International Nuclear Information System (INIS)
In the first part of this work, starting from Einstein's equations of the Classical General Relativity, a new kind of solutions for the Mixmaster model are explored. By dispensing with the extension to the complex variable field, which is usual in problems such as the Laplace equation or the harmonic oscillator, in a similar manner to that of Quantum Mechanics, the equations appear to have solutions that belong to the complex General Relativity. A first integral is performed by establishing a separation of the first derivatives. Then a second integral is obtained once the respective equations with separate variables are found and whose integrals provide a family of complex solutions. However, reality conditions do not seem to be easily imposed at this stage. Above all, it is significant that the classical Einstein's equations for the debatably integrable Mixmaster model present complex solutions. In the second part of this work, following a specific strategy in which the cosmological time variables are operated upon, a new family of solutions to the empty Taub universe is found. Among the characteristics of such a family, it stands the positive acceleration provided by the tri-curvature property of this universe to two of the three scale factors of the Taub model. This effect of the tri-curvature results not in a restoring force such as normal gravity but in the conversion of the Taub cosmology into an accelerating universe. (Author)
Palsingh, S. (Inventor)
1975-01-01
An educational toy useful in demonstrating fundamental concepts regarding the laws of gravity is described. The device comprises a sphere 10 of radius r resting on top of sphere 12 of radius R. The center of gravity of sphere 10 is displaced from its geometrical center by distance D. The dimensions are so related that D((R+r)/r) is greater than r. With the center of gravity of sphere 10 lying on a vertical line, the device is in equilibrium. When sphere 10 is rolled on the surface of sphere 12 it will return to its equilibrium position upon release. This creates an illusion that sphere 10 is defying the laws of gravity. In reality, due to the above noted relationship of D, R, and r, the center of gravity of sphere 10 rises from its equilibrium position as it rolls a short distance up or down the surface of sphere 12.
Absence of evaporation phenomena in f(T) gravity
Houndjo, M J S; Myrzakulov, R; Rodrigues, M E
2013-01-01
We formulated evaporation phenomena in a generic model of generalized teleparallel gravity in Weitzenbock spacetime. We performed the perturbation analysis around the constant torsion scalar solution named as Nariai spacetime which is an exact solution of field equations as the limiting case of the Schwarzschild-de Sitter and in limit which two back hole and cosmological horizons coincides. By carefully analyze of the horizon perturbation equation we show (anti)evaporation can not be happen. From this result it implies that a typical blackhole in any generic form of generalized teleparallel gravity is frozen in it's initial state. This is an universal feature and completely independence from the form of the model and even the form of the initial phase of horizon perturbations.
Anisotropic phenomena in gauge/gravity duality
International Nuclear Information System (INIS)
In this thesis we use gauge/gravity duality to model anisotropic effects realised in nature. Firstly we analyse transport properties in holographic systems with a broken rotational invariance. Secondly we discuss geometries dual to IR fixed points with anisotropic scaling behaviour, which are related to quantum critical points in condensed matter systems. Gauge/gravity duality relates a gravity theory in Anti-de Sitter space to a lower dimensional strongly coupled quantum field theory in Minkowski space. Over the past decade this duality provided many insights into systems at strong coupling, e.g. quark-gluon plasma and condensed matter close to quantum critical points. One very important result computed in this framework is the value of the shear viscosity divided by the entropy density in strongly coupled theories. The quantitative result agrees very well with measurements of the ratio in quark-gluon plasma. However, for isotropic two derivative Einstein gravity it is temperature independent. We show that by breaking the rotational symmetry of a system we obtain a temperature dependent shear viscosity over entropy density. This is important to make contact with real world systems, since substances in nature display such dependence. In addition, we derive various transport properties in strongly coupled anisotropic systems using the gauge/gravity dictionary. The most notable results include an electrical conductivity with Drude behaviour in the low frequency region. This resembles conductors with broken translational invariance. However, we did not implement the breaking explicitly. Furthermore, our analysis shows that this setup models effects, resembling the piezoelectric and exoelectric effects, known from liquid crystals. In a second project we discuss a geometry with non-trivial scaling behaviour in order to model an IR fixed point of condensed matter theories. We construct the UV completion of this geometry and analyse its properties by computing the
The Superheavy Elements and Anti-Gravity
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.
Localized Gravity on Branes in anti-de Sitter Spaces
Halyo, Edi
1999-01-01
We discuss the conditions under which 4D gravity is localized on domain walls in 5D anti-de Sitter spaces. Our approach is based on considering the limits in which the localized gravity decouples. We find that gravity is localized if the wall is located a finite distance from the boundary of the anti-de Sitter space and has a finite tension. In addition, it has to be a $\\delta$-function source of gravity.
Singularity phenomena in viable f(R) gravity
Lee, Chung-Chi; Yang, Louis
2012-01-01
The curvature singularity in viable f(R) gravity models is examined when the background density is dense. This singularity could be eliminated by adding the $R^{2}$ term in the Lagrangian. Some of cosmological consequences, in particular the source for the scalar mode of gravitational waves, are discussed.
