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1

Particle motion in weak relativistic gravitational fields  

NASA Astrophysics Data System (ADS)

We derive the geodesic equation of motion in the presence of weak gravitational fields produced by relativistic sources such as cosmic strings, decomposed into scalar, vector and tensor parts. To test the result, we perform the first N-body simulations with relativistic weak gravitational external fields. Our test case is a moving straight string, for which we recover the well-known result for the impulse on nonrelativistic particles. We find that the vector (gravito-magnetic) force is an essential contributor. Our results mean that it is now possible to incorporate straightforwardly into N-body simulations all weak relativistic sources, including networks of cosmic defects.

Obradovic, Miki; Kunz, Martin; Hindmarsh, Mark; Iliev, Ilian T.

2012-09-01

2

Republication of: Quantum theory of weak gravitational fields  

NASA Astrophysics Data System (ADS)

This is an English translation of a paper by Matvei Bronstein, first published in German in 1936 in a long-extinct Soviet journal, in which he presented the first attempt at quantizing a weak (linearized) gravitational field, rather modern in its approach. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Stanley Deser and Alexei Starobinsky, and Bronstein's brief biography written by Stanley Deser.

Bronstein, Matvei

2012-01-01

3

[The use of a detector of the extremely weak radiation as a variometer of gravitation field].  

PubMed

It was shown that the detector of extremely weak radiation with selectively increased sensitivity to the nonelectromagnetic, including the gravitational component of the spectrum of active physical fields can be used as the basis for constructing a variometer of gravitational field of a new type. PMID:11605376

Gorshkov, E S; Bondarenko, E G; Shapovalov, S N; Sokolovski?, V V; Troshichev, O A

4

Weak gravitational lensing  

Microsoft Academic Search

We review theory and applications of weak gravitational lensing. After summarising Friedmann–Lema??tre cosmological models, we present the formalism of gravitational lensing and light propagation in arbitrary space–times. We discuss how weak-lensing effects can be measured. The formalism is then applied to reconstructions of galaxy-cluster mass distributions, gravitational lensing by large-scale matter distributions, QSO–galaxy correlations induced by weak lensing, lensing of

Matthias Bartelmann; Peter Schneider

2001-01-01

5

Localized electromagnetic and weak gravitational fields in the source-free space  

NASA Astrophysics Data System (ADS)

Localized electromagnetic and weak gravitational time-harmonic fields in the source-free space are treated using expansions in plane waves. The presented solutions describe fields having a very small (about several wavelengths) and clearly defined core region with maximum intensity of field oscillations. In a given Lorentz frame L, a set of the obtained exact time-harmonic solutions of the free-space homogeneous Maxwell equations consists of three subsets (storms, whirls, and tornados), for which time average energy flux is identically zero at all points, azimuthal and spiral, respectively. In any other Lorentz frame L', they will be observed as a kind of electromagnetic missile moving without dispersing at speed Vweak gravitational fields with similar properties are also presented. The properties of these fields are illustrated in graphic form.

Borzdov, G. N.

2001-03-01

6

Energy-momentum tensor for a Casimir apparatus in a weak gravitational field  

SciTech Connect

The influence of the gravity acceleration on the regularized energy-momentum tensor of the quantized electromagnetic field between two plane-parallel conducting plates is derived. We use Fermi coordinates and work to first order in the constant acceleration parameter. A perturbative expansion, to this order, of the Green functions involved and of the energy-momentum tensor is derived by means of the covariant geodesic point-splitting procedure. In correspondence to the Green functions satisfying mixed and gauge-invariant boundary conditions, and Ward identities, the energy-momentum tensor is covariantly conserved and satisfies the expected relation between gauge-breaking and ghost parts, while a new simple formula for the trace anomaly is obtained to first order in the constant acceleration. A more systematic derivation is therefore obtained of the theoretical prediction according to which the Casimir device in a weak gravitational field will experience a tiny push in the upwards direction.

Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero; Rosa, Luigi [Dipartimento di Scienze Fisiche, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio N', 80126 Naples (Italy); INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio N', 80126 Naples (Italy)

2006-10-15

7

A generalized lens equation for light deflection in weak gravitational fields  

NASA Astrophysics Data System (ADS)

A generalized lens equation for weak gravitational fields of Schwarzschild metric and valid for finite distances of source and observer from the light deflecting body is suggested. The magnitude of neglected terms in the generalized lens equation is estimated to be smaller than or equal to \\frac{15\\,\\pi }{4}\\,\\frac{m^2}{{d^{\\;\\prime }}^2}, where m is the Schwarzschild radius of the massive body and d ' is Chandrasekhar's impact parameter. The main applications of this generalized lens equation are extreme astrometrical configurations, where the standard post-Newtonian approach as well as the classical lens equation cannot be applied. It is shown that in the appropriate limits, the proposed lens equation yields the known post-Newtonian terms, 'enhanced' post-post-Newtonian terms and the classical lens equation, thus providing a link between both these essential approaches for determining the light deflection.

Zschocke, Sven

2011-06-01

8

Dixon's extended bodies and weak gravitational waves  

NASA Astrophysics Data System (ADS)

General relativity considers Dixon’s theory as the standard theory to deal with the motion of extended bodies in a given gravitational background. We discuss here the features of the “reaction” of an extended body to the passage of a weak gravitational wave. We find that the body acquires a dipolar moment induced by its quadrupole structure. Furthermore, we derive the “world function” for the weak field limit of a gravitational wave background and use it to estimate the deviation between geodesics and the world lines of structured bodies. Measuring such deviations, due to the existence of cumulative effects, should be favorite with respect to measuring the amplitude of the gravitational wave itself.

Bini, Donato; Cherubini, Christian; Geralico, Andrea; Ortolan, Antonello

2009-01-01

9

Hard thermal loops, weak gravitational fields and the quark-gluon plasma energy-momentum tensor  

Microsoft Academic Search

We use an auxiliary field construction to discuss the hard thermal loop effective action associated with massless thermal SU(N) QCD interacting with a weak grav- itational field. It is demonstrated that the previous attempt to derive this effective action has only been partially successful and that it is presently only known to first order in the graviton coupling constant. This

Eamonn Gaffney

1995-01-01

10

Weak-field limit  

NASA Astrophysics Data System (ADS)

Astrophysical applications of ETGs include the possibility of replacing dark matter in galaxy and clusters with modifications of gravity, the weak-field (Newtonian and post-Newtonian) limit, and gravitational waves. Dark matter at galactic and cluster scales is traditionally included in the realm of cosmology and is discussed in Chap. 7. Here we focus on the weak-field limit of metric f(R) gravity, referring the reader to well known sources for other ETGs. We then discuss gravitational waves in ETGs.

Capozziello, Salvatore; Faraoni, Valerio

11

Weak gravitational lensing with DEIMOS  

NASA Astrophysics Data System (ADS)

We introduce a novel method for weak-lensing measurements, which is based on a mathematically exact deconvolution of the moments of the apparent brightness distribution of galaxies from the telescope's point spread function (PSF). No assumptions on the shape of the galaxy or the PSF are made. The (de)convolution equations are exact for unweighted moments only, while in practice a compact weight function needs to be applied to the noisy images to ensure that the moment measurement yields significant results. We employ a Gaussian weight function, whose centroid and ellipticity are iteratively adjusted to match the corresponding quantities of the source. The change of the moments caused by the application of the weight function can then be corrected by considering higher order weighted moments of the same source. Because of the form of the deconvolution equations, even an incomplete weighting correction leads to an excellent shear estimation if galaxies and PSF are measured with a weight function of identical size. We demonstrate the accuracy and capabilities of this new method in the context of weak gravitational lensing measurements with a set of specialized tests and show its competitive performance on the GREAT08 Challenge data. A complete C++ implementation of the method can be requested from the authors.

Melchior, P.; Viola, M.; Schäfer, B. M.; Bartelmann, M.

2011-04-01

12

Gravitational Effects in Field Gravitation Theory.  

National Technical Information Service (NTIS)

The possibilities to describe various gravitation effects of field gravitation theory (FGT) are considered. Past-Newtonian approximation of the FGT has been constructed and on the basis of this approximation it has been shown that the field theory allows ...

V. I. Denisov A. A. Logunov M. A. Mestvirishvili A. A. Vlasov

1979-01-01

13

Gravitational anomaly and Hawking radiation near a weakly isolated horizon  

NASA Astrophysics Data System (ADS)

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 means we can extend the idea of Wilczek and his collaborators to more general cases and show the relation between gravitational anomaly and Hawking radiation is a universal property of a black hole horizon.

Wu, Xiaoning; Huang, Chao-Guang; Sun, Jia-Rui

2008-06-01

14

Gravitational force in weakly correlated particle distributions  

Microsoft Academic Search

We study the statistics of the gravitational (Newtonian) force in a\\u000aparticular kind of weakly correlated distribution of point-like and unitary\\u000amass particles generated by the so-called Gauss-Poisson point process. In\\u000aparticular we extend to these distributions the analysis a' la Chandrasekhar\\u000aintroduced for purely Poisson processes. In this way we can find the asymptotic\\u000abehavior of the probability density

Andrea Gabrielli; Adolfo Paolo Masucci; Francesco Sylos Labini

2003-01-01

15

Gravitational force in weakly correlated particle spatial distributions.  

PubMed

We study the statistics of the gravitational (Newtonian) force in a particular class of weakly correlated spatial distributions of pointlike and unitary mass particles generated by the so-called Gauss-Poisson point processes. In particular we extend to these distributions the analysis that Chandrasekhar introduced for purely Poisson processes. In this way we can find the explicit asymptotic behavior of the probability density function of the force for both large and small values of the field as a generalization of the Holtzmark statistics. In particular, we show how the modifications at large fields depend on the density correlations introduced at small scales. The validity of the introduced approximations is positively tested through a direct comparison with the analysis of the statistics of the gravitational force in numerical simulations of Gauss-Poisson processes. PMID:15089268

Gabrielli, Andrea; Masucci, Adolfo Paolo; Labini, Francesco Sylos

2004-03-30

16

Gravitational force in weakly correlated particle spatial distributions  

NASA Astrophysics Data System (ADS)

We study the statistics of the gravitational (Newtonian) force in a particular class of weakly correlated spatial distributions of pointlike and unitary mass particles generated by the so-called Gauss-Poisson point processes. In particular we extend to these distributions the analysis that Chandrasekhar introduced for purely Poisson processes. In this way we can find the explicit asymptotic behavior of the probability density function of the force for both large and small values of the field as a generalization of the Holtzmark statistics. In particular, we show how the modifications at large fields depend on the density correlations introduced at small scales. The validity of the introduced approximations is positively tested through a direct comparison with the analysis of the statistics of the gravitational force in numerical simulations of Gauss-Poisson processes.

Gabrielli, Andrea; Masucci, Adolfo Paolo; Sylos Labini, Francesco

2004-03-01

17

Weak gravitational lensing by compact objects in fourth order gravity  

NASA Astrophysics Data System (ADS)

We discuss weak lensing characteristics in the gravitational field of a compact object in the low-energy approximation of fourth order f(R)-gravity theory. The particular solution is characterized by a gravitational strength parameter ? and a distance scale rc much larger than the Schwarzschild radius. Above rc gravity is strengthened and as a consequence weak lensing features are modified compared to the Schwarzschild case. We find a critical impact parameter (depending upon rc) for which the behavior of the deflection angle changes. Using the Virbhadra-Ellis lens equation we improve the computation of the image positions, Einstein ring radii, magnification factors and the magnification ratio. We demonstrate that the magnification ratio as function of image separation obeys a power law depending on the parameter ?, with a double degeneracy. No ??0 value gives the same power as the one characterizing Schwarzschild black holes. As the magnification ratio and the image separation are the lensing quantities most conveniently determined by direct measurements, future lensing surveys will be able to constrain the parameter ? based on this prediction.

Horváth, Zsolt; Gergely, László Á.; Hobill, David; Capozziello, Salvatore; De Laurentis, Mariafelicia

2013-09-01

18

Spherically Symmetric Gravitational Fields  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to investigate the quantum vacua directly implied by the wave function of a gravitational configuration characterized by the presence of an apparent horizon, namely the Vaidya space-time solution. Spherical symmetry is a main feature of this configuration, with a scalar field constituting a source [a Klein-Gordon geon or Berger-Chitre-Moncrief-Nutku (BCMN) type model]. The subsequent analysis requires solving a Wheeler-DeWitt equation near the apparent horizon (following the guidelinesintroduced by A. Tomimatsu,18; M. Pollock, 19 and developed by A. Hosoya and I. Oda20,21) with the scalar field herein expanded in terms of S2 spherical harmonics: midisuperspace quantization. The main results present in this paper are as follows. It is found that the mass function characteristic of the Vaidya metric is positive definite within this quantum approach. Furthermore, the inhomogeneous matter sector determines a descrip-tion in terms of open quantum (sub)systems, namely in the form of an harmonic oscillator whose frequency depends on the mass function. For this open (sub)system, a twofold approach is employed. On the one hand, an exact invariant observable is obtained from the effective Hamiltonian for the inhomogeneous matter modes. It is shown that this invariant admits a set of discrete eigenvalues which depend on the mass function. The corresponding set of eigenstates is constructed from a particular vacuum state. On the other hand, exact solutions are found for the Schrädinger equation associated with the inhomogeneous matter modes. This paper is concluded with a discussion, where two other issues are raised: (i) the possible application to realistic black hole dynamics of the results obtained for a simplified (BCMN) model and (ii) whether such vacuum states could be related with others defined instead within scalar field theories constructed in classical backgrounds.

Vargas Moniz, P.

19

Constraining dark energy from the abundance of weak gravitational lenses  

Microsoft Academic Search

We examine the prospect of using the observed abundance of weak gravitational lenses to constrain the equation-of-state parameter w=p\\/rho of dark energy. Dark energy modifies the distance-redshift relation, the amplitude of the matter power spectrum, and the rate of structure growth. As a result, it affects the efficiency with which dark-matter concentrations produce detectable weak-lensing signals. Here we solve the

Nevin N. Weinberg; Marc Kamionkowski

2002-01-01

20

Gravitational force in weakly correlated particle spatial distributions  

Microsoft Academic Search

We study the statistics of the gravitational (Newtonian) force in a particular class of weakly correlated spatial distributions of pointlike and unitary mass particles generated by the so-called Gauss-Poisson point processes. In particular we extend to these distributions the analysis that Chandrasekhar introduced for purely Poisson processes. In this way we can find the explicit asymptotic behavior of the probability

Andrea Gabrielli; Adolfo Paolo Masucci; Francesco Sylos Labini

2004-01-01

21

Gravitational diffusion of solar system WIMPs. [Weakly interacting massive particles  

SciTech Connect

It is shown here that, because of purely gravitational diffusion, the most important solar-bound weakly interacting massive particles (WIMPs) are populated at the same phase-space density as low-velocity unbound orbits. This diffusion occurs on time scales short compared both to the lifetime of the earth and to weak-interaction depletion. The effect is that direct capture from bound and unbound orbits together is very nearly equal to direct capture by the earth considered as a body in free space. The same gravitational diffusion virtually eliminates indirect capture. The net result is that free-space formulas for capture reported in a previous paper may be used without modification despite the fact that the earth is bound in the potential well of the sun. 10 refs.

Gould, A. (Institute for Advanced Study, Princeton, NJ (USA))

1991-02-01

22

Gravitational Attraction Fields for Population in Turkey  

Microsoft Academic Search

Inspired by the gravitational attraction of the masses in Physics, the gravitational pull between the settlements has been proven to be an important phenomenon in explaining potentials that arise among towns. Again inspired by the Electro-magnetic fields in Physics, in this paper, the gravitational attraction between the cities is assumed to be exerted on a city with a certain “charge”

Cihan Ahmet Tutluoðlu; Vedia Dokmeci

2005-01-01

23

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

24

The Gravitational Fields of the Major Planets.  

National Technical Information Service (NTIS)

The constraints placed on models of the interiors of the major planets by the nonspherical components of their gravitational fields are explained, and several methods of determining these nonspherical components are described and evaluated. (Author)

S. J. Peale

1972-01-01

25

Spin precession in inertial and gravitational fields  

NASA Astrophysics Data System (ADS)

We discuss the motion of spin in inertial and gravitational fields. The coupling of spin with rotation and the gravitomagnetic field has already been extensively studied; therefore, we focus here on the inertial and gravitational spin-orbit couplings. In particular, we investigate the classical and quantum aspects of spin precession and spin-orbit coupling in an arbitrary translationally accelerated frame of reference as well as the exterior Schwarzschild spacetime. Moreover, in connection with Einstein’s principle of equivalence, we clarify the relation between the inertial and gravitational spin-orbit couplings.

Mashhoon, Bahram; Obukhov, Yuri N.

2013-09-01

26

Structure formation, backreaction and weak gravitational fields  

SciTech Connect

There is an ongoing debate in the literature as to whether the effects of averaging out inhomogeneities ('backreaction') in cosmology can be large enough to account for the acceleration of the scale factor in the Friedmann-Lemaitre-Robertson-Walker (FLRW) models. In particular, some simple models of structure formation studied in the literature seem to indicate that this is indeed possible, and it has also been suggested that the perturbed FLRW framework is no longer a good approximation during structure formation, when the density contrast becomes non-linear. In this work we attempt to clarify the situation to some extent, using a fully relativistic model of pressureless spherical collapse. We find that whereas averaging during structure formation can lead to acceleration via a selective choice of averaging domains, the acceleration is not present when more generic domains are used for averaging. Further, we show that for most of the duration of the collapse, matter velocities remain small, and the perturbed FLRW form of the metric can be explicitly recovered, in the structure formation phase. We also discuss the fact that the magnitude of the average effects of inhomogeneities depends on the scale of averaging, and while it may not be completely negligible on intermediate scales, it is expected to remain small when averaging on suitably large scales.

Paranjape, Aseem; Singh, T P, E-mail: aseem@tifr.res.in, E-mail: tpsingh@tifr.res.in [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

2008-03-15

27

Gravitational field of a global string  

SciTech Connect

The gravitational field of a straight global string is derived in the linear approximation to general relativity, and the resulting trajectories of test particles are found. Part of the gravitational effect of global strings is a deficit angle which increases logarithmically with the distance to the string core. In this regard, a global string resembles a gauge string. A new feature, not present for gauge strings, is a repulsive gravitational potential outside the core. The lensing properties of the global string, as well as other classical effects, are studied.

Harari, D.; Sikivie, P.

1988-06-15

28

Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit  

NASA Astrophysics Data System (ADS)

We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r?/b, where M is the black hole mass, a is the angular momentum, r? = Q2/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

Gyulchev, G. N.; Yazadjiev, S. S.

2010-11-01

29

Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements  

NASA Astrophysics Data System (ADS)

Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 ?m cut-off Teledyne HgCdTe/H2RG detector. We used a 0.88 ?m LED illumination source and f/22 pupil stop to produce undersampled point spread functions similar to those expected from WFIRST. We also emulated the WFIRST image reconstruction strategy, using the image combination (IMCOM) algorithm to derive oversampled images from dithered, undersampled input images. We created shear maps for this data and computed shear correlation functions to mimic a real weak lensing analysis. After removing only second-order polynomial fits to the shear maps, we found that the correlation functions could be reduced to O(10-6). This places a conservative upper limit on the detector-induced bias to the correlation function (under our test conditions). This bias is two orders of magnitude lower than the expected weak lensing signal. Restricted to scales relevant to dark energy analyses (sky separations >0.5'), the bias is O(10-7) - comparable to the requirement for future weak lensing missions to avoid biasing cosmological parameter estimates. Our experiment will need to be upgraded and repeated under different configurations to fully characterize the shape measurement performance of WFIRST IR detectors.

Seshadri, S.; Shapiro, C.; Goodsall, T.; Fucik, J.; Hirata, C.; Rhodes, J. D.; Rowe, B. T. P.; Smith, R. M.

2013-09-01

30

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

31

On the Field Theoretic Description of Gravitation  

NASA Astrophysics Data System (ADS)

Maxwell started to describe gravitation as a field in Minkowski space. Such an approach brought Babak and Grishchuk in 1999 the gravitational energy-momentum tensor. Simple manipulations allow the Einstein equations to take the form A?? = (8?G/c4)???, where A is the acceleration tensor and ?, the total energy momentum tensor, is conserved in Minkowski space. For non-curved cosmology, the total energy density vanishes: the gravitational part is negative and cancels the one of matter due to the Friedman equation. In 1989 Logunov added to the Lagrangian a bimetric coupling between the Minkowski and Riemann metrics. The case of a positive cosmological constant allows a regularization of the interior of the Schwarzschild black hole: The components of the metric tensor donot change sign, so, inside the black hole, time keeps its usual role. Cosmology generalizes the ?CDM model, while gravitational and matter energy cancel again at all times.

Nieuwenhuizen, Theo M.

2008-09-01

32

Spin Light of Neutrino in Gravitational Fields  

NASA Astrophysics Data System (ADS)

We develop the quasiclassical theory of a massive neutrino spin evolution in the presence of gravitational fields, and the corresponding probability of the neutrino spin oscillations in gravitational fields is derived for the first time. On this basis we also predict a new mechanism for electromagnetic radiation by a neutrino moving in the vicinity of gravitating objects (the "spin light of neutrino," SL?, in gravitational fields). It is shown that the total power of this radiation is proportional to the neutrino gamma factor to the fourth power, and the emitted photon energy, for the case of an ultra relativistic neutrino, spans up to gamma-rays. We investigate the SL? caused by both gravitational and electromagnetic fields, also accounting for effects of arbitrary moving and polarized matter, in various astrophysical environments. In particular, we discuss the SL? emitted by a neutrino moving in the vicinity of a rotating neutron star, black hole surrounded by dense matter, as well as by a neutrino propagating in the relativistic jet from a quasar.

Dvornikov, Maxim; Grigoriev, Alexander; Studenikin, Alexander

33

Spin in an arbitrary gravitational field  

NASA Astrophysics Data System (ADS)

We study the quantum mechanics of a Dirac fermion on a curved spacetime manifold. The metric of the spacetime is completely arbitrary, allowing for the discussion of all possible inertial and gravitational field configurations. In this framework, we find the Hermitian Dirac Hamiltonian for an arbitrary classical external field (including the gravitational and electromagnetic ones). In order to discuss the physical content of the quantum-mechanical model, we further apply the Foldy-Wouthuysen transformation, and derive the quantum equations of motion for the spin and position operators. We analyze the semiclassical limit of these equations and compare the results with the dynamics of a classical particle with spin in the framework of the standard Mathisson-Papapetrou theory and in the classical canonical theory. The comparison of the quantum-mechanical and classical equations of motion of a spinning particle in an arbitrary gravitational field shows their complete agreement.

Obukhov, Yuri N.; Silenko, Alexander J.; Teryaev, Oleg V.

2013-10-01

34

Radiative processes in external gravitational fields  

SciTech Connect

Kinematically forbidden processes may be allowed in the presence of external gravitational fields. These can be taken into account by introducing generalized particle momenta. The corresponding transition probabilities can then be calculated to all orders in the metric deviation from the field-free expressions by simply replacing the particle momenta with their generalized counterparts. The procedure applies to particles of any spin and to any gravitational fields. Transition probabilities, emission power, and spectra are, to leading order, linear in the metric deviation. It is also shown how a small dissipation term in the particle wave equations can trigger a strong backreaction that introduces resonances in the radiative process and deeply affects the resulting gravitational background.

Papini, Giorgio [Department of Physics, University of Regina, Regina, Sask, S4S 0A2 (Canada); Prairie Particle Physics Institute, University of Regina, Regina, Sask, S4S 0A2 (Canada); International Institute for Advanced Scientific Studies, 89019 Vietri sul Mare (Saudi Arabia) (Italy)

2010-07-15

35

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

36

What is a mean gravitational field?  

Microsoft Academic Search

The equations of General Relativity are non-linear. This makes their averaging non-trivial. The notion of mean gravitational field is defined and it is proven that this field obeys the equations of General Relativity if the unaveraged field does. The workings of the averaging procedure on Maxwell’s field and on perfect fluids in curved space-times are also discussed. It is found

F. Debbasch

2003-01-01

37

RADIATION DAMPING IN A GRAVITATIONAL FIELD  

Microsoft Academic Search

The validity of the principle of equivalence is examined relative to a ; charged mass point moving in an externally given gravitational field. The ; precedure is a covariant generalization of Dirac's work on the classical ; radiating electron. Just as Dirac's calculation was kept Lorentz invariant ; throughout, the present calculation is maintained generally covariant throughout. ; With the

B. S. DeWitt; R. W. Brehme

1960-01-01

38

On the consequences of the weak field approximation  

NASA Astrophysics Data System (ADS)

General Relativity reduces to Newtonian gravity within the appropriate limit. But, what is that limit? The conventional response is that of the weak field approximation in which the gravitating source is weak and velocities are low. But, this is a far cry from a quantitative statement. In that regard, the weak field may be defined more quantitatively as one in which any error introduced is far beyond the level of precision required. Since the field can always be made incrementally weaker there is no limit as to the degree of precision that can be achieved. In this regard, GR reduces exactly to Newtonian gravity at the limit where velocity goes to zero. It is only out of convenience that we extend this to include those conditions where v << c with the argument that any error is arbitrarily small. However, in practice GR can be shown to reduce to an exact Newtonian expression at v > 0. How can this observation fit with the quantitative definition of the weak field? This paper explores the consequences of the weak field approximation and the fact that GR reduces directly to Newtonian gravity within the weak field as opposed to the more specific condition where v = zero.

Laubenstein, John

2013-04-01

39

Black hole: gravitational charge equal to field energy  

Microsoft Academic Search

In general relativity, both non-gravitational matter energy as well as gravitational field energy are sources of the field. The author proposes that a collapsing body turns into a black hole when contributions of matter energy and field energy become equal. For a measure of field energy the author uses the Brown-York quasilocal energy while for the gravitational charge (measure of

N. Dadhich

1999-01-01

40

Consistent gravitationally coupled spin-2 field theory  

NASA Astrophysics Data System (ADS)

Inspired by the translational gauge structure of teleparallel gravity, the theory for a fundamental massless spin-2 field is constructed. Accordingly, instead of being represented by a symmetric second-rank tensor, the fundamental spin-2 field is assumed to be represented by a spacetime (world) vector field assuming values in the Lie algebra of the translation group. The flat-space theory naturally emerges in the Fierz formalism and is found to be equivalent to the usual metric-based theory. However, the gravitationally coupled theory, with gravitation itself described by teleparallel gravity, is shown not to present the consistency problems of the spin-2 theory constructed on the basis of general relativity.

Arcos, H. I.; Gribl Lucas, Tiago; Pereira, J. G.

2010-07-01

41

On field theory thermalization from gravitational collapse  

NASA Astrophysics Data System (ADS)

Motivated by its field theory interpretation, we study gravitational collapse of a minimally coupled massless scalar field in Einstein gravity with a negative cosmological constant. After demonstrating the accuracy of the numerical algorithm for the questions we are interested in, we investigate various aspects of the apparent horizon formation. In particular, we study the time and radius of the apparent horizon formed as functions of the initial Gaussian profile for the scalar field. We comment on several aspects of the dual field theory picture.

Garfinkle, David; Pando Zayas, Leopoldo A.; Reichmann, Dori

2012-02-01

42

Shell sources of stationary axisymmetric gravitational fields  

NASA Astrophysics Data System (ADS)

A number of solutions for material shell sources of stationary axisymmetric gravitational fields are presented. Explicit solutions are found for shells lying on equipotential hypersurfaces (gtt - const) and generating static 'monopole' fields in prolate and oblate spheroidal coordinates (Zipoy-Voorhees fields). Numerical solutions are found for shells lying on hypersurfaces of constant gphi-t/g sub phi-phi and generating Kerr- and Tomimatsu-Sato (delta = 2) fields. The shells have minimum areas allowed by the energy conditions of Hawking and Ellis.

Babala, D.

1986-02-01

43

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

NASA Astrophysics Data System (ADS)

Weak gravitational lensing can be used to constrain cosmological parameters to high precision using the 2- and 3-point weak lensing shear correlations. The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision weak lensing measurements. We review a proposed self-calibration technique to calculate the induced gravitational lensing-galaxy intrinsic alignment correlation (GI) for the power spectrum in weak gravitational lensing surveys with photometric redshift measurements, which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the weak lensing bispectrum in order to calculate the dominant lensing-lensing-intrinsic alignment correlation (GGI). We explore the performance of the GGI self-calibration technique and show that it can potentially reduce the IA contamination by up to a factor of 5-10 for most redshift bin choices. The self-calibration thus promises to be an efficient technique to remove both the 2-point and 3-point intrinsic alignment contamination from weak gravitational lensing measurements.

Troxel, Michael; Ishak, Mustapha

2011-10-01

44

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

45

Experimental method for the determination of the gravitational interaction velocity in Newtonian gravitational fields  

Microsoft Academic Search

An experiment is proposed for measuring the velocity of the gravitational interaction in Newtonian gravitational fields. The phase difference in time between the gravitation potential of the moon and the curve of a function of the position, in regard to a point on the earth, of the natural satellite is to be experimentally measured. The detection of the delayed moon

G. Cristea

1974-01-01

46

Gravitational Descendants in Symplectic Field Theory  

Microsoft Academic Search

It was pointed out by Y. Eliashberg in his ICM 2006 plenary talk that the rich algebraic formalism of symplectic field theory\\u000a leads to a natural appearance of quantum and classical integrable systems, at least in the case when the contact manifold\\u000a is the prequantization space of a symplectic manifold. In this paper we generalize the definition of gravitational descendants

Oliver Fabert

2011-01-01

47

Relativistic, quantum theory of spinor particles in a gravitational field  

SciTech Connect

A relativistic quantum theory of spinor particles in a gravitational field is constructed on the basis of Minkowski space and a gravitational field in the spirit of Faraday and Maxwell. Relativistic equations describing the change in the generalized 4-momentum of a particle and its intrinsic angular momentum in a gravitational field are obtained in the semiclassical approximation. It is shown that that all the well-known gravitational effects can be explained by the constructed theory and that the theoretical results agree with the experimental results. It follows naturally from the theory that the vacuum is unstable and that particles are produced in a gravitational field.

Logunov, A.A.; Loskutov, Yu.M.

1986-10-01

48

Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit  

SciTech Connect

We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r{sub {alpha}}/b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}}= Q{sup 2}/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

Gyulchev, G. N. [Department of Physics, Biophysics and Roentgenology, Faculty of Medicine, St. Kliment Ohridski, University of Sofia, 1 Kozyak str., 1407 Sofia (Bulgaria); Yazadjiev, S. S. [Department of Theoretical Physics, Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria)

2010-11-25

49

Mapping the dark matter with weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We consider the problem of reconstructing the projected mass distribution in clusters from coherent distortions of background galaxies. The ellipticity of a background galaxy provides an estimate of the trace-free components of the tidal field. We present a technique for inverting this problem. The resulting surface density contains a strong, but incoherent, random component arising from the random intrinsic galaxy ellipticities. This can be removed by filtering. Our method is very similar in form to that of Tyson et al. (1990), and the latter is given a rigorous interpretation as a particular implementation of filtering. We present simulations to illustrate the application of the method.

Kaiser, Nick; Squires, Gordon

1993-02-01

50

On the gravitational field of a massless particle  

Microsoft Academic Search

The gravitational field of a massless point particle is first calculated using the linearized field equations. The result is identical with the exact solution, obtained from the Schwarzschild metric by means of a singular Lorentz transformation. The gravitational field of the particle is nonvanishing only on a plane containing the particle and orthogonal to the direction of motion. On this

Peter C. AICHELBURG; R. U. Sexl

1971-01-01

51

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

52

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

53

Heaviside's linearised gravitational theory  

Microsoft Academic Search

The development by Heaviside of an electromagnetic analogy of Maxwell, where he tried to extend the Newtonian potential theory of gravitation to incorporate dynamic effects, is discussed. Heaviside introduced a dual of the gravitational field. For weak gravitational fields Heaviside's method is seen to be a linearized, flat space-time, approximation to general relativity, although there are some unexplained scale factor

R. A. Evans

1990-01-01

54

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

55

Using Gravitational Analogies to Introduce Elementary Electrical Field Theory Concepts  

Microsoft Academic Search

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 tables to be helpful in reviewing gravitational and electrical comparisons after students have worked

Susan Saeli; Dan MacIsaac

2007-01-01

56

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

57

Neutron star equilibrium configurations within a fully relativistic theory with strong, weak, electromagnetic, and gravitational interactions  

NASA Astrophysics Data System (ADS)

We formulate the equations of equilibrium of neutron stars taking into account strong, weak, electromagnetic, and gravitational interactions within the framework of general relativity. The nuclear interactions are described by the exchange of the ?, ?, and ? virtual mesons. The equilibrium conditions are given by our recently developed theoretical framework based on the Einstein-Maxwell-Thomas-Fermi equations along with the constancy of the general relativistic Fermi energies of particles, the "Klein potentials", throughout the configuration. The equations are solved numerically in the case of zero temperatures and for selected parameterizations of the nuclear models. The solutions lead to a new structure of the star: a positively charged core at supranuclear densities surrounded by an electronic distribution of thickness ˜?/(mec)˜102?/(m?c) of opposite charge, as well as a neutral crust at lower densities. Inside the core there is a Coulomb potential well of depth ˜m?c2/e. The constancy of the Klein potentials in the transition from the core to the crust, imposes the presence of an overcritical electric field ˜(Ec, the critical field being Ec=me2c3/(e?). The electron chemical potential and the density decrease, in the boundary interface, until values ?ecrust

Belvedere, Riccardo; Pugliese, Daniela; Rueda, Jorge A.; Ruffini, Remo; Xue, She-Sheng

2012-06-01

58

[Weak magnetic fields and cognitive activity].  

PubMed

The influence of natural level of uniform magnetic field (to 200 microT) on Wistar rat cognition was studied in this work. It was found that influence of disturbed Earth magnetic field has caused a long depression of explorative activity only in the presence of information loading. Such depression was removed only after short external stimulation. After this stimulation rats were able to learn by themselves and it took them twice less time than in the control (nootropic effect). It is suggested that a weak magnetic field disturbances may be considered as a negative psychogenic factor which distorts normal conditions for cognitive activity. PMID:8962888

Nikol'skaia, K A; Shtemler, A V; Savonenko, A V; Osipov, A I; Nikol'ski?, S V

59

Fermat principle in arbitrary gravitational fields  

Microsoft Academic Search

The Fermat principle is reviewed and used to derive the zigzag path constructed for massive and massless particles in order to determine if these paths are a suitable approximation to the first order of the gravitational lens effect. It is found that such paths are suitable for thin comoving gravitational lenses to the first order in the lens effect, and

Israel Kovner

1990-01-01

60

Cosmic electromagnetic fields due to perturbations in the gravitational field  

NASA Astrophysics Data System (ADS)

We use nonlinear gauge-invariant perturbation theory to study the interaction of an inflation produced seed magnetic field with density and gravitational wave perturbations in an almost Friedmann-Lemaître-Robertson-Walker spacetime with zero spatial curvature. We compare the effects of this coupling under the assumptions of poor conductivity, perfect conductivity and the case where the electric field is sourced via the coupling of velocity perturbations to the seed field in the ideal magnetohydrodynamic regime, thus generalizing, improving on and correcting previous results. We solve our equations for long wavelength limits and numerically integrate the resulting equations to generate power spectra for the electromagnetic field variables, showing where the modes cross the horizon. We find that the interaction can seed electric fields with nonzero curl and that the curl of the electric field dominates the power spectrum on small scales, in agreement with previous arguments.

Mongwane, Bishop; Dunsby, Peter K. S.; Osano, Bob

2012-10-01

61

Gravitational lensing and the Hubble Deep Field  

NASA Astrophysics Data System (ADS)

We calculate the expected number of multiply-imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with mI<27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of strongly lensed galaxies constrains the current value of ?m-??, where ?m is the mean mass density of the universe and ?? is the normalized cosmological constant. Based on current estimates of the HDF luminosity function and associated uncertainties in individual parameters, our 95% confidence lower limit on ?m-?? ranges between -0.44, if there are no strongly lensed galaxies in the HDF, and -0.73, if there are two strongly lensed galaxies in the HDF. If the only lensed galaxy in the HDF is the one presently viable candidate, then, in a flat universe (?m+??=1), ??<0.79 (95% C.L.). These limits are compatible with estimates based on high-redshift supernovae and with previous limits based on gravitational lensing.

