DenInv3D: a geophysical software for three-dimensional density inversion of gravity field data

Science.gov (United States)

Tian, Yu; Ke, Xiaoping; Wang, Yong

2018-04-01

This paper presents a three-dimensional density inversion software called DenInv3D that operates on gravity and gravity gradient data. The software performs inversion modelling, kernel function calculation, and inversion calculations using the improved preconditioned conjugate gradient (PCG) algorithm. In the PCG algorithm, due to the uncertainty of empirical parameters, such as the Lagrange multiplier, we use the inflection point of the L-curve as the regularisation parameter. The software can construct unequally spaced grids and perform inversions using such grids, which enables changing the resolution of the inversion results at different depths. Through inversion of airborne gradiometry data on the Australian Kauring test site, we discovered that anomalous blocks of different sizes are present within the study area in addition to the central anomalies. The software of DenInv3D can be downloaded from http://159.226.162.30.

Model study of the compact gravity reconstruction; Juryoku inversion `CGR` no model kento

Energy Technology Data Exchange (ETDEWEB)

Ishii, Y; Muraoka, A [Sogo Geophysical Exploration Co. Ltd., Tokyo (Japan)

1996-05-01

An examination was made on gravity inversion using a compact gravity reconstruction (CGR) method in gravity tomography analysis. In a model analysis, an analytical region of 100m{times}50m was divided into cells of 10m{times}10m, on the assumption that two density anomalous bodies with a density difference of 1.0g/cm{sup 3} existed with one shallow and the other deep density distribution. The result of the analysis revealed that, in a linear analysis by a general inverse matrix, blurs and blotting were plenty with a tendency of making gravity anomaly attributable to an anomalous distribution of shallow density; that CGR provided a large effect in making a clear contrast of an anomalous part; that, where structures of shallow and deep density anomalies existed, the analysis by CGR was inferior in the restoration of a deep structure with errors enlarged; that, if a gravity traverse was taken long compared with the distribution depth of density anomalies, the analytical precision of a deep part was improved; that an analytical convergence was better with the restriction of density difference given on the large side than on the small side; and so on. 3 refs., 10 figs.

Using Gravity Inversion to Estimate Antarctic Geothermal Heat Flux

Science.gov (United States)

Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; (Sasha) Golynsky, A. V.; Rogozhina, Irina

2014-05-01

New modelling studies for Greenland have recently underlined the importance of GHF for long-term ice sheet behaviour (Petrunin et al. 2013). Revised determinations of top basement heat-flow for Antarctica and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning (Chappell & Kusznir 2008), using BedMap2 data have provided improved estimates of geothermal heat flux (GHF) in Antarctica where it is very poorly known. Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental and oceanic lithosphere. The sensitivity of present-day Antarctic top basement heat-flow to initial continental radiogenic heat productivity, continental rift and margin breakup age has been examined. Recognition of the East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km (Ferraccioli et al. 2011) and is comparable in scale to the well-studied East African rift system, highlights that crustal variability in interior Antarctica is much greater than previously assumed. GHF is also important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology (Bell et al. 2011). References Bell, R.E., Ferraccioli, F., Creyts, T.T., Braaten, D., Corr, H., Das, I., Damaske, D., Frearson, N., Jordan, T., Rose, K., Studinger, M. & Wolovick, M. 2011. Widespread persistent thickening of the East Antarctic Ice Sheet by freezing from the base. Science, 331 (6024), 1592-1595. Chappell, A.R. & Kusznir, N.J. 2008. Three-dimensional gravity inversion for Moho depth at rifted continental margins

Fast nonlinear gravity inversion in spherical coordinates with application to the South American Moho

Science.gov (United States)

Uieda, Leonardo; Barbosa, Valéria C. F.

2017-01-01

Estimating the relief of the Moho from gravity data is a computationally intensive nonlinear inverse problem. What is more, the modelling must take the Earths curvature into account when the study area is of regional scale or greater. We present a regularized nonlinear gravity inversion method that has a low computational footprint and employs a spherical Earth approximation. To achieve this, we combine the highly efficient Bott's method with smoothness regularization and a discretization of the anomalous Moho into tesseroids (spherical prisms). The computational efficiency of our method is attained by harnessing the fact that all matrices involved are sparse. The inversion results are controlled by three hyperparameters: the regularization parameter, the anomalous Moho density-contrast, and the reference Moho depth. We estimate the regularization parameter using the method of hold-out cross-validation. Additionally, we estimate the density-contrast and the reference depth using knowledge of the Moho depth at certain points. We apply the proposed method to estimate the Moho depth for the South American continent using satellite gravity data and seismological data. The final Moho model is in accordance with previous gravity-derived models and seismological data. The misfit to the gravity and seismological data is worse in the Andes and best in oceanic areas, central Brazil and Patagonia, and along the Atlantic coast. Similarly to previous results, the model suggests a thinner crust of 30-35 km under the Andean foreland basins. Discrepancies with the seismological data are greatest in the Guyana Shield, the central Solimões and Amazonas Basins, the Paraná Basin, and the Borborema province. These differences suggest the existence of crustal or mantle density anomalies that were unaccounted for during gravity data processing.

3D Modeling of Iran and Surrounding Areas From Simultaneous Inversion of Multiple Geophysical Datasets

Science.gov (United States)

2010-09-01

shorter periods). Figure 4 shows example fits to the dispersion values and the Bouguer gravity variations. As seen in earlier studies (Maceira and Ammon...50 100 150 150 100 50 Figure 4. Sample dispersion (top) and Bouguer gravity (bottom) for the preliminary inversion. As for other

Comparison result of inversion of gravity data of a fault by particle swarm optimization and Levenberg-Marquardt methods.

Science.gov (United States)

Toushmalani, Reza

2013-01-01

The purpose of this study was to compare the performance of two methods for gravity inversion of a fault. First method [Particle swarm optimization (PSO)] is a heuristic global optimization method and also an optimization algorithm, which is based on swarm intelligence. It comes from the research on the bird and fish flock movement behavior. Second method [The Levenberg-Marquardt algorithm (LM)] is an approximation to the Newton method used also for training ANNs. In this paper first we discussed the gravity field of a fault, then describes the algorithms of PSO and LM And presents application of Levenberg-Marquardt algorithm, and a particle swarm algorithm in solving inverse problem of a fault. Most importantly the parameters for the algorithms are given for the individual tests. Inverse solution reveals that fault model parameters are agree quite well with the known results. A more agreement has been found between the predicted model anomaly and the observed gravity anomaly in PSO method rather than LM method.

Zero-gravity cloud physics laboratory: Experiment program definition and preliminary laboratory concept studies

Science.gov (United States)

Eaton, L. R.; Greco, E. V.

1973-01-01

The experiment program definition and preliminary laboratory concept studies on the zero G cloud physics laboratory are reported. This program involves the definition and development of an atmospheric cloud physics laboratory and the selection and delineations of a set of candidate experiments that must utilize the unique environment of zero gravity or near zero gravity.

Characterising East Antarctic Lithosphere and its Rift Systems using Gravity Inversion

Science.gov (United States)

Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; Golynsky, A. V. Sasha; Rogozhina, Irina

2013-04-01

Since the International Geophysical Year (1957), a view has prevailed that East Antarctica has a relatively homogeneous lithospheric structure, consisting of a craton-like mosaic of Precambrian terranes, stable since the Pan-African orogeny ~500 million years ago (e.g. Ferracioli et al. 2011). Recent recognition of a continental-scale rift system cutting the East Antarctic interior has crystallised an alternative view of much more recent geological activity with important implications. The newly defined East Antarctic Rift System (EARS) (Ferraccioli et al. 2011) appears to extend from at least the South Pole to the continental margin at the Lambert Rift, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. New analysis of RadarSat data by Golynsky & Golynsky (2009) indicates that further rift zones may form widely distributed extension zones within the continent. A pilot study (Vaughan et al. 2012), using a newly developed gravity inversion technique (Chappell & Kusznir 2008) with existing public domain satellite data, shows distinct crustal thickness provinces with overall high average thickness separated by thinner, possibly rifted, crust. Understanding the nature of crustal thickness in East Antarctica is critical because: 1) this is poorly known along the ocean-continent transition, but is necessary to improve the plate reconstruction fit between Antarctica, Australia and India in Gondwana, which will also better define how and when these continents separated; 2) lateral variation in crustal thickness can be used to test supercontinent reconstructions and assess the effects of crystalline basement architecture and mechanical properties on rifting; 3) rift zone trajectories through East Antarctica will define the geometry of zones of crustal and lithospheric thinning at plate-scale; 4) it is not clear why or when the crust of East Antarctica became so thick and elevated, but knowing this can be used to test models of

Gravity inversion predicts the nature of the amundsen basin and its continental borderlands near greenland

DEFF Research Database (Denmark)

Døssing, Arne; Hansen, Thomas Mejer; Olesen, Arne Vestergaard

2014-01-01

the results of 3-D gravity inversion for predicting the sediment thickness and basement geometry within the Amundsen Basin and along its borderlands. We use the recently published LOMGRAV-09 gravity compilation and adopt a process-oriented iterative cycle approach that minimizes misfit between an Earth model...... and observations. The sensitivity of our results to lateral variations in depth and density contrast of the Moho is further tested by a stochastic inversion. Within their limitations, the approach and setup used herein provides the first detailed model of the sediment thickness and basement geometry in the Arctic...... above high-relief basement in the central Amundsen Basin. Significantly, an up to 7 km deep elongated sedimentary basin is predicted along the northern edge of the Morris Jesup Rise. This basin continues into the Klenova Valley south of the Lomonosov Ridge and correlates with an offshore continuation...

Graphical calculus of volume, inverse volume and Hamiltonian operators in loop quantum gravity

Energy Technology Data Exchange (ETDEWEB)

Yang, Jinsong [Guizhou University, Department of Physics, Guiyang (China); Academia Sinica, Institute of Physics, Taipei (China); Ma, Yongge [Beijing Normal University, Department of Physics, Beijing (China)

2017-04-15

To adopt a practical method to calculate the action of geometrical operators on quantum states is a crucial task in loop quantum gravity. In this paper, the graphical calculus based on the original Brink graphical method is applied to loop quantum gravity along the line of previous work. The graphical method provides a very powerful technique for simplifying complicated calculations. The closed formula of the volume operator and the actions of the Euclidean Hamiltonian constraint operator and the so-called inverse volume operator on spin-network states with trivalent vertices are derived via the graphical method. By employing suitable and non-ambiguous graphs to represent the action of operators as well as the spin-network states, we use the simple rules of transforming graphs to obtain the resulting formula. Comparing with the complicated algebraic derivation in some literature, our procedure is more concise, intuitive and visual. The resulting matrix elements of the volume operator is compact and uniform, fitting for both gauge-invariant and gauge-variant spin-network states. Our results indicate some corrections to the existing results for the Hamiltonian operator and inverse volume operator in the literature. (orig.)

Joint inversion of gravity and seismic data along a profile across the seismogenic fault of 2010 Yushu Ms7.1 earthquake

Directory of Open Access Journals (Sweden)

Yang Guangliang

2011-11-01

Full Text Available Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-reflection result. Based on the data of complete Bouguer gravity anomaly and seismic reflection, we obtained a layered interface structure in deep crust down to Moho. Our study showed that the inversion could reveal the interfaces of strata along the survey profile and the directions of regional faults in two-dimension. From the characteristics of the observed topography of the Moho basement, we tentatively confirmed that the uplift of eastern edge of Qinghai-Tibet plateau was caused by the subduction of the Indian plate.

Gravity inversion of deep-crust and mantle interfaces in the Three Gorges area

Directory of Open Access Journals (Sweden)

Wang Jian

2012-11-01

Full Text Available To better understand the heterogeneity of deep-crust and mantle interfaces in the region of the Three Gorges, China, we used the Parker-Oldenburg iterative inversion method to invert existing Bouguer gravity data from the Three Gorges area (1 : 500000, a new gravity map of the Three Gorges Dam (1 : 200000, and the results of deep seismic soundings. The inversion results show a Moho depth of 42 km between Badong and Zigui and the depth of the B2 lower-crustal interface beneath the Jianghan Plain and surrounding areas at 21–25 km. The morphology of crustal interfaces and the surface geology present an overpass structure. The mid-crust beneath the Three Gorges Dam is approximately 9 km thick, which is the thinnest in the Three Gorges area and may be related to the shallow low-density body near the Huangling anticline. The upper crust is seismogenic, and there is a close relationship between seismicity and the deep-crust and mantle interfaces. For example, the M5. 1 Zigui earthquake occurred where the gradients of the Moho and the B2 interface are the steepest, showing that deep structure has a very important effect on regional seismicity.

Internal model of gravity influences configural body processing.

Science.gov (United States)

Barra, Julien; Senot, Patrice; Auclair, Laurent

2017-01-01

Human bodies are processed by a configural processing mechanism. Evidence supporting this claim is the body inversion effect, in which inversion impairs recognition of bodies more than other objects. Biomechanical configuration, as well as both visual and embodied expertise, has been demonstrated to play an important role in this effect. Nevertheless, the important factor of body inversion effect may also be linked to gravity orientation since gravity is one of the most fundamental constraints of our biology, behavior, and perception on Earth. The visual presentation of an inverted body in a typical body inversion paradigm turns the observed body upside down but also inverts the implicit direction of visual gravity in the scene. The orientation of visual gravity is then in conflict with the direction of actual gravity and may influence configural processing. To test this hypothesis, we dissociated the orientations of the body and of visual gravity by manipulating body posture. In a pretest we showed that it was possible to turn an avatar upside down (inversion relative to retinal coordinates) without inverting the orientation of visual gravity when the avatar stands on his/her hands. We compared the inversion effect in typical conditions (with gravity conflict when the avatar is upside down) to the inversion effect in conditions with no conflict between visual and physical gravity. The results of our experiment revealed that the inversion effect, as measured by both error rate and reaction time, was strongly reduced when there was no gravity conflict. Our results suggest that when an observed body is upside down (inversion relative to participants' retinal coordinates) but the orientation of visual gravity is not, configural processing of bodies might still be possible. In this paper, we discuss the implications of an internal model of gravity in the configural processing of observed bodies. Copyright © 2016 Elsevier B.V. All rights reserved.

Invariant models in the inversion of gravity and magnetic fields and their derivatives

Science.gov (United States)

Ialongo, Simone; Fedi, Maurizio; Florio, Giovanni

2014-11-01

In potential field inversion problems we usually solve underdetermined systems and realistic solutions may be obtained by introducing a depth-weighting function in the objective function. The choice of the exponent of such power-law is crucial. It was suggested to determine it from the field-decay due to a single source-block; alternatively it has been defined as the structural index of the investigated source distribution. In both cases, when k-order derivatives of the potential field are considered, the depth-weighting exponent has to be increased by k with respect that of the potential field itself, in order to obtain consistent source model distributions. We show instead that invariant and realistic source-distribution models are obtained using the same depth-weighting exponent for the magnetic field and for its k-order derivatives. A similar behavior also occurs in the gravity case. In practice we found that the depth weighting-exponent is invariant for a given source-model and equal to that of the corresponding magnetic field, in the magnetic case, and of the 1st derivative of the gravity field, in the gravity case. In the case of the regularized inverse problem, with depth-weighting and general constraints, the mathematical demonstration of such invariance is difficult, because of its non-linearity, and of its variable form, due to the different constraints used. However, tests performed on a variety of synthetic cases seem to confirm the invariance of the depth-weighting exponent. A final consideration regards the role of the regularization parameter; we show that the regularization can severely affect the depth to the source because the estimated depth tends to increase proportionally with the size of the regularization parameter. Hence, some care is needed in handling the combined effect of the regularization parameter and depth weighting.

Implications of Preliminary Gravity and Magnetic Surveys to the Understanding of the Bartlett Springs Fault Zone, Northern California Coast Ranges

Science.gov (United States)

Langenheim, V. E.; Jachens, R. C.; Morin, R. L.; McCabe, C. M.; Page, W. D.

2007-12-01

We use new gravity and magnetic data in the Lake Pillsbury region to help understand the geometry and character of the Bartlett Springs fault zone, one of the three main strands of the San Andreas system north of the San Francisco Bay area. We collected 153 new gravity stations in the Lake Pillsbury region that complement the sparse regional dataset and are used to estimate the thickness of Quaternary deposits in the inferred Gravelly Valley (Lake Pillsbury) pull-apart basin. We also collected 38 line-km of ground magnetic data on roads and 65 line-km by boat on the lake to supplement regional aeromagnetic surveys and to map concealed fault strands beneath the lake. The new gravity data show a significant northwest-striking gravity gradient at the base of which lies the Bartlett Springs fault zone. Superposed on this major east-facing gravity gradient is a 5 mGal low centered on Lake Pillsbury and Gravelly Valley. Inversion of the gravity field for basin thickness assuming a density contrast of 400 kg/m3 indicates the deepest part of the basin is about 400 m and located in the northern part of the valley, although the inversion lacks gravity stations within the lake. The basin is about 3 km wide and 5 km long and basin edges coincide with strands of the Bartlett Springs fault zone. Our gravity data suggest that Potter Valley, which lies between the Maacama and Bartlett Springs faults, is also as much as 400 m deep in the southern part of the valley, although additional data west of the valley would better isolate the gravity low. Geomorphologic characteristics of the valley suggest that this structure has been quiescent during the late Quaternary. Ground magnetic data are very noisy but the data in conjunction with 9.6 km-spaced NURE aeromagnetic lines suggest that regional analog aeromagnetic data flown in 1962 may suffer from location errors. The regional and NURE data show a northwest-striking magnetic high that extends across Lake Pillsbury. The northeast edge

Terrain Classification on Venus from Maximum-Likelihood Inversion of Parameterized Models of Topography, Gravity, and their Relation

Science.gov (United States)

Eggers, G. L.; Lewis, K. W.; Simons, F. J.; Olhede, S.

2013-12-01

Venus does not possess a plate-tectonic system like that observed on Earth, and many surface features--such as tesserae and coronae--lack terrestrial equivalents. To understand Venus' tectonics is to understand its lithosphere, requiring a study of topography and gravity, and how they relate. Past studies of topography dealt with mapping and classification of visually observed features, and studies of gravity dealt with inverting the relation between topography and gravity anomalies to recover surface density and elastic thickness in either the space (correlation) or the spectral (admittance, coherence) domain. In the former case, geological features could be delineated but not classified quantitatively. In the latter case, rectangular or circular data windows were used, lacking geological definition. While the estimates of lithospheric strength on this basis were quantitative, they lacked robust error estimates. Here, we remapped the surface into 77 regions visually and qualitatively defined from a combination of Magellan topography, gravity, and radar images. We parameterize the spectral covariance of the observed topography, treating it as a Gaussian process assumed to be stationary over the mapped regions, using a three-parameter isotropic Matern model, and perform maximum-likelihood based inversions for the parameters. We discuss the parameter distribution across the Venusian surface and across terrain types such as coronoae, dorsae, tesserae, and their relation with mean elevation and latitudinal position. We find that the three-parameter model, while mathematically established and applicable to Venus topography, is overparameterized, and thus reduce the results to a two-parameter description of the peak spectral variance and the range-to-half-peak variance (in function of the wavenumber). With the reduction the clustering of geological region types in two-parameter space becomes promising. Finally, we perform inversions for the JOINT spectral variance of

Inversion of gravity data in the Big Bear Lake Area to recover depth to basement using Cauchy-type integrals

DEFF Research Database (Denmark)

Cai, Hongzhu; Zhdanov, Michael

2014-01-01

One of the important applications of the gravity method is evaluation of the depth to the basement, which is characterized by a significant density contrast with the sedimental layeres. We have introduced recently a new method of modeling and inversion of potential field data generated by a densi...

Testing the inverse-square law of gravity: Error and design with the upward continuation integral

International Nuclear Information System (INIS)

Thomas, J.

1989-01-01

It has been reported that the inverse-square law of gravity is violated over a range of a few hundred meters. I present a different method for the analysis of the data from that experiment. In this method, the experimental error can be evaluated analytically and I confirm the previous analysis but show that it is a 2σ effect. The method can also be used to design new experiments that will yield minimum errors for a fixed number of data points

Tectonic evolution of the Tualatin basin, northwest Oregon, as revealed by inversion of gravity data

Science.gov (United States)

McPhee, Darcy K.; Langenheim, Victoria E.; Wells, Ray; Blakely, Richard J.

2014-01-01

The Tualatin basin, west of Portland (Oregon, USA), coincides with a 110 mGal gravity low along the Puget-Willamette lowland. New gravity measurements (n = 3000) reveal a three-dimensional (3-D) subsurface geometry suggesting early development as a fault-bounded pull-apart basin. A strong northwest-trending gravity gradient coincides with the Gales Creek fault, which forms the southwestern boundary of the Tualatin basin. Faults along the northeastern margin in the Portland Hills and the northeast-trending Sherwood fault along the southeastern basin margin are also associated with gravity gradients, but of smaller magnitude. The gravity low reflects the large density contrast between basin fill and the mafic crust of the Siletz terrane composing basement. Inversions of gravity data indicate that the Tualatin basin is ∼6 km deep, therefore 6 times deeper than the 1 km maximum depth of the Miocene Columba River Basalt Group (CRBG) in the basin, implying that the basin contains several kilometers of low-density pre-CRBG sediments and so formed primarily before the 15 Ma emplacement of the CRBG. The shape of the basin and the location of parallel, linear basin-bounding faults along the southwest and northeast margins suggest that the Tualatin basin originated as a pull-apart rhombochasm. Pre-CRBG extension in the Tualatin basin is consistent with an episode of late Eocene extension documented elsewhere in the Coast Ranges. The present fold and thrust geometry of the Tualatin basin, the result of Neogene compression, is superimposed on the ancestral pull-apart basin. The present 3-D basin geometry may imply stronger ground shaking along basin edges, particularly along the concealed northeast edge of the Tualatin basin beneath the greater Portland area.

Uncertainty reduction of gravity and magnetic inversion through the integration of petrophysical constraints and geological data

Science.gov (United States)

Giraud, Jérémie; Jessell, Mark; Lindsay, Mark; Martin, Roland; Pakyuz-Charrier, Evren; Ogarko, Vitaliy

2016-04-01

measurements and standard values obtained from the literature. Finally, we ran the different inversions on gravity and magnetic data generated using this model. As a result, the use of petrophysical constraints permits us to retrieve sharper boundaries while prior structural information from geology on the shallow lithologies permits to retrieve the contacts more accurately. The integration of the different constraints provides a better-resolved model, with reduced uncertainties such as improved posterior covariance and resolution matrices. The analysis of the sensitivity to and resolution indicators using geological a priori information and petrophysical constraints shows complementarity between the resolution matrices. Moreover, the comparison of the posterior covariance matrices (diagonal and non-diagonal elements) shows that when geological prior information and petrophysical constraints are used together higher values coincide with poorly resolved lithologies. This is not always the case when either only geological prior information or no constraints are used. However, the improvement of the inversion results due to the constraints and prior information are more pronounced on gravity inversion than on magnetic inversion.

3D Structure of Iran and Surrounding Areas From The Simultaneous Inversion of Complementary Geophysical Observations

Science.gov (United States)

Ammon, C. J.; Maceira, M.; Cleveland, M.

2010-12-01

We present a three-dimensional seismic-structure model of the Arabian-Eurasian collision zone obtained via simultaneous, joint inversion of surface-wave dispersion measurements, teleseismic P-wave receiver functions, and gravity observations. We use a simple, approximate relationship between density and seismic velocities so that the three data sets may be combined in a single inversion. The sensitivity of the different data sets are well known: surface waves provide information on the smooth variations in elastic properties, receiver functions provide information on abrupt velocity contrasts, and gravity measurements provide information on broad-wavenumber shallow density variations and long-wavenumber components of deeper density structures. The combination of the data provides improved resolution of shallow-structure variations, which in turn help produce the smooth features at depth with less contamination from the strong heterogeneity often observed in the upper crust. We also explore geologically based smoothness constraints to help resolve sharp features in the underlying shallow 3D structure. Our focus is on the region surrounding Iran from east Turkey and Iraq in the west, to Pakistan and Afghanistan in the east. We use Bouguer gravity anomalies derived from the global gravity model extracted from the GRACE satellite mission. Surface-wave dispersion velocities in the period range between 7 and 150 s are taken from previously published tomographic maps for the region. Preliminary results show expected strong variations in the Caspian region as well as the deep sediment regions of the Persian Gulf. Regions constrained with receiver-function information generally show sharper crust-mantle boundary structure than that obtained by inversion of the surface waves alone (with thin layers and smoothing constraints). Final results of the simultaneous inversion will help us to better understand one of the most prominent examples of continental collision. Such models

Testing joint inversion techniques of gravity data and cosmic ray muon flux at a well-characterized site for use in the detection of subsurface density structures beneath volcanoes.

Science.gov (United States)

Cosburn, K.; Roy, M.; Rowe, C. A.; Guardincerri, E.

2017-12-01

Obtaining accurate static and time-dependent shallow subsurface density structure beneath volcanic, hydrogeologic, and tectonic targets can help illuminate active processes of fluid flow and magma transport. A limitation of using surface gravity measurements for such imaging is that these observations are vastly underdetermined and non-unique. In order to hone in on a more accurate solution, other data sets are needed to provide constraints, typically seismic or borehole observations. The spatial resolution of these techniques, however, is relatively poor, and a novel solution to this problem in recent years has been to use attenuation of the cosmic ray muon flux, which provides an independent constraint on density. In this study we present a joint inversion of gravity and cosmic ray muon flux observations to infer the density structure of a target rock volume at a well-characterized site near Los Alamos, New Mexico, USA. We investigate the shallow structure of a mesa formed by the Quaternary ash-flow tuffs on the Pajarito Plateau, flanking the Jemez volcano in New Mexico. Gravity measurements were made using a Lacoste and Romberg D meter on the surface of the mesa and inside a tunnel beneath the mesa. Muon flux measurements were also made at the mesa surface and at various points within the same tunnel using a muon detector having an acceptance region of 45 degrees from the vertical and a track resolution of several milliradians. We expect the combination of muon and gravity data to provide us with enhanced resolution as well as the ability to sense deeper structures in our region of interest. We use Bayesian joint inversion techniques on the gravity-muon dataset to test these ideas, building upon previous work using gravity inversion alone to resolve density structure in our study area. Both the regional geology and geometry of our study area is well-known and we assess the inferred density structure from our gravity-muon joint inversion within this known

Earthquake epicentroids in the Beijing-Tianjin-Tangshan-Zhangjiakou region inversed by gravity variation data

Science.gov (United States)

Zheng, Jin-Han; Song, Sheng-He; Liu, Ke-Ren; Lu, Hong-Yan; Kuo, J. T.

2003-07-01

Gravity variation data observed in the process of seismogenesis and occurrences of earthquakes show that the location with the greatest gravity changes does not necessarily coincide with the epicenter. To explain this we defined the center of effective mass of stress volume as "hypocentroid", and the vertical projection of which on the earth’s surface as "epicentroid". Here we adopt three rotating models, including spheroid, ellipsoid and cylinder, to represent the region of an impending earthquake. Based on the models of gravity variations induced by uniform dilatancy, epicentroids associated with sixteen earthquakes with M>4.0 occurred in 1981 2000 in the Beijing-Tianjin-Tangshan-Zhangjiakou region are determined by means of a proposed least squares iterative inversion method. The results indicate that cylinder model is preferable to the other two, and epicentroids obtained by the cylinder model separate from the epicenters by a range of 0 40 km. Epicentroids are inevitably located within intact tectonic blocks, and usually cluster in groups; while the epicenters are generally located at the terminations of faults or at the intersections of faults. It seems that there exist earthquake-hatching areas in the block among faults. Earthquakes hatch in these areas, but occur around these areas, meanwhile the existence of faults may play an important role in controlling the processes.

Moho geometry gravity inversion experiment (MoGGIE): A refined model of the Australian Moho, and its tectonic and isostatic implications

Science.gov (United States)

Aitken, Alan R. A.

2010-08-01

At the continent-scale, models of Moho depth based on seismic estimates alone can be inadequate due to irregular or sparse data. Gravity-based Moho modelling provides better coverage, however, the methods used are typically hampered by an inability to explicitly honour seismic constraints and are also limited by over simplistic model conditions, e.g. laterally-homogenous layering. I present a new method to generate a continent-scale Moho model, based on the constrained inversion of free-air gravity data. This method explicitly honours seismic Moho estimates and accounts for a laterally heterogeneous crust and mantle. Resolution and sensitivity testing shows that, for wavelengths greater than 200 km, crustal density and Moho depth are recovered with reasonable accuracy, ± 30 kg m - 3 and ± 3 km respectively. MoGGIE uses a six layer model incorporating ocean, sedimentary basin, upper crust, lower/oceanic crust, eclogitised crust and mantle. Inversion variables were the density of the crustal layers, constrained by a standard density model, and the depths to intra-crustal boundaries and the Moho, constrained by 230 seismic depth estimates. The results demonstrate that a balanced approach to seismically-constrained gravity inversion has the capability to generate detailed and well-constrained models of the Moho and crustal density at the continent-scale. For Australia, this is a clear improvement on the sparse and irregular resolution of the Moho provided by seismic estimates of crustal thickness, which fail to resolve short-wavelength features. Newly defined tectonic features include extensive magmatic underplates, crustal-scale shear zones, and the boundaries between tectonic blocks. Isostatic analysis reveals that little of the continent is close to isostatic equilibrium, with isostatic disequilibria preserved at multiple scales, from hundreds of kilometres to the entire continent. These disequilibria are interpreted to indicate long-wavelength flexure of highly

Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

Science.gov (United States)

Laughman, Brian; Wang, Ling; Lund, Thomas S.; Collins, Richard L.

2018-01-01

Abstract An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus, MILs can cause large‐amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller‐amplitude GWs encountering a MIL do not lead to instability and turbulence but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying. PMID:29576994

Shallow structure of the Somma Vesuvius volcano from 3D inversion of gravity data

Science.gov (United States)

Cella, Federico; Fedi, Maurizio; Florio, Giovanni; Grimaldi, Marino; Rapolla, Antonio

2007-04-01

A gravity investigation was carried out in the Somma-Vesuvius complex area (Campania, Italy) based on a dataset recently enlarged with new measurements. These cover the volcanic top and fill some other important spatial gaps in previous surveys. Besides the new gravity map of the Vesuvius, we also present the results of a 3D inverse modelling, carried out by using constraints from deep well exploration and seismic reflection surveys. The resulting density model provides a complete reconstruction of the top of the carbonate basement. This is relevant mostly on the western side of the survey area, where no significant information was previously available. Other new information regards the Somma-Vesuvius structure. It consists of an annular volume of rocks around the volcanic vent and that extends down to the carbonate basement. It results to be denser with respect to the surrounding sedimentary cover of the Campanian Plain and to the material located just along the central axis of the volcanic structure. The coherence between these features and other geophysical evidences from previous studies, will be discussed together with the other results of this research.

Multi-GPU parallel algorithm design and analysis for improved inversion of probability tomography with gravity gradiometry data

Science.gov (United States)

Hou, Zhenlong; Huang, Danian

2017-09-01

In this paper, we make a study on the inversion of probability tomography (IPT) with gravity gradiometry data at first. The space resolution of the results is improved by multi-tensor joint inversion, depth weighting matrix and the other methods. Aiming at solving the problems brought by the big data in the exploration, we present the parallel algorithm and the performance analysis combining Compute Unified Device Architecture (CUDA) with Open Multi-Processing (OpenMP) based on Graphics Processing Unit (GPU) accelerating. In the test of the synthetic model and real data from Vinton Dome, we get the improved results. It is also proved that the improved inversion algorithm is effective and feasible. The performance of parallel algorithm we designed is better than the other ones with CUDA. The maximum speedup could be more than 200. In the performance analysis, multi-GPU speedup and multi-GPU efficiency are applied to analyze the scalability of the multi-GPU programs. The designed parallel algorithm is demonstrated to be able to process larger scale of data and the new analysis method is practical.

Gravity and magnetic anomaly modeling and correlation using the SPHERE program and Magsat data

Science.gov (United States)

Braile, L. W.; Hinze, W. J. (Principal Investigator); Vonfrese, R. R. B.

1980-01-01

The spherical Earth inversion, modeling, and contouring software were tested and modified for processing data in the Southern Hemisphere. Preliminary geologic/tectonic maps and selected cross sections for South and Central America and the Caribbean region are being compiled and as well as gravity and magnetic models for the major geological features of the area. A preliminary gravity model of the Andeas Beniff Zone was constructed so that the density columns east and west of the subducted plates are in approximate isostatic equilibrium. The magnetic anomaly for the corresponding magnetic model of the zone is being computed with the SPHERE program. A test tape containing global magnetic measurements was converted to a tape compatible with Purdue's CDC system. NOO data were screened for periods of high diurnal activity and reduced to anomaly form using the IGS-75 model. Magnetic intensity anomaly profiles were plotted on the conterminous U.S. map using the track lines as the anomaly base level. The transcontinental magnetic high seen in POGO and MAGSAT data is also represented in the NOO data.

Dilaton gravity, Poisson sigma models and loop quantum gravity

International Nuclear Information System (INIS)

Bojowald, Martin; Reyes, Juan D

2009-01-01

Spherically symmetric gravity in Ashtekar variables coupled to Yang-Mills theory in two dimensions and its relation to dilaton gravity and Poisson sigma models are discussed. After introducing its loop quantization, quantum corrections for inverse triad components are shown to provide a consistent deformation without anomalies. The relation to Poisson sigma models provides a covariant action principle of the quantum-corrected theory with effective couplings. Results are also used to provide loop quantizations of spherically symmetric models in arbitrary D spacetime dimensions.

Inversion of Density Interfaces Using the Pseudo-Backpropagation Neural Network Method

Science.gov (United States)

Chen, Xiaohong; Du, Yukun; Liu, Zhan; Zhao, Wenju; Chen, Xiaocheng

2018-05-01

This paper presents a new pseudo-backpropagation (BP) neural network method that can invert multi-density interfaces at one time. The new method is based on the conventional forward modeling and inverse modeling theories in addition to conventional pseudo-BP neural network arithmetic. A 3D inversion model for gravity anomalies of multi-density interfaces using the pseudo-BP neural network method is constructed after analyzing the structure and function of the artificial neural network. The corresponding iterative inverse formula of the space field is presented at the same time. Based on trials of gravity anomalies and density noise, the influence of the two kinds of noise on the inverse result is discussed and the scale of noise requested for the stability of the arithmetic is analyzed. The effects of the initial model on the reduction of the ambiguity of the result and improvement of the precision of inversion are discussed. The correctness and validity of the method were verified by the 3D model of the three interfaces. 3D inversion was performed on the observed gravity anomaly data of the Okinawa trough using the program presented herein. The Tertiary basement and Moho depth were obtained from the inversion results, which also testify the adaptability of the method. This study has made a useful attempt for the inversion of gravity density interfaces.

Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory

International Nuclear Information System (INIS)

Chan, H.A.; Paik, H.J.

1987-01-01

Because of the equivalence principle, a global measurement is necessary to distinguish gravity from acceleration of the reference frame. A gravity gradiometer is therefore an essential instrument needed for precision tests of gravity laws and for applications in gravity survey and inertial navigation. Superconductivity and SQUID (superconducting quantum interference device) technology can be used to obtain a gravity gradiometer with very high sensitivity and stability. A superconducting gravity gradiometer has been developed for a null test of the gravitational inverse-square law and space-borne geodesy. Here we present a complete theoretical model of this instrument. Starting from dynamical equations for the device, we derive transfer functions, a common mode rejection characteristic, and an error model of the superconducting instrument. Since a gradiometer must detect a very weak differential gravity signal in the midst of large platform accelerations and other environmental disturbances, the scale factor and common mode rejection stability of the instrument are extremely important in addition to its immunity to temperature and electromagnetic fluctuations. We show how flux quantization, the Meissner effect, and properties of liquid helium can be utilized to meet these challenges

Causal role for inverse reasoning on obsessive-compulsive symptoms: Preliminary evidence from a cognitive bias modification for interpretation bias study.

Science.gov (United States)

Wong, Shiu F; Grisham, Jessica R

2017-12-01

The inference-based approach (IBA) is a cognitive account of the genesis and maintenance of obsessive-compulsive disorder (OCD). According to the IBA, individuals with OCD are prone to using inverse reasoning, in which hypothetical causes form the basis of conclusions about reality. Several studies have provided preliminary support for an association between features of the IBA and OCD symptoms. However, there are currently no studies that have investigated the proposed causal relationship of inverse reasoning in OCD. In a non-clinical sample (N = 187), we used an interpretive cognitive bias procedure to train a bias towards using inverse reasoning (n = 64), healthy sensory-based reasoning (n = 65), or a control condition (n = 58). Participants were randomly allocated to these training conditions. This manipulation allowed us to assess whether, consistent with the IBA, inverse reasoning training increased compulsive-like behaviours and self-reported OCD symptoms. Results indicated that compared to a control condition, participants trained in inverse reasoning reported more OCD symptoms and were more avoidant of potentially contaminated objects. Moreover, change in inverse reasoning bias was a small but significant mediator of the relationship between training condition and behavioural avoidance. Conversely, training in a healthy (non-inverse) reasoning style did not have any effect on symptoms or behaviour relative to the control condition. As this study was conducted in a non-clinical sample, we were unable to generalise our findings to a clinical population. Findings generally support the IBA model by providing preliminary evidence of a causal role for inverse reasoning in OCD. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of the Effect of Horizontal Vibrations on Interfacial Waves in a Two-Layer System of Inviscid Liquids to Effective Gravity Inversion

Science.gov (United States)

Pimenova, Anastasiya V.; Goldobin, Denis S.; Lyubimova, Tatyana P.

2018-02-01

We study the waves at the interface between two thin horizontal layers of immiscible liquids subject to high-frequency tangential vibrations. Nonlinear governing equations are derived for the cases of two- and three-dimensional flows and arbitrary ratio of layer thicknesses. The derivation is performed within the framework of the long-wavelength approximation, which is relevant as the linear instability of a thin-layers system is long-wavelength. The dynamics of equations is integrable and the equations themselves can be compared to the Boussinesq equation for the gravity waves in shallow water, which allows one to compare the action of the vibrational field to the action of the gravity and its possible effective inversion.

Structural interpretation of El Hierro (Canary Islands) rifts system from gravity inversion modelling

Science.gov (United States)

Sainz-Maza, S.; Montesinos, F. G.; Martí, J.; Arnoso, J.; Calvo, M.; Borreguero, A.

2017-08-01

Recent volcanism in El Hierro Island is mostly concentrated along three elongated and narrow zones which converge at the center of the island. These zones with extensive volcanism have been identified as rift zones. The presence of similar structures is common in many volcanic oceanic islands, so understanding their origin, dynamics and structure is important to conduct hazard assessment in such environments. There is still not consensus on the origin of the El Hierro rift zones, having been associated with mantle uplift or interpreted as resulting from gravitational spreading and flank instability. To further understand the internal structure and origin of the El Hierro rift systems, starting from the previous gravity studies, we developed a new 3D gravity inversion model for its shallower layers, gathering a detailed picture of this part of the island, which has permitted a new interpretation about these rifts. Previous models already identified a main central magma accumulation zone and several shallower high density bodies. The new model allows a better resolution of the pathways that connect both levels and the surface. Our results do not point to any correspondence between the upper parts of these pathways and the rift identified at the surface. Non-clear evidence of progression toward deeper parts into the volcanic system is shown, so we interpret them as very shallow structures, probably originated by local extensional stresses derived from gravitational loading and flank instability, which are used to facilitate the lateral transport of magma when it arrives close to the surface.

Inverse dualization and non-local dualities between Einstein gravity and supergravities

International Nuclear Information System (INIS)

Chen Chiangmei; Gal'tsov, Dmitri V; Sharakin, Sergei A

2002-01-01

We investigate non-local dualities between suitably compactified higher dimensional Einstein gravity and supergravities which can be revealed if one reinterprets the dualized Kaluza-Klein 2-forms in D>4 as antisymmetric forms belonging to supergravities. We find several examples of such a correspondence including one between the six-dimensional Einstein gravity and the four-dimensional Einstein-Maxwell-dilaton-axion theory (truncated N=4 supergravity), and others between the compactified eleven- and ten-dimensional supergravities and the eight- or ten-dimensional pure gravity. The Killing spinor equation of the D=11 supergravity is shown to be equivalent to the geometric Killing spinor equation in the dual gravity. We give several examples of using new dualities for solution generation and demonstrate how p-branes can be interpreted as non-local duals of pure gravity solutions. New supersymmetric solutions are presented including M2 subset of 5-brane with two rotation parameters

Total variation regularization of the 3-D gravity inverse problem using a randomized generalized singular value decomposition

Science.gov (United States)

Vatankhah, Saeed; Renaut, Rosemary A.; Ardestani, Vahid E.

2018-04-01

We present a fast algorithm for the total variation regularization of the 3-D gravity inverse problem. Through imposition of the total variation regularization, subsurface structures presenting with sharp discontinuities are preserved better than when using a conventional minimum-structure inversion. The associated problem formulation for the regularization is nonlinear but can be solved using an iteratively reweighted least-squares algorithm. For small-scale problems the regularized least-squares problem at each iteration can be solved using the generalized singular value decomposition. This is not feasible for large-scale, or even moderate-scale, problems. Instead we introduce the use of a randomized generalized singular value decomposition in order to reduce the dimensions of the problem and provide an effective and efficient solution technique. For further efficiency an alternating direction algorithm is used to implement the total variation weighting operator within the iteratively reweighted least-squares algorithm. Presented results for synthetic examples demonstrate that the novel randomized decomposition provides good accuracy for reduced computational and memory demands as compared to use of classical approaches.

Gravity model development for precise orbit computations for satellite altimetry

Science.gov (United States)

Marsh, James G.; Lerch, Francis, J.; Smith, David E.; Klosko, Steven M.; Pavlis, Erricos

1986-01-01

Two preliminary gravity models developed as a first step in reaching the TOPEX/Poseidon modeling goals are discussed. They were obtained by NASA-Goddard from an analysis of exclusively satellite tracking observations. With the new Preliminary Gravity Solution-T2 model, an improved global estimate of the field is achieved with an improved description of the geoid.

Surface mass redistribution inversion from global GPS deformation and Gravity Recovery and Climate Experiment (GRACE) gravity data

NARCIS (Netherlands)

Kusche, J.; Schrama, E.J.O.

2005-01-01

Monitoring hydrological redistributions through their integrated gravitational effect is the primary aim of the Gravity Recovery and Climate Experiment (GRACE) mission. Time?variable gravity data from GRACE can be uniquely inverted to hydrology, since mass transfers located at or near the Earth's

Influences of crustal thickening in the Tibetan Plateau on loading modeling and inversion associated with water storage variation

Directory of Open Access Journals (Sweden)

Hansheng Wang

2015-05-01

Full Text Available We use the average crustal structure of the CRUST1.0 model for the Tibetan Plateau to establish a realistic earth model termed as TC1P, and data from the Global Land Data Assimilation System (GLDAS hydrology model and Gravity Recovery and Climate Experiment (GRACE data, to generate the hydrology signals assumed in this study. Modeling of surface radial displacements and gravity variation is performed using both TC1P and the global Preliminary Reference Earth Model (PREM. Furthermore, inversions of the hydrology signals based on simulated Global Positioning System (GPS and GRACE data are performed using PREM. Results show that crust in TC1P is harder and softer than that in PREM above and below a depth of 15 km, respectively, causing larger differences in the computed load Love numbers and loading Green's functions. When annual hydrology signals are assumed, the differences of the radial displacements are found to be as large as approximately 0.6 mm for the truncated degree of 180; while for hydrology-trend signals the differences are very small. When annual hydrology signals and the trends are assumed, the differences in the surface gravity variation are very small. It is considered that TC1P can be used to efficiently remove the hydrological effects on the monitoring of crustal movement. It was also found that when PREM is used inappropriately, the inversion of the hydrology signals from simulated annual GPS signals can only recover approximately 88.0% of the annual hydrology signals for the truncated degree of 180, and the inversion of hydrology signals from the simulated trend GPS signals can recover approximately 92.5% for the truncated degree of 90. However, when using the simulated GRACE data, it is possible to recover almost 100%. Therefore, in future, the TC1P model can be used in the inversions of hydrology signals based on GPS network data. PREM is also valid for use with inversions of hydrology signals from GRACE data at resolutions

Thermal infrared sounding observations of lower atmospheric variances at Mars and their implications for gravity wave activity: a preliminary examination

Science.gov (United States)

Heavens, N. G.

2017-12-01

It has been recognized for over two decades that the mesoscale statistical variance observed by Earth-observing satellites at temperature-sensitive frequencies above the instrumental noise floor is a measure of gravity wave activity. These types of observation have been made by a variety of satellite instruments have been an important validation tool for gravity wave parameterizations in global and mesoscale models. At Mars, the importance of topographic and non-topographic sources of gravity waves for the general circulation is now widely recognized and the target of recent modeling efforts. However, despite several ingenious studies, gravity wave activity near hypothetical lower atmospheric sources has been poorly and unsystematically characterized, partly because of the difficulty of separating the gravity wave activity from baroclinic wave activity and the thermal tides. Here will be presented a preliminary analysis of calibrated radiance variance at 15.4 microns (635-665 cm-1) from nadir, off-nadir, and limb observations by the Mars Climate Sounder on board Mars Reconnaissance Orbiter. The overarching methodology follows Wu and Waters (1996, 1997). Nadir, off-nadir, and lowest detector limb observations should sample variability with vertical weighting functions centered high in the lower atmosphere (20-30 km altitude) and full width half maximum (FWHM) 20 km but be sensitive to gravity waves with different horizontal wavelengths and slightly different vertical wavelengths. This work is supported by NASA's Mars Data Analysis Program (NNX14AM32G). References Wu, D.L. and J.W. Waters, 1996, Satellite observations of atmospheric variances: A possible indication of gravity waves, GRL, 23, 3631-3634. Wu D.L. and J.W. Waters, 1997, Observations of Gravity Waves with the UARS Microwave Limb Sounder. In: Hamilton K. (eds) Gravity Wave Processes. NATO ASI Series (Series I: Environmental Change), vol 50. Springer, Berlin, Heidelberg.

Structural appraisal of the Gadag schist belt from gravity investigations

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

From qualitative analysis of the gravity data, several tectonic features are ... major types of schist belts are identified in the ... Dharwar craton; Gadag schist belt; gravity method; inversion. ..... the Research Associateship of Dr D Himabindu.

Using time-lapse gravity for groundwater model calibration: An application to alluvial aquifer storage

DEFF Research Database (Denmark)

Christiansen, Lars; Binning, Philip John; Rosbjerg, Dan

2011-01-01

hydrogeophysical inversion to decrease parameter correlation in groundwater models. This is demonstrated for a model of riverbank infiltration where combined inversion successfully constrains hydraulic conductivity and specific yield in both an analytical and a numerical groundwater model. A sensitivity study...... shows that time-lapse gravity data are especially useful to constrain specific yield. Furthermore, we demonstrate that evapotranspiration, and riverbed conductance are better constrained by coupled inversion to gravity and head data than to head data alone. When estimating the four parameters...... simultaneously, the six correlation coefficients were reduced from unity when only head data were employed to significantly lower values when gravity and head data were combined. Our analysis reveals that the estimated parameter values are not very sensitive to the choice of weighting between head and gravity...

Crustal and Upper Mantle Structure from Joint Inversion of Body Wave and Gravity Data

Science.gov (United States)

2012-09-01

We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity data provide...relocation analysis. We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity...topographic relief this effect needs to be removed; thus, we converted free-air anomalies into Bouguer anomalies assuming a standard density for crustal rocks

3D stochastic inversion and joint inversion of potential fields for multi scale parameters

Science.gov (United States)

Shamsipour, Pejman

In this thesis we present the development of new techniques for the interpretation of potential field (gravity and magnetic data), which are the most widespread economic geophysical methods used for oil and mineral exploration. These new techniques help to address the long-standing issue with the interpretation of potential fields, namely the intrinsic non-uniqueness inversion of these types of data. The thesis takes the form of three papers (four including Appendix), which have been published, or soon to be published, in respected international journals. The purpose of the thesis is to introduce new methods based on 3D stochastical approaches for: 1) Inversion of potential field data (magnetic), 2) Multiscale Inversion using surface and borehole data and 3) Joint inversion of geophysical potential field data. We first present a stochastic inversion method based on a geostatistical approach to recover 3D susceptibility models from magnetic data. The aim of applying geostatistics is to provide quantitative descriptions of natural variables distributed in space or in time and space. We evaluate the uncertainty on the parameter model by using geostatistical unconditional simulations. The realizations are post-conditioned by cokriging to observation data. In order to avoid the natural tendency of the estimated structure to lay near the surface, depth weighting is included in the cokriging system. Then, we introduce algorithm for multiscale inversion, the presented algorithm has the capability of inverting data on multiple supports. The method involves four main steps: i. upscaling of borehole parameters (It could be density or susceptibility) to block parameters, ii. selection of block to use as constraints based on a threshold on kriging variance, iii. inversion of observation data with selected block densities as constraints, and iv. downscaling of inverted parameters to small prisms. Two modes of application are presented: estimation and simulation. Finally, a novel

Singularity resolution in quantum gravity

International Nuclear Information System (INIS)

Husain, Viqar; Winkler, Oliver

2004-01-01

We examine the singularity resolution issue in quantum gravity by studying a new quantization of standard Friedmann-Robertson-Walker geometrodynamics. The quantization procedure is inspired by the loop quantum gravity program, and is based on an alternative to the Schroedinger representation normally used in metric variable quantum cosmology. We show that in this representation for quantum geometrodynamics there exists a densely defined inverse scale factor operator, and that the Hamiltonian constraint acts as a difference operator on the basis states. We find that the cosmological singularity is avoided in the quantum dynamics. We discuss these results with a view to identifying the criteria that constitute 'singularity resolution' in quantum gravity

Bouguer gravity anomalies for terrain modeling | Orupabo | Journal ...

African Journals Online (AJOL)

Gravity anomalies have been applied in geodesy to determine the geoid, and the associated composition and crustal properties of the earth. Applications of solution of the gravity inversion problems include the study of crustal dynamics as a result of the extraction of fluids in the form of oil, gas and water from ...

High-resolution gravity model of Venus

Science.gov (United States)

Reasenberg, R. D.; Goldberg, Z. M.

1992-01-01

The anomalous gravity field of Venus shows high correlation with surface features revealed by radar. We extract gravity models from the Doppler tracking data from the Pioneer Venus Orbiter by means of a two-step process. In the first step, we solve the nonlinear spacecraft state estimation problem using a Kalman filter-smoother. The Kalman filter has been evaluated through simulations. This evaluation and some unusual features of the filter are discussed. In the second step, we perform a geophysical inversion using a linear Bayesian estimator. To allow an unbiased comparison between gravity and topography, we use a simulation technique to smooth and distort the radar topographic data so as to yield maps having the same characteristics as our gravity maps. The maps presented cover 2/3 of the surface of Venus and display the strong topography-gravity correlation previously reported. The topography-gravity scatter plots show two distinct trends.

