and the time integral of the field-induced mRNA concentration are calculated as a function of exposure time duration. The results are applied to explain the experimentally observed time duration window effects. The primary interaction of the imposed electric field is assumed to occur at the cell surface, and be quantified by either the counter-ion redistribution ([tilde n]) or the electromechanical stress ([rvec S]). This interaction is introduced into the chemical model by assuming that the change in the reaction rates is proportional to either [tilde n] or [rvec S]. The results of the bio-response can be calculated as a function of the strength of the imposed field and its frequency. The results are applied to explain the amplitude window and the frequency window effects observed in experiments, and to successfully fit some experimental data. The implications of the chemical model in experimental study are explored. The bio-response for various exposure conditions representing possible experimental situations is predicted.

Wang, W.

1993-01-01

342

Gravitational astrophysics  

NASA Astrophysics Data System (ADS)

Like the surface of a busy swimming pool, spacetime is awash with waves generated by the local and distant motions of mass and, in principle, much of this activity can be reconstructed by analysing the waveforms. However, instrumentation with a reasonable chance of directly detecting these gravitational waves has only become available within the past year, with the LIGO detectors now running at design sensitivity. Here we review the burgeoning field of observational gravitational astrophysics: using gravitational wave detectors as telescopes to help answer a wide range of astrophysical questions from neutron-star physics to cosmology. The next generation of ground-based telescopes should be able to make extensive gravitational observations of some of the more energetic events in our local universe. Looking only slightly further ahead, the space-based LISA observatory will reveal the gravitational universe in phenomenal detail, supplying high-quality data on perhaps thousands of sources, and tackling some of the most fascinating questions in contemporary astronomy.

Hendry, Martin; Woan, Graham

2007-02-01

343

Use of fluorescent probes for determination of yeast cell viability by gravitational field-flow fractionation.  

PubMed

The quality of wine greatly depends on the features of the yeast used in its production, and yeast cell viability is one of the most important quality control issues to consider in this regard. In the first steps of winemaking, the use of a low-cost and simple methodology for monitoring the cell viability of yeast inoculates is of paramount importance. Gravitational field-flow fractionation is a useful technique for the determination of cell viability because it provides gentle experimental conditions, although the proper use of fluorophore probes as biomass indicators is required. In this paper the use of different fluorescent probes such as carboxyfluorescein diacetate (cFDA), calcein-AM, and SYTO-13 were considered as viability biomarkers. Calceina-AM allowed the establishment of a direct GrFFF method to determine cell viability, with a limit of detection of 5.0 x 10(4) viable cell/mL. SYTO-13 could be used as biomass indicator with a limit of detection of 3.5 x 10(4) total cells/mL. The suitability of the procedure was tested with three commercial yeast samples, and the results were compared with those obtained using standard techniques. PMID:16739970

Garcia, M T; Sanz, R; Galceran, M T; Puignou, L

2006-01-01

344

Hubble Space Telescope Wide Field Camera imaging of the gravitational lens 2237 + 0305  

NASA Technical Reports Server (NTRS)

Images of the gravitational lens system 2237 + 0305, taken with the HST Wide Field Camera, are analyzed. Positions for the four quasar images, accurate to +/-0.015 arcsec, and relative magnitudes in U and R, accurate to +/-0.06 and 0.04 mag, respectively, are determined. The upper limits on the observed brightness of the fifth image are found to be less than or approximately equal to 7 percent of the brightest quasar image. The mass of the lens inside 0.9 arcsec is found to be 1.08 +/-0.02 x 10 exp 10 solar masses/h100 corresponding to a mass-to-light ratio in B of 12.3h100. This solar mass/solar luminosity estimate agrees with values obtained from stellar dynamics for other elliptical galaxies. A comparison of predictions from this mass model with the measured central velocity dispersion yields a distance-independent agreement to within 10 percent, assuming isotropic velocity dispersions.

Rix, Hans-Walter; Schneider, Donald P.; Bahcall, John N.

1992-01-01

345

Synchronization dynamics induced on pairs of neurons under applied weak alternating magnetic fields.  

PubMed

Pairs of Helix aspersa neurons show an alternating magnetic field dependent frequency synchronization (AMFS) when exposed to a weak (amplitude B0 between 0.2 and 150 Gauss (G)) alternating magnetic field (AMF) of extremely low frequency (ELF, fM = 50 Hz). We have compared the AMFS patterns of discharge with: i) the synaptic activity promoted by glutamate and acetylcholine; ii) the activity induced by caffeine; iii) the bioelectric activity induced on neurons interconnected by electric synapses. AMFS activity reveals several specific features: i) a tight coincidence in time of the pattern and frequency, f, of discharge; ii) it is induced in the time interval of field application; iii) it is dependent on the intensity of the sinusoidal applied magnetic field; iv) elicited biphasic responses (excitation followed by inhibition) run in parallel for the pair of neurons; and v) some neuron pairs either spontaneously or AMF synchronized can be desynchronized under applied higher AMF. Our electron microscopy studies reveal gap-like junctions confirming our immunocytochemistry results about expression of connexin 26 (Cx26) in 4.7% of Helix neurons. AMF and carbenoxolone did not induce any significant effect on spontaneous synchronization through electric synapses. PMID:24012769

Azanza, María J; del Moral, A; Calvo, A C; Pérez-Bruzón, R N; Junquera, C

2013-12-01

346

Varying interplanetary magnetic field By effects on interhemispheric conjugate auroral features during a weak substorm  

NASA Astrophysics Data System (ADS)

Interhemispheric conjugate auroral features during a weak substorm interval were investigated using simultaneous all-sky camera (ASC) measurements at the northern and southern geomagnetic conjugate points at Tjörnes (TJO; 66.2°N, 342.9°E) in Iceland and Syowa Station (SYO; 69.0°S, 39.6°E) in Antarctica. Around postmidnight, just after the substorm onset, the ASC field of view (FOV) at TJO was first filled with dynamic auroral activations; however, its counterpart was not detected over the zenith at SYO at that time. In contrast, in the late stage (about 20 min after the onset) of substorm development we observed spiral-like auroral arcs with a similar shape drifting eastward across the center of each ASC FOV, although the one at TJO preceded the one at SYO. The time sequence of the interhemispheric conjugate auroral features was well reflected in the geomagnetic field variations at both stations. On the basis of a detailed comparison of both ASC images, we identified that the northern geomagnetic footprint of SYO was displaced poleward of TJO by up to 3.0° or more in the initial stage of substorm development, whereas in the late stage it was displaced eastward by up to ˜1 h relative to TJO and then moved closer to TJO. We emphasize that the dynamic motion of the conjugate points is a consequence of the time-dependent magnetotail field reconfiguration process, controlled by the varying interplanetary magnetic field By polarity.

Motoba, T.; Hosokawa, K.; Sato, N.; Kadokura, A.; Bjornsson, G.

2010-09-01

347

Detection of a weak surface magnetic field on Sirius A: are all tepid stars magnetic?  

NASA Astrophysics Data System (ADS)

Aims: We aim at a highly sensitive search for weak magnetic fields in main sequence stars of intermediate mass, by scanning classes of stars with no previously reported magnetic members. After detecting a weak magnetic field on the normal, rapidly rotating A-type star Vega, we concentrate here on the bright star Sirius A, taken as a prototypical, chemically peculiar, moderately rotating Am star. Methods: We employed the NARVAL and ESPaDOnS high-resolution spectropolarimeters to collect 442 circularly polarized spectra, complemented by 60 linearly polarized spectra. Using a list of about 1100 photospheric spectral lines, we computed a cross correlation line profile from every spectrum, leading to a signal-to-noise ratio of up to 30 000 in the polarized profile. Results: We report the repeated detection of circularly polarized, highly asymmetric signatures in the line profiles, interpreted as Zeeman signatures of a large-scale photospheric magnetic field, with a line-of-sight component equal to 0.2 ± 0.1 G. Conclusions: This is the first polarimetric detection of a surface magnetic field on an Am star. Using rough estimates of the physical properties of the upper layers of Sirius A, we suggest that a dynamo operating in the shallow convective envelope cannot account for the field strength reported here. Together with the magnetic field of Vega, this result confirms that a new class of magnetic objects exists among non Ap/Bp intermediate-mass stars, and it may indicate that a significant fraction of tepid stars are magnetic. Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Petit, P.; Lignières, F.; Aurière, M.; Wade, G. A.; Alina, D.; Ballot, J.; Böhm, T.; Jouve, L.; Oza, A.; Paletou, F.; Théado, S.