Cooray, Asantha R.; Quashnock, Jean M.; Miller, M. Coleman

1999-04-01

62

The effect of a gravitational field on magnetohydrodynamic waves  

NASA Astrophysics Data System (ADS)

A system of linearized magnetohydrodynamic equations is used to study the influence of a gravitational field on the propagation of magnetohydrodynamic waves in a compressible medium. It is assumed that the density of the medium depends both on pressure and entropy. Oscillation frequencies are obtained for particular cases of wave propagation across and along the magnetic field. The gravitational field on the solar surface is shown to affect these frequencies under certain conditions.

Shishkina, L. P.; Shishkin, L. A.

1981-02-01

63

Gravitational interaction of a geometric scalar field with a vortex gravitational field in five-dimensional spacetime  

NASA Astrophysics Data System (ADS)

Within the framework of the five-dimensional geometric theory, the problem of gravitational interaction of a vortex gravitational and scalar fields is investigated. A solution of the five-dimensional Einstein vacuum equations is derived. The results obtained are compared with those obtained previously within the framework of the four-dimensional theory.

Kiselev, A. S.; Krechet, V. G.

2012-10-01

64

Non-Gaussian gravitational clustering field statistics  

NASA Astrophysics Data System (ADS)

In this work we investigate the multivariate statistical description of the matter distribution in the non-linear regime. We introduce the multivariate Edgeworth expansion of the lognormal distribution to model the cosmological matter field. Such a technique could be useful to generate and reconstruct three-dimensional non-linear cosmological density fields with the information of higher order correlation functions. We explicitly calculate the expansion up to third order in perturbation theory making use of the multivariate Hermite polynomials up to sixth order. The probability distribution function for the matter field includes at this level the two-point, the three-point and the four-point correlation functions. We use the hierarchical model to formulate the higher order correlation functions based on combinations of the two-point correlation function. This permits us to find compact expressions for the skewness and kurtosis terms of the expanded lognormal field which can be efficiently computed. The method is, however, flexible to incorporate arbitrary higher order correlation functions which have analytical expressions. The applications of such a technique can be especially useful to perform weak-lensing or neutral hydrogen 21-cm line tomography, as well as to directly use the galaxy distribution or the Lyman ? forest to study structure formation.

Kitaura, Francisco-Shu

2012-03-01

65

Primordial magnetic seed field amplification by gravitational waves  

Microsoft Academic Search

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-Lemaître-Robertson-Walker (FLRW) cosmology

Gerold Betschart; Caroline Zunckel; Peter K. S. Dunsby; Mattias Marklund

2005-01-01

66

Effect of weak gravitation on the plane Poiseuille flow of a highly rarefied gas  

NASA Astrophysics Data System (ADS)

Plane Poiseuille flow of a highly rarefied gas that flows horizontally in the presence of weak gravitation is studied based on the Boltzmann equation for a hard sphere molecular gas and the diffuse reflection boundary condition. The behavior of the solution in the regime of large mean free path and small strength of gravity is studied numerically based on the one-dimensional Boltzmann equation derived by means of the asymptotic analysis for a slow variation in the flow direction. It is clarified that the effect of weak gravity on the flow is not negligible when the gas is so rarefied that the mean free path is comparable to the maximum range that the molecules travel along the parabolic path within the channel. When the mean free path is much larger than this range, the effect of gravity that makes the molecules fall plays the dominant role in determining the distribution function, and thus the over-concentration in the distribution function as well as the flow velocity does not increase further even if the mean free path is increased. The upper bound of the flow velocity and the mass flow rate of the gas are obtained as a function of the gravitational acceleration.

Doi, Toshiyuki

2012-12-01

67

Study of weak solar magnetic fields  

NASA Astrophysics Data System (ADS)

There have been two major gains in this period: first, the completion and analysis of round-the-clock observations in cooperation with the Huairou Observatory in the People's Republic of China, which enabled us to obtained the first longterm observations of weak solar magnetic fields, and the application of the magneto-optic filter to the measurement of magnetic fields. The observations in collaboration with China have enabled us to make observations for as long as seven days of solar magnetic regions, with only short interruptions when the sun could not be seen from the U.S. and China. The stronger elements of the chromospheric network are rather long lived, lasting about 70 hours. In fact, it is possible that they last longer, because although the shape changes, it is often possible to still identify a magnetic entity. The second important result was that one could find definite evidence of magnetic field cancellation occurring after solar flares. The increased time coverage enabled us to check the evolution of the magnetic fields during this period. The other development, the use of the magneto-optic filter, is full of promise for the future. This filter is made by using a glass tube filled with potassium which is placed in a strong magnetic field.

Zirin, Harold

68

Hamiltonian structure of gravitational field theory  

SciTech Connect

Hamiltonian generalizations of Einstein`s theory of gravitation introducing a laminar structure of spacetime are discussed. The concepts of general relativity and of quasi-inertial coordinate systems are extended beyond their traditional scope. Not only the metric, but also the coordinate system, if quantized, undergoes quantum fluctuations.

Rayski, J. [Jagellonian Univ., Krakow (Poland)

1992-02-01

69

Gravitational radiation generated by cosmological phase transition magnetic fields  

SciTech Connect

We study gravitational waves generated by the cosmological magnetic fields induced via bubble collisions during the electroweak (EW) and QCD phase transitions. The magnetic field generation mechanisms considered here are based on the use of the fundamental EW minimal supersymmetric and QCD Lagrangians. The gravitational waves spectrum is computed using a magnetohydrodynamic turbulence model. We find that the gravitational wave spectrum amplitude generated by the EW phase transition peaks at a frequency of approximately 1-2 mHz, and is of the order of 10{sup -20}-10{sup -21}; thus this signal is possibly detectable by the Laser Interferometer Space Antenna (LISA). The gravitational waves generated during the QCD phase transition, however, are outside the LISA sensitivity bands.

Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics, Laurentian University, Sudbury, Ontario P3E 2C6 (Canada); National Astrophysical Observatory, Ilia Chavchavadze State University, Tbilisi, GE-0160 (Georgia); Kisslinger, Leonard [McWilliams Center for Cosmology and Department of Physics, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Stevens, Trevor [Department of Physics, West Virginia Wesleyan College, Buckhannon, West Virginia 26201 (United States)

2010-01-15

70

Gravitational Fields with 2-Dimensional Killing Leaves and the Gravitational Interaction of Light  

NASA Astrophysics Data System (ADS)

Gravitational fields invariant for a non Abelian Lie algebra generating a 2-dimensional distribution, are explicitly described. When the orthogonal distribution is integrable and the metric is not degenerate along the orbits, these solutions are parameterized either by solutions of a transcendental equation (the tortoise equation), or by solutions of Darboux equation. Metrics, corresponding to solutions of the tortoise equation, are characterized as those that admit a 3-dimensional Lie algebra of Killing fields with 2-dimensional leaves. It is shown that the remaining metrics represent nonlinear gravitational waves obeying to two nonlinearsuperposition laws. The energy and the polarization of this family of waves are explicitly evaluated; it is shown that they have spin-1 and their possible sources are also described. Old results by Tolman, Ehrenfest, Podolsky and Wheeler on the gravitational interaction of photons are naturally reinterpreted.

Vilasi, Gaetano

71

REVIEWS OF TOPICAL PROBLEMS: Motion of particles and photons in the gravitational field of a rotating body (In memory of Vladimir Afanas'evich Ruban)  

NASA Astrophysics Data System (ADS)

A study is made of the trajectories of free motion of test particles and photons in the Kerr metric, which describes the gravitational field of a rotating massive body. The trajectories are classified on the basis of the integrals of the motion, which have a clear physical meaning. The cases of a strong gravitational field in the neighborhood of a rotating black hole as well as the weak-field approximation describing the motion of particles in the gravitational field of a rotating star or galaxy are considered. The review includes bound states (orbits) in the field of a rotating mass, scattering and gravitational capture of particles and photons by a rotating black hole, trajectories of falling into a black hole, and the bending of light rays and the gravitational time delay of signals in the gravitational field of a rotating body.

Dymnikova, I. G.

1986-03-01

72

Fermion-Antifermion Mixing in Gravitational Fields  

NASA Astrophysics Data System (ADS)

Mixing of fermion and antifermion states occurs in gravitational interactions, leading to non-conservation of fermion number above temperatures determined by the particle masses. We study the evolution of a (f, \\bar {f})-system and calculate the cross-sections for the reactions f\\rightleftharpoons \\bar {f}. Their values are identical in both directions. However, if \\bar {f} changes quickly into a lighter antiparticle, then the reaction symmetry is broken, resulting in an increased production of matter over antimatter.

Papini, Giorgio

2013-06-01

73

Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales  

PubMed

Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting 'cosmic shear' can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model. PMID:10821262

Wittman; Tyson; Kirkman; Dell'Antonio; Bernstein

2000-05-11

74

Lorentz covariant theory of light propagation in gravitational fields of arbitrary-moving bodies  

NASA Astrophysics Data System (ADS)

The Lorentz covariant theory of the propagation of light in the (weak) gravitational fields of N-body systems consisting of arbitrarily moving pointlike bodies with constant masses ma (a=1,2,...,N) is constructed. The theory is based on the Liénard-Wiechert representation of the metric tensor which describes a retarded type solution of the gravitational field equations. A new approach for integrating the equations of motion of light particles (photons) depending on the retarded time argument is invented. Its application in the first post-Minkowskian approximation, which is linear with respect to the universal gravitational constant G makes it evident that the equations of light propagation admit to be integrated straightforwardly by quadratures. Explicit expressions for the trajectory of a light ray and its tangent vector are obtained in algebraically closed form in terms of functionals of retarded time. General expressions for the relativistic time delay, the angle of light deflection, and the gravitational shift of electromagnetic frequency are derived in the form of instantaneous functions of retarded time. They generalize previously known results for the case of static or uniformly moving bodies. The most important applications of the theory to relativistic astrophysics and astrometry are given. They include a discussion of the velocity-dependent terms in the gravitational lens equation, the Shapiro time delay in binary pulsars, gravitational Doppler shift, and a precise theoretical formulation of the general relativistic algorithms of data processing of radio and optical astrometric measurements made in the nonstationary gravitational field of the solar system. Finally, proposals for future theoretical work being important for astrophysical applications are formulated.

Kopeikin, Sergei M.; Schäfer, Gerhard

1999-12-01

75

Spin Hall effect induced by a gravitational field  

SciTech Connect

The experiment by Collela et al. (1975) evidenced in a striking manner how the gravitational field appears in quantum mechanics. Within the modern framework of gauge theories, one can ascribe such effect as due to gauge fields originated from fundamental symmetries of spacetime: local transformations of the Lorentz-Poincare group. When this gauge principle is applied to the Dirac equation, we obtain kinematical correlations between the gravitational field and the spin of the particles. The phenomenon is similar to the spin Hall effect found in condensed matter systems, although much smaller in magnitude. Actual measurements may require highly precision interferometric techniques with spin-polarized neutrons.

Dartora, C.A., E-mail: cadartora@yahoo.com.b [Electrical Engineering Department, Federal University of Parana (UFPR) (Brazil); Cabrera, G.G. [Instituto de Fisica 'Gleb Wataghin', Universidade Estadual de Campinas (UNICAMP), C.P. 6165, Campinas 13.083-970 SP (Brazil)

2010-06-15

76

Gravitational field and topography of Venus: static vs. dynamic models  

NASA Astrophysics Data System (ADS)

The gravitational field and topography of Venus are strongly correlated. In distinction to the Earth the correlation is significant not only at intermediate and short wavelengths but also at the long-wavelength part of the spectrum. Several studies have attempted to explain this fact by isostatic compensation of the surface topography (with a depth of compensation usually smaller than 50 km) while some others have argued for a dynamical origin of surface features. In the present study we examine the both concepts mentioned above using the most recent spherical harmonic models of topography (GTDR.3) and gravity (MGNP180U) of the planet. We show that these models are consistent with the concept of Airy isostasy at degrees greater than 40, with the apparent depth of compensation (ADC) around 35 km. At degrees 2-40 the ADC decreases more or less monotonously from 200 km to 40 km. This behavior cannot be explained by a simple model of Airy isostasy. The topography and gravity signals in this spectral interval can be, however, well predicted dynamically by a quasi steady-state model of thermal convection in the mantle of Venus. Assuming that the lateral distribution of the buoyancy force does not vary with depth (which roughly corresponds to a plume-like style of mantle convection) we obtain a very good agreement between the observed and predicted data. The best fit to the data is found for the profile in which the viscosity increases only weakly with depth.

Pauer, M.

2003-04-01

77

A Tilted Plane as a Gravitational Field Model.  

ERIC Educational Resources Information Center

Describes an experiment for the use of a tilted plane as a two-dimensional uniform gravitational field to demonstrate the motion of projectiles, to determine the fundamental laws of mechanics, or to study the focusing properties of the uniform field. (SK)

Hale, D. P.

1980-01-01

78

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

79

Estimation of the degree variance of the lunar gravitational field  

Microsoft Academic Search

The degree variance of the lunar gravitational field is estimated to 16th order inclusive on the basis of an autocorrelation analysis of the field of radial-acceleration gravity anomalies at a height of 100 km above the equatorial region of the moon. Degree variances of orders two through five agree well with values obtained by Ferrari (1977).

P. M. Zazuliak; V. E. Zinger; V. V. Kirichuk

1981-01-01

80

Interactions of cosmological gravitational waves and magnetic fields  

SciTech Connect

The energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress and therefore generates gravitational waves. It has been argued in the literature (Caprini and Durrer [C. Caprini and R. Durrer, Phys. Rev. D 65, 023517 (2001)]) that this gravitational wave production can be very strong and that backreaction cannot be neglected. On the other hand, a gravitational wave background does affect the evolution of magnetic fields. It has also been argued (Tsagas et al.[C. G. Tsagas, P. K. S. Dunsby, and M. Marklund, Phys. Lett. B 561, 17 (2003)][C. Tsagas, Phys. Rev. D 72, 123509 (2005)]) that this can lead to a very strong amplification of a primordial magnetic field. In this paper we revisit these claims and study backreaction to second order.

Fenu, Elisa; Durrer, Ruth [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, 1211 Geneve 4, Switzerland. (Switzerland)

2009-01-15

81

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

82

A Direct View of the Large-Scale Distribution of Mass, from Weak Gravitational Lensing in the HST COSMOS Survey  

Microsoft Academic Search

We present the first direct maps of the large-scale distribution of mass in the Universe. Measurements of weak gravitational lensing from the Hubble Space Telescope COSMOS survey directly trace the 3D distribution of mass, regardless of its nature or state. They reveal a filamentary network of structures that encompass large voids and meet in massive clusters of galaxies. By comparing

Richard Massey; J. Rhodes; A. Leauthaud; R. Ellis; N. Scoville; A. Finoguenov

2006-01-01

83

Reconnection in a Weakly Stochastic Field  

NASA Astrophysics Data System (ADS)

We examine the effect of weak, small-scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale for reconnection flows and by allowing many independent flux reconnection events to occur simultaneously. Allowing only for the first effect and using Goldreich & Sridhar's model of strong turbulence in a magnetized plasma with negligible intermittency, we find a lower limit for the reconnection speed ~V_AR^-3/16_LM^3/4, where V_A is the Alfvén speed, R_L is the Lundquist number, and M is the large-scale magnetic Mach number of the turbulence. We derive an upper limit of ~V_AM^2 by invoking both effects. We argue that generic reconnection in turbulent plasmas will normally occur at close to this upper limit. The fraction of magnetic energy that goes directly into electron heating scales as R^-2/5_LM^8/5, and the thickness of the current sheet scales as R^-3/5_LM^-2/5. A significant fraction of the magnetic energy goes into high-frequency Alfvén waves. The angle between adjacent field lines on the same side of the reconnection layer is ~R^-1/5_LM^6/5 on the scale of the current sheet thickness. We claim that the qualitative sense of these conclusions, that reconnection is fast even though current sheets are narrow, is almost independent of the local physics of reconnection and the nature of the turbulent cascade. As the consequence of this the Galactic and solar dynamos are generically fast, i.e., do not depend on the plasma resistivity.

Lazarian, A.; Vishniac, Ethan T.

1999-06-01

84

Axially Symmetric, Stationary Gravitational Field Equations and Pseudospherical Surfaces.  

National Technical Information Service (NTIS)

For axially symmetric, stationary gravitational field equations, a new Lax pair of the inverse scattering method is presented from a geometrical point of view. The metric coefficient e sup(2 gamma ) (= -g sub(rho rho)g sub(tt)sup(-1)) is taken as the basi...

A. Tomimatsu

1981-01-01

85

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

Microsoft Academic Search

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

Tsagas; Christos G

2007-01-01

86

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

Microsoft Academic Search

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

Christos G. Tsagas

2007-01-01

87

The Gravitational Field and the Shape of Intrusive Bodies.  

National Technical Information Service (NTIS)

Gravitational field anomalies have been observed over many igneous intrusives of medium (4000 sq km) to small (100 sq km) size in outcrop area. These studies give good results because the residual anomalies can be separated from larger scale crustal anoma...

W. E. Bonini

1967-01-01

88

Gravitational collapse of massless scalar field and cosmic censorship  

SciTech Connect

We present a numerical study of the gravitational collapse of a massless scalar field. We calculate the future evolution of new initial data, suggested by Christodoulou, and we show that in spite of the original expectations these data lead only to singularities engulfed by an event horizon.

Goldwirth, D.S.; Piran, T.

1987-12-15

89

Self-restriction of Gravitational Field and its Role in the Universe  

Microsoft Academic Search

It is shown in the article that according to the Relativistic Theory of Gravitation the gravitational field providing slowing down of the time rate nevertheless stops itself this slowing down in strong fields. So a physical tendency of this field to self-restriction of the gravitational potential is demonstrated. This property of the field leads to a stopping of the collapse

S. S. Gershtein; A. A. Logunov; M. A. Mestvirishvili

2006-01-01

90

On gravitational waves  

NASA Astrophysics Data System (ADS)

Gravitational wave is produced whenever massive bodies accelerate under gravitational or nongravitational driving forces. The equations of Einstein's general theory of relativity have solutions in the weak field approximations which are very similar to those of electrodynamics. Analogies may be made between gravitational radiation and the electromagnetic radiation from accelerated charges although care has to be taken to recognize the limitations of such analogies. Because of the weakness of the Einstein's qravitational constant, the rate of energy radiated is normally very small. It is very desirable to be able to generate dynamic Newtonian gravitational field with sufficient intensity to be detected in the small laboratory. Experimental techniques used in generation and detection of dynamic Newtonian gravitational fields are reviewed and their application to Morse code communication in very near zone, as one approach to the gravitational wave technology.

Chiba, J.

1984-11-01

91

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

92

Self-calibration of Gravitational Shear-Galaxy Intrinsic Ellipticity Correlation in Weak Lensing Surveys  

NASA Astrophysics Data System (ADS)

The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose self-calibrating the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation) in weak lensing surveys with photometric redshift measurements. (1) We propose a method to extract the intrinsic ellipticity-galaxy density cross-correlation (I-g) from the galaxy ellipticity-density measurement in the same redshift bin. (2) We also find a generic scaling relation to convert the extracted I-g correlation to the necessary GI correlation. We perform a concept study under simplified conditions and demonstrate its capability to significantly reduce GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method for extracting the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect that none of them will likely be able to completely invalidate the proposed self-calibration technique.

Zhang, Pengjie

2010-09-01

93

On the energy-momentum tensor of the gravitional field  

Microsoft Academic Search

Summary  In a previous note it was suggested that x-1?g??, with ?>0 fulfills the basic requirements of a generally covariant energy-momentum tensor for the gravitational field. Some\\u000a further justification is given for this hypothesis bya) studying the character of the field equations in the absence of the cosmological term;b) a re-interpretation of the line element based on Mach’s principle;c) calculating the

P. E. Tangherlini

1961-01-01

94

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

95

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

96

Gravitational renormalization of quantum field theory  

Microsoft Academic Search

We propose to include gravity in quantum field theory non-perturbatively by modifying the propagators so that each virtual particle in a Feynman graph move in the space-time determined by the momenta of the other particles in the same graph. By making additional working assumptions, we are able to put this idea at work and obtain a modified Feynman propagator for

Roberto Casadio

2008-01-01

97

CFHTLenS: combined probe cosmological model comparison using 2D weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We present cosmological constraints from 2D weak gravitational lensing by the large-scale structure in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) which spans 154 deg2 in five optical bands. Using accurate photometric redshifts and measured shapes for 4.2 million galaxies between redshifts of 0.2 and 1.3, we compute the 2D cosmic shear correlation function over angular scales ranging between 0.8 and 350 arcmin. Using non-linear models of the dark-matter power spectrum, we constrain cosmological parameters by exploring the parameter space with Population Monte Carlo sampling. The best constraints from lensing alone are obtained for the small-scale density-fluctuations amplitude ?8 scaled with the total matter density ?m. For a flat ?cold dark matter (?CDM) model we obtain ?8(?m/0.27)0.6 = 0.79 ± 0.03. We combine the CFHTLenS data with 7-year Wilkinson Microwave Anisotropy Probe (WMAP7), baryonic acoustic oscillations (BAO): SDSS-III (BOSS) and a Hubble Space Telescope distance-ladder prior on the Hubble constant to get joint constraints. For a flat ?CDM model, we find ?m = 0.283 ± 0.010 and ?8 = 0.813 ± 0.014. In the case of a curved wCDM universe, we obtain ?m = 0.27 ± 0.03, ?8 = 0.83 ± 0.04, w0 = -1.10 ± 0.15 and ?K = 0.006+ 0.006- 0.004. We calculate the Bayesian evidence to compare flat and curved ?CDM and dark-energy CDM models. From the combination of all four probes, we find models with curvature to be at moderately disfavoured with respect to the flat case. A simple dark-energy model is indistinguishable from ?CDM. Our results therefore do not necessitate any deviations from the standard cosmological model.

Kilbinger, Martin; Fu, Liping; Heymans, Catherine; Simpson, Fergus; Benjamin, Jonathan; Erben, Thomas; Harnois-Déraps, Joachim; Hoekstra, Henk; Hildebrandt, Hendrik; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Benabed, Karim; Bonnett, Christopher; Coupon, Jean; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin

2013-04-01

98

Aspects of nonlinear conform-affine gravitational gauge field theory  

NASA Astrophysics Data System (ADS)

A local gauge theory of gravity based on the Conform-Affine (CA) group of symmetry transformations is proposed. Requiring tetrads be gauge fields on the same footing as gauge potentials, the representation of the CA group is nonlinearly realized over the quotient space CA(3, 1)/SO(3, 1). The transformation behavior of coset fields parameterizing this quotient space is determined. The gauge connections and fundamental vector field operators of the theory are obtained. A generalized gauge transformation law allowing for both spacetime-like and internal diffeomorphisms is employed. The nonlinear translational connection coefficient---transforming as a 4-covector under the Lorentz group---is identified as a coframe field. The tetrads together with the Lorentz group metric are used to induce a spacetime metric. Some connection coefficients serve as auxiliary dynamical fields (associated with spacetime-like dilation, shear and special conformal 4-boosts), while the remaining one serves as a gravitational gauge potential used to define nonlinear covariant derivatives accommodating minimal couplings of matter and gauge fields. The curvature forms of the theory, whose components represent interaction field strengths, are determined. Bulk topological invariants are constructed. They provide a means of "deriving" a prototype gravitational action. Fields belonging to a linear representation of the Lorentz group under the action of CA transformations are introduced as matter sources. The Bianchi identities, covariant field equations, frame and gauge currents are obtained. The Noether and Hilbert identities as well as their corresponding charges are deduced.

Ali, Saleem A.

99

New symbolic tools for differential geometry, gravitation, and field theory  

NASA Astrophysics Data System (ADS)

DifferentialGeometry is a Maple software package which symbolically performs fundamental operations of calculus on manifolds, differential geometry, tensor calculus, spinor calculus, Lie algebras, Lie groups, transformation groups, jet spaces, and the variational calculus. These capabilities, combined with dramatic recent improvements in symbolic approaches to solving algebraic and differential equations, have allowed for development of powerful new tools for solving research problems in gravitation and field theory. The purpose of this paper is to describe some of these new tools and present some advanced applications involving: Killing vector fields and isometry groups, Killing tensors, algebraic classification of solutions of the Einstein equations, and symmetry reduction of field equations.

Anderson, I. M.; Torre, C. G.

2012-01-01

100

Analytic perturbative theories in highly inhomogeneous gravitational fields  

NASA Astrophysics Data System (ADS)

Orbital motion about irregular bodies is highly nonlinear due to inhomogeneities in the gravitational field. Classical theories of motion close to spheroidal bodies cannot be applied as for inhomogeneous bodies the Keplerian forces do not provide a good approximation of the system dynamics. In this paper a closed form, analytical method for developing the motion of a spacecraft around small bodies is presented, for the so called fast rotating case, which generalize previous results to second order, arbitrary degree, gravitational fields. Through the application of two different Lie transformations, suitable changes of coordinates are found, which reduce the initial nonintegrable Hamiltonian of the system into an integrable one plus a negligible, perturbative remainder of higher degree. In addition, an explicit analytical formulation for the relegated, first and second order, arbitrary degree Hamiltonian for relatively high altitude motion in any inhomogeneous gravitational field is derived in closed-form. Applications of this algorithm include a method for determining initial conditions for frozen orbits around any irregular body by simply prescribing the desired inclination and eccentricity of the orbit. This method essentially reduces the problem of computing frozen orbits to a problem of solving a 2-D algebraic equation. Results are shown for the Asteroid 433-Eros.

Ceccaroni, Marta; Biggs, James

2013-05-01

101

Gravitational collapse of a scalar field  

SciTech Connect

A self-similar collapse of massless scalar waves is considered, and the Einstein field equations in classical general relativity are solved to obtain the metric for the collapse. These scalar waves satisfy the massless wave equation and the energy momentum tensor associated with them is derived from their Lagrangian density. The collapse begins at t = 0 before which spacetime is flat, empty spacetime described by the Minkowski metric. Self similarity assumes that a homothetic Killing vector exists for the collapse, which satisfies the corresponding homothetic Killing equation. The solution obtained contains a constant c/sup 2/ whose value determines the nature of the collapse and the kind of singularity formed by the collapsing scalar waves. The three different cases are outlined and the corresponding Penrose diagrams are given. The apparent horizons, defined by Hawking as the limit of the trapped surfaces surrounding the singularity, are calculated for each case. A quantum correction is given for the above classical picture using the method developed originally by Hawking, to study particle creation by a black hole.

Maithreyan, T.

1985-01-01

102

Magnetic field amplification during gravitational collapse - influence of turbulence, rotation and gravitational compression  

NASA Astrophysics Data System (ADS)

We study the influence of initial conditions on the magnetic field amplification during the collapse of a magnetized gas cloud. We focus on the dependence of the growth and saturation level of the dynamo-generated field on the turbulent properties of the collapsing cloud. In particular, we explore the effect of varying the initial strength and injection scale of turbulence and the initial uniform rotation of the collapsing magnetized cloud. In order to follow the evolution of the magnetic field in both the kinematic and the non-linear regime, we choose an initial field strength of ? with the magnetic to kinetic energy ratio, Em/Ek˜ 10-4. Both gravitational compression and the small-scale dynamo initially amplify the magnetic field. Further into the evolution, the dynamo-generated magnetic field saturates but the total magnetic field continues to grow because of compression. The saturation of the small-scale dynamo is marked by a change in the slope of B/?2/3 and by a shift in the peak of the magnetic energy spectrum from small scales to larger scales. For the range of initial Mach numbers explored in this study, the dynamo growth rate increases as the Mach number increases from vrms/cs˜ 0.2 to 0.4 and then starts decreasing from vrms/cs˜ 1.0. We obtain saturation values of Em/Ek= 0.2-0.3 for these runs. Simulations with different initial injection scales of turbulence also show saturation at similar levels. For runs with different initial rotation of the cloud, the magnetic energy saturates at Em/Ek˜ 0.2-0.4 of the equipartition value. The overall saturation level of the magnetic energy, obtained by varying the initial conditions, is in agreement with previous analytical and numerical studies of small-scale dynamo action where turbulence is driven by an external forcing instead of gravitational collapse.

Sur, Sharanya; Federrath, Christoph; Schleicher, Dominik R. G.; Banerjee, Robi; Klessen, Ralf S.

2012-07-01

103

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

104

Statistics of Weak Gravitational Lensing in Cold Dark Matter Models: Magnification Bias on Quasar Luminosity Functions  

NASA Astrophysics Data System (ADS)

We compute statistical properties of weak gravitational lensing by large-scale structure in three cold dark matter (CDM) models: two flat models with (?0,?0)=(1, 0) and (0.3, 0.7) and one open model with (?0,?0)=(0.3, 0), where ?0 and ?0 are the density parameter and cosmological constant, respectively. We use a particle-particle/particle-mesh (P3M) N-body code to simulate the formation and evolution of large-scale structure in the universe. We perform 1.1x107 ray-tracing experiments for each model, by computing the Jacobian matrix along random lines of sight, using the multiple lens-plane algorithm. From the results of these experiments, we calculate the probability distribution functions of the convergences, shears, and magnifications, and their rms values. We find that the rms values of the convergence and shear agree with the predictions of a nonlinear analytical model. We also find that the probability distribution functions of the magnifications ? have a peak at values slightly smaller than ?=1 and are strongly skewed toward large magnifications. In particular, for the high-density (?0=1) model, a power-law tail appears in the distribution function at large magnifications for sources at redshifts zs>2. The rms values of the magnifications essentially agree with the nonlinear analytical predictions for sources at low redshift but exceed these predictions for high redshift sources, once the power-law tail appears. We study the effect of magnification bias on the luminosity functions of high-redshift quasars, using the calculated probability distribution functions of the magnifications. We show that the magnification bias is moderate in the absence of the power-law tail in the magnification distribution but depends strongly on the value of the density parameter ?0. In presence of the power-law tail, the bias becomes considerable, especially at the bright end of the luminosity functions where its logarithmic slope steepens. We present a specific example that demonstrates that the bias flattens the bright-side logarithmic slope of a double power-law luminosity function.

Hamana, Takashi; Martel, Hugo; Futamase, Toshifumi

2000-01-01

105

Gravitational fields with a non-Abelian, bidimensional Lie algebra of symmetries  

NASA Astrophysics Data System (ADS)

Vacuum gravitational fields invariant for a bidimensional non-Abelian Lie algebra of Killing fields, are explicitly described. They are parameterized either by solutions of a transcendental equation (the tortoise equation) or by solutions of a linear second order differential equation on the plane. Gravitational fields determined via the tortoise equation, are invariant for a /3-dimensional Lie algebra of Killing fields with bidimensional leaves. Global gravitational fields out of local ones are also constructed.

Sparano, G.; Vilasi, G.; Vinogradov, A. M.

2001-07-01

106

Constraints on the shapes of galaxy dark matter haloes from weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We study the shapes of galaxy dark matter haloes by measuring the anisotropy of the weak gravitational lensing signal around galaxies in the second Red-sequence Cluster Survey (RCS2). We determine the average shear anisotropy within the virial radius for three lens samples: the "all" sample, which contains all galaxies with 19 < mr' < 21.5, and the "red" and "blue" samples, whose lensing signals are dominated by massive low-redshift early-type and late-type galaxies, respectively. To study the environmental dependence of the lensing signal, we separate each lens sample into an isolated and clustered part and analyse them separately. We address the impact of several complications on the halo ellipticity measurement, including PSF residual systematics in the shape catalogues, multiple deflections, and the clustering of lenses. We estimate that the impact of these is small for our lens selections. Furthermore, we measure the azimuthal dependence of the distribution of physically associated galaxies around the lens samples. We find that these satellites preferentially reside near the major axis of the lenses, and constrain the angle between the major axis of the lens and the average location of the satellites to ??? = 43.7° ± 0.3° for the "all" lenses, ??? = 41.7° ± 0.5° for the "red" lenses and ??? = 42.0° ± 1.4° for the "blue" lenses. We do not detect a significant shear anisotropy for the average "red" and "blue" lenses, although for the most elliptical "red" and "blue" galaxies it is marginally positive and negative, respectively. For the "all" sample, we find that the anisotropy of the galaxy-mass cross-correlation function ?f - f45? = 0.23 ± 0.12, providing weak support for the view that the average galaxy is embedded in, and preferentially aligned with, a triaxial dark matter halo. Assuming an elliptical Navarro-Frenk-White profile, we find that the ratio of the dark matter halo ellipticity and the galaxy ellipticity fh = eh/eg = 1.50-1.01+1.03, which for a mean lens ellipticity of 0.25 corresponds to a projected halo ellipticity of eh = 0.38-0.25+0.26 if the halo and the lens are perfectly aligned. For isolated galaxies of the "all" sample, the average shear anisotropy increases to ?f-f45? = 0.51-0.25+0.26 and fh = 4.73-2.05+2.17, whilst for clustered galaxies the signal is consistent with zero. These constraints provide lower limits on the average dark matter halo ellipticity, as scatter in the relative position angle between the galaxies and the dark matter haloes is expected to reduce the shear anisotropy by a factor ~2.

van Uitert, E.; Hoekstra, H.; Schrabback, T.; Gilbank, D. G.; Gladders, M. D.; Yee, H. K. C.

2012-09-01

107

Weakness  

MedlinePLUS

Lack of strength; Muscle weakness ... weak, but there is no real loss of strength. For example, you may feel weak if you ... flu . Objective means there is a loss of strength that can be noted during a physical exam.

108

Effects and molecular mechanisms of the biological action of weak and extremely weak magnetic fields  

Microsoft Academic Search

A number of effects of weak combined (static and alternating) magnetic fields with an alternating component of tens and hundreds\\u000a nT at a collinear static field of 42 ?T, which is equivalent to the geomagnetic field, have been found: activation of fission\\u000a and regeneration of planarians Dugesia tigrina, inhibition of the growth of the Ehrlich ascites carcinoma in mice, stimulation

V. V. Novikov; V. O. Ponomarev; G. V. Novikov; V. V. Kuvichkin; E. V. Yablokova; E. E. Fesenko

2010-01-01

109

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 G1 phase in many plant species (and of G2 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 Ca2+ 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 Ca2+ 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

110

Gravitational field equations on and off a 3-brane world  

NASA Astrophysics Data System (ADS)

The effective gravitational field equations on and off a 3-brane world possessing a &Z_{2}; mirror symmetry and embedded in a five-dimensional bulk spacetime with cosmological constant were derived by Shiromizu, Maeda and Sasaki (SMS) in the framework of the Gauss Codazzi projective approach with the subsequent specialization to the Gaussian normal coordinates in the neighbourhood of the brane. However, the Gaussian normal coordinates imply a very special slicing of spacetime and clearly, the consistent analysis of the brane dynamics would benefit from complete freedom in the slicing of spacetime, pushing the layer surfaces in the fifth dimension at any rates of evolution and in arbitrary positions. We rederive the SMS effective gravitational field equations on a 3-brane and generalize the off-brane equations to the case where there is an arbitrary energy momentum tensor in the bulk. We use a more general setting to allow for acceleration of the normals to the brane surface through the lapse function and the shift vector in the spirit of Arnowitt, Deser and Misner. We show that the gravitational influence of the bulk spacetime on the brane may be described by a traceless second-rank tensor &W_{ij};, constructed from the 'electric' part of the bulk Riemann tensor. We also present the evolution equations for the tensor &W_{ij};, as well as for the corresponding 'magnetic' part of the bulk curvature. These equations involve terms determined by both the nonvanishing acceleration of normals in the nongeodesic slicing of spacetime and the presence of other fields in the bulk.

Aliev, A. N.; Gümrükçüoglu, A. E.

