Crooks, David E.; Evans, Nick
2003-01-01
We describe a ten dimensional supergravity geometry which is dual to a gauge theory that is non-supersymmetric Yang Mills in the infra-red but reverts to N=4 super Yang Mills in the ultra-violet. A brane probe of the geometry shows that the scalar potential of the gauge theory is stable. We discuss the infra-red behaviour of the solution. The geometry describes a Schroedinger equation potential that determines the glueball spectrum of the theory; there is a mass gap and a discrete spectrum. The glueball mass predictions match previous AdS/CFT Correspondence computations in the non-supersymmetric Yang Mills theory, and lattice data, at the 10% level. (author)
Twisted covariant noncommutative self-dual gravity
Estrada-Jimenez, S.; Garcia-Compean, H.; Obregon, O.; Ramirez, C.
2008-01-01
A twisted covariant formulation of noncommutative self-dual gravity is presented. The formulation for constructing twisted noncommutative Yang-Mills theories is used. It is shown that the noncommutative torsion is solved at any order of the θ expansion in terms of the tetrad and some extra fields of the theory. In the process the first order expansion in θ for the Plebanski action is explicitly obtained.
Gravity duals of supersymmetric gauge theories on three-manifolds
Farquet, Daniel; Lorenzen, Jakob; Martelli, Dario; Sparks, James
2016-01-01
We study gravity duals to a broad class of N=2 supersymmetric gauge theories defined on a general class of three-manifold geometries. The gravity backgrounds are based on Euclidean self-dual solutions to four-dimensional gauged supergravity. As well as constructing new examples, we prove in general that for solutions defined on the four-ball the gravitational free energy depends only on the supersymmetric Killing vector, finding a simple closed formula when the solution has U(1)×U(1) symmetry. Our result agrees with the large N limit of the free energy of the dual gauge theory, computed using localization. This constitutes an exact check of the gauge/gravity correspondence for a very broad class of gauge theories with a large N limit, defined on a general class of background three-manifold geometries.
Distinguishing modified gravity models
Brax, Philippe; Davis, Anne-Christine
2015-01-01
Modified gravity models with screening in local environments appear in three different guises: chameleon, K-mouflage and Vainshtein mechanisms. We propose to look for differences between these classes of models by considering cosmological observations at low redshift. In particular, we analyse the redshift dependence of the fine structure constant and the proton to electron mass ratio in each of these scenarios. When the absorption lines belong to unscreened regions of space such as dwarf galaxies, a time variation would be present for chameleons. For both K-mouflage and Vainshtein mechanisms, the cosmological time variation of the scalar field is not suppressed in both unscreened and screened environments, therefore enhancing the variation of constants and their detection prospect. We also consider the time variation of the redshift of distant objects using their spectrocopic velocities. We find that models of the K-mouflage and Vainshtein types have very different spectroscopic velocities as a function of redshift and that their differences with the Λ-CDM template should be within reach of the future ELT-HIRES observations
Distinguishing modified gravity models
Brax, Philippe [Institut de Physique Théorique, Université Paris-Saclay, CEA, CNRS, F-91191 Gif/Yvette Cedex (France); Davis, Anne-Christine, E-mail: philippe.brax@cea.fr, E-mail: A.C.Davis@damtp.cam.ac.uk [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge, CB3 0WA (United Kingdom)
2015-10-01
Modified gravity models with screening in local environments appear in three different guises: chameleon, K-mouflage and Vainshtein mechanisms. We propose to look for differences between these classes of models by considering cosmological observations at low redshift. In particular, we analyse the redshift dependence of the fine structure constant and the proton to electron mass ratio in each of these scenarios. When the absorption lines belong to unscreened regions of space such as dwarf galaxies, a time variation would be present for chameleons. For both K-mouflage and Vainshtein mechanisms, the cosmological time variation of the scalar field is not suppressed in both unscreened and screened environments, therefore enhancing the variation of constants and their detection prospect. We also consider the time variation of the redshift of distant objects using their spectrocopic velocities. We find that models of the K-mouflage and Vainshtein types have very different spectroscopic velocities as a function of redshift and that their differences with the Λ-CDM template should be within reach of the future ELT-HIRES observations.
Terrestrial gravity data analysis for interim gravity model improvement
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.
General heavenly equation governs anti-self-dual gravity
Malykh, A A [Department of Numerical Modelling, Russian State Hydrometeorlogical University, Malookhtinsky pr 98, 195196 St Petersburg (Russian Federation); Sheftel, M B, E-mail: andrei-malykh@mail.ru, E-mail: mikhail.sheftel@boun.edu.tr [Department of Physics, Bogazici University, 34342 Bebek, Istanbul (Turkey)
2011-04-15
We show that the general heavenly equation, suggested recently by Doubrov and Ferapontov (2010 arXiv:0910.3407v2 [math.DG]), governs anti-self-dual (ASD) gravity. We derive ASD Ricci-flat vacuum metric governed by the general heavenly equation, null tetrad and basis of 1-forms for this metric. We present algebraic exact solutions of the general heavenly equation as a set of zeros of homogeneous polynomials in independent and dependent variables. A real solution is obtained for the case of a neutral signature.
Spin foam models for quantum gravity
Perez, Alejandro
2003-01-01
In this topical review, we review the present status of the spin foam formulation of non-perturbative (background-independent) quantum gravity. The topical review is divided into two parts. In the first part, we present a general introduction to the main ideas emphasizing their motivation from various perspectives. Riemannian three-dimensional gravity is used as a simple example to illustrate conceptual issues and the main goals of the approach. The main features of the various existing models for four-dimensional gravity are also presented here. We conclude with a discussion of important questions to be addressed in four dimensions (gauge invariance, discretization independence, etc). In the second part, we concentrate on the definition of the Barrett-Crane model. We present the main results obtained in this framework from a critical perspective. Finally, we review the combinatorial formulation of spin foam models based on the dual group field theory technology. We present the Barrett-Crane model in this framework and review the finiteness results obtained for both its Riemannian and its Lorentzian variants. (topical review)
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.
Inversion of Gravity Anomalies Using Primal-Dual Interior Point Methods
Aaron A. Velasco
2016-06-01
Full Text Available Structural inversion of gravity datasets based on the use of density anomalies to derive robust images of the subsurface (delineating lithologies and their boundaries constitutes a fundamental non-invasive tool for geological exploration. The use of experimental techniques in geophysics to estimate and interpret di erences in the substructure based on its density properties have proven e cient; however, the inherent non-uniqueness associated with most geophysical datasets make this the ideal scenario for the use of recently developed robust constrained optimization techniques. We present a constrained optimization approach for a least squares inversion problem aimed to characterize 2-Dimensional Earth density structure models based on Bouguer gravity anomalies. The proposed formulation is solved with a Primal-Dual Interior-Point method including equality and inequality physical and structural constraints. We validate our results using synthetic density crustal structure models with varying complexity and illustrate the behavior of the algorithm using di erent initial density structure models and increasing noise levels in the observations. Based on these implementations, we conclude that the algorithm using Primal-Dual Interior-Point methods is robust, and its results always honor the geophysical constraints. Some of the advantages of using this approach for structural inversion of gravity data are the incorporation of a priori information related to the model parameters (coming from actual physical properties of the subsurface and the reduction of the solution space contingent on these boundary conditions.
Dual geometric-gauge field aspects of gravity
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
Taniguchi, Tadahiro; Sawaragi, Tetsuo
In this paper, a new machine-learning method, called Dual-Schemata model, is presented. Dual-Schemata model is a kind of self-organizational machine learning methods for an autonomous robot interacting with an unknown dynamical environment. This is based on Piaget's Schema model, that is a classical psychological model to explain memory and cognitive development of human beings. Our Dual-Schemata model is developed as a computational model of Piaget's Schema model, especially focusing on sensori-motor developing period. This developmental process is characterized by a couple of two mutually-interacting dynamics; one is a dynamics formed by assimilation and accommodation, and the other dynamics is formed by equilibration and differentiation. By these dynamics schema system enables an agent to act well in a real world. This schema's differentiation process corresponds to a symbol formation process occurring within an autonomous agent when it interacts with an unknown, dynamically changing environment. Experiment results obtained from an autonomous facial robot in which our model is embedded are presented; an autonomous facial robot becomes able to chase a ball moving in various ways without any rewards nor teaching signals from outside. Moreover, emergence of concepts on the target movements within a robot is shown and discussed in terms of fuzzy logics on set-subset inclusive relationships.
Algebraic solutions of anti-self-dual gravity
Sheftel, M.B.
2011-01-01
Full text: (author)It is considered a four-dimensional PDE: complex Monge-Amp'ere equation (CMA), solutions of which govern anti-self-dual gravity, i.e. determine anti-self-dual Ricci-flat Kahler metrics, solutions of the vacuum Einstein equations with the Euclidean signature. It is used simultaneously two mutually complex conjugate pairs of partner symmetries of CMA related by a recursion relation. For both pairs of partner symmetries, using Lie equations, it is introduced explicitly group parameters as additional variables, replacing symmetry characteristics and their complex conjugates by derivatives of the unknown with respect to group parameters. It is studied the resulting system of six equations in the eight-dimensional space, that includes CMA, four equations of the recursion between partner symmetries and one integrability condition of this system. It is used point symmetries of this extended system for performing its symmetry reduction with respect to group parameters that facilitates solving the extended system. This procedure does not imply a reduction in the number of physical variables and hence it is ended up with orbits of non-invariant solutions of CMA, generated by one partner symmetry, not used in the reduction. These solutions are determined by six linear equations with constant coefficients in the five-dimensional space which are obtained by a three-dimensional Legendre transformation of the reduced extended system. It is presented an example of algebraic solutions that govern Legendre-transformed Ricci-flat Kahler metrics with no Killing vectors. It is defined as a set of roots of a homogeneous polynomial of degree 6 in the six complex variables which determines a four-dimensional compact manifold in a five-dimensional complex projective space
Equation of state and viscosities from a gravity dual of the gluon plasma
R. Yaresko
2015-07-01
Full Text Available Employing new precision data of the equation of state of the SU(3 Yang–Mills theory (gluon plasma the dilaton potential of a gravity-dual model is adjusted in the temperature range (1–10Tc within a bottom-up approach. The ratio of bulk viscosity to shear viscosity follows then as ζ/η≈πΔvs2 for Δvs2<0.2 and achieves a maximum value of 0.94 at Δvs2≈0.3, where Δvs2≡1/3−vs2 is the non-conformality measure and vs2 is the velocity of sound squared, while the ratio of shear viscosity to entropy density is known as (4π−1 for the considered set-up with Hilbert action on the gravity side.
Dilaton gravity, Poisson sigma models and loop quantum gravity
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.
Spin foam models for quantum gravity
Perez, Alejandro
The definition of a quantum theory of gravity is explored following Feynman's path-integral approach. The aim is to construct a well defined version of the Wheeler-Misner- Hawking ``sum over four geometries'' formulation of quantum general relativity (GR). This is done by means of exploiting the similarities between the formulation of GR in terms of tetrad-connection variables (Palatini formulation) and a simpler theory called BF theory. One can go from BF theory to GR by imposing certain constraints on the BF-theory configurations. BF theory contains only global degrees of freedom (topological theory) and it can be exactly quantized á la Feynman introducing a discretization of the manifold. Using the path integral for BF theory we define a path integration for GR imposing the BF-to-GR constraints on the BF measure. The infinite degrees of freedom of gravity are restored in the process, and the restriction to a single discretization introduces a cut- off in the summed-over configurations. In order to capture all the degrees of freedom a sum over discretization is implemented. Both the implementation of the BF-to-GR constraints and the sum over discretizations are obtained by means of the introduction of an auxiliary field theory (AFT). 4-geometries in the path integral for GR are given by the Feynman diagrams of the AFT which is in this sense dual to GR. Feynman diagrams correspond to 2-complexes labeled by unitary irreducible representations of the internal gauge group (corresponding to tetrad rotation in the connection to GR). A model for 4-dimensional Euclidean quantum gravity (QG) is defined which corresponds to a different normalization of the Barrett-Crane model. The model is perturbatively finite; divergences appearing in the Barrett-Crane model are cured by the new normalization. We extend our techniques to the Lorentzian sector, where we define two models for four-dimensional QG. The first one contains only time-like representations and is shown to be
Counterterms and dual holographic anomalies in CS gravity
Banados, Maximo [Departamento de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago 22, Chile (Chile); Olea, Rodrigo [Departamento de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago 22, Chile (Chile); Theisen, Stefan [Max-Planck-Institut fuer Gravitationphysik, Albert-Einstein-Institut, 14476 Golm (Germany)
2005-10-15
The holographic Weyl anomaly associated to Chern-Simons gravity in 2n+1 dimensions is proportional to the Euler term in 2n dimensions, with no contributions from the Weyl tensor. We compute the holographic energy-momentum tensor associated to Chern-Simons gravity directly from the action, in an arbitrary odd-dimensional spacetime. We show, in particular, that the counterterms rendering the action finite contain only terms of the Lovelock type.
High-resolution gravity model of Venus
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.
Lanczos–Lovelock models of gravity
Padmanabhan, T.; Kothawala, D.
2013-01-01
Lanczos–Lovelock models of gravity represent a natural and elegant generalization of Einstein’s theory of gravity to higher dimensions. They are characterized by the fact that the field equations only contain up to second derivatives of the metric even though the action functional can be a quadratic or higher degree polynomial in the curvature tensor. Because these models share several key properties of Einstein’s theory they serve as a useful set of candidate models for testing the emergent paradigm for gravity. This review highlights several geometrical and thermodynamical aspects of Lanczos–Lovelock models which have attracted recent attention
The distance-decay function of geographical gravity model: Power law or exponential law?
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
Ginsparg, P.
1991-01-01
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date
New Spin Foam Models of Quantum Gravity
Miković, A.
We give a brief and a critical review of the Barret-Crane spin foam models of quantum gravity. Then we describe two new spin foam models which are obtained by direct quantization of General Relativity and do not have some of the drawbacks of the Barret-Crane models. These are the model of spin foam invariants for the embedded spin networks in loop quantum gravity and the spin foam model based on the integration of the tetrads in the path integral for the Palatini action.
Schwinger type processes via branes and their gravity duals
Gorsky, A.S.; Saraikin, K.A.; Selivanov, K.G.
2002-01-01
We consider Schwinger type processes involving the creation of the charge and monopole pairs in the external fields and propose interpretation of these processes via corresponding brane configurations in type IIB string theory. We suggest simple description of some new interesting nonperturbative processes like monopole/dyon transitions in the electric field and W-boson decay in the magnetic field using the brane language. Nonperturbative pair production in the strong coupling regime using the AdS/CFT correspondence is studied. The treatment of the similar processes in the noncommutative theories when noncommutativity is traded for the background fields is presented and the possible role of the critical magnetic field which is S-dual to the critical electric field is discussed
Gravity duals of half-BPS Wilson loops
D'Hoker, Eric; Estes, John; Gutperle, Michael
2007-01-01
We explicitly construct the fully back-reacted half-BPS solutions in Type IIB supergravity which are dual to Wilson loops with 16 supersymmetries in N = 4 super Yang-Mills. In a first part, we use the methods of a companion paper to derive the exact general solution of the half-BPS equations on the space AdS 2 x S 2 x S 4 x Σ, with isometry group SO(2, 1) x SO(3) x SO(5) in terms of two locally harmonic functions on a Riemann surface Σ with boundary. These solutions, generally, have varying dilaton and axion, and non-vanishing 3-form fluxes. In a second part, we impose regularity and topology conditions. These non-singular solutions may be parametrized by a genus g ≥ 0 hyperelliptic surface Σ, all of whose branch points lie on the real line. Each genus g solution has only a single asymptotic AdS 5 x S 5 region, but exhibits g homology 3-spheres, and an extra g homology 5-spheres, carrying respectively RR 3-form and RR 5-form charges. For genus 0, we recover AdS 5 x S 5 with 3 free parameters, while for genus g ≥ 1, the solution has 2g+5 free parameters. The genus 1 case is studied in detail. Numerical analysis is used to show that the solutions are regular throughout the g = 1 parameter space. Collapse of a branch cut on Σ subtending either a homology 3-sphere or a homology 5-sphere is non-singular and yields the genus g-1 solution. This behavior is precisely expected of a proper dual to a Wilson loop in gauge theory
Consistent deformations of dual formulations of linearized gravity: A no-go result
Bekaert, Xavier; Boulanger, Nicolas; Henneaux, Marc
2003-01-01
The consistent, local, smooth deformations of the dual formulation of linearized gravity involving a tensor field in the exotic representation of the Lorentz group with Young symmetry type (D-3,1) (one column of length D-3 and one column of length 1) are systematically investigated. The rigidity of the Abelian gauge algebra is first established. We next prove a no-go theorem for interactions involving at most two derivatives of the fields
Gravity Dual for Reggeon Field Theory and Non-linear Quantum Finance
Yu Nakayama
2009-01-01
We study scale invariant but not necessarily conformal invariant deformations of non-relativistic conformal field theories from the dual gravity viewpoint. We present the corresponding metric that solves the Einstein equation coupled with a massive vector field. We find that, within the class of metric we study, when we assume the Galilean invariance, the scale invariant deformation always preserves the non-relativistic conformal invariance. We discuss applications to scaling regime of Reggeo...
Circulation-based Modeling of Gravity Currents
Meiburg, E. H.; Borden, Z.
2013-05-01
Atmospheric and oceanic flows driven by predominantly horizontal density differences, such as sea breezes, thunderstorm outflows, powder snow avalanches, and turbidity currents, are frequently modeled as gravity currents. Efforts to develop simplified models of such currents date back to von Karman (1940), who considered a two-dimensional gravity current in an inviscid, irrotational and infinitely deep ambient. Benjamin (1968) presented an alternative model, focusing on the inviscid, irrotational flow past a gravity current in a finite-depth channel. More recently, Shin et al. (2004) proposed a model for gravity currents generated by partial-depth lock releases, considering a control volume that encompasses both fronts. All of the above models, in addition to the conservation of mass and horizontal momentum, invoke Bernoulli's law along some specific streamline in the flow field, in order to obtain a closed system of equations that can be solved for the front velocity as function of the current height. More recent computational investigations based on the Navier-Stokes equations, on the other hand, reproduce the dynamics of gravity currents based on the conservation of mass and momentum alone. We propose that it should therefore be possible to formulate a fundamental gravity current model without invoking Bernoulli's law. The talk will show that the front velocity of gravity currents can indeed be predicted as a function of their height from mass and momentum considerations alone, by considering the evolution of interfacial vorticity. This approach does not require information on the pressure field and therefore avoids the need for an energy closure argument such as those invoked by the earlier models. Predictions by the new theory are shown to be in close agreement with direct numerical simulation results. References Von Karman, T. 1940 The engineer grapples with nonlinear problems, Bull. Am. Math Soc. 46, 615-683. Benjamin, T.B. 1968 Gravity currents and related
Thermo-electric transport in gauge/gravity models with momentum dissipation
Amoretti, Andrea; Braggio, Alessandro; Maggiore, Nicola; Magnoli, Nicodemo; Musso, Daniele
2014-09-01
We present a systematic definition and analysis of the thermo-electric linear response in gauge/gravity systems focusing especially on models with massive gravity in the bulk and therefore momentum dissipation in the dual field theory. A precise treatment of finite counter-terms proves to be essential to yield a consistent physical picture whose hydrodynamic and beyond-hydrodynamics behaviors noticeably match with field theoretical expectations. The model furnishes a possible gauge/gravity description of the crossover from the quantum-critical to the disorder-dominated Fermi-liquid behaviors, as expected in graphene.
Testing a Dilaton Gravity Model Using Nucleosynthesis
Boran, S.; Kahya, E. O.
2014-01-01
Big bang nucleosynthesis (BBN) offers one of the most strict evidences for the Λ-CDM cosmology at present, as well as the cosmic microwave background (CMB) radiation. In this work, our main aim is to present the outcomes of our calculations related to primordial abundances of light elements, in the context of higher dimensional steady-state universe model in the dilaton gravity. Our results show that abundances of light elements (primordial D, 3 He, 4 He, T, and 7 Li) are significantly different for some cases, and a comparison is given between a particular dilaton gravity model and Λ-CDM in the light of the astrophysical observations
Terrestrial Sagnac delay constraining modified gravity models
Karimov, R. Kh.; Izmailov, R. N.; Potapov, A. A.; Nandi, K. K.
2018-04-01
Modified gravity theories include f(R)-gravity models that are usually constrained by the cosmological evolutionary scenario. However, it has been recently shown that they can also be constrained by the signatures of accretion disk around constant Ricci curvature Kerr-f(R0) stellar sized black holes. Our aim here is to use another experimental fact, viz., the terrestrial Sagnac delay to constrain the parameters of specific f(R)-gravity prescriptions. We shall assume that a Kerr-f(R0) solution asymptotically describes Earth's weak gravity near its surface. In this spacetime, we shall study oppositely directed light beams from source/observer moving on non-geodesic and geodesic circular trajectories and calculate the time gap, when the beams re-unite. We obtain the exact time gap called Sagnac delay in both cases and expand it to show how the flat space value is corrected by the Ricci curvature, the mass and the spin of the gravitating source. Under the assumption that the magnitude of corrections are of the order of residual uncertainties in the delay measurement, we derive the allowed intervals for Ricci curvature. We conclude that the terrestrial Sagnac delay can be used to constrain the parameters of specific f(R) prescriptions. Despite using the weak field gravity near Earth's surface, it turns out that the model parameter ranges still remain the same as those obtained from the strong field accretion disk phenomenon.
Vacuum transitions in dual models
Pashnev, A.I.; Volkov, D.V.; Zheltukhin, A.A.
1976-01-01
The investigation is continued of the spontaneous vacuum transition problem in the Neview-Schwartz dual model (NSDM). It is shown that vacuum transitions allow disclosing of supplementary degeneration in the resonance state spectrum. The dual amplitudes possess an internal structure corresponding to the presence of an infinite number of quarks with increasing masses and retained charges. The Adler principle holds. Analytic continuation on the constant of induced vacuum transitions makes it possible to establish the existence of spontaneous vacuum transitions in the NSDM. The consequence of this fact is the exact SU(2) symmetry of π, rho meson trajectories and the Higgs mechanism in the model. In this case the ratios of masses of particles leading trajectories are analogous to those obtained in the current algebra. It is shown that in the NSDM there arises chiral SU(2) x SU(2) x U(1) x U(1) x ... symmetry resulting from spontaneous vacuum transitions
Three-dimensional simplicial quantum gravity and generalized matrix models
Ambjoern, J.; Durhuus, B.; Jonsson, T.
1990-11-01
We consider a discrete model of Euclidean quantum gravity in three dimensions based on a summation over random simplicial manifolds. We derive some elementary properties of the model and discuss possible 'matrix' models for 3d gravity. (orig.)
The Gravity Model for High School Students
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)
Gravity dual of spin and charge density waves
Jokela, Niko; Järvinen, Matti; Lippert, Matthew
2014-12-01
At high enough charge density, the homogeneous state of the D3-D7' model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.
Karami, K.; Abdolmaleki, A.; Asadzadeh, S. [University of Kurdistan, Department of Physics, Sanandaj (Iran, Islamic Republic of); Safari, Z. [Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)
2013-09-15
Within the framework of modified teleparallel gravity, we reconstruct a f(T) model corresponding to the QCD ghost dark energy scenario. For a spatially flat FRW universe containing only the pressureless matter, we obtain the time evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate the effective torsion equation of state parameter of the QCD ghost f(T)-gravity model as well as the deceleration parameter of the universe. Furthermore, we fit the model parameters by using the latest observational data including SNeIa, CMB and BAO data. We also check the viability of our model using a cosmographic analysis approach. Moreover, we investigate the validity of the generalized second law (GSL) of gravitational thermodynamics for our model. Finally, we point out the growth rate of matter density perturbation. We conclude that in QCD ghost f(T)-gravity model, the universe begins a matter dominated phase and approaches a de Sitter regime at late times, as expected. Also this model is consistent with current data, passes the cosmographic test, satisfies the GSL and fits the data of the growth factor well as the {Lambda}CDM model. (orig.)
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
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.
The gravity model of labor migration behavior
Alexandr, Tarasyev; Alexandr, Tarasyev
2017-07-01
In this article, we present a dynamic inter-regional model, that is based on the gravity approach to migration and describes in continuous time the labor force dynamics between a number of conjugate regions. Our modification of the gravity migration model allows to explain the migration processes and to display the impact of migration on the regional economic development both for regions of origin and attraction. The application of our model allows to trace the dependency between salaries levels, total workforce, the number of vacancies and the number unemployed people in simulated regions. Due to the gravity component in our model the accuracy of prediction for migration flows is limited by the distance range between analyzed regions, so this model is tested on a number of conjugate neighbor regions. Future studies will be aimed at development of a multi-level dynamic model, which allows to construct a forecast for unemployment and vacancies trends on the first modeling level and to use these identified parameters on the second level for describing dynamic trajectories of migration flows.
Hydrodynamics dual to Einstein-Gauss-Bonnet gravity: all-order gradient resummation
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.
Gravity model improvement investigation. [improved gravity model for determination of ocean geoid
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.
Tests and comparisons of gravity models.
Marsh, J. G.; Douglas, B. C.
1971-01-01
Optical observations of the GEOS satellites were used to obtain orbital solutions with different sets of geopotential coefficients. The solutions were compared before and after modification to high order terms (necessary because of resonance) and were then analyzed by comparing subsequent observations with predicted trajectories. The most important source of error in orbit determination and prediction for the GEOS satellites is the effect of resonance found in most published sets of geopotential coefficients. Modifications to the sets yield greatly improved orbits in most cases. The results of these comparisons suggest that with the best optical tracking systems and gravity models, satellite position error due to gravity model uncertainty can reach 50-100 m during a heavily observed 5-6 day orbital arc. If resonant coefficients are estimated, the uncertainty is reduced considerably.
Systematic simulations of modified gravity: chameleon models
Brax, Philippe; Davis, Anne-Christine; Li, Baojiu; Winther, Hans A.; Zhao, Gong-Bo
2013-01-01
In this work we systematically study the linear and nonlinear structure formation in chameleon theories of modified gravity, using a generic parameterisation which describes a large class of models using only 4 parameters. For this we have modified the N-body simulation code ecosmog to perform a total of 65 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a significant portion of the parameter space. We have studied the effects of modified gravity on the matter power spectrum and mass function, and found a rich and interesting phenomenology where the difference with the ΛCDM paradigm cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc −1 , since the latter incorrectly assumes that the modification of gravity depends only on the background matter density. Our results show that the chameleon screening mechanism is significantly more efficient than other mechanisms such as the dilaton and symmetron, especially in high-density regions and at early times, and can serve as a guidance to determine the parts of the chameleon parameter space which are cosmologically interesting and thus merit further studies in the future
Systematic simulations of modified gravity: chameleon models
Brax, Philippe [Institut de Physique Theorique, CEA, IPhT, CNRS, URA 2306, F-91191Gif/Yvette Cedex (France); Davis, Anne-Christine [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Li, Baojiu [Institute for Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Winther, Hans A. [Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo (Norway); Zhao, Gong-Bo, E-mail: philippe.brax@cea.fr, E-mail: a.c.davis@damtp.cam.ac.uk, E-mail: baojiu.li@durham.ac.uk, E-mail: h.a.winther@astro.uio.no, E-mail: gong-bo.zhao@port.ac.uk [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom)
2013-04-01
In this work we systematically study the linear and nonlinear structure formation in chameleon theories of modified gravity, using a generic parameterisation which describes a large class of models using only 4 parameters. For this we have modified the N-body simulation code ecosmog to perform a total of 65 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a significant portion of the parameter space. We have studied the effects of modified gravity on the matter power spectrum and mass function, and found a rich and interesting phenomenology where the difference with the ΛCDM paradigm cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc{sup −1}, since the latter incorrectly assumes that the modification of gravity depends only on the background matter density. Our results show that the chameleon screening mechanism is significantly more efficient than other mechanisms such as the dilaton and symmetron, especially in high-density regions and at early times, and can serve as a guidance to determine the parts of the chameleon parameter space which are cosmologically interesting and thus merit further studies in the future.
Towards a Gravity Dual for the Large Scale Structure of the Universe
Kehagias, A.
2016-01-01
The dynamics of the large-scale structure of the universe enjoys at all scales, even in the highly non-linear regime, a Lifshitz symmetry during the matter-dominated period. In this paper we propose a general class of six-dimensional spacetimes which could be a gravity dual to the four-dimensional large-scale structure of the universe. In this set-up, the Lifshitz symmetry manifests itself as an isometry in the bulk and our universe is a four-dimensional brane moving in such six-dimensional bulk. After finding the correspondence between the bulk and the brane dynamical Lifshitz exponents, we find the intriguing result that the preferred value of the dynamical Lifshitz exponent of our observed universe, at both linear and non-linear scales, corresponds to a fixed point of the RGE flow of the dynamical Lifshitz exponent in the dual system where the symmetry is enhanced to the Schrodinger group containing a non-relativistic conformal symmetry. We also investigate the RGE flow between fixed points of the Lifshitz...
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.
Polytropic and Chaplygin f(T)-gravity models
Karami, K; Abdolmaleki, A
2012-01-01
We reconstruct different f(T)-gravity models corresponding to a set of dark energy scenarios containing the polytropic, the standard Chaplygin and the generalized Chaplygin gas models. We also derive the equation of state parameter of the selected f(T)-gravity models and obtain the necessary conditions for crossing the phantom-divide line.
Gravity model development for precise orbit computations for satellite altimetry
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.
Quantum gravity and Standard-Model-like fermions
Eichhorn, Astrid; Lippoldt, Stefan
2017-01-01
We discover that chiral symmetry does not act as an infrared attractor of the renormalization group flow under the impact of quantum gravity fluctuations. Thus, observationally viable quantum gravity models must respect chiral symmetry. In our truncation, asymptotically safe gravity does, as a chiral fixed point exists. A second non-chiral fixed point with massive fermions provides a template for models with dark matter. This fixed point disappears for more than 10 fermions, suggesting that an asymptotically safe ultraviolet completion for the standard model plus gravity enforces chiral symmetry.
Quantum Gravity Mathematical Models and Experimental Bounds
Fauser, Bertfried; Zeidler, Eberhard
2007-01-01
The construction of a quantum theory of gravity is the most fundamental challenge confronting contemporary theoretical physics. The different physical ideas which evolved while developing a theory of quantum gravity require highly advanced mathematical methods. This book presents different mathematical approaches to formulate a theory of quantum gravity. It represents a carefully selected cross-section of lively discussions about the issue of quantum gravity which took place at the second workshop "Mathematical and Physical Aspects of Quantum Gravity" in Blaubeuren, Germany. This collection covers in a unique way aspects of various competing approaches. A unique feature of the book is the presentation of different approaches to quantum gravity making comparison feasible. This feature is supported by an extensive index. The book is mainly addressed to mathematicians and physicists who are interested in questions related to mathematical physics. It allows the reader to obtain a broad and up-to-date overview on ...
Modeling human perception of orientation in altered gravity
Clark, Torin K.; Newman, Michael C.; Oman, Charles M.; Merfeld, Daniel M.; Young, Laurence R.
2015-01-01
Altered gravity environments, such as those experienced by astronauts, impact spatial orientation perception, and can lead to spatial disorientation and sensorimotor impairment. To more fully understand and quantify the impact of altered gravity on orientation perception, several mathematical models have been proposed. The utricular shear, tangent, and the idiotropic vector models aim to predict static perception of tilt in hyper-gravity. Predictions from these prior models are compared to the available data, but are found to systematically err from the perceptions experimentally observed. Alternatively, we propose a modified utricular shear model for static tilt perception in hyper-gravity. Previous dynamic models of vestibular function and orientation perception are limited to 1 G. Specifically, they fail to predict the characteristic overestimation of roll tilt observed in hyper-gravity environments. To address this, we have proposed a modification to a previous observer-type canal-otolith interaction model based upon the hypothesis that the central nervous system (CNS) treats otolith stimulation in the utricular plane differently than stimulation out of the utricular plane. Here we evaluate our modified utricular shear and modified observer models in four altered gravity motion paradigms: (a) static roll tilt in hyper-gravity, (b) static pitch tilt in hyper-gravity, (c) static roll tilt in hypo-gravity, and (d) static pitch tilt in hypo-gravity. The modified models match available data in each of the conditions considered. Our static modified utricular shear model and dynamic modified observer model may be used to help quantitatively predict astronaut perception of orientation in altered gravity environments. PMID:25999822
Modeling Human Perception of Orientation in Altered Gravity
Torin K. Clark
2015-05-01
Full Text Available Altered gravity environments, such as those experienced by astronauts, impact spatial orientation perception and can lead to spatial disorientation and sensorimotor impairment. To more fully understand and quantify the impact of altered gravity on orientation perception, several mathematical models have been proposed. The utricular shear, tangent, and the idiotropic vector models aim to predict static perception of tilt in hyper-gravity. Predictions from these prior models are compared to the available data, but are found to systematically err from the perceptions experimentally observed. Alternatively, we propose a modified utricular shear model for static tilt perception in hyper-gravity. Previous dynamic models of vestibular function and orientation perception are limited to 1 G. Specifically, they fail to predict the characteristic overestimation of roll tilt observed in hyper-gravity environments. To address this, we have proposed a modification to a previous observer-type canal otolith interaction model based upon the hypothesis that the central nervous system treats otolith stimulation in the utricular plane differently than stimulation out of the utricular plane. Here we evaluate our modified utricular shear and modified observer models in four altered gravity motion paradigms: a static roll tilt in hyper-gravity, b static pitch tilt in hyper-gravity, c static roll tilt in hypo-gravity, and d static pitch tilt in hypo-gravity. The modified models match available data in each of the conditions considered. Our static modified utricular shear model and dynamic modified observer model may be used to help quantitatively predict astronaut perception of orientation in altered gravity environments.
Venus spherical harmonic gravity model to degree and order 60
Konopliv, Alex S.; Sjogren, William L.
1994-01-01
The Magellan and Pioneer Venus Orbiter radiometric tracking data sets have been combined to produce a 60th degree and order spherical harmonic gravity field. The Magellan data include the high-precision X-band gravity tracking from September 1992 to May 1993 and post-aerobraking data up to January 5, 1994. Gravity models are presented from the application of Kaula's power rule for Venus and an alternative a priori method using surface accelerations. Results are given as vertical gravity acceleration at the reference surface, geoid, vertical Bouguer, and vertical isostatic maps with errors for the vertical gravity and geoid maps included. Correlation of the gravity with topography for the different models is also discussed.
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
Dual model for parton densities
El Hassouni, A.; Napoly, O.
1981-01-01
We derive power-counting rules for quark densities near x=1 and x=0 from parton interpretations of one-particle inclusive dual amplitudes. Using these rules, we give explicit expressions for quark distributions (including charm) inside hadrons. We can then show the compatibility between fragmentation and recombination descriptions of low-p/sub perpendicular/ processes
Gravity loop corrections to the standard model Higgs in Einstein gravity
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)
New classes of modified teleparallel gravity models
Bahamonde, Sebastian; Böhmer, Christian G.; Krššák, Martin
2017-12-01
New classes of modified teleparallel theories of gravity are introduced. The action of this theory is constructed to be a function of the irreducible parts of torsion f (Tax ,Tten ,Tvec), where Tax ,Tten and Tvec are squares of the axial, tensor and vector components of torsion, respectively. This is the most general (well-motivated) second order teleparallel theory of gravity that can be constructed from the torsion tensor. Different particular second order theories can be recovered from this theory such as new general relativity, conformal teleparallel gravity or f (T) gravity. Additionally, the boundary term B which connects the Ricci scalar with the torsion scalar via R = - T + B can also be incorporated into the action. By performing a conformal transformation, it is shown that the two unique theories which have an Einstein frame are either the teleparallel equivalent of general relativity or f (- T + B) = f (R) gravity, as expected.
An AdS3 dual for minimal model CFTs
Gaberdiel, Matthias R.; Gopakumar, Rajesh
2011-01-01
We propose a duality between the 2d W N minimal models in the large N't Hooft limit, and a family of higher spin theories on AdS 3 . The 2d conformal field theories (CFTs) can be described as Wess-Zumino-Witten coset models, and include, for N=2, the usual Virasoro unitary series. The dual bulk theory contains, in addition to the massless higher spin fields, two complex scalars (of equal mass). The mass is directly related to the 't Hooft coupling constant of the dual CFT. We give convincing evidence that the spectra of the two theories match precisely for all values of the 't Hooft coupling. We also show that the renormalization group flows in the 2d CFT agree exactly with the usual AdS/CFT prediction of the gravity theory. Our proposal is in many ways analogous to the Klebanov-Polyakov conjecture for an AdS 4 dual for the singlet sector of large N vector models.
(2 + 1)-dimensional interacting model of two massless spin-2 fields as a bi-gravity model
Hoseinzadeh, S.; Rezaei-Aghdam, A.
2018-06-01
We propose a new group-theoretical (Chern-Simons) formulation for the bi-metric theory of gravity in (2 + 1)-dimensional spacetime which describe two interacting massless spin-2 fields. Our model has been formulated in terms of two dreibeins rather than two metrics. We obtain our Chern-Simons gravity model by gauging mixed AdS-AdS Lie algebra and show that it has a two dimensional conformal field theory (CFT) at the boundary of the anti de Sitter (AdS) solution. We show that the central charge of the dual CFT is proportional to the mass of the AdS solution. We also study cosmological implications of our massless bi-gravity model.
Tscherning, Carl Christian; Herceg, Matija; Fredenslund Levinsen, Joanna
GOCE TRF (terrestrial reference frame) vertical anomalous gradients (Tzz) from two periods have been used to determine gravity anomalies changes in mid-west Greenland, where a large mass-loss has been detected using GRACE (Fig. 1). As additional data were used the GOCE DIR-3 model and ground...... gravity at the coast on solid rock, where no mass loss is expected. The methods of Least-Squares Collocation (LSC) and the Reduced Point Mass (RPM) methods have been used, however only LSC included the ground data....
Nonword Reading: Comparing Dual-Route Cascaded and Connectionist Dual-Process Models with Human Data
Pritchard, Stephen C.; Coltheart, Max; Palethorpe, Sallyanne; Castles, Anne
2012-01-01
Two prominent dual-route computational models of reading aloud are the dual-route cascaded (DRC) model, and the connectionist dual-process plus (CDP+) model. While sharing similarly designed lexical routes, the two models differ greatly in their respective nonlexical route architecture, such that they often differ on nonword pronunciation. Neither…
A dynamic model of Venus's gravity field
Kiefer, W. S.; Richards, M. A.; Hager, B. H.; Bills, B. G.
1984-01-01
Unlike Earth, long wavelength gravity anomalies and topography correlate well on Venus. Venus's admittance curve from spherical harmonic degree 2 to 18 is inconsistent with either Airy or Pratt isostasy, but is consistent with dynamic support from mantle convection. A model using whole mantle flow and a high viscosity near surface layer overlying a constant viscosity mantle reproduces this admittance curve. On Earth, the effective viscosity deduced from geoid modeling increases by a factor of 300 from the asthenosphere to the lower mantle. These viscosity estimates may be biased by the neglect of lateral variations in mantle viscosity associated with hot plumes and cold subducted slabs. The different effective viscosity profiles for Earth and Venus may reflect their convective styles, with tectonism and mantle heat transport dominated by hot plumes on Venus and by subducted slabs on Earth. Convection at degree 2 appears much stronger on Earth than on Venus. A degree 2 convective structure may be unstable on Venus, but may have been stabilized on Earth by the insulating effects of the Pangean supercontinental assemblage.
Chiral symmetry breaking and pions in nonsupersymmetric gauge/gravity duals
Babington, J.; Erdmenger, J.; Guralnik, Z.; Kirsch, I.; Evans, N.
2004-01-01
We study gravity duals of large N nonsupersymmetric gauge theories with matter in the fundamental representation by introducing a D7-brane probe into deformed AdS backgrounds. In particular, we consider a D7-brane probe in both the AdS Schwarzschild black hole solution and in the background found by Constable and Myers, which involves a nonconstant dilaton and S 5 radius. Both these backgrounds exhibit confinement of fundamental matter and a discrete glueball and meson spectrum. We numerically compute the Ψ-barΨ condensate and meson spectrum associated with these backgrounds. In the AdS-black-hole background, a quark-bilinear condensate develops only at a nonzero quark mass. We speculate on the existence of a third order phase transition at a critical quark mass where the D7 embedding undergoes a geometric transition. In the Constable-Myers background, we find a chiral symmetry breaking condensate as well as the associated Goldstone boson in the limit of small quark mass. The existence of the condensate ensures that the D7-brane never reaches the naked singularity at the origin of the deformed AdS space
Internal model of gravity influences configural body processing.
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.
State sum models for quantum gravity
Barrett, John W.
2000-01-01
This paper reviews the construction of quantum field theory on a 4-dimensional spacetime by combinatorial methods, and discusses the recent developments in the direction of a combinatorial construction of quantum gravity.
New Gravity Wave Treatments for GISS Climate Models
Geller, Marvin A.; Zhou, Tiehan; Ruedy, Reto; Aleinov, Igor; Nazarenko, Larissa; Tausnev, Nikolai L.; Sun, Shan; Kelley, Maxwell; Cheng, Ye
2011-01-01
Previous versions of GISS climate models have either used formulations of Rayleigh drag to represent unresolved gravity wave interactions with the model-resolved flow or have included a rather complicated treatment of unresolved gravity waves that, while being climate interactive, involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive. Here, the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic gravity waves and their interaction with the resolved flow. Comparisons of the GISS model winds and temperatures with no gravity wave parameterization; with only orographic gravity wave parameterization; and with both orographic and nonorographic gravity wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations. The authors also show that the specifications of orographic and nonorographic gravity waves must be different in the Northern and Southern Hemispheres. Then results are presented where the nonorographic gravity wave sources are specified to represent sources from convection in the intertropical convergence zone and spontaneous emission from jet imbalances. Finally, a strategy to include these effects in a climate-dependent manner is suggested.
Conductivity in the gravity dual to massive ABJM and the membrane paradigm
Lopez-Arcos, Cristhiam; Nastase, Horatiu; Rojas, Francisco; Murugan, Jeff
2014-01-01
In this paper we analyze the effect of the massive deformation of the ABJM model on the calculation of conductivity of the dual theory. We show that some of the difficulties presented by the dual geometry, in particular the construction of black holes therein, can be at least partially circumvented by adopting a membrane paradigm-like computation of the conductivity, which requires us to know just the effect of the deformation on the horizon of a black hole in AdS 4 . The deformation at the horizon itself is found by first deforming the flat space near the horizon, and then using the corresponding solution near the horizon as initial conditions for the Einstein’s equations. We find the same result, showing an increase in conductivity, using two types of membrane paradigm computations
Gravity dual to a quantum critical point with spontaneous symmetry breaking.
Gubser, Steven S; Rocha, Fábio D
2009-02-13
We consider zero-temperature solutions to the Abelian Higgs model coupled to gravity with a negative cosmological constant. With appropriate choices of parameters, the geometry contains two copies of anti-de Sitter space, one describing conformal invariance in the ultraviolet, and one in the infrared. The effective speed of signal propagation is smaller in the infrared. Green's functions and associated transport coefficients can have unusual power-law scaling in the infrared. We provide an example in which the real part of the conductivity scales approximately as omega;{3.5} for small omega.
We study the cosmological dynamics for R p exp( λ R ) gravity theory in the metric formalism, using dynamical systems approach. Considering higher-dimensional FRW geometries in case of an imperfect fluid which has two different scale factors in the normal and extra dimensions, we find the exact solutions, and study its ...
Animal Modeling and Neurocircuitry of Dual Diagnosis
Chambers, R. Andrew
2010-01-01
Dual diagnosis is a problem of tremendous depth and scope, spanning many classes of mental disorders and addictive drugs. Animal models of psychiatric disorders studied in addiction paradigms suggest a unitary nature of mental illness and addiction vulnerability both on the neurocircuit and clinical-behavioral levels. These models provide platforms for exploring the interactive roles of biological, environmental and developmental factors on neurocircuits commonly involved in psychiatric and addiction diseases. While suggestive of the artifice of segregated research, training, and clinical cultures between psychiatric and addiction fields, this research may lead to more parsimonious, integrative and preventative treatments for dual diagnosis. PMID:20585464
Dual resonance models and their currents
Johnson, E.A.
1978-01-01
It is shown how dual resonance models were rederived from the concept of a string tracing out a surface in space-time. Thus, interacting strings reproduce the dual amplitudes. A scheme for tackling the unitarity problem began to develop. As a consistent theory of hadronic processes began to be built, workers at the same time were naturally led to expect that leptons could be included with hadrons in a unified dual theory. Thus, there is a search for dual amplitudes which would describe interactions between hadrons and currents (for example, electrons), as well as interactions involving only hadrons. Such amplitudes, it is believed, will be the correct ones, describing the real world. Such amplitudes will provide valuable information concerning such things as hadronic form factors. The great difficulties in building current-amplitudes with the required properties of proper factorization on a good spectrum, duality, current algebra, and proper asymptotic behavior are described. Dual models at the present time require for consistency, an intercept value of α 0 = 1 and a dimension value of d = 26 (or d = 10). There have been speculations that the unphysical dimension may be made physical by associating the ''extra dimensions'' with certain internal degrees of freedom. However, it is desired that the theory itself, force the dimension d = 4. It is quite possible that the dimension problem and the intercept problem are tied together and that resolving either problem will resolve the other. Order by order, a new dual current is constructed that is manifestly factorizable and which appears to be valid for arbitrary space-time dimension. The fact that this current is not bound at d = 26, leads to interesting speculations on the nature of dual currents
On combined gravity gradient components modelling for applied geophysics
Veryaskin, Alexey; McRae, Wayne
2008-01-01
Gravity gradiometry research and development has intensified in recent years to the extent that technologies providing a resolution of about 1 eotvos per 1 second average shall likely soon be available for multiple critical applications such as natural resources exploration, oil reservoir monitoring and defence establishment. Much of the content of this paper was composed a decade ago, and only minor modifications were required for the conclusions to be just as applicable today. In this paper we demonstrate how gravity gradient data can be modelled, and show some examples of how gravity gradient data can be combined in order to extract valuable information. In particular, this study demonstrates the importance of two gravity gradient components, Txz and Tyz, which, when processed together, can provide more information on subsurface density contrasts than that derived solely from the vertical gravity gradient (Tzz)
2D higher spin gravity and the multimatrix models
Awada, M.; Qiu Zongan
1990-01-01
We quantize W-gravity coupled to matter fields in the conformal gauge and obtain the critical exponents. We demonstrate explicitly how the generators of the W-algebra are described by an infinite set of conserved charges of the KdV hierarchy. We obtain the generalized hamiltonian equation of motion and show that it contains the class of universal differential equations of the matrix models. Thus we propose that these models describe pure W-gravity theories of the A-type. Consequently we give a new set of universal equations that correspond to other types of W-gravity theories. (orig.)
Venus gravity and topography: 60th degree and order model
Konopliv, A. S.; Borderies, N. J.; Chodas, P. W.; Christensen, E. J.; Sjogren, W. L.; Williams, B. G.; Balmino, G.; Barriot, J. P.
1993-01-01
We have combined the most recent Pioneer Venus Orbiter (PVO) and Magellan (MGN) data with the earlier 1978-1982 PVO data set to obtain a new 60th degree and order spherical harmonic gravity model and a 120th degree and order spherical harmonic topography model. Free-air gravity maps are shown over regions where the most marked improvement has been obtained (Ishtar-Terra, Alpha, Bell and Artemis). Gravity versus topography relationships are presented as correlations per degree and axes orientation.
Universe before Planck time: A quantum gravity model
Padmanabhan, T.
1983-01-01
A model for quantum gravity can be constructed by treating the conformal degree of freedom of spacetime as a quantum variable. An isotropic, homogeneous cosmological solution in this quantum gravity model is presented. The spacetime is nonsingular for all the three possible values of three-space curvature, and agrees with the classical solution for time scales larger than the Planck time scale. A possibility of quantum fluctuations creating the matter in the universe is suggested
Regularization of quantum gravity in the matrix model approach
Ueda, Haruhiko
1991-02-01
We study divergence problem of the partition function in the matrix model approach for two-dimensional quantum gravity. We propose a new model V(φ) = 1/2Trφ 2 + g 4 /NTrφ 4 + g'/N 4 Tr(φ 4 ) 2 and show that in the sphere case it has no divergence problem and the critical exponent is of pure gravity. (author)
Dual elaboration models in attitude change processes
Žeželj Iris
2005-01-01
Full Text Available This article examines empirical and theoretical developments in research on attitude change in the past 50 years. It focuses the period from 1980 till present as well as cognitive response theories as the dominant theoretical approach in the field. The postulates of Elaboration Likelihood Model, as most-researched representative of dual process theories are studied, based on review of accumulated research evidence. Main research findings are grouped in four basic factors: message source, message content, message recipient and its context. Most influential criticisms of the theory are then presented regarding its empirical base and dual process assumption. Some possible applications and further research perspectives are discussed at the end.
Distributed Model Predictive Control via Dual Decomposition
Biegel, Benjamin; Stoustrup, Jakob; Andersen, Palle
2014-01-01
This chapter presents dual decomposition as a means to coordinate a number of subsystems coupled by state and input constraints. Each subsystem is equipped with a local model predictive controller while a centralized entity manages the subsystems via prices associated with the coupling constraints...
Modeling of gravity-imbibition and gravity-drainage processes: Analytic and numerical solutions
Bech, N.; Jensen, O.K.; Nielsen, B.
1991-01-01
A matrix/fracture exchange model for a fractured reservoir simulator is described. Oil/water imbibition is obtained from a diffusion equation with water saturation as the dependent variable. Gas/oil gravity drainage and imbibition are calculated by taking into account the vertical saturation...... distribution in the matrix blocks....