2011-08-01

348

Gravitational Analog of the Electromagnetic  

Microsoft Academic Search

The gravitational analog of the electromagnetic Poynting vector is constructed us- ing the field equations of general relativity in the Hilbert gauge. It is found that when the gravitational Poynting vector is applied to the solution of the linear mass quadrupole oscillator, the correct gravitational quadrupole radiation flux is ob- tained. Further to this, the Maxwell-like gravitational Poynting vector gives

Poynting Vector

349

Effective Field Theory for Heavy Weakly Interacting Massive Particles Scattering with Nucleons  

NASA Astrophysics Data System (ADS)

The discovery of a standard-model-like Higgs boson and the hitherto absence of evidence for other new states may indicate that if weakly interacting massive particles (WIMPs) comprise cosmological dark matter, they are heavy compared to electroweak scale particles, M ?mW±, mZ0. In this limit, the absolute cross section for a WIMP of given electroweak quantum numbers to scatter from a nucleon becomes computable in terms of standard model parameters. We develop effective field theory techniques to analyze the heavy WIMP limit of WIMP-nucleon scattering and present the first complete calculation of the leading spin-independent cross section in standard model extensions consisting of one or two electroweak SU(2)W×U(1)Y multiplets. The impact on scattering cross sections of the choice of WIMP quantum numbers and an extended Higgs sector is investigated.

Hill, Richard J.; Solon, Mikhail P.

2014-05-01

350

Temperature and magnetic field dependence of a Kondo system in the weak coupling regime  

PubMed Central

The Kondo effect arises due to the interaction between a localized spin and the electrons of a surrounding host. Studies of individual magnetic impurities by scanning tunneling spectroscopy have renewed interest in Kondo physics; however, a quantitative comparison with theoretical predictions remained challenging. Here we show that the zero-bias anomaly detected on an organic radical weakly coupled to a Au (111) surface can be described with astonishing agreement by perturbation theory as originally developed by Kondo 60 years ago. Our results demonstrate that Kondo physics can only be fully conceived by studying both temperature and magnetic field dependence of the resonance. The identification of a spin 1/2 Kondo system is of relevance not only as a benchmark for predictions for Kondo physics but also for correlated electron materials in general.

Zhang, Yong-hui; Kahle, Steffen; Herden, Tobias; Stroh, Christophe; Mayor, Marcel; Schlickum, Uta; Ternes, Markus; Wahl, Peter; Kern, Klaus

2013-01-01

351

Effect of a magnetic field gradient and gravitational acceleration on a time-domain grating-echo interferometer  

SciTech Connect

We have observed the effects of magnetic field gradients and gravitational acceleration on grating echoes in a time-domain single state atom interferometer that uses laser cooled Rb atoms. These observations are compared to theoretical predictions based on a simplified model. The oscillatory dependence of the echo amplitude due to the magnetic field gradient is in agreement with the predicted quadratic scaling as a function of the time between excitation pulses. We also observe a linear dependence of this oscillation frequency as a function of the magnetic field gradient which is predicted by theory. In the presence of gravity, the calculations predict a quadratic dependence for the echo phase on the time between excitation pulses as well as a change in the shape of the echo envelope. We have observed both of these effects in the experiment, and we find that the change in shape is qualitatively consistent with our prediction. It is necessary to understand these effects in order to carry out high precision studies of the atomic fine-structure constant and gravitational acceleration using this interferometric technique. We also present an improved measurement of gravitational acceleration using this technique that is precise to {approx}15 ppm by exploiting the quadratic phase dependence.

Weel, M.; Chan, I.; Beattie, S.; Kumarakrishnan, A.; Gosset, D.; Yavin, I. [Department of Physics and Astronomy, York University, Toronto, Ontario, M3J 1P3 (Canada); Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2006-06-15

352

Interaction of Gravitationally Contracting Gas Having Angular Momentum with Magnetic Field, and the Acceleration and Collimation of Astrophysical Jets  

NASA Astrophysics Data System (ADS)

In the present paper, we stress the importance of the magnetic field in the problem of acceleration and collimation of astrophysical jets, and discuss our proposed generic picture for such ``central gravitator + jets + lobes" systems and inherent interpretations of the various observational characteristics of such systems: Mechanisms are proposed for (1) the enhanced liberation of gravitational energy at the central object, (2) the transfer of a part of the liberated energy along the large-scale magnetic field by large-amplitude, torsional Alfven wave trains that form collimated jets (we call this a sweeping pinch process), (3) the dumping of the transferred energy at the end of the jets when they impinge on the denser region outside the border of the ``cavity" from which the mass contracted to the central condensation (central gravitator + accretion disk, as well as the larger-scale condensation surrounding them), and (4) the formation of wiggled jets and lobes as helical kinks and the tucked-up magnetic field produced in the sweeping pinch process, respectively.

Uchida, Y.; Nakamura, M.; Miyagoshi, T.; Kobayashi, T.; Mukawa, T.; Hirose, S.

2000-05-01

353

Stellar explosion in the weak field approximation of the Brans Dicke theory  

NASA Astrophysics Data System (ADS)

We treat a very crude model of an exploding star, in the weak field approximation of the Brans Dicke theory, in a scenario that resembles some characteristic data of a type Ia supernova. The most noticeable feature, in the electromagnetic component, is the relationship between the absolute magnitude at maximum brightness of the star and the decline rate in one magnitude from that maximum. This characteristic has become one of the most accurate methods to measure luminosity distances to objects at cosmological distances (Phillips M M 1993 Astrophys. J. 413 L105; see www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Supernova, for a brief description of supernovae types). An interesting result is that the active mass associated with the scalar field is totally radiated to infinity, representing a mass loss in the ratio of the 'tensor' component to the scalar component of 1 to (2? + 3) (? is the Brans Dicke parameter), in agreement with a general result of Hawking (1972 Commun. Math. Phys. 25 167). Then, this model shows explicitly, in a dynamical case, the mechanism of the radiation of a scalar field, which is necessary to understand the Hawking result.

Hamity, Victor H.; Barraco, Daniel E.

2005-10-01

354

Investigation of electron energy distribution function in a weak magnetic field in solenoidal inductive discharge  

NASA Astrophysics Data System (ADS)

Plasma parameters such as electron temperatures, plasma densities, and dc plasma potential in the vicinity of electron cyclotron resonance (ECR) in the solenoidal inductive argon discharge have been investigated by observing electron energy distribution function (EEDF). Langmuir probe method system was built to study the EEDF dependencies on the radial position and rf driving frequency. The measurement was performed on the bulk plasma under range of weak dc magnetic field (0 - 20 G) at low pressure and power. In this study, the changes in the radial profile of the plasma parameters with respect to the varying the magnetic field was discussed. It was experimentally verified that no effective electron temperature maximum appear at ECR condition due to the characteristics of the local electron kinetics, while plasma density maximum appears at different magnetic field. Furthermore, the measured dc plasma potential largely increases with the rf driving frequency. These results are also compared with that of the typical planner inductive discharge [1].[4pt] [1] C.W. Chung, S. S. Kim, and H.Y. Chang, Phys. Rev. E 69, 016406 (2004)

Lee, Yeong-Kwang; Ku, Ju-Hwan; Chung, Chin-Wook

2009-10-01

355

The Origin of Gravitation  

NASA Astrophysics Data System (ADS)

In the natural world, people have discovered four kinds of forces: electromagnetic force, gravitation, weak force, and strong force. Although the gravitation has been discovered more than three hundred years, its mechanism of origin is unclear until today. While investigating the origin of gravitation, I do some experiments discover the moving photons produce gravitation. This discovery shows the origin of gravitation. Meanwhile I do some experiments discover the light interference fringes are produced by the gravitation: my discovery demonstrate light is a particle, but is not a wave-particle duality. Furthermore, applications of this discovery to other moving particles show a similar effect. In a word: the micro particle moving produce gravitation and electromagnetic force. Then I do quantity experiment get a general formula: Reveal the essence of gravitational mass and the essence of electric charge; reveal the origin of gravitation and the essence of matter wave. Along this way, I unify the gravitation and electromagnetic force. Namely I find a natural law that from atomic world to star world play in moving track. See website: https://www.lap-publishing.com/catalog/details/store/gb/book/978-3-8473-2658-8/mechanism-of-interaction-in-moving-matter

Zheng, Sheng Ming

2012-10-01

356

Constraints of thermal noise on the effects of weak 60-Hz magnetic fields acting on biological magnetite.  

PubMed

Previous calculations of limits imposed by thermal noise on the effects of weak 60-Hz magnetic fields on biological magnetite are generalized and extended to consider multiple signals, the possibility of anomalously large magnetosome structures, and the possibility of anomalously small cytoplasm viscosities. The results indicate that the energies transmitted to the magnetite elements by fields less than 5 microT, characteristic of the electric power distribution system, will be much less than thermal noise energies. Hence, the effects of such weak fields will be masked by that noise and cannot be expected to affect biology or, therefore, the health of populations. PMID:8159681

Adair, R K

1994-04-12

357

Constraints of thermal noise on the effects of weak 60-Hz magnetic fields acting on biological magnetite.  