On the joint inversion of SGG and SST data from the GOCE mission

Directory of Open Access Journals (Sweden)

P. Ditmar

2003-01-01

Full Text Available The computation of spherical harmonic coefficients of the Earth’s gravity field from satellite-to-satellite tracking (SST data and satellite gravity gradiometry (SGG data is considered. As long as the functional model related to SST data contains nuisance parameters (e.g. unknown initial state vectors, assembling of the corresponding normal matrix must be supplied with the back-substitution operation, so that the nuisance parameters are excluded from consideration. The traditional back-substitution algorithm, however, may result in large round-off errors. Hence an alternative approach, back-substitution at the level of the design matrix, is implemented. Both a stand-alone inversion of either type of data and a joint inversion of both types are considered. The conclusion drawn is that the joint inversion results in a much better model of the Earth’s gravity field than a standalone inversion. Furthermore, two numerical techniques for solving the joint system of normal equations are compared: (i the Cholesky method based on an explicit computation of the normal matrix, and (ii the pre-conditioned conjugate gradient method (PCCG, for which an explicit computation of the entire normal matrix is not needed. The comparison shows that the PCCG method is much faster than the Cholesky method.Key words. Earth’s gravity field, GOCE, satellite-tosatellite tracking, satellite gravity gradiometry, backsubstitution

Self Completeness of Einstein Gravity

CERN Document Server

Dvali, Gia

2010-01-01

We argue, that in Einsteinian gravity the Planck length is the shortest length of nature, and any attempt of resolving trans-Planckian physics bounces back to macroscopic distances due to black hole formation. In Einstein gravity trans-Planckian propagating quantum degrees of freedom cannot exist, instead they are equivalent to the classical black holes that are fully described by lighter infra-red degrees of freedom and give exponentially-soft contribution into the virtual processes. Based on this property we argue that pure-Einstein (super)gravity and its high-dimensional generalizations are self-complete in deep-UV, but not in standard Wilsonian sense. We suggest that certain strong-coupling limit of string theory is built-in in pure Einstein gravity, whereas the role of weakly-coupled string theory limit is to consistently couple gravity to other particle species, with their number being set by the inverse string coupling. We also discuss some speculative ideas generalizing the notion of non-Wilsonian sel...

3D Gravity Modeling of Complex Salt Features in the Southern Gulf of Mexico

Directory of Open Access Journals (Sweden)

Mauricio Nava-Flores

2016-01-01

Full Text Available We present a three-dimensional (3D gravity modeling and inversion approach and its application to complex geological settings characterized by several allochthonous salt bodies embedded in terrigenous sediments. Synthetic gravity data were computed for 3D forward modeling of salt bodies interpreted from Prestack Depth Migration (PSDM seismic images. Density contrasts for the salt bodies surrounded by sedimentary units are derived from density-compaction curves for the northern Gulf of Mexico’s oil exploration surveys. By integrating results from different shape- and depth-source estimation algorithms, we built an initial model for the gravity anomaly inversion. We then applied a numerically optimized 3D simulated annealing gravity inversion method. The inverted 3D density model successfully retrieves the synthetic salt body ensemble. Results highlight the significance of integrating high-resolution potential field data for salt and subsalt imaging in oil exploration.

Superconducting gravity gradiometer for sensitive gravity measurements. II. Experiment

International Nuclear Information System (INIS)

Chan, H.A.; Moody, M.V.; Paik, H.J.

1987-01-01

A sensitive superconducting gravity gradiometer has been constructed and tested. Coupling to gravity signals is obtained by having two superconducting proof masses modulate magnetic fields produced by persistent currents. The induced electrical currents are differenced by a passive superconducting circuit coupled to a superconducting quantum interference device. The experimental behavior of this device has been shown to follow the theoretical model closely in both signal transfer and noise characteristics. While its intrinsic noise level is shown to be 0.07 E Hz/sup -1/2/ (1 Eequivalent10/sup -9/ sec/sup -2/), the actual performance of the gravity gradiometer on a passive platform has been limited to 0.3--0.7 E Hz/sup -1/2/ due to its coupling to the environmental noise. The detailed structure of this excess noise is understood in terms of an analytical error model of the instrument. The calibration of the gradiometer has been obtained by two independent methods: by applying a linear acceleration and a gravity signal in two different operational modes of the instrument. This device has been successfully operated as a detector in a new null experiment for the gravitational inverse-square law. In this paper we report the design, fabrication, and detailed test results of the superconducting gravity gradiometer. We also present additional theoretical analyses which predict the specific dynamic behavior of the gradiometer and of the test

Is gravity as simple as we thought?

International Nuclear Information System (INIS)

Stacey, F.; Tuck, G.

1988-01-01

Geophysical observations that indicate a subtle defect in Newton's law of gravity may provide a clue to the unification of gravity with the other fundamental forces. But the search for an accompanying breakdown in the equivalence principle of general relativity has yielded conflicting evidence. A summary of the geophysical evidence is given, along with a description of the experiments on the equivalence principle and the inverse-square-law effects. (Author)

Classical limit of quantum gravity in an accelerating universe

International Nuclear Information System (INIS)

Schuller, Frederic P.; Wohlfarth, Mattias N.R.

2005-01-01

A one-parameter deformation of Einstein-Hilbert gravity with an inverse Riemann curvature term is derived as the classical limit of quantum gravity compatible with an accelerating universe. This result is based on the investigation of semi-classical theories with sectional curvature bounds which are shown not to admit static spherically symmetric black holes if otherwise of phenomenological interest. We discuss the impact on the canonical quantization of gravity, and observe that worldsheet string theory is not affected

Joint Inversion Modelling of Geophysical Data From Lough Neagh Basin

Science.gov (United States)

Vozar, J.; Moorkamp, M.; Jones, A. G.; Rath, V.; Muller, M. R.

2015-12-01

Multi-dimensional modelling of geophysical data collected in the Lough Neagh Basin is presented in the frame of the IRETHERM project. The Permo-Triassic Lough Neagh Basin, situated in the southeastern part of Northern Ireland, exhibits elevated geothermal gradient (~30 °C/km) in the exploratory drilled boreholes. This is taken to indicate good geothermal exploitation potential in the Sherwood Sandstone aquifer for heating, and possibly even electricity production, purposes. We have used a 3-D joint inversion framework for modelling the magnetotelluric (MT) and gravity data collected to the north of the Lough Neagh to derive robust subsurface geological models. Comprehensive supporting geophysical and geological data (e.g. borehole logs and reflection seismic images) have been used in order to analyze and model the MT and gravity data. The geophysical data sets were provided by the Geological Survey of Northern Ireland (GSNI). Considering correct objective function weighting in favor of noise-free MT response functions is particularly important in joint inversion. There is no simple way how to correct distortion effects the 3-D responses as can be done in 1-D or 2-D case. We have used the Tellus Project airborne EM data to constrain magnetotelluric data and correct them for near surface effects. The shallow models from airborne data are used to constrain the uppermost part of 3-D inversion model. Preliminary 3-D joint inversion modeling reveals that the Sherwood Sandstone Group and the Permian Sandstone Formation are imaged as a conductive zone at the depth range of 500 m to 2000 m with laterally varying thickness, depth, and conductance. The conductive target sediments become shallower and thinner to the north and they are laterally continuous. To obtain better characterization of thermal transport properties of investigated area we used porosity and resistivity data from the Annaghmore and Ballymacilroy boreholes to estimate the relations between porosity

And what if gravity is intrinsically quantic?

International Nuclear Information System (INIS)

Ziaeepour, Houri

2009-01-01

Since the early days of search for a quantum theory of gravity the attempts have been mostly concentrated on the quantization of an otherwise classical system. The two most contentious candidate theories of gravity, string theory and quantum loop gravity are based on a quantum field theory - the latter is a quantum field theory of connections on a SU(2) group manifold and the former is a quantum field theory in two dimensional spaces. Here we argue that there is a very close relation between quantum mechanics (QM) and gravity. Without gravity, QM becomes ambiguous. We consider this observation as the evidence for an intrinsic relation between these fundamental laws of nature. We suggest a quantum role and definition for gravity in the context of a quantum Universe, and present a preliminary formulation for gravity in a system with a finite number of particles.

Inverse design-momentum, a method for the preliminary design of horizontal axis wind turbines

International Nuclear Information System (INIS)

Battisti, L; Soraperra, G; Fedrizzi, R; Zanne, L

2007-01-01

Wind turbine rotor prediction methods based on generalized momentum theory BEM routinely used in industry and vortex wake methods demand the use of airfoil tabulated data and geometrical specifications such as the blade spanwise chord distribution. They belong to the category of 'direct design' methods. When, on the other hand, the geometry is deduced from some design objective, we refer to 'inverse design' methods. This paper presents a method for the preliminary design of wind turbine rotors based on an inverse design approach. For this purpose, a generalized theory was developed without using classical tools such as BEM. Instead, it uses a simplified meridional flow analysis of axial turbomachines and is based on the assumption that knowing the vortex distribution and appropriate boundary conditions is tantamount to knowing the velocity distribution. The simple conservation properties of the vortex components consistently cope with the forces and specific work exchange expressions through the rotor. The method allows for rotor arbitrarily radial load distribution and includes the wake rotation and expansion. Radial pressure gradient is considered in the wake. The capability of the model is demonstrated first by a comparison with the classical actuator disk theory in investigating the consistency of the flow field, then the model is used to predict the blade planform of a commercial wind turbine. Based on these validations, the authors postulate the use of a different vortex distribution (i.e. not-uniform loading) for blade design and discuss the effect of such choices on blade chord and twist, force distribution and power coefficient. In addition to the method's straightforward application to the pre-design phase, the model clearly shows the link between blade geometry and performance allowing quick preliminary evaluation of non uniform loading on blade structural characteristics

Solitons in Newtonian gravity

International Nuclear Information System (INIS)

Goetz, G.

1988-01-01

It is shown that the plane-wave solutions for the equations governing the motion of a self-gravitating isothermal fluid in Newtonian hydrodynamics are generated by a sine-Gordon equation which is solvable by an 'inverse scattering' transformation. A transformation procedure is outlined by means of which one can construct solutions of the gravity system out of a pair of solutions of the sine-Gordon equation, which are interrelated via an auto-Baecklund transformation. In general the solutions to the gravity system are obtained in a parametric representation in terms of characteristic coordinates. All solutions of the gravity system generated by the one-and two-soliton solutions of the sine-Gordon equation can be constructed explicitly. These might provide models for the evolution of flat structures as they are predicted to arise in the process of galaxy formation. (author)

Anisotropic wave-equation traveltime and waveform inversion

KAUST Repository

Feng, Shihang

2016-09-06

The wave-equation traveltime and waveform inversion (WTW) methodology is developed to invert for anisotropic parameters in a vertical transverse isotropic (VTI) meidum. The simultaneous inversion of anisotropic parameters v0, ε and δ is initially performed using the wave-equation traveltime inversion (WT) method. The WT tomograms are then used as starting background models for VTI full waveform inversion. Preliminary numerical tests on synthetic data demonstrate the feasibility of this method for multi-parameter inversion.

The quest for the perfect gravity anomaly: Part 2 - Mass effects and anomaly inversion

Science.gov (United States)

Keller, Gordon R.; Hildenbrand, T.G.; Hinze, W. J.; Li, X.; Ravat, D.; Webring, M.

2006-01-01

Gravity anomalies have become an important tool for geologic studies since the widespread use of high-precision gravimeters after the Second World War. More recently the development of instrumentation for airborne gravity observations, procedures for acquiring data from satellite platforms, the readily available Global Positioning System for precise vertical and horizontal control, improved global data bases, and enhancement of computational hardware and software have accelerated the use of the gravity method. As a result, efforts are being made to improve the gravity databases that are made available to the geoscience community by broadening their observational holdings and increasing the accuracy and precision of the included data. Currently the North American Gravity Database as well as the individual databases of Canada, Mexico, and the United States of America are being revised using new formats and standards. The objective of this paper is to describe the use of the revised standards for gravity data processing and modeling and there impact on geological interpretations. ?? 2005 Society of Exploration Geophysicists.

Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling

Science.gov (United States)

2011-09-01

2005). We implemented a method to increase the usefulness of gravity data by filtering the Bouguer anomaly map. Though commonly applied 40 km 30 35...remove the long-wavelength components from the Bouguer gravity map we follow Tessema and Antoine (2004), who use an upward continuation method and...inversion of group velocities and gravity. (a) Top: Group velocities from a representative cell in the model. Bottom: Filtered Bouguer anomalies. (b

Radar time delays in the dynamic theory of gravity

Directory of Open Access Journals (Sweden)

Haranas I.I.

2004-01-01

Full Text Available There is a new theory gravity called the dynamic theory, which is derived from thermodynamic principles in a five dimensional space, radar signals traveling times and delays are calculated for the major planets in the solar system, and compared to those of general relativity. This is done by using the usual four dimensional spherically symmetric space-time element of classical general relativistic gravity which has now been slightly modified by a negative inverse radial exponential term due to the dynamic theory of gravity potential.

3D fast adaptive correlation imaging for large-scale gravity data based on GPU computation

Science.gov (United States)

Chen, Z.; Meng, X.; Guo, L.; Liu, G.

2011-12-01

In recent years, large scale gravity data sets have been collected and employed to enhance gravity problem-solving abilities of tectonics studies in China. Aiming at the large scale data and the requirement of rapid interpretation, previous authors have carried out a lot of work, including the fast gradient module inversion and Euler deconvolution depth inversion ,3-D physical property inversion using stochastic subspaces and equivalent storage, fast inversion using wavelet transforms and a logarithmic barrier method. So it can be say that 3-D gravity inversion has been greatly improved in the last decade. Many authors added many different kinds of priori information and constraints to deal with nonuniqueness using models composed of a large number of contiguous cells of unknown property and obtained good results. However, due to long computation time, instability and other shortcomings, 3-D physical property inversion has not been widely applied to large-scale data yet. In order to achieve 3-D interpretation with high efficiency and precision for geological and ore bodies and obtain their subsurface distribution, there is an urgent need to find a fast and efficient inversion method for large scale gravity data. As an entirely new geophysical inversion method, 3D correlation has a rapid development thanks to the advantage of requiring no a priori information and demanding small amount of computer memory. This method was proposed to image the distribution of equivalent excess masses of anomalous geological bodies with high resolution both longitudinally and transversely. In order to tranform the equivalence excess masses into real density contrasts, we adopt the adaptive correlation imaging for gravity data. After each 3D correlation imaging, we change the equivalence into density contrasts according to the linear relationship, and then carry out forward gravity calculation for each rectangle cells. Next, we compare the forward gravity data with real data, and

The distance-decay function of geographical gravity model: Power law or exponential law?

International Nuclear Information System (INIS)

Chen, Yanguang

2015-01-01

Highlights: •The distance-decay exponent of the gravity model is a fractal dimension. •Entropy maximization accounts for the gravity model based on power law decay. •Allometric scaling relations relate gravity models with spatial interaction models. •The four-parameter gravity models have dual mathematical expressions. •The inverse power law is the most probable distance-decay function. -- Abstract: The distance-decay function of the geographical gravity model is originally an inverse power law, which suggests a scaling process in spatial interaction. However, the distance exponent of the model cannot be reasonably explained with the ideas from Euclidean geometry. This results in a dimension dilemma in geographical analysis. Consequently, a negative exponential function was used to replace the inverse power function to serve for a distance-decay function. But a new puzzle arose that the exponential-based gravity model goes against the first law of geography. This paper is devoted for solving these kinds of problems by mathematical reasoning and empirical analysis. New findings are as follows. First, the distance exponent of the gravity model is demonstrated to be a fractal dimension using the geometric measure relation. Second, the similarities and differences between the gravity models and spatial interaction models are revealed using allometric relations. Third, a four-parameter gravity model possesses a symmetrical expression, and we need dual gravity models to describe spatial flows. The observational data of China's cities and regions (29 elements indicative of 841 data points) in 2010 are employed to verify the theoretical inferences. A conclusion can be reached that the geographical gravity model based on power-law decay is more suitable for analyzing large, complex, and scale-free regional and urban systems. This study lends further support to the suggestion that the underlying rationale of fractal structure is entropy maximization. Moreover

Anomaly freedom in perturbative loop quantum gravity

International Nuclear Information System (INIS)

Bojowald, Martin; Hossain, Golam Mortuza; Kagan, Mikhail; Shankaranarayanan, S.

2008-01-01

A fully consistent linear perturbation theory for cosmology is derived in the presence of quantum corrections as they are suggested by properties of inverse volume operators in loop quantum gravity. The underlying constraints present a consistent deformation of the classical system, which shows that the discreteness in loop quantum gravity can be implemented in effective equations without spoiling space-time covariance. Nevertheless, nontrivial quantum corrections do arise in the constraint algebra. Since correction terms must appear in tightly controlled forms to avoid anomalies, detailed insights for the correct implementation of constraint operators can be gained. The procedures of this article thus provide a clear link between fundamental quantum gravity and phenomenology.

Anomalous Structure of Oceanic Lithosphere in the North Atlantic and Arctic Oceans: A Preliminary Analysis Based on Bathymetry, Gravity and Crustal Structure

Science.gov (United States)

Barantsrva, O.

2014-12-01

We present a preliminary analysis of the crustal and upper mantle structure for off-shore regions in the North Atlantic and Arctic oceans. These regions have anomalous oceanic lithosphere: the upper mantle of the North Atlantic ocean is affected by the Iceland plume, while the Arctic ocean has some of the slowest spreading rates. Our specific goal is to constrain the density structure of the upper mantle in order to understand the links between the deep lithosphere dynamics, ocean spreading, ocean floor bathymetry, heat flow and structure of the oceanic lithosphere in the regions where classical models of evolution of the oceanic lithosphere may not be valid. The major focus is on the oceanic lithosphere, but the Arctic shelves with a sufficient data coverage are also included into the analysis. Out major interest is the density structure of the upper mantle, and the analysis is based on the interpretation of GOCE satellite gravity data. To separate gravity anomalies caused by subcrustal anomalous masses, the gravitational effect of water, crust and the deep mantle is removed from the observed gravity field. For bathymetry we use the global NOAA database ETOPO1. The crustal correction to gravity is based on two crustal models: (1) global model CRUST1.0 (Laske, 2013) and, for a comparison, (2) a regional seismic model EUNAseis (Artemieva and Thybo, 2013). The crustal density structure required for the crustal correction is constrained from Vp data. Previous studies have shown that a large range of density values corresponds to any Vp value. To overcome this problem and to reduce uncertainty associated with the velocity-density conversion, we account for regional tectonic variations in the Northern Atlantics as constrained by numerous published seismic profiles and potential-field models across the Norwegian off-shore crust (e.g. Breivik et al., 2005, 2007), and apply different Vp-density conversions for different parts of the region. We present preliminary results

Self-constrained inversion of potential fields

Science.gov (United States)

Paoletti, V.; Ialongo, S.; Florio, G.; Fedi, M.; Cella, F.

2013-11-01

We present a potential-field-constrained inversion procedure based on a priori information derived exclusively from the analysis of the gravity and magnetic data (self-constrained inversion). The procedure is designed to be applied to underdetermined problems and involves scenarios where the source distribution can be assumed to be of simple character. To set up effective constraints, we first estimate through the analysis of the gravity or magnetic field some or all of the following source parameters: the source depth-to-the-top, the structural index, the horizontal position of the source body edges and their dip. The second step is incorporating the information related to these constraints in the objective function as depth and spatial weighting functions. We show, through 2-D and 3-D synthetic and real data examples, that potential field-based constraints, for example, structural index, source boundaries and others, are usually enough to obtain substantial improvement in the density and magnetization models.

3D Gravity Inversion by Growing Bodies and Shaping Layers at Mt. Vesuvius (Southern Italy)

Science.gov (United States)

Berrino, Giovanna; Camacho, Antonio G.

2008-06-01

To improve our knowledge of the structural pattern of Mt. Vesuvius and its magmatic system, which represents one of the three volcanoes located in the Neapolitan area (together with Campi Flegrei and Ischia; southern Italy), we analyze here the Bouguer gravity map that is already available through its interpretation by means of 2.5-dimensional modelling. We have carried out a three-dimensional interpretation using a new and original algorithm, known as ‘Layers’, that has been especially processed for this purpose. Layers works in an automatic and non-subjective way, and allows the definition of the structural settings in terms of several layers, each representing a specific geological formation. The same data are also interpreted in terms of isolated and shallow anomalous density bodies using a well tested algorithm known as ‘Growth’. We focus our inversions on the Mt. Vesuvius volcano, while globally analyzing the entire Neapolitan area, in order to investigate the deep structures, and in particular the deep extended ‘sill’ that has been revealed by seismic tomography. The final models generally confirm the global setting of the area as outlined by previous investigations, mainly for the shape and depth of the carbonate basement below Mt. Vesuvius. The presence of lateral density contrasts inside the volcano edifice is also shown, which was only hypothesized in the 2.5-dimensional inversion. Moreover, the models allow us to note a high density body that rises from the top of the carbonate basement and further elongates above sea level. This probably represents an uprising of the same basement, which is just below the volcano and which coincides with the VP and VP/VS anomalies detected under the crater. The three-dimensional results also reveal that the two inversion methods provide very similar models, where the high density isolated body in the Growth model can be associated with the rising high density anomaly in the Layers model. Taking into account

Reconciling ocean mass content change based on direct and inverse approaches by utilizing data from GRACE, altimetry and Swarm

Science.gov (United States)

Rietbroek, R.; Uebbing, B.; Lück, C.; Kusche, J.

2017-12-01

Ocean mass content (OMC) change due to the melting of the ice-sheets in Greenland and Antarctica, melting of glaciers and changes in terrestrial hydrology is a major contributor to present-day sea level rise. Since 2002, the GRACE satellite mission serves as a valuable tool for directly measuring the variations in OMC. As GRACE has almost reached the end of its lifetime, efforts are being made to utilize the Swarm mission for the recovery of low degree time-variable gravity fields to bridge a possible gap until the GRACE-FO mission and to fill up periods where GRACE data was not existent. To this end we compute Swarm monthly normal equations and spherical harmonics that are found competitive to other solutions. In addition to directly measuring the OMC, combination of GRACE gravity data with altimetry data in a global inversion approach allows to separate the total sea level change into individual mass-driven and steric contributions. However, published estimates of OMC from the direct and inverse methods differ not only depending on the time window, but also are influenced by numerous post-processing choices. Here, we will look into sources of such differences between direct and inverse approaches and evaluate the capabilities of Swarm to derive OMC. Deriving time series of OMC requires several processing steps; choosing a GRACE (and altimetry) product, data coverage, masks and filters to be applied in either spatial or spectral domain, corrections related to spatial leakage, GIA and geocenter motion. In this study, we compare and quantify the effects of the different processing choices of the direct and inverse methods. Our preliminary results point to the GIA correction as the major source of difference between the two approaches.

Inversion of Gravity and Magnetic Field Data for Tyrrhena Patera

Science.gov (United States)

Milbury, C.; Schubert, G.; Raymond, C. A.; Smrekar, S. E.

2011-01-01

Tyrrhena Patera is located to the southeast/northeast of the Isidis/Hellas impact basin. It was geologically active into the Late Amazonian, although the main edifice was formed in the Noachian(approximately 3.7-4.0 Ga). Tyrrhena Patera and the surrounding area contain gravity and magnetic anomalies that appear to be correlated. The results presented here are for the anomalies 1a and 1b (closest to Tyrrhena Patera), however other anomalies in this region have been modeled and will be presented at the conference.The Mars Global Surveyor (MGS) free-air gravity signature of Tyrrhena Patera has been studied by Kiefer, who inferred the existence of an extinct magma chamber below it. The magnetic signature has been mapped by Lillis R. J. et al., who compared electron reflectometer data, analogous to the total magnetic field, for Syrtis Major and Tyrrhena Patera and argued for demagnetization of both volcanoes.

Venus - Ishtar gravity anomaly

Science.gov (United States)

Sjogren, W. L.; Bills, B. G.; Mottinger, N. A.

1984-01-01

The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.

Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

Science.gov (United States)

Bhatia, Pramod; Singh, Ravinder

2017-06-01

Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

Supersoft Symmetry Energy Encountering Non-Newtonian Gravity in Neutron Stars

International Nuclear Information System (INIS)

Wen Dehua; Li Baoan; Chen Liewen

2009-01-01

Considering the non-Newtonian gravity proposed in grand unification theories, we show that the stability and observed global properties of neutron stars cannot rule out the supersoft nuclear symmetry energies at suprasaturation densities. The degree of possible violation of the inverse-square law of gravity in neutron stars is estimated using an equation of state of neutron-rich nuclear matter consistent with the available terrestrial laboratory data.

Large Airborne Full Tensor Gradient Data Inversion Based on a Non-Monotone Gradient Method

Science.gov (United States)

Sun, Yong; Meng, Zhaohai; Li, Fengting

2018-03-01

Following the development of gravity gradiometer instrument technology, the full tensor gravity (FTG) data can be acquired on airborne and marine platforms. Large-scale geophysical data can be obtained using these methods, making such data sets a number of the "big data" category. Therefore, a fast and effective inversion method is developed to solve the large-scale FTG data inversion problem. Many algorithms are available to accelerate the FTG data inversion, such as conjugate gradient method. However, the conventional conjugate gradient method takes a long time to complete data processing. Thus, a fast and effective iterative algorithm is necessary to improve the utilization of FTG data. Generally, inversion processing is formulated by incorporating regularizing constraints, followed by the introduction of a non-monotone gradient-descent method to accelerate the convergence rate of FTG data inversion. Compared with the conventional gradient method, the steepest descent gradient algorithm, and the conjugate gradient algorithm, there are clear advantages of the non-monotone iterative gradient-descent algorithm. Simulated and field FTG data were applied to show the application value of this new fast inversion method.

Children's strategies to solving additive inverse problems: a preliminary analysis

Science.gov (United States)

Ding, Meixia; Auxter, Abbey E.

2017-03-01

Prior studies show that elementary school children generally "lack" formal understanding of inverse relations. This study goes beyond lack to explore what children might "have" in their existing conception. A total of 281 students, kindergarten to third grade, were recruited to respond to a questionnaire that involved both contextual and non-contextual tasks on inverse relations, requiring both computational and explanatory skills. Results showed that children demonstrated better performance in computation than explanation. However, many students' explanations indicated that they did not necessarily utilize inverse relations for computation. Rather, they appeared to possess partial understanding, as evidenced by their use of part-whole structure, which is a key to understanding inverse relations. A close inspection of children's solution strategies further revealed that the sophistication of children's conception of part-whole structure varied in representation use and unknown quantity recognition, which suggests rich opportunities to develop students' understanding of inverse relations in lower elementary classrooms.

Inverse Scattering Method and Soliton Solution Family for String Effective Action

International Nuclear Information System (INIS)

Ya-Jun, Gao

2009-01-01

A modified Hauser–Ernst-type linear system is established and used to develop an inverse scattering method for solving the motion equations of the string effective action describing the coupled gravity, dilaton and Kalb–Ramond fields. The reduction procedures in this inverse scattering method are found to be fairly simple, which makes the proposed inverse scattering method applied fine and effective. As an application, a concrete family of soliton solutions for the considered theory is obtained

Preliminary results of gravity investigations at Yucca Mountain and vicinity, Southern Nye County, Nevada

International Nuclear Information System (INIS)

Snyder, D.B.; Carr, W.J.

1982-01-01

Exploration for a high-level-nuclear-waste-repository site in the Yucca Mountain area, Nevada, resulted in the addition of 423 new gravity stations during the past 2 years to the 934 existing stations to form the data base of this study. About 100 surface-rock samples, three borehole gamma-gamma logs, and one borehole gravity study provide excellent density control. A linear increase in density of 0.26 g/cm 3 per km is indicated in the tuff sequences makes the density contrast across the basal contact of the tuff the only strong source of gravity fluctuations. Isostatic and 2.0g/cm 3 Bouguer corrections were applied to the observed gravity values to remove deep-crust-related regional gradients and topographic effects, respectively. The resulting residual-gravity plot shows significant gravity anomalies that correlate closely with the structures inferred from drill-hole and surface geologic studies. Gravity highs over the three Paleozoic rock outcrops within the study area - Bare Mountain, the Calico Hills, and the Striped Hills - served as reference points for the gravity models. At least 3000 m of tuff fills a large steep-sided depression in the prevolcanic rocks beneath Yucca Mountain and Crater Flat. The gravity low and thick tuff section probably lie within a large collapse area comprising the Crater Flat-Timber Mountain-Silent Canyon caldera complexes. Gravity lows in Crater Flat itself are thought to coincide with the source areas of the Prow Pass Member, the Bullfrog Member, and the unnamed member of the Crater Flat Tuff. Southward extension of the broad gravity low associated with Crater Flat into the Amargosa Desert is evidence for sector graben-type collapse segments related to the Timber Mountain caldera and superimposed on the other structures within Crater Flat. 13 figures, 4 tables

Improving the Coastal Marine Gravity from CryoSat-2 Altimetry

Science.gov (United States)

Abulaitijiang, A.; Andersen, O. B.; Knudsen, P.

2017-12-01

The 7 years of CryoSat-2 satellite altimetry data can be potentially used to extract the high frequency components of the Earth gravity field beyond the Global Geopotential Models (GGMs) which corresponds to a resolution of 9.2 Km at the degree 2160. The Synthetic Aperture Radar (SAR) mode of the CryoSat-2 produced high precision along track observations and pushed the limits (qualified observations) to even closer to the coast by several kilometers. The conventional FFT method in deriving the marine gravity anomalies requires the input height anomalies to be gridded, and gridding in the irregular coastal zones (land-ocean transition zone) could introduce high frequency noise to the inversion. Therefore, Least Square Collocation (LSC) is preferred for the inversion. As part of a phd project, in this work, we will make use of the covariance function of the height anomalies in the coastal zones to derive the marine gravity anomalies. Using the conventional remove-compute-restore (only considering the GGMs) technique, the theoretical assumption of homogeneity and isotropy in the LSC algorithm is not always satisfied in the coastal regions and mountainous regions. Hence, the Topographic Correction (TC) using high resolution topographic grids is a critical step in the reduction of the gravity functionals (e.g., height anomaly and gravity anomaly), to comply with the theoretical assumption of LSC. In this work, the TC computation (both w.r.t. the height anomalies and gravity) will be conducted to test the performance of the signal reduction in several regions (patches) around Mediterranean, Chile, islands of Indonesia and Australian coast where the true gravity data is available. The derived marine gravity will be cross-validated against the ship-borne gravity observations. Earlier studies show that due to the presence of additional altimetry observations, 4 mGal accuracy can be achieved in the Greenland fjords, and equally good accuracy is expected from this work.

Test of Newton's inverse-square law in the Greenland ice cap

International Nuclear Information System (INIS)

Ander, M.E.; Zumberge, M.A.; Lautzenhiser, T.

1989-01-01

An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 and 1673 m to test for possible violations of Newton's inverse-square law. An anomalous gravity gradient was observed. We cannot unambiguously attribute it to a breakdown of Newtonian gravity because we have shown that it might be due to unexpected geological features in the rock below the ice

Possible evidence for non-Newtonian gravity in the Greenland ice gap

International Nuclear Information System (INIS)

Ander, M.E.

1988-01-01

An Airy-type geophysical experiment was conducted down a 2 km deep hole in the Greenland ice cap in order to test for possible violations of Newton's inverse square law by making gravity measurements over a range of 213 m to 1460 m. A significant departure from Newtonian gravity was observed. This result can be explained by the existence of an attractive non-Newtonian component of gravity with a strength of about 3.4% that of Newtonian gravity at a scale of 1460 m. Unfortunately, we cannot completely, unambiguously attribute it to a breakdown of Newtonian gravity because we have shown that lateral density variations in the bedrock beneath the ice can cause such apparent departures. If such variations existed, they would have to be rather unusual but certainly no impossible. 8 refs

Tests of gravity with future space-based experiments

Science.gov (United States)

Sakstein, Jeremy

2018-03-01

Future space-based tests of relativistic gravitation—laser ranging to Phobos, accelerometers in orbit, and optical networks surrounding Earth—will constrain the theory of gravity with unprecedented precision by testing the inverse-square law, the strong and weak equivalence principles, and the deflection and time delay of light by massive bodies. In this paper, we estimate the bounds that could be obtained on alternative gravity theories that use screening mechanisms to suppress deviations from general relativity in the Solar System: chameleon, symmetron, and Galileon models. We find that space-based tests of the parametrized post-Newtonian parameter γ will constrain chameleon and symmetron theories to new levels, and that tests of the inverse-square law using laser ranging to Phobos will provide the most stringent constraints on Galileon theories to date. We end by discussing the potential for constraining these theories using upcoming tests of the weak equivalence principle, and conclude that further theoretical modeling is required in order to fully utilize the data.

Testing the gravitational inverse-square law

International Nuclear Information System (INIS)

Adelberger, Eric; Heckel, B.; Hoyle, C.D.

2005-01-01

If the universe contains more than three spatial dimensions, as many physicists believe, our current laws of gravity should break down at small distances. When Isaac Newton realized that the acceleration of the Moon as it orbited around the Earth could be related to the acceleration of an apple as it fell to the ground, it was the first time that two seemingly unrelated physical phenomena had been 'unified'. The quest to unify all the forces of nature is one that still keeps physicists busy today. Newton showed that the gravitational attraction between two point bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. Newton's theory, which assumes that the gravitational force acts instantaneously, remained essentially unchallenged for roughly two centuries until Einstein proposed the general theory of relativity in 1915. Einstein's radical new theory made gravity consistent with the two basic ideas of relativity: the world is 4D - the three directions of space combined with time - and no physical effect can travel faster than light. The theory of general relativity states that gravity is not a force in the usual sense but a consequence of the curvature of this space-time produced by mass or energy. However, in the limit of low velocities and weak gravitational fields, Einstein's theory still predicts that the gravitational force between two point objects obeys an inverse-square law. One of the outstanding challenges in physics is to finish what Newton started and achieve the ultimate 'grand unification' - to unify gravity with the other three fundamental forces (the electromagnetic force, and the strong and weak nuclear forces) into a single quantum theory. In string theory - one of the leading candidates for an ultimate theory - the fundamental entities of nature are 1D strings and higher-dimensional objects called 'branes', rather than the point-like particles we are familiar with. String

A global mean ocean circulation estimation using goce gravity models - the DTU12MDT mean dynamic topography model

DEFF Research Database (Denmark)

Knudsen, Per; Andersen, Ole Baltazar

2012-01-01

The Gravity and Ocean Circulation Experiment - GOCE satellite mission measure the Earth gravity field with unprecedented accuracy leading to substantial improvements in the modelling of the ocean circulation and transport. In this study of the performance of GOCE, a newer gravity model have been...... combined with the DTU10MSS mean sea surface model to construct a global mean dynamic topography model named DTU10MDT. The results of preliminary analyses using preliminary GOCE gravity models clearly demonstrated the potential of GOCE mission. Both the resolution and the estimation of the surface currents...... have been improved significantly compared to results obtained using pre-GOCE gravity field models. The results of this study show that geostrophic surface currents associated with the mean circulation have been further improved and that currents having speeds down to 5 cm/s have been recovered....

Astrophysical black holes in screened modified gravity

Energy Technology Data Exchange (ETDEWEB)

Davis, Anne-Christine; Jha, Rahul; Muir, Jessica [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); Gregory, Ruth, E-mail: acd@damtp.cam.ac.uk, E-mail: r.a.w.gregory@durham.ac.uk, E-mail: r.jha@damtp.cam.ac.uk, E-mail: jlmuir@umich.edu [Centre for Particle Theory, South Road, Durham, DH1 3LE (United Kingdom)

2014-08-01

Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect.

Astrophysical black holes in screened modified gravity

International Nuclear Information System (INIS)

Davis, Anne-Christine; Jha, Rahul; Muir, Jessica; Gregory, Ruth

2014-01-01

Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect

Source Parameter Inversion for Recent Great Earthquakes from a Decade-long Observation of Global Gravity Fields

Science.gov (United States)

Han, Shin-Chan; Riva, Ricccardo; Sauber, Jeanne; Okal, Emile

2013-01-01

We quantify gravity changes after great earthquakes present within the 10 year long time series of monthly Gravity Recovery and Climate Experiment (GRACE) gravity fields. Using spherical harmonic normal-mode formulation, the respective source parameters of moment tensor and double-couple were estimated. For the 2004 Sumatra-Andaman earthquake, the gravity data indicate a composite moment of 1.2x10(exp 23)Nm with a dip of 10deg, in agreement with the estimate obtained at ultralong seismic periods. For the 2010 Maule earthquake, the GRACE solutions range from 2.0 to 2.7x10(exp 22)Nm for dips of 12deg-24deg and centroid depths within the lower crust. For the 2011 Tohoku-Oki earthquake, the estimated scalar moments range from 4.1 to 6.1x10(exp 22)Nm, with dips of 9deg-19deg and centroid depths within the lower crust. For the 2012 Indian Ocean strike-slip earthquakes, the gravity data delineate a composite moment of 1.9x10(exp 22)Nm regardless of the centroid depth, comparing favorably with the total moment of the main ruptures and aftershocks. The smallest event we successfully analyzed with GRACE was the 2007 Bengkulu earthquake with M(sub 0) approx. 5.0x10(exp 21)Nm. We found that the gravity data constrain the focal mechanism with the centroid only within the upper and lower crustal layers for thrust events. Deeper sources (i.e., in the upper mantle) could not reproduce the gravity observation as the larger rigidity and bulk modulus at mantle depths inhibit the interior from changing its volume, thus reducing the negative gravity component. Focal mechanisms and seismic moments obtained in this study represent the behavior of the sources on temporal and spatial scales exceeding the seismic and geodetic spectrum.

Inversion of gravity and gravity gradiometry data for density contrast surfaces using Cauchy-type integrals

DEFF Research Database (Denmark)

Zhdanov, Michael; Cai, Hongzhu

2014-01-01

We introduce a new method of modeling and inversion of potential field data generated by a density contrast surface. Our method is based on 3D Cauchy-type integral representation of the potential fields. Traditionally, potential fields are calculated using volume integrals of the domains occupied...

Cosmological dynamics of mimetic gravity

Science.gov (United States)

Dutta, Jibitesh; Khyllep, Wompherdeiki; Saridakis, Emmanuel N.; Tamanini, Nicola; Vagnozzi, Sunny

2018-02-01

We present a detailed investigation of the dynamical behavior of mimetic gravity with a general potential for the mimetic scalar field. Performing a phase-space and stability analysis, we show that the scenario at hand can successfully describe the thermal history of the universe, namely the successive sequence of radiation, matter, and dark-energy eras. Additionally, at late times the universe can either approach a de Sitter solution, or a scaling accelerated attractor where the dark-matter and dark-energy density parameters are of the same order, thus offering an alleviation of the cosmic coincidence problem. Applying our general analysis to various specific potential choices, including the power-law and the exponential ones, we show that mimetic gravity can be brought into good agreement with the observed behavior of the universe. Moreover, with an inverse square potential we find that mimetic gravity offers an appealing unified cosmological scenario where both dark energy and dark matter are characterized by a single scalar field, and where the cosmic coincidence problem is alleviated.

The Gravity Model for High School Students

Science.gov (United States)

Tribble, Paul; Mitchell, William A.

1977-01-01

The authors suggest ways in which the gravity model can be used in high school geography classes. Based on Newton's Law of Molecular Gravitation, the law states that gravitation is in direct ratio to mass and inverse ratio to distance. One activity for students involves determination of zones of influence of cities of various sizes. (Author/AV)

OCT structure, COB location and magmatic type of the SE Brazilian & S Angolan margins from integrated quantitative analysis of deep seismic reflection and gravity anomaly data

Science.gov (United States)

Cowie, L.; Kusznir, N. J.; Horn, B.

2013-12-01

Knowledge of ocean-continent transition (OCT) structure, continent-ocean boundary (COB) location and magmatic type are of critical importance for understanding rifted continental margin formation processes and in evaluating petroleum systems in deep-water frontier oil and gas exploration. The OCT structure, COB location and magmatic type of the SE Brazilian and S Angolan rifted continental margins are much debated; exhumed and serpentinised mantle have been reported at these margins. Integrated quantitative analysis using deep seismic reflection data and gravity inversion have been used to determine OCT structure, COB location and magmatic type for the SE Brazilian and S Angolan margins. Gravity inversion has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning. Residual Depth Anomaly (RDA) analysis has been used to investigate OCT bathymetric anomalies with respect to expected oceanic bathymetries and subsidence analysis has been used to determine the distribution of continental lithosphere thinning. These techniques have been validated on the Iberian margin for profiles IAM9 and ISE-01. In addition a joint inversion technique using deep seismic reflection and gravity anomaly data has been applied to the ION-GXT BS1-575 SE Brazil and ION-GXT CS1-2400 S Angola. The joint inversion method solves for coincident seismic and gravity Moho in the time domain and calculates the lateral variations in crustal basement densities and velocities along profile. Gravity inversion, RDA and subsidence analysis along the S Angolan ION-GXT CS1-2400 profile has been used to determine OCT structure and COB location. Analysis suggests that exhumed mantle, corresponding to a magma poor margin, is absent beneath the allochthonous salt. The thickness of earliest oceanic crust, derived from gravity and deep seismic reflection data is approximately 7km. The joint inversion predicts crustal basement densities and seismic velocities which are

Computer simulations of 3d Lorentzian quantum gravity

NARCIS (Netherlands)

Ambjørn, J.; Jurkiewicz, J.; Loll, R.

2000-01-01

We investigate the phase diagram of non-perturbative three-dimensional Lorentzian quantum gravity with the help of Monte Carlo simulations. The system has a first-order phase transition at a critical value kc 0 of the bare inverse gravitational coupling constant k0. For k0 > kc0 the system

Progress towards CSR RL06 GRACE gravity solutions

Science.gov (United States)

Save, Himanshu

2017-04-01

The GRACE project plans to re-processes the GRACE mission data in order to be consistent with the first gravity products released by the GRACE-FO project. The next generation Release-06 (RL06) gravity products from GRACE will include the improvements in GRACE Level-1 data products, background gravity models and the processing methodology. This paper will outline the planned improvements for CSR - RL06 and discuss the preliminary results. This paper will discuss the evolution of the quality of the GRACE solutions, especially over the past few years. We will also discuss the possible challenges we may face in connecting/extending the measurements of mass fluxes from the GRACE era to the GRACE-FO era due quality of the GRACE solutions from recent years.

Gravity Variation in Siberia: GRACE Observation and Possible Causes

Directory of Open Access Journals (Sweden)

Benjamin Fong Chao

2011-01-01

Full Text Available We report the finding, from the GRACE observation, of an increasing trend in the gravity anomaly in Siberia at the rate of up to 0.5 ugal yr-1 during 2003/1 - 2009/12, in the backdrop of a negative anomaly of magnitude on the order of ~-10 mgal. In consideration of the non-uniqueness of the gravitational inverse problem, we examine in some detail the various possible geophysical causes to explain the increasing gravity signal. We find two geophysical mechanisms being the most plausible, namely the melting of permafrost and the GIA post-glacial rebound. We conclude that these two mechanisms cannot be ruled out as causes for the regional gravity increase in Siberia, based on gravity data and in want of ancillary geophysical data in the region. More definitive identification of the contributions of the various causes awaits further studies.

The inverse problem: Ocean tides derived from earth tide observations

Science.gov (United States)

Kuo, J. T.

1978-01-01

Indirect mapping ocean tides by means of land and island-based tidal gravity measurements is presented. The inverse scheme of linear programming is used for indirect mapping of ocean tides. Open ocean tides were measured by the numerical integration of Laplace's tidal equations.

Beyond metric gravity: Progress on PS-200

International Nuclear Information System (INIS)

Goldman, T.; Brown, R.E.; Camp, J.B.; Darling, T.; Dyer, P.; Holzscheiter, M.H.; Hughes, R.J.; Jarmie, N.; King, N.S.P.; Lizon, D.C.; Nieto, M.M.; Schauer, M.M.M.; Schecker, J.A.; Cornford, S.; Hosea, K.; Kenefick, R.A.; Hoibraaten, S.; Midzor, M.M.; Parry, S.P.; Ristenen, R.A.; Witteborn, F.C.

1993-01-01

The reconciliation of quantum mechanics and gravity on varying distance scales requires changes to General Relativity that may be testable implications. We briefly review the status of tests with matter of the inverse square law and the principle of equivalence, then report on progress on the drift-tube measurement section of PS- 200, the experiment to measure the gravitational acceleration of antiprotons

Three Least-Squares Minimization Approaches to Interpret Gravity Data Due to Dipping Faults

Science.gov (United States)

Abdelrahman, E. M.; Essa, K. S.

2015-02-01

We have developed three different least-squares minimization approaches to determine, successively, the depth, dip angle, and amplitude coefficient related to the thickness and density contrast of a buried dipping fault from first moving average residual gravity anomalies. By defining the zero-anomaly distance and the anomaly value at the origin of the moving average residual profile, the problem of depth determination is transformed into a constrained nonlinear gravity inversion. After estimating the depth of the fault, the dip angle is estimated by solving a nonlinear inverse problem. Finally, after estimating the depth and dip angle, the amplitude coefficient is determined using a linear equation. This method can be applied to residuals as well as to measured gravity data because it uses the moving average residual gravity anomalies to estimate the model parameters of the faulted structure. The proposed method was tested on noise-corrupted synthetic and real gravity data. In the case of the synthetic data, good results are obtained when errors are given in the zero-anomaly distance and the anomaly value at the origin, and even when the origin is determined approximately. In the case of practical data (Bouguer anomaly over Gazal fault, south Aswan, Egypt), the fault parameters obtained are in good agreement with the actual ones and with those given in the published literature.

OCT structure, COB location and magmatic type of the S Angolan & SE Brazilian margins from integrated quantitative analysis of deep seismic reflection and gravity anomaly data

Science.gov (United States)

Cowie, Leanne; Kusznir, Nick; Horn, Brian

2014-05-01

Integrated quantitative analysis using deep seismic reflection data and gravity inversion have been applied to the S Angolan and SE Brazilian margins to determine OCT structure, COB location and magmatic type. Knowledge of these margin parameters are of critical importance for understanding rifted continental margin formation processes and in evaluating petroleum systems in deep-water frontier oil and gas exploration. The OCT structure, COB location and magmatic type of the S Angolan and SE Brazilian rifted continental margins are much debated; exhumed and serpentinised mantle have been reported at these margins. Gravity anomaly inversion, incorporating a lithosphere thermal gravity anomaly correction, has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning. Residual Depth Anomaly (RDA) analysis has been used to investigate OCT bathymetric anomalies with respect to expected oceanic bathymetries and subsidence analysis has been used to determine the distribution of continental lithosphere thinning. These techniques have been validated for profiles Lusigal 12 and ISE-01 on the Iberian margin. In addition a joint inversion technique using deep seismic reflection and gravity anomaly data has been applied to the ION-GXT BS1-575 SE Brazil and ION-GXT CS1-2400 S Angola deep seismic reflection lines. The joint inversion method solves for coincident seismic and gravity Moho in the time domain and calculates the lateral variations in crustal basement densities and velocities along the seismic profiles. Gravity inversion, RDA and subsidence analysis along the ION-GXT BS1-575 profile, which crosses the Sao Paulo Plateau and Florianopolis Ridge of the SE Brazilian margin, predict the COB to be located SE of the Florianopolis Ridge. Integrated quantitative analysis shows no evidence for exhumed mantle on this margin profile. The joint inversion technique predicts oceanic crustal thicknesses of between 7 and 8 km thickness with

Sofalica Region (GAZIANTEP Chromium on Microgravity Anomalies Modelling of Normalized Full Gradient and Nonlinear Inversion

Directory of Open Access Journals (Sweden)

Birgül Kınalıbalaban

2013-08-01

Full Text Available In this study, the province of Gaziantep, Şehitkamil district, there are thought to be chrome-metallic mine in the village of Sofalıca the localization of gravity and economical method was to investigate whether it has a reserve. Approximately 189 hectares of land gravity measurements over the measurement point in the study area was 220. By differentiating regional and residual Bouguer gravity map of the generated residual maps were obtained on areas likely to be created on the source. The inversion method of pre-NTG was required for the selection model is the appropriate start. On the structure of polygon slices as a result of application received in the form of the inversion in the range of 125 meters and 450 meters long, 25 meters to 70 meters in thickness in the range of existence of geometric structures have been identified.

Quantum gravity effects on scalar particle tunneling from rotating BTZ black hole

Science.gov (United States)

Meitei, I. Ablu; Singh, T. Ibungochouba; Devi, S. Gayatri; Devi, N. Premeshwari; Singh, K. Yugindro

2018-04-01

Tunneling of scalar particles across the event horizon of rotating BTZ black hole is investigated using the Generalized Uncertainty Principle to study the corrected Hawking temperature and entropy in the presence of quantum gravity effects. We have determined explicitly the various correction terms in the entropy of rotating BTZ black hole including the logarithmic term of the Bekenstein-Hawking entropy (SBH), the inverse term of SBH and terms with inverse powers of SBH, in terms of properties of the black hole and the emitted particles — mass, energy and angular momentum. In the presence of quantum gravity effects, for the emission of scalar particles, the Hawking radiation and thermodynamics of rotating BTZ black hole are observed to be related to the metric element, hence to the curvature of space-time.

Estimating Moho basement and faults using gravity inversion in Yushu-earthquake area, China

Directory of Open Access Journals (Sweden)

Yang Guangliang

2012-05-01

Full Text Available A gravity survey was conducted one month after the 2010 Yushu earthquake in the epicenter area. The cross-fault survey line was 500 km long, from Langqian county to Qingshuihe county, in a transition zone between Bayan Har block and Qiangtang block, in an area of high elevation, large undulating terrain, and complex geological features. An interpretation of the data was carried out together with other kinds of data, such as seismic exploration and magnetic exploration. The result shows that gravity is sensitive to fault boundary; the geologic structure of the region is complex at middle and upper depths, and the density profile reveals an eastward-pushing fault movement.

Deep structure of Pyrenees range (SW Europe) imaged by joint inversion of gravity and teleseismic delay time

Science.gov (United States)

Dufréchou, G.; Tiberi, C.; Martin, R.; Bonvalot, S.; Chevrot, S.; Seoane, L.