Calibrating Vadose Zone Models with Time-Lapse Gravity Data
Christiansen, Lars; Hansen, A. B.; Looms, M. C.
2009-01-01
A change in soil water content is a change in mass stored in the subsurface. Given that the mass change is big enough, the change can be measured with a gravity meter. Attempts have been made with varying success over the last decades to use ground-based time-lapse gravity measurements to infer...... hydrogeological parameters. These studies focused on the saturated zone with specific yield as the most prominent target parameter. Any change in storage in the vadose zone has been considered as noise. Our modeling results show a measureable change in gravity from the vadose zone during a forced infiltration...... experiment on 10m by 10m grass land. Simulation studies show a potential for vadose zone model calibration using gravity data in conjunction with other geophysical data, e.g. cross-borehole georadar. We present early field data and calibration results from a forced infiltration experiment conducted over 30...
On Goldstone particles and the Adler principle in dual models
Volkov, D.V.; Zheltukhin, A.A.; Pashnev, A.I.
1975-01-01
The results that have been obtained on the basis of considering the spontaneous vacuum transitions for the cases of Veneziano dual model and dual M-model are generalized to model containing internal quantum numbers of SU(N)-group. This generalization allows to consider how in dual models the spontaneous violation of symmetry occurs, which Goldstone particles appear in this process, how Adler's principle is realized for dual amplitudes and their topics related of spontaneous violation of symmetry
Gravity model development for TOPEX/POSEIDON: Joint gravity models 1 and 2
Nerem, R. S.; Lerch, F. J.; Marshall, J. A.; Pavlis, E. C.; Putney, B. H.; Tapley, B. D.; Eanes, R. J.; Ries, J. C.; Schutz, B. E.; Shum, C. K.
1994-01-01
The TOPEX/POSEIDON (T/P) prelaunch Joint Gravity Model-1 (JGM-1) and the postlaunch JGM-2 Earth gravitational models have been developed to support precision orbit determination for T/P. Each of these models is complete to degree 70 in spherical harmonics and was computed from a combination of satellite tracking data, satellite altimetry, and surface gravimetry. While improved orbit determination accuracies for T/P have driven the improvements in the models, the models are general in application and also provide an improved geoid for oceanographic computations. The postlaunch model, JGM-2, which includes T/P satellite laser ranging (SLR) and Doppler orbitography and radiopositioning integrated by satellite (DORIS) tracking data, introduces radial orbit errors for T/P that are only 2 cm RMS with the commission errors of the marine geoid for terms to degree 70 being +/- 25 cm. Errors in modeling the nonconservative forces acting on T/P increase the total radial errors to only 3-4 cm root mean square (RMS), a result much better than premission goals. While the orbit accuracy goal for T/P has been far surpassed geoid errors still prevent the absolute determination of the ocean dynamic topography for wavelengths shorter than about 2500 km. Only a dedicated gravitational field satellite mission will likely provide the necessary improvement in the geoid.
A dynamic ventilation model for gravity sewer networks.
Wang, Y C; Nobi, N; Nguyen, T; Vorreiter, L
2012-01-01
To implement any effective odour and corrosion control technology in the sewer network, it is imperative that the airflow through gravity sewer airspaces be quantified. This paper presents a full dynamic airflow model for gravity sewer systems. The model, which is developed using the finite element method, is a compressible air transport model. The model has been applied to the North Head Sewerage Ocean Outfall System (NSOOS) and calibrated using the air pressure and airflow data collected during October 2008. Although the calibration is focused on forced ventilation, the model can be applied to natural ventilation as well.
Dark-energy cosmological models in f(G) gravity
Shamir, M. F., E-mail: farasat.shamir@nu.edu.pk [National University of Computer and Emerging Sciences Lahore Campus, Department of Sciences and Humanities (Pakistan)
2016-10-15
We discuss dark-energy cosmological models in f(G) gravity. For this purpose, a locally rotationally symmetric Bianchi type I cosmological model is considered. First, exact solutions with a well-known form of the f(G) model are explored. One general solution is discussed using a power-law f(G) gravity model and physical quantities are calculated. In particular, Kasner’s universe is recovered and the corresponding f(G) gravity models are reported. Second, the energy conditions for the model under consideration are discussed using graphical analysis. It is concluded that solutions with f(G) = G{sup 5/6} support expansion of universe while those with f(G) = G{sup 1/2} do not favor the current expansion.
Gravity model improvement using GEOS-3 (GEM 9 and 10)
Lerch, F. J.; Klosko, S. M.; Laubscher, R. E.; Wagner, C. A.
1977-01-01
The use of collocation permitted GEM 9 to be a larger field than previous derived satellite models, GEM 9 having harmonics complete to 20 x 20 with selected higher degree terms. The satellite data set has approximately 840,000 observations, of which 200,000 are laser ranges taken on 9 satellites equipped with retroreflectors. GEM 10 is complete to 22 x 22 with selected higher degree terms out to degree and order 30 amounting to a total of 592 coefficients. Comparisons with surface gravity and altimeter data indicate a substantial improvement in GEM 9 over previous satellite solutions; GEM 9 is in even closer agreement with surface data than the previously published GEM 6 solution which contained surface gravity. In particular the free air gravity anomalies calculated from GEM 9 and a surface gravity solution are in excellent agreement for the high degree terms.
Spherical collapse and cluster counts in modified gravity models
Martino, Matthew C.; Stabenau, Hans F.; Sheth, Ravi K.
2009-01-01
Modifications to the gravitational potential affect the nonlinear gravitational evolution of large scale structures in the Universe. To illustrate some generic features of such changes, we study the evolution of spherically symmetric perturbations when the modification is of Yukawa type; this is nontrivial, because we should not and do not assume that Birkhoff's theorem applies. We then show how to estimate the abundance of virialized objects in such models. Comparison with numerical simulations shows reasonable agreement: When normalized to have the same fluctuations at early times, weaker large scale gravity produces fewer massive halos. However, the opposite can be true for models that are normalized to have the same linear theory power spectrum today, so the abundance of rich clusters potentially places interesting constraints on such models. Our analysis also indicates that the formation histories and abundances of sufficiently low mass objects are unchanged from standard gravity. This explains why simulations have found that the nonlinear power spectrum at large k is unaffected by such modifications to the gravitational potential. In addition, the most massive objects in models with normalized cosmic microwave background and weaker gravity are expected to be similar to the high-redshift progenitors of the most massive objects in models with stronger gravity. Thus, the difference between the cluster and field galaxy populations is expected to be larger in models with stronger large scale gravity.
Terrestrial Microgravity Model and Threshold Gravity Simulation using Magnetic Levitation
Ramachandran, N.
2005-01-01
What is the threshold gravity (minimum gravity level) required for the nominal functioning of the human system? What dosage is required? Do human cell lines behave differently in microgravity in response to an external stimulus? The critical need for such a gravity simulator is emphasized by recent experiments on human epithelial cells and lymphocytes on the Space Shuttle clearly showing that cell growth and function are markedly different from those observed terrestrially. Those differences are also dramatic between cells grown in space and those in Rotating Wall Vessels (RWV), or NASA bioreactor often used to simulate microgravity, indicating that although morphological growth patterns (three dimensional growth) can be successfully simulated using RWVs, cell function performance is not reproduced - a critical difference. If cell function is dramatically affected by gravity off-loading, then cell response to stimuli such as radiation, stress, etc. can be very different from terrestrial cell lines. Yet, we have no good gravity simulator for use in study of these phenomena. This represents a profound shortcoming for countermeasures research. We postulate that we can use magnetic levitation of cells and tissue, through the use of strong magnetic fields and field gradients, as a terrestrial microgravity model to study human cells. Specific objectives of the research are: 1. To develop a tried, tested and benchmarked terrestrial microgravity model for cell culture studies; 2. Gravity threshold determination; 3. Dosage (magnitude and duration) of g-level required for nominal functioning of cells; 4. Comparisons of magnetic levitation model to other models such as RWV, hind limb suspension, etc. and 5. Cellular response to reduced gravity levels of Moon and Mars. The paper will discuss experiments md modeling work to date in support of this project.
Zhao, Qile; Guo, Jing; Hu, Zhigang; Shi, Chuang; Liu, Jingnan; Cai, Hua; Liu, Xianglin
2011-05-01
The GRACE (Gravity Recovery And Climate Experiment) monthly gravity models have been independently produced and published by several research institutions, such as Center for Space Research (CSR), GeoForschungsZentrum (GFZ), Jet Propulsion Laboratory (JPL), Centre National d’Etudes Spatiales (CNES) and Delft Institute of Earth Observation and Space Systems (DEOS). According to their processing standards, above institutions use the traditional variational approach except that the DEOS exploits the acceleration approach. The background force models employed are rather similar. The produced gravity field models generally agree with one another in the spatial pattern. However, there are some discrepancies in the gravity signal amplitude between solutions produced by different institutions. In particular, 10%-30% signal amplitude differences in some river basins can be observed. In this paper, we implemented a variant of the traditional variational approach and computed two sets of monthly gravity field solutions using the data from January 2005 to December 2006. The input data are K-band range-rates (KBRR) and kinematic orbits of GRACE satellites. The main difference in the production of our two types of models is how to deal with nuisance parameters. This type of parameters is necessary to absorb low-frequency errors in the data, which are mainly the aliasing and instrument errors. One way is to remove the nuisance parameters before estimating the geopotential coefficients, called NPARB approach in the paper. The other way is to estimate the nuisance parameters and geopotential coefficients simultaneously, called NPESS approach. These two types of solutions mainly differ in geopotential coefficients from degree 2 to 5. This can be explained by the fact that the nuisance parameters and the gravity field coefficients are highly correlated, particularly at low degrees. We compare these solutions with the official and published ones by means of spectral analysis. It is
Terrestrial Microgravity Model and Threshold Gravity Simulation sing Magnetic Levitation
Ramachandran, N.
2005-01-01
What is the threshold gravity (minimum gravity level) required for the nominal functioning of the human system? What dosage is required? Do human cell lines behave differently in microgravity in response to an external stimulus? The critical need for such a gravity simulator is emphasized by recent experiments on human epithelial cells and lymphocytes on the Space Shuttle clearly showing that cell growth and function are markedly different from those observed terrestrially. Those differences are also dramatic between cells grown in space and those in Rotating Wall Vessels (RWV), or NASA bioreactor often used to simulate microgravity, indicating that although morphological growth patterns (three dimensional growth) can be successiblly simulated using RWVs, cell function performance is not reproduced - a critical difference. If cell function is dramatically affected by gravity off-loading, then cell response to stimuli such as radiation, stress, etc. can be very different from terrestrial cell lines. Yet, we have no good gravity simulator for use in study of these phenomena. This represents a profound shortcoming for countermeasures research. We postulate that we can use magnetic levitation of cells and tissue, through the use of strong magnetic fields and field gradients, as a terrestrial microgravity model to study human cells. Specific objectives of the research are: 1. To develop a tried, tested and benchmarked terrestrial microgravity model for cell culture studies; 2. Gravity threshold determination; 3. Dosage (magnitude and duration) of g-level required for nominal functioning of cells; 4. Comparisons of magnetic levitation model to other models such as RWV, hind limb suspension, etc. and 5. Cellular response to reduced gravity levels of Moon and Mars.
Dual superconductor models of color confinement
Ripka, Georges
2004-01-01
The lectures, delivered at ECT (European Centre for Theoretical Studies in Nuclear Physics and Related Areas) in Trento (Italy) in 2002 and 2003, are addressed to physicists who wish to acquire a minimal background to understand present day attempts to model the confinement of quantum chromo-dynamics (QCD) in terms of dual superconductors. The lectures focus more on the models than on attempts to derive them from QCD. They discuss the Dirac theory of magnetic monopoles, the world sheet swept out by Dirac strings, deformations of Dirac strings and charge quantization, gauge fields associated to the field tensor and to the dual field tensor, the Landau-Ginzburg (Abelian Higgs) model of a dual superconductor, the flux tube joining two equal and opposite color-electric charges, the Abrikosov-Nielsen-Olesen vortex, the divergencies of the London limit, the comparison of the calculated flux tube and string tension with lattice data, duality transformations and the use of Kalb-Ramond fields, the two-potential Zwanzi...
An improved model for the Earth's gravity field
Tapley, B. D.; Shum, C. K.; Yuan, D. N.; Ries, J. C.; Schutz, B. E.
1989-01-01
An improved model for the Earth's gravity field, TEG-1, was determined using data sets from fourteen satellites, spanning the inclination ranges from 15 to 115 deg, and global surface gravity anomaly data. The satellite measurements include laser ranging data, Doppler range-rate data, and satellite-to-ocean radar altimeter data measurements, which include the direct height measurement and the differenced measurements at ground track crossings (crossover measurements). Also determined was another gravity field model, TEG-1S, which included all the data sets in TEG-1 with the exception of direct altimeter data. The effort has included an intense scrutiny of the gravity field solution methodology. The estimated parameters included geopotential coefficients complete to degree and order 50 with selected higher order coefficients, ocean and solid Earth tide parameters, Doppler tracking station coordinates and the quasi-stationary sea surface topography. Extensive error analysis and calibration of the formal covariance matrix indicate that the gravity field model is a significant improvement over previous models and can be used for general applications in geodesy.
Modelling Technique for Demonstrating Gravity Collapse Structures in Jointed Rock.
Stimpson, B.
1979-01-01
Described is a base-friction modeling technique for studying the development of collapse structures in jointed rocks. A moving belt beneath weak material is designed to simulate gravity. A description is given of the model frame construction. (Author/SA)
An extended gravity model with substitution applied to international trade
Bikker, J.A.|info:eu-repo/dai/nl/06912261X
The traditional gravity model has been applied many times to international trade flows, especially in order to analyze trade creation and trade diversion. However, there are two fundamental objections to the model: it cannot describe substitutions between flows and it lacks a cogent theoretical
Modeling sintering of multilayers under influence of gravity
Frandsen, Henrik Lund; Olevsky, Eugene; Tadesse Molla, Tesfaye
2013-01-01
, which describes the combined effect of sintering and gravity of thin multilayers, is derived and later compared with experimental results. It allows for consideration of both uniaxial and biaxial stress states. The model is based on the Skorohod-Olevsky viscous sintering framework, the classical...... laminate theory and the elastic-viscoelastic correspondence principle. The modeling approach is then applied to illustrate the effect of gravity during sintering of thin layers of cerium gadolinium oxide (CGO), and it is found to be significant. © 2012 The American Ceramic Society....
Impact Of GOCE On The Nordic Gravity Field Modelling
Yidiz, Hasan; Forsberg, René; Tscherning, C. C.
2011-01-01
GOCE level-2 Tzz and Txx gravity gradients at satellite altitude are used in combination as input data to predict surface free air gravity anomalies over the Nordic region using Least Square Collocation. We test the performance of using covariance functions created separately from Tzz gradients a...... Surface model, both the NKG-2004 quasi-geoid model of the Nordic and Baltic Area and the one obtained using second generation GOCE spherical harmonic coefficients based on time-wise method can successfully reproduce the higher level of the Baltic Sea relative to the Atlantic Ocean....
Approaches to Validation of Models for Low Gravity Fluid Behavior
Chato, David J.; Marchetta, Jeffery; Hochstein, John I.; Kassemi, Mohammad
2005-01-01
This paper details the author experiences with the validation of computer models to predict low gravity fluid behavior. It reviews the literature of low gravity fluid behavior as a starting point for developing a baseline set of test cases. It examines authors attempts to validate their models against these cases and the issues they encountered. The main issues seem to be that: Most of the data is described by empirical correlation rather than fundamental relation; Detailed measurements of the flow field have not been made; Free surface shapes are observed but through thick plastic cylinders, and therefore subject to a great deal of optical distortion; and Heat transfer process time constants are on the order of minutes to days but the zero-gravity time available has been only seconds.
Simplicity constraints: A 3D toy model for loop quantum gravity
Charles, Christoph
2018-05-01
In loop quantum gravity, tremendous progress has been made using the Ashtekar-Barbero variables. These variables, defined in a gauge fixing of the theory, correspond to a parametrization of the solutions of the so-called simplicity constraints. Their geometrical interpretation is however unsatisfactory as they do not constitute a space-time connection. It would be possible to resolve this point by using a full Lorentz connection or, equivalently, by using the self-dual Ashtekar variables. This leads however to simplicity constraints or reality conditions which are notoriously difficult to implement in the quantum theory. We explore in this paper the possibility of using completely degenerate actions to impose such constraints at the quantum level in the context of canonical quantization. To do so, we define a simpler model, in 3D, with similar constraints by extending the phase space to include an independent vielbein. We define the classical model and show that a precise quantum theory by gauge unfixing can be defined out of it, completely equivalent to the standard 3D Euclidean quantum gravity. We discuss possible future explorations around this model as it could help as a stepping stone to define full-fledged covariant loop quantum gravity.
An improved gravity model for Mars: Goddard Mars Model 1
Smith, D. E.; Lerch, F. J.; Nerem, R. S.; Zuber, M. T.; Patel, G. B.; Fricke, S. K.; Lemoine, F. G.
1993-01-01
Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, Goddard Mars Model 1 (GMM-1). This model employs nearly all available data, consisting of approximately 1100 days of S band tracking data collected by NASA's Deep Space Network from the Mariner 9 and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM-1 is complete to spherical harmonic degree and order 50, which corresponds to a half-wavelength spatial resolution of 200-300 km where the data permit. GMM-1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM-1 over previous models is a consequence of several factors: improved computational capabilities, the use of otpimum weighting and least squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X band tracking data from the 379-km altitude, nnear-polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM-1, particularly at high latitudes where current data poorly resolve the gravitational signature of the planet.
Systematic simulations of modified gravity: symmetron and dilaton models
Brax, Philippe; Davis, Anne-Christine; Li, Baojiu; Winther, Hans A.; Zhao, Gong-Bo
2012-01-01
We study the linear and nonlinear structure formation in the dilaton and symmetron models of modified gravity using a generic parameterisation which describes a large class of scenarios using only a few parameters, such as the coupling between the scalar field and the matter, and the range of the scalar force on very large scales. For this we have modified the N-body simulation code ECOSMOG, which is a variant of RAMSES working in modified gravity scenarios, to perform a set of 110 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a large portion of the parameter space. We have studied the effects of modified gravity on the matter power spectrum and mass function, and found a rich and interesting phenomenology where the difference with the ΛCDM template cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc −1 . Our results show the full effect of screening on nonlinear structure formation and the associated deviation from ΛCDM. We also investigate how differences in the force mediated by the scalar field in modified gravity models lead to qualitatively different features for the nonlinear power spectrum and the halo mass function, and how varying the individual model parameters changes these observables. The differences are particularly large in the nonlinear power spectra whose shapes for f(R), dilaton and symmetron models vary greatly, and where the characteristic bump around 1 hMpc −1 of f(R) models is preserved for symmetrons, whereas an increase on much smaller scales is particular to symmetrons. No bump is present for dilatons where a flattening of the power spectrum takes place on small scales. These deviations from ΛCDM and the differences between modified gravity models, such as dilatons and symmetrons, could be tested with future surveys
Numerical Models of Human Circulatory System under Altered Gravity: Brain Circulation
Kim, Chang Sung; Kiris, Cetin; Kwak, Dochan; David, Tim
2003-01-01
A computational fluid dynamics (CFD) approach is presented to model the blood flow through the human circulatory system under altered gravity conditions. Models required for CFD simulation relevant to major hemodynamic issues are introduced such as non-Newtonian flow models governed by red blood cells, a model for arterial wall motion due to fluid-wall interactions, a vascular bed model for outflow boundary conditions, and a model for auto-regulation mechanism. The three-dimensional unsteady incompressible Navier-Stokes equations coupled with these models are solved iteratively using the pseudocompressibility method and dual time stepping. Moving wall boundary conditions from the first-order fluid-wall interaction model are used to study the influence of arterial wall distensibility on flow patterns and wall shear stresses during the heart pulse. A vascular bed modeling utilizing the analogy with electric circuits is coupled with an auto-regulation algorithm for multiple outflow boundaries. For the treatment of complex geometry, a chimera overset grid technique is adopted to obtain connectivity between arterial branches. For code validation, computed results are compared with experimental data for steady and unsteady non-Newtonian flows. Good agreement is obtained for both cases. In sin-type Gravity Benchmark Problems, gravity source terms are added to the Navier-Stokes equations to study the effect of gravitational variation on the human circulatory system. This computational approach is then applied to localized blood flows through a realistic carotid bifurcation and two Circle of Willis models, one using an idealized geometry and the other model using an anatomical data set. A three- dimensional anatomical Circle of Willis configuration is reconstructed from human-specific magnetic resonance images using an image segmentation method. The blood flow through these Circle of Willis models is simulated to provide means for studying gravitational effects on the brain
Lorentzian 3d gravity with wormholes via matrix models
Ambjørn, J.; Jurkiewicz, J.; Loll, R.; Vernizzi, G.
2001-01-01
We uncover a surprising correspondence between a non-perturbative formulation of three-dimensional Lorentzian quantum gravity and a hermitian two-matrix model with ABAB-interaction. The gravitational transfer matrix can be expressed as the logarithm of a two-matrix integral, and we deduce from
Phase diagram of the mean field model of simplicial gravity
Bialas, P.; Burda, Z.; Johnston, D.
1999-01-01
We discuss the phase diagram of the balls in boxes model, with a varying number of boxes. The model can be regarded as a mean-field model of simplicial gravity. We analyse in detail the case of weights of the form p(q) = q -β , which correspond to the measure term introduced in the simplicial quantum gravity simulations. The system has two phases: elongated (fluid) and crumpled. For β ε (2, ∞) the transition between these two phases is first-order, while for β ε (1, 2) it is continuous. The transition becomes softer when β approaches unity and eventually disappears at β = 1. We then generalise the discussion to an arbitrary set of weights. Finally, we show that if one introduces an additional kinematic bound on the average density of balls per box then a new condensed phase appears in the phase diagram. It bears some similarity to the crinkled phase of simplicial gravity discussed recently in models of gravity interacting with matter fields
Astrophysical constraints on unparticle-inspired models of gravity
Bertolami, O.; Paramos, J.; Santos, P.
2009-01-01
We use stellar dynamics arguments to constrain the relevant parameters of unparticle-inspired models of gravity. We show that resulting bounds do constrain the parameters of the theory of unparticles, as far as its energy scale satisfies the condition Λ U ≥1 TeV and d U is close to unity.
Further stable neutron star models from f(R) gravity
Astashenok, Artyom V. [I. Kant Baltic Federal University, Institute of Physics and Technology, Nevskogo st. 14, Kaliningrad, 236041 (Russian Federation); Capozziello, Salvatore [Dipartimento di Fisica, Università di Napoli ' ' Federico II' ' , Via Cinthia, 9, Napoli, I–80126 (Italy); Odintsov, Sergei D., E-mail: artyom.art@gmail.com, E-mail: capozziello@na.infn.it, E-mail: odintsov@ieec.uab.es [Instituciò Catalana de Recerca i Estudis Avançats (ICREA), Barcelona (Spain)
2013-12-01
Neutron star models in perturbative f(R) gravity are considered with realistic equations of state. In particular, we consider the FPS, SLy and other equations of state and a case of piecewise equation of state for stars with quark cores. The mass-radius relations for f(R) = R+R(e{sup −R/R{sub 0}}−1) model and for R{sup 2} models with logarithmic and cubic corrections are obtained. In the case of R{sup 2} gravity with cubic corrections, we obtain that at high central densities (ρ > 10ρ{sub ns}, where ρ{sub ns} = 2.7 × 10{sup 14} g/cm{sup 3} is the nuclear saturation density), stable star configurations exist. The minimal radius of such stars is close to 9 km with maximal mass ∼ 1.9M{sub ⊙} (SLy equation). A similar situation takes place for AP4 and BSK20 EoS. Such an effect can give rise to more compact stars than in General Relativity. If observationally identified, such objects could constitute a formidable signature for modified gravity at astrophysical level. Another interesting result can be achieved in modified gravity with only a cubic correction. For some EoS, the upper limit of neutron star mass increases and therefore these EoS can describe realistic star configurations (although, in General Relativity, these EoS are excluded by observational constraints)
Further stable neutron star models from f(R) gravity
Astashenok, Artyom V.; Capozziello, Salvatore; Odintsov, Sergei D.
2013-01-01
Neutron star models in perturbative f(R) gravity are considered with realistic equations of state. In particular, we consider the FPS, SLy and other equations of state and a case of piecewise equation of state for stars with quark cores. The mass-radius relations for f(R) = R+R(e −R/R 0 −1) model and for R 2 models with logarithmic and cubic corrections are obtained. In the case of R 2 gravity with cubic corrections, we obtain that at high central densities (ρ > 10ρ ns , where ρ ns = 2.7 × 10 14 g/cm 3 is the nuclear saturation density), stable star configurations exist. The minimal radius of such stars is close to 9 km with maximal mass ∼ 1.9M ⊙ (SLy equation). A similar situation takes place for AP4 and BSK20 EoS. Such an effect can give rise to more compact stars than in General Relativity. If observationally identified, such objects could constitute a formidable signature for modified gravity at astrophysical level. Another interesting result can be achieved in modified gravity with only a cubic correction. For some EoS, the upper limit of neutron star mass increases and therefore these EoS can describe realistic star configurations (although, in General Relativity, these EoS are excluded by observational constraints)
The dual of the Carroll-Field-Jackiw model
Guimaraes, M.S.; Grigorio, L.; Wotzasek, C.
2006-01-01
In this work we apply different duality techniques, both the dual projection, based on the soldering formalism and the master action, in order to obtain and study the dual description of the Carroll- Field-Jackiw model [1], a theory with a Chern-Simons-like explicitly Lorentz and CPT violating term, including the interaction with external charges. This Maxwell-Chern-Simons-like model may be rewritten in terms of the interacting modes of a massless scalar model and a topologically massive model [2], that are mapped, through duality, into interacting massless Maxwell and massive self-dual modes [3]. It is also shown that these dual modes might be represented into an unified rank-two self-dual model that represents the direct dual of the vector Maxwell-Chern-Simons-like model
Unitary truncations and critical gravity : a toy model
Bergshoeff, Eric A.; de Haan, Sjoerd; Merbis, Wout; Porrati, Massimo; Rosseel, Jan
We investigate a higher-derivative scalar field model in a fixed d+1 dimensional AdS background as a toy model for a gravitational dual to a higher-rank logarithmic CFT. The holographic two-point correlation functions on the boundary agree with higher-rank LCFT correlation functions. For odd rank,
Chameleon halo modeling in f(R) gravity
Li Yin; Hu, Wayne
2011-01-01
We model the chameleon effect on cosmological statistics for the modified gravity f(R) model of cosmic acceleration. The chameleon effect, required to make the model compatible with local tests of gravity, reduces force enhancement as a function of the depth of the gravitational potential wells of collapsed structure and so is readily incorporated into a halo model by including parameters for the chameleon mass threshold and rapidity of transition. We show that the abundance of halos around the chameleon mass threshold is enhanced by both the merging from below and the lack of merging to larger masses. This property also controls the power spectrum in the nonlinear regime and we provide a description of the transition to the linear regime that is valid for a wide range of f(R) models.
Assessing GOCE Gravity Models using Altimetry and Drifters
Knudsen, Per; Andersen, Ole Baltazar
The improved gravity models provided by the GOCE mission have enhanced the resolution and sharpened the boundaries of those features and the associated geostrophic surface currents reveal improvements for all of the ocean’s current systems. There are still important signals to be recovered...... and issues related to errors in the models have been identified.In this study, a series of newer gravity models including observations from GRACE and GOCE are compared with the DTU15MSS mean sea surface to analyse resolution capacities and to identify issues caused by errors in the models. The comparisons...... are carried out in regional analyses using Fourier techniques to derive the spectral characteristics as well as anisotropic patterns to identify differences and to quantify quality measures associated with the models. In addition, regional analyses are carried out using in-situ observations of the geostrophic...
Neutron Star Models in Alternative Theories of Gravity
Manolidis, Dimitrios
We study the structure of neutron stars in a broad class of alternative theories of gravity. In particular, we focus on Scalar-Tensor theories and f(R) theories of gravity. We construct static and slowly rotating numerical star models for a set of equations of state, including a polytropic model and more realistic equations of state motivated by nuclear physics. Observable quantities such as masses, radii, etc are calculated for a set of parameters of the theories. Specifically for Scalar-Tensor theories, we also calculate the sensitivities of the mass and moment of inertia of the models to variations in the asymptotic value of the scalar field at infinity. These quantities enter post-Newtonian equations of motion and gravitational waveforms of two body systems that are used for gravitational-wave parameter estimation, in order to test these theories against observations. The construction of numerical models of neutron stars in f(R) theories of gravity has been difficult in the past. Using a new formalism by Jaime, Patino and Salgado we were able to construct models with high interior pressure, namely pc > rho c/3, both for constant density models and models with a polytropic equation of state. Thus, we have shown that earlier objections to f(R) theories on the basis of the inability to construct viable neutron star models are unfounded.
High-Resolution Gravity Field Modeling for Mercury to Estimate Crust and Lithospheric Properties
Goossens, S.; Mazarico, E.; Genova, A.; James, P. B.
2018-05-01
We estimate a gravity field model for Mercury using line-of-sight data to improve the gravity field model at short wavelengths. This can be used to infer crustal density and infer the support mechanism of the lithosphere.
A high resolution gravity model for Venus - GVM-1
Nerem, R. S.; Bills, B. G.; Mcnamee, J. B.
1993-01-01
A spherical harmonic model of the gravitational field of Venus complete to degree and order 50 has been developed using the S-band Doppler tracking data of the Pioneer Venus Orbiter (PVO) collected between 1979 and 1982. The short wavelengths of this model could only be resolved near the PVO periapse location (about 14 deg N latitude), therefore a priori constraints were applied to the model to bias poorly observed coefficients towards zero. The resulting model has a half-wavelength resolution of 400 km near the PVO periapse location, but the resolution degrades to greater than 1000 km near the poles. This gravity model correlates well with a degree 50 spherical harmonic expansion of the Venus topography derived from a combination of Magellan and PVO data. New tracking data from Magellan's gravity mission should provide some improvement to this model, although a complete model of the Venusian gravity field will depend on tracking of Magellan after the circularization of its orbit using aerobraking.
Dual models with SL(2, C) symmetry
Brink, L
1972-01-01
Making use of homogeneous space techniques, the authors construct a class of dual models, which is a generalization of the Virasoro- Shapiro type of model. The integrand in the integral representation for the N-point function depends not only on the modulus of the distances between two-dimensional Koba-Nielsen variables, but also on the corresponding phases. This is in fact the most general SL(2, C) invariant amplitude that can be constructed using complex integration variables. The extra phase factors in the integrand provide a possible means of avoiding tachyons both as external particles and as intermediate states in the amplitude. When factorized in a simple- minded fashion the intercepts are fixed to be integers. Although the external particles can be chosen not to be tachyons, such states appear as intermediate states. Within this factorization one can show that there are gauge conditions for the amplitude that can provide a ghostkilling mechanism. (19 refs).
Modeling of zero gravity venting: Studies of two-phase heat transfer under reduced gravity
Merte, H., Jr.
1986-01-01
The objective is to predict the pressure response of a saturated liquid-vapor system when undergoing a venting or depressurization process in zero gravity at low vent rates. An experimental investigation of the venting of cylindrical containers partially filled with initially saturated liquids was previously conducted under zero-gravity conditions and compared with an analytical model which incorporated the effect of interfacial mass transfer on the ullage pressure response during venting. A new model is presented to improve the estimation of the interfacial mass transfer. Duhammel's superposition integral is incorporated to approximate the transient temperature response of the interface, treating the liquid as a semi-infinite solid with conduction heat transfer. Account is also taken of the condensation taking place within the bulk of a saturated vapor as isentropic expansion takes place. Computational results are presented for the venting of R-11 from a given vessel and initial state for five different venting rates over a period of three seconds, and compared to prior NASA experiments. An improvement in the prediction of the final pressure takes place, but is still considerably below the measurements.
Renormalization group flow of scalar models in gravity
Guarnieri, Filippo
2014-01-01
In this Ph.D. thesis we study the issue of renormalizability of gravitation in the context of the renormalization group (RG), employing both perturbative and non-perturbative techniques. In particular, we focus on different gravitational models and approximations in which a central role is played by a scalar degree of freedom, since their RG flow is easier to analyze. We restrict our interest in particular to two quantum gravity approaches that have gained a lot of attention recently, namely the asymptotic safety scenario for gravity and the Horava-Lifshitz quantum gravity. In the so-called asymptotic safety conjecture the high energy regime of gravity is controlled by a non-Gaussian fixed point which ensures non-perturbative renormalizability and finiteness of the correlation functions. We then investigate the existence of such a non trivial fixed point using the functional renormalization group, a continuum version of the non-perturbative Wilson's renormalization group. In particular we quantize the sole conformal degree of freedom, which is an approximation that has been shown to lead to a qualitatively correct picture. The question of the existence of a non-Gaussian fixed point in an infinite-dimensional parameter space, that is for a generic f(R) theory, cannot however be studied using such a conformally reduced model. Hence we study it by quantizing a dynamically equivalent scalar-tensor theory, i.e. a generic Brans-Dicke theory with ω=0 in the local potential approximation. Finally, we investigate, using a perturbative RG scheme, the asymptotic freedom of the Horava-Lifshitz gravity, that is an approach based on the emergence of an anisotropy between space and time which lifts the Newton's constant to a marginal coupling and explicitly preserves unitarity. In particular we evaluate the one-loop correction in 2+1 dimensions quantizing only the conformal degree of freedom.
Dual Numbers Approach in Multiaxis Machines Error Modeling
Jaroslav Hrdina
2014-01-01
Full Text Available Multiaxis machines error modeling is set in the context of modern differential geometry and linear algebra. We apply special classes of matrices over dual numbers and propose a generalization of such concept by means of general Weil algebras. We show that the classification of the geometric errors follows directly from the algebraic properties of the matrices over dual numbers and thus the calculus over the dual numbers is the proper tool for the methodology of multiaxis machines error modeling.
ORBSIM- ESTIMATING GEOPHYSICAL MODEL PARAMETERS FROM PLANETARY GRAVITY DATA
Sjogren, W. L.
1994-01-01
The ORBSIM program was developed for the accurate extraction of geophysical model parameters from Doppler radio tracking data acquired from orbiting planetary spacecraft. The model of the proposed planetary structure is used in a numerical integration of the spacecraft along simulated trajectories around the primary body. Using line of sight (LOS) Doppler residuals, ORBSIM applies fast and efficient modelling and optimization procedures which avoid the traditional complex dynamic reduction of data. ORBSIM produces quantitative geophysical results such as size, depth, and mass. ORBSIM has been used extensively to investigate topographic features on the Moon, Mars, and Venus. The program has proven particulary suitable for modelling gravitational anomalies and mascons. The basic observable for spacecraft-based gravity data is the Doppler frequency shift of a transponded radio signal. The time derivative of this signal carries information regarding the gravity field acting on the spacecraft in the LOS direction (the LOS direction being the path between the spacecraft and the receiving station, either Earth or another satellite). There are many dynamic factors taken into account: earth rotation, solar radiation, acceleration from planetary bodies, tracking station time and location adjustments, etc. The actual trajectories of the spacecraft are simulated using least squares fitted to conic motion. The theoretical Doppler readings from the simulated orbits are compared to actual Doppler observations and another least squares adjustment is made. ORBSIM has three modes of operation: trajectory simulation, optimization, and gravity modelling. In all cases, an initial gravity model of curved and/or flat disks, harmonics, and/or a force table are required input. ORBSIM is written in FORTRAN 77 for batch execution and has been implemented on a DEC VAX 11/780 computer operating under VMS. This program was released in 1985.
Transcendental Political Systems and the Gravity Model
Lock, Connor
2012-01-01
This summer I have been working on an Army Deep Futures Model project named Themis. Themis is a JPL based modeling framework that anticipates possible future states for the world within the next 25 years. The goal of this framework is to determine the likelihood that the US Army will need to intervene on behalf of the US strategic interests. Key elements that are modeled within this tool include the world structure and major decisions that are made by key actors. Each actor makes decisions based on their goals and within the constraints of the structure of the system in which they are located. In my research I have focused primarily on the effects of structures upon the decision-making processes of the actors within them. This research is a natural extension of my major program at Georgetown University, where I am studying the International Political Economy and the structures that make it up. My basic goal for this summer project was to be a helpful asset to the Themis modeling team, with any research done or processes learned constituting a bonus.
Computer modeling describes gravity-related adaptation in cell cultures.
Alexandrov, Ludmil B; Alexandrova, Stoyana; Usheva, Anny
2009-12-16
Questions about the changes of biological systems in response to hostile environmental factors are important but not easy to answer. Often, the traditional description with differential equations is difficult due to the overwhelming complexity of the living systems. Another way to describe complex systems is by simulating them with phenomenological models such as the well-known evolutionary agent-based model (EABM). Here we developed an EABM to simulate cell colonies as a multi-agent system that adapts to hyper-gravity in starvation conditions. In the model, the cell's heritable characteristics are generated and transferred randomly to offspring cells. After a qualitative validation of the model at normal gravity, we simulate cellular growth in hyper-gravity conditions. The obtained data are consistent with previously confirmed theoretical and experimental findings for bacterial behavior in environmental changes, including the experimental data from the microgravity Atlantis and the Hypergravity 3000 experiments. Our results demonstrate that it is possible to utilize an EABM with realistic qualitative description to examine the effects of hypergravity and starvation on complex cellular entities.
Globally covering a-priori regional gravity covariance models
D. Arabelos
2003-01-01
Full Text Available Gravity anomaly data generated using Wenzel’s GPM98A model complete to degree 1800, from which OSU91A has been subtracted, have been used to estimate covariance functions for a set of globally covering equal-area blocks of size 22.5° × 22.5° at Equator, having a 2.5° overlap. For each block an analytic covariance function model was determined. The models are based on 4 parameters: the depth to the Bjerhammar sphere (determines correlation, the free-air gravity anomaly variance, a scale factor of the OSU91A error degree-variances and a maximal summation index, N, of the error degree-variances. The depth of Bjerhammar-sphere varies from -134km to nearly zero, N varies from 360 to 40, the scale factor from 0.03 to 38.0 and the gravity variance from 1081 to 24(10µms-22. The parameters are interpreted in terms of the quality of the data used to construct OSU91A and GPM98A and general conditions such as the occurrence of mountain chains. The variation of the parameters show that it is necessary to use regional covariance models in order to obtain a realistic signal to noise ratio in global applications.Key words. GOCE mission, Covariance function, Spacewise approach`
Investigation of Global Imbalances Based on a Gravity Model
Hyun-Hoon Lee
2011-06-01
Full Text Available Using the US Treasury International Capital (TIC data, this paper attempts to analyze the size and trend of foreign investment in the U.S. in the form of equities, bonds and bank lending during the period of 2001-2007. In addition, this paper assesses the determinants of foreign investment in the U.S., using the financial gravity model which includes an East Asian dummy as an explanatory variable. The results show that most East Asian countries have invested more in the U.S. than the optimal level suggested by the gravity model. Such an over-investment is more evident in long-term bond investment than in equity investment or bank lending. Thus, the results confirm that global imbalance does exist between East Asian countries and the U.S.
Dynamical 3-Space Gravity Theory: Effects on Polytropic Solar Models
May R. D.
2011-01-01
Full Text Available Numerous experiments and observations have confirmed the existence of a dynamical 3-space, detectable directly by light-speed anisotropy experiments, and indirectly by means of novel gravitational effects, such as bore hole g anomalies, predictable black hole masses, flat spiral-galaxy rotation curves, and the expansion of the universe, all without dark matter and dark energy. The dynamics for this 3-space follows from a unique generalisation of Newtonian gravity, once that is cast into a velocity formalism. This new theory of gravity is applied to the solar model of the sun to compute new density, pressure and temperature profiles, using polytrope modelling of the equation of state for the matter. These results should be applied to a re-analysis of solar neutrino production, and to stellar evolution in general.
Topics in dual models and extended solutions
Roth, R.S.
1977-01-01
Two main topics are explored. The first deals with the infinities arising from the one loop planar string diagram of the standard dual model. It is shown that for the number of dimensions d = 25 or 26, these infinities lead to a renormalization of the slope of the Regge trajectories, in addition to a renormalization of the coupling constant. The second topic deals with the propagator for a confined particle (monopole) in a field theory. When summed to all orders, this propagator is altogether free of singularities in the finite momentum plane, and an attempt is made to illustrate this. The Bethe-Salpeter equation is examined and it is shown that ladder diagrams are not sufficient to obtain this result. However, in a nonrelativistic approximation confinement is obtained and all poles disappear
New results in the Dual Parton Model
Van, J.T.T.; Capella, A.
1984-01-01
In this paper, the similarity between the x distribution for particle production and the fragmentation functions are observed in e+e- collisions and in deep inelastic scattering are presented. Based on the observation, the authors develop a complete approach to multiparticle production which incorporates the most important features and concepts learned about high energy collisions. 1. Topological expansion : the dominant diagram at high energy corresponds to the simplest topology. 2. Unitarity : diagrams of various topology contribute to the cross sections in a way that unitary is preserved. 3. Regge behaviour and Duality. 4. Partonic structure of hadrons. These general theoretical ideas, result from many joint experimental and theoretical efforts on the study of soft hadron physics. The dual parton model is able to explain all the experimental features from FNAL to SPS collider energies. It has all the properties of an S-matrix theory and provides a unified description of hadron-hadron, hadron-nucleus and nucleus-nucleus collisions
Type I Shell Galaxies as a Test of Gravity Models
Vakili, Hajar; Rahvar, Sohrab [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Kroupa, Pavel, E-mail: vakili@physics.sharif.edu [Helmholtz-Institut für Strahlen-und Kernphysik, Universität Bonn, Nussallee 14-16, D-53115 Bonn (Germany)
2017-10-10
Shell galaxies are understood to form through the collision of a dwarf galaxy with an elliptical galaxy. Shell structures and kinematics have been noted to be independent tools to measure the gravitational potential of the shell galaxies. We compare theoretically the formation of shells in Type I shell galaxies in different gravity theories in this work because this is so far missing in the literature. We include Newtonian plus dark halo gravity, and two non-Newtonian gravity models, MOG and MOND, in identical initial systems. We investigate the effect of dynamical friction, which by slowing down the dwarf galaxy in the dark halo models limits the range of shell radii to low values. Under the same initial conditions, shells appear on a shorter timescale and over a smaller range of distances in the presence of dark matter than in the corresponding non-Newtonian gravity models. If galaxies are embedded in a dark matter halo, then the merging time may be too rapid to allow multi-generation shell formation as required by observed systems because of the large dynamical friction effect. Starting from the same initial state, the observation of small bright shells in the dark halo model should be accompanied by large faint ones, while for the case of MOG, the next shell generation patterns iterate with a specific time delay. The first shell generation pattern shows a degeneracy with the age of the shells and in different theories, but the relative distance of the shells and the shell expansion velocity can break this degeneracy.
Quantum Gravity and Maximum Attainable Velocities in the Standard Model
Alfaro, Jorge
2007-01-01
A main difficulty in the quantization of the gravitational field is the lack of experiments that discriminate among the theories proposed to quantize gravity. Recently we showed that the Standard Model(SM) itself contains tiny Lorentz invariance violation(LIV) terms coming from QG. All terms depend on one arbitrary parameter α that set the scale of QG effects. In this talk we review the LIV for mesons nucleons and leptons and apply it to study several effects, including the GZK anomaly
The use of gravity models in setting and location analysis
Zbigniew Drewniak
2014-12-01
Full Text Available The article discusses the gravity models as an example of a tool that helps to analyze localization and the market coverage. Especially Reilly’s law of retail gravitation was presented in details as the milestone. The discussion was supported by calculations concerning two cities – Torun and Bydgoszcz and thus their impact on shopping preferences of inhabitants of neighboring places. The issues are mainly used in logistics, but also in marketing, advertising and sales.
The dual model of perfectionism and depression among Chinese ...
The dual model of perfectionism was adopted to explore the influence of adaptive and maladaptive perfectionism on depression in college students. The results support the dual process model of perfectionism in Chinese undergraduates. A sample of 206 Chinese undergraduates completed measures of perfectionism, ...
A GOCE only gravity model GOSG01S and the validation of GOCE related satellite gravity models
Xinyu Xu
2017-07-01
Full Text Available We compile the GOCE-only satellite model GOSG01S complete to spherical harmonic degree of 220 using Satellite Gravity Gradiometry (SGG data and the Satellite-to-Satellite Tracking (SST observations along the GOCE orbit based on applying a least-squares analysis. The diagonal components (Vxx, Vyy, Vzz of the gravitational gradient tensor are used to form the system of observation equations with the band-pass ARMA filter. The point-wise acceleration observations (ax, ay, az along the orbit are used to form the system of observation equations up to the maximum spherical harmonic degree/order 130. The analysis of spectral accuracy characteristics of the newly derived gravitational model GOSG01S and the existing models GOTIM04S, GODIR04S, GOSPW04S and JYY_GOCE02S based on their comparison with the ultra-high degree model EIGEN-6C2 reveals a significant consistency at the spectral window approximately between 80 and 190 due to the same period SGG data used to compile these models. The GOCE related satellite gravity models GOSG01S, GOTIM05S, GODIR05S, GOTIM04S, GODIR04S, GOSPW04S, JYY_GOCE02S, EIGEN-6C2 and EGM2008 are also validated by using GPS-leveling data in China and USA. According to the truncation at degree 200, the statistic results show that all GGMs have very similar differences at GPS-leveling points in USA, and all GOCE related gravity models have better performance than EGM2008 in China. This suggests that all these models provide much more information on the gravity field than EGM2008 in areas with low terrestrial gravity coverage. And STDs of height anomaly differences in China for the selected truncation degrees show that GOCE has improved the accuracy of the global models beyond degree 90 and the accuracies of the models improve from 24 cm to 16 cm. STDs of geoid height differences in USA show that GOSG01S model has best consistency comparing with GPS-leveling data for the frequency band of the degree between 20 and 160.
Gravity dual corrections to the heavy quark potential at finite-temperature
Grigoryan, Hovhannes R.; Kovchegov, Yuri V.
2011-01-01
We apply gauge/gravity duality to compute 1/N c 2 corrections to the heavy quark potentials of a quark-anti-quark pair (QQ-bar) and of a quark-quark pair (QQ) immersed into the strongly coupled N=4 SYM plasma. On the gravity side these corrections come from the exchanges of supergravity modes between two string worldsheets stretching from the UV boundary of AdS space to the black hole horizon in the bulk and smeared over S 5 . We find that the contributions to the QQ-bar potential coming from the exchanges of all of the relevant modes (such as dilaton, massive scalar, 2-form field, and graviton) are all attractive, leading to an attractive net QQ-bar potential. We show that at large separations r and/or high-temperature T the potential is of Yukawa-type, dominated by the graviton exchange, in agreement with earlier findings. On the other hand, at small-rT the QQ-bar potential scales as ∼(1/r)ln(1/rT). In the case of QQ potential the 2-form contribution changes sign and becomes repulsive: however, the net QQ potential remains attractive. At large-rT it is dominated by the graviton exchange, while at small-rT the QQ potential becomes Coulomb-like.
Equivalence principle implications of modified gravity models
Hui, Lam; Nicolis, Alberto; Stubbs, Christopher W.
2009-01-01
Theories that attempt to explain the observed cosmic acceleration by modifying general relativity all introduce a new scalar degree of freedom that is active on large scales, but is screened on small scales to match experiments. We demonstrate that if such screening occurs via the chameleon mechanism, such as in f(R) theory, it is possible to have order unity violation of the equivalence principle, despite the absence of explicit violation in the microscopic action. Namely, extended objects such as galaxies or constituents thereof do not all fall at the same rate. The chameleon mechanism can screen the scalar charge for large objects but not for small ones (large/small is defined by the depth of the gravitational potential and is controlled by the scalar coupling). This leads to order one fluctuations in the ratio of the inertial mass to gravitational mass. We provide derivations in both Einstein and Jordan frames. In Jordan frame, it is no longer true that all objects move on geodesics; only unscreened ones, such as test particles, do. In contrast, if the scalar screening occurs via strong coupling, such as in the Dvali-Gabadadze-Porrati braneworld model, equivalence principle violation occurs at a much reduced level. We propose several observational tests of the chameleon mechanism: 1. small galaxies should accelerate faster than large galaxies, even in environments where dynamical friction is negligible; 2. voids defined by small galaxies would appear larger compared to standard expectations; 3. stars and diffuse gas in small galaxies should have different velocities, even if they are on the same orbits; 4. lensing and dynamical mass estimates should agree for large galaxies but disagree for small ones. We discuss possible pitfalls in some of these tests. The cleanest is the third one where the mass estimate from HI rotational velocity could exceed that from stars by 30% or more. To avoid blanket screening of all objects, the most promising place to look is in
Analog model for quantum gravity effects: phonons in random fluids.
Krein, G; Menezes, G; Svaiter, N F
2010-09-24
We describe an analog model for quantum gravity effects in condensed matter physics. The situation discussed is that of phonons propagating in a fluid with a random velocity wave equation. We consider that there are random fluctuations in the reciprocal of the bulk modulus of the system and study free phonons in the presence of Gaussian colored noise with zero mean. We show that, in this model, after performing the random averages over the noise function a free conventional scalar quantum field theory describing free phonons becomes a self-interacting model.
Seasonal Gravity Field Variations from GRACE and Hydrological Models
Andersen, Ole Baltazar; Hinderer, Jacques; Lemoine, Frank G.
2004-01-01
. Four global hydrological models covering the same period in 2002–2003 as the GRACE observations were investigated to for their mutual consistency in estimates of annual variation in terrestrial water storage and related temporal changes in gravity field. The hydrological models differ by a maximum of 2...... µGal or nearly 5 cm equivalent water storage in selected regions. Integrated over all land masses the standard deviation among the annual signal from the four hydrological models are 0.6 µGal equivalent to around 1.4 cm in equivalent water layer thickness. The estimated accuracy of the annual...