PubMed Central

Previous calculations of limits imposed by thermal noise on the effects of weak 60-Hz magnetic fields on biological magnetite are generalized and extended to consider multiple signals, the possibility of anomalously large magnetosome structures, and the possibility of anomalously small cytoplasm viscosities. The results indicate that the energies transmitted to the magnetite elements by fields less than 5 microT, characteristic of the electric power distribution system, will be much less than thermal noise energies. Hence, the effects of such weak fields will be masked by that noise and cannot be expected to affect biology or, therefore, the health of populations.

Adair, R K

1994-01-01

358

Supersymmetry approach to delocalization transitions in a network model of the weak-field quantum Hall effect and related models  

NASA Astrophysics Data System (ADS)

We consider a recently proposed network model of the integer quantum Hall (IQH) effect in a weak magnetic field. Using a supersymmetry approach, we reformulate the network model in terms of a superspin ladder. A subsequent analysis of the superspin ladder and the corresponding supersymmetric nonlinear sigma model allows us to establish the phase diagram of the network model, and the form of the critical line of the weak-field IQH transition. Our results confirm the universality of the IQH transition, which is described by the same sigma model in strong and weak magnetic fields. We apply the suspersymmetry method to several related network models that were introduced in the literature to describe the quantum Hall effect in graphene, the spin-degenerate Landau levels, and localization of electrons in a random magnetic field.

Bhardwaj, S.; Mkhitaryan, V. V.; Gruzberg, I. A.

2014-06-01

359

Weak Field-Induced Evolution of Spiral Wave in Small-World Networks of Hodgkin—Huxley Neurons  

NASA Astrophysics Data System (ADS)

An external weak electric field is introduced into the small-world networks of Hodgkin-Huxley neurons to study the control and breakup of a spiral wave. The effect of an external electric field on the neurons in the small-world network is described by an additive perturbation on the membrane potentials of neurons at the cellular level, in which an additive term VE is imposed on the physiological membrane potential. A statistical factor of synchronization is used to measure the collective behaviour of spiral waves by changing the electric field; it is confirmed that a smaller factor of synchronization is associated with the survival of a spiral wave. In the case of no channel noise, the spiral wave could be removed under a certain intensity of constant electric field; it keeps robustly to the weak electric field when the electric field changes periodically. In the case of weak channel noise, a breakup of the spiral wave is observed when the intensity of the electric field exceeds certain thresholds, which could be measured from the curve for synchronization factors. No drift of the spiral wave is observed under the weak electric field.

Wang, Ya-Min; Liu, Yong; Wang, Jing; Liu, Yu-Rong

2012-08-01

360

Gravitational field and equations of motion of spinning compact binaries to 2.5 post-Newtonian order  

NASA Astrophysics Data System (ADS)

We derive spin-orbit coupling effects on the gravitational field and equations of motion of compact binaries in the 2.5 post-Newtonian approximation to general relativity, one PN order beyond where spin effects first appear. Our method is based on that of Blanchet, Faye, and Ponsot, who use a post-Newtonian metric valid for general (continuous) fluids and represent pointlike compact objects with a ?-function stress-energy tensor, regularizing divergent terms by taking the Hadamard finite part. To obtain post-Newtonian spin effects, we use a different ?-function stress-energy tensor introduced by Bailey and Israel. In a future paper we will use the 2.5PN equations of motion for spinning bodies to derive the gravitational-wave luminosity and phase evolution of binary inspirals, which will be useful in constructing matched filters for signal analysis. The gravitational field derived here may help in posing initial data for numerical evolutions of binary black hole mergers.

Tagoshi, Hideyuki; Ohashi, Akira; Owen, Benjamin J.

2001-02-01

361

Possible measurement of the coefficient of the second zonal harmonic of the sun's gravitational field with a solar probe  

NASA Technical Reports Server (NTRS)

The use of radio tracking of a solar probe to estimate accurately the coefficient of the second zonal harmonic of the sun's gravitational field was examined. Preliminary results indicate that the coefficient can be estimated with a standard error of 10 to the minus 8th power or less, provided that the probe is equipped with a suitable drag-free system to compensate for the effects of non-gravitational accelerations. For signal paths that pass near the sun, dual-band ranging to the probe can provide the tracking accuracy needed to insure that the standard of error is equal to or less than 10 to minus 8th power. The possibility of achieving such accuracy with a single-band radio uplink and a dual-band downlink is discussed.

Reasenberg, R. D.; Shapiro, I. I.

1978-01-01

362

General relativistic N-body simulations in the weak field limit  

NASA Astrophysics Data System (ADS)

We develop a formalism for general relativistic N-body simulations in the weak field regime, suitable for cosmological applications. The problem is kept tractable by retaining the metric perturbations to first order, the first derivatives to second order, and second derivatives to all orders, thus taking into account the most important nonlinear effects of Einstein gravity. It is also expected that any significant “backreaction” should appear at this order. We show that the simulation scheme is feasible in practice by implementing it for a plane-symmetric situation and running two test cases, one with only cold dark matter, and one which also includes a cosmological constant. For these plane-symmetric situations, the deviations from the usual Newtonian N-body simulations remain small and, apart from a nontrivial correction to the background, can be accurately estimated within the Newtonian framework. The correction to the background scale factor, which is a genuine backreaction effect, can be robustly obtained with our algorithm. Our numerical approach is also naturally suited for the inclusion of extra relativistic fields and thus for dark energy or modified gravity simulations.

Adamek, Julian; Daverio, David; Durrer, Ruth; Kunz, Martin

2013-11-01

363

Magnetorotational instability of a weakly ionized accretion disk with vertical and azimuthal magnetic fields  

NASA Astrophysics Data System (ADS)

Magnetorotational instability of a weakly ionized accretion disk with an admixture of charged dust grains in a magnetic field with the axial and toroidal components is analyzed. The dispersion relation for perturbations perpendicular to the disk plane is derived with allowance for both the Hall current and the finite transverse plasma conductivity. It is shown that dust grains play an important role in the disk magnetic dynamics. Due to the effect of dust grains, the Hall current can reverse its direction as compared to the case of electron-ion plasma. As a result, the instability threshold shifts toward the short-wavelength range. Under certain conditions, electromagnetic fluctuations of any length can become unstable. It is established that the instability criterion for waves of any scale length is satisfied within a finite interval of the density ratio between the dust and electron plasma components. The width of this interval and the instability growth rate as functions of the plasma parameters and the configuration of the magnetic field in the disk are analyzed.

Prudskikh, V. V.

2014-05-01

364

Deprotonation of glutamic acid induced by weak magnetic field: an FTIR-ATR study.  

PubMed

It has been claimed that weak extremely low frequency electromagnetic fields (ELF-EMFs) can affect biochemical reactions and a wide-ranging body of literature is available on this topic. Nevertheless, the physical nature of these effects remains largely unknown. We investigated the influence of ELF-EMF on glutamic acid solutions using Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectra. Samples were exposed for 10, 20, or 30?min to a weak EMF generated by Helmoltz coils, and then placed in a spectrometer. After exposure, those solutions that had a pH lower than the isoelectric point tended to show a shift toward the deprotonation of the carboxylic group, while solutions having a pH greater than the isoelectric point showed the deprotonation of the residual amine group. Moreover, at low pH values, we also detected a shift of the ?(antisym) band of the amine. The effects lasted a few minutes after exposure before the native configuration was restored. The spectral modifications were observed after each independent exposure to EMFs, and the same effects were seen by varying the frequencies in the range of 0-7?kHz. Therefore, the hypothesis of the existence of a resonant frequency that has been proposed elsewhere cannot be supported by the results of this study. The most surprising characteristic of this effect is the long-lasting nature of the perturbation, which is hard to be explained in terms of short-living excitations in biological matter. PMID:21125576

De Ninno, A; Congiu Castellano, A

2011-04-01

365

Application of internal gravitational field equations to geophysical measurement of G  

NASA Astrophysics Data System (ADS)

The spherical harmonic equation for the gravitational potential inside the earth is presented. The equation satisfies Poisson's equation and converges uniformly. It obviates the need for downward continuation of the exterior potential with its attendant convergence difficulties but of course requires some knowledge of the earth's density distribution. The equation is used to derive the general expression for the geophysical measurement of the gravitational constant G made inside the earth, such as in boreholes and mine shafts. Numerical evidence is also presented to show that the long- to intermediate-wavelength gravity anomalies can masquerade as the 'fifth force' if not properly corrected for.

Rubincam, David Parry; Chao, B. Fong; Schatten, Kenneth H.

