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Sample records for gravity gradiometer agg

  1. Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  2. Superconducting gravity gradiometer for sensitive gravity measurements. II. Experiment

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  3. Quantum Gravity Gradiometer Development for Space

    Science.gov (United States)

    Kohel, James M.; Yu, Nan; Kellogg, James R.; Thompson, Robert J.; Aveline, David C.; Maleki, Lute

    2006-01-01

    Funded by the Advanced Technology Component Program, we have completed the development of a laboratory-based quantum gravity gradiometer based on atom interferometer technology. This is our first step towards a new spaceborne gradiometer instrument, which can significantly contribute to global gravity mapping and monitoring important in the understanding of the solid earth, ice and oceans, and dynamic processes. In this paper, we will briefly review the principles and technical benefits of atom-wave interferometer-based inertial sensors in space. We will then describe the technical implementation of the laboratory setup and report its status. We will also discuss our implementation plan for the next generation instrument.

  4. Progress towards a space-borne quantum gravity gradiometer

    Science.gov (United States)

    Yu, Nan; Kohel, James M.; Ramerez-Serrano, Jaime; Kellogg, James R.; Lim, Lawrence; Maleki, Lute

    2004-01-01

    Quantum interferometer gravity gradiometer for 3D mapping is a project for developing the technology of atom interferometer-based gravity sensor in space. The atom interferometer utilizes atomic particles as free fall test masses to measure inertial forces with unprecedented sensitivity and precision. It also allows measurements of the gravity gradient tensor components for 3D mapping of subsurface mass distribution. The overall approach is based on recent advances of laser cooling and manipulation of atoms in atomic and optical physics. Atom interferometers have been demonstrated in research laboratories for gravity and gravity gradient measurements. In this approach, atoms are first laser cooled to micro-kelvin temperatures. Then they are allowed to freefall in vacuum as true drag-free test masses. During the free fall, a sequence of laser pulses is used to split and recombine the atom waves to realize the interferometric measurements. We have demonstrated atom interferometer operation in the Phase I period, and we are implementing the second generation for a complete gradiometer demonstration unit in the laboratory. Along with this development, we are developing technologies at component levels that will be more suited for realization of a space instrument. We will present an update of these developments and discuss the future directions of the quantum gravity gradiometer project.

  5. Atom interferometric gravity gradiometer: Disturbance compensation and mobile gradiometry

    Science.gov (United States)

    Mahadeswaraswamy, Chetan

    First ever mobile gravity gradient measurement based on Atom Interferometric sensors has been demonstrated. Mobile gravity gradiometers play a significant role in high accuracy inertial navigation systems in order to distinguish inertial acceleration and acceleration due to gravity. The gravity gradiometer consists of two atom interferometric accelerometers. In each of the accelerometer an ensemble of laser cooled Cesium atoms is dropped and using counter propagating Raman pulses (pi/2-pi-pi/2) the ensemble is split into two states for carrying out atom interferometry. The interferometer phase is proportional to the specific force experienced by the atoms which is a combination of inertial acceleration and acceleration due to gravity. The difference in phase between the two atom interferometric sensors is proportional to gravity gradient if the platform does not undergo any rotational motion. However, any rotational motion of the platform induces spurious gravity gradient measurements. This apparent gravity gradient due to platform rotation is considerably different for an atom interferometric sensor compared to a conventional force rebalance type sensor. The atoms are in free fall and are not influenced by the motion of the case except at the instants of Raman pulses. A model for determining apparent gravity gradient due to rotation of platform was developed and experimentally verified for different frequencies. This transfer function measurement also lead to the development of a new technique for aligning the Raman laser beams with the atom clusters to within 20 mu rad. This gravity gradiometer is situated in a truck for the purpose of undertaking mobile surveys. A disturbance compensation system was designed and built in order to compensate for the rotational disturbances experienced on the floor of a truck. An electric drive system was also designed specifically to be able to move the truck in a uniform motion at very low speeds of about 1cm/s. A 250 x10-9 s-2

  6. Assessment and Risk Mitigation Strategies for the Atom Interferometer Gravity Gradiometer Seed Lasers

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA GSFC has been working on an ESTO IIP - Cold Atom Gravity Gradiometer (CAGG)/Atom Interferometer Gravity Gradiometer (AIGG) for Geodesy since 2014 (Saif/551 –...

  7. Superconducting gravity gradiometer and a test of inverse square law

    International Nuclear Information System (INIS)

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

    1989-01-01

    The equivalence principle prohibits the distinction of gravity from acceleration by a local measurement. However, by making a differential measurement of acceleration over a baseline, platform accelerations can be cancelled and gravity gradients detected. In an in-line superconducting gravity gradiometer, this differencing is accomplished with two spring-mass accelerometers in which the proof masses are confined to motion in a single degree of freedom and are coupled together by superconducting circuits. Platform motions appear as common mode accelerations and are cancelled by adjusting the ratio of two persistent currents in the sensing circuit. The sensing circuit is connected to a commercial SQUID amplifier to sense changes in the persistent currents generated by differential accelerations, i.e., gravity gradients. A three-axis gravity gradiometer is formed by mounting six accelerometers on the faces of a precision cube, with the accelerometers on opposite faces of the cube forming one of three in-line gradiometers. A dedicated satellite mission for mapping the earth's gravity field is an important one. Additional scientific goals are a test of the inverse square law to a part in 10(exp 10) at 100 km, and a test of the Lense-Thirring effect by detecting the relativistic gravity magnetic terms in the gravity gradient tensor for the earth

  8. Gravity gradiometer system for Earth Exploration

    NARCIS (Netherlands)

    Cuperus, R.; Flokstra, F.F.; Droogendijk, H.; Wiegerink, Remco J.; Flokstra, Jakob; Flokstra, Jan

    2009-01-01

    We develop a gravity gradiometer (GG) for use on planetary missions to planets like Mars and Jupiter. With some modifications this development is extended to include (airborne) applications for the Dutch exploratory industry. We adapt key technology of the space based GG for the use in an

  9. A Transportable Gravity Gradiometer Based on Atom Interferometry

    Science.gov (United States)

    Yu, Nan; Thompson, Robert J.; Kellogg, James R.; Aveline, David C.; Maleki, Lute; Kohel, James M.

    2010-01-01

    A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving

  10. Development of an Atom Interferometer Gravity Gradiometer for Earth Sciences

    Science.gov (United States)

    Rakholia, A.; Sugarbaker, A.; Black, A.; Kasecivh, M.; Saif, B.; Luthcke, S.; Callahan, L.; Seery, B.; Feinberg, L.; Mather, J.; hide

    2017-01-01

    We report progress towards a prototype atom interferometer gravity gradiometer for Earth science studies from a satellite in low Earth orbit.The terrestrial prototype has a target sensitivity of 8 x 10(exp -2) E/Hz(sup 1/2) and consists of two atom sources running simultaneous interferometers with interrogation time T = 300 ms and 12 hk photon recoils, separated by a baseline of 2 m. By employing Raman side band cooling and magnetic lensing, we will generate atomic ensembles with N = 10(exp 6) atoms at a temperature of 3 nK. The sensitivity extrapolates to 7 x 10(exp -5) E/Hz(sup 1/2) in microgravity on board a satellite. Simulations derived from this sensitivity demonstrate a monthly time-variable gravity accuracy of 1 cm equivalent water height at 200 km resolution, yielding an improvement over GRACE by 1-2 orders of magnitude. A gravity gradiometer with this sensitivity would also benefit future planetary, lunar, and asteroidal missions.

  11. Semiconductor Master Oscillator Power Amplifier for Gravity Gradiometer and Other Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA GSFC has been working on an ESTO funded Instrument Incubator Program (IIP) Cold Atom Gravity Gradiometer for Geodesy since 2014. Significant progresses have...

  12. Towards a space-borne quantum gravity gradiometer: progress in laboratory demonstration

    Science.gov (United States)

    Yu, Nan; Kohel, James M.; Kellogg, James R.; Maleki, Lute

    2005-01-01

    This paper describes the working principles and technical benefits of atom-wave interferometer-based inertial sensors, and gives a progress report on the development of a quantum gravity gradiometer for space applications at JPL.

  13. Tunable Superconducting Gravity Gradiometer for Mars Climate, Atmosphere, and Gravity Field Investigation

    Science.gov (United States)

    Griggs, C. E.; Paik, H. J.; Moody, M. V.; Han, S.-C.; Rowlands, D. D.; Lemoine, F. G.; Shirron, P. J.

    2015-01-01

    We are developing a compact tensor superconducting gravity gradiometer (SGG) for obtaining gravimetric measurements from planetary orbits. A new and innovative design gives a potential sensitivity of approximately 10(sup -4) E Hz(sup - 1/2)( 1 E = 10(sup -9 S(sup -2) in the measurement band up to 0.1 Hz (suitale for short wavelength static gravity) and of approximately 10(sup -4) E Hz(sup - 1/2) in the frequency band less than 1 mHz (for long wavelength time-variable gravity) from the same device with a baseline just over 10 cm. The measurement band and sensitiy can be optimally tuned in-flight during the mission by changing resonance frequencies, which allows meaurements of both static and time-variable gravity fields from the same mission. Significant advances in the technologies needed for space-based cryogenic instruments have been made in the last decade. In particular, the use of cryocoolers will alleviate the previously severe constraint on mission lifetime imposed by the use of liquid helium, enabling mission durations in the 5 - 10 year range.

  14. Simulation-based evaluation of a cold atom interferometry gradiometer concept for gravity field recovery

    Science.gov (United States)

    Douch, Karim; Wu, Hu; Schubert, Christian; Müller, Jürgen; Pereira dos Santos, Franck

    2018-03-01

    The prospects of future satellite gravimetry missions to sustain a continuous and improved observation of the gravitational field have stimulated studies of new concepts of space inertial sensors with potentially improved precision and stability. This is in particular the case for cold-atom interferometry (CAI) gradiometry which is the object of this paper. The performance of a specific CAI gradiometer design is studied here in terms of quality of the recovered gravity field through a closed-loop numerical simulation of the measurement and processing workflow. First we show that mapping the time-variable field on a monthly basis would require a noise level below 5mE /√{Hz } . The mission scenarios are therefore focused on the static field, like GOCE. Second, the stringent requirement on the angular velocity of a one-arm gradiometer, which must not exceed 10-6 rad/s, leads to two possible modes of operation of the CAI gradiometer: the nadir and the quasi-inertial mode. In the nadir mode, which corresponds to the usual Earth-pointing satellite attitude, only the gradient Vyy , along the cross-track direction, is measured. In the quasi-inertial mode, the satellite attitude is approximately constant in the inertial reference frame and the 3 diagonal gradients Vxx,Vyy and Vzz are measured. Both modes are successively simulated for a 239 km altitude orbit and the error on the recovered gravity models eventually compared to GOCE solutions. We conclude that for the specific CAI gradiometer design assumed in this paper, only the quasi-inertial mode scenario would be able to significantly outperform GOCE results at the cost of technically challenging requirements on the orbit and attitude control.

  15. Sensitive Superconducting Gravity Gradiometer Constructed with Levitated Test Masses

    Science.gov (United States)

    Griggs, C. E.; Moody, M. V.; Norton, R. S.; Paik, H. J.; Venkateswara, K.

    2017-12-01

    We demonstrate basic operations of a two-component superconducting gravity gradiometer (SGG) that is constructed with a pair of magnetically levitated test masses coupled to superconducting quantum-interference devices. A design that gives a potential sensitivity of 1.4 ×10-4 E Hz-1 /2 (1 E ≡10-9 s-2 ) in the frequency band of 1 to 50 mHz and better than 2 ×10-5 E Hz-1 /2 between 0.1 and 1 mHz for a compact tensor SGG that fits within a 22-cm-diameter sphere. The SGG has the capability of rejecting the platform acceleration and jitter in all 6 degrees of freedom to one part in 109 . Such an instrument has applications in precision tests of fundamental laws of physics, earthquake early warning, and gravity mapping of Earth and the planets.

  16. Status of the planar electrostatic gradiometer GREMLIT for airborne geodesy

    Science.gov (United States)

    Lebat, V.; Foulon, B.; Christophe, B.; Huynh, P. A.; Liorzou, F.; Boulanger, D.

    2017-12-01

    Taking advantage of technologies, developed by ONERA for the GRACE, GOCE and GRACE FOLLOW-ON space missions, the GREMLIT airborne gravity gradiometer is based of a planar electrostatic gradiometer configuration. The feasibility of the instrument and of its performance was proved by realistic simulations, based on actual data and recorded environmental aircraft perturbations, with performance of about one Eötvös along the two horizontal components of the gravity gradient. The performance of the gradiometer is directly linked to the stabilized platform, controlled by the common mode outputs of the instrument itself, in order to reject the perturbations induced by the airborne environment in the horizontal directions. After the definition of the architecture of the stabilized platform to achieve the global performance of the gradiometer, the platform has been manufactured and integrated. In order to assess the operation of the electrostatic gradiometer on its associated stabilized platform, a one axis prototype has also been built. The poster will emphasize the status of realization and first tests of the instrument and of its stabilized platform.

  17. Bragg gravity-gradiometer using the 1S0–3P1 intercombination transition of 88Sr

    Science.gov (United States)

    del Aguila, R. P.; Mazzoni, T.; Hu, L.; Salvi, L.; Tino, G. M.; Poli, N.

    2018-04-01

    We present a gradiometer based on matter-wave interference of alkaline-earth-metal atoms, namely 88Sr. The coherent manipulation of the atomic external degrees of freedom is obtained by large-momentum-transfer Bragg diffraction, driven by laser fields detuned away from the narrow 1S0–3P1 intercombination transition. We use a well-controlled artificial gradient, realized by changing the relative frequencies of the Bragg pulses during the interferometer sequence, in order to characterize the sensitivity of the gradiometer. The sensitivity reaches 1.5 × 10‑5 s‑2 for an interferometer time of 20 ms, limited only by geometrical constraints. We observed extremely low sensitivity of the gradiometric phase to magnetic field gradients, approaching a value 104 times lower than the sensitivity of alkali-atom based gradiometers, limited by the interferometer sensitivity. An efficient double-launch technique employing accelerated red vertical lattices from a single magneto-optical trap cloud is also demonstrated. These results highlight strontium as an ideal candidate for precision measurements of gravity gradients, with potential application in future precision tests of fundamental physics.

  18. STMD Laser Lifetest Program Space Gradiometer

    Data.gov (United States)

    National Aeronautics and Space Administration — Design and initiate lifetest activities on laser transmitter for the Cold Atom Gravity Gradiometer (CAGG) with funding from NASA STMD.This proposed task is to...

  19. Characterization of a dc SQUID based accelerometer circuit for a superconducting gravity gradiometer

    International Nuclear Information System (INIS)

    Scharnweber, R.; Lumley, J.M.

    1999-01-01

    A demonstrator set-up to test superconducting components has been designed and fabricated in order to characterize their functionality for use in a superconducting gravity gradiometer. The displacement of a freely oscillating levitated niobium proof mass in this acceleration transducer is measured inductively and read out by a direct current superconducting quantum interference device. It has been confirmed experimentally that the oscillation frequency depends on the current of the levitation magnet that is operated in persistent-current mode. The results allow us to establish testing and operational procedures that can be used in a more complex multichannel system to confirm functionality and to adjust the levitated proof mass. (author)

  20. Characterization of a dc SQUID based accelerometer circuit for a superconducting gravity gradiometer

    Energy Technology Data Exchange (ETDEWEB)

    Scharnweber, R.; Lumley, J.M. [Oxford Instruments, Scientific Research Division, Research Instruments (Cambridge), Newton House, Cambridge Business Park, Cowley Road, Cambridge CB4 4WZ (United Kingdom)

    1999-11-01

    A demonstrator set-up to test superconducting components has been designed and fabricated in order to characterize their functionality for use in a superconducting gravity gradiometer. The displacement of a freely oscillating levitated niobium proof mass in this acceleration transducer is measured inductively and read out by a direct current superconducting quantum interference device. It has been confirmed experimentally that the oscillation frequency depends on the current of the levitation magnet that is operated in persistent-current mode. The results allow us to establish testing and operational procedures that can be used in a more complex multichannel system to confirm functionality and to adjust the levitated proof mass. (author)

  1. Tuning the Stiffness Balance Using Characteristic Frequencies as a Criterion for a Superconducting Gravity Gradiometer

    Science.gov (United States)

    Liu, Xikai; Ma, Dong; Chen, Liang; Liu, Xiangdong

    2018-01-01

    Tuning the stiffness balance is crucial to full-band common-mode rejection for a superconducting gravity gradiometer (SGG). A reliable method to do so has been proposed and experimentally tested. In the tuning scheme, the frequency response functions of the displacement of individual test mass upon common-mode accelerations were measured and thus determined a characteristic frequency for each test mass. A reduced difference in characteristic frequencies between the two test masses was utilized as the criterion for an effective tuning. Since the measurement of the characteristic frequencies does not depend on the scale factors of displacement detection, stiffness tuning can be done independently. We have tested this new method on a single-component SGG and obtained a reduction of two orders of magnitude in stiffness mismatch. PMID:29419796

  2. Calibration of a rotating accelerometer gravity gradiometer using centrifugal gradients

    Science.gov (United States)

    Yu, Mingbiao; Cai, Tijing

    2018-05-01

    The purpose of this study is to calibrate scale factors and equivalent zero biases of a rotating accelerometer gravity gradiometer (RAGG). We calibrate scale factors by determining the relationship between the centrifugal gradient excitation and RAGG response. Compared with calibration by changing the gravitational gradient excitation, this method does not need test masses and is easier to implement. The equivalent zero biases are superpositions of self-gradients and the intrinsic zero biases of the RAGG. A self-gradient is the gravitational gradient produced by surrounding masses, and it correlates well with the RAGG attitude angle. We propose a self-gradient model that includes self-gradients and the intrinsic zero biases of the RAGG. The self-gradient model is a function of the RAGG attitude, and it includes parameters related to surrounding masses. The calibration of equivalent zero biases determines the parameters of the self-gradient model. We provide detailed procedures and mathematical formulations for calibrating scale factors and parameters in the self-gradient model. A RAGG physical simulation system substitutes for the actual RAGG in the calibration and validation experiments. Four point masses simulate four types of surrounding masses producing self-gradients. Validation experiments show that the self-gradients predicted by the self-gradient model are consistent with those from the outputs of the RAGG physical simulation system, suggesting that the presented calibration method is valid.

  3. A Room-Temperature Pre-calibration Procedure for Gradiometer Sifting

    International Nuclear Information System (INIS)

    Zhang Shu-Lin; Liu Yang-Bo; Wang Yong-Liang; Kong Xiang-Yan; Xie Xiao-Ming; Liu Ming

    2011-01-01

    In order to detect extremely weak magnetic signals, superconducting quantum interference device (SQUID) gradiometers are widely used to suppress environmental noise. A hardware SQUID gradiometer consists of a niobium gradio-antenna and an SQUID, which are coupled via an input coil. Here gradiometer imbalance may greatly reduce its noise suppression performance. The gradiometer balance depends on the geometrical forms of the antenna wound by niobium wire. We describe a simple method based on Faraday's law for the pre-calibration of the gradiometer balance at room temperature, before the gradiometer is set up. The pre-calibrating results are compared with the measured balance of an SQUID gradiometer system. This method may be used for sifting hardware gradiometers for multi-channel systems. (cross-disciplinary physics and related areas of science and technology)

  4. AGG Maailmameistrivõistluste eel

    Index Scriptorium Estoniae

    2008-01-01

    12.-14. juunini toimuvad Torontos Aesthetic Group Gymnastics (AGG) maailmameistrivõistlused Toronto Ülikooli võimlemiskeskuses. Nende võistluste korraldamise raske ülesande on võtnud oma õlule Kanada eestlaste võimlemisklubid Kalev Estienne ja Ritmika vastavalt Evelyn Koobi ja Annely Riga juhtimisel

  5. Preprocessing of gravity gradients at the GOCE high-level processing facility

    NARCIS (Netherlands)

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

    2008-01-01

    One of the products derived from the gravity field and steady-state ocean circulation explorer (GOCE) observations are the gravity gradients. These gravity gradients are provided in the gradiometer reference frame (GRF) and are calibrated in-flight using satellite shaking and star sensor data. To

  6. Choice of Magnetometers and Gradiometers after Signal Space Separation.

    Science.gov (United States)

    Garcés, Pilar; López-Sanz, David; Maestú, Fernando; Pereda, Ernesto

    2017-12-16

    Modern Elekta Neuromag MEG devices include 102 sensor triplets containing one magnetometer and two planar gradiometers. The first processing step is often a signal space separation (SSS), which provides a powerful noise reduction. A question commonly raised by researchers and reviewers relates to which data should be employed in analyses: (1) magnetometers only, (2) gradiometers only, (3) magnetometers and gradiometers together. The MEG community is currently divided with regard to the proper answer. First, we provide theoretical evidence that both gradiometers and magnetometers result from the backprojection of the same SSS components. Then, we compare resting state and task-related sensor and source estimations from magnetometers and gradiometers in real MEG recordings before and after SSS. SSS introduced a strong increase in the similarity between source time series derived from magnetometers and gradiometers (r² = 0.3-0.8 before SSS and r² > 0.80 after SSS). After SSS, resting state power spectrum and functional connectivity, as well as visual evoked responses, derived from both magnetometers and gradiometers were highly similar (Intraclass Correlation Coefficient > 0.8, r² > 0.8). After SSS, magnetometer and gradiometer data are estimated from a single set of SSS components (usually ≤ 80). Equivalent results can be obtained with both sensor types in typical MEG experiments.

  7. High-Tc SQUID gradiometer system for magnetocardiography in an unshielded environment

    International Nuclear Information System (INIS)

    Liao, S H; Hsu, S C; Lin, C C; Horng, H E; Chen, J C; Chen, M J; Wu, C H; Yang, H C

    2003-01-01

    We set up an electronic gradiometer for magnetocardiography (MCG) in an unshielded environment. The electronically balanced gradiometer consists of high-temperature radio-frequency superconducting quantum interference device (rf SQUID) magnetometers. The rf SQUID magnetometers are arranged to form the electronic first-order, four-vector gradiometer, or second-order gradiometer. The output of the MCG signal was filtered by a band pass (1-30 Hz) and power line filters. We can reduce the noise to ∼1 pT Hz -1/2 at 1 Hz for second-order or four-vector gradiometers. Two-dimensional MCG imaging is demonstrated. The results are discussed with data measured in the moderate magnetically shielded environment

  8. Development of new test procedures for measuring fine and coarse aggregates specific gravity.

    Science.gov (United States)

    2009-09-01

    The objective of the research is to develop and evaluate new test methods at determining the specific gravity and absorption of both fine and coarse aggregates. Current methods at determining the specific gravity and absorption of fine and coarse agg...

  9. DU-AGG pilot plant design study

    International Nuclear Information System (INIS)

    Lessing, P.A.; Gillman, H.

    1996-07-01

    The Idaho National Engineering Laboratory (INEL) is developing new methods to produce high-density aggregate (artificial rock) primarily consisting of depleted uranium oxide. The objective is to develop a low-cost method whereby uranium oxide powder (UO[sub 2], U[sub 3]O[sub ]8, or UO[sub 3]) can be processed to produce high-density aggregate pieces (DU-AGG) having physical properties suitable for disposal in low-level radioactive disposal facilities or for use as a component of high-density concrete used as shielding for radioactive materials. A commercial company, G-M Systems, conducted a design study for a manufacturing pilot plant to process DU-AGG. The results of that study are included and summarized in this report. Also explained are design considerations, equipment capacities, the equipment list, system operation, layout of equipment in the plant, cost estimates, and the proposed plan and schedule

  10. On gradiometer imbalance

    NARCIS (Netherlands)

    Uzunbajakau, S.A.; Rijpma, A.P.; Brake, ter H.J.M.; Peters, M.J.

    2006-01-01

    We present methods to compute the imbalance in a gradiometer of arbitrary shape due to imperfections in its geometry, eddy currents induced in the radio-frequency interference shield, and screening currents induced in the modules of the superconducting quantum interference devices (SQUIDs). As an

  11. Calibration of triaxial fluxgate gradiometer

    International Nuclear Information System (INIS)

    Vcelak, Jan

    2006-01-01

    The description of simple and fast calibration procedures used for double-probe triaxial fluxgate gradiometer is provided in this paper. The calibration procedure consists of three basic steps. In the first step both probes are calibrated independently in order to reach constant total field reading in every position. Both probes are numerically aligned in the second step in order that the gradient reading is zero in homogenous magnetic field. The third step consists of periodic drift calibration during measurement. The results and detailed description of each calibration step are presented and discussed in the paper. The gradiometer is finally verified during the detection of the metal object in the measuring grid

  12. L’Allgemeine Gleichbehandlungsgesetz (AGG: Lex sum, nihil humani a me alienum puto

    Directory of Open Access Journals (Sweden)

    Stefano Testa Bappenheim

    2011-03-01

    Full Text Available SOMMARIO: 1. Introduzione – 2. Il contesto europeo maieuta delle «4 direttive» - 3. Le «4 direttive» - 4. L’ubi consistam costituzionale tedesco - 5. Le discriminazioni vietate – 6. Fenotipi laburistici dell’AGG - 7. Fenotipi civilistici dell’AGG – 8. Le discriminazioni ammesse - 9. Il § 9, extra Ecclesiis nulla exceptio.

  13. Morphometry and Distribution of Senecio Nemorensis agg. Species (Asteraceae in Poland

    Directory of Open Access Journals (Sweden)

    Rola Kaja

    2014-07-01

    Full Text Available A morphometric analysis based on 316 herbarium specimens of Senecio nemorensis agg. indicated the occurrence of the following four species in Poland: S. germanicus Wallr., S. hercynicus Herborg, S. ovatus (G. Gaertn. et al. Willd. and S. ucranicus Hodálová. Principal component analysis (PCA, analysis of variance (ANOVA/Kruskal-Wallis test and canonical discriminant analysis (CDA were applied. Quantitative characters such as supplementary bract length, leaf base width, ligule length and the supplementary/involucral bract length ratio clearly discriminated taxa within S. nemorensis agg. Included is a distribution map of the investigated species based on the examined material, with particular emphasis on the course of the northeastern boundary of S. hercynicus and the northwestern boundary of S. ucranicus. Also given is a determination key for species within S. nemorensis agg. in Poland, together with morphological descriptions of particular species

  14. An EM System With Dramatic Multi-Axis Transmitter and Tensor Gradiometer Receiver

    Science.gov (United States)

    2011-06-01

    Thus, the main difference between the spatial behavior of target anomalies measured with a magnetometer and those we measured with an EM system is in...current efforts include the development of tensor magnetic gradiometers based on triaxial fluxgate technology by the USGS (Snyder & Bracken, Development...Superconducting gradiometer/ Magnetometer Arrays and a Novel Signal Processing Technique. IEEE Trans. on Magnetics, MAG-11(2), 701-707. EM Tensor Gradiometer

  15. Moving base Gravity Gradiometer Survey System (GGSS) program

    Science.gov (United States)

    Pfohl, Louis; Rusnak, Walter; Jircitano, Albert; Grierson, Andrew

    1988-04-01

    The GGSS program began in early 1983 with the objective of delivering a landmobile and airborne system capable of fast, accurate, and economical gravity gradient surveys of large areas anywhere in the world. The objective included the development and use of post-mission data reduction software to process the survey data into solutions for the gravity disturbance vector components (north, east and vertical). This document describes the GGSS equipment hardware and software, integration and lab test procedures and results, and airborne and land survey procedures and results. Included are discussions on test strategies, post-mission data reduction algorithms, and the data reduction processing experience. Perspectives and conclusions are drawn from the results.

  16. On alternative solutions of interchannel crosstalk problem in multichannel gradiometers

    International Nuclear Information System (INIS)

    Manka, J.; Zrubec, V.

    1990-01-01

    For biomagnetic measurement, the multichannel systems has become the most prospective solution which is, however, associated with the problem of mutual affection of individual signals caused by mutual inductances between the gradiometers. H.J.M. ter Brake et. al. solved this problem by installation of the negative feedback into the input circuit, so that input inductivity of the magnetometer arose to a great value and gradiometer currents were attenuated. Heat breaking of the superconducting state was used for the proof of damping of crosstalk between two gradiometers. This paper deals with specifying the crosstalk coefficients in systems with internal feedback in the working regime

  17. Recovery of the Earth's Gravity Field Based on Spaceborne Atom-interferometry and Its Accuracy Estimation

    Directory of Open Access Journals (Sweden)

    ZHU Zhu

    2017-09-01

    Full Text Available The electrostatic gravity gradiometer has been successfully applied as a core sensor in satellite gravity gradiometric mission GOCE, and its observations are used to recover the Earth's static gravity field with a degree and order above 200. The lifetime of GOCE has been over, and the next generation satellite gravity gradiometry with higher resolution is urgently required in order to recover the global steady-state gravity field with a degree and order of 200~360. High potential precision can be obtained in space by atom-interferometry gravity gradiometer due to its long interference time, and thus the atom-interferometry-based satellite gravity gradiometry has been proposed as one of the candidate techniques for the next satellite gravity gradiometric mission. In order to achieve the science goal for high resolution gravity field measurement in the future, a feasible scheme of atom-interferometry gravity gradiometry in micro-gravity environment is given in this paper, and the gravity gradient measurement can be achieved with a noise of 0.85mE/Hz1/2. Comparison and estimation of the Earth's gravity field recovery precision for different types of satellite gravity gradiometry is discussed, and the results show that the satellite gravity gradiometry based on atom-interferometry is expected to provide the global gravity field model with an improved accuracy of 7~8cm in terms of geoid height and 3×10-5 m/s2 in terms of gravity anomaly respectively at a degree and order of 252~290.

  18. Calibration and Distortion Field Compensation of Gradiometer and the Improvement in Object Remote Sensing

    Directory of Open Access Journals (Sweden)

    Hu Xiangchao

    2016-01-01

    Full Text Available Magnetometer, misalignment error and distortion field can reduce the accuracy of gradiometers. So, it is important to calibrate and compensate gradiometers error. Scale factor, bias, nonorthogonality, misalignment and distortion field should be considered. A gradiometer is connected by an aluminium frame, which contains two fluxgate magnetometers. A nonmagnetic rotation equipment is used to change gradiometer attitude, and the compensation parameters are estimated. Experiment results show that, after calibration and compensation, error of each axis is reduced from 888.4 nT, 1292.6 nT and 168.9 nT to 15.3 nT, 22.1 nT and 9.9 nT, respectively. It shows that the proposed method can calibrate gradiometer and compensate distortion field. After calibration and compensation, the object remote sensing performance is improved.

  19. A Portable Single Axis Magnetic Gradiometer

    DEFF Research Database (Denmark)

    Merayo, José M.G.; Petersen, Jan Raagaard; Nielsen, Otto V

    2001-01-01

    not provide vector information about the magnetic field. Secondly, one of the sensors measures the ambient magnetic field and is used to compensate for the main field at both sensors. Several methods have been developed for characterization of the 2 gradiometer, and the calibration of the gradient......The single axis magnetic gradiometer based on two compact detector compensation (CDC) fluxgate ringcore sensors separated 20 cm is described. Despite its high stability and precision better than 1 nT, the calibration procedures are not straightforward. Firstly, the mono-axial measurement does...... measurements is achieved by using a magnetic dipole of strength 2 mAm(2). In a coil facility, the gradient can be determined with an accuracy of 0.3 nT/m(RMS)....

  20. Use of a superconductive gradiometer in an ultrasensitive electromagnetic metal detector

    International Nuclear Information System (INIS)

    Czipott, P.V.; Podney, W.N.

    1989-01-01

    The authors present a new instrument that we call an electromagnetic gradiometer. It uses a SQUID sensor as the receiver in an active, electromagnetic detector of nonferrous as well as ferrous objects. The gradiometer pickup loops sit in the center of magnet coils that generate a time-varying magnetic field inducing eddy currents in conductive bodies. The gradiometer measures the secondary magnetic field of the eddy currents. The SQUID's sensitivity at frequencies below 1 kHz makes electromagnetic metal detectors practical in the marine environment, where the electrical conductivity of seawater precludes conventional systems. The authors describe a prototype system that attains a detection range of 10 m in seawater for targets 50 cm in diameter. It operates at frequencies from 1 Hz to a few hundred Hz. Uses of the electromagnetic gradiometer include locating naval mines and undersea treasure. The system's response to seawater enables application to airborne electromagnetic bathymetry. On land, its sensitivity to crustal conductivity contrasts suits it to mineral exploration

  1. Sessile oak (Quercus petraea agg. Ehrendorfer 1967) rare ...

    African Journals Online (AJOL)

    Sessile oak ( Quercus petraea agg. Ehrendorfer 1967) genetic variability in Serbia was estimated applying cpDNA universal primer pairs. Five different haplotypes were detected in the analyzed sample material from populations in Serbia. The areas in West and Southwest Serbia, with all their specificities, represent an ...

  2. CGG repeat length and AGG interruptions as indicators of fragile X-associated diminished ovarian reserve.

    Science.gov (United States)

    Lekovich, Jovana; Man, Limor; Xu, Kangpu; Canon, Chelsea; Lilienthal, Debra; Stewart, Joshua D; Pereira, Nigel; Rosenwaks, Zev; Gerhardt, Jeannine

    2017-12-21

    PurposeFragile X premutation (PM) carriers may experience difficulties conceiving a child probably due to fragile X-associated diminished ovarian reserve (FXDOR). We investigated which subgroups of carriers with a PM are at higher risk of FXDOR, and whether the number of AGG interruptions within the repeat sequence further ameliorates the risk.MethodsWe compared markers of ovarian reserve, including anti-Müllerian hormone, antral follicle count, and number of oocytes retrieved between different subgroups of patients with a PM.ResultsWe found that carriers with midrange repeats size (70-90 CGG) demonstrate significantly lower ovarian reserve. Additionally, the number of AGG interruptions directly correlated with parameters of ovarian reserve. Patients with longer uninterrupted CGG repeats post-AGG interruptions had the lowest ovarian reserve.ConclusionThis study connects AGG interruptions and certain CGG repeat length to reduced ovarian reserve in carriers with a PM. A possible explanation for our findings is the proposed gonadotoxicity of the FMR1 transcripts. Reduction of AGG interruptions could increase the likelihood that secondary RNA structures in the FMR1 messenger RNA are formed, which could cause cell dysfunction within the ovaries. These findings may provide women with guidance regarding their fertility potential and accordingly assist with their family planning.GENETICS in MEDICINE advance online publication, 21 December 2017; doi:10.1038/gim.2017.220.

  3. A simple method for checking the balance of gradiometers used with squids

    International Nuclear Information System (INIS)

    Eghrari, I.R.; Ribeiro, P.C.

    1978-11-01

    A simple technique for detecting the degree of balance of first order gradiometers before connecting them to the SQUID is described. The effect of thermal cycling on this balance is given for different materials used in the construction of the gradiometers [pt

  4. Compact integrated dc SQUID gradiometer

    Science.gov (United States)

    de Waal, V. J.; Klapwijk, T. M.

    1982-10-01

    An all-niobium integrated system of first-order gradiometer and dc suprconducting quantum interference device (SQUID) has been developed. It is relatively simple to fabricate, has an overall size of 17×12 mm and a sensitivity of 3.5×10-12 T m-1 Hz-1/2.

  5. High-Tc dc-SQUID gradiometers in flip-chip configuration

    International Nuclear Information System (INIS)

    Peiselt, K; Schmidl, F; Linzen, S; Anton, A S; Huebner, U; Seidel, P

    2003-01-01

    We describe a new design of a gradiometric flip-chip antenna, which is inductively coupled to a dc-SQUID gradiometer. Both components are patterned out of thin films of the high-T c superconductor YBa 2 Cu 3 O 7-x (YBCO). For the flip-chip antenna, a 40 mm x 10 mm SrTiO 3 single crystalline substrate is used, while the gradiometer sensors are prepared on 10 mm x 10 mm SrTiO 3 bicrystal substrates. Special attention is paid to the inductive coupling between the flip-chip antenna and the read-out gradiometer antenna. We investigate different designs of coupling loops in order to optimize the coupling inductance between both components of the sensor. With optimized coupling the sensor achieves a field-gradient resolution of 12 fT cm -1 Hz -1/2 in the white noise region and of 310 fT cm -1 Hz -1/2 at 1 Hz in the unshielded laboratory environment

  6. High-Tc dc-SQUID gradiometers in flip-chip configuration

    Science.gov (United States)

    Peiselt, K.; Schmidl, F.; Linzen, S.; Anton, A. S.; Hübner, U.; Seidel, P.

    2003-12-01

    We describe a new design of a gradiometric flip-chip antenna, which is inductively coupled to a dc-SQUID gradiometer. Both components are patterned out of thin films of the high-Tc superconductor YBa2Cu3O7-x (YBCO). For the flip-chip antenna, a 40 mm × 10 mm SrTiO3 single crystalline substrate is used, while the gradiometer sensors are prepared on 10 mm × 10 mm SrTiO3 bicrystal substrates. Special attention is paid to the inductive coupling between the flip-chip antenna and the read-out gradiometer antenna. We investigate different designs of coupling loops in order to optimize the coupling inductance between both components of the sensor. With optimized coupling the sensor achieves a field-gradient resolution of 12 fT cm-1 Hz-1/2 in the white noise region and of 310 fT cm-1 Hz-1/2 at 1 Hz in the unshielded laboratory environment.

  7. Single-layer 2nd-order high-Tc SQUID gradiometer for use in unshielded environments

    International Nuclear Information System (INIS)

    Lee, Soon-Gul; Park, Seung Moon; Kang, Chan Seok; Kim, In-Seon; Kim, Sang-Jae

    2006-01-01

    We have studied the fabrication of second-order SQUID gradiometers from single-layer high-T c film and the feasibility of using those gradiometers in magnetocardiography. The gradiometer contains three parallel-connected pickup loops that are directly coupled to a step-edge junction SQUID with the coupling polarity of the center loop opposite to those of the two side loops. For a well-balanced gradiometer with a balancing factor of 10 3 , we achieved an unshielded gradient noise of 0.84 pT/cm 2 /Hz 1/2 at 1 Hz, which corresponds to an equivalent field noise of 280 fT/Hz 1/2 . A gradiometer with a 5.8-mm baseline successfully recorded the magnetocardic signals of a human subject, demonstrating the feasibility of using the device in biomagnetism. We have also studied the use of submicron YBCO bridges as Josephson elements of long-baseline gradiometers. The bridges were fabricated from 3-μm-wide, 300-nm-thick YBCO lines with a thin layer of Au on top by using a focused-ion-beam (FIB) patterning method. The temperature-dependent critical currents, I c (T), and the normal state resistances, R N (T), showed SIS-type behaviors, which are believed to be due to naturally formed grain boundaries.

  8. Compact integrated dc SQUID gradiometer

    Energy Technology Data Exchange (ETDEWEB)

    de Waal, V.J.; Klapwijk, T.M.

