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The Speed of Gravity: Einstein Was Right!
(Released July 2003)

  by Salvatore Vittorio  


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Key Citations Short Format Full Format
  1. Gaussianity of cosmic velocity fields and linearity of the velocity-gravity relation

    Ciecielag, P; Chodorowski, M J; Kiraga, M; Strauss, M A; Kudlicki, A; Bouchet, F R

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 339, no. 3, 1 Mar. 2003, p. 641-651

    We present a numerical study of the relation between the cosmic peculiar velocity field and the gravitational acceleration field. We show that on mildly non-linear scales (4-10/h Mpc Gaussian smoothing), the distribution of the Cartesian coordinates of each of these fields is well approximated by a Gaussian. In particular, their kurtoses and negentropies are small compared to those of the velocity divergence and density fields. We find that at these scales the relation between the velocity and gravity field follows linear theory to good accuracy. Specifically, the systematic errors in velocity-velocity comparisons due to assuming the linear model do not exceed 6 percent in beta. To correct for them, we test various non-linear estimators of velocity from density. We show that a slight modification of the co-formula proposed by Kudlicki et al. (1996, 2000) yields an estimator that is essentially unbiased and has a small variance. (Author)

  2. Self-gravity and quasi-stellar object discs

    Goodman, J

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 339, no. 4, 11 Mar. 2003, p. 937-948

    The outer parts of standard steady-state accretion disks around quasi-stellar objects (QSOs) are prone to self-gravity, and they might be expected to fragment into stars rather than feed the central black hole. Possible solutions to this well-known problem are examined with an emphasis on general dynamic constraints. Irradiation by the QSO is insufficient for stability even if the outer disk is strongly warped. Marginal local gravitational instability enhances viscous transport but extends the stable regions only modestly. Compton cooling in the observed QSO radiation field rules out hot thick disks unless the local accretion rate is vastly super-Eddington. The formation of stars or stellar-mass black holes, and the release of energy in these objects by fusion or accretion, may help to stabilize the remaining gas in an otherwise standard disk. But at fixed mass accretion rate, the energy inputs required for stability increase with radius; beyond a parsec, they approach the total QSO luminosity and are probably unsustainable by stars. Magnetic torques from a wind or corona, and gravitational torques from bars or global spirals, may increase the accretion speed and reduce the density of the disk. But dynamical arguments suggest that the accretion speed is at most sonic, so that instability still sets in beyond about a parsec. Alternatively, the QSO could be fed by stellar collisions in a very dense stellar cluster, but the velocity dispersion would have to be much higher than observed in nearby galactic nuclei containing quiescent black holes. In view of these difficulties, we suggest that QSO disks do not extend beyond a thousand Schwarzschild radii or so. Then they must be frequently replenished with gas of small specific angular momentum. (Author)

  3. Gravitational lens time delays for distant supernovae - Breaking the degeneracy between radial mass profiles and the Hubble constant

    Oguri, M; Kawano, Y

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 338, no. 4, 1 Feb. 2003, p. L25-L29

    Any attempt to measure the Hubble constant with gravitational lens time delays is often limited by the strong degeneracy between radial mass profiles of lens galaxies and the Hubble constant. We show that strong gravitational lensing of Type Ia supernovae breaks this degeneracy; the standard candle nature of the Type Ia supernova luminosity function allows one to measure the magnification factor directly, and this information is essential to constrain radial mass profiles and the Hubble constant separately. Our numerical simulation demonstrates that the Hubble constant can be determined with approximately 5 percent accuracy from several lens events only if magnification factors are used as constraints. Therefore, a distant supernova survey is a promising way to measure the global Hubble constant independently with the local estimates. (Author)

  4. CLASS B0445+123 - A new two-image gravitational lens system

    Argo, M K; Jackson, N J; Browne, I W A; York, T; McKean, J P; Biggs, A D; Blandford, R D; de Bruyn, A G; Chae, K H; Fassnacht, C D

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 338, no. 4, 1 Feb. 2003, p. 957-961

    A new two-image gravitational lens system has been discovered as a result of the Cosmic Lens All-Sky Survey. Radio observations with the Very Large Array (VLA), the MultiElement Radio Linked Interferometer Network and the Very Long Baseline Array at increasingly higher resolutions all show two components with a flux density ratio of about 7 : 1 and a separation of 1.34 arcsec. Both components are compact and have the same spectral index. Follow-up observations made with the VLA at 8.4 GHz show evidence of a feature to the south-east of the brighter component and a corresponding extension of the weaker component to the northwest. Optical observations with the William Herschel Telescope show approximately 1.7-arcsec extended emission aligned in approximately the same direction as the separation between the radio components with an R-band magnitude of 21.8 +/- 0.4. (Author)

  5. B0850+054 - a new gravitational lens system from CLASS

    Biggs, A D; Rusin, D; Browne, I W A; de Bruyn, A G; Jackson, N J; Koopmans, L V E; McKean, J P; Myers, S T; Blandford, R D; Chae, K-H

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 338, no. 4, 1 Feb. 2003, p. 1084-1088

    We report the discovery of a new gravitational lens system from the CLASS survey. Radio observations with the VLA, WSRT and MERLIN show that the radio source B0850+054 is composed of two compact components with identical spectra, a separation of 0.7 arcsec and a flux density ratio of 6:1. VLBA observations at 5 GHz reveal structures that are consistent with the gravitational lens hypothesis. The brighter of the two images is resolved into a linear string of at least six subcomponents, while the weaker image is radially stretched towards the lens galaxy. UKIRT K-band imaging detects an 18.7-mag extended object, but the resolution of the observations is not sufficient to resolve the lensed images and the lens galaxy. Mass modeling has not been possible with the present data, and the acquisition of high-resolution optical data is a priority for this system. (Author)