1989-06-01

366

Unifying static analysis of gravitational structures with a scale-dependent scalar field gravity as an alternative to dark matter  

NASA Astrophysics Data System (ADS)

Aims: We investigated the gravitational effects of a scalar field within scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon, symmetron, and f(R)-gravity models, we studied a phenomenological scenario where the scalar field has both a mass (i.e. interaction length) and a coupling constant to the ordinary matter that scale with the local properties of the considered astrophysical system. Methods: We analysed the feasibility of this scenario using the modified gravitational potential obtained in its context and applied it to the galactic and hot gas/stellar dynamics in galaxy clusters and elliptical/spiral galaxies respectively. This is intended to be a first step in assessing the viability of this new approach in the context of "alternative gravity" models. Results: The main results are 1. the velocity dispersion of elliptical galaxies can be fitted remarkably well by the suggested scalar field, with model significance similar to a classical Navarro-Frenk-White dark halo profile; 2. the analysis of the stellar dynamics and the gas equilibrium in elliptical galaxies has shown that the scalar field can couple with ordinary matter with different strengths (different coupling constants), producing and/or depending on the different clustering state of matter components; 3. elliptical and spiral galaxies, combined with clusters of galaxies, show evident correlations among theory parameters, which suggest both the general validity of our results on all scales and a way toward a possible unification of the theory for all types of the gravitational systems we considered. All these results demonstrate that the proposed scalar field scenario can work fairly well as an alternative to dark matter.

Salzano, V.; Mota, D. F.; Capozziello, S.; Napolitano, N. R.

2014-01-01

367

Modified Gravitational Theory and Galaxy Rotation Curves  

Microsoft Academic Search

The nonsymmetric gravitational theory predicts an acceleration law that\\u000amodifies the Newtonian law of attraction between particles. For weak fields a\\u000afit to the flat rotation curves of galaxies is obtained in terms of the mass\\u000a(mass-to-light ratio M\\/L) of galaxies. The fits assume that the galaxies are\\u000anot dominated by exotic dark matter. The equations of motion for test

J. W. Moffat

2004-01-01

368

Modified Gravitational Theory and Galaxy Rotation Curves  

Microsoft Academic Search

The nonsymmetric gravitational theory predicts an acceleration law that modifies the Newtonian law of attraction between particles. For weak fields a fit to the flat rotation curves of galaxies is obtained in terms of the mass (mass-to-light ratio M\\/L) of galaxies. The fits assume that the galaxies are not dominated by exotic dark matter. The equations of motion for test

J. W. Moffat

2004-01-01

369

Accretion onto Neutron Stars: Radiative Transfer in a Strong Gravitational Field.  

National Technical Information Service (NTIS)

The beam shape of binary X-ray pulsars is partly determined by the transfer of X-rays through accreting magnetized plasma. An extension of the iterative scattering method of radiative transfer is reported. It allows incorporation of gravitational light de...

U. Kraus A. Rebetzky H. Herold H. Nollert T. Maile

1989-01-01

370

Accretion onto neutron stars: Radiative transfer in a strong gravitational field  

Microsoft Academic Search

The beam shape of binary X-ray pulsars is partly determined by the transfer of X-rays through accreting magnetized plasma. An extension of the iterative scattering method of radiative transfer is reported. It allows incorporation of gravitational light deflection into a radiative transfer calculation and includes the effects of plasma bulk motion. A model of an accretion column consistent with an

U. Kraus; A. Rebetzky; H. Herold; H.-P. Nollert; T. Maile; H. Ruder

1989-01-01

371

The scaling rule for environmental organizing systems in a gravitational field  

Microsoft Academic Search

A recent thermodynamics and information study examined the basis of a scaling rule for simple living organisms. The present paper examines a scaling rule for the relationship between the integrated scaled metabolic energy and the mass of a system for a wide range of masses, from animals to the 4He cores of main-sequence stars, considering the effect of gravitational energy.

Noboru Fujiwara

2004-01-01

372

Theoretical model of gravitational perturbation of current collector axisymmetric flow field  

Microsoft Academic Search

Some designs of liquid metal collectors in homopolar motors and generators are essentially rotating liquid metal fluids in cylindrical channels with free surfaces and will, at critical rotational speeds, become unstable. The role of gravity in modifying this ejection instability is investigated. Some gravitational effects can be theoretically treated by perturbation techniques on the axisymmetric base flow of the liquid

John S. Walker; Samuel H. Brown; Neal A. Sondergaard

1989-01-01

373

Theoretical model of gravitational perturbation of current collector axisymmetric flow field  

Microsoft Academic Search

Some designs of liquid-metal current collectors in homopolar motors and generators are essentially rotating liquid-metal fluids in cylindrical channels with free surfaces and will, at critical rotational speeds, become unstable. An investigation at David Taylor Research Center is being performed to understand the role of gravity in modifying this ejection instability. Some gravitational effects can be theoretically treated by perturbation

John S. Walker; Samuel H. Brown; Neal A. Sondergaard

1990-01-01

374

Theoretical model of gravitational perturbation of current collector axisymmetric flow field. Research and development report  

Microsoft Academic Search

Some designs of liquid-metal collectors in homopolar motors and generators are essentially rotating liquid-metal fluids in cylindrical channels with free surfaces and will, at critical rotational speeds, become unstable. An investigation is being performed to understand the role of gravity in modifying this ejection instability. Some gravitational effects can be theoretically treated by perturbation techniques on the axisymmetric base flow

J. S. Walker; S. H. Brown; N. A. Sondergaard

1989-01-01

375

Endothelial Cell Morphology and Migration are Altered by Changes in Gravitational Fields  

NASA Technical Reports Server (NTRS)

Many of the physiological changes of the cardiovascular system during space flight may originate from the dysfunction of basic biological mechanisms caused by microgravity. The weightlessness affects the system when blood and other fluids move to the upper body causing the heart to enlarge to handle the increased blood flow to the upper extremities and decrease circulating volume. Increase arterial pressure triggers baroreceptors which signal the brain to adjust heart rate. Hemodynarnic studies indicate that the microgravity-induced headward fluid redistribution results in various cardiovascular changes such as; alteration of vascular permeability resulting in lipid accumulation in the lumen of the vasculature and degeneration of the the vascular wall, capillary alteration with extensive endothelial invagination. Achieving a true microgravity environment in ground based studies for prolonged periods is virtually impossible. The application of vector-averaged gravity to mammalian cells using horizontal clinostat produces alterations of cellular behavior similar to those observed in microgravity. Similarly, the low shear, horizontally rotating bioreactor (originally designed by NASA) also duplicates several properties of microgravity. Additionally, increasing gravity, i.e., hypcrgravity is easily achieved. Hypergravity has been found to increase the proliferation of several different cell lines (e.g., chick embryo fibroblasts) while decreasing cell motility and slowing liver regeneration following partial hepatectomy. The effect of altered gravity on cells maybe similar to those of other physical forces, i.e. shear stress. Previous studies examining laminar flow and shear stress on endothelial cells found that the cells elongate, orient with the direction of flow, and reorganize their F-actin structure, with concomitant increase in cell stiffness. These studies suggest that alterations in the gravity environment will change the behavior of most cells, including vascular cells. However, few studies have been directed at assessing the effect of altered gravitational field on vascular cell fiction and metabolism, Using image analysis we examined how bovine aortic endothelial cells altered their morphological characteristics and their response to a denudation injury when cells were subjected to simulated microgravity and hypergravity.

Melhado, Caroline; Sanford, Gary; Harris-Hooker, Sandra

1997-01-01

376

Ideal gas in a strong gravitational field: Area dependence of entropy  

SciTech Connect

We study the thermodynamic parameters like entropy, energy etc. of a box of gas made up of indistinguishable particles when the box is kept in various static background spacetimes having a horizon. We compute the thermodynamic variables using both statistical mechanics as well as by solving the hydrodynamical equations for the system. When the box is far away from the horizon, the entropy of the gas depends on the volume of the box except for small corrections due to background geometry. As the box is moved closer to the horizon with one (leading) edge of the box at about Planck length (L{sub p}) away from the horizon, the entropy shows an area dependence rather than a volume dependence. More precisely, it depends on a small volume A{sub perpendicular}L{sub p}/2 of the box, up to an order O(L{sub p}/K){sup 2} where A{sub perpendicular} is the transverse area of the box and K is the (proper) longitudinal size of the box related to the distance between leading and trailing edge in the vertical direction (i.e. in the direction of the gravitational field). Thus the contribution to the entropy comes from only a fraction O(L{sub p}/K) of the matter degrees of freedom and the rest are suppressed when the box approaches the horizon. Near the horizon all the thermodynamical quantities behave as though the box of gas has a volume A{sub perpendicular}L{sub p}/2 and is kept in a Minkowski spacetime. These effects are: (i) purely kinematic in their origin and are independent of the spacetime curvature (in the sense that the Rindler approximation of the metric near the horizon can reproduce the results) and (ii) observer dependent. When the equilibrium temperature of the gas is taken to be equal to the horizon temperature, we get the familiar A{sub perpendicular}/L{sub p}{sup 2} dependence in the expression for entropy. All these results hold in a D+1 dimensional spherically symmetric spacetime. The analysis based on methods of statistical mechanics and the one based on thermodynamics applied to the gas treated as a fluid in static geometry, lead to the same results showing the consistency. The implications are discussed.