2004-11-01

111

Gravitational field of a spinning pencil of light  

SciTech Connect

An exact solution of Einstein's equations in a vacuum (outside of singularities), belonging to Kundt's class and Petrov type N, is interpreted as the metric of a spinning pencil of light (a linear source infinitely extended in one direction and moving with the speed of light). It is shown that the gravitational fields of two parallel pencils of light do not interact with each other, i.e., the superposition of the metrics of two parallel pencils of light is an exact solution of Einstein's equations in a vacuum.

Mitskievic, N.V.; Kumaradtya, K.K.

1989-05-01

112

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

113

The Gravitational Fields of the Galilean Satellites -- Revisited  

NASA Astrophysics Data System (ADS)

One of the major scientific results from the Galileo mission to the Jovian system was the determination of the gravitational fields of the Galilean satellites. Schubert et al. summarize those results in chapter 13 of Jupiter: The planet, satellites and magnetosphere (Bagenal, Dowling, and McKinnon, eds., Cambridge U. Press, 2004). As a part of our recent update of the ephemerides of the Galilean satellites, we redetermined the satellite gravitational fields from the Galileo data. Our reprocessing of the data included, for the first time, calibrations for the effects of Io's plasma torus. We also removed some close encounter data at Europa and Callisto which was corrupted by the encountered satellite ionosphere. In fitting the data we employed a data whitening algorithm, developed for Cassini gravity science data processing, which takes into account the effect of the solar plasma on the Doppler data. Our new results confirm the previous ones for Io and Europa; the Io torus has a negligible effect on the fit to the Io encounter data. However, for Ganymede we found that the data whitening removes the data signature which was previous attributed to mass anomalies (Palguta et al. 2006, Icarus 180), and for Callisto we found that removing the ionosphere corruption significantly reduced the J2. Our overall conclusion is that a quadrupole field in hydrostatic equilibrium is sufficient to fit the data for all four satellites.

Jacobson, Robert A.

2013-10-01

114

Gravitational fields and the cosmological constant in multidimensional Newtonian universes  

SciTech Connect

The distance dependence of gravity is found in Newtonian universes with any number n-italic of space dimensions. Two independent derivations given are based either on (i) requiring that a (hyper) spherical mass gravitate as if all its mass were concentrated at its center, or (ii) using the field equations of general relativity with the cosmological constant ..lambda... Both approaches lead to identical results. The gravity field at distance r-italic from a point mass has two parts, one going as r-italic/sup 1-//sup n-italic/, the other as r-italic, i.e., Hooke's law. The Hookian field obeys a novel form of Gauss's (flux) law, and is closely related to ..lambda... The simple mechanical interpretation which emerges gives insight into the meaning of ..lambda.. and helps counteract certain prevalent misconceptions.

Wilkins, D.

1986-08-01

115

The electric field induced by a gravitational wave in a superconductor: A principle for a new gravitational wave antenna  

SciTech Connect

In this paper the authors investigate the effect of gravitational waves (GW) on a superconductor. They find that the key properties of a superconductor, namely zero resistance and perfect diamagnetism, give rise to an important new effect, the presence of an induced electric field E(r,t) in the interior of the superconductor. The E field reacts with the ions and superelectrons. They argue, that not only is the finding of the coupled interactions of gravitation, electromagnetism and superconductivity inherently interesting, but that the induced E field might provide a significantly more sensitive means of detecting gravitational waves. It appears likely that existing resonant-mss superconducting antennas with L {approx equal} 3m, Q {approx equal} 10{sup 8} could be readily modified to detect E fields induced by GWs of dimensionless amplitude h {approx equal} 10{sup {minus}24}.

Peng, Huei (Univ. of Alabama, Huntsville (USA) Academia Sinica, Beijing (China)); Torr, D.G. (Univ. of Alabama, Huntsville (USA))

1990-01-01

116

Unfolding the matter distribution using three-dimensional weak gravitational lensing  

NASA Astrophysics Data System (ADS)

Combining redshift and galaxy shape information offers new exciting ways of exploiting the gravitational lensing effect for studying the large scales of the cosmos. One application is the three-dimensional (3D) reconstruction of the matter density distribution which is explored in this paper. We give a generalization of an already known minimum-variance estimator of the 3D matter density distribution that facilitates the combination of thin redshift slices of sources with samples of broad redshift distributions for an optimal reconstruction; sources can be given individual statistical weights. We show how, in principle, intrinsic alignments of source ellipticities or shear/intrinsic alignment correlations can be accommodated, albeit these effects are not the focus of this paper. We describe an efficient and fast way to implement the estimator on a contemporary desktop computer. Analytic estimates for the noise and biases in the reconstruction are given. Some regularization (Wiener filtering) of the estimator, adjustable by a tuning parameter, is necessary to increase the signal-to-noise ratio (S/N) to a sensible level and to suppress oscillations in radial direction. This, however, introduces as side effect a systematic shift and stretch of structures in radial direction. This bias can be expressed in terms of a radial point-spread function (PSF) comprising the limitations of the reconstruction due to given source shot noise and a lack of knowledge of the exact source redshifts. We conclude that a 3D mass-density reconstruction on galaxy cluster scales (~1Mpc) is feasible but, for foreseeable surveys, a map with a S/N >~ 3 threshold is limited to structures with M200 >~ 1 × 1014 or 7 × 1014Msolarh-1, at low to moderate redshifts (z = 0.1 or 0.6). However, we find that a heavily smoothed full-sky map of the very large-scale density field may also be possible as the S/N of reconstructed modes increases towards larger scales. Future improvements of the method may be obtained by including higher order lensing information (flexion) which could also be implemented into our algorithm.

Simon, P.; Taylor, A. N.; Hartlap, J.

2009-10-01

117

Mapping Gravitational and Magnetic Fields with Children 9-11: Relevance, difficulties and prospects  

Microsoft Academic Search

This paper presents an investigation centered on a guided conceptual path concerning magnetic and gravitational fields, proposed for children aged 9–11. The goal is to appreciate to what extent the idea of “mapping” two fields of interaction is accessible and fruitful for children of that age. The conceptual target is to link magnetic and gravitational sources with their respective field

F. Bradamante; L. Viennot

2007-01-01

118

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

119

The MOG weak field approximation and observational test of galaxy rotation curves  

NASA Astrophysics Data System (ADS)

As an alternative to dark matter models, Modified Gravity (MOG) theory is a covariant modification of Einstein gravity. The theory introduces two additional scalar fields and one vector field. The aim is to explain the dynamics of astronomical systems based only on their baryonic matter. The effect of the vector field in the theory resembles a Lorentz force where each particle has a charge proportional to its inertial mass. The weak field approximation of MOG is derived by perturbing the metric and the fields around Minkowski space-time. We obtain an effective gravitational potential which yields the Newtonian attractive force plus a repulsive Yukawa force. This potential, in addition to the Newtonian gravitational constant, GN, has two additional constant parameters ? and ?. We use The H I Nearby Galaxy Survey catalogue of galaxies and fix the two parameters ? and ? of the theory to be ? = 8.89 ± 0.34 and ? = 0.042 ± 0.004 kpc-1. We then apply the effective potential with the fixed universal parameters to the Ursa Major catalogue of galaxies and obtain good fits to galaxy rotation curve data with an average value of overline{? ^2} = 1.07. In the fitting process, only the stellar mass-to-light ratio (M/L) of the galaxies is a free parameter. As predictions of MOG, our derived M/L is shown to be correlated with the colour of galaxies. We also fit the Tully-Fisher relation for galaxies. As an alternative to dark matter, introducing an effective weak field potential for MOG opens a new window to the astrophysical applications of the theory.

Moffat, J. W.; Rahvar, S.

2013-09-01

120

Scattering of Electromagnetic and Gravitational Waves by a Static Gravitational Field: Comparison Between the Classical (General-Relativistic) and Quantum Field-Theoretic Results  

Microsoft Academic Search

The classical general-relativistic cross sections for the scattering of either an electromagnetic wave or a gravitational wave by a scalar particle are calculated and found to agree with the results of the quantized linearized field theory.

Peter J. Westervelt

1971-01-01

121

Neutron Interference in the Gravitational Field of a Ring Laser  

NASA Astrophysics Data System (ADS)

A number of analyses of neutron interference effects due to various metric perturbations have been found in the literature [1,2]. However, the approach of each author depends on a specific metric. I will present a new general technique giving the Foldy-Wouthuysen transformed Hamiltonian for a Dirac particle in the most general linearized space-time metric. I will then apply this new technique to calculate the phase shift on a neutron beam interferometer due to the gravitational field of a ring laser [3].[4pt] [1] D. M Greenberger and A. W. Overhauser, Rev. Mod. Phys. 51, 43--78 (1979).[0pt] [2] F. W. Hehl and W. T. Ni, Phys. Rev. D, vol 42, no. 6, pp. 2045-2048, 1990.[0pt] [3] R. L. Mallett, Phys. Lett. A 269, 214 (2000).

Fischetti, Robert

2013-04-01

122

The condensation of ideal Bose gas in a gravitational field  

NASA Astrophysics Data System (ADS)

Bose-Einstein condensation of two- and three-dimensional boson gases confined in the one-dimensional gravitational field is investigated. Using the semiclassical approximation method, the expressions for the BEC transition temperature, condensate fraction, heat capacity and the entropy of the system are obtained. The heat capacities of the systems with D=1, 2, 3 (D is the dimension) at the critical temperature are discussed. We find that for the 1-D and 2-D boson systems, the heat capacities are continuous, but for the 3-D case there is a gap at the critical temperature Tc. The entropies of the systems with D=1, 2, 3 are also studied in detail. It is found that the entropies increase with the increasing of the temperature T.

Du, Cong-Fei; Li, Hong; Lin, Zhen-Quan; Kong, Xiang-Mu

2012-11-01

123

Einstein-Podolsky-Rosen correlation in a gravitational field  

SciTech Connect

For quantum communication in a gravitational field, the properties of the Einstein-Podolsky-Rosen (EPR) correlation are studied within the framework of general relativity. Acceleration and gravity are shown to deteriorate the perfect anticorrelation of an EPR pair of spins in the same direction, and apparently decrease the degree of the violation of Bell's inequality. To maintain the perfect EPR correlation and the maximal violation of Bell's inequality, observers must measure the spins in appropriately chosen different directions which depend on the velocity of the particles, the curvature of the space-time, and the positions of the observers. Near the event horizon of a black hole, the appropriate directions depend so sensitively on the positions of the observers that even a very small uncertainty in the identification of the observers' positions leads to a fatal error in quantum communication, unless the observers fall into the black hole together with the particles.

Terashima, Hiroaki [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); Ueda, Masahito [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); CREST, Japan Science and Technology Corporation (JST), Saitama 332-0012 (Japan)

2004-03-01

124

Charged Tori in Spherical Gravitational and Dipolar Magnetic Fields  

NASA Astrophysics Data System (ADS)

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.

Slaný, P.; Ková?, J.; Stuchlík, Z.; Karas, V.

2013-03-01

125

Transition from weak- to strong-field coherent control  

SciTech Connect

We trace out the transition from weak- to strong-field coherent control, focusing on multiphoton population transfer in atomic sodium. We show how dynamic Stark shifts and ground-state depletion mark the departure from perturbative to strong-field excitation, and how a time-domain picture yields insight into the dynamics when a static resonance, frequency-domain approach breaks down. Experimental measurements are interpreted with the help of calculations that numerically integrate the Schroedinger equation.

Trallero-Herrero, Carlos; Weinacht, Thomas C. [Department of Physics, Stony Brook University, Stony Brook, New York 11794 (United States)

2007-06-15

126

Nontidal oceanic contributions to gravitational field changes: Predictions of the Parallel Ocean Climate Model  

Microsoft Academic Search

This study examines the nontidal contributions of the oceans to the Earth's gravitational field variations as predicted by a global ocean general circulation model: the Parallel Ocean Climate Model. Such variations in the gravitational field Stokes coefficient are determined up to spherical harmonic degree and order 20 and compared with satellite laser ranging (SLR) data from LAGEOS I and LAGEOS

Thomas J. Johnson; Clark R. Wilson; Benjamin F. Chao

2001-01-01

127

Weak and strong magnetic fields in the solar photosphere  

SciTech Connect

We discuss very high-resolution (1/2'') magnetograms of quiet Sun and plage, which were obtained by using a tunable birefringent filter in Fe I lambda6302. A search for a turbulent bipolar field, using co-added and spatially filtered frames, is unsuccessful. Statistical analysis sets an upper limit of 50 gauss on the rms vertical component of such a field and probably rules out the possibility of field strengths exceeding 100 gauss in the inner network field observed at Kitt Peak. The area, total flux, and energy content of the strong (kilogauss) network fields are measured and compared with the upper limits for these properties of a hypothetical, widespread weak field. In quiet photosphere, a weak background field may contain interesting amounts of flux and energy, but the strong fields are dominant at higher levels and in plage. The total magnetic energy in quiet photosphere is roughly equal to the kinetic energy of granular and oscillatory velocities at the same level. By flux conservation, field strengths in the transition region are greater than 25 gauss in quiet network and 100 gauss in plage.

Tarbell, T.D.; Title, A.M.; Schoolman, S.A.

1979-04-01

128

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

SciTech Connect

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. [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049 Lisboa (Portugal); Cardoso, Vitor [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049 Lisboa (Portugal); Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677 (United States)

2011-05-15

129

Gravitational collapse with tachyon field and barotropic fluid  

NASA Astrophysics Data System (ADS)

A particular class of space-time, with a tachyon field, ? , and a barotropic fluid constituting the matter content, is considered herein as a model for gravitational collapse. For simplicity, the tachyon potential is assumed to be of inverse square form i.e., V(? )˜ ? ^{-2}. Our purpose, by making use of the specific kinematical features of the tachyon, which are rather different from a standard scalar field, is to establish the several types of asymptotic behavior that our matter content induces. Employing a dynamical system analysis, complemented by a thorough numerical study, we find classical solutions corresponding to a naked singularity or a black hole formation. In particular, there is a subset where the fluid and tachyon participate in an interesting tracking behaviour, depending sensitively on the initial conditions for the energy densities of the tachyon field and barotropic fluid. Two other classes of solutions are present, corresponding respectively, to either a tachyon or a barotropic fluid regime. Which of these emerges as dominant, will depend on the choice of the barotropic parameter, ? . Furthermore, these collapsing scenarios both have as final state the formation of a black hole.

Tavakoli, Yaser; Marto, João; Ziaie, Amir Hadi; Moniz, Paulo Vargas

2013-04-01

130

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

131

New Series of Exact Solutions for Gravitational Fields of Spinning Masses.  

National Technical Information Service (NTIS)

Solutions for space-times which are regarded as representing the gravitational fields of spinning bound masses are derived from a series of Weyl metrics following Ernst's formulation on the axisymmetric stationary fields. This series of solutions includes...

A. Tomimatsu H. Sato

1973-01-01

132

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

133

Neutron star mass-radius relation with gravitational field shielding by a scalar field  

NASA Astrophysics Data System (ADS)

The currently well-developed models for equations of state (EoSs) have been severely impacted by recent measurements of neutron stars with a small radius and/or large mass. To explain these measurements, the theory of gravitational field shielding by a scalar field is applied. This theory was recently developed in accordance with the five-dimensional (5D) fully covariant Kaluza-Klein (KK) theory that has successfully unified Einstein's general relativity and Maxwell's electromagnetic theory. It is shown that a massive, compact neutron star can generate a strong scalar field, which can significantly shield or reduce its gravitational field, thus making it more massive and more compact. The mass-radius relation developed under this type of modified gravity can be consistent with these recent measurements of neutron stars. In addition, the effect of gravitational field shielding helps explain why the supernova explosions of some very massive stars (e.g., 40 Msolar as measured recently) actually formed neutron stars rather than black holes as expected. The EoS models, ruled out by measurements of small radius and/or large mass neutron stars according to the theory of general relativity, can still work well in terms of the 5D fully covariant KK theory with a scalar field.

Zhang, Bo-Jun; Zhang, Tian-Xi; Guggilla, Padmaja; Dokhanian, Mostafa

2013-05-01

134

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

NASA Astrophysics Data System (ADS)

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.; Martins, A. G.

2010-10-01

135

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

136

Influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction  

SciTech Connect

The interaction between gravitational and electromagnetic waves in the presence of a static magnetic field is studied. The field strength of the static field is allowed to surpass the Schwinger critical field, such that the QED effects of vacuum polarization and magnetization are significant. Equations governing the interaction are derived and analyzed. It turns out that the energy conversion from gravitational to electromagnetic waves can be significantly altered due to the QED effects. The consequences of our results are discussed.

Forsberg, M.; Brodin, G. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Papadopoulos, D. [Department of Physics, Section of Astrophysics, Astronomy and Mechanics, 54124 Thessaloniki (Greece)

2010-07-15

137

Gravitational field of vacuum domain walls and strings  

Microsoft Academic Search

The gravitational properties of vacuum domain walls and strings are studied in the linear approximation of general relativity. These properties are shown to be very different from those of regular massive planes and rods. It is argued that the domain walls are gravitationally unstable and collapse at a certain time approx.t\\/sub c\\/ after their creation. If the vacuum walls ever

Alexander Vilenkin

1981-01-01

138

Relativistic Mass Change in the Fields of Gravitation, Non-Holonomity, and Deformation  

NASA Astrophysics Data System (ADS)

This study targets solving the scalar geodesic equation (equation of energy) of a mass-bearing particle travelling in the gravitational field, the field of non-holonomity (rotation) of space, and the field of deformation of space, which are the only three external factors present in the equation. The obtained solutions manifest a change in the mass of the particle according to the distance travelled in the corresponding field. The mass defect due to the field of gravitation is known. The effects of the fields of space non-holonomity and space deformation have not been studied before. In contrast to the gravitational mass defect, registered in the gravitational field near the Earth, these two effects are much smaller: they reach the measurable limit 10-10 only in space travel within cosmological distances. A complete report of this study has been submitted to The Abraham Zelmanov Journal.

Rabounski, Dmitri

2010-10-01

139

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

140

A weak combined magnetic field changes root gravitropism  

NASA Astrophysics Data System (ADS)

Although gravitropism has been studied for many decades, many questions on plant gravitropism, including the participation of Ca2+ ions in graviperception and signal transduction, remain open and require new experiments. We have studied gravistimulation and root gravitropism in the presence of the weak, alternating magnetic field that consisted of a sinusoidal frequency of 32 Hz inside a ?-metal shield. We discovered that this field changes normally positively gravitropic cress root to exhibit negative gravitropism. Because the combined magnetic field was adjusted to the cyclotron frequency of Ca2+ ions, the obtained data suggest that calcium ion participate in root gravitropism. Simultaneous application of the oscillating magnetic field of the same frequency ion induce oscillation of Ca2+ ions and can change the rate and/or the direction of Ca2+ ion flux in roots. Control and magnetic field-exposed roots were examined for change in the distribution of amyloplasts and cellular organelles by light, electron, and confocal laser microscopy.

Kordyum, E. L.; Bogatina, N. I.; Kalinina, Ya. M.; Sheykina, N. V.

141

Means of confusion: how pixel noise affects shear estimates for weak gravitational lensing  

NASA Astrophysics Data System (ADS)

Weak-lensing shear estimates show a troublesome dependence on the apparent brightness of the galaxies used to measure the ellipticity: in several studies, the amplitude of the inferred shear falls sharply with decreasing source significance. This dependence limits the overall ability of upcoming large weak-lensing surveys to constrain cosmological parameters. We seek to provide a concise overview of the impact of pixel noise on weak-lensing measurements, covering the entire path from noisy images to shear estimates. We show that there are at least three distinct layers, where pixel noise not only obscures but also biases the outcome of the measurements: (1) the propagation of pixel noise to the non-linear observable ellipticity; (2) the response of the shape-measurement methods to limited amount of information extractable from noisy images and (3) the reaction of shear estimation statistics to the presence of noise and outliers in the measured ellipticities. We identify and discuss several fundamental problems and show that each of them is able to introduce biases in the range of a few tens to a few per cent for galaxies with typical significance levels. Furthermore, all of these biases do not only depend on the brightness of galaxies but also depend on their ellipticity, with more elliptical galaxies often being harder to measure correctly. We also discuss existing possibilities to mitigate and novel ideas to avoid the biases induced by pixel noise. We present a new shear estimator that shows a more robust performance for noisy ellipticity samples. Finally, we release the open-source PYTHON code to predict and efficiently sample from the noisy ellipticity distribution and the shear estimators used in this work at https://github.com/pmelchior/epsnoise.

Melchior, P.; Viola, M.

2012-08-01

142

Generation of magnetic seed fields in self-gravitating protogalactic clouds  

Microsoft Academic Search

The seed magnetization of protogalaxies can be provided by relative shear flows and collisional friction of the ionized and the neutral fluid components in partially ionized self-gravitating and rotating protogalactic clouds. The gravitational potential of a collapsing protogalactic cloud is the ultimate energy source that partly is converted to magnetic fields and the associated electric currents by collisional momentum transfer

G. T. Birk; H. Wiechen; H. Lesch

2002-01-01

143

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

144

The kinetics of a bounded collisionless plasma in a gravitational radiation field  

Microsoft Academic Search

The possibility of collective mode generation in a semibounded collisionless plasma in a plasma layer due to the effect of an incident plane gravitational wave is discussed. The particle distribution function, electric current, and electric and magnetic field intensities are calculated for a plasma with plane boundaries, parallel and perpendicular to the gravitational wave front, in the case of mirror

A. B. Balakin

1986-01-01

145

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

NASA Astrophysics Data System (ADS)

The weak lensing signal (cosmic shear) has been shown to be contaminated by correlations between the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements in planned surveys. We review recent work to extend the self-calibration approach to the cosmic shear bispectrum. The 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. We outline the proposed self-calibration techniques for the 3-point cosmic shear auto- and cross-correlations and summarize their performance. Using conservative estimates of photo-z accuracy, we find that planned surveys will be able to measure the IA redshift separation dependence over ranges of |?z^P|<=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 on the cosmic shear signal.

Troxel, Michael; Ishak, Mustapha

2012-10-01

146

Higher-Dimensional Gravitational Objects with External Fields  

NASA Astrophysics Data System (ADS)

This thesis summarizes a study of higher-dimensional distorted objects such as a distorted 5-dimensional Schwarzschild-Tangherlini black hole. It considers a particular type of distortion corresponding to an external, static distribution of matter and fields around this object. The corresponding spacetime can be presented in the generalized Weyl form which has an R xU(1) x U(1) group of isometries. This is a natural generalization of the 4-dimensional Weyl form which was presented in the paper by Emparan and Reall [1]. In the frame of this generalized Weyl form one can derive an exact analytic solution to the Einstein equations which describes the non-linear interaction of the black hole with external matter and gravitational fields. This research focuses on the effects of such interaction on the event horizon and the interior of the black hole. A similar study was presented in the papers [2] for 4-dimensional neutral black holes, where special duality relations between a neutral black hole horizon and singularity were derived. In relation to this work it is interesting to study which properties of distorted black holes remain present in the 5-dimensional case. This thesis also gives an investigation of the d-dimensional Fisher solution which represents a static, spherically symmetric, asymptotically flat spacetime with a massless scalar field. This solution has a naked singularity. It is shown that the d-dimensional Schwarzschild-Tangherlini solution and the Fisher solution are dual to each other. [1] R. Emparan and H. S. Reall, Phys. Rev. D, 65, 084025 (2002). [2] V. P. Frolov and A. A. Shoom, Phys. Rev. D, 76, 064037 (2007).

Abdolrahimi, Shohreh

147

Ultrafast heating and magnetic switching with weak external magnetic field  

NASA Astrophysics Data System (ADS)

The TbFeCo magneto-optical media with the coercivity of bigger than 1.0 kOe are used for the investigation of ultrafast heating and magnetic switching with the weak external magnetic field. It has been found that the laser-induced active region becomes larger with an external magnetic field because the boundary of the active region is magnetized with the assistance of the external field during the ultrafast heating. According to this physical phenomenon, the so called ``mark expansion method'' has been proposed for visual observation of ultrafast switching marks. Using this method, the ultrafast magnetic switching in TbFeCo media has been studied using 40 fs laser pulse with linear polarization. The result shows that the ultrafast magnetic switching can be implemented by the laser pulse with assistance of the weak external field of about 0.7 kOe. Further studies show that the area percentage of the magnetic mark expansion relative to its thermal mark decreases with the increasing of the laser pulse energy. There exists the threshold pulse energy that the active region is fully magnetized. The theoretical analysis of electron, spin, and lattice temperatures has been conducted to the active region of the media where the maximum spin temperature is close to the Curie temperature of the media. The result indicates that the media become active at 4.137 ps and the ultrafast heating plays a key role for the ultrafast magnetic switching. The weak external magnetic field provides sufficient driving force to control the magnetization direction in the media.

Li, J. M.; Xu, B. X.; Zhang, J.; Ye, K. D.

2013-01-01

148

On holographic thermalization and gravitational collapse of tachyonic scalar fields  

NASA Astrophysics Data System (ADS)

In this paper we study the thermalization of a spatially homogeneous system in a strongly coupled CFT. The non-equilibrium initial state is created by switching on a relevant perturbation in the CFT vacuum during ? t ? t ? - ? t. Via AdS/CFT, the thermalization process corresponds to the gravitational collapse of a tachyonic scalar field ( m 2 = -3) in the Poincare patch of AdS 5. In the limit \\varDelta t<0.02 /T , the thermalization time t T is found to be quantitatively the same as that of a non-equilibrium state created by a marginal perturbation discussed in ref. [5]. In the case \\varDelta t? 1/T we also obtain double- collapse solutions but with a non-equilibrium intermediate state at t = 0. In all the cases our results show that the system thermalizes in a typical time {t_T}˜eq O(1) /T . Besides, a conserved energy-moment current in the bulk is found, which helps understand the qualitative difference of the collapse process in the Poincare patch from that in global AdS [10, 11].

Wu, Bin

2013-04-01

149

Human lymphocyte sorting by gravitational field-flow fractionation.  

PubMed

Interest in biological studies on various cell types for many biomedical applications, from research to patient treatments, is constantly increasing. The ability to discriminate (sort) and/or quantify distinct subpopulations of cells has become increasingly important. For instance, not only detection but also the highest depletion of neoplastic cells from normal cells is an important requisite in the autologous transplantation of lymphocytes for blood cancer treatments. In this work, gravitational field-flow fractionation (GrFFF) is shown to be effective for sorting a heterogeneous mixture of human, living lymphocytes constituted of neoplastic B cells from a Burkitt lymphoma cell line and healthy T and B lymphocytes from blood samples. GrFFF does not require the use of fluorescent immunotags for sorting cells, and the sorted cells can be collected for their further characterization. Flow cytometry was used to assess the viability of the cells collected, and to evaluate the cell fractionation achieved. A low amount of neoplastic B lymphocytes (less than 2%) was found in a specific fraction obtained by GrFFF. The high depletion from neoplastic cells (more than 98%) was confirmed by a clonogenicity test. PMID:18649074

Roda, Barbara; Reschiglian, Pierluigi; Zattoni, Andrea; Tazzari, Pier Luigi; Buzzi, Marina; Ricci, Francesca; Bontadini, Andrea

2008-07-24

150

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

151

Gravitational lensing from compact bodies: Analytical results for strong and weak deflection limits  

SciTech Connect

We develop a nonperturbative method that yields analytical expressions for the deflection angle of light in a general static and spherically symmetric metric. The method works by introducing into the problem an artificial parameter, called {delta}, and by performing an expansion in this parameter to a given order. The results obtained are analytical and nonperturbative because they do not correspond to a polynomial expression in the physical parameters. Already to first order in {delta} the analytical formulas obtained using our method provide at the same time accurate approximations both at large distances (weak deflection limit) and at distances close to the photon sphere (strong deflection limit). We have applied our technique to different metrics and verified that the error is at most 0.5% for all regimes. We have also proposed an alternative approach which provides simpler formulas, although with larger errors.

Amore, Paolo; Cervantes, Mayra; De Pace, Arturo; Fernandez, Francisco M. [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima (Mexico) and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, via P.Giuria 1, I-10125 Turin (Italy); INIFTA (Conicet, UNLP), Division Quimica Teorica, Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)

2007-04-15

152

Effective Field Theory Methods in Gravitational Physics and Tests of Gravity  

NASA Astrophysics Data System (ADS)

In this PhD thesis I make use of the "Effective Field Theory of Gravity for Extended Objects" by Goldberger and Rothstein in order to investigate theories of gravity and to take a different point of view on the physical information that can be extracted from experiments. In the first work I present, I study a scalar-tensor theory of gravity and I address the renormalization of the energy-momentum tensor for point-like and string-like sources. The second and third study I report are set in the context of testing gravity. So far experiments have probed dynamical regimes only up to order (v/c)^5 in the post-Newtonian expansion, which corresponds to the very first term of the radiative sector in General Relativity. In contrast, by means of gravitational-wave astronomy, one aims at testing General Relativity up to (v/c)^(12)! It is then relevant to envisage testing frameworks which are appropriate to this strong-field/radiative regime. In the last two chapters of this thesis a new such framework is presented. Using the effective field theory approach, General Relativity non-linearities are described by Feynman diagrams in which classical gravitons interact with matter sources and among themselves. Tagging the self-interaction vertices of gravitons with parameters it is possible, for example, to translate the measure of the period decay of Hulse-Taylor pulsar in a constraint on the three-graviton vertex at the 0.1% level; for comparison, LEP constraints on the triple-gauge-boson couplings of weak interactions are accurate at 3%. With future observations of gravitational waves, higher order graviton vertices can in principle be constrained through a Fisher matrix analysis.

Cannella, Umberto

2011-03-01

153

Weak magnetic fields in early-type stars: failed fossils  

NASA Astrophysics Data System (ADS)

Weak magnetic fields have recently been detected in Vega and Sirius. Here, we explore the possibility that these fields are the remnants of some field inherited or created during or shortly after star formation and are still evolving dynamically as we observe them. The time-scale of this evolution is given in terms of the Alfvén time-scale and the rotation frequency by ?evol ˜ ?2A ?, which is then comparable to the age of the star. According to this theory, all intermediate- and high-mass stars should contain fields of at least the strength found so far in Vega and Sirius. Faster rotators are expected to have stronger magnetic fields. Stars may experience an increase in surface field strength during their early main sequence, but for most of their lives field strength will decrease slowly. The length scale of the magnetic structure on the surface may be small in very young stars but should quickly increase to at least very approximately a fifth of the stellar radius. The field strength may be higher at the poles than at the equator.

Braithwaite, Jonathan; Cantiello, Matteo

2013-02-01

154

Velocity Fields and Alignments of Clusters in Gravitational Instability Scenarios  

NASA Astrophysics Data System (ADS)

The structure and evolution of the outskirts of clusters in several gravitational instability scenarios are studied. By means of the Hoffman-Ribak constrained random field code we generate realizations of fluctuation fields containing protoclusters of a specified height and shape. The samples generated consist of 643 particles in a box with a size of 50 h-1 Mpc. By means of a P3M N-body code, using a 1283 grid, the evolution of the resulting particle distribution is followed into the nonlinear regime. The protoclusters are 3?0 fluctuations [?0 = ?0(4 h-1 Mpc)] in a cold dark matter scenario and in two scale-free scenarios [P(k) ?kn, n = 0 or -2], ?0 = 1. We find that power in the initial fluctuation spectrum on small scales leads to the formation of substructure. The accretion of this substructure prevents the cluster from becoming as flattened as in the case of smooth ellipsoids. The shape of the clusters is derived from the inertia tensor; the two axis ratios that it yields are approximately constant in time. The mass distribution on scales of a few megaparsecs has a triaxial shape. Axis ratios typically vary between ˜0.6 and 0.8. Despite the small changes in shape, the orientation of the major axis of the cluster is heavily affected by the infall of small-scale structure. In general, the elongated cluster points in the direction from which the last subcluster fell into the core. Sometimes the orientation changes by as much as 70°. These changes in orientation cast doubt on the alignments of clusters that have been reported in the past. The presence of alignments is found to be consistent with a picture where the substructure falls into the cluster along a filament. The more isotropic the initial distribution of groups and small scale structure, the greater the changes in orientation of the major axis of the cluster. We also find that all clusters have evolved significantly in the recent past. The accretion of small-scale structure severely disrupts the velocity field. As a result, techniques that use the velocity field on scales of a few megaparsecs as a means of constraining ? are severely hindered by the disruptions in the cluster halo. These disruptions can persist for some time after the substructure has fallen into the cluster. The application of the spherical infall model to a smooth and apparently relaxed cluster may not result in the detection of the caustics. This provides a plausible explanation of why no caustics have been detected around the Coma Cluster.

van Haarlem, Michiel; van de Weygaert, Rien

1993-12-01

155

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

156

Determination of the Gravitational Field of the Moon by the Movement of the Artificial Moon Satellite Luna-10.  

National Technical Information Service (NTIS)

To determine the noncentral gravitational field of the Moon, the motion of the artificial Moon satellite 'Luna 10' is analyzed with gravitational forces of the Earth and the Sun taken into account. From the statistically processed measurements of the traj...

E. L. Akim

1967-01-01

157

New exact solution for the exterior gravitational field of a charged spinning mass  

SciTech Connect

An exact asymptotically flat solution of the Einstein-Maxwell equations describing the exterior gravitational field of a charged rotating axisymmetric mass possessing an arbitrary set of multipole moments is presented explicitly.

Chamorro, A. (Departamento de Fisica Teorica, Universidad del Pais Vasco, Apartado 644, 48080 Bilbao (Spain)); Manko, V.S. (Department of Theoretical Physics, Peoples' Friendship University, Ordzhonikidze Street 3, Moscow 117198 (U.S.S.R.)); Denisova, T.E. (Department of Mathematical Analysis, Peoples' Friendship University, Ordzhonikidze Street 3, Moscow 117198 (U.S.S.R.))

1991-11-15

158

New exact solution for the exterior gravitational field of a spinning mass  

SciTech Connect

An exact asymptotically flat solution of the vacuum Einstein equations representing the exterior gravitational field of a stationary axisymmetric mass with an arbitrary mass-multipole structure is presented.

Manko, V.S. (School of Mathematical Sciences, Queen Mary and Westfield College, University of London, London E14NS, United Kingdom (GB) Department of Theoretical Physics, Peoples' Friendship University, Ordzhonikidze Street 3, Moscow 117198, U.S.S.R. (SU))

1990-04-02

159

The Simulation of a Gravitational Field with a Point Mass Model.  

National Technical Information Service (NTIS)

The authors compute a point mass representation of an artificial model of the earth's anomalous gravitational field: a scaled version of the (8.4) solid spherical harmonic which is even in longitude. (Modified author abstract)

J. C. Perry J. Pinker

1974-01-01

160

Exploring the connection of weak winds and magnetic fields  

NASA Astrophysics Data System (ADS)

The theory of radiatively driven winds successfully explains the key points of the stellar winds of hot massive stars. However, there is an apparent break-down of this paradigm at log L/L_&odot <5.2: the stellar wind momentum is smaller than predicted for low luminosity early-type stars from metal poor environments, and there are also some Galactic examples. We present a preliminary analysis of a small sample of stars of this luminosity regime in the Orion Nebula region and evaluate whether magnetic fields may play some role in the weak wind problem.

Garcia, Miriam; Najarro, Francisco; Herrero, Artemio

2011-01-01

161

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

162

[Periodical changes of various hematological parameters of the human body adaptation and gravitation fields variations].  