Modeling and control of a gravity gradient stabilised satellite
Aage Skullestad
1999-01-01
Full Text Available This paper describes attitude control, i.e., 3-axes stabilisation and pointing, of a proposed Norwegian small gravity gradient stabilized satellite to be launched into low earth orbit. Generally, a gravity gradient stabilised system has limited stability and pointing capabilities, and wheels and/or magnetic coils are added in order to improve the attitude control. The best attitude accuracy is achieved using wheels, which can give accuracies down to less than one degree, but wheels increase the complexity and cost of the satellite. Magnetic coils allow cheaper satellites, and are an attractive solution to small, inexpensive satellites in low earth orbits and may provide an attitude control accuracy of a few degrees. Scientific measurements often require accurate attitude control in one or two axes only. Combining wheel and coil control may, in these cases, provide the best solutions. The simulation results are based on a linearised mathematical model of the satellite.
Spin foam models of matter coupled to gravity
Mikovic, A
2002-01-01
We construct a class of spin foam models describing matter coupled to gravity, such that the gravitational sector is described by the unitary irreducible representations of the appropriate symmetry group, while the matter sector is described by the finite-dimensional irreducible representations of that group. The corresponding spin foam amplitudes in the four-dimensional gravity case are expressed in terms of the spin network amplitudes for pentagrams with additional external and internal matter edges. We also give a quantum field theory formulation of the model, where the matter degrees of freedom are described by spin network fields carrying the indices from the appropriate group representation. In the non-topological Lorentzian gravity case, we argue that the matter representations should be appropriate SO(3) or SO(2) representations contained in a given Lorentz matter representation, depending on whether one wants to describe a massive or a massless matter field. The corresponding spin network amplitudes are given as multiple integrals of propagators which are matrix spherical functions
Testing the gravity p-median model empirically
Kenneth Carling
2015-12-01
Full Text Available Regarding the location of a facility, the presumption in the widely used p-median model is that the customer opts for the shortest route to the nearest facility. However, this assumption is problematic on free markets since the customer is presumed to gravitate to a facility by the distance to and the attractiveness of it. The recently introduced gravity p-median model offers an extension to the p-median model that account for this. The model is therefore potentially interesting, although it has not yet been implemented and tested empirically. In this paper, we have implemented the model in an empirical problem of locating vehicle inspections, locksmiths, and retail stores of vehicle spare-parts for the purpose of investigating its superiority to the p-median model. We found, however, the gravity p-median model to be of limited use for the problem of locating facilities as it either gives solutions similar to the p-median model, or it gives unstable solutions due to a non-concave objective function.
Butterfly effect in 3D gravity
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.
N = 6 superconformal Chern-Simons-matter theories, M2-branes and their gravity duals
Aharony, Ofer; Bergman, Oren; Maldacena, Juan; Jafferis, Daniel Louis
2008-01-01
We construct three dimensional Chern-Simons-matter theories with gauge groups U(N) x U(N) and SU(N) x SU(N) which have explicit N = 6 superconformal symmetry. Using brane constructions we argue that the U(N) x U(N) theory at level k describes the low energy limit of N M2-branes probing a C 4 /Z k singularity. At large N the theory is then dual to M-theory on AdS 4 x S 7 /Z k . The theory also has a 't Hooft limit (of large N with a fixed ratio N/k) which is dual to type IIA string theory on AdS 4 x CP 3 . For k = 1 the theory is conjectured to describe N M2-branes in flat space, although our construction realizes explicitly only six of the eight supersymmetries. We give some evidence for this conjecture, which is similar to the evidence for mirror symmetry in d = 3 gauge theories. When the gauge group is SU(2) x SU(2) our theory has extra symmetries and becomes identical to the Bagger-Lambert theory.
Embedded model control GNC for the Next Generation Gravity Mission
Colangelo, Luigi; Massotti, Luca; Canuto, Enrico; Novara, Carlo
2017-11-01
A Next Generation Gravity Mission (NGGM) concept for measuring the Earth's variable gravity field has been recently proposed by ESA. The mission objective consists in measuring the temporal variations of the Earth gravity field over a long-time span, with very high spatial and temporal resolutions. This paper focuses on the guidance, navigation and control (GNC) design for the science phase of the NGGM mission. NGGM will consist of a two-satellite long-distance formation like GRACE, where each satellite will be controlled to be drag-free like GOCE. Satellite-to-satellite distance variations, encoding gravity anomalies, will be measured by laser interferometry. The formation satellites, distant up to 200 km, will fly in a quasi-polar orbit at an Earth altitude between 300 and 450 km. Orbit and formation control counteract bias and drift of the residual drag-free accelerations, in order to reach orbit/formation long-term stability. Drag-free control allows the formation to fly counteracting the atmospheric drag, ideally subject only to gravity. Orbit and formation control, designed through the innovative Integrated Formation Control (IFC), have been integrated into a unique control system, aiming at stabilizing the formation triangle consisting of satellites and Earth Center of Masses. In addition, both spacecraft must align their control axis to the satellite-to-satellite line (SSL) with micro-radian accuracy. This is made possible by specific optical sensors and the inter-satellite laser interferometer, capable of materializing the SSL. Such sensors allow each satellite to pursue an autonomous alignment after a suitable acquisition procedure. Pointing control is severely constrained by the angular drag-free control, which must ideally zero the angular acceleration vector, in the science frequency band. The control unit has been designed according to the Embedded Model Control methodology and is organized in a hierarchical way, where the drag-free control plays the
Assessing GOCE Gravity Models using Altimetry and In-situ Ocean Current Observation
Knudsen, Per; Andersen, Ole Baltazar; Honecker, Johanna
gravity models provided by the GOCE mission have enhanced the resolution and sharpened the boundaries of those features and the associated geostrophic surface currents reveal improvements for all of the ocean's current systems. In this study, a series of 23 newer gravity models including observations from...... as quantified quality measures associated with the 23 GOCE gravity models.......The Gravity and steady state Ocean Circulation Explorer (GOCE) satellite mission measures Earth's gravity field with an unprecedented accuracy at short spatial scales. Previous results have demonstrated a significant advance in our ability to determine the ocean's general circulation. The improved...
Affine group formulation of the Standard Model coupled to gravity
Chou, Ching-Yi, E-mail: l2897107@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Taiwan (China); Ita, Eyo, E-mail: ita@usna.edu [Department of Physics, US Naval Academy, Annapolis, MD (United States); Soo, Chopin, E-mail: cpsoo@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Taiwan (China)
2014-04-15
In this work we apply the affine group formalism for four dimensional gravity of Lorentzian signature, which is based on Klauder’s affine algebraic program, to the formulation of the Hamiltonian constraint of the interaction of matter and all forces, including gravity with non-vanishing cosmological constant Λ, as an affine Lie algebra. We use the hermitian action of fermions coupled to gravitation and Yang–Mills theory to find the density weight one fermionic super-Hamiltonian constraint. This term, combined with the Yang–Mills and Higgs energy densities, are composed with York’s integrated time functional. The result, when combined with the imaginary part of the Chern–Simons functional Q, forms the affine commutation relation with the volume element V(x). Affine algebraic quantization of gravitation and matter on equal footing implies a fundamental uncertainty relation which is predicated upon a non-vanishing cosmological constant. -- Highlights: •Wheeler–DeWitt equation (WDW) quantized as affine algebra, realizing Klauder’s program. •WDW formulated for interaction of matter and all forces, including gravity, as affine algebra. •WDW features Hermitian generators in spite of fermionic content: Standard Model addressed. •Constructed a family of physical states for the full, coupled theory via affine coherent states. •Fundamental uncertainty relation, predicated on non-vanishing cosmological constant.
Inflation and reheating in induced-gravity models
Barr, S.; Segre, G.
1990-01-01
The Planck mass is generated dynamically in induced-gravity models, typically being related to the vacuum expectation value of a scalar field φ, ε 1/2 left-angle φ right-angle=M Pl / √8π , where ε is a dimensionless parameter, typically smaller than one. We discuss in this paper the decay of the φ particle, which is mainly into gravitons, and the consequences this has for models in which the φ field is responsible for inflation. We show in particular that too much energy is stored in φ oscillations and adequate reheating does not occur
The Complexity of Developmental Predictions from Dual Process Models
Stanovich, Keith E.; West, Richard F.; Toplak, Maggie E.
2011-01-01
Drawing developmental predictions from dual-process theories is more complex than is commonly realized. Overly simplified predictions drawn from such models may lead to premature rejection of the dual process approach as one of many tools for understanding cognitive development. Misleading predictions can be avoided by paying attention to several…
A Dual System Model of Preferences under Risk
Mukherjee, Kanchan
2010-01-01
This article presents a dual system model (DSM) of decision making under risk and uncertainty according to which the value of a gamble is a combination of the values assigned to it independently by the affective and deliberative systems. On the basis of research on dual process theories and empirical research in Hsee and Rottenstreich (2004) and…
Kuroishi, Y.; Lemoine, F. G.; Rowlands, D. D.
2006-12-01
The latest gravimetric geoid model for Japan, JGEOID2004, suffers from errors at long wavelengths (around 1000 km) in a range of +/- 30 cm. The model was developed by combining surface gravity data with a global marine altimetric gravity model, using EGM96 as a foundation, and the errors at long wavelength are presumably attributed to EGM96 errors. The Japanese islands and their vicinity are located in a region of plate convergence boundaries, producing substantial gravity and geoid undulations in a wide range of wavelengths. Because of the geometry of the islands and trenches, precise information on gravity in the surrounding oceans should be incorporated in detail, even if the geoid model is required to be accurate only over land. The Kuroshio Current, which runs south of Japan, causes high sea surface variability, making altimetric gravity field determination complicated. To reduce the long-wavelength errors in the geoid model, we are investigating GRACE data for regional gravity field modeling at long wavelengths in the vicinity of Japan. Our approach is based on exclusive use of inter- satellite range-rate data with calibrated accelerometer data and attitude data, for regional or global gravity field recovery. In the first step, we calibrate accelerometer data in terms of scales and biases by fitting dynamically calculated orbits to GPS-determined precise orbits. The calibration parameters of accelerometer data thus obtained are used in the second step to recover a global/regional gravity anomaly field. This approach is applied to GRACE data obtained for the year 2005 and resulting global/regional gravity models are presented and discussed.
Charge distribution in an two-chain dual model
Fialkowski, K.; Kotanski, A.
1983-01-01
Charge distributions in the multiple production processes are analysed using the dual chain model. A parametrisation of charge distributions for single dual chains based on the νp and anti vp data is proposed. The rapidity charge distributions are then calculated for pp and anti pp collisions and compared with the previous calculations based on the recursive cascade model of single chains. The results differ at the SPS collider energies and in the energy dependence of the net forward charge supplying the useful tests of the dual chain model. (orig.)
High-degree Gravity Models from GRAIL Primary Mission Data
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.;
2013-01-01
We have analyzed Ka?band range rate (KBRR) and Deep Space Network (DSN) data from the Gravity Recovery and Interior Laboratory (GRAIL) primary mission (1 March to 29 May 2012) to derive gravity models of the Moon to degree 420, 540, and 660 in spherical harmonics. For these models, GRGM420A, GRGM540A, and GRGM660PRIM, a Kaula constraint was applied only beyond degree 330. Variance?component estimation (VCE) was used to adjust the a priori weights and obtain a calibrated error covariance. The global root?mean?square error in the gravity anomalies computed from the error covariance to 320×320 is 0.77 mGal, compared to 29.0 mGal with the pre?GRAIL model derived with the SELENE mission data, SGM150J, only to 140×140. The global correlations with the Lunar Orbiter Laser Altimeter?derived topography are larger than 0.985 between l = 120 and 330. The free?air gravity anomalies, especially over the lunar farside, display a dramatic increase in detail compared to the pre?GRAIL models (SGM150J and LP150Q) and, through degree 320, are free of the orbit?track?related artifacts present in the earlier models. For GRAIL, we obtain an a posteriori fit to the S?band DSN data of 0.13 mm/s. The a posteriori fits to the KBRR data range from 0.08 to 1.5 micrometers/s for GRGM420A and from 0.03 to 0.06 micrometers/s for GRGM660PRIM. Using the GRAIL data, we obtain solutions for the degree 2 Love numbers, k20=0.024615+/-0.0000914, k21=0.023915+/-0.0000132, and k22=0.024852+/-0.0000167, and a preliminary solution for the k30 Love number of k30=0.00734+/-0.0015, where the Love number error sigmas are those obtained with VCE.
On the universal hydrodynamics of strongly coupled CFTs with gravity duals
Gupta, Rajesh Kumar; Mukhopadhyay, Ayan
2009-01-01
It is known that the solutions of pure classical 5D gravity with AdS 5 asymptotics can describe strongly coupled large N dynamics in a universal sector of 4D conformal gauge theories. We show that when the boundary metric is flat we can uniquely specify the solution by the boundary stress tensor. We also show that in the Fefferman-Graham coordinates all these solutions have an integer Taylor series expansion in the radial coordinate (i.e. no log terms). Specifying an arbitrary stress tensor can lead to two types of pathologies, it can either destroy the asymptotic AdS boundary condition or it can produce naked singularities. We show that when solutions have no net angular momentum, all hydrodynamic stress tensors preserve the asymptotic AdS boundary condition, though they may produce naked singularities. We construct solutions corresponding to arbitrary hydrodynamic stress tensors in Fefferman-Graham coordinates using a derivative expansion. In contrast to Eddington-Finkelstein coordinates here the constraint equations simplify and at each order it is manifestly Lorentz covariant. The regularity analysis, becomes more elaborate, but we can show that there is a unique hydrodynamic stress tensor which gives us solutions free of naked singularities. In the process we write down explicit first order solutions in both Fefferman-Graham and Eddington-Finkelstein coordinates for hydrodynamic stress tensors with arbitrary η/s. Our solutions can describe arbitrary (slowly varying) velocity configurations. We point out some field-theoretic implications of our general results.
CFD Modeling of a Multiphase Gravity Separator Vessel
Narayan, Gautham
2017-05-23
The poster highlights a CFD study that incorporates a combined Eulerian multi-fluid multiphase and a Population Balance Model (PBM) to study the flow inside a typical multiphase gravity separator vessel (GSV) found in oil and gas industry. The simulations were performed using Ansys Fluent CFD package running on KAUST supercomputer, Shaheen. Also, a highlight of a scalability study is presented. The effect of I/O bottlenecks and using Hierarchical Data Format (HDF5) for collective and independent parallel reading of case file is presented. This work is an outcome of a research collaboration on an Aramco project on Shaheen.
CFD Modeling of a Multiphase Gravity Separator Vessel
Narayan, Gautham; Khurram, Rooh Ul Amin; Elsaadawy, Ehab
2017-01-01
The poster highlights a CFD study that incorporates a combined Eulerian multi-fluid multiphase and a Population Balance Model (PBM) to study the flow inside a typical multiphase gravity separator vessel (GSV) found in oil and gas industry. The simulations were performed using Ansys Fluent CFD package running on KAUST supercomputer, Shaheen. Also, a highlight of a scalability study is presented. The effect of I/O bottlenecks and using Hierarchical Data Format (HDF5) for collective and independent parallel reading of case file is presented. This work is an outcome of a research collaboration on an Aramco project on Shaheen.
Hadronic form factor models and spectroscopy within the gauge/gravity correspondence
de Teramond, Guy
2012-01-01
We show that the nonperturbative light-front dynamics of relativistic hadronic bound states has a dual semiclassical gravity description on a higher dimensional warped AdS space in the limit of zero quark masses. This mapping of AdS gravity theory to the boundary quantum field theory, quantized at fixed light-front time, allows one to establish a precise relation between holographic wave functions in AdS space and the light-front wavefunctions describing the internal structure of hadrons. The resulting AdS/QCD model gives a remarkably good accounting of the spectrum, elastic and transition form factors of the light-quark hadrons in terms of one parameter, the QCD gap scale. The light-front holographic approach described here thus provides a frame-independent first approximation to the light-front Hamiltonian problem for QCD. This article is based on lectures at the Niccolo Cabeo International School of Hadronic Physics, Ferrara, Italy, May 2011.
Hadronic form factor models and spectroscopy within the gauge/gravity correspondence
de Teramond, Guy F.; /Costa Rica U.; Brodsky, Stanley J.; /SLAC
2012-03-20
We show that the nonperturbative light-front dynamics of relativistic hadronic bound states has a dual semiclassical gravity description on a higher dimensional warped AdS space in the limit of zero quark masses. This mapping of AdS gravity theory to the boundary quantum field theory, quantized at fixed light-front time, allows one to establish a precise relation between holographic wave functions in AdS space and the light-front wavefunctions describing the internal structure of hadrons. The resulting AdS/QCD model gives a remarkably good accounting of the spectrum, elastic and transition form factors of the light-quark hadrons in terms of one parameter, the QCD gap scale. The light-front holographic approach described here thus provides a frame-independent first approximation to the light-front Hamiltonian problem for QCD. This article is based on lectures at the Niccolo Cabeo International School of Hadronic Physics, Ferrara, Italy, May 2011.
Gravity duals for the Coulomb branch of marginally deformed N=4 Yang-Mills
Hernández, R; Zoakos, D; Hernandez, Rafael; Sfetsos, Konstadinos; Zoakos, Dimitrios
2006-01-01
Supergravity backgrounds dual to a class of exactly marginal deformations of N supersymmetric Yang-Mills can be constructed through an SL(2,R) sequence of T-dualities and coordinate shifts. We apply this transformation to multicenter solutions and derive supergravity backgrounds describing the Coulomb branch of N=1 theories at strong 't Hooft coupling as marginal deformations of N=4 Yang-Mills. For concreteness we concentrate to cases with an SO(4)xSO(2) symmetry preserved by continuous distributions of D3-branes on a disc and on a three-dimensional spherical shell. We compute the expectation value of the Wilson loop operator and confirm the Coulombic behaviour of the heavy quark-antiquark potential in the conformal case. When the vev is turned on we find situations where a complete screening of the potential arises, as well as a confining regime where a linear or a logarithmic potential prevails depending on the ratio of the quark-antiquark separation to the typical vev scale. The spectra of massless excitat...
ANALISIS DETERMINAN EKSPOR PROVINSI SUMATERA UTARA: PENDEKATAN GRAVITY MODEL
Efori Telambanua
2013-06-01
Full Text Available Export Growth has been being one of important component in enhancing of economic growth of North Sumatera Province. During 2005-2010, the average growth of export rate of North Sumatera Province is 16,5 percent per year with 5,23 percent per year the average of it’s contribution to growth. The aim of this research is to detect the factors which affect the enhancement of export rate of North Sumatera Province during 2005-2010. With augmented gravity model approach, this research analyzes the effect of gross domestic product percapita rate and the population of each trading partner countries, geographical distance between North Sumatera Province and every trading partner countries, foreign direct investment and real effective exchange rate of North Sumatera Province, to the export rate of North Sumatera Province to every trading countries, such as United States of America, Netherland, China, India, Italy, Japan, Malaysia, Egypt, Singapore, and Ukraine. By using random effect model in pooled data processing, the result of this research describes that the gross domestic product percapita and the population of each trading partner countries affect positively and significantly to the export rate of North Sumatera Province. As well as foreign direct investment rate and real effective exchange rate of North Sumatera Province show the positive and significant effect. Whereas, geographical distance as the trade barrier, correlate negatively and significantly to the export rate of North Sumatera Province. _________________________________ Keywords:Export rate, gravity model approach, export destination country
Guo, Zhikui; Chen, Chao; Tao, Chunhui
2016-04-01
Since 2007, there are four China Da yang cruises (CDCs), which have been carried out to investigate polymetallic sulfides in the southwest Indian ridge (SWIR) and have acquired both gravity data and bathymetry data on the corresponding survey lines(Tao et al., 2014). Sandwell et al. (2014) published a new global marine gravity model including the free air gravity data and its first order vertical gradient (Vzz). Gravity data and its gradient can be used to extract unknown density structure information(e.g. crust thickness) under surface of the earth, but they contain all the mass effect under the observation point. Therefore, how to get accurate gravity and its gradient effect of the existing density structure (e.g. terrain) has been a key issue. Using the bathymetry data or ETOPO1 (http://www.ngdc.noaa.gov/mgg/global/global.html) model at a full resolution to calculate the terrain effect could spend too much computation time. We expect to develop an effective method that takes less time but can still yield the desired accuracy. In this study, a constant-density polyhedral model is used to calculate the gravity field and its vertical gradient, which is based on the work of Tsoulis (2012). According to gravity field attenuation with distance and variance of bathymetry, we present an adaptive mesh refinement and coarsening strategies to merge both global topography data and multi-beam bathymetry data. The local coarsening or size of mesh depends on user-defined accuracy and terrain variation (Davis et al., 2011). To depict terrain better, triangular surface element and rectangular surface element are used in fine and coarse mesh respectively. This strategy can also be applied to spherical coordinate in large region and global scale. Finally, we applied this method to calculate Bouguer gravity anomaly (BGA), mantle Bouguer anomaly(MBA) and their vertical gradient in SWIR. Further, we compared the result with previous results in the literature. Both synthetic model
Modeling of the Earth's gravity field using the New Global Earth Model (NEWGEM)
Kim, Yeong E.; Braswell, W. Danny
1989-01-01
Traditionally, the global gravity field was described by representations based on the spherical harmonics (SH) expansion of the geopotential. The SH expansion coefficients were determined by fitting the Earth's gravity data as measured by many different methods including the use of artificial satellites. As gravity data have accumulated with increasingly better accuracies, more of the higher order SH expansion coefficients were determined. The SH representation is useful for describing the gravity field exterior to the Earth but is theoretically invalid on the Earth's surface and in the Earth's interior. A new global Earth model (NEWGEM) (KIM, 1987 and 1988a) was recently proposed to provide a unified description of the Earth's gravity field inside, on, and outside the Earth's surface using the Earth's mass density profile as deduced from seismic studies, elevation and bathymetric information, and local and global gravity data. Using NEWGEM, it is possible to determine the constraints on the mass distribution of the Earth imposed by gravity, topography, and seismic data. NEWGEM is useful in investigating a variety of geophysical phenomena. It is currently being utilized to develop a geophysical interpretation of Kaula's rule. The zeroth order NEWGEM is being used to numerically integrate spherical harmonic expansion coefficients and simultaneously determine the contribution of each layer in the model to a given coefficient. The numerically determined SH expansion coefficients are also being used to test the validity of SH expansions at the surface of the Earth by comparing the resulting SH expansion gravity model with exact calculations of the gravity at the Earth's surface.
Space-Wise approach for airborne gravity data modelling
Sampietro, D.; Capponi, M.; Mansi, A. H.; Gatti, A.; Marchetti, P.; Sansò, F.
2017-05-01
Regional gravity field modelling by means of remove-compute-restore procedure is nowadays widely applied in different contexts: it is the most used technique for regional gravimetric geoid determination, and it is also used in exploration geophysics to predict grids of gravity anomalies (Bouguer, free-air, isostatic, etc.), which are useful to understand and map geological structures in a specific region. Considering this last application, due to the required accuracy and resolution, airborne gravity observations are usually adopted. However, due to the relatively high acquisition velocity, presence of atmospheric turbulence, aircraft vibration, instrumental drift, etc., airborne data are usually contaminated by a very high observation error. For this reason, a proper procedure to filter the raw observations in both the low and high frequencies should be applied to recover valuable information. In this work, a software to filter and grid raw airborne observations is presented: the proposed solution consists in a combination of an along-track Wiener filter and a classical Least Squares Collocation technique. Basically, the proposed procedure is an adaptation to airborne gravimetry of the Space-Wise approach, developed by Politecnico di Milano to process data coming from the ESA satellite mission GOCE. Among the main differences with respect to the satellite application of this approach, there is the fact that, while in processing GOCE data the stochastic characteristics of the observation error can be considered a-priori well known, in airborne gravimetry, due to the complex environment in which the observations are acquired, these characteristics are unknown and should be retrieved from the dataset itself. The presented solution is suited for airborne data analysis in order to be able to quickly filter and grid gravity observations in an easy way. Some innovative theoretical aspects focusing in particular on the theoretical covariance modelling are presented too
Dual processing model of medical decision-making
Djulbegovic, Benjamin; Hozo, Iztok; Beckstead, Jason; Tsalatsanis, Athanasios; Pauker, Stephen G
2012-01-01
Abstract Background Dual processing theory of human cognition postulates that reasoning and decision-making can be described as a function of both an intuitive, experiential, affective system (system I) and/or an analytical, deliberative (system II) processing system. To date no formal descriptive model of medical decision-making based on dual processing theory has been developed. Here we postulate such a model and apply it to a common clinical situation: whether treatment should be administe...
Gravity Model for Topological Features on a Cylindrical Manifold
Bayak I.
2008-04-01
Full Text Available A model aimed at understanding quantum gravity in terms of Birkho’s approach is discussed. The geometry of this model is constructed by using a winding map of Minkowski space into a R3 S1 -cylinder. The basic field of this model is a field of unit vectors defined through the velocity field of a flow wrapping the cylinder. The degeneration of some parts of the flow into circles (topological features results in in- homogeneities and gives rise to a scalar field, analogous to the gravitational field. The geometry and dynamics of this field are briefly discussed. We treat the intersections be- tween the topological features and the observer’s 3-space as matter particles and argue that these entities are likely to possess some quantum properties.
Establishment of animal model of dual liver transplantation in rat.
Ying Zhang
Full Text Available The animal model of the whole-size and reduced-size liver transplantation in both rat and mouse has been successfully established. Because of the difficulties and complexities in microsurgical technology, the animal model of dual liver transplantation was still not established for twelve years since the first human dual liver transplantation has been made a success. There is an essential need to establish this animal model to lay a basic foundation for clinical practice. To study the physiological and histopathological changes of dual liver transplantation, "Y" type vein from the cross part between vena cava and two iliac of donor and "Y' type prosthesis were employed to recanalize portal vein and the bile duct between dual liver grafts and recipient. The dual right upper lobes about 45-50% of the recipient liver volume were taken as donor, one was orthotopically implanted at its original position, the other was rotated 180° sagitally and heterotopically positioned in the left upper quadrant. Microcirculation parameters, liver function, immunohistochemistry and survival were analyzed to evaluate the function of dual liver grafts. No significant difference in the hepatic microcirculatory flow was found between two grafts in the first 90 minutes after reperfusion. Light and electronic microscope showed the liver architecture was maintained without obvious features of cellular destruction and the continuity of the endothelium was preserved. Only 3 heterotopically positioned graft appeared patchy desquamation of endothelial cell, mitochondrial swelling and hepatocytes cytoplasmic vacuolization. Immunohistochemistry revealed there is no difference in hepatocyte activity and the ability of endothelia to contract and relax after reperfusion between dual grafts. Dual grafts made a rapid amelioration of liver function after reperfusion. 7 rats survived more than 7 days with survival rate of 58.3.%. Using "Y" type vein and bile duct prosthesis, we
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...
Einstein’s gravity from a polynomial affine model
Castillo-Felisola, Oscar; Skirzewski, Aureliano
2018-03-01
We show that the effective field equations for a recently formulated polynomial affine model of gravity, in the sector of a torsion-free connection, accept general Einstein manifolds—with or without cosmological constant—as solutions. Moreover, the effective field equations are partially those obtained from a gravitational Yang–Mills theory known as Stephenson–Kilmister–Yang theory. Additionally, we find a generalization of a minimally coupled massless scalar field in General Relativity within a ‘minimally’ coupled scalar field in this affine model. Finally, we present a brief (perturbative) analysis of the propagators of the gravitational theory, and count the degrees of freedom. For completeness, we prove that a Birkhoff-like theorem is valid for the analyzed sector.
Modeling of solidification of MMC composites during gravity casting process
R. Zagórski
2013-04-01
Full Text Available The paper deals with computer simulation of gravity casting of the metal matrix composites reinforced with ceramics (MMC into sand mold. The subject of our interest is aluminum matrix composite (AlMMC reinforced with ceramic particles i.e. silicon carbide SiC and glass carbon Cg. The created model describes the process taking into account solidification and its influence on the distribution of reinforcement particles. The computer calculation has been carried out in 2D system with the use of Navier-Stokes equations using ANSYS FLUENT 13. The Volume of Fluid approach (VOF and enthalpy method have been used to model the air-fluid free surface (and also volume fraction of particular continuous phases and the solidification of the cast, respectively.
Thermodynamic behavior of particular f(R,T)-gravity models
Sharif, M.; Zubair, M.
2013-01-01
We investigate the thermodynamics at the apparent horizon of the FRW universe in f(R, T) theory in the nonequilibrium description. The laws of thermodynamics are discussed for two particular models of the f(R, T) theory. The first law of thermodynamics is expressed in the form of the Clausius relation T h dS-circumflex h = δ Q , where δQ is the energy flux across the horizon and dS-circumflex is the entropy production term. Furthermore, the conditions for the generalized second law of thermodynamics to be preserved are established with the constraints of positive temperature and attractive gravity. We illustrate our results for some concrete models in this theory
Superoperators in the dual model with coloured quarks
Manida, S.N.
1978-01-01
The derivation of the dual model with coloured quarks is considered. The model is represented as a superoperator generalization of the Bardakci-Halpern model. It is shown that the three-regeon vertex of the model appears to be more compact and transparent
[The dual process model of addiction. Towards an integrated model?].
Vandermeeren, R; Hebbrecht, M
2012-01-01
Neurobiology and cognitive psychology have provided us with a dual process model of addiction. According to this model, behavior is considered to be the dynamic result of a combination of automatic and controlling processes. In cases of addiction the balance between these two processes is severely disturbed. Automated processes will continue to produce impulses that ensure the continuance of addictive behavior. Weak, reflective or controlling processes are both the reason for and the result of the inability to forgo addiction. To identify features that are common to current neurocognitive insights into addiction and psychodynamic views on addiction. The picture that emerges from research is not clear. There is some evidence that attentional bias has a causal effect on addiction. There is no evidence that automatic associations have a causal effect, but there is some evidence that automatic action-tendencies do have a causal effect. Current neurocognitive views on the dual process model of addiction can be integrated with an evidence-based approach to addiction and with psychodynamic views on addiction.
Dynamics and phenomenology of higher order gravity cosmological models
Moldenhauer, Jacob Andrew
2010-10-01
I present here some new results about a systematic approach to higher-order gravity (HOG) cosmological models. The HOG models are derived from curvature invariants that are more general than the Einstein-Hilbert action. Some of the models exhibit late-time cosmic acceleration without the need for dark energy and fit some current observations. The open question is that there are an infinite number of invariants that one could select, and many of the published papers have stressed the need to find a systematic approach that will allow one to study methodically the various possibilities. We explore a new connection that we made between theorems from the theory of invariants in general relativity and these cosmological models. In summary, the theorems demonstrate that curvature invariants are not all independent from each other and that for a given Ricci Segre type and Petrov type (symmetry classification) of the space-time, there exists a complete minimal set of independent invariants (a basis) in terms of which all the other invariants can be expressed. As an immediate consequence of the proposed approach, the number of invariants to consider is dramatically reduced from infinity to four invariants in the worst case and to only two invariants in the cases of interest, including all Friedmann-Lemaitre-Robertson-Walker metrics. We derive models that pass stability and physical acceptability conditions. We derive dynamical equations and phase portrait analyses that show the promise of the systematic approach. We consider observational constraints from magnitude-redshift Supernovae Type Ia data, distance to the last scattering surface of the Cosmic Microwave Background radiation, and Baryon Acoustic Oscillations. We put observational constraints on general HOG models. We constrain different forms of the Gauss-Bonnet, f(G), modified gravity models with these observations. We show some of these models pass solar system tests. We seek to find models that pass physical and
Rowe, Charlotte Anne [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-11-21
We can measure changes in gravity from place to place on the earth. These measurements require careful recording of location, elevation and time for each reading. These readings must be adjusted for known effects (such as elevation, latitude, tides) that can bias our data and mask the signal of interest. After making corrections to our data, we can remove regional trends to obtain local Bouguer anomalies. The Bouguer anomalies arise from variations in the subsurface density structure. We can build models to explain our observations, but these models must be consistent with what is known about the local geology. Combining gravity models with other information – geologic, seismic, electromagnetic, will improve confidence in the results.
Influence of World and Gravity Model Selection on Surface Interacting Vehicle Simulations
Madden, Michael M.
2007-01-01
A vehicle simulation is surface-interacting if the state of the vehicle (position, velocity, and acceleration) relative to the surface is important. Surface-interacting simulations perform ascent, entry, descent, landing, surface travel, or atmospheric flight. Modeling of gravity is an influential environmental factor for surface-interacting simulations. Gravity is the free-fall acceleration observed from a world-fixed frame that rotates with the world. Thus, gravity is the sum of gravitation and the centrifugal acceleration due to the world s rotation. In surface-interacting simulations, the fidelity of gravity at heights above the surface is more significant than gravity fidelity at locations in inertial space. A surface-interacting simulation cannot treat the gravity model separately from the world model, which simulates the motion and shape of the world. The world model's simulation of the world's rotation, or lack thereof, produces the centrifugal acceleration component of gravity. The world model s reproduction of the world's shape will produce different positions relative to the world center for a given height above the surface. These differences produce variations in the gravitation component of gravity. This paper examines the actual performance of world and gravity/gravitation pairs in a simulation using the Earth.
Zwei-Dreibein Gravity : A Two-Frame-Field Model of 3D Massive Gravity
Bergshoeff, Eric A.; de Haan, Sjoerd; Hohm, Olaf; Merbis, Wout; Townsend, Paul K.
2013-01-01
We present a generally covariant and parity-invariant two-frame field ("zwei-dreibein") action for gravity in three space-time dimensions that propagates two massive spin-2 modes, unitarily, and we use Hamiltonian methods to confirm the absence of unphysical degrees of freedom. We show how
Solving the Standard Model Problems in Softened Gravity
Salvio, Alberto
2016-11-16
The Higgs naturalness problem is solved if the growth of Einstein's gravitational interaction is softened at an energy $ \\lesssim 10^{11}\\,$GeV (softened gravity). We work here within an explicit realization where the Einstein-Hilbert Lagrangian is extended to include terms quadratic in the curvature and a non-minimal coupling with the Higgs. We show that this solution is preserved by adding three right-handed neutrinos with masses below the electroweak scale, accounting for neutrino oscillations, dark matter and the baryon asymmetry. The smallness of the right-handed neutrino masses (compared to the Planck scale) and the QCD $\\theta$-term are also shown to be natural. We prove that a possible gravitational source of CP violation cannot spoil the model, thanks to the presence of right-handed neutrinos. Starobinsky inflation can occur in this context, even if we live in a metastable vacuum.
An extended dual search space model of scientific discovery learning
van Joolingen, Wouter; de Jong, Anthonius J.M.
1997-01-01
This article describes a theory of scientific discovery learning which is an extension of Klahr and Dunbar''s model of Scientific Discovery as Dual Search (SDDS) model. We present a model capable of describing and understanding scientific discovery learning in complex domains in terms of the SDDS
On the quark structure of resonance states in dual models
Volkov, D.V.; Zheltukhin, A.A.; Pashnev, A.I.
1975-01-01
It is shown using as an example the Veneziano dual model, that each particular dual model already contains a certain latent quark structure unambiauously determined by internal properties of the dual model. To prove this degeneration of the resonance state spectrum is studied by introducing an additional disturbing interaction into the model being considered. Induced transitions of particles into a vacuum act as such an additional disturbance. This method complements the known factorization method of Fubini, Gordon and Veneziano and turns out to be free from an essential limitation of the latter connected with implicit assumption about the basence of internal additive laws of conservation in the model. By using the method of induced transitions of particles into a vacuum it has been possible to show that the resonance state spectrum is indeed more degenerated than it should be expected from the factorization theorem, and that the supplementary degeneration corresponds to the quark model with an infinite number of quarks of the increasing mass. Structures of some terms of the dual amplitude expansion over the degrees of the constant of the induced transition of particles to vacuum are considered; it is shown that the summation of this expansion may be reduced to a solution of a certain integral equation. On the basis of the integral equation obtained an integral representation ofr dual amplitudes is established. The problems related with degeneration of resonance states and with determination of additive quantum numbers leading to the quark interpretation of the degeneration being considered are discussed
Bucha, Blažej; Hirt, Christian; Kuhn, Michael
2018-04-01
Spectral gravity forward modelling is a technique that converts a band-limited topography into its implied gravitational field. This conversion implicitly relies on global integration of topographic masses. In this paper, a modification of the spectral technique is presented that provides gravity effects induced only by the masses located inside or outside a spherical cap centred at the evaluation point. This is achieved by altitude-dependent Molodensky's truncation coefficients, for which we provide infinite series expansions and recurrence relations with a fixed number of terms. Both representations are generalized for an arbitrary integer power of the topography and arbitrary radial derivative. Because of the altitude-dependency of the truncation coefficients, a straightforward synthesis of the near- and far-zone gravity effects at dense grids on irregular surfaces (e.g. the Earth's topography) is computationally extremely demanding. However, we show that this task can be efficiently performed using an analytical continuation based on the gradient approach, provided that formulae for radial derivatives of the truncation coefficients are available. To demonstrate the new cap-modified spectral technique, we forward model the Earth's degree-360 topography, obtaining near- and far-zone effects on gravity disturbances expanded up to degree 3600. The computation is carried out on the Earth's surface and the results are validated against an independent spatial-domain Newtonian integration (1 μGal RMS agreement). The new technique is expected to assist in mitigating the spectral filter problem of residual terrain modelling and in the efficient construction of full-scale global gravity maps of highest spatial resolution.
From polymers to quantum gravity: Triple-scaling in rectangular random matrix models
Myers, R.C.; Periwal, V.
1993-01-01
Rectangular NxM matrix models can be solved in several qualitatively distinct large-N limits, since two independent parameters govern the size of the matrix. Regarded as models of random surfaces, these matrix models interpolate between branched polymer behaviour and two-dimensional quantum gravity. We solve such models in a 'triple-scaling' regime in this paper, with N and M becoming large independently. A correspondence between phase transitions and singularities of mappings from R 2 to R 2 is indicated. At different critical points, the scaling behaviour is determined by (i) two decoupled ordinary differential equations; (ii) an ordinary differential equation and a finite-difference equation; or (iii) two coupled partial differential equations. The Painleve II equation arises (in conjunction with a difference equation) at a point associated with branched polymers. For critical points described by partial differential equations, there are dual weak-coupling/strong-coupling expansions. It is conjectured that the new physics is related to microscopic topology fluctuations. (orig.)
Interference of Spin-2 Self-Dual Modes
Ilha, Anderson; Wotzasek, Clovis
2001-01-01
We study the effects of interference between the self-dual and anti self-dual massive modes of the linearized Einstein-Chern-Simons topological gravity. The dual models to be used in the interference process are carefully analyzed with special emphasis on their propagating spectrum. We identify the opposite dual aspects, necessary for the application of the interference formalism on this model. The soldered theory so obtained displays explicitly massive modes of the Proca type. It may also be...
Spin foam models of Yang-Mills theory coupled to gravity
Mikovic, A
2003-01-01
We construct a spin foam model of Yang-Mills theory coupled to gravity by using a discretized path integral of the BF theory with polynomial interactions and the Barrett-Crane ansatz. In the Euclidean gravity case, we obtain a vertex amplitude which is determined by a vertex operator acting on a simple spin network function. The Euclidean gravity results can be straightforwardly extended to the Lorentzian case, so that we propose a Lorentzian spin foam model of Yang-Mills theory coupled to gravity
Zago, Myrka; Lacquaniti, Francesco
2005-08-01
Internal model is a neural mechanism that mimics the dynamics of an object for sensory motor or cognitive functions. Recent research focuses on the issue of whether multiple internal models are learned and switched to cope with a variety of conditions, or single general models are adapted by tuning the parameters. Here we addressed this issue by investigating how the manual interception of a moving target changes with changes of the visual environment. In our paradigm, a virtual target moves vertically downward on a screen with different laws of motion. Subjects are asked to punch a hidden ball that arrives in synchrony with the visual target. By using several different protocols, we systematically found that subjects do not develop a new internal model appropriate for constant speed targets, but they use the default gravity model and reduce the central processing time. The results imply that adaptation to zero-gravity targets involves a compression of temporal processing through the cortical and subcortical regions interconnected with the vestibular cortex, which has previously been shown to be the site of storage of the internal model of gravity.
A dynamic dual process model of risky decision making.
Diederich, Adele; Trueblood, Jennifer S
2018-03-01
Many phenomena in judgment and decision making are often attributed to the interaction of 2 systems of reasoning. Although these so-called dual process theories can explain many types of behavior, they are rarely formalized as mathematical or computational models. Rather, dual process models are typically verbal theories, which are difficult to conclusively evaluate or test. In the cases in which formal (i.e., mathematical) dual process models have been proposed, they have not been quantitatively fit to experimental data and are often silent when it comes to the timing of the 2 systems. In the current article, we present a dynamic dual process model framework of risky decision making that provides an account of the timing and interaction of the 2 systems and can explain both choice and response-time data. We outline several predictions of the model, including how changes in the timing of the 2 systems as well as time pressure can influence behavior. The framework also allows us to explore different assumptions about how preferences are constructed by the 2 systems as well as the dynamic interaction of the 2 systems. In particular, we examine 3 different possible functional forms of the 2 systems and 2 possible ways the systems can interact (simultaneously or serially). We compare these dual process models with 2 single process models using risky decision making data from Guo, Trueblood, and Diederich (2017). Using this data, we find that 1 of the dual process models significantly outperforms the other models in accounting for both choices and response times. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
Matthews, Samuel J.; O'Neill, Craig; Lackie, Mark A.
2017-06-01
Gravity gradiometry has a long legacy, with airborne/marine applications as well as surface applications receiving renewed recent interest. Recent instrumental advances has led to the emergence of downhole gravity gradiometry applications that have the potential for greater resolving power than borehole gravity alone. This has promise in both the petroleum and geosequestration industries; however, the effect of inherent uncertainties in the ability of downhole gravity gradiometry to resolve a subsurface signal is unknown. Here, we utilise the open source modelling package, Fatiando a Terra, to model both the gravity and gravity gradiometry responses of a subsurface body. We use a Monte Carlo approach to vary the geological structure and reference densities of the model within preset distributions. We then perform 100 000 simulations to constrain the mean response of the buried body as well as uncertainties in these results. We varied our modelled borehole to be either centred on the anomaly, adjacent to the anomaly (in the x-direction), and 2500 m distant to the anomaly (also in the x-direction). We demonstrate that gravity gradiometry is able to resolve a reservoir-scale modelled subsurface density variation up to 2500 m away, and that certain gravity gradient components (Gzz, Gxz, and Gxx) are particularly sensitive to this variation in gravity/gradiometry above the level of uncertainty in the model. The responses provided by downhole gravity gradiometry modelling clearly demonstrate a technique that can be utilised in determining a buried density contrast, which will be of particular use in the emerging industry of CO2 geosequestration. The results also provide a strong benchmark for the development of newly emerging prototype downhole gravity gradiometers.
Bouguer gravity anomalies for terrain modeling | Orupabo | Journal ...
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 ...
A marked correlation function for constraining modified gravity models
White, Martin
2016-11-01
Future large scale structure surveys will provide increasingly tight constraints on our cosmological model. These surveys will report results on the distance scale and growth rate of perturbations through measurements of Baryon Acoustic Oscillations and Redshift-Space Distortions. It is interesting to ask: what further analyses should become routine, so as to test as-yet-unknown models of cosmic acceleration? Models which aim to explain the accelerated expansion rate of the Universe by modifications to General Relativity often invoke screening mechanisms which can imprint a non-standard density dependence on their predictions. This suggests density-dependent clustering as a `generic' constraint. This paper argues that a density-marked correlation function provides a density-dependent statistic which is easy to compute and report and requires minimal additional infrastructure beyond what is routinely available to such survey analyses. We give one realization of this idea and study it using low order perturbation theory. We encourage groups developing modified gravity theories to see whether such statistics provide discriminatory power for their models.
A marked correlation function for constraining modified gravity models
White, Martin, E-mail: mwhite@berkeley.edu [Department of Physics, University of California, Berkeley, CA 94720 (United States)
2016-11-01
Future large scale structure surveys will provide increasingly tight constraints on our cosmological model. These surveys will report results on the distance scale and growth rate of perturbations through measurements of Baryon Acoustic Oscillations and Redshift-Space Distortions. It is interesting to ask: what further analyses should become routine, so as to test as-yet-unknown models of cosmic acceleration? Models which aim to explain the accelerated expansion rate of the Universe by modifications to General Relativity often invoke screening mechanisms which can imprint a non-standard density dependence on their predictions. This suggests density-dependent clustering as a 'generic' constraint. This paper argues that a density-marked correlation function provides a density-dependent statistic which is easy to compute and report and requires minimal additional infrastructure beyond what is routinely available to such survey analyses. We give one realization of this idea and study it using low order perturbation theory. We encourage groups developing modified gravity theories to see whether such statistics provide discriminatory power for their models.
Renormalization group flows in σ-models coupled to two-dimensional dynamical gravity
Penati, S.; Santambrogio, A.; Zanon, D.
1997-01-01
We consider a bosonic σ-model coupled to two-dimensional gravity. In the semiclassical limit, c→-∞, we compute the gravity dressing of the β-functions at two-loop order in the matter fields. We find that the corrections due to the presence of dynamical gravity are not expressible simply in terms of a multiplicative factor as previously obtained at the one-loop level. Our result indicates that the critical points of the theory are non-trivially influenced and modified by the induced gravity. (orig.)
Gravity modelling of the lower crust in Sardinia (Italy
T. Quarta
1997-06-01
Full Text Available In this paper an example is given of an application of statistical techniques to the Bouguer anomalies analysis in order to design a simple crustal model using few a priori assumptions. All gravity measurements carried out in Sardinia have been collected and processed. The Bouguer anomalies have been calculated according to local density estimates. Spectral analysis of the Bouguer anomalies has been carried out along selected profiles in order to estimate the mean depth of the Moho discontinuity and that of an infracrustal discontinuity. The use of this technique inferred the presence of a discontinuity at a mean depth of ~ 28 km, interpreted as Moho and the likely presence of an infracrustal discontinuity at a mean depth of ~18 km, interpreted as the upper-lower crust transition. In order to roughly reconstruct the shape of these interfaces, 2D inversion techniques were applied to the large wavelength components of the Bouguer anomalies, relative to profiles oriented along the E-W direction, extracted from low-pass filtered Bouguer anomaly maps. The density model obtained is compatible with some velocity models achieved from the interpretation of the seismic refraction profiles carried out within the European Geotraverse project.
A refined gravity model from Lageos /GEM-L2/
Lerch, F. J.; Klosko, S. M.; Patel, G. B.
1982-01-01
Lageos satellite laser ranging (SLR) data taken over a 2.5 yr period were employed to develop the Goddard Earth Model GEM-L2, a refined gravity field model. Additional data was gathered with 30 other satellites, resulting in spherical harmonics through degree and order 20, based on over 600,000 measurements. The Lageos data was accurate down to 10 cm, after which the GEM 9 data were used to make adjustments past order 7. The resolution of long wavelength activity, through degree and order 4, was made possible by the Lageos data. The GEM-L2 model features a 20 x 20 geopotential, tracking station coordinates (20), 5-day polar motion and A1-UT1 values, and a GM value of 398,600.607 cu km/sq sec. The accuracy of station positioning has been raised to within 6 cm total position globally and within 1.8 cm in baselines. It is concluded that SLR is useful for measuring tectonic plate motions and inter-plate deformations.
Constraints on modified gravity models from white dwarfs
Banerjee, Srimanta; Singh, Tejinder P. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai 400005, Maharashtra (India); Shankar, Swapnil, E-mail: srimanta.banerjee@tifr.res.in, E-mail: swapnil.shankar@cbs.ac.in, E-mail: tpsingh@tifr.res.in [Department of Physics, Centre for Excellence in Basic Sciences, Mumbai 400098, Maharashtra (India)
2017-10-01
Modified gravity theories can introduce modifications to the Poisson equation in the Newtonian limit. As a result, we expect to see interesting features of these modifications inside stellar objects. White dwarf stars are one of the most well studied stars in stellar astrophysics. We explore the effect of modified gravity theories inside white dwarfs. We derive the modified stellar structure equations and solve them to study the mass-radius relationships for various modified gravity theories. We also constrain the parameter space of these theories from observations.
Constraining the interacting dark energy models from weak gravity conjecture and recent observations
Chen Ximing; Wang Bin; Pan Nana; Gong Yungui
2011-01-01
We examine the effectiveness of the weak gravity conjecture in constraining the dark energy by comparing with observations. For general dark energy models with plausible phenomenological interactions between dark sectors, we find that although the weak gravity conjecture can constrain the dark energy, the constraint is looser than that from the observations.
The anisotropic cosmological models in f ( R , T ) gravity with Λ
The general class of anisotropic Bianchi cosmological models in f ( R , T ) modified theories of gravity with Λ ( T ) has been considered. This paper deals with f ( R , T ) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar R and the trace of the stress-energy tensor T ...
A Comparison Between Gravity Wave Momentum Fluxes in Observations and Climate Models
Geller, Marvin A.; Alexadner, M. Joan; Love, Peter T.; Bacmeister, Julio; Ern, Manfred; Hertzog, Albert; Manzini, Elisa; Preusse, Peter; Sato, Kaoru; Scaife, Adam A.;
2013-01-01
For the first time, a formal comparison is made between gravity wave momentum fluxes in models and those derived from observations. Although gravity waves occur over a wide range of spatial and temporal scales, the focus of this paper is on scales that are being parameterized in present climate models, sub-1000-km scales. Only observational methods that permit derivation of gravity wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high-vertical-resolution radiosonde data. The models discussed include two high-resolution models in which gravity waves are explicitly modeled, Kanto and the Community Atmosphere Model, version 5 (CAM5), and three climate models containing gravity wave parameterizations,MAECHAM5, Hadley Centre Global Environmental Model 3 (HadGEM3), and the Goddard Institute for Space Studies (GISS) model. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of wavelengths, although other factors may contribute. When one accounts for this more rapid fall off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the nonorographic gravity wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between gravity wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of gravity wave sources in climate models.