Kolekar, Sanved; Padmanabhan, T. [IUCAA, Pune University Campus, Ganeshkhind, Pune 411007 (India)

2011-03-15

377

Application of photoionization models based on radiative transfer and the Helmholtz equations to studies of streamers in weak electric fields  

SciTech Connect

Recent advances in development of photoionization models in air based on radiative transfer and Helmholtz equations open new perspectives for efficient solution of nonthermal gas discharge problems involving complex geometries. Many practical applications require accurate modeling of streamer discharges developing in weak electric fields, in which the photoionization process significantly contributes to discharge dynamics. This paper (1) reports original studies, which demonstrate the validity and accuracy of the recently proposed photoionization models for studies of streamers in weak electric fields, and (2) introduces efficient boundary conditions for the photoinization models based on radiative transfer theory.

Liu Ningyu; Celestin, Sebastien; Bourdon, Anne; Pasko, Victor P.; Segur, Pierre; Marode, Emmanuel [Communications and Space Sciences Laboratory, Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Ecole Centrale Paris, EM2C, UPR CNRS 288, Grande voie des vignes, 92295 Chatenay-Malabry Cedex (France); Communications and Space Sciences Laboratory, Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Universite de Toulouse, LAPLACE, CNRS, INPT, UPS, 118 route de Narbonne, 31062 Toulouse Cedex 9 (France); Ecole Superieure d'Electricite, LPGP, UMR CNRS 8578, Plateau du moulon, 3 rue Joliot Curie, 91192 Gif-sur-Yvette (France)

2007-11-19

378

I. Ash ejection and exposure during radius expansion type I X-ray bursts, II. Stellar dynamics at the galactic center, III. Weak gravitational lensing by dark matter concentrations  

NASA Astrophysics Data System (ADS)

The studies presented herein are on three distinct topics in astrophysics: I. We solve for the evolution of the vertical extent of the convective region of a neutron star atmosphere during a type I X-ray burst. The convective region is well-mixed with ashes of nuclear burning, and its extent determines the burst rise time. We show that the maximum extent of the convective region during photospheric radius expansion (PRE) bursts can be sufficiently great that some ashes of burning are: (1) ejected by the radiation-driven wind during the PRE phase and, (2) exposed at the neutron star surface following the PRE phase. We calculate the expected column density of ashes in hydrogen-like states and find that the resulting photoionization edges should be detectable with current high spectral resolution X-ray telescopes. A detection would probe the burst nuclear burning processes and might enable a measurement of the neutron star gravitational redshift. II. We discuss physical experiments achievable via the monitoring of stellar dynamics near the massive black hole (MBH) at the Galactic center with a next- generation, extremely large telescope (ELT). We use the Markov Chain Monte Carlo method to evaluate the constraints that the monitoring of these orbits will place on the matter content at the Galactic center. We compare these future constraints with those obtained with the current data. We also describe how the monitoring of stellar proper motions can be used to probe directly the masses of isolated stellar remnants near the MBH. III. We calculate the abundance of dark-matter concentrations that are sufficiently overdense to produce a detectable weak-gravitational-lensing signal. Most of these overdensities are virialized halos containing identifiable X-ray and/or optical clusters. However, a significant fraction are nonvirialized, cluster-mass overdensities still in the process of gravitational collapse---these should produce significantly weaker or no X-ray emission. Our predicted abundance of such dark clusters is consistent with the abundance implied by the detection of apparent dark lenses. We also examine the prospect of using weak gravitational lenses to constrain the dark energy equation-of- state.

Weinberg, Nevin Nachum

379

Subtle consequences of exposure to weak microwave fields: Are there non-thermal effects?  

NASA Astrophysics Data System (ADS)

When we speak of subtle consequences of exposure we mean only that the effects were observed in the absence of changes in core temperature due to microwave exposure. When we measure + delta T degree C in core temperature consequent to microwave exposure, we are witnessing a breakdown of thermoregulatory mechanisms. Short of this event, the exposed subject makes a number of thermoregulatory and metabolic accommodations to maintain a constant body temperature and to deal effectively with the energy being deposited in its tissues. These latter changes should interest us for they are the subtle consequences exposure to weak microwave fields. The long-term accommodations, which accompany subchronic exposure, can lead to a number of interesting effects some of which are described below. Two fundamentally different types of experimental protocol were employed. In Experiment 1A, independent groups of male rats were either exposed or sham-exposed to 915 MHz microwaves for 10 hr/night for up to 4 mo. In Experiment 1B, independent groups of rats were similarly exposed, or sham-exposed, to 2450 MHz microwaves for 10 hr/night for 4 mo. In Experiment 2, using a different type of protocol, pregnant female rats were exposed for 20 hr/day for 19 days of gestation. Control groups were either sham-exposed or served as caged controls. The main focus of the study attended to assessment of various functions and the developmental status of the gravid rats' progeny.

Lovely, R. H.; Mizumori, S. J. Y.; Johnson, R. B.; Guy, A. W.

380

Cosmology with Minkowski functionals and moments of the weak lensing convergence field  

NASA Astrophysics Data System (ADS)

We compare the efficiency of moments and Minkowski functionals (MFs) in constraining the subset of cosmological parameters (?m,w,?8) using simulated weak lensing convergence maps. We study an analytic perturbative expansion of the MFs [T. Matsubara, Phys. Rev. D 81, 083505 (2010); D. Munshi et al., Mon. Not. R. Astron. Soc. 419, 536 (2012)] in terms of the moments of the convergence field and of its spatial derivatives. We show that this perturbation series breaks down on smoothing scales below 5', while it shows a good degree of convergence on larger scales (˜15'). Most of the cosmological distinguishing power is lost when the maps are smoothed on these larger scales. We also show that, on scales comparable to 1', where the perturbation series does not converge, cosmological constraints obtained from the MFs are approximately 1.5-2 times better than the ones obtained from the first few moments of the convergence distribution—provided that the latter include spatial information, either from moments of gradients or by combining multiple smoothing scales. Including a set of either these moments or the MFs can significantly tighten constraints on cosmological parameters, compared to the conventional method of using the power spectrum alone.

Petri, Andrea; Haiman, Zoltán; Hui, Lam; May, Morgan; Kratochvil, Jan M.

2013-12-01

381

Non-thermal mechanism of weak microwave fields influence on neurons  

NASA Astrophysics Data System (ADS)

A non-thermal mechanism of weak microwave field impact on a nerve fiber is proposed. It is shown that in the range of about 30-300 GHz, there are strongly pronounced resonances associated with the excitation of ultrasonic vibrations in the membrane as a result of interaction with electromagnetic radiation. The viscous dissipation limits the resonances and results in their broadening. These forced vibrations create acoustic pressure, which may lead to the redistribution of the protein transmembrane channels, and thus changing the threshold of the action potential excitation in the axons of the neural network. The influence of the electromagnetic microwave radiation on various specific areas of myelin nerve fibers was analyzed: the nodes of Ranvier, and the initial segment--the area between the neuron hillock and the first part of the axon covered with the myelin layer. It was shown that the initial segment is the most sensitive area of the myelined neurons from which the action potential normally starts.

Shneider, M. N.; Pekker, M.

2013-09-01

382

Sensory transduction of weak electromagnetic fields: role of glutamate neurotransmission mediated by NMDA receptors.  

PubMed

Subliminal electromagnetic fields (EMFs) triggered nonlinear evoked potentials in awake but not anesthetized animals, and increased glucose metabolism in the hindbrain. Field detection occurred somewhere in the head and possibly was an unrecognized function of sensory neurons in facial skin, which synapse in the trigeminal nucleus and project to the thalamus via glutamate-dependent pathways. If so, anesthetic agents that antagonize glutamate neurotransmission would be expected to degrade EMF-evoked potentials (EEPs) to a greater extent than agents having different pharmacological effects. We tested the hypothesis using ketamine which blocks N-methyl-d-aspartate (NMDA) receptors (NMDARs), and xylazine which is an ??-adrenoreceptor agonist. Electroencephalograms (EEGs) of rats were examined using recurrence analysis to observe EEPs in the presence and absence of ketamine and/or xylazine anesthesia. Auditory evoked potentials (AEPs) served as positive controls. The frequency of observation of evoked potentials in a given condition (wake or anesthesia) was compared with that due to chance using the Fisher's exact test. EEPs were observed in awake rats but not while they were under anesthesia produced using a cocktail of xylazine and ketamine. In another experiment each rat was measured while awake and while under anesthesia produced using either xylazine or ketamine. EEPs and AEPs were detected during wake and under xylazine (P<0.05 in each of the four measurements). In contrast, neither EEPs nor AEPs were observed when anesthesia was produced partly or wholly using ketamine. The duration and latency of the EEPs was unaltered by xylazine anesthesia. The afferent signal triggered by the transduction of weak EMFs was likely mediated by NMDAR-mediated glutamate neurotransmission. PMID:24239718

Frilot, C; Carrubba, S; Marino, A A

2014-01-31

383

Reduction of Organic Matter in Macroporous Weak Anion Exchanger and Scavenger Filter. Field Studies.  