PubMed

Monitoring the content of lymphocytes and nucleated neutrophils (observation period 10.5 months) and the determination of the values of leucocytes coefficient and erythrocyte sedimentation rate in chronic patients revealed rhythms of oscillations of these parameters (from 3-5 to 33 days). The coincidence of these rhythms with the rhythms of variations of gravitational field indicates that gravitational field affects the quantitative blood cell composition and the rheological properties of blood. PMID:11605380

Gederim, V V; Sokolovski?, V V; Gorshkov, E S; Shapovalov, S N; Troshichev, O A

163

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

164

Effective field theory of weakly coupled inflationary models  

NASA Astrophysics Data System (ADS)

The application of Effective Field Theory (EFT) methods to inflation has taken a central role in our current understanding of the very early universe. The EFT perspective has been particularly useful in analyzing the self-interactions determining the evolution of co-moving curvature perturbations (Goldstone boson modes) and their influence on low-energy observables. However, the standard EFT formalism, to lowest order in spacetime differential operators, does not provide the most general parametrization of a theory that remains weakly coupled throughout the entire low-energy regime. Here we study the EFT formulation by including spacetime differential operators implying a scale dependence of the Goldstone boson self-interactions and its dispersion relation. These operators are shown to arise naturally from the low-energy interaction of the Goldstone boson with heavy fields that have been integrated out. We find that the EFT then stays weakly coupled all the way up to the cutoff scale at which ultraviolet degrees of freedom become operative. This opens up a regime of new physics where the dispersion relation is dominated by a quadratic dependence on the momentum ? ~ p2. In addition, provided that modes crossed the Hubble scale within this energy range, the predictions of inflationary observables — including non-Gaussian signatures — are significantly affected by the new scales characterizing it.

Gwyn, Rhiannon; Palma, Gonzalo A.; Sakellariadou, Mairi; Sypsas, Spyros

2013-04-01

165

On the Gravitational Fields of Pandora and Prometheus  

NASA Astrophysics Data System (ADS)

Utilizing topographic models of Saturn's F-ring shepherd satellites Prometheus (S16 1980S27) and Pandora (S15 1980S26), derived by Stooke (1994), and supposing that their mass density is constant, we derived basic geometrical and dynamical characteristics of the moons. They include the volume and mass, the mean radii, the tensor of inertia, and Stokes coefficients of the harmonic expansions of external gravitational potential. The best fitting ellipsoid approximations of the topography were calculated. A simple method of determining the gravitational potential on the surface of an irregular satellite is presented. Examples of equipotential surfaces of the satellites are shown

Go?dziewski, Krzysztof; Maciejewski, Andrzej J.

1995-01-01

166

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

167

Gravity Effects of Solar Eclipse and Inducted Gravitational Field  

Microsoft Academic Search

During solar eclipses in recent decades, gravity anomalies were observed and difficult to be explained by Newton's gravitational theory. During the solar eclipse of 1995, India scientists Mishra et al. recorded a gravity valley in amplitude of 12 mu Gal; they interpreted that qualitatively as atmospheric effects. During the total solar eclipse of March 1997, we conducted a comprehensive geophysical

K. Tang; Q. Wang; H. Zhang; C. Hua; F. Peng; K. Hu

2003-01-01

168

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

169

Beryllium Atom from Weak to Strong Magnetic Fields  

NASA Astrophysics Data System (ADS)

The energy levels involving the 10+, 1/3(-1)+, and 3(-1)- states of the beryllium atom in magnetic fields of 0-10 a.u. (1 a.u. corresponding to 4.7011 × 105 T) are investigated. To deal with the four-electron atomic system in magnetic fields, two related methods based on the anisotropic Gaussian basis set are applied. In the field region of 0 ? ? < 0.5 a.u., owing to the relatively weak correlation between an inner core electron and an outer valence electron, we apply the freezing full-core method. In the field region of 0.5 ? ? ? 10 a.u., we carry out the full-core-plus-correlation calculation, which has a better consideration about the additional correlations. Compared to the full configuration-interaction method, significant improvement on precision of energies of spin-singlet states is achieved. For spin-triplet states, energies of similar precision are attained using a smaller basis set. The corresponding one-electron ionization energies are presented and analyzed.

Wang, X. F.; Qiao, H. X.

2012-10-01

170

Proton-Proton Weak Capture in Chiral Effective Field Theory  

NASA Astrophysics Data System (ADS)

The astrophysical S factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0-100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants entering the weak current operators are fixed so as to reproduce the A=3 binding energies and magnetic moments and the Gamow-Teller matrix element in tritium ? decay. Contributions from S and P partial waves in the incoming two-proton channel are retained. The S factor at zero energy is found to be S(0)=(4.030±0.006)×10-23MeVfm2, with a P-wave contribution of 0.020×10-23MeVfm2. The theoretical uncertainty is due to the fitting procedure of the low-energy constants and to the cutoff dependence.

Marcucci, L. E.; Schiavilla, R.; Viviani, M.

2013-05-01

171

Proton-proton weak capture in chiral effective field theory.  

PubMed

The astrophysical S factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0-100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants entering the weak current operators are fixed so as to reproduce the A=3 binding energies and magnetic moments and the Gamow-Teller matrix element in tritium ? decay. Contributions from S and P partial waves in the incoming two-proton channel are retained. The S factor at zero energy is found to be S(0)=(4.030±0.006)×10(-23) MeV fm(2), with a P-wave contribution of 0.020×10(-23) MeV fm(2). The theoretical uncertainty is due to the fitting procedure of the low-energy constants and to the cutoff dependence. PMID:23705703

Marcucci, L E; Schiavilla, R; Viviani, M

2013-05-10

172

A New Study about the Two Formulations of Conservation Laws for Matter Plus Gravitational Field and Their Experimental Test  

Microsoft Academic Search

The debate on conservation laws in general relativity eighty years ago is reviewed and restudied. The physical meaning of the identities in the conservation laws for matter plus gravitational field is reexamined and new interpretations for gravitational wave are given. The conclusions of these studies are distinct from the prevalent views, it can be demonstrated that gravitational wave does not

Fang-Pei Chen

2000-01-01

173

The stress-energy tensor of matter as a gravitational field source  

Microsoft Academic Search

This article discusses the hypothesis that the universally conserved stress-energy tensor of matter is the source of the gravitational\\u000a field. From this hypothesis, it immediately follows that space-time must be Riemannian. In contrast to the general theory\\u000a of relativity, in the gravitational theory based on this hypothesis, the concept of an inertial coordinate system, acceleration\\u000a relative to space, and the

A. A. Logunov; M. A. Mestvirishvili

1997-01-01

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

Validation of GOCE global gravitational field models by comparison with regional geoid and gravity anomaly surfaces  

NASA Astrophysics Data System (ADS)

The satellite gravitational gradiometry mission GOCE provides various products related to the Earth's gravitational field. One of these products is a global gravitational field model, i.e. representation of the Earth's gravitational field in terms of spherical harmonic coefficients. Such a model is used in realizing vertical reference frames in geodesy, exploring the interior of the Earth in geophysics and geology, studying the behavior of currents in oceanography, or discovering sea level rise and ice-melting in climatology. Numerous Earth's gravitational field representations have already been derived from GOCE. These representations differ according to the time span of GOCE measurements and the theoretical approach used in the harmonic analysis. To assess the quality of the GOCE models validation by independent knowledge of the gravitational field has to be performed. Global gravitational field models with limited spectral/spatial resolution are validated by terrestrial data. In this case, spectral inconsistency between the two sources of data has to be treated properly. An intuitive approach to perform the validation in a consistent way is offered by an adequate filtering. Transformation of the regional data into the spectral domain is performed firstly. Then a low-pass filter is applied to generate a smoothed version of the regional model with the same spectral content as the global GOCE model. Subsequently, the filtered signal is transformed back into the space domain where comparison with a GOCE geoid surface is performed. Despite its conceptual simplicity, the development of an optimal filtering procedure is still challenging. In this contribution we address some aspects of the filtering method. Firstly, a simulation study based on EGM2008 is performed to investigate the accuracy of the direct transformation from space to frequency domain and its inverse. Moreover, various mathematical filters are considered to filter out the short wavelengths. Secondly, the most accurate filtering procedure is applied in validation of real GOCE models. The validation experiment is performed with respect to gravity anomalies and geoid undulations over the territory of Scandinavia.

Sprlak, M.; Gerlach, C.; Pettersen, B. R.; Omang, O. C. D.

2012-04-01

176

GRAVITATIONAL STABILITY OF A CYLINDRICAL PLASMA WITH AN AZIMUTHAL AND AN AXIAL MAGNETIC FIELD  

SciTech Connect

We consider the gravitational stability of a current-carrying filamentary cloud in the presence of both axial and azimuthal magnetic fields using a simple analytic model. The azimuthal magnetic field is shown to give rise to a new contribution, dictated by Ampere's law, in the corresponding virial equation for magnetohydrodynamic equilibrium. From this we obtain a computationally inexpensive guidance on the gravitational stability of current-carrying filamentary clouds. The approach not only provides a fresh insight into the essential physical mechanisms involved but also demonstrates clearly that, for sufficiently large and yet astronomically realistic currents, the azimuthal magnetic field can cause filamentary clouds to undergo instability.

McLeman, J. A.; Wang, C. H.-T. [SUPA Department of Physics, University of Aberdeen, King's College, Aberdeen AB24 3UE (United Kingdom); Bingham, R. [STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)

2012-09-10

177

Relation Between the Einstein and the Komar Expressions for the Energy of the Gravitational Field.  

National Technical Information Service (NTIS)

It is shown that the interpretation of the Einstein energy-momentum ''pseudo-tensor'', ''covariantized'' with the help of a background metric, as the energy-momentum tensor of the gravitational field with respect to a background field is consistent with a...

P. T. Chrusciel

1983-01-01

178

Vacuum solutions of the gravitational field equations in the brane world model  

Microsoft Academic Search

We consider some classes of solutions of the static, spherically symmetric gravitational field equations in the vacuum in the brane world scenario, in which our Universe is a three-brane embedded in a higher dimensional space-time. The vacuum field equations on the brane are reduced to a system of two ordinary differential equations, which describe all the geometric properties of the

T. Harko; M. K. Mak

2004-01-01

179

Singular Behaviour of electric and magnetic fields in dielectric media in a non-linear gravitational wave background  

Microsoft Academic Search

Evolution of electric and magnetic fields in dielectric media, driven by the\\u000ainfluence of a strong gravitational wave, is considered for four exactly\\u000aintegrable models. It is shown that the gravitational wave field gives rise to\\u000anew effects and to singular behaviour in the electromagnetic field.

Alexander B. Balakin; Jose' P. S. Lemos

2001-01-01

180

Mass and Light Correlated with Galaxies on Local and Cosmic Scales: Weak Gravitational Lensing in the Deep Lens Survey  

NASA Astrophysics Data System (ADS)

In this dissertation, we describe the results of applying weak gravitational lensing techniques to probe the connection between luminous galaxies and the dark matter halos in which they live. Specifically, we study galaxy-shear correlations in the Deep Lens Survey, and we investigate how this function changes with observable galaxy properties such as stellar mass, luminosity, color, and redshift. In Chapter 3, we examine the galaxy-shear correlation function on a large range of scales from small radii where the dominant contribution is from halos associated with individual galaxies to large radii where the dominant contribution is from neighboring galaxies and large-scale structure. We study the lensing signal for galaxies binned by luminosity and find that more luminous galaxies are more massive. More interestingly, the galaxy-shear correlation function shows features consistent with satellite and 2-halo terms from the halo model and cannot be fit with a single power law out to 15 Mpc. We also find more correlated large scale structure mass at lower redshift, consistent with the paradigm of bottom-up hierarchical structure formation. In Chapter 4, we focus on a subset of the survey with ancillary infrared data that allow estimates of stellar mass. We study the lensing signal for galaxies binned by stellar mass and infer the nature and evolution of the relationship between virial mass and stellar mass. We show that stellar mass and virial mass scale such that galaxies with smaller stellar masses also have smaller virial masses. This work has implications for the idea of downsizing, but does not yet have the S/N to provide competitive constraints. In the process of making lensing measurements on the Deep Lens Survey, we have also investigated errors related to the two most important variables: shapes and photometric redshifts. we discuss our findings in the context of the survey characteristics in Chapter 2 and in the simulations section of Chapter 3. While neither the shapes nor the photometric redshifts are perfect, their associated errors can be reasonably controlled such that the results of the scientific analysis discussed above are meaningful. We conclude and comment on future work in Chapter 5. The Appendix contains a useful reference for equations related to lensing formalism and the halo model.

Choi, Ami

181

Field of a charged particle in a scalar-tensor theory of gravitation  

NASA Astrophysics Data System (ADS)

Field equations in the scalar-tensor theory of gravitation, proposed by Saez and Ballester (Phys. Lett. A 113: 467, 1986), are obtained for a static charged point mass with the aid of a spherically symmetric 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.

Reddy, D. R. K.; Vidyasagar, T.; Satyanarayana, B.

2012-11-01

182

Studies of Weak, ELF Electromagnetic Fields Effects on the Early Embryonic Development.  

National Technical Information Service (NTIS)

Studies of the embryonic response to weak changes of the electromagnetic environment were performed, in vivo, on chick embryos. Fertile eggs were exposed to weak, extremely low frequencies, bipolar, pulsed magnetic fields during their first 48 hours of in...

A. Ubeda A. M. Trillo J. Leal L. Chacon

1988-01-01

183

The Nature of Gravitational Field and its Legitimate Energy-Momentum Tensor  

NASA Astrophysics Data System (ADS)

In this paper we show how a gravitational field generated by a given energy-momentum distribution (for all realistic cases) can be represented by distinct geometrical structures (Lorentzian, teleparallel and nonnull nonmetricity spacetimes) or that we even can dispense all those geometrical structures and simply represent the gravitational field as a field, in the Faraday sense, living in Minkowski spacetime. The explicit Lagrangian density for this theory is given and the field equations (which are a set of four Maxwell's-like equations) are shown to be equivalent to Einstein's equations. We also analyze whether the teleparallel formulation can give a mathematical meaning to "Einstein's most happy thought", i.e. the equivalence principle. Moreover we discuss the Hamiltonian formalism for our theory and its relation to one of the possible concepts for energy of the gravitational field which emerges from it and the concept of ADM energy. One of the main results of the paper is the identification in our theory of a legitimate energy-momentum tensor for the gravitational field expressible through a really nice formula. This article is based on the talk given by the author at the 9-th International Conference on Clifford Algebras and their Applications (ICCA9) Weimar, 15-20 July 2011.

Rodrigues, Waldyr A.

2012-04-01

184

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.

185

GMM-1: A 50 degree and order gravitational field model for Mars  

NASA Astrophysics Data System (ADS)

Knowledge of the gravitational field, in combination with surface topography, provides one of the principal means of inferring the internal structure of a planetary body. The highest resolution gravitational field for Mars published thus far was derived from Doppler tracking data from the Mariner 9 and Viking 1 and 2 spacecraft and is complete to degree and order 18 corresponding to a half wavelength resolution of approximately 600 km. This field, which is characterized by a spatial resolution that is slightly better than that of the highest resolution (16x16) topographic model, has been utilized extensively in analyses of the state of stress and isostatic compensation of the Martian lithosphere. However, the resolution and quality of current gravity and topographic fields are such that the origin and evolution of even the major physiographic features on Mars, such as the hemispheric dichotomy and Tharsis rise, are not well understood. We have re-analyzed the Viking and Mariner data sets and have derived a new gravitational field, which we designated GMM-1 (Goddard Mars Model-1). This model is complete to spherical harmonic degree and order 50 with a corresponding (half wavelength) spatial resolution of 200-300 km where the data permit. In contrast to previous models, GMM-1 was solved to as high degree and order as necessary to nearly exhaust the attenuated gravitational signal contained in the tracking data.

Smith, D. E.; Lerch, F. J.; Nerem, R. S.; Zuber, M. T.; Patel, G. B.; Fricke, S. K.; Lemoine, F. G.

1993-03-01

186

Lifetime and decay of unstable particles in strong gravitational fields  

SciTech Connect

We consider here the decay of unstable particles in geodesic circular motion around compact objects. For the neutron, in particular, strong and weak decay are calculated by means of a semiclassical approach. Noticeable effects are expected to occur as one approaches the photonic circular orbit of realistic black holes. We argue that, in such a limit, the quasithermal spectrum inherent to extremely relativistic observers in circular motion plays a role similar to the Unruh radiation for uniformly accelerated observers.

Fregolente, Douglas; Saa, Alberto [Departamento de Matematica Aplicada, IMECC-UNICAMP, C.P. 6065, 13083-859 Campinas, SP (Brazil)

2008-05-15

187

Seasonal variations of the Earth's gravitational field: An analysis of atmospheric pressure, ocean tidal, and surface water excitation  

Microsoft Academic Search

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

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

1996-01-01

188

Seasonal variations of the Earth's gravitational field: An analysis of atmospheric pressure, ocean tidal, and surface water excitation  

Microsoft Academic Search

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

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

1996-01-01

189

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

190

Exact solution for the gravitational field of a string with a nonzero cosmological constant  

NASA Astrophysics Data System (ADS)

We generalize arguments presented by Gott and Hiscock regarding the external gravitational field of a string, in order to allow for larger values of the string's linear density. In this way we are able to envision the string as being related to fundamental states of bosons of arbitrary mass.

Novello, M.; Motta da Silva, M. C.

1993-11-01

191

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

192

Variations of Mars Gravitational Field and Rotation Due to Seasonal CO 2 Exchange  

Microsoft Academic Search

About a quarter of the Martian atmospheric mass is exchanged between the atmosphere and the polar caps in the course of a Martian year: CO2 condenses to form (or add to) the polar caps in winter and sublimes into the atmosphere in summer. This paper studies the effect of this CO2 mass redistribution on Martian rotation and gravitational field. Two

B. Fong Chao; David Parry Rubincam

1990-01-01

193

Some practical applications of the horizontal gradients Txz and Tyz of the gravitational field  

Microsoft Academic Search

In practical compilation of the gravity maps for geodetic- or geophysical purposes we argue that the horizontal gradients Txz and Tyz are valuable transformations of the measured gravitational field. One reason is that such transformation can reveal inconsistencies in the collected gravity data which are not easily detectable in the gravity anomalies. For marine areas where the depth to the

G. Strykowski

2009-01-01

194

Motion of a rigid body with a viscoelastic membrane in a gravitational field  

Microsoft Academic Search

The motion of a system consisting of a supporting rigid body and a viscoelastic circular membrane in a central Newtonian gravitational field in circular orbit is examined analytically. The axis of symmetry of the membrane coincides with one of the main central axes of inertia of the nondeformed system. A system of differential equations of motion is obtained in the

O. V. Kholostova

1992-01-01

195

Passive ranging of a low observable ballistic missile in a gravitational field  

Microsoft Academic Search

In this paper we present an estimation algorithm for tracking the motion of a low-observable target in a gravitational field, for example, an incoming ballistic missile (BM), using angle-only measurements. The measurements, which are obtained from a single stationary sensor, are available only for a short time. Also, the low target detection probability and high false alarm density present a

T. Kirubarajan; Y. Bar-Shalom; YUEYONG WANG

2001-01-01

196

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

197

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

Microsoft Academic Search

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

Christos G. Tsagas

2005-01-01

198

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

Microsoft Academic Search

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.

Gerold Betschart; Caroline Zunckel; Peter K. S. Dunsby; Mattias Marklund

2007-01-01

199

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

Microsoft Academic Search

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.

Gerold Betschart; Caroline Zunckel; Peter K S Dunsby; Mattias Marklund

2007-01-01

200

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

201

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…

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

2007-01-01

202

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

203

Accurate determination of highly eccentric orbits in earth's gravitational field with axial symmetry  

Microsoft Academic Search

An algorithm is constructed for the determination of the perturbed motion, in both, the rectangular and the orbital elements of highly eccentric orbits in Earth's gravitational field with axial symmetry whatever the number N of the zonal harmonic coefficients may be. An application of the algorithm for the Explorer 28 satellite (e > 0.94) is given for two geopotential models

A. Abdel Aziz Bakry

1988-01-01

204

Prediction of trajectories in the Earth's gravitational field with axial symmetry using KS uniform regular elements  

Microsoft Academic Search

In this paper, a motion prediction algorithm based on the KS regular elements is developed for the motion in the Earth's gravitational field with axial symmetry. The algorithm is of recursive nature and general in the sense that it could be applied for any conic motion whatever the number of zonal harmonic coefficientsN = 2 may be. Applications of the

Amr A. Sharaf

1993-01-01

205

Completing magnetic field generation from gravitationally coupled electrodynamics with the curvaton mechanism  

NASA Astrophysics Data System (ADS)

Primordial magnetic fields of cosmologically interesting field strengths can be generated from gravitationally coupled electrodynamics during inflation. As the cosmological constraints require this to be power law inflation it is not possible to generate at the same time the curvature perturbation from inflation. Therefore here a completion is considered whereby the large scale magnetic field is generated during inflation and the primordial curvature mode in a subsequent era from a curvaton field. It is found that constraints on the model to obtain strong magnetic fields and those to suppress the amplitude of the curvature perturbation generated during inflation can be simultaneously satisfied for magnetic seed fields Bs?10-30G.

Kunze, Kerstin E.

2013-03-01

206

Weak field magnetoresistance of narrow-gap semiconductor InSb  

NASA Astrophysics Data System (ADS)

The weak antilocalization effect of InSb film in perpendicular as well as tilted magnetic field is investigated. It is found that the InSb film has quasi-two-dimensional feature and the Nyquist mechanism dominates decoherence. The two dimensionality is also verified further and the influence of roughness effect and Zeeman effect on weak antilocalization effect is studied by systematically investigating the anisotropy of weak field magnetoresistance with respect to magnetic field. It is also found that the existence of in-plane field can effectively suppress the weak antilocalization effect of InSb film and the roughness effect plays an important role in the anisotropy.

Yang, R.; Gao, K. H.; Zhang, Y. H.; Chen, P. P.; Yu, G.; Wei, L. M.; Lin, T.; Dai, N.; Chu, J. H.

2011-03-01

207

Gravitational scalar field coupled directly to the Maxwell field and its effect on solar-system experiments  

SciTech Connect

The effect of the massless gravitational scalar field assumed to couple directly to the Maxwell field on the solar-system experiments is estimated. We start with discussing the theoretical significance of this coupling. Rather disappointingly, however, we find that the scalar-field parameters never affect the observation in the limit of geometric optics, indicating a marked difference from the well-known contribution through the spacetime metric.

Fujii, Yasunori [Advanced Research Institute for Science and Engineering, Waseda University, Tokyo, 169-8555 (Japan); Sasaki, Misao [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502 (Japan)

2007-03-15

208

Next-to-leading order gravitational spin-orbit coupling in an effective field theory approach  

SciTech Connect

We use an effective field theory (EFT) approach to calculate the next-to-leading order (NLO) gravitational spin-orbit interaction between two spinning compact objects. The NLO spin-orbit interaction provides the most computationally complex sector of the NLO spin effects, previously derived within the EFT approach. In particular, it requires the inclusion of nonstationary cubic self-gravitational interaction, as well as the implementation of a spin supplementary condition (SSC) at higher orders. The EFT calculation is carried out in terms of the nonrelativistic gravitational field parametrization, making the calculation more efficient with no need to rely on automated computations, and illustrating the coupling hierarchy of the different gravitational field components to the spin and mass sources. Finally, we show explicitly how to relate the EFT derived spin results to the canonical results obtained with the Arnowitt-Deser-Misner (ADM) Hamiltonian formalism. This is done using noncanonical transformations, required due to the implementation of covariant SSC, as well as canonical transformations at the level of the Hamiltonian, with no need to resort to the equations of motion or the Dirac brackets.

Levi, Michele [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)

2010-11-15

209

Large scale magnetic fields from gravitationally coupled electrodynamics  

Microsoft Academic Search

The generation of primordial magnetic seed fields during inflation is studied in a theory derived from the one-loop vacuum polarization effective action of the photon in a curved background. This includes terms which couple the curvature to the Maxwell tensor. The resulting magnetic field strength is estimated in a model where the inflationary phase is directly matched to the standard

Kerstin E. Kunze

2010-01-01

210

A classical unified field theory of gravitation, electromagnetism and spin - Foundations  

Microsoft Academic Search

A classical unified field theory (UFT) of gravitation and electromagnetism, based on the SU(2) bundle for the kinematic background and the generalized Einstein equation of M for the dynamic content, is derived and discussed. The principal fiber-bundle structure of the classical universe is explored, and the fundamental field equations of the UFT are presented. The space-time structure obtained is shown

X. Yu

1986-01-01

211

Inhomogeneous magnetic seed fields and gravitational waves within the magnetohydrodynamic limit  

Microsoft Academic Search

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-Lemaître-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

Caroline Zunckel; Gerold Betschart; Peter K. S. Dunsby; Mattias Marklund

2006-01-01

212

Gravitational field-flow fractionation for the characterisation of active dry wine yeast  

Microsoft Academic Search

Gravitational field-flow fractionation (GrFFF) is applied to the fractionation of active dry wine yeast. An experimental approach to the analysis of the effects that field variation by changing mobile phase composition and flow-rate have on the fractionation process of standard particles (polystyrene) was first developed to further obtain effective fractionation of wine yeast by GrFFF. Scanning electron microscopy and Coulter

R Sanz; L Puignou; P Reschiglian; M. T Galceran

2001-01-01

213

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

214

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

215

Ultra-cold anti-neutrons (UCN) (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 n-nucleus potentials. We integrate over the UCN phase space including the effects of the earth's gravitational field. Present address: Technical University Berlin, Germany.

Yoshiki, H.; Golub, R.

1992-01-01

216

Zero Rest-Mass Fields Including Gravitation: Asymptotic Behaviour  

Microsoft Academic Search

A zero rest-mass field of arbitrary spin s determines, at each event in space-time, a set of 2s principal null directions which are related to the radiative behaviour of the field. These directions exhibit the characteristic 'peeling-off' behaviour of Sachs, namely that to order r-k-1 (k = 0, ldots, 2s), 2s-k of them coincide radially, r being a linear parameter

R. Penrose

1965-01-01

217

Large scale magnetic fields from gravitationally coupled electrodynamics  

Microsoft Academic Search

The generation of primordial magnetic seed fields during inflation is studied\\u000ain a theory derived from the one-loop vacuum polarization effective action of\\u000athe photon in a curved background. This includes terms which couple the\\u000acurvature to the Maxwell tensor. The resulting magnetic field strength is\\u000aestimated in a model where the inflationary phase is directly matched to the\\u000astandard

Kerstin E. Kunze; Plaza de la Merced

2010-01-01

218

Shapes and Gravitational Fields of Two-Layer Maclaurin Spheroids: Application to Planets and Satellites  

NASA Astrophysics Data System (ADS)

The shapes and gravitational fields of rotationally and tidally distorted planets and satellites depend on their interior mass distributions. Measurements of these observable characteristics are therefore used to infer the internal structure of planetary bodies. Interpretations are based on approximate formulae such as the Radau-Darwin relation derivable from the theory of figures or more accurate evaluations of the theory. The exact solution for the shape and gravitational field of the rotationally distorted constant density Maclaurin spheroid has, until now, provided one of the only ways to assess the accuracy and range of validity of approximate theory of figure predictions. We generalize the Maclaurin spheroid solution to a 2-layer core-envelope body, a more realistic model of a real planet or moon. The exact 2-layer Maclaurin spheroid solution, e. g., the shapes of the surface and core-envelope interface, depend on 3 parameters, the core-envelope density ratio, the fractional volume of the core, and ?2/2?G?2, where ? is the rotation rate, G is the gravitational constant, and ?2 is the envelope density. For realistic parameter values, the flattening of the interface is smaller than that of the surface. Results of the exact solution are compared with predictions of the theory of figures up to order 3 in the small rotational parameter of the theory. The exact solution serves as a benchmark for numerical models that attempt to invert gravitational and shape data to infer internal planetary structure.

Schubert, G.; Zhang, K.; Kong, D.; Anderson, J. D.; Helled, R.

2010-12-01

219

Gravitational quantum states of Antihydrogen  

SciTech Connect

We present a theoretical study of the motion of the antihydrogen atom (H) in the gravitational field of Earth above a material surface. We predict that the H atom, falling in the gravitational field of Earth above a material surface, would settle into long-lived quantum states. We point out a method of measuring the difference in the energy of H in such states. The method allows for spectroscopy of gravitational levels based on atom-interferometric principles. We analyze the general feasibility of performing experiments of this kind. We point out that such experiments provide a method of measuring the gravitational force (Mg) acting on H and that they might be of interest in the context of testing the weak equivalence principle for antimatter.

Voronin, A. Yu. [P. N. Lebedev Physical Institute, 53 Leninsky Prospect, 117924 Moscow (Russian Federation); Froelich, P. [Department of Quantum Chemistry, Uppsala University, Box 518, SE-75120 Uppsala (Sweden); Nesvizhevsky, V. V. [Institut Laue-Langevin (ILL), 6 rue Jules Horowitz, F-38042 Grenoble (France)

2011-03-15

220

Horizon thermodynamics and gravitational field equations in Ho?ava-Lifshitz gravity  

NASA Astrophysics Data System (ADS)

We explore the relationship between the first law of thermodynamics and gravitational field equation at a static, spherically symmetric black hole horizon in Ho?ava-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 Ho?ava-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, Rong-Gen; Ohta, Nobuyoshi

2010-04-01

221

Charge Separation within Superconductors in the Presence of Tidal Gravitational Fields  

SciTech Connect

Tidal gravitational fields affect the Cooper-pair electrons and lattice ions of a type I superconductor differently. The quantum nonlocalizability of the Cooper pairs, which will remain coherent in the presence of interacting fields corresponding to frequencies less than that of the Bardeen-Cooper-Schrieffer (BCS) gap frequency, causes the superconducting electrons to undergo non-classical, non-geodesic motion, in contrast to the classical, geodesic motion of the lattice ions. The ensuing relative motion between the electrons and the ionic lattice causes a charge separation that leads to a measurable voltage potential when a macroscopic, quantum-coherent superconducting system undergoes free fall in the Earth's inhomogeneous gravitational field. Theoretical and experimental implications will be discussed.

Minter, Stephen J. [University of California, Merced, Department of Natural Sciences, 5200 N. Lake Rd., Merced, CA 95343 (United States); Wegter-McNelly, Kirk [Boston University, School of Theology, 745 Commonwealth Ave., Boston, MA 02215 (United States); Chiao, Raymond Y. [University of California, Merced, Departments of Natural Sciences and Engineering, 5200N Lake Rd, Merced, CA 95343 (United States)

2009-09-09

222

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

223

Radiation reaction and gravitational waves in the effective field theory approach  

SciTech Connect

We compute the contribution to the Lagrangian from the leading order (2.5 post-Newtonian) radiation reaction and the quadrupolar gravitational waves emitted from a binary system using the effective field theory (EFT) approach of Goldberger and Rothstein. We use an initial value formulation of the underlying (quantum) framework to implement retarded boundary conditions and describe these real-time dissipative processes. We also demonstrate why the usual scattering formalism of quantum field theory inadequately accounts for these. The methods discussed here should be useful for deriving real-time quantities (including radiation reaction forces and gravitational wave emission) and hereditary terms in the post-Newtonian approximation (including memory, tail and other causal, history-dependent integrals) within the EFT approach. We also provide a consistent formulation of the radiation sector in the equivalent effective field theory approach of Kol and Smolkin.

Galley, Chad R.; Tiglio, Manuel [Center for Scientific Computation and Mathematical Modeling and Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland, 20742 (United States)

2009-06-15

224

Duality for symmetric second rank tensors. II. The linearized gravitational field  

NASA Astrophysics Data System (ADS)

The construction of dual theories for linearized gravity in four dimensions is considered. Our approach is based on the parent Lagrangian method previously developed for the massive spin-two case, but now considered for the zero mass case. This leads to a dual theory described in terms of a rank two symmetric tensor, analogous to the usual gravitational field, and an auxiliary antisymmetric field. This theory has an enlarged gauge symmetry, but with an adequate partial gauge fixing it can be reduced to a gauge symmetry similar to the standard one of linearized gravitation. We present examples illustrating the general procedure and the physical interpretation of the dual fields. The zero mass case of the massive theory dual to the massive spin-two theory is also examined, but we show that it only contains a spin-zero excitation.

Casini, H.; Montemayor, R.; Urrutia, Luis F.

2003-09-01

225

Two-dimensional electron liquid in a weak magnetic field  

Microsoft Academic Search

We present an effective theory describing the low-energy properties of an interacting two-dimensional electron gas at large noninteger filling factors nu>>1. Assuming that the interaction is sufficiently weak, rs<1, we integrate out all the fast degrees of freedom, and derive the effective Hamiltonian acting in the Fock space of the partially filled Landau level only. This theory enables us to

I. L. Aleiner; L. I. Glazman

1995-01-01

226

Nonminimally coupled gravitational and electromagnetic fields: pp-wave solutions  

SciTech Connect

We give the Lagrangian formulation of a generic nonminimally extended Einstein-Maxwell theory with an action that is linear in the curvature and quadratic in the electromagnetic field. We derive the coupled field equations by a first-order variational principle using the method of Lagrange multipliers. We look for solutions describing plane-fronted Einstein-Maxwell waves with parallel rays. We give a family of exact pp-wave solutions associated with a partially massless spin-2 photon and a partially massive spin-2 graviton.

Dereli, Tekin; Sert, Oezcan [Department of Physics, Koc University, 34450 Sariyer, Istanbul (Turkey); Department of Physics Engineering, Istanbul Technical University, 34469 Maslak, Istanbul (Turkey)

2011-03-15

227

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

228

Global Structure of the Kerr Family of Gravitational Fields  

Microsoft Academic Search

The Kerr family of solutions of the Einstein and Einstein-Maxwell equations is the most general class of solutions known at present which could represent the field of a rotating neutral or electrically charged body in asymptotically flat space. When the charge and specific angular momentum are small compared with the mass, the part of the manifold which is stationary in

Brandon Carter

1968-01-01

229

Gravitating tensor monopole in a Lorentz-violating field theory  

NASA Astrophysics Data System (ADS)

We present a solution of the coupled Einstein and rank-two antisymmetric tensor field equations where Lorentz symmetry is spontaneously broken, and we discuss its observational signatures. Especially, the deflection angles have important qualitative differences between tensor and scalar monopoles. If a monopole were to be detected, it would be discriminated whether or not to correspond to a tensor one. This phenomenon might open up new directions in the search of Lorentz violation with future astrophysical observations.

Li, Xin-zhou; Xi, Ping; Zhang, Qun

2012-04-01

230

On the structure of gravitational U4-field equations  

NASA Astrophysics Data System (ADS)

The exterior calculus is used, together with some decomposition techniques within this formalism, in order to make the generally very complex structure of the U sub 4-field equations of gravity more transparent. As a result of this treatment, some of the equations acquire a comparatively simple form which may be given in several equivalent versions according to various requirements. Attention is also given to models in various dimensions, giving classes of solutions under certain assumptions.

Wallner, R. P.

1985-11-01

231

Towards a perturbative treatment of gravitational wave memory  

NASA Astrophysics Data System (ADS)

Despite the weakness of gravitational radiation, the analysis of gravitational wave memory is usually taken to require the full nonlinear apparatus of general relativity. However, one form of gravitational wave memory has to do with fields such as the electromagnetic field and neutrinos which can get to null infinity. We show how to derive the memory effects of these fields using only first order perturbation theory. We expect that this method, when extended to second order perturbation theory, can also be used to account for the memory effect due to the loss in energy by gravitational radiation.

Garfinkle, David; Bieri, Lydia

2013-04-01

232

Gravitation: Field theory par excellence Newton, Einstein, and beyond  

SciTech Connect

Newtonian gravity satifies the two principles of equivalence m/sub i/ = m/sub p/ (the passive principle) and m/sub a/ = m/sub p/ (the active principle). A relativistic gauge field concept in D = s+1 dimensional curved-space will, in general, violate these two principles as in m/sub p/ = ..cap alpha..m/sub i/, m/sub a/ = lambdam/sub p/ where ..cap alpha.. = D: 3 and lambda measures the presence of the field stress-energy t/sup ..nu..//sub ..mu../ in the field equations. It is shown that ..cap alpha.. = 1, lambda = 0 corresponds to general relativity and ..cap alpha.. = 1, lambda = 1 to the theory of the author. It is noted that the correspondence limit of general relativity is not Newton's theory but a theory suggested by Robert Hooke a few years before Newton published his in Principia. The gauge is independent of the two principles but had to do with local special relativistic correspondence and compatibility with quantum mechanics. It is shown that unless ..cap alpha.. = 1, lambda = 1 the generalized theory cannot predict correctly many observables effects, including the 532'' per century Newtonian part in Mercury's perihelion advance.