    1982-10-01

    An all-niobium integrated system of first-order gradiometer and dc suprconducting quantum interference device (SQUID) has been developed. It is relatively simple to fabricate, has an overall size of 17 x 12 mm and a sensitivity of 3.5 x 10/sup -12/ T m/sup -1/ Hz/sup -1/2/.

  9. Superparamagnetic nanoparticle detection system by using a fundamental mode orthogonal fluxgate (FM-OFG gradiometer

    Directory of Open Access Journals (Sweden)

    Hikaru Karo

    2017-05-01

    Full Text Available A new magnetic nanoparticle detection system by using a fundamental mode orthogonal fluxgate (FM-OFG gradiometer and ac magnetizing coil has been developed. The FM-OFG gradiometer has an active canceling coil on each of its sensor heads against the common magnetic field input to avoid the saturation of the amorphous wire core by a strong ac magnetic field. In addition, the ac magnetizing coil has an adjusting capability to make ac magnetic field strength affecting each of the gradiometer heads equal, which allows us to use a high gain amplifier at the latter stage. Two types of the gradiometer are tested: one is parallel configuration in which two sensor heads are placed in parallel side by side, the other is axial configuration in which two sensor heads are placed axially. Detectable distance was investigated using a 5μL (≈100μg in Fe atomic amount magnetic nanoparticle sample. The maximum detectable distance for the parallel gradiometer is 17 mm, and that for the axial one is 18 mm.

  10. Development of improved superconductive axial gradiometers for biomagnetic SQUID applications

    Science.gov (United States)

    Budnyk, M. M.; Minov, Yu. D.; Lyakhno, V. Yu.; Desnenko, V. A.; Linnik, A. S.; Shopen, O. B.

    2018-03-01

    SQUID magnetometers for biomagnetic measurements are equipped with superconductive gradiometers which are required to provide a high signal-to-noise ratio at low frequencies, sufficient mechanical strength and sustained performance under repeated thermal cycles, as well as a low level of intrinsic magnetic noise. This paper describes the design of a gradiometer made with a carbon-fiber reinforced composite material for magnetic cardiography measurements. The thermal coefficient of linear expansion (TCLE) of the carbon fiber composite can be precisely adjusted to match that of the superconducting detector coil wire. This is achieved thanks to the difference in the TCLE of carbon fibers in the longitudinal and transverse directions and is realized by varying the laying directions of the fiber in the composite. The data of magnetic susceptibility measurements on carbon fiber composite are reported, showing the magnetic susceptibility about six times smaller than that of graphite. The presented gradiometer design provides a high degree of balancing and is patented along side other specific techniques.

  11. The Compensation Method of Vehicle Magnetic Interference for the Magnetic Gradiometer

    OpenAIRE

    Lv, Junwei; Yu, Zhentao; Huang, Jingli; Zhou, Jing

    2013-01-01

    The magnetic interference of vehicle imposes a strong influence on the magnetic gradiometer. Based on the mechanism of the vehicle magnetic interference, we firstly use the difference algorithm of the magnetic gradient tensor to fuse the magnetic interference of each vector magnetometer and establish a mathematical model of vehicle magnetic interference for the magnetic gradiometer. Next, we propose a compensation method for the vehicle magnetic interference and a recognition method for the e...

  12. An EM System with Dynamic Multi-Axis Transmitter and Tensor Gradiometer Receiver

    Science.gov (United States)

    2011-06-01

    main difference between the spatial behavior of target anomalies measured with a magnetometer and those we measured with an EM system is in the nature...environmental and UXO applications, current efforts include the development of tensor magnetic gradiometers based on triaxial fluxgate technology by the USGS...Superconducting gradiometer/ Magnetometer Arrays and a Novel Signal Processing Technique. IEEE Trans. on Magnetics, MAG-11(2), 701-707. EM Tensor

  13. A SQUID gradiometer module with wire-wound pickup antenna and integrated voltage feedback circuit

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Guofeng [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Peter Gruenberg Institute (PGI-8), Forschungszentrum Juelich (FZJ), D-52425 Juelich (Germany); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Yi, E-mail: y.zhang@fz-juelich.de [Peter Gruenberg Institute (PGI-8), Forschungszentrum Juelich (FZJ), D-52425 Juelich (Germany); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); Zhang Shulin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); Krause, Hans-Joachim [Peter Gruenberg Institute (PGI-8), Forschungszentrum Juelich (FZJ), D-52425 Juelich (Germany); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); and others

    2012-10-15

    The performance of the direct readout schemes for dc SQUID, Additional Positive Feedback (APF), noise cancellation (NC) and SQUID bootstrap circuit (SBC), have been studied in conjunction with planar SQUID magnetometers. In this paper, we examine the NC technique applied to a niobium SQUID gradiometer module with an Nb wire-wound antenna connecting to a dual-loop SQUID chip with an integrated voltage feedback circuit for suppression of the preamplifier noise contribution. The sensitivity of the SQUID gradiometer module is measured to be about 1 fT/(cm {radical}Hz) in the white noise range in a magnetically shielded room. Using such gradiometer, both MCG and MEG signals are recorded.

  14. Highly balanced gradiometer systems based on HTS-SQUIDs for the use in magnetically unshielded environment

    NARCIS (Netherlands)

    Borgmann, H.J.R.; Rijpma, A.P.; ter Brake, Hermanus J.M.; Rogalla, Horst; David, P.

    1999-01-01

    Two different concepts for gradiometer formation were tested applying high-temperature rf SQUIDs operated at 77 K in liquid nitrogen. All gradiometer systems are fully based on magnetometers. The first concept applies a compensating magnetometer at different positions to actively cancel the magnetic

  15. Atom Interferometer Technologies in Space for Gravity Mapping and Gravity Science

    Science.gov (United States)

    Williams, Jason; Chiow, Sheng-Wey; Kellogg, James; Kohel, James; Yu, Nan

    2015-05-01

    Atom interferometers utilize the wave-nature of atomic gases for precision measurements of inertial forces, with potential applications ranging from gravity mapping for planetary science to unprecedented tests of fundamental physics with quantum gases. The high stability and sensitivity intrinsic to these devices already place them among the best terrestrial sensors available for measurements of gravitational accelerations, rotations, and gravity gradients, with the promise of several orders of magnitude improvement in their detection sensitivity in microgravity. Consequently, multiple precision atom-interferometer-based projects are under development at the Jet Propulsion Laboratory, including a dual-atomic-species interferometer that is to be integrated into the Cold Atom Laboratory onboard the International Space Station and a highly stable gravity gradiometer in a transportable design relevant for earth science measurements. We will present JPL's activities in the use of precision atom interferometry for gravity mapping and gravitational wave detection in space. Our recent progresses bringing the transportable JPL atom interferometer instrument to be competitive with the state of the art and simulations of the expected capabilities of a proposed flight project will also be discussed. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  16. Battlefield Applications for the Polatomic 2000 Magnetometer/Gradiometer

    National Research Council Canada - National Science Library

    Kuhlman, G

    2002-01-01

    ... He(4) scalar magnetometer/gradiometer. A major innovation in the P-2000 helium magnetometer is the introduction of a laser pump source to replace the conventional RF discharge helium lamp used in the Navy AN/ASQ-81/208 MAD Set...

  17. Electronic structure of Co islands grown on the {radical}3 x {radical}3-Ag/Ge(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiao-Lan; Chou, Chi-Hao; Lin, Chun-Liang; Tomaszewska, Agnieszka; Fu, Tsu-Yi, E-mail: phtifu@phy.ntnu.edu.tw

    2011-09-30

    By means of room temperature scanning tunneling spectroscopy (RT STS), we have studied the electronic structure of two different Ag/Ge(111) phases as well as Co islands grown on the {radical}3 x {radical}3-Ag/Ge (111) forming either {radical}13 x {radical}13 or 2 x 2 patterns. The spectrum obtained from 4 x 4-Ag/Ge(111) structure shows the existence of a shoulder at 0.7 V which is also present in the electronic structure of the Ge(111)-c2 x 8 and indicates donation of Ge electrons to electronic states of the Ag-driven phase. However, this fact is not supported by the electronic spectrum taken from the {radical}3 x {radical}3-Ag/Ge (111). The complexity of the Co-{radical}13 x {radical}13 islands bonding with the substrate is mirrored by a large number of peaks in their electronic spectra. The spectra obtained from the Co-2 x 2 islands which had grown on the step differ from those taken from Co-2 x 2 islands located along the edge of the terrace by a number of peaks at negative sample bias. This discrepancy is elucidated in terms of dissimilarities of Co-substrate interaction accompanying Co islands growth on different areas of the stepped surface.

  18. Cold Atom Interferometers Used In Space (CAIUS) for Measuring the Earth's Gravity Field

    Science.gov (United States)

    Carraz, O.; Luca, M.; Siemes, C.; Haagmans, R.; Silvestrin, P.

    2016-12-01

    In the past decades, it has been shown that atomic quantum sensors are a newly emerging technology that can be used for measuring the Earth's gravity field. There are two ways of making use of that technology: One is a gravity gradiometer concept and the other is in a low-low satellite-to-satellite ranging concept. Whereas classical accelerometers typically suffer from high noise at low frequencies, Cold Atom Interferometers are highly accurate over the entire frequency range. We recently proposed a concept using cold atom interferometers for measuring all diagonal elements of the gravity gradient tensor and the full spacecraft angular velocity in order to achieve better performance than the GOCE gradiometer over a larger part of the spectrum, with the ultimate goals of determining the fine structures in the gravity field better than today. This concept relies on a high common mode rejection, which relaxes the drag free control compare to GOCE mission, and benefits from a long interaction time with the free falling clouds of atoms due to the micro gravity environment in space as opposed to the 1-g environment on-ground. Other concept is also being studied in the frame of NGGM, which relies on the hybridization between quantum and classical techniques to improve the performance of accelerometers. This could be achieved as it is realized in frequency measurements where quartz oscillators are phase locked on atomic or optical clocks. This technique could correct the spectrally colored noise of the electrostatic accelerometers in the lower frequencies. In both cases, estimation of the Earth gravity field model from the instruments has to be evaluated taking into account different system parameters such as attitude control, altitude of the satellite, time duration of the mission, etc. Miniaturization, lower consumptions and upgrading Technical Readiness Level are the key engineering challenges that have to be faced for these space quantum technologie.

  19. Optimization of field homogeneity of Helmholtz-like coils for measuring the balance of planar gradiometers

    International Nuclear Information System (INIS)

    Nordahn, M.A.; Holst, T.; Shen, Y.Q.

    1999-01-01

    Measuring the balance of planar SQUID gradiometers using a relatively small Helmholtz-like coil system requires a careful design of the coils in order to have a high degree of field uniformity along the radial direction. The level to which planar gradiometers can be balanced will be affected by any misalignment of the gradiometer relative to the ideal central position. Therefore, the maximum degree of balancing possible is calculated numerically for the Helmholtz geometry under various perturbations, including misalignment of the gradiometer along the cylindrical and the radial axis, and angular tilting relative to the normal plane. Furthermore, if the ratio between the coil separation and coil radius is chosen to be less than unity, calculations show that the expected radial uniformity of the field can be improved considerably compared to the traditional Helmholtz geometry. The optimized coil geometry is compared to the Helmholtz geometry and is found to yield up to an order of magnitude improvement of the worst case error signal within a volume spanned by the uncertainty in the alignment. (author)

  20. Second order gradiometer and dc SQUID integrated on a planar substrate

    Science.gov (United States)

    van Nieuwenhuyzen, G. J.; de Waal, V. J.

    1985-02-01

    An integrated system of a thin-film niobium dc superconducting quantum interference device (SQUID) and a second order gradiometer on a planar substrate is described. The system consists of a dc SQUID with eight loops in parallel, each sensitive to the second derivative ∂2Bz/∂x2 of the magnetic field. The calculated SQUID inductance is 1.3 nH. With an overall size of 16×16.5 mm2 a sensitivity of 1.5×10-9 Tm-2 Hz-1/2 is obtained. The measured transfer function for uniform fields perpendicular to the plane of the gradiometer is 2.1×10-7 T Φ-10.

  1. Construction of an Overhauser magnetic gradiometer and the applications in geomagnetic observation and ferromagnetic target localization

    Science.gov (United States)

    Liu, H.; Dong, H.; Liu, Z.; Ge, J.; Bai, B.; Zhang, C.

    2017-10-01

    The proton precession magnetometer with single sensor is commonly used in geomagnetic observation and magnetic anomaly detection. Due to technological limitations, the measurement accuracy is restricted by several factors such as the sensor performance, frequency measurement precision, instability of polarization module, etc. Aimed to improve the anti-interference ability, an Overhauser magnetic gradiometer with dual sensor structure was designed. An alternative design of a geomagnetic sensor with differential dual-coil structure was presented. A multi-channel frequency measurement algorithm was proposed to increase the measurement accuracy. A silicon oscillator was adopted to resolve the instability of polarization system. This paper briefly discusses the design and development of the gradiometer and compares the data recorded by this instrument with a commonly used commercially Overhauser magnetometer in the world market. The proposed gradiometer records the earth magnetic field in 24 hours with measurement accuracy of ± 0.3 nT and a sampling rate of 3 seconds per sample. The quality of data recorded is excellent and consistent with the commercial instrument. In addition, experiments of ferromagnetic target localization were conducted. This gradiometer shows a strong ability in magnetic anomaly detection and localization. To sum up, it has the advantages of convenient operation, high precision, strong anti-interference, etc., which proves the effectiveness of the dual sensor structure Overhauser magnetic gradiometer.

  2. Construction of an Overhauser magnetic gradiometer and the applications in geomagnetic observation and ferromagnetic target localization

    International Nuclear Information System (INIS)

    Liu, H.; Dong, H.; Ge, J.; Zhang, C.; Liu, Z.; Bai, B.

    2017-01-01

    The proton precession magnetometer with single sensor is commonly used in geomagnetic observation and magnetic anomaly detection. Due to technological limitations, the measurement accuracy is restricted by several factors such as the sensor performance, frequency measurement precision, instability of polarization module, etc. Aimed to improve the anti-interference ability, an Overhauser magnetic gradiometer with dual sensor structure was designed. An alternative design of a geomagnetic sensor with differential dual-coil structure was presented. A multi-channel frequency measurement algorithm was proposed to increase the measurement accuracy. A silicon oscillator was adopted to resolve the instability of polarization system. This paper briefly discusses the design and development of the gradiometer and compares the data recorded by this instrument with a commonly used commercially Overhauser magnetometer in the world market. The proposed gradiometer records the earth magnetic field in 24 hours with measurement accuracy of ± 0.3 nT and a sampling rate of 3 seconds per sample. The quality of data recorded is excellent and consistent with the commercial instrument. In addition, experiments of ferromagnetic target localization were conducted. This gradiometer shows a strong ability in magnetic anomaly detection and localization. To sum up, it has the advantages of convenient operation, high precision, strong anti-interference, etc., which proves the effectiveness of the dual sensor structure Overhauser magnetic gradiometer.

  3. Use of GOCE L2 Gravity Gradients for full resolution Geoid

    DEFF Research Database (Denmark)

    Herceg, Matija; Tscherning, Carl Christian; Knudsen, Per

    The objective of this study is to develop methodology to use GOCE gravity gradients for enhanced geoid modelling and ocean circulation modelling. In specific regions with a rough gravity field, the resolution of the geoid may be enhanced substantially if GOCE gradiometer data are used in addition...... of the GOCE spherical harmonic coefficient model (EGMs) since in such areas the GOCE gradients contain more information than the EGM itself. Hence, the use of gradients may lead to improve the resolution of e.g. the marine geoid which in turn will improve the estimation of the ocean circulation....... This is tested using GOCE gravity gradient data, the GEOCOL program (GRAVSOFT) and Reduced Point Mass (RPM) program. Tests are carried out in the GOCINA region and in the Mediterranean basin. Furthermore, the effect of the decreasing height of the GOCE satellite on gravity gradients and associated MDT...

  4. Shortening of the Lactobacillus paracasei subsp. paracasei BGNJ1-64 AggLb protein switches its activity from auto-aggregation to biofilm formation

    Directory of Open Access Journals (Sweden)

    Marija Miljković

    2016-09-01

    Full Text Available AggLb is the largest (318.6 kDa aggregation-promoting protein of Lactobacillus paracasei subsp. paracasei BGNJ1-64 responsible for forming large cell aggregates, which causes auto-aggregation, collagen binding and pathogen exclusion in vitro. It contains an N-terminus leader peptide, followed by six successive collagen binding domains, 20 successive repeats (CnaB-like domains and an LPXTG sorting signal at the C-terminus for cell wall anchoring. Experimental information about the roles of the domains of AggLb is currently unknown. To define the domain that confers cell aggregation and the key domains for interactions of specific affinity between AggLb and components of the extracellular matrix (ECM, we constructed a series of variants of the aggLb gene and expressed them in Lactococcus lactis subsp. lactis BGKP1-20 using a lactococcal promoter. All of the variants contained a leader peptide, an inter collagen binding-CnaB domain region (used to raise an anti-AggLb antibody, an anchor domain and a different number of collagen binding and CnaB-like domains. The role of the collagen binding repeats of the N-terminus in auto-aggregation and binding to collagen and fibronectin was confirmed. Deletion of the collagen binding repeats II, III and IV resulted in a loss of the strong auto-aggregation, collagen and fibronectin binding abilities whereas the biofilm formation capability was increased. The strong auto-aggregation, collagen and fibronectin binding abilities of AggLb were negatively correlated to biofilm formation.

  5. Performance Evaluation and Requirements Assessment for Gravity Gradient Referenced Navigation

    Directory of Open Access Journals (Sweden)

    Jisun Lee

    2015-07-01

    Full Text Available In this study, simulation tests for gravity gradient referenced navigation (GGRN are conducted to verify the effects of various factors such as database (DB and sensor errors, flight altitude, DB resolution, initial errors, and measurement update rates on the navigation performance. Based on the simulation results, requirements for GGRN are established for position determination with certain target accuracies. It is found that DB and sensor errors and flight altitude have strong effects on the navigation performance. In particular, a DB and sensor with accuracies of 0.1 E and 0.01 E, respectively, are required to determine the position more accurately than or at a level similar to the navigation performance of terrain referenced navigation (TRN. In most cases, the horizontal position error of GGRN is less than 100 m. However, the navigation performance of GGRN is similar to or worse than that of a pure inertial navigation system when the DB and sensor errors are 3 E or 5 E each and the flight altitude is 3000 m. Considering that the accuracy of currently available gradiometers is about 3 E or 5 E, GGRN does not show much advantage over TRN at present. However, GGRN is expected to exhibit much better performance in the near future when accurate DBs and gravity gradiometer are available.

  6. Gravity gradient preprocessing at the GOCE HPF

    Science.gov (United States)

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

    2009-04-01

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

  7. Characteristics of an HTS-SQUID gradiometer with ramp-edge Josephson junctions and its application on robot-based 3D-mobile compact SQUID NDE system

    Energy Technology Data Exchange (ETDEWEB)

    Hatsukade, Y., E-mail: hatukade@ens.tut.ac.jp [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Hayashi, K.; Shinyama, Y.; Kobayashi, Y. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Adachi, S.; Tanabe, K. [International Superconductivity Technology Center/Superconductivity Research Laboratory, 10-13, Shinonome 1-chome, Koto-ku, Tokyo 135-0062 (Japan); Tanaka, S. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan)

    2011-11-15

    We investigated behavior of HTS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in ac and dc magnetic fields. In the both fields, the gradiometers show higher durability against entry of flux vortices than SQUIDs with bicrystal JJs. A robot-based SQUID NDE system utilizing the gradiometer was developed in an unshielded environment. Detectability of the system to detect non-through cracks in double-layer structures was demonstrated. A new excitation coil was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer. In this paper, we investigated detailed behavior of novel HTS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in both an ac magnetic field and a dc magnetic field. In the both fields, the novel gradiometers shows the superior performance to the conventional YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) HTS-dc-SQUID gradiometer and a bare HTS-dc-SQUID ring with bicrystal JJs concerning durability against entry and hopping of flux vortices, probably due to their differential pickup coils without a grain boundary and multilayer structure of the ramp-edge JJs. A robot-based compact HTS-SQUID NDE system utilizing the novel gradiometer was reviewed, and detectability of the system to detect non-through cracks in a carbon fiber reinforced plastic (CFRP)/Al double-layer structure was demonstrated. A new excitation coil in which the supplied currents flowed in the orthogonal directions was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer.

  8. HTS planar gradiometer consisting of SQUID with multi-turn input coil and large pickup coil made of GdBCO coated conductor

    International Nuclear Information System (INIS)

    Tsukamoto, Akira; Adachi, Seiji; Oshikubo, Yasuo; Hato, Tsunehiro; Enpuku, Keiji; Sugisaki, Masaki; Arai, Eiichi; Tanabe, Keiichi

    2013-01-01

    Highlights: ► We fabricated a large HTS gradiometer with 350-mm-long baseline. ► A 6-turn gradiometric planar pickup was made of a HTS coated conductor. ► A 26-turn HTS input coil chip was stacked on a HTS thin film gradiometer chip. ► A mechanical balancing structure was also implemented. ► The fabricated gradiometer showed a gradient field noise of 0.8 fT/cm Hz 1/2 . -- Abstract: We have investigated the fabrication of a high-temperature superconducting (HTS) gradiometer with long baseline for geophysical applications. The proof-of-concept gradiometer using a 1-turn pickup coil made of a GdBa 2 Cu 3 O y coated conductor (GCC) and 5.5-turn input coil integrated on a SQUID was fabricated in our previous work. In this study, we have optimized the device structure to improve the frequency response, gradient field sensitivity and gradiometer balance. The fabricated flux transformer consists of a 6-turn planar gradiometric pickup coil and a 26-turn input coil made of an HTS thin film. A low-melting-point alloy was used to connect polished Ag surfaces of the CGG pickup coil and Au pads of the input coil. An HTS SQUID was formed on another substrate and stacked on the input coil. A mechanical balancing structure using three pieces of GCC as a superconducting shield was also implemented. The fabricated gradiometer showed a gradient field noise of 0.8 fT/cm Hz 1/2 in the white noise regions, a gradiometer balance of 1/142, and a cutoff frequency of 9 Hz corresponding to a 2 mΩ contact resistance between the pickup coil and the input coil

  9. Second order gradiometer and dc SQUID integrated on a planar substrate

    Energy Technology Data Exchange (ETDEWEB)

    van Nieuwenhuyzen, G.J.; de Waal, V.J.

    1985-02-15

    An integrated system of a thin-film niobium dc superconducting quantum interference device (SQUID) and a second order gradiometer on a planar substrate is described. The system consists of a dc SQUID with eight loops in parallel, each sensitive to the second derivative partial/sup 2/B/sub z//partialx/sup 2/ of the magnetic field. The calculated SQUID inductance is 1.3 nH. With an overall size of 16 x 16.5 mm/sup 2/ a sensitivity of 1.5 x 10/sup -9/ Tm/sup -2/ Hz/sup -1//sup ///sup 2/ is obtained. The measured transfer function for uniform fields perpendicular to the plane of the gradiometer is 2.1 x 10/sup -7/ T Phi/sup -1//sub 0/.

  10. Automated gravity gradient tensor inversion for underwater object detection

    International Nuclear Information System (INIS)

    Wu, Lin; Tian, Jinwen

    2010-01-01

    Underwater abnormal object detection is a current need for the navigation security of autonomous underwater vehicles (AUVs). In this paper, an automated gravity gradient tensor inversion algorithm is proposed for the purpose of passive underwater object detection. Full-tensor gravity gradient anomalies induced by an object in the partial area can be measured with the technique of gravity gradiometry on an AUV. Then the automated algorithm utilizes the anomalies, using the inverse method to estimate the mass and barycentre location of the arbitrary-shaped object. A few tests on simple synthetic models will be illustrated, in order to evaluate the feasibility and accuracy of the new algorithm. Moreover, the method is applied to a complicated model of an abnormal object with gradiometer and AUV noise, and interference from a neighbouring illusive smaller object. In all cases tested, the estimated mass and barycentre location parameters are found to be in good agreement with the actual values

  11. Active tensor magnetic gradiometer system final report for Project MM–1514

    Science.gov (United States)

    Smith, David V.; Phillips, Jeffrey D.; Hutton, S. Raymond

    2014-01-01

    An interactive computer simulation program, based on physical models of system sensors, platform geometry, Earth environment, and spheroidal magnetically-permeable targets, was developed to generate synthetic magnetic field data from a conceptual tensor magnetic gradiometer system equipped with an active primary field generator. The system sensors emulate the prototype tensor magnetic gradiometer system (TMGS) developed under a separate contract for unexploded ordnance (UXO) detection and classification. Time-series data from different simulation scenarios were analyzed to recover physical dimensions of the target source. Helbig-Euler simulations were run with rectangular and rod-like source bodies to determine whether such a system could separate the induced component of the magnetization from the remanent component for each target. This report concludes with an engineering assessment of a practical system design.

  12. Calibrating a tensor magnetic gradiometer using spin data

    Science.gov (United States)

    Bracken, Robert E.; Smith, David V.; Brown, Philip J.

    2005-01-01

    Scalar magnetic data are often acquired to discern characteristics of geologic source materials and buried objects. It is evident that a great deal can be done with scalar data, but there are significant advantages to direct measurement of the magnetic gradient tensor in applications with nearby sources, such as unexploded ordnance (UXO). To explore these advantages, we adapted a prototype tensor magnetic gradiometer system (TMGS) and successfully implemented a data-reduction procedure. One of several critical reduction issues is the precise determination of a large group of calibration coefficients for the sensors and sensor array. To resolve these coefficients, we devised a spin calibration method, after similar methods of calibrating space-based magnetometers (Snare, 2001). The spin calibration procedure consists of three parts: (1) collecting data by slowly revolving the sensor array in the Earth?s magnetic field, (2) deriving a comprehensive set of coefficients from the spin data, and (3) applying the coefficients to the survey data. To show that the TMGS functions as a tensor gradiometer, we conducted an experimental survey that verified that the reduction procedure was effective (Bracken and Brown, in press). Therefore, because it was an integral part of the reduction, it can be concluded that the spin calibration was correctly formulated with acceptably small errors.

  13. Comparative Mitogenomics of Plant Bugs (Hemiptera: Miridae): Identifying the AGG Codon Reassignments between Serine and Lysine

    Science.gov (United States)

    Wang, Pei; Song, Fan; Cai, Wanzhi

    2014-01-01

    Insect mitochondrial genomes are very important to understand the molecular evolution as well as for phylogenetic and phylogeographic studies of the insects. The Miridae are the largest family of Heteroptera encompassing more than 11,000 described species and of great economic importance. For better understanding the diversity and the evolution of plant bugs, we sequence five new mitochondrial genomes and present the first comparative analysis of nine mitochondrial genomes of mirids available to date. Our result showed that gene content, gene arrangement, base composition and sequences of mitochondrial transcription termination factor were conserved in plant bugs. Intra-genus species shared more conserved genomic characteristics, such as nucleotide and amino acid composition of protein-coding genes, secondary structure and anticodon mutations of tRNAs, and non-coding sequences. Control region possessed several distinct characteristics, including: variable size, abundant tandem repetitions, and intra-genus conservation; and was useful in evolutionary and population genetic studies. The AGG codon reassignments were investigated between serine and lysine in the genera Adelphocoris and other cimicomorphans. Our analysis revealed correlated evolution between reassignments of the AGG codon and specific point mutations at the antidocons of tRNALys and tRNASer(AGN). Phylogenetic analysis indicated that mitochondrial genome sequences were useful in resolving family level relationship of Cimicomorpha. Comparative evolutionary analysis of plant bug mitochondrial genomes allowed the identification of previously neglected coding genes or non-coding regions as potential molecular markers. The finding of the AGG codon reassignments between serine and lysine indicated the parallel evolution of the genetic code in Hemiptera mitochondrial genomes. PMID:24988409

  14. Gradiometry coexperiments to the gravity probe B and step missions

    International Nuclear Information System (INIS)

    Tapley, M.; Breakwell, J.; Everitt, C.W.F.; Vanpatten, R.; Worden, P.

    1990-01-01

    The Gravity Probe-B (GP-B) spacecraft, designed to test predictions of general relativity, will fly in the mid 1990s. It will carry four electrostatically suspended gyroscopes in a cryogenic environment and will have a drag-free control system to minimize disturbances on the gyroscopes. The Stanford Test of Equivalence Principle (STEP) spacecraft, to fly later, will carry a set of test masses under very similar conditions. The possibility of using differential measurements of the GP-B gyroscopes suspension forces and the STEP tests mass displacement readout to form single-axis gravity gradiometers is explored. It is shown that the noise in the suspension systems is sufficiently small in the relevant frequency range, and that enough information is collected to compensate for the spacecrafts' attitude motion. Finally, using Breakwell's flat-earth approximation, these experiments are compared to other geodesy experiments and predict the contribution they can make to the knowledge of the Earth's geopotential

  15. Mean-Square Error Due to Gradiometer Field Measuring Devices

    Science.gov (United States)

    1991-06-01

    convolving the gradiometer data with the inverse transform of I /T(a, 13), applying an ap- Hence (2) may be expressed in the transform domain as propriate... inverse transform of I / T(ot, 1) will not be possible quency measurements," Superconductor Applications: SQUID’s and because its inverse does not exist...and because it is a high- Machines, B. B. Schwartz and S. Foner, Eds. New York: Plenum pass function its use in an inverse transform technique Press

  16. Inversion of gravity gradient tensor data: does it provide better resolution?

    Science.gov (United States)

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

    2016-04-01

    The gravity gradient tensor (GGT) has been increasingly used in practical applications, but the advantages and the disadvantages of the analysis of GGT components versus the analysis of the vertical component of the gravity field are still debated. We analyse the performance of joint inversion of GGT components versus separate inversion of the gravity field alone, or of one tensor component. We perform our analysis by inspection of the Picard Plot, a Singular Value Decomposition tool, and analyse both synthetic data and gradiometer measurements carried out at the Vredefort structure, South Africa. We show that the main factors controlling the reliability of the inversion are algebraic ambiguity (the difference between the number of unknowns and the number of available data points) and signal-to-noise ratio. Provided that algebraic ambiguity is kept low and the noise level is small enough so that a sufficient number of SVD components can be included in the regularized solution, we find that: (i) the choice of tensor components involved in the inversion is not crucial to the overall reliability of the reconstructions; (ii) GGT inversion can yield the same resolution as inversion with a denser distribution of gravity data points, but with the advantage of using fewer measurement stations.

  17. Preprocessing of gravity gradients at the GOCE high-level processing facility

    Science.gov (United States)

    Bouman, Johannes; Rispens, Sietse; Gruber, Thomas; Koop, Radboud; Schrama, Ernst; Visser, Pieter; Tscherning, Carl Christian; Veicherts, Martin

    2009-07-01

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

  18. [The Swedish ambulance services 1935-1936 of Gunnar Agge].

    Science.gov (United States)

    Gustavsson, Pär; Nilsson, Peter M

    2006-01-01

    The fact that Sweden has been spared from war on its soil for almost 200 years, has not stopped Swedish citizens from participating in conflicts worldwide during this period. This has been described, especially from the soldiers perspective. The contribution of Swedish physicians has not been written about to the same extent. When Mussolini's Italy in October 1935 invaded the poor and underdeveloped country of Ethiopia (former Abyssinia) an ambulance was immediately organized by the Swedish Red Cross. To lead such an expedition, a great knowledge of Ethiopian culture och maybe most importantly, of the weather and geographical conditions, was undoubtedly demanded. Therefore, the Swedish Red Cross turned to two Ethiopian veterans. Doctor Fride Hylander, a missionary-son who had been working on a hospital project in the Ethiopian province of Harrar and his friend since school years, doctor Gunnar Agge, were assigned the leadership of the ambulance. Dr Agge had also participated in improving the Ethiopian health care both in Harrar and later as civilian and military doctor in the province of Ogaden, where he was medically responsible for the more than 9 000 men strong army that the Ethiopian emperor had stationed there after Italian provocations. Most of the other members of the ambulance were handpicked by these two leaders and many of them had, just like themselves, a stong religious belief. A money-raise was immediately initiated and in less than six weeks 700 000 Swedish crowns had been collected, more then twice the sum the ambulance was calculated to cost. In early november 1935 the ambulance was clear to go. Their primary objective was to travel through British Somaliland and establish a field-hospital in the province of Harrar. However, the Ethiopian emperor had other things in mind. He wanted to reorganize the ambulance and divide it in two and place it closer to the front line. The ambulance decided to go along with his wish. Both groups started eventually

  19. Gravity gradiometry difference measurement as a tool for monitoring pumping and injection; forward modeling results

    International Nuclear Information System (INIS)

    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

  20. Carex flava agg. (section Ceratocystis, Cyperaceae in Poland: taxonomy, morphological variation, and soil conditions

    Directory of Open Access Journals (Sweden)

    Więcław Helena

    2014-03-01

    Full Text Available Sedges of Carex flava agg., typical of moist or wet habitats, are difficult to classify because of a lack of clear-cut morphological differences between them and the existence of numerous hybrids. This monograph presents results of research conducted in 2007-2012 in various parts of Poland. The plant material consisted of 1852 living specimens of Carex flava agg., collected from 80 localities, and dried specimens from 26 herbaria and from 7 private collections. The analysis involved 45 morphological characters (34 quantitative and 11 qualitative and 9 soil parameters. Univariate, bivariate, and multivariate statistical methods were used to process the data. The results confirm the taxonomic classification dividing the C. flava group into 4 species: C. flava s.s., C. lepidocarpa, C. demissa, and C. viridula. This classification is based on (i a high observed level of morphological separation of these taxa, resulting mostly from differences in generative characters, i.e. length of the utricle and its beak, and percentage ratio of beak length to total utricle length; (ii integrity of the taxa at the sites where they coexist, although some intermediate forms resulting from hybridization are also present; (iii habitat preferences of the taxa, especially the preference of C. lepidocarpa for calcareous sites and of C. demissa for slightly acidic soils. Thus in Poland the analysed taxa are morphologically well-defined and show clear ecological preferences. Continuous variation of morphological characters was observed among specimens of C. viridula, so it is not justifiable to distinguish its subspecies (sometimes classified even as separate species, described previously in literature. Consequently, the 2 subgroups of C. viridula were treated as local variants (i.e. varieties: var. viridula and var. pulchella, considering their different habitat requirements. Additionally, 5 hybrids were distinguished within C. flava agg.: C. ×alsatica [= C. demissa

  1. A Monte Carlo approach to constraining uncertainties in modelled downhole gravity gradiometry applications

    Science.gov (United States)

    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.

  2. The effect of dielectric constants on noble metal/semiconductor SERS enhancement: FDTD simulation and experiment validation of Ag/Ge and Ag/Si substrates.

    Science.gov (United States)

    Wang, Tao; Zhang, Zhaoshun; Liao, Fan; Cai, Qian; Li, Yanqing; Lee, Shuit-Tong; Shao, Mingwang

    2014-02-11

    The finite-difference time-domain (FDTD) method was employed to simulate the electric field distribution for noble metal (Au or Ag)/semiconductor (Ge or Si) substrates. The simulation showed that noble metal/Ge had stronger SERS enhancement than noble metal/Si, which was mainly attributed to the different dielectric constants of semiconductors. In order to verify the simulation, Ag nanoparticles with the diameter of ca. 40 nm were grown on Ge or Si wafer (Ag/Ge or Ag/Si) and employed as surface-enhanced Raman scattering substrates to detect analytes in solution. The experiment demonstrated that both the two substrates exhibited excellent performance in the low concentration detection of Rhodamine 6G. Besides, the enhancement factor (1.3 × 10(9)) and relative standard deviation values (less than 11%) of Ag/Ge substrate were both better than those of Ag/Si (2.9 × 10(7) and less than 15%, respectively), which was consistent with the FDTD simulation. Moreover, Ag nanoparticles were grown in-situ on Ge substrate, which kept the nanoparticles from aggregation in the detection. To data, Ag/Ge substrates showed the best performance for their sensitivity and uniformity among the noble metal/semiconductor ones.

  3. Development of non-destructive evaluation system using an HTS-SQUID gradiometer for magnetized materials

    Science.gov (United States)

    Kawano, J.; Tsukamoto, A.; Adachi, S.; Oshikubo, Y.; Hato, T.; Tanabe, K.; Okamura, T.

    We have developed a new eddy-current non-destructive evaluation (NDE) system using an HTS SQUID gradiometer with the aim of applying it to practical materials with magnetization. The new NDE system employs a LN2-cooled external Cu pickup coil and an HTS SQUID chip placed in a magnetic shield made of HTS material. The HTS SQUID chip consists of an HTS planar gradiometer manufactured by using a ramp-edge junction technology and a multi-turn HTS thin film input coil coupled with the flip-chip configuration. The first-order coaxial gradiometric Cu pickup coil with a diameter of 16 mm and the baseline of 5.6 mm was used in the present NDE experiments. By using this NDE system, we could observe defect-induced magnetic signals without an appreciable influence of magnetization up to 10 mT. We also examined the ability of detecting deep-lying defects and compared with the results obtained using our previous NDE system.

  4. Earth System Data Records of Mass Transport from Time-Variable Gravity Data

    Science.gov (United States)

    Zlotnicki, V.; Talpe, M.; Nerem, R. S.; Landerer, F. W.; Watkins, M. M.

    2014-12-01

    Satellite measurements of time variable gravity have revolutionized the study of Earth, by measuring the ice losses of Greenland, Antarctica and land glaciers, changes in groundwater including unsustainable losses due to extraction of groundwater, the mass and currents of the oceans and their redistribution during El Niño events, among other findings. Satellite measurements of gravity have been made primarily by four techniques: satellite tracking from land stations using either lasers or Doppler radio systems, satellite positioning by GNSS/GPS, satellite to satellite tracking over distances of a few hundred km using microwaves, and through a gravity gradiometer (radar altimeters also measure the gravity field, but over the oceans only). We discuss the challenges in the measurement of gravity by different instruments, especially time-variable gravity. A special concern is how to bridge a possible gap in time between the end of life of the current GRACE satellite pair, launched in 2002, and a future GRACE Follow-On pair to be launched in 2017. One challenge in combining data from different measurement systems consists of their different spatial and temporal resolutions and the different ways in which they alias short time scale signals. Typically satellite measurements of gravity are expressed in spherical harmonic coefficients (although expansions in terms of 'mascons', the masses of small spherical caps, has certain advantages). Taking advantage of correlations among spherical harmonic coefficients described by empirical orthogonal functions and derived from GRACE data it is possible to localize the otherwise coarse spatial resolution of the laser and Doppler derived gravity models. This presentation discusses the issues facing a climate data record of time variable mass flux using these different data sources, including its validation.