Model study of the compact gravity reconstruction; Juryoku inversion `CGR` no model kento
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.
Donovan, F. M.; Gresser, A. L.; Sato, Kevin Y.; Taylor, Elizabeth M.
2018-01-01
Laboratory strains of mice and rat are widely used to study mammalian responses to stimulus, and both have been studied under a variety of gravity conditions, including space flight. We compared results obtained from exposure to spaceflight and microgravity, hyper gravity via centrifugation, earth gravity, and models of simulated partial gravity (hind-limb unloading and partial weight bearing treatments). We examined the reported changes in survival, body mass, circadian rhythm (body temperature and activity levels), behavior, bone, muscle, immune, cardio-vasculature, vestibular, reproduction and neonate survival, microbiome, and the visual system. Not all categories have published data for both species, some have limited data, and there are variations in experiment design that allow for only relative comparisons to be considered. The data reveal species differences in both the level of gravity required to obtain a response, degree of response, and in temporal expression of responses. Examination of the data across the gravity levels allows consideration of the hypothesis that gravitational responses follow a continuum, and organ specific differences are noted. In summary, we present advantages and caveats of each model system as pertains to gravitational biology research and identify gaps in our knowledge of how these mammals respond to gravity.
Temporal gravity field modeling based on least square collocation with short-arc approach
ran, jiangjun; Zhong, Min; Xu, Houze; Liu, Chengshu; Tangdamrongsub, Natthachet
2014-05-01
After the launch of the Gravity Recovery And Climate Experiment (GRACE) in 2002, several research centers have attempted to produce the finest gravity model based on different approaches. In this study, we present an alternative approach to derive the Earth's gravity field, and two main objectives are discussed. Firstly, we seek the optimal method to estimate the accelerometer parameters, and secondly, we intend to recover the monthly gravity model based on least square collocation method. The method has been paid less attention compared to the least square adjustment method because of the massive computational resource's requirement. The positions of twin satellites are treated as pseudo-observations and unknown parameters at the same time. The variance covariance matrices of the pseudo-observations and the unknown parameters are valuable information to improve the accuracy of the estimated gravity solutions. Our analyses showed that introducing a drift parameter as an additional accelerometer parameter, compared to using only a bias parameter, leads to a significant improvement of our estimated monthly gravity field. The gravity errors outside the continents are significantly reduced based on the selected set of the accelerometer parameters. We introduced the improved gravity model namely the second version of Institute of Geodesy and Geophysics, Chinese Academy of Sciences (IGG-CAS 02). The accuracy of IGG-CAS 02 model is comparable to the gravity solutions computed from the Geoforschungszentrum (GFZ), the Center for Space Research (CSR) and the NASA Jet Propulsion Laboratory (JPL). In term of the equivalent water height, the correlation coefficients over the study regions (the Yangtze River valley, the Sahara desert, and the Amazon) among four gravity models are greater than 0.80.
Dual peripheral model up to Serpukhov energies
Schrempp, Barbara
1974-01-01
The high energy behaviour of the s-channel Regge residues is inferred from three plausible requirements. The resulting s-channel helicity amplitudes allow-in a dual sense-the following t-channel interpretation: for -t>or=0.25 GeV/sup 2/ the flip amplitude has the form of a t-channel Regge pole, while the non-flip amplitude looks like a Regge cut. Finally, a quantitative comparison of the predictions with the data available for the set of SU(3) related processes pi N CEX, KN, KN CEX and pi /sup -/p to eta n is performed, covering the energy range 2
A dual model approach to ground water recovery trench design
Clodfelter, C.L.; Crouch, M.S.
1992-01-01
The design of trenches for contaminated ground water recovery must consider several variables. This paper presents a dual-model approach for effectively recovering contaminated ground water migrating toward a trench by advection. The approach involves an analytical model to determine the vertical influence of the trench and a numerical flow model to determine the capture zone within the trench and the surrounding aquifer. The analytical model is utilized by varying trench dimensions and head values to design a trench which meets the remediation criteria. The numerical flow model is utilized to select the type of backfill and location of sumps within the trench. The dual-model approach can be used to design a recovery trench which effectively captures advective migration of contaminants in the vertical and horizontal planes
Calibrating vadose zone models with time-lapse gravity data: a forced infiltration experiment
Christiansen, Lars; Hansen, Allan Bo; Zibar, Majken Caroline Looms
A change in soil water content is a change in mass stored in the subsurface, and when large enough, can be measured with a gravity meter. Over the last few decades there has been increased use of ground-based time-lapse gravity measurements to infer hydrogeological parameters. These studies have...... focused on the saturated zone, with specific yield as the most prominent target parameter and with few exceptions, changes in storage in the vadose zone have been considered as noise. Here modeling results are presented suggesting that gravity changes will be measureable when soil moisture changes occur...... in the unsaturated zone. These results are confirmed by field measurements of gravity and georadar data at a forced infiltration experiment conducted over 14 days on a grassland area of 10 m by 10 m. An unsaturated zone infiltration model can be calibrated using the gravity data with good agreement to the field data...
MODELING AND DESIGN OF INNOVATIVE SMALL DIAMETER GRAVITY SEWERAGE SYSTEM
Tadeusz Nawrot
2017-05-01
Full Text Available The article presents modern methods of hydraulic design of an innovative small diameter gravity sewerage system. In this system, domestic wastewater is preliminary treated in septic tanks equipped with outlet filters, thus the effluent features are similar to those of clear water. Innovative non-return valves at the outlets eliminate introduction of air to the system and thus the flows can be treated as one-phase ones. Computer codes EPANET 2 and SWMM 5.0 were applied and compared. Two flow schemes typical for the sewerage system were implemented in EPANET 2, and the third - in a slightly modified SWMM 5.0. Simulation results were validated on empirical data obtained on a laboratory physical model, consisting of four tanks of minimum volumes 600 dm3 each, connecting PE pipelines of diameters 25 mm and 36 mm and relevant sanitary fittings. Water inflows, typical for domestic wastewater outflows from single homesteads, were provided by a pump. Water flows were measured using water meters with pulse outputs, and water levels in tanks by pressure transducers. Hydraulic characteristics of filters and non-return valves were provided. Simulation results showed good agreement with the empirical data. Ranges of values of design parameters, needed for successful application of both codes, were established and discussed.
3D modeling of dual wind-up extensional rheometers
Yu, Kaijia; Román Marín, José Manuel; Rasmussen, Henrik K.
2010-01-01
Fully three-dimensional numerical simulations of a dual wind-up drum rheometer of the Sentmanat Extensional Rheometer (SER; Sentmanat, 2004 [1]) or the Extensional Viscosity Fixture (EVF; Garritano and Berting, 2006 [2]) type have been performed. In the SER and EVF a strip of rectangular shape...... is attached onto two drums, followed by a rotation of both drums in opposite direction. The numerical modeling is based on integral constitutive equations of the K-BKZ type. Generally, to ensure a proper uni-axial extensional deformation in dual wind-up drum rheometers the simulations show that a very small...
The early years of string theory: The dual resonance model
Ramond, P.
1987-10-01
This paper reviews the past quantum mechanical history of the dual resonance model which is an early string theory. The content of this paper is listed as follows: historical review, the Veneziano amplitude, the operator formalism, the ghost story, and the string story
International Family Migration and the Dual-Earner Model
Munk, Martin D.; Nikolka, Till; Poutvaara, Panu
2018-01-01
Gender differences in labor force participation are exceptionally small in Nordic countries. We investigate how couples emigrating from Denmark self-select and sort into different destinations and whether couples pursue the dual-earner model, in which both partners work, when abroad. Female labor...
Scale-invariant inclusive spectra in a dual model
Chikovani, Z.E.; Jenkovsky, L.L.; Martynov, E.S.
1979-01-01
One-particle inclusive distributions at large transverse momentum phisub(tr) are shown to scale, Edσ/d 3 phi approximately phisub(tr)sup(-N)(1-Xsub(tr))sup(1+N/2)lnphisub(tr), in a dual model with Mandelstam analyticity if the Regge trajectories are logarithmic asymptotically
Modeling and estimation of a low degree geopotential model from terrestrial gravity data
Pavlis, Nikolaos K.
1988-01-01
The development of appropriate modeling and adjustment procedures for the estimation of harmonic coefficients of the geopotential, from surface gravity data was studied, in order to provide an optimum way of utilizing the terrestrial gravity information in combination solutions currently developed at NASA/Goddard Space Flight Center, for use in the TOPEX/POSEIDON mission. The mathematical modeling was based on the fundamental boundary condition of the linearized Molodensky boundary value problem. Atmospheric and ellipsoidal corrections were applied to the surface anomalies. Terrestrial gravity solutions were found to be in good agreement with the satellite ones over areas which are well surveyed (gravimetrically), such as North America or Australia. However, systematic differences between the terrestrial only models and GEMT1, over extended regions in Africa, the Soviet Union, and China were found. In Africa, gravity anomaly differences on the order of 20 mgals and undulation differences on the order of 15 meters, over regions extending 2000 km in diameter, occur. Comparisons of the GEMT1 implied undulations with 32 well distributed Doppler derived undulations gave an RMS difference of 2.6 m, while corresponding comparison with undulations implied by the terrestrial solution gave RMS difference on the order of 15 m, which implies that the terrestrial data in that region are substantially in error.
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....
Functional Dual Adaptive Control with Recursive Gaussian Process Model
Prüher, Jakub; Král, Ladislav
2015-01-01
The paper deals with dual adaptive control problem, where the functional uncertainties in the system description are modelled by a non-parametric Gaussian process regression model. Current approaches to adaptive control based on Gaussian process models are severely limited in their practical applicability, because the model is re-adjusted using all the currently available data, which keeps growing with every time step. We propose the use of recursive Gaussian process regression algorithm for significant reduction in computational requirements, thus bringing the Gaussian process-based adaptive controllers closer to their practical applicability. In this work, we design a bi-criterial dual controller based on recursive Gaussian process model for discrete-time stochastic dynamic systems given in an affine-in-control form. Using Monte Carlo simulations, we show that the proposed controller achieves comparable performance with the full Gaussian process-based controller in terms of control quality while keeping the computational demands bounded. (paper)
Martinec, Zdeněk; Fullea, Javier
2015-03-01
We aim to interpret the vertical gravity and vertical gravity gradient of the GOCE-GRACE combined gravity model over the southeastern part of the Congo basin to refine the published model of sedimentary rock cover. We use the GOCO03S gravity model and evaluate its spherical harmonic representation at or near the Earth's surface. In this case, the gradiometry signals are enhanced as compared to the original measured GOCE gradients at satellite height and better emphasize the spatial pattern of sedimentary geology. To avoid aliasing, the omission error of the modelled gravity induced by the sedimentary rocks is adjusted to that of the GOCO03S gravity model. The mass-density Green's functions derived for the a priori structure of the sediments show a slightly greater sensitivity to the GOCO03S vertical gravity gradient than to the vertical gravity. Hence, the refinement of the sedimentary model is carried out for the vertical gravity gradient over the basin, such that a few anomalous values of the GOCO03S-derived vertical gravity gradient are adjusted by refining the model. We apply the 5-parameter Helmert's transformation, defined by 2 translations, 1 rotation and 2 scale parameters that are searched for by the steepest descent method. The refined sedimentary model is only slightly changed with respect to the original map, but it significantly improves the fit of the vertical gravity and vertical gravity gradient over the basin. However, there are still spatial features in the gravity and gradiometric data that remain unfitted by the refined model. These may be due to lateral density variation that is not contained in the model, a density contrast at the Moho discontinuity, lithospheric density stratifications or mantle convection. In a second step, the refined sedimentary model is used to find the vertical density stratification of sedimentary rocks. Although the gravity data can be interpreted by a constant sedimentary density, such a model does not correspond to
A dual-trace model for visual sensory memory.
Cappiello, Marcus; Zhang, Weiwei
2016-11-01
Visual sensory memory refers to a transient memory lingering briefly after the stimulus offset. Although previous literature suggests that visual sensory memory is supported by a fine-grained trace for continuous representation and a coarse-grained trace of categorical information, simultaneous separation and assessment of these traces can be difficult without a quantitative model. The present study used a continuous estimation procedure to test a novel mathematical model of the dual-trace hypothesis of visual sensory memory according to which visual sensory memory could be modeled as a mixture of 2 von Mises (2VM) distributions differing in standard deviation. When visual sensory memory and working memory (WM) for colors were distinguished using different experimental manipulations in the first 3 experiments, the 2VM model outperformed Zhang and Luck (2008) standard mixture model (SM) representing a mixture of a single memory trace and random guesses, even though SM outperformed 2VM for WM. Experiment 4 generalized 2VM's advantages of fitting visual sensory memory data over SM from color to orientation. Furthermore, a single trace model and 4 other alternative models were ruled out, suggesting the necessity and sufficiency of dual traces for visual sensory memory. Together these results support the dual-trace model of visual sensory memory and provide a preliminary inquiry into the nature of information loss from visual sensory memory to WM. (PsycINFO Database Record (c) 2016 APA, all rights reserved).
Spin foam model for pure gauge theory coupled to quantum gravity
Oriti, Daniele; Pfeiffer, Hendryk
2002-01-01
We propose a spin foam model for pure gauge fields coupled to Riemannian quantum gravity in four dimensions. The model is formulated for the triangulation of a four-manifold which is given merely combinatorially. The Riemannian Barrett-Crane model provides the gravity sector of our model and dynamically assigns geometric data to the given combinatorial triangulation. The gauge theory sector is a lattice gauge theory living on the same triangulation and obtains from the gravity sector the geometric information which is required to calculate the Yang-Mills action. The model is designed so that one obtains a continuum approximation of the gauge theory sector at an effective level, similarly to the continuum limit of lattice gauge theory, when the typical length scale of gravity is much smaller than the Yang-Mills scale
Evaluation of using digital gravity field models for zoning map creation
Loginov, Dmitry
2018-05-01
At the present time the digital cartographic models of geophysical fields are taking a special significance into geo-physical mapping. One of the important directions to their application is the creation of zoning maps, which allow taking into account the morphology of geophysical field in the implementation automated choice of contour intervals. The purpose of this work is the comparative evaluation of various digital models in the creation of integrated gravity field zoning map. For comparison were chosen the digital model of gravity field of Russia, created by the analog map with scale of 1 : 2 500 000, and the open global model of gravity field of the Earth - WGM2012. As a result of experimental works the four integrated gravity field zoning maps were obtained with using raw and processed data on each gravity field model. The study demonstrates the possibility of open data use to create integrated zoning maps with the condition to eliminate noise component of model by processing in specialized software systems. In this case, for solving problem of contour intervals automated choice the open digital models aren't inferior to regional models of gravity field, created for individual countries. This fact allows asserting about universality and independence of integrated zoning maps creation regardless of detail of a digital cartographic model of geo-physical fields.
Predicting sugar consumption: Application of an integrated dual-process, dual-phase model.
Hagger, Martin S; Trost, Nadine; Keech, Jacob J; Chan, Derwin K C; Hamilton, Kyra
2017-09-01
Excess consumption of added dietary sugars is related to multiple metabolic problems and adverse health conditions. Identifying the modifiable social cognitive and motivational constructs that predict sugar consumption is important to inform behavioral interventions aimed at reducing sugar intake. We tested the efficacy of an integrated dual-process, dual-phase model derived from multiple theories to predict sugar consumption. Using a prospective design, university students (N = 90) completed initial measures of the reflective (autonomous and controlled motivation, intentions, attitudes, subjective norm, perceived behavioral control), impulsive (implicit attitudes), volitional (action and coping planning), and behavioral (past sugar consumption) components of the proposed model. Self-reported sugar consumption was measured two weeks later. A structural equation model revealed that intentions, implicit attitudes, and, indirectly, autonomous motivation to reduce sugar consumption had small, significant effects on sugar consumption. Attitudes, subjective norm, and, indirectly, autonomous motivation to reduce sugar consumption predicted intentions. There were no effects of the planning constructs. Model effects were independent of the effects of past sugar consumption. The model identified the relative contribution of reflective and impulsive components in predicting sugar consumption. Given the prominent role of the impulsive component, interventions that assist individuals in managing cues-to-action and behavioral monitoring are likely to be effective in regulating sugar consumption. Copyright © 2017 Elsevier Ltd. All rights reserved.
Recent developments in high-resolution global altimetric gravity field modeling
Andersen, Ole Baltazar; Knudsen, Per; Berry, P. A .M.
2010-01-01
older gravity fields show accuracy improvement of the order of 20-40% due to a combination of retracking, enhanced processing, and the use of the new EGM2008 geoid model. In coastal and polar regions, accuracy improved in many places by 40-50% (or more) compared with older global marine gravity fields.......In recent years, dedicated effort has been made to improve high-resolution global marine gravity fields. One new global field is the Danish National Space Center (DNSC) 1-minute grid called DNSC08GRA, released in 2008. DNSC08GRA was derived from double-retracked satellite altimetry, mainly from...... the ERS-1 geodetic mission data, augmented with new retracked GEOSAT data which have significantly enhanced the range and hence the gravity field accuracy. DNSC08GRA is the first high-resolution global gravity field to cover the entire Arctic Ocean all the way to the North Pole. Comparisons with other...
Estimating Gravity Biases with Wavelets in Support of a 1-cm Accurate Geoid Model
Ahlgren, K.; Li, X.
2017-12-01
Systematic errors that reside in surface gravity datasets are one of the major hurdles in constructing a high-accuracy geoid model at high resolutions. The National Oceanic and Atmospheric Administration's (NOAA) National Geodetic Survey (NGS) has an extensive historical surface gravity dataset consisting of approximately 10 million gravity points that are known to have systematic biases at the mGal level (Saleh et al. 2013). As most relevant metadata is absent, estimating and removing these errors to be consistent with a global geopotential model and airborne data in the corresponding wavelength is quite a difficult endeavor. However, this is crucial to support a 1-cm accurate geoid model for the United States. With recently available independent gravity information from GRACE/GOCE and airborne gravity from the NGS Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project, several different methods of bias estimation are investigated which utilize radial basis functions and wavelet decomposition. We estimate a surface gravity value by incorporating a satellite gravity model, airborne gravity data, and forward-modeled topography at wavelet levels according to each dataset's spatial wavelength. Considering the estimated gravity values over an entire gravity survey, an estimate of the bias and/or correction for the entire survey can be found and applied. In order to assess the accuracy of each bias estimation method, two techniques are used. First, each bias estimation method is used to predict the bias for two high-quality (unbiased and high accuracy) geoid slope validation surveys (GSVS) (Smith et al. 2013 & Wang et al. 2017). Since these surveys are unbiased, the various bias estimation methods should reflect that and provide an absolute accuracy metric for each of the bias estimation methods. Secondly, the corrected gravity datasets from each of the bias estimation methods are used to build a geoid model. The accuracy of each geoid model
Calibrating vadose zone models with time-lapse gravity data
Christiansen, Lars; Binning, Philip John; Rosbjerg, Dan
2011-01-01
The vadose zone plays an important role in the hydrologic cycle. Various geophysical methods can determine soil water content variations in time and space in volumes ranging from a few cubic centimeters to several cubic meters. In contrast to the established methods, time-lapse gravity measurements...... of changes in soil water content do not rely on a petrophysical relationship between the measured quantity and the water content but give a direct measure of the mass change in the soil. Only recently has the vadose zone been systematically incorporated when ground-based gravity data are used to infer...... hydrologic information. In this study, changes in the soil water content gave rise to a measurable signal in a forced infiltration experiment on a 107-m2 grassland area. Time-lapse gravity data were able to constrain the van Genuchten soil hydraulic parameters in both a synthetic example and a field...
Chiral gravity, log gravity, and extremal CFT
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.
New Interpretations of the Rayn Anticlines in the Arabian Basin Inferred from Gravity Modelling
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
3D Gravity Modeling of Complex Salt Features in the Southern Gulf of Mexico
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.
Exactly solvable models of 2D-quantum gravity on the lattice. Course 5
Kazakov, V.A.
1990-01-01
It is shown that statistical mechanical models defined on randomly triangulated surfaces can be solved exactly and that thereby the results on 2-D quantum gravity can be confirmed. (author). 32 refs.; 4 figs.; 2 tabs
Finiteness of PST self-dual models
Del Cima, Oswaldo M.; Piguet, Olivier; Sarandy, Marcelo S.
2000-12-01
The Pasti-Sorokin-Tonin model for describing chiral forms is considered at the quantum level. We study the ultraviolet and infrared behaviour of the model in two, four and six dimensions in the framework of algebraic renormalization. The absence of anomalies, as well as the finiteness, up to non-physical renormalizations, are shown in all dimensions analyzed. (author)
Dual Value Creation and Business Model Design
Turcan, Romeo V.
This ethnographic research explores the process of business model design in the context of an NGO internationalizing to an emerging market. It contributes to the business model literature by investigating how this NGO - targeting multiple key stakeholders - was experimenting (1) with value...
Quantum mechanics vs. general covariance in gravity and string models
Martinec, E.J.
1984-01-01
Quantization of simple low-dimensional systems embodying general covariance is studied. Functional methods are employed in the calculation of effective actions for fermionic strings and 1 + 1 dimensional gravity. The author finds that regularization breaks apparent symmetries of the theory, providing new dynamics for the string and non-trivial dynamics for 1 + 1 gravity. The author moves on to consider the quantization of some generally covariant systems with a finite number of physical degrees of freedom, assuming the existence of an invariant cutoff. The author finds that the wavefunction of the universe in these cases is given by the solution to simple quantum mechanics problems
Comparing single- and dual-process models of memory development.
Hayes, Brett K; Dunn, John C; Joubert, Amy; Taylor, Robert
2017-11-01
This experiment examined single-process and dual-process accounts of the development of visual recognition memory. The participants, 6-7-year-olds, 9-10-year-olds and adults, were presented with a list of pictures which they encoded under shallow or deep conditions. They then made recognition and confidence judgments about a list containing old and new items. We replicated the main trends reported by Ghetti and Angelini () in that recognition hit rates increased from 6 to 9 years of age, with larger age changes following deep than shallow encoding. Formal versions of the dual-process high threshold signal detection model and several single-process models (equal variance signal detection, unequal variance signal detection, mixture signal detection) were fit to the developmental data. The unequal variance and mixture signal detection models gave a better account of the data than either of the other models. A state-trace analysis found evidence for only one underlying memory process across the age range tested. These results suggest that single-process memory models based on memory strength are a viable alternative to dual-process models for explaining memory development. © 2016 John Wiley & Sons Ltd.
Isostatic Model and Isostatic Gravity Anomalies of the Arabian Plate and Surroundings
M. K. Kaban; Sami El Khrepy; Nassir Al-Arifi
2016-01-01
The isostatic modeling represents one of the most useful ‘‘geological’’ reduction methods of the gravity field. With the isostatic correction, it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. Although there exist several isostatic compensation schemes, it is usually supposed that a choice of the model is not an important factor to first order, since the total weight of compensating m...
Slope wavenumber spectrum models of capillary and capillary-gravity waves
贾永君; 张杰; 王岩峰
2010-01-01
Capillary and capillary-gravity waves possess a random character, and the slope wavenumber spectra of them can be used to represent mean distributions of wave energy with respect to spatial scale of variability. But simple and practical models of the slope wavenumber spectra have not been put forward so far. In this article, we address the accurate definition of the slope wavenumber spectra of water surface capillary and capillary-gravity waves. By combining the existing slope wavenumber models and using th...
Deluna, Roperto Jr
2013-01-01
This study was conducted to investigate the issue of what Philippine merchandise trade flows would be if countries operated at the frontier of the gravity model. The study sought to estimate the coefficients of the gravity model. The estimated coefficients were used to estimate merchandise export potentials and technical efficiency of each country in the sample and these were also aggregated to measure impact of country groups, RTAs and inter-regional trading agreements. Result of the ...
Forward modeling of gravity data using geostatistically generated subsurface density variations
Phelps, Geoffrey
2016-01-01
Using geostatistical models of density variations in the subsurface, constrained by geologic data, forward models of gravity anomalies can be generated by discretizing the subsurface and calculating the cumulative effect of each cell (pixel). The results of such stochastically generated forward gravity anomalies can be compared with the observed gravity anomalies to find density models that match the observed data. These models have an advantage over forward gravity anomalies generated using polygonal bodies of homogeneous density because generating numerous realizations explores a larger region of the solution space. The stochastic modeling can be thought of as dividing the forward model into two components: that due to the shape of each geologic unit and that due to the heterogeneous distribution of density within each geologic unit. The modeling demonstrates that the internally heterogeneous distribution of density within each geologic unit can contribute significantly to the resulting calculated forward gravity anomaly. Furthermore, the stochastic models match observed statistical properties of geologic units, the solution space is more broadly explored by producing a suite of successful models, and the likelihood of a particular conceptual geologic model can be compared. The Vaca Fault near Travis Air Force Base, California, can be successfully modeled as a normal or strike-slip fault, with the normal fault model being slightly more probable. It can also be modeled as a reverse fault, although this structural geologic configuration is highly unlikely given the realizations we explored.
High effective inverse dynamics modelling for dual-arm robot
Shen, Haoyu; Liu, Yanli; Wu, Hongtao
2018-05-01
To deal with the problem of inverse dynamics modelling for dual arm robot, a recursive inverse dynamics modelling method based on decoupled natural orthogonal complement is presented. In this model, the concepts and methods of Decoupled Natural Orthogonal Complement matrices are used to eliminate the constraint forces in the Newton-Euler kinematic equations, and the screws is used to express the kinematic and dynamics variables. On this basis, the paper has developed a special simulation program with symbol software of Mathematica and conducted a simulation research on the a dual-arm robot. Simulation results show that the proposed method based on decoupled natural orthogonal complement can save an enormous amount of CPU time that was spent in computing compared with the recursive Newton-Euler kinematic equations and the results is correct and reasonable, which can verify the reliability and efficiency of the method.
A dual porosity model of nutrient uptake by root hairs
Zygalakis, K. C.; Kirk, G. J. D.; Jones, D. L.; Wissuwa, M.; Roose, T.
2011-01-01
Summary: • The importance of root hairs in the uptake of sparingly soluble nutrients is understood qualitatively, but not quantitatively, and this limits efforts to breed plants tolerant of nutrient-deficient soils. • Here, we develop a mathematical model of nutrient uptake by root hairs allowing for hair geometry and the details of nutrient transport through soil, including diffusion within and between soil particles. We give illustrative results for phosphate uptake. • Compared with conventional 'single porosity' models, this 'dual porosity' model predicts greater root uptake because more nutrient is available by slow release from within soil particles. Also the effect of soil moisture is less important with the dual porosity model because the effective volume available for diffusion in the soil is larger, and the predicted effects of hair length and density are different. • Consistent with experimental observations, with the dual porosity model, increases in hair length give greater increases in uptake than increases in hair density per unit main root length. The effect of hair density is less in dry soil because the minimum concentration in solution for net influx is reached more rapidly. The effect of hair length is much less sensitive to soil moisture. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.
A dual porosity model of nutrient uptake by root hairs
Zygalakis, K. C.
2011-08-09
Summary: • The importance of root hairs in the uptake of sparingly soluble nutrients is understood qualitatively, but not quantitatively, and this limits efforts to breed plants tolerant of nutrient-deficient soils. • Here, we develop a mathematical model of nutrient uptake by root hairs allowing for hair geometry and the details of nutrient transport through soil, including diffusion within and between soil particles. We give illustrative results for phosphate uptake. • Compared with conventional \\'single porosity\\' models, this \\'dual porosity\\' model predicts greater root uptake because more nutrient is available by slow release from within soil particles. Also the effect of soil moisture is less important with the dual porosity model because the effective volume available for diffusion in the soil is larger, and the predicted effects of hair length and density are different. • Consistent with experimental observations, with the dual porosity model, increases in hair length give greater increases in uptake than increases in hair density per unit main root length. The effect of hair density is less in dry soil because the minimum concentration in solution for net influx is reached more rapidly. The effect of hair length is much less sensitive to soil moisture. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.
Measured and modelled absolute gravity changes in Greenland
Nielsen, Jens Emil; Forsberg, René; Strykowski, Gabriel
2014-01-01
in Greenland. Theresult is compared with the initial measurements of absolute gravity (AG) change at selected GreenlandNetwork (GNET) sites.We find that observations are highly influenced by the direct attraction from the ice and ocean. Thisis especially evident in the measurements conducted at the GNET...
Global gravity and the geodynamic model of the Earth
Nedoma, J.
1988-01-01
Plate tectonic hypotheses require the formation of a new oceanic lithosphere at mid-oceanic ridges and imply the further modification and continued evolution towards the continental type of lithosphere in the regions of island arcs and orogenic belts. All these phenomena observed on the Earths's surface are results of all geodynamic processes passing through the Earth's interior. Since geodynamic processes change through the geological epochs, the gravity field also changes during the same geological periods. Thus, the paper is concerned with physical relationships between the global gravity field and the geodynamic processes as well as all geophysical fields affected by the geodynamic processes inside the Earth. The aim of this paper is to analyse the inner and outer gravity field of the Earth during the evolution of the Earth in the course of the geological epochs, and to build the generalized theory of the global gravity field of the Earth from the point of view of the global and local geodynamic processes taking place within the Earth's interior. (author)
Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.
2010-01-01
As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.
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...
Creed, R.; Edwards, A.
1997-01-01
Gravity gradiometry forward models have been developed at the Idaho National Engineering and Environmental laboratory (INEEL) that can characterize gravity gradient changes with the development of a cone of depression or injection mound in water table aquifers. Difference measurements at long time intervals reduce delayed drainage effects and eliminate the need for determining an initial density structure. Qualitative or semi-quantitative analysis of the gradient signal to determine changes in groundwater distribution with injection or pumping may be possible, particularly if the time varying nature of the signal is of interest. Gravity gradiometer instruments (such as the Gravity Gradient Survey System) have progressed to the point where the complete second order gravity gradient tensor can be measured with an instrument noise level of less than 1 Eotvos (0.1 microgals/meter). Modeling indicates direct gravity measurements for the injection mound perched aquifier case could produce similar signal to noise ratios. However gravity gradients provide 5 independent measurements and due to the common mode nature of the instruments are less susceptible to other effects (tide, latitude, elevation, etc.). The gradients also provide a sharper image of the edge of the anomaly. The systematic identification and removal of specific retention, rainfall and subsidence or uplift effects may be required to make gradiometry difference imaging practical for field use
Adler zero and the dual multiperipheral model
Balazs, L.A.P.
1978-01-01
We show that the ππ → ππ Adler PCAC (partial conservation of axial-vector current) condition requires a Reggeon intercept α (0) approx. = 0.5 within a broad class of multiperipheral models at the planar and cylinder levels. In the planar approximation this is closely related to the cancellation of the Reggeon-Reggeon cut
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
Lerch, F. J.; Nerem, R. S.; Chinn, D. S.; Chan, J. C.; Patel, G. B.; Klosko, S. M.
1993-01-01
A new method has been developed to provide a direct test of the error calibrations of gravity models based on actual satellite observations. The basic approach projects the error estimates of the gravity model parameters onto satellite observations, and the results of these projections are then compared with data residual computed from the orbital fits. To allow specific testing of the gravity error calibrations, subset solutions are computed based on the data set and data weighting of the gravity model. The approach is demonstrated using GEM-T3 to show that the gravity error estimates are well calibrated and that reliable predictions of orbit accuracies can be achieved for independent orbits.
Model tracking dual stochastic controller design under irregular internal noises
Lee, Jong Bok; Heo, Hoon; Cho, Yun Hyun; Ji, Tae Young
2006-01-01
Although many methods about the control of irregular external noise have been introduced and implemented, it is still necessary to design a controller that will be more effective and efficient methods to exclude for various noises. Accumulation of errors due to model tracking, internal noises (thermal noise, shot noise and l/f noise) that come from elements such as resistor, diode and transistor etc. in the circuit system and numerical errors due to digital process often destabilize the system and reduce the system performance. New stochastic controller is adopted to remove those noises using conventional controller simultaneously. Design method of a model tracking dual controller is proposed to improve the stability of system while removing external and internal noises. In the study, design process of the model tracking dual stochastic controller is introduced that improves system performance and guarantees robustness under irregular internal noises which can be created internally. The model tracking dual stochastic controller utilizing F-P-K stochastic control technique developed earlier is implemented to reveal its performance via simulation
Farahani, H.H.
2013-01-01
The main focus of the thesis is modelling the static and time-varying parts of the Earth's gravity field at the global scale based on data acquired by the Gravity Recovery And Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE). In addition, a new
A dual system model of preferences under risk.
Mukherjee, Kanchan
2010-01-01
This article presents a dual system model (DSM) of decision making under risk and uncertainty according to which the value of a gamble is a combination of the values assigned to it independently by the affective and deliberative systems. On the basis of research on dual process theories and empirical research in Hsee and Rottenstreich (2004) and Rottenstreich and Hsee (2001) among others, the DSM incorporates (a) individual differences in disposition to rational versus emotional decision making, (b) the affective nature of outcomes, and (c) different task construals within its framework. The model has good descriptive validity and accounts for (a) violation of nontransparent stochastic dominance, (b) fourfold pattern of risk attitudes, (c) ambiguity aversion, (d) common consequence effect, (e) common ratio effect, (f) isolation effect, and (g) coalescing and event-splitting effects. The DSM is also used to make several novel predictions of conditions under which specific behavior patterns may or may not occur.
Charm production in the dual topological unitarization model
Batunin, A.V.
1986-01-01
The open and hidden charm hadroproduction has been traced up to the SPS energies in the framework of the dual parton model. The free parameter (the suppression of the charmed sea) comes from the experiments on D-meson hadroproduction. Then the hidden-charm production data are described assuming that the J/ψ-meson production suggests only one cc-bar pair in the string, while the pair ψψ production suggests two cc-bar pairs
COLA with scale-dependent growth: applications to screened modified gravity models
Winther, Hans A.; Koyama, Kazuya; Wright, Bill S. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom); Manera, Marc [Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Zhao, Gong-Bo, E-mail: hans.a.winther@gmail.com, E-mail: kazuya.koyama@port.ac.uk, E-mail: manera.work@gmail.com, E-mail: bill.wright@port.ac.uk, E-mail: gong-bo.Zhao@port.ac.uk [National Astronomy Observatories, Chinese Academy of Science, Beijing, 100012 (China)
2017-08-01
We present a general parallelized and easy-to-use code to perform numerical simulations of structure formation using the COLA (COmoving Lagrangian Acceleration) method for cosmological models that exhibit scale-dependent growth at the level of first and second order Lagrangian perturbation theory. For modified gravity theories we also include screening using a fast approximate method that covers all the main examples of screening mechanisms in the literature. We test the code by comparing it to full simulations of two popular modified gravity models, namely f ( R ) gravity and nDGP, and find good agreement in the modified gravity boost-factors relative to ΛCDM even when using a fairly small number of COLA time steps.
Jomegi, A.
2007-01-01
Nowadays, satellite altimetry observations had made it possible to determine sea surface variations, in the global scale, to high degree of precision. Using satellite altimetry observations, Mean Sea Level (MSL) can be determined, which by Kowing Sea Surface Topography (SST), can be converted into high-resolution marine geoid. In this paper we are proposing a method for computation of the Earth's gravity field at the sea areas, which is different from usual methods. Indeed, our method is based on conversion of geoidal heights into gravity potential values at the reference ellipsoid 2 Ea,b , by using ellipsoidal Brun's formula, and forward application of solution of Fixed-Free Two Boundary Value Problem (FFTBVP), previously proposed by the authors for the geoid computations without application of Stokes formula. Numerical results of application of the proposed method at the test area of CoastalFars (at southern part of Iran) show the success of the method. Considering the low cost and high precision of satellite altimetry observations, the proposed method suggests an efficient substitution to shipborne gravity observations for gravity field molding at the sea areas
Multisensory integration and internal models for sensing gravity effects in primates.
Lacquaniti, Francesco; Bosco, Gianfranco; Gravano, Silvio; Indovina, Iole; La Scaleia, Barbara; Maffei, Vincenzo; Zago, Myrka
2014-01-01
Gravity is crucial for spatial perception, postural equilibrium, and movement generation. The vestibular apparatus is the main sensory system involved in monitoring gravity. Hair cells in the vestibular maculae respond to gravitoinertial forces, but they cannot distinguish between linear accelerations and changes of head orientation relative to gravity. The brain deals with this sensory ambiguity (which can cause some lethal airplane accidents) by combining several cues with the otolith signals: angular velocity signals provided by the semicircular canals, proprioceptive signals from muscles and tendons, visceral signals related to gravity, and visual signals. In particular, vision provides both static and dynamic signals about body orientation relative to the vertical, but it poorly discriminates arbitrary accelerations of moving objects. However, we are able to visually detect the specific acceleration of gravity since early infancy. This ability depends on the fact that gravity effects are stored in brain regions which integrate visual, vestibular, and neck proprioceptive signals and combine this information with an internal model of gravity effects.
Multisensory Integration and Internal Models for Sensing Gravity Effects in Primates
Francesco Lacquaniti
2014-01-01
Full Text Available Gravity is crucial for spatial perception, postural equilibrium, and movement generation. The vestibular apparatus is the main sensory system involved in monitoring gravity. Hair cells in the vestibular maculae respond to gravitoinertial forces, but they cannot distinguish between linear accelerations and changes of head orientation relative to gravity. The brain deals with this sensory ambiguity (which can cause some lethal airplane accidents by combining several cues with the otolith signals: angular velocity signals provided by the semicircular canals, proprioceptive signals from muscles and tendons, visceral signals related to gravity, and visual signals. In particular, vision provides both static and dynamic signals about body orientation relative to the vertical, but it poorly discriminates arbitrary accelerations of moving objects. However, we are able to visually detect the specific acceleration of gravity since early infancy. This ability depends on the fact that gravity effects are stored in brain regions which integrate visual, vestibular, and neck proprioceptive signals and combine this information with an internal model of gravity effects.
Mitchell, Myles A.; He, Jian-hua; Arnold, Christian; Li, Baojiu
2018-06-01
We propose a new framework for testing gravity using cluster observations, which aims to provide an unbiased constraint on modified gravity models from Sunyaev-Zel'dovich (SZ) and X-ray cluster counts and the cluster gas fraction, among other possible observables. Focusing on a popular f(R) model of gravity, we propose a novel procedure to recalibrate mass scaling relations from Λ cold dark matter (ΛCDM) to f(R) gravity for SZ and X-ray cluster observables. We find that the complicated modified gravity effects can be simply modelled as a dependence on a combination of the background scalar field and redshift, fR(z)/(1 + z), regardless of the f(R) model parameter. By employing a large suite of N-body simulations, we demonstrate that a theoretically derived tanh fitting formula is in excellent agreement with the dynamical mass enhancement of dark matter haloes for a large range of background field parameters and redshifts. Our framework is sufficiently flexible to allow for tests of other models and inclusion of further observables, and the one-parameter description of the dynamical mass enhancement can have important implications on the theoretical modelling of observables and on practical tests of gravity.
Cosmological models in energy-momentum-squared gravity
Board, Charles V. R.; Barrow, John D.
2017-12-01
We study the cosmological effects of adding terms of higher order in the usual energy-momentum tensor to the matter Lagrangian of general relativity. This is in contrast to most studies of higher-order gravity which focus on generalizing the Einstein-Hilbert curvature contribution to the Lagrangian. The resulting cosmological theories give rise to field equations of similar form to several particular theories with different fundamental bases, including bulk viscous cosmology, loop quantum gravity, k -essence, and brane-world cosmologies. We find a range of exact solutions for isotropic universes, discuss their behaviors with reference to the early- and late-time evolution, accelerated expansion, and the occurrence or avoidance of singularities. We briefly discuss extensions to anisotropic cosmologies and delineate the situations where the higher-order matter terms will dominate over anisotropies on approach to cosmological singularities.
Multiparticle production in a two-component dual parton model
Aurenche, P.; Bopp, F.W.; Capella, A.; Kwiecinski, J.; Maire, M.; Ranft, J.; Tran Thanh Van, J.
1992-01-01
The dual parton model (DPM) describes soft and semihard multiparticle production. The version of the DPM presented in this paper includes soft and hard mechanisms as well as diffractive processes. The model is formulated as a Monte Carlo event generator. We calculate in this model, in the energy range of the hadron colliders, rapidity distributions and the rise of the rapidity plateau with the collision energy, transverse-momentum distributions and the rise of average transverse momenta with the collision energy, multiplicity distributions in different pseudorapidity regions, and transverse-energy distributions. For most of these quantities we find a reasonable agreement with experimental data
Active Absorption of Irregular Gravity Waves in BEM-Models
Brorsen, Michael; Frigaard, Peter
1992-01-01
The boundary element method is applied to the computation of irregular gravity waves. The boundary conditions at the open boundaries are obtained by a digital filtering technique, where the surface elevations in front of the open boundary are filtered numerically yielding the velocity to be presc...... to be prescribed at the boundary. By numerical examples it is shown that well designed filters can reduce the wave reflection to a few per cent over a frequency range corresponding to a Jonswap spectrum....
Progress in the development of the GMM-2 gravity field model for Mars
Lemoine, F. G.; Smith, D. E.; Lerch, F. J.; Zuber, M. T.; Patel, G. B.
1994-01-01
Last year we published the GMM-1 (Goddard Mars Model-1) gravity model for Mars. We have completely re-analyzed the Viking and Mariner 9 tracking data in the development of the new field, designated GMM-2. The model is complete to degree and order 70. Various aspects of the model are discussed.
Brustein, Ram
2011-01-01
We reconsider, from a novel perspective, how unitarity constrains the corrections to the ratio of shear viscosity \\eta\\ to entropy density s. We start with higher-derivative extensions of Einstein gravity in asymptotically anti-de Sitter spacetimes. It is assumed that these theories are derived from string theory and thus have a unitary UV completion that is dual to a unitary, UV-complete boundary gauge theory. We then propose that the gravitational perturbations about a solution of the UV complete theory are described by an effective theory whose linearized equations of motion have at most two time derivatives. Our proposal leads to a concrete prescription for the calculation of \\eta/s for theories of gravity with arbitrary higher-derivative corrections. The resulting ratio can take on values above or below 1/4\\pi\\ and is consistent with all the previous calculations, even though our reasoning is substantially different. For the purpose of calculating \\eta/s, our proposal also leads to only two possible cand...
Classically scale-invariant B–L model and conformal gravity
Oda, Ichiro
2013-01-01
We consider a coupling of conformal gravity to the classically scale-invariant B–L extended standard model which has been recently proposed as a phenomenologically viable model realizing the Coleman–Weinberg mechanism of breakdown of the electroweak symmetry. As in a globally scale-invariant dilaton gravity, it is also shown in a locally scale-invariant conformal gravity that without recourse to the Coleman–Weinberg mechanism, the B–L gauge symmetry is broken in the process of spontaneous symmetry breakdown of the local scale invariance (Weyl invariance) at the tree level and as a result the B–L gauge field becomes massive via the Higgs mechanism. As a bonus of conformal gravity, the massless dilaton field does not appear and the parameters in front of the non-minimal coupling of gravity are completely fixed in the present model. This observation clearly shows that the conformal gravity has a practical application even if the scalar field does not possess any dynamical degree of freedom owing to the local scale symmetry
Lunar Prospector Orbit Determination Uncertainties Using the High Resolution Lunar Gravity Models
Carranza, Eric; Konopliv, Alex; Ryne, Mark
1999-01-01
The Lunar Prospector (LP) mission began on January 6, 1998, when the LP spacecraft was launched from Cape Canaveral, Florida. The objectives of the mission were to determine whether water ice exists at the lunar poles, generate a global compositional map of the lunar surface, detect lunar outgassing, and improve knowledge of the lunar magnetic and gravity fields. Orbit determination of LP performed at the Jet Propulsion Laboratory (JPL) is conducted as part of the principal science investigation of the lunar gravity field. This paper will describe the JPL effort in support of the LP Gravity Investigation. This support includes high precision orbit determination, gravity model validation, and data editing. A description of the mission and its trajectory will be provided first, followed by a discussion of the orbit determination estimation procedure and models. Accuracies will be examined in terms of orbit-to-orbit solution differences, as a function of oblateness model truncation, and inclination in the plane-of-sky. Long term predictions for several gravity fields will be compared to the reconstructed orbits to demonstrate the accuracy of the orbit determination and oblateness fields developed by the Principal Gravity Investigator.
A GOCE-only global gravity field model by the space-wise approach
Migliaccio, Frederica; Reguzzoni, Mirko; Gatti, Andrea
2011-01-01
The global gravity field model computed by the spacewise approach is one of three official solutions delivered by ESA from the analysis of the GOCE data. The model consists of a set of spherical harmonic coefficients and the corresponding error covariance matrix. The main idea behind this approach...... the orbit to reduce the noise variance and correlation before gridding the data. In the first release of the space-wise approach, based on a period of about two months, some prior information coming from existing gravity field models entered into the solution especially at low degrees and low orders...... degrees; the second is an internally computed GOCE-only prior model to be used in place of the official quick-look model, thus removing the dependency on EIGEN5C especially in the polar gaps. Once the procedure to obtain a GOCE-only solution has been outlined, a new global gravity field model has been...
Three-dimensional gravity modeling and focusing inversion using rectangular meshes.
Commer, M.
2011-03-01
Rectangular grid cells are commonly used for the geophysical modeling of gravity anomalies, owing to their flexibility in constructing complex models. The straightforward handling of cubic cells in gravity inversion algorithms allows for a flexible imposition of model regularization constraints, which are generally essential in the inversion of static potential field data. The first part of this paper provides a review of commonly used expressions for calculating the gravity of a right polygonal prism, both for gravity and gradiometry, where the formulas of Plouff and Forsberg are adapted. The formulas can be cast into general forms practical for implementation. In the second part, a weighting scheme for resolution enhancement at depth is presented. Modelling the earth using highly digitized meshes, depth weighting schemes are typically applied to the model objective functional, subject to minimizing the data misfit. The scheme proposed here involves a non-linear conjugate gradient inversion scheme with a weighting function applied to the non-linear conjugate gradient scheme's gradient vector of the objective functional. The low depth resolution due to the quick decay of the gravity kernel functions is counteracted by suppressing the search directions in the parameter space that would lead to near-surface concentrations of gravity anomalies. Further, a density parameter transformation function enabling the imposition of lower and upper bounding constraints is employed. Using synthetic data from models of varying complexity and a field data set, it is demonstrated that, given an adequate depth weighting function, the gravity inversion in the transform space can recover geologically meaningful models requiring a minimum of prior information and user interaction.
Interacting-string picture of dual-resonance models
Mandelstam, S.
1985-01-01
Dual-resonance models are an alyzed by means of operators which act within the physical Hilbert space of positive-metric states. The basis of the method is to extend the relativistic-string picture of a previous study to interacting particles. Functional methods are used, but their relation to the operator is evident, and factorization is maintained. An expression is given for the N-point amplitude in terms of physical-particle operators. For the three-point function the Neumann functions which occur in this expression are evaluated, so that we have a formula for the on- and off-energy-shell vertex. The authors assume that the string has no longitudinal degrees of freedom, and their results are Lorentz invariant and dual only if d=26
A 3D gravity and magnetic model for the Entenschnabel area (German North Sea)
Dressel, Ingo; Barckhausen, Udo; Heyde, Ingo
2018-01-01
In this study, we focus on structural configuration of the Entenschnabel area, a part of the German exclusive economic zone within the North Sea, by means of gravity and magnetic modelling. The starting point of the 3D modelling approach is published information on subseafloor structures for shallow depths, acquired by wells and seismic surveys. Subsequent gravity and magnetic modelling of the structures of the deeper subsurface builds on this geophysical and geological information and on gravity and magnetic data acquired during a research cruise to the Entenschnabel area. On the one hand, our 3D model shows the density and susceptibility distribution of the sediments and the crust. In addition, the potential field modelling provides evidence for a differentiation between lower and upper crust. The thickness distribution of the crust is also discussed with respect to the tectonic framework. Furthermore, gravity as well as magnetic modelling points to an intrusive complex beneath the Central Graben within the Entenschnabel area. On the other hand, this work provides a geological-geophysical consistent 3D gravity and magnetic model that can be used as a starting point for further investigation of this part of the German North Sea.
Dual coding: a cognitive model for psychoanalytic research.