Yilmaz, H.

1984-09-01

233

Weak Lensing PSF Correction of Wide-field CCD Mosaic Images (SULI Paper)  

SciTech Connect

Gravitational lensing provides some of the most compelling evidence for the existence of dark matter. Dark matter on galaxy cluster scales can be mapped due to its weak gravitational lensing effect: a cluster mass distribution can be inferred from the net distortion of many thousands of faint background galaxies that it induces. Because atmospheric aberration and defects in the detector distort the apparent shape of celestial objects, it is of great importance to characterize accurately the point spread function (PSF) across an image. In this research, the PSF is studied in images from the Canada-France-Hawaii Telescope (CFHT), whose camera is divided into 12 CCD chips. Traditional weak lensing methodology involves averaging the PSF across the entire image: in this work we investigate the effects of measuring the PSF in each chip independently. This chip-by-chip analysis was found to reduce the strength of the correlation between star and galaxy shapes, and predicted more strongly the presence of known galaxy clusters in mass maps. These results suggest correcting the CFHT PSF on an individual chip basis significantly improves the accuracy of detecting weak lensing.

Cevallos, Marissa; /Caltech /SLAC

2006-01-04

234

Gravitational Radiation  

Microsoft Academic Search

Gravity is one of the fundamental forces of nature, and it is the dominant force in most astronomical systems. In common with all other phenomena, gravity must obey the principles of SPECIAL RELATIVITY. In particular, gravitational forces must not be transmitted or communicated faster than light. This means that, when the gravitational field of an object changes, the changes ripple

Bernard F. Schutz; Max Planck

2000-01-01

235

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

Microsoft Academic Search

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

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

1988-01-01

236

Dynamics of a gravitational field within a wave front and thermodynamics of black holes  

SciTech Connect

Hamiltonian dynamics of a gravitational field contained in a spacetime region with boundary S being a null-like hypersurface (a wave front) is discussed. A complete Hamiltonian formula for the dynamics (with no surface integrals neglected) is derived. A quasilocal proof of the first law of black holes thermodynamics is obtained as a consequence, in the case when S is a nonexpanding horizon. The zeroth law and Penrose inequalities are discussed from this point of view.

Czuchry, Ewa [Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto 606-8502 (Japan); Jezierski, Jacek [Department of Mathematical Methods in Physics, University of Warsaw, ulica Hoza 69, 00-682 Warsaw (Poland); Kijowski, Jerzy [Center for Theoretical Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland)

2004-12-15

237

Snow Load Effect on the Earth's Rotation and Gravitational Field, 1979–1985  

Microsoft Academic Search

A global, monthly snow depth data set has been generated from the Nimbus 7 satellite observations using passive microwave remote-sensing techniques. In this paper we analyze 7 years of data, 1979-1985, to compute the snow load effects on the earth's rotation and low-degree zonal gravitational field. A uniform sea level decrease has been assumed in order to conserve water mass.

B. Fong Chao; William P. O'Connor; Alfred T. C. Chang; Dorothy K. Hall; James L. Foster

1987-01-01

238

Advances in Magnetic and Gravitational Potential Field Data in the Arctic  

Microsoft Academic Search

Integration of Magnetics and Gravity in Northern Exploration (iMAGINE); Tromsø, Norway, 1-2 June 2010; Magnetic and gravitational potential field data are crucial components of regional tectonic framework studies and resource exploration in the Arctic. Special data acquisition difficulties at high latitudes include extreme weather conditions, ice-covered waters, and magnetic disturbances from the aurora borealis. Improved techniques in sub-ice, sub-salt, and

Odleiv Olesen; Rick Saltus

2010-01-01

239

Physical equivalence between nonlinear gravity theories and a general-relativistic self-gravitating scalar field  

Microsoft Academic Search

We argue that in a nonlinear gravity theory (the Lagrangian being an arbitrary function of the curvature scalar R), which according to well-known results is dynamically equivalent to a self-gravitating scalar field in general relativity, the true physical variables are exactly those which describe the equivalent general-relativistic model (these variables are known as the Einstein frame). Whenever such variables cannot

Guido Magnano; Leszek M. Sokolowski

1994-01-01

240

Improved performance of gravitational field-flow fractionation for screening wine-making yeast varieties  

Microsoft Academic Search

Performance of gravitational field-flow fractionation (GFFF) is improved here with respect to the ability to fractionate and distinguish different varieties of wine-making yeast from Saccharomyces cerevisiae. A new GFFF channel with non-polar walls has been employed to enhance fractionation selectivity and reproducibility. Since GFFF retention depends from first principles on particle size, Coulter counter measurements were performed in order to

R Sanz; B Torsello; P Reschiglian; L Puignou; M. T Galceran

2002-01-01

241

Quantum electrodynamics in the gravitational field of a cosmic string  

SciTech Connect

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 [ital M], and at ultrahigh energies, much larger than [ital M]/[delta], with [delta] the string mass per unit length in Planck units.

Skarzhinsky, V.D. (P. N. Lebedev Physical Institute, Leninsky prospect 53, Moscow 117924 (Russian Federation) Fakultaet fuer Physik der Universitaet Konstanz, Postfach 5560, D78434 Konstanz (Germany)); Harari, D.D. (Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (enPab. 1, 1428 Buenos Aires (Argentina))); Jasper, U. (Fakultaet fuer Physik der Universitaet Konstanz, Postfach 5560, D78434 Konstanz (Germany))

1994-01-15

242

Convergent Weak Coupling Expansions for Lattice Field Theories that Look like Perturbation Series  

NASA Astrophysics Data System (ADS)

We propose a new form of convergent weak coupling expansion for the lattice field theory. It has the advantage that it is very similar to standard (Feynman) perturbation theory. Convergence is proven for sufficiently weak local coupling, i.e. when the theory is close to a free field theory. In the proof, use of analyticity in field variables, as pioneered by Kupiainen and Gawedzki, is supplemented with techniques for handling derivatives with respect to free propagators.

Mack, Gerhard; Pordt, Andreas

243

Off-equatorial orbits in strong gravitational fields near compact objects  

NASA Astrophysics Data System (ADS)

Near a black hole or an ultracompact star, the motion of particles is governed by a strong gravitational field. Electrically charged particles also feel the electromagnetic force arising due to currents inside the star or plasma circling around. We study the possibility that the interplay between gravitational and electromagnetic actions may allow for the stable, energetically bound off-equatorial motion of charged particles. This would represent the well-known generalized Störmer's 'halo orbits', which have been discussed in connection with the motion of dust grains in planetary magnetospheres. We demonstrate that such orbits exist and can be astrophysically relevant when a compact star or a black hole is endowed with a dipole-type magnetic field. In the case of the Kerr Newman solution, numerical analysis shows that the mutually connected gravitational and electromagnetic fields do not allow the existence of stable halo orbits above the outer horizon of black holes. Such orbits are either hidden under the inner black-hole horizon, or they require the presence of a naked singularity.

Ková?, Ji?í; Stuchlík, Zden?k; Karas, Vladimír

2008-05-01

244

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

245

A scalar Euclidean theory of gravitation: motion in a static spherically symmetric field  

NASA Astrophysics Data System (ADS)

The motion of a particle in a static, spherically symmetric gravitational field is investigated in Euclidean space. The gravitational effects are described as due to a scalar field: To every point in space there is assigned a refractive index deciding the velocity of light in that point. The motion of light in the vacuum is described by the equation of classical optics. An equation of motion for material test particles is then derived by employing the usual Lagrangian formalism. The motion of the planets around the sun is explained, in particular the perihelion motion of Mercury. The present theory fully explains the four “classical” tests of general relativity in a mathematically far simpler way, and it can be equivalent to the Schwarzschild solution. It is also found that the effect of gravitation depends on the velocity of the particle, becoming repulsive for radial velocities larger than c/sqrt 3 ( c is the velocity of light). This seemingly odd result can also be obtained from the equations of general relativity, as was shown by Cavalleri and Spinelli.

Sjödin, Torgny

1990-12-01

246

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

247

Melt motion in a Czochralski puller with a weak transverse magnetic field  

NASA Astrophysics Data System (ADS)

The melt motion in a Czochralski silicon crystal puller with a uniform transverse magnetic field is intrinsically three-dimensional. When the magnetic field is relatively weak, the motion consists of an axisymmetric base solution, plus two perturbations which behave as sin 2? and cos 2?, neglecting terms which are proportional to the fourth power of the magnetic field strength. A 700 G magnetic field stabilizes a melt motion which is unsteady without a magnetic field. As the strength of the magnetic field increases, the magnitudes of the axial and radial velocities increase to maxima at some field strength above 1000 G. This contrasts with an axial magnetic field for which the axial and radial velocities always decrease as the field strength increases. We estimate that 1500 G is the maximum field strength for which our weak-field asymptotic solution is valid.

Williams, M. G.; Walker, J. S.; Langlois, W. E.

1990-02-01

248

On inhomogeneous magnetic seed fields and gravitational waves within the MHD limit  

Microsoft Academic Search

In this paper we apply second-order gauge-invariant perturbation theory to\\u000ainvestigate the possibility that the non-linear coupling between gravitational\\u000awaves (GW) and a large scale inhomogeneous magnetic field acts as an\\u000aamplification mechanism in an `almost' Friedmann-Lemaitre-Robertson-Walker\\u000a(FLRW) Universe. The spatial inhomogeneities in the magnetic field are\\u000aconsistently implemented using the magnetohydrodynamic (MHD) approximation,\\u000awhich yields an additional source term

Caroline Zunckel; Gerold Betschart; Peter K S Dunsby; Mattias Marklund

2006-01-01

249

Gravitational Potential Evolution in Unified Dark Matter Scalar Field Cosmologies:. AN Analytical Approach  

NASA Astrophysics Data System (ADS)

We investigate the time evolution of the gravitational potential ? for a special class of non-adiabatic Unified Dark matter Models described by scalar field Lagrangians. These models predict the same background evolution as in the ?CDM and possess a non-vanishing speed of sound. We provide a very accurate approximation of ?, valid after the recombination epoch, in the form of a Bessel function of the first kind. This approximation may be useful for a future deeper analysis of Unified Dark Matter scalar field models.

Piattella, Oliver F.; Bertacca, Daniele

250

A Quantum Weak Energy Inequality¶for Dirac Fields in Curved Spacetime  

Microsoft Academic Search

:   Quantum fields are well known to violate the weak energy condition of general relativity: the renormalised energy density\\u000a at any given point is unbounded from below as a function of the quantum state. By contrast, for the scalar and electromagnetic\\u000a fields it has been shown that weighted averages of the energy density along timelike curves satisfy “quantum weak energy

Christopher J. Fewster; Rainer Verch

2002-01-01

251

Modulation of cardiac rhythm in the humans exposed to extremely weak alternating magnetic fields  

Microsoft Academic Search

The effect of extremely weak alternating magnetic fields of various types with the amplitudes ? of 2 ?T on the heart rate\\u000a variability in humans was studied. Volunteers were placed in a large-volume coil system (2?2?2 m), which provided exposure\\u000a of the whole body to extremely weak alternating magnetic fields uniform in their amplitude. It was shown for the first

V. V. Lednev; N. A. Belova; A. M. Ermakov; E. B. Akimov; A. G. Tonevitsky

2008-01-01

252

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

253

Multiple D/p-branes in weak background fields  

NASA Astrophysics Data System (ADS)

We find the terms in the non-abelian world-volume action of a system of many D/p-branes which describe the leading coupling to all type II supergravity background fields. These results are found by T-dualizing earlier results for D0-branes, which in turn were determined from calculations of the M(atrix) theory description of the supercurrent of 11D supergravity. Our results are compatible with earlier results on the supersymmetric Born-Infeld action for a single D-brane in a general background and with Tseytlin's symmetrized trace proposal for extending the abelian Born-Infeld action to a non-abelian theory. In the case /p=3, the operators we find on the D-brane world-volume are closely related to those which couple to supergravity fields in the AdS5×S5 IIB supergravity background. This gives an explicit construction, including normalization, of some of the operators used in the celebrated AdS/CFT correspondence for 3-branes. We also discuss the S-duality of the action in the case /p=3, finding that the S-duality of the action determines how certain operators in the /N=4 4D SYM theory transform under S-duality. These S-duality results give some new insight into the puzzle of the transverse 5-brane in M(atrix) theory.

Taylor, W., IV; Van Raamsdonk, M.

2000-05-01

254

Dielectronic recombination and autoionization yields in weak static electric fields  

SciTech Connect

Dielectronic recombination (DR) of ions and electrons occurs via intermediate doubly excited Rydberg states converging to an excited state of the ion, and the total energy-integrated rate is the sum of the rates through the n,l Rydberg states. To make stringent comparisons between calculated and observed rates, it is useful to resolve the contributions to DR of different n and l states. It is possible to separate experimentally the n states due to their different energies, but it is not possible to separate the nearly degenerate high-l states. We propose that it should be possible to measure the contribution to DR of energetically unresolved high-l states by measuring the recombination rate as a function of electric field. As the field is raised, progressively lower l states are converted to Stark states. Autoionization rates increase as l is decreased, and when the field is raised to the point that an l state with an autoionization rate in excess of the radiative decay rate is added to the manifold of Stark states, the DR rate will exhibit an observable increase. To test this proposal we have made measurements of autoionization yields of the autoionizing Ba 6p{sub 1/2}nk and 6p{sub 3/2}nk Stark states. The autoionization yield is complementary to DR, and the measurements indicate that the proposed approach should work well. Although it is not surprising that this approach works for excited ion states that are isotropic, such as the Ba{sup +} 6p{sub 1/2} state, it is less obvious that it should work for an anisotropic ion state, such as the Ba{sup +} 6p{sub 3/2} state. In the latter case there are four quantum defects for each l state instead of one, and the Stark effect of the Ba 6p{sub 3/2}nk Stark states is far more complex than that of the Ba 6p{sub 1/2}nk Stark states. Calculations of the Stark effect reveal that, while there are four times as many 6p{sub 3/2}nk levels as 6p{sub 1/2}nk levels, many of the interactions of the 6p{sub 3/2}nk levels are negligible, and in practice the problem is no more complicated than the 6p{sub 1/2}nk Stark problem.

Nunkaew, J.; Gallagher, T. F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2010-02-15

255

Stark deceleration of CaF molecules in strong- and weak-field seeking states.  

PubMed

We report the Stark deceleration of CaF molecules in the strong-field seeking ground state and in a weak-field seeking component of a rotationally-excited state. We use two types of decelerator, a conventional Stark decelerator for the weak-field seekers and an alternating gradient decelerator for the strong-field seekers, and we compare their relative merits. We also consider the application of laser cooling to increase the phase-space density of decelerated molecules. PMID:21776450

Wall, T E; Kanem, J F; Dyne, J M; Hudson, J J; Sauer, B E; Hinds, E A; Tarbutt, M R

2011-07-20

256

BAYESIAN INFERENCE OF SOLAR AND STELLAR MAGNETIC FIELDS IN THE WEAK-FIELD APPROXIMATION  

SciTech Connect

The weak-field approximation is one of the simplest models that allows us to relate the observed polarization induced by the Zeeman effect with the magnetic field vector present on the plasma of interest. It is usually applied for diagnosing magnetic fields in the solar and stellar atmospheres. A fully Bayesian approach to the inference of magnetic properties in unresolved structures is presented. The analytical expression for the marginal posterior distribution is obtained, from which we can obtain statistically relevant information about the model parameters. The role of a priori information is discussed and a hierarchical procedure is presented that gives robust results that are almost insensitive to the precise election of the prior. The strength of the formalism is demonstrated through an application to IMaX data. Bayesian methods can optimally exploit data from filter polarimeters given the scarcity of spectral information as compared with spectro-polarimeters. The effect of noise and how it degrades our ability to extract information from the Stokes profiles is analyzed in detail.

Asensio Ramos, A., E-mail: aasensio@iac.es [Instituto de Astrofisica de Canarias, 38205, La Laguna, Tenerife (Spain); Departamento de Astrofisica, Universidad de La Laguna, E-38205 La Laguna, Tenerife (Spain)

2011-04-10

257

Bayesian Inference of Solar and Stellar Magnetic Fields in the Weak-field Approximation  

NASA Astrophysics Data System (ADS)

The weak-field approximation is one of the simplest models that allows us to relate the observed polarization induced by the Zeeman effect with the magnetic field vector present on the plasma of interest. It is usually applied for diagnosing magnetic fields in the solar and stellar atmospheres. A fully Bayesian approach to the inference of magnetic properties in unresolved structures is presented. The analytical expression for the marginal posterior distribution is obtained, from which we can obtain statistically relevant information about the model parameters. The role of a priori information is discussed and a hierarchical procedure is presented that gives robust results that are almost insensitive to the precise election of the prior. The strength of the formalism is demonstrated through an application to IMaX data. Bayesian methods can optimally exploit data from filter polarimeters given the scarcity of spectral information as compared with spectro-polarimeters. The effect of noise and how it degrades our ability to extract information from the Stokes profiles is analyzed in detail.

Asensio Ramos, A.

2011-04-01

258

Effects of a classical homogeneous gravitational field on the cavity-field entropy and generation of the Schrödinger-cat states in the Jaynes-Cummings model  

NASA Astrophysics Data System (ADS)

In this paper, we examine the effects of the gravitational field on the dynamical evolution of the cavity-field entropy and the creation of the Schrödinger-cat state in the Jaynes-Cummings model. We consider a moving two-level atom interacting with a single mode quantized cavity-field in the presence of a classical homogeneous gravitational field. Based on an su(2) algebra, as the dynamical symmetry group of the model, we derive the reduced density operator of the cavity-field which includes the effects of the atomic motion and the gravitational field. Also, we obtain the exact solution and the approximate solution for the system-state vector, and examine the atomic dynamics. By considering the temporal evolution of the cavity-field entropy as well as the dynamics of the Q-function of the cavity-field we study the effects of the gravitational field on the generation of the Schrödinger-cat states of the cavity-field by using the Q-function, field entropy and approximate solution for the system-state vector. The results show that the gravitational field destroys the generation of the Schrödinger-cat state of the cavity-field.

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

2008-04-01

259

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

260

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

261

Relativistic Gravitation Theory.  

National Technical Information Service (NTIS)

On the basis of the special relativity and geometrization principle a relativistic gravitation theory (RGT) is unambiguously constructed with the help of a notion of a gravitational field as a physical field in Faraday-Maxwell spirit, which posesses energ...

A. A. Logunov M. A. Mestvirishvili

1984-01-01

262

Origin of Magnetic Fields in the Universe due to Nonminimal Gravitational-Electromagnetic Coupling  

SciTech Connect

Basically the only existing theories for the creation of a magnetic field ({ital B}) in the Universe are the creation of a seed field {approximately}10{sup -20} G in spiral galaxy which is subsequently supposedly amplified up to the observed 10{sup -6}{endash}10{sup -5} G by a dynamo process or a seed intergalactic field of {approximately}10{sup -12}{endash} 10{sup -10} G which is amplified by collapse and differential rotation. No satisfactory dynamo theory, however, exists today. We show that a {approximately}10{sup -6}{endash} 10{sup -5} G magnetic field in spiral galaxies is directly obtained from a nonminimal gravitational-electromagnetic coupling, without the need of significant dynamo amplification. {copyright} {ital 1997} {ital The American Physical Society}

Opher, R. [Instituto de Astronomia e Geofisica, Universidade de Sao Paulo, Av.Miguel Stefano, 4.200, CEP 04301-904, Sao Paulo, SP (Brazil); Wichoski, U.F. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Wichoski, U.F. [Depto.Fisica-Matematica, Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, CEP 05389-970, Sao Paulo, SP (Brazil)

1997-02-01

263

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

PubMed

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. PMID:9591693

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

1998-05-01

264

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

265

A Solution of the Einstein Equation in a Stationary Gravitational Field Due to a Rotating Source  

NASA Astrophysics Data System (ADS)

The stationary and axially symmetric gravitational field due to a rotating deformed source can be treated by the Ernst equation. We prove analytically the validity of the solution of the Ernst equation that was presented as a possible solution in a previous paper for arbitrary real values of the deformation parameter &delta. By means of analytic continuations of the solution we obtain a new solution in oblate spheroidal coordinates. This leads to a metric different from the Tomimatsu-Sato metric. From these solutions for real &delta we determine the metric functions both in prolate and oblate spheroidal coordinates.

Tanimura, O.; Hori, S.

1999-02-01

266

Binary-pulsar tests of strong-field gravity and gravitational radiation damping  

Microsoft Academic Search

This talk reviews the constraints imposed by binary-pulsar data on gravity\\u000atheories, focusing on ``tensor-scalar'' ones which are the best motivated\\u000aalternatives to general relativity. We recall that binary-pulsar tests are\\u000aqualitatively different from solar-system experiments, because of\\u000anonperturbative strong-field effects which can occur in compact objects like\\u000aneutron stars, and because one can observe the effect of gravitational\\u000aradiation

Gilles Esposito-Farese

2004-01-01

267

TASI Lectures on Holographic Space-Time, SUSY, and Gravitational Effective Field Theory  

NASA Astrophysics Data System (ADS)

I argue that the conventional field theoretic notion of vacuum state is not valid in quantum gravity. The arguments use gravitational effective field theory, as well as results from string theory, particularly the AdS/CFT correspondence. Different solutions of the same low energy gravitational field equations correspond to different quantum systems, rather than different states in the same system. I then introduce holographic space-time a quasi-local quantum mechanical construction based on the holographic principle. I argue that models of quantum gravity in asymptotically flat space-time will be exactly super-Poincare invariant, because the natural variables of holographic space-time for such a system, are the degrees of freedom of massless superparticles. The formalism leads to a non-singular quantum Big Bang cosmology, in which the asymptotic future is required to be a de Sitter space, with cosmological constant (c.c.) determined by cosmological initial conditions. It is also approximately SUSic in the future, with the gravitino mass K?1/4.

Banks, Tom

2012-11-01

268

REVIEWS OF TOPICAL PROBLEMS Gravitational radiation of systems and the role of their force field  

NASA Astrophysics Data System (ADS)

Gravitational radiation (GR) from compact relativistic systems with a known energy-momentum tensor (EMT) and GR from two masses elliptically orbiting their common center of inertia are considered. In the ultrarelativistic limit, the GR spectrum of a charge rotating in a uniform magnetic field, a Coulomb field, a magnetic moment field, and a combination of the last two fields differs by a factor 4?Gm2?2/e2 (? being of the order of the charge Lorentz factor) from its electromagnetic radiation (EMR) spectrum. This factor is independent of the radiation frequency but does depend on the wave vector direction and the way the field behaves outside of the orbit. For a plane wave external field, the proportionality between the gravitational and electromagnetic radiation spectra is exact, whatever the velocity of the charge. Qualitative estimates of ? are given for a charge moving ultrarelativistically in an arbitrary field, showing that it is of the order of the ratio of the nonlocal and local source contributions to the GR. The localization of external forces near the orbit violates the proportionality of the spectra and reduces GR by about the Lorentz factor squared. The GR spectrum of a rotating relativistic string with masses at the ends is given, and it is shown that the contributions by the masses and string are of the same order of magnitude. In the nonrelativistic limit, the harmonics of GR spectra behave universally for all the rotating systems considered. A trajectory method is developed for calculating the GR spectrum. In this method, the spatial (and hence polarization) components of the conserved EMT are calculated in the long wavelength approximation from the time component of the EMTs of the constituent masses of the system. Using this method, the GR spectrum of two masses moving in elliptic orbits about their common center of inertia is calculated, as are the relativistic corrections to it.

Nikishov, Anatolii I.; Ritus, Vladimir I.

2011-02-01

269

Solitary waves in two-dimensional dusty plasma crystal: Effects of weak magnetic field  

SciTech Connect

It is shown that in the presence of weak magnetic field, the dust lattice solitary wave in two-dimensional (2D) hexagonal dusty plasma crystal is governed by a gyration-modified 2D Korteweg-de Vries equation due to the action of Lorentz force on the dust particles. Numerical solutions reveal that only for weak magnetic field an apparently single hump solitary wave solution exist. But, for strong magnetic field dust lattice solitary wave becomes unstable showing repetitive solitary hump of increasing magnitude with time.

Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700 009 (India); Gupta, M. R. [Department of Instrumentation Science, Jadavpur University, Kolkata-700 032 (India)

2010-03-15

270

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

Microsoft Academic Search

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,

Alexander Pazur; Valentina Rassadina

2009-01-01

271

The ionospheric effects of a weak intrinsic magnetic field at Mars  

Microsoft Academic Search

An improved model of the Martian ionosphere which allows the magnetic field to have any direction in the horizontal plane is presented, as well as results of calculations for several different intrinsic magnetic field strengths and directions. When the solar wind dynamic pressure exceeds the Martian ionospheric thermal pressure, the plasma motion is weakly downward throughout the ionosphere for the

H. Shinagawa; T. E. Cravens

1992-01-01

272

Weak ferromagnetism induced by the external field above [ital T][sub [ital N  

SciTech Connect

A detailed study of the temperature and field dependence of the dc magnetization near the antiferromagnetic (AF) transition in Gd[sub 2]CuO[sub 4] shows the presence of field-induced weak ferromagnetism (WF) well above the Neel temperature [ital T][sub [ital N

Steren, L.B.; Fainstein, A.; Tovar, M. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche, 8400 San Carlos de Bariloche (Argentina)); Rouco, A.; Perez, F.; Obradors, X. (Institut de Ciencia de Materials de Barcelona, Campus UAB, 08193 Bellaterra (Spain)); Mira, J.; Rivas, J. (Universidad de Santiago Comision Nacional de Energia Atomica, Centro Atomico Bariloche, 8400 San Carlos de Bariloche (Argentina)); Oseroff, S.B. (San Diego State University, San Diego, California 92182-0325 (United States)); Fisk, Z. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1993-05-15

273

Unveiling chameleon fields in tests of the gravitational inverse-square law  

SciTech Connect

Scalar self-interactions are known to weaken considerably the current constraints on scalar-mediated fifth forces. We consider a scalar field with a quartic self-interaction and gravitation-strength Yukawa couplings to matter particles. After discussing the phenomenology of this scalar field, we assess the ability of ongoing and planned experiments to detect the fifth force mediated by such a field. Assuming that the quartic and matter couplings are of order unity, the current-generation Eoet-Wash experiment at the University of Washington will be able to explore an interesting subset of parameter space. The next-generation Eoet-Wash experiment is expected to be able to detect, or to rule out, the fifth force due to such a scalar with unit quartic and matter couplings at the 3{sigma} confidence level.

Upadhye, Amol; Gubser, Steven S. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Khoury, Justin [Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, ON, N2L 2Y5 (Canada)

2006-11-15

274

Unveiling chameleon fields in tests of the gravitational inverse-square law  

NASA Astrophysics Data System (ADS)

Scalar self-interactions are known to weaken considerably the current constraints on scalar-mediated fifth forces. We consider a scalar field with a quartic self-interaction and gravitation-strength Yukawa couplings to matter particles. After discussing the phenomenology of this scalar field, we assess the ability of ongoing and planned experiments to detect the fifth force mediated by such a field. Assuming that the quartic and matter couplings are of order unity, the current-generation Eöt-Wash experiment at the University of Washington will be able to explore an interesting subset of parameter space. The next-generation Eöt-Wash experiment is expected to be able to detect, or to rule out, the fifth force due to such a scalar with unit quartic and matter couplings at the 3? confidence level.

Upadhye, Amol; Gubser, Steven S.; Khoury, Justin

2006-11-01

275

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

276

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

277

Constraints on biological effects of weak extremely-low-frequency electromagnetic fields  

NASA Astrophysics Data System (ADS)

Concerns have been raised over the possibility that extremely-low-frequency (ELF) electromagnetic fields are carcinogenic and leukegenic. An examination of the physical interaction of such fields with the body shows that such interactions are too weak to have a significant effect on human biology at the cell level. Because of the high electrical conductivity of tissues, the coupling of external electric fields in air to tissue in the body is such that the effects of the internal fields on cells is smaller than thermal noise. Static magnetic fields smaller than the earth's field of 50 ?T and varying fields weaker than the 4-?T 60-Hz fields that are equivalent in effect to that from walking in the earth's field, cannot be expected to generate significant biological effects. Moreover, the interactions of such weak fields at the cell level are also small compared to thermal noise. These conclusions would be modified by 60-Hz cell resonances. But such resonances are shown to be incompatible with cell characteristics and the requirement from equipartition that the mean resonance energy must be kT. Hence, any biological effects of weak ELF fields on the cellular level must be found outside of the scope of conventional physics.

Adair, Robert K.

1991-01-01

278

Elution mode of Pneumocystis carinii cysts in gravitational field-flow fractionation.  

PubMed

The simplest field-flow fractionation technique, i.e. gravitational, was used in an attempt to purify a Pneumocystis carinii cyst suspension. This parasite is an opportunistic invader in immunocompromised patients, especially those suffering from AIDS. The cyst stage is spherical and 5 microns in diameter. Unexpected retention times, not systematically related to the size and the density of the parasite, were obtained under various experimental conditions. When silicone-coated walls were used, Pneumocystis carinii cysts were eluted in the void volume, whereas when uncoated walls were used with a sodium dodecyl sulphate-enriched carrier phase, retention was observed. These phenomena are probably related to the high degree of hydrophobicity of these micrometre-sized biological particles; this degree can be easily determined. The use of the gravitational field-flow fractionation technique can be of a great interest for the development of new methods for diagnostic purposes. Particle-wall interactions and their modifications due to the carrier phase or to the wall treatment can be employed in the search for new bronchoalveolar lavage solutions. PMID:1447341

Bories, C; Cardot, P J; Abramowski, V; Poüs, C; Merino-Dugay, A; Baron, B; Mougeot, G

1992-08-01

279

Cell separation on microfabricated electrodes using dielectrophoretic/gravitational field-flow fractionation.  

PubMed

Dielectrophoretic/gravitational field-flow fractionation (DEP/G-FFF) was used to separate cultured human breast cancer MDA-435 cells from normal blood cells mixed together in a sucrose/dextrose medium. An array of microfabricated, interdigitated electrodes of 50 microns widths and spacings, and lining the bottom surface of a thin chamber (0.42 mm H x 25 mm W x 300 mm L), was used to generate DEP forces that levitated the cells. A 10-microL cell mixture sample containing approximately 50,000 cells was introduced into the chamber, and cancerous and normal blood cells were levitated to different heights according to the balance of DEP and gravitational forces. The cells at different heights were transported at different velocities under the influence of a parabolic flow profile that was established in the chamber and were thereby separated. Separation performance depended on the frequency and voltage of the applied DEP field and the fluid-flow rate. It took as little as 5 min to achieve cell separation. An analysis of the DEP/G-FFF results revealed that the separation exploited the difference in dielectric and density properties between cell populations. The DEP/G-FFF technique is potentially applicable to many biological and biomedical problems, especially those related to microfluidic systems. PMID:10079757

Yang, J; Huang, Y; Wang, X B; Becker, F F; Gascoyne, P R

1999-03-01

280

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

NASA Astrophysics Data System (ADS)

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 evaluation of the theory of figures based on numerical integration of ordinary differential equations is presented. The classical Radau-Darwin formula is found not to be valid for the rotational parameter ?2 = ?2/(2 ?G ?2) ? 0.17 since the formula then predicts a surface eccentricity that is smaller than the eccentricity of the core-envelope boundary. Interface eccentricity must be smaller than surface eccentricity. In the formula for ?2, ? is the angular velocity of the two-layer body, ?2 is the density of the outer layer, and G is the gravitational constant. For an envelope density of 3000 kg m -3 the failure of the Radau-Darwin formula corresponds to a rotation period of about 3 h. Application of the exact solution and the theory of figures is made to models of Earth, Mars, Uranus, and Neptune. The two-layer model with constant densities in the layers can provide realistic approximations to terrestrial planets and icy outer planet satellites. The two-layer model needs to be generalized to allow for a continuous envelope (outer layer) radial density profile in order to realistically model a gas or ice giant planet.

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

2011-08-01

281

Theory of weak bipolar fields and electron holes with applications to space plasmas.  

PubMed

A theoretical model of weak electron phase-space holes is used to interpret bipolar field structures observed in space. In the limit ephi(max)/Te < 1 the potential of the structure has the unique form, phi(x) = phi(max)sech4(x/alpha), where phi(max) depends on the derivative of the trapped distribution at the separatrix, while alpha depends only on a screening integral over the untrapped distribution. Idealized trapped and passing electron distributions are inferred from the speed, amplitude, and shape of satellite waveform measurements of weak bipolar field structures. PMID:17930679

Goldman, Martin V; Newman, David L; Mangeney, André

2007-10-05

282

Theory of Weak Bipolar Fields and Electron Holes with Applications to Space Plasmas  

SciTech Connect

A theoretical model of weak electron phase-space holes is used to interpret bipolar field structures observed in space. In the limit e{phi}{sub max}/T{sub e}<<1 the potential of the structure has the unique form, {phi}(x)={phi}{sub max}sech{sup 4}(x/{alpha}), where {phi}{sub max} depends on the derivative of the trapped distribution at the separatrix, while {alpha} depends only on a screening integral over the untrapped distribution. Idealized trapped and passing electron distributions are inferred from the speed, amplitude, and shape of satellite waveform measurements of weak bipolar field structures.

Goldman, Martin V.; Newman, David L. [Department of Physics and CIPS, University of Colorado, Boulder, Colorado 80309 (United States); Mangeney, Andre [DESPA, Observatoire de Meudon, Paris (France)

2007-10-05

283

Equilibrium of a system of superconducting rings in a uniform gravitational field  

NASA Astrophysics Data System (ADS)

To construct a plasma trap with levitating magnetic coils in the thin ring approximation, we derive the expression for the potential energy of a system of several superconducting rings (one of which is fixed) capturing the preset flows in the uniform gravitational field as a function of the coordinates of the free ring (or rings). Calculations performed in the Mathcad system show that the potential energy of such a system has a local minimum for certain values of parameters. Stable levitation of a superconducting ring in the position corresponding to calculations is realized in the field of another superconducting ring, and this leads to the conclusion that a magnetic Galatea trap can be prepared on the basis of a levitating quadrupole.

Bishaev, A. M.; Bush, A. A.; Gavrikov, M. B.; Gordeev, I. S.; Denisyuk, A. I.; Kamentsev, K. E.; Kozintseva, M. V.; Savel'ev, V. V.; Sigov, A. S.

2013-05-01

284

A null-tetrad approach to Kerr{endash}Schild gravitational fields in matter  

SciTech Connect

The null tetrad formalism is used to investigate the structure of the Einstein field equations for Kerr{endash}Schild gravitational fields in the presence of an elastic solid source. It is shown that such equations may be reduced to five nonlinear partial differential equations for five variables. It turns out that, when the interior solutions admit the same preferred null congruence of the vacuum ones and some compatibility conditions hold, it is possible to reduce them to a linear system and to develop a method of solution which closely resembles the {open_quote}{open_quote}variation of the arbitrary constants{close_quote}{close_quote} for ordinary differential equations. In the present paper, the above technical framework is developed in general and applied to two simple examples, deferring to future work the approach to the Kerr{endash}interior problem. {copyright} {ital 1996 American Institute of Physics.}

Udeschini, E.B.; Magli, G. [Dipartimento di Matematica del Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy)

1996-11-01

285

Weak massive gravity  

NASA Astrophysics Data System (ADS)

We find a new class of theories of massive gravity with five propagating degrees of freedom where only rotations are preserved. Our results are based on a nonperturbative and background-independent Hamiltonian analysis. In these theories the weak field approximation is well behaved and the static gravitational potential is typically screened à la Yukawa at large distances, while at short distances no van Dam-Veltman-Zakharov discontinuity is found and there is no need to rely on nonlinear effects to pass the solar system tests. The effective field theory analysis shows that the ultraviolet cutoff is (mMPl)1/2?1/?m, the highest possible. Thus, these theories can be studied in the weak-field regime at all the phenomenologically interesting scales and are candidates for a calculable large-distance modified gravity.