National Technical Information Service (NTIS)

In project K18 reduction of organic water has been tested in four plants with macroporous weak anion exchanger. In project K19 the reduction of organic matter has been tested in five plants. The plants have macroporous weak anion exchanger and scavenger f...

F. Persson

1982-01-01

384

COMMENTS AND REPLIES: Comment on 'Late-time tails of a self-gravitating massless scalar field revisited'  

NASA Astrophysics Data System (ADS)

Bizo? et al (2009 Class. Quantum Grav. 26 175006) discuss the power-law tail in the long-time evolution of a spherically symmetric self-gravitating massless scalar field in odd spatial dimensions. They derive explicit expressions for the leading-order asymptotics for solutions with small initial data by using formal series expansions. Unfortunately, this approach misses an interesting observation that the actual decay rate is a product of asymptotic cancellations occurring due to a special structure of the nonlinear terms. Here, we show that one can calculate the leading asymptotics more directly by recognizing the special structure and cancellations already on the level of the wave equation.

Szpak, Nikodem

2009-12-01

385

Cavities of weak magnetic field strength in the wake of FTEs: Results from global magnetospheric MHD simulations  

NASA Astrophysics Data System (ADS)

We use the global magnetohydrodynamic (MHD) code BATS-R-US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi-point Cluster observations of traveling magnetopause erosion regions (TMERs).

Kuznetsova, M. M.; Sibeck, D. G.; Hesse, M.; Wang, Y.; Rastaetter, L.; Toth, G.; Ridley, A.

2009-05-01

386

Cavities of Weak Magnetic Field Strength in the Wake of FTEs: Results from Global Magnetospheric MHD Simulations  

NASA Technical Reports Server (NTRS)

We use the global magnetohydrodynamic (MHD) code BATS-R-US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi-point Cluster observations of traveling magnetopause erosion regions (TMERs).

Kuznetsova, M. M.; Sibeck, D. G.; Hesse, M.; Wang, Y.; Rastaetter, L.; Toth, G.; Ridley, A.

2009-01-01

387

Activating persulfate by Fe(0) coupling with weak magnetic field: Performance and mechanism.  

PubMed

Weak magnetic field (WMF) and Fe(0) were proposed to activate PS synergistically (WMF-Fe(0)/PS) to degrade dyes and aromatic contaminants. The removal rates of orange G (OG) by WMF-Fe(0)/PS generally decreased with increasing initial pH (3.0-10.0) and increased with increasing Fe(0) (0.5-3.0 mM) or PS dosages (0.5-3.0 mM). Compared to its counterpart without WMF, the WMF-Fe(0)/PS process could induce a 5.4-28.2 fold enhancement in the removal rate of OG under different conditions. Moreover, the application of WMF significantly enhanced the decolorization rate and the mineralization of OG. The degradation rates of caffeine, 4-nitrophenol, benzotriazole and diuron by Fe(0)/PS were improved by 2.1-11.1 fold due to the superimposed WMF. Compared to many other sulfate radical-based advanced oxidation technologies under similar reaction conditions, WMF-Fe(0)/PS technology could degrade selected organic contaminants with much greater rates. Sulfate radical was identified to be the primary radical species responsible for the OG degradation at pH 7.0 in WMF-Fe(0)/PS process. This study unraveled that the presence of WMF accelerated the corrosion rate of Fe(0) and thus promoted the release of Fe(2+), which induced the increased production of sulfate radicals from PS and promoted the degradation of organic contaminants. Employing WMF to enhance oxidation capacity of Fe(0)/PS is a novel, efficient, promising and environmental-friendly method since it does not need extra energy and costly reagents. PMID:24934323

Xiong, Xinmei; Sun, Bo; Zhang, Jing; Gao, Naiyun; Shen, Jimin; Li, Jialing; Guan, Xiaohong

2014-10-01

388

Particle content and degrees of freedom of a gravitational field in 4th order theories of gravity  

NASA Astrophysics Data System (ADS)

In gravitational theories of fourth order, the influence of certain properties of the field equations (tracelessness, conformal invariance, scale invariance, or their breaking) for the particle content (number of degrees of freedom, mass, and spin) is investigated. Using the Cauchy initial-value problem and a counting method first developed by Einstein, it is possible to get a useful definition of the concept of the degrees of freedom for the full nonlinear theory. This is due to the fact that this method incorporates the concrete structure of the field equations (and thus their nonlinearities). Analyzing different general-relativistic field theories via these approaches, the influence of the various structures of nonlinearities is discussed. It is, in particular, shown that those results obtained by the spin projection formalism can be reproduced by nonlinear methods.

Moebius, K.

389

On the Resonant Orbit of a Solar Companion Star in the Gravitational Field of the Galaxy  

NASA Astrophysics Data System (ADS)

For the motion of a weakly bound solar companion star, we have investigated the resonance effects that arise when the Keplerian period of the system is half the period with which the system oscillates through the galactic plane. This resonance could be important in the motion of the putative solar companion star Nemesis. The resonant perturbation of the Keplerian motion is a dynamic tidal compression of the Sun-Nemesis system by the galactic field. We have expressed the Hamiltonian in terms of the action-angle variables that describe the unperturbed Keplerian motion and the oscillation through the galactic plane. By averaging the Hamiltonian over the fast angle variables, we have reduced the problem to a motion in two degrees of freedom. Our study of the averaged motion includes the isolation of the periodic orbits, the determination of the stability of the periodic orbits, and numerical solutions for the nonperiodic orbits. We have delineated the resonance phenomena with the aid of surfaces of section and other diagnostic tools. We have tested the orbits derived from the averaged Hamiltonian with the said of numerical solutions of the equations of motion derived from the "exact" Hamiltonian of the system. The resonance is strong enough to produce a well-defined population of resonant orbits in which the Keplerian motion of Nemesis locks onto the oscillation of the system through the galactic plane. Orbits of large inclinations relative to the galactic plane tend to be chaotic. Only a small population of resonant and nonresonant orbits with low inclinations would penetrate the Oort cloud and trigger comet showers at every perihelion passage.

Vandervoort, Peter O.; Sather, Eric A.

1993-09-01

390

Statistical inference of weakly correlated subthermocline fields from satellite altimeter data  

NASA Astrophysics Data System (ADS)

To initialize the barotropic and baroclinic modes, numerical ocean prediction models need information both above and below the main thermocline. Forecasts of upper ocean mesoscale variability using real and simulated data show high sensitivity to the Subthermocline pressure (STP) field. Results using simulated data indicate that the accuracy of this field may be the limiting factor on the time scale for mesoscale oceanic predictive skill. Satellite altimetry provides a potentially abundant source of sea surface height (SSH) data, but there is no comparable source of Subthermocline information on the horizon. We investigate statistical techniques to infer Subthermocline pressure anomalies from SSH data, a problem complicated by the weak correlation between the fields. This problem is addressed by using the degrees of freedom available in the data and by describing them in an efficient manner to suppress noise, eliminate unskilled or redundant estimators and to prevent ill-conditioned matrix inversions. Multilinear regression, empirical orthogonal function (EOF) regression and principal estimator patterns are compared using data simulated by a numerical ocean model and error models. Numerous questions that need to be addressed for proper application of the statistical techniques are investigated. Topics include noise suppression and the impact of the noise on accuracy. These topics are studied as a function of decorrelation distance in the noise and the presence or absence of noise in dependent and independent data sets. In this context we also investigate dependent data set size requirements, the criteria for choosing estimators, the number, areal coverage, and spacing of sampling locations used in the estimators, the effect of the ocean dynamical regime on the results, the effects of ocean model imperfections or changes in population statistics on the results, SSH versus ?SSH in an orbital repeat period as estimators, and the effect of orbital repeat period on Subthermocline estimates from ?SSH data. In the presence of 40% rms noise the usual significance tests are much too conservative for this application. (However, we also found that EOFs calculated from spatially correlated, temporally uncorrelated noise can pass a popular EOF significance test based on uncorrelated noise.) Although more difficult to suppress than uncorrelated noise, correlated noise did not markedly increase the error in these tests. Spatial coverage of the estimators was found to be an important parameter, and four to five ascending-or descending tracks per wavelength were sufficient for uniformly accurate estimates whether beneath or between altimeter tracks. In most of these tests, ?SSH proved a better estimator than SSH, but for ?SSH resolving the shortest major time scale is a necessity. High accuracy is not required for Subthermocline pressure anomalies to substantially enhance upper ocean forecast skill in a numerical ocean prediction model. In results to be reported elsewhere, a statistically inferred STP field substantially enhanced the skill of a Gulf Stream forecast model where the SSH was initialized from oceanic observations. The inferred STP field allowed the model to show forecast skill in comparison to persistence of the initial state.