2018-04-01

We present a new model of the lithosphere and asthenosphere structure down to 300 km depth beneath the Pyrenees from the joint inversion of recent gravity and teleseismic data. Unlike previous studies, crustal correction were not applied on teleseismic data in order (i) to preserve the consistency between gravity data, which are mainly sensitive to the density structure of the crust.lithosphere, and travel time data, and (ii) to avoid the introduction of biases resulting from crustal reductions. The density model down to 100 km depth is preferentially used here to discuss the lithospheric structure of the Pyrenees, whereas the asthenospheric structure from 100 km to 300 km depth is discussed from our velocity model. The absence of a high density anomaly in our model between 30-100 km depth (except the Labourd density anomaly) in the northern part of the Pyrenees seems to preclude eclogitization of the subducted Iberian crust at the scale of the entire Pyrenean range. Local eclogitization of the deep Pyrenean crust beneath the western part of the Axial Zone (West of Andorra) associated with the positive Central density anomaly is proposed. The Pyrenean lithosphere in density and velocity models appears segmented from East to West. No clear relation between the along-strike segmentation and mapped major faults is visible in our models. The Pyrenees' lithosphere segments are associated to different seismicity pattern in the Pyrenees suggesting a possible relation between the deep structure of the Pyrenees and its seismicity in the upper crust. The concentration of earthquakes localized just straight up the Central density anomaly can result of the subsidence and/or delamination of an eclogitized Pyrenean deep root. The velocity model in the asthenosphere is similar to previous studies. The absence of a high-velocity anomaly in the upper mantle and transition zone (i.e. 125 to 225 km depth) seems to preclude the presence of a detached oceanic lithosphere beneath the

Preliminary results of absolute and high-precision gravity measurements at the Nevada Test Site and vicinity, Nevada

International Nuclear Information System (INIS)

Zumberge, M.A.; Harris, R.N.; Oliver, H.W.; Sasagawa, G.S.; Ponce, D.A.

1988-01-01

Absolute gravity measurements were made at 4 sites in southern Nevada using the absolute gravity free-fall apparatus. Three of the sites are located on the Nevada Test Site at Mercury, Yucca Pass, and in northern Jackass Flats. The fourth site is at Kyle Canyon ranger station near Charleston Park where observed gravity is 216.19 mGal lower than at Mercury. Although there is an uncertainty of about 0.02 mGal in the absolute measured values, their gravity differences are considered accurate to about 0.03 mGal. Therefore, the absolute measurements should provide local control for the calibration of gravity meters between Mercury and Kyle Canyon ranger station to about 1 to 2 parts in 10,000. The average gravity differences between Mercury and Kyle Canyon obtained using LaCoste and Romberg gravity meters is 216.13 mGal, 0.06 mGal lower, or 3 parts in 10,000 lower than using the absolute gravity meter. Because of the discrepancy between the comparison of the absolute and relative gravity meters, more absolute and relative gravity control in southern Nevada, as well as the Mt. Hamilton area where the LaCoste and Romberg instruments were calibrated, is needed. Multiple gravity meter ties were also made between each of the four absolute stations to nearby base stations located on bedrock. These stations were established to help monitor possible real changes in gravity at the absolute sites that could result from seasonal variations in the depth to the water table or other local mass changes. 8 refs., 16 figs., 7 tabs

Implicit structural inversion of gravity data using linear programming, a validation study

NARCIS (Netherlands)

Zon, A.T. van; Roy Chowdhury, K.

2010-01-01

In this study, a regional scale gravity data set has been inverted to infer the structure (topography) of the top of the basement underlying sub-horizontal strata. We apply our method to this real data set for further proof of concept, validation and benchmarking against results from an earlier

New Interpretations of the Rayn Anticlines in the Arabian Basin Inferred from Gravity Modelling

Science.gov (United States)

AlMogren, S. M.; Mukhopadhyay, M.

2014-12-01

The Ryan Anticlines comprise of a regularly-spaced set of super-giant anticlines oriented NNW, developed due to E-W compression in the Arabian Basin. Most prominent of these being: the Ghawar Anticline, followed by the Summan, Khurais Anticlines and Qatar Arch. Gravity anomaly is largely characteristic for both Ryan Anticlines and its smaller size version the Jinadriah Anticline in the Riyadh Salt Basin. It displays a bipolar gravity field - a zone of gravity high running along the fold axis that is flanked by asymmetric gravity lows. Available structural models commonly infer structural uplift for the median gravity high but ignore the flanking lows. Here we interpret the bipolar gravity anomaly due primarily to such anticline structures, while, the flanking gravity lows are due to greater sediment thickness largely compacted and deformed over the basement depressions. Further complexities are created due to the salt layer and its migration at the lower horizons of sediment strata. Such diagnostic gravity anomaly pattern is taken here as an evidence for basement tectonics due to prevailing crustal dynamics in the Arabian Basin. Density inversion provides details on the subsurface density variation due to the folding and structural configuration for the sediment layers, including the salt layer, affected by basement deformation. This interpretation is largely supported by gravity forward and inversion models given in the present study what is partly constrained by the available seismic, MT and deep resistivity lines and surface geologic mapping. Most of the oil-gas fields in this part of the Arabian Basin are further known for salt diapirism. In this study the gravity interpretation help in identification of salt diapirism directly overlying the basement is firstly given here for Jinadriah Anticline; that is next extended to a regional geologic cross-section traversing the Ryan Anticlines to infer probable subsurface continuation of salt diapirs directly overlying

Gauges and functional measures in quantum gravity II: higher-derivative gravity

Energy Technology Data Exchange (ETDEWEB)

Ohta, N. [Kindai University, Department of Physics, Higashi-Osaka, Osaka (Japan); Percacci, R. [International School for Advanced Studies, Trieste (Italy); INFN, Sezione di Trieste, Trieste (Italy); Pereira, A.D. [UERJ-Universidade do Estado do Rio de Janeiro, Departamento de Fisica Teorica, Rio de Janeiro (Brazil)

2017-09-15

We compute the one-loop divergences in a higher-derivative theory of gravity including Ricci tensor squared and Ricci scalar squared terms, in addition to the Hilbert and cosmological terms, on an (generally off-shell) Einstein background. We work with a two-parameter family of parametrizations of the graviton field, and a two-parameter family of gauges. We find that there are some choices of gauge or parametrization that reduce the dependence on the remaining parameters. The results are invariant under a recently discovered ''duality'' that involves the replacement of the densitized metric by a densitized inverse metric as the fundamental quantum variable. (orig.)

Application of generalized inverse for analysis of magnetic anomalies due to a dyke model - Some numerical experiments

Digital Repository Service at National Institute of Oceanography (India)

Rao, M.M.M.; Murty, T.V.R.; SuryaPrakash, S.; Chandramouli, P.; Murthy, K.S.R.

. Indust. Appl. Math, 11 (1963) 431-441. 10. Pedersen L B, Interpretation of potential field data – A generalised inverse approach, Geophy. Prosp. 25 (1977) 199-230. 11. Radhakrishna Murthy I V, Swamy K V & Jagannadha Rao S, Automatic inversion... generalised inverse technique in reconstruction of gravity anomalies due to a fault, Indian J. Pure. Appl. Math., 34 (2003) 31-47. 16. Ramana Murty T V, Somayajulu Y K & Murty C S, Reconstruction of sound speed profile through natural generalised inverse...

The First Time Ever I Saw Your Feet: Inversion Effect in Newborns' Sensitivity to Biological Motion

Science.gov (United States)

Bardi, Lara; Regolin, Lucia; Simion, Francesca

2014-01-01

Inversion effect in biological motion perception has been recently attributed to an innate sensitivity of the visual system to the gravity-dependent dynamic of the motion. However, the specific cues that determine the inversion effect in naïve subjects were never investigated. In the present study, we have assessed the contribution of the local…

Constraining f(T) gravity in the Solar System

Energy Technology Data Exchange (ETDEWEB)

Iorio, Lorenzo [Ministero dell' Istruzione dell' Università e della Ricerca (M.I.U.R), Viale Unità di Italia 68, 70125 Bari (Italy); Radicella, Ninfa [Dipartimento di Fisica E.R. Caianiello, Università di Salerno, Via Giovanni Paolo II 132, Fisciano (Italy); Ruggiero, Matteo Luca, E-mail: lorenzo.iorio@libero.it, E-mail: ninfa.radicella@sa.infn.it, E-mail: matteo.ruggiero@polito.it [DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino (Italy)

2015-08-01

In the framework of f(T) theories of gravity, we solve the field equations for f(T)=T+α T{sup n} in the weak-field approximation and for spherical symmetry spacetime. Since f(T)=T corresponds to Teleparallel Gravity, which is equivalent to General Relativity, the non linearity of the Lagrangian are expected to produce perturbations of the general relativistic solutions, parameterized by α. Hence, we use the f(T) solutions to model the gravitational field of the Sun and exploit data from accurate radio-tracking of spacecrafts orbiting Mercury and Saturn to infer preliminary bounds on the model parameter α and on the cosmological constant Λ.

Ground-based self-gravity tests for LISA Pathfinder and LISA

International Nuclear Information System (INIS)

Trenkel, C; Warren, C; Wealthy, D

2009-01-01

Gravitational coupling between the free-falling test masses and the surrounding spacecraft is one of the dominant noise sources for both LISA Pathfinder and LISA. At present, there are no plans to verify any of the self-gravity requirements by test, on the ground. Here, we explore the possibilities of conducting such tests, using a customised torsion balance. We discuss the main sources of systematic and statistical uncertainty present in such a set-up. Our preliminary assessment indicates that the sensitivity is sufficient to carry out meaningful self-gravity tests.

1D inversion and analysis of marine controlled-source EM data

DEFF Research Database (Denmark)

Christensen, N.B.; Dodds, Kevin; Bulley, Ian

2006-01-01

been displaced by resistive oil or gas. We present preliminary results from an investigation of the applicability of one-dimensional inversion of the data. A noise model for the data set is developed and inversion is carried out with multi-layer models and 4-layer models. For the data set in question...

Accounting for time- and space-varying changes in the gravity field to improve the network adjustment of relative-gravity data

Science.gov (United States)

Kennedy, Jeffrey R.; Ferre, Ty P.A.

2015-01-01

The relative gravimeter is the primary terrestrial instrument for measuring spatially and temporally varying gravitational fields. The background noise of the instrument—that is, non-linear drift and random tares—typically requires some form of least-squares network adjustment to integrate data collected during a campaign that may take several days to weeks. Here, we present an approach to remove the change in the observed relative-gravity differences caused by hydrologic or other transient processes during a single campaign, so that the adjusted gravity values can be referenced to a single epoch. The conceptual approach is an example of coupled hydrogeophysical inversion, by which a hydrologic model is used to inform and constrain the geophysical forward model. The hydrologic model simulates the spatial variation of the rate of change of gravity as either a linear function of distance from an infiltration source, or using a 3-D numerical groundwater model. The linear function can be included in and solved for as part of the network adjustment. Alternatively, the groundwater model is used to predict the change of gravity at each station through time, from which the accumulated gravity change is calculated and removed from the data prior to the network adjustment. Data from a field experiment conducted at an artificial-recharge facility are used to verify our approach. Maximum gravity change due to hydrology (observed using a superconducting gravimeter) during the relative-gravity field campaigns was up to 2.6 μGal d−1, each campaign was between 4 and 6 d and one month elapsed between campaigns. The maximum absolute difference in the estimated gravity change between two campaigns, two months apart, using the standard network adjustment method and the new approach, was 5.5 μGal. The maximum gravity change between the same two campaigns was 148 μGal, and spatial variation in gravity change revealed zones of preferential infiltration and areas of relatively

Inverse problem of solar oscillations

International Nuclear Information System (INIS)

Sekii, T.; Shibahashi, H.

1987-01-01

The authors present some preliminary results of numerical simulation to infer the sound velocity distribution in the solar interior from the oscillation data of the Sun as the inverse problem. They analyze the acoustic potential itself by taking account of some factors other than the sound velocity, and infer the sound velocity distribution in the deep interior of the Sun

On the functional measure for quantum gravity in the light-cone gauge

International Nuclear Information System (INIS)

Endo, Ryusuke; Kimura, Toshiei

1978-01-01

It is shown that the argument of Kaku and Senjanovic on the functional measure for quantum gravity holds irrespective of the order of the perturbation expansion in powers of the gravitational constant. Accordingly, the functional measure for quantum gravity coincides with that of Fradkin and Vilkovisky in the strict sense. The argument is carried out with the aid of two propositions in which we postulate that the inverse of the differential operator deltasub(-) = delta/delta x - (x - = (x 0 - x 3 )/√2) exists uniquely. (author)

Slab Geometry and Segmentation on Seismogenic Subduction Zone; Insight from gravity gradients

Science.gov (United States)

Saraswati, A. T.; Mazzotti, S.; Cattin, R.; Cadio, C.

2017-12-01

Slab geometry is a key parameter to improve seismic hazard assessment in subduction zones. In many cases, information about structures beneath subduction are obtained from geophysical dedicated studies, including geodetic and seismic measurements. However, due to the lack of global information, both geometry and segmentation in seismogenic zone of many subductions remain badly-constrained. Here we propose an alternative approach based on satellite gravity observations. The GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission enables to probe Earth deep mass structures from gravity gradients, which are more sensitive to spatial structure geometry and directional properties than classical gravitational data. Gravity gradients forward modeling of modeled slab is performed by using horizontal and vertical gravity gradient components to better determine slab geophysical model rather than vertical gradient only. Using polyhedron method, topography correction on gravity gradient signal is undertaken to enhance the anomaly signal of lithospheric structures. Afterward, we compare residual gravity gradients with the calculated signals associated with slab geometry. In this preliminary study, straightforward models are used to better understand the characteristic of gravity gradient signals due to deep mass sources. We pay a special attention to the delineation of slab borders and dip angle variations.

Rainfall assimilation in RAMS by means of the Kuo parameterisation inversion: method and preliminary results

Science.gov (United States)

Orlandi, A.; Ortolani, A.; Meneguzzo, F.; Levizzani, V.; Torricella, F.; Turk, F. J.

2004-03-01

In order to improve high-resolution forecasts, a specific method for assimilating rainfall rates into the Regional Atmospheric Modelling System model has been developed. It is based on the inversion of the Kuo convective parameterisation scheme. A nudging technique is applied to 'gently' increase with time the weight of the estimated precipitation in the assimilation process. A rough but manageable technique is explained to estimate the partition of convective precipitation from stratiform one, without requiring any ancillary measurement. The method is general purpose, but it is tuned for geostationary satellite rainfall estimation assimilation. Preliminary results are presented and discussed, both through totally simulated experiments and through experiments assimilating real satellite-based precipitation observations. For every case study, Rainfall data are computed with a rapid update satellite precipitation estimation algorithm based on IR and MW satellite observations. This research was carried out in the framework of the EURAINSAT project (an EC research project co-funded by the Energy, Environment and Sustainable Development Programme within the topic 'Development of generic Earth observation technologies', Contract number EVG1-2000-00030).

Joint inversion of ambient noise surface wave and gravity data to image the upper crustal structure of the Tanlu fault zone to the southeast of Hefei, China

Science.gov (United States)

Wang, K.; Gu, N.; Zhang, H.; Zhou, G.

2017-12-01

The Tanlu fault is a major fault located in the eastern China, which stretches 2400 km long from Tancheng in the north to Lujiang in the south. It is generally believed that the Tanlu fault zone was formed in Proterozoic era and underwent a series of complicated processes since then. To understand the upper crustal structure around the southern segment of the Tanlu fault zone, in 2017 we deployed 53 short period seismic stations around the fault zone to the southeast of Hefei, capital city of Anhui province. The temporary array continuously recorded the data for about one month from 17 March to 26 April 2017. The seismic array spans an area of about 30km x 30Km with an average station spacing of about 5-6km. The vertical component data were used for extracting Rayleigh wave phase and group velocity dispersion data for the period of 0.2 to 5 seconds. To improve imaging the upper crustal structure of the fault zone, we jointly inverted the surface wave dispersion data and the gravity data because they have complementary strengths. To combine surface wave dispersion data and gravity observations into a single inversion framework, we used an empirical relationship between seismic velocity and density of Maceira and Ammon (2009). By finding the optimal relative weighting between two data types, we are able to find a shear wave velocity (Vs) model that fits both data types. The joint inversion can resolve the upper crustal fault zone structure down to about 7 km in depth. The Vs model shows that in this region the Tanlu fault is associated with high velocity anomalies, corresponding well to the Feidong complex seen on the surface. This indicates that the Tanlu fault zone may provide a channel for the intrusion of hot materials.

Pulsar spin down and cosmologies with varying gravity

International Nuclear Information System (INIS)

Mansfield, V.N.

1976-01-01

Reference is made to the measured spin down of the pulsar JP1953 and it is stated that this conflicts with conclusions concerning cosmologies having weakening gravity. An explanation is also given for the lack of long period pulsars in terms of group theory cosmologies with strengthening gravity. The implications of Dirac's large number hypothesis are considered, including possibilities for the implied continuous creation of matter, both 'additive creation' in which nucleons are created uniformly throughout space and 'multiplicative creation' in which matter is created where it already exists in proportion to the amount existing. Malin's suggestion (Phys. Rev. D9:3228 (1974)) that the mass of all particles varies inversely as the four-dimensional radius of curvature of the universe is also considered. (U.K.)

Massive gravity from bimetric gravity

International Nuclear Information System (INIS)

Baccetti, Valentina; Martín-Moruno, Prado; Visser, Matt

2013-01-01

We discuss the subtle relationship between massive gravity and bimetric gravity, focusing particularly on the manner in which massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure is more delicate than currently appreciated. Specifically, this limiting procedure should not unnecessarily constrain the background metric, which must be externally specified by the theory of massive gravity itself. The fact that in bimetric theories one always has two sets of metric equations of motion continues to have an effect even in the massive gravity limit, leading to additional constraints besides the one set of equations of motion naively expected. Thus, since solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true, there is no complete continuity in the parameter space of the theory. In particular, we study the massive cosmological solutions which are continuous in the parameter space, showing that many interesting cosmologies belong to this class. (paper)

Neutron stars in screened modified gravity: Chameleon versus dilaton

Science.gov (United States)

Brax, Philippe; Davis, Anne-Christine; Jha, Rahul

2017-04-01

We consider the scalar field profile around relativistic compact objects such as neutron stars for a range of modified gravity models with screening mechanisms of the chameleon and Damour-Polyakov types. We focus primarily on inverse power law chameleons and the environmentally dependent dilaton as examples of both mechanisms. We discuss the modified Tolman-Oppenheimer-Volkoff equation and then implement a relaxation algorithm to solve for the scalar profiles numerically. We find that chameleons and dilatons behave in a similar manner and that there is a large degeneracy between the modified gravity parameters and the neutron star equation of state. This is exemplified by the modifications to the mass-radius relationship for a variety of model parameters.

Stochastic quantization and gravity

International Nuclear Information System (INIS)

Rumpf, H.

1984-01-01

We give a preliminary account of the application of stochastic quantization to the gravitational field. We start in Section I from Nelson's formulation of quantum mechanics as Newtonian stochastic mechanics and only then introduce the Parisi-Wu stochastic quantization scheme on which all the later discussion will be based. In Section II we present a generalization of the scheme that is applicable to fields in physical (i.e. Lorentzian) space-time and treat the free linearized gravitational field in this manner. The most remarkable result of this is the noncausal propagation of conformal gravitons. Moreover the concept of stochastic gauge-fixing is introduced and a complete discussion of all the covariant gauges is given. A special symmetry relating two classes of covariant gauges is exhibited. Finally Section III contains some preliminary remarks on full nonlinear gravity. In particular we argue that in contrast to gauge fields the stochastic gravitational field cannot be transformed to a Gaussian process. (Author)

Seasonal gravity change at Yellowstone caldera

Science.gov (United States)

Poland, M. P.; de Zeeuw-van Dalfsen, E.

2017-12-01

The driving forces behind Yellowstone's dynamic deformation, vigorous hydrothermal system, and abundant seismicity are usually ascribed to "magmatic fluids," which could refer to magma, water, volatiles, or some combination. Deformation data alone cannot distinguish the relative importance of these fluids. Gravity measurements, however, provide an indication of mass change over time and, when combined with surface displacements, can constrain the density of subsurface fluids. Unfortunately, several decades of gravity surveys at Yellowstone have yielded ambiguous results. We suspect that the difficulty in interpreting Yellowstone gravity data is due to seasonal variations in environmental conditions—especially surface and ground water. Yellowstone gravity surveys are usually carried out at the same time of year (generally late summer) to minimize the impact of seasonality. Nevertheless, surface and subsurface water levels are not likely to be constant from year to year, given annual differences in precipitation. To assess the overall magnitude of seasonal gravity changes, we conducted gravity surveys of benchmarks in and around Yellowstone caldera in May, July, August, and October 2017. Our goal was to characterize seasonal variations due to snow melt/accumulation, changes in river and lake levels, changes in groundwater levels, and changes in hydrothermal activity. We also hope to identify sites that show little variation in gravity over the course of the 2017 surveys, as these locations may be less prone to seasonal changes and more likely to detect small variations due to magmatic processes. Preliminary examination of data collected in May and July 2017 emphasizes the importance of site location relative to sources of water. For example, a site on the banks of the Yellowstone River showed a gravity increase of several hundred microgals associated with a 50 cm increase in the river level. A high-altitude site far from rivers and lakes, in contrast, showed a

Galileo's Treatment for the Centre of Gravity of Solids

Science.gov (United States)

Worner, C. H.; Iommi-Amunategui, G.

2007-01-01

The appendix on the centres of gravity that appears at the end of Galileo's book, "Two New Sciences", is analysed. It is shown that the method used by Galileo in this work has an interesting reasoning and also shows preliminary ideas about scaling and advances some ideas about series convergence. In addition, we note that the geometrical language…

Preliminary Assessment of Artificial Gravity Impacts to Deep-Space Vehicle Design

Science.gov (United States)

Joosten, B. Kent

2007-01-01

Even after more than thirty years of scientific investigation, serious concerns regarding human physiological effects of long-duration microgravity exposure remain. These include loss of bone mineral density, skeletal muscle atrophy, and orthostatic hypertension, among others. In particular, "Safe Passage: Astronaut Care for Exploration Missions," states "loss of bone density, which apparently occurs at a rate of 1% per month in microgravity, is relatively manageable on the short-duration missions of the space shuttle, but it becomes problematic on the ISS [International Space Station]. ...If this loss is not mitigated, interplanetary missions will be impossible." While extensive investigations into potential countermeasures are planned on the ISS, the delay in attaining full crew complement and onboard facilities, and the potential for extending crews tours of duty threaten the timely (definitive design requirements, especially acceptable artificial gravity levels and rotation rates, the perception of high vehicle mass and performance penalties, the incompatibility of resulting vehicle configurations with space propulsion options (i.e., aerocapture), the perception of complications associated with de-spun components such as antennae and photovoltaic arrays, and the expectation of effective crew micro-gravity countermeasures. These perception and concerns may have been overstated, or may be acceptable alternatives to countermeasures of limited efficacy. This study was undertaken as an initial step to try to understand the implications of and potential solutions to incorporating artificial gravity in the design of human deep-space exploration vehicles. Of prime interest will be the mass penalties incurred by incorporating AG, along with any mission performance degradation.

A global mean dynamic topography and ocean circulation estimation using a preliminary GOCE gravity model

DEFF Research Database (Denmark)

Knudsen, Per; Bingham, R.; Andersen, Ole Baltazar

2011-01-01

The Gravity and steady-state Ocean Circulation Explorer (GOCE) satellite mission measures Earth’s gravity field with an unprecedented accuracy at short spatial scales. In doing so, it promises to significantly advance our ability to determine the ocean’s general circulation. In this study, an ini...

AI-guided parameter optimization in inverse treatment planning

International Nuclear Information System (INIS)

Yan Hui; Yin Fangfang; Guan Huaiqun; Kim, Jae Ho

2003-01-01

An artificial intelligence (AI)-guided inverse planning system was developed to optimize the combination of parameters in the objective function for intensity-modulated radiation therapy (IMRT). In this system, the empirical knowledge of inverse planning was formulated with fuzzy if-then rules, which then guide the parameter modification based on the on-line calculated dose. Three kinds of parameters (weighting factor, dose specification, and dose prescription) were automatically modified using the fuzzy inference system (FIS). The performance of the AI-guided inverse planning system (AIGIPS) was examined using the simulated and clinical examples. Preliminary results indicate that the expected dose distribution was automatically achieved using the AI-guided inverse planning system, with the complicated compromising between different parameters accomplished by the fuzzy inference technique. The AIGIPS provides a highly promising method to replace the current trial-and-error approach

Einstein versus the Simple Pendulum Formula: Does Gravity Slow All Clocks?

Science.gov (United States)

Puri, Avinash

2015-01-01

According to the Newtonian formula for a simple pendulum, the period of a pendulum is inversely proportional to the square root of "g", the gravitational field strength. Einstein's theory of general relativity leads to the result that time slows down where gravity is intense. The two claims look contradictory and can muddle student and…

Gravity and Nonconservative Force Model Tuning for the GEOSAT Follow-On Spacecraft

Science.gov (United States)

Lemoine, Frank G.; Zelensky, Nikita P.; Rowlands, David D.; Luthcke, Scott B.; Chinn, Douglas S.; Marr, Gregory C.; Smith, David E. (Technical Monitor)

2000-01-01

The US Navy's GEOSAT Follow-On spacecraft was launched on February 10, 1998 and the primary objective of the mission was to map the oceans using a radar altimeter. Three radar altimeter calibration campaigns have been conducted in 1999 and 2000. The spacecraft is tracked by satellite laser ranging (SLR) and Doppler beacons and a limited amount of data have been obtained from the Global Positioning Receiver (GPS) on board the satellite. Even with EGM96, the predicted radial orbit error due to gravity field mismodelling (to 70x70) remains high at 2.61 cm (compared to 0.88 cm for TOPEX). We report on the preliminary gravity model tuning for GFO using SLR, and altimeter crossover data. Preliminary solutions using SLR and GFO/GFO crossover data from CalVal campaigns I and II in June-August 1999, and January-February 2000 have reduced the predicted radial orbit error to 1.9 cm and further reduction will be possible when additional data are added to the solutions. The gravity model tuning has improved principally the low order m-daily terms and has reduced significantly the geographically correlated error present in this satellite orbit. In addition to gravity field mismodelling, the largest contributor to the orbit error is the non-conservative force mismodelling. We report on further nonconservative force model tuning results using available data from over one cycle in beta prime.

Western Aphrodite Terra, tectonics, geology, and line-of-sight gravity

Science.gov (United States)

Hays, John E.; Morgan, Paul

1992-01-01

Aphrodite Terra is the largest area of high-standing topography on Venus, and isostatic considerations strongly suggest that this high topography is supported at least in part by thickened crust. Previous studies of line-of-sight gravity data from the Pioneer Venus Orbiter indicate rapidly changing apparent depths of compensation across Aphrodite Terra. Magellan imaging data provide the first detailed images of this region, and we are mapping the region along Pioneer Venus orbit 440 to investigate whether the changing apparent depths of compensation correlate with changes in surficial tectonics. Preliminary mapping of geological features on Magellan images along the path of Pioneer Venus orbit 440 do not indicate a first-order correlation among surface features and changes in the apparent depth of compensation of line-of-sight gravity data. The apparent depth of compensation appears to be most variable in regions dominated by tessera, but not all areas of tessera have distinct gravity signatures. There is a weak correlation among areas in which impact craters are relatively common and areas in which the observed and predicted gravity anomalies are poorly correlated.

Quantum Gravity corrections and entropy at the Planck time

International Nuclear Information System (INIS)

Basilakos, Spyros; Vagenas, Elias C.; Das, Saurya

2010-01-01

We investigate the effects of Quantum Gravity on the Planck era of the universe. In particular, using different versions of the Generalized Uncertainty Principle and under specific conditions we find that the main Planck quantities such as the Planck time, length, mass and energy become larger by a factor of order 10−10 4 compared to those quantities which result from the Heisenberg Uncertainty Principle. However, we prove that the dimensionless entropy enclosed in the cosmological horizon at the Planck time remains unchanged. These results, though preliminary, indicate that we should anticipate modifications in the set-up of cosmology since changes in the Planck era will be inherited even to the late universe through the framework of Quantum Gravity (or Quantum Field Theory) which utilizes the Planck scale as a fundamental one. More importantly, these corrections will not affect the entropic content of the universe at the Planck time which is a crucial element for one of the basic principles of Quantum Gravity named Holographic Principle

Joint 1D inversion of TEM and MT data and 3D inversion of MT data in the Hengill area, SW Iceland

Energy Technology Data Exchange (ETDEWEB)

Arnason, Knutur; Eysteinsson, Hjalmar; Hersir, Gylfi Pall [ISOR-Iceland GeoSurvey, Grensasvegi 9, 108 Reykjavik (Iceland)

2010-03-15

An extensive study of the resistivity structure of the Hengill area in SW Iceland was carried out by the combined use of TEM and MT soundings. Joint inversion of the collected data can correct for static shifts in the MT data, which can be severe due to large near-surface resistivity contrasts. Joint 1D inversion of 148 TEM/MT sounding pairs and a 3D inversion of a 60 sounding subset of the MT data were performed. The 3D inversion was based on full MT impedance tensors previously corrected for static shift. Both inversion approaches gave qualitatively similar results, and revealed a shallow resistivity layer reflecting conductive alteration minerals at temperatures of 100-240 C. They also delineated a deep conductor at 3-10 km depth. The reason for this deep-seated high conductivity is not fully understood. The distribution of the deep conductors correlates with a positive residual Bouguer gravity anomaly, and with transform tectonics inferred from seismicity. One model of the Hengill that is consistent with the well temperature data and the deep conductor that does not attenuate S-waves, is a group of hot, solidified, but still ductile magmatic intrusions that are closely associated with the heat source for the geothermal system. (author)

A test of Newton's Law of Gravity using the BREN Tower, Nevada

International Nuclear Information System (INIS)

Kasameyer, P.; Thomas, J.; Fackler, O.; Mugge, M.; Kammeraad, J.; Millett, M.; Harris, B.; Felske, D.

1989-01-01

We predicted gravity values on a tower by upward continuing an extensive set of surface data in order to test the 1/r 2 dependence of Newton's Law of Universal Gravitation. We measured gravity at 12 heights up to 454 m on a tower at the Nevada Test Site, and at 91 locations on the surface of the earth within 2.5 kilometers of the tower. These data have been combined with 60,000 surface gravity measurements within 300 kilometers of the tower and have been used to predict the gravitational field on the tower via a solution of Laplace's equation. A discrepancy between the observed gravity values and the prediction could suggest a breakdown of Newtonian Gravity, but we observe none. Our preliminary results are consistent with the Newtonian hypothesis to within 93 +- 95 μgals at the top of the tower, a result which conflicts with the previously reported 500 μgal non-Newtonian signal seen at 562 meters above the earth. 24 refs., 2 figs

A method of inversion of satellite magnetic anomaly data

Science.gov (United States)

Mayhew, M. A.

1977-01-01

A method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described. Magnetization is expressed as a Fourier Series in a segment of spherical shell. Input to this procedure is an equivalent source representation of the observed anomaly field. Instability of the inversion occurs when high frequency noise is present in the input data, or when the series is carried to an excessively high wave number. Preliminary results are given for the United States and adjacent areas.

Gravity and Extreme Magnetism SMEX

Science.gov (United States)

2012-01-01

The Gravity and Extreme Magnetism SMEX mission will be the first mission to catalogue the X-ray polarisation of many astrophysical objects including black-holes and pulsars. This first of its kind mission is enabled by the novel use of a time projection chamber as an X-ray polarimeter. The detector has been developed over the last 5 years, with the current effort charged toward a demonstration of it's technical readiness to be at level 6 prior to the preliminary design review. This talk will describe the design GEMS polarimeter and the results to date from the engineering test unit.

Particle Swarm Optimization and Uncertainty Assessment in Inverse Problems

Directory of Open Access Journals (Sweden)

José L. G. Pallero

2018-01-01

Full Text Available Most inverse problems in the industry (and particularly in geophysical exploration are highly underdetermined because the number of model parameters too high to achieve accurate data predictions and because the sampling of the data space is scarce and incomplete; it is always affected by different kinds of noise. Additionally, the physics of the forward problem is a simplification of the reality. All these facts result in that the inverse problem solution is not unique; that is, there are different inverse solutions (called equivalent, compatible with the prior information that fits the observed data within similar error bounds. In the case of nonlinear inverse problems, these equivalent models are located in disconnected flat curvilinear valleys of the cost-function topography. The uncertainty analysis consists of obtaining a representation of this complex topography via different sampling methodologies. In this paper, we focus on the use of a particle swarm optimization (PSO algorithm to sample the region of equivalence in nonlinear inverse problems. Although this methodology has a general purpose, we show its application for the uncertainty assessment of the solution of a geophysical problem concerning gravity inversion in sedimentary basins, showing that it is possible to efficiently perform this task in a sampling-while-optimizing mode. Particularly, we explain how to use and analyze the geophysical models sampled by exploratory PSO family members to infer different descriptors of nonlinear uncertainty.

Application of tomographic inversion in studying airglow in the mesopause region

Directory of Open Access Journals (Sweden)

T. Nygrén

Full Text Available It is pointed out that observations of periodic nightglow structures give excellent information on atmospheric gravity waves in the mesosphere and lower thermosphere. The periods, the horizontal wavelengths and the phase speeds of the waves can be determined from airglow images and, using several cameras, the approximate altitude of the luminous layer can also be determined by triangulation. In this paper the possibility of applying tomographic methods for reconstructing the airglow structures is investigated using numerical simulations. A ground-based chain of cameras is assumed, two-dimensional airglow models in the vertical plane above the chain are constructed, and simulated data are calculated by integrating the models along a great number of rays with different elevation angles for each camera. After addition of random noise, these data are then inverted to obtain reconstructions of the models. A tomographic analysis package originally designed for satellite radiotomography is used in the inversion. The package is based on a formulation of stochastic inversion which allows the input of a priori information to the solver in terms of regularization variances. The reconstruction is carried out in two stages. In the first inversion, constant regularization variances are used within a wide altitude range. The results are used in determining the approximate altitude range of the airglow structures. Then, in the second inversion, constant non-zero regularization variances are used inside this region and zero variances outside it. With this method reliable reconstructions of the models are obtained. The number of cameras as well as their separations are varied in order to find out the limitations of the method.

Key words. Tomography · Airglow · Mesopause · Gravity waves

Gravity Data Interpretation in the Northern Edge of the Congo Craton, South-Cameroon

Directory of Open Access Journals (Sweden)

James Derek Fairhead

2010-01-01

Full Text Available Gravity data in the southern Cameroon are interpreted to better understand the organization of underlying structuresthroughout the northern edge of the Congo craton. The Bouguer anomaly maps of the region are characterized by an elongated trending trending negative gravity anomaly which correspond to a collapsed structure associated with a granitic intrusion beneath the cente center of the region r of the region of the region and limited by fault systems. �e applied 3�D gravity modelling and inversion in order to obtain the 3D density structure of the area. Our result demonstrated that observed gravity anomalies in the region are associated to tectonic structures in the subsurface. The resulting model agrees with the hypothesis of the existence of a major continental collision zone between the Congo Craton and the Pan�African belt. The presence of deep granulites structures in the northern part of the region expresses a continental collision.

On the covariant formalism of the effective field theory of gravity and leading order corrections

DEFF Research Database (Denmark)

Codello, Alessandro; Jain, Rajeev Kumar

2016-01-01

We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well...... as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology...... on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime....

Sub-Millimeter Tests of the Newtonian Inverse Square Law

International Nuclear Information System (INIS)

Adelberger, Eric

2005-01-01

It is remarkable that small-scale experiments can address important open issues in fundamental science such as: 'why is gravity so weak compared to the other interactions?' and 'why is the cosmological constant so small compared to the predictions of quantum mechanics?' String theory ideas (new scalar particles and extra dimensions) and other notions hint that Newton's Inverse-Square Law could break down at distances less than 1 mm. I will review some motivations for testing the Inverse-Square Law, and discuss recent mechanical experiments with torsion balances, small-scillators, micro-cantilevers, and ultra-cold neutrons. Our torsion-balance experiments have probed for gravitational-strength interactions with length scales down to 70 micrometers, which is approximately the diameter of a human hair.

Induced gravity II: grand unification

Energy Technology Data Exchange (ETDEWEB)

Einhorn, Martin B. [Kavli Institute for Theoretical Physics, Kohn Hall,University of California,Santa Barbara, CA 93106-4030 (United States); Jones, D.R. Timothy [Kavli Institute for Theoretical Physics, Kohn Hall,University of California,Santa Barbara, CA 93106-4030 (United States); Dept. of Mathematical Sciences, University of Liverpool,Peach Street, Liverpool L69 3BX (United Kingdom)

2016-05-31

As an illustration of a renormalizable, asymptotically-free model of induced gravity, we consider an SO(10) gauge theory interacting with a real scalar multiplet in the adjoint representation. We show that dimensional transmutation can occur, spontaneously breaking SO(10) to SU(5)⊗U(1), while inducing the Planck mass and a positive cosmological constant, all proportional to the same scale v. All mass ratios are functions of the values of coupling constants at that scale. Below this scale (at which the Big Bang may occur), the model takes the usual form of Einstein-Hilbert gravity in de Sitter space plus calculable corrections. We show that there exist regions of parameter space in which the breaking results in a local minimum of the effective action giving a positive dilaton (mass){sup 2} from two-loop corrections associated with the conformal anomaly. Furthermore, unlike the singlet case we considered previously, some minima lie within the basin of attraction of the ultraviolet fixed point. Moreover, the asymptotic behavior of the coupling constants also lie within the range of convergence of the Euclidean path integral, so there is hope that there will be candidates for sensible vacua. Although open questions remain concerning unitarity of all such renormalizable models of gravity, it is not obvious that, in curved backgrounds such as those considered here, unitarity is violated. In any case, any violation that may remain will be suppressed by inverse powers of the reduced Planck mass.

The Crustal Structure of the North-South Earthquake Belt in China Revealed from Deep Seismic Soundings and Gravity Data

Science.gov (United States)

Zhao, Yang; Guo, Lianghui; Shi, Lei; Li, Yonghua

2018-01-01

The North-South earthquake belt (NSEB) is one of the major earthquake regions in China. The studies of crustal structure play a great role in understanding tectonic evolution and in evaluating earthquake hazards in this region. However, some fundamental crustal parameters, especially crustal interface structure, are not clear in this region. In this paper, we reconstructed the crustal interface structure around the NSEB based on both the deep seismic sounding (DSS) data and the gravity data. We firstly reconstructed the crustal structure of crystalline basement (interface G), interface between upper and lower crusts (interface C) and Moho in the study area by compiling the results of 38 DSS profiles published previously. Then, we forwardly calculated the gravity anomalies caused by the interfaces G and C, and then subtracted them from the complete Bouguer gravity anomalies, yielding the regional gravity anomalies mainly due to the Moho interface. We then utilized a lateral-variable density interface inversion technique with constraints of the DSS data to invert the regional anomalies for the Moho depth model in the study area. The reliability of our Moho depth model was evaluated by comparing with other Moho depth models derived from other gravity inversion technique and receiver function analysis. Based on our Moho depth model, we mapped the crustal apparent density distribution in the study area for better understanding the geodynamics around the NSEB.

Gravity in minesmdashAn investigation of Newton's law

International Nuclear Information System (INIS)

Holding, S.C.; Stacey, F.D.; Tuck, G.J.

1986-01-01

The evidence that the value of the Newtonian gravitational constant G inferred from measurements of gravity g in mines and boreholes is of order 1% higher than the laboratory value is hardened with new and improved data from two mines in northwest Queensland. Surface-gravity surveys and more than 14 000 bore-core density values have been used to establish density structures for the mines, permitting full three-dimensional inversion to obtain G. Further constraint is imposed by requiring that the density structure give the same value of G for several vertical profiles of g, separated by hundreds of meters. The only residual doubt arises from the possibility of bias by an anomalous regional gravity gradient. Neither measurements of gravity gradient above ground level (in tall chimneys) nor surface surveys are yet adequate to remove this doubt, but the coincidence of conclusions derived from mine data obtained in different parts of the world makes such an anomaly appear an improbable explanation. If Newton's law is modified by adding a Yukawa term to the gravitational potential of a point mass m at distance r, V = -(G/sub infinity/m/r)(1+αe/sup -r/lambda/), then the mine data provide a mutual constraint on the values of α and lambda, although they cannot be determined independently. Our results give αroughly-equal-0.0075 if lambda or =10 4 m, with intermediate values of α between these ranges, but values greater than α = -0.010, lambda = 800 m appear to be disallowed by a comparison of satellite and land-surface estimates of gravity

Simplicial quantum gravity with higher derivative terms: Formalism and numerical results in four dimensions

International Nuclear Information System (INIS)

Hamber, H.W.; Williams, R.M.; Cambridge Univ.

1986-01-01

Higher derivative terms for Regge's formulation of lattice gravity are discussed. The analytic weak-field expansion for the regular tessellation α 5 of the four-sphere is presented. Preliminary numerical results for some computations in four dimensions are also discussed. (orig.)

Some technical details concerning a new method of gravimetric-seismic inversion

DEFF Research Database (Denmark)

Strykowski, Gabriel

1999-01-01

In this paper a number of technical details related to a new method of gravimetric-seismic inversion, which is still under development, are explained. Although the present contribution aims on providing general statements on how to formulate and solve complex gravimetric-seismic modeling; problems......, the inspiration comes from the practical modeling problems in the area of Jutland peninsula (Denmark). More specifically, the methodological aspects of the proposed inversion method are illustrated on a problem of 3D modeling of the intra crustal intrusion associated with the Silkeborg Gravity High. The existing...... refraction seismic profile locates the source of the anomaly in depths 10 km - 18 km. In an earlier publication, (Strykowski, 1998), and for the same test area, a method of complex geological stripping is described. The present contribution is a continuation of this paper in the direction of inversion...

Evidence for active hotspots on Venus from analysis of Magellan gravity data

Science.gov (United States)

Smrekar, Suzanne E.

1994-01-01

The 500-Myr average crater retention age for Venus has raised questions about the present-day level of tectonic activity. In this study we examine the relationship between the gravity and topography of four large volcanic swells, Beta, Atla, Bell, and Western Eistla Regiones, for clues about their stage evolution. The Magellan line-of-sight gravity data are inverted using a point mass model of the anomalous mass to solve for the local vertical gravity field. Spectral admittance calculated from both the local gravity inversions and a spherical harmonic model is compared to three models of compensation: local compensation, a 'flexural' model with local and regional compensation of surface and subsurface loads, and a 'hotspot' model of compensation that includes top loading by volcanoes and subsurface loading due to a deep, low density mass anomaly. The coherence is also calculated in each region, but yields an elastic thickness estimate only at Bell Regio. In all models, the long wavelengths are compensated locally. Our results may indicate a relatively old, possibly inactive plume.

A Combined Gravity Compensation Method for INS Using the Simplified Gravity Model and Gravity Database.

Science.gov (United States)

Zhou, Xiao; Yang, Gongliu; Wang, Jing; Wen, Zeyang

2018-05-14

In recent decades, gravity compensation has become an important way to reduce the position error of an inertial navigation system (INS), especially for a high-precision INS, because of the extensive application of high precision inertial sensors (accelerometers and gyros). This paper first deducts the INS's solution error considering gravity disturbance and simulates the results. Meanwhile, this paper proposes a combined gravity compensation method using a simplified gravity model and gravity database. This new combined method consists of two steps all together. Step 1 subtracts the normal gravity using a simplified gravity model. Step 2 first obtains the gravity disturbance on the trajectory of the carrier with the help of ELM training based on the measured gravity data (provided by Institute of Geodesy and Geophysics; Chinese Academy of sciences), and then compensates it into the error equations of the INS, considering the gravity disturbance, to further improve the navigation accuracy. The effectiveness and feasibility of this new gravity compensation method for the INS are verified through vehicle tests in two different regions; one is in flat terrain with mild gravity variation and the other is in complex terrain with fierce gravity variation. During 2 h vehicle tests, the positioning accuracy of two tests can improve by 20% and 38% respectively, after the gravity is compensated by the proposed method.

Ancient igneous intrusions and early expansion of the Moon revealed by GRAIL gravity gradiometry.

Science.gov (United States)

Andrews-Hanna, Jeffrey C; Asmar, Sami W; Head, James W; Kiefer, Walter S; Konopliv, Alexander S; Lemoine, Frank G; Matsuyama, Isamu; Mazarico, Erwan; McGovern, Patrick J; Melosh, H Jay; Neumann, Gregory A; Nimmo, Francis; Phillips, Roger J; Smith, David E; Solomon, Sean C; Taylor, G Jeffrey; Wieczorek, Mark A; Williams, James G; Zuber, Maria T

2013-02-08

The earliest history of the Moon is poorly preserved in the surface geologic record due to the high flux of impactors, but aspects of that history may be preserved in subsurface structures. Application of gravity gradiometry to observations by the Gravity Recovery and Interior Laboratory (GRAIL) mission results in the identification of a population of linear gravity anomalies with lengths of hundreds of kilometers. Inversion of the gravity anomalies indicates elongated positive-density anomalies that are interpreted to be ancient vertical tabular intrusions or dikes formed by magmatism in combination with extension of the lithosphere. Crosscutting relationships support a pre-Nectarian to Nectarian age, preceding the end of the heavy bombardment of the Moon. The distribution, orientation, and dimensions of the intrusions indicate a globally isotropic extensional stress state arising from an increase in the Moon's radius by 0.6 to 4.9 kilometers early in lunar history, consistent with predictions of thermal models.

Black-hole horizons in modified spacetime structures arising from canonical quantum gravity

International Nuclear Information System (INIS)

Bojowald, Martin; Paily, George M; Reyes, Juan D; Tibrewala, Rakesh

2011-01-01

Several properties of canonical quantum gravity modify spacetime structures, sometimes to the degree that no effective line elements exist to describe the geometry. An analysis of solutions, for instance in the context of black holes, then requires new insights. In this paper, standard definitions of horizons in spherical symmetry are first reformulated canonically, and then evaluated for solutions of equations and constraints modified by inverse-triad corrections of loop quantum gravity. When possible, a spacetime analysis is performed which reveals a mass threshold for black holes and small changes to Hawking radiation. For more general conclusions, canonical perturbation theory is developed to second order to include back-reaction from matter. The results shed light on the questions of whether renormalization of Newton's constant or other modifications of horizon conditions should be taken into account in computations of black-hole entropy in loop quantum gravity.

Application of a two-and-a-half dimensional model-based algorithm to crosswell electromagnetic data inversion

International Nuclear Information System (INIS)

Li, Maokun; Abubakar, Aria; Habashy, Tarek M

2010-01-01

In this paper, we apply a model-based inversion scheme for the interpretation of the crosswell electromagnetic data. In this approach, we use open and closed polygons to parameterize the unknown configuration. The parameters that define these polygons are then inverted for by minimizing the data misfit cost function. Compared with the pixel-based inversion approach, the model-based inversion uses only a few number of parameters; hence, it is more efficient. Furthermore, with sufficient sensitivity in the data, the model-based approach can provide quantitative estimates of the inverted parameters such as the conductivity. The model-based inversion also provides a convenient way to incorporate a priori information from other independent measurements such as seismic, gravity and well logs

On the covariant formalism of the effective field theory of gravity and leading order corrections

International Nuclear Information System (INIS)

Codello, Alessandro; Jain, Rajeev Kumar

2016-01-01

We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime. (paper)

On the inversion of geodetic integrals defined over the sphere using 1-D FFT

Science.gov (United States)

García, R. V.; Alejo, C. A.

2005-08-01

An iterative method is presented which performs inversion of integrals defined over the sphere. The method is based on one-dimensional fast Fourier transform (1-D FFT) inversion and is implemented with the projected Landweber technique, which is used to solve constrained least-squares problems reducing the associated 1-D cyclic-convolution error. The results obtained are as precise as the direct matrix inversion approach, but with better computational efficiency. A case study uses the inversion of Hotine’s integral to obtain gravity disturbances from geoid undulations. Numerical convergence is also analyzed and comparisons with respect to the direct matrix inversion method using conjugate gradient (CG) iteration are presented. Like the CG method, the number of iterations needed to get the optimum (i.e., small) error decreases as the measurement noise increases. Nevertheless, for discrete data given over a whole parallel band, the method can be applied directly without implementing the projected Landweber method, since no cyclic convolution error exists.

Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere

Directory of Open Access Journals (Sweden)

Y. Deng

2014-04-01

Full Text Available The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionosphere–thermosphere model (GITM, which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2° long × 0.2° lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s−1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

A three-dimensional gravity inversion applied to São Miguel Island (Azores)

Science.gov (United States)

Camacho, A. G.; Montesinos, F. G.; Vieira, R.

1997-04-01

Gravimetric studies are becoming more and more widely acknowledged as a useful tool for studying and modeling the distributions of subsurface masses that are associated with volcanic activity. In this paper, new gravimetric data for the volcanic island of São Miguel (Azores) were analyzed and interpreted by a stabilized linear inversion methodology. An inversion model of higher resolution was calculated for the Caldera of Furnas, which has a larger density of data. In order to filter out the noncorrelatable anomalies, least squares prediction was used, resulting in a correlated gravimetric signal model with an accuracy of the order of 0.9 mGal. The gravimetric inversion technique is based on the adjustment of a three-dimensional (3-D) model of cubes of unknown density that represents the island's subsurface. The problem of non-uniqueness is solved by minimization with appropriate covariance matrices of the data (resulting from the least squares prediction) and of the unknowns. We also propose a criterion for choosing a balance between the data fit (which in this case corresponds to residues with rms of the order of 0.6 mGal) and the smoothness of the solution. The global model of the island includes a low-density zone in a WNW-ESE direction and a depth of the order of 20 km, associated with the Terceira rift spreading center. The minimums located at a depth of 4 km may be associated with shallow magmatic chambers beneath the main volcanoes of the island. The main high-density area is related to the Nordeste basaltic shield. With regard to the Caldera Furnas, in addition to the minimum that can be associated with a magmatic chamber, there are other shallow minimums that correspond to eruptive processes.

Newtonian gravity in loop quantum gravity

OpenAIRE

Smolin, Lee

2010-01-01

We apply a recent argument of Verlinde to loop quantum gravity, to conclude that Newton's law of gravity emerges in an appropriate limit and setting. This is possible because the relationship between area and entropy is realized in loop quantum gravity when boundaries are imposed on a quantum spacetime.

Preliminary gravity and magnetic models across Midway Valley and Yucca Wash, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Ponce, D.A.; Langenheim, V.E.