Comelli, D.; Nesti, F.; Pilo, L.

2013-06-01

286

MTV-G experiment : probing a non-standard strong gravitational field at nuclear scale using geodetic precession  

NASA Astrophysics Data System (ADS)

The MTV-G project has started in 2011 to explore a strong gravitational field around nuclei utilizing an experimental technique developed to search time reversal symmetry violation in nuclear beta decay experiment at a radioactive beam facility. A large electron spin-precession due to a possible strong gravitational field, which has been predicted by a large extra dimension model, is investigated in an electron-nuclear scattering experiment at TRIUMF. The experimental design, which use a spin polarized electron source and a Mott-spin analyzer, the commissioning experiment, the preliminary results, together with an introduction to the next generation device, are described in this article.

Tanaka, Saki; Nakaya, Yusuke; Ninomiya, Kazufumi; Nishio, Hironori; Onishi, Junichi; Openshaw, Robert; Pearson, Matthew; Totsuka, Yumi; Murata, Jiro

2013-08-01

287

Relativistic theory of gravitation  

SciTech Connect

This paper constructs a relativistic theory of gravitation based on the special principle of relativity and the principle of geometrization. The gravitational field is regarded as a physical field in the spirit of Faraday and Maxwell, possessing energy, momentum, and spin 2 and 0. The source of the gravitational field is the total conserved energy momentum tensor of the matter and the gravitational field in Minkowski space. Conservation laws hold rigorously for the energy, momentum, and angular momentum of the matter and the gravitational field. The theory explains all the existing gravitational experiments. By virtue of the geometrization principle, the Riemann space has a field origin in the theory, arising as an effective force space through the action of the gravitational field on the matter.

Logunov, A.A.; Mestvirishvili, M.A.

1985-06-01

288

Gravitational anomalies  

Microsoft Academic Search

The effective action for fermions moving in external gravitational and gauge fields is analyzed in terms of the corresponding external field propagator. The central object in our approach is the covariant energy-momentum tensor which is extracted from the regular part of the propagator at short distances. It is shown that the Lorentz anomaly, the conformal anomaly and the gauge anomaly

H. Leutwyler; S. Mallik

1986-01-01

289

Magnetite in human tissues: A mechanism for the biological effects of weak ELF magnetic fields  

SciTech Connect

Due to the apparent lack of a biophysical mechanism, the question of whether weak, low-frequency magnetic fields are able to influence living organisms has long been one of the most controversial subjects in any field of science. However, two developments during the past decade have changed this perception dramatically, the first being the discovery that many organisms, including humans, biochemically precipitate the ferrimagnetic mineral magnetite (Fe3O4). In the magnetotactic bacteria, the geomagnetic response is based on either biogenic magnetite or greigite (Fe3S4), and reasonably good evidence exists that this is also the case in higher animals such as the honey bee. Second, the development of simple behavioral conditioning experiments for training honey bees to discriminate magnetic fields demonstrates conclusively that at least one terrestrial animal is capable of detecting earth-strength magnetic fields through a sensory process. In turn, the existence of this ability implies the presence of specialized receptors which interact at the cellular level with weak magnetic fields in a fashion exceeding thermal noise. A simple calculation shows that magnetosomes moving in response to earth-strength ELF fields are capable of opening trans-membrane ion channels, in a fashion similar to those predicted by ionic resonance models. Hence, the presence of trace levels of biogenic magnetite in virtually all human tissues examined suggests that similar biophysical processes may explain a variety of weak field ELF bioeffects. 61 refs.

Kirschvink, J.L.; Kobayashi-Kirschvink, A.; Diaz-Ricci, J.C.; Kirschvink, S.J. (California Institute of Technology, Pasadena (United States))

1992-01-01

290

Thermal analgesic effects from weak, complex magnetic fields and pharmacological interactions.  

PubMed

In several experiments, robust analgesia (equivalent to about 4 mg/kg of morphine) in male rats to thermal stimuli following exposures to weak (1 microT) complex magnetic fields was explored. The analgesia occurred when patterns of magnetic fields with burst-firing-like configurations were presented for 30 min once every approximately 4 s. The analgesic effects were intensity dependent. A different frequency-modulated pattern produced analgesia more quickly. The analgesic effects following exposure to the burst-firing magnetic fields were augmented conspicuously by preinjections of morphine (4 mg/kg) or agmatine (10 mg/kg), but blocked by naloxone (1 mg/kg). The results of these experiments suggest that rational design of the temporal structure of weak magnetic fields may be a novel, inexpensive, and reliable technique for elevating thresholds to some classes of painful stimuli. PMID:15219761

Martin, L J; Koren, S A; Persinger, M A

2004-06-01

291

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

292

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

293

Form factor of a quantum graph in a weak magnetic field  

NASA Astrophysics Data System (ADS)

Using the periodic orbit theory, we evaluate the form factor of a quantum graph to which a very weak magnetic field is applied. The first correction to the diagonal approximation describing the transition between the universality classes is shown to be in agreement with Pandey and Mehta's formula of parametric random matrix theory.

Nagao, Taro; Saito, Keiji

2003-05-01

294

Rotational diffusion of a tracer colloid particle III. Weak external field effects  

Microsoft Academic Search

We study the orientational time correlation functions of a tracer colloid particle which carries a magnetic moment in the presence of a weak external magnetic field. The tracer interacts with other particles in a low density suspension through hard sphere pair potentials and hydrodynamic forces. We show that at intemediate times the approximation for the correlation functions, introduced in the

F. N. Alavi; R. B. Jones

1990-01-01

295

What Can We Learn About Electron Distributions From Measurements of Weak Bipolar Fields?^*  

NASA Astrophysics Data System (ADS)

A given bipolar field that is stationary in a co-moving frame can correspond either to an ion soliton or an electron phase-space hole. In the limit of weak potential, ?, with e?max/Te1, either of these structures can have the asymptotic shape ?= ?maxsech^4(x/?). For ion solitons, the half width (?) depends on ?max, whereas for electron holes the half-width is independent of ?max. We show analytically for holes in this limit that ?max depends on the (finite) energy derivative of the trapped distribution at the separatrix, while ? depends only on a ``screening'' integral over the untrapped distribution. Idealized trapped and passing electron distributions are shown to be inferrable from the speed, amplitude, and shape of weak bipolar waveform measurements. For measurements^1 of hundreds of weak bipolar field events in Earth's cusp, the theory is shown to be consistent with the most frequently observed half-width between bipolar field peaks, and with various other features of the measured^1 distribution of hole velocities vs hole half-widths. ^* Work supported by NSF, NASA, and DOE, and submitted in part to Phys. Rev. Lett. as ``Theory of Weak Bipolar Fields and Electron Holes with Space Applications,'' (2007). ^1 Franz, J.R., et al., J. Geophys. Res. 110, A09212, 2005.

Goldman, Martin V.; Newman, David L.; Mangeney, André

2007-11-01

296

Mean-field analysis of the super weak ferrimagnetism of strongly coupled paramagnetic systems: II  

Microsoft Academic Search

We reconsider here the so-called super weak ferrimagnetism problem, arising from two strongly coupled paramagnetic sublattices, of Pauli or Curie—Weiss type, within a continuous Landau model. The parameters of the model are the absolute temperature T, the applied magnetic field H, the coupling C between the two sublattices, and two coupling constants b and B that traditionally multiply the quartic

Boutayeb El Houari; Mabrouk Benhamou

1997-01-01

297

Thermal analgesic effects from weak, complex magnetic fields and pharmacological interactions  

Microsoft Academic Search

In several experiments, robust analgesia (equivalent to about 4 mg\\/kg of morphine) in male rats to thermal stimuli following exposures to weak (1 ?T) complex magnetic fields was explored. The analgesia occurred when patterns of magnetic fields with burst-firing-like configurations were presented for 30 min once every approximately 4 s. The analgesic effects were intensity dependent. A different frequency-modulated pattern

L. J Martin; S. A Koren; M. A Persinger

2004-01-01

298

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

299

Variations of Mars gravitational field and rotation due to seasonal CO sub 2 exchange  

SciTech Connect

About a quarter of the Martian atmospheric mass is exchanged between the atmosphere and the polar caps in the course of a Martian year: CO{sub 2} condenses to form (or add to) the polar caps in winter and sublimes into the atmosphere in summer. This paper studies the effect of this CO{sub 2} mass redistribution on Martian rotation and gravitational field. Two mechanisms are examined: (1) the waxing and waning of solid CO{sub 2} in the polar caps and (2) the geographical distribution of gaseous CO{sub 2} in the atmosphere. In particular, the net peak-to-peak changes in J{sub 2} and J{sub 3} over a Martian year are both found to be as much as {approximately}6 {times} 10{sup {minus}9}. A simulation suggests that these changes may be detected by the upcoming Mars Observer under favorable but realistic conditions.

Chao, B.F.; Rubincam, D.P. (Goddard Space Flight Center, Greenbelt, MD (USA))

1990-08-30

300

Motion of a rigid body with a viscoelastic membrane in a gravitational field  

NASA Astrophysics Data System (ADS)

The motion of a system consisting of a supporting rigid body and a viscoelastic circular membrane in a central Newtonian gravitational field in circular orbit is examined analytically. The axis of symmetry of the membrane coincides with one of the main central axes of inertia of the nondeformed system. A system of differential equations of motion is obtained in the context of linear elasticity. The quasi-static regime of motion is considered. Relative equilibrium positions are determined for the case where the membrane is deformed but remains stationary with respect to the supporting body, and the orientation of the system (the supporting body and the membrane) in orbital coordinates coincides with the relative equilibrium positions of a triaxial satellite, an absolutely rigid body. The stability of these equilibriums is investigated.

Kholostova, O. V.

1992-02-01

301

Wave convection regimes in a binary mixture in a modulated gravitational field  

SciTech Connect

Nonlinear wave convection regimes are studied in a horizontal layer of an incompressible binary mixture with anomalous thermal diffusion in the gravitational field modulated with an arbitrary amplitude and finite frequency. Oscillation regimes are numerically simulated by the finite difference method for the case of a layer with impenetrable rigid boundaries, which better corresponds to experimental laboratory conditions. A qualitative difference is found in the dynamics of nonlinear quasi-periodic and subharmonic oscillations appearing in the initially stratified mixture and behaving as modulated and regular standing waves. The dependences of the intensity of convective flows on the modulation amplitude are obtained. The results of nonlinear calculations are compared with data on the boundaries of the equilibrium stability found from the linear theory. It is shown that a region of parameters exists where alternating action suppresses the convective motion.

Myznikova, B. I. [Russian Academy of Sciences, Institute of Mechanics of Continuous Media, Ural Branch (Russian Federation); Smorodin, B. L., E-mail: bsmorodin@yandex.ru [Perm State University (Russian Federation)

2011-03-15

302

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

303

Antimatter gravity and the weak equivalence principle  

NASA Astrophysics Data System (ADS)

Ideas are presented for an experiment to compare the acceleration, g, of antiprotons in the Earth's gravitational field with that of particles of normed matter, such as protons or hydrogen ions. The experiments will test whether antiprotons obey the weak equivalence principle.(AIP)

Holzscheiter, M. H.; Brown, R. E.; Camp, J.; Darling, T.; Dyer, P.; Holtkamp, D. B.; Jarmie, N.; King, N. S. P.; Schauer, M. M.; Cornford, S.; Hosea, K.; Kenefick, R. A.; Midzor, M.; Oakley, D.; Ristinen, R.; Witteborn, F. C.

1991-08-01

304

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

305

Compact self-gravitating solutions of quartic (K) fields in brane cosmology  

NASA Astrophysics Data System (ADS)

Recently we proposed that K fields, that is, fields with a non-standard kinetic term, may provide a mechanism for the generation of thick branes, based on the following observations. First, K field theories allow for soliton solutions with compact support, i.e., compactons. Compactons in 1+1 dimensions may give rise to topological defects of the domain wall type and with finite thickness in higher dimensions. Second, propagation of linear perturbations is confined inside the compacton domain wall. Further, these linear perturbations inside the topological defect are of the standard type, in spite of the non-standard kinetic term. Third, when gravity is taken into account, location of gravity in the sense of Randall-Sundrum works for these compacton domain walls provided that the backreaction of gravity does not destabilize the compacton domain wall. It is the purpose of the present paper to investigate in detail the existence and stability of compacton domain walls in the full K field and gravity system, using both analytical and numerical methods. We find that the existence of the domain wall in the full system requires a correlation between the gravitational constant and the bulk cosmological constant.

Adam, C.; Grandi, N.; Klimas, P.; Sánchez-Guillén, J.; Wereszczy?ski, A.

2008-09-01

306

Dust acoustic shock wave in electronegative dusty plasma: Roles of weak magnetic field  

SciTech Connect

The effects of nonsteady dust charge variations and weak magnetic field on small but finite amplitude nonlinear dust acoustic wave in electronegative dusty plasma are investigated. The dynamics of the nonlinear wave are governed by a Korteweg-de Vries Burger equation that possesses dispersive shock wave. The weak magnetic field is responsible for the dispersive term, whereas nonsteady dust charge variation is responsible for dissipative term, i.e., the Burger term. The coefficient of dissipative term depends only on the obliqueness of the magnetic field. It is found that for parallel propagation the dynamics of the nonlinear wave are governed by the Burger equation that possesses monotonic shock wave. The relevances of the findings to cometary dusty plasma, e.g., Comet Halley are briefly discussed.

Ghosh, Samiran [Government College of Engineering and Textile Technology, 4, Cantonment Road, Berhampore, Murshidabad 742101, West Bengal (India); Ehsan, Z.; Murtaza, G. [Salam Chair and Department of Physics, G. C. University Lahore, 54000 Lahore (Pakistan)

2008-02-15

307

Numerical investigation of micro-macro coupling in magneto-impedance sensors for weak field measurements  

NASA Astrophysics Data System (ADS)

There is strong interest in the use of small low-cost highly sensitive magnetic field sensors for applications (e.g. biomedical devices) requiring weak field measurements. Among weak-field sensors, the magneto-impedance (MI) sensor has demonstrated an absolute resolution of 10-11 T. The MI effect is a sensitive realignment of a periodic magnetization in response to an external field in small ferromagnets. However, design of MI sensors has relied primarily on trial and error experimental methods along with decoupled models describing the MI effect. To offer a basis for more cost-effective designs, this thesis research begins with a general formulation describing MI sensors, which relaxes assumptions commonly made for decoupling. The coupled set of nonlinear equations is solved numerically using an efficient meshless method in a point collocation formulation. For the problem considered, the chosen method is shown to offer advantages over alternative methods including the finite element method. Projection methods are used to stabilize the time discretization while quasi-Newton methods (nonlinear solver) are shown to be more computationally efficient, as well. Specifically, solutions for two MI sensor element geometries are presented, which were validated against published experimental data. While the examples illustrated here are for MI sensors, the approach presented can also be extended to other weak-field sensors like fluxgate and Hall effect sensors.

Eason, Kwaku

308

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

309

The motion of an absolutely rigid body on a two-degrees-of-freedom joint in a uniform gravitational field  

Microsoft Academic Search

The motion of an absolutely rigid body attached to a fixed base by a two-degrees-of-freedom joint in a uniform gravitational field parallel to the fixed axis of the joint is studied qualitatively. Various kinds of motion are described and analysed, depending on the total mechanical energy and the projection of the angular momentum of the body onto the fixed axis

N. N Bolotnik

1995-01-01

310

A Measurement of the Deflection of 9.602-Ghz Radiation From 3C279 in the Solar Gravitational Field.  

National Technical Information Service (NTIS)

During its occultation by the sun in October 1969, the position of the radio source 3C279 was interferometrically monitored to determine the deviation of its 9.602-GHz radiation in the solar gravitational field. Rapid instrumental calibration and negligib...

G. A. Seielstad R. A. amek K. W. Weiler

1970-01-01

311

Nature of singularity formed by the gravitational collapse in Husain space-time with electromagnetic field and scalar field  

NASA Astrophysics Data System (ADS)

In this work, we have investigated the outcome of gravitational collapse in Husain space-time in the presence of electro-magnetic and a scalar field with potential. In order to study the nature of the singularity, global behavior of radial null geodesics have been taken into account. The nature of singularities formed has been thoroughly studied for all possible variations of the parameters. These choices of parameters has been presented in tabular form in various dimensions. It is seen that irrespective of whatever values of the parameters chosen, the collapse always results in a naked singularity in all dimensions. There is less possibility of formation of a black hole. Hence this work is a significant counterexample of the cosmic censorship hypothesis.

Debnath, Ujjal; Rudra, Prabir; Biswas, Ritabrata

2012-05-01

312

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

NASA Astrophysics Data System (ADS)

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 n ? M 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 3 R {5/4} with 1-dimensional fiber x 5 and 4-dimensional Minkowski space-time as a base is naturally interpreted as classical electrodynamics. Semi-Riemannian geometry 3 V {5/4} with the general relativity pseudo-Riemannian space-time 3 V 4, and 1-dimensional fiber x 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.

2009-05-01

313

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

314

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

315

On the incidence of weak magnetic fields in DA white dwarfs  

NASA Astrophysics Data System (ADS)

Context. About 10% of white dwarfs have magnetic fields with strength in the range between about 105 and 5 × 108 G. It is not known whether the remaining white dwarfs are not magnetic, or if they have magnetic fields too weak to be detected with the techniques adopted in the large surveys. Information is particularly lacking for the cooler (and generally fainter) white dwarfs. Aims: We describe the results of the first survey specifically devised to clarify the detection frequency of kG-level magnetic fields in cool DA white dwarfs. Methods: Using the FORS1 instrument of the ESO VLT, we have obtained Balmer line circular spectropolarimetric measurements of a small sample of cool (DA6 - DA8) white dwarfs. Using FORS and UVES archive data, we have also revised numerous white dwarf field measurements previously published in the literature. Results: We have discovered an apparently constant longitudinal magnetic field of ~9.5 kG in the DA6 white dwarf WD 2105-820. This star is the first weak-field white dwarf that has been observed sufficiently to roughly determine the characteristics of its field. The available data are consistent with a simple dipolar morphology with magnetic axis nearly parallel to the rotation axis, and a polar strength of ? 56 kG. Our re-evaluation of the FORS archive data for white dwarfs indicates that longitudinal magnetic fields weaker than 10 kG have previously been correctly identified in at least three white dwarfs. However, for one of these three weak-field stars (WD 2359-434), UVES archive data show a ~100 kG mean field modulus. Either at the time of the FORS observations the star's magnetic field axis was nearly perpendicular to the line of sight, or the star's magnetic field has rather complex structure. Conclusions: We find that the probability of detecting a field of kG strength in a DA white dwarf is of the order of 10% for each of the cool and hot DA stars. If there is a lower cutoff to field strength in white dwarfs, or a field below which all white dwarfs are magnetic, the current precision of measurements is not yet sufficient to reveal it. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under observing programme 073.D-0516, and obtained from the ESO/ST-ECF Science Archive Facility.Table 3 is available in electronic form at http://www.aanda.org

Landstreet, J. D.; Bagnulo, S.; Valyavin, G. G.; Fossati, L.; Jordan, S.; Monin, D.; Wade, G. A.

2012-09-01

316

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

317

Vibrational spectra of free and intracellular DNA in the weak electromagnetic field  

NASA Astrophysics Data System (ADS)

Vibrational bands of DNA molecules from birds' erythrocytes, as well as Dunaliella viridis alga cells and Escherichia coli bacteria clinical strains in the weak microwave field were investigated with IR spectroscopy. Drastic changes were detected in the intensities and fine structure of C equals O and PL2 bands for polarized spectra of irradiated samples of DNA molecules as compared with the reference samples in the 1700-1000 cm-1 region. No essential changes were detected in the IR spectra in the region of PO2 bands of DNA for the Escherichia coli, irradiated by the weak electromagnetic field, but essential redistribution of intensities and change in halfwidths of the PO2 symmetrical bonds were detected for Dunaliella viridis alga cells.

Dovbeshko, Galina I.

1998-09-01

318

Multiparameter investigation of gravitational slip  

SciTech Connect

A detailed analysis of gravitational slip, a new post-general relativity cosmological parameter characterizing the degree of departure of the laws of gravitation from general relativity on cosmological scales, is presented. This phenomenological approach assumes that cosmic acceleration is due to new gravitational effects; the amount of spacetime curvature produced per unit mass is changed in such a way that a universe containing only matter and radiation begins to accelerate as if under the influence of a cosmological constant. Changes in the law of gravitation are further manifest in the behavior of the inhomogeneous gravitational field, as reflected in the cosmic microwave background, weak lensing, and evolution of large-scale structure. The new parameter {pi}{sub 0} is naively expected to be of order unity. However, a multiparameter analysis, allowing for variation of all of the standard cosmological parameters, finds that {pi}{sub 0}=0.09{sub -0.59}{sup +0.74}(2{sigma}), where {pi}{sub 0}=0 corresponds to a cosmological constant plus cold dark matter universe under general relativity. Future probes of the cosmic microwave background (Planck) and large-scale structure (Euclid) may improve the limits by a factor of 4.

Daniel, Scott F.; Caldwell, Robert R. [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Cooray, Asantha; Serra, Paolo [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Melchiorri, Alessandro [Physics Department and Sezione INFN, University of Rome, 'La Sapienza', Piazzale Aldo Moro 2, 00185 Rome (Italy)

2009-07-15

319

Spectral form factor for chaotic dynamics in a weak magnetic field  

NASA Astrophysics Data System (ADS)

Using semiclassical periodic orbit theory for a chaotic system in a weak magnetic field, we obtain the form factor predicted by Pandey and Mehta's two matrix model up to the third order. The third order contribution has a peculiar term which exists only in the intermediate crossover domain between the GOE (Gaussian orthogonal ensemble) and the GUE (Gaussian unitary ensemble) universality classes. The exact expression is obtained by taking account of the contribution from encounter regions where orbit loops are connected.

Saito, Keiji; Nagao, Taro

2006-04-01

320

Weak field control of remanent magnetization changes produced by uniaxial stress cycling  

NASA Astrophysics Data System (ADS)

The effect of weak fields (˜0.01 mT.) upon the remanent magnetization of basalts, granodiorites and polycrystalline magnetite during uniaxial compression has been investigated. Samples carrying NRM and AF demagnetized NRM were used. The demagnetized samples showed the largest effects. In the low stress range of less than 100 bars, the influence of stress was demagnetization. In the absence of an applied field, the magnetization rotated away from the compression axis, as is commonly observed. However, with the application of a field of between .01 to .02 mT., the magnetization rotated into alignment with the field as stress was increased. AF demagnetization after the application of 1 kbar of load produced large and repeatable magnetization increases confined to a very narrow coercivity band. AF demagnetization to 10 mT. removed most of the stress induced remanence. These observations are explained in terms of enhanced remanence acquisition in the presence of stress. This reversible effect unblocks soft domain wall sections which can respond to weak applied fields, or to internal demagnetizing fields.

Lanham, M.; Fuller, M.

1988-05-01

321

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

322

Advances in Magnetic and Gravitational Potential Field Data in the Arctic  

NASA Astrophysics Data System (ADS)

Integration of Magnetics and Gravity in Northern Exploration (iMAGINE); Tromsø, Norway, 1-2 June 2010; Magnetic and gravitational potential field data are crucial components of regional tectonic framework studies and resource exploration in the Arctic. Special data acquisition difficulties at high latitudes include extreme weather conditions, ice-covered waters, and magnetic disturbances from the aurora borealis. Improved techniques in sub-ice, sub-salt, and sub-basalt exploration are required. The Integration of Magnetics and Gravity in Northern Exploration (iMAGINE) meeting (part of Arctic Days 2010) featured discussion of the most recent advances in potential field methods with particular attention to Arctic challenges. Presentations concentrated on regional interpretations in the Arctic Ocean, Barents Sea, Siberia, and northeastern Atlantic Ocean. Talks also touched on regional petroleum exploration and on the interpretation of weathered bedrock in Norway. In addition, a group of talks dealt with geomagnetic disturbances and their effect on magnetic data collection and in magnetic orientation for directional drilling.

Olesen, Odleiv; Saltus, Rick

2010-10-01

323

Surface electrostatic field below weak precipitation and stratiform regions of mid-latitude storms  

NASA Astrophysics Data System (ADS)

The electrostatic field is measured below thunderstorms at two sites in south-western France thanks to a field mill. It is recorded with a 1-s time resolution, simultaneously to the precipitation current measured with a specific sensor. The variations of both parameters are analyzed for two cases out of three storms considered in the study. Cloud-to-Ground (CG) lightning data from Météorage network and scans from a C-band radar included in the French network ARAMIS are used to characterize the storms. The magnitude of the electrostatic field can reach large values below the weak precipitation regions compared to the convective regions: between 5 and 6 kV m? 1, and between 2 and 3 kV m? 1, respectively. The field polarity is commonly negative (downward field) but it can reverse as the rainfall carries positive charge to the ground. So, the mirror effect is generally observed between the electrostatic field and the precipitation current. The electrostatic field magnitude can indicate the presence of large amounts of charge within the weak precipitation region above, although the lightning ground strokes remain relatively far. The fast field variations produced by CG flashes are analyzed. A strong dissymmetry for both CG polarities is observed: the + CG flashes can produce larger field discontinuities (~ 10 kV m? 1) even when their striking points are at about a distance of 40 km from the sensor, while the ? CG flashes produce discontinuities lower than 4 kV m? 1 even when the striking points are within 4 km around the sensor. This indicates that either the charge removed by a + CG flash can be horizontally displaced with respect to the ground stroke location, or it can be much larger compared to that removed by a negative CG flash. Our observations suggest the surface electrostatic field measured below these regions may provide valuable information for estimating local lightning risk.

Soula, S.; Georgis, J. F.

2013-10-01

324

Decay of a weakly bound level in a monochromatic electromagnetic field and a static magnetic field  

SciTech Connect

We consider an electron that is bound by a zero-range potential and a constant magnetic field and which becomes disturbed by a monochromatic laser beam with elliptical polarization. The exact solution of the Schroedinger equation for an electron in the presence of an arbitrary electromagnetic wave and a static magnetic field is obtained. Exact expressions have been found for the complex energy, whose real and imaginary parts yield the level position and the width of an electron in a zero-range force field, a constant magnetic field, and a monochromatic electromagnetic field. These expressions have been analyzed in details for the case of a circularly polarized laser light.

Rylyuk, V.M. [Department of Theoretical Physics, University of Odessa, Dvorjanskaja 2, 270100 Odessa (Ukraine); Ortner, J. [Institut fuer Physik, Humboldt Universitaet zu Berlin, Invalidenstrasse 110, 10115 Berlin (Germany)

2003-01-01

325

Short-wave limit of the gravitational focusing effect imposed by asphericity of the gravity field of the lens star  

SciTech Connect

At short wavelengths (visible light, x rays, ..gamma.. rays), the gravitational focusing effect will be significantly influenced by deviations of the gravitational field of the lens star from sphericity. The dependence of the lens amplification on the wavelength lambda of the electromagnetic wave and on the asphericity of the gravitational field is analyzed qualitatively. There is a limiting wavelength lambda/sub min/ below which asphericity effects become important. For a homogeneous model ellipsoid of revolution with a relative oblateness of 5 x 10/sup -5/, a gravitational radius r/sub g/=3 km, and a mean radius R=7 x 10/sup 5/ km, the limit will be lambda/sub min/approx. =5(R/l)/sup 2/ cm, where l=2r/sub g//(D/sub s//sup -1/ +D/sub p//sup -1/))/sup 1/2/ (D/sub s/, D/sub p/ are the distances from the lens to the source and the observer, respectively).

Minakov, A.A.

1978-09-01

326

Searching for Complex, Weak or Tangled Magnetic Fields in the Blue Supergiant Rigel  

NASA Astrophysics Data System (ADS)

Seventy-eight high-resolution Stokes V, Q and U spectra of the B8 Iae supergiant Rigel were obtained with the ESPaDOnS instrument at the CFHT, and its clone NARVAL at the TBL in the context of the Magnetism in Massive Stars (MiMeS) Large Program, with the aim of scrutinizing this core-collapse supernova progenitor for direct evidence of weak and/or complex magnetic fields. In this paper we describe the reduction and analysis of the data, the constraints obtained on any magnetic field present in the stellar photosphere, and the variability of photospheric and wind lines.

Shultz, M.; Wade, G. A.; Neiner, C.; Manset, N.; Petit, V.; Grunhut, J.; Guinan, E.; Hanes, D.; Mimes Collaboration

327

Searching for weak or complex magnetic fields in polarized spectra of Rigel  

NASA Astrophysics Data System (ADS)

Seventy-eight high-resolution Stokes V, Q and U spectra of the B8Iae supergiant Rigel were obtained with the ESPaDOnS spectropolarimeter at CFHT and its clone NARVAL at TBL in the context of the Magnetism in Massive Stars (MiMeS) Large Program, in order to scrutinize this core-collapse supernova progenitor for evidence of weak and/or complex magnetic fields. In this paper we describe the reduction and analysis of the data, the constraints obtained on any photospheric magnetic field, and the variability of photospheric and wind lines.

Shultz, Matthew; Wade, Gregg A.; Neiner, Coralie; Manset, Nadine; Petit, Véronique; Grunhut, Jason H.; Guinan, Edward; Hanes, David A.; Hanes

2011-07-01

328

Superconducting Film Flux Transformer for a Sensor of a Weak Magnetic Field  

NASA Astrophysics Data System (ADS)

The object of study is a superconducting film flux transformer in the form of a square shaped loop with the tapering operative strip used in a sensor of a weak magnetic field. The magnetosensitive film element based on the giant magnetoresistance effect is overlapped with the tapering operative strip of the flux transformer; it is separated from the latter by the insulator film. It is shown that the topological nanostructuring of the operative strip of the flux transformer increases its gain factor by one or more orders of magnitude, i.e. increases its efficiency, which leads to a significant improvement of important parameters of a magnetic-field sensor.

Ichkitidze, L.; Mironyuk, A.

2012-12-01

329

Collisionless kinetic equations for massive particles with spins 1/2 and 0 in gravitational and electromagnetic fields  

NASA Astrophysics Data System (ADS)

We define a covariant and gauge-invariant generalization of the Wigner functions of particles with spins 1/2 and 0. The collisionless kinetic equations are obtained for these particles in external gravitational and electromagnetic fields in the quasiclassical approximation; also obtained are the momentum representations of the energy-momentum tensor, current, and spin tensor, taking into account the effects of the spin's interaction with the gravitational field an electromagnetic field. The following notation is used: e and m are the charge and mass of the particles; is Planck's constant; ??(x) are the covariant-fixed Dirac matrices; ??,?=(1/4)[??, ??]: a(?b?)=(1/2) ( a ? b ? + a?b ?); [A, B]=A·B - B·A; A,B=A·B+B·A; g(x)=det( g ??( x)); R ? ???=???{??/??}-...; the speed of light c=1.

Fonarev, O. A.

1990-09-01

330

Sensitivity of calcium binding in cerebral tissue to weak environmental electric fields oscillating at low frequency.  

PubMed Central

Weak sinusoidal electric fields modify the calcium efflux from freshly isolated chick and cat cerebral tissues bathed in Ringer's solution, at 36 degrees. Following incubation (30 min) with radioactive calcium (45Ca2+), each sample, immersed in fresh solution, was exposed for 20 min to fields at 1, 6, 16, 32, or 75 Hz, with electric gradients of 5, 10, 56, and 100 V/m in air. 45Ca2+ efflux in the solution was then measured in 0.2 ml aliquots and compared with efflux from unexposed control samples. Field exposures resulted in a general trend toward a reduction in the release of the preincubated 45Ca2+. Both frequency and amplitude sensitivities were observed. Maximum decreases occurred at 6 and 16 Hz (12-15%). Thresholds were around 10 and 56 V/m for chick and cat tissues, respectively. Similar but nonsignificant trends occurred during other field exposures. All results were statistically compared with matched samples of controls. Tissue gradients could not be measured, but estimates were of the order of 0.1 muV/cm. The susceptibility of the electrochemical equilibrium in the neuronal membrane to small extracellular perturbations is discussed and a possible role for weak intrinsic cerebral fields in neuronal excitability is suggested. Images

Bawin, S M; Adey, W R

1976-01-01

331

Floating-zone growth of silicon in magnetic fields. I. Weak static axial fields  

Microsoft Academic Search

Silicon floating-zone experiments, employing P- and Sb-doped crystals of 8 mm diameter and zones of 10–12 mm length, were carried out in a mirror furnace under static axial magnetic fields (magnetic induction B ? 500 mT). A strong influence of the magnetic field on the formation of dopant striations could be detected: Whereas crystals grown without field show an irregular

P. Dold; A. Cröll; K. W. Benz

1998-01-01

332

Behavioral changes with brief exposures to weak magnetic fields patterned to stimulate long-term potentiation.  

PubMed

Brief whole body exposures of rats to weak (1 microT) complex magnetic fields whose patterns induce long term potential (LTP) when applied as electric current to hippocampal slices produced powerful behavioral changes. Rats exposed for 30 min before but not 30 min after hourly training sessions for spatial memory displayed impairments comparable to those elicited by complete electrode-induced saturation of hippocampal activity. Exposure to the same LTP-patterned magnetic fields after weaning during the induction of limbic seizures produced diminished learning of conditioned contextual fear during adulthood. However exposure to magnetic fields designed to simulate a "virtual" hippocampal state during acquisition of a timed inhibitory task (DRL) facilitated performance. These results show that physiologically-patterned magnetic fields can produce dramatic changes in behavior when they are applied during states associated with marked synaptic plasticity. PMID:19210956

Mach, Quoc Hao; Persinger, Michael A

2009-01-10

333

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

334

Experimental and Theoretical Investigations of the Interaction Between the ELF Earth Electromagnetic Field and the Gravitational Fields of Geophysical and Astrophysical Origin  

Microsoft Academic Search

While solving the main problem of the project related to the investigations of the interaction of the ELF electromagnetic fields in the atmosphere lower surface layer with the moon and solar tides and astrophysical gravitational and wave sources, a number of important results was got. In this direction the experimental and theoretical investigations got by the group of scientists of

Lubov V. Grunskaya; V. A. Efimov; V. V. Isakevich

2007-01-01

335

Analysis of network traffic flow dynamics based on gravitational field theory  

NASA Astrophysics Data System (ADS)

For further research on the gravity mechanism of the routing protocol in complex networks, we introduce the concept of routing awareness depth, which is represented by ?. On this basis, we define the calculation formula of the gravity of the transmission route for the packet, and propose a routing strategy based on the gravitational field of the node and the routing awareness depth. In order to characterize the efficiency of the method, we introduce an order parameter, ?, to measure the throughput of the network by the critical value of phase transition from free flow to congestion, and use the node betweenness centrality, B, to test the transmission efficiency of the network and congestion distribution. We simulate the network transmission performance under different values of the routing awareness depth, ?. Simulation results show that if the value of the routing awareness depth ? is too small, then the gravity of the route is composed of the attraction of very few nodes on the route, which cannot improve the capacity of the network effectively. If the value of the routing awareness depth ? is greater than the network's average distance , then the capacity of the network may be improved greatly and no longer change with the sustainable increment of routing awareness depth ?, and the routing strategy performance enters into a constant state. Moreover, whatever the value of the routing awareness depth ?, our algorithm always effectively balances the distribution of the betweenness centrality and realizes equal distribution of the network load.

Liu, Gang; Li, Yong-Shu; Zhang, Xi-Ping

2013-06-01

336

Light deflection in the postlinear gravitational field of bounded pointlike masses  

SciTech Connect

Light deflection in the postlinear gravitational field of two bounded pointlike masses is treated. Both the light source and the observer are assumed to be located at infinity in an asymptotically flat space. The equations of light propagation are explicitly integrated to the second order in G/c{sup 2}. Some of the integrals are evaluated by making use of an expansion in powers of the ratio of the relative separation distance to the impact parameter (r{sub 12}/{xi}). A discussion of which orders must be retained to be consistent with the expansion in terms of G/c{sup 2} is given. It is shown that the expression obtained in this paper for the angle of light deflection is fully equivalent to the expression obtained by Kopeikin and Schaefer up to the order given there. The deflection angle takes a particularly simple form for a light ray originally propagating orthogonal to the orbital plane of a binary with equal masses. Application of the formulas for the deflection angle to the double pulsar PSR J0737-3039 for an impact parameter 5 times greater than the relative separation distance of the binary's components shows that the corrections to the Epstein-Shapiro light deflection angle of about 10{sup -6} arcsec lie between 10{sup -7} and 10{sup -8} arcsec.