  6. The cosmic gravity-velocity relation

    Kudlicki, A; Chodorowski, M J; Strauss, M A; Ciecielag, P

    Small Satellites for Astrophysical Research, the Copernican Principle and Homogeneity of the Universe, Advances in Space Research (0273-1177), vol. 31, no. 2, Jan. 2003, p. 469-474

    We present a numerical study of the relation between the cosmic peculiar velocity field and the gravitational acceleration field. We show that on mildly non-linear scales (3-10 Mpc Gaussian smoothing), the distribution of the Cartesian coordinates of each of these fields is very well approximated by a Gaussian. In particular, their negentropies are small compared to those of the velocity divergence and density fields. We find that at these scales the relation between the velocity and acceleration fields follows linear theory to high accuracy. The non-linear correction of Kudlicki et al. (2000) works still better: its reconstruction errors are several times smaller than those of the linear theory approximation. (Author)

  7. How fast is gravity?

    Fomalont, E; Kopeikin, S

    New Scientist (0262-4079), vol. 177, no. 2377, 11 Jan. 2003, p. 32-35

    This article describes the efforts of National Radio Astronomy Observatory (NRAO) scientist Ed Fomalont and University of Missouri theoretical physics professor Sergei Kopeikin at measuring the speed of gravity, one of the fundamental constants of nature. The problem was to obtain information on the gravitational field of a moving body, which is difficult information to obtain. An opportunity would come on September 8, 2002, when the planet Jupiter would make a close passage to the strong radio quasar J0842+1835. A gravitational lensing effect due to Jupiter's moving gravitational field would then be measured. The lensing effect that they were planning to measure would cause the apparent position of the quasar to shift slightly. This would be measured by an array of radio telescopes spaced as far apart as possible. The telescope used, therefore, was the U.S. NRAO's Very Long Baseline Array. Although one of the telescopes, the one at Saint Croix in the U.S. Virgin Islands, malfunctioned on September 8, 2002, the data from the other telescopes was able to compensate for the loss. Comparing the position of J0842+1835 on September 8 with its average position on the off-Jupiter days preceeding the September 8 passage, and plugging this into a formula by Kopeikin of the gravitational field of the moving Jupiter, gave the answer. The result was that gravity moves at the same speed as light. The actual figure was 1.06 times the speed of light, but the error was +/-0.21. The results were planned to be announced in January 2003 at the American Astronomical Society's annual meeting in Seattle, Washington. (CSA)

  8. Global 8.4-GHz VLBI observations of JVAS B0218+357

    Biggs, A D; Wucknitz, O; Porcas, R W; Browne, I W A; Jackson, N J; Mao, S; Wilkinson, P N

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 338, no. 3, 21 Jan. 2003, p. 599-608

    In this paper we present new observations of the gravitational lens system JVAS B0218+357 made with a global very long baseline interferometry (VLBI) network at a frequency of 8.4 GHz. Our maps have an rms noise of 30 microJy/beam, and with these we have been able to image much of the extended structure of the radio jet in both the A and B images at high resolution (1 mas). The main use of these maps will be to enable us to further constrain the lens model for the purposes of H0 determination. We are able to identify several subcomponents common to both images with the expected parity reversal, including one which we identify as a counter-jet. We have not been successful in detecting either the core of the lensing galaxy or a third image. Using a model of the lensing galaxy we have back-projected both of the images to the source plane and find that they agree well. However, there are small, but significant, differences which we suggest may arise from multipath scattering in the interstellar medium (ISM) of the lensing galaxy. We also find an exponent of the radial mass distribution of 1.04, in agreement with lens modeling of published 15-GHz VLBI data. Polarization maps of each image are presented which show that the distributions of polarization across images A and B are different. We suggest that this results from Faraday rotation and associated depolarization in the lensing galaxy. (Author)

  9. Gravitational microlensing and blazar variability - The case of AO 0235+164

    Webb, J R; Howard, E S

    Cosmology and Elementary Particle Physics; Coral Gables Conference on Cosmology and Elementary Particle Physics, Fort Lauderdale, FL, Dec. 12-16, 2001, Melville, NY, American Institute of Physics, 2002, p. 95-102

    We review the basics of gravitational lens phenomena in astrophysics, concentrating on its applicability to Blazar variability. A brief discussion of gravitational lenses in the context of AGN is presented, followed by a more detailed model to explain the high amplitude outburst observed in Blazar AO 0235+164. We find some preliminary model parameters for the 1997-98 outburst of AO 0235+164. (Author)

  10. Quantum discontinuity for massive gravity with a cosmological term

    Sati, H

    Cosmology and Elementary Particle Physics; Coral Gables Conference on Cosmology and Elementary Particle Physics, Fort Lauderdale, FL, Dec. 12-16, 2001, Melville, NY, American Institute of Physics, 2002, p. 344-347

    The question of whether the graviton has a small non-zero mass or exactly zero mass has been addressed by van Dam and Veltman, and Zkharov. This paper reports on recent work on the van Dam-Veltman-Zakharov discontinuity for massive and partially massless gravitons in A(dS) space at one-loop. (CSA)

  11. Constructing spacetime - No strings attached

    Cho, Adrian

    Science (0036-8075), vol. 298, no. 5596, 8 Nov. 2002, p. 1166, 1167

    In the ongoing quest to meld quantum mechanics and gravity, loop quantum gravity - an alternative theory to string theory - aims to steal the stage. Whereas string theory begins by assuming how spacetime stretches and twists, loop quantum gravity builds the "geometry of spacetime" from scratch, a crucial feature of any fundamental theory of quantum gravity. (CSA)

  12. An investigation of gravitational lens determinations of H0 in quintessence cosmologies

    Lewis, G F; Ibata, R A

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 337, no. 1, 21 Nov. 2002, p. 26-33