1994-01-01

Detailed gravity and ground magnetic data collected along ten traverses across Midway Valley and Yucca Wash on the eastern flank of Yucca Mountain in southwest Nevada are interpreted. These data were collected as part of an effort to evaluate faulting in the vicinity of proposed surface facilities for a potential nuclear waste repository at Yucca Mountain. Geophysical data show that Midway Valley is bounded by large gravity and magnetic anomalies associated with the Bow Ridge and Paintbrush Canyon faults, on the west side of Exile Hill and on the west flank of Fran Ridge, respectively. In addition, Midway Valley itself is characterized by a number of small-amplitude anomalies that probably reflect small-scale faulting beneath Midway Valley. Gravity and magnetic data across the northwest trending Yucca Wash and the inferred Yucca Wash fault indicate no major vertical offsets greater than 100 m using a density contrast of 0.2 to 0.3 g/cm 3 along the proposed Yucca Wash fault. In addition, a broad magnetic high coincides with the approximate location of the hydrologic gradient and probably reflects moderately magnetic Topopah Spring Tuff or lavas in the Calico Hills Formation

Chiral gravity, log gravity, and extremal CFT

International Nuclear Information System (INIS)

Maloney, Alexander; Song Wei; Strominger, Andrew

2010-01-01

We show that the linearization of all exact solutions of classical chiral gravity around the AdS 3 vacuum have positive energy. Nonchiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity--the theory with logarithmically relaxed boundary conditions--has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic conformal field theories (CFT). Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.

Research Regarding High Gravity Brewing in the Pilot Station USAMV Cluj-Napoca

Directory of Open Access Journals (Sweden)

Andrei Borsa

2013-11-01

Full Text Available This paper aims to present preliminary research results obtained while developing and implementing a high gravity beer fermentation process. Production trials were performed in brewery pilot plant from University of Agricultural Sciences and Veterinary Medicine, Faculty of Food Science and Technology. The tehnological parameters were adapted and monitored during the making.

Coseismic gravity and displacement changes of Japan Tohoku earthquake (Mw 9.0

Directory of Open Access Journals (Sweden)

Xinlin Zhang

2016-03-01

Full Text Available The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku. Large tsunami and ground motions caused severe damage in wide areas, particularly many towns along the Pacific coast. So far, gravity change caused by such a great earthquake has been reported for the 1964 Alaska and the 2010 Maule events. However, the spatial-temporal resolution of the gravity data for these cases is insufficient to depict a co-seismic gravity field variation in a spatial scale of a plate subduction zone. Here, we report an unequivocal co-seismic gravity change over the Japanese Island, obtained from a hybrid gravity observation (combined absolute and relative gravity measurements. The time interval of the observation before and after the earthquake is within 1 year at almost all the observed sites, including 13 absolute and 16 relative measurement sites, which deduced tectonic and environmental contributions to the gravity change. The observed gravity agrees well with the result calculated by a dislocation theory based on a self-gravitating and layered spherical earth model. In this computation, a co-seismic slip distribution is determined by an inversion of Global Positioning System (GPS data. Of particular interest is that the observed gravity change in some area is negative where a remarkable subsidence is observed by GPS, which can not be explained by simple vertical movement of the crust. This indicated that the mass redistribution in the underground affects the gravity change. This result supports the result that Gravity Recovery and Climate Experiment (GRACE satellites detected a crustal dilatation due to the 2004 Sumatra earthquake by the terrestrial observation with a higher spatial and temporal resolution.

String duality transformations in f(R) gravity from Noether symmetry approach

Energy Technology Data Exchange (ETDEWEB)

Capozziello, Salvatore [Dipartimento di Fisica, Università di Napoli ' ' Federico II' ' , Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126, Napoli (Italy); Gionti, Gabriele S.J. [Specola Vaticana, Vatican City, V-00120, Vatican City State (Vatican City State, Holy See); Vernieri, Daniele, E-mail: capozziello@na.inf.it, E-mail: ggionti@as.arizona.edu, E-mail: vernieri@iap.fr [Sorbonne Universités, UPMC Univ Paris 6 et CNRS, UMR 7095, Institut d' Astrophysique de Paris, GReCO, 98bis Bd Arago, 75014 Paris (France)

2016-01-01

We select f(R) gravity models that undergo scale factor duality transformations. As a starting point, we consider the tree-level effective gravitational action of bosonic String Theory coupled with the dilaton field. This theory inherits the Busher's duality of its parent String Theory. Using conformal transformations of the metric tensor, it is possible to map the tree-level dilaton-graviton string effective action into f(R) gravity, relating the dilaton field to the Ricci scalar curvature. Furthermore, the duality can be framed under the standard of Noether symmetries and exact cosmological solutions are derived. Using suitable changes of variables, the string-based f(R) Lagrangians are shown in cases where the duality transformation becomes a parity inversion.

String duality transformations in f(R) gravity from Noether symmetry approach

International Nuclear Information System (INIS)

Capozziello, Salvatore; Gionti, Gabriele S.J.; Vernieri, Daniele

2016-01-01

We select f(R) gravity models that undergo scale factor duality transformations. As a starting point, we consider the tree-level effective gravitational action of bosonic String Theory coupled with the dilaton field. This theory inherits the Busher's duality of its parent String Theory. Using conformal transformations of the metric tensor, it is possible to map the tree-level dilaton-graviton string effective action into f(R) gravity, relating the dilaton field to the Ricci scalar curvature. Furthermore, the duality can be framed under the standard of Noether symmetries and exact cosmological solutions are derived. Using suitable changes of variables, the string-based f(R) Lagrangians are shown in cases where the duality transformation becomes a parity inversion

Comparison of publically available Moho depth and crustal thickness grids with newly derived grids by 3D gravity inversion for the High Arctic region.

Science.gov (United States)

Lebedeva-Ivanova, Nina; Gaina, Carmen; Minakov, Alexander; Kashubin, Sergey

2016-04-01

We derived Moho depth and crustal thickness for the High Arctic region by 3D forward and inverse gravity modelling method in the spectral domain (Minakov et al. 2012) using lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2013) was modified according to the most recently published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. The results are numerically compared with publically available grids of the Moho depth and crustal thickness for the High Arctic region (CRUST 1 and GEMMA global grids; the deep Arctic Ocean grids by Glebovsky et al., 2013) and seismic crustal scale profiles. The global grids provide coarser resolution of 0.5-1.0 geographic degrees and not focused on the High Arctic region. Our grids better capture all main features of the region and show smaller error in relation to the seismic crustal profiles compare to CRUST 1 and GEMMA grids. Results of 3D gravity modelling by Glebovsky et al. (2013) with separated geostructures approach show also good fit with seismic profiles; however these grids cover the deep part of the Arctic Ocean only. Alvey A, Gaina C, Kusznir NJ, Torsvik TH (2008). Integrated crustal thickness mapping and plate recon-structions for the high Arctic. Earth Planet Sci Lett 274:310-321. Gaina C, Werner SC, Saltus R, Maus S (2011). Circum-Arctic mapping project: new magnetic and gravity anomaly maps of the Arctic. Geol Soc Lond Mem 35, 39-48. Glebovsky V.Yu., Astafurova E.G., Chernykh A.A., Korneva M.A., Kaminsky V.D., Poselov V.A. (2013). Thickness of the Earth's crust in the

A high-order 3-D spectral-element method for the forward modelling and inversion of gravimetric data—Application to the western Pyrenees

Science.gov (United States)

Martin, Roland; Chevrot, Sébastien; Komatitsch, Dimitri; Seoane, Lucia; Spangenberg, Hannah; Wang, Yi; Dufréchou, Grégory; Bonvalot, Sylvain; Bruinsma, Sean

2017-04-01

We image the internal density structure of the Pyrenees by inverting gravity data using an a priori density model derived by scaling a Vp model obtained by full waveform inversion of teleseismic P-waves. Gravity anomalies are computed via a 3-D high-order finite-element integration in the same high-order spectral-element grid as the one used to solve the wave equation and thus to obtain the velocity model. The curvature of the Earth and surface topography are taken into account in order to obtain a density model as accurate as possible. The method is validated through comparisons with exact semi-analytical solutions. We show that the spectral-element method drastically accelerates the computations when compared to other more classical methods. Different scaling relations between compressional velocity and density are tested, and the Nafe-Drake relation is the one that leads to the best agreement between computed and observed gravity anomalies. Gravity data inversion is then performed and the results allow us to put more constraints on the density structure of the shallow crust and on the deep architecture of the mountain range.

A computationally efficient tool for assessing the depth resolution in large-scale potential-field inversion

DEFF Research Database (Denmark)

Paoletti, Valeria; Hansen, Per Christian; Hansen, Mads Friis

2014-01-01

In potential-field inversion, careful management of singular value decomposition components is crucial for obtaining information about the source distribution with respect to depth. In principle, the depth-resolution plot provides a convenient visual tool for this analysis, but its computational...... on memory and computing time. We used the ApproxDRP to study retrievable depth resolution in inversion of the gravity field of the Neapolitan Volcanic Area. Our main contribution is the combined use of the Lanczos bidiagonalization algorithm, established in the scientific computing community, and the depth...

Total body irradiation with an arc and a gravity-oriented compensator

International Nuclear Information System (INIS)

Chui, C.-S.; Fontenla, Doracy P.; Mullokandov, Edward; Kapulsky, Alex; Lo, Y.-C.; Lo, C.-J.

1997-01-01

Purpose: To deliver uniform dose distributions for total-body irradiation (TBI) with an arc field and a gravity-oriented compensator. This technique allows the patient to be treated lying on the floor in a small treatment room. Methods and Materials: Through the sweeping motion of the gantry, a continuous arc field can deliver a large field to a patient lying on the floor. The dose profile, however, would not be uniform if no compensator were used, due to the effects of inverse square variation of beam intensity with distance as well as the slanted depth in patient. To solve this problem, a gravity-oriented compensator made of cerrobend alloy was designed. This compensator has a cross-section of an inverted isosceles triangle, with the apex always pointing downward, due to gravity. By properly selecting the thickness of the compensator, the width of the base, and the distance between the pivots to the base, the difference in the path length through the compensator can be made just right to compensate the effects of inverse-square and slanted depth, thus producing a uniform dose profile. Results: Arc fields with a gravity-oriented compensator were used for 6, 10, 15, and 18 MV photon beams. The arc field can cover a patient with a height up to 180 cm. The field width was chosen from 32 to 40 cm at the machine isocenter. The optimal thickness of the compensator was found to be 2.5 cm, and its base was 25 cm wide. The distance from the pivot points to the flat surface of the compensator proximal to the beam ranges from 13 to 14 cm for different beam energies. The dose uniformity at a depth of 10 cm is within ±5% for all beam energies used in this study. Conclusion: Highly uniform dose profiles for TBI treatments can be delivered with an arc and a gravity-oriented compensator. The proposed technique is simple and versatile. A single compensator can be used for all energies, because the amount of compensation can be adjusted by changing the distance to the pivot and

Joint inversion of geophysical data using petrophysical clustering and facies deformation wth the level set technique

Science.gov (United States)

Revil, A.

2015-12-01

Geological expertise and petrophysical relationships can be brought together to provide prior information while inverting multiple geophysical datasets. The merging of such information can result in more realistic solution in the distribution of the model parameters, reducing ipse facto the non-uniqueness of the inverse problem. We consider two level of heterogeneities: facies, described by facies boundaries and heteroegenities inside each facies determined by a correlogram. In this presentation, we pose the geophysical inverse problem in terms of Gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geological cross-section, including the definition of spatial boundaries for the geological facies. The petrophysical relationship problem is formulated as a regression problem upon each facies. The inversion of the geophysical data is performed in a Bayesian framework. We demonstrate the usefulness of this strategy using a first synthetic case for which we perform a joint inversion of gravity and galvanometric resistivity data with the stations located at the ground surface. The joint inversion is used to recover the density and resistivity distributions of the subsurface. In a second step, we consider the possibility that the facies boundaries are deformable and their shapes are inverted as well. We use the level set approach to perform such deformation preserving prior topological properties of the facies throughout the inversion. With the help of prior facies petrophysical relationships and topological characteristic of each facies, we make posterior inference about multiple geophysical tomograms based on their corresponding geophysical data misfits. The method is applied to a second synthetic case showing that we can recover the heterogeneities inside the facies, the mean values for the petrophysical properties, and, to some extent, the facies boundaries using the 2D joint inversion of

Inferring Shallow Subsurface Density Structure from Surface and Underground Gravity Measurements: Calibrating Models for Relatively Undeformed Volcanic Strata at the Jemez Volcanic Field, New Mexico, USA

Science.gov (United States)

Roy, Mousumi; Lewis, Megan; Johnson, Alex; George, Nicolas; Rowe, Charlotte; Guardincerri, Elena

2018-03-01

Imaging shallow subsurface density structure is an important goal in a variety of applications, from hydrogeology to seismic and volcanic hazard assessment. We assess the effectiveness of surface and subsurface gravity measurements in estimating the density structure of a well-characterized rock volume: the mesa (a small, flat-topped plateau) upon which the town of Los Alamos, New Mexico, USA is located. Our gravity measurements were made on the mesa surface above a horizontal tunnel and underground, within the tunnel. We demonstrate that, in the absence of other geophysical data such as seismic data or muon attenuation, subsurface (tunnel) gravity measurements are critical to accurately recovering geologic structure. Without the tunnel data, our resolution is limited to roughly the surface gravity station spacing, but by including the tunnel data we can resolve structure to a depth of 10 times the surface gravity station spacing. Densities were obtained using both forward modeling and a Bayesian inverse modeling approach, incorporating relevant constraints from geologic observations. We find that Bayesian inversion, with geologically relevant prior, is a superior approach to the forward models in terms of both robustness and efficiency and correctly predicts the orientation and elevation of important geologic features.

A new method for optimization of low-thrust gravity-assist sequences

Science.gov (United States)

Maiwald, V.

2017-09-01

Recently missions like Hayabusa and Dawn have shown the relevance and benefits of low-thrust spacecraft concerning the exploration of our solar system. In general, the efficiency of low-thrust propulsion is one means of improving mission payload mass. At the same time, gravity-assist maneuvers can serve as mission enablers, as they have the capability to provide "free energy." A combination of both, gravity-assist and low-thrust propulsion, has the potential to generally improve mission performance, i.e. planning and optimization of gravity-assist sequences for low-thrust missions is a desirable asset. Currently no established methods exist to include the gravity-assist partners as optimization variable for low-thrust missions. The present paper explains how gravity-assists are planned and optimized, including the gravity-assist partners, for high-thrust missions and discusses the possibility to transfer the established method, based on the Tisserand Criterion, to low-thrust missions. It is shown how the Tisserand Criterion needs to be adapted using a correction term for the low-thrust situation. It is explained why this necessary correction term excludes an a priori evaluation of sequences and therefore their planning and an alternate approach is proposed. Preliminary results of this method, by application of a Differential Evolution optimization algorithm, are presented and discussed, showing that the method is valid but can be improved. Two constraints on the search space are briefly presented for that aim.

Isostatic Implications of Different Seismic and Gravity Derived Moho Depths for Antarctica

Science.gov (United States)

Ferraccioli, F.; Pappa, F.; Ebbing, J.

2017-12-01

Several studies with different methods have been performed to investigate the lithospheric structure of Antarctica, in particular the Moho as the crust-mantle boundary. Yet, seismological surveys are regionally limited or suffer from sparse station coverage due to the remoteness and size of the continent. On the other hand, gravity studies are inherently ambiguous and therefore not able to determine both the geometry and the density contrast of the Moho. Existing Moho depth models for Antarctica show large discrepancies, even among different seismological methods, but all the more between seismological and gravity models. As a first step towards a possible reconcilement, we perform non-linear gravity inversions with simultaneous consideration of seismological data. Depending on the seismological input data, different depths and density contrasts yield the best fit. The results, however, are not in line with the pure seismological models. Subsequently, we compute simple Airy-isostatic Moho depth models and evaluate these together with multiple Moho models from previous studies in terms of their gravitational signal, applying different values for the density contrast. The models' responses are checked against observational data: vertical gravity at 50 km altitude from the spherical harmonics expansion model GOCO05s, and the gravity gradient tensor at 225 km altitude from the GOCE gravity gradient grids. While the gravity responses from the seismological models show strong disagreements with the data, the Airy-isostatic models fit better. Yet, differences of up to 10 km in depth exist between the isostatic and the gravity-inverted Moho models. From these differences in vertical gravity, in the gravity gradients and in Moho depth, we identify regions where a simple density contrast is not sufficient to explain the observed gravitational field. We conclude that lateral and vertical density variations must be considered, which might originate from high-density lower

Seismic and gravity signature of the Ischia Island Caldera (Italy)

Science.gov (United States)

Capuano, P.; de Matteis, R.; Russo, G.

2009-04-01

The Campania (Italy) coasts are characterized by the presence of several volcanoes. The island of Ischia, located at the northwestern end of the Gulf of Naples, belongs to the Neapolitan Volcanic District together with Phlegrean Fields and Vesuvius, having all these Pleistocene volcanoes erupted in historical times, and it is characterized by diffuse hydrothermal phenomena The island represents the emergent part of a more extensive volcanic area developed mainly westward of the island, with underwater volcanoes aligned along regional fault patterns. The activity of Ischia volcano is testified by the occurrence of eruptions in historical times, the presence of intense hydrothermal phenomena, and by seismic activity (e.g. the 1883 Casamicciola earthquake). Ischia is populated by about 50,000 inhabitants increasing, mainly in the summer, due to thriving tourism business, partially due to its active volcanic state. Hazard assessment at active, densely populated volcanoes is critically based on knowledge of the volcanoes past behavior and the definition of its present state. As a contribution to the definition of the present state of the Ischia island volcano, we obtain a model of the shallow crust using geophysical observables through seismic tomography and 3D gravity inversion. In particular we use travel times collected during the Serapis experiment on the island and its surroundings and free air anomaly. A new 3D gravity inversion procedure has been developed to take better into account the shape and the effects of topography approximating it by a triangular mesh. Below each triangle, a sequence of triangular prisms is built, the uppermost prism having the upper face coincident with the triangle following the topography. The inversion is performed searching for a regularized solution using the minimum norm stabilizer. The main results inferable from the 3D seismic and gravity images are the definition of the caldera rims hypothesize by many authors along the

ISOSTATICALLY DISTURBED TERRAIN OF NORTHWESTERN ANDES MOUNTAINS FROM SPECTRALLY CORRELATED FREE-AIR AND GRAVITY TERRAIN DATA

Directory of Open Access Journals (Sweden)

Hernández P Orlando

2006-12-01

Full Text Available Recently revised models on global tectonics describe the convergence of the North Andes, Nazca, Caribbean and South American Plates and their seismicity, volcanism, active faulting and extreme
topography. The current plate boundaries of the area are mainly interpreted from volcanic and seismic datasets with variable confidence levels. New insights on the isostatic state and plate boundaries of
the northwestern Andes Mountains can be obtained from the spectral analysis of recently available gravity and topography data.
Isostatically disturbed terrain produces free-air anomalies that are highly correlated with the gravity effects of the terrain. The terrain gravity effects (TGE and free air gravity anomalies (FAGA of the
Andes mountains spectral correlation data confirms that these mountains are isostatically disturbed. Strong negative terrain-correlated FAGA along western South America and the Greater and Lesser Antilles are consistent with anomalously deepened mantle displaced by subducting oceanic plates.

Inversion of the compensated terrain gravity effects (CTGE reveals plate subduction systems with alternating shallower and steeper subduction angles. The gravity modeling highlights crustal
deformation from plate collision and subduction and other constraints on the tectonism of the plate boundary zones for the region.

Study on the effect of micro-gravity on bio-functions; Seitai kino eno bisho juryoku no eikyo ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

The effect of micro-gravity on bio-functions and vital reaction was studied using the facility of Underground Gravity-free Experiment Center Co. On the effect on osteoblast shape and gene expression, although fluorochrome reacting with Ca was well taken into cells, no significant difference in Ca content in cells was observed before/after falling. Expression of genes related to cell propagation was controlled under micro-gravity. Protoplast fusion of Lentinus was unaffected by micro-gravity. The mRNA fragments of gravity sensitive mutant of rice plant were affected by micro-gravity. Paramecium was set swimming in solutions with different specific gravities. The reaction behavior of Paramecium was affected by the difference in specific gravity between cell bodies and solutions. The water content metabolism functions of a mouse with needle stimulus, in particular excretory, were slightly promoted by micro- gravity. The cortisol level in blood of a falling mouse group rose showing strong stress. As the preliminary study on the geotaxis of insects, motion of bagworm was observed. 12 refs., 38 figs., 4 tabs.

A refined model of sedimentary rock cover in the southeastern part of the Congo basin from GOCE gravity and vertical gravity gradient observations

Science.gov (United States)

Martinec, Zdeněk; Fullea, Javier

2015-03-01

the gravitational compaction of sedimentary rocks. Therefore, the density model is extended by including a linear increase in density with depth. Subsequent L2 and L∞ norm minimization procedures are applied to find the density parameters by adjusting both the vertical gravity and the vertical gravity gradient. We found that including the vertical gravity gradient in the interpretation of the GOCO03S-derived data reduces the non-uniqueness of the inverse gradiometric problem for density determination. The density structure of the sedimentary formations that provide the optimum predictions of the GOCO03S-derived gravity and vertical gradient of gravity consists of a surface density contrast with respect to surrounding rocks of 0.24-0.28 g/cm3 and its decrease with depth of 0.05-0.25 g/cm3 per 10 km. Moreover, the case where the sedimentary rocks are gravitationally completely compacted in the deepest parts of the basin is supported by L∞ norm minimization. However, this minimization also allows a remaining density contrast at the deepest parts of the sedimentary basin of about 0.1 g/cm3.

Estimating Jupiter’s Gravity Field Using Juno Measurements, Trajectory Estimation Analysis, and a Flow Model Optimization

International Nuclear Information System (INIS)

Galanti, Eli; Kaspi, Yohai; Durante, Daniele; Finocchiaro, Stefano; Iess, Luciano

2017-01-01

The upcoming Juno spacecraft measurements have the potential of improving our knowledge of Jupiter’s gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spatial gravity variations, but these measurements will be very accurate only over a limited latitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially regarding the Jovian flow structure and its depth, which can influence the measured gravity field. In this study we propose a new iterative method for the estimation of the Jupiter gravity field, using a simulated Juno trajectory, a trajectory estimation model, and an adjoint-based inverse model for the flow dynamics. We test this method both for zonal harmonics only and with a full gravity field including tesseral harmonics. The results show that this method can fit some of the gravitational harmonics better to the “measured” harmonics, mainly because of the added information from the dynamical model, which includes the flow structure. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the expected gravity harmonics estimated from the Juno and Cassini radio science experiments.

Estimating Jupiter’s Gravity Field Using Juno Measurements, Trajectory Estimation Analysis, and a Flow Model Optimization

Energy Technology Data Exchange (ETDEWEB)

Galanti, Eli; Kaspi, Yohai [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot (Israel); Durante, Daniele; Finocchiaro, Stefano; Iess, Luciano, E-mail: eli.galanti@weizmann.ac.il [Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Universita di Roma, Rome (Italy)

2017-07-01

The upcoming Juno spacecraft measurements have the potential of improving our knowledge of Jupiter’s gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spatial gravity variations, but these measurements will be very accurate only over a limited latitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially regarding the Jovian flow structure and its depth, which can influence the measured gravity field. In this study we propose a new iterative method for the estimation of the Jupiter gravity field, using a simulated Juno trajectory, a trajectory estimation model, and an adjoint-based inverse model for the flow dynamics. We test this method both for zonal harmonics only and with a full gravity field including tesseral harmonics. The results show that this method can fit some of the gravitational harmonics better to the “measured” harmonics, mainly because of the added information from the dynamical model, which includes the flow structure. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the expected gravity harmonics estimated from the Juno and Cassini radio science experiments.

Effect of colostrum on gravity separation of milk somatic cells in skim milk.

Science.gov (United States)

Geer, S R; Barbano, D M

2014-02-01

Our objective was to determine if immunoglobulins play a role in the gravity separation (rising to the top) of somatic cells (SC) in skim milk. Other researchers have shown that gravity separation of milk fat globules is enhanced by IgM. Our recent research found that bacteria and SC gravity separate in both raw whole and skim milk and that heating milk to >76.9 °C for 25s stopped gravity separation of milk fat, SC, and bacteria. Bovine colostrum is a good natural source of immunoglobulins. An experiment was designed where skim milk was heated at high temperatures (76 °C for 7 min) to stop the gravity separation of SC and then colostrum was added back to try to restore the gravity separation of SC in increments to achieve 0, 0.4, 0.8, 2.0, and 4.0 g/L of added immunoglobulins. The milk was allowed to gravity separate for 22 h at 4 °C. The heat treatment of skim milk was sufficient to stop the gravity separation of SC. The treatment of 4.0 g/L of added immunoglobulins was successful in restoring the gravity separation of SC as compared with raw skim milk. Preliminary spore data on the third replicate suggested that bacterial spores gravity separate the same way as the SC in heated skim milk and heated skim milk with 4.0 g/L of added immunoglobulins. Strong evidence exists that immunoglobulins are at least one of the factors necessary for the gravity separation of SC and bacterial spores. It is uncertain at this time whether SC are a necessary component for gravity separation of fat, bacteria, and spores to occur. Further research is needed to determine separately the role of immunoglobulins and SC in gravity separation of bacteria and spores. Understanding the mechanism of gravity separation may allow the development of a continuous flow technology to remove SC, bacteria, and spores from milk. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Seismic surface wave tomography of waste sites. 1997 annual progress report

International Nuclear Information System (INIS)

Long, T.L.

1997-01-01

'The objective of the Seismic Surface Wave Tomography of Waste Sites is to develop a robust technique for field acquisition and analysis of surface wave data for the interpretation of shallow structures, such as those associated with the burial of wastes. The analysis technique is to be developed and tested on an existing set of seismic data covering the K-901 burial site at the East Tennessee Technology Park. Also, a portable prototype for a field acquisition system will be designed and developed to obtain additional data for analysis and testing of the technique. The K-901 data have been examined and a preliminary Single Valued Decomposition inversion has been obtained. The preliminary data indicates a need for additional seismic data to ground-truth the inversion. The originally proposed gravity data acquisition has been dropped because sufficient gravity data are now available for a preliminary analysis and because the seismic data are considered more critical to the interpretation. The proposed prototype for the portable acquisition and analysis system was developed during the first year and will be used in part of the acquisition of additional seismic data.'

Even-dimensional topological gravity from Chern-Simons gravity

International Nuclear Information System (INIS)

Merino, N.; Perez, A.; Salgado, P.

2009-01-01

It is shown that the topological action for gravity in 2n-dimensions can be obtained from the (2n+1)-dimensional Chern-Simons gravity genuinely invariant under the Poincare group. The 2n-dimensional topological gravity is described by the dynamics of the boundary of a (2n+1)-dimensional Chern-Simons gravity theory with suitable boundary conditions. The field φ a , which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associated with the non-linear realizations of the Poincare group ISO(d-1,1).

A time-lapse gravity survey of the Coso geothermal field, China Lake Naval Air Weapons Station, California

Science.gov (United States)

Phelps, Geoffrey; Cronkite-Ratcliff, Collin; Blake, Kelly

2018-04-19

We have conducted a gravity survey of the Coso geothermal field to continue the time-lapse gravity study of the area initiated in 1991. In this report, we outline a method of processing the gravity data that minimizes the random errors and instrument bias introduced into the data by the Scintrex CG-5 relative gravimeters that were used. After processing, the standard deviation of the data was estimated to be ±13 microGals. These data reveal that the negative gravity anomaly over the Coso geothermal field, centered on gravity station CER1, is continuing to increase in magnitude over time. Preliminary modeling indicates that water-table drawdown at the location of CER1 is between 65 and 326 meters over the last two decades. We note, however, that several assumptions on which the model results depend, such as constant elevation and free-water level over the study period, still require verification.

Polar gravity fields from GOCE and airborne gravity

DEFF Research Database (Denmark)

Forsberg, René; Olesen, Arne Vestergaard; Yidiz, Hasan

2011-01-01

Airborne gravity, together with high-quality surface data and ocean satellite altimetric gravity, may supplement GOCE to make consistent, accurate high resolution global gravity field models. In the polar regions, the special challenge of the GOCE polar gap make the error characteristics...... of combination models especially sensitive to the correct merging of satellite and surface data. We outline comparisons of GOCE to recent airborne gravity surveys in both the Arctic and the Antarctic. The comparison is done to new 8-month GOCE solutions, as well as to a collocation prediction from GOCE gradients...... in Antarctica. It is shown how the enhanced gravity field solutions improve the determination of ocean dynamic topography in both the Arctic and in across the Drake Passage. For the interior of Antarctica, major airborne gravity programs are currently being carried out, and there is an urgent need...

Improvements in GRACE Gravity Fields Using Regularization

Science.gov (United States)

Save, H.; Bettadpur, S.; Tapley, B. D.

2008-12-01

The unconstrained global gravity field models derived from GRACE are susceptible to systematic errors that show up as broad "stripes" aligned in a North-South direction on the global maps of mass flux. These errors are believed to be a consequence of both systematic and random errors in the data that are amplified by the nature of the gravity field inverse problem. These errors impede scientific exploitation of the GRACE data products, and limit the realizable spatial resolution of the GRACE global gravity fields in certain regions. We use regularization techniques to reduce these "stripe" errors in the gravity field products. The regularization criteria are designed such that there is no attenuation of the signal and that the solutions fit the observations as well as an unconstrained solution. We have used a computationally inexpensive method, normally referred to as "L-ribbon", to find the regularization parameter. This paper discusses the characteristics and statistics of a 5-year time-series of regularized gravity field solutions. The solutions show markedly reduced stripes, are of uniformly good quality over time, and leave little or no systematic observation residuals, which is a frequent consequence of signal suppression from regularization. Up to degree 14, the signal in regularized solution shows correlation greater than 0.8 with the un-regularized CSR Release-04 solutions. Signals from large-amplitude and small-spatial extent events - such as the Great Sumatra Andaman Earthquake of 2004 - are visible in the global solutions without using special post-facto error reduction techniques employed previously in the literature. Hydrological signals as small as 5 cm water-layer equivalent in the small river basins, like Indus and Nile for example, are clearly evident, in contrast to noisy estimates from RL04. The residual variability over the oceans relative to a seasonal fit is small except at higher latitudes, and is evident without the need for de-striping or

A new field experiment in the Greenland ice cap to test Newton's inverse square law

International Nuclear Information System (INIS)

Ander, M.E.; Nieto, M.M.; Zumberge, M.A.; Parker, R.L.; Lautzenhiser, T.; Aiken, C.L.V.; Ferguson, J.F.; McMechan, G.A.

1989-01-01

Recent experimental evidence suggests that Newton's law of gravity may not be precise. There are modern theories of quantum gravity that, in their attempts to unify gravity with other forces of nature, predict non-Newtonian gravitational forces that could have ranges on the order of 10 2 --10 5 m. If they exist, these forces would be apparent as violations of Newton's inverse square law. A geophysical experiment was carried out to search for possible finite-range, non-Newtonian gravity over depths of 213--1673 m in the glacial ice of the Greenland ice cap. The principal reason for this choice of experimental site is that a hole drilled through the ice cap already existed and the uniformity of the ice eliminates one of the major sources of uncertainty arising in the first of earlier studies, namely, the heterogeneity of the rocks through which a mine shaft or drill hole passes. This paper presents observations made in the summer of 1987 at Dye 3, Greenland, in the 2033-m-deep borehole, which reached the basement rock

How to deal with the high condition number of the noise covariance matrix of gravity field functionals synthesised from a satellite-only global gravity field model?

Science.gov (United States)

Klees, R.; Slobbe, D. C.; Farahani, H. H.

2018-03-01

The posed question arises for instance in regional gravity field modelling using weighted least-squares techniques if the gravity field functionals are synthesised from the spherical harmonic coefficients of a satellite-only global gravity model (GGM), and are used as one of the noisy datasets. The associated noise covariance matrix, appeared to be extremely ill-conditioned with a singular value spectrum that decayed gradually to zero without any noticeable gap. We analysed three methods to deal with the ill-conditioned noise covariance matrix: Tihonov regularisation of the noise covariance matrix in combination with the standard formula for the weighted least-squares estimator, a formula of the weighted least-squares estimator, which does not involve the inverse noise covariance matrix, and an estimator based on Rao's unified theory of least-squares. Our analysis was based on a numerical experiment involving a set of height anomalies synthesised from the GGM GOCO05s, which is provided with a full noise covariance matrix. We showed that the three estimators perform similar, provided that the two regularisation parameters each method knows were chosen properly. As standard regularisation parameter choice rules do not apply here, we suggested a new parameter choice rule, and demonstrated its performance. Using this rule, we found that the differences between the three least-squares estimates were within noise. For the standard formulation of the weighted least-squares estimator with regularised noise covariance matrix, this required an exceptionally strong regularisation, much larger than one expected from the condition number of the noise covariance matrix. The preferred method is the inversion-free formulation of the weighted least-squares estimator, because of its simplicity with respect to the choice of the two regularisation parameters.

The contribution of gravity method in geothermal exploration of southern part of the Gulf of Suez–Sinai region, Egypt

Directory of Open Access Journals (Sweden)

H. Atef

2016-06-01

The Bouguer anomaly map of the study area was used for delineating the subsurface structures and tectonic trends that have resulted in a potential heat source. The gravity inversion revealed a good correlation between areas of high temperature gradients, high heat flow and positive gravity anomalies. The high temperature gradient and heat flow values suggested being associated with a noticeable hydrothermal source of heat anomaly located at relatively shallow depths which is expected to be due to the uplift of the basement in the area.

Transient Inverse Calibration of the Site-Wide Groundwater Flow Model (ACM-2): FY03 Progress Report

International Nuclear Information System (INIS)

Vermeul, Vince R.; Bergeron, Marcel P.; Cole, C R.; Murray, Christopher J.; Nichols, William E.; Scheibe, Timothy D.; Thorne, Paul D.; Waichler, Scott R.; Xie, YuLong

2003-01-01

DOE and PNNL are working to strengthen the technical defensibility of the groundwater flow and transport model at the Hanford Site and to incorporate uncertainty into the model. One aspect of the initiative is developing and using a three-dimensional transient inverse model to estimate the hydraulic conductivities, specific yields, and other parameters using data from Hanford since 1943. The focus of the alternative conceptual model (ACM-2) inverse modeling initiative documented in this report was to address limitations identified in the ACM-1 model, complete the facies-based approach for representing the hydraulic conductivity distribution in the Hanford and middle Ringold Formations, develop the approach and implementation methodology for generating multiple ACMs based on geostatistical data analysis, and develop an approach for inverse modeling of these stochastic ACMs. The primary modifications to ACM-2 transient inverse model include facies-based zonation of Units 1 (Hanford ) and 5 (middle Ringold); an improved approach for handling run-on recharge from upland areas based on watershed modeling results; an improved approach for representing artificial discharges from site operations; and minor changes to the geologic conceptual model. ACM-2 is the first attempt to fully incorporate the facies-based approach to represent the hydrogeologic structure. Further refinement and additional improvements to overall model fit will be realized during future inverse simulations of groundwater flow and transport. In addition, preliminary work was completed on an approach and implementation for generating an inverse modeling of stochastic ACMs. These techniques were applied to assess the uncertainty in the facies-based zonation of the Hanford formation and the geological structure of Ringold mud units. The geostatistical analysis used a preliminary interpretation of the facies-based zonation that was not consistent with that used in ACM-2. Although the overall objective of

Effects of artificial gravity on the cardiovascular system: Computational approach

Science.gov (United States)

Diaz Artiles, Ana; Heldt, Thomas; Young, Laurence R.

2016-09-01

Artificial gravity has been suggested as a multisystem countermeasure against the negative effects of weightlessness. However, many questions regarding the appropriate configuration are still unanswered, including optimal g-level, angular velocity, gravity gradient, and exercise protocol. Mathematical models can provide unique insight into these questions, particularly when experimental data is very expensive or difficult to obtain. In this research effort, a cardiovascular lumped-parameter model is developed to simulate the short-term transient hemodynamic response to artificial gravity exposure combined with ergometer exercise, using a bicycle mounted on a short-radius centrifuge. The model is thoroughly described and preliminary simulations are conducted to show the model capabilities and potential applications. The model consists of 21 compartments (including systemic circulation, pulmonary circulation, and a cardiac model), and it also includes the rapid cardiovascular control systems (arterial baroreflex and cardiopulmonary reflex). In addition, the pressure gradient resulting from short-radius centrifugation is captured in the model using hydrostatic pressure sources located at each compartment. The model also includes the cardiovascular effects resulting from exercise such as the muscle pump effect. An initial set of artificial gravity simulations were implemented using the Massachusetts Institute of Technology (MIT) Compact-Radius Centrifuge (CRC) configuration. Three centripetal acceleration (artificial gravity) levels were chosen: 1 g, 1.2 g, and 1.4 g, referenced to the subject's feet. Each simulation lasted 15.5 minutes and included a baseline period, the spin-up process, the ergometer exercise period (5 minutes of ergometer exercise at 30 W with a simulated pedal cadence of 60 RPM), and the spin-down process. Results showed that the cardiovascular model is able to predict the cardiovascular dynamics during gravity changes, as well as the expected

From Lorentz-Chern-Simons to Massive Gravity in 2+1 dimensions

Energy Technology Data Exchange (ETDEWEB)

Pino, Simón del [Instituto de Física, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso,Av. Universidad 330, Curauma, Valparaíso (Chile); Giribet, Gaston [Physique Théorique et Mathématique, Université Libre de Bruxelles andInternational Solvay Institutes,Campus Plaine C.P. 231, Bruxelles, B-1050 (Belgium); Departamento de Física, Universidad de Buenos Aires and IFIBA-CONICET,Ciudad Universitaria, Pabellón I, Buenos Aires, 1428 (Argentina); Instituto de Física, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso,Av. Universidad 330, Curauma, Valparaíso (Chile); Toloza, Adolfo [Instituto de Física, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso,Av. Universidad 330, Curauma, Valparaíso (Chile); Centro de Estudios Científicos CECs,Arturo Prat 514, Valdivia (Chile); Zanelli, Jorge [Centro de Estudios Científicos CECs,Arturo Prat 514, Valdivia (Chile)

2015-06-17

We propose a generalization of Chiral Gravity, which follows from considering a Chern-Simons action for the spin connection with anti-symmetric contorsion. The theory corresponds to Topologically Massive Gravity at the chiral point non-minimally coupled to an additional scalar mode that gathers the torsion degree of freedom. In this setup, the effective cosmological constant (the inverse of the curvature radius of maximally symmetric solutions) is either negative or zero, and it enters as an integration constant associated to the value of the contorsion at infinity. We explain how this is not in conflict with the Zamolodchikov’s c-theorem holding in the dual boundary theory. In fact, we conjecture that the theory formulated about three-dimensional Anti-de Sitter space is dual to a two-dimensional conformal field theory whose right- and left-moving central charges are given by c{sub R}=24k and c{sub L}=0, respectively, being k the level of the Chern-Simons action. We study the classical theory both at the linear and non-linear level. In particular, we show how Chiral Gravity is included as a special sector. In addition, the theory has other sectors, which we explore; we exhibit analytic exact solutions that are not solutions of Topologically Massive Gravity (and, consequently, neither of General Relativity) and still satisfy Brown-Henneaux asymptotically AdS{sub 3} boundary conditions.

Massive Gravity

OpenAIRE

de Rham, Claudia

2014-01-01

We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware–Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...

Momentum and charge transport in non-relativistic holographic fluids from Hořava gravity

Energy Technology Data Exchange (ETDEWEB)

Davison, Richard A. [Department of Physics, Harvard University, Cambridge, MA 02138 (United States); Grozdanov, Sašo [Instituut-Lorentz for Theoretical Physics, Leiden University, Niels Bohrweg 2, Leiden 2333 CA (Netherlands); Janiszewski, Stefan [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8W 3P6 (Canada); Kaminski, Matthias [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States)

2016-11-28

We study the linearized transport of transverse momentum and charge in a conjectured field theory dual to a black brane solution of Hořava gravity with Lifshitz exponent z=1. As expected from general hydrodynamic reasoning, we find that both of these quantities are diffusive over distance and time scales larger than the inverse temperature. We compute the diffusion constants and conductivities of transverse momentum and charge, as well the ratio of shear viscosity to entropy density, and find that they differ from their relativistic counterparts. To derive these results, we propose how the holographic dictionary should be modified to deal with the multiple horizons and differing propagation speeds of bulk excitations in Hořava gravity. When possible, as a check on our methods and results, we use the covariant Einstein-Aether formulation of Hořava gravity, along with field redefinitions, to re-derive our results from a relativistic bulk theory.

A new approach for gravity localization in six-dimensional geometries

International Nuclear Information System (INIS)

Santos, Victor Pereira do Nascimento; Almeida, Carlos Alberto Santos de

2011-01-01

Full text: The idea that spacetime may have more than four dimensions is old, originally presented as an attempt to unify Maxwell's theory of Electromagnetism with the brand-new gravitation theory of Einstein. Such extra dimensions are in principle unobservable to the energy scales currently available. However, its effects can be seen in short distance gravity experiments and in observations in cosmology. Also, it is used as a mechanism to explain the difference between the energy scales of the weak force and gravity, which is called the hierarchy problem. The current framework for the extra dimension scenario is consider the four-dimensional known universe as embedded in a higher dimensional space called bulk. The form of this bulk determines how we perceive gravity in our universe; then, the behaviour of gravitational field depends on the geometry of the bulk. Metric solutions were already presented for string-like defect, with and without matter sources, where was shown that the gravity Newtonian potential grows with the inverse cube of distance. Such correction arises from a very particular mass spectrum for the gravitational field, which already contains the orbital angular momentum contributions. In this work we study the behaviour of gravitational field in a extra-dimensional braneworld scenario, using non-factorizable geometries (which preserves Poincare symmetry) and setting suitable matter distributions in order to verify its localization, for several geometries. For such geometries it is possible to find explicit solutions for the tensor fluctuations of the metric. (author)

Scales of gravity

International Nuclear Information System (INIS)

Dvali, Gia; Kolanovic, Marko; Nitti, Francesco; Gabadadze, Gregory

2002-01-01

We propose a framework in which the quantum gravity scale can be as low as 10 -3 eV. The key assumption is that the standard model ultraviolet cutoff is much higher than the quantum gravity scale. This ensures that we observe conventional weak gravity. We construct an explicit brane-world model in which the brane-localized standard model is coupled to strong 5D gravity of infinite-volume flat extra space. Because of the high ultraviolet scale, the standard model fields generate a large graviton kinetic term on the brane. This kinetic term 'shields' the standard model from the strong bulk gravity. As a result, an observer on the brane sees weak 4D gravity up to astronomically large distances beyond which gravity becomes five dimensional. Modeling quantum gravity above its scale by the closed string spectrum we show that the shielding phenomenon protects the standard model from an apparent phenomenological catastrophe due to the exponentially large number of light string states. The collider experiments, astrophysics, cosmology and gravity measurements independently point to the same lower bound on the quantum gravity scale, 10 -3 eV. For this value the model has experimental signatures both for colliders and for submillimeter gravity measurements. Black holes reveal certain interesting properties in this framework

PPN-limit of Fourth Order Gravity inspired by Scalar-Tensor Gravity

OpenAIRE

Capozziello, S.; Troisi, A.

2005-01-01

Based on the {\\it dynamical} equivalence between higher order gravity and scalar-tensor gravity the PPN-limit of fourth order gravity is discussed. We exploit this analogy developing a fourth order gravity version of the Eddington PPN-parameters. As a result, Solar System experiments can be reconciled with higher order gravity, if physical constraints descending from experiments are fulfilled.

The ring structure of chiral operators for minimal models coupled to 2D gravity

International Nuclear Information System (INIS)

Sarmadi, M.H.

1992-09-01

The BRST cohomology ring for (p,q) models coupled to gravity is discussed. In addition to the generators of the ghost number zero ring, the existence of a generator of ghost number - 1 and its inverse is proved and used to construct the entire ring. Some comments are made regarding the algebra of the vector fields on the ring and the supersymmetric extension. (author). 13 refs

Terrestrial gravity data analysis for interim gravity model improvement

Science.gov (United States)

1987-01-01

This is the first status report for the Interim Gravity Model research effort that was started on June 30, 1986. The basic theme of this study is to develop appropriate models and adjustment procedures for estimating potential coefficients from terrestrial gravity data. The plan is to use the latest gravity data sets to produce coefficient estimates as well as to provide normal equations to NASA for use in the TOPEX/POSEIDON gravity field modeling program.

Studies on the geological environment of the Nanjido waste disposal site: Gravity and magnetic investigations

Energy Technology Data Exchange (ETDEWEB)

Kwon, Byung Doo; Kim, Cha Seop; Chung, Ho Joon; Oh, Seok Hoon [Seoul National Univ., Seoul (Korea, Republic of)

1995-10-01

Gravity and magnetic surveys were carried out to investigate the three dimensional configuration and characteristics of the landfills at Nanjido waste disposal site. For terrain correction and three dimensional density inversion of gravity data an algorithm, which calculates the gravity effect of a three dimensional body by using the solid angle method, is developed. This algorithm has been proved to give more accurate terrain correction values for the small survey area having varied topography like Nanjido site as compared with widely used methods such as Hammer`s method and multiquadric equation method. Density inversion of gravity anomaly data gives very useful information about the lateral and vertical variation of the landfills, which can be used to discriminate the kinds of wastes. The average density of filled materials appears to be 1.7 g/cm{sup 3} which is much higher than the value (0.8 g/cm{sup 3}) estimated by Seoul City. The lateral variation of density shows high correlation with the pattern of ongoing depression of the landfills. The northern region of the landfill no. 1, which shows low density and high depression, is closely associated with the industrial waste and sludge filled area. The magnetic anomaly data provide information about relative concentration of magnetic materials, which is also very useful to investigate characteristics of the fills. Several high positive anomaly regions on the reduced-to-pole magnetic anomaly map are appeared to be associated with the industrial waste fills, but certain industrial waste fills show low negative anomalies. This kind of magnetic information can be used in selecting drilling locations over landfills away from buried metal products during the stabilization process. (author). 15 refs., 2 tabs., 15 figs.

Preliminary trajectory design for a solar polar observatory using SEP and multiple gravity assists

NARCIS (Netherlands)

Corpaccioli, L.; Noomen, R.; De Smet, S.; Parker, J.S.; Herman, J.F.C.

2015-01-01

Satellite solar observatories have always been of central importance to heliophysics; while there have been numerous such missions, the solar poles have been extremely under-observed. This paper proposes to use low-thrust as well as multiple gravity assists to reach the enormous energies required

Multiscale estimation of excess mass from gravity data

Science.gov (United States)

Castaldo, Raffaele; Fedi, Maurizio; Florio, Giovanni

2014-06-01

We describe a multiscale method to estimate the excess mass of gravity anomaly sources, based on the theory of source moments. Using a multipole expansion of the potential field and considering only the data along the vertical direction, a system of linear equations is obtained. The choice of inverting data along a vertical profile can help us to reduce the interference effects due to nearby anomalies and will allow a local estimate of the source parameters. A criterion is established allowing the selection of the optimal highest altitude of the vertical profile data and truncation order of the series expansion. The inversion provides an estimate of the total anomalous mass and of the depth to the centre of mass. The method has several advantages with respect to classical methods, such as the Gauss' method: (i) we need just a 1-D inversion to obtain our estimates, being the inverted data sampled along a single vertical profile; (ii) the resolution may be straightforward enhanced by using vertical derivatives; (iii) the centre of mass is also estimated, besides the excess mass; (iv) the method is very robust versus noise; (v) the profile may be chosen in such a way to minimize the effects from interfering anomalies or from side effects due to the a limited area extension. The multiscale estimation of excess mass method can be successfully used in various fields of application. Here, we analyse the gravity anomaly generated by a sulphide body in the Skelleftea ore district, North Sweden, obtaining source mass and volume estimates in agreement with the known information. We show also that these estimates are substantially improved with respect to those obtained with the classical approach.

Structural model Soapaga failure from spectral correlation and magnetic gravity anomalies in the eastern cordillera, Colombia

International Nuclear Information System (INIS)

Rodriguez Diana Marcela; Hernandez Orlando; Kammer Andreas

2009-01-01

The aim of this research is to apply spectral correlation, local favorability indexes and Poisson's theorem as numerical methods for data processing and interpretation of potential field data associated with structural features; these techniques are applied to theoretical and real gravity and magnetic data of the Soapaga fault, located in the Boyaca Department, in the eastern Andean Mountains. Theoretical data of the Soapaga fault was obtained by forward modeling of geological and structural sections. Real data of the Soapaga fault included compiled gravity data and acquired magnetic data along four profiles oriented perpendicular to the fault. As a result, the geometry of the fault and its structural characteristics were obtained by interactive forward and inverse modeling. This methodology allows highlighting anomaly trends associated with density and magnetic susceptibility contrast that occur along the Soapaga fault zone. Additionally, this work provides a quantitative approach to establish the relationship between gravity and magnetic anomalies, supported by a rigorous mathematical methodology rather than isolated data interpretation to better understand the gravity and magnetic signatures of outcropping and hidden structural features.

Investigation of inversion polymorphisms in the human genome using principal components analysis.

Science.gov (United States)

Ma, Jianzhong; Amos, Christopher I

2012-01-01

Despite the significant advances made over the last few years in mapping inversions with the advent of paired-end sequencing approaches, our understanding of the prevalence and spectrum of inversions in the human genome has lagged behind other types of structural variants, mainly due to the lack of a cost-efficient method applicable to large-scale samples. We propose a novel method based on principal components analysis (PCA) to characterize inversion polymorphisms using high-density SNP genotype data. Our method applies to non-recurrent inversions for which recombination between the inverted and non-inverted segments in inversion heterozygotes is suppressed due to the loss of unbalanced gametes. Inside such an inversion region, an effect similar to population substructure is thus created: two distinct "populations" of inversion homozygotes of different orientations and their 1:1 admixture, namely the inversion heterozygotes. This kind of substructure can be readily detected by performing PCA locally in the inversion regions. Using simulations, we demonstrated that the proposed method can be used to detect and genotype inversion polymorphisms using unphased genotype data. We applied our method to the phase III HapMap data and inferred the inversion genotypes of known inversion polymorphisms at 8p23.1 and 17q21.31. These inversion genotypes were validated by comparing with literature results and by checking Mendelian consistency using the family data whenever available. Based on the PCA-approach, we also performed a preliminary genome-wide scan for inversions using the HapMap data, which resulted in 2040 candidate inversions, 169 of which overlapped with previously reported inversions. Our method can be readily applied to the abundant SNP data, and is expected to play an important role in developing human genome maps of inversions and exploring associations between inversions and susceptibility of diseases.

Gravity resonance spectroscopy constrains dark energy and dark matter scenarios.

Science.gov (United States)

Jenke, T; Cronenberg, G; Burgdörfer, J; Chizhova, L A; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Rotter, S; Saul, H; Schmidt, U; Abele, H

2014-04-18

We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14  eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β>5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ=20  μm (95% C.L.).