Bucci, W
1985-01-01
Four theories of mental representation derived from current experimental work in cognitive psychology have been discussed in relation to psychoanalytic theory. These are: verbal mediation theory, in which language determines or mediates thought; perceptual dominance theory, in which imagistic structures are dominant; common code or propositional models, in which all information, perceptual or linguistic, is represented in an abstract, amodal code; and dual coding, in which nonverbal and verbal information are each encoded, in symbolic form, in separate systems specialized for such representation, and connected by a complex system of referential relations. The weight of current empirical evidence supports the dual code theory. However, psychoanalysis has implicitly accepted a mixed model-perceptual dominance theory applying to unconscious representation, and verbal mediation characterizing mature conscious waking thought. The characterization of psychoanalysis, by Schafer, Spence, and others, as a domain in which reality is constructed rather than discovered, reflects the application of this incomplete mixed model. The representations of experience in the patient's mind are seen as without structure of their own, needing to be organized by words, thus vulnerable to distortion or dissolution by the language of the analyst or the patient himself. In these terms, hypothesis testing becomes a meaningless pursuit; the propositions of the theory are no longer falsifiable; the analyst is always more or less "right." This paper suggests that the integrated dual code formulation provides a more coherent theoretical framework for psychoanalysis than the mixed model, with important implications for theory and technique. In terms of dual coding, the problem is not that the nonverbal representations are vulnerable to distortion by words, but that the words that pass back and forth between analyst and patient will not affect the nonverbal schemata at all. Using the dual code
Correspondence of f(R,∇R) Modified Gravity with Scalar Field Models
Jawad, Abdul; Debnath, Ujjal
2014-01-01
This paper is devoted to study the scalar field dark energy models by taking its different aspects in the framework of f(R,∇R) gravity. We consider flat FRW universe to construct the equation of state parameter governed by f(R,∇R) gravity. The stability of the model is discussed with the help of squared speed of sound parameter. It is found that models show quintessence behavior of the universe in stable as well as unstable modes. We also develop the correspondence of f(R,∇R) model with some scalar field dark energy models like quintessence, tachyonic field, k-essence, dilaton, hessence, and DBI-essence. The nature of scalar fields and corresponding scalar potentials is being analyzed in f(R,∇R) gravity graphically which show consistency with the present day observations about accelerated phenomenon
Influence of the Choice of Lunar Gravity Model on Orbit Determination for Lunar Orbiters
Young-Rok Kim
2018-01-01
Full Text Available We examine the influence of the lunar gravity model on the orbit determination (OD of a lunar orbiter operating in a 100 km high, lunar polar orbit. Doppler and sequential range measurements by three Deep Space Network antennas and one Korea Deep Space Antenna were used. For measurement simulation and OD analysis, STK11 and ODTK6 were utilized. GLGM2, LP100K, LP150Q, GRAIL420A, and GRAIL660B were used for investigation of lunar gravity model selection effect. OD results were assessed by position and velocity uncertainties with error covariance and an external orbit comparison using simulated true orbit. The effect of the lunar gravity models on the long-term OD, degree and order level, measurement-acquisition condition, and lunar altitude was investigated. For efficiency verification, computational times for the five lunar gravity models were compared. Results showed that significant improvements to OD accuracy are observed by applying a GRAIL-based model; however, applying a full order and degree gravity modeling is not always the best strategy, owing to the computational burden. Consequently, we consider that OD using GRAIL660B with 70 × 70 degree and order is the most efficient strategy for mission preanalysis. This study provides useful guideline for KPLO OD analysis during nominal mission operation.
Study of some chaotic inflationary models in f(R) gravity
Sharif, M.; Nawazish, Iqra
2018-04-01
In this paper, we discuss an inflationary scenario via scalar field and fluid cosmology for an anisotropic homogeneous universe model in f(R) gravity. We consider an equation of state which corresponds to a quasi-de Sitter expansion and investigate the effect of the anisotropy parameter for different values of the deviation parameter. We evaluate potential models like linear, quadratic and quartic models which correspond to chaotic inflation. We construct the observational parameters for a power-law model of f(R) gravity and construct the graphical analysis of tensor-scalar ratio and spectral index which indicates the consistency of these parameters with Planck 2015 data.
3D modeling of dual-gate FinFET.
Mil'shtein, Samson; Devarakonda, Lalitha; Zanchi, Brian; Palma, John
2012-11-13
The tendency to have better control of the flow of electrons in a channel of field-effect transistors (FETs) did lead to the design of two gates in junction field-effect transistors, field plates in a variety of metal semiconductor field-effect transistors and high electron mobility transistors, and finally a gate wrapping around three sides of a narrow fin-shaped channel in a FinFET. With the enhanced control, performance trends of all FETs are still challenged by carrier mobility dependence on the strengths of the electrical field along the channel. However, in cases when the ratio of FinFET volume to its surface dramatically decreases, one should carefully consider the surface boundary conditions of the device. Moreover, the inherent non-planar nature of a FinFET demands 3D modeling for accurate analysis of the device performance. Using the Silvaco modeling tool with quantization effects, we modeled a physical FinFET described in the work of Hisamoto et al. (IEEE Tran. Elec. Devices 47:12, 2000) in 3D. We compared it with a 2D model of the same device. We demonstrated that 3D modeling produces more accurate results. As 3D modeling results came close to experimental measurements, we made the next step of the study by designing a dual-gate FinFET biased at Vg1 >Vg2. It is shown that the dual-gate FinFET carries higher transconductance than the single-gate device.
An econometric model on bilateral trade in education using an augmented gravity model
Christina Tay
2014-05-01
Full Text Available Purpose: Trade in education has become one of the most important trades for many economies. Yet, studies of education as a trade are scant owing to the conventional view of it being non-tradable. The purpose of this paper is to econometrically investigate trade in education using a nexus of international trade theories and the gravity model, one of the most widely used models in international trade in goods that has been scantly investigated on in studies on trade in education.Design/methodology/approach: A panel data analysis is broken down for 21 exporting countries and 50 importing countries, covering 1050 observations using new UNESCO database. A number of determinants of international trade including wealth of exporter & importer, domestic capacity of exporter & importer, transport costs, common religion, common language and trade restrictiveness of the importer are empirically tested on bilateral trade flows in education. An econometric model is formulated to test determinants of trade in education using an augmented gravity model.Findings: The augmented gravity model used in this study explains with high significance the determinants of trade in education including wealth of exporter & importer, domestic capacity of exporter & importer, transport costs, common religion, common language and trade restrictiveness of the importer.Research limitations/implications: Taking a macroscopic view of education as a trade may give us a myopic view of the elements important to determine what students or parents of students as well as institutions are concerned with. Nevertheless, the nexus of international trade theories and the gravity model used in this study that are largely and traditionally used on trade in goods and services, but scantly used in trade in education have been found to be highly significant and relevant in trade in education. Future studies on macro-level of analysis involving trade in education could include other determinants of
Dual processing model of medical decision-making
2012-01-01
Background Dual processing theory of human cognition postulates that reasoning and decision-making can be described as a function of both an intuitive, experiential, affective system (system I) and/or an analytical, deliberative (system II) processing system. To date no formal descriptive model of medical decision-making based on dual processing theory has been developed. Here we postulate such a model and apply it to a common clinical situation: whether treatment should be administered to the patient who may or may not have a disease. Methods We developed a mathematical model in which we linked a recently proposed descriptive psychological model of cognition with the threshold model of medical decision-making and show how this approach can be used to better understand decision-making at the bedside and explain the widespread variation in treatments observed in clinical practice. Results We show that physician’s beliefs about whether to treat at higher (lower) probability levels compared to the prescriptive therapeutic thresholds obtained via system II processing is moderated by system I and the ratio of benefit and harms as evaluated by both system I and II. Under some conditions, the system I decision maker’s threshold may dramatically drop below the expected utility threshold derived by system II. This can explain the overtreatment often seen in the contemporary practice. The opposite can also occur as in the situations where empirical evidence is considered unreliable, or when cognitive processes of decision-makers are biased through recent experience: the threshold will increase relative to the normative threshold value derived via system II using expected utility threshold. This inclination for the higher diagnostic certainty may, in turn, explain undertreatment that is also documented in the current medical practice. Conclusions We have developed the first dual processing model of medical decision-making that has potential to enrich the current medical
Dual processing model of medical decision-making.
Djulbegovic, Benjamin; Hozo, Iztok; Beckstead, Jason; Tsalatsanis, Athanasios; Pauker, Stephen G
2012-09-03
Dual processing theory of human cognition postulates that reasoning and decision-making can be described as a function of both an intuitive, experiential, affective system (system I) and/or an analytical, deliberative (system II) processing system. To date no formal descriptive model of medical decision-making based on dual processing theory has been developed. Here we postulate such a model and apply it to a common clinical situation: whether treatment should be administered to the patient who may or may not have a disease. We developed a mathematical model in which we linked a recently proposed descriptive psychological model of cognition with the threshold model of medical decision-making and show how this approach can be used to better understand decision-making at the bedside and explain the widespread variation in treatments observed in clinical practice. We show that physician's beliefs about whether to treat at higher (lower) probability levels compared to the prescriptive therapeutic thresholds obtained via system II processing is moderated by system I and the ratio of benefit and harms as evaluated by both system I and II. Under some conditions, the system I decision maker's threshold may dramatically drop below the expected utility threshold derived by system II. This can explain the overtreatment often seen in the contemporary practice. The opposite can also occur as in the situations where empirical evidence is considered unreliable, or when cognitive processes of decision-makers are biased through recent experience: the threshold will increase relative to the normative threshold value derived via system II using expected utility threshold. This inclination for the higher diagnostic certainty may, in turn, explain undertreatment that is also documented in the current medical practice. We have developed the first dual processing model of medical decision-making that has potential to enrich the current medical decision-making field, which is still to the
Dual processing model of medical decision-making
Djulbegovic Benjamin
2012-09-01
Full Text Available Abstract Background Dual processing theory of human cognition postulates that reasoning and decision-making can be described as a function of both an intuitive, experiential, affective system (system I and/or an analytical, deliberative (system II processing system. To date no formal descriptive model of medical decision-making based on dual processing theory has been developed. Here we postulate such a model and apply it to a common clinical situation: whether treatment should be administered to the patient who may or may not have a disease. Methods We developed a mathematical model in which we linked a recently proposed descriptive psychological model of cognition with the threshold model of medical decision-making and show how this approach can be used to better understand decision-making at the bedside and explain the widespread variation in treatments observed in clinical practice. Results We show that physician’s beliefs about whether to treat at higher (lower probability levels compared to the prescriptive therapeutic thresholds obtained via system II processing is moderated by system I and the ratio of benefit and harms as evaluated by both system I and II. Under some conditions, the system I decision maker’s threshold may dramatically drop below the expected utility threshold derived by system II. This can explain the overtreatment often seen in the contemporary practice. The opposite can also occur as in the situations where empirical evidence is considered unreliable, or when cognitive processes of decision-makers are biased through recent experience: the threshold will increase relative to the normative threshold value derived via system II using expected utility threshold. This inclination for the higher diagnostic certainty may, in turn, explain undertreatment that is also documented in the current medical practice. Conclusions We have developed the first dual processing model of medical decision-making that has potential to
Jan Kostelecký
2015-06-01
Full Text Available The combined gravity field model EIGEN-6C4 (Förste et al., 2014 is the latest combined global gravity field model of GFZ Potsdam and GRGS Toulouse. EIGEN-6C4 has been generated including the satellite gravity gradiometry data of the entire GOCE mission (November 2009 till October 2013 and is of maximum spherical degree and order 2190. In this study EIGEN-6C4 has been compared with EGM2008 to its maximum degree and order via gravity disturbances and Tzz part of the Marussi tensor of the second derivatives of the disturbing potential. The emphasis is put on such areas where GOCE data (complete set of gradiometry measurements after reductions in EIGEN-6C4 obviously contributes to an improvement of the gravity field description. GNSS/levelling geoid heights are independent data source for the evaluation of gravity field models. Therefore, we use the GNSS/levelling data sets over the territories of Europe, Czech Republic and Slovakia for the evaluation of EIGEN-6C4 w.r.t. EGM2008.
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.
Semi-Infinite Geology Modeling Algorithm (SIGMA): a Modular Approach to 3D Gravity
Chang, J. C.; Crain, K.
2015-12-01
Conventional 3D gravity computations can take up to days, weeks, and even months, depending on the size and resolution of the data being modeled. Additional modeling runs, due to technical malfunctions or additional data modifications, only compound computation times even further. We propose a new modeling algorithm that utilizes vertical line elements to approximate mass, and non-gridded (point) gravity observations. This algorithm is (1) magnitudes faster than conventional methods, (2) accurate to less than 0.1% error, and (3) modular. The modularity of this methodology means that researchers can modify their geology/terrain or gravity data, and only the modified component needs to be re-run. Additionally, land-, sea-, and air-based platforms can be modeled at their observation point, without having to filter data into a synthesized grid.
Tests of local Lorentz invariance violation of gravity in the standard model extension with pulsars.
Shao, Lijing
2014-03-21
The standard model extension is an effective field theory introducing all possible Lorentz-violating (LV) operators to the standard model and general relativity (GR). In the pure-gravity sector of minimal standard model extension, nine coefficients describe dominant observable deviations from GR. We systematically implemented 27 tests from 13 pulsar systems to tightly constrain eight linear combinations of these coefficients with extensive Monte Carlo simulations. It constitutes the first detailed and systematic test of the pure-gravity sector of minimal standard model extension with the state-of-the-art pulsar observations. No deviation from GR was detected. The limits of LV coefficients are expressed in the canonical Sun-centered celestial-equatorial frame for the convenience of further studies. They are all improved by significant factors of tens to hundreds with existing ones. As a consequence, Einstein's equivalence principle is verified substantially further by pulsar experiments in terms of local Lorentz invariance in gravity.
Theoretical modeling of mechanical homeostasis of a mammalian cell under gravity-directed vector.
Zhou, Lüwen; Zhang, Chen; Zhang, Fan; Lü, Shouqin; Sun, Shujin; Lü, Dongyuan; Long, Mian
2018-02-01
Translocation of dense nucleus along gravity vector initiates mechanical remodeling of a eukaryotic cell. In our previous experiments, we quantified the impact of gravity vector on cell remodeling by placing an MC3T3-E1 cell onto upward (U)-, downward (D)-, or edge-on (E)- orientated substrate. Our experimental data demonstrate that orientation dependence of nucleus longitudinal translocation is positively correlated with cytoskeletal (CSK) remodeling of their expressions and structures and also is associated with rearrangement of focal adhesion complex (FAC). However, the underlying mechanism how CSK network and FACs are reorganized in a mammalian cell remains unclear. In this paper, we developed a theoretical biomechanical model to integrate the mechanosensing of nucleus translocation with CSK remodeling and FAC reorganization induced by a gravity vector. The cell was simplified as a nucleated tensegrity structure in the model. The cell and CSK filaments were considered to be symmetrical. All elements of CSK filaments and cytomembrane that support the nucleus were simplified as springs. FACs were simplified as an adhesion cluster of parallel bonds with shared force. Our model proposed that gravity vector-directed translocation of the cell nucleus is mechanically balanced by CSK remodeling and FAC reorganization induced by a gravitational force. Under gravity, dense nucleus tends to translocate and exert additional compressive or stretching force on the cytoskeleton. Finally, changes of the tension force acting on talin by microfilament alter the size of FACs. Results from our model are in qualitative agreement with those from experiments.
Covariant introduction of quark spin into the dual resonance model
Iroshnikov, G.S.
1979-01-01
A very simple method of insertion of a quark spin into the dual resonance model of hadron interaction is proposed. The method is suitable for amplitudes with an arbitrary number of particles. The amplitude of interaction of real particles is presented as a product of contribution of oscillatory excitations in the (q anti q) system and of a spin factor. The latter is equal to the trace of the product of the external particle wave functions constructed from structural quarks and satisfying the relativistic Bargman-Wigner equations. Two examples of calculating the meson interaction amplitudes are presented
Nonscaling parametrization of hadronic spectra and dual parton model
Gaponenko, O.N.
2001-01-01
Using the popular Wdowczyk-Wolfendale parametrization (WW-parametrization) as an example one studies restrictions imposed by a dual parton model for different nonscaling parametrizations of the pulsed hadron spectra in soft hadron-hadron and hadron-nuclear interactions. One derived a new parametrization free from basic drawback of the WW-formulae. In the central range the determined parametrization show agreement with the Wdowczyk-Wolfendale formula, but in contrast to the last-named one it does not result in contradiction with the experiment due to fast reduction of inelastic factor reduction with energy increase [ru
Conical Refraction: new observations and a dual cone model.
Sokolovskii, G S; Carnegie, D J; Kalkandjiev, T K; Rafailov, E U
2013-05-06
We propose a paraxial dual-cone model of conical refraction involving the interference of two cones of light behind the exit face of the crystal. The supporting experiment is based on beam selecting elements breaking down the conically refracted beam into two separate hollow cones which are symmetrical with one another. The shape of these cones of light is a product of a 'competition' between the divergence caused by the conical refraction and the convergence due to the focusing by the lens. The developed mathematical description of the conical refraction demonstrates an excellent agreement with experiment.
Solid holography and massive gravity
Alberte, Lasma; Baggioli, Matteo; Khmelnitsky, Andrei; Pujolàs, Oriol
2016-01-01
Momentum dissipation is an important ingredient in condensed matter physics that requires a translation breaking sector. In the bottom-up gauge/gravity duality, this implies that the gravity dual is massive. We start here a systematic analysis of holographic massive gravity (HMG) theories, which admit field theory dual interpretations and which, therefore, might store interesting condensed matter applications. We show that there are many phases of HMG that are fully consistent effective field theories and which have been left overlooked in the literature. The most important distinction between the different HMG phases is that they can be clearly separated into solids and fluids. This can be done both at the level of the unbroken spacetime symmetries as well as concerning the elastic properties of the dual materials. We extract the modulus of rigidity of the solid HMG black brane solutions and show how it relates to the graviton mass term. We also consider the implications of the different HMGs on the electric response. We show that the types of response that can be consistently described within this framework is much wider than what is captured by the narrow class of models mostly considered so far.
Solid holography and massive gravity
Alberte, Lasma [Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34151, Trieste (Italy); Baggioli, Matteo [Institut de Física d’Altes Energies (IFAE),The Barcelona Institute of Science and Technology (BIST), Campus UAB, 08193 Bellaterra, Barcelona (Spain); Department of Physics, Institute for Condensed Matter Theory, University of Illinois,1110 W. Green Street, Urbana, IL 61801 (United States); Khmelnitsky, Andrei [Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Pujolàs, Oriol [Institut de Física d’Altes Energies (IFAE),The Barcelona Institute of Science and Technology (BIST), Campus UAB, 08193 Bellaterra, Barcelona (Spain)
2016-02-17
Momentum dissipation is an important ingredient in condensed matter physics that requires a translation breaking sector. In the bottom-up gauge/gravity duality, this implies that the gravity dual is massive. We start here a systematic analysis of holographic massive gravity (HMG) theories, which admit field theory dual interpretations and which, therefore, might store interesting condensed matter applications. We show that there are many phases of HMG that are fully consistent effective field theories and which have been left overlooked in the literature. The most important distinction between the different HMG phases is that they can be clearly separated into solids and fluids. This can be done both at the level of the unbroken spacetime symmetries as well as concerning the elastic properties of the dual materials. We extract the modulus of rigidity of the solid HMG black brane solutions and show how it relates to the graviton mass term. We also consider the implications of the different HMGs on the electric response. We show that the types of response that can be consistently described within this framework is much wider than what is captured by the narrow class of models mostly considered so far.
Power-law and intermediate inflationary models in f(T)-gravity
Rezazadeh, K. [Department of Physics, University of Kurdistan,Pasdaran St., Sanandaj (Iran, Islamic Republic of); Abdolmaleki, A. [Research Institute for Astronomy Astrophysics of Maragha (RIAAM),P.O. Box 55134-441, Maragha (Iran, Islamic Republic of); Karami, K. [Department of Physics, University of Kurdistan,Pasdaran St., Sanandaj (Iran, Islamic Republic of)
2016-01-21
We study inflation in the framework of f(T)-gravity in the presence of a canonical scalar field. After reviewing the basic equations governing the background cosmology in f(T)-gravity, we turn to study the cosmological perturbations and obtain the evolutionary equations for the scalar and tensor perturbations. Solving those equations, we find the power spectra for the scalar and tensor perturbations. Then, we consider a power-law f(T) function and investigate the inflationary models with the power-law and intermediate scale factors. We see that in contrast with the standard inflationary scenario based on the Einstein gravity, the power-law and intermediate inflationary models in f(T)-gravity can be compatible with the observational results of Planck 2015 at 68% CL. We find that in our f(T) setting, the potentials responsible for the both power-law and intermediate inflationary models have the power-law form V(ϕ)∝ϕ{sup m} but the power m is different for them. Therefore, we can refine some of power-law inflationary potentials in the framework of f(T)-gravity while they are disfavored by the observational data in the standard inflationary scenario. Interestingly enough, is that the self-interacting quartic potential V(ϕ)∝ϕ{sup 4} which has special reheating properties, can be consistent with the Planck 2015 data in our f(T) scenario while it is ruled out in the standard inflationary scenario.
Power-law and intermediate inflationary models in f(T)-gravity
Rezazadeh, K.; Abdolmaleki, A.; Karami, K.
2016-01-01
We study inflation in the framework of f(T)-gravity in the presence of a canonical scalar field. After reviewing the basic equations governing the background cosmology in f(T)-gravity, we turn to study the cosmological perturbations and obtain the evolutionary equations for the scalar and tensor perturbations. Solving those equations, we find the power spectra for the scalar and tensor perturbations. Then, we consider a power-law f(T) function and investigate the inflationary models with the power-law and intermediate scale factors. We see that in contrast with the standard inflationary scenario based on the Einstein gravity, the power-law and intermediate inflationary models in f(T)-gravity can be compatible with the observational results of Planck 2015 at 68% CL. We find that in our f(T) setting, the potentials responsible for the both power-law and intermediate inflationary models have the power-law form V(ϕ)∝ϕ m but the power m is different for them. Therefore, we can refine some of power-law inflationary potentials in the framework of f(T)-gravity while they are disfavored by the observational data in the standard inflationary scenario. Interestingly enough, is that the self-interacting quartic potential V(ϕ)∝ϕ 4 which has special reheating properties, can be consistent with the Planck 2015 data in our f(T) scenario while it is ruled out in the standard inflationary scenario.
Kennedy, Jeffrey R.; Ferre, Ty P.A.; Creutzfeldt, Benjamin
2016-01-01
Groundwater-level measurements in monitoring wells or piezometers are the most common, and often the only, hydrologic measurements made at artificial recharge facilities. Measurements of gravity change over time provide an additional source of information about changes in groundwater storage, infiltration, and for model calibration. We demonstrate that for an artificial recharge facility with a deep groundwater table, gravity data are more sensitive to movement of water through the unsaturated zone than are groundwater levels. Groundwater levels have a delayed response to infiltration, change in a similar manner at many potential monitoring locations, and are heavily influenced by high-frequency noise induced by pumping; in contrast, gravity changes start immediately at the onset of infiltration and are sensitive to water in the unsaturated zone. Continuous gravity data can determine infiltration rate, and the estimate is only minimally affected by uncertainty in water-content change. Gravity data are also useful for constraining parameters in a coupled groundwater-unsaturated zone model (Modflow-NWT model with the Unsaturated Zone Flow (UZF) package).
Dual degree partnership in nursing: an innovative undergraduate educational model.
Bastable, Susan B; Markowitz, Marianne
2012-10-01
We report the success of a unique articulation Dual Degree Partnership in Nursing (DDPN) model. The process used to establish and implement this approach is described. Unlike typical 2+2 agreements between associate degree (AD) and bachelor degree (BS) nursing education programs, the DDPN is designed with a 1+2+1 sequence. Intended to attract high school students, this model provides the opportunity to earn two degrees (AD and BS) while experiencing a 4-year campus living and learning environment. This configuration was accomplished without compromising the integrity of either of the established programs. After collecting data over the past 6 years, this model demonstrates popularity with the traditional-aged student, as well as success from an academic perspective. Statistics on retention, graduation, and NCLEX® pass rates indicate the feasibility and success of the model. Based on the findings, the potential for replication is promising for other colleges interested in a similar collaboration. Copyright 2012, SLACK Incorporated.
Mathematical Modeling of Dual Intake Transparent Transpired Solar Collector
Thomas Semenou
2015-01-01
Full Text Available Nowadays, in several types of commercial or institutional buildings, a significant rise of transpired solar collectors used to preheat the fresh air of the building can be observed. Nevertheless, when the air mass flow rate is low, the collector efficiency collapses and a large amount of energy remains unused. This paper presents a simple yet effective mathematical model of a transparent transpired solar collector (TTC with dual intake in order to remove stagnation problems in the plenum and ensure a better thermal efficiency and more heat recovery. A thermal model and a pressure loss model were developed. Then, the combined model was validated with experimental data from the Solar Rating and Certification Corporation (SRCC. The results show that the collector efficiency can be up to 70% and even 80% regardless of operating conditions. The temperature gain is able to reach 20°K when the solar irradiation is high.
Effect of lunar gravity models on Chang'E-2 orbit determination using VLBI tracking data
Erhu Wei
2016-11-01
Full Text Available The precise orbit determination of Chang'E-2 is the most important issue for successful mission and scientific applications, while the lunar gravity field model with big uncertainties has large effect on Chang'E-2 orbit determination. Recently, several new gravity models have been produced using the latest lunar satellites tracking data, such as LP165P, SGM150J, GL0900D and GRGM900C. In this paper, the four gravity models mentioned above were evaluated through the power spectra analysis, admittance and coherence analysis. Effect of four lunar gravity models on Chang'E-2 orbit determination performance is investigated and assessed using Very Long Baseline Interferometry (VLBI tracking data. The overlap orbit analysis, the posteriori data residual, and the orbit prediction are used to evaluate the orbit precision between successive arcs. The LP165P model has better orbit overlap performance than the SGM150J model for Chang'E-2100 km × 100 km orbit and the SGM150J model performs better for Chang'E-2100 km × 15 km orbit, while GL0900D and GRGM900C have the best orbit overlap results for the two types of Chang'E-2 orbit. For the orbit prediction, GRGM900C has the best orbit prediction performance in the four models.
Using a Gravity Model to Predict Circulation in a Public Library System.
Ottensmann, John R.
1995-01-01
Describes the development of a gravity model based upon principles of spatial interaction to predict the circulation of libraries in the Indianapolis-Marion County Public Library (Indiana). The model effectively predicted past circulation figures and was tested by predicting future library circulation, particularly for a new branch library.…
GOCE in ocean modelling - Point mass method applied on GOCE gravity gradients
Herceg, Matija; Knudsen, Per
This presentation is an introduction to my Ph.D project. The main objective of the study is to improve the methodology for combining GOCE gravity field models with satellite altimetry to derive optimal dynamic ocean topography models for oceanography. Here a method for geoid determination using...
Using the gravity model to estimate the spatial spread of vector-borne diseases
Barrios, J.M.; Verstraeten, W.W.; Maes, P.; Aerts, J.; Farifteh, J.; Coppin, P.
2012-01-01
The gravity models are commonly used spatial interaction models. They have been widely applied in a large set of domains dealing with interactions amongst spatial entities. The spread of vector-borne diseases is also related to the intensity of interaction between spatial entities, namely, the
Identification of the Skirt Piled Gullfaks C Gravity Platform using ARMAV Models
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
This paper presents the results from the system identification of the Gullfaks C gravity offshore platform excited by natural loads. The paper describes how modal parameters and mode shapes can be estimated by use of ARMAV models. The results estimated by an ARMAV model are compared with results...
Identification of the Skirt Piled Gullfaks C Gravity Platform using ARMAV Models
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
1996-01-01
This paper presents the results from the system identification of the Gullfaks C gravity offshore platform excited by natural loads. The paper describes how modal parameters and mode shapes can be estimated by use of ARMAV models. The results estimated by an ARMAV model are compared with results...
2 + 1 quantum gravity as a toy model for the 3 + 1 theory
Ashtekar, A.; Husain, V.; Smolin, L.; Samuel, J.; Utah Univ., Salt Lake City, UT
1989-01-01
2 + 1 Einstein gravity is used as a toy model for testing a program for non-perturbative canonical quantisation of the 3 + 1 theory. The program can be successfully implemented in the model and leads to a surprisingly rich quantum theory. (author)
Modeling of micro thrusters for gravity probe B
Jones, Kenneth M.
1996-01-01
The concept of testing Einstein's general theory of relativity by means of orbiting gyroscopes was first proposed in 1959, which lead to the development of the Gravity Probe B experiment. Einstein's theory concerns the predictions of the relativistic precession of a gyroscope in orbit around earth. According to his theory, there will be two precessions due to the warping of space-time by the earth's gravitational field: the geodetic precession in the plane of the orbit, and the frame-dragging effect, in the direction of earth rotation. For a polar orbit, these components are orthogonal. In order to simplify the measurement of the precessions, Gravity Probe B (GP-B) will be placed in a circular polar orbit at 650 km, for which the predicted precessions will be 6.6 arcsec/year (geodetic) and 42 milli-arcsec/year (frame-dragging). As the gyroscope precesses, the orientation of its spin-axis will be measured with respect to the line-of-sight to Rigel, a star whose proper motion is known to be within the required accuracy. The line-of-sight to Rigel will be established using a telescope, and the orientation of the gyroscope spin axis will be measured using very sensitive SQUID (Superconducting Quantum Interference Device) magnetometers. The four gyroscopes will be coated with niobium. Below 2K, the niobium becomes superconducting and a dipole field will be generated which is precisely aligned with the gyroscope spin-axis. The change in orientation of these fields, as well as the spin-axis, is sensed by the SQUID magnetometers. In order to attain the superconducting temperatures for the gyroscopes and the SQUID's, the experiment package will be housed in a dewar filled with liquid helium. The helium flow through a GP-B micro thruster and into a vacuum is investigated using the Direct Simulation Monte Carlo method.
Gravity modeling of the Muertos Trough and tectonic implications (north-eastern Caribbean)
Granja, Bruna J.L.; Muñoz-Martín, A.; ten Brink, Uri S.; Carbó-Gorosabel, Andrés; Llanes, Estrada P.; Martín-Dávila, J.; Cordoba-Barba, D.; Catalan, Morollon M.
2010-01-01
The Muertos Trough in the northeast Caribbean has been interpreted as a subduction zone from seismicity, leading to infer a possible reversal subduction polarity. However, the distribution of the seismicity is very diffuse and makes definition of the plate geometry difficult. In addition, the compressive deformational features observed in the upper crust and sandbox kinematic modeling do not necessarily suggest a subduction process. We tested the hypothesized subduction of the Caribbean plate's interior beneath the eastern Greater Antilles island arc using gravity modeling. Gravity models simulating a subduction process yield a regional mass deficit beneath the island arc independently of the geometry and depth of the subducted slab used in the models. This mass deficit results from sinking of the less dense Caribbean slab beneath the lithospheric mantle replacing denser mantle materials and suggests that there is not a subducted Caribbean plateau beneath the island arc. The geologically more realistic gravity model which would explain the N-S shortening observed in the upper crust requires an overthrusted Caribbean slab extending at least 60 km northward from the deformation front, a progressive increase in the thrusting angle from 8?? to 30?? reaching a maximum depth of 22 km beneath the insular slope. This new tectonic model for the Muertos Margin, defined as a retroarc thrusting, will help to assess the seismic and tsunami hazard in the region. The use of gravity modeling has provided targets for future wide-angle seismic surveys in the Muertos Margin. ?? 2010 Springer Science+Business Media B.V.
Bazr-Afkan, S.
2012-01-01
To simulate fluid flow in Naturally Fractured Reservoirs (NFRs), a new Descrete Fracture and Matrix (DFM) simulation technique is developed as a physically more realistic alternative to the dual continuum approach. This Finite-Element Centered Finite-Volume method (FECFVM) has the advantage over earlier FECFVM approaches that it honors saturation dicontinuities that can arise at material interfaces from the interplay of viscous, capillary and gravitational forces. By contrast with an earlier embedded-discontinuity DFEFVM method, the FECFVM achieves this without introducing additional degrees of freedom. It also allows to simulate capillary- and other fracture-matrix exchange processes using a lower dimensional representation of fractures, simplifying model construction and unstructured meshing as well as speeding up computations. A further step-up is obtained by solving the two-phase fluid-flow and saturation transport equations only on 'active elements'. This also diminishes round-off and truncation errors, reducing numerical diffusion during the solution of the transport equation. The FECFVM is verified by comparing IMPES operator-splitting sequential solutions with analytical ones, as well as benchmarking it against commercial reservoir simulators on simple geometries that these can represent. This testing confirms that my 2D FECFVM implementation simulates gravitational segregation, capillary redistribution, capillary barriers, and combinations thereof physically realistically, achieving (at least) first-order solution accuracy. Following this verification, the FECFVM is applied to study Gas-Oil Gravity Drainage (GOGD) process in cross-sectional models of layered NFRs. Here comparisons with dual continua simulations show that these do not capture a range of block-to-block effects, yielding over-optimistic drainage rates. Observations made on individual matrix blocks in the DFM simulations further reveal that their saturation evolution is at odds with the
A 2D model of causal set quantum gravity: the emergence of the continuum
Brightwell, Graham; Henson, Joe; Surya, Sumati
2008-01-01
Non-perturbative theories of quantum gravity inevitably include configurations that fail to resemble physically reasonable spacetimes at large scales. Often, these configurations are entropically dominant and pose an obstacle to obtaining the desired classical limit. We examine this 'entropy problem' in a model of causal set quantum gravity corresponding to a discretization of 2D spacetimes. Using results from the theory of partial orders we show that, in the large volume or continuum limit, its partition function is dominated by causal sets which approximate to a region of 2D Minkowski space. This model of causal set quantum gravity thus overcomes the entropy problem and predicts the emergence of a physically reasonable geometry
P. Gasparini
1997-06-01
Full Text Available The results of about 120 magnetotelluric soundings carried out in the Vulsini, Vico and Sabatini volcanic areas were modeled along with Bouguer and aeromagnetic anomalies to reconstruct a model of the structure of the shallow (less than 5 km of depth crust. The interpretations were constrained by the information gathered from the deep boreholes drilled for geothermal exploration. MT and aeromagnetic anomalies allow the depth to the top of the sedimentary basement and the thickness of the volcanic layer to be inferred. Gravity anomalies are strongly affected by the variations of morphology of the top of the sedimentary basement, consisting of a Tertiary flysch, and of the interface with the underlying Mesozoic carbonates. Gravity data have also been used to extrapolate the thickness of the neogenic unit indicated by some boreholes. There is no evidence for other important density and susceptibility heterogeneities and deeper sources of magnetic and/or gravity anomalies in all the surveyed area.
Yazid, N. M.; Din, A. H. M.; Omar, K. M.; Som, Z. A. M.; Omar, A. H.; Yahaya, N. A. Z.; Tugi, A.
2016-09-01
Global geopotential models (GGMs) are vital in computing global geoid undulations heights. Based on the ellipsoidal height by Global Navigation Satellite System (GNSS) observations, the accurate orthometric height can be calculated by adding precise and accurate geoid undulations model information. However, GGMs also provide data from the satellite gravity missions such as GRACE, GOCE and CHAMP. Thus, this will assist to enhance the global geoid undulations data. A statistical assessment has been made between geoid undulations derived from 4 GGMs and the airborne gravity data provided by Department of Survey and Mapping Malaysia (DSMM). The goal of this study is the selection of the best possible GGM that best matches statistically with the geoid undulations of airborne gravity data under the Marine Geodetic Infrastructures in Malaysian Waters (MAGIC) Project over marine areas in Sabah. The correlation coefficients and the RMS value for the geoid undulations of GGM and airborne gravity data were computed. The correlation coefficients between EGM 2008 and airborne gravity data is 1 while RMS value is 0.1499.In this study, the RMS value of EGM 2008 is the lowest among the others. Regarding to the statistical analysis, it clearly represents that EGM 2008 is the best fit for marine geoid undulations throughout South China Sea.
Improved dual sided doped memristor: modelling and applications
Anup Shrivastava
2014-05-01
Full Text Available Memristor as a novel and emerging electronic device having vast range of applications suffer from poor frequency response and saturation length. In this paper, the authors present a novel and an innovative device structure for the memristor with two active layers and its non-linear ionic drift model for an improved frequency response and saturation length. The authors investigated and compared the I–V characteristics for the proposed model with the conventional memristors and found better results in each case (different window functions for the proposed dual sided doped memristor. For circuit level simulation, they developed a SPICE model of the proposed memristor and designed some logic gates based on hybrid complementary metal oxide semiconductor memristive logic (memristor ratioed logic. The proposed memristor yields improved results in terms of noise margin, delay time and dynamic hazards than that of the conventional memristors (single active layer memristors.
Herceg, Matija; Thybo, Hans; Artemieva, Irina
2013-01-01
We present a new regional model for the density structure of the upper mantle below Siberia. The residual mantle gravity anomalies are based on gravity data derived from the GOCE gravity gradients and geopotential models, with crustal correction to the gravity field being calculated from a new...... on regional and global crustal models. We analyze how uncertainties and errors in the crustal model propagate from crustal densities to mantle residual gravity anomalies and the density model of the upper mantle. The new regional density model for the Siberian craton and the West Siberian Basin complements...... regional crustal model. This newly compiled database on the crustal seismic structure, complemented by additional constraints from petrological analysis of near-surface rocks and lower crustal xenoliths, allows for a high-resolution correction of the crustal effects as compared to previous studies based...
Asgharian, Bahman; Price, Owen; Oberdörster, Gunter
2006-06-01
Inhalation of particles generated as a result of thermal degradation from fire or smoke, as may occur on spacecraft, is of major health concern to space-faring countries. Knowledge of lung airflow and particle transport under different gravity environments is required to addresses this concern by providing information on particle deposition. Gravity affects deposition of particles in the lung in two ways. First, the airflow distribution among airways is changed in different gravity environments. Second, particle losses by sedimentation are enhanced with increasing gravity. In this study, a model of airflow distribution in the lung that accounts for the influence of gravity was used for a mathematical description of particle deposition in the human lung to calculate lobar, regional, and local deposition of particles in different gravity environments. The lung geometry used in the mathematical model contained five lobes that allowed the assessment of lobar ventilation distribution and variation of particle deposition. At zero gravity, it was predicted that all lobes of the lung expanded and contracted uniformly, independent of body position. Increased gravity in the upright position increased the expansion of the upper lobes and decreased expansion of the lower lobes. Despite a slight increase in predicted deposition of ultrafine particles in the upper lobes with decreasing gravity, deposition of ultrafine particles was generally predicted to be unaffected by gravity. Increased gravity increased predicted deposition of fine and coarse particles in the tracheobronchial region, but that led to a reduction or even elimination of deposition in the alveolar region for coarse particles. The results from this study show that existing mathematical models of particle deposition at 1 G can be extended to different gravity environments by simply correcting for a gravity constant. Controlled studies in astronauts on future space missions are needed to validate these predictions.
A RENORMALIZATION PROCEDURE FOR TENSOR MODELS AND SCALAR-TENSOR THEORIES OF GRAVITY
SASAKURA, NAOKI
2010-01-01
Tensor models are more-index generalizations of the so-called matrix models, and provide models of quantum gravity with the idea that spaces and general relativity are emergent phenomena. In this paper, a renormalization procedure for the tensor models whose dynamical variable is a totally symmetric real three-tensor is discussed. It is proven that configurations with certain Gaussian forms are the attractors of the three-tensor under the renormalization procedure. Since these Gaussian config...
THE ANALYSIS OF FLAT GLASS EXPORTS FOR ROMANIA USING THE GRAVITY MODEL
Draghescu Florin
2015-07-01
Full Text Available The intense international competition and reduced rates of economics growth force the companies at dynamic and appropriate strategies to address internal and external market. The manufacturing industry from Romania has competitive advantages defined by tradition, qualified labour force, indigenous raw materials, and its products serve various industries – construction, automotive, food – that is expected to experience a future sustained development. With approximately 2,500 employees, the glassware sector from Romania is part of the manufacturing industry which has constantly decreased in the last 25 years. Romania has a long tradition in the glassware sector and remains a strategic player in the region being integrated in the global flows from the industry. Geographical orientation of Romanian trade of flat glass for export is analyzed using the gravity model. The purpose of this article is to determine the essential factors of flat glass export level from Romania to states with which has commercial partnerships using both a gravity static model, but also a gravity dynamic model – a common model in the literature, used to analyze the trade flows between world countries or polarization strength of cities and commercial centres. The empirical results of both models have shown that the gravity attraction of local and destination economies, transport costs – measured by the distances between capitals and lack of common border –, language interconnectivity, and also belonging to the BSEC (Organization of the Black Sea Economic Cooperation are the most important factors affecting the Romanian exports of the flat glass.
Risk analysis of gravity dam instability using credibility theory Monte Carlo simulation model.
Xin, Cao; Chongshi, Gu
2016-01-01
Risk analysis of gravity dam stability involves complicated uncertainty in many design parameters and measured data. Stability failure risk ratio described jointly by probability and possibility has deficiency in characterization of influence of fuzzy factors and representation of the likelihood of risk occurrence in practical engineering. In this article, credibility theory is applied into stability failure risk analysis of gravity dam. Stability of gravity dam is viewed as a hybrid event considering both fuzziness and randomness of failure criterion, design parameters and measured data. Credibility distribution function is conducted as a novel way to represent uncertainty of influence factors of gravity dam stability. And combining with Monte Carlo simulation, corresponding calculation method and procedure are proposed. Based on a dam section, a detailed application of the modeling approach on risk calculation of both dam foundation and double sliding surfaces is provided. The results show that, the present method is feasible to be applied on analysis of stability failure risk for gravity dams. The risk assessment obtained can reflect influence of both sorts of uncertainty, and is suitable as an index value.
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.
Constraint on reconstructed f(R) gravity models from gravitational waves
Lee, Seokcheon
2018-06-01
The gravitational wave (GW) detection of a binary neutron star inspiral made by the Advanced LIGO and Advanced Virgo paves the unprecedented way for multi-messenger observations. The propagation speed of this GW can be scrutinized by comparing the arrival times between GW and neutrinos or photons. It provides the constraint on the mass of the graviton. f(R) gravity theories have the habitual non-zero mass gravitons in addition to usual massless ones. Previously, we show that the model independent f(R) gravity theories can be constructed from the both background evolution and the matter growth with one undetermined parameter. We show that this parameter can be constrained from the graviton mass bound obtained from GW detection. Thus, the GW detection provides the invaluable constraint on the validity of f(R) gravity theories.
Exact solution in the cosmological chaotic inflation model with induced gravity
Wang Wenfu
2004-01-01
We present a new, exact solution in the cosmological chaotic inflation model with induced gravity. The spectral index of the scalar density fluctuations, n s , is computed, and is consistent with the analyses of BOOMERANG data. The effective cosmological constant Λ eff tends to zero when inflation ends
Logit Estimation of a Gravity Model of the College Enrollment Decision.
Leppel, Karen
1993-01-01
A study investigated the factors influencing students' decisions about attending a college to which they had been admitted. Logit analysis confirmed gravity model predictions that geographic distance and student ability would most influence the enrollment decision and found other variables, although affecting earlier stages of decision making, did…
The Footfall of Shopping Centres in Olomouc (Czech Republic): An Application of the Gravity Model
Klapka, Pavel; Erlebach, M.; Král, O.; Lehnert, M.; Mička, T.
2013-01-01
Roč. 21, č. 3 (2013), s. 12-26 ISSN 1210-8812 Institutional support: RVO:68145535 Keywords : footfall * spatial interaction * gravity model * shopping centre * Olomouc Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.341, year: 2013 http://www.geonika.cz/EN/research/ENMgr/MGR_2013_03.pdf
Modeling corewood-outerwood transition in loblolly pine using wood specific gravity
Christian R. Mora; H. Lee Allen; Richard F. Daniels; Alexander Clark
2007-01-01
A modified logistic function was used for modeling specific-gravity profiles obtained from X-ray densitometry analysis in 675 loblolly pine (Pinus taeda L.) trees in four regeneration trials. Trees were 21 or 22 years old at the time of the study. The function was used for demarcating corewood, transitional, and outerwood zones. Site and silvicultural effects were...
Gravitational waves during inflation from a 5D large-scale repulsive gravity model
Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio
2012-01-01
We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.
Gravitational waves during inflation from a 5D large-scale repulsive gravity model
Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio
2012-10-01
We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.
Gravitational waves during inflation from a 5D large-scale repulsive gravity model
Reyes, Luz M., E-mail: luzmarinareyes@gmail.com [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Moreno, Claudia, E-mail: claudia.moreno@cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Madriz Aguilar, Jose Edgar, E-mail: edgar.madriz@red.cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Bellini, Mauricio, E-mail: mbellini@mdp.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMdP), Funes 3350, C.P. 7600, Mar del Plata (Argentina); Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR) - Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)
2012-10-22
We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.
Gravity field models from kinematic orbits of CHAMP, GRACE and GOCE satellites
Bezděk, Aleš; Sebera, Josef; Klokočník, Jaroslav; Kostelecký, J.
2014-01-01
Roč. 53, č. 3 (2014), s. 412-429 ISSN 0273-1177 R&D Projects: GA MŠk LH13071; GA ČR GA13-36843S Institutional support: RVO:67985815 Keywords : gravity field models * kinematic orbits * generalized least squares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.358, year: 2014
The anisotropic cosmological models in f(R, T) gravity with (T )
2017-03-15
Mar 15, 2017 ... Recent evidences coming from the observational data [1–6] on the late-time ... theoretical challenge to gravitational theories.The cosmic microwave ... that at large scales the Einstein gravity model of general relativity breaks ...
(2+1) gravity for higher genus in the polygon model
Kádár, Zoltán; Loll, R.
2004-01-01
We construct explicitly a (12g − 12)-dimensional space P of unconstrained and independent initial data for ’t Hooft’s polygon model of (2+1) gravity for vacuum spacetimes with compact genus-g spacelike slices, for any g ≥ 2. Our method relies on interpreting the boost parameters of the gluing
Wińska, Małgorzata; Nastula, Jolanta
2017-04-01
Large scale mass redistribution and its transport within the Earth system causes changes in the Earth's rotation in space, gravity field and Earth's ellipsoid shape. These changes are observed in the ΔC21, ΔS21, and ΔC20 spherical harmonics gravity coefficients, which are proportional to the mass load-induced Earth rotational excitations. In this study, linear trend, decadal, inter-annual, and seasonal variations of low degree spherical harmonics coefficients of Earth's gravity field, determined from different space geodetic techniques, Gravity Recovery and Climate Experiment (GRACE), satellite laser ranging (SLR), Global Navigation Satellite System (GNSS), Earth rotation, and climate models, are examined. In this way, the contribution of each measurement technique to interpreting the low degree surface mass density of the Earth is shown. Especially, we evaluate an usefulness of several climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) to determine the low degree Earth's gravity coefficients using GRACE satellite observations. To do that, Terrestrial Water Storage (TWS) changes from several CMIP5 climate models are determined and then these simulated data are compared with the GRACE observations. Spherical harmonics ΔC21, ΔS21, and ΔC20 changes are calculated as the sum of atmosphere and ocean mass effect (GAC values) taken from GRACE and a land surface hydrological estimate from the selected CMIP5 climate models. Low degree Stokes coefficients of the surface mass density determined from GRACE, SLR, GNSS, Earth rotation measurements and climate models are compared to each other in order to assess their consistency. The comparison is done by using different types of statistical and signal processing methods.
A dual resonance model for high energy electroweak reactions
Picard, Jean-Francois
1995-01-01
The aim of this work is to propose an original model for the weak interaction at high energy (about 1 TeV) that is inspired from resonance dual models established for hadron physics. The first chapter details the basis and assumptions of the standard model. The second chapter deals with various scenarios that go beyond the standard model and that involve a strong interaction and a perturbative approach to assess coupling. The third chapter is dedicated to the main teachings of hadron physics concerning resonances, the model of Regge poles and the concept of duality. We present our new model in the fourth chapter, we build a scenario in which standard fermions and the 3 massive gauge bosons would have a sub-structure alike that of hadrons. In order to give non-null values to the width of resonances we use the K matrix method, we describe this method in the last chapter and we apply it for the computation of the width of the Z 0 boson. Our model predicts a large spectra of states particularly with the 143-up-lets of ff-bar states. The K matrix method has allowed us to compute amplitudes for helicity, then to collapse them in amplitudes invariant with SU(2) and to project these amplitudes in partial waves of helicity. For most resonances partial widths are very low compared to their mass
Assessing performance of gravity models in the Arctic and the implications for polar oceanography
Thomas, S. F.; McAdoo, D. C.; Farrell, S. L.; Brozena, J. M.; Childers, V. A.; Ziebart, M. K.; Shepherd, A.
2014-12-01
The circulation of the Arctic Ocean is of great interest to both the oceanographic and cryospheric communities. Understanding both the steady state and variations of this circulation is essential to building our knowledge of Arctic climate. With the advent of high inclination altimeter missions such as CryoSat and ICESat, it is now feasible to produce Mean Dynamic Topography (MDT) products for the region, which allow a comprehensive investigation of geostrophic currents. However, the accuracy of these products is largely limited by our knowledge of the marine geoid in the Arctic. There are a number of publicly available gravity models commonly used to derive the geoid. These use different combinations of available data (satellite gravimetry, altimetry, laser ranging, and in-situ) and are calculated using different mathematical techniques. However, the effect of these differences on the real world performance of these models when used for oceanographic studies in the Arctic is not well known. Given the unique problems for gravimetry in the region (especially data gaps) and their potential impact on MDT products, it is especially important that the relative performance of these models be assessed We consider the needs of the "end user" satellite oceanographer in the Arctic with respect to gravimetry, and the relationship between the precision of gravity data and the accuracy of a final MDT/current velocity product. Using high-precision aerogravity data collected over 3 years of campaigns by NASA's Operation IceBridge we inter-compare 10 of the leading gravity models and assess their performance in the Arctic. We also use historical data from campaigns flown by the US Naval Research Laboratory (NRL) to demonstrate the impact of gravity errors on MDT products. We describe how gravity models for the region might be improved in the future, in an effort to maximize the level at which Arctic currents may be resolved.
Speeding up N -body simulations of modified gravity: chameleon screening models
Bose, Sownak; Li, Baojiu; He, Jian-hua; Llinares, Claudio [Institute for Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Barreira, Alexandre [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany); Hellwing, Wojciech A.; Koyama, Kazuya [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom); Zhao, Gong-Bo, E-mail: sownak.bose@durham.ac.uk, E-mail: baojiu.li@durham.ac.uk, E-mail: barreira@mpa-garching.mpg.de, E-mail: jianhua.he@durham.ac.uk, E-mail: wojciech.hellwing@port.ac.uk, E-mail: kazuya.koyama@port.ac.uk, E-mail: claudio.llinares@durham.ac.uk, E-mail: gbzhao@nao.cas.cn [National Astronomy Observatories, Chinese Academy of Science, Beijing, 100012 (China)
2017-02-01
We describe and demonstrate the potential of a new and very efficient method for simulating certain classes of modified gravity theories, such as the widely studied f ( R ) gravity models. High resolution simulations for such models are currently very slow due to the highly nonlinear partial differential equation that needs to be solved exactly to predict the modified gravitational force. This nonlinearity is partly inherent, but is also exacerbated by the specific numerical algorithm used, which employs a variable redefinition to prevent numerical instabilities. The standard Newton-Gauss-Seidel iterative method used to tackle this problem has a poor convergence rate. Our new method not only avoids this, but also allows the discretised equation to be written in a form that is analytically solvable. We show that this new method greatly improves the performance and efficiency of f ( R ) simulations. For example, a test simulation with 512{sup 3} particles in a box of size 512 Mpc/ h is now 5 times faster than before, while a Millennium-resolution simulation for f ( R ) gravity is estimated to be more than 20 times faster than with the old method. Our new implementation will be particularly useful for running very high resolution, large-sized simulations which, to date, are only possible for the standard model, and also makes it feasible to run large numbers of lower resolution simulations for covariance analyses. We hope that the method will bring us to a new era for precision cosmological tests of gravity.