    There is growing evidence that the majority of the energy density of the universe is not baryonic or dark matter, but rather it resides in an exotic component with negative pressure. The nature of this 'quintessence' influences our view of the universe, modifying angular diameter and luminosity distances. Here, we examine the influence of a quintessence component upon gravitational lens time-delays. As well as a static quintessence component, an evolving equation of state is also considered. It is found that the equation of state of the quintessence component and its evolution influence the value of the Hubble constant derived from gravitational lenses. However, the differences between evolving and non-evolving cosmologies are relatively small. We undertake a suite of Monte Carlo simulations to examine the potential constraints that can be placed on the universal equation of state from the monitoring of gravitational lens systems, and demonstrate that at least an order of magnitude more lenses than currently known will have to be discovered and analyzed to accurately probe any quintessence component. (Author)

  13. Equipotential surface and normal gravity of the Galilean satellites

    Zhang, Hong; Zhang, Cheng-zhi

    Chinese Astronomy and Astrophysics (0275-1062), vol. 26, no. 4, Oct. 2002, p. 481-488

    In this article, expanded equations of normal gravity on the equipotential surface are proposed for a natural satellite whose orbital plane is close to its equatorial plane. Tidal effects on the normal gravity are also discussed. The authors apply these to the Galilean satellites. Calculations suggest that the tides raised by Jupiter weakly affect the Galilean satellites. The radial displacements of the gravity due to the tides are in the range between 10 exp -3 and 10 exp -5 m per sec per sec, which are similar to the latitudinal and longitudinal displacements. The variations along the latitude circle are larger than those along the longitude circle. We conclude that the tidal effects on most of the Galilean satellites are larger than those on the Moon. (Author)

  14. Global lunar gravity mapping using SELENE sub-satellites

    Iwata, T; Hanada, H; Kawano, N; Takano, T; Namiki, N

    The Moon Beyond 2002: Next Steps in Lunar Science and Exploration, Taos, NM, Sept. 12-14, 2002, Houston, TX, Lunar and Planetary Institute, 2002, p. 28

    The SELENE explorer is under development by NASDA of Japan and the Institute of Space and Astronautical Science (ISAS) of Japan. SELENE will be launched in 2005 to elucidate lunar origin and evolution. SELENE is composed of a Main Orbiter and two micro sub-satellites: the Relay Satellite (Rstar) and the VLBI Radio Satellite (Vstar), which will be used for selenodesy experiments. These satellites will be used to obtain selenodetic data of higher accuracy by four-way Doppler measurements and differential VLBI observations. The Relay Satellite Transponder, RSAT-1 on Rstar and RSAT-2 on the Main Orbiter, will relay two-way ranging signals and four-way carrier signals at S band or X band transmitted from a 64-m antenna at the Usada Deep Space Center (UDSC). The Doppler measurements will provide a global gravity map of the moon. The differential VLBI observations for determining Rstar and Vstar orbits are carried out by the differential VLBI Radio Sources VRAD-1 on Rstar and VRAD-2 on Vstar. They transmit three pairs of S-band and a pair of X-band carrier signals to a VLBI radio telescope at seven ground stations. This paper describes the RSAT and the VRAD. (CSA)

  15. L2-gain and stability analysis for a rigid spacecraft under gravity-gradient torque

    Damaren, Christopher J

    AIAA Guidance, Navigation, and Control Conference and Exhibit, Monterey, CA, Aug. 5-8, 2002

    The nonlinear H(infinity) or L2-gain control methodology is applied to the disturbance attenuation problem for a rigid spacecraft in a circular orbit which is subjected to a gravity-gradient torque. Simple rate feedback is shown to provide global disturbance attenuation for the angular velocity relative to the orbital frame. When a quaternion feedback term is added, local disturbance attenuation of the attitude relative to the orbiting frame is also shown to be possible, and a stability analysis shows that the (undisturbed) attitude tends towards an arbitrarily small invariant set. (Author)

  16. A near optimal midcourse guidance law based on spherical gravity

    Deihoul, Ali; Massoumnia, Mohammad

    AIAA Guidance, Navigation, and Control Conference and Exhibit, Monterey, CA, Aug. 5-8, 2002

    In Massoumnia (1995), an optimal midcourse guidance law for close distances where the difference of gravity for interceptor and ballistic missile is negligible was introduced. There, a closed form solution based on an optimization problem was found with very good performance for close distances but degraded performance in real problems with unequal gravity for missile and interceptor. In this paper, we take into account the difference of gravity by considering a spherical gravity model. A new equation to express the relative motion between missile and interceptor is used to derive a "Near Optimal Guidance Law". The results found using the new derivation are similar to those in Massoumnia, but it results in a guidance law with matrix coefficients. Next, we improve the performance of the guidance law using Kepler's algorithm. This modified approach results in an almost perfect intercept even for large distances between missile and interceptor. (Author)

  17. Design and optimization of low-thrust gravity-assist trajectories to selected planets

    Debban, Theresa J; McConaghy, T T; Longuski, James M

    AIAA/AAS Astrodynamics Specialist Conference and Exhibit, Monterey, CA, Aug. 5-8, 2002

    Highly efficient low-thrust engines are providing new opportunities in mission design. Applying gravity assists to low-thrust trajectories can shorten mission durations and reduce propellant costs from conventional methods. In this paper, an efficient approach is applied to the design and optimization of low-thrust gravity-assist trajectories to such challenging targets as Mercury, Jupiter, and Pluto. Our results for the missions to Mercury and Pluto compare favorably with similar trajectories in the literature, while the mission to Jupiter yields a new option for solar system exploration. (Author)