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

    Directory of Open Access Journals (Sweden)

    Shitao Yan

    2017-11-01

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

  6. A sapphire monolithic differential accelerometer as core sensor for gravity gradiometric geophysical instrumentation

    Directory of Open Access Journals (Sweden)

    F. Mango

    2006-06-01

    Full Text Available Gradiometric gravimetry is a survey technique widely used in geological structure investigation. This work demonstrates the feasibility of a new class of low frequency accelerometers for geodynamics studies and space applications. We present the design features of a new low noise single-axis differential accelerometer; the sensor is suitable to be used in a Gravity Gradiometer (GG system for land geophysical survey and gravity gradient measurements. A resolution of 1 Eötvös (1 Eö=10?9s?2 at one sample per second is achievable in a compact, lightweight (less than 2 kg portable instrument, operating at room temperature. The basic components of the sensor are two identical rigidly connected accelerometers separated by a 15-cm baseline vector and the useful signal is extracted as the subtraction of the two outputs, by means of an interferometric microwave readout system. The structure will be engraved in a monocrystal of sapphire by means of Computer-Numerically-Controlled (CNC ultrasonic machining: the material was chosen because of its unique mix of outstanding mechanical and dielectric properties.

  7. Investigation of a geodesy coexperiment to the Gravity Probe B relativity gyroscope program

    Science.gov (United States)

    Everitt, C. W. F.; Parkinson, Bradford W.; Tapley, Mark

    1993-01-01

    Geodesy is the science of measuring the gravitational field of and positions on the Earth. Estimation of the gravitational field via gravitation gradiometry, the measurement of variations in the direction and magnitude of gravitation with respect to position, is this dissertation's focus. Gravity Probe B (GP-B) is a Stanford satellite experiment in gravitational physics. GP-B will measure the precession the rotating Earth causes on the space time around it by observing the precessions of four gyroscopes in a circular, polar, drag-free orbit at 650 km altitude. The gyroscopes are nearly perfect niobium-coated spheres of quartz, operating at 1.8 K to permit observations with extremely low thermal noise. The permissible gyroscope drift rate is miniscule, so the torques on the gyros must be tiny. A drag-free control system, by canceling accelerations caused by nongravitational forces, minimizes the support forces and hence torques. The GP-B system offers two main possibilities for geodesy. One is as a drag-free satellite to be used in trajectory-based estimates of the Earth's gravity field. We described calculations involving that approach in our previous reports, including comparison of laser only, GPS only, and combined tracking and a preliminary estimate of the possibility of estimating relativistic effects on the orbit. The second possibility is gradiometry. This technique has received a more cursory examination in previous reports, so we concentrate on it here. We explore the feasibility of using the residual suspension forces centering the GP-B gyros as gradiometer signals for geodesy. The objective of this work is a statistical prediction of the formal uncertainty in an estimate of the Earth's gravitation field using data from GP-B. We perform an instrument analysis and apply two mathematical techniques to predict uncertainty. One is an analytical approach using a flat-Earth approximation to predict geopotential information quality as a function of spatial

  8. Magnetic particle detection in unshielded environment using orthogonal fluxgate gradiometer

    Energy Technology Data Exchange (ETDEWEB)

    Elrefai, Ahmed L., E-mail: a.lotfyelrefai@gmail.com; Sasada, Ichiro [Applied Science for Electronics and Materials, Kyushu University, Kasuga (Japan)

    2015-05-07

    A new detection system for magnetic particles, which can operate in an unshielded environment, is developed using a fundamental mode orthogonal fluxgate gradiometer. The proposed detection system offers the advantages of cost, size, and weight reduction as compared to contamination detection systems using superconducting quantum interference device sensor. The detection system can be used to detect metallic contamination in foods or lithium ion battery production lines. The system has been investigated numerically to optimize various design parameters of the system. Experimental setup has been developed to evaluate some of the numerically predicted results. Steel balls were successfully detected down to the diameter of 50 μm.

  9. Growth of two-dimensional Ge crystal by annealing of heteroepitaxial Ag/Ge(111) under N2 ambient

    Science.gov (United States)

    Ito, Koichi; Ohta, Akio; Kurosawa, Masashi; Araidai, Masaaki; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

    2018-06-01

    The growth of a two-dimensional crystal of Ge atoms on an atomically flat Ag(111) surface has been demonstrated by the thermal annealing of a heteroepitaxial Ag/Ge structure in N2 ambient at atmospheric pressure. The surface morphology and chemical bonding features of heteroepitaxial Ag(111) grown on wet-cleaned Ge(111) after annealing at different temperatures and for various times have been systematically investigated to control the surface segregation of Ge atoms and the planarization of the heteroepitaxial Ag(111) surface.

  10. Step edge Josephson junctions and high temperature superconducting quantum interference device (SQUID) gradiometers

    International Nuclear Information System (INIS)

    Millar, Alasdair J.

    2002-01-01

    This thesis is concerned with the development of Superconducting Quantum Interference Device (SQUID) gradiometers based on the high temperature superconductor YBa 2 Cu 3 O 7-δ (YBCO). A step-edge Josephson junction fabrication process was developed to produce sufficiently steep (>60 deg) step-edges such that junctions exhibited RSJ-like current-voltage characteristics. The mean I C R N product of a sample of twenty step-edge junctions was 130μV. Step-edge dc SQUIDs with inductances between 67pH and 114pH were fabricated. Generally the SQUIDs had an intrinsic white flux noise in the 10-30μΦ 0 /√Hz range, with the best device, a 70pH SQUID, exhibiting a white flux noise of 5μΦ 0 /√Hz. Different first-order SQUID gradiometer designs were fabricated from single layers of YBCO. Two single-layer gradiometer (SLG) designs were fabricated on 10x10mm 2 substrates. The best balance and lowest gradient sensitivity measured for these devices were 1/300 and 308fT/cm√Hz (at 1 kHz) respectively. The larger baseline and larger flux capture area of the pick-up loops in a large area SLG design, fabricated on 30x10mm 2 substrates, resulted in significant improvements in the balance and gradient field sensitivity with 1/1000 and 50fT/cm√Hz (at 1kHz) measured respectively. To reduce the uniform field effective area of SLOs and therefore reduce the direct pick-up of environmental field noise when operated unshielded, a novel gradiometric SQUID (G-SQUID) device was developed. Fabricated from a single layer of YBCO, the G-SQUIDs with inductances of 67pH, had small uniform field effective areas of approximately 2μm 2 - more than two orders of magnitude smaller than the uniform field effective areas of conventional narrow linewidth SQUIDs of similar inductance. Two designs of G-SQUID were fabricated on 10x10mm 2 substrates. Due to their small effective areas, when cooled unshielded these devices showed no increase in their white flux noise. The best balance achieved for a G

  11. The potential of quantum technology gravity sensors in civil engineering

    Science.gov (United States)

    Tuckwell, G.; Metje, N.; Boddice, D.; Usher, C.

    2017-12-01

    Potential field techniques have advantages over active geophysical techniques as they are not limited to the depth they can image features, provided the signals of interest are detectable amongst the other variations recorded by the instrument. A new generation of gravity instruments based on quantum technology promise greatly increased measurement sensitivity, but with this comes significant challenges in data processing and noise suppression. In the UK Innovate UK funded SIGMA project (http://www.rsksigma.co.uk/) the field of opportunity for a step change in gravity sensor accuracy has been evaluated by comparison with existing geophysical sensors, identifying the range of targets and depths of interest to commercial end users that are currently undetectable and might become visible. Forward modelling was used to quantify the potential of a Quantum Technology (QT) gravity and gravity gradiometer sensor. A substantive improvement in detectability of targets is predicted, which can be considered as a factor of 1.5 to 2 increase in the depth of detectability, or in the reduction of the size of the feature of interest. To take further advantage of new instrument sensitivity, new survey workflows are required. The accuracy of measured gravity maps is limited by environmental vibration noise, and by the accuracy with which tidal variations and terrain signals can be removed. It is still common practice in engineering scale surveys for gravity values to be reduced to Bouguer residuals. However, with a more sensitive instrument comes the need to measure the terrain more accurately. This can be achieved within a commercially viable workflow using a laser scanner for rapid data acquisition and advanced processing to produce an accurate DEM. Initial tests on 4 commercial sites have shown that an improvement of 10s of mGal can be achieved if applying a full digital terrain model correction to the microgravity data even on sites with very minor topographic height variations

  12. Capability assessment and challenges for quantum technology gravity sensors for near surface terrestrial geophysical surveying

    Science.gov (United States)

    Boddice, Daniel; Metje, Nicole; Tuckwell, George

    2017-11-01

    Geophysical surveying is widely used for the location of subsurface features. Current technology is limited in terms of its resolution (thus size of features it can detect) and penetration depth and a suitable technique is needed to bridge the gap between shallow near surface investigation using techniques such as EM conductivity mapping and GPR commonly used to map the upper 5 m below ground surface, and large features at greater depths detectable using conventional microgravity (> 5 m below ground surface). This will minimise the risks from unknown features buried in and conditions of the ground during civil engineering work. Quantum technology (QT) gravity sensors potentially offer a step-change in technology for locating features which lie outside of the currently detectable range in terms of size and depth, but that potential is currently unknown as field instruments have not been developed. To overcome this, a novel computer simulation was developed for a large range of different targets of interest. The simulation included realistic noise modelling of instrumental, environmental and location sources of noise which limit the accuracy of current microgravity measurements, in order to assess the potential capability of the new QT instruments in realistic situations and determine some of the likely limitations on their implementation. The results of the simulations for near surface features showed that the new technology is best employed in a gradiometer configuration as opposed to the traditional single sensor gravimeter used by current instruments due to the ability to suppress vibrational environmental noise effects due to common mode rejection between the sensors. A significant improvement in detection capability of 1.5-2 times was observed, putting targets such as mineshafts into the detectability zone which would be a major advantage for subsurface surveying. Thus this research, for the first time, has demonstrated clearly the benefits of QT gravity

  13. Nondestructive evaluation of braided carbon fiber composites with artificial defect using HTS-SQUID gradiometer

    International Nuclear Information System (INIS)

    Shinyama, Y.; Yamaji, T.; Hatsukade, Y.; Takai, Y.; Aly-Hassan, M.S.; Nakai, A.; Hamada, H.; Tanaka, S.

    2011-01-01

    We applied a current-injection-based NDE method using a HTS-SQUID gradiometer to a braided CFRP with artificial cracks. Current distributions in the braided CFRP were estimated from measured field gradient distributions. A small crack, in which a few carbon-fiber bundles were cut, was well detected from the current distributions. A cross-section of the CFRP showed that a density of the bundles at edges is higher than the other part. The experimental results demonstrated the capability of the method to detect sub-mm cracks. Braided carbon fiber reinforced plastics (CFRPs) are one of multifunctional materials with superior properties such as mechanical strength to normal CFRPs since the braided CFRPs have continuous fiber bundles. In this paper, we applied the current-injection-based nondestructive evaluation (NDE) method using a HTS-SQUID gradiometer to the braided CFRP for the detection of the breakage of the bundles. We prepared planar braided CFRP samples with and without artificial cracks of 1 and 2 mm lengths, and measured the current density distribution above the samples using the NDE method. In the measurement results, not only a few completely-cut bundles but also the additional partially-cut bundles were detected from decrease in the measured current density along the cut bundle around the cracks. From these results, we showed that it is possible to inspect a few partially-cut bundles in the braided CFRPs by the NDE method.

  14. A contrastive study on the influences of radial and three-dimensional satellite gravity gradiometry on the accuracy of the Earth's gravitational field recovery

    International Nuclear Information System (INIS)

    Zheng Wei; Hsu Hou-Tse; Zhong Min; Yun Mei-Juan

    2012-01-01

    The accuracy of the Earth's gravitational field measured from the gravity field and steady-state ocean circulation explorer (GOCE), up to 250 degrees, influenced by the radial gravity gradient V zz and three-dimensional gravity gradient V ij from the satellite gravity gradiometry (SGG) are contrastively demonstrated based on the analytical error model and numerical simulation, respectively. Firstly, the new analytical error model of the cumulative geoid height, influenced by the radial gravity gradient V zz and three-dimensional gravity gradient V ij are established, respectively. In 250 degrees, the GOCE cumulative geoid height error measured by the radial gravity gradient V zz is about 2 ½ times higher than that measured by the three-dimensional gravity gradient V ij . Secondly, the Earth's gravitational field from GOCE completely up to 250 degrees is recovered using the radial gravity gradient V zz and three-dimensional gravity gradient V ij by numerical simulation, respectively. The study results show that when the measurement error of the gravity gradient is 3 × 10 −12 /s 2 , the cumulative geoid height errors using the radial gravity gradient V zz and three-dimensional gravity gradient V ij are 12.319 cm and 9.295 cm at 250 degrees, respectively. The accuracy of the cumulative geoid height using the three-dimensional gravity gradient V ij is improved by 30%–40% on average compared with that using the radial gravity gradient V zz in 250 degrees. Finally, by mutual verification of the analytical error model and numerical simulation, the orders of magnitude from the accuracies of the Earth's gravitational field recovery make no substantial differences based on the radial and three-dimensional gravity gradients, respectively. Therefore, it is feasible to develop in advance a radial cold-atom interferometric gradiometer with a measurement accuracy of 10 −13 /s 2 −10 −15 /s 2 for precisely producing the next-generation GOCE Follow-On Earth gravity field

  15. The high temperature superconductor YBa2Cu3O7-δ: symmetry of the order parameter, and gradiometers for biomagnetic applications

    International Nuclear Information System (INIS)

    Kouznetsov, Konstantin A.

    1999-01-01

    The cuprate YBa 2 Cu 3 O 7-δ is the material that drives the majority of the technological applications of high transition temperature (Tc) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-Tc superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-Tc superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa 2 Cu 3 O 7-δ . A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa 2 Cu 3 O 7-δ . These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa 2 Cu 3 O 7-δ , and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa 2 Cu 3 O 7-δ in superconducting electronics. The authors introduce a novel Superconducting Quantum Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T c SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the pickup up loop of a directly coupled magnetometer. The long baseline of the gradiometer, 48 mm, and the intrinsic. Balance of better than 1 part in 100 make it an ideal candidate

  16. Apparatus and method for detecting a magnetic anomaly contiguous to remote location by SQUID gradiometer and magnetometer systems

    Science.gov (United States)

    Overton, W.C. Jr.; Steyert, W.A. Jr.

    1981-05-22

    A superconducting quantum interference device (SQUID) magnetic detection apparatus detects magnetic fields, signals, and anomalies at remote locations. Two remotely rotatable SQUID gradiometers may be housed in a cryogenic environment to search for and locate unambiguously magnetic anomalies. The SQUID magnetic detection apparatus can be used to determine the azimuth of a hydrofracture by first flooding the hydrofracture with a ferrofluid to create an artificial magnetic anomaly therein.

  17. Prototype Moving Base Rotating Gravity Gradiometer

    Science.gov (United States)

    1975-05-01

    investigation oi the lubrication filling procedures, and review and correction of the design deficiencies . B. Isoelastic Arm 1« Design and Tests...bl bilJ il (15A) tK2 +2K8] = tea2 "ajZ + eb2 nbj2^ n J2 (16A) [K. + 2K-] 4 [e _ n .7 + e, 7 n, ._]/ L 1 7J L a? ai7

  18. MEMS-based gradiometer for the complete characterization of Martian magnetic environment

    Science.gov (United States)

    Mesa, Jose Luis; Ciudad, David; McHenry, Michael E.; Aroca, Claudio; Díaz-Michelena, Marina

    2013-04-01

    The in-situ determination of the Martian magnetic field is one of the most important and ambitious objectives in Mars exploration, because its implications in paleomagnetism, tectonics and mineral determination. To place sensors on Mars is a complicated task, due to the extreme conditions of the planet surface and also because of the relative low budget devoted to this kind of instrument: low power, mass, volume and the need to operate in a magnetically noise environment. A complete and accurate measurement of the magnetic environment includes the determination of both magnitude and gradient of the magnetic field (B). There are many developments of magnetometers with the characteristics mentioned before [2], but the question about gradient is not that well solved and most gradient sensors are based on a couple of magnetometers separated a certain distance [2, 3]. The aim of this abstract is to introduce a new MEMS based robust gradiometer for the point measurement of the field gradient with the ultimate goal to perform in situ measurement on Mars and shed some light in the magnetic anomalies explanation of the Red Planet. Since in some conditions ?ׯB = 0, we assume knowing six of the nine components is sufficient to reconstruct entirely the magnetic field gradient. The device proposed consists of a set of six cantilevers to measure these six components (with resolution in the order of 1 nT/mm) combined either with another miniaturized and more accurate magnetometer (with resolution below the nT) for the measurement of the field vector. Every component system consists of a cantilever with an appropriate geometry, an excitation coil and a mechanism to generate a field gradient. The cantilevers are made of piezoelectric material (bimorph, with two piezoelectric layers) covered by a soft ferromagnetic material (of Iron-Nickel base). Is explained below the working principle for one component. When the excitation system generates an alternating magnetic field (enough

  19. Lunar Navigator - A Miniature, Fully Autonomous, Lunar Navigation, Surveyor, and Range Finder System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Microcosm proposes to design and develop a fully autonomous Lunar Navigator based on our MicroMak miniature star sensor and a gravity gradiometer similar to one on a...

  20. Visualization of flowing current in braided carbon fiber reinforced plastics using SQUID gradiometer for nondestructive evaluation

    International Nuclear Information System (INIS)

    Hatsukade, Y; Yoshida, K; Kage, T; Tanaka, S; Takai, Y; Aly-Hassan, M S; Hamada, H; Nakai, A

    2013-01-01

    In this paper, visualization of flowing current in various braided carbon fiber reinforced plastics (CFRPs) was demonstrated using high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) gradiometer, in order to study electrical properties and integrity of the braided CFRP samples. Step-by-step tensile loading was also applied to the samples, in order to study their mechanical properties and destructive mechanism. Experimental results indicated that the addition of carbon nano fibers and middle-end carbon fiber bundles attributed to modify not only the mechanical properties, but also the electrical properties of the samples. Combining the results by the both methods, a scenario of the destructive mechanism of one sample was estimated.

  1. DC current distribution mapping system of the solar panels using a HTS-SQUID gradiometer

    International Nuclear Information System (INIS)

    Miyazaki, Shingo; Kasuya, Syohei; Saari, Mohd Mawardi; Sakai, Kenji; Kiwa, Toshihiko; Tsukada, Keiji; Tsukamoto, Akira; Adachi, Seiji; Tanabe, Keiichi

    2014-01-01

    Solar panels are expected to play a major role as a source of sustainable energy. In order to evaluate solar panels, non-destructive tests, such as defect inspections and response property evaluations, are necessary. We developed a DC current distribution mapping system of the solar panels using a High Critical Temperature Superconductor Superconducting Quantum Interference Device (HTS-SQUID) gradiometer with ramp edge type Josephson junctions. Two independent components of the magnetic fields perpendicular to the panel surface (∂Bz/∂x, ∂Bz/∂y) were detected. The direct current of the solar panel is visualized by calculating the composition of the two signal components, the phase angle, and mapping the DC current vector. The developed system can evaluate the uniformity of DC current distributions precisely and may be applicable for defect detection of solar panels.

  2. Manifestations of strain–relaxation in the structure of nano-sized Co-2 × 2 islands grown on Ag/Ge(111)-√3 × √3 surface

    International Nuclear Information System (INIS)

    Huang, Xiao-Lan; Tomaszewska, Agnieszka; Lin, Chun-Liang; Tsay, Sung-Lin; Chou, Chi-Hao; Fu, Tsu-Yi

    2012-01-01

    We have examined strain–relaxation of Co-2 × 2 islands grown on the Ag/Ge(111)-√3 × √3 surface by analyzing scanning tunneling microscopy images. We have found that the Co-2 × 2 islands commonly adopt a more compact arrangement as compared to that of the Ge(111) substrate, however they differ in a degree of an atomic compactness. We have not found a distinct relation between strain–relaxation and the island height. Three groups of islands have been identified upon analyzing a correspondence between strain–relaxation and the island size: (i) small islands (not bigger than 80 nm 2 ) with a high atomic compactness, displaying fixed inter-row distances, (ii) small islands with unfixed distances between atomic rows, and (iii) big islands (bigger than 80 nm 2 ) with fixed inter-row distances, but with a less compact atomic arrangement compared to that of the first two groups. We propose a model to account for the relation between the relaxation and the island size. - Highlights: ► We examine strain–relaxation of Co-2 × 2 islands grown on Ag/Ge(111)-√3 × √3 surface. ► The Co-2 × 2 islands are more compact as compared to the substrate. ► No relation between the relaxation and the island height. ► Atomic compactness and atomic order as manifestations of strain–relaxation.

  3. The high temperature superconductor YBa2Cu3O7-δ: symmetry of the order parameter, and gradiometers for biomagnetic applications

    Energy Technology Data Exchange (ETDEWEB)

    Kouznetsov, Konstantin Alexander [Univ. of California, Berkeley, CA (US). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    1999-12-01

    The cuprate YBa2Cu3O7-δ is the material that drives the majority of the technological applications of high transition temperature (Tc) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-Tc superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-Tc superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa2Cu3O7-δ. A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa2Cu3O7-δ. These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa2Cu3O7-δ, and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa2Cu3O7-δ in superconducting electronics. The authors introduce a novel Superconducting Quantum Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T{sub c} SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the

  4. Massive gravity from bimetric gravity

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  5. Metallic Contaminant Detection using a High-Temperature Superconducting Quantum Interference Devices Gradiometer

    International Nuclear Information System (INIS)

    Tanaka, Saburo; Akai, Tomohiro; Takemoto, Makoto; Hatsukade, Yoshimi; Ohtani, Takeyoshi; Ikeda, Yoshio; Suzuki, Shuichi

    2010-01-01

    We develop magnetic metallic contaminant detectors using high-temperature superconducting quantum interference devices (HTS-SQUIDs) for industrial products. Finding ultra-small metallic contaminants is an important issue for manufacturers producing commercial products such as lithium ion batteries. If such contaminants cause damages, the manufacturer of the product suffers a big financial loss due to having to recall the faulty products. Previously, we described a system for finding such ultra-small particles in food. In this study, we describe further developments of the system, for the reduction of the effect of the remnant field of the products, and we test the parallel magnetization of the products to generate the remnant field only at both ends of the products. In addition, we use an SQUID gradiometer in place of the magnetometer to reduce the edge effect by measuring the magnetic field gradient. We test the performances of the system and find that tiny iron particles as small as 50 × 50 μm 2 on the electrode of a lithium ion battery could be clearly detected. This detection level is difficult to achieve when using other methods. (cross-disciplinary physics and related areas of science and technology)

  6. AggNet: Deep Learning From Crowds for Mitosis Detection in Breast Cancer Histology Images.

    Science.gov (United States)

    Albarqouni, Shadi; Baur, Christoph; Achilles, Felix; Belagiannis, Vasileios; Demirci, Stefanie; Navab, Nassir

    2016-05-01

    The lack of publicly available ground-truth data has been identified as the major challenge for transferring recent developments in deep learning to the biomedical imaging domain. Though crowdsourcing has enabled annotation of large scale databases for real world images, its application for biomedical purposes requires a deeper understanding and hence, more precise definition of the actual annotation task. The fact that expert tasks are being outsourced to non-expert users may lead to noisy annotations introducing disagreement between users. Despite being a valuable resource for learning annotation models from crowdsourcing, conventional machine-learning methods may have difficulties dealing with noisy annotations during training. In this manuscript, we present a new concept for learning from crowds that handle data aggregation directly as part of the learning process of the convolutional neural network (CNN) via additional crowdsourcing layer (AggNet). Besides, we present an experimental study on learning from crowds designed to answer the following questions. 1) Can deep CNN be trained with data collected from crowdsourcing? 2) How to adapt the CNN to train on multiple types of annotation datasets (ground truth and crowd-based)? 3) How does the choice of annotation and aggregation affect the accuracy? Our experimental setup involved Annot8, a self-implemented web-platform based on Crowdflower API realizing image annotation tasks for a publicly available biomedical image database. Our results give valuable insights into the functionality of deep CNN learning from crowd annotations and prove the necessity of data aggregation integration.

  7. Method and apparatus for balancing the magnetic field detecting loops of a cryogenic gradiometer using trimming coils and superconducting disks

    International Nuclear Information System (INIS)

    Lutes, C.L.

    1982-01-01

    An apparatus for and a method of measuring the difference in intensity between two coplanar magnetic field vector components at two different points in space. The device is comprised of two interconnected, relatively large, loop patterns of opposite, flux cancelling, winding sense. One or both loops include a trimming element that is itself formed of two interconnected, relatively small, loop patterns of opposite, flux cancelling, winding sense. The device is analyzed for imbalance between the two large loops and is then balanced by placing a balancing superconducting disk of the proper characteristic in or near one of the two small loops of the trimming element. The so-trimmed apparatus forms a gradiometer of substantially improved mensuration

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

    Science.gov (United States)

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

    2018-05-14

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

  9. Newtonian gravity in loop quantum gravity

    OpenAIRE

    Smolin, Lee

    2010-01-01

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

  10. Chiral gravity, log gravity, and extremal CFT

    International Nuclear Information System (INIS)

    Maloney, Alexander; Song Wei; Strominger, Andrew

    2010-01-01

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

  11. Modeling and Error Analysis of a Superconducting Gravity Gradiometer.

    Science.gov (United States)

    1979-08-01

    quantum (bij magnetic flux linking elements i and u b N noise flux of SQUID W natural angular frequency W f angular frequency of forcing function Wi...SQUID superconducting quantum interference device TBAN tolerable background acceleration noise VIC voltage to current converter -xxiii- .4 Chapter I...to detect the minute vibrations induced in a 1 ton, cryogenically cooled and magnetically levitated gravitational wave antenna. The antenna concept

  12. Animal magnetocardiography using superconducting quantum interference device gradiometers assisted with magnetic nanoparticle injection: A sensitive method for early detecting electromagnetic changes induced by hypercholesterolemia

    Science.gov (United States)

    Wu, C. C.; Hong, B. F.; Wu, B. H.; Yang, S. Y.; Horng, H. E.; Yang, H. C.; Tseng, W. Y. Isaac; Tseng, W. K.; Liu, Y. B.; Lin, L. C.; Lu, L. S.; Lee, Y. H.

    2007-01-01

    In this work, the authors used a superconducting quantum interference device (SQUID) magnetocardiography (MCG) system consisted of 64-channel low-transition-temperature SQUID gradiometers to detect the MCG signals of hepercholesterolemic rabbits. In addition, the MCG signals were recorded before and after the injection of magnetic nanoparticles into the rabbits' ear veins to investigate the effects of magnetic nanoparticles on the MCG signals. These MCG data were compared to those of normal rabbits to reveal the feasibility for early detection of the electromagnetic changes induced by hypercholesterolemia using MCG with the assistance of magnetic nanoparticle injection.

  13. Even-dimensional topological gravity from Chern-Simons gravity

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  14. Polar gravity fields from GOCE and airborne gravity

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  15. Massive Gravity

    OpenAIRE

    de Rham, Claudia

    2014-01-01

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

  16. Scales of gravity

    International Nuclear Information System (INIS)

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

    2002-01-01

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

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

    OpenAIRE

    Capozziello, S.; Troisi, A.

    2005-01-01

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

  18. Terrestrial gravity data analysis for interim gravity model improvement

    Science.gov (United States)

    1987-01-01

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

  19. Dualities and emergent gravity: Gauge/gravity duality

    Science.gov (United States)

    de Haro, Sebastian

    2017-08-01

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

  20. Contravariant gravity on Poisson manifolds and Einstein gravity

    International Nuclear Information System (INIS)

    Kaneko, Yukio; Watamura, Satoshi; Muraki, Hisayoshi

    2017-01-01

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

  1. Is nonrelativistic gravity possible?

    International Nuclear Information System (INIS)

    Kocharyan, A. A.

    2009-01-01

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

  2. Gravity-matter entanglement in Regge quantum gravity

    International Nuclear Information System (INIS)

    Paunković, Nikola; Vojinović, Marko

    2016-01-01

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

  3. Lovelock gravities from Born-Infeld gravity theory

    Science.gov (United States)

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

    2017-02-01

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

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

    OpenAIRE

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

    2004-01-01

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

  5. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

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

  6. Lower dimensional gravity

    International Nuclear Information System (INIS)

    Brown, J.D.

    1988-01-01

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

  7. Lovelock gravities from Born–Infeld gravity theory

    Directory of Open Access Journals (Sweden)

    P.K. Concha

    2017-02-01

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

  8. Nonlocal gravity

    CERN Document Server

    Mashhoon, Bahram

    2017-01-01

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

  9. Geometric Liouville gravity

    International Nuclear Information System (INIS)

    La, H.

    1992-01-01

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

  10. Covariant w∞ gravity

    NARCIS (Netherlands)

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

    1990-01-01

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

  11. Analogue Gravity

    Directory of Open Access Journals (Sweden)

    Carlos Barceló

    2011-05-01

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

  12. Quantum Gravity Phenomenology

    OpenAIRE

    Amelino-Camelia, Giovanni

    2003-01-01

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

  13. Automated borehole gravity meter system

    International Nuclear Information System (INIS)

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

    1984-01-01

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

  14. Gravity is Geometry.

    Science.gov (United States)

    MacKeown, P. K.

    1984-01-01

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

  15. Gravity inversion code

    International Nuclear Information System (INIS)

    Burkhard, N.R.

    1979-01-01

    The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables

  16. Gravity brake

    Science.gov (United States)

    Lujan, Richard E.

    2001-01-01

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

  17. The Cause of Gravity

    OpenAIRE

    Byrne, Michael

    1999-01-01

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

  18. Gene and stress history interplay in emergence of PTSD-like features.

    Science.gov (United States)

    Chakraborty, Nabarun; Meyerhoff, James; Gautam, Aarti; Muhie, Seid; Jibitu, Meskerem; De Lima, Thereza C M; Hammamieh, Rasha; Jett, Marti

    2015-10-01

    Systematically distinguishing genetic liability from other contributing factors is critical for designing a preventive strategy for post-traumatic stress disorder (PTSD). To address this issue, we investigated a murine model exposing C57BL/6j, DBA/2j and BALB/cj mice to repeated stress via exposure to conspecific aggressors (Agg-E). Naïve mice from each strain were subjected to the proximity of aggressor (Agg) mice for 6h using a 'cage-within-a-cage' paradigm, which was repeated for 5 or 10 days with intermittent and unpredictable direct contact with Agg mice. During the Agg-E stress, DBA/2j developed a different strategy to evade Agg mice, which potentially contributed to its phenotypic resilience to Agg-E stress. Although Agg mice inflicted C57BL/6j and BALB/cj with equivalent numbers of strikes, BALB/cj displayed a distinct behavioral phenotype with delayed exhibition of a number of PTSD-like features. By contrast, C57BL/6j mice displayed unique vulnerability to Agg-E stress induced myocardopathy, possibly attributable to their particular susceptibility to hypoxia. A group of genes (Bdnf, Ngf, Zwint, Cckbr, Slc6a4, Fkbp5) linked to PTSD and synaptic plasticity were significantly altered in C57BL/6j and BALB/cj Agg-E mice. Contributions of Agg-E stress history and genotypic heterogeneity emerged as the key mediators of PTSD-like features. Linking genetic components to specific phenotypic and pathological features could have potential clinical implications. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Cutoff for extensions of massive gravity and bi-gravity

    International Nuclear Information System (INIS)

    Matas, Andrew

    2016-01-01

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

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

    Science.gov (United States)

    Asghar, Anila; Libarkin, Julie C.

    2010-01-01

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

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

    Science.gov (United States)

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

    2018-01-01

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

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

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

    Data.gov (United States)

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

  4. The earth's shape and gravity

    CERN Document Server

    Garland, G D; Wilson, J T

    2013-01-01

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

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

    Data.gov (United States)

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

  6. Identification, quantification, spatiotemporal distribution and genetic variation of major latex secondary metabolites in the common dandelion (Taraxacum officinale agg.).

    Science.gov (United States)

    Huber, Meret; Triebwasser-Freese, Daniella; Reichelt, Michael; Heiling, Sven; Paetz, Christian; Chandran, Jima N; Bartram, Stefan; Schneider, Bernd; Gershenzon, Jonathan; Erb, Matthias

    2015-07-01

    The secondary metabolites in the roots, leaves and flowers of the common dandelion (Taraxacum officinale agg.) have been studied in detail. However, little is known about the specific constituents of the plant's highly specialized laticifer cells. Using a combination of liquid and gas chromatography, mass spectrometry and nuclear magnetic resonance spectrometry, we identified and quantified the major secondary metabolites in the latex of different organs across different growth stages in three genotypes, and tested the activity of the metabolites against the generalist root herbivore Diabrotica balteata. We found that common dandelion latex is dominated by three classes of secondary metabolites: phenolic inositol esters (PIEs), triterpene acetates (TritAc) and the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G). Purification and absolute quantification revealed concentrations in the upper mgg(-1) range for all compound classes with up to 6% PIEs, 5% TritAc and 7% TA-G per gram latex fresh weight. Contrary to typical secondary metabolite patterns, concentrations of all three classes increased with plant age. The highest concentrations were measured in the main root. PIE profiles differed both quantitatively and qualitatively between plant genotypes, whereas TritAc and TA-G differed only quantitatively. Metabolite concentrations were positively correlated within and between the different compound classes, indicating tight biosynthetic co-regulation. Latex metabolite extracts strongly repelled D. balteata larvae, suggesting that the latex constituents are biologically active. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Artificial gravity - The evolution of variable gravity research

    Science.gov (United States)

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

    1987-01-01

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

  1. Analogue Gravity

    Directory of Open Access Journals (Sweden)

    Barceló Carlos

    2005-12-01

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

  2. NGS Absolute Gravity Data

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

  5. Classical Weyl transverse gravity

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-05-15

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

  6. Southern Africa Gravity Data

    Data.gov (United States)

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

  7. Einstein gravity emerging from quantum weyl gravity

    International Nuclear Information System (INIS)

    Zee, A.

    1983-01-01

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

  8. influence of gravity

    Directory of Open Access Journals (Sweden)

    Animesh Mukherjee

    1991-01-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  10. Is Gravity an Entropic Force?

    Directory of Open Access Journals (Sweden)

    Shan Gao

    2011-04-01

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

  11. Strings and quantum gravity

    International Nuclear Information System (INIS)

    Vega, H.J. de

    1990-01-01

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

  12. Gravity interpretation via EULDPH

    International Nuclear Information System (INIS)

    Ebrahimzadeh Ardestani, V.

    2003-01-01

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

  13. Anomalies and gravity

    International Nuclear Information System (INIS)

    Mielke, Eckehard W.

    2006-01-01

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

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

    Data.gov (United States)

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

  15. Gravity loop corrections to the standard model Higgs in Einstein gravity

    International Nuclear Information System (INIS)

    Yugo Abe; Masaatsu Horikoshi; Takeo Inami

    2016-01-01

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

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

    Science.gov (United States)

    Hurtado-Cardador, Manuel; Urrutia-Fucugauchi, Jaime

    2006-12-01

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

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

    Data.gov (United States)

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

  18. Quantum gravity from noncommutative spacetime

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-15

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

  19. Quantum gravity from noncommutative spacetime

    International Nuclear Information System (INIS)

    Lee, Jungjai; Yang, Hyunseok

    2014-01-01

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

  20. The gravity field and GGOS

    DEFF Research Database (Denmark)

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

    2005-01-01

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

  3. Gravity wave astronomy

    International Nuclear Information System (INIS)

    Pinheiro, R.

    1979-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Katsuya Hasegawa

    2014-04-01

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

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

    NARCIS (Netherlands)

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

    2013-01-01

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Directory of Open Access Journals (Sweden)

    R. A. Arko

    1999-06-01

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

  9. Cosmological tests of modified gravity.

    Science.gov (United States)

    Koyama, Kazuya

    2016-04-01

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

  10. Gravity signatures of terrane accretion

    Science.gov (United States)

    Franco, Heather; Abbott, Dallas

    1999-01-01

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

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

    Data.gov (United States)

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

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

    Science.gov (United States)

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

    2018-03-16

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

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

    Science.gov (United States)

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

    2018-01-01

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

  14. BOOK REVIEW: Quantum Gravity: third edition Quantum Gravity: third edition

    Science.gov (United States)

    Rovelli, Carlo

    2012-09-01

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

  15. DNAG Gravity Data

    Data.gov (United States)

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

  16. Measuring Gravity in International Trade Flows

    Directory of Open Access Journals (Sweden)

    E. Young Song

    2004-12-01

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

  17. Quantum Gravity

    International Nuclear Information System (INIS)

    Giribet, G E

    2005-01-01

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

  18. Butterfly effect in 3D gravity

    Science.gov (United States)

    Qaemmaqami, Mohammad M.

    2017-11-01

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

  19. Induced quantum conformal gravity

    International Nuclear Information System (INIS)

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

    1988-11-01

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

  20. Nonsingular universe in massive gravity's rainbow

    Science.gov (United States)

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

    2017-06-01

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

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

    Data.gov (United States)

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

  2. Genetic Virulence Profile of Enteroaggregative Escherichia coli Strains Isolated from Danish Children with Either Acute or Persistent Diarrhea

    DEFF Research Database (Denmark)

    Hebbelstrup Jensen, Betina; Poulsen, Anja; Hebbelstrup Rye Rasmussen, Stig

    2017-01-01

    targeting the genes sat, sepA, pic, sigA, pet, astA, aatA, aggR, aaiC, aap, agg3/4C, ORF3, aafA, aggA, agg3A, agg4A, and agg5A. Furthermore, the distribution of EAEC genes in strains collected from cases of bloody, mucoid, and watery diarrhea was investigated. The classification and regression tree analysis...... was associated with the combination of the genes aatA and astA (p = 0.03). Non-mucoid diarrhea was associated with strains lacking the aatA gene (p = 0.004). Acute diarrhea was associated with the genes aggR, aap, and aggA by individual odds ratios. Resistance toward gentamicin and ciprofloxacin was observed......-negative-to identify additional factors predisposing to disease. The duration of breastfeeding was positively correlated with the likelihood of belonging to the EAEC-negative group of children....

  3. Interior Alaska Bouguer Gravity Anomaly

    Data.gov (United States)

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

  4. GOCE, la Ferrari dei satelliti

    Directory of Open Access Journals (Sweden)

    Fabrizio Bernardini

    2009-03-01

    Full Text Available GOCE, a "Ferrari" between satellitesGOCE is a new exciting European Space Agency mission within the Living Earth programme. The design of the satellite and its sensor, the Electrostatic Gravity Gradiometer, are intimately linked to produce the most advanced geodetical satellite ever put into orbit. The main result of GOCE will be the accurate mapping of the Earth's gravitational field to provide insight into the geoid as close up as 1-2 centimetres. Additional application will be applicable to studies of ocean circulation and continental drift.

  5. GOCE, la Ferrari dei satelliti

    Directory of Open Access Journals (Sweden)

    Fabrizio Bernardini

    2009-03-01

    Full Text Available GOCE, a "Ferrari" between satellites GOCE is a new exciting European Space Agency mission within the Living Earth programme. The design of the satellite and its sensor, the Electrostatic Gravity Gradiometer, are intimately linked to produce the most advanced geodetical satellite ever put into orbit. The main result of GOCE will be the accurate mapping of the Earth's gravitational field to provide insight into the geoid as close up as 1-2 centimetres. Additional application will be applicable to studies of ocean circulation and continental drift.