High-resolution Moho model for Greenland from EIGEN-6C4 gravity data
Steffen, Rebekka; Strykowski, Gabriel; Lund, Björn
2017-01-01
are difficult to obtain. Here, we take advantage of the global gravity model EIGEN-6C4, together with the Parker-Oldenburg algorithm, to estimate the depth to the Moho beneath Greenland and surroundings. The available free-air gravity data are corrected for the topographic effect and the effect of sedimentary...... basins. We also correct for the effect on gravity due to the weight of the ice sheet and the accompanying deflection of the Earth's surface, which has not previously been taken into account in gravity studies of currently glaciated regions. Our final Moho depth model for Greenland has an associated...... uncertainty of ±4.5 km for areas with sedimentary basins and ±4 km for areas without sedimentary basins. The model shows maximum Moho depths below east Greenland of up to 55 km and values less than 20 km offshore east Greenland. There is a marked increase in Moho depth of 10–15 km from northern to central...
Gravity and Nonconservative Force Model Tuning for the GEOSAT Follow-On Spacecraft
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.
Speeding up N-body simulations of modified gravity: chameleon screening models
Bose, Sownak; Li, Baojiu; Barreira, Alexandre; He, Jian-hua; Hellwing, Wojciech A.; Koyama, Kazuya; Llinares, Claudio; Zhao, Gong-Bo
2017-02-01
We describe and demonstrate the potential of a new and very efficient method for simulating certain classes of modified gravity theories, such as the widely studied f(R) gravity models. High resolution simulations for such models are currently very slow due to the highly nonlinear partial differential equation that needs to be solved exactly to predict the modified gravitational force. This nonlinearity is partly inherent, but is also exacerbated by the specific numerical algorithm used, which employs a variable redefinition to prevent numerical instabilities. The standard Newton-Gauss-Seidel iterative method used to tackle this problem has a poor convergence rate. Our new method not only avoids this, but also allows the discretised equation to be written in a form that is analytically solvable. We show that this new method greatly improves the performance and efficiency of f(R) simulations. For example, a test simulation with 5123 particles in a box of size 512 Mpc/h is now 5 times faster than before, while a Millennium-resolution simulation for f(R) gravity is estimated to be more than 20 times faster than with the old method. Our new implementation will be particularly useful for running very high resolution, large-sized simulations which, to date, are only possible for the standard model, and also makes it feasible to run large numbers of lower resolution simulations for covariance analyses. We hope that the method will bring us to a new era for precision cosmological tests of gravity.
Speeding up N -body simulations of modified gravity: chameleon screening models
Bose, Sownak; Li, Baojiu; He, Jian-hua; Llinares, Claudio; Barreira, Alexandre; Hellwing, Wojciech A.; Koyama, Kazuya; Zhao, Gong-Bo
2017-01-01
We describe and demonstrate the potential of a new and very efficient method for simulating certain classes of modified gravity theories, such as the widely studied f ( R ) gravity models. High resolution simulations for such models are currently very slow due to the highly nonlinear partial differential equation that needs to be solved exactly to predict the modified gravitational force. This nonlinearity is partly inherent, but is also exacerbated by the specific numerical algorithm used, which employs a variable redefinition to prevent numerical instabilities. The standard Newton-Gauss-Seidel iterative method used to tackle this problem has a poor convergence rate. Our new method not only avoids this, but also allows the discretised equation to be written in a form that is analytically solvable. We show that this new method greatly improves the performance and efficiency of f ( R ) simulations. For example, a test simulation with 512 3 particles in a box of size 512 Mpc/ h is now 5 times faster than before, while a Millennium-resolution simulation for f ( R ) gravity is estimated to be more than 20 times faster than with the old method. Our new implementation will be particularly useful for running very high resolution, large-sized simulations which, to date, are only possible for the standard model, and also makes it feasible to run large numbers of lower resolution simulations for covariance analyses. We hope that the method will bring us to a new era for precision cosmological tests of gravity.
Modeling and Testing Dark Energy and Gravity with Galaxy Cluster Data
Rapetti, David; Cataneo, Matteo; Heneka, Caroline; Mantz, Adam; Allen, Steven W.; Von Der Linden, Anja; Schmidt, Fabian; Lombriser, Lucas; Li, Baojiu; Applegate, Douglas; Kelly, Patrick; Morris, Glenn
2018-06-01
The abundance of galaxy clusters is a powerful probe to constrain the properties of dark energy and gravity at large scales. We employed a self-consistent analysis that includes survey, observable-mass scaling relations and weak gravitational lensing data to obtain constraints on f(R) gravity, which are an order of magnitude tighter than the best previously achieved, as well as on cold dark energy of negligible sound speed. The latter implies clustering of the dark energy fluid at all scales, allowing us to measure the effects of dark energy perturbations at cluster scales. For this study, we recalibrated the halo mass function using the following non-linear characteristic quantities: the spherical collapse threshold, the virial overdensity and an additional mass contribution for cold dark energy. We also presented a new modeling of the f(R) gravity halo mass function that incorporates novel corrections to capture key non-linear effects of the Chameleon screening mechanism, as found in high resolution N-body simulations. All these results permit us to predict, as I will also exemplify, and eventually obtain the next generation of cluster constraints on such models, and provide us with frameworks that can also be applied to other proposed dark energy and modified gravity models using cluster abundance observations.
GRGM900C: A Degree 900 Lunar Gravity Model from GRAIL Primary and Extended Mission Data
Lemoine, Frank G.; Goossens, Sander; Sabaka, Terence J.; Nicholas, Joseph B.; Mazarico, Erwan; Rowlands, David D.; Bryant, D. Loomis; Chinn, Douglas S.; Neumann, Gregory A.; Smith, David E.;
2014-01-01
We have derived a gravity field solution in spherical harmonics to degree and order 900, GRGM900C, from the tracking data of the Gravity Recovery and Interior Laboratory (GRAIL) Primary (1 March to 29 May 2012) and Extended Missions (30 August to 14 December 2012). A power law constraint of 3.6 × 10(exp -4)/l(exp 2) was applied only for degree l greater than 600. The model produces global correlations of gravity, and gravity predicted from lunar topography of greater than or equal to 0.98 through degree 638. The model's degree strength varies from a minimum of 575-675 over the central nearside and farside to 900 over the polar regions. The model fits the Extended Mission Ka-Band Range Rate data through 17 November 2012 at 0.13 micrometers/s RMS, whereas the last month of Ka-Band Range-Rate data obtained from altitudes of 2-10 km fit at 0.98 micrometers/s RMS, indicating that there is still signal inherent in the tracking data beyond degree 900.
Improvement of density models of geological structures by fusion of gravity data and cosmic muon radiographies
Jourde, K.; Gibert, D.; Marteau, J.
2015-08-01
This paper examines how the resolution of small-scale geological density models is improved through the fusion of information provided by gravity measurements and density muon radiographies. Muon radiography aims at determining the density of geological bodies by measuring their screening effect on the natural flux of cosmic muons. Muon radiography essentially works like a medical X-ray scan and integrates density information along elongated narrow conical volumes. Gravity measurements are linked to density by a 3-D integration encompassing the whole studied domain. We establish the mathematical expressions of these integration formulas - called acquisition kernels - and derive the resolving kernels that are spatial filters relating the true unknown density structure to the density distribution actually recovered from the available data. The resolving kernel approach allows one to quantitatively describe the improvement of the resolution of the density models achieved by merging gravity data and muon radiographies. The method developed in this paper may be used to optimally design the geometry of the field measurements to be performed in order to obtain a given spatial resolution pattern of the density model to be constructed. The resolving kernels derived in the joined muon-gravimetry case indicate that gravity data are almost useless for constraining the density structure in regions sampled by more than two muon tomography acquisitions. Interestingly, the resolution in deeper regions not sampled by muon tomography is significantly improved by joining the two techniques. The method is illustrated with examples for the La Soufrière volcano of Guadeloupe.
Dual deep modeling: multi-level modeling with dual potencies and its formalization in F-Logic.
Neumayr, Bernd; Schuetz, Christoph G; Jeusfeld, Manfred A; Schrefl, Michael
2018-01-01
An enterprise database contains a global, integrated, and consistent representation of a company's data. Multi-level modeling facilitates the definition and maintenance of such an integrated conceptual data model in a dynamic environment of changing data requirements of diverse applications. Multi-level models transcend the traditional separation of class and object with clabjects as the central modeling primitive, which allows for a more flexible and natural representation of many real-world use cases. In deep instantiation, the number of instantiation levels of a clabject or property is indicated by a single potency. Dual deep modeling (DDM) differentiates between source potency and target potency of a property or association and supports the flexible instantiation and refinement of the property by statements connecting clabjects at different modeling levels. DDM comes with multiple generalization of clabjects, subsetting/specialization of properties, and multi-level cardinality constraints. Examples are presented using a UML-style notation for DDM together with UML class and object diagrams for the representation of two-level user views derived from the multi-level model. Syntax and semantics of DDM are formalized and implemented in F-Logic, supporting the modeler with integrity checks and rich query facilities.
Selfduality of d=2 reduction of gravity coupled to a σ-model
Paulot, Louis
2005-01-01
Dimensional reduction in two dimensions of gravity in higher dimension, or more generally of d=3 gravity coupled to a σ-model on a symmetric space, is known to possess an infinite number of symmetries. We show that such a bidimensional model can be embedded in a covariant way into a σ-model on an infinite symmetric space, built on the semidirect product of an affine group by the Witt group. The finite theory is the solution of a covariant selfduality constraint on the infinite model. It has therefore the symmetries of the infinite symmetric space. (We give explicit transformations of the gauge algebra.) The usual physical fields are recovered in a triangular gauge, in which the equations take the form of the usual linear systems which exhibit the integrable structure of the models. Moreover, we derive the constraint equation for the conformal factor, which is associated to the central term of the affine group involved
Akbar, M.M.; D'Eath, P.D.
2003-01-01
The classical boundary-value problem of the Einstein field equations is studied with an arbitrary cosmological constant, in the case of a compact (S 3 ) boundary given a biaxial Bianchi-IX positive-definite three-metric, specified by two radii (a,b). For the simplest, four-ball, topology of the manifold with this boundary, the regular classical solutions are found within the family of Taub-NUT-(anti)de Sitter metrics with self-dual Weyl curvature. For arbitrary choice of positive radii (a,b), we find that there are three solutions for the infilling geometry of this type. We obtain exact solutions for them and for their Euclidean actions. The case of negative cosmological constant is investigated further. For reasonable squashing of the three-sphere, all three infilling solutions have real-valued actions which possess a 'cusp catastrophe' structure with a non-self-intersecting 'catastrophe manifold' implying that the dominant contribution comes from the unique real positive-definite solution on the ball. The positive-definite solution exists even for larger deformations of the three-sphere, as long as a certain inequality between a and b holds. The action of this solution is proportional to -a 3 for large a (∼b) and hence larger radii are favoured. The same boundary-value problem with more complicated interior topology containing a 'bolt' is investigated in a forthcoming paper
Xiang, Yongqing; Yakushin, Sergei B; Cohen, Bernard; Raphan, Theodore
2006-12-01
A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular vestibuloocular reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal-otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal-otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal-otolith-convergent neurons are adapted for a given head orientation.
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.
Uncertainty in dual permeability model parameters for structured soils
Arora, B.; Mohanty, B. P.; McGuire, J. T.
2012-01-01
Successful application of dual permeability models (DPM) to predict contaminant transport is contingent upon measured or inversely estimated soil hydraulic and solute transport parameters. The difficulty in unique identification of parameters for the additional macropore- and matrix-macropore interface regions, and knowledge about requisite experimental data for DPM has not been resolved to date. Therefore, this study quantifies uncertainty in dual permeability model parameters of experimental soil columns with different macropore distributions (single macropore, and low- and high-density multiple macropores). Uncertainty evaluation is conducted using adaptive Markov chain Monte Carlo (AMCMC) and conventional Metropolis-Hastings (MH) algorithms while assuming 10 out of 17 parameters to be uncertain or random. Results indicate that AMCMC resolves parameter correlations and exhibits fast convergence for all DPM parameters while MH displays large posterior correlations for various parameters. This study demonstrates that the choice of parameter sampling algorithms is paramount in obtaining unique DPM parameters when information on covariance structure is lacking, or else additional information on parameter correlations must be supplied to resolve the problem of equifinality of DPM parameters. This study also highlights the placement and significance of matrix-macropore interface in flow experiments of soil columns with different macropore densities. Histograms for certain soil hydraulic parameters display tri-modal characteristics implying that macropores are drained first followed by the interface region and then by pores of the matrix domain in drainage experiments. Results indicate that hydraulic properties and behavior of the matrix-macropore interface is not only a function of saturated hydraulic conductivity of the macroporematrix interface (Ksa) and macropore tortuosity (lf) but also of other parameters of the matrix and macropore domains.
Extended charge banking model of dual path shocks for implantable cardioverter defibrillators.
Dosdall, Derek J; Sweeney, James D
2008-08-01
Single path defibrillation shock methods have been improved through the use of the Charge Banking Model of defibrillation, which predicts the response of the heart to shocks as a simple resistor-capacitor (RC) circuit. While dual path defibrillation configurations have significantly reduced defibrillation thresholds, improvements to dual path defibrillation techniques have been limited to experimental observations without a practical model to aid in improving dual path defibrillation techniques. The Charge Banking Model has been extended into a new Extended Charge Banking Model of defibrillation that represents small sections of the heart as separate RC circuits, uses a weighting factor based on published defibrillation shock field gradient measures, and implements a critical mass criteria to predict the relative efficacy of single and dual path defibrillation shocks. The new model reproduced the results from several published experimental protocols that demonstrated the relative efficacy of dual path defibrillation shocks. The model predicts that time between phases or pulses of dual path defibrillation shock configurations should be minimized to maximize shock efficacy. Through this approach the Extended Charge Banking Model predictions may be used to improve dual path and multi-pulse defibrillation techniques, which have been shown experimentally to lower defibrillation thresholds substantially. The new model may be a useful tool to help in further improving dual path and multiple pulse defibrillation techniques by predicting optimal pulse durations and shock timing parameters.
Cultural differences of a dual-motivation model on health risk behaviour
Ohtomo, S.; Hirose, Y.; Midden, C.J.H.
2011-01-01
This study investigated the cultural differences of a dual-motivation model of unhealthy risk behaviour in the Netherlands and Japan. Our model assumes dual motivations involved in unhealthy eating behaviour, a behavioural willingness that leads behaviour unintentionally or subconsciously and a
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.
Kepaptsoglou, Konstantinos; Karlaftis, Matthew G.; Tsamboulas, Dimitrios
2010-01-01
The gravity model has been extensively used in international trade research for the last 40 years because of its considerable empirical robustness and explanatory power. Since their introduction in the 1960's, gravity models have been used for assessing trade policy implications and, particularly recently, for analyzing the effects of Free Trade Agreements on international trade. The objective of this paper is to review the recent empirical literature on gravity models, highlight best practic...
Kaluza–Klein-type models of de Sitter and Poincaré gauge theories of gravity
Lu Jiaan; Huang Chaoguang
2013-01-01
We construct Kaluza–Klein-type models with a de Sitter or Minkowski bundle in the de Sitter or Poincaré gauge theory of gravity, respectively. A manifestly gauge-invariant formalism has been given. The gravitational dynamics is constructed by the geometry of the de Sitter or Minkowski bundle and a global section which plays an important role in the gauge-invariant formalism. Unlike the old Kaluza–Klein-type models of gauge theory of gravity, a suitable cosmological term can be obtained in the Lagrangian of our models and the models in the spin-current-free and torsion-free limit will come back to general relativity with a corresponding cosmological term. We also generalize the results to the case with a variable cosmological term. (paper)
An improved gravity model for Mars: Goddard Mars Model-1 (GMM-1)
Smith, D. E.; Lerch, F. J.; Nerem, R. S.; Zuber, M. T.; Patel, G. B.; Fricke, S. K.; Lemoine, F. G.
1993-01-01
Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, GMM-1 (Goddard Mars Model-1). This model employs nearly all available data, consisting of approximately 1100 days of S-bank tracking data collected by NASA's Deep Space Network from the Mariner 9, and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM-1 is complete to spherical harmonic degree and order 50, which corresponds to a half-wavelength spatial resolution of 200-300 km where the data permit. GMM-1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM-1 over previous models is a consequence of several factors: improved computational capabilities, the use of optimum weighting and least-squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X-band tracking data from the 379-km altitude, near-polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM-1, particularly at high latitudes where current data poorly resolves the gravitational signature of the planet.
Hamayun, H.
2014-01-01
Currently, a tremendous improvement is observed in the accuracy and spatial resolution of global Earth’s gravity field models. This improvement is achieved due to using various new data, including those from satellite gravimetry missions (CHAMP, GRACE, and GOCE); terrestrial and airborne gravity
A Computer Model for Determining Operational Centers of Gravity
2002-05-31
current state of AI. For the beginner , the student text Artificial Intelligence: An Executive Overview (USMA 1994) is still useful for surveying the... flowchart that guides the determination. In preparing the model, the authors consulted numerous sources of opinion on the topic, to include doctrine...the logic of the general model in this manner resulted in a compact, unambiguous flowchart -style representation. The depiction of the general model
The Linked Dual Representation model of vocal perception and production
Sean eHutchins
2013-11-01
Full Text Available The voice is one of the most important media for communication, yet there is a wide range of abilities in both the perception and production of the voice. In this article, we review this range of abilities, focusing on pitch accuracy as a particularly informative case, and look at the factors underlying these abilities. Several classes of models have been posited describing the relationship between vocal perception and production, and we review the evidence for and against each class of model. We look at how the voice is different from other musical instruments and review evidence about both the association and the dissociation between vocal perception and production abilities. Finally, we introduce the Linked Dual Representation model, a new approach which can account for the broad patterns in prior findings, including trends in the data which might seem to be countervailing. We discuss how this model interacts with higher-order cognition and examine its predictions about several aspects of vocal perception and production.
NLO QCD Corrections to Drell-Yan in TeV-scale Gravity Models
Mathews, Prakash; Ravindran, V.
2006-01-01
In TeV scale gravity models, we present the NLO-QCD corrections for the double differential cross sections in the scattering angle for dilepton production at hadron colliders. The quantitative impact of QCD corrections for extra dimension searches at LHC and Tevatron are investigated for both ADD and RS models through K-factors. We also show how the inclusion of QCD corrections to NLO stabilises the cross section with respect to renormalisation and factorisation scale variations
Late time acceleration of the universe in f(R) gravity model
Mukherjee, Ankan
2014-01-01
In this work, a new way to look at the nature of late time dynamics of the universe for f(R) gravity models using the contracted Bianchi Identity has been proposed. As the Einstein field equations contain derivatives of the curvature scalar R, the contracted Bianchi identity yields a second order nonlinear differential equation in H, the Hubble parameter. This equation is studied for two particular forms of f(R), and the late time behaviour of the model is discussed. (author)
BRST cohomology ring in 2D gravity coupled to minimal models
Kanno, H.; Sarmadi, M.H.
1992-08-01
The ring structure of Lian-Zuckerman states for (q,p) minimal models coupled to gravity is shown to be R=R 0 xC[w,w -1 ] where R 0 is the ring of ghost number zero operators generated by two elements and w is an operator of ghost number -1. Some examples are discussed in detail. For these models the currents are also discussed and their algebra is shown to contain the Virasoro algebra. (author). 21 refs
Dyon Condensation and Dual Superconductivity in Abelian Higgs Model of QCD
B. S. Rajput
2010-01-01
Full Text Available Constructing the effective action for dyonic field in Abelian projection of QCD, it has been demonstrated that any charge (electrical or magnetic of dyon screens its own direct potential to which it minimally couples and antiscreens the dual potential leading to dual superconductivity in accordance with generalized Meissner effect. Taking the Abelian projection of QCD, an Abelian Higgs model, incorporating dual superconductivity and confinement, has been constructed and its representation has been obtained in terms of average of Wilson loop.
Modeling Repulsive Gravity with Creation R. G. Vishwakarma & J. V. ...
nation to the various explosive phenomena occurring in local (z < 0.1) and extra galactic ... to scalar field models called quintessence whose function is to cause the scale factor .... to be general outliers which are missed by all the models.
Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.
2017-12-01
Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments
Development and analysis of a twelfth degree and order gravity model for Mars
Christensen, E. J.; Balmino, G.
1979-01-01
Satellite geodesy techniques previously applied to artificial earth satellites have been extended to obtain a high-resolution gravity field for Mars. Two-way Doppler data collected by 10 Deep Space Network (DSN) stations during Mariner 9 and Viking 1 and 2 missions have been processed to obtain a twelfth degree and order spherical harmonic model for the martian gravitational potential. The quality of this model was evaluated by examining the rms residuals within the fit and the ability of the model to predict the spacecraft state beyond the fit. Both indicators show that more data and higher degree and order harmonics will be required to further refine our knowledge of the martian gravity field. The model presented shows much promise, since it resolves local gravity features which correlate highly with the martian topography. An isostatic analysis based on this model, as well as an error analysis, shows rather complete compensation on a global (long wavelength) scale. Though further model refinements are necessary to be certain, local (short wavelength) features such as the shield volcanos in Tharsis appear to be uncompensated. These are interpreted to place some bounds on the internal structure of Mars.
New models of gauge- and gravity-mediated supersymmetry breaking
Poppitz, E.; Trivedi, S.P.
1997-01-01
We show that supersymmetry breaking in a class of theories with SU(N)xSU(N-2) gauge symmetry can be studied in a calculable σ model. We use the σ model to show that the supersymmetry-breaking vacuum in these theories leaves a large subgroup of flavor symmetries intact, and to calculate the masses of the low-lying states. By embedding the standard model gauge groups in the unbroken flavor symmetry group we construct a class of models in which supersymmetry breaking is communicated by both gravitational and gauge interactions. One distinguishing feature of these models is that the messenger fields, responsible for the gauge-mediated communication of supersymmetry breaking, are an integral part of the supersymmetry-breaking sector. We also show how, by lowering the scale that suppresses the nonrenormalizable operators, a class of purely gauge-mediated models with a combined supersymmetry-breaking-cum-messenger sector can be built. We briefly discuss the phenomenological features of the models we construct. copyright 1997 The American Physical Society
Models of non-relativistic quantum gravity: the good, the bad and the healthy
Blas, Diego; Sibiryakov, Sergey
2011-01-01
Horava's proposal for non-relativistic quantum gravity introduces a preferred time foliation of space-time which violates the local Lorentz invariance. The foliation is encoded in a dynamical scalar field which we call `khronon'. The dynamics of the khronon field is sensitive to the symmetries and other details of the particular implementations of the proposal. In this paper we examine several consistency issues present in three non-relativistic gravity theories: Horava's projectable theory, the healthy non-projectable extension, and a new extension related to ghost condensation. We find that the only model which is free from instabilities and strong coupling is the non-projectable one. We elaborate on the phenomenology of the latter model including a discussion of the couplings of the khronon to matter. In particular, we obtain the parameters of the post-Newtonian expansion in this model and show that they are compatible with current observations.
Modelling airborne gravity data by means of adapted Space-Wise approach
Sampietro, Daniele; Capponi, Martina; Hamdi Mansi, Ahmed; Gatti, Andrea
2017-04-01
Regional gravity field modelling by means of remove - restore procedure is nowadays widely applied to predict grids of gravity anomalies (Bouguer, free-air, isostatic, etc.) in gravimetric geoid determination as well as in exploration geophysics. Considering this last application, due to the required accuracy and resolution, airborne gravity observations are generally adopted. However due to the relatively high acquisition velocity, presence of atmospheric turbulence, aircraft vibration, instrumental drift, etc. airborne data are contaminated by a very high observation error. For this reason, a proper procedure to filter the raw observations both in the low and high frequency should be applied to recover valuable information. In this work, a procedure to predict a grid or a set of filtered along track gravity anomalies, by merging GGM and airborne dataset, is presented. The proposed algorithm, like the Space-Wise approach developed by Politecnico di Milano in the framework of GOCE data analysis, is based on a combination of along track Wiener filter and Least Squares Collocation adjustment and properly considers the different altitudes of the gravity observations. Among the main differences with respect to the satellite application of the Space-Wise approach there is the fact that, while in processing GOCE data the stochastic characteristics of the observation error can be considered a-priori well known, in airborne gravimetry, due to the complex environment in which the observations are acquired, these characteristics are unknown and should be retrieved from the dataset itself. Some innovative theoretical aspects focusing in particular on the theoretical covariance modelling are presented too. In the end, the goodness of the procedure is evaluated by means of a test on real data recovering the gravitational signal with a predicted accuracy of about 0.25 mGal.
On the two-dimensional model of quantum Regge gravity
Khatsimovskij, V.M.
1991-01-01
The Ashtekar-like variables are introduced in the Regge calculus. A simplified model of the resulting theory is quantized canonically. The consequences related to quantization of Regge areas are obtained. 10 refs
Relativistic strings and dual models of strong interactions
Marinov, M.S.
1977-01-01
The theory of strong interactions,based on the model depicting a hardon as a one-dimentional elastic relativistic system(''string'') is considered. The relationship between this model and the concepts of quarks and partons is discussed. Presented are the principal results relating to the Veneziano dual theory, which may be considered as the consequence of the string model, and to its modifications. The classical string theory is described in detail. Attention is focused on questions of importance to the construction of the quantum theory - the Hamilton mechanisms and conformal symmetry. Quantization is described, and it is shown that it is not contradictory only in the 26-dimentional space and with a special requirement imposed on the spectrum of states. The theory of a string with a distributed spin is considered. The spin is introduced with the aid of the Grassman algebra formalism. In this case quantization is possible only in the 10-dimentional space. The strings interact by their ruptures and gluings. A method for calculating the interaction amplitudes is indicated
De Sá Teixeira, Nuno Alexandre
2014-12-01
Given its conspicuous nature, gravity has been acknowledged by several research lines as a prime factor in structuring the spatial perception of one's environment. One such line of enquiry has focused on errors in spatial localization aimed at the vanishing location of moving objects - it has been systematically reported that humans mislocalize spatial positions forward, in the direction of motion (representational momentum) and downward in the direction of gravity (representational gravity). Moreover, spatial localization errors were found to evolve dynamically with time in a pattern congruent with an anticipated trajectory (representational trajectory). The present study attempts to ascertain the degree to which vestibular information plays a role in these phenomena. Human observers performed a spatial localization task while tilted to varying degrees and referring to the vanishing locations of targets moving along several directions. A Fourier decomposition of the obtained spatial localization errors revealed that although spatial errors were increased "downward" mainly along the body's longitudinal axis (idiotropic dominance), the degree of misalignment between the latter and physical gravity modulated the time course of the localization responses. This pattern is surmised to reflect increased uncertainty about the internal model when faced with conflicting cues regarding the perceived "downward" direction.
Can representational trajectory reveal the nature of an internal model of gravity?
De Sá Teixeira, Nuno; Hecht, Heiko
2014-05-01
The memory for the vanishing location of a horizontally moving target is usually displaced forward in the direction of motion (representational momentum) and downward in the direction of gravity (representational gravity). Moreover, this downward displacement has been shown to increase with time (representational trajectory). However, the degree to which different kinematic events change the temporal profile of these displacements remains to be determined. The present article attempts to fill this gap. In the first experiment, we replicate the finding that representational momentum for downward-moving targets is bigger than for upward motions, showing, moreover, that it increases rapidly during the first 300 ms, stabilizing afterward. This temporal profile, but not the increased error for descending targets, is shown to be disrupted when eye movements are not allowed. In the second experiment, we show that the downward drift with time emerges even for static targets. Finally, in the third experiment, we report an increased error for upward-moving targets, as compared with downward movements, when the display is compatible with a downward ego-motion by including vection cues. Thus, the errors in the direction of gravity are compatible with the perceived event and do not merely reflect a retinotopic bias. Overall, these results provide further evidence for an internal model of gravity in the visual representational system.
GRACE gravity data help constraining seismic models of the 2004 Sumatran earthquake
Cambiotti, G.; Bordoni, A.; Sabadini, R.; Colli, L.
2011-10-01
The analysis of Gravity Recovery and Climate Experiment (GRACE) Level 2 data time series from the Center for Space Research (CSR) and GeoForschungsZentrum (GFZ) allows us to extract a new estimate of the co-seismic gravity signal due to the 2004 Sumatran earthquake. Owing to compressible self-gravitating Earth models, including sea level feedback in a new self-consistent way and designed to compute gravitational perturbations due to volume changes separately, we are able to prove that the asymmetry in the co-seismic gravity pattern, in which the north-eastern negative anomaly is twice as large as the south-western positive anomaly, is not due to the previously overestimated dilatation in the crust. The overestimate was due to a large dilatation localized at the fault discontinuity, the gravitational effect of which is compensated by an opposite contribution from topography due to the uplifted crust. After this localized dilatation is removed, we instead predict compression in the footwall and dilatation in the hanging wall. The overall anomaly is then mainly due to the additional gravitational effects of the ocean after water is displaced away from the uplifted crust, as first indicated by de Linage et al. (2009). We also detail the differences between compressible and incompressible material properties. By focusing on the most robust estimates from GRACE data, consisting of the peak-to-peak gravity anomaly and an asymmetry coefficient, that is given by the ratio of the negative gravity anomaly over the positive anomaly, we show that they are quite sensitive to seismic source depths and dip angles. This allows us to exploit space gravity data for the first time to help constraining centroid-momentum-tensor (CMT) source analyses of the 2004 Sumatran earthquake and to conclude that the seismic moment has been released mainly in the lower crust rather than the lithospheric mantle. Thus, GRACE data and CMT source analyses, as well as geodetic slip distributions aided
Second generation diffusion model of interacting gravity waves on the surface of deep fluid
A. Pushkarev
2004-01-01
Full Text Available We propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum.
Holographic dark energy from fluid/gravity duality constraint by cosmological observations
Pourhassan, Behnam; Bonilla, Alexander; Faizal, Mir; Abreu, Everton M. C.
2018-06-01
In this paper, we obtain a holographic model of dark energy using the fluid/gravity duality. This model will be dual to a higher dimensional Schwarzschild black hole, and we would use fluid/gravity duality to relate to the parameters of this black hole to such a cosmological model. We will also analyze the thermodynamics of such a solution, and discuss the stability model. Finally, we use cosmological data to constraint the parametric space of this dark energy model. Thus, we will use observational data to perform cosmography for this holographic model based on fluid/gravity duality.
Hinderer, J.; Andersen, Ole Baltazar; Lemoine, F.
2006-01-01
This paper is devoted to the investigation of seasonal changes of the Earth's gravity field from GRACE satellites and the comparison with surface gravity measurements in Europe from the Global Geodynamics Project (GGP) sub-network, as well as with recent hydrology models for continental soil...... moisture and snow. We used gravity maps in Europe retrieved from the initial GRACE monthly solutions spanning a 21 -month duration from April 2002 to December 2003 for various truncation levels of the initial spherical harmonic decomposition of the field. The transfer function between satellite......-derived and ground gravity changes due to continental hydrology is studied and we also compute the theoretical ratio of gravity versus radial displacement (in mu Gal/mm) involved in the hydrological loading process. The 'mean' value (averaged in time and in space over Europe) from hydrologic forward modeling...
An Evaluation of Recent Gravity Models wrt. Altimeter Satellite Missions
Lemoine, Frank G.; Zelensky, N. P.; Luthcke, S. B.; Beckley, B. D.; Chinn, D. S.; Rowlands, D. D.
2003-01-01
With the launch of CHAMP and GRACE, we have entered a new phase in the history of satellite geodesy. For the first time, geopotential models are now available based almost exclusively on satellite-satellite tracking either with GPS in the case of the CHAMP-based geopotential models, or co-orbital intersatellite ultra-precise ranging in the case of GRACE. Different groups have analyzed these data, and produced a series of geopotential models (e.g., EIGENlS, EIGEN2, GGM0lS, GGMOlC) that incorporate the new data. We will compare the performance of these "newer" geopotential models with the standard models now used for computations, (e.g., JGM-3, BGM-96, PGS7727, and GRIMS-C1) for TOPEX, JASON, Geosat-Follow-On (GFO), and Envisat using standard metrics such as SLR RMS of fit, altimeter crossovers, and orbit overlaps. Where covariances are available we can evaluate the predicted geographically correlated orbit error. These predicted results can be compared with the Earth-fixed differences between dynamic and reduced-dynamic orbits to test the predictive accuracy of the covariances, as well as to calibrate the error of the solutions.
Signal analysis of accelerometry data using gravity-based modeling
Davey, Neil P.; James, Daniel A.; Anderson, Megan E.
2004-03-01
Triaxial accelerometers have been used to measure human movement parameters in swimming. Interpretation of data is difficult due to interference sources including interaction of external bodies. In this investigation the authors developed a model to simulate the physical movement of the lower back. Theoretical accelerometery outputs were derived thus giving an ideal, or noiseless dataset. An experimental data collection apparatus was developed by adapting a system to the aquatic environment for investigation of swimming. Model data was compared against recorded data and showed strong correlation. Comparison of recorded and modeled data can be used to identify changes in body movement, this is especially useful when cyclic patterns are present in the activity. Strong correlations between data sets allowed development of signal processing algorithms for swimming stroke analysis using first the pure noiseless data set which were then applied to performance data. Video analysis was also used to validate study results and has shown potential to provide acceptable results.
Emergent gravity on covariant quantum spaces in the IKKT model
Steinacker, Harold C. [Faculty of Physics, University of Vienna,Boltzmanngasse 5, A-1090 Vienna (Austria)
2016-12-30
We study perturbations of 4-dimensional fuzzy spheres as backgrounds in the IKKT or IIB matrix model. Gauge fields and metric fluctuations are identified among the excitation modes with lowest spin, supplemented by a tower of higher-spin fields. They arise from an internal structure which can be viewed as a twisted bundle over S{sup 4}, leading to a covariant noncommutative geometry. The linearized 4-dimensional Einstein equations are obtained from the classical matrix model action under certain conditions, modified by an IR cutoff. Some one-loop contributions to the effective action are computed using the formalism of string states.
Bielik, M.; Tasarova, Z. A.; Goetze, H.; Mikuska, J.; Pasteka, R.
2007-12-01
The 3-D forward modeling was performed for the Western Carpathians and the Pannonian Basin system. The density model includes 31 cross-sections, extends to depth of 220 km. By means of the combined 3-D modeling, new estimates of the density distribution of the crust and upper mantle, as well as depths of the Moho were derived. These data allowed to perform gravity stripping, which in the area of the Pannonian Basin is crucial for the signal analysis of the gravity field. In this region, namely, two pronounced features (i.e. the deep sedimentary basins and shallow Moho) with opposite gravity effects make it impossible to analyze the Bouguer anomaly by field separation or filtering. The results revealed a significantly different nature of the Western Carpathian- Pannonian region (ALACAPA and Tisza-Dacia microplates) from the European Platform lithosphere (i.e. these microplates to be much less dense than the surrounding European Platform lithosphere). The calculation of the transformed gravity maps by means of new method provided the additional information on the lithospheric structure. The use of existing elevation information represents an independent approach to the problem of transformation of gravity maps. Instead of standard separation and transformation methods both in wave-number and spatial domains, this method is based on the estimating of really existing linear trends within the values of complete Bouguer anomalies (CBA), which are understood as a function defined in 3D space. An important assumption that the points with known input values of CBA lie on a horizontal plane is therefore not required. Instead, the points with known CBA and elevation values are treated in their original positions, i.e. on the Earth surface.
Gravity Models of Trade-based Money Laundering
Ferwerda, J.|info:eu-repo/dai/nl/314405526; Kattenberg, M.A.C.|info:eu-repo/dai/nl/357208986; Chang, H.-S.; Unger, B.|info:eu-repo/dai/nl/290994926; Groot, L.F.M.|info:eu-repo/dai/nl/073642398; Bikker, J.A.|info:eu-repo/dai/nl/06912261X
2011-01-01
Several attempts have been made in the economics literature to measure money laundering. However, the adequacy of these models is difficult to assess, as money laundering takes place secretly and, hence, goes unobserved. An exception is tradebased money laundering (TBML), a special form of trade
Gravity Models of Trade-Based Money Laundering
Ferwerda, Joras|info:eu-repo/dai/nl/314405526; Kattenberg, Marc|info:eu-repo/dai/nl/357208986; Chang, Han-Hsin|info:eu-repo/dai/nl/357209370; Unger, Brigitte|info:eu-repo/dai/nl/290994926; Groot, Loek|info:eu-repo/dai/nl/073642398; Bikker, Jaap|info:eu-repo/dai/nl/06912261X
Several attempts have been made in the economics literature to measure money laundering. However, the adequacy of these models is difficult to assess, as money laundering takes place secretly and, hence, goes unobserved. An exception is trade-based money laundering (TBML), a special form of trade
Quantum analysis of Jackiw and Teitelboim's model for (1+1)D gravity and topological gauge theory
Terao, Haruhiko
1993-01-01
We study the BRST quantization of the (1+1)-dimensional gravity model proposed by Jackiw and Teitelboim and also the topological gauge model which is equivalent to the gravity model at least classically. The gravity model quantized in the light-cone gauge is found to be a free theory with a nilpotent BRST charge. We show also that there exist twisted N=2 superconformal algebras in the Jackiw-Teitelboim model as well as in the topological gauge model. We discuss the quantum equivalence between the gravity theory and the topological gauge theory. It is shown that these theories are indeed equivalent to each other in the light-cone gauge. (orig.)
High-resolution Local Gravity Model of the South Pole of the Moon from GRAIL Extended Mission Data
Goossens, Sander Johannes; Sabaka, Terence J.; Nicholas, Joseph B.; Lemoine, Frank G.; Rowlands, David D.; Mazarico, Erwan; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.
2014-01-01
We estimated a high-resolution local gravity field model over the south pole of the Moon using data from the Gravity Recovery and Interior Laboratory's extended mission. Our solution consists of adjustments with respect to a global model expressed in spherical harmonics. The adjustments are expressed as gridded gravity anomalies with a resolution of 1/6deg by 1/6deg (equivalent to that of a degree and order 1080 model in spherical harmonics), covering a cap over the south pole with a radius of 40deg. The gravity anomalies have been estimated from a short-arc analysis using only Ka-band range-rate (KBRR) data over the area of interest. We apply a neighbor-smoothing constraint to our solution. Our local model removes striping present in the global model; it reduces the misfit to the KBRR data and improves correlations with topography to higher degrees than current global models.
War and peace: morphemes and full forms in a noninteractive activation parallel dual-route model.
Baayen, H; Schreuder, R
This article introduces a computational tool for modeling the process of morphological segmentation in visual and auditory word recognition in the framework of a parallel dual-route model. Copyright 1999 Academic Press.
Relating covariant and canonical approaches to triangulated models of quantum gravity
Arnsdorf, Matthias
2002-01-01
In this paper we explore the relation between covariant and canonical approaches to quantum gravity and BF theory. We will focus on the dynamical triangulation and spin-foam models, which have in common that they can be defined in terms of sums over spacetime triangulations. Our aim is to show how we can recover these covariant models from a canonical framework by providing two regularizations of the projector onto the kernel of the Hamiltonian constraint. This link is important for the understanding of the dynamics of quantum gravity. In particular, we will see how in the simplest dynamical triangulation model we can recover the Hamiltonian constraint via our definition of the projector. Our discussion of spin-foam models will show how the elementary spin-network moves in loop quantum gravity, which were originally assumed to describe the Hamiltonian constraint action, are in fact related to the time-evolution generated by the constraint. We also show that the Immirzi parameter is important for the understanding of a continuum limit of the theory
Gravity model improvement using GEOS 3 /GEM 9 and 10/. [and Seasat altimetry data
Lerch, F. J.; Wagner, C. A.; Klosko, S. M.; Laubscher, R. E.
1979-01-01
Although errors in previous gravity models have produced large uncertainties in the orbital position of GEOS 3, significant improvement has been obtained with new geopotential solutions, Goddard Earth Model (GEM) 9 and 10. The GEM 9 and 10 solutions for the potential coefficients and station coordinates are presented along with a discussion of the new techniques employed. Also presented and discussed are solutions for three fundamental geodetic reference parameters, viz. the mean radius of the earth, the gravitational constant, and mean equatorial gravity. Evaluation of the gravity field is examined together with evaluation of GEM 9 and 10 for orbit determination accuracy. The major objectives of GEM 9 and 10 are achieved. GEOS 3 orbital accuracies from these models are about 1 m in their radial components for 5-day arc lengths. Both models yield significantly improved results over GEM solutions when compared to surface gravimetry, Skylab and GEOS 3 altimetry, and highly accurate BE-C (Beacon Explorer-C) laser ranges. The new values of the parameters discussed are given.
Using the Gravity Model to Estimate the Spatial Spread of Vector-Borne Diseases
Jean-Marie Aerts
2012-11-01
Full Text Available The gravity models are commonly used spatial interaction models. They have been widely applied in a large set of domains dealing with interactions amongst spatial entities. The spread of vector-borne diseases is also related to the intensity of interaction between spatial entities, namely, the physical habitat of pathogens’ vectors and/or hosts, and urban areas, thus humans. This study implements the concept behind gravity models in the spatial spread of two vector-borne diseases, nephropathia epidemica and Lyme borreliosis, based on current knowledge on the transmission mechanism of these diseases. Two sources of information on vegetated systems were tested: the CORINE land cover map and MODIS NDVI. The size of vegetated areas near urban centers and a local indicator of occupation-related exposure were found significant predictors of disease risk. Both the land cover map and the space-borne dataset were suited yet not equivalent input sources to locate and measure vegetated areas of importance for disease spread. The overall results point at the compatibility of the gravity model concept and the spatial spread of vector-borne diseases.
Establishing a Near Term Lunar Farside Gravity Model via Inexpensive Add-on Navigation Payload
Folta, David; Mesarch, Michael; Miller, Ronald; Bell, David; Jedrey, Tom; Butman, Stanley; Asmar, Sami
2007-01-01
The Space Communications and Navigation, Constellation Integration Project (SCIP) is tasked with defining, developing, deploying and operating an evolving multi-decade communications and navigation (C/N) infrastructure including services and subsystems that will support both robotic and human exploration activities at the Moon. This paper discusses an early far side gravitational mapping service and related telecom subsystem that uses an existing spacecraft (WIND) and the Lunar Reconnaissance Orbiter (LRO) to collect data that would address several needs of the SCIP. An important aspect of such an endeavor is to vastly improve the current lunar gravity model while demonstrating the navigation and stationkeeping of a relay spacecraft. We describe a gravity data acquisition activity and the trajectory design of the relay orbit in an Earth-Moon L2 co-linear libration orbit. Several phases of the transfer from an Earth-Sun to the Earth-Moon region are discussed along with transfers within the Earth-Moon system. We describe a proposed, but not integrated, add-on to LRO scheduled to be launched in October of 2008. LRO provided a real host spacecraft against which we designed the science payload and mission activities. From a strategic standpoint, LRO was a very exciting first flight opportunity for gravity science data collection. Gravity Science data collection requires the use of one or more low altitude lunar polar orbiters. Variations in the lunar gravity field will cause measurable variations in the orbit of a low altitude lunar orbiter. The primary means to capture these induced motions is to monitor the Doppler shift of a radio signal to or from the low altitude spacecraft, given that the signal is referenced to a stable frequency reference. For the lunar far side, a secondary orbiting radio signal platform is required. We provide an in-depth look at link margins, trajectory design, and hardware implications. Our approach posed minimum risk to a host mission while
Hernandez, Orlando; Khurama, Sait; Alexander, Gretta C
2011-01-01
A prominent positive free-air gravity anomaly mapped over a roughly 50-km diameter basin is consistent with a mascon centered on (4 degrades 30 minutes N, 69 degrades 15 minutes W) in the Vichada Department, Colombia, South America. Ground follow up gravity and magnetic anomalies were modeled confirming the regional free air gravity anomalies. These potential field anomalies infer a hidden complex impact basin structure filled with tertiary sedimentary rocks and recent quaternary deposits. Negative Bouguer anomalies of 8 mgals to 15 mgals amplitude are associated with a concentric sedimentary basin with a varying thickness from 100 m to 500 m in the outer rings to 700 m to 1000 m at the center of the impact crater basin. Strong positive magnetic anomalies of 100 nt to 300 nt amplitude infer the presence of a local Precambrian crystalline basement that was affected by intensive faulting producing tectonic blocks dipping to the center of the structure, showing a typical domino structure of impact craters such as that of Sudbury, Ontario, Canada. Basic to intermediate mineralized veins and dikes with contrasting density and magnetic susceptibility properties could be emplaced along these faulting zones, as inferred from local gravity and magnetic highs. The geologic mapping of the area is limited by the flat topography and absence of outcrops/ geomorphologic units. Nevertheless, local normal faults along the inner ring together with radially sparse irregular blocks over flat terrains can be associated with terraced rims or collapse of the inner crater structure and eject blanket, respectively. A detailed airborne electromagnetic survey is recommended to confirm the gravity and magnetic anomalies together with a seismic program to evaluate the economic implications for energy and mineral exploration of the Vichada impact structure.
A gravity model for crustal dynamics (GEM-L2)
Lerch, F. J.; Klosko, S. M.; Patel, G. B.; Wagner, C. A.
1985-01-01
The Laser Geodynamics Satellite (Lageos) was the first NASA satellite which was placed into orbit exclusively for laser ranging applications. Lageos was designed to permit extremely accurate measurements of the earth's rotation and the movement of the tectonic plates. The Goddard earth model, GEM-L2, was derived mainly on the basis of the precise laser ranging data taken on many satellites. Douglas et al. (1984) have demonstrated the utility of GEM-L2 in detecting the broadest ocean circulations. As Lageos data constitute the most extensive set of satellite laser observations ever collected, the incorporation of 2-1/2 years of these data into the Goddard earth models (GEM) has substantially advanced the geodynamical objectives. The present paper discusses the products of the GEM-L2 solution.
A schematic model of crater modification by gravity
Melosh, H. J.
1982-01-01
The morphology of craters found on planets and moons of the solar system is examined and a development model which can account for the observed crater characteristics is discussed. The prompt collapse of craters to form flat floors, terraced walls, and central peak structures is considered to be the result of an approximate Bingham plastic rheology of the material surrounding the crater. This rheology is induced dynamically by the strong incoherent acoustic 'noise' accompanying excavation of the crater. Central pits, peak rings, and other multiple symmetric-profile rings originate by oscillation of this fluid. Large craters with transient depths comparable to the lithosphere thickness are subject to collapse by fragmentation of the lithosphere as well as fluidization. The considered concepts are developed mathematically. A model emerges which appears capable of explaining most of the qualitative features of large impact structures.
Surface state decoherence in loop quantum gravity, a first toy model
Feller, Alexandre; Livine, Etera R
2017-01-01
The quantum-to-classical transition through decoherence is a major facet of the semi-classical analysis of quantum models that are supposed to admit a classical regime, as quantum gravity should be. A particular problem of interest is the decoherence of black hole horizons and holographic screens induced by the bulk-boundary coupling with interior degrees of freedom. Here in this paper we present a first toy-model, in the context of loop quantum gravity, for the dynamics of a surface geometry as an open quantum system. We discuss the resulting decoherence and recoherence and compare the exact density matrix evolution to the commonly used master equation approximation à la Lindblad underlining its merits and limitations. The prospect of this study is to have a clearer understanding of the boundary decoherence of black hole horizons seen by outside observers. (paper)
Quantization of coset space σ-models coupled to two-dimensional gravity
Korotkin, D.; Samtleben, H.
1996-07-01
The mathematical framework for an exact quantization of the two-dimensional coset space σ-models coupled to dilaton gravity, that arise from dimensional reduction of gravity and supergravity theories, is presented. The two-time Hamiltonian formulation is obtained, which describes the complete phase space of the model in the whole isomonodromic sector. The Dirac brackets arising from the coset constraints are calculated. Their quantization allows to relate exact solutions of the corresponding Wheeler-DeWitt equations to solutions of a modified (Coset) Knizhnik-Zamolodchikov system. On the classical level, a set of observables is identified, that is complete for essential sectors of the theory. Quantum counterparts of these observables and their algebraic structure are investigated. Their status in alternative quantization procedures is discussed, employing the link with Hamiltonian Chern-Simons theory. (orig.)
Gauge vs. gravity mediation in models with anomalous U(1)'s
Dudas, E.; Mambrini, Y.; Romagnoni, A.; Trapletti, M.; Pokorski, S.
2009-01-01
In an attempt to implement gauge mediation in string theory, we study string effective supergravity models of supersymmetry breaking, containing anomalous gauge factors. We discuss subtleties related to gauge invariance and the stabilization of the Green-Schwarz moduli, which set non-trivial constraints on the transmission of supersymmetry breaking to MSSM via gauge interactions. Given those constraints, it is difficult to obtain the dominance of gauge mediation over gravity mediation. Furthermore, generically the gauge contributions to soft terms contain additional non-standard terms coming from D-term contributions. Motivated by this, we study the phenomenology of recently proposed hybrid models, where gravity and gauge mediations compete at the GUT scale, and show that such a scenario can respect WMAP constraints and would be easily testable at LHC.