Hurlburt, Harley E.; Fox, Daniel N.; Metzger, E. Joseph

1990-07-01

391

Dark Haloes as Seen with Gravitational Lensing  

NASA Astrophysics Data System (ADS)

Dark matter is an important ingredient of galaxies, as was recognized early on by Ken Freeman himself! Evidence for dark matter halos is still indirect, based on analysing motions of tracers such as gas and stars. In a sense the visible galaxy is the mask through which we can study the dark matter. Light rays are also sensitive to gravitational fields and dark haloes cause observable gravitational lensing effects. There are three regimes: microlensing (which probes the clumpiness of dark matter haloes), strong lensing (sensitive to the inner mass distribution) and weak lensing (which can probe haloes out to 100 s of kpc from the centre). This review will concentrate on weak lensing and describe a new survey, the Kilo-Degree Survey (KiDS), that is designed to study galaxy halo masses, extents, and shapes as a function of environment, galaxy type, and redshift.

Kuijken, Konrad

392

Mean-field analysis of dimensional crossover from two dimensions to three dimensions in a weakly interacting Fermi gas  

SciTech Connect

We investigate theoretically the transition from two to three dimensions in a weakly interacting ultracold Fermi gas. This transition was recently observed by Dyke et al.[Phys. Rev. Lett. 106, 105304 (2011)] in a cloud of fermionic {sup 6}Li atoms trapped in an oblate harmonic potential. We calculate the density distribution and cloud size of the Fermi cloud by numerically solving three-dimensional Hartree-Fock mean-field equations. Local density approximation is used to ease the calculations in the weakly confined radial direction. Our theoretical results are shown to be in good agreement with the experimental measurements.

Hu Hui [ARC Centre of Excellence for Quantum-Atom Optics, Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne, Victoria 3122 (Australia)

2011-11-15

393

SIMULATIONS OF TURBULENCE INDUCED ELLIPTICITY OVER LARGE FIELDS-OF-VIEW: THE FIRST STEP TOWARDS ENABLING LSST WEAK LENSING SCIENCE  

SciTech Connect

Atmospheric turbulence can mimic the effects of weak lensing in astronomical images, so it is necessary to understand to what degree turbulence affects weak lensing measurements. In particular, we studied the ellipticity induced upon the point-spread functions (PSFs) of a grid of simulated stars separated by distances (d {approx} 1{prime}) that will be characteristic of Large Synoptic Survey Telescope (LSST) images. We observe that atmospherically induced ellipticity changes on small scales (d < 0.5{prime}) and use linear interpolation between stars separated by d = 0.5{prime} to determine the induced ellipticity everywhere in the field-of-view.

Schlaufman, K

2004-10-11

394

Seasonal variations of the Earth's gravitational field: An analysis of atmospheric pressure, ocean tidal, and surface water excitation  

NASA Astrophysics Data System (ADS)

Monthly mean gravitational field parameters (denoted here as Ceven) that represent linear combinations of the primarily even-degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National Meteorological Center (NMC) spanning 1984-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant causes of the observed annual Ceven variations. Closure with observations is seen at the 1? level when atmospheric pressure, ocean tide and surface water effects are included. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1ó level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed Ceven variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed.

Dong, D.; Gross, R. S.; Dickey, J. O.

395

Seasonal Variations of the Earth's Gravitational Field: An Analysis of Atmospheric Pressure, Ocean Tidal, and Surface Water Excitation  

NASA Technical Reports Server (NTRS)

Monthly mean gravitational field parameters (denoted here as C(sub even)) that represent linear combinations of the primarily even degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National meteorological center (NMC) spanning 1983-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant cause of observed annual C(sub even) variations. Closure with observations is seen at the 1sigma level when atmospheric pressure, ocean tide and surface water effects are include. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1sigma level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed C(sub even) variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed.

Dong, D,; Gross, R.S.; Dickey, J.

1996-01-01

396

A Signal-adaptive Method for Sparse Global and Regional Modeling of the Gravitational Field  

NASA Astrophysics Data System (ADS)

We propose a novel algorithm to solve inverse problems appearing in the geosciences by taking the example of downward continuation of the gravitational potential. The method expands the signal in terms of trial functions which are iteratively picked from a large redundant set containing different types of functions. In particular, we are able to combine spherical harmonics of low degrees as well as wavelets and/or scaling functions for the reconstruction of global trends and regional details, respectively. The outcome is adapted to the data density and also to the detail structure of the signal which yields a certain sparsity of the solution. Numerical experiments are presented.

Telschow, R.

2013-12-01

397

Effect of an atom on a quantum guided field in a weakly driven fiber-Bragg-grating cavity  

SciTech Connect

We study the interaction of an atom with a quantum guided field in a weakly driven fiber-Bragg-grating (FBG) cavity. We present an effective Hamiltonian and derive the density-matrix equations for the combined atom-cavity system. We calculate the mean photon number, the second-order photon correlation function, and the atomic excited-state population. We show that due to the confinement of the guided cavity field in the fiber cross-section plane and in the space between the FBG mirrors, the presence of the atom in the FBG cavity can significantly affect the mean photon number and the photon statistics even though the cavity finesse is moderate, the cavity is long, and the probe field is weak.

Le Kien, Fam; Hakuta, K. [Department of Applied Physics and Chemistry, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan)

2010-02-15

398

Gravitational effects from earthquakes  

NASA Astrophysics Data System (ADS)

Two types of propagating gravitational effects, from the mass redistribution within the Earth due to a large earthquake, are investigated: (i) the velocity of the change of the Newtonian potential field; and (ii) the gravitational luminosity of the seismic source. The mass redistribution caused by an earthquake and the resulting change in the gravitational potential field is computed through application of geophysical dislocation theory. The global mass redistribution is postulated to be progressive, starting at the instant (and location) of the nucleation of the earthquake fault rupture, and then spreading globally at the velocities of various seismic waves. Information about the changes of the gravitational potential is postulated to travel at the velocity of light. Superconducting gravimeters (SG) can resolve changes of the order of 10 nGal, i.e., (10(-9) cm/s(2)) (1 Gal = 0.001 0197g), sufficient to detect the changes in the potential field. The time difference between observation of the change of the potential field and the arrival of the primary seismic wave from the earthquake would allow a crude estimation of the velocity of the gravitational effect. A preliminary search for the preseismic gravitational signal using an SG has given inconclusive results, primarily due to the limitations of the spline curve fitting methods. Despite this, we suggest that the observation of preseismic gravitational potential changes should be feasible, with the existing array of SGs in the Global Geodynamics Project (GGP) network, and by detectors designed to observe gravitational radiation (e.g., the Laser Interferometer Gravitational-wave Observatory (LIGO)). We have used published values of the changes in the Earth's inertia tensor due to the Alaska earthquake of 1964 to estimate the magnitude of the metric perturbation of the gravitational wave produced by such an earthquake. The gravitational luminosity is estimated at 1.90 x 10(-10)erg/s (1 erg/s = 10(-7) W D 1 J/s).

Hayes, T. J.; Valluri, S. R.; Mansinha, L.

2004-12-01

399

Modeling Gravitational Radiation Waveforms from Black Hole Mergers  

NASA Technical Reports Server (NTRS)

Gravitational radiation from merging binary black hole systems is anticipated as a key source for gravitational wave observations. Ground-based instruments, such as the Laser Interferometer Gravitational-wave Observatory (LIGO) may observe mergers of stellar-scale black holes, while the space-based Laser Interferometer Space Antenna (LISA) observatory will be sensitive to mergers of massive galactic-center black holes over a broad range of mass scales. These cataclysmic events may emit an enormous amount of energy in a brief time. Gravitational waves from comparable mass mergers carry away a few percent of the system's mass-energy in just a few wave cycles, with peak gravitational wave luminosities on the order of 10^23 L_Sun. Optimal analysis and interpretation of merger observation data will depend on developing a detailed understanding, based on general relativistic modeling, of the radiation waveforms. We discuss recent progress in modeling radiation from equal mass mergers using numerical simulations of Einstein's gravitational field equations, known as numerical relativity. Our simulations utilize Adaptive Mesh Refinement (AMR) to allow high-resolution near the black holes while simultaneously keeping the outer boundary of the computational domain far from the black holes, and making it possible to read out gravitational radiation waveforms in the weak-field wave zone. We discuss the results from simulations beginning with the black holes orbiting near the system's innermost stable orbit, comparing the recent simulations with earlier "Lazarus" waveform estimates based on an approximate hybrid numerical/perturbative technique.

Baker, J. G.; Centrelia, J. M.; Choi, D.; Koppitz, M.; VanMeter, J.