  6. Metastable gravity on classical defects

    International Nuclear Information System (INIS)

    Ringeval, Christophe; Rombouts, Jan-Willem

    2005-01-01

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

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

    Science.gov (United States)

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

    2005-01-01

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

  8. Scale-invariant gravity: geometrodynamics

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  9. Dual geometric-gauge field aspects of gravity

    International Nuclear Information System (INIS)

    Huei Peng; Wang, K.

    1992-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-08-07

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

  11. Focus on quantum Einstein gravity Focus on quantum Einstein gravity

    Science.gov (United States)

    Ambjorn, Jan; Reuter, Martin; Saueressig, Frank

    2012-09-01

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

  12. Gravity a very short introduction

    CERN Document Server

    Clifton, Timothy

    2017-01-01

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

  13. Quantum Gravity

    OpenAIRE

    Alvarez, Enrique

    2004-01-01

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

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

    Science.gov (United States)

    Dorais, Gregory A.

    2015-01-01

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

  15. Black holes in pure Lovelock gravities

    International Nuclear Information System (INIS)

    Cai Ronggen; Ohta, Nobuyoshi

    2006-01-01

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

  16. Active Response Gravity Offload System

    Science.gov (United States)

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

    2011-01-01

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

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

    Science.gov (United States)

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

    1973-01-01

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

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

    International Nuclear Information System (INIS)

    Kobayashi, Tsutomu

    2008-01-01

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

  19. Quantum Gravity Effects in Cosmology

    Directory of Open Access Journals (Sweden)

    Gu Je-An

    2018-01-01

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

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

    Data.gov (United States)

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

  1. Urine specific gravity test

    Science.gov (United States)

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

  2. Northern Oklahoma Gravity Data

    Data.gov (United States)

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

  3. Vaidya spacetime in massive gravity's rainbow

    Directory of Open Access Journals (Sweden)

    Yaghoub Heydarzade

    2017-11-01

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

  4. Physics of Trans-Planckian Gravity

    CERN Document Server

    Dvali, Gia; Germani, Cristiano

    2011-01-01

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

  5. Stochastic Gravity: Theory and Applications

    Directory of Open Access Journals (Sweden)

    Hu Bei Lok

    2008-05-01

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

  6. Active Response Gravity Offload and Method

    Science.gov (United States)

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

    2015-01-01

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

  7. Lactococcus lactis Subsp. Lactis Suşlarında Yüksek Sıklıkta Konjugal Transfer Sistemlerinin Analizi

    Directory of Open Access Journals (Sweden)

    Çağla Tükel

    2015-02-01

    Full Text Available Bu çalışmada L. lactis subsp. lactis suşlarında laktoz fermentasyonu özelliğini kodlayan altı farklı plazmidin yüksek sıklıkta konjugal aktarım yeteneği araştırıldı. Bu plazmidlerin konjugal transfer sıklıkları; iki seks faktörünün interaksiyonuna bağlı olarak (Clu ve Agg, Clu-/Agg-, Agg+ x Clu-/Agg+, Agg- ya da Clu+/Agg- x Clu-/Agg- konjugasyon eşleri için 1.5x10-5–1.0x10-7 ve Clu+/Agg- x Clu-/Agg+ konjugasyon eşleri için 7.1x10-2-2.7x10-3 oranlarında değişim gösterdi. Laktoz plazmidlerinin stabiliteleri ise; doğal suşlarda %82-96, MG1390 alıcı suşu için tanımlanan konjugantlarda %77-98 ve MCL8060 alıcı suşu için tanımlanan konjugantlarda ise %44-67 arasında saptandı.

  8. Idaho State Gravity Data

    Data.gov (United States)

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

  9. Physics of trans-Planckian gravity

    International Nuclear Information System (INIS)

    Dvali, Gia; Folkerts, Sarah; Germani, Cristiano

    2011-01-01

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

  10. Dilaton gravity, Poisson sigma models and loop quantum gravity

    International Nuclear Information System (INIS)

    Bojowald, Martin; Reyes, Juan D

    2009-01-01

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

  11. Andes 1997 Gravity Data

    Data.gov (United States)

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

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

    International Nuclear Information System (INIS)

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

    1980-12-01

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

  13. The Superheavy Elements and Anti-Gravity

    International Nuclear Information System (INIS)

    Anastasovski, Petar K.

    2004-01-01

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

  14. Cadiz, California Gravity Data

    Data.gov (United States)

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

  15. Extended Theories of Gravity

    International Nuclear Information System (INIS)

    Capozziello, Salvatore; De Laurentis, Mariafelicia

    2011-01-01

    Extended Theories of Gravity can be considered as a new paradigm to cure shortcomings of General Relativity at infrared and ultraviolet scales. They are an approach that, by preserving the undoubtedly positive results of Einstein’s theory, is aimed to address conceptual and experimental problems recently emerged in astrophysics, cosmology and High Energy Physics. In particular, the goal is to encompass, in a self-consistent scheme, problems like inflation, dark energy, dark matter, large scale structure and, first of all, to give at least an effective description of Quantum Gravity. We review the basic principles that any gravitational theory has to follow. The geometrical interpretation is discussed in a broad perspective in order to highlight the basic assumptions of General Relativity and its possible extensions in the general framework of gauge theories. Principles of such modifications are presented, focusing on specific classes of theories like f(R)-gravity and scalar–tensor gravity in the metric and Palatini approaches. The special role of torsion is also discussed. The conceptual features of these theories are fully explored and attention is paid to the issues of dynamical and conformal equivalence between them considering also the initial value problem. A number of viability criteria are presented considering the post-Newtonian and the post-Minkowskian limits. In particular, we discuss the problems of neutrino oscillations and gravitational waves in extended gravity. Finally, future perspectives of extended gravity are considered with possibility to go beyond a trial and error approach.

  16. No slip gravity

    Science.gov (United States)

    Linder, Eric V.

    2018-03-01

    A subclass of the Horndeski modified gravity theory we call No Slip Gravity has particularly interesting properties: 1) a speed of gravitational wave propagation equal to the speed of light, 2) equality between the effective gravitational coupling strengths to matter and light, Gmatter and Glight, hence no slip between the metric potentials, yet difference from Newton's constant, and 3) suppressed growth to give better agreement with galaxy clustering observations. We explore the characteristics and implications of this theory, and project observational constraints. We also give a simple expression for the ratio of the gravitational wave standard siren distance to the photon standard candle distance, in this theory and others, and enable a direct comparison of modified gravity in structure growth and in gravitational waves, an important crosscheck.

  17. Zero-gravity movement studies

    Science.gov (United States)

    Badler, N. I.; Fishwick, P.; Taft, N.; Agrawala, M.

    1985-01-01

    The use of computer graphics to simulate the movement of articulated animals and mechanisms has a number of uses ranging over many fields. Human motion simulation systems can be useful in education, medicine, anatomy, physiology, and dance. In biomechanics, computer displays help to understand and analyze performance. Simulations can be used to help understand the effect of external or internal forces. Similarly, zero-gravity simulation systems should provide a means of designing and exploring the capabilities of hypothetical zero-gravity situations before actually carrying out such actions. The advantage of using a simulation of the motion is that one can experiment with variations of a maneuver before attempting to teach it to an individual. The zero-gravity motion simulation problem can be divided into two broad areas: human movement and behavior in zero-gravity, and simulation of articulated mechanisms.

  18. Global detailed gravimetric geoid. [based on gravity model derived from satellite tracking and surface gravity data

    Science.gov (United States)

    Vincent, S.; Marsh, J. G.

    1973-01-01

    A global detailed gravimetric geoid has been computed by combining the Goddard Space Flight Center GEM-4 gravity model derived from satellite and surface gravity data and surface 1 deg-by-1 deg mean free air gravity anomaly data. The accuracy of the geoid is + or - 2 meters on continents, 5 to 7 meters in areas where surface gravity data are sparse, and 10 to 15 meters in areas where no surface gravity data are available. Comparisons have been made with the astrogeodetic data provided by Rice (United States), Bomford (Europe), and Mather (Australia). Comparisons have also been carried out with geoid heights derived from satellite solutions for geocentric station coordinates in North America, the Caribbean, Europe, and Australia.

  19. Partial gravity - Human impacts on facility design

    Science.gov (United States)

    Capps, Stephen; Moore, Nathan

    1990-01-01

    Partial gravity affects the body differently than earth gravity and microgravity environments. The main difference from earth gravity is human locomotion; while the main dfference from microgravity is the specific updown orientation and reach envelopes which increase volume requirements. Much data are available on earth gravity and microgravity design; however, very little information is available on human reactions to reduced gravity levels in IVA situations (without pressure suits). Therefore, if humans commit to permanent lunar habitation, much research should be conducted in the area of partial gravity effects on habitat design.

  20. Generalized uncertainty principle, quantum gravity and Horava-Lifshitz gravity

    International Nuclear Information System (INIS)

    Myung, Yun Soo

    2009-01-01

    We investigate a close connection between generalized uncertainty principle (GUP) and deformed Horava-Lifshitz (HL) gravity. The GUP commutation relations correspond to the UV-quantum theory, while the canonical commutation relations represent the IR-quantum theory. Inspired by this UV/IR quantum mechanics, we obtain the GUP-corrected graviton propagator by introducing UV-momentum p i =p 0i (1+βp 0 2 ) and compare this with tensor propagators in the HL gravity. Two are the same up to p 0 4 -order.

  1. Quantum W3 gravity

    International Nuclear Information System (INIS)

    Schoutens, K.; van Nieuwenhuizen, P.; State Univ. of New York, Stony Brook, NY

    1991-11-01

    We briefly review some results in the theory of quantum W 3 gravity in the chiral gauge. We compare them with similar results in the analogous but simpler cases of d = 2 induced gauge theories and d = 2 induced gravity

  2. Radion and holographic brane gravity

    International Nuclear Information System (INIS)

    Kanno, Sugumi; Soda, Jiro

    2002-01-01

    The low energy effective theory for the Randall-Sundrum two-brane system is investigated with an emphasis on the role of the nonlinear radion in the brane world. The equations of motion in the bulk are solved using a low energy expansion method. This allows us, through the junction conditions, to deduce the effective equations of motion for gravity on the brane. It is shown that the gravity on the brane world is described by a quasi-scalar-tensor theory with a specific coupling function ω(Ψ)=3Ψ/2(1-Ψ) on the positive tension brane and ω(Φ)=-3Φ/2(1+Φ) on the negative tension brane, where Ψ and Φ are nonlinear realizations of the radion on the positive and negative tension branes, respectively. In contrast with the usual scalar-tensor gravity, the quasi-scalar-tensor gravity couples with two kinds of matter; namely, the matter on both positive and negative tension branes, with different effective gravitational coupling constants. In particular, the radion disguised as the scalar fields Ψ and Φ couples with the sum of the traces of the energy-momentum tensor on both branes. In the course of the derivation, it is revealed that the radion plays an essential role in converting the nonlocal Einstein gravity with generalized dark radiation to local quasi-scalar-tensor gravity. For completeness, we also derive the effective action for our theory by substituting the bulk solution into the original action. It is also shown that quasi-scalar-tensor gravity works as a hologram at low energy in the sense that the bulk geometry can be reconstructed from the solution of quasi-scalar-tensor gravity

  3. Failures in sand in reduced gravity environments

    Science.gov (United States)

    Marshall, Jason P.; Hurley, Ryan C.; Arthur, Dan; Vlahinic, Ivan; Senatore, Carmine; Iagnemma, Karl; Trease, Brian; Andrade, José E.

    2018-04-01

    The strength of granular materials, specifically sand is important for understanding physical phenomena on other celestial bodies. However, relatively few experiments have been conducted to determine the dependence of strength properties on gravity. In this work, we experimentally investigated relative values of strength (the peak friction angle, the residual friction angle, the angle of repose, and the peak dilatancy angle) in Earth, Martian, Lunar, and near-zero gravity. The various angles were captured in a classical passive Earth pressure experiment conducted on board a reduced gravity flight and analyzed using digital image correlation. The data showed essentially no dependence of the peak friction angle on gravity, a decrease in the residual friction angle between Martian and Lunar gravity, no dependence of the angle of repose on gravity, and an increase in the dilation angle between Martian and Lunar gravity. Additionally, multiple flow surfaces were seen in near-zero gravity. These results highlight the importance of understanding strength and deformation mechanisms of granular materials at different levels of gravity.

  4. Topological gravity with minimal matter

    International Nuclear Information System (INIS)

    Li Keke

    1991-01-01

    Topological minimal matter, obtained by twisting the minimal N = 2 supeconformal field theory, is coupled to two-dimensional topological gravity. The free field formulation of the coupled system allows explicit representations of BRST charge, physical operators and their correlation functions. The contact terms of the physical operators may be evaluated by extending the argument used in a recent solution of topological gravity without matter. The consistency of the contact terms in correlation functions implies recursion relations which coincide with the Virasoro constraints derived from the multi-matrix models. Topological gravity with minimal matter thus provides the field theoretic description for the multi-matrix models of two-dimensional quantum gravity. (orig.)

  5. Teleparallel equivalent of Lovelock gravity

    Science.gov (United States)

    González, P. A.; Vásquez, Yerko

    2015-12-01

    There is a growing interest in modified gravity theories based on torsion, as these theories exhibit interesting cosmological implications. In this work inspired by the teleparallel formulation of general relativity, we present its extension to Lovelock gravity known as the most natural extension of general relativity in higher-dimensional space-times. First, we review the teleparallel equivalent of general relativity and Gauss-Bonnet gravity, and then we construct the teleparallel equivalent of Lovelock gravity. In order to achieve this goal, we use the vielbein and the connection without imposing the Weitzenböck connection. Then, we extract the teleparallel formulation of the theory by setting the curvature to null.

  6. What Is Gravity?

    Science.gov (United States)

    Nelson, George

    2004-01-01

    Gravity is the name given to the phenomenon that any two masses, like you and the Earth, attract each other. One pulls on the Earth and the Earth pulls on one the same amount. And one does not have to be touching. Gravity acts over vast distances, like the 150 million kilometers (93 million miles) between the Earth and the Sun or the billions of…

  7. Human manual control performance in hyper-gravity.

    Science.gov (United States)

    Clark, Torin K; Newman, Michael C; Merfeld, Daniel M; Oman, Charles M; Young, Laurence R

    2015-05-01

    Hyper-gravity provides a unique environment to study how misperceptions impact control of orientation relative to gravity. Previous studies have found that static and dynamic roll tilts are perceptually overestimated in hyper-gravity. The current investigation quantifies how this influences control of orientation. We utilized a long-radius centrifuge to study manual control performance in hyper-gravity. In the dark, subjects were tasked with nulling out a pseudo-random roll disturbance on the cab of the centrifuge using a rotational hand controller to command their roll rate in order to remain perceptually upright. The task was performed in 1, 1.5, and 2 G's of net gravito-inertial acceleration. Initial performance, in terms of root-mean-square deviation from upright, degraded in hyper-gravity relative to 1 G performance levels. In 1.5 G, initial performance degraded by 26 % and in 2 G, by 45 %. With practice, however, performance in hyper-gravity improved to near the 1 G performance level over several minutes. Finally, pre-exposure to one hyper-gravity level reduced initial performance decrements in a different, novel, hyper-gravity level. Perceptual overestimation of roll tilts in hyper-gravity leads to manual control performance errors, which are reduced both with practice and with pre-exposure to alternate hyper-gravity stimuli.

  8. Gravity/Fluid Correspondence and Its Application on Bulk Gravity with U(1) Gauge Field

    International Nuclear Information System (INIS)

    Hu, Ya-Peng; Zhang, Jian-Hui

    2014-01-01

    As the long wavelength limit of the AdS/CFT correspondence, the gravity/fluid correspondence has been shown to be a useful tool for extracting properties of the fluid on the boundary dual to the gravity in the bulk. In this paper, after briefly reviewing the algorithm of gravity/fluid correspondence, we discuss the results of its application on bulk gravity with a U(1) gauge field. In the presence of a U(1) gauge field, the dual fluid possesses more interesting properties such as its charge current. Furthermore, an external field A_μ"e"x"t could affect the charge current, and the U(1) Chern-Simons term also induces extra structures to the dual current giving anomalous transport coefficients.

  9. Gravity and strings

    CERN Document Server

    Ortín, Tomás

    2015-01-01

    Self-contained and comprehensive, this definitive new edition of Gravity and Strings is a unique resource for graduate students and researchers in theoretical physics. From basic differential geometry through to the construction and study of black-hole and black-brane solutions in quantum gravity - via all the intermediate stages - this book provides a complete overview of the intersection of gravity, supergravity, and superstrings. Now fully revised, this second edition covers an extensive array of topics, including new material on non-linear electric-magnetic duality, the electric-tensor formalism, matter-coupled supergravity, supersymmetric solutions, the geometries of scalar manifolds appearing in 4- and 5-dimensional supergravities, and much more. Covering reviews of important solutions and numerous solution-generating techniques, and accompanied by an exhaustive index and bibliography, this is an exceptional reference work.

  10. Recent advancements in conformal gravity

    International Nuclear Information System (INIS)

    O’Brien, James G.; Chaykov, Spasen S.; Moss, Robert J.; Dentico, Jeremy; Stulge, Modestas; Stefanski, Brian

    2017-01-01

    In recent years, due to the lack of direct observed evidence of cold dark matter, coupled with the shrinking parameter space to search for new dark matter particles, there has been increased interest in Alternative Gravitational theories. This paper, addresses three recent advances in conformal gravity, a fourth order renormalizable metric theory of gravitation originally formulated by Weyl, and later advanced by Mannheim and Kazanas. The first section of the paper applies conformal gravity to the rotation curves of the LITTLE THINGS survey, extending the total number of rotation curves successfully fit by conformal gravity to well over 200 individual data sets without the need for additional dark matter. Further, in this rotation curve study, we show how MOND and conformal gravity compare for each galaxy in the sample. Second, we look at the original Zwicky problem of applying the virial theorem to the Coma cluster in order to get an estimate for the cluster mass. However, instead of using the standard Newtonian potential, here we use the weak field approximation of conformal gravity. We show that in the conformal case we can get a much smaller mass estimate and thus there is no apparent need to include dark matter. We then show that this calculation is in agreement with the observational data from other well studied clusters. Last, we explore the calculation of the deflection of starlight through conformal gravity, as a first step towards applying conformal gravity to gravitaitonal lensing. (paper)

  11. Effect of External Disturbing Gravity Field on Spacecraft Guidance and Surveying Line Layout for Marine Gravity Survey

    Directory of Open Access Journals (Sweden)

    HUANG Motao

    2016-11-01

    Full Text Available Centred on the support requirement of flying track control for a long range spacecraft, a detail research is made on the computation of external disturbing gravity field, the survey accuracy of gravity anomaly on the earth' surface and the program of surveying line layout for marine gravity survey. Firstly, the solution expression of navigation error for a long range spacecraft is analyzed and modified, and the influence of the earth's gravity field on flying track of spacecraft is evaluated. Then with a given limited quota of biased error of spacecraft drop point, the accuracy requirement for calculating the external disturbing gravity field is discussed and researched. Secondly, the data truncation error and the propagated data error are studied and estimated, and the quotas of survey resolution and computation accuracy for gravity anomaly on the earth' surface are determined. Finally, based on the above quotas, a corresponding program of surveying line layout for marine gravity survey is proposed. A numerical test has been made to prove the reasonableness and validity of the suggested program.

  12. Abrus agglutinin promotes irreparable DNA damage by triggering ROS generation followed by ATM-p73 mediated apoptosis in oral squamous cell carcinoma.

    Science.gov (United States)

    Sinha, Niharika; Panda, Prashanta K; Naik, Prajna P; Das, Durgesh N; Mukhopadhyay, Subhadip; Maiti, Tapas K; Shanmugam, Muthu K; Chinnathambi, Arunachalam; Zayed, M E; Alharbi, Sulaiman A; Sethi, Gautam; Agarwal, Rajesh; Bhutia, Sujit K

    2017-11-01

    Oral cancer, a type of head and neck cancer, is ranked as one of the top most malignancies in India. Herein, we evaluated the anticancer efficacy of Abrus agglutinin (AGG), a plant lectin, in oral squamous cell carcinoma. AGG selectively inhibited cell growth, and caused cell cycle arrest and mitochondrial apoptosis through a reactive oxygen species (ROS)-mediated ATM-p73 dependent pathway in FaDu cells. AGG-induced ROS accumulation was identified as the major mechanism regulating apoptosis, DNA damage and DNA-damage response, which were significantly reversed by ROS scavenger N-acetylcysteine (NAC). Moreover, AGG was found to interact with mitochondrial manganese-dependent superoxide dismutase that might inhibit its activity and increase ROS in FaDu cells. In oral cancer p53 is mutated, thus we focused on p73; AGG resulted in p73 upregulation and knock down of p73 caused a decrease in AGG-induced apoptosis. Interestingly, AGG-dependent p73 expression was found to be regulated by ROS, which was reversed by NAC treatment. A reduction in the level of p73 in AGG-treated shATM cells was found to be associated with a decreased apoptosis. Moreover, administration of AGG (50 μg/kg body weight) significantly inhibited the growth of FaDu xenografts in athymic nude mice. In immunohistochemical analysis, the xenografts from AGG-treated mice displayed a decrease in PCNA expression and an increase in caspase-3 activation as compared to the controls. In conclusion, we established a connection among ROS, ATM and p73 in AGG-induced apoptosis, which might be useful in enhancing the therapeutic targeting of p53 deficient oral squamous cell carcinoma. © 2017 Wiley Periodicals, Inc.

  13. Newton-Cartan gravity revisited

    NARCIS (Netherlands)

    Andringa, Roel

    2016-01-01

    In this research Newton's old theory of gravity is rederived using an algebraic approach known as the gauging procedure. The resulting theory is Newton's theory in the mathematical language of Einstein's General Relativity theory, in which gravity is spacetime curvature. The gauging procedure sheds

  14. High-resolution gravity model of Venus

    Science.gov (United States)

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

    1992-01-01

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

  15. Horizon thermodynamics in fourth-order gravity

    Directory of Open Access Journals (Sweden)

    Meng-Sen Ma

    2017-03-01

    Full Text Available In the framework of horizon thermodynamics, the field equations of Einstein gravity and some other second-order gravities can be rewritten as the thermodynamic identity: dE=TdS−PdV. However, in order to construct the horizon thermodynamics in higher-order gravity, we have to simplify the field equations firstly. In this paper, we study the fourth-order gravity and convert it to second-order gravity via a so-called “Legendre transformation” at the cost of introducing two other fields besides the metric field. With this simplified theory, we implement the conventional procedure in the construction of the horizon thermodynamics in 3 and 4 dimensional spacetime. We find that the field equations in the fourth-order gravity can also be written as the thermodynamic identity. Moreover, we can use this approach to derive the same black hole mass as that by other methods.

  16. Adaptive topographic mass correction for satellite gravity and gravity gradient data

    Science.gov (United States)

    Holzrichter, Nils; Szwillus, Wolfgang; Götze, Hans-Jürgen

    2014-05-01

    Subsurface modelling with gravity data includes a reliable topographic mass correction. Since decades, this mandatory step is a standard procedure. However, originally methods were developed for local terrestrial surveys. Therefore, these methods often include defaults like a limited correction area of 167 km around an observation point, resampling topography depending on the distance to the station or disregard the curvature of the earth. New satellite gravity data (e.g. GOCE) can be used for large scale lithospheric modelling with gravity data. The investigation areas can include thousands of kilometres. In addition, measurements are located in the flight height of the satellite (e.g. ~250 km for GOCE). The standard definition of the correction area and the specific grid spacing around an observation point was not developed for stations located in these heights and areas of these dimensions. This asks for a revaluation of the defaults used for topographic correction. We developed an algorithm which resamples the topography based on an adaptive approach. Instead of resampling topography depending on the distance to the station, the grids will be resampled depending on its influence at the station. Therefore, the only value the user has to define is the desired accuracy of the topographic correction. It is not necessary to define the grid spacing and a limited correction area. Furthermore, the algorithm calculates the topographic mass response with a spherical shaped polyhedral body. We show examples for local and global gravity datasets and compare the results of the topographic mass correction to existing approaches. We provide suggestions how satellite gravity and gradient data should be corrected.

  17. Scaling in quantum gravity

    Directory of Open Access Journals (Sweden)

    J. Ambjørn

    1995-07-01

    Full Text Available The 2-point function is the natural object in quantum gravity for extracting critical behavior: The exponential falloff of the 2-point function with geodesic distance determines the fractal dimension dH of space-time. The integral of the 2-point function determines the entropy exponent γ, i.e. the fractal structure related to baby universes, while the short distance behavior of the 2-point function connects γ and dH by a quantum gravity version of Fisher's scaling relation. We verify this behavior in the case of 2d gravity by explicit calculation.

  18. Self Completeness of Einstein Gravity

    CERN Document Server

    Dvali, Gia

    2010-01-01

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

  19. Venus gravity - Analysis of Beta Regio

    Science.gov (United States)

    Esposito, P. B.; Sjogren, W. L.; Mottinger, N. A.; Bills, B. G.; Abbott, E.

    1982-01-01

    Radio tracking data acquired over Beta Regio were analyzed to obtain a surface mass distribution from which a detailed vertical gravity field was derived. In addition, a corresponding vertical gravity field was evaluated solely from the topography of the Beta region. A comparison of these two maps confirms the strong correlation between gravity and topography which was previously seen in line-of-sight gravity maps. It also demonstrates that the observed gravity is a significant fraction of that predicted from the topography alone. The effective depth of complete isostatic compensation for the Beta region is estimated to be 330 km, which is somewhat deeper than that found for other areas of Venus.

  20. Consistency of orthodox gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bellucci, S. [INFN, Frascati (Italy). Laboratori Nazionali di Frascati; Shiekh, A. [International Centre for Theoretical Physics, Trieste (Italy)

    1997-01-01

    A recent proposal for quantizing gravity is investigated for self consistency. The existence of a fixed-point all-order solution is found, corresponding to a consistent quantum gravity. A criterion to unify couplings is suggested, by invoking an application of their argument to more complex systems.

  1. BOOK REVIEW: Canonical Gravity and Applications: Cosmology, Black Holes, and Quantum Gravity Canonical Gravity and Applications: Cosmology, Black Holes, and Quantum Gravity

    Science.gov (United States)

    Husain, Viqar

    2012-03-01

    Research on quantum gravity from a non-perturbative 'quantization of geometry' perspective has been the focus of much research in the past two decades, due to the Ashtekar-Barbero Hamiltonian formulation of general relativity. This approach provides an SU(2) gauge field as the canonical configuration variable; the analogy with Yang-Mills theory at the kinematical level opened up some research space to reformulate the old Wheeler-DeWitt program into what is now known as loop quantum gravity (LQG). The author is known for his work in the LQG approach to cosmology, which was the first application of this formalism that provided the possibility of exploring physical questions. Therefore the flavour of the book is naturally informed by this history. The book is based on a set of graduate-level lectures designed to impart a working knowledge of the canonical approach to gravitation. It is more of a textbook than a treatise, unlike three other recent books in this area by Kiefer [1], Rovelli [2] and Thiemann [3]. The style and choice of topics of these authors are quite different; Kiefer's book provides a broad overview of the path integral and canonical quantization methods from a historical perspective, whereas Rovelli's book focuses on philosophical and formalistic aspects of the problems of time and observables, and gives a development of spin-foam ideas. Thiemann's is much more a mathematical physics book, focusing entirely on the theory of representing constraint operators on a Hilbert space and charting a mathematical trajectory toward a physical Hilbert space for quantum gravity. The significant difference from these books is that Bojowald covers mainly classical topics until the very last chapter, which contains the only discussion of quantization. In its coverage of classical gravity, the book has some content overlap with Poisson's book [4], and with Ryan and Shepley's older work on relativistic cosmology [5]; for instance the contents of chapter five of the

  2. Quantum gravito-optics: a light route from semiclassical gravity to quantum gravity

    International Nuclear Information System (INIS)

    Unnikrishnan, C S; Gillies, George T

    2015-01-01

    Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation, ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for the detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity. (paper)

  3. Stability in designer gravity

    International Nuclear Information System (INIS)

    Hertog, Thomas; Hollands, Stefan

    2005-01-01

    We study the stability of designer gravity theories, in which one considers gravity coupled to a tachyonic scalar with anti-de Sitter (AdS) boundary conditions defined by a smooth function W. We construct Hamiltonian generators of the asymptotic symmetries using the covariant phase space method of Wald et al and find that they differ from the spinor charges except when W = 0. The positivity of the spinor charge is used to establish a lower bound on the conserved energy of any solution that satisfies boundary conditions for which W has a global minimum. A large class of designer gravity theories therefore have a stable ground state, which the AdS/CFT correspondence indicates should be the lowest energy soliton. We make progress towards proving this by showing that minimum energy solutions are static. The generalization of our results to designer gravity theories in higher dimensions involving several tachyonic scalars is discussed

  4. Carroll versus Galilei gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bergshoeff, Eric [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Gomis, Joaquim [Departament de Física Cuàntica i Astrofísica and Institut de Ciències del Cosmos,Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain); Rollier, Blaise [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Rosseel, Jan [Faculty of Physics, University of Vienna,Boltzmanngasse 5, A-1090 Vienna (Austria); Veldhuis, Tonnis ter [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2017-03-30

    We consider two distinct limits of General Relativity that in contrast to the standard non-relativistic limit can be taken at the level of the Einstein-Hilbert action instead of the equations of motion. One is a non-relativistic limit and leads to a so-called Galilei gravity theory, the other is an ultra-relativistic limit yielding a so-called Carroll gravity theory. We present both gravity theories in a first-order formalism and show that in both cases the equations of motion (i) lead to constraints on the geometry and (ii) are not sufficient to solve for all of the components of the connection fields in terms of the other fields. Using a second-order formalism we show that these independent components serve as Lagrange multipliers for the geometric constraints we found earlier. We point out a few noteworthy differences between Carroll and Galilei gravity and give some examples of matter couplings.

  5. New special operators in W-gravity theories

    International Nuclear Information System (INIS)

    Rama, S.K.

    1991-01-01

    This paper reports on special physical operators of W 3 -gravity having non-trivial ghost sectors. Some of these operators may be viewed as the Liouville dressings of the energy operator of the Ising model coupled to two-dimensional (2D) gravity and this fills in the gap in the connection between pure W 3 -gravity and Ising model coupled to 2D gravity found in the authors' previous work. The authors formulate a selection rule required for the calculation of correlators in W-gravity theories. Using this rule, the authors construct the non-ghost part of the new operators of W N -gravity and find that they represent the (N,N + 1) minimal model operators from both inside and outside the minimal table. Along the way the authors obtain the canonical spectrum of W N -gravity for all N

  6. Nonlinearities in modified gravity cosmology: Signatures of modified gravity in the nonlinear matter power spectrum

    International Nuclear Information System (INIS)

    Cui Weiguang; Zhang Pengjie; Yang Xiaohu

    2010-01-01

    A large fraction of cosmological information on dark energy and gravity is encoded in the nonlinear regime. Precision cosmology thus requires precision modeling of nonlinearities in general dark energy and modified gravity models. We modify the Gadget-2 code and run a series of N-body simulations on modified gravity cosmology to study the nonlinearities. The modified gravity model that we investigate in the present paper is characterized by a single parameter ζ, which determines the enhancement of particle acceleration with respect to general relativity (GR), given the identical mass distribution (ζ=1 in GR). The first nonlinear statistics we investigate is the nonlinear matter power spectrum at k < or approx. 3h/Mpc, which is the relevant range for robust weak lensing power spectrum modeling at l < or approx. 2000. In this study, we focus on the relative difference in the nonlinear power spectra at corresponding redshifts where different gravity models have the same linear power spectra. This particular statistics highlights the imprint of modified gravity in the nonlinear regime and the importance of including the nonlinear regime in testing GR. By design, it is less susceptible to the sample variance and numerical artifacts. We adopt a mass assignment method based on wavelet to improve the power spectrum measurement. We run a series of tests to determine the suitable simulation specifications (particle number, box size, and initial redshift). We find that, the nonlinear power spectra can differ by ∼30% for 10% deviation from GR (|ζ-1|=0.1) where the rms density fluctuations reach 10. This large difference, on one hand, shows the richness of information on gravity in the corresponding scales, and on the other hand, invalidates simple extrapolations of some existing fitting formulae to modified gravity cosmology.

  7. A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

    Science.gov (United States)

    2015-09-30

    Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves...interaction of surface and internal gravity waves in the South China Sea. We will seek answers to the following questions: 1) How does the wind-wave

  8. Renormalization and asymptotic freedom in quantum gravity

    International Nuclear Information System (INIS)

    Tomboulis, E.T.

    1984-01-01

    The article reviews some recent attempts to construct satisfactory theories of quantum gravity within the framework of local, continuum field theory. Quantum gravity; the renormalization group and its fixed points; fixed points and dimensional continuation in gravity; and quantum gravity at d=4-the 1/N expansion-asymptotic freedom; are all discussed. (U.K.)

  9. 2-Dim. gravity and string theory

    International Nuclear Information System (INIS)

    Narain, K.S.

    1991-01-01

    The role of 2-dim. gravity in string theory is discussed. In particular d=25 string theory coupled to 2-d. gravity is described and shown to give rise to the physics of the usual 26-dim. string theory (where one does not quantise 2-d. gravity. (orig.)

  10. Observational constraints on transverse gravity: A generalization of unimodular gravity

    International Nuclear Information System (INIS)

    Lopez-Villarejo, J J

    2010-01-01

    We explore the hypothesis that the set of symmetries enjoyed by the theory that describes gravity is not the full group of diffeomorphisms (Diff(M)), as in General Relativity, but a maximal subgroup of it (TransverseDiff(M)), with its elements having a jacobian equal to unity; at the infinitesimal level, the parameter describing the coordinate change x μ → x μ + ξ μ (x) is transverse, i.e., δ μ ξ μ = 0. Incidentally, this is the smaller symmetry one needs to propagate consistently a graviton, which is a great theoretical motivation for considering these theories. Also, the determinant of the metric, g, behaves as a 'transverse scalar', so that these theories can be seen as a generalization of the better-known unimodular gravity. We present our results on the observational constraints on transverse gravity, in close relation with the claim of equivalence with general scalar-tensor theory. We also comment on the structure of the divergences of the quantum theory to the one-loop order.

  11. Lattice gravity and strings

    International Nuclear Information System (INIS)

    Jevicki, A.; Ninomiya, M.

    1985-01-01

    We are concerned with applications of the simplicial discretization method (Regge calculus) to two-dimensional quantum gravity with emphasis on the physically relevant string model. Beginning with the discretization of gravity and matter we exhibit a discrete version of the conformal trace anomaly. Proceeding to the string problem we show how the direct approach of (finite difference) discretization based on Nambu action corresponds to unsatisfactory treatment of gravitational degrees. Based on the Regge approach we then propose a discretization corresponding to the Polyakov string. In this context we are led to a natural geometric version of the associated Liouville model and two-dimensional gravity. (orig.)

  12. The Future of Gravity

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    Of the four fundamental forces, gravity has been studied the longest, yet gravitational physics is one of the most rapidly developing areas of science today. This talk will give a broad brush survey of the past achievements and future prospects of general relativistic gravitational physics. Gravity is a two frontier science being important on both the very largest and smallest length scales considered in contemporary physics. Recent advances and future prospects will be surveyed in precision tests of general relativity, gravitational waves, black holes, cosmology and quantum gravity. The aim will be an overview of a subject that is becoming increasingly integrated with experiment and other branches of physics.

  13. And what if gravity is intrinsically quantic?

    International Nuclear Information System (INIS)

    Ziaeepour, Houri

    2009-01-01

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

  14. Spin Entanglement Witness for Quantum Gravity

    NARCIS (Netherlands)

    Bose, Sougato; Mazumdar, Anupam; Morley, Gavin W.; Ulbricht, Hendrik; Toros, Marko; Paternostro, Mauro; Geraci, Andrew A.; Barker, Peter F.; Kim, M. S.; Milburn, Gerard

    2017-01-01

    Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. However, the lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Despite varied proposed probes for quantum gravity, it is fair to say that there are no

  15. Light fermions in quantum gravity

    International Nuclear Information System (INIS)

    Eichhorn, Astrid; Gies, Holger

    2011-01-01

    We study the impact of quantum gravity, formulated as a quantum field theory of the metric, on chiral symmetry in a fermionic matter sector. Specifically we address the question of whether metric fluctuations can induce chiral symmetry breaking and bound state formation. Our results based on the functional renormalization group indicate that chiral symmetry is left intact even at strong gravitational coupling. In particular, we found that asymptotically safe quantum gravity where the gravitational couplings approach a non-Gaußian fixed point generically admits universes with light fermions. Our results thus further support quantum gravity theories built on fluctuations of the metric field such as the asymptotic-safety scenario. A study of chiral symmetry breaking through gravitational quantum effects may also serve as a significant benchmark test for other quantum gravity scenarios, since a completely broken chiral symmetry at the Planck scale would not be in accordance with the observation of light fermions in our universe. We demonstrate that this elementary observation already imposes constraints on a generic UV completion of gravity. (paper)

  16. The Juno Gravity Science Instrument

    Science.gov (United States)

    Asmar, Sami W.; Bolton, Scott J.; Buccino, Dustin R.; Cornish, Timothy P.; Folkner, William M.; Formaro, Roberto; Iess, Luciano; Jongeling, Andre P.; Lewis, Dorothy K.; Mittskus, Anthony P.; Mukai, Ryan; Simone, Lorenzo

    2017-11-01

    The Juno mission's primary science objectives include the investigation of Jupiter interior structure via the determination of its gravitational field. Juno will provide more accurate determination of Jupiter's gravity harmonics that will provide new constraints on interior structure models. Juno will also measure the gravitational response from tides raised on Jupiter by Galilean satellites. This is accomplished by utilizing Gravity Science instrumentation to support measurements of the Doppler shift of the Juno radio signal by NASA's Deep Space Network at two radio frequencies. The Doppler data measure the changes in the spacecraft velocity in the direction to Earth caused by the Jupiter gravity field. Doppler measurements at X-band (˜ 8 GHz) are supported by the spacecraft telecommunications subsystem for command and telemetry and are used for spacecraft navigation as well as Gravity Science. The spacecraft also includes a Ka-band (˜ 32 GHz) translator and amplifier specifically for the Gravity Science investigation contributed by the Italian Space Agency. The use of two radio frequencies allows for improved accuracy by removal of noise due to charged particles along the radio signal path.

  17. Gravity measurements in southeastern Alaska reveal negative gravity rate of change caused by glacial isostatic adjustment

    Science.gov (United States)

    Sun, W.; Miura, S.; Sato, T.; Sugano, T.; Freymueller, J.; Kaufman, M.; Larsen, C. F.; Cross, R.; Inazu, D.