Modification of the gravity model and application to the metropolitan Seoul subway system.
Goh, Segun; Lee, Keumsook; Park, Jong Soo; Choi, M Y
2012-08-01
The Metropolitan Seoul Subway system is examined through the use of the gravity model. Exponents describing the power-law dependence on the time distance between stations are obtained, which reveals a universality for subway lines of the same topology. In the short (time) distance regime the number of passengers between stations does not grow with the decrease in the distance, thus deviating from the power-law behavior. It is found that such reduction in passengers is well described by the Hill function. Further, temporal fluctuations in the passenger flow data, fitted to the gravity model modified by the Hill function, are analyzed to reveal the Yule-type nature inherent in the structure of Seoul.
Emergent gravity and noncommutative branes from Yang-Mills matrix models
Steinacker, Harold
2009-01-01
The framework of emergent gravity arising from Yang-Mills matrix models is developed further, for general noncommutative branes embedded in R D . The effective metric on the brane turns out to have a universal form reminiscent of the open string metric, depending on the dynamical Poisson structure and the embedding metric in R D . A covariant form of the tree-level equations of motion is derived, and the Newtonian limit is discussed. This points to the necessity of branes in higher dimensions. The quantization is discussed qualitatively, which singles out the IKKT model as a prime candidate for a quantum theory of gravity coupled to matter. The Planck scale is then identified with the scale of N=4 SUSY breaking. A mechanism for avoiding the cosmological constant problem is exhibited
Finite element modeling of ground deformation and gravity field at Mt. Etna
G. Ganci
2008-06-01
Full Text Available An elastic 3-D axi-symmetric model based on Finite Element Method (FEM is proposed to compute ground deformation and gravity changes caused by overpressure sources in volcanic areas. The numerical computations are focused on the modeling of a complex description of Mt Etna in order to evaluate the effect of topography, medium heterogeneities and source geometries. Both ground deformation and gravity changes are investigated by solving a coupled numerical problem considering a simplified ground surface profile and a multi-layered crustal structure inferred from seismic tomography. The role of the source geometry is also explored taking into account spherical and ellipsoidal volumetric sources. The comparison between numerical results and those predicted by analytical solutions disclosed significant discrepancies. These differences constrain the applicability of simple spherical source and homogeneous half-space hypotheses, which are usually implicitly assumed when analytical solutions are applied.
The Gravity Model Approach: An Application on the Eco Was Trading Bloc
Luqman Afolabi O.
2016-04-01
Full Text Available This study aims to examine bilateral trade flows across ECOWAS-15 nations with the use of a panel and cross section for the period of 1981-2013. The methodology carried out to achieve this objective involves the use of various techniques of estimation for the gravity model (Static and dynamic. More specifically, this study aims to investigate the formational impact of regional trade integration agreements on trade flows within a group of countries using the same currencies and ECOWAS at large. The main use of regional variables into gravity models is intended to determine whether RTAs lead to trade creation, or diversion. The results show the presence of a strong relationship among the factors of both RIAs and trade flows.
Gravity mediated Dark Matter models in the de Sitter space
Vancea, Ion V.
2018-01-01
In this paper, we generalize the simplified Dark Matter models with graviton mediator to the curved space-time, in particular to the de Sitter space. We obtain the generating functional of the Green's functions in the Euclidean de Sitter space for the covariant free gravitons. We determine the generating functional of the interacting theory between Dark Matter particles and the covariant gravitons. Also, we calculate explicitly the 2-point and 3-point interacting Green's functions for the sym...
Gravity, CPT, and the standard-model extension
Tasson, Jay D., E-mail: tasson1@stolaf.edu [St. Olaf College (United States)
2015-08-15
Exotic atoms provide unique opportunities to search for new physics. The search for CPT and Lorentz violation in the context of the general field-theory based framework of the gravitational Standard-Model Extension (SME) is one such opportunity. This work summarizes the implications of Lorentz and CPT violation for gravitational experiments with antiatoms and atoms containing higher-generation matter as well as recent nongravitational proposals to test CPT and Lorentz symmetry with muons and muonic systems.
Gravity Models of Trade-Based Money Laundering
Ferwerda, Joras; Kattenberg, Marc; Chang, Han-Hsin; Unger, Brigitte; Groot, Loek; Bikker, Jaap
2011-01-01
Several attempts have been made in the economics literature to measure money laundering. However, the adequacy of these models is difficult to assess, as money laundering takes place secretly and, hence, goes unobserved. An exception is tradebased money laundering (TBML), a special form of trade abuse that has been discovered only recently. TBML refers to criminal proceeds that are transferred around the world using fake invoices that under- or overvalue imports and exports. This article is a...
A Test of Two Alternative Cognitive Processing Models: Learning Styles and Dual Coding
Cuevas, Joshua; Dawson, Bryan L.
2018-01-01
This study tested two cognitive models, learning styles and dual coding, which make contradictory predictions about how learners process and retain visual and auditory information. Learning styles-based instructional practices are common in educational environments despite a questionable research base, while the use of dual coding is less…
The ring structure of chiral operators for minimal models coupled to 2D gravity
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
Gravity models of forest products trade: applications to forecasting and policy analysis
Joseph Buongiorno
2016-01-01
To predict the value of trade between countries, a differential gravity model of bilateral trade flowswas formulatedÂ and estimated with panel data from 2005 to 2014 for each of the commodity groups HS44 (wood and articles ofÂ wood), HS47 (pulp of wood, fibrous cellulosic material) and HS48 (paper and paperboard). The parameters wereÂ estimated with a large database by...
Instability of a two-step Rankine vortex in a reduced gravity QG model
Perrot, Xavier [Laboratoire de Météorologie Dynamique, Ecole Normale Supérieure, 24 rue Lhomond, F-75005 Paris (France); Carton, Xavier, E-mail: xperrot@lmd.ens.fr, E-mail: xcarton@univ-brest.fr [Laboratoire de Physique des Océans, Université de Bretagne Occidentale, 6 avenue Le Gorgeu, F-29200 Brest (France)
2014-06-01
We investigate the stability of a steplike Rankine vortex in a one-active-layer, reduced gravity, quasi-geostrophic model. After calculating the linear stability with a normal mode analysis, the singular modes are determined as a function of the vortex shape to investigate short-time stability. Finally we determine the position of the critical layer and show its influence when it lies inside the vortex. (papers)
An Improved Model of Cryogenic Propellant Stratification in a Rotating, Reduced Gravity Environment
Oliveira, Justin; Kirk, Daniel R.; Schallhorn, Paul A.; Piquero, Jorge L.; Campbell, Mike; Chase, Sukhdeep
2007-01-01
This paper builds on a series of analytical literature models used to predict thermal stratification within rocket propellant tanks. The primary contribution to the literature is to add the effect of tank rotation and to demonstrate the influence of rotation on stratification times and temperatures. This work also looks levels of thermal stratification for generic propellant tanks (cylindrical shapes) over a parametric range of upper-stage coast times, heating levels, rotation rates, and gravity levels.
Vacuum solutions of a gravity model with vector-induced spontaneous Lorentz symmetry breaking
Bertolami, O.; Paramos, J.
2005-01-01
We study the vacuum solutions of a gravity model where Lorentz symmetry is spontaneously broken once a vector field acquires a vacuum expectation value. Results are presented for the purely radial Lorentz symmetry breaking (LSB), radial/temporal LSB and axial/temporal LSB. The purely radial LSB result corresponds to new black hole solutions. When possible, parametrized post-Newtonian parameters are computed and observational boundaries used to constrain the Lorentz symmetry breaking scale
New force or model-dependent effect in the mine gravity measurements?
Kim, Y.E.; Klepacki, D.J.; Hinze, W.J.
1987-01-01
The exact solution for the oblate spheroidal layer model of the earth is applied to recent gravity data measured at the Hilton mine, Mount Isa, Queensland. We find that our extracted values of the gravitational constant from the Hilton mine data are consistent with the laboratory value within the accuracy of the mass density profile determination made at the Hilton mine and the surrounding area. (orig.)
Cosmology of a holographic induced gravity model with curvature effects
Bouhmadi-Lopez, Mariam; Errahmani, Ahmed; Ouali, Taoufiq
2011-01-01
We present a holographic model of the Dvali-Gabadadze-Porrati scenario with a Gauss-Bonnet term in the bulk. We concentrate on the solution that generalizes the normal Dvali-Gabadadze-Porrati branch. It is well known that this branch cannot describe the late-time acceleration of the universe even with the inclusion of a Gauss-Bonnet term. Here, we show that this branch in the presence of a Gauss-Bonnet curvature effect and a holographic dark energy with the Hubble scale as the infrared cutoff can describe the late-time acceleration of the universe. It is worthwhile to stress that such an energy density component cannot do the same job on the normal Dvali-Gabadadze-Porrati branch (without Gauss-Bonnet modifications) nor in a standard four-dimensional relativistic model. The acceleration on the brane is also presented as being induced through an effective dark energy which corresponds to a balance between the holographic one and geometrical effects encoded through the Hubble parameter.
Why did the apple fall? A new model to explain Einstein’s gravity
Stannard, Warren; Blair, David; Zadnik, Marjan; Kaur, Tejinder
2017-01-01
Newton described gravity as an attractive force between two masses but Einstein’s General Theory of Relativity provides a very different explanation. Implicit in Einstein’s theory is the idea that gravitational effects are the result of a distortion in the shape of space-time. Despite its elegance, Einstein’s concept of gravity is rarely encountered outside of an advanced physics course as it is often considered to be too complex and too mathematical. This paper describes a new conceptual and quantitative model of gravity based on General Relativity at a level most science students should be able to understand. The model illustrates geodesics using analogies with paths of navigation on the surface of the Earth. This is extended to space and time maps incorporating the time warping effects of General Relativity. Using basic geometry, the geodesic path of a falling object near the surface of the Earth is found. From this the acceleration of an object in free fall is calculated. The model presented in this paper can answer the question, ‘Why do things fall?’ without resorting to Newton’s gravitational force. (paper)
Why did the apple fall? A new model to explain Einstein’s gravity
Stannard, Warren; Blair, David; Zadnik, Marjan; Kaur, Tejinder
2017-01-01
Newton described gravity as an attractive force between two masses but Einstein’s General Theory of Relativity provides a very different explanation. Implicit in Einstein’s theory is the idea that gravitational effects are the result of a distortion in the shape of space-time. Despite its elegance, Einstein’s concept of gravity is rarely encountered outside of an advanced physics course as it is often considered to be too complex and too mathematical. This paper describes a new conceptual and quantitative model of gravity based on General Relativity at a level most science students should be able to understand. The model illustrates geodesics using analogies with paths of navigation on the surface of the Earth. This is extended to space and time maps incorporating the time warping effects of General Relativity. Using basic geometry, the geodesic path of a falling object near the surface of the Earth is found. From this the acceleration of an object in free fall is calculated. The model presented in this paper can answer the question, ‘Why do things fall?’ without resorting to Newton’s gravitational force.
Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves.
Ripepe, M; Barfucci, G; De Angelis, S; Delle Donne, D; Lacanna, G; Marchetti, E
2016-11-10
Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models.
Zlotnicki, V.; Stammer, D.; Fukumori, I.
2003-01-01
Here we assess the new generation of gravity models, derived from GRACE data. The differences between a global geoid model (one from GRACE data and one the well-known EGM-96), minus a Mean Sea Surface derived from over a decade of altimetric data are compared to hydrographic data from the Levitus compilation and to the ECCO numerical ocean model, which assimilates altimetry and other data.
Chen, Pengzhen; Wang, Xiaoqing; Liu, Li; Chong, Jinsong
2016-06-01
According to Bragg theory, capillary waves are the predominant scatterers of high-frequency band (such as Ka-band) microwave radiation from the surface of the ocean. Therefore, understanding the modulation mechanism of capillary waves is an important foundation for interpreting high-frequency microwave remote sensing images of the surface of the sea. In our experiments, we discovered that modulations of capillary waves are significantly larger than the values predicted by the classical theory. Further, analysis shows that the difference in restoring force results in an inflection point while the phase velocity changes from gravity waves region to capillary waves region, and this results in the capillary waves being able to resonate with gravity waves when the phase velocity of the gravity waves is equal to the group velocity of the capillary waves. Consequently, we propose a coupling modulation model in which the current modulates the capillary wave indirectly by modulating the resonant gravity waves, and the modulation of the former is approximated by that of the latter. This model very effectively explains the results discovered in our experiments. Further, based on Bragg scattering theory and this coupling modulation model, we simulate the modulation of normalized radar cross section (NRCS) of typical internal waves and show that the high-frequency bands are superior to the low-frequency bands because of their greater modulation of NRCS and better radiometric resolution. This result provides new support for choice of radar band for observation of wave-current modulation oceanic phenomena such as internal waves, fronts, and shears.
Modeling of Perpendicularly Driven Dual-Frequency Capacitively Coupled Plasma
Wang Hongyu; Sun Peng; Zhao Shuangyun; Li Yang; Jiang Wei
2016-01-01
We analyzed perpendicularly configured dual-frequency (DF) capacitively coupled plasmas (CCP). In this configuration, two pairs of electrodes are arranged oppositely, and the discharging is perpendicularly driven by two radio frequency (RF) sources. Particle-in-cell/Monte Carlo (PIC/MC) simulation showed that the configuration had some advantages as this configuration eliminated some dual frequency coupling effects. Some variation and potential application of the discharging configuration is discussed briefly. (paper)
Small vacuum energy from small equivalence violation in scalar gravity
Agrawal, Prateek; Sundrum, Raman
2017-01-01
The theory of scalar gravity proposed by Nordström, and refined by Einstein and Fokker, provides a striking analogy to general relativity. In its modern form, scalar gravity appears as the low-energy effective field theory of the spontaneous breaking of conformal symmetry within a CFT, and is AdS/CFT dual to the original Randall-Sundrum I model, but without a UV brane. Scalar gravity faithfully exhibits several qualitative features of the cosmological constant problem of standard gravity coupled to quantum matter, and the Weinberg no-go theorem can be extended to this case as well. Remarkably, a solution to the scalar gravity cosmological constant problem has been proposed, where the key is a very small violation of the scalar equivalence principle, which can be elegantly formulated as a particular type of deformation of the CFT. In the dual AdS picture this involves implementing Goldberger-Wise radion stabilization where the Goldberger-Wise field is a pseudo-Nambu Goldstone boson. In quantum gravity however, global symmetries protecting pNGBs are not expected to be fundamental. We provide a natural six-dimensional gauge theory origin for this global symmetry and show that the violation of the equivalence principle and the size of the vacuum energy seen by scalar gravity can naturally be exponentially small. Our solution may be of interest for study of non-supersymmetric CFTs in the spontaneously broken phase.
Small vacuum energy from small equivalence violation in scalar gravity
Agrawal, Prateek [Department of Physics, Harvard University,Cambridge, MA 02138 (United States); Sundrum, Raman [Department of Physics, University of Maryland,College Park, MD 20742 (United States)
2017-05-29
The theory of scalar gravity proposed by Nordström, and refined by Einstein and Fokker, provides a striking analogy to general relativity. In its modern form, scalar gravity appears as the low-energy effective field theory of the spontaneous breaking of conformal symmetry within a CFT, and is AdS/CFT dual to the original Randall-Sundrum I model, but without a UV brane. Scalar gravity faithfully exhibits several qualitative features of the cosmological constant problem of standard gravity coupled to quantum matter, and the Weinberg no-go theorem can be extended to this case as well. Remarkably, a solution to the scalar gravity cosmological constant problem has been proposed, where the key is a very small violation of the scalar equivalence principle, which can be elegantly formulated as a particular type of deformation of the CFT. In the dual AdS picture this involves implementing Goldberger-Wise radion stabilization where the Goldberger-Wise field is a pseudo-Nambu Goldstone boson. In quantum gravity however, global symmetries protecting pNGBs are not expected to be fundamental. We provide a natural six-dimensional gauge theory origin for this global symmetry and show that the violation of the equivalence principle and the size of the vacuum energy seen by scalar gravity can naturally be exponentially small. Our solution may be of interest for study of non-supersymmetric CFTs in the spontaneously broken phase.
A 70th Degree Lunar Gravity Model (GLGM-2) from Clementine and other tracking data
Lemonie, Frank G. R.; Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.
1997-01-01
A spherical harmonic model of the lunar gravity field complete to degree and order 70 has been developed from S band Doppler tracking data from the Clementine mission, as well as historical tracking data from Lunar Orbiters 1-5 and the Apollo 15 and 16 subsatellites. The model combines 361,000 Doppler observations from Clementine with 347,000 historical observations. The historical data consist of mostly 60-s Doppler with a noise of 0.25 to several mm/s. The Clementine data consist of mostly 10-s Doppler data, with a data noise of 0.25 mm/s for the observations from the Deep Space Network, and 2.5 mm/s for the data from a naval tracking station at Pomonkey, Maryland. Observations provided Clementine, provide the strongest satellite constraint on the Moon's low-degree field. In contrast the historical data, collected by spacecraft that had lower periapsis altitudes, provide distributed regions of high-resolution coverage within +/- 29 deg of the nearside lunar equator. To obtain the solution for a high-degree field in the absence of a uniform distribution of observations, we applied an a priori power law constraint of the form 15 x 10(exp -5)/sq l which had the effect of limiting the gravitational power and noise at short wavelengths. Coefficients through degree and order 18 are not significantly affected by the constraint, and so the model permits geophysical analysis of effects of the major basins at degrees 10-12. The GLGM-2 model confirms major features of the lunar gravity field shown in previous gravitational field models but also reveals significantly more detail, particularly at intermediate wavelengths (10(exp 3) km). Free-air gravity anomaly maps derived from the new model show the nearside and farside highlands to be gravitationally smooth, reflecting a state of isostatic compensation. Mascon basins (including Imbrium, Serenitatis, Crisium, Smythii, and Humorum) are denoted by gravity highs first recognized from Lunar Orbiter tracking. All of the major
The dual-gate lumen model of renal monoamine transport
Marty Hinz
2010-07-01
Full Text Available Marty Hinz1, Alvin Stein2, Thomas Uncini31Clinical Research, NeuroResearch Clinics, Inc. Cape Coral, Florida, USA; 2Stein Orthopedic Associates, Plantation, Florida, USA; 3DBS Labs, Duluth, Minnesota, USAAbstract: The three-phase response of urinary serotonin and dopamine in subjects simultaneously taking amino acid precursors of serotonin and dopamine has been defined.1,2 No model exists regarding the renal etiology of the three-phase response. This writing outlines a model explaining the origin of the three-phase response of urinary serotonin and dopamine. A “dual-gate lumen transporter model” for the basolateral monoamine transporters of the kidneys is proposed as being the etiology of the three-phase urinary serotonin and dopamine responses.Purpose: The purpose of this writing is to document the internal renal function model that has evolved in research during large-scale assay with phase interpretation of urinary serotonin and dopamine.Patients and methods: In excess of 75,000 urinary monoamine assays from more than 7,500 patients were analyzed. The serotonin and the dopamine phase were determined for specimens submitted in the competitive inhibition state. The phase determination findings were then correlated with peer-reviewed literature.Results: The correlation between the three-phase response of urinary serotonin and dopamine with internal renal processes of the bilateral monoamine transporter and the apical monoamine transporter of the proximal convoluted renal tubule cells is defined.Conclusion: The phase of urinary serotonin and dopamine is dependent on the status of the serotonin gate, dopamine gate, and lumen of the basolateral monoamine transporter while in the competitive inhibition state.Keywords: serotonin, dopamine, basolateral, apical, kidney, proximal
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
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.
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.
Trade potential of climate smart goods of Vietnam: An application of gravity model
Trung Van Vu
2016-01-01
Full Text Available This paper examines the trade potential of climate smart goods (CSG of Vietnam. In particular, the study employs gravity model with panel data for bilateral trade between Vietnam and its 45 partners from 2002 to 2013 with an objective of identifying the determinants explaining Vietnam's trade of climate smart products. The estimation results reveal that economic size, market size, distance, real exchange rate, border, and the quality of infrastructure of both Vietnam and its trading partners play a major role in bilateral trade of CSG. Additionally, the paper applies the method using speed of convergence and the estimated gravity equation to answer whether Vietnam has fully realized the potential trade of CSG. Accordingly, Vietnam has strong opportunity for trade expansion with 19 out of 45 countries in the scope of this paper.
MODEL FOR THE CORRECTION OF THE SPECIFIC GRAVITY OF BIODIESEL FROM RESIDUAL OIL
Tatiana Aparecida Rosa da Silva
2013-06-01
Full Text Available Biodiesel is a important fuel with economic benefits, social and environmental. The production cost of the biodiesel can be significantly lowered if the raw material is replaced by a alternative material as residual oil. In this study, the variation of specific gravity with temperature increase for diesel and biodiesel from residual oil obtained by homogeneous basic catalysis. All properties analyzed for biodiesel are within specification Brazil. The determination of the correction algorithm for the specific gravity function of temperature is also presented, and the slope of the line to diesel fuel, methylic biodiesel (BMR and ethylic biodiesel (BER from residual oil were respectively the values -0.7089, -0.7290 and -0.7277. This demonstrates the existence of difference of the model when compared chemically different fuels, like diesel and biodiesel from different sources, indicating the importance of determining the specific algorithm for the operations of conversion of volume to the reference temperature.
Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Jones, Scott B.; Tuller, Markus
2014-01-01
utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions....... Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air...... that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using...
Slow Steps towards Dual Earner/Dual Carer Family Model: Why Do Fathers Not Take Parental Leave
Marre Karu
2011-06-01
Full Text Available The article looks at the transition of Estonian society towards dual earner/dual carer family model and focuses on fathers’ decision regarding taking their parental leave. Based on theory of planned behaviour by Ajzen, data from 20 qualitative interviews with fathers of small children are analysed to explore the beliefs fathers have when it comes to parental leave. The analysis distinguishes between two images of ‘good parenting’ that play a role in the fathers’ intention to take parental leave. First, there is an image of an outcome-oriented ‘project manager’ aﬀected by failure anxiety, and second, there is a much more relaxed image of a ‘good parent’ as a ‘companion’ who values everyday contact and a close relationship with the child(ren.
Godah, Walyeldeen; Krynski, Jan; Szelachowska, Malgorzata
2018-05-01
The objective of this paper is to demonstrate the usefulness of absolute gravity data for the validation of Global Geopotential Models (GGMs). It is also aimed at improving quasigeoid heights determined from satellite-only GGMs using absolute gravity data. The area of Poland, as a unique one, covered with a homogeneously distributed set of absolute gravity data, has been selected as a study area. The gravity anomalies obtained from GGMs were validated using the corresponding ones determined from absolute gravity data. The spectral enhancement method was implemented to overcome the spectral inconsistency in data being validated. The quasigeoid heights obtained from the satellite-only GGM as well as from the satellite-only GGM in combination with absolute gravity data were evaluated with high accuracy GNSS/levelling data. Estimated accuracy of gravity anomalies obtained from GGMs investigated is of 1.7 mGal. Considering omitted gravity signal, e.g. from degree and order 101 to 2190, satellite-only GGMs can be validated at the accuracy level of 1 mGal using absolute gravity data. An improvement up to 59% in the accuracy of quasigeoid heights obtained from the satellite-only GGM can be observed when combining the satellite-only GGM with absolute gravity data.
Model-based crosstalk compensation in simultaneous dual isotope SPECT
Frey, E.C.; Tsui, B.M.W.; Du, A.Y.; Song, X.Y.
2002-01-01
Simultaneous dual isotope imaging has the potential of allowing imaging of two different physiological processes at the same time. Two examples are Tc-99m stress and Tl-201 rest myocardial perfusion imaging and Tc-99m perfusion and I-123 neuroreceptor brain imaging. However, for both of these cases crosstalk is a significant problem that results in degradation of the simultaneously acquired images. For the Tc-99m and Tl-201 case, the crosstalk includes downscatter and the generation of Pb x-rays detected in the Tl-201 energy window. For the Tc-99m/I-123 case, the crosstalk includes overlap of the two photopeaks, downscatter, especially of the 159 keV photons into the Tc-99m energy window, and contamination of the images of both isotopes by low abundance, high-energy I-123 photons. We have developed methods to accurately model the crosstalk in both cases. For the Tc-99m/Tl-201 case, the crosstalk model uses a previously described method for modeling scatter, effective source scatter estimation (ESSE). The scatter estimates are combined with a parameterization of the Pb x-ray response of the collimator to estimate the crosstalk. For the I-123/Tc-99m case we combine ESSE with a MC simulated collimator scatter and penetration responses to model the contamination due to the high-energy photons from I-123. In both cases the crosstalk models have been incorporated into an iterative reconstruction procedure that allows simultaneous reconstruction of the activity distributions from two isotopes including crosstalk compensation We have evaluated these methods both by Monte Carlo simulation studies and using physical phantom experiments. We find that the methods perform well and produce images with a quality and contrast approaching that of separately acquired images. However, the compensated simultaneously acquired images do have an increase in image noise. To reduce the noise we have applied ideal observer methodology to determine optimal energy windows and relative
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)
Dual permeability FEM models for distributed fiber optic sensors development
Aguilar-López, Juan Pablo; Bogaard, Thom
2017-04-01
Fiber optic cables are commonly known for being robust and reliable mediums for transferring information at the speed of light in glass. Billions of kilometers of cable have been installed around the world for internet connection and real time information sharing. Yet, fiber optic cable is not only a mean for information transfer but also a way to sense and measure physical properties of the medium in which is installed. For dike monitoring, it has been used in the past for detecting inner core and foundation temperature changes which allow to estimate water infiltration during high water events. The DOMINO research project, aims to develop a fiber optic based dike monitoring system which allows to directly sense and measure any pore pressure change inside the dike structure. For this purpose, questions like which location, how many sensors, which measuring frequency and which accuracy are required for the sensor development. All these questions may be initially answered with a finite element model which allows to estimate the effects of pore pressure change in different locations along the cross section while having a time dependent estimation of a stability factor. The sensor aims to monitor two main failure mechanisms at the same time; The piping erosion failure mechanism and the macro-stability failure mechanism. Both mechanisms are going to be modeled and assessed in detail with a finite element based dual permeability Darcy-Richards numerical solution. In that manner, it is possible to assess different sensing configurations with different loading scenarios (e.g. High water levels, rainfall events and initial soil moisture and permeability conditions). The results obtained for the different configurations are later evaluated based on an entropy based performance evaluation. The added value of this kind of modelling approach for the sensor development is that it allows to simultaneously model the piping erosion and macro-stability failure mechanisms in a time
High resolution time-lapse gravity field from GRACE for hydrological modelling
Krogh, Pernille Engelbredt
Calibration of large scale hydrological models have traditionally been performed using point observations, which are often sparsely distributed. The Gravity Recovery And Climate Experiment (GRACE) mission provides global remote sensing information about mass fluxes with unprecedented accuracy...... than for the mascon only solution, but later than the GLDAS/Noah TWS and the CNES/GRGS SH solutions. The deviations are 10–20 days. From this point of view, the tuning of hydrological models with KBRR data is certainly feasible, though highly time consuming and complicated at the moment. The method...
Modelling the Interior Structure of Enceladus Based on the 2014's Cassini Gravity Data.
Taubner, R-S; Leitner, J J; Firneis, M G; Hitzenberger, R
2016-06-01
We present a model for the internal structure of Saturn's moon Enceladus. This model allows us to estimate the physical conditions at the bottom of the satellite's potential subsurface water reservoir and to determine the radial distribution of pressure and gravity. This leads to a better understanding of the physical and chemical conditions at the water/rock boundary. This boundary is the most promising area on icy moons for astrobiological studies as it could serve as a potential habitat for extraterrestrial life similar to terrestrial microbes that inhabit rocky mounds on Earth's sea floors.
Cosmological models with a hybrid scale factor in an extended gravity theory
Mishra, B.; Tripathy, S. K.; Tarai, Sankarsan
2018-03-01
A general formalism to investigate Bianchi type V Ih universes is developed in an extended theory of gravity. A minimally coupled geometry and matter field is considered with a rescaled function of f(R,T) substituted in place of the Ricci scalar R in the geometrical action. Dynamical aspects of the models are discussed by using a hybrid scale factor (HSF) that behaves as power law in an initial epoch and as an exponential form at late epoch. The power law behavior and the exponential behavior appear as two extreme cases of the present model.
Mixmaster cosmological model in theories of gravity with a quadratic Lagrangian
Barrow, J.D.; Sirousse-Zia, H.
1989-01-01
We use the method of matched asymptotic expansions to examine the behavior of the vacuum Bianchi type-IX mixmaster universe in a gravity theory derived from a purely quadratic gravitational Lagrangian. The chaotic behavior characteristic of the general-relativistic mixmaster model disappears and the asymptotic behavior is of the monotonic, nonchaotic form found in the exactly soluble Bianchi type-I models of the quadratic theory. The asymptotic behavior far from the singularity is also found to be of monotonic nonchaotic type
Nontopological bare solutions in the relativistic self-dual Maxwell-Chern-Simons-Higgs model
Han, Jongmin; Jang, Jaeduk
2005-01-01
In this paper we prove the existence of the radially symmetric nontopological bare solutions in the relativistic self-dual Maxwell-Chern-Simons-Higgs model. We also verify the Chern-Simons limit for those solutions
Borsa, Adrian
2008-01-01
The salar de Uyuni is a massive dry salt lake that lies at the lowest point of an internal drainage basin in the Bolivian Altiplano. A kinematic GPS survey of the salar in September 2002 found a topographic range of only 80 cm over a 54 × 45 km area and subtle surface features that appeared to correlate with mapped gravity. In order to confirm the correlation between topography and gravity/geopotential, we use local gravity measurements and the EGM96 global geopotential model to construct a c...
A gravity model for the spread of a pollinator-borne plant pathogen.
Ferrari, Matthew J; Bjørnstad, Ottar N; Partain, Jessica L; Antonovics, Janis
2006-09-01
Many pathogens of plants are transmitted by arthropod vectors whose movement between individual hosts is influenced by foraging behavior. Insect foraging has been shown to depend on both the quality of hosts and the distances between hosts. Given the spatial distribution of host plants and individual variation in quality, vector foraging patterns may therefore produce predictable variation in exposure to pathogens. We develop a "gravity" model to describe the spatial spread of a vector-borne plant pathogen from underlying models of insect foraging in response to host quality using the pollinator-borne smut fungus Microbotryum violaceum as a case study. We fit the model to spatially explicit time series of M. violaceum transmission in replicate experimental plots of the white campion Silene latifolia. The gravity model provides a better fit than a mean field model or a model with only distance-dependent transmission. The results highlight the importance of active vector foraging in generating spatial patterns of disease incidence and for pathogen-mediated selection for floral traits.
Root, Bart; Tarasov, Lev; van der Wal, Wouter
2014-05-01
The global ice budget is still under discussion because the observed 120-130 m eustatic sea level equivalent since the Last Glacial Maximum (LGM) can not be explained by the current knowledge of land-ice melt after the LGM. One possible location for the missing ice is the Barents Sea Region, which was completely covered with ice during the LGM. This is deduced from relative sea level observations on Svalbard, Novaya Zemlya and the North coast of Scandinavia. However, there are no observations in the middle of the Barents Sea that capture the post-glacial uplift. With increased precision and longer time series of monthly gravity observations of the GRACE satellite mission it is possible to constrain Glacial Isostatic Adjustment in the center of the Barents Sea. This study investigates the extra constraint provided by GRACE data for modeling the past ice geometry in the Barents Sea. We use CSR release 5 data from February 2003 to July 2013. The GRACE data is corrected for the past 10 years of secular decline of glacier ice on Svalbard, Novaya Zemlya and Frans Joseph Land. With numerical GIA models for a radially symmetric Earth, we model the expected gravity changes and compare these with the GRACE observations after smoothing with a 250 km Gaussian filter. The comparisons show that for the viscosity profile VM5a, ICE-5G has too strong a gravity signal compared to GRACE. The regional calibrated ice sheet model (GLAC) of Tarasov appears to fit the amplitude of the GRACE signal. However, the GRACE data are very sensitive to the ice-melt correction, especially for Novaya Zemlya. Furthermore, the ice mass should be more concentrated to the middle of the Barents Sea. Alternative viscosity models confirm these conclusions.
Model predictive control for a dual active bridge inverter with a floating bridge
Chowdhury, Shajjad; Wheeler, Patrick W.; Gerada, C.; Patel, Chintan
2016-01-01
This paper presents a Model Predictive Control technique applied to a dual active bridge inverter where one of the bridges is floating. The proposed floating bridge topology eliminates the need for isolation transformer in a dual inverter system and therefore reduces the size, weight and losses in the system. To achieve multilevel output voltage waveforms the floating inverter DC link capacitor is charged to the half of the main DC link voltage. A finite-set Model Predictive Control technique...
E. Majchrzak
2008-12-01
Full Text Available The dual reciprocity boundary element method is applied for numerical modelling of solidification process. This variant of the BEM is connected with the transformation of the domain integral to the boundary integrals. In the paper the details of the dual reciprocity boundary element method are presented and the usefulness of this approach to solidification process modelling is demonstrated. In the final part of the paper the examples of computations are shown.
Quark-parton model from dual topological unitarization
Cohen-Tannoudji, G.; El Hassouni, A.; Kalinowski, J.; Peschanski, R.
1979-01-01
Topology, which occurs in the topological expansion of quantum chromodynamics (QCD) and in the dual topological unitarization (DTU) schemes, allows us to establish a quantitative correspondence between QCD and the dual S-matrix approaches. This topological correspondence, proposed by Veneziano and made more explicit in a recent paper for current-induced reactions, provides a clarifying and unifying quark-parton interpretation of soft inclusive processes. Precise predictions for inclusive cross sections in hadron-hadron collisions, structure functions of hadrons, and quark fragmentation functions including absolute normalizations are shown to agree with data. On a more theoretical ground the proposed scheme suggests a new approach to the confinement problem
Pricing Model for Dual Sales Channel with Promotion Effect Consideration
Chuiri Zhou
2016-01-01
We focus on the pricing strategy of a dual sales channel member when his/her online retailer faces an upcoming overloaded express delivery service due to the sales peak of online shopping, especially referring to the occurring affairs in China. We characterize the pricing problem of the dual selling channel system as a two-period game. When the price discount is only provided by the online seller, we find that the prices of the traditional channel and the online channel in the two periods are...
Modeling and Control of a Dual-Input Isolated Full-Bridge Boost Converter
Zhang, Zhe; Thomsen, Ole Cornelius; Andersen, Michael A. E.
2012-01-01
In this paper, a steady-state model, a large-signal (LS) model and an ac small-signal (SS) model for a recently proposed dual-input transformer-isolated boost converter are derived respectively by the switching flow-graph (SFG) nonlinear modeling technique. Based upon the converter’s model...
A fuzzy-stochastic power system planning model: Reflection of dual objectives and dual uncertainties
Zhang, X.Y.; Huang, G.H.; Zhu, H.; Li, Y.P.
2017-01-01
In this study, a fuzzy stochastic dynamic fractional programming (FSDFP) method is proposed for supporting sustainable management of electric power system (EPS) under dual uncertainties. As an improvement upon the mixed-integer linear fractional programming, FSDFP can not only tackle multi-objective issues effectively without setting weights, but also can deal with uncertain parameters which have both stochastic and fuzzy characteristics. Thus, the developed method can help provide valuable information for supporting capacity-expansion planning and in-depth policy analysis of EPS management problems. For demonstrating these advantages, FSDFP has been applied to a case study of a typical regional EPS planning, where the decision makers have to deal with conflicts between economic development that maximizes the system profit and environmental protection that minimizes the carbon dioxide emissions. The obtained results can be analyzed to generate several decision alternatives, and can then help decision makers make suitable decisions under different input scenarios. Furthermore, comparisons of the solution from FSDFP method with that from fuzzy stochastic dynamic linear programming, linear fractional programming and dynamic stochastic fractional programming methods are undertaken. The contrastive analysis reveals that FSDFP is a more effective approach that can better characterize the complexities and uncertainties of real EPS management problems. - Highlights: • A fuzzy stochastic dynamic fractional programming (FSDFP) method is proposed. • FSDFP can address multiple conflicting objectives without setting weights. • FSDFP can reflect dual uncertainties with both stochastic and fuzzy characteristics. • Some reasonable solutions for a case of power system sustainable planning are generated. • Comparisons of the solutions from FSDFP with other optimization methods are undertaken.
Structure formation in the Deser-Woodard nonlocal gravity model: a reappraisal
Nersisyan, Henrik; Cid, Adrian Fernandez; Amendola, Luca, E-mail: h.nersisyan@thphys.uni-heidelberg.de, E-mail: fernandez@thphys.uni-heidelberg.de, E-mail: l.amendola@thphys.uni-heidelberg.de [Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany)
2017-04-01
In this work, we extend previous analyses of the structure formation in the f (□{sup −1} R ) model of nonlocal gravity proposed by Deser and Woodard (DW), which reproduces the background expansion of ΛCDM with no need of a cosmological constant nor of any dimensional constant beside Newton's one. A previous analysis based on redshift-space distortions (RSD) data concluded that the model was ruled out. In this work we revisit the issue and find that, when recast in a localized model, the DW model is not ruled out and actually gives a better fit to RSD data than ΛCDM. In fact, the DW model presents a suppressed growth of matter perturbations with respect to ΛCDM and a slightly lower value of σ{sub 8}, as favored by observations. We also produce analytical approximations of the two modified gravity functions, i.e. the anisotropic stress η and the relative change of Newton's constant Y , and of f σ{sub 8}( z ) as a function of redshift. Finally, we also show how much the fit depends on initial conditions when these are generalized with respect to a standard matter-dominated era.
Gravity and magnetic anomaly modeling and correlation using the SPHERE program and Magsat data
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.
Flavor changing processes in supersymmetric models with hybrid gauge- and gravity-mediation
Hiller, Gudrun; Hochberg, Yonit; Nir, Yosef
2009-01-01
We consider supersymmetric models where gauge mediation provides the dominant contributions to the soft supersymmetry breaking terms while gravity mediation provides sub-dominant yet non-negligible contributions. We further assume that the gravity-mediated contributions are subject to selection rules that follow from a Froggatt-Nielsen symmetry. This class of models constitutes an example of viable and natural non-minimally flavor violating models. The constraints from K 0 -K-bar 0 mixing imply that the modifications to the Standard Model predictions for B d -B-bar d and B s - B-bar s mixing are generically at most at the percent level, but can be of order ten percent for large tan β. The modifications for D 0 -D-bar 0 mixing are generically at most of order a few percent, but in a special subclass of models they can be of order one. We point out ΔB = 1 processes relevant for flavor violation in hybrid mediation.
Structure formation in the Deser-Woodard nonlocal gravity model: a reappraisal
Nersisyan, Henrik; Cid, Adrian Fernandez; Amendola, Luca
2017-01-01
In this work, we extend previous analyses of the structure formation in the f (□ −1 R ) model of nonlocal gravity proposed by Deser and Woodard (DW), which reproduces the background expansion of ΛCDM with no need of a cosmological constant nor of any dimensional constant beside Newton's one. A previous analysis based on redshift-space distortions (RSD) data concluded that the model was ruled out. In this work we revisit the issue and find that, when recast in a localized model, the DW model is not ruled out and actually gives a better fit to RSD data than ΛCDM. In fact, the DW model presents a suppressed growth of matter perturbations with respect to ΛCDM and a slightly lower value of σ 8 , as favored by observations. We also produce analytical approximations of the two modified gravity functions, i.e. the anisotropic stress η and the relative change of Newton's constant Y , and of f σ 8 ( z ) as a function of redshift. Finally, we also show how much the fit depends on initial conditions when these are generalized with respect to a standard matter-dominated era.
Direct Evidence for a Dual Process Model of Deductive Inference
Markovits, Henry; Brunet, Marie-Laurence; Thompson, Valerie; Brisson, Janie
2013-01-01
In 2 experiments, we tested a strong version of a dual process theory of conditional inference (cf. Verschueren et al., 2005a, 2005b) that assumes that most reasoners have 2 strategies available, the choice of which is determined by situational variables, cognitive capacity, and metacognitive control. The statistical strategy evaluates inferences…
Koneshov, V. N.; Nepoklonov, V. B.
2018-05-01
The development of studies on estimating the accuracy of the Earth's modern global gravity models in terms of the spherical harmonics of the geopotential in the problematic regions of the world is discussed. The comparative analysis of the results of reconstructing quasi-geoid heights and gravity anomalies from the different models is carried out for two polar regions selected within a radius of 1000 km from the North and South poles. The analysis covers nine recently developed models, including six high-resolution models and three lower order models, including the Russian GAOP2012 model. It is shown that the modern models determine the quasi-geoid heights and gravity anomalies in the polar regions with errors of 5 to 10 to a few dozen cm and from 3 to 5 to a few dozen mGal, respectively, depending on the resolution. The accuracy of the models in the Arctic is several times higher than in the Antarctic. This is associated with the peculiarities of gravity anomalies in every particular region and with the fact that the polar part of the Antarctic has been comparatively less explored by the gravity methods than the polar Arctic.
The role of satellite altimetry in gravity field modelling in coastal areas
Andersen, Ole Baltazar; Knudsen, Per
2000-01-01
global uniform gravity information with very high resolution, and these global marine gravity fields are registered on a two by two minute grid corresponding to 4 by 4 kilometres at the equator. In this presentation several coastal complications in deriving the marine gravity field from satellite...... altimetry will be investigated using the KMS98 gravity field. Comparison with other sources of gravity field information like airborne and marine gravity observations will be carried out and two fundamentally different test areas (Azores and Skagerak) will be studied to investigated the different role...
Invariant models in the inversion of gravity and magnetic fields and their derivatives
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.
Isostatic models and isostatic gravity anomalies of the Arabian plate and surroundings
Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir
2015-04-01
Isostaic anomalies represent one of the most useful "geological" reduction of the gravity field. With the isostatic correction it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. This correction is based on the fact that a major part of the near-surface load is compensated by variations of the lithosphere boundaries (chiefly the Moho and LAB) and by density variations within the crust and upper mantle. It is usually supposed that it is less important to a first order, what is the actual compensation model when reducing the effect of compensating masses, since their total weight is exactly opposite to the near-surface load. We compare several compensating models for the Arabian plate and surrounding area. The Airy model gives very significant regional isostatic anomalies, which can not be explained by the upper crust structure or disturbances of the isostatic equilibrium. Also the predicted "isostatic" Moho is very different from the existing observations. The second group of the isostatic models includes the Moho, which is based on existing seismic determinations. Additional compensation is provided by density variations within the lithosphere (chiefly in the upper mantle). In this way we minimize regional anomalies over the Arabian plate. The residual local anomalies well correspond to tectonic structure of the plate. Still very significant anomalies are associated with the Zagros fold belt, the collision zone of the Arabian and Eurasian plates.
Drell-Yan and diphoton production at hadron colliders and low scale gravity model
Cheung, Kingman; Landsberg, Greg
2000-01-01
In the model of Arkani-Hamed, Dimopoulos, and Dvali where gravity is allowed to propagate in the extra dimensions of very large size, virtual graviton exchange between the standard model particles can give rise to signatures that can be tested in collider experiments. We study these effects in dilepton and diphoton production at hadron colliders. Specifically, we examine the double differential cross section in the invariant mass and scattering angle, which is found to be useful in separating the gravity effects from the standard model. In this work, sensitivity obtained using the double differential cross section is higher than that in previous studies based on single differential distributions. Assuming no excess of events over the standard model predictions, we obtain the following 95% confidence level lower limits on the effective Planck scale: 0.9-1.5 TeV in the Fermilab Tevatron run I, 1.3-2.5 TeV in run IIa, 1.7-3.5 TeV in run IIb, and 6.5-12.8 TeV at the CERN LHC. The range of numbers corresponds to the number of extra dimensions n=7-2. (c) 2000 The American Physical Society
Gravity and Macro-Model Tuning for the Geosat Follow-on Spacecraft
Lemoine, Frank G.; Rowlands, David D.; Marr, Gregory C.; Zelensky, Nikita P.; Luthcke, Scott B.; Cox, Christopher M.
1999-01-01
The US Navy's GEOSAT Follow-On (GFO) spacecraft was launched on February 10, 1998 and the primary objective of the mission was to map the oceans using a radar altimeter. The spacecraft tracking complement consisted of GPS receivers, a laser retroreflector and Doppler beacons. Since the GPS receivers have not yet returned reliable data, the only means of providing high-quality precise orbits has been though satellite laser ranging (SLR). The spacecraft has been tracked by the international satellite laser ranging network since April 22, 1998, and an average of 7.4 passes per day have been obtained from US and participating foreign stations. Since the predicted radial orbit error due to the gravity field is two to three cm, the largest contributor to the high SLR residuals (7-10 cm RMS for five day arcs) is the mismodelling of the non-conservative forces, not withstanding the development of a three-dimensional eight-panel model and an analytical attitude model for the GFO spacecraft. The SLR residuals show a clear correlation with beta-prime (solar elevation) angle, peaking in mid-August 1998 when the beta-prime angle reached -80 to -90 degrees. In this paper we discuss the tuning of the non-conservative force model, for GFO and report the subsequent addition of the GFO tracking data to the Earth gravity model solutions.
Localizing gravity on Maxwell gauged CP1 model in six dimensions
Kodama, Yuta; Kokubu, Kento; Sawado, Nobuyuki
2008-01-01
We shall consider a 3-brane embedded in six-dimensional space-time with a negative bulk cosmological constant. The 3-brane is constructed by a topological soliton solution living in two-dimensional axially symmetric transverse subspace. Similar to most previous works of six-dimensional soliton models, our Maxwell gauged CP 1 brane model can also achieve localizing gravity around the 3-brane. The CP 1 field is described by a scalar doublet and derived from the O(3) sigma model by projecting it onto two-dimensional complex space. In that sense, our framework is more effective than other solitonic brane models concerning gauge theory. We shall also discuss the linear stability analysis for our new model by fluctuating all fields.
The quantum group structure of 2D gravity and minimal models. Pt. 1
Gervais, J.L.
1990-01-01
On the unit circle, an infinite family of chiral operators is constructed, whose exchange algebra is given by the universal R-matrix of the quantum group SL(2) q . This establishes the precise connection between the chiral algebra of two dimensional gravity or minimal models and this quantum group. The method is to relate the monodromy properties of the operator differential equations satisfied by the generalized vertex operators with the exchange algebra of SL(2) q . The formulae so derived, which generalize an earlier particular case worked out by Babelon, are remarkably compact and may be entirely written in terms of 'q-deformed' factorials and binomial coefficients. (orig.)
Exact solution to the 'auxiliary extra-dimension' model of massive gravity
Hassan, S.F.; Rosen, Rachel A.
2011-01-01
The 'auxiliary extra-dimension' model was proposed in order to provide a geometrical interpretation to modifications of general relativity, in particular to non-linear massive gravity. In this context, the theory was shown to be ghost free to third order in perturbations, in the decoupling limit. In this work, we exactly solve the equation of motion in the extra dimension, to obtain a purely 4-dimensional theory. Using this solution, it is shown that the ghost appears at the fourth order and beyond. We explore potential modifications to address the ghost issue and find that their consistent implementation requires going beyond the present framework.
Higgs mass range from standard model false vacuum inflation in scalar-tensor gravity
Masina, I.; Notari, A.
2012-01-01
If the standard model is valid up to very high energies it is known that the Higgs potential can develop a local minimum at field values around 10(15)-10(17) GeV, for a narrow band of values of the top quark and Higgs masses. We show that in a scalar-tensor theory of gravity such Higgs false vacu....... This prediction could be soon tested at the Large Hadron Collider. Our inflationary scenario could also be further checked by better constraining the spectral index and the tensor-to-scalar ratio....
Cascading Gravity Extending the Dvali-Gabadadze-Porrati Model to Higher Dimension
de Rham, Claudia; Hofmann, Stefan; Khoury, Justin; Pujolas, Oriol; Redi, Michele; Tolley, Andrew J
2008-01-01
We present a higher codimension generalization of the DGP scenario which, unlike previous attempts, is free of ghost instabilities. The 4D propagator is made regular by embedding our visible 3-brane within a 4-brane, each with their own induced gravity terms, in a flat 6D bulk. The model is ghost-free if the tension on the 3-brane is larger than a certain critical value, while the induced metric remains flat. The gravitational force law `cascades' from a 6D behavior at the largest distances followed by a 5D and finally a 4D regime at the shortest scales.
Cascading Gravity: Extending the Dvali-Gabadadze-Porrati Model to Higher Dimension
Rham, Claudia de; Dvali, Gia; Hofmann, Stefan; Khoury, Justin; Tolley, Andrew J.; Pujolas, Oriol; Redi, Michele
2008-01-01
We present a generalization of the Dvali-Gabadadze-Porrati scenario to higher codimensions which, unlike previous attempts, is free of ghost instabilities. The 4D propagator is made regular by embedding our visible 3-brane within a 4-brane, each with their own induced gravity terms, in a flat 6D bulk. The model is ghost-free if the tension on the 3-brane is larger than a certain critical value, while the induced metric remains flat. The gravitational force law ''cascades'' from a 6D behavior at the largest distances followed by a 5D and finally a 4D regime at the shortest scales
Connection between Einstein equations, nonlinear sigma models, and self-dual Yang-Mills theory
Sanchez, N.; Whiting, B.