  18. Space-time foam - A ground-state candidate for quantum gravity

    Garattini, R

    Journal of Optics B: Quantum and Semiclassical Optics (1464-4266), vol. 4, no. 4, Aug. 2002, p. S285-S288

    A model of space-time foam made by N wormholes is considered. The Casimir energy leading to such a model is computed by means of the phase shift method. The collection of Schwarzschild and Reissner-Nordstrom (RN) wormholes are separately considered to represent the foam. The Casimir energy shows that the RN wormholes cannot be used to represent the foam. (Author)

  19. Reconstruction of the strip brightness distribution in a quasar accretion disk from gravitational microlensing data

    Bogdanov, M B; Cherepashchuk, A M

    Astronomicheskij Zhurnal (0004-6299), vol. 79, no. 8, Aug. 2002, p. 693-701

    A technique is proposed for the successive reconstruction of the branches of the strip brightness distribution for a quasar accretion disk via the analysis of observations of high magnification flux events in the multiple quasar images produced by a gravitational lens. The distribution branches are searched for on compact sets of nonnegative, monotonically nonincreasing, convex downward functions. The results of numerical simulations and application of the technique to real observations show that the solution obtained is stable against random noise. Analysis of the light curve of a high magnification event in image C of the gravitational lens QSO 2237+0305 observed by the OGLE group in summer 1999 has yielded the form of the strip brightness distribution in the accretion disk of the lensed quasar. The results are consistent with the hypothesis that the quasar disk w s scanned by a fold caustic. The form of the strip distribution is consistent with the expected appearance of an accretion disk rotating around a supermassive black hole. (Author)

  20. Physical principles of advanced space propulsion based on Heims's field theory

    Droescher, Walter; Haeuser, Jochem

    38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Indianapolis, IN, July 7-10, 2002

    An overview is given of the results of a completely geometrized unified field theory that gives rise to a novel concept for an advanced space transportation technology, permitting, in principle, superluminal travel. This theory predicts the existence of a quasi-antigravitational force, and allows the design of an experiment for the verification of this theory. This theory of quantum gravity, based on publications by Helm , introduces new physics at the quantum scale, predicting that a transformation of electromagnetic wave energy into gravitational-like energy that is eventually transformed into gravitons at specific frequencies is possible, thus reducing the inertial mass of a material (ponderable) test body. The theory has been extended to eight dimensions. The predicted reduction of inertia (mass) can be used as the design principle for an innovative space transportation system. In this paper, Helm's field equations along with the extensions mentioned above, are presented and discussed, and the magnitude of the coupling constant between the conversion of electromagnetic energy and gravitational-like energy is given. (Author)

  21. Chaotic attitude tumbling of an asymmetric gyrostat in a gravitational field

    Kuang, J; Tan, S; Leung, A Y T

    Journal of Guidance, Control, and Dynamics (0731-5090), vol. 25, no. 4, July 2002, p. 804-814

    The chaotic attitude tumbling of an asymmetric gyrostat is investigated in detail. The gyrostat has three symmetrical wheels along the principal axes rotating about a fixed point under the influence of either the gravity torques or the gravity-gradient torques. Using the Deprit canonical variables, the Euler attitude equations are transformed into Hamiltonian form. This makes the Poincare-Arnold-Melnikov (PAM) function developed by Holmes and Marsden applicable. The physical parameters triggering the chaotic attitude are established. The analytical results are checked by using the fourth-order Runge-Kutta simulation in terms of the Euler parameters (quaternions). The relationships of the following physical parameters are established: moments of inertia of carriers and wheels, positions of the mass center, kinetic energy and moment of momentum of the torque-free gyrostat, and initial attitude leading to chaotic motion. The results show that the PAM function is a powerful analytical tool for the treatment of the dynamics of nonlinear gyrostat orientations. (Author)

  22. Reducing the Earth entry velocity for a comet nucleus sample return mission

    Sims, J A

    Astrodynamics 2001; AAS/AIAA Astrodynamics Conference; Proceedings, Quebec, July 30-Aug.2, 2001, San Diego, CA, Univelt, Incorporated, 2002, p. 2255-2268

    Direct return to Earth after rendezvousing with a comet entails a very high entry velocity. Several methods for reducing the entry velocity, including using additional propellant on a direct return or using planetary gravity assists, are presented. The entry velocity can be reduced to a regime commensurate with current deep space sample return missions. The best method is a function of the mission parameters and the target comet. (Author)

  23. 2016+112 - A gravitationally lensed type II quasar

    Koopmans, L V E; Garrett, M A; Blandford, R D; Lawrence, C R; Patnaik, A R; Porcas, R W

    Monthly Notices of the Royal Astronomical Society (0035-8711), vol. 334, no. 1, 21 July 2002, p. 39-47

    A single-screen model of the gravitational lens system 2016+112 is proposed, that explains recent HST infrared (NICMOS-F160W) observations and new high-resolution European VLBI Network (EVN) 5-GHz radio observations, presented in this paper. In particular, we find that a massive 'dark' structure at the lens position, previously suggested by X-ray, optical and spectroscopic observations of the field around 2016+112, is not necessarily required to accommodate the strong-lensing constraints. A massive structure to the north-west of the lens system, suggested from a weak-lensing analysis of the field, is included in the model. The lensed source is an X-ray bright active galaxy at z = 3.273 with a central bright optical continuum core and strong narrow emission lines, suggestive of a type II quasar. The EVN 5-GHz radio maps show a radio jet structure with at least two compact subcomponents. We propose that the diamond caustic crosses the counter-jet of the radio source, so that part of the counter-jet, host galaxy and narrow-fine emission regions is quadruply imaged. The remainder of the radio source, including the core, is doubly imaged. Our lens model predicts a very high magnification (mu about 300) at the brightness peaks of the inner two radio components of complex C. If the jet exhibits relativistic velocities on microarsecond scales, it might result in apparent hyperluminal motion. However, the lack of strong radio variability and the peaked radio spectrum imply that these motions need not be present in the source. Our model furthermore implies that the optical spectrum of C-prime can only show features of the active galactic nuclei and its host galaxy. (Author)