Preliminary results of training with gravity compensation of the arm in chronic stroke survivors

NARCIS (Netherlands)

van der Kooij, Herman; Prange, Grada Berendina; Prange, G.B.; Krabben, T.; Krabben, T.; Renzenbrink, G.H.; Boer, J.; Hermens, Hermanus J.; Jannink, M.J.A.

2009-01-01

After stroke, arm function can be limited by a reduction in the selectivity of movements, due to involuntary coupling of shoulder abduction and elbow flexion, limiting the ability to reach. Gravity compensation of the arm reduces the required active shoulder abduction torques, which results in a

Dualities and emergent gravity: Gauge/gravity duality

Science.gov (United States)

de Haro, Sebastian

2017-08-01

In this paper I develop a framework for relating dualities and emergence: two notions that are close to each other but also exclude one another. I adopt the conception of duality as 'isomorphism', from the physics literature, cashing it out in terms of three conditions. These three conditions prompt two conceptually different ways in which a duality can be modified to make room for emergence; and I argue that this exhausts the possibilities for combining dualities and emergence (via coarse-graining). I apply this framework to gauge/gravity dualities, considering in detail three examples: AdS/CFT, Verlinde's scheme, and black holes. My main point about gauge/gravity dualities is that the theories involved, qua theories of gravity, must be background-independent. I distinguish two senses of background-independence: (i) minimalistic and (ii) extended. I argue that the former is sufficiently strong to allow for a consistent theory of quantum gravity; and that AdS/CFT is background-independent on this account; while Verlinde's scheme best fits the extended sense of background-independence. I argue that this extended sense should be applied with some caution: on pain of throwing the baby (general relativity) out with the bath-water (extended background-independence). Nevertheless, it is an interesting and potentially fruitful heuristic principle for quantum gravity theory construction. It suggests some directions for possible generalisations of gauge/gravity dualities. The interpretation of dualities is discussed; and the so-called 'internal' vs. 'external' viewpoints are articulated in terms of: (i) epistemic and metaphysical commitments; (ii) parts vs. wholes. I then analyse the emergence of gravity in gauge/gravity dualities in terms of the two available conceptualisations of emergence; and I show how emergence in AdS/CFT and in Verlinde's scenario differ from each other. Finally, I give a novel derivation of the Bekenstein-Hawking black hole entropy formula based on

A progressive methodology for seismic safety evaluation of gravity dams

International Nuclear Information System (INIS)

Ghrib, F.; Leger, P.; Tinawi, R.; Lupien, R.; Veilleux, M.

1995-01-01

A progressive methodology for the seismic safety evaluation of existing concrete gravity dams was described. The methodology was based on five structural analysis levels with increasing complexity to represent inertia forces, dam-foundation and dam-interaction mechanisms, as well as concrete cracking. The five levels were (1) preliminary screening, (2) pseudo-static method, (3) pseudo-dynamic method, (4) linear time history analysis, and (5) non-linear history analysis. The first four levels of analysis were applied for the seismic safety evaluation of Paugan gravity dam (Quebec). Results showed that internal forces from pseudo-dynamic, response spectra and transient finite element analyses could be used to interpret the dynamic stability of dams from familiar strength-based criteria. However, as soon as the base was cracked, the seismically induced forces were modified, and level IV analyses proved more suitable to handle rationally these complexities. 8 refs., 7 figs., 1 tab

Contravariant gravity on Poisson manifolds and Einstein gravity

International Nuclear Information System (INIS)

Kaneko, Yukio; Watamura, Satoshi; Muraki, Hisayoshi

2017-01-01

A relation between gravity on Poisson manifolds proposed in Asakawa et al (2015 Fortschr. Phys . 63 683–704) and Einstein gravity is investigated. The compatibility of the Poisson and Riemann structures defines a unique connection, the contravariant Levi-Civita connection, and leads to the idea of the contravariant gravity. The Einstein–Hilbert-type action yields an equation of motion which is written in terms of the analog of the Einstein tensor, and it includes couplings between the metric and the Poisson tensor. The study of the Weyl transformation reveals properties of those interactions. It is argued that this theory can have an equivalent description as a system of Einstein gravity coupled to matter. As an example, it is shown that the contravariant gravity on a two-dimensional Poisson manifold can be described by a real scalar field coupled to the metric in a specific manner. (paper)

The Gravity Probe B experiment and early results

Energy Technology Data Exchange (ETDEWEB)

Conklin, John W [Stanford University (United States)], E-mail: johnwc@stanford.edu

2008-11-01

The NASA Gravity Probe B orbiting gyroscope test of General Relativity, launched from Vandenberg Air Force Base on 20 April, 2004 tests two consequences of Einstein's theory: 1) the predicted 6.6 arcs/yr geodetic effect due to the motion of the gyroscope through the curved space-time around the Earth; 2) the predicted 0.039 arcs/yr frame-dragging effect due to the rotating Earth. The mission required the development of many technologies that did not exist when experiment was conceived in 1960. Cryogenic gyroscopes with drift-rates 7 orders of magnitude better than the best inertial navigation gyroscopes, a < 1 marcs star tracking telescope, and other essential technologies were developed as a result of an intensive collaboration between Stanford physicists and engineers, NASA and industry. Gravity Probe B collected science data from August 27, 2004 through September 29, 2005. Analysis of the data began during the mission and is on-going. This paper describes the main features and challenges of the experiment and presents the preliminary results to date.

The Gravity Probe B experiment and early results

International Nuclear Information System (INIS)

Conklin, John W

2008-01-01

The NASA Gravity Probe B orbiting gyroscope test of General Relativity, launched from Vandenberg Air Force Base on 20 April, 2004 tests two consequences of Einstein's theory: 1) the predicted 6.6 arcs/yr geodetic effect due to the motion of the gyroscope through the curved space-time around the Earth; 2) the predicted 0.039 arcs/yr frame-dragging effect due to the rotating Earth. The mission required the development of many technologies that did not exist when experiment was conceived in 1960. Cryogenic gyroscopes with drift-rates 7 orders of magnitude better than the best inertial navigation gyroscopes, a < 1 marcs star tracking telescope, and other essential technologies were developed as a result of an intensive collaboration between Stanford physicists and engineers, NASA and industry. Gravity Probe B collected science data from August 27, 2004 through September 29, 2005. Analysis of the data began during the mission and is on-going. This paper describes the main features and challenges of the experiment and presents the preliminary results to date.

Is nonrelativistic gravity possible?

International Nuclear Information System (INIS)

Kocharyan, A. A.

2009-01-01

We study nonrelativistic gravity using the Hamiltonian formalism. For the dynamics of general relativity (relativistic gravity) the formalism is well known and called the Arnowitt-Deser-Misner (ADM) formalism. We show that if the lapse function is constrained correctly, then nonrelativistic gravity is described by a consistent Hamiltonian system. Surprisingly, nonrelativistic gravity can have solutions identical to relativistic gravity ones. In particular, (anti-)de Sitter black holes of Einstein gravity and IR limit of Horava gravity are locally identical.

Gravity-matter entanglement in Regge quantum gravity

International Nuclear Information System (INIS)

Paunković, Nikola; Vojinović, Marko

2016-01-01

We argue that Hartle-Hawking states in the Regge quantum gravity model generically contain non-trivial entanglement between gravity and matter fields. Generic impossibility to talk about “matter in a point of space” is in line with the idea of an emergent spacetime, and as such could be taken as a possible candidate for a criterion for a plausible theory of quantum gravity. Finally, this new entanglement could be seen as an additional “effective interaction”, which could possibly bring corrections to the weak equivalence principle. (paper)

Lovelock gravities from Born-Infeld gravity theory

Science.gov (United States)

Concha, P. K.; Merino, N.; Rodríguez, E. K.

2017-02-01

We present a Born-Infeld gravity theory based on generalizations of Maxwell symmetries denoted as Cm. We analyze different configuration limits allowing to recover diverse Lovelock gravity actions in six dimensions. Further, the generalization to higher even dimensions is also considered.

Euler–Chern–Simons gravity from Lovelock–Born–Infeld gravity

OpenAIRE

Izaurieta, F.; Rodriguez, E.; Salgado, P.

2004-01-01

In the context of a gauge theoretical formulation, higher dimensional gravity invariant under the AdS group is dimensionally reduced to Euler-Chern-Simons gravity. The dimensional reduction procedure of Grignani-Nardelli [Phys. Lett. B 300, 38 (1993)] is generalized so as to permit reducing D-dimensional Lanczos Lovelock gravity to d=D-1 dimensions.

Laboratory testing of rock and salt samples for determination of specific gravity and total porosity of the Zeeck No. 1 well (PD-7), Palo Duro Basin, Texas: unanalyzed data

International Nuclear Information System (INIS)

1984-07-01

This report contains the specific gravity and total porosity determinations for rock and salt samples from Zeeck No. 1 Well of the Permian Basin. The laboratory test samples were measured for water content, apparent specific gravity, specific gravity of solids, total porosity and effective porosity. Specimen descriptions including specimen number, formation/group, and lithologic description as well as typical data sheets are included in the appendices. These data are preliminary. They have been neither analyzed nor evaluated

Gravity

CERN Document Server

Gamow, George

2003-01-01

A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

Agradient velocity, vortical motion and gravity waves in a rotating shallow-water model

Science.gov (United States)

Sutyrin Georgi, G.

2004-07-01

A new approach to modelling slow vortical motion and fast inertia-gravity waves is suggested within the rotating shallow-water primitive equations with arbitrary topography. The velocity is exactly expressed as a sum of the gradient wind, described by the Bernoulli function,B, and the remaining agradient part, proportional to the velocity tendency. Then the equation for inverse potential vorticity,Q, as well as momentum equations for agradient velocity include the same source of intrinsic flow evolution expressed as a single term J (B, Q), where J is the Jacobian operator (for any steady state J (B, Q) = 0). Two components of agradient velocity are responsible for the fast inertia-gravity wave propagation similar to the traditionally used divergence and ageostrophic vorticity. This approach allows for the construction of balance relations for vortical dynamics and potential vorticity inversion schemes even for moderate Rossby and Froude numbers assuming the characteristic value of |J(B, Q)| = to be small. The components of agradient velocity are used as the fast variables slaved to potential vorticity that allows for diagnostic estimates of the velocity tendency, the direct potential vorticity inversion with the accuracy of 2 and the corresponding potential vorticity-conserving agradient velocity balance model (AVBM). The ultimate limitations of constructing the balance are revealed in the form of the ellipticity condition for balanced tendency of the Bernoulli function which incorporates both known criteria of the formal stability: the gradient wind modified by the characteristic vortical Rossby wave phase speed should be subcritical. The accuracy of the AVBM is illustrated by considering the linear normal modes and coastal Kelvin waves in the f-plane channel with topography.

Lower dimensional gravity

International Nuclear Information System (INIS)

Brown, J.D.

1988-01-01

This book addresses the subject of gravity theories in two and three spacetime dimensions. The prevailing philosophy is that lower dimensional models of gravity provide a useful arena for developing new ideas and insights, which are applicable to four dimensional gravity. The first chapter consists of a comprehensive introduction to both two and three dimensional gravity, including a discussion of their basic structures. In the second chapter, the asymptotic structure of three dimensional Einstein gravity with a negative cosmological constant is analyzed. The third chapter contains a treatment of the effects of matter sources in classical two dimensional gravity. The fourth chapter gives a complete analysis of particle pair creation by electric and gravitational fields in two dimensions, and the resulting effect on the cosmological constant

Lovelock gravities from Born–Infeld gravity theory

Directory of Open Access Journals (Sweden)

P.K. Concha

2017-02-01

Full Text Available We present a Born–Infeld gravity theory based on generalizations of Maxwell symmetries denoted as Cm. We analyze different configuration limits allowing to recover diverse Lovelock gravity actions in six dimensions. Further, the generalization to higher even dimensions is also considered.

Hydrodynamics dual to Einstein-Gauss-Bonnet gravity: all-order gradient resummation

Energy Technology Data Exchange (ETDEWEB)

Bu, Yanyan; Lublinsky, Michael; Sharon, Amir [Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel)

2015-06-24

Relativistic hydrodynamics dual to Einstein-Gauss-Bonnet gravity in asymptotic AdS{sub 5} space is under study. To linear order in the amplitude of the fluid velocity and temperature, we derive the fluid’s stress-energy tensor via an all-order resummation of the derivative terms. Each order is accompanied by new transport coefficients, which all together could be compactly absorbed into two functions of momenta, referred to as viscosity functions. Via inverse Fourier transform, these viscosities appear as memory functions in the constitutive relation between components of the stress-energy tensor.

Analytic rotating black-hole solutions in N-dimensional f(T) gravity

Energy Technology Data Exchange (ETDEWEB)

Nashed, G.G.L. [The British University in Egypt, Centre for Theoretical Physics, P.O. Box 43, Cairo (Egypt); Ain Shams University, Faculty of Science, Mathematics Department, Cairo (Egypt); Egyptian Relativity Group (ERG), Cairo (Egypt); El Hanafy, W. [The British University in Egypt, Centre for Theoretical Physics, P.O. Box 43, Cairo (Egypt); Egyptian Relativity Group (ERG), Cairo (Egypt)

2017-02-15

A non-diagonal vielbein ansatz is applied to the N-dimension field equations of f(T) gravity. An analytical vacuum solution is derived for the quadratic polynomial f(T)=T+εT{sup 2} and an inverse relation between the coupling constant ε and the cosmological constant Λ. Since the induced metric has off-diagonal components, it cannot be removed by a mere coordinate transformation, the solution has a rotating parameter. The curvature and torsion scalars invariants are calculated to study the singularities and horizons of the solution. In contrast to general relativity, the Cauchy horizon differs from the horizon which shows the effect of the higher order torsion. The general expression of the energy-momentum vector of f(T) gravity is used to calculate the energy of the system. Finally, we have shown that this kind of solution satisfies the first law of thermodynamics in the framework of f(T) gravitational theories. (orig.)

Joint Inversion of Vp, Vs, and Resistivity at SAFOD

Science.gov (United States)

Bennington, N. L.; Zhang, H.; Thurber, C. H.; Bedrosian, P. A.

2010-12-01

Seismic and resistivity models at SAFOD have been derived from separate inversions that show significant spatial similarity between the main model features. Previous work [Zhang et al., 2009] used cluster analysis to make lithologic inferences from trends in the seismic and resistivity models. We have taken this one step further by developing a joint inversion scheme that uses the cross-gradient penalty function to achieve structurally similar Vp, Vs, and resistivity images that adequately fit the seismic and magnetotelluric MT data without forcing model similarity where none exists. The new inversion code, tomoDDMT, merges the seismic inversion code tomoDD [Zhang and Thurber, 2003] and the MT inversion code Occam2DMT [Constable et al., 1987; deGroot-Hedlin and Constable, 1990]. We are exploring the utility of the cross-gradients penalty function in improving models of fault-zone structure at SAFOD on the San Andreas Fault in the Parkfield, California area. Two different sets of end-member starting models are being tested. One set is the separately inverted Vp, Vs, and resistivity models. The other set consists of simple, geologically based block models developed from borehole information at the SAFOD drill site and a simplified version of features seen in geophysical models at Parkfield. For both starting models, our preliminary results indicate that the inversion produces a converging solution with resistivity, seismic, and cross-gradient misfits decreasing over successive iterations. We also compare the jointly inverted Vp, Vs, and resistivity models to borehole information from SAFOD to provide a "ground truth" comparison.

Nonlocal gravity

CERN Document Server

Mashhoon, Bahram

2017-01-01

Relativity theory is based on a postulate of locality, which means that the past history of the observer is not directly taken into account. This book argues that the past history should be taken into account. In this way, nonlocality---in the sense of history dependence---is introduced into relativity theory. The deep connection between inertia and gravitation suggests that gravity could be nonlocal, and in nonlocal gravity the fading gravitational memory of past events must then be taken into account. Along this line of thought, a classical nonlocal generalization of Einstein's theory of gravitation has recently been developed. A significant consequence of this theory is that the nonlocal aspect of gravity appears to simulate dark matter. According to nonlocal gravity theory, what astronomers attribute to dark matter should instead be due to the nonlocality of gravitation. Nonlocality dominates on the scale of galaxies and beyond. Memory fades with time; therefore, the nonlocal aspect of gravity becomes wea...

Optimization of a Time-Lapse Gravity Network for Carbon Sequestration

Science.gov (United States)

Appriou, D.; Strickland, C. E.; Ruprecht Yonkofski, C. M.

2017-12-01

The objective of this study is to evaluate what could be a comprehensive and optimal state of the art gravity monitoring network that would meet the UIC class VI regulation and insure that 90% of the CO2 injected remain underground. Time-lapse gravity surveys have a long history of effective applications of monitoring temporal density changes in the subsurface. For decades, gravity measurements have been used for a wide range of applications. The interest of time-lapse gravity surveys for monitoring carbon sequestration sites started recently. The success of their deployment in such sites depends upon a combination of favorable conditions, such as the reservoir geometry, depth, thickness, density change over time induced by the CO2 injection and the location of the instrument. In most cases, the density changes induced by the CO2 plume in the subsurface are not detectable from the surface but the use of borehole gravimeters can provide excellent results. In the framework of the National Assessment and Risk Partnership (NRAP) funded by the Department of Energy, the evaluation of the effectiveness of the gravity monitoring of a CO2 storage site has been assessed using multiple synthetic scenarios implemented on a community model developed for the Kimberlina site (e.g., fault leakage scenarios, borehole leakage). The Kimberlina carbon sequestration project was a pilot project located in southern San Joaquin Valley, California, aimed to safely inject 250,000 t CO2/yr for four years. Although the project was cancelled in 2012, the site characterization efforts resulted in the development of a geologic model. In this study, we present the results of the time-lapse gravity monitoring applied on different multiphase flow and reactive transport models developed by Lawrence Berkeley National Laboratory (i.e., no leakage, permeable fault zone, wellbore leakage). Our monitoring approach considers an ideal network, consisting of multiple vertical and horizontal instrumented

Utility of natural generalised inverse technique in the interpretation of dyke structures

Digital Repository Service at National Institute of Oceanography (India)

Rao, M.M.M.; Murty, T.V.R.; Rao, P.R.; Lakshminarayana, S.; Subrahmanyam, A.S.; Murthy, K.S.R.

environs along the central west coast of India: analysis using EOF, J. Geophys.Res.,91(1986) 8523 -8526. 9 Marquardt D W, An algorithm for least-squares estimation of non-linear parameters, J. Soc. Indust. Appl. Math, 11 (1963) 431-441. INDIAN J. MAR... technique in reconstruction of gravity anomalies due to a fault, Indian J. Pure. Appl. Math., 34 (2003) 31-47. 16 Ramana Murty T V, Somayajulu Y K & Murty C S, Reconstruction of sound speed profile through natural generalised inverse technique, Indian J...

LISA Pathfinder E2E performance simulation: optical and self-gravity stability analysis

Science.gov (United States)

Brandt, N.; Fichter, W.; Kersten, M.; Lucarelli, S.; Montemurro, F.

2005-05-01

End-to-end (E2E) modelling and simulation, i.e. verifying the science performance of LISA Pathfinder (spacecraft and payload), is mandatory in order to minimize mission risks. In this paper, focus is on two particular applications of the E2E performance simulator currently being developed at EADS Astrium GmbH: the opto-dynamical stability and the self-gravity disturbance stability analysis. The E2E models applied here comprise the opto-dynamical modelling of the optical metrology systems (OMS) laser interferometry, the thermo-elastic distortion modelling of the OMS optical elements and the self-gravity disturbance model accounting for structural distortions. Preliminary analysis results are presented in detail, identifying shortcomings of the current LISA technology package (LTP) mounting baseline. As a consequence, the design is now being revised.

LISA Pathfinder E2E performance simulation: optical and self-gravity stability analysis

International Nuclear Information System (INIS)

Brandt, N; Fichter, W; Kersten, M; Lucarelli, S; Montemurro, F

2005-01-01

End-to-end (E2E) modelling and simulation, i.e. verifying the science performance of LISA Pathfinder (spacecraft and payload), is mandatory in order to minimize mission risks. In this paper, focus is on two particular applications of the E2E performance simulator currently being developed at EADS Astrium GmbH: the opto-dynamical stability and the self-gravity disturbance stability analysis. The E2E models applied here comprise the opto-dynamical modelling of the optical metrology systems (OMS) laser interferometry, the thermo-elastic distortion modelling of the OMS optical elements and the self-gravity disturbance model accounting for structural distortions. Preliminary analysis results are presented in detail, identifying shortcomings of the current LISA technology package (LTP) mounting baseline. As a consequence, the design is now being revised

Searching for modified gravity with baryon oscillations: From SDSS to wide field multiobject spectroscopy (WFMOS)

International Nuclear Information System (INIS)

Yamamoto, Kazuhiro; Bassett, Bruce A.; Nichol, Robert C.; Suto, Yasushi; Yahata, Kazuhiro

2006-01-01

We discuss how the baryon acoustic oscillation (BAO) signatures in the galaxy power spectrum can distinguish between modified gravity and the cosmological constant as the source of cosmic acceleration. To this end we consider a model characterized by a parameter n, which corresponds to the Dvali-Gabadadze-Porrati (DGP) model if n=2 and reduces to the standard spatially flat cosmological constant concordance model for n equal to infinity. We find that the different expansion histories of the modified gravity models systematically shifts the peak positions of BAO. A preliminary analysis using the current SDSS luminous red galaxy (LRG) sample indicates that the original DGP model is disfavored unless the matter density parameter exceeds 0.3. The constraints will be strongly tightened with future spectroscopic samples of galaxies at high redshifts. We demonstrate that WFMOS, in collaboration with other surveys such as Planck, will powerfully constrain modified gravity alternatives to dark energy as the explanation of cosmic acceleration

On the track of gravity modes: study of the dynamics of the solar core

International Nuclear Information System (INIS)

Mathur, Savita

2007-01-01

This thesis is dedicated to the study of the dynamics of the solar radiative zone through gravity modes. Though the core represents more than 50% of the solar mass, we still do not have an accurate vision of the rotation profile in the very inner part of the Sun. To understand the evolution of stars, we try to put constraints on dynamic processes. Several paths have been followed in this thesis to tackle this issue: solar modeling, the study of a new instrument, observations and inversions of the rotation. The necessity of the detection of gravity modes is driven by the will for a better comprehension of the solar dynamics. With a technological prototype built at the CEA (GOLF-NG), we want to validate a few technical points and prepare the scientific mission which aim will be to detect these gravity modes. We studied first the photodetector and then the whole instrument response. We show the feasibility of the instrument. The observation of the resonance in all the channels proves that it works the way we expected. However, before this mission takes place, the analysis of GOLF data enabled us to detect one gravity-mode candidate as well as the signature of dipole gravity modes. This work benefited from a more theoretical approach on the prediction of gravity-mode frequencies. We show the influence of several physical processes and quantities. Finally, as the dynamical processes in the Sun are not well constrained, we tried to understand the impact of the introduction of one and several gravity modes on the inferred rotation profiles. We also tried to give constraints on the observations so that we could obtain some information on the rotation profile in the core. (author) [fr

Geometric Liouville gravity

International Nuclear Information System (INIS)

La, H.

1992-01-01

A new geometric formulation of Liouville gravity based on the area preserving diffeo-morphism is given and a possible alternative to reinterpret Liouville gravity is suggested, namely, a scalar field coupled to two-dimensional gravity with a curvature constraint

Wenchuan Ms8.0 earthquake coseismic slip distribution inversion

Directory of Open Access Journals (Sweden)

Hongbo Tan

2015-05-01

Full Text Available By using GPS and gravity data before and after the Wenchuan Ms8.0 earthquake and combining data from geological surveys and geophysical inversion studies, an initial coseismic fault model is constructed. The dip angle changes of the fault slip distribution on the fault plane are inversed, and the inversion results show that the shape of the fault resembles a double-shovel. The Yingxiu–Beichuan Fault is approximately 330 km long, the surface fault dip angle is 65.1°, which gradually reduces with increasing depth to 0° at the detachment layer at a depth of 19.62 km. The Guanxian–Jiangyou Fault is approximately 90 km long, and its dip angle at the surface is 55.3°, which gradually reduces with increasing depth; the fault joins the Yingxiu–Beichuan Fault at 13.75 km. Coseismic slip mainly occurs above a depth of 19 km. There are five concentrated rupture areas, Yingxiu, Wenchuan, Hanwang, Beichuan, and Pingwu, which are consistent with geological survey results and analyses of the aftershock distribution. The rupture mainly has a thrust component with a small dextral strike–slip component. The maximum slip was more than 10 m, which occurred near Beichuan and Hanwang. The seismic moment is 7.84 × 1020 Nm (Mw7.9, which is consistent with the seismological results.

Covariant w∞ gravity

NARCIS (Netherlands)

Bergshoeff, E.; Pope, C.N.; Stelle, K.S.

1990-01-01

We discuss the notion of higher-spin covariance in w∞ gravity. We show how a recently proposed covariant w∞ gravity action can be obtained from non-chiral w∞ gravity by making field redefinitions that introduce new gauge-field components with corresponding new gauge transformations.

Preliminary targeting of geothermal resources in Delaware. Progress report, July 15, 1978-July 14, 1979

Energy Technology Data Exchange (ETDEWEB)

Woodruff, K.D.

1979-07-01

Results of temperature logging the five DOE 1000 foot test wells in Delaware indicate that the potential is good for a relatively low temperature geothermal resource (temperatures less than about 80/sup 0/C). A preliminary Bouguer gravity map was made for portions of Kent and Sussex counties in order to detect gravity anomalies possibly related to granitic plutons. The map indicates a gravity low trending northeast-southwest across Sussex County that could be indicative of other structural features within the basement rocks beneath the Coastal Plain. Other logging activities and study of the cores and drill cuttings in the DOE test holes were useful in better defining the stratigraphic framework and in determining the fresh-salt water interface in southern Delaware.

Preliminary assessment of the waveform inversion method for interpretation of cross-well seismic data from the thermal production test, JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well

Energy Technology Data Exchange (ETDEWEB)

Watanabe, T. [Nagoya Univ., Nagoya (Japan). Research Center for Seismology and Volcanology; Shimizu, S. [Japan National Oil Co., Chiba (Japan); Asakawa, E. [JGI Inc., Tokyo (Japan); Kamei, R.; Matsuoka, T. [Kyoto Univ., Kyoto (Japan). Dept. of Civil and Earth Resources Engineering

2005-07-01

The JAPEX/JNOC/GSC et al. Mallik 3L-38 and 4L-38 test wells were subjected to repeated cross-well seismic surveys before and during the gas production test from the gas-hydrate-bearing layer at a depth of about 905 to 920 m. High-resolution velocity images in the gas-hydrate-bearing layer were obtained using the frequency-domain nonlinear waveform inversion method. An acoustic waveform inversion method was used along with the frequency-domain approach in order to detect the change in acoustic properties of the gas-hydrate-bearing layer resulting from gas production. The layered structures with small lateral heterogeneities were reconstructed by tomography analysis of preprocessed waveform data using a smaller number of source-receiver pairs. Preliminary results reveal high velocity and very high attenuation in the gas-hydrate-bearing layers. No obvious velocity decreases were noted. Information for further detailed processing was also gathered.

Analogue Gravity

Directory of Open Access Journals (Sweden)

Carlos Barceló

2011-05-01

Full Text Available Analogue gravity is a research programme which investigates analogues of general relativistic gravitational fields within other physical systems, typically but not exclusively condensed matter systems, with the aim of gaining new insights into their corresponding problems. Analogue models of (and for gravity have a long and distinguished history dating back to the earliest years of general relativity. In this review article we will discuss the history, aims, results, and future prospects for the various analogue models. We start the discussion by presenting a particularly simple example of an analogue model, before exploring the rich history and complex tapestry of models discussed in the literature. The last decade in particular has seen a remarkable and sustained development of analogue gravity ideas, leading to some hundreds of published articles, a workshop, two books, and this review article. Future prospects for the analogue gravity programme also look promising, both on the experimental front (where technology is rapidly advancing and on the theoretical front (where variants of analogue models can be used as a springboard for radical attacks on the problem of quantum gravity.

Quantum Gravity Phenomenology

OpenAIRE

Amelino-Camelia, Giovanni

2003-01-01

Comment: 9 pages, LaTex. These notes were prepared while working on an invited contribution to the November 2003 issue of Physics World, which focused on quantum gravity. They intend to give a non-technical introduction (accessible to readers from outside quantum gravity) to "Quantum Gravity Phenomenology"

Automated borehole gravity meter system

International Nuclear Information System (INIS)

Lautzenhiser, Th.V.; Wirtz, J.D.

1984-01-01

An automated borehole gravity meter system for measuring gravity within a wellbore. The gravity meter includes leveling devices for leveling the borehole gravity meter, displacement devices for applying forces to a gravity sensing device within the gravity meter to bring the gravity sensing device to a predetermined or null position. Electronic sensing and control devices are provided for (i) activating the displacement devices, (ii) sensing the forces applied to the gravity sensing device, (iii) electronically converting the values of the forces into a representation of the gravity at the location in the wellbore, and (iv) outputting such representation. The system further includes electronic control devices with the capability of correcting the representation of gravity for tidal effects, as well as, calculating and outputting the formation bulk density and/or porosity

Solving of L0 norm constrained EEG inverse problem.

Science.gov (United States)

Xu, Peng; Lei, Xu; Hu, Xiao; Yao, Dezhong

2009-01-01

l(0) norm is an effective constraint used to solve EEG inverse problem for a sparse solution. However, due to the discontinuous and un-differentiable properties, it is an open issue to solve the l(0) norm constrained problem, which is usually instead solved by using some alternative functions like l(1) norm to approximate l(0) norm. In this paper, a continuous and differentiable function having the same form as the transfer function of Butterworth low-pass filter is introduced to approximate l(0) norm constraint involved in EEG inverse problem. The new approximation based approach was compared with l(1) norm and LORETA solutions on a realistic head model using simulated sources. The preliminary results show that this alternative approximation to l(0) norm is promising for the estimation of EEG sources with sparse distribution.

Gravity is Geometry.

Science.gov (United States)

MacKeown, P. K.

1984-01-01

Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)

Gravity brake

Science.gov (United States)

Lujan, Richard E.

2001-01-01

A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

The Cause of Gravity

OpenAIRE

Byrne, Michael

1999-01-01

Einstein said that gravity is an acceleration like any other acceleration. But gravity causes relativistic effects at non-relativistic speeds; so gravity could have relativistic origins. And since the strong force is thought to cause most of mass, and mass is proportional to gravity; the strong force is therefore also proportional to gravity. The strong force could thus cause relativistic increases of mass through the creation of virtual gluons; along with a comparable contraction of space ar...

Gravity anomalies of the Northern Hawaiian Islands: Implications on the shield evolutions of Kauai and Niihau

Science.gov (United States)

Flinders, Ashton F.; Ito, Garrett; Garcia, Michael O.

2010-08-01

New land and marine gravity data reveal two positive residual gravity anomalies in the Northern Hawaiian Islands: one over Kaua'i, the other between the islands of Kaua'i and Ni'ihau. These gravitational highs are similar in size and magnitude to those of other Hawaiian volcanoes, indicating local zones of high-density crust, attributed to olivine cumulates in solidified magma reservoirs. The residual gravity high over Kaua'i is located in the Līhu'e Basin, offset 8-12 km east of Kaua'i's geologically mapped caldera. This offset suggests that the mapped caldera is a collapsed feature later filled in with lava and not the long-term center of Kaua'i shield volcanism. A second residual gravity high, in the submarine channel between Kaua'i and Ni'ihau, marks the volcanic center of the Ni'ihau shield volcano. This second residual gravity anomaly implies that Ni'ihau's eastern boundary extended ˜20 km east of its present location. Through inversion, the residual gravity anomalies were modeled as being produced by two solidified magma reservoirs with average densities of 3100 kg/m3 and volumes between 2470 and 2540 km3. Considering the locations and sizes of the residual gravity anomalies/magma reservoirs, the extent of the two islands' paleoshorelines and potassium-argon dating of shield-stage lavas, we conclude that the two islands were not connected subaerially during their respective shield stages and that Ni'ihau's topographic summit was removed by an eastern flank collapse between 4.3 and 5.6 Ma. Continued constructional volcanism on western Kaua'i likely covered much of the submerged remains of eastern Ni'ihau.

From Moon-fall to motions under inverse square laws

International Nuclear Information System (INIS)

Foong, S K

2008-01-01

The motion of two bodies, along a straight line, under the inverse square law of gravity is considered in detail, progressing from simpler cases to more complex ones: (a) one body fixed and one free, (b) both bodies free and identical mass, (c) both bodies free and different masses and (d) the inclusion of electrostatic forces for both bodies free and different masses. The equations of motion (EOM) are derived starting from Newton's second law or from conservation of energy. They are then reduced to dimensionless EOM using appropriate scales for time and distance. Solutions of the dimensionless EOM as well as the original EOM are given. The time interval for the bodies to fall is expressed as a function of the distance fallen. Formulae for the inverse were obtained. The coalescence times for the different cases are (a) π/2√2 √(L 3 /(Gm 1 )) where L is the initial separation of the two bodies and m 1 is the mass of the fixed body, (b) and (c) t=π/2√2 √(L 3 /(Gm T )) where m T is the total mass of the two bodies and (d) t=π/2√2 √(L 3 /[Gm T (1-Λ)]) where Λ=(kq 1 q 2 )/(Gm 1 m 2 ) and is a measure of the ratio of the electrostatic force to gravity. The last formula may also be used when Λ≥1 with the interpretation that there is no collision if t is infinity or imaginary. We also discuss this motion along the straight line as a special case of the general elliptic motion of two bodies. I believe that this paper will be useful to university tutors as well as undergraduate and even graduate students who prefer to consider the special case before the general case, and their relationship

Crustal structure beneath the Paleozoic Parnaíba Basin revealed by airborne gravity and magnetic data, Brazil

Science.gov (United States)

de Castroa, David L.; Fuck, Reinhardt A.; Phillips, Jeffrey D.; Vidotti, Roberta M.; Bezerra, Francisco H. R.; Dantas, Elton L.

2014-01-01

The Parnaíba Basin is a large Paleozoic syneclise in northeastern Brazil underlain by Precambrian crystalline basement, which comprises a complex lithostructural and tectonic framework formed during the Neoproterozoic–Eopaleozoic Brasiliano–Pan African orogenic collage. A sag basin up to 3.5 km thick and 1000 km long formed after the collage. The lithologic composition, structure, and role in the basin evolution of the underlying basement are the focus of this study. Airborne gravity and magnetic data were modeled to reveal the general crustal structure underneath the Parnaíba Basin. Results indicate that gravity and magnetic signatures delineate the main boundaries and structural trends of three cratonic areas and surrounding Neoproterozoic fold belts in the basement. Triangular-shaped basement inliers are geophysically defined in the central region of this continental-scale Neoproterozoic convergence zone. A 3-D gravity inversion constrained by seismological data reveals that basement inliers exhibit a 36–40.5 km deep crustal root, with borders defined by a high-density and thinner crust. Forward modeling of gravity and magnetic data indicates that lateral boundaries between crustal units are limited by Brasiliano shear zones, representing lithospheric sutures of the Amazonian and São Francisco Cratons, Tocantins Province and Parnaíba Block. In addition, coincident residual gravity, residual magnetic, and pseudo-gravity lows indicate two complex systems of Eopaleozoic rifts related to the initial phase of the sag deposition, which follow basement trends in several directions.

Cutoff for extensions of massive gravity and bi-gravity

International Nuclear Information System (INIS)

Matas, Andrew

2016-01-01

Recently there has been interest in extending ghost-free massive gravity, bi-gravity, and multi-gravity by including non-standard kinetic terms and matter couplings. We first review recent proposals for this class of extensions, emphasizing how modifications of the kinetic and potential structure of the graviton and modifications of the coupling to matter are related. We then generalize existing no-go arguments in the metric language to the vielbein language in second-order form. We give an ADM argument to show that the most promising extensions to the kinetic term and matter coupling contain a Boulware–Deser ghost. However, as recently emphasized, we may still be able to view these extensions as effective field theories below some cutoff scale. To address this possibility, we show that there is a decoupling limit where a ghost appears for a wide class of matter couplings and kinetic terms. In particular, we show that there is a decoupling limit where the linear effective vielbein matter coupling contains a ghost. Using the insight we gain from this decoupling limit analysis, we place an upper bound on the cutoff for the linear effective vielbein coupling. This result can be generalized to new kinetic interactions in the vielbein language in second-order form. Combined with recent results, this provides a strong uniqueness argument on the form of ghost-free massive gravity, bi-gravity, and multi-gravity. (paper)

Volcanic source inversion using a genetic algorithm and an elastic-gravitational layered earth model for magmatic intrusions

Science.gov (United States)

Tiampo, K. F.; Fernández, J.; Jentzsch, G.; Charco, M.; Rundle, J. B.

2004-11-01

Here we present an inversion methodology using the combination of a genetic algorithm (GA) inversion program, and an elastic-gravitational earth model to determine the parameters of a volcanic intrusion. Results from the integration of the elastic-gravitational model, a suite of FORTRAN 77 programs developed to compute the displacements due to volcanic loading, with the GA inversion code, written in the C programming language, are presented. These codes allow for the calculation of displacements (horizontal and vertical), tilt, vertical strain and potential and gravity changes on the surface of an elastic-gravitational layered Earth model due to the magmatic intrusion. We detail the appropriate methodology for examining the sensitivity of the model to variation in the constituent parameters using the GA, and present, for the first time, a Monte Carlo technique for evaluating the propagation of error through the GA inversion process. One application example is given at Mayon volcano, Philippines, for the inversion program, the sensitivity analysis, and the error evaluation. The integration of the GA with the complex elastic-gravitational model is a blueprint for an efficient nonlinear inversion methodology and its implementation into an effective tool for the evaluation of parameter sensitivity. Finally, the extension of this inversion algorithm and the error assessment methodology has important implications to the modeling and data assimilation of a number of other nonlinear applications in the field of geosciences.

Preliminary results of sugar maple carbohydrate and growth response under vacuum and gravity sap extraction

Science.gov (United States)

Mark L. Isselhardt; Timothy D. Perkins; Abby K. van den Berg; Paul G. Schaberg

2016-01-01

Recent technological advancements have increased the amount of sugar-enriched sap that can be extracted from sugar maple (Acer saccharum). This pilot study quantified overall sugar removal and the impacts of vacuum (60 cm Hg) and gravity sap extraction on residual nonstructural carbohydrate (NSC) concentrations and on stem and twig growth. Vacuum...

Gravity, Magnetism, and "Down": Non-Physics College Students' Conceptions of Gravity

Science.gov (United States)

Asghar, Anila; Libarkin, Julie C.

2010-01-01

This study investigates how students enrolled in entry-level geology, most of whom would graduate from college without university-level physics courses, thought about and applied the concept of gravity while solving problems concerning gravity. The repercussions of students' gravity concepts are then considered in the context of non-physics…

Gsolve, a Python computer program with a graphical user interface to transform relative gravity survey measurements to absolute gravity values and gravity anomalies

Science.gov (United States)

McCubbine, Jack; Tontini, Fabio Caratori; Stagpoole, Vaughan; Smith, Euan; O'Brien, Grant

2018-01-01

A Python program (Gsolve) with a graphical user interface has been developed to assist with routine data processing of relative gravity measurements. Gsolve calculates the gravity at each measurement site of a relative gravity survey, which is referenced to at least one known gravity value. The tidal effects of the sun and moon, gravimeter drift and tares in the data are all accounted for during the processing of the survey measurements. The calculation is based on a least squares formulation where the difference between the absolute gravity at each surveyed location and parameters relating to the dynamics of the gravimeter are minimized with respect to the relative gravity observations, and some supplied gravity reference site values. The program additionally allows the user to compute free air gravity anomalies, with respect to the GRS80 and GRS67 reference ellipsoids, from the determined gravity values and calculate terrain corrections at each of the surveyed sites using a prism formula and a user supplied digital elevation model. This paper reviews the mathematical framework used to reduce relative gravimeter survey observations to gravity values. It then goes on to detail how the processing steps can be implemented using the software.

Simultaneous measurement of gravity acceleration and gravity gradient with an atom interferometer

International Nuclear Information System (INIS)

Sorrentino, F.; Lien, Y.-H.; Rosi, G.; Tino, G. M.; Bertoldi, A.; Bodart, Q.; Cacciapuoti, L.; Angelis, M. de; Prevedelli, M.

2012-01-01

We demonstrate a method to measure the gravitational acceleration with a dual cloud atom interferometer; the use of simultaneous atom interferometers reduces the effect of seismic noise on the gravity measurement. At the same time, the apparatus is capable of accurate measurements of the vertical gravity gradient. The ability to determine the gravity acceleration and gravity gradient simultaneously and with the same instrument opens interesting perspectives in geophysical applications.

Airborne Gravity: NGS' Gravity Data for EN08 (2013)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Vermont, New Hampshire, Massachusettes, Maine, and Canada collected in 2013 over 1 survey. This data set is part of the Gravity...

A Stochastic Inversion Method for Potential Field Data: Ant Colony Optimization

Science.gov (United States)

Liu, Shuang; Hu, Xiangyun; Liu, Tianyou

2014-07-01

Simulating natural ants' foraging behavior, the ant colony optimization (ACO) algorithm performs excellently in combinational optimization problems, for example the traveling salesman problem and the quadratic assignment problem. However, the ACO is seldom used to inverted for gravitational and magnetic data. On the basis of the continuous and multi-dimensional objective function for potential field data optimization inversion, we present the node partition strategy ACO (NP-ACO) algorithm for inversion of model variables of fixed shape and recovery of physical property distributions of complicated shape models. We divide the continuous variables into discrete nodes and ants directionally tour the nodes by use of transition probabilities. We update the pheromone trails by use of Gaussian mapping between the objective function value and the quantity of pheromone. It can analyze the search results in real time and promote the rate of convergence and precision of inversion. Traditional mapping, including the ant-cycle system, weaken the differences between ant individuals and lead to premature convergence. We tested our method by use of synthetic data and real data from scenarios involving gravity and magnetic anomalies. The inverted model variables and recovered physical property distributions were in good agreement with the true values. The ACO algorithm for binary representation imaging and full imaging can recover sharper physical property distributions than traditional linear inversion methods. The ACO has good optimization capability and some excellent characteristics, for example robustness, parallel implementation, and portability, compared with other stochastic metaheuristics.

The earth's shape and gravity

CERN Document Server

Garland, G D; Wilson, J T

2013-01-01

The Earth's Shape and Gravity focuses on the progress of the use of geophysical methods in investigating the interior of the earth and its shape. The publication first offers information on gravity, geophysics, geodesy, and geology and gravity measurements. Discussions focus on gravity measurements and reductions, potential and equipotential surfaces, absolute and relative measurements, and gravity networks. The text then elaborates on the shape of the sea-level surface and reduction of gravity observations. The text takes a look at gravity anomalies and structures in the earth's crust; interp

Airborne Gravity: NGS' Gravity Data for AN08 (2016)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2016 over one survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...

Artificial gravity - The evolution of variable gravity research

Science.gov (United States)

Fuller, Charles A.; Sulzman, Frank M.; Keefe, J. Richard

1987-01-01

The development of a space life science research program based on the use of rotational facilities is described. In-flight and ground centrifuges can be used as artificial gravity environments to study the following: nongravitational biological factors; the effects of 0, 1, and hyper G on man; counter measures for deconditioning astronauts in weightlessness; and the development of suitable artificial gravity for long-term residence in space. The use of inertial fields as a substitute for gravity, and the relations between the radius of the centrifuge and rotation rate and specimen height and rotation radius are examined. An example of a centrifuge study involving squirrel monkeys is presented.

Enhancement of subsurface geologic structure model based on gravity, magnetotelluric, and well log data in Kamojang geothermal field

Science.gov (United States)

Yustin Kamah, Muhammad; Armando, Adilla; Larasati Rahmani, Dinda; Paramitha, Shabrina

2017-12-01

Geophysical methods such as gravity and magnetotelluric methods commonly used in conventional and unconventional energy exploration, notably for exploring geothermal prospect. They used to identify the subsurface geology structures which is estimated as a path of fluid flow. This study was conducted in Kamojang Geothermal Field with the aim of highlighting the volcanic lineament in West Java, precisely in Guntur-Papandayan chain where there are three geothermal systems. Kendang Fault has predominant direction NE-SW, identified by magnetotelluric techniques and gravity data processing techniques. Gravity techniques such as spectral analysis, derivative solutions, and Euler deconvolution indicate the type and geometry of anomaly. Magnetotelluric techniques such as inverse modeling and polar diagram are required to know subsurface resistivity charactersitics and major orientation. Furthermore, the result from those methods will be compared to geology information and some section of well data, which is sufficiently suitable. This research is very useful to trace out another potential development area.

Airborne Gravity: NGS' Gravity Data for AS01 (2008)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2008 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for CS04 (2009)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas collected in 2009 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for AN05 (2011)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for TS01 (2014)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Puerto Rico and the Virgin Islands collected in 2009 over 1 survey. This data set is part of the Gravity for the Re-definition of the...

Airborne Gravity: NGS' Gravity Data for AN06 (2011)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for AS02 (2010)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for EN01 (2011)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Canada, and Lake Ontario collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the...

Airborne Gravity: NGS' Gravity Data for AN03 (2010)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 and 2012 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...

Airborne Gravity: NGS' Gravity Data for AN04 (2010)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for CS05 (2014)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas collected in 2014 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for EN06 (2016)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Maine, Canada, and the Atlantic Ocean collected in 2012 over 2 surveys. This data set is part of the Gravity for the Re-definition of the...

Airborne Gravity: NGS' Gravity Data for AN02 (2010)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for ES01 (2013)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Florida, the Bahamas, and the Atlantic Ocean collected in 2013 over 1 survey. This data set is part of the Gravity for the Re-definition of...

Analogue Gravity

Directory of Open Access Journals (Sweden)

Barceló Carlos

2005-12-01

Full Text Available Analogue models of (and for gravity have a long and distinguished history dating back to the earliest years of general relativity. In this review article we will discuss the history, aims, results, and future prospects for the various analogue models. We start the discussion by presenting a particularly simple example of an analogue model, before exploring the rich history and complex tapestry of models discussed in the literature. The last decade in particular has seen a remarkable and sustained development of analogue gravity ideas, leading to some hundreds of published articles, a workshop, two books, and this review article. Future prospects for the analogue gravity programme also look promising, both on the experimental front (where technology is rapidly advancing and on the theoretical front (where variants of analogue models can be used as a springboard for radical attacks on the problem of quantum gravity.

NGS Absolute Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NGS Absolute Gravity data (78 stations) was received in July 1993. Principal gravity parameters include Gravity Value, Uncertainty, and Vertical Gradient. The...

Airborne Gravity: NGS' Gravity Data for CS08 (2015)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for CS08 collected in 2006 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

Airborne Gravity: NGS' Gravity Data for ES02 (2013)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Florida and the Gulf of Mexico collected in 2013 over 1 survey. This data set is part of the Gravity for the Re-definition of the American...

Classical Weyl transverse gravity

Energy Technology Data Exchange (ETDEWEB)

Oda, Ichiro [University of the Ryukyus, Department of Physics, Faculty of Science, Nishihara, Okinawa (Japan)

2017-05-15

We study various classical aspects of the Weyl transverse (WTDiff) gravity in a general space-time dimension. First of all, we clarify a classical equivalence among three kinds of gravitational theories, those are, the conformally invariant scalar tensor gravity, Einstein's general relativity and the WTDiff gravity via the gauge-fixing procedure. Secondly, we show that in the WTDiff gravity the cosmological constant is a mere integration constant as in unimodular gravity, but it does not receive any radiative corrections unlike the unimodular gravity. A key point in this proof is to construct a covariantly conserved energy-momentum tensor, which is achieved on the basis of this equivalence relation. Thirdly, we demonstrate that the Noether current for the Weyl transformation is identically vanishing, thereby implying that the Weyl symmetry existing in both the conformally invariant scalar tensor gravity and the WTDiff gravity is a ''fake'' symmetry. We find it possible to extend this proof to all matter fields, i.e. the Weyl-invariant scalar, vector and spinor fields. Fourthly, it is explicitly shown that in the WTDiff gravity the Schwarzschild black hole metric and a charged black hole one are classical solutions to the equations of motion only when they are expressed in the Cartesian coordinate system. Finally, we consider the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology and provide some exact solutions. (orig.)

Southern Africa Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This data base (14,559 records) was received in January 1986. Principal gravity parameters include elevation and observed gravity. The observed gravity values are...

Einstein gravity emerging from quantum weyl gravity

International Nuclear Information System (INIS)

Zee, A.

1983-01-01

We advocate a conformal invariant world described by the sum of the Weyl, Dirac, and Yang-Mills action. Quantum fluctuations bring back Einstein gravity so that the long-distance phenomenology is as observed. Formulas for the induced Newton's constant and Eddington's constant are derived in quantized Weyl gravity. We show that the analogue of the trace anomaly for the Weyl action is structurally similar to that for the Yang-Mills action

influence of gravity

Directory of Open Access Journals (Sweden)

Animesh Mukherjee

1991-01-01

Full Text Available Based upon Biot's [1965] theory of initial stresses of hydrostatic nature produced by the effect of gravity, a study is made of surface waves in higher order visco-elastic media under the influence of gravity. The equation for the wave velocity of Stonely waves in the presence of viscous and gravitational effects is obtained. This is followed by particular cases of surface waves including Rayleigh waves and Love waves in the presence of viscous and gravity effects. In all cases the wave-velocity equations are found to be in perfect agreement with the corresponding classical results when the effects of gravity and viscosity are neglected.

Small-sized test of gravity separation and preliminary assessment of technology and economics in Guangshigou granite pegmatite type uranium deposit

Energy Technology Data Exchange (ETDEWEB)

Zhifu, Sun; Mingyue, Feng; Jiashu, Rong; Ziyang, Xu [Beijing Research Inst. of Uranium Geology (China)

1994-11-01

The small-sized test of gravity separation in Guangshigou granite pegmatite type uranium deposit has found a new avenue for the industrial utilization of ores from such uranium deposit, especially those low grade ones. The test has proved that the gravity separation is superior to hydrometallurgy in the aspect of uranium recovery from ores of the granite pegmatite type uranium deposit, by-product recovery and protection against environmental pollution.

Small-sized test of gravity separation and preliminary assessment of technology and economics in Guangshigou granite pegmatite type uranium deposit

International Nuclear Information System (INIS)

Sun Zhifu; Feng Mingyue; Rong Jiashu; Xu Ziyang

1994-01-01

The small-sized test of gravity separation in Guangshigou granite pegmatite type uranium deposit has found a new avenue for the industrial utilization of ores from such uranium deposit, especially those low grade ones. The test has proved that the gravity separation is superior to hydrometallurgy in the aspect of uranium recovery from ores of the granite pegmatite type uranium deposit, by-product recovery and protection against environmental pollution

Radio-Frequency Illuminated Superconductive Disks: Reverse Josephson Effects and Implications for Precise Measuring of Proposed Gravity Effects

Science.gov (United States)

Noever, David A.; Koczor, Ronald J.