1986-01-01
The authors analyze the connection between nonlinear sigma models self-dual Yang-Mills theory, and general relativity (self-dual and non-self-dual, with and without killing vectors), both at the level of the equations and at the level of the different type of solutions (solitons and calorons) of these theories. They give a manifestly gauge invariant formulation of the self-dual gravitational field analogous to that given by Yang for the self-dual Yang-Mills field. This formulation connects in a direct and explicit way the self-dual Yang-Mills and the general relativity equations. They give the ''R gauge'' parametrization of the self-dual gravitational field (which corresponds to modified Yang's-type and Ernst equations) and analyze the correspondence between their different types of solutions. No assumption about the existence of symmetries in the space-time is needed. For the general case (non-self-dual), they show that the Einstein equations contain an O nonlinear sigma model. This connection with the sigma model holds irrespective of the presence of symmetries in the space-time. They found a new class of solutions of Einstein equations depending on holomorphic and antiholomorphic functions and we relate some subclasses of these solutions to solutions of simpler nonlinear field equations that are well known in other branches of physics, like sigma models, SineGordon, and Liouville equations. They include gravitational plane wave solutions. They analyze the response of different accelerated quantum detector models, compare them to the case when the detectors are linterial in an ordinary Planckian gas at a given temperature, and discuss the anisotropy of the detected response for Rindler observers
Wu, Dong L.; Zhang, Fuqing
2004-01-01
Satellite microwave data are used to study gravity wave properties and variabilities over the northeastern United States and the North Atlantic in the December-January periods. The gravity waves in this region, found in many winters, can reach the stratopause with growing amplitude. The Advanced Microwave Sounding Unit-A (AMSU-A) observations show that the wave occurrences are correlated well with the intensity and location of the tropospheric baroclinic jet front systems. To further investigate the cause(s) and properties of the North Atlantic gravity waves, we focus on a series of wave events during 19-21 January 2003 and compare AMSU-A observations to simulations from a mesoscale model (MM5). The simulated gravity waves compare qualitatively well with the satellite observations in terms of wave structures, timing, and overall morphology. Excitation mechanisms of these large-amplitude waves in the troposphere are complex and subject to further investigations.
Kohn, Florian P M; Ritzmann, Ramona
2018-03-01
For decades it has been shown that acute changes in gravity have an effect on neuronal systems of human and animals on different levels, from the molecular level to the whole nervous system. The functional properties and gravity-dependent adaptations of these system levels have been investigated with no or barely any interconnection. This review summarizes the gravity-dependent adaptation processes in human and animal organisms from the in vitro cellular level with its biophysical properties to the in vivo motor responses and underlying sensorimotor functions of human subjects. Subsequently, a first model for short-term adaptation of neuronal transmission is presented and discussed for the first time, which integrates the responses of the different levels of organization to changes in gravity.
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.
Application of the spherical harmonic gravity model in high precision inertial navigation systems
Wang, Jing; Yang, Gongliu; Zhou, Xiao; Li, Xiangyun
2016-01-01
The spherical harmonic gravity model (SHM) may, in general, be considered as a suitable alternative to the normal gravity model (NGM), because it represents the Earth’s gravitational field more accurately. However, the high-resolution SHM has never been used in current inertial navigation systems (INSs) due to its extremely complex expression. In this paper, the feasibility and accuracy of a truncated SHM are discussed for application in a real-time free-INS with a precision demand better than 0.8 nm h −1 . In particular, the time and space complexity are analyzed mathematically to verify the feasibility of the SHM. Also, a test on a typical navigation computer shows a storable range of cut-off degrees. To further evaluate the appropriate degree and accuracy of the truncated SHM, analyses of covariance and truncation error are proposed. Finally, a SHM of degree 12 is demonstrated to be the appropriate model for routine INSs in the precision range of 0.4–0.75 nm h −1 . Flight simulations and road tests show its outstanding performance over the traditional NGM. (paper)
Physically based model for extracting dual permeability parameters using non-Newtonian fluids
Abou Najm, M. R.; Basset, C.; Stewart, R. D.; Hauswirth, S.
2017-12-01
Dual permeability models are effective for the assessment of flow and transport in structured soils with two dominant structures. The major challenge to those models remains in the ability to determine appropriate and unique parameters through affordable, simple, and non-destructive methods. This study investigates the use of water and a non-Newtonian fluid in saturated flow experiments to derive physically-based parameters required for improved flow predictions using dual permeability models. We assess the ability of these two fluids to accurately estimate the representative pore sizes in dual-domain soils, by determining the effective pore sizes of macropores and micropores. We developed two sub-models that solve for the effective macropore size assuming either cylindrical (e.g., biological pores) or planar (e.g., shrinkage cracks and fissures) pore geometries, with the micropores assumed to be represented by a single effective radius. Furthermore, the model solves for the percent contribution to flow (wi) corresponding to the representative macro and micro pores. A user-friendly solver was developed to numerically solve the system of equations, given that relevant non-Newtonian viscosity models lack forms conducive to analytical integration. The proposed dual-permeability model is a unique attempt to derive physically based parameters capable of measuring dual hydraulic conductivities, and therefore may be useful in reducing parameter uncertainty and improving hydrologic model predictions.
He, Jun; Gao, Feng; Bai, Yongjun; Wu, Shengfu
2013-11-01
The large capacity servo press is traditionally realized by means of redundant actuation, however there exist the over-constraint problem and interference among actuators, which increases the control difficulty and the product cost. A new type of press mechanism with parallel topology is presented to develop the mechanical servo press with high stamping capacity. The dynamic model considering gravity counterbalance is proposed based on the virtual work principle, and then the effect of counterbalance cylinder on the dynamic performance of the servo press is studied. It is found that the motor torque required to operate the press is a lot less than the others when the ratio of the counterbalance force to the gravity of ram is in the vicinity of 1.0. The stamping force of the real press prototype can reach up to 25 MN on the position of 13 mm away from the bottom dead center. The typical deep-drawing process with 1 200 mm stroke at 8 strokes per minute is proposed by means of five order polynomial. On this process condition, the driving torques are calculated based on the above dynamic model and the torque measuring test is also carried out on the prototype. It is shown that the curve trend of calculation torque is consistent to the measured result and that the average error is less than 15%. The parallel mechanism is introduced into the development of large capacity servo press to avoid the over-constraint and interference of traditional redundant actuation, and its dynamic characteristics with gravity counterbalance are presented.
Oscar H. Lücke
2010-01-01
Full Text Available The map of complete Bouguer anomaly of Costa Rica shows an elongated NW-SE trending gravity low in the central region. This gravity low coincides with the geographical region known as the Cordillera Volcánica Central. It is built by geologic and morpho-tectonic units which consist of Quaternary volcanic edifices. For quantitative interpretation of the sources of the anomaly and the characterization of fluid pathways and reservoirs of arc magmatism, a constrained 3D density model of the upper crust was designed by means of forward modeling. The density model is constrained by simplified surface geology, previously published seismic tomography and P-wave velocity models, which stem from wide-angle refraction seismic, as well as results from methods of direct interpretation of the gravity field obtained for this work. The model takes into account the effects and influence of subduction-related Neogene through Quaternary arc magmatism on the upper crust.
Probabilistic Modeling of Seismic Risk Based Design for a Dual System Structure
Sidi, Indra Djati
2017-01-01
The dual system structure concept has gained popularity in the construction of high-rise buildings over the last decades. Meanwhile, earthquake engineering design provisions for buildings have moved from the uniform hazard concept to the uniform risk concept upon recognizing the uncertainties involved in the earthquake resistance of concrete structures. In this study, a probabilistic model for the evaluation of such risk is proposed for a dual system structure consisting of shear walls or cor...
Modeling and simulation of a dual-junction CIGS solar cell using Silvaco ATLAS
Fotis, Konstantinos
2012-01-01
Approved for public release; distribution is unlimited. The potential of designing a dual-junction Copper Indium Gallium Selenide (CIGS) photovoltaic cell is investigated in this thesis. Research into implementing a dual-junction solar cell, using a CIGS bottom cell and different thin-film designs as a top cell, was conducted in order to increase the current record efficiency of 20.3% for a single CIGS cell. This was accomplished through modeling and simulation using Silvaco ATLASTM, an ad...
Estimating dual deposit insurance premium rates and forecasting non-performing loans: Two new models
Yoshino, Naoyuki; Taghizadeh-Hesary, Farhad; Nili, Farhad
2015-01-01
Risky banks that endanger the stability of the financial system should pay higher deposit insurance premiums than healthy banks and other financial institutions that have shown good financial performance. It is necessary, therefore, to have at least a dual fair premium rate system. In this paper, we develop a model for calculating dual fair premium rates. Our definition of a fair premium rate in this paper is a rate that could cover the operational expenditures of the deposit insuring organiz...
The dual-electrode DC arc furnace-modelling brush arc conditions
Reynolds, Q.G.
2012-01-01
The dual-electrode DC arc furnace, an alternative design using an anode and cathode electrode instead of a hearth anode, was studied at small scale using computational modelling methods. Particular attention was paid to the effect of two key design variables, the arc length and the electrode separation, on the furnace behaviour. It was found that reducing the arc length to brush arc conditions was a valid means of overcoming several of the limitations of the dual-electrode design, namely high...
Large scale structures in the kinetic gravity braiding model that can be unbraided
Kimura, Rampei; Yamamoto, Kazuhiro
2011-01-01
We study cosmological consequences of a kinetic gravity braiding model, which is proposed as an alternative to the dark energy model. The kinetic braiding model we study is characterized by a parameter n, which corresponds to the original galileon cosmological model for n = 1. We find that the background expansion of the universe of the kinetic braiding model is the same as the Dvali-Turner's model, which reduces to that of the standard cold dark matter model with a cosmological constant (ΛCDM model) for n equal to infinity. We also find that the evolution of the linear cosmological perturbation in the kinetic braiding model reduces to that of the ΛCDM model for n = ∞. Then, we focus our study on the growth history of the linear density perturbation as well as the spherical collapse in the nonlinear regime of the density perturbations, which might be important in order to distinguish between the kinetic braiding model and the ΛCDM model when n is finite. The theoretical prediction for the large scale structure is confronted with the multipole power spectrum of the luminous red galaxy sample of the Sloan Digital Sky survey. We also discuss future prospects of constraining the kinetic braiding model using a future redshift survey like the WFMOS/SuMIRe PFS survey as well as the cluster redshift distribution in the South Pole Telescope survey
Models of color confinement based on dual superconductors
Ripka, Georges; Hosek, Jiri
2003-01-01
Recently, the relatively old speculation that the physical QCD vacuum might be a kind of dual superconductor, in which color-magnetic monopoles have condensed, seems to have received some 'experimental' confirmation in lattice calculations. The lattice calculations do not dictate, however, the form of the effective low-energy theory. And indeed, a rather wide panoply of possible effective theories has been proposed. The purpose of this talk is to review them in order to contrast their properties
Modeling of dual cylinder wind-up extensional rheometers
Yu, Kaijia; Marin, Jose; Jensen, Mette
measurements are useful for polymer characterization. The Sentmanat extensional Rheometer[1] is an new testing platform for the study of polymers and elastomers in extensional flow. This technique employs a dual wind-up drum technique to perform an uni-axial extensional deformation during experiments......). *The title of this submission has been modified to remove the name of a commercial product or company to bring the title into compliance with SOR policy....
Effect of gravity on liquid plug transport through an airway bifurcation model.
Zheng, Y; Anderson, J C; Suresh, V; Grotberg, J B
2005-10-01
Many medical therapies require liquid plugs to be instilled into and delivered throughout the pulmonary airways. Improving these treatments requires a better understanding of how liquid distributes throughout these airways. In this study, gravitational and surface mechanisms determining the distribution of instilled liquids are examined experimentally using a bench-top model of a symmetrically bifurcating airway. A liquid plug was instilled into the parent tube and driven through the bifurcation by a syringe pump. The effect of gravity was adjusted by changing the roll angle (phi) and pitch angle (gamma) of the bifurcation (phi = gamma =0 deg was isogravitational). Phi determines the relative gravitational orientation of the two daughter tubes: when phi not equal to 0 deg, one daughter tube was lower (gravitationally favored) compared to the other. Gamma determines the component of gravity acting along the axial direction of the parent tube: when gamma not equal to 0 deg, a nonzero component of gravity acts along the axial direction of the parent tube. A splitting ratio Rs, is defined as the ratio of the liquid volume in the upper daughter to the lower just after plug splitting. We measured the splitting ratio, Rs, as a function of: the parent-tube capillary number (Cap); the Bond number (Bo); phi; gamma; and the presence of pre-existing plugs initially blocking either daughter tube. A critical capillary number (Cac) was found to exist below which no liquid entered the upper daughter (Rs = 0), and above which Rs increased and leveled off with Cap. Cac increased while Rs decreased with increasing phi, gamma, and Bo for blocked and unblocked cases at a given Cap > Ca,. Compared to the nonblockage cases, Rs decreased (increased) at a given Cap while Cac increased (decreased) with an upper (lower) liquid blockage. More liquid entered the unblocked daughter with a blockage in one daughter tube, and this effect was larger with larger gravity effect. A simple theoretical
Isostatic Model and Isostatic Gravity Anomalies of the Arabian Plate and Surroundings
Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir
2016-04-01
The isostatic modeling represents one of the most useful "geological" reduction methods of the gravity field. With the isostatic correction, it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. Although there exist several isostatic compensation schemes, it is usually supposed that a choice of the model is not an important factor to first order, since the total weight of compensating masses remains the same. We compare two alternative models for the Arabian plate and surrounding area. The Airy model gives very significant regional isostatic anomalies, which cannot be explained by the upper crust structure or disturbances of the isostatic equilibrium. Also, the predicted "isostatic" Moho is very different from existing seismic observations. The second isostatic model includes the Moho, which is based on seismic determinations. Additional compensation is provided by density variations within the lithosphere (chiefly in the upper mantle). According to this model, the upper mantle under the Arabian Shield is less dense than under the Platform. In the Arabian platform, the maximum density coincides with the Rub' al Khali, one of the richest oil basin in the world. This finding agrees with previous studies, showing that such basins are often underlain by dense mantle, possibly related to an eclogite layer that has caused their subsidence. The mantle density variations might be also a result of variations of the lithosphere thickness. With the combined isostatic model, it is possible to minimize regional anomalies over the Arabian plate. The residual local anomalies correspond well to tectonic structure of the plate. Still very significant anomalies, showing isostatic disturbances of the lithosphere, are associated with the Zagros fold belt, the collision zone of the Arabian and Eurasian plates.
Towards Spherical Mesh Gravity and Magnetic Modelling in an HPC Environment
Lane, R. J.; Brodie, R. C.; de Hoog, M.; Navin, J.; Chen, C.; Du, J.; Liang, Q.; Wang, H.; Li, Y.
2013-12-01
Staff at Geoscience Australia (GA), Australia's Commonwealth Government geoscientific agency, have routinely performed 3D gravity and magnetic modelling as part of geoscience investigations. For this work, we have used software programs that have been based on a Cartesian mesh spatial framework. These programs have come as executable files that were compiled to operate in a Windows environment on single core personal computers (PCs). To cope with models with higher resolution and larger extents, we developed an approach whereby a large problem could be broken down into a number of overlapping smaller models (';tiles') that could be modelled separately, with the results combined back into a single output model. To speed up the processing, we established a Condor distributed network from existing desktop PCs. A number of factors have caused us to consider a new approach to this modelling work. The drivers for change include; 1) models with very large lateral extents where the effects of Earth curvature are a consideration, 2) a desire to ensure that the modelling of separate regions is carried out in a consistent and managed fashion, 3) migration of scientific computing to off-site High Performance Computing (HPC) facilities, and 4) development of virtual globe environments for integration and visualization of 3D spatial objects. Some of the more surprising realizations to emerge have been that; 1) there aren't any readily available commercial software packages for modelling gravity and magnetic data in a spherical mesh spatial framework, 2) there are many different types of HPC environments, 3) no two HPC environments are the same, and 4) the most common virtual globe environment (i.e., Google Earth) doesn't allow spatial objects to be displayed below the topographic/bathymetric surface. Our response has been to do the following; 1) form a collaborative partnership with researchers at the Colorado School of Mines (CSM) and the China University of Geosciences (CUG
Softened Gravity and the Extension of the Standard Model up to Infinite Energy
Giudice, Gian F.; Salvio, Alberto; Strumia, Alessandro
2015-02-23
Attempts to solve naturalness by having the weak scale as the only breaking of classical scale invariance have to deal with two severe difficulties: gravity and the absence of Landau poles. We show that solutions to the first problem require premature modifications of gravity at scales no larger than $10^{11}$ GeV, while the second problem calls for many new particles at the weak scale. To build models that fulfil these properties, we classify 4-dimensional Quantum Field Theories that satisfy Total Asymptotic Freedom (TAF): the theory holds up to infinite energy, where all coupling constants flow to zero. We develop a technique to identify such theories and determine their low-energy predictions. Since the Standard Model turns out to be asymptotically free only under the unphysical conditions $g_1 = 0$, $M_t = 186$ GeV, $M_\\tau = 0$, $M_h = 163$ GeV, we explore some of its weak-scale extensions that satisfy the requirements for TAF.
Softened gravity and the extension of the standard model up to infinite energy
Giudice, Gian F. [CERN, Theory Division,CH-1211 Geneva 23 (Switzerland); Isidori, Gino [Physik-Institut, Universität Zürich,CH-8057, Zürich (Switzerland); INFN, Laboratori Nazionali di Frascati,I-00044 Frascati (Italy); Salvio, Alberto [Departamento de Física Teórica, Universidad Autónoma de Madridand Instituto de Física Teórica IFT-UAM/CSIC, Cantoblanco, Madrid 28049 (Spain); Strumia, Alessandro [INFN - Sezione di Pisa e Dipartimento di Fisica dell’Università di Pisa,I-56127 Pisa (Italy); National Institute of Chemical Physics and Biophysics,Akadeemia tee 23, 12618 Tallinn (Estonia)
2015-02-23
Attempts to solve naturalness by having the weak scale as the only breaking of classical scale invariance have to deal with two severe difficulties: gravity and the absence of Landau poles. We show that solutions to the first problem require premature modifications of gravity at scales no larger than 10{sup 11} GeV, while the second problem calls for many new particles at the weak scale. To build models that fulfill these properties, we classify 4-dimensional Quantum Field Theories that satisfy Total Asymptotic Freedom (TAF): the theory holds up to infinite energy, where all coupling constants flow to zero. We develop a technique to identify such theories and determine their low-energy predictions. Since the Standard Model turns out to be asymptotically free only under the unphysical conditions g{sub 1}=0, M{sub t}=186 GeV, M{sub τ}=0, M{sub h}=163 GeV, we explore some of its weak-scale extensions that satisfy the requirements for TAF.
Charged black holes in a generalized scalar–tensor gravity model
Yves Brihaye
2017-09-01
Full Text Available We study 4-dimensional charged and static black holes in a generalized scalar–tensor gravity model, in which a shift symmetry for the scalar field exists. For vanishing scalar field the solution corresponds to the Reissner–Nordström (RN solution, while solutions of the full scalar-gravity model have to be constructed numerically. We demonstrate that these black holes support Galilean scalar hair up to a maximal value of the scalar–tensor coupling that depends on the value of the charge and can be up to roughly twice as large as that for uncharged solutions. The Hawking temperature TH of the hairy black holes at maximal scalar–tensor coupling decreases continuously with the increase of the charge and reaches TH=0 for the highest possible charge that these solutions can carry. However, in this limit, the scalar–tensor coupling needs to vanish. The limiting solution hence corresponds to the extremal RN solution, which does not support regular Galilean scalar hair due to its AdS2×S2 near-horizon geometry.
Constraining models of f(R) gravity with Planck and WiggleZ power spectrum data
Dossett, Jason; Parkinson, David; Hu, Bin
2014-01-01
In order to explain cosmic acceleration without invoking ''dark'' physics, we consider f(R) modified gravity models, which replace the standard Einstein-Hilbert action in General Relativity with a higher derivative theory. We use data from the WiggleZ Dark Energy survey to probe the formation of structure on large scales which can place tight constraints on these models. We combine the large-scale structure data with measurements of the cosmic microwave background from the Planck surveyor. After parameterizing the modification of the action using the Compton wavelength parameter B 0 , we constrain this parameter using ISiTGR, assuming an initial non-informative log prior probability distribution of this cross-over scale. We find that the addition of the WiggleZ power spectrum provides the tightest constraints to date on B 0 by an order of magnitude, giving log 10 (B 0 ) < −4.07 at 95% confidence limit. Finally, we test whether the effect of adding the lensing amplitude A Lens and the sum of the neutrino mass ∑m ν is able to reconcile current tensions present in these parameters, but find f(R) gravity an inadequate explanation
Memduh Alper Demir
2017-12-01
Full Text Available The purpose of this study is to examine the bilateral machinery and transport equipment trade efficiency of selected fourteen Asian countries by applying stochastic frontier gravity model. These selected countries have the top machinery and transport equipment trade (both export and import volumes in Asia. The model we use includes variables such as income, market size of trading partners, distance, common culture, common border, common language and global economic crisis similar to earlier studies using the stochastic frontier gravity models. Our work, however, includes an extra variable called normalized revealed comparative advantage (NRCA index additionally. The NRCA index is comparable across commodity, country and time. Thus, the NRCA index is calculated and then included in our stochastic frontier gravity model to see the impact of competitiveness (here measured by the NRCA index on the efficiency of trade.
Beyond the Standard Model with noncommutative geometry, strolling towards quantum gravity
Martinetti, Pierre
2015-01-01
Noncommutative geometry in its many incarnations appears at the crossroad of many researches in theoretical and mathematical physics: from models of quantum spacetime(with or without breaking of Lorentz symmetry) to loop gravity and string theory, from early considerations on UV-divergenciesin quantum field theory to recent models of gauge theories on noncommutatives pacetime, from Connes description of the standard model of elementary particles to recent Pati-Salam like extensions. We list several of these applications, emphasizing also the original point of view brought by noncommutative geometry on the nature of time. This text serves as an introduction to the volume of proceedings of the parallel session “Noncommutative geometry and quantum gravity”, as a part of the conference “Conceptual and technical challenges in quantum gravity” organized at the University of Rome La Sapienza sin September 2014. (paper)
A Possible Universe in Pulsation by Using a Hydro-Dynamical Model for Gravity
Corneliu BERBENTE
2016-12-01
Full Text Available By using a hydro-dynamical model for gravity previously given by the author, a pulsating universe is possible to describe. This is possible because two hydro-dynamical sources are in attraction both when they are emitting and absorbing fluid. In our model, bodies (matter and energy are interacting via an incompressible fluid made of gravitons (photon-like particles having a wave length of the order of magnitude of the radius of universe. One considers the universe uniform at large scale, the effects of general relativity type being local and negligible at global scale. An “elastic sphere” model for the universe is suggested to describe the possible inversion. The expansion of the universe stops when the “elastic energy” overcomes the kinetic one; this takes place near the point of maximal emission speed of the fluid of gravitons. The differential equation for the universe in expansion is adapted to contraction. Analytical solutions are given.
A model of unified quantum chromodynamics and Yang-Mills gravity
HSU Jong-Ping
2012-01-01
Based on a generalized Yang-Mills framework,gravitational and strong interactions can be unified in analogy with the unification in the clectroweak theory.By gauging T(4) × [SU(3)]color in fiat space-time,we have a unified model of chromo-gravity with a new tensor gauge field,which couples universally to all gluons,quarks and anti-quarks.The space-time translational gauge symmetry assures that all wave equations of quarks and gluons reduce to a Hamilton-Jacobi equation with the same ‘effective Riemann metric tensors' in the geometric-optics (or classical) limit.The emergence of effective metric tensors in the classical limit is essential for the unified model to agree with experiments.The unified model suggests that all gravitational,strong and electroweak interactions appear to be dictated by gauge symmetries in the generalized Yang-Mills framework.
Estimating Small-Body Gravity Field from Shape Model and Navigation Data
Park, Ryan S.; Werner, Robert A.; Bhaskaran, Shyam
2008-01-01
This paper presents a method to model the external gravity field and to estimate the internal density variation of a small-body. We first discuss the modeling problem, where we assume the polyhedral shape and internal density distribution are given, and model the body interior using finite elements definitions, such as cubes and spheres. The gravitational attractions computed from these approaches are compared with the true uniform-density polyhedral attraction and the level of accuracies are presented. We then discuss the inverse problem where we assume the body shape, radiometric measurements, and a priori density constraints are given, and estimate the internal density variation by estimating the density of each finite element. The result shows that the accuracy of the estimated density variation can be significantly improved depending on the orbit altitude, finite-element resolution, and measurement accuracy.
Propagator with positive cosmological constant in the 3D Euclidean quantum gravity toy model
Bunting, William E; Rovelli, Carlo
2014-01-01
We study the propagator on a single tetrahedron in a three-dimensional toy model of quantum gravity with positive cosmological constant. The cosmological constant is included in the model via q-deformation of the spatial symmetry algebra, that is, we use the Turaev–Viro amplitude. The expected repulsive effect of dark energy is recovered in numerical and analytic calculations of the propagator at large scales comparable to the infrared cutoff. However, due to the simplicity of the model, we do not obtain the exact Newton limit of the propagator. This is a first step toward the similar calculation in the full 3+1 dimensional theory with larger numbers of simplicies. (paper)
Testing a generalized cubic Galileon gravity model with the Coma Cluster
Terukina, Ayumu; Yamamoto, Kazuhiro; Okabe, Nobuhiro [Department of Physical Sciences, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Matsushita, Kyoko; Sasaki, Toru, E-mail: telkina@theo.phys.sci.hiroshima-u.ac.jp, E-mail: kazuhiro@hiroshima-u.ac.jp, E-mail: okabe@hiroshima-u.ac.jp, E-mail: matusita@rs.kagu.tus.ac.jp, E-mail: j1213703@ed.tus.ac.jp [Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)
2015-10-01
We obtain a constraint on the parameters of a generalized cubic Galileon gravity model exhibiting the Vainshtein mechanism by using multi-wavelength observations of the Coma Cluster. The generalized cubic Galileon model is characterized by three parameters of the turning scale associated with the Vainshtein mechanism, and the amplitude of modifying a gravitational potential and a lensing potential. X-ray and Sunyaev-Zel'dovich (SZ) observations of the intra-cluster medium are sensitive to the gravitational potential, while the weak-lensing (WL) measurement is specified by the lensing potential. A joint fit of a complementary multi-wavelength dataset of X-ray, SZ and WL measurements enables us to simultaneously constrain these three parameters of the generalized cubic Galileon model for the first time. We also find a degeneracy between the cluster mass parameters and the gravitational modification parameters, which is influential in the limit of the weak screening of the fifth force.
A model of unified quantum chromodynamics and Yang-Mills gravity
HSU Jongping
2012-01-01
Based on a generalized Yang-Mills framework, gravitational and strong interactions can be unified in analogy with the unification in the electroweak theory. By gauging T(4) × [SU(3)] color in flat space-time, we have a unified model of chromo-gravity with a new tensor gauge field, which couples universally to all gluons, quarks and anti-quarks. The space-time translational gauge symmetry assures that all wave equations of quarks and gluons reduce to a Hamilton-Jacobi equation with the same 'effective Riemann metric tensors’ in the geometric-optics (or classical) limit. The emergence of effective metric tensors in the classical limit is essential for the unified model to agree with experiments. The unified model suggests that all gravitational, strong and electroweak interactions appear to be dictated by gauge symmetries in the generalized Yang-Mills framework. (author)
A Dual-Process Model of the Alcohol-Behavior Link for Social Drinking
Moss, Antony C.; Albery, Ian P.
2009-01-01
A dual-process model of the alcohol-behavior link is presented, synthesizing 2 of the major social-cognitive approaches: expectancy and myopia theories. Substantial evidence has accrued to support both of these models, and recent neurocognitive models of the effects of alcohol on thought and behavior have provided evidence to support both as well.…
Logical Reasoning versus Information Processing in the Dual-Strategy Model of Reasoning
Markovits, Henry; Brisson, Janie; de Chantal, Pier-Luc
2017-01-01
One of the major debates concerning the nature of inferential reasoning is between counterexample-based strategies such as mental model theory and statistical strategies underlying probabilistic models. The dual-strategy model, proposed by Verschueren, Schaeken, & d'Ydewalle (2005a, 2005b), which suggests that people might have access to both…
Raichlen, David A
2008-09-01
The dynamic similarity hypothesis (DSH) suggests that differences in animal locomotor biomechanics are due mostly to differences in size. According to the DSH, when the ratios of inertial to gravitational forces are equal between two animals that differ in size [e.g. at equal Froude numbers, where Froude = velocity2/(gravity x hip height)], their movements can be made similar by multiplying all time durations by one constant, all forces by a second constant and all linear distances by a third constant. The DSH has been generally supported by numerous comparative studies showing that as inertial forces differ (i.e. differences in the centripetal force acting on the animal due to variation in hip heights), animals walk with dynamic similarity. However, humans walking in simulated reduced gravity do not walk with dynamically similar kinematics. The simulated gravity experiments did not completely account for the effects of gravity on all body segments, and the importance of gravity in the DSH requires further examination. This study uses a kinematic model to predict the effects of gravity on human locomotion, taking into account both the effects of gravitational forces on the upper body and on the limbs. Results show that dynamic similarity is maintained in altered gravitational environments. Thus, the DSH does account for differences in the inertial forces governing locomotion (e.g. differences in hip height) as well as differences in the gravitational forces governing locomotion.
Unified cosmic history in modified gravity: From F(R) theory to Lorentz non-invariant models
Nojiri, Shin'Ichi; Odintsov, Sergei D.
2011-08-01
The classical generalization of general relativity is considered as the gravitational alternative for a unified description of the early-time inflation with late-time cosmic acceleration. The structure and cosmological properties of a number of modified theories, including traditional F(R) and Hořava-Lifshitz F(R) gravity, scalar-tensor theory, string-inspired and Gauss-Bonnet theory, non-local gravity, non-minimally coupled models, and power-counting renormalizable covariant gravity are discussed. Different representations of and relations between such theories are investigated. It is shown that some versions of the above theories may be consistent with local tests and may provide a qualitatively reasonable unified description of inflation with the dark energy epoch. The cosmological reconstruction of different modified gravities is provided in great detail. It is demonstrated that eventually any given universe evolution may be reconstructed for the theories under consideration, and the explicit reconstruction is applied to an accelerating spatially flat Friedmann-Robertson-Walker (FRW) universe. Special attention is paid to Lagrange multiplier constrained and conventional F(R) gravities, for latter F(R) theory, the effective ΛCDM era and phantom divide crossing acceleration are obtained. The occurrences of the Big Rip and other finite-time future singularities in modified gravity are reviewed along with their solutions via the addition of higher-derivative gravitational invariants.
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.
Gravity Data Analysis and Modelling for Basin Sedimen of Eastern Java Blocks
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)
A one-dimensional model of the semiannual oscillation driven by convectively forced gravity waves
Sassi, Fabrizio; Garcia, Rolando R.
1994-01-01
A one-dimensional model that solves the time-dependent equations for the zonal mean wind and a wave of specified zonal wavenumber has been used to illustrate the ability of gravity waves forced by time-dependent tropospheric heating to produce a semiannual oscillation (SAO) in the middle atmosphere. When the heating has a strong diurnal cycle, as observed over tropical landmasses, gravity waves with zonal wavelengths of a few thousand kilometers and phase velocities in the range +/- 40-50 m/sec are excited efficiently by the maximum vertical projection criterion (vertical wavelength approximately equals 2 x forcing depth). Calculations show that these waves can account for large zonal mean wind accelerations in the middle atmosphere, resulting in realistic stratopause and mesopause oscillations. Calculations of the temporal evolution of a quasi-conserved tracer indicate strong down-welling in the upper stratosphere near the equinoxes, which is associated with the descent of the SAO westerlies. In the upper mesosphere, there is a semiannual oscillation in tracer mixing ratio driven by seasonal variability in eddy mixing, which increases at the solstices and decreases at the equinoxes.
Nesseris, Savvas
2009-01-01
We consider theories with an arbitrary coupling between matter and gravity and obtain the perturbation equation of matter on subhorizon scales. Also, we derive the effective gravitational constant $G_{eff}$ and two parameters $\\Sigma$ and $\\eta$, which along with the perturbation equation...... of the matter density are useful to constrain the theory from growth factor and weak lensing observations. Finally, we use a completely solvable toy model which exhibits nontrivial phenomenology to investigate specific features of the theory. We obtain the analytic solution of the modified Friedmann equation...... for the scale factor $a$ in terms of time $t$ and use the age of the oldest star clusters and the primordial nucleosynthesis bounds in order to constrain the parameters of our toy model....
An assessment of gravity model improvements using TOPEX/Poseidon TDRSS observations
Putney, B. H.; Teles, J.; Eddy, W. F.; Klosko, S. M.
1992-01-01
The contribution of TOPEX/Poseidon (T/P) TDRSS data to geopotential model recovery is assessed. Simulated TDRSS one-way and Bilateration Ranging Transponder System (BRTS) observations have been generated and orbitally reduced to form normal equations for geopotential parameters. These normals have been combined with those of the latest prelaunch T/P gravity model solution using data from over 30 satellites. A study of the resulting solution error covariance shows that TDRSS can make important contributions to geopotential recovery, especially for improving T/P specific effects like those arising from orbital resonance. It is argued that future effort is desirable both to establish TDRSS orbit determination limits in a reference frame compatible with that used for the precise laser/DORIS orbits, and the reduction of these TDRSS data for geopotential recovery.
Constraining models of f(R) gravity with Planck and WiggleZ power spectrum data
Dossett, Jason; Hu, Bin; Parkinson, David
2014-03-01
In order to explain cosmic acceleration without invoking ``dark'' physics, we consider f(R) modified gravity models, which replace the standard Einstein-Hilbert action in General Relativity with a higher derivative theory. We use data from the WiggleZ Dark Energy survey to probe the formation of structure on large scales which can place tight constraints on these models. We combine the large-scale structure data with measurements of the cosmic microwave background from the Planck surveyor. After parameterizing the modification of the action using the Compton wavelength parameter B0, we constrain this parameter using ISiTGR, assuming an initial non-informative log prior probability distribution of this cross-over scale. We find that the addition of the WiggleZ power spectrum provides the tightest constraints to date on B0 by an order of magnitude, giving log10(B0) explanation.
Nesseris, Savvas
2009-01-01
We consider theories with an arbitrary coupling between matter and gravity and obtain the perturbation equation of matter on subhorizon scales. Also, we derive the effective gravitational constant G eff and two parameters Σ and η, which along with the perturbation equation of the matter density are useful to constrain the theory from growth factor and weak lensing observations. Finally, we use a completely solvable toy model which exhibits nontrivial phenomenology to investigate specific features of the theory. We obtain the analytic solution of the modified Friedmann equation for the scale factor a in terms of time t and use the age of the oldest star clusters and the primordial nucleosynthesis bounds in order to constrain the parameters of our toy model.
Gauge/gravity duality. A road towards reality
Kerner, Patrick
2012-01-01
In this dissertation we use gauge/gravity duality to investigate various phenomena of strongly coupled systems. In particular, we consider applications of the duality to real-world systems such as condensed matter systems and the quark-gluon plasma created by heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Gauge/gravity duality which originates from string theory relates strongly coupled gauge theories to weakly coupled gravity theories. This duality allows for computations of non-perturbative results on the field theory side by perturbative calculations on the gravity side. As we have learned in the recent years, the duality is especially suitable to describe hot and dense plasmas as well as real-time processes related to transport properties or spectral functions. Unfortunately, so far there is no dual gravity description modeling every aspect of a strongly coupled real-world system. However, there are many gravity duals which describe several phenomena. The general idea of this thesis is to study different gravity duals in order to develop a gravity description of hot and dense plasmas. In particular, we focus on physics in thermal equilibrium and close to equilibrium. Motivated by the experimentally observed mesonic resonances in the quark-gluon plasma, we first study quasinormal modes of a gravity dual which contains such resonances. The quasinormal modes on the gravity side are identified with the poles of the Green's function on the field theory side. By studying these quasinormal modes, we observe how quasiparticle resonances develop in a hot and dense plasma. We find interesting trajectories of quasinormal frequencies which may be found experimentally as the temperature and density is varied. In addition, we find an instability in the quasinormal mode spectrum at large chemical potential or magnetic field. At large chemical potential, this instability triggers the condensation of a field which breaks
Gauge/gravity duality. A road towards reality
Kerner, Patrick
2012-02-23
In this dissertation we use gauge/gravity duality to investigate various phenomena of strongly coupled systems. In particular, we consider applications of the duality to real-world systems such as condensed matter systems and the quark-gluon plasma created by heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Gauge/gravity duality which originates from string theory relates strongly coupled gauge theories to weakly coupled gravity theories. This duality allows for computations of non-perturbative results on the field theory side by perturbative calculations on the gravity side. As we have learned in the recent years, the duality is especially suitable to describe hot and dense plasmas as well as real-time processes related to transport properties or spectral functions. Unfortunately, so far there is no dual gravity description modeling every aspect of a strongly coupled real-world system. However, there are many gravity duals which describe several phenomena. The general idea of this thesis is to study different gravity duals in order to develop a gravity description of hot and dense plasmas. In particular, we focus on physics in thermal equilibrium and close to equilibrium. Motivated by the experimentally observed mesonic resonances in the quark-gluon plasma, we first study quasinormal modes of a gravity dual which contains such resonances. The quasinormal modes on the gravity side are identified with the poles of the Green's function on the field theory side. By studying these quasinormal modes, we observe how quasiparticle resonances develop in a hot and dense plasma. We find interesting trajectories of quasinormal frequencies which may be found experimentally as the temperature and density is varied. In addition, we find an instability in the quasinormal mode spectrum at large chemical potential or magnetic field. At large chemical potential, this instability triggers the condensation of a field which
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
A Dual Coding Theoretical Model of Decoding in Reading: Subsuming the LaBerge and Samuels Model
Sadoski, Mark; McTigue, Erin M.; Paivio, Allan
2012-01-01
In this article we present a detailed Dual Coding Theory (DCT) model of decoding. The DCT model reinterprets and subsumes The LaBerge and Samuels (1974) model of the reading process which has served well to account for decoding behaviors and the processes that underlie them. However, the LaBerge and Samuels model has had little to say about…
Gravity model improvement using the DORIS tracking system on the SPOT 2 satellite
Nerem, R. S.; Lerch, F. J.; Williamson, R. G.; Klosko, S. M.; Robbins, J. W.; Patel, G. B.
1994-01-01
A high-precision radiometric satellite tracking system, Doppler Orbitography and Radio-positioning Integrated by Satellite system (DORIS), has recently been developed by the French space agency, Centre National d'Etudes Spatiales (CNES). DORIS was designed to provide tracking support for missions such as the joint United States/French TOPEX/Poseidon. As part of the flight testing process, a DORIS package was flown on the French SPOT 2 satellite. A substantial quantity of geodetic quality tracking data was obtained on SPOT 2 from an extensive international DORIS tracking network. These data were analyzed to assess their accuracy and to evaluate the gravitational modeling enhancements provided by these data in combination with the Goddard Earth Model-T3 (GEM-T3) gravitational model. These observations have noise levels of 0.4 to 0.5 mm/s, with few residual systematic effects. Although the SPOT 2 satellite experiences high atmospheric drag forces, the precision and global coverage of the DORIS tracking data have enabled more extensive orbit parameterization to mitigate these effects. As a result, the SPOT 2 orbital errors have been reduced to an estimated radial accuracy in the 10-20 cm RMS range. The addition of these data, which encompass many regions heretofore lacking in precision satellite tracking, has significantly improved GEM-T3 and allowed greatly improved orbit accuracies for Sun-synchronous satellites like SPOT 2 (such as ERS 1 and EOS). Comparison of the ensuing gravity model with other contemporary fields (GRIM-4C2, TEG2B, and OSU91A) provides a means to assess the current state of knowledge of the Earth's gravity field. Thus, the DORIS experiment on SPOT 2 has provided a strong basis for evaluating this new orbit tracking technology and has demonstrated the important contribution of the DORIS network to the success of the TOPEX/Poseidon mission.
Pricing Model for Dual Sales Channel with Promotion Effect Consideration
Chuiri Zhou
2016-01-01
Full Text Available We focus on the pricing strategy of a dual sales channel member when his/her online retailer faces an upcoming overloaded express delivery service due to the sales peak of online shopping, especially referring to the occurring affairs in China. We characterize the pricing problem of the dual selling channel system as a two-period game. When the price discount is only provided by the online seller, we find that the prices of the traditional channel and the online channel in the two periods are higher while the overloaded degree of express delivery is lower and the overloaded delivery services can decrease the profits of both channels. When the price discounts are provided by both traditional and online sellers, we find that the derived Nash price equilibrium of both channels includes five possible combinations of prices. Both traditional and online sellers will choose their price strategies, respectively, according to their cost advantages which are affected by the overloaded degree of express delivery.
Glöckner, A.; Witteman, C.L.M.
2010-01-01
Intuitive-automatic processes are crucial for making judgements and decisions. The fascinating complexity of these processes has attracted many decision researchers, prompting them to start investigating intuition empirically and to develop numerous models. Dual-process models assume a clear
The Dual-Factor Model of Mental Health: Further Study of the Determinants of Group Differences
Lyons, Michael D.; Huebner, E. Scott; Hills, Kimberly J.; Shinkareva, Svetlana V.
2012-01-01
Consistent with a positive psychology framework, this study examined the contributions of personality, environmental, and perceived social support variables in classifying adolescents using Greenspoon and Saklofske's Dual-Factor model of mental health. This model incorporates information about positive subjective well-being (SWB), along with…
The dual pathway model of overeating. Replication and extension with actual food consumption
Ouwens, M.A.; Strien, T. van; Leeuwe, J.F.J. van; Staak, C.P.F. van der
2009-01-01
van Strien et al. [van Strien, T., Engels, R. C. M. E., van Leeuwe, J., Snoek, H. M. (2005). The Stice model of overeating: tests in clinical and non-clinical samples. Appetite, 45, 205–213] extended the negative affect pathway of Stice's dual pathway model of overeating Stice [Stice, E. (1994).
The dual pathway model of overeating. Replication and extension with actual food consumption
Ouwens, Machteld A; van Strien, T; Leeuwe, J.F.J.; van der Staak, C P F
van Strien et al. [van Strien, T., Engels, R. C. M. E., van Leeuwe, J., Snoek, H. M. (2005). The Stice model of overeating: tests in clinical and non-clinical samples. Appetite, 45, 205-213] extended the negative affect pathway of Stice's dual pathway model of overeating Stice [Stice, E. (1994).
Dual-Extrusion 3D Printing of Anatomical Models for Education
Smith, Michelle L.; Jones, James F. X.
2018-01-01
Two material 3D printing is becoming increasingly popular, inexpensive and accessible. In this paper, freely available printable files and dual extrusion fused deposition modelling were combined to create a number of functional anatomical models. To represent muscle and bone FilaFlex[superscript 3D] flexible filament and polylactic acid (PLA)…
A Dual-Stage Two-Phase Model of Selective Attention
Hubner, Ronald; Steinhauser, Marco; Lehle, Carola
2010-01-01
The dual-stage two-phase (DSTP) model is introduced as a formal and general model of selective attention that includes both an early and a late stage of stimulus selection. Whereas at the early stage information is selected by perceptual filters whose selectivity is relatively limited, at the late stage stimuli are selected more efficiently on a…
Forward-backward correlations in pp interactions in a dual model
Fialkowsky, K.; Kotanski, A.; Uniwersytet Jagiellonski, Krakow
1982-01-01
Forward-backward correlations in lepton and hadron induced processes are compared according to the dual model. It is indicated that the effect of the chain energy spread in hadron processes is important. After including this effect the model is shown to explain the forward-backward correlations in pp data assuming no dynamical correlations within a single chain. (orig.)
Chrysikopoulos, Constantinos V; Syngouna, Vasiliki I
2014-06-17
The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition.
Michael Leitch
2018-01-01
Full Text Available Complex engineering systems often require extensive coordination between different expert areas in order to avoid costly design iterations and rework. Cyber-physics system (CPS engineering methods could provide valuable insights to help model these interactions and optimize the design of such systems. In this work, steam assisted gravity drainage (SAGD, a complex oil extraction process that requires deep understanding of several physical-chemical phenomena, is examined whereby the complexities and interdependencies of the system are explored. Based on an established unified feature modeling scheme, a software modeling framework is proposed to manage the design process of the production tools used for SAGD oil extraction. Applying CPS methods to unify complex phenomenon and engineering models, the proposed CPS model combines effective simulation with embedded knowledge of completion tooling design in order to optimize reservoir performance. The system design is expressed using graphical diagrams of the unified modelling language (UML convention. To demonstrate the capability of this system, a distributed research group is described, and their activities coordinated using the described CPS model.
Astronomical Constraints on Some Long-Range Models of Modified Gravity
Lorenzo Iorio
2007-01-01
Full Text Available We use the corrections to the Newton-Einstein secular precessions of the longitudes of the perihelia of the inner planets, phenomenologically estimated E.V. Pitjeva by fitting almost one century of data with the EPM2004 ephemerides, to constrain some long-range models of modified gravity recently put forth to address the dark energy and dark matter problems. They are the four-dimensional ones obtained with the addition of inverse powers and logarithm of some curvature invariants, and the DGP multidimensional braneworld model. After working out the analytical expressions of the secular perihelion precessions induced by the corrections to the Newtonian potential of such models, we compare them to the estimated extra-rates of perihelia by taking their ratio for different pairs of planets instead of using one perihelion at a time for each planet separately, as done so far in literature. The curvature invariants-based models are ruled out, even by rescaling by a factor 10 the errors in the estimated planetary orbital parameters. Less neat is the situation for the DGP model. Only the general relativistic Lense-Thirring effect, not included, as the other exotic models considered here, by Pitjeva in the EPM force models, passes such a test.
Shear-free axial model in massive Brans–Dicke gravity
Sharif, M., E-mail: msharif.math@pu.edu.pk [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan); Manzoor, Rubab, E-mail: rubab.manzoor@umt.edu.pk [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan); Department of Mathematics, University of Management and Technology, Johar Town Campus, Lahore-54782 (Pakistan)
2017-01-15
This paper explores the influences of dark energy on the shear-free axially symmetric evolution by considering self-interacting Brans–Dicke gravity as a dark energy candidate. We describe energy source of the model and derive all the effective dynamical variables as well as effective structure scalars. It is found that scalar field is one of the sources of anisotropy and dissipation. The resulting effective structure scalars help to study the dynamics associated with dark energy in any axial configuration. In order to investigate shear-free evolution, we formulate a set of governing equations along with heat transport equation. We discuss consequences of shear-free condition upon different SBD fluid models like dissipative non-geodesic and geodesic models. For dissipative non-geodesic case, the rotational distribution turns out to be the necessary and sufficient condition for radiating model. The dissipation depends upon inhomogeneous expansion. The geodesic model is found to be irrotational and non-radiating. The non-dissipative geodesic model leads to FRW model for positive values of the expansion parameter.
Sharma, S; Turner, M M
2013-01-01
Dual-frequency capacitive discharges are widespread in the semiconductor industry and are used, for example, in etching of semiconductor materials to manufacture microchips. In low-pressure dual radio-frequency capacitive discharges, stochastic heating is an important phenomenon. Recent theoretical work on this problem using several different approaches has produced results that are broadly in agreement insofar as scaling with the discharge parameters is concerned, but there remains some disagreement in detail concerning the absolute size of the effect for the case of dual-frequency capacitive discharges. In this work, we investigate the dependence of stochastic heating on various discharge parameters with the help of particle-in-cell (PIC) simulation. The dual-frequency analytical models are in fair agreement with PIC results for values of the low-frequency current density amplitude J lf (or dimensionless control parameter H lf ∼ 5) typical of many modern experiments. However, for higher values of J lf (or higher H lf ), new physical phenomena (like field reversal, reflection of ions, etc) appear and the simulation results deviate from existing dual-frequency analytical models. On the other hand, for lower J lf (or lower H lf ) again the simulation results deviate from analytical models. So this research work produces a relatively extensive set of simulation data that may be used to validate theories over a wide range of parameters. (paper)
New Higgs transitions between dual N=2 string models
Berglund, P.; Katz, S.; Klemm, A.; Mayr, P.
1997-01-01
We describe a new kind of transition between topologically distinct N=2 type II Calabi-Yau vacua through points with enhanced non-abelian gauge symmetries together with fundamental charged matter hyper multiplets. We connect the appearance of matter to the local geometry of the singularity and discuss the relation between the instanton numbers of the Calabi-Yau manifolds taking part in the transition. In a dual heterotic string theory on K3 x T 2 the process corresponds to Higgsing a semi-classical gauge group or equivalently to a variation of the gauge bundle. In special cases the situation reduces to simple conifold transitions in the Coulomb phase of the non-abelian gauge symmetries. (orig.)
Modeling the Salar de Uyuni, Bolivia as an Equipotential Surface of Earth's Gravity Field
Borsa, Adrian; Bills, Bruce
2004-01-01
The salar de Uyuni is a massive dry salt lake that lies at the lowest point of an internal/drainage basin in the Bolivian Altiplano. Its topography is remarkable for its extraordinary flatness over almost a full degree of latitude and longitude. We surveyed a 54 x 45 km region of the salar with kinematic GPS in September, 2002 and found a topographic range of only 80 cm over the entire surveyed area. Furthermore, the survey revealed distinct surface features with several dominant wavelengths and orientations. Some of these appear to be aligned with orographic features that intersect the salar, leading us to conjecture that they are the surface expression of high-density mountains that have been buried by low-density basin sediments. Over the oceans, a similar correspondence between basin bathymetry and surface topography is exploited to map the seafloor using sea-surface satellite altimetry measurements, with the sea surface following geoid undulations due to the underwater mass distribution. On the salar, annual flooding creates a shallow lake whose surface also lies on a equipotential surface shaped by the distribution of underlying mass. The link to the actual salar surface is via the dissolution and redeposition of salt by the lake waters, which appears to push the system to an equilibrium of constant water depth and the coincidence of the shapes of the lake surface and bottom. To test our hypothesis about the origin of the surface features on the salar, we compare our GPS survey elevations with the equipotential surface generated from local gravity measurements in conjunction with gravity and potential values from the EGM96 global geopotential model. 50% of the variance of the GPS elevations can be explained by equipotential surface undulations from the EGM96 model alone, and an additional 40% is explained by the shorter-wavelength equipotential surface derived from local gravity. We examine the unexplained 10% of elevation variance from the standpoint of