  24. Operational cryogenic experience with the Gravity Probe B payload

    Taber, M A; Murray, D O; Maddocks, J R; Burns, K M

    Advances in cryogenic engineering. Volume 47B; Cryogenic engineering conference - CEC; Proceedings, Madison, WI, Jul. 16-20, 2001, Melville, NY, American Institute of Physics, 2002, p. 1241-1248

    The Gravity Probe B Relativity Mission is a satellite-based experimental test of two predictions of Einstein's General Theory of Relativity. The experimental design makes substantial use of cryogenic technology. The flight payload, which includes the dewar, the cryostat probe, and the science instrument, is now in final test in preparation for integration with the spacecraft. We review the unique aspects of the cryogenic subsystem and discuss the implications they have for cryogenic operations. We also review cryogenic performance of the payload and compare it to thermal model predictions. (Author)

  25. Is There a Cosmological Constant?

    Kochanek, Christopher

    RECON no. 20020061284.

    The grant contributed to the publication of 18 refereed papers and 5 conference proceedings. The primary uses of the funding have been for page charges, travel for invited talks related to the grant research, and the support of a graduate student, Charles Keeton. The refereed papers address four of the primary goals of the proposal: (1) the statistics of radio lenses as a probe of the cosmological model (#1), (2) the role of spiral galaxies as lenses (#3), (3) the effects of dust on statistics of lenses (#7, #8), and (4) the role of groups and clusters as lenses (#2, #6, #10, #13, #15, #16). Four papers (#4, #5, #11, #12) address general issues of lens models, calibrations, and the relationship between lens galaxies and nearby galaxies. One considered cosmological effects in lensing X-ray sources (#9), and two addressed issues related to the overall power spectrum and theories of gravity (#17, #18). Our theoretical studies combined with the explosion in the number of lenses and the quality of the data obtained for them is greatly increasing our ability to characterize and understand the lens population. We can now firmly conclude both from our study of the statistics of radio lenses and our survey of extinctions in individual lenses that the statistics of optically selected quasars were significantly affected by extinction. However, the limits on the cosmological constant remain at lambda < 0.65 at a 2-sigma confidence level, which is in mild conflict with the results of the Type la supernova surveys. We continue to find that neither spiral galaxies nor groups and clusters contribute significantly to the production of gravitational lenses. The lack of group and cluster lenses is strong evidence for the role of baryonic cooling in increasing the efficiency of galaxies as lenses compared to groups and clusters of higher mass but lower central density. Unfortunately for the ultimate objective of the proposal, improved constraints on the cosmological constant, the next large survey for gravitational lenses did not release its results during the term of the proposal. The research supported the career development. of six graduate students (polar, Fletcher, Herold, Keeton, Deng and Rusin) and two post-docs (Labor and Munoz).

  26. From the cosmological term to the Planck constant

    Vargas, J G; Torr, D G

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 1-10

    This paper shows the potential of classical differential geometry to unify gravity with the other interactions and, especially, quantum mechanics. The topics addressed include the affine connection of spacetime, the gravitational sector of teleparallelism, the completion of the classical sector of teleparallelism, the quantum sector of teleparallelism, and the relation between gravitation and quantum physics in teleparallelism. Finally, the Sakharov-Puthoff conjecture as an integral part of teleparallel physics is dealt with. (CSA)

  27. Whitehead meets Feynman and the Big Bang

    Chew, G F

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 51-58

    Historical quantum cosmology (HQC) is based not on matter but on a chain of local history, a chain lengthened by many local steps in each global step that expands a double-cone spacetime. The universe's forward-light cone lower bound corresponds to the Big Bang, while its backward-light cone upper bound corresponds to the present. (All history occurs after the Big Bang and before the present.) HQC adapts continuous string-theoretical and Feynman-graphical notions to a discrete Whiteheadian process. While standard physics-cosmology posits a spatially unbounded universe of matter that (continuously) carries conserved energy, momentum, angular momentum, and electric charge, in HQC only a tiny "rigid" component ("enduring process" in Whitehead's terminology) of a discrete and finite history corresponds to matter. The huge majority of history is "nonrigidly meandering" in time as well as in space and carries none of the above conserved quantities. Dense "vacuonic" history, unobservable by the scientific method, nevertheless carries conserved magnetic charge, contacts material history, and participates in magnetodynamic action at a distance. One outcome is zitterbewegung for most standard-model elementary particles, leading to rest mass and collapse of the material wave function. Another is the probabilistic nature of predictions based solely on past material history. There is the prospect of understanding gravity as the outcome of the interplay between magnetically polarized vacuum and matter. The origin of the standard model's three colors, three generations, and (approximately) 30-deg Weinberg angle are sketched and related to the internal structure of the photon and other "elementary" particles. (Author)

  28. Can one unify gravity and electromagnetic fields?

    Vigier, J-P; Amoroso, R L

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 241-258

    This paper presents an attempt to unify gravity and electromagnetism associated with "holes" and "bumps" in the covariant density distribution of a real average covariant Dirac ether built with extended random elements filling flat space-time. Some possible experimental tests are also discussed. (Author)