1998-01-01

We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. It have been indicated three essential components to achieve anomalous gravity effects, namely large, two-layer high-temperature YBCO superconductors, magnetic levitation and AC input in the form of radio-frequency (RF) electromagnetic fields. We report experiments on RF-illuminated (1-15 MHz) superconducting disks with corresponding gravity readings indicating an apparent increase in observed gravity of approximately 3-5 x l0(exp -5)cm/sq s, above and to the side of the superconductor. In this preliminary study, RF- illumination is achieved using a series of large radius (15 cm) spiral antenna with RF power inputs equal to or greater than 90 W. The observed gravitational modification range is significantly lower than the 2.1% gravity modification. The error analyses of thermal and electromagnetic interference in a magnetically shielded gravimeter with vacuum enclosures, Faraday cages and shielded instrument leads, are outlined both experimentally and theoretically. The nearly exact correspondence between the peak gravity effects reported and the well-known peak in AC resistance in superconductors (2-7 MHz, owing to reverse Josephson quantum effects) suggests that electrical resistance will arise in this frequency range and subsequently any trapped magnetic fields in the superconductor may disperse partially into the measuring instrument's local environment. Implications for propulsion initiatives and RF-heating in superconductors will be discussed.

Comparing scalar-tensor gravity and f(R)-gravity in the Newtonian limit

International Nuclear Information System (INIS)

Capozziello, S.; Stabile, A.; Troisi, A.

2010-01-01

Recently, a strong debate has been pursued about the Newtonian limit (i.e. small velocity and weak field) of fourth order gravity models. According to some authors, the Newtonian limit of f(R)-gravity is equivalent to the one of Brans-Dicke gravity with ω BD =0, so that the PPN parameters of these models turn out to be ill-defined. In this Letter, we carefully discuss this point considering that fourth order gravity models are dynamically equivalent to the O'Hanlon Lagrangian. This is a special case of scalar-tensor gravity characterized only by self-interaction potential and that, in the Newtonian limit, this implies a non-standard behavior that cannot be compared with the usual PPN limit of General Relativity. The result turns out to be completely different from the one of Brans-Dicke theory and in particular suggests that it is misleading to consider the PPN parameters of this theory with ω BD =0 in order to characterize the homologous quantities of f(R)-gravity. Finally the solutions at Newtonian level, obtained in the Jordan frame for an f(R)-gravity, reinterpreted as a scalar-tensor theory, are linked to those in the Einstein frame.

Inversion of GPS meteorology data

Directory of Open Access Journals (Sweden)

K. Hocke

Full Text Available The GPS meteorology (GPS/MET experiment, led by the Universities Corporation for Atmospheric Research (UCAR, consists of a GPS receiver aboard a low earth orbit (LEO satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by radio waves which propagate from the GPS satellite to the LEO satellite. From the observed phase path increases, which are due to refraction of the radio waves by the ionosphere and the neutral atmosphere, the atmospheric parameter refractivity, density, pressure and temperature are calculated with high accuracy and resolution (0.5–1.5 km. In the present study, practical aspects of the GPS/MET data analysis are discussed. The retrieval is based on the Abelian integral inversion of the atmospheric bending angle profile into the refractivity index profile. The problem of the upper boundary condition of the Abelian integral is described by examples. The statistical optimization approach which is applied to the data above 40 km and the use of topside bending angle profiles from model atmospheres stabilize the inversion. The retrieved temperature profiles are compared with corresponding profiles which have already been calculated by scientists of UCAR and Jet Propulsion Laboratory (JPL, using Abelian integral inversion too. The comparison shows that in some cases large differences occur (5 K and more. This is probably due to different treatment of the upper boundary condition, data runaways and noise. Several temperature profiles with wavelike structures at tropospheric and stratospheric heights are shown. While the periodic structures at upper stratospheric heights could be caused by residual errors of the ionospheric correction method, the periodic temperature fluctuations at heights below 30 km are most likely caused by atmospheric waves (vertically

Using aerogravity and seismic data to model the bathymetry and upper crustal structure beneath the Pine Island Glacier ice shelf, West Antarctica

Science.gov (United States)

Muto, A.; Peters, L. E.; Anandakrishnan, S.; Alley, R. B.; Riverman, K. L.

2013-12-01

Recent estimates indicate that ice shelves along the Amundsen Sea coast in West Antarctica are losing substantial mass through sub-ice-shelf melting and contributing to the accelerating mass loss of the grounded ice buttressed by them. For Pine Island Glacier (PIG), relatively warm Circumpolar Deep Water has been identified as the key driver of the sub-ice-shelf melting although poor constraints on PIG sub-ice shelf have restricted thorough understanding of these ice-ocean interactions. Aerogravity data from NASA's Operation IceBridge (OIB) have been useful in identifying large-scale (on the order of ten kilometers) features but the results have relatively large uncertainties due to the inherent non-uniqueness of the gravity inversion. Seismic methods offer the most direct means of providing water thickness and upper crustal geological constraints, but availability of such data sets over the PIG ice shelf has been limited due to logistical constraints. Here we present a comparative analysis of the bathymetry and upper crustal structure beneath the ice shelf of PIG through joint inversion of OIB aerogravity data and in situ active-source seismic measurements collected in the 2012-13 austral summer. Preliminary results indicate improved resolution of the ocean cavity, particularly in the interior and sides of the PIG ice shelf, and sedimentary drape across the region. Seismically derived variations in ice and ocean water densities are also applied to the gravity inversion to produce a more robust model of PIG sub-ice shelf structure, as opposed to commonly used single ice and water densities across the entire study region. Misfits between the seismically-constrained gravity inversion and that estimated previously from aerogravity alone provide insights on the sensitivity of gravity measurements to model perturbations and highlight the limitations of employing gravity data to model ice shelf environments when no other sub-ice constraints are available.

The potential of ground gravity measurements to validate GRACE data

Directory of Open Access Journals (Sweden)

D. Crossley

2003-01-01

Full Text Available New satellite missions are returning high precision, time-varying, satellite measurements of the Earth’s gravity field. The GRACE mission is now in its calibration/- validation phase and first results of the gravity field solutions are imminent. We consider here the possibility of external validation using data from the superconducting gravimeters in the European sub-array of the Global Geodynamics Project (GGP as ‘ground truth’ for comparison with GRACE. This is a pilot study in which we use 14 months of 1-hour data from the beginning of GGP (1 July 1997 to 30 August 1998, when the Potsdam instrument was relocated to South Africa. There are 7 stations clustered in west central Europe, and one station, Metsahovi in Finland. We remove local tides, polar motion, local and global air pressure, and instrument drift and then decimate to 6-hour samples. We see large variations in the time series of 5–10µgal between even some neighboring stations, but there are also common features that correlate well over the 427-day period. The 8 stations are used to interpolate a minimum curvature (gridded surface that extends over the geographical region. This surface shows time and spatial coherency at the level of 2– 4µgal over the first half of the data and 1–2µgal over the latter half. The mean value of the surface clearly shows a rise in European gravity of about 3µgal over the first 150 days and a fairly constant value for the rest of the data. The accuracy of this mean is estimated at 1µgal, which compares favorably with GRACE predictions for wavelengths of 500 km or less. Preliminary studies of hydrology loading over Western Europe shows the difficulty of correlating the local hydrology, which can be highly variable, with large-scale gravity variations.Key words. GRACE, satellite gravity, superconducting gravimeter, GGP, ground truth

Gravity Data Analysis and Modelling for Basin Sedimen of Eastern Java Blocks

International Nuclear Information System (INIS)

Khoirunnia, Luthfia

2016-01-01

The study of Eastern Java Basin was conducted by 3D modelling subsurface structure using gravity anomaly. The aims of this research are to describe and 3D modelling basin sedimentary system of Eastern Java Blocks based on gravity anomaly. The modelling construction was performed by inversion technique applying Singular Value Decomposition (SVD) method and Occam optimization. This projection method used equivalent central mass of Dampney with height 5.5 km and error data 1,84 × 10 -17 . Separation of residual anomaly from the complete Bouguer anomaly on a flat plane was done using the upward continuation. This process uses the principle of low pass filter which passes low frequency. Sedimentary basin appears at a depth of 0.2 km to 1.4 km, is shown by their low anomaly in the area, as well as the visible appearance of basin in 3D modeling shown in figure. The result of inversion with Occam h has an error of 1,2% and the SVD has an error of 11%. Sedimentary basin was dominant in Probolinggo, partially in Besuki and Lumajang. The formation occurs due to tectonic processes where the tectonic evolution of the material without significant lateral shift is called as the otokton models, and accompanied by the formation of the basin that follows the development of the subduction system, which is semi-concentric pattern. Sediments are dominated by volcanic sediment, the result of sedimentation because of volcanism events and types of volcanic sediments pyroclasts generally occur in a process or event explosive volcanic magma degassing (paper)

Inverse photoemission

International Nuclear Information System (INIS)

Namatame, Hirofumi; Taniguchi, Masaki

1994-01-01

Photoelectron spectroscopy is regarded as the most powerful means since it can measure almost perfectly the occupied electron state. On the other hand, inverse photoelectron spectroscopy is the technique for measuring unoccupied electron state by using the inverse process of photoelectron spectroscopy, and in principle, the similar experiment to photoelectron spectroscopy becomes feasible. The development of the experimental technology for inverse photoelectron spectroscopy has been carried out energetically by many research groups so far. At present, the heightening of resolution of inverse photoelectron spectroscopy, the development of inverse photoelectron spectroscope in which light energy is variable and so on are carried out. But the inverse photoelectron spectroscope for vacuum ultraviolet region is not on the market. In this report, the principle of inverse photoelectron spectroscopy and the present state of the spectroscope are described, and the direction of the development hereafter is groped. As the experimental equipment, electron guns, light detectors and so on are explained. As the examples of the experiment, the inverse photoelectron spectroscopy of semimagnetic semiconductors and resonance inverse photoelectron spectroscopy are reported. (K.I.)

Stellar pulsations in beyond Horndeski gravity theories

Science.gov (United States)

Sakstein, Jeremy; Kenna-Allison, Michael; Koyama, Kazuya

2017-03-01

Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

Gravity distribution characteristics and their relationship with the distribution of earthquakes and tectonic units in the North–South seismic belt, China

Directory of Open Access Journals (Sweden)

Guiju Wu

2015-05-01

Full Text Available The North–South Seismic Belt (NSSB is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relationship with the distribution of earthquakes and faults in the study area, we first analyze the spatial gravity anomaly to achieve the Bouguer gravity anomaly (EGM2008 BGA and the regional gravity survey Bouguer gravity anomaly. Next, we ascertain the Moho depth and crustal thickness of the study area using interface inversion with the control points derived from the seismic and magnetotelluric sounding profiles achieved in recent years. In this paper, we summarize the relief, trend, Moho gradient, and crustal nature, in addition to their relationship with the distribution of earthquakes and faults in the study area. The findings show that earthquakes with magnitudes greater than Ms7.0 are mainly distributed in the Moho Bouguer anomaly variation belt and faults. The results of the study are important for future research on tectonic characteristics, geological and geophysical surveys, and seismicity patterns.

Is Gravity an Entropic Force?

Directory of Open Access Journals (Sweden)

Shan Gao

2011-04-01

Full Text Available The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde’s example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde’s argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.

Preliminary isostatic residual gravity anomaly map of Paso Robles 30 x 60 minute quadrangle, California

Science.gov (United States)

McPhee, D.K.; Langenheim, V.E.; Watt, J.T.

2011-01-01

This isostatic residual gravity map is part of an effort to map the three-dimensional distribution of rocks in the central California Coast Ranges and will serve as a basis for modeling the shape of basins and for determining the location and geometry of faults within the Paso Robles quadrangle. Local spatial variations in the Earth\\'s gravity field, after accounting for variations caused by elevation, terrain, and deep crustal structure reflect the distribution of densities in the mid- to upper crust. Densities often can be related to rock type, and abrupt spatial changes in density commonly mark lithological or structural boundaries. High-density rocks exposed within the central Coast Ranges include Mesozoic granitic rocks (exposed northwest of Paso Robles), Jurassic to Cretaceous marine strata of the Great Valley Sequence (exposed primarily northeast of the San Andreas fault), and Mesozoic sedimentary and volcanic rocks of the Franciscan Complex [exposed in the Santa Lucia Range and northeast of the San Andreas fault (SAF) near Parkfield, California]. Alluvial sediments and Tertiary sedimentary rocks are characterized by low densities; however, with increasing depth of burial and age, the densities of these rocks may become indistinguishable from those of older basement rocks.

Strings and quantum gravity

International Nuclear Information System (INIS)

Vega, H.J. de

1990-01-01

One of the main challenges in theoretical physics today is the unification of all interactions including gravity. At present, string theories appear as the most promising candidates to achieve such a unification. However, gravity has not completely been incorporated in string theory, many technical and conceptual problems remain and a full quantum theory of gravity is still non-existent. Our aim is to properly understand strings in the context of quantum gravity. Attempts towards this are reviewed. (author)

Gravity interpretation via EULDPH

International Nuclear Information System (INIS)

Ebrahimzadeh Ardestani, V.

2003-01-01

Euler's homogeneity equation for determining the coordinates of the source body especially to estimate the depth (EULDPH) is discussed at this paper. This method is applied to synthetic and high-resolution real data such as gradiometric or microgravity data. Low-quality gravity data especially in the areas with a complex geology structure has rarely been used. The Bouguer gravity anomalies are computed from absolute gravity data after the required corrections. Bouguer anomaly is transferred to residual gravity anomaly. The gravity gradients are estimated from residual anomaly values. Bouguer anomaly is the gravity gradients, using EULDPH. The coordinates of the perturbing body will be determined. Two field examples one in the east of Tehran (Mard Abad) where we would like to determine the location of the anomaly (hydrocarbon) and another in the south-east of Iran close to the border with Afghanistan (Nosrat Abad) where we are exploring chromite are presented

Preliminary isostatic residual gravity map of the Tremonton 30' x 60' quadrangle, Box Elder and Cache Counties, Utah, and Franklin and Oneida Counties, Idaho

Science.gov (United States)

Langenheim, Victoria; Oaks, R.Q.; Willis, H.; Hiscock, A.I.; Chuchel, Bruce A.; Rosario, Jose J.; Hardwick, C.L.

2014-01-01

A new isostatic residual gravity map of the Tremonton 30' x 60' quadrangle of Utah is based on compilation of preexisting data and new data collected by the Utah and U.S. Geological Surveys. Pronounced gravity lows occur over North Bay, northwest of Brigham City, and Malad and Blue Creek Valleys, indicating significant thickness of low-density Tertiary sedimentary rocks and deposits. Gravity highs coincide with exposures of dense pre-Cenozoic rocks in the Promontory, Clarkston, and Wellsville Mountains. The highest gravity values are located in southern Curlew Valley and may be produced in part by deeper crustal density variations or crustal thinning. Steep, linear gravity gradients coincide with Quaternary faults bounding the Wellsville and Clarkston Mountains. Steep gradients also coincide with the margins of the Promontory Mountains, Little Mountain, West Hills, and the eastern margin of the North Promontory Mountains and may define concealed basin-bounding faults.

Anomalies and gravity

International Nuclear Information System (INIS)

Mielke, Eckehard W.

2006-01-01

Anomalies in Yang-Mills type gauge theories of gravity are reviewed. Particular attention is paid to the relation between the Dirac spin, the axial current j5 and the non-covariant gauge spin C. Using diagrammatic techniques, we show that only generalizations of the U(1)- Pontrjagin four-form F and F = dC arise in the chiral anomaly, even when coupled to gravity. Implications for Ashtekar's canonical approach to quantum gravity are discussed

Preliminary appraisal of gravity and magnetic data at Syncline Ridge, Western Yucca Flat, Nevada Test Site, Nye County, Nevada

International Nuclear Information System (INIS)

Ponce, D.A.; Hanna, W.F.

1982-01-01

A gravity and magnetic study of the Syncline Ridge area was conducted as part of an investigation of argillite rocks of the Eleana Formation under consideration as a medium for the possible storage of high-level radioactive waste. Bouguer gravity anomaly, low-level aeromagnetic anomaly, density, and magnetization data collectively indicate the following, relative to the Eleana Formation, the principal target of the investigation: (1) in an area extending northwestward from Mine Mountain, through Syncline Ridge, to the Eleana Range, the Eleana Formation, where not exposed, occurs at depths of less than approx. 200 m, except for a small region of exposed older Paleozoic rocks; (2) in the region of shallowly buried Eleana Formation, occurrences of volcanic rock cover are delineated by low-level aeromagnetic anomaly data, which also discriminate normally polarized from reversely polarized tuff units; and (3) selective detection of high-quartz argillite relative to low-quartz argillite using surface gravity data is not feasible if the high-quartz and low-quartz varieties are intimately interbedded, as observed in boreholes. 4 figures, 2 tables

Airborne Gravity: NGS' Gravity Data for CN02 (2013 & 2014)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Nebraska collected in 2013 & 2014 over 3 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical...

Gravity loop corrections to the standard model Higgs in Einstein gravity

International Nuclear Information System (INIS)

Yugo Abe; Masaatsu Horikoshi; Takeo Inami

2016-01-01

We study one-loop quantum gravity corrections to the standard model Higgs potential V(φ) à la Coleman-Weinberg and examine the stability question of V(φ) in the energy region of Planck mass scale, μ ≃ M_P_l (M_P_l = 1.22x10"1"9 GeV). We calculate the gravity one-loop corrections to V(φ) in Einstein gravity by using the momentum cut-off Λ. We have found that even small gravity corrections compete with the standard model term of V(φ) and affect the stability argument of the latter part alone. This is because the latter part is nearly zero in the energy region of M_P_l. (author)

Data reduction and tying in regional gravity surveys—results from a new gravity base station network and the Bouguer gravity anomaly map for northeastern Mexico

Science.gov (United States)

Hurtado-Cardador, Manuel; Urrutia-Fucugauchi, Jaime

2006-12-01

Since 1947 Petroleos Mexicanos (Pemex) has conducted oil exploration projects using potential field methods. Geophysical exploration companies under contracts with Pemex carried out gravity anomaly surveys that were referred to different floating data. Each survey comprises observations of gravity stations along highways, roads and trails at intervals of about 500 m. At present, 265 separate gravimeter surveys that cover 60% of the Mexican territory (mainly in the oil producing regions of Mexico) are available. This gravity database represents the largest, highest spatial resolution information, and consequently has been used in the geophysical data compilations for the Mexico and North America gravity anomaly maps. Regional integration of gravimeter surveys generates gradients and spurious anomalies in the Bouguer anomaly maps at the boundaries of the connected surveys due to the different gravity base stations utilized. The main objective of this study is to refer all gravimeter surveys from Pemex to a single new first-order gravity base station network, in order to eliminate problems of gradients and spurious anomalies. A second objective is to establish a network of permanent gravity base stations (BGP), referred to a single base from the World Gravity System. Four regional loops of BGP covering eight States of Mexico were established to support the tie of local gravity base stations from each of the gravimeter surveys located in the vicinity of these loops. The third objective is to add the gravity constants, measured and calculated, for each of the 265 gravimeter surveys to their corresponding files in the Pemex and Instituto Mexicano del Petroleo database. The gravity base used as the common datum is the station SILAG 9135-49 (Latin American System of Gravity) located in the National Observatory of Tacubaya in Mexico City. We present the results of the installation of a new gravity base network in northeastern Mexico, reference of the 43 gravimeter surveys

High-heat geodynamic setting during the Palaeozoic evolution of the Mount Painter Province, SA, Australia: evidence from combined field structural geology and potential-field inversions

Science.gov (United States)

Armit, R. J.; Ailleres, L.; Betts, P. G.; Schaefer, B. F.; Blaikie, T. N.

2014-10-01

A method for subsurface recognition of blind geological bodies is presented using combined surface constraints and 3-D structural modelling that incorporates constraints from detailed mapping, and potential-field inversion modelling. This method is applied to the Mount Painter Province and demonstrates that addition of low density material is required to reconcile the gravity signature of the region. This method may be an effective way to construct 3-D models in regions of excellent structural control, and can be used to assess the validity of surface structures with 3-D architecture. Combined geological and potential-field constrained inversion modelling of the Mount Painter Province was conducted to assess the validity of the geological models of the region. Magnetic susceptibility constrained stochastic property inversions indicates that the northeast to southwest structural trend of the relatively magnetic meta-sedimentary rocks of the Radium Creek Group in the Mount Painter Inlier is reconcilable with the similar, northeast to southwest trending positive magnetic anomalies in the region. Radium Creek Group packages are the major contributor of the total magnetic response of the region. However field mapping and the results of initial density constrained stochastic property inversion modelling do not correlate with a large residual negative gravity anomaly central to the region. Further density constrained inversion modelling indicates that an additional large body of relatively low density material is needed within the model space to account for this negative density anomaly. Through sensitivity analysis of multiple geometrical and varied potential-field property inversions, the best-fitting model records a reduction in gravity rms misfit from 21.9 to 1.69 mGal, representing a reduction from 56 to 4.5 per cent in respect to the total dynamic range of 37.5 mGal of the residual anomaly. This best-fitting model incorporates a volumetrically significant source

Airborne Gravity: NGS' Gravity Data for CS02 (2008-2009)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Louisana and Mississippi collected in 2008-2009 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American...

Quantum gravity from noncommutative spacetime

Energy Technology Data Exchange (ETDEWEB)

Lee, Jungjai [Daejin University, Pocheon (Korea, Republic of); Yang, Hyunseok [Korea Institute for Advanced Study, Seoul (Korea, Republic of)

2014-12-15

We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative *-algebra) of quantum gravity.

Quantum gravity from noncommutative spacetime

International Nuclear Information System (INIS)

Lee, Jungjai; Yang, Hyunseok

2014-01-01

We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative *-algebra) of quantum gravity.

The gravity field and GGOS

DEFF Research Database (Denmark)

Forsberg, René; Sideris, M.G.; Shum, C.K.

2005-01-01

The gravity field of the earth is a natural element of the Global Geodetic Observing System (GGOS). Gravity field quantities are like spatial geodetic observations of potential very high accuracy, with measurements, currently at part-per-billion (ppb) accuracy, but gravity field quantities are also...... unique as they can be globally represented by harmonic functions (long-wavelength geopotential model primarily from satellite gravity field missions), or based on point sampling (airborne and in situ absolute and superconducting gravimetry). From a GGOS global perspective, one of the main challenges...... is to ensure the consistency of the global and regional geopotential and geoid models, and the temporal changes of the gravity field at large spatial scales. The International Gravity Field Service, an umbrella "level-2" IAG service (incorporating the International Gravity Bureau, International Geoid Service...

Airborne Gravity: NGS' Gravity Data for EN07 (2012-2013)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Maine and Canada collected in 2012 and 2013 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American...

Airborne Gravity: NGS' Gravity Data for AS03 (2010-2012)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 and 2012 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...

Gravity wave astronomy

International Nuclear Information System (INIS)

Pinheiro, R.

1979-01-01

The properties and production of gravitational radiation are described. The prospects for their detection are considered including the Weber apparatus and gravity-wave telescopes. Possibilities of gravity-wave astronomy are noted

Cineradiographic Analysis of Mouse Postural Response to Alteration of Gravity and Jerk (Gravity Deceleration Rate

Directory of Open Access Journals (Sweden)

Katsuya Hasegawa

2014-04-01

Full Text Available The ability to maintain the body relative to the external environment is important for adaptation to altered gravity. However, the physiological limits for adaptation or the disruption of body orientation are not known. In this study, we analyzed postural changes in mice upon exposure to various low gravities. Male C57BL6/J mice (n = 6 were exposed to various gravity-deceleration conditions by customized parabolic flight-maneuvers targeting the partial-gravity levels of 0.60, 0.30, 0.15 and μ g (<0.001 g. Video recordings of postural responses were analyzed frame-by-frame by high-definition cineradiography and with exact instantaneous values of gravity and jerk. As a result, the coordinated extension of the neck, spine and hindlimbs was observed during the initial phase of gravity deceleration. Joint angles widened to 120%–200% of the reference g level, and the magnitude of the thoracic-curvature stretching was correlated with gravity and jerk, i.e., the gravity deceleration rate. A certain range of jerk facilitated mouse skeletal stretching efficiently, and a jerk of −0.3~−0.4 j (g/s induced the maximum extension of the thoracic-curvature. The postural response of animals to low gravity may undergo differential regulation by gravity and jerk.

A Least Squares Collocation Approach with GOCE gravity gradients for regional Moho-estimation

Science.gov (United States)

Rieser, Daniel; Mayer-Guerr, Torsten

2014-05-01

The depth of the Moho discontinuity is commonly derived by either seismic observations, gravity measurements or combinations of both. In this study, we aim to use the gravity gradient measurements of the GOCE satellite mission in a Least Squares Collocation (LSC) approach for the estimation of the Moho depth on regional scale. Due to its mission configuration and measurement setup, GOCE is able to contribute valuable information in particular in the medium wavelengths of the gravity field spectrum, which is also of special interest for the crust-mantle boundary. In contrast to other studies we use the full information of the gradient tensor in all three dimensions. The problem outline is formulated as isostatically compensated topography according to the Airy-Heiskanen model. By using a topography model in spherical harmonics representation the topographic influences can be reduced from the gradient observations. Under the assumption of constant mantle and crustal densities, surface densities are directly derived by LSC on regional scale, which in turn are converted in Moho depths. First investigations proofed the ability of this method to resolve the gravity inversion problem already with a small amount of GOCE data and comparisons with other seismic and gravitmetric Moho models for the European region show promising results. With the recently reprocessed GOCE gradients, an improved data set shall be used for the derivation of the Moho depth. In this contribution the processing strategy will be introduced and the most recent developments and results using the currently available GOCE data shall be presented.

Preliminary evaluation of sweet spot size in virtual sound reproduction using dipoles

DEFF Research Database (Denmark)

Lacouture Parodi, Yesenia; Rubak, Per

2009-01-01

to the loudspeakers. In this paper we present a follow up evaluation of the performance of the three inversion techniques when these conditions are violated. A setup to measure the sweet spot of different loudspeakers arrangements is described. Preliminary measurement results are presented for loudspeakers placed...

Calculation of the inverse data space via sparse inversion

KAUST Repository

Saragiotis, Christos

2011-01-01

The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function by constraining the $ell_1$ norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal.

Estimating Antarctica land topography from GRACE gravity and ICESat altimetry data

Science.gov (United States)

Wu, I.; Chao, B. F.; Chen, Y.

2009-12-01

We propose a new method combining GRACE (Gravity Recovery and Climate Experiment) gravity and ICESat (Ice, Cloud, and land Elevation Satellite) altimetry data to estimate the land topography for Antarctica. Antarctica is the fifth-largest continent in the world and about 98% of Antarctica is covered by ice, where in-situ measurements are difficult. Some experimental airborne radar and ground-based radar data have revealed very limited land topography beneath heavy ice sheet. To estimate the land topography for the full coverage of Antarctica, we combine GRACE data that indicate the mass distribution, with data of ICESat laser altimetry that provide high-resolution mapping of ice topography. Our approach is actually based on some geological constraints: assuming uniform densities of the land and ice considering the Airy-type isostasy. In the beginning we construct an initial model for the ice thickness and land topography based on the BEDMAP ice thickness and ICESat data. Thereafter we forward compute the model’s gravity field and compare with the GRACE observed data. Our initial model undergoes the adjustments to improve the fit between modeled results and the observed data. Final examination is done by comparing our results with previous but sparse observations of ice thickness to reconfirm the reliability of our results. As the gravitational inversion problem is non-unique, our estimating result is just one of all possibilities constrained by available data in optimal way.

Ricci dark energy in Chern-Simons modified gravity

Energy Technology Data Exchange (ETDEWEB)

Silva, J.G.; Santos, A.F. [Universidade Federal de Mato Grosso (UFMT), Campo Grande, MT (Brazil)

2013-07-01

Full text: Currently the accelerated expansion of the universe has been strongly confirmed by some independent experiments such as the Cosmic Microwave Background Radiation (CMBR) and Sloan Digital Sky Survey (SDSS). In an attempt to explain this phenomenon there are two possible paths; first option - propose corrections to general relativity, second option - assuming that there is a dominant component of the universe, a kind of antigravity called dark energy. Any way that we intend to follow, there are numerous models that attempt to explain this effect. One of the models of modified gravity that has stood out in recent years is the Chern-Simons modified gravity. This modification consists in the addition of the Pontryagin density, which displays violation of parity symmetry in Einstein-Hilbert action. From among the various models proposed for dark energy there are some that are based on the holographic principle, known as holographic dark energy. Such models are based on the idea that the energy density of a given system is proportional to the inverse square of some characteristic length of the system. From these studies, here we consider the model proposed by Gao et. al., a model of dark energy where the characteristic length is given by the average radius of the Ricci scalar. Thus, the dark energy density is proportional to the Ricci scalar, i.e., ρ{sub x} ∝ R. It is a phenomenologically viable model and displays results similar to that presented by the cosmological model ACDM. In this work, we have considered the Ricci dark energy model in the dynamic Chern-Simons modified gravity. We show that in this context the evolution of the scale factor is similar to that displayed by the modified Chaplygin gas. (author)

Ricci dark energy in Chern-Simons modified gravity

International Nuclear Information System (INIS)

Silva, J.G.; Santos, A.F.

2013-01-01

Full text: Currently the accelerated expansion of the universe has been strongly confirmed by some independent experiments such as the Cosmic Microwave Background Radiation (CMBR) and Sloan Digital Sky Survey (SDSS). In an attempt to explain this phenomenon there are two possible paths; first option - propose corrections to general relativity, second option - assuming that there is a dominant component of the universe, a kind of antigravity called dark energy. Any way that we intend to follow, there are numerous models that attempt to explain this effect. One of the models of modified gravity that has stood out in recent years is the Chern-Simons modified gravity. This modification consists in the addition of the Pontryagin density, which displays violation of parity symmetry in Einstein-Hilbert action. From among the various models proposed for dark energy there are some that are based on the holographic principle, known as holographic dark energy. Such models are based on the idea that the energy density of a given system is proportional to the inverse square of some characteristic length of the system. From these studies, here we consider the model proposed by Gao et. al., a model of dark energy where the characteristic length is given by the average radius of the Ricci scalar. Thus, the dark energy density is proportional to the Ricci scalar, i.e., ρ x ∝ R. It is a phenomenologically viable model and displays results similar to that presented by the cosmological model ACDM. In this work, we have considered the Ricci dark energy model in the dynamic Chern-Simons modified gravity. We show that in this context the evolution of the scale factor is similar to that displayed by the modified Chaplygin gas. (author)

Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

NARCIS (Netherlands)

Fuchs, M.J.; Bouman, J.; Broerse, D.B.T.; Visser, P.N.A.M.; Vermeersen, L.L.A.

2013-01-01

The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and

A Subnano-g Electrostatic Force-Rebalanced Flexure Accelerometer for Gravity Gradient Instruments

Directory of Open Access Journals (Sweden)

Shitao Yan

2017-11-01

Full Text Available A subnano-g electrostatic force-rebalanced flexure accelerometer is designed for the rotating accelerometer gravity gradient instrument. This accelerometer has a large proof mass, which is supported inversely by two pairs of parallel leaf springs and is centered between two fixed capacitor plates. This novel design enables the proof mass to move exactly along the sensitive direction and exhibits a high rejection ratio at its cross-axis directions. Benefiting from large proof mass, high vacuum packaging, and air-tight sealing, the thermal Brownian noise of the accelerometer is lowered down to less than 0.2 ng / Hz with a quality factor of 15 and a natural resonant frequency of about 7.4 Hz . The accelerometer’s designed measurement range is about ±1 mg. Based on the correlation analysis between a commercial triaxial seismometer and our accelerometer, the demonstrated self-noise of our accelerometers is reduced to lower than 0.3 ng / Hz over the frequency ranging from 0.2 to 2 Hz, which meets the requirement of the rotating accelerometer gravity gradiometer.

Inverse Monte Carlo: a unified reconstruction algorithm for SPECT

International Nuclear Information System (INIS)

Floyd, C.E.; Coleman, R.E.; Jaszczak, R.J.

1985-01-01

Inverse Monte Carlo (IMOC) is presented as a unified reconstruction algorithm for Emission Computed Tomography (ECT) providing simultaneous compensation for scatter, attenuation, and the variation of collimator resolution with depth. The technique of inverse Monte Carlo is used to find an inverse solution to the photon transport equation (an integral equation for photon flux from a specified source) for a parameterized source and specific boundary conditions. The system of linear equations so formed is solved to yield the source activity distribution for a set of acquired projections. For the studies presented here, the equations are solved using the EM (Maximum Likelihood) algorithm although other solution algorithms, such as Least Squares, could be employed. While the present results specifically consider the reconstruction of camera-based Single Photon Emission Computed Tomographic (SPECT) images, the technique is equally valid for Positron Emission Tomography (PET) if a Monte Carlo model of such a system is used. As a preliminary evaluation, experimentally acquired SPECT phantom studies for imaging Tc-99m (140 keV) are presented which demonstrate the quantitative compensation for scatter and attenuation for a two dimensional (single slice) reconstruction. The algorithm may be expanded in a straight forward manner to full three dimensional reconstruction including compensation for out of plane scatter

Airborne Gravity: NGS' Gravity Data for ES05 (2015-2016)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Florida and the Atlantic Ocean collected in two surveys, FL15-1 and FL15-2. This data set is part of the Gravity for the Re-definition of...

Airborne Gravity: NGS' Gravity Data for AS04 (2015-2016)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2015 and 2016 over 2 surveys, AK15 and AK16. This data set is part of the Gravity for the Re-definition of the American...

Tectonics of the Philippines and ambient regions from geophysical inversions

Science.gov (United States)

Liu, W.; Li, C.; Zhou, Z.; Fairhead, J. D.

2012-12-01

The geological study in the Philippines and ambient regions is relatively low so far for the rather scanty data and complex geological structure. Therefore it is a challenge to do the research with limited data. In this paper, an investigation of the Philippines and surrounding area has been carried out using regional magnetic and gravity anomalies. Owing to the difficulties and limitations in reduction to the pole at the low latitudes, analytical signal amplitudes of magnetic anomalies are calculated as the equivalent substitute. Application of the Parker-Oldenburg algorithm to Bouguer gravity anomalies yields a 3D Moho topography. Curie-point depths are estimated from the magnetic anomalies using a windowed wavenumber-domain algorithm. This paper aims to reveal the structure of the Manila subduction zone accurately, and moreover, to clarify the interplay between the magmatism and subduction in the Manila Trench and East Luzon Trough. On the basis of Bouguer gravity anomaly and AS(analytical signal) of magnetic anomaly, the positions of hydrated mantle wedge in the subduction zones of this area are identified in the areas charicterizd by the distribution of high-and low value of Bouguer gravity anomaly or the paralell high value of Bouguer gravity anomaly and AS. Using our inversion results together with some other published information, the boundaries of Palawan Block, Philippine Mobile Belt and Sulu-Celebes Block are defined and the collision history of PCB(Palawan continental block)-PMB (Philippine mobile belt) and PCB-Sulu Sea is also discussed. A "seismic gap" near the 14 degree north latitude on Manila Trench, mentioned in previous studies, is thought to be induced by the slab melting and plastic behavior due to the relatively high geothermal gradient. In the central Philippines, it is likely that an incipient collision-related rifting is proceeding. Furthermore, a possible new evolution model of Sulu Sea, in which the Cagayan Ridge area is thought to be the

Development of a new generation gravity map of Antarctica: ADGRAV Antarctic Digital Gravity Synthesis

Directory of Open Access Journals (Sweden)

R. A. Arko

1999-06-01

Full Text Available The U.S. National Science Foundation (NSF has agreed to support the development of a new generation gravity map of Antarctica (ADGRAV - Antarctic Digital Gravity Synthesis, funding the development of a web based access tool. The goal of this project is the creation of an on-line Antarctic gravity database which will facilitate access to improved high resolution satellite gravity models, in conjunction with shipboard, airborne, and land based gravity measurements for the continental regions. This database will complement parallel projects underway to develop new continental bedrock (BEDMAP and magnetic (ADMAP maps of Antarctica.

A mini-library of TBA analogues containing 3'-3' and 5'-5' inversion of polarity sites.

Science.gov (United States)

Esposito, V; Galeone, A; Mayol, L; Randazzo, A; Virgilio, A; Virno, A

2007-01-01

Several researches have been devoted to structure-activity relationship and to post-SELEX modifications of the thrombin binding aptamer (TBA), one of the first aptamers discovered by the SELEX methodology. However, no studies on TBA dealing with the effects of introduction of inversion of polarity sites have been reported yet. In this frame, we have undertaken the synthesis and the study of a mini-library composed of several TBA analogues containing a 3'-3' or a 5'-5' inversion of polarity site at different positions into the sequence. Particularly, in this article, we present preliminary results about their structural and biological properties.

Cosmological tests of modified gravity.

Science.gov (United States)

Koyama, Kazuya

2016-04-01

We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

Microwave Imaging of Three-Dimensional Targets by Means of an Inexact-Newton-Based Inversion Algorithm

Directory of Open Access Journals (Sweden)

Claudio Estatico

2013-01-01

Full Text Available A microwave imaging method previously developed for tomographic inspection of dielectric targets is extended to three-dimensional objects. The approach is based on the full vector equations of the electromagnetic inverse scattering problem. The ill-posedness of the problem is faced by the application of an inexact-Newton method. Preliminary reconstruction results are reported.

Gravity signatures of terrane accretion

Science.gov (United States)

Franco, Heather; Abbott, Dallas

1999-01-01

In modern collisional environments, accreted terranes are bracketed by forearc gravity lows, a gravitational feature which results from the abandonment of the original trench and the initiation of a new trench seaward of the accreted terrane. The size and shape of the gravity low depends on the type of accreted feature and the strength of the formerly subducting plate. Along the Central American trench, the accretion of Gorgona Island caused a seaward trench jump of 48 to 66 km. The relict trench axes show up as gravity lows behind the trench with minimum values of -78 mgal (N of Gorgona) and -49 mgal (S of Gorgona) respectively. These forearc gravity lows have little or no topographic expression. The active trench immediately seaward of these forearc gravity lows has minimum gravity values of -59 mgal (N of Gorgona) and -58 mgal (S of Gorgona), respectively. In the north, the active trench has a less pronounced gravity low than the sediment covered forearc. In the Mariana arc, two Cretaceous seamounts have been accreted to the Eocene arc. The northern seamount is most likely a large block, the southern seamount may be a thrust slice. These more recent accretion events have produced modest forearc topographic and gravity lows in comparison with the topographic and gravity lows within the active trench. However, the minimum values of the Mariana forearc gravity lows are modest only by comparison to the Mariana Trench (-216 mgal); their absolute values are more negative than at Gorgona Island (-145 to -146 mgal). We speculate that the forearc gravity lows and seaward trench jumps near Gorgona Island were produced by the accretion of a hotspot island from a strong plate. The Mariana gravity lows and seaward trench jumps (or thrust slices) were the result of breaking a relatively weak plate close to the seamount edifice. These gravity lows resulting from accretion events should be preserved in older accreted terranes.

Analysis of gravity data beneath Endut geothermal prospect using horizontal gradient and Euler deconvolution

Science.gov (United States)

Supriyanto, Noor, T.; Suhanto, E.

2017-07-01

The Endut geothermal prospect is located in Banten Province, Indonesia. The geological setting of the area is dominated by quaternary volcanic, tertiary sediments and tertiary rock intrusion. This area has been in the preliminary study phase of geology, geochemistry, and geophysics. As one of the geophysical study, the gravity data measurement has been carried out and analyzed in order to understand geological condition especially subsurface fault structure that control the geothermal system in Endut area. After precondition applied to gravity data, the complete Bouguer anomaly have been analyzed using advanced derivatives method such as Horizontal Gradient (HG) and Euler Deconvolution (ED) to clarify the existance of fault structures. These techniques detected boundaries of body anomalies and faults structure that were compared with the lithologies in the geology map. The analysis result will be useful in making a further realistic conceptual model of the Endut geothermal area.

Airborne Gravity: NGS' Gravity Data for CS07 (2014 & 2016)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas collected in 2014 & 2016 over 3 surveys,TX14-2, TX16-1 and TX16-2. This data set is part of the Gravity for the Re-definition of...

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation.

Science.gov (United States)

Tie, Junbo; Cao, Juliang; Chang, Lubing; Cai, Shaokun; Wu, Meiping; Lian, Junxiang

2018-03-16

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method.

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation

Science.gov (United States)

Cao, Juliang; Cai, Shaokun; Wu, Meiping; Lian, Junxiang

2018-01-01

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method. PMID:29547552

BOOK REVIEW: Quantum Gravity: third edition Quantum Gravity: third edition

Science.gov (United States)

Rovelli, Carlo

2012-09-01

The request by Classical and Quantum Gravity to review the third edition of Claus Kiefer's 'Quantum Gravity' puts me in a slightly awkward position. This is a remarkably good book, which every person working in quantum gravity should have on the shelf. But in my opinion quantum gravity has undergone some dramatic advances in the last few years, of which the book makes no mention. Perhaps the omission only attests to the current vitality of the field, where progress is happening fast, but it is strange for me to review a thoughtful, knowledgeable and comprehensive book on my own field of research, which ignores what I myself consider the most interesting results to date. Kiefer's book is unique as a broad introduction and a reliable overview of quantum gravity. There are numerous books in the field which (often notwithstanding titles) focus on a single approach. There are also countless conference proceedings and article collections aiming to be encyclopaedic, but offering disorganized patchworks. Kiefer's book is a careful and thoughtful presentation of all aspects of the immense problem of quantum gravity. Kiefer is very learned, and brings together three rare qualities: he is pedagogical, he is capable of simplifying matter to the bones and capturing the essential, and he offers a serious and balanced evaluation of views and ideas. In a fractured field based on a major problem that does not yet have a solution, these qualities are precious. I recommend Kiefer's book to my students entering the field: to work in quantum gravity one needs a vast amount of technical knowledge as well as a grasp of different ideas, and Kiefer's book offers this with remarkable clarity. This novel third edition simplifies and improves the presentation of several topics, but also adds very valuable new material on quantum gravity phenomenology, loop quantum cosmology, asymptotic safety, Horava-Lifshitz gravity, analogue gravity, the holographic principle, and more. This is a testament

Directed Neutron Beams From Inverse Kinematic Reactions

Science.gov (United States)

Vanhoy, J. R.; Guardala, N. A.; Glass, G. A.

2011-06-01

Kinematic focusing of an emitted fairly mono-energetic neutron beam by the use of inverse-kinematic reactions, i.e. where the projectile mass is greater than the target atom's mass, can provide for the utilization of a significant fraction of the fast neutron yield and also provide for a safer radiation environment. We examine the merit of various neutron production reactions and consider the practicalities of producing the primary beam using the suitable accelerator technologies. Preliminary progress at the NSWC-Carderock Positive Ion Accelerator Facility is described. Possible important applications for this type of neutron-based system can be both advanced medical imaging techniques and active "stand-off" interrogation of contraband items.

DNAG Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Decade of North American Geology (DNAG) gravity grid values, spaced at 6 km, were used to produce the Gravity Anomaly Map of North America (1987; scale...

Temperature Inversions and Permafrost Distribution in a Mountain Valley: Preliminary Results From Wolf Creek, Yukon Territory, Canada

Science.gov (United States)

Lewkowicz, A. G.; Smith, K. M.

2004-12-01

The BTS (Basal Temperature of Snow) method to predict permafrost probability in mountain basins uses elevation as an easily available and spatially distributed independent variable. The elevation coefficient in the BTS regression model is, in effect, a substitute for ground temperature lapse rates. Previous work in Wolf Creek (60° 8'N 135° W), a mountain basin near Whitehorse, has shown that the model breaks down in a mid-elevation valley (1250 m asl) where actual permafrost probability is roughly twice that predicted by the model (60% vs. 20-30%). The existence of a double tree-line at the site suggested that air temperature inversions might be the cause of this inaccuracy (Lewkowicz and Ednie, 2004). This paper reports on a first year (08/2003-08/2004) of hourly air and ground temperature data collected along an altitudinal transect within the valley in upper Wolf Creek. Measurements were made at sites located 4, 8, 22, 82 and 162 m above the valley floor. Air temperature inversions between the lowest and highest measurement points occurred 42% of the time and in all months, but were most frequent and intense in winter (>60% of December and January) and least frequent in September (snow cover. In many cases, however, air temperature inversions are not duplicated in the ground temperature record. Nevertheless, the annual altitudinal ground temperature gradient is much lower than would be expected from a standard atmospheric lapse rate, suggesting that the inversions do have an important impact on permafrost distribution at this site. More generally, therefore, it appears probable that any reduction in inversion frequency resulting from a more vigorous atmospheric circulation in the context of future climate change, would have a significant effect on permafrost distribution in mountain basins.

Stellar pulsations in beyond Horndeski gravity theories

Energy Technology Data Exchange (ETDEWEB)

Sakstein, Jeremy [Center for Particle Cosmology, Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104 (United States); Kenna-Allison, Michael; Koyama, Kazuya, E-mail: sakstein@physics.upenn.edu, E-mail: mka1g13@soton.ac.uk, E-mail: kazuya.koyama@port.ac.uk [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom)

2017-03-01

Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

Integrated geophysical study of the northeastern margin of Tibetan Plateau

Science.gov (United States)

Shi, L.; Meng, X.; Guo, L.

2011-12-01

Tibetan Plateau, the so-called "Roof of the World", is a direct consequence of collision of the Indian plate with the Eurasian plate starting in the early Cenozoic time. The continent-continent collision is still going on. The northeastern margin of Tibetan Plateau is the front part of the Tibetan Plateau extends to mainland and favorable area for studying uplift and deformation of the Tibetan Plateau. In the past decades, a variety of geophysical methods were conducted to study geodynamics and geological tectonics of this region. We assembled satellite-derived free-air gravity anomalies with a resolution of one arc-minute from the Scripps Institution of Oceanography, and reduced them to obtain Complete Bouguer Gravity Anomalies. Then we gridded Complete Bouguer Gravity Anomalies on a regular grid, and subsequently processed them with the preferential continuation method to attenuate high-frequency noise and analyzed regional and residual anomalies. We also calculated tilt-angle derivative of Complete Bouguer Gravity Anomalies to derive clearer geological structures with more details. Then we calculated the depth distribution of the Moho discontinuity surface in this area by 3D density interface inversion. From the results of preliminary processing, we analyzed the main deep faults and geological tectonics in this region. We extracted seven important profiles' data of Complete Bouguer Gravity Anomalies in this area, and then did forward modeling and inversion on each profile with constraints of geological information and other geophysical data. In the future, we will perform 3D constrained inversion of Complete Bouguer Gravity Anomalies in this region for better understanding deep structure and tectonics of the northeastern margin of Tibetan Plateau. Acknowledgment: We acknowledge the financial support of the SinoProbe project (201011039), the Fundamental Research Funds for the Central Universities (2010ZY26 2011PY0184), and the National Natural Science Foundation

3D density model of the upper mantle of Asia based on inversion of gravity and seismic tomography data

NARCIS (Netherlands)

Kaban, Mikhail K.; Stolk, Ward; Tesauro, Magdala; El Khrepy, Sami; Al-Arifi, Nassir; Beekman, Fred; Cloetingh, Sierd A P L

2016-01-01

We construct a new-generation 3D density model of the upper mantle of Asia and its surrounding areas based on a joint interpretation of several data sets. A recent model of the crust combining nearly all available seismic data is employed to calculate the impact of the crust on the gravity anomalies

Measuring Gravity in International Trade Flows

Directory of Open Access Journals (Sweden)

E. Young Song

2004-12-01

Full Text Available The purpose of this paper is two-fold. One is to clarify the concept of gravity in international trade flows. The other is to measure the strength of gravity in international trade flows in a way that is consistent with a well-defined concept of gravity. This paper shows that the widely accepted belief that specialization is the source of gravity is not well grounded on theory. We propose to define gravity in international trade as the force that makes the market shares of an exporting country constant in all importing countries, regardless of their sizes. In a stochastic context, we should interpret it as implying that the strength of gravity increases i as the correlation between market shares and market sizes gets weaker and ii as the variance of market shares gets smaller. We estimate an empirical gravity equation thoroughly based on this definition of gravity. We find that a strong degree of gravity exists in most bilateral trade, regardless of income levels of countries, and in trade of most manThe purpose of this paper is two-fold. One is to clarify the concept of gravity in international trade flows. The other is to measure the strength of gravity in international trade flows in a way that is consistent with a well-defined concept of gravity. This paper shows that the widely accepted belief that specialization is the source of gravity is not well grounded on theory. We propose to define gravity in international trade as the force that makes the market shares of an exporting country constant in all importing countries, regardless of their sizes. In a stochastic context, we should interpret it as implying that the strength of gravity increases i as the correlation between market shares and market sizes gets weaker and ii as the variance of market shares gets smaller. We estimate an empirical gravity equation thoroughly based on this definition of gravity. We find that a strong degree of gravity exists in most bilateral trade, regardless of

High-degree Gravity Models from GRAIL Primary Mission Data

Science.gov (United States)

Lemoine, Frank G.; Goossens, Sander J.; Sabaka, Terence J.; Nicholas, Joseph B.; Mazarico, Erwan; Rowlands, David D.; Loomis, Bryant D.; Chinn, Douglas S.; Caprette, Douglas S.; Neumann, Gregory A.;

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

Science.gov (United States)

Syracuse, E. M.; Zhang, H.; Maceira, M.

2017-10-01

We present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body wave first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region. Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. Without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.

Was Newton right? A search for non-Newtonian behavior of weak-field gravity

Directory of Open Access Journals (Sweden)

Boynton Paul

2014-06-01

Full Text Available Empirical tests of Einstein’s metric theory of gravitation, even in the non-relativistic, weak-field limit, could play an important role in judging theory-driven extensions of the current Standard Model of fundamental interactions. Guided by Galileo's work and his own experiments, Newton formulated a theory of gravity in which the force of attraction between two bodies is independent of composition and proportional to the inertia of each, thereby transparently satisfying Galileo's empirically informed conjecture regarding the Universality of Free Fall. Similarly, Einstein honored the manifest success of Newton’s theory by assuring that the linearized equations of GTR matched the Newtonian formalism under “classical” conditions. Each of these steps, however, was explicitly an approximation raised to the status of principle. Perhaps, at some level, Newtonian gravity does not accurately describe the physical interaction between uncharged, unmagnetized, macroscopic bits of ordinary matter. What if Newton were wrong? Detecting any significant deviation from Newtonian behavior, no matter how small, could provide new insights and possibly reveal new physics. In the context of physics as an empirical science, for us this yet unanswered question constitutes sufficient motivation to attempt precision measurements of the kind described here. In this paper we report the current status of a project to search for violation of the Newtonian inverse square law of gravity.