Bruegmann, Michael H. [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany)

2005-07-15

337

A Dust-Penetrated Classification Scheme for Bars as Inferred from their Gravitational Force Fields  

NASA Astrophysics Data System (ADS)

The division of galaxies into barred (SB) and normal (S) spirals is a fundamental aspect of the Hubble galaxy classification system. This tuning fork view was revised by de Vaucouleurs, whose classification volume recognized apparent bar strength (SA, SAB, SB) as a continuous property of galaxies called the ``family.'' However, the SA, SAB, and SB families are purely visual judgments that can have little bearing on the actual bar strength in a given galaxy. Until recently, published bar judgments were based exclusively on blue light images, where internal extinction or star formation can completely mask a bar. Near-infrared camera arrays, which principally trace the old stellar population in both normal and barred galaxies, now facilitate a quantification of bar strength in terms of gravitational potentials and force fields. In this paper, we show that the maximum value of the ratio of the tangential force to the mean axisymmetric radial force is a quantitative measure of the strength of a bar that can be straightforwardly derived for many galaxies. We show that a wide range of true bar strengths characterizes the category SB, while category SAB corresponds to a narrower range of bar strengths. Based on the force ratio, we define seven classes of bar strength and incorporate these classes into a dust-penetrated classification system for spiral galaxies. This work was supported by NSF grant AST 9617154 and the Anglo-American Chairman's Fund, Mrs. M. Keeton, CEO.

Buta, R.; Block, D. L.

2001-05-01

338

Damping of a plasma wave with trapped electrons in a weak transverse magnetic field  

SciTech Connect

A study is made of the time evolution of a Langmuir wave with trapped electrons in a weak magnetic field perpendicular to the wave propagation direction. The wave damping due to the acceleration of trapped electrons along the wave front under the action of a weak Lorentz force is investigated. The dynamics of the accelerated bunches of electrons bouncing in the potential wells of the wave is analyzed in the adiabatic approximation. Equations are derived that self-consistently describe the interaction of the wave with trapped electrons. In order for the description to be closed, the equations are supplemented with a nonlinear dispersion relation that accounts for the contribution of trapped electrons and determines the correction to the wave phase velocity. Various interaction regimes in the parameter space of the physical system are examined, and constraints under which the problem at hand has the simplest solutions are established.

Krasovsky, V. L. [Russian Academy of Sciences, Space Research Institute (Russian Federation)

2007-10-15

339

Travelling wave deceleration of heavy polar molecules in weak-field seeking states  

NASA Astrophysics Data System (ADS)

Electrostatic forces can be used to decelerate neutral molecules via the Stark interaction. Most Stark decelerators to date use switched dc electric fields to manipulate light molecules in weak field seeking states. More massive molecules have smaller rotational constants and greater kinetic energies at a given velocity, and would require very long decelerators to bring them to rest. We have combined a new cryogenic source of YbF molecules, based on a pulsed solenoid valve cooled to 4K, with a 48cm long travelling wave Stark decelerator that is suitable for decelerating heavy molecules in weak-field seeking states. This decelerator uses continuously modulated sinusoidal electric fields to produce a series of moving 3-dimensional traps that can be continuously slowed to decelerate the molecules within them. We have decelerated YbF molecules from 300m/s to 276m/s. This implies that a 3 metre long decelerator could produce trapped YbF molecules at rest. In a different configuration, our source produces broader pulses of YbF molecules with speeds of 200m/s or less that could be brought to rest with a decelerator that is just 1 metre in length.

Hendricks, Richard; Bulleid, Nicholas; Skoff, Sarah; Segal, Daniel; Sauer, Ben; Tarbutt, Michael; Hinds, Edward; Meek, Samuel; Osterwalder, Andreas; Parsons, Maxwell; Santambrogio, Gabriele; Meijer, Gerard

2012-06-01

340

Non-linear evolution of the elliptical instability in the presence of weak magnetic fields  

NASA Astrophysics Data System (ADS)

We investigate whether the elliptical instability is important for tidal dissipation in gaseous planets and stars. In a companion paper, we found that the conventional elliptical instability results in insufficient dissipation because it produces long-lived vortices that then quench further instability. Here, we study whether the addition of a magnetic field prevents those vortices from forming, and hence leads to enhanced dissipation. We present results from magnetohydrodynamic simulations that evolve the elliptical instability in a local patch of a rotating planet or star, in the presence of a weak magnetic field. We find that magnetic fields do indeed prevent vortices from forming, and hence greatly enhance the steady-state dissipation rate. In addition, the resulting turbulence acts as a small-scale dynamo, amplifying the initially weak field. The inferred tidal dissipation is potentially important at short orbital periods. For example, it can circularize hot Jupiters with orbital periods shorter than 2.5 d and synchronize their spins with their orbits out to 6 d. However, it appears unable to account for the hot Jupiters that appear to have been circularized out to 6-10 d orbital periods. It also cannot account for the inferred circularization of many close binary stars.

Barker, Adrian J.; Lithwick, Yoram

2013-10-01

341

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

1996-12-31

342

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

343

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

344

Continuous weak measurement of a trapped electron using a percolation field effect transistor  

NASA Astrophysics Data System (ADS)

We investigate the use of a percolation-field-effect-transistor for the continuous weak measurement of a spatially Rabi oscillating trapped electron through the change in percolation pathway of the transistor channel. In contrast to conventional devices, this detection mechanism in principle does not require a change in the stored energy of the gate capacitance to modify the drain current, so reducing the measurement back-action. The signal-to-noise ratio and measurement bandwidth are seen to be improved compared to conventional devices, allowing further aspects of the dynamic behaviour to be observed.

Fleming, S.; Milne, W. I.; Hasko, D. G.

2013-08-01

345

Detection of weak signals through nonlinear relaxation times for a Brownian particle in an electromagnetic field.  

PubMed

The detection of weak signals through nonlinear relaxation times for a Brownian particle in an electromagnetic field is studied in the dynamical relaxation of the unstable state, characterized by a two-dimensional bistable potential. The detection process depends on a dimensionless quantity referred to as the receiver output, calculated as a function of the nonlinear relaxation time and being a characteristic time scale of our system. The latter characterizes the complete dynamical relaxation of the Brownian particle as it relaxes from the initial unstable state of the bistable potential to its corresponding steady state. The one-dimensional problem is also studied to complement the description. PMID:21867143

Jiménez-Aquino, J I; Romero-Bastida, M

2011-07-25

346

Weak-field, multiple-cycle carrier envelope phase effects in laser excitation.  

PubMed

Although the absolute or carrier envelope phase (CEP) of a laser pulse is usually assumed to be effective for ultrashort and/or ultrastrong pulses only, it is demonstrated that these limitations can eventually be removed. Therefore, the excitation of a model positively charged homonuclear diatomic molecule, in which four electronic states are coupled by the laser field, is studied. In an initial step, nuclear wave packets in two dissociative states are prepared. Upon reaching the fragment channel, a weak pulse interacts with the system and prepares CEP-dependent asymmetries associated with electron density localized on one or the other fragmentation product. PMID:23436555

Renziehausen, Klaus; Hader, Kilian; Jakubetz, Werner; Engel, Volker

2013-02-21

347

Optical orientation of Mn2+ ions in GaAs in weak longitudinal magnetic fields.  

PubMed

We report on optical orientation of Mn2+ ions in bulk GaAs subject to weak longitudinal magnetic fields (B?100??mT). A manganese spin polarization of 25% is directly evaluated by using spin-flip Raman scattering. The dynamical Mn2+ polarization occurs due to the s-d exchange interaction with optically oriented conduction band electrons. Time-resolved photoluminescence reveals a nontrivial electron spin dynamics, where the oriented Mn2+ ions tend to stabilize the electron spins. PMID:21561222

Akimov, I A; Dzhioev, R I; Korenev, V L; Kusrayev, Yu G; Sapega, V F; Yakovlev, D R; Bayer, M

2011-04-05

348

Binomial states and the phase distribution measurement of weak optical fields  

SciTech Connect

We show that the eight-port interferometer used by Noh, Fougeres, and Mandel [Phys. Rev. Lett. 71, 2579 (1993)] to measure their operational phase distribution of light can also be used to measure the canonical phase distribution of weak optical fields, where canonical phase is defined as the complement of photon number. A binomial reference state is required for this purpose, which we show can be obtained to an excellent degree of approximation from a suitably squeezed state. The proposed method requires only photodetectors that can distinguish among zero photons, one photon, and more than one photon and is not particularly sensitive to photodetector imperfections.

Pregnell, K. L.; Pegg, D. T. [Center for Quantum Computer Technology, School of Science, Griffith University, Nathan, Brisbane 4111, (Australia)

2003-06-01

349

Developmental effects of physiologically weak electric fields and heat: an overview.  

PubMed

This study summarizes the possible effects on prenatal development of physiologically weak electric fields induced in the body by exposure to extremely low frequency (ELF) electromagnetic fields and of elevated temperature levels that might result from exposure to radiofrequency (RF) radiation. Both topics have been discussed at recent international workshops organized by WHO in collaboration with other bodies. Mammalian development is characterized by a highly ordered sequence of cell proliferation and differentiation, migration, and programmed cell death. These processes, particularly proliferation and migration, are susceptible to a variety of environmental agents including raised maternal temperature. In addition, there is growing evidence that physiologically weak endogenous DC electric fields and ionic currents have a role in guiding developmental processes, including cell orientation and migration, by establishing electrical potential gradients. Disruption of these fields can adversely affect development in amphibian and bird embryos, which are experimentally accessible, and may well do so in mammalian embryos. The extent to which induced ELF electric fields might influence these and other processes that take place during prenatal development, childhood, and adolescence is less clear. Organogenesis, which takes place primarily during the embryonic period, is susceptible to raised maternal temperatures; a large number of studies have shown that RF exposure produces developmental effects that can be attributed to heat. The development of the central nervous system is particularly susceptible to raised temperatures; a reduction in brain size, which results in a smaller head, is one of the most sensitive markers of heat-induced developmental abnormalities and can be correlated with heat-induced behavioral deficits. However, some aspects of CNS development have been less well explored, particularly effects on corticogenesis. In addition, the persistence of CNS developmental sensitivity through to childhood and adolescence is not clear. PMID:15931677

Saunders, Richard D; McCaig, C D

2005-01-01

350

Twee-Dimensionale Fourieranalyse van Het Aardse Zwaartekrachtsveld Gebruikmakend van Het Programmapakket TIM (Two Dimensional Fourier Analysis of the Earth Gravitational Field Using the Program Package TIM).  

National Technical Information Service (NTIS)

The program package TIM for image processing was used for spectral analysis, in particular of the earth gravitational field. Fourier analysis using TIM is described. The multiplication and scaling factors have to be handled very carefully to calculate the...

J. G. A. Jansen

1989-01-01

351

Reorientation of Seedlings in the Earth's Gravitational Field Induces Cytosolic Calcium Transients1  

PubMed Central

The gravitational field controls plant growth, morphology, and development. However, the underlying transduction mechanisms are not well understood. Much indirect evidence has implicated the cytoplasmic free calcium concentration ([Ca2+]c) as an important factor, but direct evidence for changes in [Ca2+]c is currently lacking. We now have made measurements of [Ca2+]c in groups of young seedlings of Arabidopsis expressing aequorin in the cytoplasm and reconstituted in vivo with cp-coelenterazine, a synthetic high-affinity luminophore. Distinct [Ca2+]c signaling occurs in response to gravistimulation with kinetics very different from [Ca2+]c transients evoked by other mechanical stimuli (e.g. movement and wind). [Ca2+]c changes produced in response to gravistimulation are transient but with a duration of many minutes and dependent on stimulus strength (i.e. the angle of displacement). The auxin transport blockers 2,3,5-tri-iodo benzoic acid and N-(1-naphthyl) phthalamic acid interfere with gravi-induced [Ca2+]c responses and addition of methyl indole-3-acetic acid to whole seedlings induces long-lived [Ca2+]c transients, suggesting that changes in auxin transport may interact with [Ca2+]c. Permanent nonaxial rotation of seedlings on a two-dimensional clinostat, however, produced a sustained elevation of the [Ca2+]c level. This probably reflects permanent displacement of gravity-sensing cellular components and/or disturbance of cytoskeletal tension. It is concluded that [Ca2+]c is part of the gravity transduction mechanism in young Arabidopsis seedlings.

Plieth, Christoph; Trewavas, Anthony J.

2002-01-01

352

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

353

Repeated naloxone treatments and exposures to weak 60-Hz magnetic fields have 'analgesic' effects in snails.  

PubMed

Results of studies with rodents have shown that animals repeatedly injected with the opioid antagonist, naloxone, acquire a hypoalgesic response to thermal nociceptive stimuli. The present study revealed a similar response in the terrestrial pulmonate snail, Cepaea nemoralis. Snails receiving daily injections of naloxone followed by measurements of thermal nociceptive sensitivity also developed hypoalgesia. Daily brief (30-min) exposures to a weak 60-Hz magnetic field (1.0 gauss or 0.1 mT), which acutely antagonize opioid-mediated nociception and antinociception in a manner comparable to that of naloxone, also led to the expression of a hypoalgesic responses. This suggests that opioid antagonist-induced thermal hypoalgesia may be a basic feature of opioid systems. This naloxone- and magnetic field-induced 'analgesia' is consistent with either a facilitation of aversive thermal conditioning and or antagonism of the excitatory, hyperalgesic effects of low levels of endogenous opioids. PMID:8402190

Kavaliers, M; Ossenkopp, K P

1993-08-20

354

Evolution of a Langmuir wave in a weakly inhomogeneous plasma in a longitudinal electric field  

SciTech Connect

The spatial evolution of a Langmuir wave excited by external sources in a weakly inhomogeneous electron plasma in a longitudinal electrostatic field is considered. It is shown that, in a longitudinal electrostatic field, a Langmuir wave can only be amplified in an inhomogeneous plasma provided that the current of trapped electrons exceeds that of untrapped electrons. In this case, as the wave propagates through the inhomogeneous region where its phase velocity increases, some untrapped electrons become trapped in the wave potential wells. As a result, the current of trapped electrons increases and the wave is amplified. Moreover, in the regions where the bulk electrons are localized, the minima of the wave are amplified to a greater extent than its maxima.

Matveev, A. I. [South Federal University, Institute of Technology (Russian Federation)

2008-02-15

355

Constraining weak intergalactic magnetic fields: prospects for the Cherenkov Telescope Array  

NASA Astrophysics Data System (ADS)

In recent years the possibility of constraining weak intergalactic magnetic fields (IGMFs) has emerged through simultaneous spectral observations of blazars at very high energies (VHE) utilizing data from the Fermi Gamma Ray Space Telescope and the ground-based imaging atmospheric Cherenkov Telescopes (IACTs). In this submission we explore the capabilities of Fermi and CTA to advance such studies through the potential detection of gamma-ray halos around AGN and detection of delayed VHE radiation decaying after intense VHE flares of Flat Spectrum Radio Quasars (FSRQs), which have recently been observed from such astrophysical objects. CTA will be an effective tool for constraining the properties of the IGMF, due to its vastly increased collecting area, improved angular resolution, and wide field of view, all of which enhance its capability for the study of VHE transients and astrophysical source morphology.

Vassiliev, Vladimir; Arlen, Timothy

2012-07-01

356

Enhancing weak magnetic fabrics using field-impressed anisotropy: application to the Chinese loess  

NASA Astrophysics Data System (ADS)

The anisotropy of the low-field magnetic susceptibility (AMS), alternating-field-treated AMS (AF-AMS), and anisotropy of anhysteretic remanent magnetization (AARM) have been systematically examined for a sandwich sequence of loess/palaeosols crossing the upper loess unit L2 (Marine Oxygen Isotope Stage 6, MIS6) to the last interglacial maximum (palaeosol unit S1S3, MIS5e) from the Yuanbao section, northwestern China. Results show that a weak, but detectable, magnetic lineation is controlled by coarse-grained aeolian Fe3O4 (magnetite). Because the long axes of the coarse-grained magnetites are statistically parallel to the palaeowind directions, the declination of the maximum susceptibility principal axis of AMS can be used as an indicator of palaeowind direction. In contrast, fine-grained pedogenic magnetic particles are responsible for the magnetic foliation. We found that AF-AMS can indicate the domain state of the magnetic particles, which is consistent with Potter & Stephenson's earlier model. We also found that AF demagnetization can significantly alter the AMS. In conclusion, the angular dependence of AF-AMS can enhance the weak AMS fabrics.

Liu, Qingsong; Yu, Yongjae; Deng, Chenglong; Pan, Yongxin; Zhu, Rixiang

2005-08-01

357

Gravitation electromagnetic theory  

NASA Astrophysics Data System (ADS)

The interrelationship existing between gravitation and electromagnetism is examined. A brief summary of the ideas which have guided scientific thought toward an understanding of gravitation is presented. The development of the electromagnetic theory is presented. The effects of the action of electromagnetic fields on the gravitational interactions are shown. On one side is, the explanation of various important cosmological phenomena, and on the other side, the path to control the gravitational interaction, which will foster the advent of gravitational propulsion, the foundations of which are established. The implications of this theory to the biological field are explored. In this field, the local control of gravitation opens the way to the study of the biological processes under several different conditions of gravity, which, in turn, may bring forth important results in biological research.

Deaquino, Fran

1988-03-01

358

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

359

Search for gravitational lens candidates in the XMM-LSS/CFHTLS common field  

NASA Astrophysics Data System (ADS)

Our aim was to identify gravitational lens candidates among some 5500 optical counterparts of the X-ray point-like sources in the medium-deep ˜11 deg2 XMM-LSS survey. We have visually inspected the optical counterparts of each QSOs/AGN using CFHTLS T006 images. We have selected compact pairs and groups of sources which could be multiply imaged QSO/AGN. We have measured the colours and characterized the morphological types of the selected sources using the multiple point spread function fitting technique. We found three good gravitational lens candidates: J021511.4-034306, J022234.3-031616 and J022607.0-040301 which consist of pairs of point-like sources having similar colours. On the basis of a colour-colour diagram and X-ray properties we could verify that all these sources are good QSO/AGN candidates rather than stars. Additional secondary gravitational lens candidates are also reported.

Elyiv, A.; Melnyk, O.; Finet, F.; Pospieszalska-Surdej, A.; Chiappetti, L.; Pierre, M.; Sadibekova, T.; Surdej, J.

2013-10-01

360

Rotating gravitational waves  

NASA Astrophysics Data System (ADS)

We present a cylindrically symmetric solution of the gravitational field equations which describes the propagation of rotating gravitational waves in empty space. The radiation field can be represented as a superposition of incoming and outgoing waves. The singularities of the rotating waves are examined and their significance for the speed-of-light catastrophe is discussed.

Mashhoon, Bahram; Quevedo, Hernando

1990-12-01

361

Excitation of parasitic waves in forward-wave amplifiers with weak guiding fields  

NASA Astrophysics Data System (ADS)

To produce high-power coherent electromagnetic radiation at frequencies from microwaves up to terahertz, the radiation sources should have interaction circuits of large cross sections, i.e., the sources should operate in high-order modes. In such devices, the excitation of higher-order parasitic modes near cutoff where the group velocity is small and, hence, start currents are low can be a serious problem. The problem is especially severe in the sources of coherent, phase-controlled radiation, i.e., the amplifiers or phase-locked oscillators. This problem was studied earlier [Nusinovich, Sinitsyn, and Antonsen, Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.82.046404 82, 046404 (2010)] for the case of electron focusing by strong guiding magnetic fields. For many applications it is desirable to minimize these focusing fields. Therefore in this paper we analyze the problem of excitation of parasitic modes near cutoff in forward-wave amplifiers with weak focusing fields. First, we study the large-signal operation of such a device with a signal wave only. Then, we analyze the self-excitation conditions of parasitic waves near cutoff in the presence of the signal wave. It is shown that the main effect is the suppression of the parasitic wave in large-signal regimes. At the same time, there is a region of device parameters where the presence of signal waves can enhance excitation of parasitic modes. The role of focusing fields in such effects is studied.

Nusinovich, G. S.; Romero-Talamás, C. A.; Han, Y.

2012-12-01

362

Spectroscopy of barium 6p1/2nk autoionizing states in a weak electric field  

NASA Astrophysics Data System (ADS)

We have studied the Ba 6p1/2nk, n=17, 5?k?n-1 Stark autoionizing states by isolated core excitation (ICE) of the Ba 6snk Stark bound states in very weak electric fields, an unexplored regime. In zero field the broad ?=5 state overlaps all the higher ? states, and in fields less than ˜12 V/cm the Stark states composed of the ?>5 states are within the zero-field width of the nh state. In the ICE spectra the strongest transition from the 6snk Stark state is to the 6p1/2nk Stark state, and shake-up satellite transitions are observed to higher-lying Stark states but not to lower-lying Stark states, a phenomenon which we attribute to the fact that the two Stark manifolds are both incomplete and different. The observed spectra can be described by treating the 6p1/2nk Stark states, composed of the ?>5 states, as discrete states embedded in a continuum, the broad 6p1/2nh state.

Nunkaew, J.; Gallagher, T. F.

2012-07-01

363

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 150Gauss (G)) alternating magnetic field (AMF) of extremely low frequency (ELF, fM=50Hz). 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

2013-09-03

364

Increased theta activity in quantitative electroencephalographic (QEEG) measurements during exposure to complex weak magnetic fields.  

PubMed

Previous research has shown that exposure to circumcerebral weak magnetic fields with different rates of acceleration applied in a counterclockwise rotation around the head was associated with increased estimations of subjective time and as much as a 30% increase in power within the theta range within quantitative electroencephalographic (QEEG) recordings. The largest effect was associated with magnetic fields applied with 20 ms rates of change through each of the successively stimulated, equally spaced, 8 circumcerebral solenoids. The purpose of the present study was to compare the intracerebral power spectra associated with the rotation of the same patterns in either the clockwise or counterclockwise direction. The results generally replicated previous reports and showed enhanced power over regions of the left hemisphere during clockwise rotations and over the right hemisphere during counterclockwise rotations. These results were considered congruent with the creation of "interference patterns" between the rostral-caudal generation of endogenous cerebral magnetic fields putatively associated with consciousness and the spatial direction of the applied rotating magnetic fields. PMID:19037792

Booth, J N; Koren, S A; Persinger, M A

2008-01-01

365

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

366

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

Microsoft Academic Search

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

K. H. C. Castello-Branco; A. G. Martins

2010-01-01

367

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

368

Mean-Field Modeling of the Encapsulation of Weakly Acidic Particles in Polyelectrolyte Dendrimers  

NASA Astrophysics Data System (ADS)

The unique architecture of dendrimers has attracted interest in a wide-variety of biomedical applications such as drug delivery. Dendrimers act as covalent micelles and have been shown experimentally to internalize hydrophobic molecules inside their cavities. Moreover, many drugs of low water solubility are weakly acidic and have been shown to form complexes with polybasic dendrimers, with the encapsulation ability being dependent upon the solution pH. Furthermore, the grafting of neutral water soluble chains such as polyethylene glycol (PEG) have shown to increase the encapsulation of poorly soluble drug molecules. In order to gain insight into the equilibrium behavior of drug-dendrimer complexes, we have developed and numerically solved a Self-Consistent Field Theory approach for both grafted and non-grafted annealed charged dendrimer molecules in the presences of drug molecules. Specifically, this work examines the effect of drug size, dendrimer generation, grafting chain length, and solution pH upon dendrimer encapsulation abilities.

Lewis, Thomas; Ganesan, Venkat

2012-02-01

369

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

NASA Astrophysics Data System (ADS)

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

2013-07-01

370

Gravitational-wave astronomy  

Microsoft Academic Search

Like Maxwell's equations for electromagnetic waves, Einstein's field equations have radiative solutions involving gravitational waves. These waves in the curvature of space-time exist in all theories of gravity, and in Einstein's formulation they propagate at the speed of light. Gravitational waves are produced by accelerated mass-energy. Attention is given to waves in space-time, the sources of gravitational waves, compact binaries,

J. A. Tyson; R. P. Giffard

1978-01-01

371

Gravitation and Experiment.  

National Technical Information Service (NTIS)

The present lectures adopt, as systematically as possible, a field-theory approach to gravitation and try to summarize what are the present experimental constraints on any field-theoretical description of gravity. Beyond giving a catalog of existing, and ...

T. Damour

1993-01-01

372

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

373

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

374

Hanle effect in the solar Ba II D2 line: a diagnostic tool for chromospheric weak magnetic fields  

Microsoft Academic Search

Context: The physics of the solar chromosphere depends in a crucial way on its magnetic structure. However there are presently very few direct magnetic field diagnostics available for this region. Aims: Here we investigate the diagnostic potential of the Hanle effect on the Ba II D2 line resonance polarization for the determination of weak chromospheric turbulent magnetic fields. Methods: The

M. Faurobert; M. Derouich; V. Bommier; J. Arnaud

2009-01-01

375

Mean-field analysis of the super weak ferrimagnetism of strongly coupled paramagnetic systems: II  

NASA Astrophysics Data System (ADS)

We reconsider here the so-called super weak ferrimagnetism problem, arising from two strongly coupled paramagnetic sublattices, of Pauli or Curie-Weiss type, within a continuous Landau model. The parameters of the model are the absolute temperature T, the applied magnetic field H, the coupling C between the two sublattices, and two coupling constants b and B that traditionally multiply the quartic terms in magnetic moments relatively to the sublattices in the free energy. We first show that when the ratio ? = b/B < 1, the system can exhibit a compensation point. Second, we give the various curves of the magnetization versus T (H = 0), in the space of thermodynamic parameters T, C, b and B. Within the framework of this model, the classification of these curves is found to be in agreement with the classical one of Néel. We identify some temperature T, above which the hysteresis phenomena is absent, and give its explicit dependence on the coupling C. We also investigate the shape of the Arrott diagram, within the parameter space, and we deduce various curves of the magnetization versus H (for fixed T and C). In the low temperature regime (ferrimagnetic phase) and for systems exhibiting a positive compensation point, we show the existence of some characteristic field H1, termed compensation magnetic field at which the overall magnetization vanishes. It is found that this latter is negative for H < H1 and becomes positive for strong fields H > H1. Our results are found to be in good qualitative agreement with recent experiments on lamellar Curie-Weiss paramagnetic compounds like LiNi1-xCoxO2 (0 <= x < 1). This work must be considered as a natural extension of our earlier work which dealt with the critical behavior near the para-ferrimagnetic transition within these systems.

Benhamou, M.; El Houari, B.

1997-08-01

376

Phase transitions and perfectness of fluids in weakly coupled real scalar field theories  

NASA Astrophysics Data System (ADS)

We calculate the ratio ?/s, the shear viscosity (?) to entropy density (s), which characterizes how perfect a fluid is, in weakly coupled real scalar field theories with different types of phase transitions. The mean-field results of the ?/s behaviors agree with the empirical observations in atomic and molecular systems such as H2O, He, N, and all the matters with data available in the NIST database. These behaviors are expected to be the same in N component scalar theories with an O(N) symmetry. We speculate these ?/s behaviors are general properties of fluid shared by QCD and cold atoms. Finally, we clarify some issues regarding counterexamples of the conjectured universal bound ?/s?1/4? found in Refs. [T.D. Cohen, Phys. Rev. Lett. 99 (2007) 021602, hep-th/0702136; A. Cherman, T.D. Cohen, P.M. Hohler, arXiv: 0708.4201 [hep-th]; A. Dobado, F.J. Llanes-Estrada, Eur. Phys. J. C 51 (2007) 913, hep-th/0703132

Chen, Jiunn-Wei; Huang, Mei; Li, Yen-Han; Nakano, Eiji; Yang, Di-Lun

2008-12-01

377

Dark matter gravitational interactions  

Microsoft Academic Search

We argue that the conjectured dark matter in the Universe may be endowed with a new kind of gravitational charge that couples via a short-range gravitational interaction mediated by a massive vector field. A model is constructed that assimilates this concept into ideas of current inflationary cosmology. The model is also consistent with the observed behaviour of galactic rotation curves

Robin W. Tucker; Charles Wang

1998-01-01

378

On the connection between the kinetic drumhead model and the Cahn-Hilliard equation in the presence of a gravitational field  

NASA Astrophysics Data System (ADS)

The equation of motion for an interface in the presence of a gravitational field is considered, when the order parameter is conserved. The kinetic drumhead model is derived directly from the Cahn-Hilliard equation without recourse to the drumhead free energy. We append a systematic derivation of the drumhead free-energy functional for the interface in a nonuniform external field.

Shiwa, Y.

1988-02-01

379

Relativistic deflection of radio signals in the solar gravitational field measured with VLBI  

NASA Astrophysics Data System (ADS)

For an observer on Earth the general theory of relativity (GR) predicts an apparent outward displacement of a star seen at the Sun's limb of 1.75 arc s. A generalized formulation for gravitational deflection of light includes a parameter ? which ranges from 1 (GR) to -1 (no deflection). Radio interferometer measurements of deflections of extragalactic objects have all been consistent with GR with increasing accuracy. The authors report the most sensitive measurement of deflection so far achieved, in which very long baseline interferometry (VLBI) observations yield a value of ? of 1.008 with a 1 ? formal standard error of ±0.005.

Robertson, D. S.; Carter, W. E.

1984-08-01

380

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.

381

Magnetic field value in the weak energy release region of the solar corona  

SciTech Connect

Spectrographic data from observations of the polarized weak steplike (with relatively sharp growth t {approximately} 3 sec and slow decay t {approximately} 10{sup 2} sec) solar continuum radioemission are analyzed below. The main results are found using a sweeping spectrograph in the 8-12 GHz frequency range (sweep rate 1 sample per second and frequency resolution 120 MHz) and using the RT-22 radio telescope at the Crimean Astrophysical Observatory (angular resolution 4{prime}-6{prime}). In a series of events at the leading edge of the continuum a narrow-band frequency drifting emission termed {open_quotes}blip-type{close_quotes} is found. The degree of continuum circular polarization (p < 10%) is low compared to that of the narrow-band component (p {approx} 20%). Both components of the aforementioned events should be radiating on the second harmonic of the local plasma frequency in the context of a plasma generating mechanism. Based on the model proposed and using the observed degree of circular polarization of each component, we can estimate the strength of the magnetic field within the area of the source and the width of the angular spectrum from the radiating plasma turbulence. The results of analysis of the real microwave events are given below.

Levin, B.N.; Fridman, V.M.; Sheiner, O.A. [Radiophysical Research Institute, Novgorod (Russian Federation)

1995-01-01

382

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

383

Resource Letter GL-1: Gravitational Lensing  

NASA Astrophysics Data System (ADS)

This Resource Letter provides a guide to a selection of the literature on gravitational lensing and its applications. Journal articles, books, popular articles, and websites are cited for the following topics: foundations of gravitational lensing, foundations of cosmology, history of gravitational lensing, strong lensing, weak lensing, and microlensing.

Treu, Tommaso; Marshall, Philip J.; Clowe, Douglas

2012-09-01

384

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

385

On the local properties of the 'Metric Tensor' GMU nu of the unified matrix theory of gravitation, electromagnetism and the Yang-Mills field  

NASA Astrophysics Data System (ADS)

The vierbeins and the generalized gamma-matrices associated to a modification and extension of Einstein's nonsymmetric field theory which includes the gravitational, electromagnetic and Yang-Mills fields are determined. The vierbein associated to the exact spherically symmetric solution of the unified field equations without Yang-Mills field is determined. Some algebraic properties of the unified matrix tensor Gmu nu are discussed. A generalization of this formalism involving octonions is proposed.

Oliveira, C. G.

1980-03-01

386

Stress field in the middle part of Kyushu, Japan and detecting weak zone in the crust  

NASA Astrophysics Data System (ADS)

In the upper crust of Kyushu district, Japan, an area with high seismic activity is found in the middle part. This area is called Beppu-Shimabara graben because of existence many normal faults in this region. Many active volcanoes exist (i.e. Unzen, Aso, Kuju, Beppu), and historical large earthquakes occurred in this region. However, it is not always confirmed whether this region behave as a graben formation or not from other evidence. In addition, there is an active fault system at the south of the graben. The name of this is ‘Futagawa-Hinagu Fault system'. The seismicity along the fault is highest among parts of Kyushu. The major mechanism of earthquakes around the system is strike slip type. Peoples is concerning with occurrence of large earthquake on the fault. Generally, extensional (minimum principal) stress is in north-south direction in Kyushu. Only direction of maximum principal stress changes region to region. It is key to understand interaction between this fault system and Beppu-Shimabara graben for probability evaluation of earthquake occurrence on the fault. Recently, Nakao et al. (2005) estimated spatial distribution of strain rate field in Kyushu area from GPS data. The area in which higher strain rate dominates not in extension but share is found in Beppu-Shimabara graben. This can explain high seismic activity in this region. They also revealed notable contraction in east-west appear around Aso volcano. High strain rate can be seen around Aso volcano. On the other hand, information about stress field is also important to understand deformation of the crust. Elastic and anelastic feature of crust could be inferred from both of stress and strain field. We performed stress tensor inversion by using polarity data of first motion at direct P wave arrival. Directions of principal stresses are obtained at spatially distributed grid points every 20 km interval. At each grid point, we collected polarity data of events occurred nearer than 10 km apart from grid point and carried out the stress tensor inversion. The minimum axes of the principal stress are generally oriented in NNW-SSE direction. The maximum axes are almost in WSW-ENE direction. The stress rates are greater than 0.75 at most of the point, implying the maximum stress is close to the moderate principal value. The maximum stresses in Beppu-Shimabara graben incline toward vertical direction while those have direction in east-west at most of points. It implies normal faulting would dominantly occur in Beppu-Shimabara graben. In addition, the minimum axes in the graben rotate counterclockwise. This stress field change requires a mechanism either relaxing the stress in east west direction or vertically loading in this region. Strain rate field by GPS observation also show the similar pattern and support the existence of the relaxing mechanism. This could be interpreted by existence a ‘weak body' in the crust. The area would be contracted by regional stress field. This could explain the strain rate distribution. And stress in east-west could be relaxed so that second principal stress in vertical direction would be maximum one. This simple model is qualitatively reasonable as an explanation for the results. For further study, variation of stress field in vertical direction should be discussed in detail.

Matsumoto, Satoshi; Nakao, Shigeru; Saiga, Atsushi; Shimizu, Hiroshi; Uehira, Kenji; Matsushima, Takeshi

2010-05-01

387

Disk accretion in the gravitational field of a rapidly rotating neutron star with a rotationally induced quadrupole mass distribution  

NASA Astrophysics Data System (ADS)

We analyze the effect of the quadrupole component in the mass distribution of a rapidly rotating neutron star on the energy release in the equatorial (or boundary) layer on the surface of the accreting star and in the accretion disk in the cases where the stellar radius is smaller (or larger) than the radius of the last stable circular orbit. We calculate the velocities and trajectories of the particles that fall on the stellar surface from the marginally stable orbit for a low-luminosity accreting source. The corresponding external gravitational field of the star is modeled by a new exact solution of the Einstein equations in vacuum. The parameters of this solution are adjusted by reconciling the numerical data for the radius of the marginally stable orbit and the gravitational redshift of Cook et al. (1994) with the corresponding data in the analytical solution. For various equations of state, we consider 1.4M_solar normal sequences and maximum-mass normal sequences which become unstable in the static limit.

Sibgatullin, N. R.; Sunyaev, R. A.