  29. The dipolar zero-modes of Einstein action - An informal summary with some new issues

    Modanese, G

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 259-266

    In this note we describe a set of gravitational field configurations, called "dipolar zero modes", which have not been considered earlier in the literature. They give an exactly null contribution to the pure Einstein action and can thus represent large vacuum fluctuations in the quantized theory of gravity. The basic idea behind dipolar fluctuations was discussed for the first time in our earlier work on stability of Euclidean quantum gravity (Modanese, 1998); the Lorentzian case was treated in Modanese (1999). In 2000 we made the first explicit computations, and we were able to set some lower bounds on the strength of the fluctuations (Modanese, 2000). Also, we gave for the first time in Modanese (2000): (1) an estimate of possible suppression effects by cosmological or R2-terms, (2) a computation of the total ADM energy of the zero modes, (3) a clarification (in the Lorentzian case) of the influence of matter fields on the fluctuations, with possible anomalous coupling. Here, after a few general remarks about vacuum fluctuations and "spacetime foam" in quantum gravity, we set out the general features of the dipolar fluctuations and give some explicit order of magnitude calculations. Then, we show that a Lambda-term cuts, to some extent, the dipolar fluctuations; this can lead in certain cases to an anomalous coupling to matter. In conclusion, we discuss a number of new topics not addressed in Modanese (2000). (Author)

  30. Theoretical and experimental progress on the GEM (Gravity-Electro-Magnetism) theory of field unification

    Brandenburg, J E; Kline, J F; Dipietro, V

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 267-278

    Theoretical and experimental progress on the GEM (Gravity-Electro-Magnetism) theory is summarized. A portion of the Kaluza-Klein action is shown to form a "Vacuum Bernoulli Equation" showing gravitational energy density to be equated to an electromagnetic (EM) dynamic pressure that is quadratic in the local Poynting flux: g sq/(2piG) S sq/(c sq x u(0)) = constant, where G and S are the local gravity and Poynting vector magnitudes, respectively; G is the Newton-Cavendish constant, and u(0) is a local magnetic energy density. This relation satisfies the Equivalence Principle. It is shown that this equation predicts that gravity modification can occur through a Vacuum Bernoulli Effect (VBE) by creating a perturbing Poynting flux by a rotating EM field, a "Poynting Vortex", and that this effect can lead to a lifting force for human flight applications. The theory is then applied to experiments involving EM-driven gyroscopes with some success. Explorations of the possibility of a GEMS theory, including the strong force, are briefly discussed. (Author)

  31. Can gravity be included in Grand Unification?

    Rowlands, P; Cullerne, J P

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 279-286

    Grand unification of the electromagnetic, weak, and strong interactions is at present believed to occur at an energy of order 10 exp 15 GeV, about four orders below the Planck mass (M(P)), at which quantum gravity becomes significant. However, there are serious problems with the current minimal SU(5) model, which fails to predict a full convergence of the three interactions. Also, the assumed electroweak mixing parameter, sin squared theta(w) = 0.375, is at total variance with the experimental value of 0.231. The problem, the authors of this paper believe, lies in the current, rather "mechanistic", understanding of the fractional values observed for quark charges. A model of quarks, based on integral charges, suggests a value of sin squared theta(w) = 0.25, with a consequent prediction of Grand Unification at the Planck mass, and a value of 1/alpha = 118 at 14 TeV. (CSA)

  32. Spinors in affine theory of gravity

    Von Borzeszkowski, H-H; Treder, H-J

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 295-302

    We consider some mathematical aspects of purely affine theories of gravity. In particular, we show that in affine spaces one can establish a truncated spinor formalism reducing in metric-affine spaces to the standard one. As a consequence, one can formulate gravitational equations with matter sources to which there can exist solutions with a Riemann-Cartan geometry. (Author)

  33. A new approach to quantum gravity - An overview

    Bell, S B M; Cullerne, J P; Diaz, B M

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 303-312

    We quantize General Relativity for a class of energy-momentum-stress tensors. One particular type of curved spacetime is used as the building block for all the others. Its extrinsic description and relationship to the versatile Dirac and photon equations are discussed. An amended Dirac equation is formulated and solved for the spacetime of a defined Medium observer to show the derivation of the Bohr atom as a consequence of quantum electrodynamics (QED). The derivation of the Bohr and Sommerfeld models of the atom is sketched from QED. Then, the inverse is done, wherein the QED is derived from the Bohr and Sommerfeld models. The application of the new method to gravity is then undertaken. Bohrs two equations for quantum gravity are derived. Up to this point, the point of view has been taken of the Thalesium atom or Geotron for the calculations in this paper. The authors then next assume the point of view of the Small observer for whom the circular loop is temporal. Applying the method of quantization previously used, it is found that QED is the full quantum theory. Moreover, the equivalent of the electromagnetic potential is found from the Bohr equations. (CSA)

  34. Gravity and cosmology and problems of G

    Grebeniuk, M A; Melnikov, V N

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 313-320

    Main trends in modern gravitation and cosmology and their relation to unified models are analyzed. The role of multidimensional gravitational models with different matter sources in solving the basic problems of cosmology is stressed. Exact solutions in multidimensional cosmology with p-branes for some special cases are considered. The Riemann tensor squared is calculated in a general case and investigated for a number of special solutions. Singularities of the Riemann tensor squared are also discussed. Also the case of static internal spaces is considered. It is shown that the external space for this case is a de Sitter or anti-de Sitter one. The behavior of the cosmological constant and its generation by p-branes is demonstrated. (Author)

  35. Quantum gravity operators and nascent cosmologies

    Crowell, L B

    Fundamental Theories of Physics. Volume 126, Dordrecht, Netherlands, Kluwer Academic Publishers, Dordrecht, 2002, p. 321-330

    The Planck length is a fundamental scale of physics. Suppose that we have a black hole with a mass M whose Schwarzschild radius is known to be r = 2GM/c(2). Now, let this black hole have a de Broglie wavelength gamma = h/p, where p = E/c = Mc, the spacetime momentum of the black hole. Assume this wavelength is equal to its diameter defined by the Schwarzschild radius; further, the mass of the black hole is M = h/(c x lambda). The analyst finds that the de Broglie wavelength of this black hole is lambda(P) = sq rt(G /(h(bar) x c cubed)) = 1.616 x 10 exp 33 cm. This length converts into energy units, as the scale is 10 exp 19 GeV. (Author)

  36. The Case for General Relativistic Effects in the Fe K(alpha) Profile of an Active Galaxy

    Turner, T J; Mushotzky, R; Yaqoob, T; George, I M; Snowden, S L; Netzer, H; Kraemer, S B; Nandra, K; Chelouche, D

    RECON no. 20020070381.