Search for extra spatial dimensions and TeV scale quantum gravity at LEP-2

International Nuclear Information System (INIS)

Litke, A.M.

2001-01-01

A number of measurements which probe the experimental consequences of extra spatial dimensions and TeV scale quantum gravity are accessible at the LEP-2 electron-positron collider. Preliminary results on the following processes, performed with the ALEPH detector at center of mass energies around 200 GeV, are presented: 1. search for direct graviton production in the reaction e + e - →γG; and, 2. search for effects due to virtual graviton exchange in the reactions e + e - →γγ and fermion-anti-fermion pairs

Quantum Gravity

International Nuclear Information System (INIS)

Giribet, G E

2005-01-01

Claus Kiefer presents his book, Quantum Gravity, with his hope that '[the] book will convince readers of [the] outstanding problem [of unification and quantum gravity] and encourage them to work on its solution'. With this aim, the author presents a clear exposition of the fundamental concepts of gravity and the steps towards the understanding of its quantum aspects. The main part of the text is dedicated to the analysis of standard topics in the formulation of general relativity. An analysis of the Hamiltonian formulation of general relativity and the canonical quantization of gravity is performed in detail. Chapters four, five and eight provide a pedagogical introduction to the basic concepts of gravitational physics. In particular, aspects such as the quantization of constrained systems, the role played by the quadratic constraint, the ADM decomposition, the Wheeler-de Witt equation and the problem of time are treated in an expert and concise way. Moreover, other specific topics, such as the minisuperspace approach and the feasibility of defining extrinsic times for certain models, are discussed as well. The ninth chapter of the book is dedicated to the quantum gravitational aspects of string theory. Here, a minimalistic but clear introduction to string theory is presented, and this is actually done with emphasis on gravity. It is worth mentioning that no hard (nor explicit) computations are presented, even though the exposition covers the main features of the topic. For instance, black hole statistical physics (within the framework of string theory) is developed in a pedagogical and concise way by means of heuristical arguments. As the author asserts in the epilogue, the hope of the book is to give 'some impressions from progress' made in the study of quantum gravity since its beginning, i.e., since the end of 1920s. In my opinion, Kiefer's book does actually achieve this goal and gives an extensive review of the subject. (book review)

Butterfly effect in 3D gravity

Science.gov (United States)

Qaemmaqami, Mohammad M.

2017-11-01

We study the butterfly effect by considering shock wave solutions near the horizon of the anti-de Sitter black hole in some three-dimensional gravity models including 3D Einstein gravity, minimal massive 3D gravity, new massive gravity, generalized massive gravity, Born-Infeld 3D gravity, and new bigravity. We calculate the butterfly velocities of these models and also we consider the critical points and different limits in some of these models. By studying the butterfly effect in the generalized massive gravity, we observe a correspondence between the butterfly velocities and right-left moving degrees of freedom or the central charges of the dual 2D conformal field theories.

Subsurface images of the Eastern Rift, Africa, from the joint inversion of body waves, surface waves and gravity: investigating the role of fluids in early-stage continental rifting

Science.gov (United States)

Roecker, S.; Ebinger, C.; Tiberi, C.; Mulibo, G.; Ferdinand-Wambura, R.; Mtelela, K.; Kianji, G.; Muzuka, A.; Gautier, S.; Albaric, J.; Peyrat, S.

2017-08-01

The Eastern Rift System (ERS) of northern Tanzania and southern Kenya, where a cratonic lithosphere is in the early stages of rifting, offers an ideal venue for investigating the roles of magma and other fluids in such an environment. To illuminate these roles, we jointly invert arrival times of locally recorded P and S body waves, phase delays of ambient noise generated Rayleigh waves and Bouguer anomalies from gravity observations to generate a 3-D image of P and S wave speeds in the upper 25 km of the crust. While joint inversion of gravity and arrival times requires a relationship between density and wave speeds, the improvement in resolution obtained by the combination of these disparate data sets serves to further constrain models, and reduce uncertainties. The most significant features in the 3-D model are (1) P and S wave speeds that are 10-15 per cent lower beneath the rift zone than in the surrounding regions, (2) a relatively high wave speed tabular feature located along the western edge of the Natron and Manyara rifts, and (3) low (∼1.71) values of Vp/Vs throughout the upper crust, with the lowest ratios along the boundaries of the rift zones. The low P and S wave speeds at mid-crustal levels beneath the rift valley are an expected consequence of active volcanism, and the tabular, high-wave speed feature is interpreted to be an uplifted footwall at the western edge of the rift. Given the high levels of CO2 outgassing observed at the surface along border fault zones, and the sensitivity of Vp/Vs to pore-fluid compressibility, we infer that the low Vp/Vs values in and around the rift zone are caused by the volcanic plumbing in the upper crust being suffused by a gaseous CO2 froth on top of a deeper, crystalline mush. The repository for molten rock is likely located in the lower crust and upper mantle, where the Vp/Vs ratios are significantly higher.

Induced quantum conformal gravity

International Nuclear Information System (INIS)

Novozhilov, Y.V.; Vassilevich, D.V.

1988-11-01

Quantum gravity is considered as induced by matter degrees of freedom and related to the symmetry breakdown in the low energy region of a non-Abelian gauge theory of fundamental fields. An effective action for quantum conformal gravity is derived where both the gravitational constant and conformal kinetic term are positive. Relation with induced classical gravity is established. (author). 15 refs

Nonsingular universe in massive gravity's rainbow

Science.gov (United States)

Hendi, S. H.; Momennia, M.; Eslam Panah, B.; Panahiyan, S.

2017-06-01

One of the fundamental open questions in cosmology is whether we can regard the universe evolution without singularity like a Big Bang or a Big Rip. This challenging subject stimulates one to regard a nonsingular universe in the far past with an arbitrarily large vacuum energy. Considering the high energy regime in the cosmic history, it is believed that Einstein gravity should be corrected to an effective energy dependent theory which could be acquired by gravity's rainbow. On the other hand, employing massive gravity provided us with solutions to some of the long standing fundamental problems of cosmology such as cosmological constant problem and self acceleration of the universe. Considering these aspects of gravity's rainbow and massive gravity, in this paper, we initiate studying FRW cosmology in the massive gravity's rainbow formalism. At first, we show that although massive gravity modifies the FRW cosmology, but it does not itself remove the big bang singularity. Then, we generalize the massive gravity to the case of energy dependent spacetime and find that massive gravity's rainbow can remove the early universe singularity. We bring together all the essential conditions for having a nonsingular universe and the effects of both gravity's rainbow and massive gravity generalizations on such criteria are determined.

Airborne Gravity: NGS' Airborne Gravity Data for AN01 (2009-2010)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2009-2010 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...

Retrieving current and wind vectors from ATI SAR data: airborne evidence and inversion strategy

Science.gov (United States)

Martin, Adrien; Gommenginger, Christine; Chapron, Bertrand; Marquez, José; Doody, Sam

2017-04-01

Conventional and along-track interferometric (ATI) Synthetic Aperture Radar (SAR) sense the motion of the ocean surface by measuring the Doppler shift of reflected signals. Together with the water displacement associated with ocean currents, the SAR measurements are also affected by a Wind-wave induced Artefact Surface Velocity (WASV) caused by the velocity of Bragg scatterers and the orbital velocity of ocean surface gravity waves. The WASV has been modelled theoretically in past studies but has been estimated empirically only once using Envisat ASAR. Here we propose, firstly, to evaluate this WASV from airborne ATI SAR data, secondly, to validate the airborne retrieved surface current after correction of the WASV against HF radar measurements and thirdly to examine the best inversion strategy for a an Ocean Surface Current (OSC) satellite mission to retrieve accurately both the ocean surface current vector (OSCV) and the wind vector in the frame of an OSC satellite mission. The airborne ATI SAR data were acquired in the tidally dominated Irish Sea using a Wavemill-type dual-beam SAR interferometer. A comprehensive collection of airborne Wavemill data acquired in a star pattern over a well-instrumented site made it possible to estimate the magnitude and dependence on azimuth and incidence angle of the WASV. The airborne results compare favourably with those reported for Envisat ASAR, empirical model, which has been used to correct for it. Validation of the current retrieval capabilities of the proof-of-concept has been conducted against HF radar giving a precisions typically better than 0.1 m/s for surface current speed and 7° for direction. Comparisons with POLCOMS (1.8 km) indicate that the model reproduces well the overall temporal evolution but does not capture the high spatial variability of ocean surface currents at the maximum ebb flow. Airborne retrieved currents highlight a short-scale spatial variability up to 100m related to bathymetry channels, which

Seismic b-values and its correlation with seismic moment and Bouguer gravity anomaly over Indo-Burma ranges of northeast India: Tectonic implications

Science.gov (United States)

Bora, Dipok K.; Borah, Kajaljyoti; Mahanta, Rinku; Borgohain, Jayanta Madhab

2018-03-01

b-value is one of the most significant seismic parameters for describing the seismicity of a given region at a definite time window. In this study, high-resolution map of the Gutenberg-Richter b-value, seismic moment-release, Bouguer gravity anomaly and fault-plane solutions containing faulting styles are analyzed in the Indo-Burma ranges of northeast India using the unified and homogeneous part of the seismicity record in the region (January 1964-December 2016). The study region is subdivided into few square grids of geographical window size 1° × 1° and b-values are calculated in each square grid. Our goal is to explore the spatial correlations and anomalous patterns between the b-value and parameters like seismic moment release, Bouguer gravity anomaly and faulting styles that can help us to better understand the seismotectonics and the state of present-day crustal stress within the Indo-Burma region. Most of the areas show an inverse correlation between b-value and seismic moment release as well as convergence rates. While estimating the b-value as a function of depth, a sudden increase of b-value at a depth of 50-60 km was found out and the receiver function modeling confirms that this depth corresponds to the crust-mantle transition beneath the study region. The region is also associated with negative Bouguer gravity anomalies and an inverse relation is found between Gravity anomaly and b-value. Comparing b-values with different faulting styles, reveal that the areas containing low b-values show thrust mechanism, while the areas associated with intermediate b-values show strike-slip mechanism. Those areas, where the events show thrust mechanism but containing a strike-slip component has the highest b-value.

Interior Alaska Bouguer Gravity Anomaly

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — A 1 kilometer Complete Bouguer Anomaly gravity grid of interior Alaska. Only those grid cells within 10 kilometers of a gravity data point have gravity values....

The Study of Geological Structures in Suli and Tulehu Geothermal Regions (Ambon, Indonesia Based on Gravity Gradient Tensor Data Simulation and Analytic Signal

Directory of Open Access Journals (Sweden)

Richard Lewerissa

2017-12-01

Full Text Available In early 2017, the geothermal system in the Suli and Tulehu areas of Ambon (Indonesia was investigated using a gravity gradient tensor and analytic signal. The gravity gradient tensor and analytic signal were obtained through forward modeling based on a rectangular prism. It was applied to complete Bouguer anomaly data over the study area by using Fast Fourier Transform (FFT. The analysis was conducted to enhance the geological structure like faults as a pathway of geothermal fluid circulation that is not visible on the surface because it is covered by sediment. The complete Bouguer anomaly ranges of 93 mGal up to 105 mGal decrease from the southwest in Suli to the northeast in Tulehu. A high gravity anomaly indicates a strong magmatic intrusion below the Suli region. The gravity anomalies decrease occurs in the Eriwakang mountain and most of Tulehu, and it is associated with a coral limestone. The lower gravity anomalies are located in the north to the northeast part of Tulehu are associated with alluvium. The residual anomaly shows that the drill well TLU-01 and geothermal manifestations along with the Banda, and Banda-Hatuasa faults are associated with lowest gravity anomaly (negative zone. The gravity gradient tensor simulation and an analytic signal of Suli and Tulehu give more detailed information about the geological features. The gzz component allows accurate description of the shape structures, especially the Banda fault associated with a zero value. This result will be useful as a geophysical constraint to subsurface modeling according to gravity gradient inversion over the area.

Analysis of an innovative solar water desalination system using gravity induced vacuum

International Nuclear Information System (INIS)

Ayhan, T.; Al-Madani, H.

2007-01-01

This study presents the theoretical analysis, design and appropriate models of a new desalination system using gravity induced vacuum. The system utilizes natural means (gravity and atmospheric pressure) to create a vacuum under which water can be rapidly evaporated at much lower temperatures with less energy than conventional techniques. This technique is developed to overcome water storage, in the areas where good solar radiation (or waste heat sources) and sea water (or waste water sources). The developed system consists of an evaporator connected to condenser by means of a vacuum tank. The vapour produced in the evaporator is driven to condenser through the vacuum tank, where it condenses and collected as a product. Vacuum equivalent to 7 kPa (abs) or less can be created depending on ambient temperature of Bahrain climatic conditions. The effect of various operating conditions, namely water levels in condensation and evaporating columns on the system performance were studied. The theoretical analysis and preliminary experimental results show that the performance of this system depends on the condensation temperature

Metastable gravity on classical defects

International Nuclear Information System (INIS)

Ringeval, Christophe; Rombouts, Jan-Willem

2005-01-01

We discuss the realization of metastable gravity on classical defects in infinite-volume extra dimensions. In dilatonic Einstein gravity, it is found that the existence of metastable gravity on the defect core requires violation of the dominant energy condition for codimension N c =2 defects. This is illustrated with a detailed analysis of a six-dimensional hyperstring minimally coupled to dilaton gravity. We present the general conditions under which a codimension N c >2 defect admits metastable modes, and find that they differ from lower codimensional models in that, under certain conditions, they do not require violation of energy conditions to support quasilocalized gravity

Calculation of gravity and magnetic anomalies along profiles with end corrections and inverse solutions for density and magnetization

Science.gov (United States)

Cady, John W.

1977-01-01

An equation derived for the vertical gravity field due to a body with polygonal cross section and finite strike length.  The equations consists of the 2-dimensional equation of Talwani, Worzel, and Landisman (1959), with the addition of end corrections.  Equations for the magnetic field due to a similar body were derived by Shuey and Pasquale (1973).  They coined the term "2 1/2-dimensional" to describe the geometry.

Gravity gradient preprocessing at the GOCE HPF

Science.gov (United States)

Bouman, J.; Rispens, S.; Gruber, T.; Schrama, E.; Visser, P.; Tscherning, C. C.; Veicherts, M.

2009-04-01

One of the products derived from the GOCE observations are the gravity gradients. These gravity gradients are provided in the Gradiometer Reference Frame (GRF) and are calibrated in-flight using satellite shaking and star sensor data. In order to use these gravity gradients for application in Earth sciences and gravity field analysis, additional pre-processing needs to be done, including corrections for temporal gravity field signals to isolate the static gravity field part, screening for outliers, calibration by comparison with existing external gravity field information and error assessment. The temporal gravity gradient corrections consist of tidal and non-tidal corrections. These are all generally below the gravity gradient error level, which is predicted to show a 1/f behaviour for low frequencies. In the outlier detection the 1/f error is compensated for by subtracting a local median from the data, while the data error is assessed using the median absolute deviation. The local median acts as a high-pass filter and it is robust as is the median absolute deviation. Three different methods have been implemented for the calibration of the gravity gradients. All three methods use a high-pass filter to compensate for the 1/f gravity gradient error. The baseline method uses state-of-the-art global gravity field models and the most accurate results are obtained if star sensor misalignments are estimated along with the calibration parameters. A second calibration method uses GOCE GPS data to estimate a low degree gravity field model as well as gravity gradient scale factors. Both methods allow to estimate gravity gradient scale factors down to the 10-3 level. The third calibration method uses high accurate terrestrial gravity data in selected regions to validate the gravity gradient scale factors, focussing on the measurement band. Gravity gradient scale factors may be estimated down to the 10-2 level with this method.

New standards for reducing gravity data: The North American gravity database

Science.gov (United States)

Hinze, W. J.; Aiken, C.; Brozena, J.; Coakley, B.; Dater, D.; Flanagan, G.; Forsberg, R.; Hildenbrand, T.; Keller, Gordon R.; Kellogg, J.; Kucks, R.; Li, X.; Mainville, A.; Morin, R.; Pilkington, M.; Plouff, D.; Ravat, D.; Roman, D.; Urrutia-Fucugauchi, J.; Veronneau, M.; Webring, M.; Winester, D.

2005-01-01

The North American gravity database as well as databases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, and accuracy. An important part of this effort is revising procedures for calculating gravity anomalies, taking into account our enhanced computational power, improved terrain databases and datums, and increased interest in more accurately defining long-wavelength anomaly components. Users of the databases may note minor differences between previous and revised database values as a result of these procedures. Generally, the differences do not impact the interpretation of local anomalies but do improve regional anomaly studies. The most striking revision is the use of the internationally accepted terrestrial ellipsoid for the height datum of gravity stations rather than the conventionally used geoid or sea level. Principal facts of gravity observations and anomalies based on both revised and previous procedures together with germane metadata will be available on an interactive Web-based data system as well as from national agencies and data centers. The use of the revised procedures is encouraged for gravity data reduction because of the widespread use of the global positioning system in gravity fieldwork and the need for increased accuracy and precision of anomalies and consistency with North American and national databases. Anomalies based on the revised standards should be preceded by the adjective "ellipsoidal" to differentiate anomalies calculated using heights with respect to the ellipsoid from those based on conventional elevations referenced to the geoid. ?? 2005 Society of Exploration Geophysicists. All rights reserved.

Scale-invariant gravity: geometrodynamics

International Nuclear Information System (INIS)

Anderson, Edward; Barbour, Julian; Foster, Brendan; Murchadha, Niall O

2003-01-01

We present a scale-invariant theory, conformal gravity, which closely resembles the geometrodynamical formulation of general relativity (GR). While previous attempts to create scale-invariant theories of gravity have been based on Weyl's idea of a compensating field, our direct approach dispenses with this and is built by extension of the method of best matching w.r.t. scaling developed in the parallel particle dynamics paper by one of the authors. In spatially compact GR, there is an infinity of degrees of freedom that describe the shape of 3-space which interact with a single volume degree of freedom. In conformal gravity, the shape degrees of freedom remain, but the volume is no longer a dynamical variable. Further theories and formulations related to GR and conformal gravity are presented. Conformal gravity is successfully coupled to scalars and the gauge fields of nature. It should describe the solar system observations as well as GR does, but its cosmology and quantization will be completely different

Dual geometric-gauge field aspects of gravity

International Nuclear Information System (INIS)

Huei Peng; Wang, K.

1992-01-01

We propose that the geometric and standard gauge field aspects of gravity are equally essential for a complete description of gravity and can be reconciled. We show that this dualism of gravity resolves the dimensional Newtonian constant problem in both quantum gravity and unification schemes involving gravity (i.e., the Newtonian constant is no longer the coupling constant in the gauge aspect of gravity) and reveals the profound similarity between gravity and other fields. 23 refs., 3 tabs

Inverse problem of the vibrational band gap of periodically supported beam

Science.gov (United States)

Shi, Xiaona; Shu, Haisheng; Dong, Fuzhen; Zhao, Lei

2017-04-01

The researches of periodic structures have a long history with the main contents confined in the field of forward problem. In this paper, the inverse problem is considered and an overall frame is proposed which includes two main stages, i.e., the band gap criterion and its optimization. As a preliminary investigation, the inverse problem of the flexural vibrational band gap of a periodically supported beam is analyzed. According to existing knowledge of its forward problem, the band gap criterion is given in implicit form. Then, two cases with three independent parameters, namely the double supported case and the triple one, are studied in detail and the explicit expressions of the feasible domain are constructed by numerical fitting. Finally, the parameter optimization of the double supported case with three variables is conducted using genetic algorithm aiming for the best mean attenuation within specified frequency band.

Short-range inverse-square law experiment in space

International Nuclear Information System (INIS)

Strayer, D.M.; Paik, H.J.; Moody, M.V.

2003-01-01

The objective of ISLES (inverse-square law experiment in space) is to perform a null test of Newton's law on the ISS with a resolution of one part in 10 5 at ranges from 100 mm to 1 mm. ISLES will be sensitive enough to detect axions with the strongest allowed coupling and to test the string-theory prediction with R>= 5 μm. To accomplish these goals on the rather noisy International Space Station, the experiment is set up to provide immunity from the vibrations and other common-mode accelerations. The measures to be applied for reducing the effects of disturbances will be described in this presentation. As designed, the experiment will be cooled to less than 2 K in NASA's low temperature facility the LTMPF, allowing superconducting magnetic levitation in microgravity to obtain very soft, low-loss suspension of the test masses. The low-damping magnetic levitation, combined with a low-noise SQUID, leads to extremely low intrinsic noise in the detector. To minimize Newtonian errors, ISLES employs a near-null source of gravity, a circular disk of large diameter-to-thickness ratio. Two test masses, also disk-shaped, are suspended on the two sides of the source mass at a distance of 100 μm to 1 mm. The signal is detected by a superconducting differential accelerometer, making a highly sensitive sensor of the gravity force generated by the source mass

Topological inversion for solution of geodesy-constrained geophysical problems

Science.gov (United States)

Saltogianni, Vasso; Stiros, Stathis

2015-04-01

Geodetic data, mostly GPS observations, permit to measure displacements of selected points around activated faults and volcanoes, and on the basis of geophysical models, to model the underlying physical processes. This requires inversion of redundant systems of highly non-linear equations with >3 unknowns; a situation analogous to the adjustment of geodetic networks. However, in geophysical problems inversion cannot be based on conventional least-squares techniques, and is based on numerical inversion techniques (a priori fixing of some variables, optimization in steps with values of two variables each time to be regarded fixed, random search in the vicinity of approximate solutions). Still these techniques lead to solutions trapped in local minima, to correlated estimates and to solutions with poor error control (usually sampling-based approaches). To overcome these problems, a numerical-topological, grid-search based technique in the RN space is proposed (N the number of unknown variables). This technique is in fact a generalization and refinement of techniques used in lighthouse positioning and in some cases of low-accuracy 2-D positioning using Wi-Fi etc. The basic concept is to assume discrete possible ranges of each variable, and from these ranges to define a grid G in the RN space, with some of the gridpoints to approximate the true solutions of the system. Each point of hyper-grid G is then tested whether it satisfies the observations, given their uncertainty level, and successful grid points define a sub-space of G containing the true solutions. The optimal (minimal) space containing one or more solutions is obtained using a trial-and-error approach, and a single optimization factor. From this essentially deterministic identification of the set of gridpoints satisfying the system of equations, at a following step, a stochastic optimal solution is computed corresponding to the center of gravity of this set of gridpoints. This solution corresponds to a

A comparison of Horava-Lifshitz gravity and Einstein gravity through thin-shell wormhole construction

Energy Technology Data Exchange (ETDEWEB)

Rahaman, F [Department of Mathematics, Jadavpur University, Kolkata 700032 (India); Kuhfittig, P K F [Department of Mathematics, Milwaukee School of Engineering, Milwaukee, WI 53202-3109 (United States); Kalam, M [Department of Physics, Aliah University, Sector V, Salt Lake, Kolkata 700091 (India); Usmani, A A [Department of Physics, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh (India); Ray, S, E-mail: farook-rahaman@yahoo.com, E-mail: kuhfitti@msoe.edu, E-mail: mehedikalam@yahoo.co.in, E-mail: anisul@iucaa.ernet.in, E-mail: saibal@iucaa.ernet.in [Department of Physics, Govt College of Engineering and Ceramic Technology, Kolkata 700010 (India)

2011-08-07

In this paper, we have constructed a new class of thin-shell wormholes from black holes in Horava-Lifshitz gravity. Particular emphasis is placed on those aspects that allow a comparison of Horava-Lifshitz gravity to Einstein gravity. The former enjoys a number of advantages for small values of the throat radius.

Angle-domain inverse scattering migration/inversion in isotropic media

Science.gov (United States)

Li, Wuqun; Mao, Weijian; Li, Xuelei; Ouyang, Wei; Liang, Quan

2018-07-01

The classical seismic asymptotic inversion can be transformed into a problem of inversion of generalized Radon transform (GRT). In such methods, the combined parameters are linearly attached to the scattered wave-field by Born approximation and recovered by applying an inverse GRT operator to the scattered wave-field data. Typical GRT-style true-amplitude inversion procedure contains an amplitude compensation process after the weighted migration via dividing an illumination associated matrix whose elements are integrals of scattering angles. It is intuitional to some extent that performs the generalized linear inversion and the inversion of GRT together by this process for direct inversion. However, it is imprecise to carry out such operation when the illumination at the image point is limited, which easily leads to the inaccuracy and instability of the matrix. This paper formulates the GRT true-amplitude inversion framework in an angle-domain version, which naturally degrades the external integral term related to the illumination in the conventional case. We solve the linearized integral equation for combined parameters of different fixed scattering angle values. With this step, we obtain high-quality angle-domain common-image gathers (CIGs) in the migration loop which provide correct amplitude-versus-angle (AVA) behavior and reasonable illumination range for subsurface image points. Then we deal with the over-determined problem to solve each parameter in the combination by a standard optimization operation. The angle-domain GRT inversion method keeps away from calculating the inaccurate and unstable illumination matrix. Compared with the conventional method, the angle-domain method can obtain more accurate amplitude information and wider amplitude-preserved range. Several model tests demonstrate the effectiveness and practicability.

Focus on quantum Einstein gravity Focus on quantum Einstein gravity

Science.gov (United States)

Ambjorn, Jan; Reuter, Martin; Saueressig, Frank

2012-09-01

The gravitational asymptotic safety program summarizes the attempts to construct a consistent and predictive quantum theory of gravity within Wilson's generalized framework of renormalization. Its key ingredient is a non-Gaussian fixed point of the renormalization group flow which controls the behavior of the theory at trans-Planckian energies and renders gravity safe from unphysical divergences. Provided that the fixed point comes with a finite number of ultraviolet-attractive (relevant) directions, this construction gives rise to a consistent quantum field theory which is as predictive as an ordinary, perturbatively renormalizable one. This opens up the exciting possibility of establishing quantum Einstein gravity as a fundamental theory of gravity, without introducing supersymmetry or extra dimensions, and solely based on quantization techniques that are known to work well for the other fundamental forces of nature. While the idea of gravity being asymptotically safe was proposed by Steven Weinberg more than 30 years ago [1], the technical tools for investigating this scenario only emerged during the last decade. Here a key role is played by the exact functional renormalization group equation for gravity, which allows the construction of non-perturbative approximate solutions for the RG-flow of the gravitational couplings. Most remarkably, all solutions constructed to date exhibit a suitable non-Gaussian fixed point, lending strong support to the asymptotic safety conjecture. Moreover, the functional renormalization group also provides indications that the central idea of a non-Gaussian fixed point providing a safe ultraviolet completion also carries over to more realistic scenarios where gravity is coupled to a suitable matter sector like the standard model. These theoretical successes also triggered a wealth of studies focusing on the consequences of asymptotic safety in a wide range of phenomenological applications covering the physics of black holes, early

Axion like particles and the inverse seesaw mechanism

International Nuclear Information System (INIS)

Carvajal, C.D.R.; Dias, A.G.; Nishi, C.C.; Sánchez-Vega, B.L.

2015-01-01

Light pseudoscalars known as axion like particles (ALPs) may be behind physical phenomena like the Universe transparency to ultra-energetic photons, the soft γ-ray excess from the Coma cluster, and the 3.5 keV line. We explore the connection of these particles with the inverse seesaw (ISS) mechanism for neutrino mass generation. We propose a very restrictive setting where the scalar field hosting the ALP is also responsible for generating the ISS mass scales through its vacuum expectation value on gravity induced nonrenormalizable operators. A discrete gauge symmetry protects the theory from the appearance of overly strong gravitational effects and discrete anomaly cancellation imposes strong constraints on the order of the group. The anomalous U(1) symmetry leading to the ALP is an extended lepton number and the protective discrete symmetry can be always chosen as a subgroup of a combination of the lepton number and the baryon number.

Axion like particles and the inverse seesaw mechanism

Energy Technology Data Exchange (ETDEWEB)

Carvajal, C.D.R.; Dias, A.G. [Universidade Federal do ABC, Centro de Ciências Naturais e Humanas,Av. dos Estados, 5001, 09210-580, Santo André, SP (Brazil); Nishi, C.C. [Maryland Center for Fundamental Physics, University of Maryland,College Park, MD 20742 (United States); Universidade Federal do ABC, Centro de Matemática, Computação e Cognição,Av. dos Estados, 5001, 09210-580, Santo André, SP (Brazil); Sánchez-Vega, B.L. [Argonne National Laboratory,9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

2015-05-13

Light pseudoscalars known as axion like particles (ALPs) may be behind physical phenomena like the Universe transparency to ultra-energetic photons, the soft γ-ray excess from the Coma cluster, and the 3.5 keV line. We explore the connection of these particles with the inverse seesaw (ISS) mechanism for neutrino mass generation. We propose a very restrictive setting where the scalar field hosting the ALP is also responsible for generating the ISS mass scales through its vacuum expectation value on gravity induced nonrenormalizable operators. A discrete gauge symmetry protects the theory from the appearance of overly strong gravitational effects and discrete anomaly cancellation imposes strong constraints on the order of the group. The anomalous U(1) symmetry leading to the ALP is an extended lepton number and the protective discrete symmetry can be always chosen as a subgroup of a combination of the lepton number and the baryon number.

Basement-involved faults and deep structures in the West Philippine Basin: constrains from gravity field

Science.gov (United States)

Wang, Gang; Jiang, Suhua; Li, Sanzhong; Zhang, Huixuan; Lei, Jianping; Gao, Song; Zhao, Feiyu

2017-06-01

To reveal the basement-involved faults and deep structures of the West Philippine Basin (WPB), the gravitational responses caused by these faults are observed and analyzed based on the latest spherical gravity model: WGM2012 Model. By mapping the free-air and Bouguer gravity anomalies, several main faults and some other linear structures are located and observed in the WPB. Then, by conducting a 2D discrete multi-scale wavelet decomposition, the Bouguer anomalies are decomposed into the first- to eighth-order detail and approximation fields (the first- to eighth-order Details and Approximations). The first- to third-order Details reflect detailed and localized geological information of the crust at different depths, and of which the higher-order reflects gravity field of the deeper depth. The first- to fourth-order Approximations represent the regional gravity fields at different depths of the crust, respectively. The fourth-order Approximation represents the regional gravity fluctuation caused by the density inhomogeneity of Moho interface. Therefore, taking the fourth-order Approximation as input, and adopting Parker-Oldenburg interactive inversion, We calculated the depth of Moho interface in the WPB. Results show that the Moho interface depth in the WPB ranges approximately from 8 to 12 km, indicating that there is typical oceanic crust in the basin. In the Urdaneta Plateau and the Benham Rise, the Moho interface depths are about 14 and 16 km, respectively, which provides a piece of evidence to support that the Banham Rise could be a transitional crust caused by a large igneous province. The second-order vertical derivative and the horizontal derivatives in direction 0° and 90° are computed based on the data of the third-order Detail, and most of the basement-involved faults and structures in the WPB, such as the Central Basin Fault Zone, the Gagua Ridge, the Luzon-Okinawa Fault Zone, and the Mindanao Fault Zone are interpreted by the gravity derivatives.

Gravity a very short introduction

CERN Document Server

Clifton, Timothy

2017-01-01

Gravity is one of the four fundamental interactions that exist in nature. It also has the distinction of being the oldest, weakest, and most difficult force to quantize. Understanding gravity is not only essential for understanding the motion of objects on Earth, but also the motion of all celestial objects, and even the expansion of the Universe itself. It was the study of gravity that led Einstein to his profound realizations about the nature of space and time. Gravity is not only universal, it is also essential for understanding the behavior of the Universe, and all astrophysical bodies within it. In this Very Short Introduction Timothy Clifton looks at the development of our understanding of gravity since the early observations of Kepler and Newtonian theory. He discusses Einstein's theory of gravity, which now supplants Newton's, showing how it allows us to understand why the frequency of light changes as it passes through a gravitational field, why GPS satellites need their clocks corrected as they orbi...

Quantum Gravity

OpenAIRE

Alvarez, Enrique

2004-01-01

Gravitons should have momentum just as photons do; and since graviton momentum would cause compression rather than elongation of spacetime outside of matter; it does not appear that gravitons are compatible with Swartzchild's spacetime curvature. Also, since energy is proportional to mass, and mass is proportional to gravity; the energy of matter is proportional to gravity. The energy of matter could thus contract space within matter; and because of the inter-connectedness of space, cause the...

High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash area, Joshua Tree National Park, California

Science.gov (United States)

Langenheim, Victoria E.; Rymer, Michael J.; Catchings, Rufus D.; Goldman, Mark R.; Watt, Janet T.; Powell, Robert E.; Matti, Jonathan C.

2016-03-02

We describe high-resolution gravity and seismic refraction surveys acquired to determine the thickness of valley-fill deposits and to delineate geologic structures that might influence groundwater flow beneath the Smoke Tree Wash area in Joshua Tree National Park. These surveys identified a sedimentary basin that is fault-controlled. A profile across the Smoke Tree Wash fault zone reveals low gravity values and seismic velocities that coincide with a mapped strand of the Smoke Tree Wash fault. Modeling of the gravity data reveals a basin about 2–2.5 km long and 1 km wide that is roughly centered on this mapped strand, and bounded by inferred faults. According to the gravity model the deepest part of the basin is about 270 m, but this area coincides with low velocities that are not characteristic of typical basement complex rocks. Most likely, the density contrast assumed in the inversion is too high or the uncharacteristically low velocities represent highly fractured or weathered basement rocks, or both. A longer seismic profile extending onto basement outcrops would help differentiate which scenario is more accurate. The seismic velocities also determine the depth to water table along the profile to be about 40–60 m, consistent with water levels measured in water wells near the northern end of the profile.

Modular Extended-Stay HyperGravity Facility Design Concept: An Artificial-Gravity Space-Settlement Ground Analogue

Science.gov (United States)

Dorais, Gregory A.

2015-01-01

This document defines the design concept for a ground-based, extended-stay hypergravity facility as a precursor for space-based artificial-gravity facilities that extend the permanent presence of both human and non-human life beyond Earth in artificial-gravity settlements. Since the Earth's current human population is stressing the environment and the resources off-Earth are relatively unlimited, by as soon as 2040 more than one thousand people could be living in Earthorbiting artificial-gravity habitats. Eventually, the majority of humanity may live in artificialgravity habitats throughout this solar system as well as others, but little is known about the longterm (multi-generational) effects of artificial-gravity habitats on people, animals, and plants. In order to extend life permanently beyond Earth, it would be useful to create an orbiting space facility that generates 1g as well as other gravity levels to rigorously address the numerous challenges of such an endeavor. Before doing so, developing a ground-based artificial-gravity facility is a reasonable next step. Just as the International Space Station is a microgravity research facility, at a small fraction of the cost and risk a ground-based artificial-gravity facility can begin to address a wide-variety of the artificial-gravity life-science questions and engineering challenges requiring long-term research to enable people, animals, and plants to live off-Earth indefinitely.

A preliminary design of interior structure and foundation of an inflatable lunar habitat

Science.gov (United States)

Yin, Paul K.

1989-01-01

A preliminary structural design and analysis of an inflatable habitat for installation on the moon was completed. The concept takes the shape of a sphere with a diameter of approximately 16 meters. The interior framing provides five floor levels and is enclosed by a spherical air-tight membrane holding an interior pressure of 14.7 psi (101.4kpa). The spherical habitat is to be erected on the lunar surface with the lower one third below grade and the upper two thirds covered with a layer of lunar regolith for thermal insulation and shielding against radiation and meteoroids. The total dead weight (earth weight) of the structural aluminum, which is of vital interest for the costly space transportation, is presented. This structural dead weight represents a preliminary estimate without including structural details. The design results in two versions: one supports the weight of the radiation shielding in case of deflation of the fabric enclosure and the other assumes that the radiation shielding is self supporting. To gain some indication of the amount of structural materials needed if the identical habitat were installed on Mars and Earth, three additional design versions were generated where the only difference is in gravity. These additional design versions are highly academic since the difference will be much more than in gravity alone. The lateral loading due to dust storms on Mars and wind loads on Earth are some examples. The designs under the lunar gravity are realistic. They may not be adequate for final material procurement and fabrication, however, as the connection details, among other reasons, may effect the sizes of the structural members.

Interpretation of gravity and magnetic data with geological constraints for 3D structure of the Thuringian Basin, Germany

Science.gov (United States)

Prutkin, Ilya; Vajda, Peter; Jahr, Thomas; Bleibinhaus, Florian; Novák, Pavel; Tenzer, Robert

2017-01-01

We apply a novel method for the separation of potential field sources and their 3D inversion at the regional study area of Thuringian Basin in central Germany. The gravity and magnetic data are separated into long, medium and short wavelengths and then inverted separately. The main goal is to study uniqueness of the solution and its stability in all numerical steps of the interpretation process and to demonstrate, how geological constraints can diminish the degree of non-uniqueness by the interpretation of the gravity and magnetic anomalies. Our numerical experiments with medium wavelengths reveal that if we explain negative anomalies with the topography of near-surface layers, the obtained solution is not supported by borehole data. These negative anomalies are thus explained by restricted bodies (granitic intrusions) at the depths from 4 down to 10 km. These bodies are located above a density interface with topography at the depth of approximately 10 km. The 3D inversion of magnetic data (at short wavelengths) allows investigating a detailed structure of the upper boundary of the crystalline basement: two uplifts in the depths between 2.0 and 0.7 km are found. By using the residual negative anomalies we further study the salt tectonics, showing that the geometry of a salt pillow with a thickness of approximately 200 m closely agrees with borehole data.

Black holes in pure Lovelock gravities

International Nuclear Information System (INIS)

Cai Ronggen; Ohta, Nobuyoshi

2006-01-01

Lovelock gravity is a fascinating extension of general relativity, whose action consists of dimensionally extended Euler densities. Compared to other higher order derivative gravity theories, Lovelock gravity is attractive since it has a lot of remarkable features such as the fact that there are no more than second order derivatives with respect to the metric in its equations of motion, and that the theory is free of ghosts. Recently, in the study of black strings and black branes in Lovelock gravity, a special class of Lovelock gravity is considered, which is named pure Lovelock gravity, where only one Euler density term exists. In this paper we study black hole solutions in the special class of Lovelock gravity and associated thermodynamic properties. Some interesting features are found, which are quite different from the corresponding ones in general relativity

Active Response Gravity Offload System

Science.gov (United States)

Valle, Paul; Dungan, Larry; Cunningham, Thomas; Lieberman, Asher; Poncia, Dina

2011-01-01

The Active Response Gravity Offload System (ARGOS) provides the ability to simulate with one system the gravity effect of planets, moons, comets, asteroids, and microgravity, where the gravity is less than Earth fs gravity. The system works by providing a constant force offload through an overhead hoist system and horizontal motion through a rail and trolley system. The facility covers a 20 by 40-ft (approximately equals 6.1 by 12.2m) horizontal area with 15 ft (approximately equals4.6 m) of lifting vertical range.

Gravity model improvement investigation. [improved gravity model for determination of ocean geoid

Science.gov (United States)

Siry, J. W.; Kahn, W. D.; Bryan, J. W.; Vonbun, F. F.

1973-01-01

This investigation was undertaken to improve the gravity model and hence the ocean geoid. A specific objective is the determination of the gravity field and geoid with a space resolution of approximately 5 deg and a height resolution of the order of five meters. The concept of the investigation is to utilize both GEOS-C altimeter and satellite-to-satellite tracking data to achieve the gravity model improvement. It is also planned to determine the geoid in selected regions with a space resolution of about a degree and a height resolution of the order of a meter or two. The short term objectives include the study of the gravity field in the GEOS-C calibration area outlined by Goddard, Bermuda, Antigua, and Cape Kennedy, and also in the eastern Pacific area which is viewed by ATS-F.

Study of Seulawah Agam’s Geothermal Source Using Gravity Method

Directory of Open Access Journals (Sweden)

Marwan Marwan

2015-04-01

Full Text Available Gravity method was carried out at Seulawah Agam Area to delineate the existence of geothermal source, which is specifically existed in both the geothermal filed of Heutsz’s Crater and.Cempaga’s Crater. The Seulawah Agam is located in Aceh Besar district. Geologically, the area is dominated by volcanic mudflow and Lam Teuba’s rocks having age from Tersier to Resen Period. The equipment used includes Gravimeter CG-5 Autograv, Portable GPS (Global Positioning System, Navigation type (map of the survey area, computer and the other technical supports, such as handy talky, umbrella, watch, pens and observed data notes. This research was conducted by doing two stages.  Firstly, establishing the base station which is a reference point for all gravity data measurements at each point. Secondly, measuring gravity data at each point by repeating three times following looping pattern as pathway of measurement either in Heutsz’s crater whose nine points recording or in Cempaga’s crater whose seventeen points. The data was simply processed using Microsoft Excel that can just plot the Bouguer anomaly and interpreted qualitatively due to preliminary research. The resultof this research has shown that both areas have two kinds of Bougeur anomalies which slightly attract attention who’s high and low anomaly. At Heutsz’s Crater has high and low density existed at F125 FR and B6 point. The Point whose high density means that it was formed mineralization by hydrothermal process through fracture materials, meanwhile the point whose low density indicates that there is existed the fault which is quite related to Seulimum’s Fault based on Aceh map. This result is also same as obtained at Cempaga’s Crater which means also same interpretation. In addition, it can be sum up that fault zones are essentially important in geothermal system that plays vital role in term of fluid circulation. Employing the gravity method in this research effectively can be

UV caps, IR modification of gravity, and recovery of 4D gravity in regularized braneworlds

International Nuclear Information System (INIS)

Kobayashi, Tsutomu

2008-01-01

In the context of six-dimensional conical braneworlds we consider a simple and explicit model that incorporates long-distance modification of gravity and regularization of codimension-2 singularities. To resolve the conical singularities we replace the codimension-2 branes with ringlike codimension-1 branes, filling in the interiors with regular caps. The six-dimensional Planck scale in the cap is assumed to be much greater than the bulk Planck scale, which gives rise to the effect analogous to brane-induced gravity. Weak gravity on the regularized brane is studied in the case of a sharp conical bulk. We show by a linear analysis that gravity at short distances is effectively described by the four-dimensional Brans-Dicke theory, while the higher dimensional nature of gravity emerges at long distances. The linear analysis breaks down at some intermediate scale, below which four-dimensional Einstein gravity is shown to be recovered thanks to the second-order effects of the brane bending.

Quantum Gravity Effects in Cosmology

Directory of Open Access Journals (Sweden)

Gu Je-An

2018-01-01

Full Text Available Within the geometrodynamic approach to quantum cosmology, we studied the quantum gravity effects in cosmology. The Gibbons-Hawking temperature is corrected by quantum gravity due to spacetime fluctuations and the power spectrum as well as any probe field will experience the effective temperature, a quantum gravity effect.

Airborne Gravity: NGS' Gravity Data for the US and Territories (2008-2022) - National Geospatial Data Asset (NGDA) Airborne Gravity (GRAV-D)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Gravity for the Re-definition of the American Vertical Datum (GRAV-D) is a project initiated by NOAA's National Geodetic Survey to collect and monitor gravity data...

Urine specific gravity test

Science.gov (United States)

... medlineplus.gov/ency/article/003587.htm Urine specific gravity test To use the sharing features on this page, please enable JavaScript. Urine specific gravity is a laboratory test that shows the concentration ...

Northern Oklahoma Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (710 records) were compiled by Professor Ahern. This data base was received in June 1992. Principal gravity parameters include latitude,...

Preliminary isostatic gravity map of the Grouse Creek and east part of the Jackpot 30 by 60 quadrangles, Box Elder County, Utah, and Cassia County, Idaho

Science.gov (United States)

Langenheim, Victoria; Willis, H.; Athens, N.D.; Chuchel, Bruce A.; Roza, J.; Hiscock, H.I.; Hardwick, C.L.; Kraushaar, S.M.; Knepprath, N.E.; Rosario, Jose J.

2013-01-01

A new isostatic residual gravity map of the northwest corner of Utah is based on compilation of preexisting data and new data collected by the Utah and United States Geological Surveys. Pronounced gravity lows occur over Junction, Grouse Creek, and upper Raft River Valleys, indicating significant thickness of low-density Tertiary sedimentary rocks and deposits. Gravity highs coincide with exposures of dense pre-Cenozoic rocks in the Raft River Mountains. Higher values in the eastern part of the map may be produced in part by deeper crustal density variations or crustal thinning. Steep linear gravity gradients coincide with mapped Neogene normal faults near Goose Creek and may define basin-bounding faults concealed beneath Junction and Upper Raft River Valleys.

Humanoid Walking Robot: Modeling, Inverse Dynamics, and Gain Scheduling Control

Directory of Open Access Journals (Sweden)

Elvedin Kljuno

2010-01-01

Full Text Available This article presents reference-model-based control design for a 10 degree-of-freedom bipedal walking robot, using nonlinear gain scheduling. The main goal is to show concentrated mass models can be used for prediction of the required joint torques for a bipedal walking robot. Relatively complicated architecture, high DOF, and balancing requirements make the control task of these robots difficult. Although linear control techniques can be used to control bipedal robots, nonlinear control is necessary for better performance. The emphasis of this work is to show that the reference model can be a bipedal walking model with concentrated mass at the center of gravity, which removes the problems related to design of a pseudo-inverse system. Another significance of this approach is the reduced calculation requirements due to the simplified procedure of nominal joint torques calculation. Kinematic and dynamic analysis is discussed including results for joint torques and ground force necessary to implement a prescribed walking motion. This analysis is accompanied by a comparison with experimental data. An inverse plant and a tracking error linearization-based controller design approach is described. We propose a novel combination of a nonlinear gain scheduling with a concentrated mass model for the MIMO bipedal robot system.

A Robust, Gravity-Insensitive, High-Temperature Condenser for Water Recovery

Science.gov (United States)

Chen, Weibo; Conboy, Thomas; Ewert, Michael

2016-01-01

Regenerative life support systems are vital for NASA's future long-duration human space exploration missions. A Heat Melt Compactor (HMC) system is being developed by NASA to dry and compress trash generated during space missions. The resulting water vapor is recovered and separated from the process gas flow by a gravity-insensitive condenser. Creare is developing a high-temperature condenser for this application. The entire condenser is constructed from metals that have excellent resistance to chemical attack from contaminants and is suitable for high-temperature operation. The metal construction and design configuration also offer greatest flexibility for potential coating and regeneration processes to reduce biofilm growth and thus enhancing the reliability of the condenser. The proposed condenser builds on the gravity-insensitive phase separator technology Creare developed for aircraft and spacecraft applications. This paper will first discuss the design requirements for the condenser in an HMC system that will be demonstrated on the International Space Station (ISS). Then, it will present the overall design of the condenser and the preliminary thermal test results of a subscale condenser. Finally, this paper will discuss the predicted performance of the full-size condenser and the development plan to mature the technology and enhance its long-term reliability for a flight system.

Vaidya spacetime in massive gravity's rainbow

Directory of Open Access Journals (Sweden)

Yaghoub Heydarzade

2017-11-01

Full Text Available In this paper, we will analyze the energy dependent deformation of massive gravity using the formalism of massive gravity's rainbow. So, we will use the Vainshtein mechanism and the dRGT mechanism for the energy dependent massive gravity, and thus analyze a ghost free theory of massive gravity's rainbow. We study the energy dependence of a time-dependent geometry, by analyzing the radiating Vaidya solution in this theory of massive gravity's rainbow. The energy dependent deformation of this Vaidya metric will be performed using suitable rainbow functions.

Physics of Trans-Planckian Gravity

CERN Document Server

Dvali, Gia; Germani, Cristiano

2011-01-01

We study aspects of the phenomenon of gravitational UV-self-completeness and its implications for deformations of Einstein gravity. In a ghost-free theory flowing to Einstein gravity in the IR trans-Planckian propagating quantum degrees of freedom cannot exist. The only physical meaning of a trans-Planckian pole is the one of a classical state (Black Hole) which is fully described by the light IR quantum degrees of freedom and gives exponentially-suppressed contributions to virtual processes. In this sense Einstein gravity is UV self-complete, although not Wilsonian. We show that this UV/IR correspondence puts a severe constraint on any attempt of conventional Wilsonian UV-completion of trans-Planckian gravity. In particular, there is no well-defined energy domain in which gravity could become asymptotically weak or safe.

Stochastic Gravity: Theory and Applications

Directory of Open Access Journals (Sweden)

Hu Bei Lok

2008-05-01

Full Text Available Whereas semiclassical gravity is based on the semiclassical Einstein equation with sources given by the expectation value of the stress-energy tensor of quantum fields, stochastic semiclassical gravity is based on the Einstein–Langevin equation, which has, in addition, sources due to the noise kernel. The noise kernel is the vacuum expectation value of the (operator-valued stress-energy bitensor, which describes the fluctuations of quantum-matter fields in curved spacetimes. A new improved criterion for the validity of semiclassical gravity may also be formulated from the viewpoint of this theory. In the first part of this review we describe the fundamentals of this new theory via two approaches: the axiomatic and the functional. The axiomatic approach is useful to see the structure of the theory from the framework of semiclassical gravity, showing the link from the mean value of the stress-energy tensor to the correlation functions. The functional approach uses the Feynman–Vernon influence functional and the Schwinger–Keldysh closed-time-path effective action methods. In the second part, we describe three applications of stochastic gravity. First, we consider metric perturbations in a Minkowski spacetime, compute the two-point correlation functions of these perturbations and prove that Minkowski spacetime is a stable solution of semiclassical gravity. Second, we discuss structure formation from the stochastic-gravity viewpoint, which can go beyond the standard treatment by incorporating the full quantum effect of the inflaton fluctuations. Third, using the Einstein–Langevin equation, we discuss the backreaction of Hawking radiation and the behavior of metric fluctuations for both the quasi-equilibrium condition of a black-hole in a box and the fully nonequilibrium condition of an evaporating black hole spacetime. Finally, we briefly discuss the theoretical structure of stochastic gravity in relation to quantum gravity and point out

Active Response Gravity Offload and Method

Science.gov (United States)

Dungan, Larry K. (Inventor); Valle, Paul S. (Inventor); Bankieris, Derek R. (Inventor); Lieberman, Asher P. (Inventor); Redden, Lee (Inventor); Shy, Cecil (Inventor)

2015-01-01

A variable gravity field simulator can be utilized to provide three dimensional simulations for simulated gravity fields selectively ranging from Moon, Mars, and micro-gravity environments and/or other selectable gravity fields. The gravity field simulator utilizes a horizontally moveable carriage with a cable extending from a hoist. The cable can be attached to a load which experiences the effects of the simulated gravity environment. The load can be a human being or robot that makes movements that induce swinging of the cable whereby a horizontal control system reduces swinging energy. A vertical control system uses a non-linear feedback filter to remove noise from a load sensor that is in the same frequency range as signals from the load sensor.