    2010-12-01

    For the past 300 years, southeastern Alaska has undergone rapid ice-melting and land uplift attributable to global warming. Corresponding crustal deformation (3 cm/yr) caused by the Little Ice Age retreat is detectable with modern geodetic techniques such as GPS and tidal gauge measurements. Geodetic deformation provides useful information for assessing ice-melting rates, global warming effects, and subcrustal viscosity. Nevertheless, integrated geodetic observations, including gravity measurements, are important. To detect crustal deformation caused by glacial isostatic adjustment and to elucidate the viscosity structure in southeastern Alaska, Japanese and U.S. researchers began a joint 3-year project in 2006 using GPS, Earth tide, and absolute gravity measurements. A new absolute gravity network was established, comprising five sites around Glacier Bay, near Juneau, Alaska. This paper reports the network's gravity measurements during 2006-2008. The bad ocean model in this area hindered ocean loading correction: Large tidal residuals remain in the observations. Accurate tidal correction necessitated on-site tidal observation. Results show high observation precision for all five stations: day ice thickness changes. A gravity bias of about -13.2 ± 0.1 mGal exists between the Potsdam and current FG5 gravity data.

  18. Topics in string theory and quantum gravity

    CERN Document Server

    Alvarez-Gaume, Luis

    1992-01-01

    These are the lecture notes for the Les Houches Summer School on Quantum Gravity held in July 1992. The notes present some general critical assessment of other (non-string) approaches to quantum gravity, and a selected set of topics concerning what we have learned so far about the subject from string theory. Since these lectures are long (133 A4 pages), we include in this abstract the table of contents, which should help the user of the bulletin board in deciding whether to latex and print the full file. 1-FIELD THEORETICAL APPROACH TO QUANTUM GRAVITY: Linearized gravity; Supergravity; Kaluza-Klein theories; Quantum field theory and classical gravity; Euclidean approach to Quantum Gravity; Canonical quantization of gravity; Gravitational Instantons. 2-CONSISTENCY CONDITIONS: ANOMALIES: Generalities about anomalies; Spinors in 2n dimensions; When can we expect to find anomalies?; The Atiyah-Singer Index Theorem and the computation of anomalies; Examples: Green-Schwarz cancellation mechanism and Witten's SU(2) ...

  19. Quantum Gravity Experiments

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2015-10-01

    Full Text Available A new quantum gravity experiment is reported with the data confirming the generali- sation of the Schrödinger equation to include the interaction of the wave function with dynamical space. Dynamical space turbulence, via this interaction process, raises and lowers the energy of the electron wave function, which is detected by observing conse- quent variations in the electron quantum barrier tunnelling rate in reverse-biased Zener diodes. This process has previously been reported and enabled the measurement of the speed of the dynamical space flow, which is consistent with numerous other detection experiments. The interaction process is dependent on the angle between the dynamical space flow velocity and the direction of the electron flow in the diode, and this depen- dence is experimentally demonstrated. This interaction process explains gravity as an emergent quantum process, so unifying quantum phenomena and gravity. Gravitational waves are easily detected.

  20. Stochastic quantum gravity

    International Nuclear Information System (INIS)

    Rumpf, H.

    1987-01-01

    We begin with a naive application of the Parisi-Wu scheme to linearized gravity. This will lead into trouble as one peculiarity of the full theory, the indefiniteness of the Euclidean action, shows up already at this level. After discussing some proposals to overcome this problem, Minkowski space stochastic quantization will be introduced. This will still not result in an acceptable quantum theory of linearized gravity, as the Feynman propagator turns out to be non-causal. This defect will be remedied only after a careful analysis of general covariance in stochastic quantization has been performed. The analysis requires the notion of a metric on the manifold of metrics, and a natural candidate for this is singled out. With this a consistent stochastic quantization of Einstein gravity becomes possible. It is even possible, at least perturbatively, to return to the Euclidean regime. 25 refs. (Author)

  1. Venus gravity anomalies and their correlations with topography

    Science.gov (United States)

    Sjogren, W. L.; Bills, B. G.; Birkeland, P. W.; Esposito, P. B.; Konopliv, A. R.; Mottinger, N. A.; Ritke, S. J.; Phillips, R. J.

    1983-01-01

    This report provides a summary of the high-resolution gravity data obtained from the Pioneer Venus Orbiter radio tracking data. Gravity maps, covering a 70 deg latitude band through 360 deg of longitude, are displayed as line-of-sight and vertical gravity. Topography converted to gravity and Bouguer gravity maps are also shown in both systems. Topography to gravity ratios are made over several regions of the planet. There are markedly different ratios for the Aphrodite area as compared to the Beta and Atla areas.

  2. Towards the map of quantum gravity

    Science.gov (United States)

    Mielczarek, Jakub; Trześniewski, Tomasz

    2018-06-01

    In this paper we point out some possible links between different approaches to quantum gravity and theories of the Planck scale physics. In particular, connections between loop quantum gravity, causal dynamical triangulations, Hořava-Lifshitz gravity, asymptotic safety scenario, Quantum Graphity, deformations of relativistic symmetries and nonlinear phase space models are discussed. The main focus is on quantum deformations of the Hypersurface Deformations Algebra and Poincaré algebra, nonlinear structure of phase space, the running dimension of spacetime and nontrivial phase diagram of quantum gravity. We present an attempt to arrange the observed relations in the form of a graph, highlighting different aspects of quantum gravity. The analysis is performed in the spirit of a mind map, which represents the architectural approach to the studied theory, being a natural way to describe the properties of a complex system. We hope that the constructed graphs (maps) will turn out to be helpful in uncovering the global picture of quantum gravity as a particular complex system and serve as a useful guide for the researchers.

  3. Equivalence of two-dimensional gravities

    International Nuclear Information System (INIS)

    Mohammedi, N.

    1990-01-01

    The authors find the relationship between the Jackiw-Teitelboim model of two-dimensional gravity and the SL(2,R) induced gravity. These are shown to be related to a two-dimensional gauge theory obtained by dimensionally reducing the Chern-Simons action of the 2 + 1 dimensional gravity. The authors present an explicit solution to the equations of motion of the auxiliary field of the Jackiw-Teitelboim model in the light-cone gauge. A renormalization of the cosmological constant is also given

  4. Gravity Station Data for Portugal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data total 3064 records. This data base was received in April 1997. Principal gravity parameters include Free-air Anomalies which have been...

  5. Interior Alaska Gravity Station Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data total 9416 records. This data base was received in March 1997. Principal gravity parameters include Free-air Anomalies which have been...

  6. Gravity Station Data for Spain

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data total 28493 records. This data base was received in April 1997. Principal gravity parameters include Free-air Anomalies which have been...

  7. Generalized pure Lovelock gravity

    Science.gov (United States)

    Concha, Patrick; Rodríguez, Evelyn

    2017-11-01

    We present a generalization of the n-dimensional (pure) Lovelock Gravity theory based on an enlarged Lorentz symmetry. In particular, we propose an alternative way to introduce a cosmological term. Interestingly, we show that the usual pure Lovelock gravity is recovered in a matter-free configuration. The five and six-dimensional cases are explicitly studied.

  8. Turning on gravity with the Higgs mechanism

    International Nuclear Information System (INIS)

    Alexander, Stephon; Barrow, John D; Magueijo, João

    2016-01-01

    We investigate how a Higgs mechanism could be responsible for the emergence of gravity in extensions of Einstein theory, with a suitable low energy limit. In this scenario, at high energies, symmetry restoration could ‘turn off’ gravity, with dramatic implications for cosmology and quantum gravity. The sense in which gravity is muted depends on the details of the implementation. In the most extreme case gravity’s dynamical degrees of freedom would only be unleashed after the Higgs field acquires a non-trivial vacuum expectation value, with gravity reduced to a topological field theory in the symmetric phase. We might also identify the Higgs and the Brans–Dicke fields in such a way that in the unbroken phase Newton’s constant vanishes, decoupling matter and gravity. We discuss the broad implications of these scenarios. (letter)

  9. Logamediate Inflation in f ( T ) Teleparallel Gravity

    Energy Technology Data Exchange (ETDEWEB)

    Rezazadeh, Kazem; Karami, Kayoomars [Department of Physics, University of Kurdistan, Pasdaran Street, P.O. Box 66177-15175, Sanandaj (Iran, Islamic Republic of); Abdolmaleki, Asrin, E-mail: rezazadeh86@gmail.com [Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), P.O. Box 55134-441, Maragha (Iran, Islamic Republic of)

    2017-02-20

    We study logamediate inflation in the context of f ( T ) teleparallel gravity. f ( T )-gravity is a generalization of the teleparallel gravity which is formulated on the Weitzenbock spacetime, characterized by the vanishing curvature tensor (absolute parallelism) and the non-vanishing torsion tensor. We consider an f ( T )-gravity model which is sourced by a canonical scalar field. Assuming a power-law f ( T ) function in the action, we investigate an inflationary universe with a logamediate scale factor. Our results show that, although logamediate inflation is completely ruled out by observational data in the standard inflationary scenario based on Einstein gravity, it can be compatible with the 68% confidence limit joint region of Planck 2015 TT,TE,EE+lowP data in the framework of f ( T )-gravity.

  10. Matter scattering in quadratic gravity and unitarity

    Science.gov (United States)

    Abe, Yugo; Inami, Takeo; Izumi, Keisuke; Kitamura, Tomotaka

    2018-03-01

    We investigate the ultraviolet (UV) behavior of two-scalar elastic scattering with graviton exchanges in higher-curvature gravity theory. In Einstein gravity, matter scattering is shown not to satisfy the unitarity bound at tree level at high energy. Among some of the possible directions for the UV completion of Einstein gravity, such as string theory, modified gravity, and inclusion of high-mass/high-spin states, we take R_{μν}^2 gravity coupled to matter. We show that matter scattering with graviton interactions satisfies the unitarity bound at high energy, even with negative norm states due to the higher-order derivatives of metric components. The difference in the unitarity property of these two gravity theories is probably connected to that in another UV property, namely, the renormalizability property of the two.

  11. The Superheavy Elements and Anti-Gravity

    Science.gov (United States)

    Anastasovski, Petar K.

    2004-02-01

    The essence of any propulsion concept is to overcome gravity. Anti-gravity is a natural means to achieve this. Thus, the technology to pursue anti-gravity, by using superheavy elements, may provide a new propulsion paradigm. The theory of superluminal relativity provides a hypothesis for existence of elements with atomic number up to Z = 145, some of which may possess anti-gravity properties. Analysis results show that curved space-time exists demonstrating both gravitic and anti-gravitic properties not only around nuclei but inside the nuclei as well. Two groups of elements (Z Hawking, in honour of Stephen W. Hawking.

  12. Generalized Vaidya spacetime for cubic gravity

    Science.gov (United States)

    Ruan, Shan-Ming

    2016-03-01

    We present a kind of generalized Vaidya solution of a new cubic gravity in five dimensions whose field equations in spherically symmetric spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its spherically symmetric apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally, we present the first law and second law hold in this gravity. Although all the results are analogous to those in Lovelock gravity, we in fact introduce the contribution of a new cubic term in five dimensions where the cubic Lovelock term is just zero.

  13. Generalized pure Lovelock gravity

    Directory of Open Access Journals (Sweden)

    Patrick Concha

    2017-11-01

    Full Text Available We present a generalization of the n-dimensional (pure Lovelock Gravity theory based on an enlarged Lorentz symmetry. In particular, we propose an alternative way to introduce a cosmological term. Interestingly, we show that the usual pure Lovelock gravity is recovered in a matter-free configuration. The five and six-dimensional cases are explicitly studied.

  14. Gravity changes in mid-west Greenland from GOCE gravity model and gradient data using ground and airborne gravity

    DEFF Research Database (Denmark)

    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....

  15. Gravity Data for South America

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (152,624 records) were compiled by the University of Texas at Dallas. This data base was received in June 1992. Principal gravity parameters...

  16. Why is gravity so weak?

    International Nuclear Information System (INIS)

    Goradia, S.G.

    2006-01-01

    Why is gravity weak? Gravity is plagued with this and many other questions. After decades of exhausting work we do not have a clear answer. In view of this fact it will be shown in the following pages that there are reasons for thinking that gravity is just a composite force consisting of the long-range manifestations of short range nuclear forces that are too tiny to be measured at illuminated or long ranges by particle colliders. This is consistent with Einstein's proposal in 1919

  17. Processing Marine Gravity Data Around Korea

    Science.gov (United States)

    Lee, Y.; Choi, K.; Kim, Y.; Ahn, Y.; Chang, M.

    2008-12-01

    In Korea currently 4 research ships are under operating in Korea, after the first research vessel equipped shipborne gravity meter was introduced in 1990s. These are Onnuri(launch 1991) of KORDI(Korea Ocean Research & Development Institute), Haeyang2000(launch 1996), Badaro1(launch 2002) of NORI(National Oceanographic Research Institute) and Tamhae2(launch 1997) of KIGAM(Korea Institute of Geoscience and Mineral Resources). Those of research vessel, Haeyang2000 have observed marine gravity data over 150,000 points each year from year 1996 to year 2003. Haeyang2000, about 2,500 tons, is unable to operate onshore so NORI has constructed another 600 tons research ship Badaro1 that has observed marine gravity data onshore since year 2002. Haeyang2000 finished observing marine gravity data offshore within Korean territorial waters until year 2003. Currently Badaro1 is observing marine gravity data onshore. These shipborne gravity data will be very useful and important on geodesy and geophysics research also those data can make a contribution to developing these studies. In this study NORI's shipbrne gravity data from 1996 to 2007 has been processed for fundamental data to compute Korean precise geoid. Marine gravity processing steps as followed. 1. Check the time sequence, latitude and longitude position, etc. of shipborne gravity data 2. Arrangement of the tide level below the pier and meter drift correction of each cruise. 3. Elimination of turning points. 4. The time lag correction. 5. Computation of RV's velocities, Heading angles and the Eötvös correction. 6. Kalman filtering of GPS navigation data using cross-over points. 7. Cross-over correction using least square adjustment. About 2,058,000 points have been processed with NORI's marine gravity data from 1996 to 2007 in this study. The distribution of free-air anomalies was -41.0 mgal to 136.0 mgal(mean 8.90mgal) within Korean territorial waters. The free-air anomalies processed with the marine gravity data are

  18. Is there a quantum theory of gravity

    International Nuclear Information System (INIS)

    Strominger, A.

    1984-01-01

    The paper concerns attempts to construct a unitary, renormalizable quantum field theory of gravity. Renormalizability and unitarity in quantum gravity; the 1/N expansion; 1/D expansions; and quantum gravity and particle physics; are all discussed. (U.K.)

  19. Merging of airborne gravity and gravity derived from satellite altimetry: Test cases along the coast of greenland

    DEFF Research Database (Denmark)

    Olesen, Arne Vestergaard; Andersen, Ole Baltazar; Tscherning, C.C.

    2002-01-01

    for the use of gravity data especially, when computing geoid models in coastal regions. The presence of reliable marine gravity data for independent control offers an opportunity to study procedures for the merging of airborne and satellite data around Greenland. Two different merging techniques, both based......The National Survey and Cadastre - Denmark (KMS) has for several years produced gravity anomaly maps over the oceans derived from satellite altimetry. During the last four years, KMS has also conducted airborne gravity surveys along the coast of Greenland dedicated to complement the existing...... onshore gravity coverage and fill in new data in the very-near coastal area, where altimetry data may contain gross errors. The airborne surveys extend from the coastline to approximately 100 km offshore, along 6000 km of coastline. An adequate merging of these different data sources is important...

  20. Quantum gravity

    International Nuclear Information System (INIS)

    Markov, M.A.; West, P.C.

    1984-01-01

    This book discusses the state of the art of quantum gravity, quantum effects in cosmology, quantum black-hole physics, recent developments in supergravity, and quantum gauge theories. Topics considered include the problems of general relativity, pregeometry, complete cosmological theories, quantum fluctuations in cosmology and galaxy formation, a new inflationary universe scenario, grand unified phase transitions and the early Universe, the generalized second law of thermodynamics, vacuum polarization near black holes, the relativity of vacuum, black hole evaporations and their cosmological consequences, currents in supersymmetric theories, the Kaluza-Klein theories, gauge algebra and quantization, and twistor theory. This volume constitutes the proceedings of the Second Seminar on Quantum Gravity held in Moscow in 1981

  1. Mars - Hellas Planitia gravity analysis

    Science.gov (United States)

    Sjogren, W. L.; Wimberley, R. N.

    1981-01-01

    Doppler radio tracking data from Viking Orbiter 1 has provided new detailed observations of gravity variations over Hellas Planitia. Line-of-sight Bouguer gravity definitely indicates that isostatic adjustment has occurred. Two theoretical models were tested to obtain fits to the gravity data. Results for a surface deficit model, and a model with a surface deficit and a mass excess at depth are displayed. The mass-at-depth model produced very marked improvement in the data fit as compared to the surface deficit model. The optimum depth for the mass excess is 130 km.

  2. CDT meets Horava-Lifshitz gravity

    International Nuclear Information System (INIS)

    Ambjorn, J.; Goerlich, A.; Jordan, S.; Jurkiewicz, J.; Loll, R.

    2010-01-01

    The theory of causal dynamical triangulations (CDT) attempts to define a nonperturbative theory of quantum gravity as a sum over spacetime geometries. One of the ingredients of the CDT framework is a global time foliation, which also plays a central role in the quantum gravity theory recently formulated by Horava. We show that the phase diagram of CDT bears a striking resemblance with the generic Lifshitz phase diagram appealed to by Horava. We argue that CDT might provide a unifying nonperturbative framework for anisotropic as well as isotropic theories of quantum gravity.

  3. Gauge Gravity and Space-Time

    OpenAIRE

    Wu, Ning

    2012-01-01

    When we discuss problems on gravity, we can not avoid some fundamental physical problems, such as space-time, inertia, and inertial reference frame. The goal of this paper is to discuss the logic system of gravity theory and the problems of space-time, inertia, and inertial reference frame. The goal of this paper is to set up the theory on space-time in gauge theory of gravity. Based on this theory, it is possible for human kind to manipulate physical space-time on earth, and produce a machin...

  4. Quantum gravity and the renormalisation group

    International Nuclear Information System (INIS)

    Litim, D.

    2011-01-01

    The Standard Model of particle physics is remarkably successful in describing three out of the four known fundamental forces of Nature. But what is up with gravity? Attempts to understand quantum gravity on the same footing as the other forces still face problems. Some time ago, it has been pointed out that gravity may very well exist as a fundamental quantum field theory provided its high-energy behaviour is governed by a fixed point under the renormalisation group. In recent years, this 'asymptotic safety' scenario has found significant support thanks to numerous renormalisation group studies, lattice simulations, and new ideas within perturbation theory. The lectures will give an introduction into the renormalisation group approach for quantum gravity, aimed at those who haven't met the topic before. After an introduction and overview, the key ideas and concepts of asymptotic safety for gravity are fleshed out. Results for gravitational high-energy fixed points and scaling exponents are discussed as well as key features of the gravitational phase diagram. The survey concludes with some phenomenological implications of fixed point gravity including the physics of black holes and particle physics beyond the Standard Model. (author)

  5. Discretization of 3d gravity in different polarizations

    Science.gov (United States)

    Dupuis, Maïté; Freidel, Laurent; Girelli, Florian

    2017-10-01

    We study the discretization of three-dimensional gravity with Λ =0 following the loop quantum gravity framework. In the process, we realize that different choices of polarization are possible. This allows us to introduce a new discretization based on the triad as opposed to the connection as in the standard loop quantum gravity framework. We also identify the classical nontrivial symmetries of discrete gravity, namely the Drinfeld double, given in terms of momentum maps. Another choice of polarization is given by the Chern-Simons formulation of gravity. Our framework also provides a new discretization scheme of Chern-Simons, which keeps track of the link between the continuum variables and the discrete ones. We show how the Poisson bracket we recover between the Chern-Simons holonomies allows us to recover the Goldman bracket. There is also a transparent link between the discrete Chern-Simons formulation and the discretization of gravity based on the connection (loop gravity) or triad variables (dual loop gravity).

  6. An introduction to atmospheric gravity waves

    CERN Document Server

    Nappo, Carmen J

    2012-01-01

    Gravity waves exist in all types of geophysical fluids, such as lakes, oceans, and atmospheres. They play an important role in redistributing energy at disturbances, such as mountains or seamounts and they are routinely studied in meteorology and oceanography, particularly simulation models, atmospheric weather models, turbulence, air pollution, and climate research. An Introduction to Atmospheric Gravity Waves provides readers with a working background of the fundamental physics and mathematics of gravity waves, and introduces a wide variety of applications and numerous recent advances. Nappo provides a concise volume on gravity waves with a lucid discussion of current observational techniques and instrumentation.An accompanying website contains real data, computer codes for data analysis, and linear gravity wave models to further enhance the reader's understanding of the book's material. Companion web site features animations and streaming video Foreword by George Chimonas, a renowned expert on the interac...

  7. Human Performance in Simulated Reduced Gravity Environments

    Science.gov (United States)

    Cowley, Matthew; Harvill, Lauren; Rajulu, Sudhakar

    2014-01-01

    NASA is currently designing a new space suit capable of working in deep space and on Mars. Designing a suit is very difficult and often requires trade-offs between performance, cost, mass, and system complexity. Our current understanding of human performance in reduced gravity in a planetary environment (the moon or Mars) is limited to lunar observations, studies from the Apollo program, and recent suit tests conducted at JSC using reduced gravity simulators. This study will look at our most recent reduced gravity simulations performed on the new Active Response Gravity Offload System (ARGOS) compared to the C-9 reduced gravity plane. Methods: Subjects ambulated in reduced gravity analogs to obtain a baseline for human performance. Subjects were tested in lunar gravity (1.6 m/sq s) and Earth gravity (9.8 m/sq s) in shirt-sleeves. Subjects ambulated over ground at prescribed speeds on the ARGOS, but ambulated at a self-selected speed on the C-9 due to time limitations. Subjects on the ARGOS were given over 3 minutes to acclimate to the different conditions before data was collected. Nine healthy subjects were tested in the ARGOS (6 males, 3 females, 79.5 +/- 15.7 kg), while six subjects were tested on the C-9 (6 males, 78.8 +/- 11.2 kg). Data was collected with an optical motion capture system (Vicon, Oxford, UK) and was analyzed using customized analysis scripts in BodyBuilder (Vicon, Oxford, UK) and MATLAB (MathWorks, Natick, MA, USA). Results: In all offloaded conditions, variation between subjects increased compared to 1-g. Kinematics in the ARGOS at lunar gravity resembled earth gravity ambulation more closely than the C-9 ambulation. Toe-off occurred 10% earlier in both reduced gravity environments compared to earth gravity, shortening the stance phase. Likewise, ankle, knee, and hip angles remained consistently flexed and had reduced peaks compared to earth gravity. Ground reaction forces in lunar gravity (normalized to Earth body weight) were 0.4 +/- 0.2 on

  8. Gravity on-shell diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, Enrico [Walter Burke Institute for Theoretical Physics, California Institute of Technology,Pasadena, CA 91125 (United States); Trnka, Jaroslav [Center for Quantum Mathematics and Physics (QMAP),Department of Physics, University of California,Davis, CA 95616 (United States)

    2016-11-22

    We study on-shell diagrams for gravity theories with any number of supersymmetries and find a compact Grassmannian formula in terms of edge variables of the graphs. Unlike in gauge theory where the analogous form involves only dlog-factors, in gravity there is a non-trivial numerator as well as higher degree poles in the edge variables. Based on the structure of the Grassmannian formula for N=8 supergravity we conjecture that gravity loop amplitudes also possess similar properties. In particular, we find that there are only logarithmic singularities on cuts with finite loop momentum and that poles at infinity are present, in complete agreement with the conjecture presented in http://dx.doi.org/10.1007/JHEP06(2015)202.

  9. Exact Solutions in Three-Dimensional Gravity

    Science.gov (United States)

    García-Díaz, Alberto A.

    2017-09-01

    Preface; 1. Introduction; 2. Point particles; 3. Dust solutions; 4. AdS cyclic symmetric stationary solutions; 5. Perfect fluid static stars; 6. Static perfect fluid stars with Λ; 7. Hydrodynamic equilibrium; 8. Stationary perfect fluid with Λ; 9. Friedmann–Robertson–Walker cosmologies; 10. Dilaton-inflaton FRW cosmologies; 11. Einstein–Maxwell solutions; 12. Nonlinear electrodynamics black hole; 13. Dilaton minimally coupled to gravity; 14. Dilaton non-minimally coupled to gravity; 15. Low energy 2+1 string gravity; 16. Topologically massive gravity; 17. Bianchi type spacetimes in TMG; 18. Petrov type N wave metrics; 19. Kundt spacetimes in TMG; 20. Cotton tensor in Riemannian spacetimes; References; Index.

  10. Fixed points of quantum gravity

    OpenAIRE

    Litim, D F

    2003-01-01

    Euclidean quantum gravity is studied with renormalisation group methods. Analytical results for a non-trivial ultraviolet fixed point are found for arbitrary dimensions and gauge fixing parameter in the Einstein-Hilbert truncation. Implications for quantum gravity in four dimensions are discussed.

  11. Topological strings from Liouville gravity

    International Nuclear Information System (INIS)

    Ishibashi, N.; Li, M.

    1991-01-01

    We study constrained SU(2) WZW models, which realize a class of two-dimensional conformal field theories. We show that they give rise to topological gravity coupled to the topological minimal models when they are coupled to Liouville gravity. (orig.)

  12. Neutron Stars : Magnetism vs Gravity

    Indian Academy of Sciences (India)

    however, in the magnetosphere, electromagnetic forces dominate over gravity : Fgr = mg ~ 10-18 Newton ; Fem = e V B ~ 10-5 Newton; (for a single electron of mass m and charge e ) ; Hence, the electromagnetic force is 1013 times stronger than gravity !!

  13. Algebraic definition of topological W gravity

    International Nuclear Information System (INIS)

    Hosono, S.

    1992-01-01

    In this paper, the authors propose a definition of the topological W gravity using some properties of the principal three-dimensional subalgebra of a simple Lie algebra due to Kostant. In the authors' definition, structures of the two-dimensional topological gravity are naturally embedded in the extended theories. In accordance with the definition, the authors will present some explicit calculations for the W 3 gravity

  14. Cosmic censorship in quantum Einstein gravity

    Science.gov (United States)

    Bonanno, A.; Koch, B.; Platania, A.

    2017-05-01

    We study the quantum gravity modification of the Kuroda-Papapetrou model induced by the running of the Newton’s constant at high energy in quantum Einstein gravity. We argue that although the antiscreening character of the gravitational interaction favours the formation of a naked singularity, quantum gravity effects turn the classical singularity into a ‘whimper’ singularity which remains naked for a finite amount of advanced time.

  15. The dynamic representation of gravity is suspended when the idiotropic vector is misaligned with gravity.

    Science.gov (United States)

    De Sá Teixeira, Nuno Alexandre; Hecht, Heiko

    2014-01-01

    When people are asked to indicate the vanishing location of a moving target, errors in the direction of motion (representational momentum) and in the direction of gravity (representational gravity) are usually found. These errors possess a temporal course wherein the memory for the location of the target drifts downwards with increasing temporal intervals between target's disappearance and participant's responses (representational trajectory). To assess if representational trajectory is a body-referenced or a world-referenced phenomenon. A behavioral localization method was employed with retention times between 0 and 1400 ms systematically imposed after the target's disappearance. The target could move horizontally (rightwards or leftwards) or vertically (upwards or downwards). Body posture was varied in a counterbalanced order between sitting upright and lying on the side (left lateral decubitus position). In the upright task, the memory for target location drifted downwards with time in the direction of gravity. This time course did not emerge for the decubitus task, where idiotropic dominance was found. The dynamic visual representation of gravity is neither purely body-referenced nor world-referenced. It seems to be modulated instead by the relationship between the idiotropic vector and physical gravity.

  16. Circulation-based Modeling of Gravity Currents

    Science.gov (United States)

    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

  17. Gravity Before Einstein and Schwinger Before Gravity

    Science.gov (United States)

    Trimble, Virginia L.

    2012-05-01

    Julian Schwinger was a child prodigy, and Albert Einstein distinctly not; Schwinger had something like 73 graduate students, and Einstein very few. But both thought gravity was important. They were not, of course, the first, nor is the disagreement on how one should think about gravity that is being highlighted here the first such dispute. The talk will explore, first, several of the earlier dichotomies: was gravity capable of action at a distance (Newton), or was a transmitting ether required (many others). Did it act on everything or only on solids (an odd idea of the Herschels that fed into their ideas of solar structure and sunspots)? Did gravitational information require time for its transmission? Is the exponent of r precisely 2, or 2 plus a smidgeon (a suggestion by Simon Newcomb among others)? And so forth. Second, I will try to say something about Scwinger's lesser known early work and how it might have prefigured his "source theory," beginning with "On the Interaction of Several Electrons (the unpublished, 1934 "zeroth paper," whose title somewhat reminds one of "On the Dynamics of an Asteroid," through his days at Berkeley with Oppenheimer, Gerjuoy, and others, to his application of ideas from nuclear physics to radar and of radar engineering techniques to problems in nuclear physics. And folks who think good jobs are difficult to come by now might want to contemplate the couple of years Schwinger spent teaching elementary physics at Purdue before moving on to the MIT Rad Lab for war work.

  18. Effect of Numerical Error on Gravity Field Estimation for GRACE and Future Gravity Missions

    Science.gov (United States)

    McCullough, Christopher; Bettadpur, Srinivas

    2015-04-01

    In recent decades, gravity field determination from low Earth orbiting satellites, such as the Gravity Recovery and Climate Experiment (GRACE), has become increasingly more effective due to the incorporation of high accuracy measurement devices. Since instrumentation quality will only increase in the near future and the gravity field determination process is computationally and numerically intensive, numerical error from the use of double precision arithmetic will eventually become a prominent error source. While using double-extended or quadruple precision arithmetic will reduce these errors, the numerical limitations of current orbit determination algorithms and processes must be accurately identified and quantified in order to adequately inform the science data processing techniques of future gravity missions. The most obvious numerical limitation in the orbit determination process is evident in the comparison of measured observables with computed values, derived from mathematical models relating the satellites' numerically integrated state to the observable. Significant error in the computed trajectory will corrupt this comparison and induce error in the least squares solution of the gravitational field. In addition, errors in the numerically computed trajectory propagate into the evaluation of the mathematical measurement model's partial derivatives. These errors amalgamate in turn with numerical error from the computation of the state transition matrix, computed using the variational equations of motion, in the least squares mapping matrix. Finally, the solution of the linearized least squares system, computed using a QR factorization, is also susceptible to numerical error. Certain interesting combinations of each of these numerical errors are examined in the framework of GRACE gravity field determination to analyze and quantify their effects on gravity field recovery.

  19. What goes up... gravity and scientific method

    CERN Document Server

    Kosso, Peter

    2017-01-01

    The concept of gravity provides a natural phenomenon that is simultaneously obvious and obscure; we all know what it is, but rarely question why it is. The simple observation that 'what goes up must come down' contrasts starkly with our current scientific explanation of gravity, which involves challenging and sometimes counterintuitive concepts. With such extremes between the plain and the perplexing, gravity forces a sharp focus on scientific method. Following the history of gravity from Aristotle to Einstein, this clear account highlights the logic of scientific method for non-specialists. Successive theories of gravity and the evidence for each are presented clearly and rationally, focusing on the fundamental ideas behind them. Using only high-school level algebra and geometry, the author emphasizes what the equations mean rather than how they are derived, making this accessible for all those curious about gravity and how science really works.

  20. Quantum Gravity Mathematical Models and Experimental Bounds

    CERN Document Server

    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 ...

  1. Loop Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Rovelli Carlo

    1998-01-01

    Full Text Available The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii A derivation of the Bekenstein-Hawking black hole entropy formula. (iii An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  2. 14 CFR 29.27 - Center of gravity limits.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Center of gravity limits. 29.27 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight General § 29.27 Center of gravity limits. The extreme forward and aft centers of gravity and, where critical, the extreme lateral centers of gravity...

  3. Weak lensing probes of modified gravity

    International Nuclear Information System (INIS)

    Schmidt, Fabian

    2008-01-01

    We study the effect of modifications to general relativity on large-scale weak lensing observables. In particular, we consider three modified gravity scenarios: f(R) gravity, the Dvali-Gabadadze-Porrati model, and tensor-vector-scalar theory. Weak lensing is sensitive to the growth of structure and the relation between matter and gravitational potentials, both of which will in general be affected by modified gravity. Restricting ourselves to linear scales, we compare the predictions for galaxy-shear and shear-shear correlations of each modified gravity cosmology to those of an effective dark energy cosmology with the same expansion history. In this way, the effects of modified gravity on the growth of perturbations are separated from the expansion history. We also propose a test which isolates the matter-potential relation from the growth factor and matter power spectrum. For all three modified gravity models, the predictions for galaxy and shear correlations will be discernible from those of dark energy with very high significance in future weak lensing surveys. Furthermore, each model predicts a measurably distinct scale dependence and redshift evolution of galaxy and shear correlations, which can be traced back to the physical foundations of each model. We show that the signal-to-noise for detecting signatures of modified gravity is much higher for weak lensing observables as compared to the integrated Sachs-Wolfe effect, measured via the galaxy-cosmic microwave background cross-correlation.

  4. Cosmological acceleration. Dark energy or modified gravity?

    International Nuclear Information System (INIS)

    Bludman, S.

    2006-05-01

    We review the evidence for recently accelerating cosmological expansion or ''dark energy'', either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any constituent Dark Energy. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of ''dark energy'' cannot be derived from the homogeneous expansion history alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, but also allow nearly static Dark Energy or gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish between static and ''dynamic'' ''dark energy''. But, cosmologically distinguishing the Concordance Model ΛCDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati low-curvature modifications of Einstein gravity may also be detected in refined observations in the solar system (Lue and Starkman) or at the intermediate Vainstein scale (Iorio) in isolated galaxy clusters. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence (''Why so small now?'') without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity. (Orig.)

  5. Cosmological acceleration. Dark energy or modified gravity?

    Energy Technology Data Exchange (ETDEWEB)

    Bludman, S

    2006-05-15

    We review the evidence for recently accelerating cosmological expansion or ''dark energy'', either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any constituent Dark Energy. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of ''dark energy'' cannot be derived from the homogeneous expansion history alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, but also allow nearly static Dark Energy or gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish between static and ''dynamic'' ''dark energy''. But, cosmologically distinguishing the Concordance Model {lambda}CDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati low-curvature modifications of Einstein gravity may also be detected in refined observations in the solar system (Lue and Starkman) or at the intermediate Vainstein scale (Iorio) in isolated galaxy clusters. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence (''Why so small now?'') without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity. (Orig.)

  6. FRW cosmology in F(R,T) gravity

    International Nuclear Information System (INIS)

    Myrzakulov, Ratbay

    2012-01-01

    In this paper, we consider a theory of gravity with a metric-dependent torsion namely the F(R,T) gravity, where R is the curvature scalar and T is the torsion scalar. We study the geometric root of such theory. In particular we give the derivation of the model from the geometrical point of view. Then we present the more general form of F(R,T) gravity with two arbitrary functions and give some of its particular cases. In particular, the usual F(R) and F(T) gravity theories are particular cases of the F(R,T) gravity. In the cosmological context, we find that our new gravitational theory can describe the accelerated expansion of the Universe. (orig.)

  7. Polyhedral shape model for terrain correction of gravity and gravity gradient data based on an adaptive mesh

    Science.gov (United States)

    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

  8. Subduction zones seen by GOCE gravity gradients

    DEFF Research Database (Denmark)

    Švarc, Mario; Herceg, Matija; Cammarano, Fabio

    In this study, the GOCE (Gravity field and steady state Ocean Circulation Explorer) gradiometry data were used to study geologic structures and mass variations within the lithosphere in areas of known subduction zones. The advantage of gravity gradiometry over other gravity methods is that gradie...

  9. 14 CFR 27.27 - Center of gravity limits.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Center of gravity limits. 27.27 Section 27... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight General § 27.27 Center of gravity limits. The extreme forward and aft centers of gravity and, where critical, the extreme lateral centers of gravity must be...

  10. Spin Entanglement Witness for Quantum Gravity.

    Science.gov (United States)

    Bose, Sougato; Mazumdar, Anupam; Morley, Gavin W; Ulbricht, Hendrik; Toroš, Marko; Paternostro, Mauro; Geraci, Andrew A; Barker, Peter F; Kim, M S; Milburn, Gerard

    2017-12-15

    Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. However, the lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Despite varied proposed probes for quantum gravity, it is fair to say that there are no feasible ideas yet to test its quantum coherent behavior directly in a laboratory experiment. Here, we introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. We show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. We provide a prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, through simple spin correlation measurements.

  11. Modeling human perception of orientation in altered gravity

    Science.gov (United States)

    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

  12. Modeling Human Perception of Orientation in Altered Gravity

    Directory of Open Access Journals (Sweden)

    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.

  13. Observational tests of modified gravity

    International Nuclear Information System (INIS)

    Jain, Bhuvnesh; Zhang Pengjie

    2008-01-01

    Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the Universe. Modified gravity theories have richer observational consequences for large-scale structures than conventional dark energy models, in that different observables are not described by a single growth factor even in the linear regime. We examine the relationships between perturbations in the metric potentials, density and velocity fields, and discuss strategies for measuring them using gravitational lensing, galaxy cluster abundances, galaxy clustering/dynamics, and the integrated Sachs-Wolfe effect. We show how a broad class of gravity theories can be tested by combining these probes. A robust way to interpret observations is by constraining two key functions: the ratio of the two metric potentials, and the ratio of the gravitational 'constant' in the Poisson equation to Newton's constant. We also discuss quasilinear effects that carry signatures of gravity, such as through induced three-point correlations. Clustering of dark energy can mimic features of modified gravity theories and thus confuse the search for distinct signatures of such theories. It can produce pressure perturbations and anisotropic stresses, which break the equality between the two metric potentials even in general relativity. With these two extra degrees of freedom, can a clustered dark energy model mimic modified gravity models in all observational tests? We show with specific examples that observational constraints on both the metric potentials and density perturbations can in principle distinguish modifications of gravity from dark energy models. We compare our result with other recent studies that have slightly different assumptions (and apparently contradictory conclusions).

  14. Quasi-topological Ricci polynomial gravities

    Science.gov (United States)

    Li, Yue-Zhou; Liu, Hai-Shan; Lü, H.

    2018-02-01

    Quasi-topological terms in gravity can be viewed as those that give no contribution to the equations of motion for a special subclass of metric ansätze. They therefore play no rôle in constructing these solutions, but can affect the general perturbations. We consider Einstein gravity extended with Ricci tensor polynomial invariants, which admits Einstein metrics with appropriate effective cosmological constants as its vacuum solutions. We construct three types of quasi-topological gravities. The first type is for the most general static metrics with spherical, toroidal or hyperbolic isometries. The second type is for the special static metrics where g tt g rr is constant. The third type is the linearized quasitopological gravities on the Einstein metrics. We construct and classify results that are either dependent on or independent of dimensions, up to the tenth order. We then consider a subset of these three types and obtain Lovelock-like quasi-topological gravities, that are independent of the dimensions. The linearized gravities on Einstein metrics on all dimensions are simply Einstein and hence ghost free. The theories become quasi-topological on static metrics in one specific dimension, but non-trivial in others. We also focus on the quasi-topological Ricci cubic invariant in four dimensions as a specific example to study its effect on holography, including shear viscosity, thermoelectric DC conductivities and butterfly velocity. In particular, we find that the holographic diffusivity bounds can be violated by the quasi-topological terms, which can induce an extra massive mode that yields a butterfly velocity unbound above.