    We present results from a simultaneous Chandra HETG (High Energy Transmission Grating) and XMM (X-ray Multi-mirror Mission)-Newton observation of NGC 3516. We find evidence for several narrow components of Fe K(alpha) along with a broad line. We consider the possibility that the lines arise in a blob of material ejected from the nucleus with velocity of approximately 0.25c. We also consider an origin in a neutral accretion disk, suffering enhanced illumination at 35 and 175 R(sub g), perhaps due to magnetic reconnection. The presence of these narrow features indicates there is no Comptonizing region along the line-of-sight to the nucleus. This in turn is compelling support for the hypothesis that broad Fe K(alpha) components are, in general, produced by strong gravity.

  37. Ballistic JUPITER gravity-assist, perihelion-Delta-V trajectories for a realistic interstellar explorer

    McAdams, J V; McNutt Jr, R J

    Spaceflight Mechanics 2002; Proceedings of the AAS/AIAA Space Flight Mechanics Meeting. Vol. 1, San Antonio, TX, Jan. 27-30, 2002, San Diego, CA, Univelt, Incorporated, 2002, p. 725-737

    This proposed interstellar precursor mission will penetrate into the nearby interstellar medium by achieving 1000 AU from the sun within the working lifetime (about 50 years) of the mission initiators. A variety of science goals and orbital mechanics constraints contribute to the formulation of a list of candidate stars for targeting the solar system escape trajectory direction. An approach is developed that will minimize both launch energy to Jupiter and a subsequent near-sun, high-I(SP) high-thrust maneuver in order to attain a high-speed escape from the solar system towards a target star. Detailed performance characteristics are given for selected reference trajectories. (Author)

  38. Blast from the vast (gravity wave detectors)

    Battersby, S

    New Scientist (0262-4079), vol. 172, no. 2319, 1 Dec. 2001, p. 26-29

    This article discusses two giant gravity wave detectors based on laser interferometry, one located in the U.S. and the other in Germany, which are being used to study some of the most violent events in the universe. The development of a global interferometric network of gravity wave detectors is addressed. (CSA)

  39. The current state of string theory

    Horowitz, G

    Relativistic astrophysics; 20th Texas Symposium; Proceedings, Austin, TX, Dec. 10-15, 2000, Melville, NY, American Institute of Physics, 2001, p. 3-10

    String theory is a promising candidate for a quantum theory of gravity and a unified theory of all forces and particles. I will briefly summarize the current status of this theory and discuss some recent results. The most important results involve describing quantum states of black holes in terms of strings, which has provided a fundamental explanation of black hole entropy and Hawking radiation. Further investigation of this connection between black holes and strings has led to a completely new nonperturbative formulation of string theory. (Author)

  40. Brane-world astronomy

    Hogan, C

    Relativistic astrophysics; 20th Texas Symposium; Proceedings, Austin, TX, Dec. 10-15, 2000, Melville, NY, American Institute of Physics, 2001, p. 11-21

    Unified theories suggest that space is intrinsically 10-dimensional, even though everyday phenomena seem to take place in only three large dimensions. In "Brane World" models, matter and radiation are localized to a "brane" which has a thickness less than about. (TeV) exp -1 in all but the usual three dimensions, while gravity propagates in additional dimensions, some of which may extend as far as submillimeter scales. A brief review is presented of some of these models and their astrophysical phenomenology. One distinctive possibility is a gravitational wave background originating in the mesoscopic early universe, at temperatures above about 1 TeV and on scales smaller than a millimeter, during the formation of our 3-dimensional brane within a 10-dimensional space. (Author)

  41. A universe in a global monopole

    Benson, K; Cho, I

    Relativistic astrophysics; 20th Texas Symposium; Proceedings, Austin, TX, Dec. 10-15, 2000, Melville, NY, American Institute of Physics, 2001, p. 28-33

    We investigate brane physics in a universe with an extra-dimensional global monopole and negative bulk cosmological constant. To counter divergence of the graviton zero mode, we employ a physical cut-off. This cut-off yields 4D gravity on a brane at the monopole core; it also solves the hierarchy problem, by inducing the observed hierarchy between particle and Planck scales in the effective 4D universe. Our model has a discrete spectrum of massive Kaluza Klein modes, easily made consistent with 4D gravity on the brane. Extra-dimensional matter fields also induce 4D matter fields on the brane, with the same Kaluza Klein spectrum of excited states. (Author)

  42. Visualization of gravitational lenses

    Alfaro, F

    Relativistic astrophysics; 20th Texas Symposium; Proceedings, Austin, TX, Dec. 10-15, 2000, Melville, NY, American Institute of Physics, 2001, p. 262-264

    Using C, Xforms, Mesa, and Imlib, a computer program has been developed to visualize the gravitational lens phenomenon. The program has been used to generate sequences of images of a source object and its corresponding images. It has also been used to visually test different models of gravitational lenses. (CSA)

  43. X-rays and accretion discs as probes of the strong gravity of black holes

    Fabian, A

    Relativistic astrophysics; 20th Texas Symposium; Proceedings, Austin, TX, Dec. 10-15, 2000, Melville, NY, American Institute of Physics, 2001, p. 643-655