Idaho State Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (24,284 records) were compiled by the U. S. Geological Survey. This data base was received on February 23, 1993. Principal gravity...

Physics of trans-Planckian gravity

International Nuclear Information System (INIS)

Dvali, Gia; Folkerts, Sarah; Germani, Cristiano

2011-01-01

We study the field theoretical description of a generic theory of gravity flowing to Einstein general relativity in IR. We prove that, if ghost-free, in the weakly-coupled regime such a theory can never become weaker than general relativity. Using this fact, as a by-product, we suggest that in a ghost-free theory of gravity trans-Planckian propagating quantum degrees of freedom cannot exist. The only physical meaning of a trans-Planckian pole is the one of a classical state (black hole) which is described by the light IR quantum degrees of freedom and gives exponentially-suppressed contributions to virtual processes. In this picture Einstein gravity is UV self-complete, although not Wilsonian, and sub-Planckian distances are unobservable in any healthy theory of gravity. We then finally show that this UV/IR correspondence puts a severe constraint on any attempt of conventional Wilsonian UV-completion of trans-Planckian gravity. Specifically, there is no well-defined energy domain in which gravity could become asymptotically weak or safe.

Preliminary isostatic residual gravity map of the Newfoundland Mountains 30' by 60' quadrangle and east part of the Wells 30' by 60' quadrangle, Box Elder County, Utah

Science.gov (United States)

Langenheim, Victoria; Athens, N.D.; Churchel, B.A.; Willis, H.; Knepprath, N.E.; Rosario, Jose J.; Roza, J.; Kraushaar, S.M.; Hardwick, C.L.

2013-01-01

A new isostatic residual gravity map of the Newfoundland Mountains and east of the Wells 30×60 quadrangles of Utah is based on compilation of preexisting data and new data collected by the Utah and U.S. Geological Surveys. Pronounced gravity lows occur over Grouse Creek Valley and locally beneath the Great Salt Lake Desert, indicating significant thickness of low-density Tertiary sedimentary rocks and deposits. Gravity highs coincide with exposures of dense pre-Cenozoic rocks in the Newfoundland, Silver Island, and Little Pigeon Mountains. Gravity values measured on pre-Tertiary basement to the north in the Bovine and Hogup Mountains are as much as 10mGal lower. Steep, linear gravity gradients may define basin-bounding faults concealed along the margins of the Newfoundland, Silver Island, and Little Pigeon Mountains, Lemay Island and the Pilot Range.

Andes 1997 Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Central Andes gravity data (6,151 records) were compiled by Professor Gotze and the MIGRA Group. This data base was received in April, 1997. Principal gravity...

Progress in the global standardization of gravity: an analysis of the Woollard and Rose international gravity values

International Nuclear Information System (INIS)

Woollard, G.P.; Godley, V.M.

1980-12-01

The history of improvements in the global standarization of gravity values since the advent of high range gravimeters in 1948 is reviewed. In particular the gravity base values given in SEG special publication International Gravity Measurements (Woolard and Rose, 1963) are evaluated against the most recent set of standarized gravity base values, The International Gravity Standardization Net, 1971 (Morelli et al, 1974). Adjunct IGSN 71 values prepared by the US Defense Mapping Agency Aerospace Center (unpublished) are also used to give a more comprehensive worldwide comparison of values

The Superheavy Elements and Anti-Gravity

International Nuclear Information System (INIS)

Anastasovski, Petar K.

2004-01-01

The essence of any propulsion concept is to overcome gravity. Anti-gravity is a natural means to achieve this. Thus, the technology to pursue anti-gravity, by using superheavy elements, may provide a new propulsion paradigm. The theory of superluminal relativity provides a hypothesis for existence of elements with atomic number up to Z = 145, some of which may possess anti-gravity properties. Analysis results show that curved space-time exists demonstrating both gravitic and anti-gravitic properties not only around nuclei but inside the nuclei as well. Two groups of elements (Z < 64 and 63 < Z <145) exist that demonstrate these capabilities. The nuclei of the first group of elements have the masses with only the property of gravity. The nuclei of the elements of the second group have the masses with both properties: gravity and anti-gravity in two different ranges of curved space-time around the nuclei.. The hypothetical element with Z = 145 is the unique among all elements whose nucleus has only anti-gravity property. It is proposed that this element be named Hawking, in honour of Stephen W. Hawking

Preliminary thermal design of the COLD-SAT spacecraft

Science.gov (United States)

Arif, Hugh

1991-01-01

The COLD-SAT free-flying spacecraft was to perform experiments with LH2 in the cryogenic fluid management technologies of storage, supply and transfer in reduced gravity. The Phase A preliminary design of the Thermal Control Subsystem (TCS) for the spacecraft exterior and interior surfaces and components of the bus subsystems is described. The TCS was composed of passive elements which were augmented with heaters. Trade studies to minimize the parasitic heat leakage into the cryogen storage tanks are described. Selection procedure for the thermally optimum on-orbit spacecraft attitude was defined. TRASYS-2 and SINDA'85 verification analysis was performed on the design and the results are presented.

Cadiz, California Gravity Data

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (32 records) were gathered by Mr. Seth I. Gutman for AridTech Inc., Denver, Colorado using a Worden Prospector gravity meter. This data base...

Integration of 3D geological modeling and gravity surveys for geothermal prospection in an Alpine region

Science.gov (United States)

Guglielmetti, L.; Comina, C.; Abdelfettah, Y.; Schill, E.; Mandrone, G.

2013-11-01

Thermal sources are common manifestations of geothermal energy resources in Alpine regions. The up-flow of the fluid is well-known to be often linked to cross-cutting fault zones providing a significant volume of fractures. Since conventional exploration methods are challenging in such areas of high topography and complicated logistics, 3D geological modeling based on structural investigation becomes a useful tool for assessing the overall geology of the investigated sites. Geological modeling alone is, however, less effective if not integrated with deep subsurface investigations that could provide a first order information on geological boundaries and an imaging of geological structures. With this aim, in the present paper the combined use of 3D geological modeling and gravity surveys for geothermal prospection of a hydrothermal area in the western Alps was carried out on two sites located in the Argentera Massif (NW Italy). The geothermal activity of the area is revealed by thermal anomalies with surface evidences, such as hot springs, at temperatures up to 70 °C. Integration of gravity measurements and 3D modeling investigates the potential of this approach in the context of geothermal exploration in Alpine regions where a very complex geological and structural setting is expected. The approach used in the present work is based on the comparison between the observed gravity and the gravity effect of the 3D geological models, in order to enhance local effects related to the geothermal system. It is shown that a correct integration of 3D modeling and detailed geophysical survey could allow a better characterization of geological structures involved in geothermal fluids circulation. Particularly, gravity inversions have successfully delineated the continuity in depth of low density structures, such as faults and fractured bands observed at the surface, and have been of great help in improving the overall geological model.

Extended Theories of Gravity

International Nuclear Information System (INIS)

Capozziello, Salvatore; De Laurentis, Mariafelicia

2011-01-01

Extended Theories of Gravity can be considered as a new paradigm to cure shortcomings of General Relativity at infrared and ultraviolet scales. They are an approach that, by preserving the undoubtedly positive results of Einstein’s theory, is aimed to address conceptual and experimental problems recently emerged in astrophysics, cosmology and High Energy Physics. In particular, the goal is to encompass, in a self-consistent scheme, problems like inflation, dark energy, dark matter, large scale structure and, first of all, to give at least an effective description of Quantum Gravity. We review the basic principles that any gravitational theory has to follow. The geometrical interpretation is discussed in a broad perspective in order to highlight the basic assumptions of General Relativity and its possible extensions in the general framework of gauge theories. Principles of such modifications are presented, focusing on specific classes of theories like f(R)-gravity and scalar–tensor gravity in the metric and Palatini approaches. The special role of torsion is also discussed. The conceptual features of these theories are fully explored and attention is paid to the issues of dynamical and conformal equivalence between them considering also the initial value problem. A number of viability criteria are presented considering the post-Newtonian and the post-Minkowskian limits. In particular, we discuss the problems of neutrino oscillations and gravitational waves in extended gravity. Finally, future perspectives of extended gravity are considered with possibility to go beyond a trial and error approach.

Global variations in gravity-derived oceanic crustal thickness: Implications on oceanic crustal accretion and hotspot-lithosphere interactions

Science.gov (United States)

Lin, J.; Zhu, J.

2012-12-01

We present a new global model of oceanic crustal thickness based on inversion of global oceanic gravity anomaly with constrains from seismic crustal thickness profiles. We first removed from the observed marine free-air gravity anomaly all gravitational effects that can be estimated and removed using independent constraints, including the effects of seafloor topography, marine sediment thickness, and the age-dependent thermal structure of the oceanic lithosphere. We then calculated models of gravity-derived crustal thickness through inversion of the residual mantle Bouguer anomaly using best-fitting gravity-modeling parameters obtained from comparison with seismically determined crustal thickness profiles. Modeling results show that about 5% of the global crustal volume (or 9% of the global oceanic surface area) is associated with model crustal thickness 8.6 km and is interpreted to have been affected by excess magmatism. The percentage of oceanic crustal volume that is associated with thick crustal thickness (>8.6 km) varies greatly among tectonic plates: Pacific (33%), Africa (50%), Antarctic (33%), Australia (30%), South America (34%), Nazca (23%), North America (47%), India (74%), Eurasia (68%), Cocos (20%), Philippine (26%), Scotia (41%), Caribbean (89%), Arabian (82%), and Juan de Fuca (21%). We also found that distribution of thickened oceanic crust (>8.6 km) seems to depend on spreading rate and lithospheric age: (1) On ocean basins younger than 5 Ma, regions of thickened crust are predominantly associated with slow and ultraslow spreading ridges. The relatively strong lithospheric plate at slow and ultraslow ridges might facilitate the loading of large magmatic emplacements on the plate. (2) In contrast, crustal thickness near fast and intermediately fast spreading ridges typically does not exceed 7-8 km. The relatively weak lithosphere at fast and intermediately fast ridges might make it harder for excess magmatism to accrete. We further speculate that

No slip gravity

Science.gov (United States)

Linder, Eric V.

2018-03-01

A subclass of the Horndeski modified gravity theory we call No Slip Gravity has particularly interesting properties: 1) a speed of gravitational wave propagation equal to the speed of light, 2) equality between the effective gravitational coupling strengths to matter and light, Gmatter and Glight, hence no slip between the metric potentials, yet difference from Newton's constant, and 3) suppressed growth to give better agreement with galaxy clustering observations. We explore the characteristics and implications of this theory, and project observational constraints. We also give a simple expression for the ratio of the gravitational wave standard siren distance to the photon standard candle distance, in this theory and others, and enable a direct comparison of modified gravity in structure growth and in gravitational waves, an important crosscheck.

Zero-gravity movement studies

Science.gov (United States)

Badler, N. I.; Fishwick, P.; Taft, N.; Agrawala, M.

1985-01-01

The use of computer graphics to simulate the movement of articulated animals and mechanisms has a number of uses ranging over many fields. Human motion simulation systems can be useful in education, medicine, anatomy, physiology, and dance. In biomechanics, computer displays help to understand and analyze performance. Simulations can be used to help understand the effect of external or internal forces. Similarly, zero-gravity simulation systems should provide a means of designing and exploring the capabilities of hypothetical zero-gravity situations before actually carrying out such actions. The advantage of using a simulation of the motion is that one can experiment with variations of a maneuver before attempting to teach it to an individual. The zero-gravity motion simulation problem can be divided into two broad areas: human movement and behavior in zero-gravity, and simulation of articulated mechanisms.

Global detailed gravimetric geoid. [based on gravity model derived from satellite tracking and surface gravity data

Science.gov (United States)

Vincent, S.; Marsh, J. G.

1973-01-01

A global detailed gravimetric geoid has been computed by combining the Goddard Space Flight Center GEM-4 gravity model derived from satellite and surface gravity data and surface 1 deg-by-1 deg mean free air gravity anomaly data. The accuracy of the geoid is + or - 2 meters on continents, 5 to 7 meters in areas where surface gravity data are sparse, and 10 to 15 meters in areas where no surface gravity data are available. Comparisons have been made with the astrogeodetic data provided by Rice (United States), Bomford (Europe), and Mather (Australia). Comparisons have also been carried out with geoid heights derived from satellite solutions for geocentric station coordinates in North America, the Caribbean, Europe, and Australia.

Partial gravity - Human impacts on facility design

Science.gov (United States)

Capps, Stephen; Moore, Nathan

1990-01-01

Partial gravity affects the body differently than earth gravity and microgravity environments. The main difference from earth gravity is human locomotion; while the main dfference from microgravity is the specific updown orientation and reach envelopes which increase volume requirements. Much data are available on earth gravity and microgravity design; however, very little information is available on human reactions to reduced gravity levels in IVA situations (without pressure suits). Therefore, if humans commit to permanent lunar habitation, much research should be conducted in the area of partial gravity effects on habitat design.

Inversions

Science.gov (United States)

Brown, Malcolm

2009-01-01

Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…

Generalized uncertainty principle, quantum gravity and Horava-Lifshitz gravity

International Nuclear Information System (INIS)

Myung, Yun Soo

2009-01-01

We investigate a close connection between generalized uncertainty principle (GUP) and deformed Horava-Lifshitz (HL) gravity. The GUP commutation relations correspond to the UV-quantum theory, while the canonical commutation relations represent the IR-quantum theory. Inspired by this UV/IR quantum mechanics, we obtain the GUP-corrected graviton propagator by introducing UV-momentum p i =p 0i (1+βp 0 2 ) and compare this with tensor propagators in the HL gravity. Two are the same up to p 0 4 -order.

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

Science.gov (United States)

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

2009-01-01

We perform a test of gravity on large scales (5-50 Mpc/h) using 70,000 luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) DR7 with redshifts 0.16gravity and is largely independent of galaxy bias and sigma_8. In particular, E_G is sensitive to the relation between the spatial and temporal scalar perturbations in the space-time metric. While these two potentials are equivalent in concordance cosmology (GR+LCDM) in the absence of anisotropic stress, they are not equivalent in alternative theories of gravity in general, so that different models make different predictions for E_G. We find E_G=0.37±0.05 averaged over scales 5preliminary predictions from modified gravity theories, including f(R), DGP, and TeVeS. This work serves as a proof of concept for the application of this test in future galaxy surveys such as LSST, for which a very high signal-to-noise measurement will be possible.

Quantum W3 gravity

International Nuclear Information System (INIS)

Schoutens, K.; van Nieuwenhuizen, P.; State Univ. of New York, Stony Brook, NY

1991-11-01

We briefly review some results in the theory of quantum W 3 gravity in the chiral gauge. We compare them with similar results in the analogous but simpler cases of d = 2 induced gauge theories and d = 2 induced gravity

3D depth-to-basement and density contrast estimates using gravity and borehole data

Science.gov (United States)

Barbosa, V. C.; Martins, C. M.; Silva, J. B.

2009-05-01

We present a gravity inversion method for simultaneously estimating the 3D basement relief of a sedimentary basin and the parameters defining the parabolic decay of the density contrast with depth in a sedimentary pack assuming the prior knowledge about the basement depth at a few points. The sedimentary pack is approximated by a grid of 3D vertical prisms juxtaposed in both horizontal directions, x and y, of a right-handed coordinate system. The prisms' thicknesses represent the depths to the basement and are the parameters to be estimated from the gravity data. To produce stable depth-to-basement estimates we impose smoothness on the basement depths through minimization of the spatial derivatives of the parameters in the x and y directions. To estimate the parameters defining the parabolic decay of the density contrast with depth we mapped a functional containing prior information about the basement depths at a few points. We apply our method to synthetic data from a simulated complex 3D basement relief with two sedimentary sections having distinct parabolic laws describing the density contrast variation with depth. Our method retrieves the true parameters of the parabolic law of density contrast decay with depth and produces good estimates of the basement relief if the number and the distribution of boreholes are sufficient. We also applied our method to real gravity data from the onshore and part of the shallow offshore Almada Basin, on Brazil's northeastern coast. The estimated 3D Almada's basement shows geologic structures that cannot be easily inferred just from the inspection of the gravity anomaly. The estimated Almada relief presents steep borders evidencing the presence of gravity faults. Also, we note the existence of three terraces separating two local subbasins. These geologic features are consistent with Almada's geodynamic origin (the Mesozoic breakup of Gondwana and the opening of the South Atlantic Ocean) and they are important in understanding

Radion and holographic brane gravity

International Nuclear Information System (INIS)

Kanno, Sugumi; Soda, Jiro

2002-01-01

The low energy effective theory for the Randall-Sundrum two-brane system is investigated with an emphasis on the role of the nonlinear radion in the brane world. The equations of motion in the bulk are solved using a low energy expansion method. This allows us, through the junction conditions, to deduce the effective equations of motion for gravity on the brane. It is shown that the gravity on the brane world is described by a quasi-scalar-tensor theory with a specific coupling function ω(Ψ)=3Ψ/2(1-Ψ) on the positive tension brane and ω(Φ)=-3Φ/2(1+Φ) on the negative tension brane, where Ψ and Φ are nonlinear realizations of the radion on the positive and negative tension branes, respectively. In contrast with the usual scalar-tensor gravity, the quasi-scalar-tensor gravity couples with two kinds of matter; namely, the matter on both positive and negative tension branes, with different effective gravitational coupling constants. In particular, the radion disguised as the scalar fields Ψ and Φ couples with the sum of the traces of the energy-momentum tensor on both branes. In the course of the derivation, it is revealed that the radion plays an essential role in converting the nonlocal Einstein gravity with generalized dark radiation to local quasi-scalar-tensor gravity. For completeness, we also derive the effective action for our theory by substituting the bulk solution into the original action. It is also shown that quasi-scalar-tensor gravity works as a hologram at low energy in the sense that the bulk geometry can be reconstructed from the solution of quasi-scalar-tensor gravity

Failures in sand in reduced gravity environments

Science.gov (United States)

Marshall, Jason P.; Hurley, Ryan C.; Arthur, Dan; Vlahinic, Ivan; Senatore, Carmine; Iagnemma, Karl; Trease, Brian; Andrade, José E.

2018-04-01

The strength of granular materials, specifically sand is important for understanding physical phenomena on other celestial bodies. However, relatively few experiments have been conducted to determine the dependence of strength properties on gravity. In this work, we experimentally investigated relative values of strength (the peak friction angle, the residual friction angle, the angle of repose, and the peak dilatancy angle) in Earth, Martian, Lunar, and near-zero gravity. The various angles were captured in a classical passive Earth pressure experiment conducted on board a reduced gravity flight and analyzed using digital image correlation. The data showed essentially no dependence of the peak friction angle on gravity, a decrease in the residual friction angle between Martian and Lunar gravity, no dependence of the angle of repose on gravity, and an increase in the dilation angle between Martian and Lunar gravity. Additionally, multiple flow surfaces were seen in near-zero gravity. These results highlight the importance of understanding strength and deformation mechanisms of granular materials at different levels of gravity.

Basement characterization and crustal structure beneath the Arabia-Eurasia collision (Iran): A combined gravity and magnetic study

Science.gov (United States)

Mousavi, Naeim; Ebbing, Jörg

2018-04-01

We present a study on the depth to basement and magnetic crustal domains beneath the Iranian Plateau by modeling aeromagnetic and gravity data. First, field processing of the aeromagnetic data was undertaken to estimate the general characteristics of the magnetic basement. Afterwards, inverse modeling of aeromagnetic data was carried out to estimate the depth to basement. The obtained model of basement was refined using combined gravity and magnetic forward modeling. Hereby, we were able to distinguish different magnetic domains in the uppermost crust (10-20 km depths) influencing the medium to long wavelength trends of the magnetic anomalies. Magnetic basement mapping shows that prominent shallow magnetic features are furthermore located in the volcanic areas, e.g. the Urumieh Dokhtar Magmatic Assemblage. The presence of ophiolite outcrops in SE Iran implies that shallow oceanic crust (with high magnetization) is the main source of one of the biggest magnetic anomalies in entire Iran area located north of the Makran.

Topological gravity with minimal matter

International Nuclear Information System (INIS)

Li Keke

1991-01-01

Topological minimal matter, obtained by twisting the minimal N = 2 supeconformal field theory, is coupled to two-dimensional topological gravity. The free field formulation of the coupled system allows explicit representations of BRST charge, physical operators and their correlation functions. The contact terms of the physical operators may be evaluated by extending the argument used in a recent solution of topological gravity without matter. The consistency of the contact terms in correlation functions implies recursion relations which coincide with the Virasoro constraints derived from the multi-matrix models. Topological gravity with minimal matter thus provides the field theoretic description for the multi-matrix models of two-dimensional quantum gravity. (orig.)

Teleparallel equivalent of Lovelock gravity

Science.gov (United States)

González, P. A.; Vásquez, Yerko

2015-12-01

There is a growing interest in modified gravity theories based on torsion, as these theories exhibit interesting cosmological implications. In this work inspired by the teleparallel formulation of general relativity, we present its extension to Lovelock gravity known as the most natural extension of general relativity in higher-dimensional space-times. First, we review the teleparallel equivalent of general relativity and Gauss-Bonnet gravity, and then we construct the teleparallel equivalent of Lovelock gravity. In order to achieve this goal, we use the vielbein and the connection without imposing the Weitzenböck connection. Then, we extract the teleparallel formulation of the theory by setting the curvature to null.

Revisiting the real graviton effects at CERN LHC within the quantum gravity theory with large extra dimensions

International Nuclear Information System (INIS)

Wu Xinggang; Fang Zhenyun

2008-01-01

CERN LHC provides a good experimental platform to perturbatively probe the fundamental gravity scale up to several TeV, with the precise value depending on the number of extra dimensions. The leading experimental signal of the graviton at the LHC is from the process pp→jet+Ee T , where Ee T stands for the transverse missing energy. A detailed discussion on the hadronic production of the real graviton through hard subprocesses: qq→G+g, g+q→G+q, and g+g→G+g have been studied within the quantum gravity theory with large extra dimensions. The main theoretical uncertainties together with the dominant standard model background to these processes, e.g. qq→Z 0 +g and g+q→Z 0 +q with Z 0 further decaying into neutrinos, have also been discussed. It is found that only in a certain jet energy region and with a certain number of extra dimensions can the quantum gravity signal be distinguished from the background, which inversely lead to the effective scale M D to be probed up to (8.8±0.9) TeV for two extra dimensions and (5.9±0.5) TeV for four extra dimensions with sufficient integrated luminosity, e.g. 100 fb -1 , at CERN LHC.

What Is Gravity?

Science.gov (United States)

Nelson, George

2004-01-01

Gravity is the name given to the phenomenon that any two masses, like you and the Earth, attract each other. One pulls on the Earth and the Earth pulls on one the same amount. And one does not have to be touching. Gravity acts over vast distances, like the 150 million kilometers (93 million miles) between the Earth and the Sun or the billions of…

Conformal symmetry and nonlinear extensions of nonlocal gravity

CERN Document Server

Cusin, Giulia; Maggiore, Michele; Mancarella, Michele

2016-01-01

We study two nonlinear extensions of the nonlocal $R\\,\\Box^{-2}R$ gravity theory. We extend this theory in two different ways suggested by conformal symmetry, either replacing $\\Box^{-2}$ with $(-\\Box + R/6)^{-2}$, which is the operator that enters the action for a conformally-coupled scalar field, or replacing $\\Box^{-2}$ with the inverse of the Paneitz operator, which is a four-derivative operator that enters in the effective action induced by the conformal anomaly. We show that the former modification gives an interesting and viable cosmological model, with a dark energy equation of state today $w_{\\rm DE}\\simeq -1.01$, which very closely mimics $\\Lambda$CDM and evolves asymptotically into a de Sitter solution. The model based on the Paneitz operator seems instead excluded by the comparison with observations. We also review some issues about the causality of nonlocal theories, and we point out that these nonlocal models can be modified so to nicely interpolate between Starobinski inflation in the primordia...

Human manual control performance in hyper-gravity.

Science.gov (United States)

Clark, Torin K; Newman, Michael C; Merfeld, Daniel M; Oman, Charles M; Young, Laurence R

2015-05-01

Hyper-gravity provides a unique environment to study how misperceptions impact control of orientation relative to gravity. Previous studies have found that static and dynamic roll tilts are perceptually overestimated in hyper-gravity. The current investigation quantifies how this influences control of orientation. We utilized a long-radius centrifuge to study manual control performance in hyper-gravity. In the dark, subjects were tasked with nulling out a pseudo-random roll disturbance on the cab of the centrifuge using a rotational hand controller to command their roll rate in order to remain perceptually upright. The task was performed in 1, 1.5, and 2 G's of net gravito-inertial acceleration. Initial performance, in terms of root-mean-square deviation from upright, degraded in hyper-gravity relative to 1 G performance levels. In 1.5 G, initial performance degraded by 26 % and in 2 G, by 45 %. With practice, however, performance in hyper-gravity improved to near the 1 G performance level over several minutes. Finally, pre-exposure to one hyper-gravity level reduced initial performance decrements in a different, novel, hyper-gravity level. Perceptual overestimation of roll tilts in hyper-gravity leads to manual control performance errors, which are reduced both with practice and with pre-exposure to alternate hyper-gravity stimuli.

Centrifuge modelling of granular flows

Science.gov (United States)

Cabrera, Miguel Angel; Wu, Wei

2015-04-01

A common characteristic of mass flows like debris flows, rock avalanches and mudflows is that gravity is their main driving force. Gravity defines the intensity and duration of the main interactions between particles and their surrounding media (particle-particle, particle-fluid, fluid-fluid). At the same time, gravity delimits the occurrence of phase separation, inverse segregation, and mass consolidation, among other phenomena. Therefore, in the understanding of the flow physics it is important to account for the scaling of gravity in scaled models. In this research, a centrifuge model is developed to model free surface granular flows down an incline at controlled gravity conditions. Gravity is controlled by the action of an induced inertial acceleration field resulting from the rotation of the model in a geotechnical centrifuge. The characteristics of the induced inertial acceleration field during flow are discussed and validated via experimental data. Flow heights, velocity fields, basal pressure and impact forces are measured for a range of channel inclinations and gravity conditions. Preliminary results enlighten the flow characteristics at variable gravity conditions and open a discussion on the simulation of large scale processes at a laboratory scale. Further analysis on the flow physics brings valuable information for the validation of granular flows rheology.

Gravity/Fluid Correspondence and Its Application on Bulk Gravity with U(1) Gauge Field

International Nuclear Information System (INIS)

Hu, Ya-Peng; Zhang, Jian-Hui

2014-01-01

As the long wavelength limit of the AdS/CFT correspondence, the gravity/fluid correspondence has been shown to be a useful tool for extracting properties of the fluid on the boundary dual to the gravity in the bulk. In this paper, after briefly reviewing the algorithm of gravity/fluid correspondence, we discuss the results of its application on bulk gravity with a U(1) gauge field. In the presence of a U(1) gauge field, the dual fluid possesses more interesting properties such as its charge current. Furthermore, an external field A_μ"e"x"t could affect the charge current, and the U(1) Chern-Simons term also induces extra structures to the dual current giving anomalous transport coefficients.

Moho depth variations over the Maldive Ridge and adjoining Arabian and Central Indian Basins, Western Indian Ocean, from three dimensional inversion of gravity anomalies

Science.gov (United States)

Kunnummal, Priyesh; Anand, S. P.; Haritha, C.; Rama Rao, P.

2018-05-01

Analysis of high resolution satellite derived free air gravity data has been undertaken in the Greater Maldive Ridge (GMR) (Maldive Ridge, Deep Sea Channel, northern limit of Chagos Bank) segment of the Chagos Laccadive Ridge and the adjoining Arabian and Central Indian Basins. A Complete Bouguer Anomaly (CBA) map was generated from the Indian Ocean Geoidal Low removed Free Air Gravity (hereinafter referred to as "FAG-IOGL") data by incorporating Bullard A, B and C corrections. Using the Parker method, Moho topography was initially computed by inverting the CBA data. From the CBA the Mantle Residual Gravity Anomalies (MRGA) were computed by incorporating gravity effects of sediments and lithospheric temperature and pressure induced anomalies. Further, the MRGA was inverted to get Moho undulations from which the crustal thickness was also estimated. It was found that incorporating the lithospheric thermal and pressure anomaly correction has provided substantial improvement in the computed Moho depths especially in the oceanic areas. But along the GMR, there was not much variation in the Moho thickness computed with and without the thermal and pressure gravity correction implying that the crustal thickness of the ridge does not depend on the oceanic isochrones used for the thermal corrections. The estimated Moho depths in the study area ranges from 7 km to 28 km and the crustal thickness from 2 km to 27 km. The Moho depths are shallower in regions closer to Central Indian Ridge in the Arabian Basin i.e., the region to the west of the GMR is thinner compared to the region in the east (Central Indian Basin). The thickest crust and the deepest Moho are found below the N-S trending GMR segment of the Chagos-Laccadive Ridge. Along the GMR the crustal thickness decreases from north to south with thickness of 27 km below the Maldives Ridge reducing to ∼9 km at 3°S and further increasing towards Chagos Bank. Even though there are similarities in crustal thickness between

Gravity and strings

CERN Document Server

Ortín, Tomás

2015-01-01

Self-contained and comprehensive, this definitive new edition of Gravity and Strings is a unique resource for graduate students and researchers in theoretical physics. From basic differential geometry through to the construction and study of black-hole and black-brane solutions in quantum gravity - via all the intermediate stages - this book provides a complete overview of the intersection of gravity, supergravity, and superstrings. Now fully revised, this second edition covers an extensive array of topics, including new material on non-linear electric-magnetic duality, the electric-tensor formalism, matter-coupled supergravity, supersymmetric solutions, the geometries of scalar manifolds appearing in 4- and 5-dimensional supergravities, and much more. Covering reviews of important solutions and numerous solution-generating techniques, and accompanied by an exhaustive index and bibliography, this is an exceptional reference work.

Recent advancements in conformal gravity

International Nuclear Information System (INIS)

O’Brien, James G.; Chaykov, Spasen S.; Moss, Robert J.; Dentico, Jeremy; Stulge, Modestas; Stefanski, Brian

2017-01-01

In recent years, due to the lack of direct observed evidence of cold dark matter, coupled with the shrinking parameter space to search for new dark matter particles, there has been increased interest in Alternative Gravitational theories. This paper, addresses three recent advances in conformal gravity, a fourth order renormalizable metric theory of gravitation originally formulated by Weyl, and later advanced by Mannheim and Kazanas. The first section of the paper applies conformal gravity to the rotation curves of the LITTLE THINGS survey, extending the total number of rotation curves successfully fit by conformal gravity to well over 200 individual data sets without the need for additional dark matter. Further, in this rotation curve study, we show how MOND and conformal gravity compare for each galaxy in the sample. Second, we look at the original Zwicky problem of applying the virial theorem to the Coma cluster in order to get an estimate for the cluster mass. However, instead of using the standard Newtonian potential, here we use the weak field approximation of conformal gravity. We show that in the conformal case we can get a much smaller mass estimate and thus there is no apparent need to include dark matter. We then show that this calculation is in agreement with the observational data from other well studied clusters. Last, we explore the calculation of the deflection of starlight through conformal gravity, as a first step towards applying conformal gravity to gravitaitonal lensing. (paper)

Effect of External Disturbing Gravity Field on Spacecraft Guidance and Surveying Line Layout for Marine Gravity Survey

Directory of Open Access Journals (Sweden)

HUANG Motao

2016-11-01

Full Text Available Centred on the support requirement of flying track control for a long range spacecraft, a detail research is made on the computation of external disturbing gravity field, the survey accuracy of gravity anomaly on the earth' surface and the program of surveying line layout for marine gravity survey. Firstly, the solution expression of navigation error for a long range spacecraft is analyzed and modified, and the influence of the earth's gravity field on flying track of spacecraft is evaluated. Then with a given limited quota of biased error of spacecraft drop point, the accuracy requirement for calculating the external disturbing gravity field is discussed and researched. Secondly, the data truncation error and the propagated data error are studied and estimated, and the quotas of survey resolution and computation accuracy for gravity anomaly on the earth' surface are determined. Finally, based on the above quotas, a corresponding program of surveying line layout for marine gravity survey is proposed. A numerical test has been made to prove the reasonableness and validity of the suggested program.

Newton-Cartan gravity revisited

NARCIS (Netherlands)

Andringa, Roel

2016-01-01

In this research Newton's old theory of gravity is rederived using an algebraic approach known as the gauging procedure. The resulting theory is Newton's theory in the mathematical language of Einstein's General Relativity theory, in which gravity is spacetime curvature. The gauging procedure sheds

Testing Gravity via Lunar Laser Ranging: Maximizing Data Quality

Science.gov (United States)

Murphy, Thomas

We propose to continue leading-edge observations with the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO), in an effort to subject gravity to the most stringent tests yet. APOLLO has delivered a dramatic improvement in the measurement of the lunar orbit: now at the millimeter level. Yet incomplete models are thus far unable to confirm the accuracy. We therefore seek to build a calibration system to ensure that APOLLO meets its millimeter measurement goal. Gravity--the most evident force of nature--is in fact the weakest of the fundamental forces, and consequently the most poorly tested. Einstein’s general relativity, which is currently our best description of gravity, is fundamentally incompatible with quantum mechanics and is likely to be replaced by a more complete theory in the future. A modified theory would predict small deviations in the solar system that could have profound consequences for our understanding of the Universe as a whole. Lunar laser ranging (LLR), in which short laser pulses launched from a telescope are bounced off of reflectors placed on the Moon by U.S. astronauts and Soviet landers, has for decades produced some of the leading tests of gravity by mapping the shape of the lunar orbit to high precision. These include tests of the strong equivalence principle, the time-rate-ofchange of Newton’s gravitational constant, gravitomagnetism, the inverse-square law, and many others. Among the attributes that contribute to APOLLO’s superior observations, routine ranging to all five lunar reflectors on timescales of minutes dramatically improves our ability to gauge lunar orientation and body distortion. This information produces insights into the interior structure and dynamics of the Moon, allowing a more precise determination of the path for the Moon’s center of mass, lending to tests of fundamental gravity. Simultaneously, higher precision range measurements, together with data from a superconducting gravimeter at the

Horizon thermodynamics in fourth-order gravity

Directory of Open Access Journals (Sweden)

Meng-Sen Ma

2017-03-01

Full Text Available In the framework of horizon thermodynamics, the field equations of Einstein gravity and some other second-order gravities can be rewritten as the thermodynamic identity: dE=TdS−PdV. However, in order to construct the horizon thermodynamics in higher-order gravity, we have to simplify the field equations firstly. In this paper, we study the fourth-order gravity and convert it to second-order gravity via a so-called “Legendre transformation” at the cost of introducing two other fields besides the metric field. With this simplified theory, we implement the conventional procedure in the construction of the horizon thermodynamics in 3 and 4 dimensional spacetime. We find that the field equations in the fourth-order gravity can also be written as the thermodynamic identity. Moreover, we can use this approach to derive the same black hole mass as that by other methods.

Adaptive topographic mass correction for satellite gravity and gravity gradient data

Science.gov (United States)

Holzrichter, Nils; Szwillus, Wolfgang; Götze, Hans-Jürgen

2014-05-01

Subsurface modelling with gravity data includes a reliable topographic mass correction. Since decades, this mandatory step is a standard procedure. However, originally methods were developed for local terrestrial surveys. Therefore, these methods often include defaults like a limited correction area of 167 km around an observation point, resampling topography depending on the distance to the station or disregard the curvature of the earth. New satellite gravity data (e.g. GOCE) can be used for large scale lithospheric modelling with gravity data. The investigation areas can include thousands of kilometres. In addition, measurements are located in the flight height of the satellite (e.g. ~250 km for GOCE). The standard definition of the correction area and the specific grid spacing around an observation point was not developed for stations located in these heights and areas of these dimensions. This asks for a revaluation of the defaults used for topographic correction. We developed an algorithm which resamples the topography based on an adaptive approach. Instead of resampling topography depending on the distance to the station, the grids will be resampled depending on its influence at the station. Therefore, the only value the user has to define is the desired accuracy of the topographic correction. It is not necessary to define the grid spacing and a limited correction area. Furthermore, the algorithm calculates the topographic mass response with a spherical shaped polyhedral body. We show examples for local and global gravity datasets and compare the results of the topographic mass correction to existing approaches. We provide suggestions how satellite gravity and gradient data should be corrected.

Scaling in quantum gravity

Directory of Open Access Journals (Sweden)

J. Ambjørn

1995-07-01

Full Text Available The 2-point function is the natural object in quantum gravity for extracting critical behavior: The exponential falloff of the 2-point function with geodesic distance determines the fractal dimension dH of space-time. The integral of the 2-point function determines the entropy exponent γ, i.e. the fractal structure related to baby universes, while the short distance behavior of the 2-point function connects γ and dH by a quantum gravity version of Fisher's scaling relation. We verify this behavior in the case of 2d gravity by explicit calculation.

Venus gravity - Analysis of Beta Regio

Science.gov (United States)

Esposito, P. B.; Sjogren, W. L.; Mottinger, N. A.; Bills, B. G.; Abbott, E.

1982-01-01

Radio tracking data acquired over Beta Regio were analyzed to obtain a surface mass distribution from which a detailed vertical gravity field was derived. In addition, a corresponding vertical gravity field was evaluated solely from the topography of the Beta region. A comparison of these two maps confirms the strong correlation between gravity and topography which was previously seen in line-of-sight gravity maps. It also demonstrates that the observed gravity is a significant fraction of that predicted from the topography alone. The effective depth of complete isostatic compensation for the Beta region is estimated to be 330 km, which is somewhat deeper than that found for other areas of Venus.

Effects of gravity in folding

Science.gov (United States)

Minkel, Donald Howe

Effects of gravity on buckle folding are studied using a Newtonian fluid finite element model of a single layer embedded between two thicker less viscous layers. The methods allow arbitrary density jumps, surface tension coefficients, resistance to slip at the interfaces, and tracking of fold growth to a large amplitudes. When density increases downward in two equal jumps, a layer buckles less and thickens more than with uniform density. When density increases upward in two equal jumps, it buckles more and thickens less. A low density layer with periodic thickness variations buckles more, sometimes explosively. Thickness variations form, even if not present initially. These effects are greater with; smaller viscosities, larger density jump, larger length scale, and slower shortening rate. They also depend on wavelength and amplitude, and these dependencies are described in detail. The model is applied to the explosive growth of the salt anticlines of the Paradox Basin, Colorado and Utah. There, shale (higher density) overlies salt (lower density). Methods for simulating realistic earth surface erosion and deposition conditions are introduced. Growth rates increase both with ease of slip at the salt-shale interface, and when earth surface relief stays low due to erosion and deposition. Model anticlines grow explosively, attaining growth rates and amplitudes close to those of the field examples. Fastest growing wavelengths are the same as seen in the field. It is concluded that a combination of partial-slip at the salt-shale interface, with reasonable earth surface conditions, promotes sufficiently fast buckling of the salt-shale interface due to density inversion alone. Neither basement faulting, nor tectonic shortening is required to account for the observed structures. Of fundamental importance is the strong tendency of gravity to promote buckling in low density layers with thickness variations. These develop, even if not present initially.

Consistency of orthodox gravity

Energy Technology Data Exchange (ETDEWEB)

Bellucci, S. [INFN, Frascati (Italy). Laboratori Nazionali di Frascati; Shiekh, A. [International Centre for Theoretical Physics, Trieste (Italy)

1997-01-01

A recent proposal for quantizing gravity is investigated for self consistency. The existence of a fixed-point all-order solution is found, corresponding to a consistent quantum gravity. A criterion to unify couplings is suggested, by invoking an application of their argument to more complex systems.

BOOK REVIEW: Canonical Gravity and Applications: Cosmology, Black Holes, and Quantum Gravity Canonical Gravity and Applications: Cosmology, Black Holes, and Quantum Gravity

Science.gov (United States)

Husain, Viqar

2012-03-01

Research on quantum gravity from a non-perturbative 'quantization of geometry' perspective has been the focus of much research in the past two decades, due to the Ashtekar-Barbero Hamiltonian formulation of general relativity. This approach provides an SU(2) gauge field as the canonical configuration variable; the analogy with Yang-Mills theory at the kinematical level opened up some research space to reformulate the old Wheeler-DeWitt program into what is now known as loop quantum gravity (LQG). The author is known for his work in the LQG approach to cosmology, which was the first application of this formalism that provided the possibility of exploring physical questions. Therefore the flavour of the book is naturally informed by this history. The book is based on a set of graduate-level lectures designed to impart a working knowledge of the canonical approach to gravitation. It is more of a textbook than a treatise, unlike three other recent books in this area by Kiefer [1], Rovelli [2] and Thiemann [3]. The style and choice of topics of these authors are quite different; Kiefer's book provides a broad overview of the path integral and canonical quantization methods from a historical perspective, whereas Rovelli's book focuses on philosophical and formalistic aspects of the problems of time and observables, and gives a development of spin-foam ideas. Thiemann's is much more a mathematical physics book, focusing entirely on the theory of representing constraint operators on a Hilbert space and charting a mathematical trajectory toward a physical Hilbert space for quantum gravity. The significant difference from these books is that Bojowald covers mainly classical topics until the very last chapter, which contains the only discussion of quantization. In its coverage of classical gravity, the book has some content overlap with Poisson's book [4], and with Ryan and Shepley's older work on relativistic cosmology [5]; for instance the contents of chapter five of the

Tunable Superconducting Gravity Gradiometer for Mars Climate, Atmosphere, and Gravity Field Investigation

Science.gov (United States)

Griggs, C. E.; Paik, H. J.; Moody, M. V.; Han, S.-C.; Rowlands, D. D.; Lemoine, F. G.; Shirron, P. J.

2015-01-01

We are developing a compact tensor superconducting gravity gradiometer (SGG) for obtaining gravimetric measurements from planetary orbits. A new and innovative design gives a potential sensitivity of approximately 10(sup -4) E Hz(sup - 1/2)( 1 E = 10(sup -9 S(sup -2) in the measurement band up to 0.1 Hz (suitale for short wavelength static gravity) and of approximately 10(sup -4) E Hz(sup - 1/2) in the frequency band less than 1 mHz (for long wavelength time-variable gravity) from the same device with a baseline just over 10 cm. The measurement band and sensitiy can be optimally tuned in-flight during the mission by changing resonance frequencies, which allows meaurements of both static and time-variable gravity fields from the same mission. Significant advances in the technologies needed for space-based cryogenic instruments have been made in the last decade. In particular, the use of cryocoolers will alleviate the previously severe constraint on mission lifetime imposed by the use of liquid helium, enabling mission durations in the 5 - 10 year range.

Quantum gravito-optics: a light route from semiclassical gravity to quantum gravity

International Nuclear Information System (INIS)

Unnikrishnan, C S; Gillies, George T

2015-01-01

Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation, ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for the detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity. (paper)

Stability in designer gravity

International Nuclear Information System (INIS)

Hertog, Thomas; Hollands, Stefan

2005-01-01

We study the stability of designer gravity theories, in which one considers gravity coupled to a tachyonic scalar with anti-de Sitter (AdS) boundary conditions defined by a smooth function W. We construct Hamiltonian generators of the asymptotic symmetries using the covariant phase space method of Wald et al and find that they differ from the spinor charges except when W = 0. The positivity of the spinor charge is used to establish a lower bound on the conserved energy of any solution that satisfies boundary conditions for which W has a global minimum. A large class of designer gravity theories therefore have a stable ground state, which the AdS/CFT correspondence indicates should be the lowest energy soliton. We make progress towards proving this by showing that minimum energy solutions are static. The generalization of our results to designer gravity theories in higher dimensions involving several tachyonic scalars is discussed

Carroll versus Galilei gravity

Energy Technology Data Exchange (ETDEWEB)

Bergshoeff, Eric [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Gomis, Joaquim [Departament de Física Cuàntica i Astrofísica and Institut de Ciències del Cosmos,Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain); Rollier, Blaise [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Rosseel, Jan [Faculty of Physics, University of Vienna,Boltzmanngasse 5, A-1090 Vienna (Austria); Veldhuis, Tonnis ter [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands)

2017-03-30

We consider two distinct limits of General Relativity that in contrast to the standard non-relativistic limit can be taken at the level of the Einstein-Hilbert action instead of the equations of motion. One is a non-relativistic limit and leads to a so-called Galilei gravity theory, the other is an ultra-relativistic limit yielding a so-called Carroll gravity theory. We present both gravity theories in a first-order formalism and show that in both cases the equations of motion (i) lead to constraints on the geometry and (ii) are not sufficient to solve for all of the components of the connection fields in terms of the other fields. Using a second-order formalism we show that these independent components serve as Lagrange multipliers for the geometric constraints we found earlier. We point out a few noteworthy differences between Carroll and Galilei gravity and give some examples of matter couplings.

Parts-based geophysical inversion with application to water flooding interface detection and geological facies detection

Science.gov (United States)

Zhang, Junwei

data and prior distributions. We pose the geophysical inverse problem in terms of Gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geological cross-section, including the definition of spatial boundaries for the geological facies. The petrophysical relationship problem is formulated as a regression problem upon each facies. The inversion is performed in a Bayesian framework. We demonstrate the usefulness of this strategy using a first synthetic case study, performing a joint inversion of gravity and galvanometric resistivity data with the stations all located at the ground surface. The joint inversion is used to recover the density and resistivity distributions of the subsurface. In a second step, we consider the possibility that the facies boundaries are deformable and their shapes are inverted as well. We use the level set approach to deform the facies boundaries preserving prior topological properties of the facies throughout the inversion. With the additional help of prior facies petrophysical relationships, topological characteristic of each facies, we make posterior inference about multiple geophysical tomograms based on their corresponding geophysical data misfits. The result of the inversion technique is encouraging when applied to a second synthetic case study, showing that we can recover the heterogeneities inside the facies, the mean values for the petrophysical properties, and, to some extent, the facies boundaries. A paper has been submitted to Geophysics on this topic and I am the first author of this paper. During this thesis, I also worked on the time lapse inversion problem of gravity data in collaboration with Marios Karaoulis and a paper was published in Geophysical Journal international on this topic. I also worked on the time-lapse inversion of cross-well geophysical data (seismic and resistivity) using both a structural approach named the cross-gradient approach and

New special operators in W-gravity theories

International Nuclear Information System (INIS)

Rama, S.K.

1991-01-01

This paper reports on special physical operators of W 3 -gravity having non-trivial ghost sectors. Some of these operators may be viewed as the Liouville dressings of the energy operator of the Ising model coupled to two-dimensional (2D) gravity and this fills in the gap in the connection between pure W 3 -gravity and Ising model coupled to 2D gravity found in the authors' previous work. The authors formulate a selection rule required for the calculation of correlators in W-gravity theories. Using this rule, the authors construct the non-ghost part of the new operators of W N -gravity and find that they represent the (N,N + 1) minimal model operators from both inside and outside the minimal table. Along the way the authors obtain the canonical spectrum of W N -gravity for all N

Nonlinearities in modified gravity cosmology: Signatures of modified gravity in the nonlinear matter power spectrum

International Nuclear Information System (INIS)

Cui Weiguang; Zhang Pengjie; Yang Xiaohu

2010-01-01

A large fraction of cosmological information on dark energy and gravity is encoded in the nonlinear regime. Precision cosmology thus requires precision modeling of nonlinearities in general dark energy and modified gravity models. We modify the Gadget-2 code and run a series of N-body simulations on modified gravity cosmology to study the nonlinearities. The modified gravity model that we investigate in the present paper is characterized by a single parameter ζ, which determines the enhancement of particle acceleration with respect to general relativity (GR), given the identical mass distribution (ζ=1 in GR). The first nonlinear statistics we investigate is the nonlinear matter power spectrum at k < or approx. 3h/Mpc, which is the relevant range for robust weak lensing power spectrum modeling at l < or approx. 2000. In this study, we focus on the relative difference in the nonlinear power spectra at corresponding redshifts where different gravity models have the same linear power spectra. This particular statistics highlights the imprint of modified gravity in the nonlinear regime and the importance of including the nonlinear regime in testing GR. By design, it is less susceptible to the sample variance and numerical artifacts. We adopt a mass assignment method based on wavelet to improve the power spectrum measurement. We run a series of tests to determine the suitable simulation specifications (particle number, box size, and initial redshift). We find that, the nonlinear power spectra can differ by ∼30% for 10% deviation from GR (|ζ-1|=0.1) where the rms density fluctuations reach 10. This large difference, on one hand, shows the richness of information on gravity in the corresponding scales, and on the other hand, invalidates simple extrapolations of some existing fitting formulae to modified gravity cosmology.

A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

Science.gov (United States)

2015-09-30

Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves...interaction of surface and internal gravity waves in the South China Sea. We will seek answers to the following questions: 1) How does the wind-wave

Renormalization and asymptotic freedom in quantum gravity

International Nuclear Information System (INIS)

Tomboulis, E.T.

1984-01-01

The article reviews some recent attempts to construct satisfactory theories of quantum gravity within the framework of local, continuum field theory. Quantum gravity; the renormalization group and its fixed points; fixed points and dimensional continuation in gravity; and quantum gravity at d=4-the 1/N expansion-asymptotic freedom; are all discussed. (U.K.)

2-Dim. gravity and string theory

International Nuclear Information System (INIS)

Narain, K.S.

1991-01-01

The role of 2-dim. gravity in string theory is discussed. In particular d=25 string theory coupled to 2-d. gravity is described and shown to give rise to the physics of the usual 26-dim. string theory (where one does not quantise 2-d. gravity. (orig.)

Observational constraints on transverse gravity: A generalization of unimodular gravity

International Nuclear Information System (INIS)

Lopez-Villarejo, J J

2010-01-01

We explore the hypothesis that the set of symmetries enjoyed by the theory that describes gravity is not the full group of diffeomorphisms (Diff(M)), as in General Relativity, but a maximal subgroup of it (TransverseDiff(M)), with its elements having a jacobian equal to unity; at the infinitesimal level, the parameter describing the coordinate change x μ → x μ + ξ μ (x) is transverse, i.e., δ μ ξ μ = 0. Incidentally, this is the smaller symmetry one needs to propagate consistently a graviton, which is a great theoretical motivation for considering these theories. Also, the determinant of the metric, g, behaves as a 'transverse scalar', so that these theories can be seen as a generalization of the better-known unimodular gravity. We present our results on the observational constraints on transverse gravity, in close relation with the claim of equivalence with general scalar-tensor theory. We also comment on the structure of the divergences of the quantum theory to the one-loop order.

A PRELIMINARY JUPITER MODEL