  15. Thermosyphon Flooding in Reduced Gravity Environments

    Science.gov (United States)

    Gibson, Marc Andrew

    2013-01-01

    An innovative experiment to study the thermosyphon flooding limits was designed and flown on aparabolic flight campaign to achieve the Reduced Gravity Environments (RGE) needed to obtainempirical data for analysis. Current correlation models of Faghri and Tien and Chung do not agreewith the data. A new model is presented that predicts the flooding limits for thermosyphons inearths gravity and lunar gravity with a 95 confidence level of +- 5W.

  16. Internal model of gravity influences configural body processing.

    Science.gov (United States)

    Barra, Julien; Senot, Patrice; Auclair, Laurent

    2017-01-01

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

  17. Loop-quantum-gravity vertex amplitude.

    Science.gov (United States)

    Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo

    2007-10-19

    Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.

  18. Natural inflation and quantum gravity.

    Science.gov (United States)

    de la Fuente, Anton; Saraswat, Prashant; Sundrum, Raman

    2015-04-17

    Cosmic inflation provides an attractive framework for understanding the early Universe and the cosmic microwave background. It can readily involve energies close to the scale at which quantum gravity effects become important. General considerations of black hole quantum mechanics suggest nontrivial constraints on any effective field theory model of inflation that emerges as a low-energy limit of quantum gravity, in particular, the constraint of the weak gravity conjecture. We show that higher-dimensional gauge and gravitational dynamics can elegantly satisfy these constraints and lead to a viable, theoretically controlled and predictive class of natural inflation models.

  19. Lanczos–Lovelock models of gravity

    International Nuclear Information System (INIS)

    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

  20. The covariant formulation of f ( T ) gravity

    International Nuclear Information System (INIS)

    Krššák, Martin; Saridakis, Emmanuel N

    2016-01-01

    We show that the well-known problem of frame dependence and violation of local Lorentz invariance in the usual formulation of f ( T ) gravity is a consequence of neglecting the role of spin connection. We re-formulate f ( T ) gravity starting from, instead of the ‘pure tetrad’ teleparallel gravity, the covariant teleparallel gravity, using both the tetrad and the spin connection as dynamical variables, resulting in a fully covariant, consistent, and frame-independent version of f ( T ) gravity, which does not suffer from the notorious problems of the usual, pure tetrad, f ( T ) theory. We present the method to extract solutions for the most physically important cases, such as the Minkowski, the Friedmann–Robertson–Walker (FRW) and the spherically symmetric ones. We show that in covariant f ( T ) gravity we are allowed to use an arbitrary tetrad in an arbitrary coordinate system along with the corresponding spin connection, resulting always in the same physically relevant field equations. (paper)

  1. Quantum gravity as Escher's dragon

    International Nuclear Information System (INIS)

    Smilga, A.V.

    2003-01-01

    The main obstacle in attempts to construct a consistent quantum gravity is the absence of independent flat time. This can in principle be cured by going out to higher dimensions. The modern paradigm assumes that the fundamental theory of everything is some form of string theory living in space of more than four dimensions. We advocate another possibility that the fundamental theory is a form of D = 4 higher derivative gravity. This class of theories has a nice feature of renormalizability, so that perturbative calculations are feasible. There are also finite N = 4 supersymmetric conformal supergravity theories. This possibility is particularly attractive. Einstein's gravity is obtained in a natural way as an effective low-energy theory. The N= 1 supersymmetric version of the theory has a natural higher dimensional interpretation due to V.I. Ogievetsky and E.S. Sokatchev, which involves embedding our curved Minkowski spacetime manifold into flat eight-dimensional space. Assuming that a variant of the finite N = 4 theory also admits a similar interpretation, this may eventually allow one to construct consistent quantum theory of gravity. We argue, however, that, even though future gravity theory will probably use higher dimensions as construction scaffolds, its physical content and meaning should refer to four dimensions, where an observer lives

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

    Science.gov (United States)

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

    2015-01-01

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

  3. Quantum Gravity in Two Dimensions

    DEFF Research Database (Denmark)

    Ipsen, Asger Cronberg

    The topic of this thesis is quantum gravity in 1 + 1 dimensions. We will focus on two formalisms, namely Causal Dynamical Triangulations (CDT) and Dy- namical Triangulations (DT). Both theories regularize the gravity path integral as a sum over triangulations. The difference lies in the class...

  4. Toward Joint Inversion of Gravity and Dyanamics

    Science.gov (United States)

    Jacoby, W. R.

    To better understand geodynamic processes as seafloor spreading, plumes, subduction, and isostatic adjustment, gravity is inverted with "a prioriinformation from topography/bathymetry, seismic structure and dynamic models. Examples are subduction of the Juan de Fuca plate below Vancouver Island, the passive Black Sea­Turkey margin and Iceland ridge-plume interaction. Gravity and other data are averaged 50 km wide strips. Mass balances are estimated (showing also that the free air anomaly is misleading for narrow structures). The mass balances represent plate forces and plate bending, affecting the gravity signals and the isostatic state of continental margins and ridge-plume effects, which are highly correlated in space and cannot be separated without a priori information from modelling. The examples from widely different tectonic situations demonstrate that the art of regional-scale gravity inversion requires extensive background knowledge and inclusion of dynamic processes. It is difficult to conceive any formal, globally applicable procedure taking care of this; it is even a question, what is data, what a priori information? They are not distinguishable if all are included as foreward routines. The "accuracy" of models cannot be perfectly determined, if the "real" mass distribution is not known ­ if known, gravity inversion would be unnecessary. In reality only guesses are possible on the basis of observations and physical laws governing geodynamics. A priori information and gravity data limit the resolution of gravity inversion. Different model types are indistinguishable because adjustments within their parameter uncertainties permit a good fit. But gravity excludes wrong models (Karl Popper: science evolves by falsification of wrong models), and precise gravity guides and defines aims, targets and strategies for new observations.

  5. Quantum gravity and quantum cosmology

    CERN Document Server

    Papantonopoulos, Lefteris; Siopsis, George; Tsamis, Nikos

    2013-01-01

    Quantum gravity has developed into a fast-growing subject in physics and it is expected that probing the high-energy and high-curvature regimes of gravitating systems will shed some light on how to eventually achieve an ultraviolet complete quantum theory of gravity. Such a theory would provide the much needed information about fundamental problems of classical gravity, such as the initial big-bang singularity, the cosmological constant problem, Planck scale physics and the early-time inflationary evolution of our Universe.   While in the first part of this book concepts of quantum gravity are introduced and approached from different angles, the second part discusses these theories in connection with cosmological models and observations, thereby exploring which types of signatures of modern and mathematically rigorous frameworks can be detected by experiments. The third and final part briefly reviews the observational status of dark matter and dark energy, and introduces alternative cosmological models.   ...

  6. Flavorful hybrid anomaly-gravity mediation

    International Nuclear Information System (INIS)

    Gross, Christian; Hiller, Gudrun

    2011-01-01

    We consider supersymmetric models where anomaly and gravity mediation give comparable contributions to the soft terms and discuss how this can be realized in a five-dimensional brane world. The gaugino mass pattern of anomaly mediation is preserved in such a hybrid setup. The flavorful gravity-mediated contribution cures the tachyonic slepton problem of anomaly mediation. The supersymmetric flavor puzzle is solved by alignment. We explicitly show how a working flavor-tachyon link can be realized with Abelian flavor symmetries and give the characteristic signatures of the framework, including O(1) slepton mass splittings between different generations and between doublets and singlets. This provides opportunities for same flavor dilepton edge measurements with missing energy at the Large Hadron Collider (LHC). Rare lepton decay rates could be close to their current experimental limit. Compared to pure gravity mediation, the hybrid model is advantageous because it features a heavy gravitino which can avoid the cosmological gravitino problem of gravity-mediated models combined with leptogenesis.

  7. Unifying Einstein and Palatini gravities

    International Nuclear Information System (INIS)

    Amendola, Luca; Enqvist, Kari; Koivisto, Tomi

    2011-01-01

    We consider a novel class of f(R) gravity theories where the connection is related to the conformally scaled metric g μν =C(R)g μν with a scaling that depends on the scalar curvature R only. We call them C theories and show that the Einstein and Palatini gravities can be obtained as special limits. In addition, C theories include completely new physically distinct gravity theories even when f(R)=R. With nonlinear f(R), C theories interpolate and extrapolate the Einstein and Palatini cases and may avoid some of their conceptual and observational problems. We further show that C theories have a scalar-tensor formulation, which in some special cases reduces to simple Brans-Dicke-type gravity. If matter fields couple to the connection, the conservation laws in C theories are modified. The stability of perturbations about flat space is determined by a simple condition on the Lagrangian.

  8. Venus gravity fields

    Science.gov (United States)

    Sjogren, W. L.; Ananda, M.; Williams, B. G.; Birkeland, P. W.; Esposito, P. S.; Wimberly, R. N.; Ritke, S. J.

    1981-01-01

    Results of Pioneer Venus Orbiter observations concerning the gravity field of Venus are presented. The gravitational data was obtained from reductions of Doppler radio tracking data for the Orbiter, which is in a highly eccentric orbit with periapsis altitude varying from 145 to 180 km and nearly fixed periapsis latitude of 15 deg N. The global gravity field was obtained through the simultaneous estimation of the orbit state parameters and gravity coefficients from long-period variations in orbital element rates. The global field has been described with sixth degree and order spherical harmonic coefficients, which are capable of resolving the three major topographical features on Venus. Local anomalies have been mapped using line-of-sight accelerations derived from the Doppler residuals between 40 deg N and 10 deg S latitude at approximately 300 km spatial resolution. Gravitational data is observed to correspond to topographical data obtained by radar altimeter, with most of the gravitational anomalies about 20-30 milligals. Simulations evaluating the isostatic states of two topographic features indicate that at least partial isostasy prevails, with the possibility of complete compensation.

  9. Streaming gravity mode instability

    International Nuclear Information System (INIS)

    Wang Shui.

    1989-05-01

    In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs

  10. Approaches to quantum gravity. Loop quantum gravity, spinfoams and topos approach

    International Nuclear Information System (INIS)

    Flori, Cecilia

    2010-01-01

    One of the main challenges in theoretical physics over the last five decades has been to reconcile quantum mechanics with general relativity into a theory of quantum gravity. However, such a theory has been proved to be hard to attain due to i) conceptual difficulties present in both the component theories (General Relativity (GR) and Quantum Theory); ii) lack of experimental evidence, since the regimes at which quantum gravity is expected to be applicable are far beyond the range of conceivable experiments. Despite these difficulties, various approaches for a theory of Quantum Gravity have been developed. In this thesis we focus on two such approaches: Loop Quantum Gravity and the Topos theoretic approach. The choice fell on these approaches because, although they both reject the Copenhagen interpretation of quantum theory, their underpinning philosophical approach to formulating a quantum theory of gravity are radically different. In particular LQG is a rather conservative scheme, inheriting all the formalism of both GR and Quantum Theory, as it tries to bring to its logical extreme consequences the possibility of combining the two. On the other hand, the Topos approach involves the idea that a radical change of perspective is needed in order to solve the problem of quantum gravity, especially in regard to the fundamental concepts of 'space' and 'time'. Given the partial successes of both approaches, the hope is that it might be possible to find a common ground in which each approach can enrich the other. This thesis is divided in two parts: in the first part we analyse LQG, paying particular attention to the semiclassical properties of the volume operator. Such an operator plays a pivotal role in defining the dynamics of the theory, thus testing its semiclassical limit is of uttermost importance. We then proceed to analyse spin foam models (SFM), which are an attempt at a covariant or path integral formulation of canonical Loop Quantum Gravity (LQG). In

  11. Approaches to quantum gravity. Loop quantum gravity, spinfoams and topos approach

    Energy Technology Data Exchange (ETDEWEB)

    Flori, Cecilia

    2010-07-23

    One of the main challenges in theoretical physics over the last five decades has been to reconcile quantum mechanics with general relativity into a theory of quantum gravity. However, such a theory has been proved to be hard to attain due to i) conceptual difficulties present in both the component theories (General Relativity (GR) and Quantum Theory); ii) lack of experimental evidence, since the regimes at which quantum gravity is expected to be applicable are far beyond the range of conceivable experiments. Despite these difficulties, various approaches for a theory of Quantum Gravity have been developed. In this thesis we focus on two such approaches: Loop Quantum Gravity and the Topos theoretic approach. The choice fell on these approaches because, although they both reject the Copenhagen interpretation of quantum theory, their underpinning philosophical approach to formulating a quantum theory of gravity are radically different. In particular LQG is a rather conservative scheme, inheriting all the formalism of both GR and Quantum Theory, as it tries to bring to its logical extreme consequences the possibility of combining the two. On the other hand, the Topos approach involves the idea that a radical change of perspective is needed in order to solve the problem of quantum gravity, especially in regard to the fundamental concepts of 'space' and 'time'. Given the partial successes of both approaches, the hope is that it might be possible to find a common ground in which each approach can enrich the other. This thesis is divided in two parts: in the first part we analyse LQG, paying particular attention to the semiclassical properties of the volume operator. Such an operator plays a pivotal role in defining the dynamics of the theory, thus testing its semiclassical limit is of uttermost importance. We then proceed to analyse spin foam models (SFM), which are an attempt at a covariant or path integral formulation of canonical Loop Quantum

  12. Gravity study of the Middle Aterno Valley

    Science.gov (United States)

    di Nezza, Maria; di Filippo, Michele; Cesi, Claudio; Ferri, Fernando

    2010-05-01

    A gravity study was carried out to identify the geological and structural features of the Middle Aterno Valley, and intramontane depression in the central Appennines, which was targeted to assess the seismic hazard of the city of L'Aquila and surrounding areas, after the Abruzzo 2009 earthquake. Gravity anomalies have been used for the construction of a 3D model of the area, and gravity data for the construction of Bouguer and residual anomaly maps. These data, together with geological surface data allowed for the understanding of the Plio-quaternary tectonic setting of the basins. The study area has been differentiated into different domains with respect to structural and morphological features of different styles of faults. Geology and gravity data show that the local amplification phenomena are due to the fact that the historical center of L'Aquila was built on a coarse breccias (debris-flow deposits with decameter scale limestone blocks) overlying sandy and clayey lacustrine sediments. As these sediments have a low density, gravity prospecting very easily identifies them. Residual anomalies, showing a relative gravity low corresponding to the historical center of L'Aquila, and surrounding areas, indicated that these sediments are up to 250 m-thick. Gravity prospecting also revealed the uprooting of the reliefs which outcrop in the area of Coppito. These reliefs, practically outcrop in the middle of the basin. Here, the gravity anomalies are negative and not positive as would be expected from outcropping geological bedrock.

  13. Lanczos-Lovelock gravity from a thermodynamic perspective

    International Nuclear Information System (INIS)

    Chakraborty, Sumanta

    2015-01-01

    The deep connection between gravitational dynamics and horizon thermodynamics leads to several intriguing features both in general relativity and in Lanczos-Lovelock theories of gravity. Recently in http://arxiv.org/abs/1312.3253 several additional results strengthening the above connection have been established within the framework of general relativity. In this work we provide a generalization of the above setup to Lanczos-Lovelock gravity as well. To our expectation it turns out that most of the results obtained in the context of general relativity generalize to Lanczos-Lovelock gravity in a straightforward but non-trivial manner. First, we provide an alternative and more general derivation of the connection between Noether charge for a specific time evolution vector field and gravitational heat density of the boundary surface. This will lead to holographic equipartition for static spacetimes in Lanczos-Lovelock gravity as well. Taking a cue from this, we have introduced naturally defined four-momentum current associated with gravity and matter energy momentum tensor for both Lanczos-Lovelock Lagrangian and its quadratic part. Then, we consider the concepts of Noether charge for null boundaries in Lanczos-Lovelock gravity by providing a direct generalization of previous results derived in the context of general relativity. Another very interesting feature for gravity is that gravitational field equations for arbitrary static and spherically symmetric spacetimes with horizon can be written as a thermodynamic identity in the near horizon limit. This result holds in both general relativity and in Lanczos-Lovelock gravity as well. In a previous work [http://arxiv.org/abs/1505.05297] we have shown that, for an arbitrary spacetime, the gravitational field equations near any null surface generically leads to a thermodynamic identity. In this work, we have also generalized this result to Lanczos-Lovelock gravity by showing that gravitational field equations for Lanczos

  14. Concepts and procedures required for successful reduction of tensor magnetic gradiometer data obtained from an unexploded ordnance detection demonstration at Yuma Proving Grounds, Arizona

    Science.gov (United States)

    Bracken, Robert E.; Brown, Philip J.

    2006-01-01

    On March 12, 2003, data were gathered at Yuma Proving Grounds, in Arizona, using a Tensor Magnetic Gradiometer System (TMGS). This report shows how these data were processed and explains concepts required for successful TMGS data reduction. Important concepts discussed include extreme attitudinal sensitivity of vector measurements, low attitudinal sensitivity of gradient measurements, leakage of the common-mode field into gradient measurements, consequences of thermal drift, and effects of field curvature. Spatial-data collection procedures and a spin-calibration method are addressed. Discussions of data-reduction procedures include tracking of axial data by mathematically matching transfer functions among the axes, derivation and application of calibration coefficients, calculation of sensor-pair gradients, thermal-drift corrections, and gradient collocation. For presentation, the magnetic tensor at each data station is converted to a scalar quantity, the I2 tensor invariant, which is easily found by calculating the determinant of the tensor. At important processing junctures, the determinants for all stations in the mapped area are shown in shaded relief map-view. Final processed results are compared to a mathematical model to show the validity of the assumptions made during processing and the reasonableness of the ultimate answer obtained.

  15. Quantum gravity and Standard-Model-like fermions

    International Nuclear Information System (INIS)

    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.

  16. Group field theory and simplicial quantum gravity

    International Nuclear Information System (INIS)

    Oriti, D

    2010-01-01

    We present a new group field theory for 4D quantum gravity. It incorporates the constraints that give gravity from BF theory and has quantum amplitudes with the explicit form of simplicial path integrals for first-order gravity. The geometric interpretation of the variables and of the contributions to the quantum amplitudes is manifest. This allows a direct link with other simplicial gravity approaches, like quantum Regge calculus, in the form of the amplitudes of the model, and dynamical triangulations, which we show to correspond to a simple restriction of the same.

  17. Three-dimensional dilatonic gravity's rainbow: Exact solutions

    International Nuclear Information System (INIS)

    Hossein Hendi, Seyed; Eslam Panah, Behzad; Panahiyan, Shahram

    2016-01-01

    Deep relations of dark energy scenario and string theory results into dilaton gravity, on the one hand, and the connection between quantum gravity and gravity's rainbow, on the other hand, motivate us to consider three-dimensional dilatonic black hole solutions in gravity's rainbow. We obtain two classes of the solutions, which are polynomial and logarithmic forms. We also calculate conserved and thermodynamic quantities, and examine the first law of thermodynamics for both classes. In addition, we study thermal stability and show that one of the classes is thermally stable while the other one is unstable.

  18. Analysis of Alabama Airborne Gravity at Three Altitudes: Expected Accuracy and Spatial Resolution from a Future Tibetan Airborne Gravity Survey

    Directory of Open Access Journals (Sweden)

    Chi-Hsun Huang

    2013-01-01

    Full Text Available In situ airborne gravity data at altitudes of 11, 6.3, and 1.7 km over a smooth area of Alabama are used to assess gravity accuracy and errors in upward and downward continuations. Analysis of the Alabama free-air anomaly gravity data at crossover points at the three altitudes suggests 1 - 2 mgal accuracy for the dataset. Gravity data at each altitude are then expanded into local 3D Fourier series, to prepare for continuation. This Fourier representation results in continuation errors at few-mgal level in Alabama, even in the extreme case of downward continuation from 11 km to sea level. The result in Alabama inspires an airborne gravity survey over the rough, inaccessible terrain of Tibet. Similar investigations as in Alabama are made in Tibet using EGM08-derived airborne gravity data at flight altitudes of 10, 5, and 0 km. Bouguer anomalies at the 10-km altitude preserve the major tectonic features of Tibet. Downward continuation errors increase with terrain roughness, but the survey can enhance local tectonic features. This study highlights the value of a future Tibetan airborne gravity survey and points out the expected gravity accuracy and spatial resolution from this survey.

  19. Loop Quantum Gravity.

    Science.gov (United States)

    Rovelli, Carlo

    2008-01-01

    The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime , is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i) The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii) A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler's "spacetime foam" intuition. (iii) Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv) A derivation of the Bekenstein-Hawking black-hole entropy. (v) Low-energy calculations, yielding n -point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  20. Semiclassical unimodular gravity

    International Nuclear Information System (INIS)

    Fiol, Bartomeu; Garriga, Jaume

    2010-01-01

    Classically, unimodular gravity is known to be equivalent to General Relativity (GR), except for the fact that the effective cosmological constant Λ has the status of an integration constant. Here, we explore various formulations of unimodular gravity beyond the classical limit. We first consider the non-generally covariant action formulation in which the determinant of the metric is held fixed to unity. We argue that the corresponding quantum theory is also equivalent to General Relativity for localized perturbative processes which take place in generic backgrounds of infinite volume (such as asymptotically flat spacetimes). Next, using the same action, we calculate semiclassical non-perturbative quantities, which we expect will be dominated by Euclidean instanton solutions. We derive the entropy/area ratio for cosmological and black hole horizons, finding agreement with GR for solutions in backgrounds of infinite volume, but disagreement for backgrounds with finite volume. In deriving the above results, the path integral is taken over histories with fixed 4-volume. We point out that the results are different if we allow the 4-volume of the different histories to vary over a continuum range. In this ''generalized'' version of unimodular gravity, one recovers the full set of Einstein's equations in the classical limit, including the trace, so Λ is no longer an integration constant. Finally, we consider the generally covariant theory due to Henneaux and Teitelboim, which is classically equivalent to unimodular gravity. In this case, the standard semiclassical GR results are recovered provided that the boundary term in the Euclidean action is chosen appropriately

  1. Application of Cauchy-type integrals in developing effective methods for depth-to-basement inversion of gravity and gravity gradiometry data

    DEFF Research Database (Denmark)

    Cai, Hongzhu; Zhdanov, Michael

    2015-01-01

    to be discretized for the calculation of gravity field. This was especially significant in the modeling and inversion of gravity data for determining the depth to the basement. Another important result was developing a novel method of inversion of gravity data to recover the depth to basement, based on the 3D...... Cauchy-type integral representation. Our numerical studies determined that the new method is much faster than conventional volume discretization method to compute the gravity response. Our synthetic model studies also showed that the developed inversion algorithm based on Cauchy-type integral is capable......One of the most important applications of gravity surveys in regional geophysical studies is determining the depth to basement. Conventional methods of solving this problem are based on the spectrum and/or Euler deconvolution analysis of the gravity field and on parameterization of the earth...

  2. Seasonal gravity change at Yellowstone caldera

    Science.gov (United States)

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

    2017-12-01

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

  3. Mars - Crustal structure inferred from Bouguer gravity anomalies.

    Science.gov (United States)

    Phillips, R. J.; Saunders, R. S.; Conel, J. E.

    1973-01-01

    Bouguer gravity has been computed for the equatorial region of Mars by differencing free air gravity and the gravity predicted from topographic variations. The free air gravity was generated from an eighth-order set of spherical harmonic coefficients. The gravity from topographic variations was generated by integrating a two-dimensional Green's function over each contour level. The Bouguer gravity indicates crustal inhomogeneities on Mars that are postulated to be variations in crustal thickness. The Tharsis ridge is a region of thick continental type crust. The gravity data, structural patterns, topography, and surface geology of this region lead to the interpretation of the Tharsis topographic high as a broad crustal upwarp possibly associated with local formation of lower-density crustal material and subsequent rise of a thicker crust. The Amazonis region is one of several basins of relatively thin crust, analogous to terrestrial ocean basins. The Libya and Hellas basins, which are probable impact features, are also underlain by thin crust and are possible regions of mantle upwelling.

  4. From thermodynamics to the solutions in gravity theory

    International Nuclear Information System (INIS)

    Zhang, Hongsheng; Li, Xin-Zhou

    2014-01-01

    In a recent work, we present a new point of view to the relation of gravity and thermodynamics, in which we derive the Schwarzschild solution through thermodynamic considerations by the aid of the Misner–Sharp mass in an adiabatic system. In this Letter we continue to investigate the relation between gravity and thermodynamics for obtaining solutions via thermodynamics. We generalize our studies on gravi-thermodynamics in Einstein gravity to modified gravity theories. By using the first law with the assumption that the Misner–Sharp mass is the mass for an adiabatic system, we reproduce the Boulware–Deser–Cai solution in Gauss–Bonnet gravity. Using this gravi-thermodynamic thought, we obtain a NEW class of solution in F(R) gravity in an n-dimensional (n≥3) spacetime which permits three-type (n−2)-dimensional maximally symmetric subspace, as an extension of our recent three-dimensional black hole solution, and four-dimensional Clifton–Barrow solution in F(R) gravity

  5. From thermodynamics to the solutions in gravity theory

    Directory of Open Access Journals (Sweden)

    Hongsheng Zhang

    2014-10-01

    Full Text Available In a recent work, we present a new point of view to the relation of gravity and thermodynamics, in which we derive the Schwarzschild solution through thermodynamic considerations by the aid of the Misner–Sharp mass in an adiabatic system. In this Letter we continue to investigate the relation between gravity and thermodynamics for obtaining solutions via thermodynamics. We generalize our studies on gravi-thermodynamics in Einstein gravity to modified gravity theories. By using the first law with the assumption that the Misner–Sharp mass is the mass for an adiabatic system, we reproduce the Boulware–Deser–Cai solution in Gauss–Bonnet gravity. Using this gravi-thermodynamic thought, we obtain a NEW class of solution in F(R gravity in an n-dimensional (n≥3 spacetime which permits three-type (n−2-dimensional maximally symmetric subspace, as an extension of our recent three-dimensional black hole solution, and four-dimensional Clifton–Barrow solution in F(R gravity.

  6. Cosmological footprints of loop quantum gravity.

    Science.gov (United States)

    Grain, J; Barrau, A

    2009-02-27

    The primordial spectrum of cosmological tensor perturbations is considered as a possible probe of quantum gravity effects. Together with string theory, loop quantum gravity is one of the most promising frameworks to study quantum effects in the early universe. We show that the associated corrections should modify the potential seen by gravitational waves during the inflationary amplification. The resulting power spectrum should exhibit a characteristic tilt. This opens a new window for cosmological tests of quantum gravity.

  7. New Gravity Wave Treatments for GISS Climate Models

    Science.gov (United States)

    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.

  8. Centrifuge in Free Fall: Combustion at Partial Gravity

    Science.gov (United States)

    Ferkul, Paul

    2017-01-01

    A centrifuge apparatus is developed to study the effect of variable acceleration levels in a drop tower environment. It consists of a large rotating chamber, within which the experiment is conducted. NASA Glenn Research Center 5.18-second Zero-Gravity Facility drop tests were successfully conducted at rotation rates up to 1 RPS with no measurable effect on the overall Zero-Gravity drop bus. Arbitrary simulated gravity levels from zero to 1-g (at a radius of rotation 30 cm) were produced. A simple combustion experiment was used to exercise the capabilities of the centrifuge. A total of 23 drops burning a simulated candle with heptane and ethanol fuel were performed. The effect of gravity level (rotation rate) and Coriolis force on the flames was observed. Flames became longer, narrower, and brighter as gravity increased. The Coriolis force tended to tilt the flames to one side, as expected, especially as the rotation rate was increased. The Zero-Gravity Centrifuge can be a useful tool for other researchers interested in the effects of arbitrary partial gravity on experiments, especially as NASA embarks on future missions which may be conducted in non-Earth gravity.

  9. Quintic quasi-topological gravity

    Energy Technology Data Exchange (ETDEWEB)

    Cisterna, Adolfo [Vicerrectoría académica, Universidad Central de Chile,Toesca 1783 Santiago (Chile); Instituto de Ciencias Físicas y Matemáticas, Universidad Austral de Chile,Casilla 567, Valdivia (Chile); Guajardo, Luis; Hassaïne, Mokhtar [Instituto de Matemática y Física, Universidad de Talca,Casilla 747, Talca (Chile); Oliva, Julio [Departamento de Física, Universidad de Concepción,Casilla, 160-C, Concepción (Chile)

    2017-04-11

    We construct a quintic quasi-topological gravity in five dimensions, i.e. a theory with a Lagrangian containing R{sup 5} terms and whose field equations are of second order on spherically (hyperbolic or planar) symmetric spacetimes. These theories have recently received attention since when formulated on asymptotically AdS spacetimes might provide for gravity duals of a broad class of CFTs. For simplicity we focus on five dimensions. We show that this theory fulfils a Birkhoff’s Theorem as it is the case in Lovelock gravity and therefore, for generic values of the couplings, there is no s-wave propagating mode. We prove that the spherically symmetric solution is determined by a quintic algebraic polynomial equation which resembles Wheeler’s polynomial of Lovelock gravity. For the black hole solutions we compute the temperature, mass and entropy and show that the first law of black holes thermodynamics is fulfilled. Besides of being of fourth order in general, we show that the field equations, when linearized around AdS are of second order, and therefore the theory does not propagate ghosts around this background. Besides the class of theories originally introduced in https://arxiv.org/abs/1003.4773, the general geometric structure of these Lagrangians remains an open problem.

  10. gravity

    Indian Academy of Sciences (India)

    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 ...

  11. Singularity resolution in quantum gravity

    International Nuclear Information System (INIS)

    Husain, Viqar; Winkler, Oliver

    2004-01-01

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

  12. PREFACE: Conceptual and Technical Challenges for Quantum Gravity 2014 - Parallel session: Noncommutative Geometry and Quantum Gravity

    Science.gov (United States)

    Martinetti, P.; Wallet, J.-C.; Amelino-Camelia, G.

    2015-08-01

    The conference Conceptual and Technical Challenges for Quantum Gravity at Sapienza University of Rome, from 8 to 12 September 2014, has provided a beautiful opportunity for an encounter between different approaches and different perspectives on the quantum-gravity problem. It contributed to a higher level of shared knowledge among the quantum-gravity communities pursuing each specific research program. There were plenary talks on many different approaches, including in particular string theory, loop quantum gravity, spacetime noncommutativity, causal dynamical triangulations, asymptotic safety and causal sets. Contributions from the perspective of philosophy of science were also welcomed. In addition several parallel sessions were organized. The present volume collects contributions from the Noncommutative Geometry and Quantum Gravity parallel session4, with additional invited contributions from specialists in the field. Noncommutative geometry in its many incarnations appears at the crossroad of many researches in theoretical and mathematical physics: • from models of quantum space-time (with or without breaking of Lorentz symmetry) to loop gravity and string theory, • from early considerations on UV-divergencies in quantum field theory to recent models of gauge theories on noncommutative spacetime, • from Connes description of the standard model of elementary particles to recent Pati-Salam like extensions. This volume provides an overview of these various topics, interesting for the specialist as well as accessible to the newcomer. 4partially funded by CNRS PEPS /PTI ''Metric aspect of noncommutative geometry: from Monge to Higgs''

  13. Solitons in Newtonian gravity

    International Nuclear Information System (INIS)

    Goetz, G.

    1988-01-01

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

  14. Semiclassical analysis of loop quantum gravity

    International Nuclear Information System (INIS)

    Conrady, F.

    2005-01-01

    In this Ph.D. thesis, we explore and develop new methods that should help in determining an effective semiclassical description of canonical loop quantum gravity and spin foam gravity. A brief introduction to loop quantum gravity is followed by three research papers that present the results of the Ph.D. project. In the first article, we deal with the problem of time and a new proposal for implementing proper time as boundary conditions in a sum over histories: we investigate a concrete realization of this formalism for free scalar field theory. In the second article, we translate semiclassical states of linearized gravity into states of loop quantum gravity. The properties of the latter indicate how semiclassicality manifests itself in the loop framework, and how this may be exploited for doing semiclassical expansions. In the third part, we propose a new formulation of spin foam models that is fully triangulation- and background-independent: by means of a symmetry condition, we identify spin foam models whose triangulation-dependence can be naturally removed. (orig.)

  15. Semiclassical analysis of loop quantum gravity

    Energy Technology Data Exchange (ETDEWEB)

    Conrady, F.

    2005-10-17

    In this Ph.D. thesis, we explore and develop new methods that should help in determining an effective semiclassical description of canonical loop quantum gravity and spin foam gravity. A brief introduction to loop quantum gravity is followed by three research papers that present the results of the Ph.D. project. In the first article, we deal with the problem of time and a new proposal for implementing proper time as boundary conditions in a sum over histories: we investigate a concrete realization of this formalism for free scalar field theory. In the second article, we translate semiclassical states of linearized gravity into states of loop quantum gravity. The properties of the latter indicate how semiclassicality manifests itself in the loop framework, and how this may be exploited for doing semiclassical expansions. In the third part, we propose a new formulation of spin foam models that is fully triangulation- and background-independent: by means of a symmetry condition, we identify spin foam models whose triangulation-dependence can be naturally removed. (orig.)

  16. On higher derivative gravity

    International Nuclear Information System (INIS)

    Accioly, A.J.

    1987-01-01

    A possible classical route conducting towards a general relativity theory with higher-derivatives starting, in a sense, from first principles, is analysed. A completely causal vacuum solution with the symmetries of the Goedel universe is obtained in the framework of this higher-derivative gravity. This very peculiar and rare result is the first known vcuum solution of the fourth-order gravity theory that is not a solution of the corresponding Einstein's equations.(Author) [pt

  17. Airborne Gravity: NGS' Gravity Data for ES03 (2013)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Maryland, Pennsylvania, New Jersey, West Virginia, Virginia, Delaware, and the Atlantic Ocean collected in 2013 over 1 survey. This data...

  18. On physical states in 2d (topological) gravity

    International Nuclear Information System (INIS)

    Bouwknegt, P.; McCarthy, J.; Pilch, K.

    1993-01-01

    We review the BRST computation of physical states in various 2d gravity theories. First we discuss the cohomology relevant for 2d gravity coupled to c ≤ 1 conformal matter. We then use these results to compute the cohomology of a c=26 βγ-system, i.e. restricted 2d topological gravity. We also comment on the cohomology for the complete 2d topological gravity. (author). 39 refs

  19. The Spin-Foam Approach to Quantum Gravity.

    Science.gov (United States)

    Perez, Alejandro

    2013-01-01

    This article reviews the present status of the spin-foam approach to the quantization of gravity. Special attention is payed to the pedagogical presentation of the recently-introduced new models for four-dimensional quantum gravity. The models are motivated by a suitable implementation of the path integral quantization of the Plebanski formulation of gravity on a simplicial regularization. The article also includes a self-contained treatment of 2+1 gravity. The simple nature of the latter provides the basis and a perspective for the analysis of both conceptual and technical issues that remain open in four dimensions.

  20. The Spin-Foam Approach to Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Alejandro Perez

    2013-02-01

    Full Text Available This article reviews the present status of the spin-foam approach to the quantization of gravity. Special attention is payed to the pedagogical presentation of the recently-introduced new models for four-dimensional quantum gravity. The models are motivated by a suitable implementation of the path integral quantization of the Plebanski formulation of gravity on a simplicial regularization. The article also includes a self contained treatment of 2+1 gravity. The simple nature of the latter provides the basis and a perspective for the analysis of both conceptual and technical issues that remain open in four dimensions.

  1. Quantum and gravity. Blend or melange?

    Energy Technology Data Exchange (ETDEWEB)

    Wuethrich, Christian [University of Geneva (Switzerland)

    2016-07-01

    Do we need to quantize gravity, as it is tacitly assumed in much of fundamental physics? The standard lore falls short of justifying an affirmative answer. Black hole thermodynamics is widely considered, faint though it may be, our firmest hint at a quantum theory of gravity - despite the failure to date to observe Hawking radiation or any other effect that would require going beyond a classical description of black holes. Hawking radiation hitherto merely enjoys a theoretical derivation in a semi-classical theory combining quantum matter with classical gravity. But how can a semi-classical melange of physical principles possibly justify that the quantum and gravity are blended into a unified fundamental theory when the latter is generally expected to reject at least some of the principles in the former?.

  2. The wave of the future - Searching for gravity waves

    International Nuclear Information System (INIS)

    Goldsmith, D.

    1991-01-01

    Research on gravity waves conducted by such scientists as Gamov, Wheeler, Weber and Zel'dovich is discussed. Particular attention is given to current trends in the theoretical analysis of gravity waves carried out by theorists Kip Thorne and Leonid Grishchuk. The problems discussed include the search for gravity waves; calculation of the types of gravity waves; the possibility of detecting gravity waves from localized sources, e.g., from the collision of two black holes in a distant galaxy or the collapse of a star, through the Laser Interferometer Gravitational Wave Observatory; and detection primordial gravity waves from the big bang

  3. Allowance for influence of gravity field nonuniformity

    Science.gov (United States)

    Tsysar, A. P.

    1987-03-01

    The constants of a quartz-metal pendulum used in higher-order gravimetric networks have been determined and a formula has been derived for the total correction for gravity field nonuniformity measurements made with the pendulum. Nomograms were constructed on the basis of these formulas and are used in introducing corrections into pendulum measurements. A table was prepared giving the components of the correction for some values of the derivatives of gravity potential from surrounding masses. Errors can be caused by building walls, the pedestal on which the instrument sits and other factors, and these must be taken into account since they increase the normal gravity gradient. After introducing these correction components for the nonuniform gravity field, the gravity field at the measurement point is related to the instrument point coinciding with the middle of the pendulum knife blade.

  4. No chiral truncation of quantum log gravity?

    Science.gov (United States)

    Andrade, Tomás; Marolf, Donald

    2010-03-01

    At the classical level, chiral gravity may be constructed as a consistent truncation of a larger theory called log gravity by requiring that left-moving charges vanish. In turn, log gravity is the limit of topologically massive gravity (TMG) at a special value of the coupling (the chiral point). We study the situation at the level of linearized quantum fields, focussing on a unitary quantization. While the TMG Hilbert space is continuous at the chiral point, the left-moving Virasoro generators become ill-defined and cannot be used to define a chiral truncation. In a sense, the left-moving asymptotic symmetries are spontaneously broken at the chiral point. In contrast, in a non-unitary quantization of TMG, both the Hilbert space and charges are continuous at the chiral point and define a unitary theory of chiral gravity at the linearized level.

  5. Idaho Batholith Study Area Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (32,152 records) were compiled by the U. S. Geological Survey. This data base was received on February 23, 1993. Principal gravity...

  6. Gravity Data for portions of Ohio

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (1,037 records) were compiled by Doctor Stierman. This data base was received in June 1992. Principal gravity parameters include Free-Air...