1998-11-01

388

Gravitational effects of traveling waves along global cosmic strings  

SciTech Connect

Making use of the relationship between the corresponding field configurations, we derive the metric around a straight global cosmic string with traveling waves in terms of the static metric (without traveling waves) in the weak-field limit. We discuss under which conditions the effect of the traveling waves may overcome the repulsive gravitational potential of the static straight global string. We also extend the calculation beyond the weak-field limit combining our result with the recent observation made by Garfinkle and Vachaspati that the exact solution must be of the generalized Kerr-Schild type.

Economou, A. (Fakultaet fuer Physik der Universitaet Konstanz, Postfach 5560, D 7750 Konstanz (Germany)); Harari, D. (Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)); Sakellariadou, M. (Universite Libre de Bruxelles, RGGR, Faculte des Sciences, CP231, B 1050 Bruxelles (Belgium))

1992-01-15

389

Relativistic theory of gravitation  

SciTech Connect

In the present paper a relativistic theory of gravitation (RTG) is unambiguously constructed on the basis of the special relativity and geometrization principle. In this a gravitational field is treated as the Faraday--Maxwell spin-2 and spin-0 physical field possessing energy and momentum. The source of a gravitational field is the total conserved energy-momentum tensor of matter and of a gravitational field in Minkowski space. In the RTG the conservation laws are strictly fulfilled for the energy-moment and for the angular momentum of matter and a gravitational field. The theory explains the whole available set of experiments on gravity. By virtue of the geometrization principle, the Riemannian space in our theory is of field origin, since it appears as an effective force space due to the action of a gravitational field on matter. The RTG leads to an exceptionally strong prediction: The universe is not closed but just ''flat.'' This suggests that in the universe a ''missing mass'' should exist in a form of matter.

Logunov, A.A.; Mestvirishvili, M.A.

1986-01-01

390

Conformal invariance and the conformal-traceless decomposition of the gravitational field  

SciTech Connect

Einstein's theory of general relativity is written in terms of the variables obtained from a conformal-traceless decomposition of the spatial metric and extrinsic curvature. The determinant of the conformal metric is not restricted, so the action functional and equations of motion are invariant under conformal transformations. With this approach the conformal-traceless variables remain free of density weights. The conformal invariance of the equations of motion can be broken by imposing an evolution equation for the determinant of the conformal metric g. Two conditions are considered, one in which g is constant in time and one in which g is constant along the unit normal to the spacelike hypersurfaces. This approach is used to write the Baumgarte-Shapiro-Shibata-Nakamura system of evolution equations in conformally invariant form. The presentation includes a discussion of the conformal thin sandwich construction of gravitational initial data, and the conformal flatness condition as an approximation to the evolution equations.

Brown, J. David [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2005-05-15

391

Effects of Weak Bands on Pillar Stability in Stone Mines: Field Observations and Numerical Model Assessment.  

National Technical Information Service (NTIS)

Observations of pillar conditions in limestone mines showed that the presence of weak bands in the limestone can result in pillar damage at stresses that are lower than one would otherwise expect. The objective of this National Institute for Occupational ...

G. S. Esterhuizen J. L. Ellenberger

2008-01-01

392

Gravitational lensing in fourth order gravity  

SciTech Connect

Gravitational lensing is investigated in the weak field limit of fourth order gravity in which the Lagrangian of the gravitational field is modified by replacing the Ricci scalar curvature R with an analytical expression f(R). Considering the case of a pointlike lens, we study the behavior of the deflection angle in the case of power-law Lagrangians, i.e. with f(R){proportional_to}R{sup n}. In order to investigate possible detectable signatures, the position of the Einstein ring and the solutions of the lens equation are evaluated considering the change with respect to the standard case. Effects on the amplification of the images and the Paczynski curve in microlensing experiments are also estimated.

Capozziello, S.; Troisi, A. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', and INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Edificio N, via Cinthia, 80121-Naples (Italy); Cardone, V.F. [Dipartimento di Fisica 'E. R. Caianiello', Universita di Salerno, and INFN, Sezione di Napoli, Gruppo Collegato di Salerno, via S. Allende, 84081-Baronissi (Salerno) (Italy)

2006-05-15

393

Quantum Opportunities in Gravitational Wave Detectors  

SciTech Connect

Direct observation of gravitational waves should open a new window into the Universe. Gravitational wave detectors are the most sensitive position meters ever constructed. The quantum limit in gravitational wave detectors opens up a whole new field of study. Quantum opportunities in gravitational wave detectors include applications of quantum optics techniques and new tools for quantum measurement on truly macroscopic (human) scales.

Mavalvala, Negris (MIT)

2012-03-14

394

Self-similar flow behind a spherical shock wave a non-ideal dusty gas under a gravitational field: isothermal flow  

NASA Astrophysics Data System (ADS)

Similarity solutions are obtained for one-dimensional unsteady isothermal flow of a dusty gas behind a spherical shock wave with time dependent energy input. The dusty gas is assumed to be a mixture of a non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-conditions are maintained and the viscous stress and heat conduction of the mixture are negligible. The medium is under the influence of the gravitational field due to a heavy nucleus at the origin (Roche model). The total energy of the flow-field behind the shock is increasing. The effects of an increase in the mass concentration of solid particles, the ratio of the density of the solid particles to the initial density of the gas, the gravitational parameter (or shock Mach number) and the parameter of non-idealness of the gas in the mixture, are investigated. It is shown that due to presence of gravitational field the compressibility of the medium at any point in the flow-field behind the shock decreases and all other flow-variables and the shock strength increase. A comparison has also been made between the medium with or without gravitational field.

Nath, Gorakh

2012-07-01

395

A Lower Limit on Omega_m - Omega_Lambda Using the Gravitational Lensing Rate in the Hubble Deep Field  

NASA Astrophysics Data System (ADS)

We calculate the expected number of multiply-imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with m_I < 27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of lensed sources in the HDF places a 95% confidence lower limit on the current value of Omega_m - Omega_Lambda between -0.17, if there are no strongly lensed sources in the HDF, and -0.59, if there are three strongly lensed sources in the HDF. For a flat universe, Lambda < 0.58 to 0.79. If the only lensed source in the HDF is the one presently viable candidate, then Omega_m - Omega_Lambda > -0.39. These lower limits are compatible with estimates based on high redshift supernovae and with previous limits based on gravitational lensing.

Quashnock, J. M.; Cooray, A. R.; Miller, M. C.

1998-12-01

396

Threshold and saturation properties of the field-induced twist cell with two parameters weak anchoring boundaries  

NASA Astrophysics Data System (ADS)

On the basis of two-parameter formula of weak surface coupling anchoring energy of nematic liquid crystals proposed by Zhao et al recently, the general torque equilibrium equation and boundary conditions of the director have been obtained and the threshold field as well as the saturation field of the field-induced twist cell have been analysed for three kinds of configurations, i.e. homogeneous, splay and Pi cells formed by different rubbing conditions and pretilt angles. The results indicated that the polar anchoring has no effect on the threshold field. It is determined only by the twist anchoring and pretilt angle. But, the polar anchoring and twist anchoring are coupling with each other and have a great influence on the saturation field. The formulae for calculating the threshold field and saturation field are given. These results will be very useful in understanding surface physics and the design of liquid crystal cells.

Guan, Rong-Hua; Sun, Yu-Bao

2006-05-01

397

Self-sustained firing activities of the cortical network with plastic rules in weak AC electrical fields  

NASA Astrophysics Data System (ADS)

Both external and endogenous electrical fields widely exist in the environment of cortical neurons. The effects of a weak alternating current (AC) field on a neural network model with synaptic plasticity are studied. It is found that self-sustained rhythmic firing patterns, which are closely correlated with the cognitive functions, are significantly modified due to the self-organizing of the network in the weak AC field. The activities of the neural networks are affected by the synaptic connection strength, the external stimuli, and so on. In the presence of learning rules, the synaptic connections can be modulated by the external stimuli, which will further enhance the sensitivity of the network to the external signal. The properties of the external AC stimuli can serve as control parameters in modulating the evolution of the neural network.

Qin, Ying-Mei; Wang, Jiang; Men, Cong; Zhao, Jia; Wei, Xi-Le; Deng, Bin

2012-07-01

398

Kolmogorov-Zakharov Spectrum in AdS Gravitational Collapse.  

PubMed

We study black hole formation during the gravitational collapse of a massless scalar field in asymptotically D-dimensional anti-de Sitter AdS_{D} spacetimes for D=4, 5. We conclude that spherically symmetric gravitational collapse in asymptotically AdS spaces is turbulent and characterized by a Kolmogorov-Zakharov spectrum. Namely, we find that after an initial period of weakly nonlinear evolution, there is a regime where the power spectrum of the Ricci scalar evolves as ?^{-s} with the frequency, ?, and s?1.7±0.1. PMID:23952380

de Oliveira, H P; Pando Zayas, Leopoldo A; Rodrigues, E L

2013-08-01

399

A RECIPE TO PROBE ALTERNATIVE THEORIES OF GRAVITATION VIA N-BODY NUMERICAL SIMULATIONS. I. SPIRAL GALAXIES  

SciTech Connect

A way to probe alternative theories of gravitation is to study if they could account for the structures of the universe. We therefore modified the well-known Gadget-2 code to probe alternative theories of gravitation through galactic dynamics. As an application, we simulate the evolution of spiral galaxies to probe alternative theories of gravitation whose weak field limits have a Yukawa-like gravitational potential. These simulations show that galactic dynamics can be used to constrain the parameters associated with alternative theories of gravitation. It is worth stressing that the recipe given in this study can be applied to any other alternative theory of gravitation in which the superposition principle is valid.

Brandao, C. S. S.; De Araujo, J. C. N., E-mail: claudiosoriano.uesc@gmail.com, E-mail: jcarlos.dearaujo@inpe.br [Divisao de Astrofisica, Instituto Nacional de Pesquisas Espaciais, S. J. Campos, SP 12227-010 (Brazil)

2012-05-01

400

Self-similar flow behind a spherical shock wave in a non-ideal dusty gas under a gravitational field: Isothermal flow  

NASA Astrophysics Data System (ADS)

Similarity solutions are obtained for one-dimensional unsteady isothermal flow of a dusty gas behind a spherical shock wave with time dependent energy input. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-conditions are maintained, and the viscous stress and heat conduction of the mixture are negligible. The medium is taken to be under the influence of the gravitational field due to a heavy nucleus at the origin (Roche model). The total energy of the flow-field behind the shock is increasing. The effects of an increase in the mass concentration of solid particles, the ratio of the density of the solid particles to the initial density of the gas, the gravitational parameter (or shock Mach number), and the parameter of non-idealness of the gas in the mixture, are investigated. It is shown that due to presence of gravitational field the isothermal compressibility of the medium and the flow-variables increases and the shock strength decreases. A comparison has also been made between the medium with and without gravitational field. The shock waves in dusty medium can be important for description of star formation, shocks in supernova explosions, etc.

Nath, G.

2013-10-01

401

Encke's special perturbation technique associated with the KS regularized variables. I - Satellite motions in the earth's gravitational field with axial symmetry  

Microsoft Academic Search

A special perturbation technique of Encke type associated with the Kustaanheimo-Stiefel (KS) regularized variables is developed for satellite motions in the earth's gravitational field with axial symmetry. Its computational algorithm is of recursive nature and could be applied to any perturbed conic motion, whatever the number of the zonal harmonic coefficients may be. Applications of the algorithm are also included.

Mervat El-Sayed Awad

1988-01-01

402

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

Microsoft Academic Search

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

Lubov Grunskaya; Valiriy Isakevich; Vladislav Efimov; Alexander Zakirov

2010-01-01

403

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

404

Quantum States of Neutrons in the Gravitational Field and Limits for Non-Newtonian Interaction in the Range between 1 ?m and 10 ?m  

NASA Astrophysics Data System (ADS)

Quantum states in the Earth's gravitational field can be observed, when ultra-cold neutrons fall under gravity. In an experiment at the Institut Laue-Langevin in Grenoble, neutrons are reflected and trapped in a gravitational cavity above a horizontal mirror. The population of the ground state and the lowest states follows, step by step, the quantum mechanical prediction. An efficient neutron absorber removes the higher, unwanted states. The quantum states probe Newtonian gravity on the micrometer scale and we place limits for gravity-like forces in the range between 1 m and 10 m.

Abele, Hartmut; Baeßler, Stefan; Westphal, Alexander

405

Postinflationary evolution via gravitation  

SciTech Connect

We study a class of nonlocal, purely gravitational models, which have the correct structure to reproduce the leading infrared logarithms of quantum gravitational backreaction during the inflationary regime. These models end inflation in a distinctive phase of oscillations with slight and short violations of the weak energy condition and should, when coupled to matter, lead to rapid reheating. By elaborating this class of models we exhibit one that has the same behavior during inflation, goes quiescent until the onset of matter domination, and induces a small, positive cosmological constant of about the right size thereafter.

Tsamis, N. C.; Woodard, R. P. [Department of Physics, University of Crete, GR-710 03 Heraklion (Greece); Department of Physics, University of Florida Gainesville, Gainesville, Florida 32611 (United States)

2010-05-15

406

Gravitational waves in the spectral action of noncommutative geometry  

SciTech Connect

The spectral triple approach to noncommutative geometry allows one to develop the entire standard model (and supersymmetric extensions) of particle physics from a purely geometry standpoint and thus treats both gravity and particle physics on the same footing. The bosonic sector of the theory contains a modification to Einstein-Hilbert gravity, involving a nonconformal coupling of curvature to the Higgs field and conformal Weyl term (in addition to a nondynamical topological term). In this paper we derive the weak-field limit of this gravitational theory and show that the production and dynamics of gravitational waves are significantly altered. In particular, we show that the graviton contains a massive mode that alters the energy lost to gravitational radiation, in systems with evolving quadrupole moment. We explicitly calculate the general solution and apply it to systems with periodically varying quadrupole moments, focusing, in particular, on the well-known energy loss formula for circular binaries.

Nelson, William; Ochoa, Joseph; Sakellariadou, Mairi [Institute of Gravitation and the Cosmos, Penn State University, State College, Pennsylvania 16801 (United States); Department of Physics, King's College, University of London, Strand WC2R 2LS, London (United Kingdom)

2010-10-15

407

Minimizers of the Lawrence-Doniach model under weak coupling and a parallel or slightly tilted field  

NASA Astrophysics Data System (ADS)

We consider minimizers to the Lawrence-Doniach energy for superconductors with coupled layer structures. When the exterior magnetic field is parallel or slightly tilted to the layers and the Josephson coupling between layers is weak enough, we prove that the global minimizer has no vortices on layers. From this we derive upper and lower bounds on the upper and lower critical fields of the superconductor along different directions, when the coupling is weak. Besides the N-dimensional torus formed by minimizers in the decoupled case, we consider weak coupling cases and use Lyapunov-Schmidt techniques to identify the equilibria of the energy functional with low energies as a finite number of curves of solutions connected to the torus, expressed as C1 functions of the coupling constant, with one curve being the unique global minimizers. We also prove stability and obtain detailed information on the nature of the order parameter on each layer and the induced magnetic field in this case. Our results show that in this setting, even in large magnetic fields, stable solutions without vortices can occur with the order parameters having a nearly uniform phase jump between adjacent layers.

Xie, Zhenqiu

408

Conditioned taste aversion is not disrupted in rats exposed to weak, complex magnetic fields during the CS-UCS interval.  

PubMed

40 normal male Wistar rats were trained for 8 successive days to consume water ad libitum during once-daily 20-min. sessions. On the following day (training day) the rats were presented with a novel solution of 10% sucrose for 20 min. followed by a single exposure for 2 hr. to one of two weak (200 to 500 nanoTesla) complex magnetic fields or to sham-field conditions. The patterns of the two magnetic fields and the durations of their repeated presentations (interstimulus interval) were designed to be resonant with the intrinsic firing of hippocampal pyramidal and solitary neurons, respectively. Immediately after the applications of the fields one-half the number of rats were injected with lithium to evoke gastrointestinal malaise. Although on the test day, three days later, rats previously injected with the lithium exhibited the usual robust reduction in the consumption of sucrose compared to the training day, there were no statistically significant differences between field-exposed and sham-field groups for these ratios. We conclude that a 2-hr. exposure to weak magnetic fields designed to simulate the pattern of two structures likely involved with conditioned taste aversion between the conditioned stimulus and the unconditioned stimulus did not affect this behavior. PMID:15002878

McKay, B E; Persinger, M A

2003-12-01

409

Presenting Newtonian gravitation  

NASA Astrophysics Data System (ADS)

The basic principles of the Newtonian theory of gravitation are presented in a way which students may find more logically coherent, mathematically accessible and physically interesting than other approaches. After giving relatively simple derivations of the circular hodograph and the elliptical orbit from the inverse-square law, the concept of gravitational energy is developed from vector calculus. It is argued that the energy density of a gravitational field may reasonably be regarded as -g2/8?G, and that the inverse-square law may be replaced by a Schwarzschild-like force law without the need to invoke non-Euclidean geometry.

Counihan, Martin

2007-11-01

410

Semiconductor microcavity under magnetic field: From the weak coupling to the strong coupling regime  

Microsoft Academic Search

The Landau quantization of the in plane motion of magneto-excitons allows a continuous tuning from the weak coupling regime to the strong coupling regime for the interaction between electronic states and photon states in a semiconductor microcavity. A quantitative interpretation is given in the framework of a semi-classical dispersive model.

J. Tignon; P Voisin; J Wainstain; C Delalande; M Voos; R Houdré; U Oesterle; R. P Stanley

1996-01-01

411

A mathematical model of the bathymetry-generated external gravitational field  

Microsoft Academic Search

The currently available global geopotential models and the global elevation and bathymetry data allow modelling the topography-corrected and bathymetry stripped reference gravity field to a very high spectral resolution (up to degree 2160 of spherical harmonics) using methods for a spherical harmonic analysis and synthesis of the gravity field. When modelling the topography-corrected and crust-density-contrast stripped reference gravity field, additional

Robert Tenzer; Peter Vajda; Peter Hamayun

2010-01-01

412

MSM Self-Energies at Finite Temperature in the Presence of Weak Magnetic Fields: Towards a Full Symmetry Restoration Study  

SciTech Connect

The study of the universe's primordial plasma at high temperature plays an important role when tackling different questions in cosmology, such as the origin of the matter-antimatter asymmetry. In the Minimal Standard Model (MSM) neither the amount of CP violation nor the strength of the phase transition are enough to produce and preserve baryon number during the Electroweak Phase Transition (EWPT), which are two of the three ingredients needed to develop baryon asymmetry. In this talk we present the first part of the analysis done within a scenario where it is viable to have improvements to the aforementioned situation: we work with the degrees of freedom in the broken symmetry phase of the MSM and analyze the development of the EWPT in the presence of a weak magnetic field. More specifically, we calculate the particle self-energies that include the effects of the weak magnetic field, needed for the MSM effective potential up to ring diagrams.

Tejeda-Yeomans, Maria Elena [Universidad de Sonora, Departamento de Fisica, A. Postal 1626, C.P. 83000, Sonora (Mexico); Navarro, Jorge [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico Distrito Federal 04510 (Mexico); Departamento de Fisica, Universidad del Atlantico, Km.7 antigua via a Puerto Colombia, A.A. 1890, Barranquilla (Colombia); Sanchez, Angel [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 Hidalgo, Edificio C-3, Cd. Universitaria C.P. 58040, Michoacan (Mexico); Piccinelli, Gabriella [Centro Tecnologico, FES Aragon, Universidad Nacional Autonoma de Mexico, Avenida Rancho Seco S/N, Bosques de Aragon, Nezahualcoyotl, Estado de Mexico 57130 (Mexico); Ayala, Alejandro [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico Distrito Federal 04510 (Mexico)

2008-07-02

413

ANALYTIC SOLUTIONS FOR CURRENT SHEET STRUCTURE DETERMINED BY SELF-CONSISTENT, ANISOTROPIC TRANSPORT PROCESSES IN A GRAVITATIONAL FIELD  

SciTech Connect

A Harris sheet magnetic field with maximum magnitude B{sub 0} and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.

Goodman, Michael L., E-mail: mgoodman@wvhtf.org [Advanced Technologies Group, West Virginia High Technology Consortium Foundation, 1000 Galliher Drive, Fairmont, WV 26554 (United States)

2011-04-10

414

Spatial aspects of the electric fields generated by weakly electric fish  

Microsoft Academic Search

1.The electric fields of four species of wave type, gymnotid fishes were measured and mapped using a technique that allowed accurate assessment of small electric fields, free of unknown field compression and distortion artifacts.2.Dipole moment values were calculated for each fish's electric field from measurements made at a sufficient distance (Table 1). A dipole moment is an absolute evaluation of

Eric I. Knudsen

1975-01-01

415

Aspects of the Gravitational and Thermal Physics of Solitons in Field Theory.  

NASA Astrophysics Data System (ADS)

We numerically study classical soliton solutions to two physically relevant field theories in an astrophysical setting, and through the Euclidean path integral formalism of finite-temperature field theory, we develop a new analytical method to study solitons semiclassically in a cosmological setting. By carefully considering non-Abelian gauge theories coupled to classical Einstein gravity, we demonstrate how black hole solutions to such theories can have nontrivial field structure outside the event horizon, despite the widely held belief to the contrary known as the "no-hair" conjecture. We next obtain numerical particle-like soliton and black hole solutions in the spontaneously broken phase of the Einstein-Yang-Mills-Higgs system, which consists of an SU(2) gauge field coupled to a Higgs doublet (the electroweak standard model without hypercharge). We also obtain such solutions to the related Einstein-Non-Abelian -Proca theory as a prelude to the gauge field case. Using the bosonic part of the low-energy heterotic string action, we then construct string-inspired regular and black hole solutions to Einstein-Yang-Mills theory coupled to massive dilaton and axion fields. Though we present numerical solutions only for the case of a trivial axion field, we analyze the full system and discuss the feasibility of additional solutions. Shifting from classical to quantum field theory, we next develop a general method utilizing collective coordinates and Euclidean functional constraints to study solitons semiclassically in the path integral formulation of Euclidean quantum field theory. Our method is an extension of the existing semiclassical method, which does not accomodate Euclidean time or the usual canonical Euclidean formalism, and applies to both time-independent solitons and solitons with time-dependence arising from global charge symmetries. We illustrate the method through an example finite-temperature field theory calculation: the one-loop partition function for time-dependent, nontopological soliton solutions to a complex scalar theory in (3 + 1) -dimensions.

O'Neill, Christopher M.

416

The Energy-loss Rate of Neutrinos in the Urca Process of Strange Quark Matter in Weak and Ultra-strong Magnetic Fields  

Microsoft Academic Search

The influence of magnetic field on the energy-loss rate of neutrinos in the direct Urca process of quarks in the model of strange stars is investigated in this article. First, an improvement is made on the method of approximate calculation in the case of weak field, which can be extended to other processes of weak interactions. Then, a rigorous calculation

Xue-Wen Liu; Miao Kang; Yun-Wei Yu; Xia Zhou; Xiao-Ping Zheng

2007-01-01

417

Evolution and geometries of gravitational collapse structures with examples from the StatfJord Field, northern North Sea  

Microsoft Academic Search

Gravitational collapse structures may range in scale from centimetres to hundreds of kilometres and affect both loose sediments and consolidated rocks. The area affected by gravitational failure will commonly be amphitheatre-like in map view, whereas a cross-sectional view will typically display a listric and concave upwards detachment surface. The degree of deformation increases in the direction of sliding. If movement

J. Hesthammer; H. Fossen

1999-01-01

418

The Optical Gravitational Lensing Experiment. OGLE-III Photometric Maps of the Galactic Disk Fields  

NASA Astrophysics Data System (ADS)

We present OGLE-III Photometric Maps of the Galactic disk fields observed during the OGLE-III campaigns for low luminosity transiting objects that led to the discovery of the first transitng exoplanets. The maps contain precise, calibrated VI photometry of about 9 million stars from 21 OGLE-III fields in the Galactic disk observed in the years 2002-2009 and covering more than 7 square degrees in the sky. Precise astrometry of these objects is also provided. We discuss quality of the data and present a few color-magnitude diagrams of the observed fields. All photometric data are available to the astronomical community from the OGLE Internet archive.

Szyma?ski, M. K.; Udalski, A.; Soszy?ski, I.; Kubiak, M.; Pietrzy?ski, G.; Poleski, R.; Wyrzykowski, ?.; Ulaczyk, K.

2010-12-01

419

Spin matrices for gravitons and the Humblet decomposition of the angular momentum of gravitational radiation in the linearized theory  

SciTech Connect

The authors develop spin matrices for a classical gravitational field in the linearized theory which satisfy angular-momentum commutation relations and are appropriate for a spin angular momentum of two. The same spin matrices come out of a decomposition of the angular momentum density of the linearized gravitational field into orbital and spin parts, similar to that carried out by Humblet for the electromagnetic field. To achieve this decomposition, they use the momentum density for the gravitational field obtained from the Landau-Lifshitz pseudo-tensor in the weak gravity limit. They not a formal connection between the spin angular momenta of gravitational and electromagnetic fields using the Kaluza-Klein idea.

Crichton, J.H.; Medina, T.J. (Seattle Pacific Univ., WA (USA))

1990-01-01

420

Gravitational Engine  

NASA Astrophysics Data System (ADS)

Theoretical basics of the gravitational engine's operation are discussed. The basics are based upon non-equivalence of gravitational and inertial masses, and on external origin of the gravitational force, as it follows from the stream mechanism of gravitation. The mechanism is developed from Newton's ideas about existence of streams in ether toward celestial bodies, which are squeezing things to them. Principal scheme of the engine is outlined, its thrust and mass are discussed. Technical problems of its creation are defined, spheres of its applications are named.

Uspensky, George R.

2002-01-01

421

The MHD Kelvin-Helmholtz Instability. II. The Roles of Weak and Oblique Fields in Planar Flows  

NASA Astrophysics Data System (ADS)

We have carried out high-resolution MHD simulations of the nonlinear evolution of Kelvin-Helmholtz unstable flows in 2 \\frac {1}{2} dimensions. The modeled flows and fields were initially uniform except for a thin shear layer with a hyperbolic tangent velocity profile and a small, normal mode perturbation. These simulations extend work by Frank et al. and Malagoli, Bodo, & Rosner. They consider periodic sections of flows containing magnetic fields parallel to the shear layer, but projecting over a full range of angles with respect to the flow vectors. They are intended as preparation for fully three-dimensional calculations and to address two specific questions raised in earlier work: (1) What role, if any, does the orientation of the field play in nonlinear evolution of the MHD Kelvin-Helmholtz instability in 2 \\frac {1}{2} dimensions? (2) Given that the field is too weak to stabilize against a linear perturbation of the flow, how does the nonlinear evolution of the instability depend on strength of the field? The magnetic field component in the third direction contributes only through minor pressure contributions, so the flows are essentially two-dimensional. In Frank et al. we found that fields too weak to stabilize a linear perturbation may still be able to alter fundamentally the flow so that it evolves from the classical "Cat's Eye" vortex expected in gasdynamics into a marginally stable, broad laminar shear layer. In that process the magnetic field plays the role of a catalyst, briefly storing energy and then returning it to the plasma during reconnection events that lead to dynamical alignment between magnetic field and flow vectors. In our new work we identify another transformation in the flow evolution for fields below a critical strength. That we found to be ~10% of the critical field needed for linear stabilization in the cases we studied. In this "very weak field" regime, the role of the magnetic field is to enhance the rate of energy dissipation within and around the Cat's Eye vortex, not to disrupt it. The presence of even a very weak field can add substantially to the rate at which flow kinetic energy is dissipated. In all of the cases we studied magnetic field amplification by stretching in the vortex is limited by tearing mode, "fast" reconnection events that isolate and then destroy magnetic flux islands within the vortex and relax the fields outside the vortex. If the magnetic tension developed prior to reconnection is comparable to Reynolds stresses in the flow, that flow is reorganized during reconnection. Otherwise, the primary influence on the plasma is generation of entropy. The effective expulsion of flux from the vortex is very similar to that shown by Weiss for passive fields in idealized vortices with large magnetic Reynolds numbers. We demonstrated that this expulsion cannot be interpreted as a direct consequence of steady, resistive diffusion, but must be seen as a consequence of unsteady fast reconnection.

Jones, T. W.; Gaalaas, Joseph B.; Ryu, Dongsu; Frank, Adam

1997-06-01

422

Lorentz condition and gravitational effects in the Einstein theory of gravitation  

Microsoft Academic Search

The monograph systematizes gravitational effects predicted by the Einstein General Theory of Relativity (GTR). A tetrad representation which uses Lorentz conditions as gravitational potentials is applied with generalized Lame coefficients conforming to Einstein gravitational equations. A method of analyzing physical structures of GTR effects which uses concepts of physical time and distance is proposed; the delay by a gravitational field

O. S. Ivanitskaia

1979-01-01

423

The Optical Gravitational Lensing Experiment. OGLE-III Photometric Maps of the Galactic Bulge Fields  

NASA Astrophysics Data System (ADS)

We present OGLE-III Photometric Maps of the Galactic bulge fields observed during the third phase of the OGLE project. This paper describes the last, concluding set of maps based on OGLE-III data. The maps contain precise, calibrated VI photometry of about 340 million stars from 267 fields in the Galactic bulge observed during entire OGLE-III phase (2002-2009), covering about 92 square degrees in the sky. Precise astrometry of these objects is also provided. We briefly discuss the photometry procedures and the quality of the data. We also present sample data and color-magnitude diagrams of the observed fields. All photometric data are available to the astronomical community from the OGLE Internet archive.

Szyma?ski, M. K.; Udalski, A.; Soszy?ski, I.; Kubiak, M.; Pietrzy?ski, G.; Poleski, R.; Wyrzykowski, ?.; Ulaczyk, K.

2011-06-01

424

Singularity in Gravitational Collapse of Plane Symmetric Charged Vaidya Spacetime  

NASA Astrophysics Data System (ADS)

We study the final outcome of gravitational collapse resulting from the plane symmetric charged Vaidya spacetime. Using the field equations, we show that the weak energy condition is always satisfied by collapsing fluid. It is found that the singularity formed is naked. The strength of singularity is also investigated by using Nolan's method. This turns out to be a strong curvature singularity in Tipler's sense and hence provides a counter example to the cosmic censorship hypothesis.

Sharif, M.; Siddiqa, Aisha

425

Onset of flows of weakly conducting media in an inhomogeneous electric field  

SciTech Connect

This paper attempts to take account of the effect of the inhomogeneous nature of the field occurring in real conditions on the onset of liquid flow. The electric field distribution in the liquid and the motion ensuing under its influence are described by a closed system of equations for the stationary case. The author considers the case when the field, induced by the space charge, is appreciably smaller than the applied field. The results obtained permit one to pass on to the determination of the velocity field. The procedures discussed can be considerably simplified.

Kozyrenko, V.E.

1986-04-01

426

On generation of dark solitons by gravitational waves in a strongly magnetized pulsar plasma  

SciTech Connect

In this paper, the propagation of gravitational wave perpendicular to a superstrong magnetic field immersed in an electron-positron pulsar plasma is considered. On the basis of the Einstein-Maxwell system of magnetohydrodynamic equations, both the linear and nonlinear interactions of the wave with plasma are investigated. In near-resonant interaction, a relation between gravitation perturbations to electromagnetic field perturbations shows that the field perturbations are directly proportional to the product of ambient magnetic field and the gravitational wave perturbation. Thus, a weak gravitational wave may resonate an effective field perturbation in the strongly magnetized plasma in an astrophysical context. A coupled system of equations describing the nonlinear interaction between gravitational wave and field perturbations in the magnetized plasma is obtained. The equations are solved in resonant approximation, and it is found that a linearly polarized electric field is generated with a frequency close to the plasma frequency. For nonresonant interaction, the solution shows that both electric and magnetic field perturbations in the plasma are produced. Density perturbation and field intensity variation in the plasma lead to a nonlinear frequency shift and the slowly varying field amplitude obeys the nonlinear Schroedinger equation. The solution of the equation is the dark soliton, the amplitude of which may be very significant in the case of a superstrong magnetic field in the pulsar plasma.

Mofiz, U. A. [Department of Mathematics and Natural Sciences, BRAC University, 66 Mohakhali, Dhaka-1212 (Bangladesh)

2007-11-15

427

Gravitational and centrifugal quantum states of neutrons  

NASA Astrophysics Data System (ADS)

Two related physical phenomena have recently been observed: quantum states of neutrons in the gravitational field above a flat mirror, and quantum states of neutrons in an effective centrifugal potential in the vicinity of a concave mirror. It is curious that the measurement of the near-surface quantum states of these two types is the first direct demonstration of the weak equivalence principle for a massive object in a quantum state. These two phenomena and their application to various domains of science will be explored using a new GRANIT spectrometer, which is under commissioning in the Institut Laue-Langevin, Grenoble, France. Most recent advances in these domains are mentioned.

Nesvizhevsky, V. V.; GRANIT Collaboration

2011-07-01

428

Gravitational Effects on Near-Field Flow Structure of Low-Density Gas Jets.  

National Technical Information Service (NTIS)

Experiments were conducted in Earth gravity and microgravity to acquire quantitative data on near-field flow structrue of helium jets injected into air. Microgravity conditions were simulated in the 2.2-s drop tower at NASA John H. Glenn Research Center. ...

T. W. YHep A. K. Agrawal D. V. Griffin

2005-01-01

429

Sonication effect on cellular material in sedimentation and gravitational field flow fractionation  

Microsoft Academic Search

Sonication procedures are generally used prior to field flow fractionation (FFF) separation in order to produce suspensions without aggregates. Yeast cells manufactured in active dry wine yeast (ADWY) were placed in an ultrasound water bath in order to disrupt possible clumps and to obtain a single-cell suspension to be used in optimal conditions during fermentation processes. In order to determine

R. Sanz; S. Battu; L. Puignou; M. T. Galceran; Ph. J. P. Cardot

2003-01-01

430

Universal Gravitation  

NSDL National Science Digital Library

This model shows the effect of gravitational attraction between two objects, demonstrating that gravitational forces are directly proportional to mass of each body, but inversely proportional to the square of the distance between the bodies. The model may be easily modified to demonstrate Coulomb's Law.

Trout, Charlotte

431

Effects of light on the orientation of the snail Physa pomillia in a weak magnetic field  

Microsoft Academic Search

1.The orientation of fresh-water snails (Physa pomillia) in a symmetrical magnetic field was studied from February to March and from September to October, 1965, during the hours 8:30 to 17:30.2.The orientation of the snails was studied in an augmented magnetic field, 9 times that of the earth's field at Gainesville, Florida, with a bar magnet aligned parallel and at right

David G. Badman

1966-01-01

432

Influence of Weak Self-Field Effect on Calculated Activation Energy for Superconducting Thin Film  

Microsoft Academic Search

When the applied field Ba = mu0Ha (Ha > Hp) is perpendicular to the surface of a disk-shaped superconducting thin film with the full penetrated field Hp, the radius R, and the thickness d, a quantitative relation between the average field langBrang and the magnetization M is described by langBrang = mu0[Ha + (0.81 d\\/R) M] for R gg d,

Xiao-nong Xu; Ai-min Sun; Shi-ying Ding; Xin Jin; Xi-xian Yao; Shao-lin Yan; Hai-hu Wen

1997-01-01

433

Theory of weak scattering of stochastic electromagnetic fields from deterministic and random media  

SciTech Connect

The theory of scattering of scalar stochastic fields from deterministic and random media is generalized to the electromagnetic domain under the first-order Born approximation. The analysis allows for determining the changes in spectrum, coherence, and polarization of electromagnetic fields produced on their propagation from the source to the scattering volume, interaction with the scatterer, and propagation from the scatterer to the far field. An example of scattering of a field produced by a {delta}-correlated partially polarized source and scattered from a {delta}-correlated medium is provided.

Tong Zhisong; Korotkova, Olga [Department of Physics, University of Miami, 1320 Campo Sano Drive, Coral Gables, Florida 33146 (United States)

2010-09-15

434

Effect of a weak magnetic field on stepwise deformation of lead in the large strain region  

NASA Astrophysics Data System (ADS)

Precision measurements of the strain rate of lead at constant stresses in a magnetic field and without field and changes in the strain rate resulting from field turn-on and -off have been performed by the interferometric method. It has been shown