2006-01-01

400

Theoretical model of gravitational perturbation of current collector axisymmetric flow field  

NASA Astrophysics Data System (ADS)

Some designs of liquid metal collectors in homopolar motors and generators are essentially rotating liquid metal fluids in cylindrical channels with free surfaces and will, at critical rotational speeds, become unstable. The role of gravity in modifying this ejection instability is investigated. Some gravitational effects can be theoretically treated by perturbation techniques on the axisymmetric base flow of the liquid metal. This leads to a modification of previously calculated critical current collector ejection values neglecting gravity effects. The derivation of the mathematical model which determines the perturbation of the liquid metal base flow due to gravitational effects is documented. Since gravity is a small force compared with the centrifugal effects, the base flow solutions can be expanded in inverse powers of the Froude number and modified liquid flow profiles can be determined as a function of the azimuthal angle. This model will be used in later work to theoretically study the effects of gravity on the ejection point of the current collector. A rederivation of the hydrodynamic instability threshold of a liquid metal current collector is presented.

Walker, John S.; Brown, Samuel H.; Sondergaard, Neal A.

1989-03-01

401

Chiral phase transition in relativistic heavy-ion collisions with weak magnetic fields: Ring diagrams in the linear sigma model  

SciTech Connect

Working in the linear sigma model with quarks, we compute the finite-temperature effective potential in the presence of a weak magnetic field, including the contribution of the pion ring diagrams and considering the sigma as a classical field. In the approximation where the pion self-energy is computed perturbatively, we show that there is a region of the parameter space where the effect of the ring diagrams is to preclude the phase transition from happening. Inclusion of the magnetic field has small effects that however become more important as the system evolves to the lowest temperatures allowed in the analysis.

Ayala, Alejandro [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico Distrito Federal 04510 (Mexico); Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Apartado Postal 2-82, Morelia, Michoacan 58040 (Mexico); Centro Brasileiro de Pesquisas Fisicas, CBPF-DCP, Rua Dr. Xavier Sigaud 150, 22290-180, Rio de Janeiro (Brazil); Bashir, Adnan; Raya, Alfredo; Sanchez, Angel [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Apartado Postal 2-82, Morelia, Michoacan 58040 (Mexico)

2009-08-01

402

Cosmic matter-antimatter asymmetry and gravitational force  

NASA Technical Reports Server (NTRS)

Cosmic matter-antimatter asymmetry due to the gravitational interaction alone is discussed, considering the gravitational coupling of fermion matter related to the Yang-Mills (1954) gauge symmetry with the unique generalization of the four-dimensional Poincare group. Attention is given to the case of weak static fields which determines the space-time metric where only large source terms are retained. In addition, considering lowest-order Feynman diagrams, there are presented gravitational potential energies between fermions, between antifermions, and between a fermion and an antifermion. It is concluded that the gravitational force between matter is different from that between antimatter; implications from this concerning the evolution of the universe are discussed.

Hsu, J. P.

1980-01-01

403

Variations of the gravitational field as a motive power for dynamics of physics-chemical and biological processes  

NASA Astrophysics Data System (ADS)

It is commonly accepted that linkage between the Earth,s biosphere and space environment is realized by means of electromagnetic fields. Meanwhile, the Earth is constantly subjected to influence of changeable gravitat ional field. Variations of the gravitational field affected by the Sun and the Moon while the Earth's moving along the orbit seem to be a powerful source of many rhythmical processes typical of physics - chemical and biological systems. Studies carried out in AARI revealed the obvious relationships between the dynamics of physics-chemical and biological processes and variations in velocity of the Earth's headway and rotary motion under the gravitational influence of the Sun and the Moon. The following of them are examined as an example: The rate of oxidation of the biologically important thiol compounds has been studied by the unithiol test proposed by Sokolovsky et al. [1982, 1984]. The rhythmical fluctuations of the oxidation rate can be described as superposition of variations with periods15, 35, 180 days, and one-year trend. These periods are closed to the main periods characterizing uneven headway and rotary motion of the Earth along the orbit (14.8, 31.8, 182.6, and 365.3 days). The same periodicity is typical of hematological signatures (rate of the erythrocytes sedimentation, leukocytary ratio and others) obtained from 2500 donors in St.Petersburg for period from May 2000 to March 2001. The coordinated observations of total ozone and the unithiol oxi dation rate made at related latitudes in the Antarctic and Arctic during the spring seasons showed their evident association: the rate of oxidation is retarded when total ozone decreases, and vice versa. The "computer time" corrections applied by GPS show the rhythmic fluctuations consistent with nutational variations. Along with rhythmic fluctuations typical of the temporal corrections the GPS data demonstrate the similar rhythmic fluctuations of the spatial corrections. The general conclusion is made that variations of the gravitational field are one of the main motive power for dynamics of physics- chemical and biological processes.

Troshichev, O.; Gorshkov, E.; Shapovalov, S.; Sokolovskii, V.

404

The impact of high spatial frequency atmospheric distortions on weak lensing measurements  

Microsoft Academic Search

High precision cosmology with weak gravitational lensing requires a precise measure of the Point Spread Function across the imaging data where the accuracy to which high spatial frequency variation can be modelled is limited by the stellar number density across the field. We analyse dense stellar fields imaged at the Canada-France-Hawaii Telescope to quantify the degree of high spatial frequency

Catherine Heymans; Barnaby Rowe; Henk Hoekstra; Lance Miller; Thomas Erben; Thomas Kitching; Ludovic Van Waerbeke

2011-01-01

405

Strong-field ionization and coulomb explosion of chlorine weakly bound to small water clusters.  

PubMed

Clusters exhibit an enhancement in ionization rates under intense, ultrafast laser pulses compared to their molecular/atomic counterparts. Studies of ionization enhancement of weakly bound molecules to clusters have not been previously characterized and quantified. We demonstrate that weakly bound ClO to (H(2)O)(n) (n = 1-12) clusters and weakly bound HCl to (H(2)O)(n) (n = 1-12) clusters produce high atomic charge states of chlorine via Coulomb explosion. Density functional theory (DFT) was used to qualitatively compare the interaction energy of ClO with respect to the number of water molecules as well as HCl with respect to the number of water molecules. The chlorine ion signal intensity for each atomic charge state was observed to be dependent on the molecule-cluster bond strength. The observed ionization enhancement was quantified using semiclassical tunneling theory, and it was found that the Cl(3+-5+) and O(2+) charge states are enhanced in ionization. Possible mechanisms of ionization enhancement are explored for weakly bound chlorine species. PMID:22830582

Ross, Matt W; Berkdemir, Cuneyt; Castleman, A W

2012-08-23

406

Sensed presence and mystical experiences are predicted by suggestibility, not by the application of transcranial weak complex magnetic fields.  

PubMed

Transcranial magnetic stimulation (TMS) with weak (micro Tesla) complex waveform fields have been claimed to evoke the sensed presence of a sentient being in up to 80% in the general population. These findings have had a questionable neurophysiological foundation as the fields are approximately six orders of magnitude weaker than ordinary TMS fields. Also, no independent replication has been reported. To replicate and extend previous findings, we performed a double-blind experiment (N=89), with a sham-field control group. Personality characteristics indicating suggestibility (absorption, signs of abnormal temporal lobe activity, and a "new age"-lifestyle orientation) were used as predictors. Sensed presence, mystical, and other somatosensory experiences previously reported from the magnetic field stimulation were outcome measures. We found no evidence for any effects of the magnetic fields, neither in the entire group, nor in individuals high in suggestibility. Because the personality characteristics significantly predicted outcomes, suggestibility may account for previously reported effects. Our results strongly question the earlier claims of experiential effects of weak magnetic fields. PMID:15849873

Granqvist, Pehr; Fredrikson, Mats; Unge, Patrik; Hagenfeldt, Andrea; Valind, Sven; Larhammar, Dan; Larsson, Marcus

2005-04-29

407

Potential production of Hughlings Jackson's "parasitic consciousness" by physiologically-patterned weak transcerebral magnetic fields: QEEG and source localization.  

PubMed

Exotic experiences such as the sensing of another consciousness or the detachment of consciousness from the body are occasionally reported by individuals with partial seizures from a temporal lobe focus. The experiences display the characteristics of Hughlings Jackson's "parasitic consciousness". We have hypothesized that these experiences are encouraged by slight discrepancies in hemispheric activity that can be simulated by application of weak, physiologically-patterned magnetic fields across the cerebral hemispheres. Electroencephalographic and Low Resolution Electromagnetic Tomography (sLORETA) data revealed altered activity bands within specific regions within the cerebral cortices during these experiences. The clear changes in power of brain activity were discerned after consistent durations of exposure to specifically patterned weak magnetic fields. Millisecond range point durations were required. The technology may be useful to explore the subjective components associated with complex partial seizures. PMID:23872082

Saroka, Kevin S; Persinger, Michael A

2013-09-01