  7. Reducing gravity takes the bounce out of running.

    Science.gov (United States)

    Polet, Delyle T; Schroeder, Ryan T; Bertram, John E A

    2018-02-13

    In gravity below Earth-normal, a person should be able to take higher leaps in running. We asked 10 subjects to run on a treadmill in five levels of simulated reduced gravity and optically tracked centre-of-mass kinematics. Subjects consistently reduced ballistic height compared with running in normal gravity. We explain this trend by considering the vertical take-off velocity (defined as maximum vertical velocity). Energetically optimal gaits should balance the energetic costs of ground-contact collisions (favouring lower take-off velocity), and step frequency penalties such as leg swing work (favouring higher take-off velocity, but less so in reduced gravity). Measured vertical take-off velocity scaled with the square root of gravitational acceleration, following energetic optimality predictions and explaining why ballistic height decreases in lower gravity. The success of work-based costs in predicting this behaviour challenges the notion that gait adaptation in reduced gravity results from an unloading of the stance phase. Only the relationship between take-off velocity and swing cost changes in reduced gravity; the energetic cost of the down-to-up transition for a given vertical take-off velocity does not change with gravity. Because lower gravity allows an elongated swing phase for a given take-off velocity, the motor control system can relax the vertical momentum change in the stance phase, thus reducing ballistic height, without great energetic penalty to leg swing work. Although it may seem counterintuitive, using less 'bouncy' gaits in reduced gravity is a strategy to reduce energetic costs, to which humans seem extremely sensitive. © 2018. Published by The Company of Biologists Ltd.

  8. Generalized modified gravity in large extra dimensions

    International Nuclear Information System (INIS)

    Aslan, Onder; Demir, Durmus A.

    2006-01-01

    We discuss effective interactions among brane matter induced by modifications of higher-dimensional Einstein gravity through the replacement of Einstein-Hilbert term with a generic function f(R,R AB R AB ,R ABCD R ABCD ) of the curvature tensors. We determine gravi-particle spectrum of the theory, and perform a comparative analysis of its predictions with those of the Einstein gravity within Arkani-Hamed-Dvali-Dimopoulos (ADD) setup. We find that this general higher-curvature quantum gravity theory contributes to scatterings among both massive and massless brane matter (in contrast to much simpler generalization of the Einstein gravity, f(R), which influences only the massive matter), and therefore, can be probed via various scattering processes at present and future colliders and directly confronted with the ADD expectations. In addition to collision processes which proceed with tree-level gravi-particle exchange, effective interactions among brane matter are found to exhibit a strong sensitivity to higher-curvature gravity via the gravi-particle loops. Furthermore, particle collisions with missing energy in their final states are found to be sensitive to additional gravi-particles not found in Einstein gravity. In general, road to a correct description of quantum gravity above Fermi energies depends crucially on if collider and other search methods end up with a negative or positive answer for the presence of higher-curvature gravitational interactions

  9. Gravity- and non-gravity-mediated couplings in multiple-field inflation

    International Nuclear Information System (INIS)

    Bernardeau, Francis

    2010-01-01

    Mechanisms for the generation of primordial non-Gaussian metric fluctuations in the context of multiple-field inflation are reviewed. As long as kinetic terms remain canonical, it appears that nonlinear couplings inducing non-Gaussianities can be split into two types. The extension of the one-field results to multiple degrees of freedom leads to gravity-mediated couplings that are ubiquitous but generally modest. Multiple-field inflation offers however the possibility of generating non-gravity-mediated coupling in isocurvature directions that can eventually induce large non-Gaussianities in the metric fluctuations. The robustness of the predictions of such models is eventually examined in view of a case study derived from a high-energy physics construction.

  10. Matter Loops Corrected Modified Gravity in Palatini Formulation

    International Nuclear Information System (INIS)

    Meng Xinhe; Wang Peng

    2008-01-01

    Recently, corrections to the standard Einstein-Hilbert action were proposed to explain the current cosmic acceleration in stead of introducing dark energy. In the Palatini formulation of those modified gravity models, there is an important observation due to Arkani-Hamed: matter loops will give rise to a correction to the modified gravity action proportional to the Ricci scalar of the metric. In the presence of such a term, we show that the current forms of modified gravity models in Palatini formulation, specifically, the 1/R gravity and ln R gravity, will have phantoms. Then we study the possible instabilities due to the presence of phantom fields. We show that the strong instability in the metric formulation of 1/R gravity indicated by Dolgov and Kawasaki will not appear and the decay timescales for the phantom fields may be long enough for the theories to make sense as effective field theory. On the other hand, if we change the sign of the modification terms to eliminate the phantoms, some other inconsistencies will arise for the various versions of the modified gravity models. Finally, we comment on the universal property of the Palatini formulation of the matter loops corrected modified gravity models and its implications

  11. Two-phase alkali-metal experiments in reduced gravity

    International Nuclear Information System (INIS)

    Antoniak, Z.I.

    1986-06-01

    Future space missions envision the use of large nuclear reactors utilizing either a single or a two-phase alkali-metal working fluid. The design and analysis of such reactors require state-of-the-art computer codes that can properly treat alkali-metal flow and heat transfer in a reduced-gravity environment. A literature search of relevant experiments in reduced gravity is reported on here, and reveals a paucity of data for such correlations. The few ongoing experiments in reduced gravity are noted. General plans are put forth for the reduced-gravity experiments which will have to be performed, at NASA facilities, with benign fluids. A similar situation exists regarding two-phase alkali-metal flow and heat transfer, even in normal gravity. Existing data are conflicting and indequate for the task of modeling a space reactor using a two-phase alkali-metal coolant. The major features of past experiments are described here. Data from the reduced-gravity experiments with innocuous fluids are to be combined with normal gravity data from the two-phase alkali-metal experiments. Analyses undertaken here give every expectation that the correlations developed from this data base will provide a valid representation of alkali-metal heat transfer and pressure drop in reduced gravity

  12. Physical properties of W gravities and W strings

    International Nuclear Information System (INIS)

    Das, S.R.; Dhar, A.; Rama, S.K.

    1991-01-01

    This paper investigates some basic physical properties of W gravities and W strings, using a free field realization. The authors argue that the configuration space of W gravities have global characteristics in addition to the Euler characteristic. The authors identify one such global quantity to be a monopole charge and show how this charge appears in the exponents. The free energy would then involve a θ parameter. Using a BRST procedure the authors find all the physical states of W 3 and W 4 gravities, and show that physical operators are nonsingular composites of the screening charge operators. (The latter are not physical operators for N ≥ 3.) For W strings we show how the W constraints lead to the emergence of a single (and not many) extra dimension coming from the W-gravity sector. By analyzing the resulting dispersion relations the authors find that both the lower and upper critical dimensions are lowered compared to ordinary two-dimensional gravity. The pure W gravity spectrum reveals an intriguing numerological connection with unitary minimal models coupled to ordinary gravity

  13. Lovelock-Brans-Dicke gravity

    Science.gov (United States)

    Wenjie Tian, David; Booth, Ivan

    2016-02-01

    According to Lovelock’s theorem, the Hilbert-Einstein and the Lovelock actions are indistinguishable from their field equations. However, they have different scalar-tensor counterparts, which correspond to the Brans-Dicke and the Lovelock-Brans-Dicke (LBD) gravities, respectively. In this paper the LBD model of alternative gravity with the Lagrangian density {{L}}{LBD}=\\frac{1}{16π }≤ft[φ ≤ft(R+\\frac{a}{\\sqrt{-g}}{}*{RR}+b{ G }\\right)-\\frac{{ω }{{L}}}{φ }{{{\

  14. Gravity studies of the Hanford Reservation, Richland, Washington

    International Nuclear Information System (INIS)

    Richard, B.H.; Lillie, J.T.; Deju, R.A.

    1977-07-01

    Gravity studies over Hanford added to the understanding of the geology of the Pasco Basin. The Bouguer anomaly indicated the basin is the site of the greatest thickness of Columbia River Basalt. The residual gravity anomaly delineated the major anticlinal and synclinal structures under Hanford. Three-dimensional gravity models characterized these buried folds by indicating their shape and relief. Finally, two-dimensional gravity models further delineated the shape of these buried folds and suggested locations where ancestral rivers may have breached the Umtanum anticlinal folds within the basin. Analysis of the three-dimensional model studies indicates that one-fifth of the original data would have delineated the buried structures. Two- or three-body gravity models produced better results than a poly-body model. Gravity was found to be an effective and rapid reconnaissance method of studying buried bedrock structures

  15. General relativity and gauge gravity theories of higher order

    International Nuclear Information System (INIS)

    Konopleva, N.P.

    1998-01-01

    It is a short review of today's gauge gravity theories and their relations with Einstein General Relativity. The conceptions of construction of the gauge gravity theories with higher derivatives are analyzed. GR is regarded as the gauge gravity theory corresponding to the choice of G ∞4 as the local gauge symmetry group and the symmetrical tensor of rank two g μν as the field variable. Using the mathematical technique, single for all fundamental interactions (namely variational formalism for infinite Lie groups), we can obtain Einstein's theory as the gauge theory without any changes. All other gauge approaches lead to non-Einstein theories of gravity. But above-mentioned mathematical technique permits us to construct the gauge gravity theory of higher order (for instance SO (3,1)-gravity) so that all vacuum solutions of Einstein equations are the solutions of the SO (3,1)-gravity theory. The structure of equations of SO(3,1)-gravity becomes analogous to Weeler-Misner geometrodynamics one

  16. Modifications of Einstein's theory of gravity at large distances

    CERN Document Server

    2015-01-01

    In the last few years modified gravity theories have been proposed as extensions of Einstein's theory of gravity. Their main motivation is to explain the latest cosmological and astrophysical data on dark energy and dark matter. The study of general relativity at small scales has already produced important results (cf e.g. LNP 863 Quantum Gravity and Quantum Cosmology) while its study at large scales is challenging because recent and upcoming observational results will provide important information on the validity of these modified theories.   In this volume, various aspects of modified gravity at large scales will be discussed: high-curvature gravity theories; general scalar-tensor theories; Galileon theories and their cosmological applications; F(R) gravity theories; massive, new massive and topologically massive gravity; Chern-Simons modifications of general relativity (including holographic variants) and higher-spin gravity theories, to name but a few of the most important recent developments.   Edite...

  17. Maine Offshore Free-air Anomaly Gravity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (5,363 records) were compiled by the U. S. Geological Survey. This data base was received on February 23, 1993. Principal gravity parameters...

  18. Taub-NUT black holes in third order Lovelock gravity

    International Nuclear Information System (INIS)

    Hendi, S.H.; Dehghani, M.H.

    2008-01-01

    We consider the existence of Taub-NUT solutions in third order Lovelock gravity with cosmological constant, and obtain the general form of these solutions in eight dimensions. We find that, as in the case of Gauss-Bonnet gravity and in contrast with the Taub-NUT solutions of Einstein gravity, the metric function depends on the specific form of the base factors on which one constructs the circle fibration. Thus, one may say that the independence of the NUT solutions on the geometry of the base space is not a robust feature of all generally covariant theories of gravity and is peculiar to Einstein gravity. We find that when Einstein gravity admits non-extremal NUT solutions with no curvature singularity at r=N, then there exists a non-extremal NUT solution in third order Lovelock gravity. In 8-dimensional spacetime, this happens when the metric of the base space is chosen to be CP 3 . Indeed, third order Lovelock gravity does not admit non-extreme NUT solutions with any other base space. This is another property which is peculiar to Einstein gravity. We also find that the third order Lovelock gravity admits extremal NUT solution when the base space is T 2 xT 2 xT 2 or S 2 xT 2 xT 2 . We have extended these observations to two conjectures about the existence of NUT solutions in Lovelock gravity in any even-dimensional spacetime

  19. GEODYNAMIC WAVES AND GRAVITY

    Directory of Open Access Journals (Sweden)

    A. V. Vikulin

    2014-01-01

    Full Text Available  Gravity phenomena related to the Earth movements in the Solar System and through the Galaxy are reviewed. Such movements are manifested by geological processes on the Earth and correlate with geophysical fields of the Earth. It is concluded that geodynamic processes and the gravity phenomena (including those of cosmic nature are related.  The state of the geomedium composed of blocks is determined by stresses with force moment and by slow rotational waves that are considered as a new type of movements [Vikulin, 2008, 2010]. It is shown that the geomedium has typical rheid properties [Carey, 1954], specifically an ability to flow while being in the solid state [Leonov, 2008]. Within the framework of the rotational model with a symmetric stress tensor, which is developed by the authors [Vikulin, Ivanchin, 1998; Vikulin et al., 2012a, 2013], such movement of the geomedium may explain the energy-saturated state of the geomedium and a possibility of its movements in the form of vortex geological structures [Lee, 1928]. The article discusses the gravity wave detection method based on the concept of interactions between gravity waves and crustal blocks [Braginsky et al., 1985]. It is concluded that gravity waves can be recorded by the proposed technique that detects slow rotational waves. It is shown that geo-gravitational movements can be described by both the concept of potential with account of gravitational energy of bodies [Kondratyev, 2003] and the nonlinear physical acoustics [Gurbatov et al., 2008]. Based on the combined description of geophysical and gravitational wave movements, the authors suggest a hypothesis about the nature of spin, i.e. own moment as a demonstration of the space-time ‘vortex’ properties.  

  20. Workshop on Topics in Three Dimensional Gravity

    CERN Document Server

    2016-01-01

    Gravity in three dimensions has rather special features which makes it particularly suitable for addressing questions related to the quantization of gravity and puzzles concerning black hole physics. AdS3 gravity and in particular AdS3/CFT2 has played a crucial role in black hole microstate counting, and more recently in studying holographic entanglement entropy and higher spin theories.

  1. Loop Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Rovelli Carlo

    2008-07-01

    Full Text Available The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler’s “spacetime foam” intuition. (iii Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv A derivation of the Bekenstein–Hawking black-hole entropy. (v Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  2. Studies in gravity and supergravity

    International Nuclear Information System (INIS)

    Castellani, L.

    1981-01-01

    The canonical treatment for theories with local gauge invariances is reviewed and an algorithm for the construction of all the gauge generators is found. This algorithm is then applied to Yang-Mills theories and to (metric) gravity. The first part of the work is concluded with a complete treatment of hamiltonian first order tetrad gravity. In the second part, the geometrical aspects of (super)gravity theories are concentrated on. After an interlude with path integrals in curved space (equivalence is shown with canonical quantization), N = 2 supergravity in superspace, and conformal supergravity in the group manifold scenario are studied. A progress report is added, regarding a study on higher divergences in quantum field theory

  3. Airborne Gravity: NGS' Gravity Data for EN09 (2016)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Massachusetts, Connecticut, Rhode Island, New Hampshire, New York, and the Atlantic Ocean collected in 2012 over 1 survey. This data set is...

  4. SEG US Bouguer Gravity Anomaly Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The SEG gravity data are the product of the ad hoc Gravity Anomaly Map (GAM) Committee, sponsored by the Society of Exploration Geophysicists (SEG) and the U.S....

  5. Kerr geometry in f(T) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bejarano, Cecilia; Guzman, Maria Jose [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Ferraro, Rafael [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)

    2015-02-01

    Null tetrads are shown to be a valuable tool in teleparallel theories of modified gravity. We use them to prove that Kerr geometry remains a solution for a wide family of f(T) theories of gravity. (orig.)

  6. Kerr geometry in f(T) gravity

    International Nuclear Information System (INIS)

    Bejarano, Cecilia; Guzman, Maria Jose; Ferraro, Rafael

    2015-01-01

    Null tetrads are shown to be a valuable tool in teleparallel theories of modified gravity. We use them to prove that Kerr geometry remains a solution for a wide family of f(T) theories of gravity. (orig.)

  7. Measuring wood specific gravity, correctly

    Science.gov (United States)

    G. Bruce Williamson; Michael C. Wiemann

    2010-01-01

    The specific gravity (SG) of wood is a measure of the amount of structural material a tree species allocates to support and strength. In recent years, wood specific gravity, traditionally a forester’s variable, has become the domain of ecologists exploring the universality of plant functional traits and conservationists estimating global carbon stocks. While these...

  8. f(T) teleparallel gravity and cosmology.

    Science.gov (United States)

    Cai, Yi-Fu; Capozziello, Salvatore; De Laurentis, Mariafelicia; Saridakis, Emmanuel N

    2016-10-01

    Over recent decades, the role of torsion in gravity has been extensively investigated along the main direction of bringing gravity closer to its gauge formulation and incorporating spin in a geometric description. Here we review various torsional constructions, from teleparallel, to Einstein-Cartan, and metric-affine gauge theories, resulting in extending torsional gravity in the paradigm of f (T) gravity, where f (T) is an arbitrary function of the torsion scalar. Based on this theory, we further review the corresponding cosmological and astrophysical applications. In particular, we study cosmological solutions arising from f (T) gravity, both at the background and perturbation levels, in different eras along the cosmic expansion. The f (T) gravity construction can provide a theoretical interpretation of the late-time universe acceleration, alternative to a cosmological constant, and it can easily accommodate with the regular thermal expanding history including the radiation and cold dark matter dominated phases. Furthermore, if one traces back to very early times, for a certain class of f (T) models, a sufficiently long period of inflation can be achieved and hence can be investigated by cosmic microwave background observations-or, alternatively, the Big Bang singularity can be avoided at even earlier moments due to the appearance of non-singular bounces. Various observational constraints, especially the bounds coming from the large-scale structure data in the case of f (T) cosmology, as well as the behavior of gravitational waves, are described in detail. Moreover, the spherically symmetric and black hole solutions of the theory are reviewed. Additionally, we discuss various extensions of the f (T) paradigm. Finally, we consider the relation with other modified gravitational theories, such as those based on curvature, like f (R) gravity, trying to illuminate the subject of which formulation, or combination of formulations, might be more suitable

  9. Antinociceptive activity of Astragalus gummifer gum (gum tragacanth) through the adrenergic system: A in vivo study in mice.

    Science.gov (United States)

    Bagheri, Seyyed Majid; Keyhani, Leila; Heydari, Mehrangiz; Dashti-R, Mohammad Hossein

    2015-01-01

    In Iranian traditional medicine, gum obtained from Astragalus gummifer and some other species of Astragalus was used as analgesic agent. In this study, we investigated the antinociceptive effect of several concentrations (125, 250, and 500 μg/kg body weight) of Astragalus gummifer gum (AGG) on thermal and acetic acid induced pain in mice. AGG was dissolved in distillated water and injected i.p to male mice 15 minute before the onset of experiment. Writhing and hot-plate tests were applied to study the analgesic effect of AGG and compared with that of diclofenac sodium (30 mg/kg, i.p.) or morphine (8 mg/kg, i.p). To investigate the mechanisms involved in antinociception, yohimbine, naloxone, glibenclamide, and theophylline were used in writhing test. These drugs were injected intraperitoneally 15 min before the administration of AGG. The number of writhes were counted in 30 minutes and analyzed. AGG exhibited a significant antinociceptive effect and the most effective dose of AGG was 500 μg/kg. The most maximum possible effect (%MPE) was observed (117.4%) 15 min after drug administration. The %inhibition of acetic acid-induced writhing in AGG 125, 250 and 500 was 47%, 50% and 54% vs %15 of control and 66.3% of diclofenac sodium group. The antinociceptive effect induced by this gum in the writhing test was reversed by the systemic administration of yohimbine (α2-adrenergic antagonist), but naloxone, glibenclamide, and theophylline did not reverse this effect. The findings of this study indicated that AGG induced its antinociceptive through the adrenergic system.

  10. Airborne Gravity: NGS' Gravity Data for EN10 (2013)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Pennsylvania, New Jersey, Connecticut and the Atlantic Ocean collected in 2013 over 1 survey. This data set is part of the...

  11. Nevada Isostatic Residual Gravity Over Basement

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This study of gravity data from Nevada is part of a statewide analysis of mineral resources. The main objective of the gravity study were: 1) to infer the structure...

  12. Quantum gravity

    International Nuclear Information System (INIS)

    Isham, C.

    1989-01-01

    Gravitational effects are seen as arising from a curvature in spacetime. This must be reconciled with gravity's apparently passive role in quantum theory to achieve a satisfactory quantum theory of gravity. The development of grand unified theories has spurred the search, with forces being of equal strength at a unification energy of 10 15 - 10 18 GeV, with the ''Plank length'', Lp ≅ 10 -35 m. Fundamental principles of general relativity and quantum mechanics are outlined. Gravitons are shown to have spin-0, as mediators of gravitation force in the classical sense or spin-2 which are related to the quantisation of general relativity. Applying the ideas of supersymmetry to gravitation implies partners for the graviton, especially the massless spin 3/2 fermion called a gravitino. The concept of supersymmetric strings is introduced and discussed. (U.K.)

  13. Flattening the inflaton potential beyond minimal gravity

    Directory of Open Access Journals (Sweden)

    Lee Hyun Min

    2018-01-01

    Full Text Available We review the status of the Starobinsky-like models for inflation beyond minimal gravity and discuss the unitarity problem due to the presence of a large non-minimal gravity coupling. We show that the induced gravity models allow for a self-consistent description of inflation and discuss the implications of the inflaton couplings to the Higgs field in the Standard Model.

  14. Stochastic quantum gravity-(2+1)-dimensional case

    International Nuclear Information System (INIS)

    Hosoya, Akio

    1991-01-01

    At first the amazing coincidences are pointed out in quantum field theory in curved space-time and quantum gravity, when they exhibit stochasticity. To explore the origin of them, the (2+1)-dimensional quantum gravity is considered as a toy model. It is shown that the torus universe in the (2+1)-dimensional quantum gravity is a quantum chaos in a rigorous sense. (author). 15 refs

  15. Integrating stations from the North America Gravity Database into a local GPS-based land gravity survey

    Science.gov (United States)

    Shoberg, Thomas G.; Stoddard, Paul R.

    2013-01-01

    The ability to augment local gravity surveys with additional gravity stations from easily accessible national databases can greatly increase the areal coverage and spatial resolution of a survey. It is, however, necessary to integrate such data seamlessly with the local survey. One challenge to overcome in integrating data from national databases is that these data are typically of unknown quality. This study presents a procedure for the evaluation and seamless integration of gravity data of unknown quality from a national database with data from a local Global Positioning System (GPS)-based survey. The starting components include the latitude, longitude, elevation and observed gravity at each station location. Interpolated surfaces of the complete Bouguer anomaly are used as a means of quality control and comparison. The result is an integrated dataset of varying quality with many stations having GPS accuracy and other reliable stations of unknown origin, yielding a wider coverage and greater spatial resolution than either survey alone.

  16. 40 CFR 1065.630 - 1980 international gravity formula.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false 1980 international gravity formula. 1065.630 Section 1065.630 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... international gravity formula. The acceleration of Earth's gravity, a g, varies depending on your location...

  17. The quantization of gravity

    CERN Document Server

    Gerhardt, Claus

    2018-01-01

    A unified quantum theory incorporating the four fundamental forces of nature is one of the major open problems in physics. The Standard Model combines electro-magnetism, the strong force and the weak force, but ignores gravity. The quantization of gravity is therefore a necessary first step to achieve a unified quantum theory. In this monograph a canonical quantization of gravity has been achieved by quantizing a geometric evolution equation resulting in a gravitational wave equation in a globally hyperbolic spacetime. Applying the technique of separation of variables we obtain eigenvalue problems for temporal and spatial self-adjoint operators where the temporal operator has a pure point spectrum with eigenvalues $\\lambda_i$ and related eigenfunctions, while, for the spatial operator, it is possible to find corresponding eigendistributions for each of the eigenvalues $\\lambda_i$, if the Cauchy hypersurface is asymptotically Euclidean or if the quantized spacetime is a black hole with a negative cosmological ...

  18. Topics in quantum gravity

    International Nuclear Information System (INIS)

    Lamon, Raphael

    2010-01-01

    Quantum gravity is an attempt to unify general relativity with quantum mechanics which are the two highly successful fundamental theories of theoretical physics. The main difficulty in this unification arises from the fact that, while general relativity describes gravity as a macroscopic geometrical theory, quantum mechanics explains microscopic phenomena. As a further complication, not only do both theories describe different scales but also their philosophical ramifications and the mathematics used to describe them differ in a dramatic way. Consequently, one possible starting point of an attempt at a unification is quantum mechanics, i.e. particle physics, and try to incorporate gravitation. This pathway has been chosen by particle physicists which led to string theory. On the other hand, loop quantum gravity (LQG) chooses the other possibility, i.e. it takes the geometrical aspects of gravity seriously and quantizes geometry. The first part of this thesis deals with a generalization of loop quantum cosmology (LQC) to toroidal topologies. LQC is a quantization of homogenous solutions of Einstein's field equations using tools from LQG. First the general concepts of closed topologies is introduced with special emphasis on Thurston's theorem and its consequences. It is shown that new degrees of freedom called Teichmueller parameters come into play and their dynamics can be described by a Hamiltonian. Several numerical solutions for a toroidal universe are presented and discussed. Following the guidelines of LQG this dynamics are rewritten using the Ashtekar variables and numerical solutions are shown. However, in order to find a suitable Hilbert space a canonical transformation must be performed. On the other hand this transformation makes the quantization of geometrical quantities less tractable such that two different ways are presented. It is shown that in both cases the spectrum of such geometrical operators depends on the initial value problem. Furthermore, we

  19. Experimental tests of relativistic gravity

    International Nuclear Information System (INIS)

    Damour, Thibault

    2000-01-01

    The confrontation between Einstein's gravitation theory and experimental results, notably binary pulsar data, is summarized and its significance discussed. Experiment and theory agree at the 10 -3 level or better. All the basic structures of Einstein's theory (coupling of gravity matter; propagation and self-interaction of the gravitational field, including in strong field conditions) have been verified. However, the theoretical possibility that scalar couplings be naturally driven toward zero by the cosmological expansion suggests that the present agreement between Einstein's theory and experiment might be compatible with the existence of a long-range scalar contribution to gravity (such as the dilation field, or a moduli field, of string theory). This provides a new theoretical paradigm, and new motivations for improving the experimental tests of gravity

  20. Gravity with Intermediate Goods Trade

    Directory of Open Access Journals (Sweden)

    Sujin Jang

    2017-12-01

    Full Text Available This paper derives the gravity equation with intermediate goods trade. We extend a standard monopolistic competition model to incorporate intermediate goods trade, and show that the gravity equation with intermediates trade is identical to the one without it except in that gross output should be used as the output measure instead of value added. We also show that the output elasticity of trade is significantly underestimated when value added is used as the output measure. This implies that with the conventional gravity equation, the contribution of output growth can be substantially underestimated and the role of trade costs reduction can be exaggerated in explaining trade expansion, as we demonstrate for the case of Korea's trade growth between 1995 and 2007.

  1. New classes of modified teleparallel gravity models

    Science.gov (United States)

    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.

  2. Nucleate pool boiling: High gravity to reduced gravity; liquid metals to cryogens

    Science.gov (United States)

    Merte, Herman, Jr.

    1988-01-01

    Requirements for the proper functioning of equipment and personnel in reduced gravity associated with space platforms and future space station modules introduce unique problems in temperature control; power generation; energy dissipation; the storage, transfer, control and conditioning of fluids; and liquid-vapor separation. The phase change of boiling is significant in all of these. Although both pool and flow boiling would be involved, research results to date include only pool boiling because buoyancy effects are maximized for this case. The effective application of forced convection boiling heat transfer in the microgravity of space will require a well grounded and cogent understanding of the mechanisms involved. Experimental results are presented for pool boiling from a single geometrical configuration, a flat surface, covering a wide range of body forces from a/g = 20 to 1 to a/g = 0 to -1 for a cryogenic liquid, and from a/g = 20 to 1 for water and a liquid metal. Similarities in behavior are noted for these three fluids at the higher gravity levels, and may reasonably be expected to continue at reduced gravity levels.

  3. Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation.

    Science.gov (United States)

    Yakushin, Sergei B

    2012-06-01

    The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.

  4. The generalized second law of thermodynamics in generalized gravity theories

    International Nuclear Information System (INIS)

    Wu Shaofeng; Yang Guohong; Wang Bin; Zhang Pengming

    2008-01-01

    We investigate the generalized second law of thermodynamics (GSL) in generalized theories of gravity. We examine the total entropy evolution with time including the horizon entropy, the non-equilibrium entropy production, and the entropy of all matter, field and energy components. We derive a universal condition to protect the generalized second law and study its validity in different gravity theories. In Einstein gravity (even in the phantom-dominated universe with a Schwarzschild black hole), Lovelock gravity and braneworld gravity, we show that the condition to keep the GSL can always be satisfied. In f(R) gravity and scalar-tensor gravity, the condition to protect the GSL can also hold because the temperature should be positive, gravity is always attractive and the effective Newton constant should be an approximate constant satisfying the experimental bounds

  5. Gravity on a little warped space

    International Nuclear Information System (INIS)

    George, Damien P.; McDonald, Kristian L.

    2011-01-01

    We investigate the consistent inclusion of 4D Einstein gravity on a truncated slice of AdS 5 whose bulk-gravity and UV scales are much less than the 4D Planck scale, M * Pl . Such 'Little Warped Spaces' have found phenomenological utility and can be motivated by string realizations of the Randall-Sundrum framework. Using the interval approach to brane-world gravity, we show that the inclusion of a large UV-localized Einstein-Hilbert term allows one to consistently incorporate 4D Einstein gravity into the low-energy theory. We detail the spectrum of Kaluza-Klein metric fluctuations and, in particular, examine the coupling of the little radion to matter. Furthermore, we show that Goldberger-Wise stabilization can be successfully implemented on such spaces. Our results demonstrate that realistic low-energy effective theories can be constructed on these spaces, and have relevance for existing models in the literature.

  6. High energy scattering in gravity and supergravity

    DEFF Research Database (Denmark)

    B. Giddings, Steven; Schmidt-Sommerfeld, Maximilian; Andersen, Jeppe Rosenkrantz

    2010-01-01

    We investigate features of perturbative gravity and supergravity by studying scattering in the ultraplanckian limit, and sharpen arguments that the dynamics is governed by long-distance physics. A simple example capturing aspects of the eikonal resummation suggests why short distance phenomena...... and in particular divergences or nonrenormalizability do not necessarily play a central role in this regime. A more profound problem is apparently unitarity. These considerations can be illustrated by showing that known gravity and supergravity amplitudes have the same long-distance behavior, despite the extra...... a physical scattering process, and ultraplanckian scattering exhibiting Regge behavior. These arguments sharpen the need to find a nonperturbative completion of gravity with mechanisms which restore unitarity in the strong gravity regime....

  7. Topics in Theories of Quantum Gravity

    International Nuclear Information System (INIS)

    Perelstein, M.

    2005-01-01

    In this thesis, the author addresses several issues involving gravity. The first half of the thesis is devoted to studying quantum properties of Einstein gravity and its supersymmetric extensions in the perturbative regime. String theory suggests that perturbative scattering amplitudes in the theories of gravity are related to the amplitudes in gauge theories. This connection has been studied at classical (tree) level by Kawai, Lewellen and Tye. Here, they will explore the relationship between gravity and gauge theory at quantum (loop) level. This relationship, together with the cut-based approach to computing loop amplitudes, allow us to obtain new non-trivial results for quantum gravity. IN particular, they present two infinite sequences of one-loop n-graviton scattering amplitudes: the maximally helicity violating amplitudes in N = 8 supergravity, and the ''all-plus'' helicity amplitudes in Einstein gravity with any minimally coupled massless matter content. The results for n (le) 6 will be obtained by an explicit calculation, while those for n > 6 is inferred from the soft and collinear properties of the amplitudes. They also present an explicit expression for the two-loop contribution to the four-particle scattering amplitude in N = 8 supergravity, and observe a simple relation between this result and its counterpart in N = 4 super-Yang-Mills theory. Furthermore, the simple structure of the two-particle unitarity cuts in these theories suggests that similar relations exist to all loop orders. If this is the case, the first ultraviolet divergence in N = 8 supergravity should appear at five loops, contrary to the earlier expectation of a three-loop counterterm

  8. Evolution of curvature perturbation in generalized gravity theories

    International Nuclear Information System (INIS)

    Matsuda, Tomohiro

    2009-01-01

    Using the cosmological perturbation theory in terms of the δN formalism, we find the simple formulation of the evolution of the curvature perturbation in generalized gravity theories. Compared with the standard gravity theory, a crucial difference appears in the end-boundary of the inflationary stage, which is due to the non-ideal form of the energy-momentum tensor that depends explicitly on the curvature scalar. Recent study shows that ultraviolet-complete quantum theory of gravity (Horava-Lifshitz gravity) can be approximated by using a generalized gravity action. Our paper may give an important step in understanding the evolution of the curvature perturbation during inflation, where the energy-momentum tensor may not be given by the ideal form due to the corrections from the fundamental theory.

  9. Airborne Gravity: NGS' Gravity Data for MS02 (2016)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data over southern Arizona and New Mexico overlapping into Mexico collected in 2016 over 2 surveys, AZ16-1 and AZ16-2. This data set is part of the...

  10. Gauge/gravity duality. A road towards reality

    International Nuclear Information System (INIS)

    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

  11. Gauge/gravity duality. A road towards reality

    Energy Technology Data Exchange (ETDEWEB)

    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

  12. Holographic Lovelock gravities and black holes

    NARCIS (Netherlands)

    de Boer, J.; Kulaxizi, M.; Parnachev, A.

    2010-01-01

    We study holographic implications of Lovelock gravities in AdS spacetimes. For a generic Lovelock gravity in arbitrary spacetime dimensions we formulate the existence condition of asymptotically AdS black holes. We consider small fluctuations around these black holes and determine the constraint on

  13. Hunting Sea Mines with UUV-Based Magnetic and Electro-Optic Sensors

    Science.gov (United States)

    2010-06-01

    assembly of four 3-axis fluxgate magnetometers and (c) magnetometer package for underwater deployment in flooded body section. data are automatically...features the Real-time Tracking Gradiometer (RTG), which is a multi-channel tensor gradiometer using conventional fluxgate technology. Also in this...integrated together into a Bluefin12 AUV [5]. A. RTG Sensor Technology The RTG is a multi-channel tensor gradiometer using conventional fluxgate

  14. Thermodynamics and phases in quantum gravity

    International Nuclear Information System (INIS)

    Husain, Viqar; Mann, R B

    2009-01-01

    We give an approach for studying quantum gravity effects on black hole thermodynamics. This combines a quantum framework for gravitational collapse with quasi-local definitions of energy and surface gravity. Our arguments suggest that (i) the specific heat of a black hole becomes positive after a phase transition near the Planck scale,(ii) its entropy acquires a logarithmic correction and (iii) the mass loss rate is modified such that Hawking radiation stops near the Planck scale. These results are due essentially to a realization of fundamental discreteness in quantum gravity, and are in this sense potentially theory independent.

  15. Induced gravity and gauge interactions revisited

    International Nuclear Information System (INIS)

    Broda, Boguslaw; Szanecki, Michal

    2009-01-01

    It has been shown that the primary, old-fashioned idea of Sakharov's induced gravity and gauge interactions, in the 'one-loop dominance' version, works astonishingly well yielding phenomenologically reasonable results. As a byproduct, the issue of the role of the UV cutoff in the context of the induced gravity has been reexamined (an idea of self-cutoff induced gravity). As an additional check, the black hole entropy has been used in the place of the action. Finally, it has been explicitly shown that the induced coupling constants of gauge interactions of the standard model assume qualitatively realistic values.

  16. Vertebrate gravity sensors as dynamic systems

    Science.gov (United States)

    Ross, M. D.

    1985-01-01

    This paper considers verterbrate gravity receptors as dynamic sensors. That is, it is hypothesized that gravity is a constant force to which an acceleration-sensing system would readily adapt. Premises are considered in light of the presence of kinocilia on hair cells of vertebrate gravity sensors; differences in loading of the sensors among species; and of possible reduction in loading by inclusion of much organic material in otoconia. Moreover, organic-inorganic interfaces may confer a piezoelectric property upon otoconia, which increase the sensitivity of the sensory system to small accelerations. Comparisons with man-made accelerometers are briefly taken up.

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

    NARCIS (Netherlands)

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

    2005-01-01

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

  18. 14 CFR 25.27 - Center of gravity limits.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Center of gravity limits. 25.27 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.27 Center of gravity limits. The extreme forward and the extreme aft center of gravity limitations must be established for each practicably...

  19. 46 CFR 45.157 - Scuppers and gravity drains.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Scuppers and gravity drains. 45.157 Section 45.157 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Conditions of Assignment § 45.157 Scuppers and gravity drains. Scuppers and gravity deck drains from spaces...

  20. Absolute gravity measurements in California

    Science.gov (United States)

    Zumberge, M. A.; Sasagawa, G.; Kappus, M.

    1986-08-01

    An absolute gravity meter that determines the local gravitational acceleration by timing a freely falling mass with a laser interferometer has been constructed. The instrument has made measurements at 11 sites in California, four in Nevada, and one in France. The uncertainty in the results is typically 10 microgal. Repeated measurements have been made at several of the sites; only one shows a substantial change in gravity.

  1. Gravity as a thermodynamic phenomenon

    OpenAIRE

    Moustos, Dimitris

    2017-01-01

    The analogy between the laws of black hole mechanics and the laws of thermodynamics led Bekenstein and Hawking to argue that black holes should be considered as real thermodynamic systems that are characterised by entropy and temperature. Black hole thermodynamics indicates a deeper connection between thermodynamics and gravity. We review and examine in detail the arguments that suggest an interpretation of gravity itself as a thermodynamic theory.

  2. Principal facts of gravity stations with gravity and magnetic profiles from the southwest Nevada Test Site, Nye County, Nevada, as of January 1982

    International Nuclear Information System (INIS)

    Jansma, P.E.; Snyder, D.B.; Ponce, D.A.

    1983-01-01

    Three gravity profiles and principal facts of 2604 gravity stations in the southwest quadrant of the Nevada Test Site are documented in this data report. The residual gravity profiles show the gravity measurements and the smoothed curves derived from these points that were used in geophysical interpretations. The principal facts include station label, latitude, longitude, elevation, observed gravity value, and terrain correction for each station as well as the derived complete Bouguer and isostatic anomalies, reduced at 2.67 g/cm 3 . Accuracy codes, where available, further document the data

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

    Science.gov (United States)

    Martinec, Zdeněk; Fullea, Javier

    2015-03-01

    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

  4. Exploring plane-symmetric solutions in f(R) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Shamir, M. F., E-mail: farasat.shamir@nu.edu.pk [National University of Computer and Emerging Sciences, Department of Sciences and Humanities (Pakistan)

    2016-02-15

    The modified theories of gravity, especially the f(R) gravity, have attracted much attention in the last decade. This paper is devoted to exploring plane-symmetric solutions in the context of metric f(R) gravity. We extend the work on static plane-symmetric vacuum solutions in f(R) gravity already available in the literature [1, 2]. The modified field equations are solved using the assumptions of both constant and nonconstant scalar curvature. Some well-known solutions are recovered with power-law and logarithmic forms of f(R) models.