    The observations and interpretation of broad iron lines in the X-ray spectra of Seyfert 1 galaxies are reviewed. The line profiles observed from MCG-6-30-15 and NGC 3516 show extended red wings to the line explained by large gravitational red-shifts. The results are consistent with the emission expected from an X-ray irradiated flat accretion disc orbiting very close to a black hole. Results from XMM-Newton and Chandra are presented, and the possibility of broad oxygen lines is discussed. (Author)

  44. Estimation of post-Newtonian approximation of gravity that affects satellites of planet

    Zhong, M-Q

    Acta Physica Sinica (1000-3290), vol. 50, no. 12, Dec. 2001, p. 2497-2500

    The post-Newtonian approximation in general relativity is used to estimate the gravity for the Jovian system and the comet Shoemaker-Levy 9 that collided with Jupiter. We calculate and discuss the post-Newtonian corrections to the gravity of Jupiter and the precessions of its satellites, which are compared with the Earth-moon system. (Author)

  45. Microlensing by a noncompact spheroidal gravitational lens

    Bogdanov, M B

    Astronomicheskij Zhurnal (0004-6299), vol. 78, no. 12, Dec. 2001, p. 1059-1065

    In the process of their evolution, small-scale clusters of weakly interacting massive particles (WIMPs) that formed in the early Universe can acquire rotational momentum and spheroidal shape. Even small oblateness of a cluster similar to that of the critical Roche surface can lead to the appearance of caustics in the plane of a source lensed by the object. The multiple source images that form in this case cannot be resolved in modern observations, and the cluster behaves like a noncompact spheroidal lens. The caustic crossing that occurs in the case of relative motion of the observer, the cluster of particles, and the lensed star can produce a large variety of flux curves, including those such as have been observed during microlensing events and interpreted as manifestations of binary gravitational lenses. Therefore, we cannot rule out the possibility that at least some of these events might actually be associated with clusters of WIMPs. (Author)

  46. Gravity's kaleidoscope

    Wambsganss, J

    Scientific American (0836-8733), vol. 285, no. 5, Nov. 2001, p. 65-71

    The astronomical uses of gravitational lenses are examined. What such lenses can reveal about quasars, the cosmological constant, dark matter, and extrasolar planets is discussed. (CSA)

  47. Measurements of the gravity waves velocity

    Dubrovskiy, V A; Smirnov, N N

    IAF, International Astronautical Congress, 52nd, Toulouse, France, Oct. 1-5, 2001

    Results of studies on the Earth's microseismic background are presented. It is assumed that background peaks should correspond to the resonance gravity-wave exchange in the system of two gravity-connected bodies. The microseismic spectrum is compared with the distribution of the gravity potential of the nearest stars. A close peak-to-peak correspondence is found. This correspondence and resonance condition led to an evaluation of the gravity-wave velocity. The resulting value is nine orders of magnitude more than the velocity of light. Some consequences of these results are discussed. (Author)

  48. NASA's Cosmic Journeys - Space science missions to the limits of gravity, space and time

    Diaz, A V

    IAF, International Astronautical Congress, 52nd, Toulouse, France, Oct. 1-5, 2001

    I outline NASA's "Cosmic Journeys" roadmap - designed to observe the extremes of gravity throughout the universe - and explain how this roadmap's space science missions systematically build upon the technological advances mastered in preceding science missions. Cosmic Journeys will travel through the major epochs of the universe, from the era of galaxy and black hole formation to the beginning of time. It will probe the regions surrounding black holes, ultimately obtaining a direct image of the event horizon. It will trace the history of the first crucial seconds after the Big Bang in search for the highest energy processes, where gravity may have been united with the other fundamental forces. The key technologies needed for these fantastic endeavors are currently being developed for space missions today. Cosmic Journeys missions include the recently launched MAP, which will help determine the shape and density of the universe. In development are Swift, which will detect gamma-ray bursts and relay their location to other telescopes within seconds, and GLAST, a next-generation gamma-ray observatory. Missions under formulation include the Constellation X-ray Observatory, which would map regions of dark matter and measure the spin of black holes; LISA, which will measure gravity waves; and a set of "vision missions" such as MAXIM, whose goal to image a black hole event horizon further stretches the scientific imagination and technology challenges for our field. (Author)

  49. LISA - The technology challenge

    Gianolio, A; Whitcomb, G

    IAF, International Astronautical Congress, 52nd, Toulouse, France, Oct. 1-5, 2001

    LISA is a mission configured to detect and observe gravitational waves from massive black holes and galactic binary stars with periods in the range of a few seconds to a few hours. To do this, three spacecraft fly in an isosceles triangle formation of side 5 x 10 exp 6 km and with one spacecraft at each apex. In each spacecraft are cubical proof-masses that are kept in a drag-free environment shielded from all forces except that due to gravity. The mutual position of the proof-masses is continuously measured by means of a laser interferometer. The configuration thus forms a large Michelson type interferometer in which the proof masses are effectively adjustable elements. Gravitational waves differentially disturb the proof-masses, generating a measurable signal. The real challenge will consist in the isolation and reduction of all the noise sources which will limit the sensitivity of the measurement. (Author)

  50. Testing the effective scale of quantum gravity with the next generation of gamma ray telescopes

    Blanch, O; Lopez, J; Martinez, M

    Astroparticle Physics (0927-6505), vol. 19, no. 2, May 2003, p. 245-252

    The actual potential of the next generation of gamma ray telescopes in improving the existing tests of an effective quantum gravity scale from the study of the propagation delay for gamma rays of different energies coming from a distant astrophysical source is discussed. It is shown that the existence of a cosmological gamma ray horizon, will impose very demanding conditions on the observations of the telescopes to try to test a quantum gravity scale close to the Planck mass. (Author)