  5. Review of lattice supersymmetry and gauge-gravity duality

    International Nuclear Information System (INIS)

    Joseph, Anosh

    2015-12-01

    We review the status of recent investigations on validating the gauge-gravity duality conjecture through numerical simulations of strongly coupled maximally supersymmetric thermal gauge theories. In the simplest setting, the gauge-gravity duality connects systems of D0-branes and black hole geometries at finite temperature to maximally supersymmetric gauged quantum mechanics at the same temperature. Recent simulations show that non-perturbative gauge theory results give excellent agreement with the quantum gravity predictions, thus proving strong evidence for the validity of the duality conjecture and more insight into quantum black holes and gravity.

  6. Emergence in holographic scenarios for gravity

    NARCIS (Netherlands)

    Dieks, D.; van Dongen, J.; de Haro, S.

    2015-01-01

    ‘Holographic’ relations between theories have become an important theme in quantum gravity research. These relations entail that a theory without gravity is equivalent to a gravitational theory with an extra spatial dimension. The idea of holography was first proposed in 1993 by Gerard ׳t Hooft on

  7. Holographic entanglement entropy in Lovelock gravities

    NARCIS (Netherlands)

    de Boer, J.; Kulaxizi, M.; Parnachev, A.

    2011-01-01

    We study entanglement entropies of simply connected surfaces in field theories dual to Lovelock gravities. We consider Gauss-Bonnet and cubic Lovelock gravities in detail. In the conformal case the logarithmic terms in the entanglement entropy are governed by the conformal anomalies of the CFT; we

  8. Antinociceptive activity of Astragalus gummifer gum (gum tragacanth through the adrenergic system: A in vivo study in mice

    Directory of Open Access Journals (Sweden)

    Seyyed Majid Bagheri

    2015-01-01

    Full Text Available Background: In Iranian traditional medicine, gum obtained from Astragalus gummifer and some other species of Astragalus was used as analgesic agent. Objective: In this study, we investigated the antinociceptive effect of several concentrations (125, 250, and 500 μg/kg body weight of Astragalus gummifer gum (AGG on thermal and acetic acid induced pain in mice. Materials and Methods: AGG was dissolved in distillated water and injected i.p to male mice 15 minute before the onset of experiment. Writhing and hot-plate tests were applied to study the analgesic effect of AGG and compared with that of diclofenac sodium (30 mg/kg, i.p. or morphine (8 mg/kg, i.p. To investigate the mechanisms involved in antinociception, yohimbine, naloxone, glibenclamide, and theophylline were used in writhing test. These drugs were injected intraperitoneally 15 min before the administration of AGG. The number of writhes were counted in 30 minutes and analyzed. Results: AGG exhibited a significant antinociceptive effect and the most effective dose of AGG was 500 μg/kg. The most maximum possible effect (%MPE was observed (117.4% 15 min after drug administration. The %inhibition of acetic acid-induced writhing in AGG 125, 250 and 500 was 47%, 50% and 54% vs %15 of control and 66.3% of diclofenac sodium group. The antinociceptive effect induced by this gum in the writhing test was reversed by the systemic administration of yohimbine (α2 -adrenergic antagonist, but naloxone, glibenclamide, and theophylline did not reverse this effect. Conclusions: The findings of this study indicated that AGG induced its antinociceptive through the adrenergic system.

  9. Cosmology and modifications of gravity at large distances

    International Nuclear Information System (INIS)

    Ziour, R.

    2010-01-01

    In the framework of General Relativity, the observed current acceleration of the expansion of the Universe requires the presence of a Dark Energy component, whose nature is not well understood. In order to explain the acceleration of the Universe without introducing such a tantalizing source of energy, other gravitation theories have been designed. This thesis is devoted to the study of some of these modified gravity theories, as well as to the observation methods that could constrain them. The first part of this thesis presents a review of modified gravity theories and their motivations. The second part is devoted to the study of the massive gravity theories and of the so-called Vainshtein's mechanism, which allows some of the solutions of Massive Gravity to strongly differ from General Relativity at cosmological scales while satisfying the experimental constraints inside the solar system. For the first time, the validity of the Vainshtein's mechanism is demonstrated, through the study of specific spherically symmetric solutions. The third part deals with scalar modification of gravity; a new model of this sort is presented, inspired by the Vainshtein's mechanism in Massive Gravity. Finally, the fourth part discusses local, astrophysical and cosmological observations that might constrain modified gravity theories. (author)

  10. Density and Specific Gravity Metrics in Biomass Research

    Science.gov (United States)

    Micheal C. Wiemann; G. Bruce Williamson

    2012-01-01

    Following the 2010 publication of Measuring Wood Specific Gravity… Correctly in the American Journal of Botany, readers contacted us to inquire about application of wood density and specific gravity to biomass research. Here we recommend methods for sample collection, volume measurement, and determination of wood density and specific gravity for...

  11. From Discrete Gravity Survey Data to a High-resolution Gravity Field Representation in the Nordic-Baltic Region

    DEFF Research Database (Denmark)

    Märdla, Silja; Ågren, Jonas; Strykowski, Gabriel

    2017-01-01

    The deduction of a regularly spaced gravity anomaly grid from scattered survey data is studied, addressing mainly two aspects: reduction of gravity to anomalies and subsequent interpolation by various methods. The problem is illustrated in a heterogeneous study area and contrasting test areas inc...

  12. Soft collinear effective theory for gravity

    Science.gov (United States)

    Okui, Takemichi; Yunesi, Arash

    2018-03-01

    We present how to construct a soft collinear effective theory (SCET) for gravity at the leading and next-to-leading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the next-to-leading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations. The effective Lagrangian is highly constrained by effectively multiple copies of diffeomorphism invariance that are inevitably present in gravity SCET due to mode separation, an essential ingredient of any SCET. Further explorations of effective theories of gravity with mode separation may shed light on Lagrangian-level understandings of some of the surprising properties of gravitational scattering amplitudes. A gravity SCET with an appropriate inclusion of Glauber modes may serve as a powerful tool for studying gravitational scattering in the Regge limit.

  13. Black holes in loop quantum gravity.

    Science.gov (United States)

    Perez, Alejandro

    2017-12-01

    This is a review of results on black hole physics in the context of loop quantum gravity. The key feature underlying these results is the discreteness of geometric quantities at the Planck scale predicted by this approach to quantum gravity. Quantum discreteness follows directly from the canonical quantization prescription when applied to the action of general relativity that is suitable for the coupling of gravity with gauge fields, and especially with fermions. Planckian discreteness and causal considerations provide the basic structure for the understanding of the thermal properties of black holes close to equilibrium. Discreteness also provides a fresh new look at more (at the moment) speculative issues, such as those concerning the fate of information in black hole evaporation. The hypothesis of discreteness leads, also, to interesting phenomenology with possible observational consequences. The theory of loop quantum gravity is a developing program; this review reports its achievements and open questions in a pedagogical manner, with an emphasis on quantum aspects of black hole physics.

  14. Black holes, strings and quantum gravity

    International Nuclear Information System (INIS)

    Maldacena, Juan

    2001-01-01

    Most physical phenomena can be explained by 'Quantum Mechanics' and 'Einstein Theory of Gravity'. Quantum mechanics is needed for descriptions involving small objects (atoms, nuclei, molecules, etc.) whereas gravity is required for understanding big objects (planets, galaxies). Since, usually small objects are light while big ones are heavy, when one theory is called for, the other is not relevant. Interestingly enough, if we pretend to use both theories simultaneously, for instance when small and very heavy objects are considered (as those in the beginning of our universe), we find that they are mutually inconsistent. Thus, a new theory, so called 'Quantum Gravity', is needed. This works comments on above inconsistencies and indicates how the string theory, rather than a pointlike particle theory, could provide us with a quantum theory of gravity. Though a discussion of black holes it shows us how a string theory on certain space, ca be equivalently described by a particle theory on its boundary, like a sort of hologram. (author)

  15. Magnetic branes in Gauss-Bonnet gravity with nonlinear electrodynamics: correction of magnetic branes in Einstein-Maxwell gravity

    Energy Technology Data Exchange (ETDEWEB)

    Hendi, Seyed Hossein [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Panahiyan, Shahram; Panah, Behzad Eslam [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of)

    2015-06-15

    In this paper, we consider two first order corrections to both the gravity and the gauge sides of the Einstein-Maxwell gravity: Gauss-Bonnet gravity and quadratic Maxwell invariant as corrections. We obtain horizonless magnetic solutions by implying a metric representing a topological defect. We analyze the geometric properties of the solutions and investigate the effects of both corrections, and find that these solutions may be interpreted as magnetic branes. We study the singularity condition and find a nonsingular spacetime with a conical geometry. We also investigate the effects of different parameters on the deficit angle of spacetime near the origin. (orig.)

  16. Magnetic branes in Gauss-Bonnet gravity with nonlinear electrodynamics: correction of magnetic branes in Einstein-Maxwell gravity

    International Nuclear Information System (INIS)

    Hendi, Seyed Hossein; Panahiyan, Shahram; Panah, Behzad Eslam

    2015-01-01

    In this paper, we consider two first order corrections to both the gravity and the gauge sides of the Einstein-Maxwell gravity: Gauss-Bonnet gravity and quadratic Maxwell invariant as corrections. We obtain horizonless magnetic solutions by implying a metric representing a topological defect. We analyze the geometric properties of the solutions and investigate the effects of both corrections, and find that these solutions may be interpreted as magnetic branes. We study the singularity condition and find a nonsingular spacetime with a conical geometry. We also investigate the effects of different parameters on the deficit angle of spacetime near the origin. (orig.)

  17. Fundamental Structure of Loop Quantum Gravity

    Science.gov (United States)

    Han, Muxin; Ma, Yongge; Huang, Weiming

    In the recent twenty years, loop quantum gravity, a background independent approach to unify general relativity and quantum mechanics, has been widely investigated. The aim of loop quantum gravity is to construct a mathematically rigorous, background independent, non-perturbative quantum theory for a Lorentzian gravitational field on a four-dimensional manifold. In the approach, the principles of quantum mechanics are combined with those of general relativity naturally. Such a combination provides us a picture of, so-called, quantum Riemannian geometry, which is discrete on the fundamental scale. Imposing the quantum constraints in analogy from the classical ones, the quantum dynamics of gravity is being studied as one of the most important issues in loop quantum gravity. On the other hand, the semi-classical analysis is being carried out to test the classical limit of the quantum theory. In this review, the fundamental structure of loop quantum gravity is presented pedagogically. Our main aim is to help non-experts to understand the motivations, basic structures, as well as general results. It may also be beneficial to practitioners to gain insights from different perspectives on the theory. We will focus on the theoretical framework itself, rather than its applications, and do our best to write it in modern and precise langauge while keeping the presentation accessible for beginners. After reviewing the classical connection dynamical formalism of general relativity, as a foundation, the construction of the kinematical Ashtekar-Isham-Lewandowski representation is introduced in the content of quantum kinematics. The algebraic structure of quantum kinematics is also discussed. In the content of quantum dynamics, we mainly introduce the construction of a Hamiltonian constraint operator and the master constraint project. At last, some applications and recent advances are outlined. It should be noted that this strategy of quantizing gravity can also be extended to

  18. f(R) gravity cosmology in scalar degree of freedom

    International Nuclear Information System (INIS)

    Goswami, Umananda Dev; Deka, Kabita

    2014-01-01

    The models of f(R) gravity belong to an important class of modified gravity models where the late time cosmic accelerated expansion is considered as the manifestation of the large scale modification of the force of gravity. f(R) gravity models can be expressed in terms of a scalar degree of freedom by explicit redefinition of model's variable. Here we report about the study of the features of cosmological parameters and hence the cosmological evolution using the scalar degree of freedom of the f(R) = ξR n gravity model in the Friedmann-Lemaître-Robertson-Walker (FLRW) background

  19. Normal gravity field in relativistic geodesy

    Science.gov (United States)

    Kopeikin, Sergei; Vlasov, Igor; Han, Wen-Biao

    2018-02-01

    Modern geodesy is subject to a dramatic change from the Newtonian paradigm to Einstein's theory of general relativity. This is motivated by the ongoing advance in development of quantum sensors for applications in geodesy including quantum gravimeters and gradientometers, atomic clocks and fiber optics for making ultra-precise measurements of the geoid and multipolar structure of the Earth's gravitational field. At the same time, very long baseline interferometry, satellite laser ranging, and global navigation satellite systems have achieved an unprecedented level of accuracy in measuring 3-d coordinates of the reference points of the International Terrestrial Reference Frame and the world height system. The main geodetic reference standard to which gravimetric measurements of the of Earth's gravitational field are referred is a normal gravity field represented in the Newtonian gravity by the field of a uniformly rotating, homogeneous Maclaurin ellipsoid of which mass and quadrupole momentum are equal to the total mass and (tide-free) quadrupole moment of Earth's gravitational field. The present paper extends the concept of the normal gravity field from the Newtonian theory to the realm of general relativity. We focus our attention on the calculation of the post-Newtonian approximation of the normal field that is sufficient for current and near-future practical applications. We show that in general relativity the level surface of homogeneous and uniformly rotating fluid is no longer described by the Maclaurin ellipsoid in the most general case but represents an axisymmetric spheroid of the fourth order with respect to the geodetic Cartesian coordinates. At the same time, admitting a post-Newtonian inhomogeneity of the mass density in the form of concentric elliptical shells allows one to preserve the level surface of the fluid as an exact ellipsoid of rotation. We parametrize the mass density distribution and the level surface with two parameters which are

  20. Consistency of canonical formulation of Horava gravity

    International Nuclear Information System (INIS)

    Soo, Chopin

    2011-01-01

    Both the non-projectable and projectable version of Horava gravity face serious challenges. In the non-projectable version, the constraint algebra is seemingly inconsistent. The projectable version lacks a local Hamiltonian constraint, thus allowing for an extra graviton mode which can be problematic. A new formulation (based on arXiv:1007.1563) of Horava gravity which is naturally realized as a representation of the master constraint algebra (instead of the Dirac algebra) studied by loop quantum gravity researchers is presented. This formulation yields a consistent canonical theory with first class constraints; and captures the essence of Horava gravity in retaining only spatial diffeomorphisms as the physically relevant non-trivial gauge symmetry. At the same time the local Hamiltonian constraint is equivalently enforced by the master constraint.

  1. Consistency of canonical formulation of Horava gravity

    Energy Technology Data Exchange (ETDEWEB)

    Soo, Chopin, E-mail: cpsoo@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Tainan, Taiwan (China)

    2011-09-22

    Both the non-projectable and projectable version of Horava gravity face serious challenges. In the non-projectable version, the constraint algebra is seemingly inconsistent. The projectable version lacks a local Hamiltonian constraint, thus allowing for an extra graviton mode which can be problematic. A new formulation (based on arXiv:1007.1563) of Horava gravity which is naturally realized as a representation of the master constraint algebra (instead of the Dirac algebra) studied by loop quantum gravity researchers is presented. This formulation yields a consistent canonical theory with first class constraints; and captures the essence of Horava gravity in retaining only spatial diffeomorphisms as the physically relevant non-trivial gauge symmetry. At the same time the local Hamiltonian constraint is equivalently enforced by the master constraint.

  2. Topics in quantum gravity

    Energy Technology Data Exchange (ETDEWEB)

    Lamon, Raphael

    2010-06-29

    Quantum gravity is an attempt to unify general relativity with quantum mechanics which are the two highly successful fundamental theories of theoretical physics. The main difficulty in this unification arises from the fact that, while general relativity describes gravity as a macroscopic geometrical theory, quantum mechanics explains microscopic phenomena. As a further complication, not only do both theories describe different scales but also their philosophical ramifications and the mathematics used to describe them differ in a dramatic way. Consequently, one possible starting point of an attempt at a unification is quantum mechanics, i.e. particle physics, and try to incorporate gravitation. This pathway has been chosen by particle physicists which led to string theory. On the other hand, loop quantum gravity (LQG) chooses the other possibility, i.e. it takes the geometrical aspects of gravity seriously and quantizes geometry. The first part of this thesis deals with a generalization of loop quantum cosmology (LQC) to toroidal topologies. LQC is a quantization of homogenous solutions of Einstein's field equations using tools from LQG. First the general concepts of closed topologies is introduced with special emphasis on Thurston's theorem and its consequences. It is shown that new degrees of freedom called Teichmueller parameters come into play and their dynamics can be described by a Hamiltonian. Several numerical solutions for a toroidal universe are presented and discussed. Following the guidelines of LQG this dynamics are rewritten using the Ashtekar variables and numerical solutions are shown. However, in order to find a suitable Hilbert space a canonical transformation must be performed. On the other hand this transformation makes the quantization of geometrical quantities less tractable such that two different ways are presented. It is shown that in both cases the spectrum of such geometrical operators depends on the initial value problem

  3. Finite field-dependent symmetries in perturbative quantum gravity

    International Nuclear Information System (INIS)

    Upadhyay, Sudhaker

    2014-01-01

    In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and non-linear gauges. Further, we analyze the finite field-dependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gauge-fixing and ghost parts of the perturbative quantum gravity within functional integration. However, the operation of such symmetry transformation on the generating functional of perturbative quantum gravity does not affect the theory on physical ground. The FFBRST transformation with appropriate choices of finite BRST parameter connects non-linear Curci–Ferrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using Batalin–Vilkovisky (BV) formulation. -- Highlights: •The perturbative quantum gravity is treated as gauge theory. •BRST and anti-BRST transformations are developed in linear and non-linear gauges. •BRST transformation is generalized by making it finite and field dependent. •Connection between linear and non-linear gauges is established. •Using BV formulation the results are established at quantum level also

  4. A general framework to test gravity using galaxy clusters - I. Modelling the dynamical mass of haloes in f(R) gravity

    Science.gov (United States)

    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.

  5. The quest for quantum gravity

    International Nuclear Information System (INIS)

    Au, G.

    1995-03-01

    One of the greatest challenges facing theoretical physics lies in reconciling Einstein's classical theory of gravity - general relativity -with quantum field theory. Although both theories have been experimentally supported in their respective regimes, they are as compatible as a square peg and a round hole. This article summarises the current status of the superstring approach to the problem, the status of the Ashtekar program, and problem of time in quantum gravity

  6. Decoherence in quantum gravity: issues and critiques

    Energy Technology Data Exchange (ETDEWEB)

    Anastopoulos, C [Department of Physics, University of Patras, 26500 Patras (Greece); Hu, B L [Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)

    2007-05-15

    An increasing number of papers have appeared in recent years on decoherence in quantum gravity at the Planck energy. We discuss the meaning of decoherence in quantum gravity starting from the common notion that quantum gravity is a theory for the microscopic structures of spacetime, and invoking some generic features of quantum decoherence from the open systems viewpoint. We dwell on a range of issues bearing on this process including the relation between statistical and quantum, noise from effective field theory, the meaning of stochasticity, the origin of non-unitarity and the nature of nonlocality in this and related contexts. To expound these issues we critique on two representative theories: One claims that decoherence in quantum gravity scale leads to the violation of CPT symmetry at sub-Planckian energy which is used to explain today's particle phenomenology. The other uses this process in place with the Brownian motion model to prove that spacetime foam behaves like a thermal bath. A companion paper will deal with intrinsic and fundamental decoherence which also bear on issues in classical and quantum gravity.

  7. Unitarity bounds on low scale quantum gravity

    International Nuclear Information System (INIS)

    Atkins, Michael; Calmet, Xavier

    2010-01-01

    We study the unitarity of models with low scale quantum gravity both in four dimensions and in models with a large extra-dimensional volume. We find that models with low scale quantum gravity have problems with unitarity below the scale at which gravity becomes strong. An important consequence of our work is that their first signal at the Large Hadron Collider would not be of a gravitational nature such as graviton emission or small black holes, but rather would be linked to the mechanism which fixes the unitarity problem. We also study models with scalar fields with non-minimal couplings to the Ricci scalar. We consider the strength of gravity in these models and study the consequences for inflation models with non-minimally coupled scalar fields. We show that a single scalar field with a large non-minimal coupling can lower the Planck mass in the TeV region. In that model, it is possible to lower the scale at which gravity becomes strong down to 14 TeV without violating unitarity below that scale. (orig.)

  8. Decoherence in quantum gravity: issues and critiques

    International Nuclear Information System (INIS)

    Anastopoulos, C; Hu, B L

    2007-01-01

    An increasing number of papers have appeared in recent years on decoherence in quantum gravity at the Planck energy. We discuss the meaning of decoherence in quantum gravity starting from the common notion that quantum gravity is a theory for the microscopic structures of spacetime, and invoking some generic features of quantum decoherence from the open systems viewpoint. We dwell on a range of issues bearing on this process including the relation between statistical and quantum, noise from effective field theory, the meaning of stochasticity, the origin of non-unitarity and the nature of nonlocality in this and related contexts. To expound these issues we critique on two representative theories: One claims that decoherence in quantum gravity scale leads to the violation of CPT symmetry at sub-Planckian energy which is used to explain today's particle phenomenology. The other uses this process in place with the Brownian motion model to prove that spacetime foam behaves like a thermal bath. A companion paper will deal with intrinsic and fundamental decoherence which also bear on issues in classical and quantum gravity

  9. Discussion of entanglement entropy in quantum gravity

    International Nuclear Information System (INIS)

    Ma, Chen-Te

    2018-01-01

    We study entanglement entropy in gravity theory with quantum effects. A simplest model is a two dimensional Einstein gravity theory. We use an n-sheet manifold to obtain an area term of entanglement entropy by summing over all background fields. Based on AdS/CFT correspondence, strongly coupled conformal field theory is expected to describe perturbative quantum gravity theory. An ultraviolet complete quantum gravity theory should not depend on a choice of an entangling surface. To analysis the problem explicitly, we analyze two dimensional conformal field theory. We find that a coefficient of a universal term of entanglement entropy is independent of a choice of an entangling surface in two dimensional conformal field theory for one interval to show a tentative evidence. Finally, we discuss that translational invariance in a quantum system at zero temperature, size goes to infinity and no mass scales, except for cut-off, possibly be a necessary condition in quantum gravity theory by ruing out a volume law of entanglement entropy. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Topics in Theories of Quantum Gravity

    Energy Technology Data Exchange (ETDEWEB)

    Perelstein, M.

    2005-04-05

    In this thesis, the author addresses several issues involving gravity. The first half of the thesis is devoted to studying quantum properties of Einstein gravity and its supersymmetric extensions in the perturbative regime. String theory suggests that perturbative scattering amplitudes in the theories of gravity are related to the amplitudes in gauge theories. This connection has been studied at classical (tree) level by Kawai, Lewellen and Tye. Here, they will explore the relationship between gravity and gauge theory at quantum (loop) level. This relationship, together with the cut-based approach to computing loop amplitudes, allow us to obtain new non-trivial results for quantum gravity. IN particular, they present two infinite sequences of one-loop n-graviton scattering amplitudes: the maximally helicity violating amplitudes in N = 8 supergravity, and the ''all-plus'' helicity amplitudes in Einstein gravity with any minimally coupled massless matter content. The results for n {le} 6 will be obtained by an explicit calculation, while those for n > 6 is inferred from the soft and collinear properties of the amplitudes. They also present an explicit expression for the two-loop contribution to the four-particle scattering amplitude in N = 8 supergravity, and observe a simple relation between this result and its counterpart in N = 4 super-Yang-Mills theory. Furthermore, the simple structure of the two-particle unitarity cuts in these theories suggests that similar relations exist to all loop orders. If this is the case, the first ultraviolet divergence in N = 8 supergravity should appear at five loops, contrary to the earlier expectation of a three-loop counterterm.

  11. Cellular gravity

    NARCIS (Netherlands)

    F.C. Gruau; J.T. Tromp (John)

    1999-01-01

    textabstractWe consider the problem of establishing gravity in cellular automata. In particular, when cellular automata states can be partitioned into empty, particle, and wall types, with the latter enclosing rectangular areas, we desire rules that will make the particles fall down and pile up on

  12. Flow Boiling Critical Heat Flux in Reduced Gravity

    Science.gov (United States)

    Mudawar, Issam; Zhang, Hui; Hasan, Mohammad M.

    2004-01-01

    This study provides systematic method for reducing power consumption in reduced gravity systems by adopting minimum velocity required to provide adequate CHF and preclude detrimental effects of reduced gravity . This study proves it is possible to use existing 1 ge flow boiling and CHF correlations and models to design reduced gravity systems provided minimum velocity criteria are met

  13. Conformal Gravity

    International Nuclear Information System (INIS)

    Hooft, G.

    2012-01-01

    The dynamical degree of freedom for the gravitational force is the metric tensor, having 10 locally independent degrees of freedom (of which 4 can be used to fix the coordinate choice). In conformal gravity, we split this field into an overall scalar factor and a nine-component remainder. All unrenormalizable infinities are in this remainder, while the scalar component can be handled like any other scalar field such as the Higgs field. In this formalism, conformal symmetry is spontaneously broken. An imperative demand on any healthy quantum gravity theory is that black holes should be described as quantum systems with micro-states as dictated by the Hawking-Bekenstein theory. This requires conformal symmetry that may be broken spontaneously but not explicitly, and this means that all conformal anomalies must cancel out. Cancellation of conformal anomalies yields constraints on the matter sector as described by some universal field theory. Thus black hole physics may eventually be of help in the construction of unified field theories. (author)

  14. 27 CFR 30.25 - Use of precision specific gravity hydrometers.

    Science.gov (United States)

    2010-04-01

    ... gravity hydrometers. 30.25 Section 30.25 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX... precision specific gravity hydrometers. The provisions of § 30.23 respecting the care, handling, and use of... specific gravity hydrometers. Specific gravity hydrometers shall be read to the nearest subdivision...

  15. Standardized UXO Technology Demonstration Site Blind Grid Scoring Record Number 891

    Science.gov (United States)

    2008-08-01

    magnetometers (Foerster CON650 gradiometers) and RTK-DGPS georeferencing will be used. The spacing between the individual fluxgate sensors will be 25 cm...used for data acquisition usually ranges from 8 to 32. b. For the demonstration at Aberdeen Proving Ground, a system with eight fluxgate ...up to 32 fluxgate gradiometers (for the APG demonstration: eight fluxgate gradiometers), a robust, all-terrain trailer, the MonMX data acquisition

  16. Bringing Artificial Gravity into the Classroom

    Science.gov (United States)

    Thompson, Grant; Aning, Isaac

    2018-01-01

    We recently conducted an experimental test of artificial gravity by placing various species of plants in centrifuges and analyzed the plants’ germination and growth. This research project incorporated several topics covered in undergraduate astronomy, biology, and physics courses. Given the interest of introductory astronomy students in artificial gravity and their pre-existing images of applications such as rotating spacecraft from pop culture, the results of the experiment may provide a gateway to discuss artificial gravity beyond teaching the traditional examples of Newton’s laws. We will discuss the experiment in detail and provide suggestions for how the experiment could be incorporated into your classroom.

  17. 2D gravity and random matrices

    International Nuclear Information System (INIS)

    Zinn-Justin, J.

    1990-01-01

    Recent progress in 2D gravity coupled to d ≤ 1 matter, based on a representation of discrete gravity in terms of random matrices, is reported. The matrix problem can be solved in many cases by the introduction of suitable orthogonal polynomials. Alternatively in the continuum limit the orthogonal polynomial method can be shown to be equivalent to the construction of representation of the canonical commutation relations in terms of differential operators. In the case of pure gravity or discrete Ising-like matter the sum over topologies is reduced to the solution of non-linear differential equations. The d = 1 problem can be solved by semiclassical methods

  18. Massive gravity and Fierz-Pauli theory

    Energy Technology Data Exchange (ETDEWEB)

    Blasi, Alberto [Universita di Genova, Dipartimento di Fisica, Genova (Italy); Maggiore, Nicola [I.N.F.N.-Sezione di Genova, Genoa (Italy)

    2017-09-15

    Linearized gravity is considered as an ordinary gauge field theory. This implies the need for gauge fixing in order to have well-defined propagators. Only after having achieved this, the most general mass term is added. The aim of this paper is to study of the degrees of freedom of the gauge fixed theory of linearized gravity with mass term. The main result is that, even outside the usual Fierz-Pauli constraint on the mass term, it is possible to choose a gauge fixing belonging to the Landau class, which leads to a massive theory of gravity with the five degrees of freedom of a spin-2 massive particle. (orig.)

  19. Does time exist in quantum gravity?

    Directory of Open Access Journals (Sweden)

    Claus Kiefer

    2015-12-01

    Full Text Available Time is absolute in standard quantum theory and dynamical in general relativity. The combination of both theories into a theory of quantum gravity leads therefore to a “problem of time”. In my essay, I investigate those consequences for the concept of time that may be drawn without a detailed knowledge of quantum gravity. The only assumptions are the experimentally supported universality of the linear structure of quantum theory and the recovery of general relativity in the classical limit. Among the consequences are the fundamental timelessness of quantum gravity, the approximate nature of a semiclassical time, and the correlation of entropy with the size of the Universe.

  20. Massive gravity and Fierz-Pauli theory

    International Nuclear Information System (INIS)

    Blasi, Alberto; Maggiore, Nicola

    2017-01-01

    Linearized gravity is considered as an ordinary gauge field theory. This implies the need for gauge fixing in order to have well-defined propagators. Only after having achieved this, the most general mass term is added. The aim of this paper is to study of the degrees of freedom of the gauge fixed theory of linearized gravity with mass term. The main result is that, even outside the usual Fierz-Pauli constraint on the mass term, it is possible to choose a gauge fixing belonging to the Landau class, which leads to a massive theory of gravity with the five degrees of freedom of a spin-2 massive particle. (orig.)

  1. Topspin networks in loop quantum gravity

    International Nuclear Information System (INIS)

    Duston, Christopher L

    2012-01-01

    We discuss the extension of loop quantum gravity to topspin networks, a proposal which allows topological information to be encoded in spin networks. We will show that this requires minimal changes to the phase space, C*-algebra and Hilbert space of cylindrical functions. We will also discuss the area and Hamiltonian operators, and show how they depend on the topology. This extends the idea of ‘background independence’ in loop quantum gravity to include topology as well as geometry. It is hoped this work will confirm the usefulness of the topspin network formalism and open up several new avenues for research into quantum gravity. (paper)

  2. Granular Superconductors and Gravity

    Science.gov (United States)

    Noever, David; Koczor, Ron

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.

  3. Gravity Data for Indiana (300 records compiled)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity data (300 records) were compiled by Purdue University. This data base was received in February 1993. Principal gravity parameters include Free-air...

  4. Micro-system inertial sensing technology overview.

    Energy Technology Data Exchange (ETDEWEB)

    Allen, James Joe

    2009-02-01

    The purpose of this report is to provide an overview of Micro-System technology as it applies to inertial sensing. Transduction methods are reviewed with capacitance and piezoresistive being the most often used in COTS Micro-electro-mechanical system (MEMS) inertial sensors. Optical transduction is the most recent transduction method having significant impact on improving sensor resolution. A few other methods are motioned which are in a R&D status to hopefully allow MEMS inertial sensors to become viable as a navigation grade sensor. The accelerometer, gyroscope and gravity gradiometer are the type of inertial sensors which are reviewed in this report. Their method of operation and a sampling of COTS sensors and grade are reviewed as well.

  5. Evaluation of gravity field model EIGEN-6C4 by means of various functions of gravity potential, and by GNSS/levelling

    Directory of Open Access Journals (Sweden)

    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.

  6. Noether symmetry approach in f(G,T) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Shamir, M.F.; Ahmad, Mushtaq [National University of Computer and Emerging Sciences, Lahore Campus (Pakistan)

    2017-01-15

    We explore the recently introduced modified Gauss-Bonnet gravity (Sharif and Ikram in Eur Phys J C 76:640, 2016), f(G,T) pragmatic with G, the Gauss-Bonnet term, and T, the trace of the energy-momentum tensor. Noether symmetry approach has been used to develop some cosmologically viable f(G,T) gravity models. The Noether equations of modified gravity are reported for flat FRW universe. Two specific models have been studied to determine the conserved quantities and exact solutions. In particular, the well known deSitter solution is reconstructed for some specific choice of f(G,T) gravity model. (orig.)

  7. Cosmology of Horava-Lifshitz f(R) gravity

    International Nuclear Information System (INIS)

    Chakrabarti, Sayan K.; Sen, Anjan A.

    2011-08-01

    We discuss the cosmology of recently proposed Horava-Lifshitz f(R) gravity. In particular, we derive the modified Hubble equation that reduces to the standard HL gravity case in appropriate limit. We show how the bounce solutions in this theory are modified due to nonlinear effect of f(R) gravity. In addition we find that the solutions exist when the Universe can make turn around for large scale-factor. Therefore, in principle, the Universe in this set-up can show cyclic behavior. (orig.)

  8. Cosmology of Horava-Lifshitz f(R) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarti, Sayan K. [Univ. Tecnica de Lisboa (Portugal). Inst. Superior Tecnico; Dutta, Koushik [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Sen, Anjan A. [Centre of Theoretical Physics, Jamia Millia Islamia, New Dehli (India)

    2011-08-15

    We discuss the cosmology of recently proposed Horava-Lifshitz f(R) gravity. In particular, we derive the modified Hubble equation that reduces to the standard HL gravity case in appropriate limit. We show how the bounce solutions in this theory are modified due to nonlinear effect of f(R) gravity. In addition we find that the solutions exist when the Universe can make turn around for large scale-factor. Therefore, in principle, the Universe in this set-up can show cyclic behavior. (orig.)

  9. REVIEW: A GRAMMAR OF GUÌQIÓNG

    Directory of Open Access Journals (Sweden)

    Jesse P. Gates

    2018-05-01

    Full Text Available Jiāng Lì. 2015. A Grammar of Guìqióng: A Language of Sichuan. Leiden: Brill. xiv + 452 pp. ISBN 9789004292093 (hardback 213USD - E-ISBN 9789004293045 (electronic 217USD. Jiang Li's A Grammar of Guìqióng (henceforth, AGG is a revision of her PhD dissertation at the University of Berne under the supervision of George Van Driem. It is a most welcome contribution to our understanding of this under-described language. The primary dialects of Guiqiong described in AGG are spoken in Changma Village of Maibeng Township and Qianxi Village of Qianxi Township, both in Kangding County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China. Some praiseworthy aspects of AGG include a plethora of examples sentences; a total of about 1500 example sentences are in the book. Included in the list of abbreviations are the linguistic forms from Guiqiong. The inclusion of photographs of the Guiqiong people and their geographic setting adds interest and appeal to the book. Appendix 1 (321-347 contains six texts of "sayings, stories, and recollections." This review is divided into sections similar to the divisions that the chapters of AGG provide: Introduction to AGG, Phonology, Morphology, Syntax, Errata, and Conclusion. Comments on AGG's chapter on pragmatics will be incorporated into the section on syntax since AGG's chapter on pragmatics is very short. Back-matter will also be briefly overviewed in the syntax section. ...

  10. Wisconsin Gravity Data for the Marshfield Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (8388 records) were compiled by Professor Ervin. This data base was received in April 1993. Principal gravity parameters include Free-Air...

  11. Wisconsin Gravity Data for the Rhinelader Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (195 records) were compiled by Barbara Eckstein. This data base was received in January 1987. Principal gravity parameters include Free-Air...

  12. Gravity Data for the Greater Portland Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (1,522 records) were compiled by the Portland State University. This data base was received in August 1990. Principal gravity parameters...

  13. Wisconsin Gravity Data for the Sawyers Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (3814 records) were compiled by Professor Ervin. This data base was received in April 1993. Principal gravity parameters include Free-Air...

  14. Wisconsin Gravity Data for the Prentice Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (898 records) were compiled by Professor Ervin. This data base was received in January 1987. Principal gravity parameters include Free-Air...

  15. Newton-Cartan gravity and torsion

    Science.gov (United States)

    Bergshoeff, Eric; Chatzistavrakidis, Athanasios; Romano, Luca; Rosseel, Jan

    2017-10-01

    We compare the gauging of the Bargmann algebra, for the case of arbitrary torsion, with the result that one obtains from a null-reduction of General Relativity. Whereas the two procedures lead to the same result for Newton-Cartan geometry with arbitrary torsion, the null-reduction of the Einstein equations necessarily leads to Newton-Cartan gravity with zero torsion. We show, for three space-time dimensions, how Newton-Cartan gravity with arbitrary torsion can be obtained by starting from a Schrödinger field theory with dynamical exponent z = 2 for a complex compensating scalar and next coupling this field theory to a z = 2 Schrödinger geometry with arbitrary torsion. The latter theory can be obtained from either a gauging of the Schrödinger algebra, for arbitrary torsion, or from a null-reduction of conformal gravity.

  16. Universality of quantum gravity corrections.

    Science.gov (United States)

    Das, Saurya; Vagenas, Elias C

    2008-11-28

    We show that the existence of a minimum measurable length and the related generalized uncertainty principle (GUP), predicted by theories of quantum gravity, influence all quantum Hamiltonians. Thus, they predict quantum gravity corrections to various quantum phenomena. We compute such corrections to the Lamb shift, the Landau levels, and the tunneling current in a scanning tunneling microscope. We show that these corrections can be interpreted in two ways: (a) either that they are exceedingly small, beyond the reach of current experiments, or (b) that they predict upper bounds on the quantum gravity parameter in the GUP, compatible with experiments at the electroweak scale. Thus, more accurate measurements in the future should either be able to test these predictions, or further tighten the above bounds and predict an intermediate length scale between the electroweak and the Planck scale.

  17. Airborne Gravity: NGS' Gravity Data for ES04 (2013-2014)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for North Carolina, South Carolina, Virginia, and the Atlantic Ocean collected in 2013 and 2014 over two surveys. This data set is part of the...

  18. Airborne Gravity: NGS' Gravity Data for EN02 (2011-2012)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Pennsylvania, Ohio, Michigan, Canada and Lake Erie collected in 2011 and 2012 over 3 surveys. This data set is part of the...

  19. A class of solutions for the strong gravity equations

    International Nuclear Information System (INIS)

    Salam, A.; Strathdee, J.

    1976-12-01

    We solve the Einstein equation for strong gravity in the limit that weak gravity is neglected. The class of solutions we find reduces to the Schwarzschild solution (with the weak gravity Newtonian constant replaced by a strong coupling parameter) in the limit M 2 →0 where M is the mass of the strong gravity spin-2 meson. These solutions may be of relevance for the problem of defining temperature in hadronic physics

  20. Quark stars in f(T, T)-gravity

    Energy Technology Data Exchange (ETDEWEB)

    Pace, Mark; Said, Jackson Levi [University of Malta, Department of Physics, Msida (Malta); University of Malta, Institute of Space Sciences and Astronomy, Msida (Malta)

    2017-02-15

    We derive a working model for the Tolman-Oppenheimer-Volkoff equation for quark star systems within the modified f(T, T)-gravity class of models. We consider f(T, T)-gravity for a static spherically symmetric space-time. In this instance the metric is built from a more fundamental tetrad vierbein from which the metric tensor can be derived. We impose a linear f(T) parameter, namely taking f = αT(r) + βT(r) + φ and investigate the behaviour of a linear energy-momentum tensor trace, T. We also outline the restrictions which modified f(T, T)-gravity imposes upon the coupling parameters. Finally we incorporate the MIT bag model in order to derive the mass-radius and mass-central density relations of the quark star within f(T, T)-gravity. (orig.)