Energy Technology Data Exchange (ETDEWEB)
Melendez L, L
2004-07-01
In the first part of this work, starting from Einstein's equations of the Classical General Relativity, a new kind of solutions for the Mixmaster model are explored. By dispensing with the extension to the complex variable field, which is usual in problems such as the Laplace equation or the harmonic oscillator, in a similar manner to that of Quantum Mechanics, the equations appear to have solutions that belong to the complex General Relativity. A first integral is performed by establishing a separation of the first derivatives. Then a second integral is obtained once the respective equations with separate variables are found and whose integrals provide a family of complex solutions. However, reality conditions do not seem to be easily imposed at this stage. Above all, it is significant that the classical Einstein's equations for the debatably integrable Mixmaster model present complex solutions. In the second part of this work, following a specific strategy in which the cosmological time variables are operated upon, a new family of solutions to the empty Taub universe is found. Among the characteristics of such a family, it stands the positive acceleration provided by the tri-curvature property of this universe to two of the three scale factors of the Taub model. This effect of the tri-curvature results not in a restoring force such as normal gravity but in the conversion of the Taub cosmology into an accelerating universe. (Author)
Anti-Newtonian cosmologies in f(R) gravity
Abebe, Amare
2014-01-01
In this paper, we investigate a class of perfect-fluid "anti-Newtonian" cosmological models in the context of f(R) gravity. In particular, we study the integrability conditions of such gravity models using covariant consistency analysis formalisms. We show that, unlike the results in General Relativity, anti-Newtonian cosmologies are not silent models and that they can exist subject to the solution of an integrability condition equation we derive. We also present the set of evolution equation...
Gravity and Anti-gravity of Fermions: the Unification of Dark Matter and Dark Energy
Chen, X S
2005-01-01
Massive gravity with second and fourth derivatives is shown to give both attractive and repulsive gravity between fermions. In contrast to the attractive gravity correlated with energy-momentum tensor, the repulsive gravity is proportional to the graviton mass. Therefore, weakly interacting fermions with energy smaller than the graviton mass are both dark matter and dark energy: Their overall gravity is attractive with normal matter but repulsive among themselves. Detailed analyses reveal that this unified dark scenario can properly account for the observed dark matter/energy phenomena: galaxy rotation curves, transition from early cosmic deceleration to recent acceleration; and naturally overcome other dark scenarios' difficulties: the substructure and cuspy core problems, the difference of dark halo distributions in galaxies and clusters, and the cosmic coincidence.
BRST and Anti-BRST Symmetries in Perturbative Quantum Gravity
Faizal, Mir
2010-01-01
In perturbative quantum gravity, the sum of the classical Lagrangian density, a gauge fixing term and a ghost term is invariant under two sets of supersymmetric transformations called the BRST and the anti-BRST transformations. In this paper we will analyse the BRST and the anti-BRST symmetries of perturbative quantum gravity in curved spacetime, in linear as well as non-linear gauges. We will show that even though the sum of ghost term and the gauge fixing term can always be expressed as a t...
Critical phenomena in a low gravity environment. [in fluids as materials science models
Sengers, J. V.; Moldover, M. R.
1978-01-01
Various types of critical point phenomena are discussed including the gas-liquid phase transition of a fluid, the spontaneous magnetization of a ferromagnet below the Curie temperature, and structural phase transitions of solid materials. The interrelation of thermodynamic properties by scaling laws is considered noting theories for the validity of scaling laws and the principle of universality. Gravity effects are reviewed noting that in earth-based experiments the phenomena are significantly influenced by the earth's gravitational field and that fluid samples that are spatially homogeneous cannot be realized near the gas-liquid critical point.
Dynamically broken Anti-de Sitter action for gravity
Tresguerres, Romualdo
2008-01-01
Due to a suitable Higgs mechanism, a standard Anti-de Sitter gauge theory becomes spontaneously broken. The resulting Lorentz invariant gravitational action includes the Hilbert-Einstein term of ordinary Einstein-Cartan gravity with cosmological constant, plus contributions quadratic in curvature and torsion, and a scalar Higgs sector.
Fermions in (Anti) de Sitter Gravity in Four Dimensions
Ikeda, Noriaki; Fukuyama, Takeshi
2009-01-01
Fermions in (anti) de Sitter gravity theory in four dimensions are considered. Especially we propose new fermion actions to derive a Weyl or Majorana fermion action if we break the AdS (dS) group to the Lorentz group in curved spacetime.
Entanglement entropy in critical phenomena and analog models of quantum gravity
International Nuclear Information System (INIS)
A general geometrical structure of the entanglement entropy for spatial partition of a relativistic QFT system is established by using methods of the effective gravity action and the spectral geometry. A special attention is payed to the subleading terms in the entropy in different dimensions and to behavior in different states. It is conjectured, on the base of relation between the entropy and the action, that in a fundamental theory the ground state entanglement entropy per unit area equals 1/(4GN), where GN is the Newton constant in the low-energy gravity sector of the theory. The conjecture opens a new avenue in analogue gravity models. For instance, in higher-dimensional condensed matter systems, which near a critical point are described by relativistic QFT's, the entanglement entropy density defines an effective gravitational coupling. By studying the properties of this constant one can get new insights in quantum gravity phenomena, such as the universality of the low-energy physics, the renormalization group behavior of GN, the statistical meaning of the Bekenstein-Hawking entropy
Fluid Physics and Transport Phenomena in a Simulated Reduced Gravity Environment
Lipa, J.
2004-01-01
We describe a ground-based apparatus that allows the cancellation of gravity on a fluid using magnetic forces. The present system was designed for liquid oxygen studies over the range 0.001 - 5 g s. This fluid is an essential component of any flight mission using substantial amounts of liquid propellant, especially manned missions. The apparatus has been used to reduce the hydrostatic compression near the oxygen critical point and to demonstrate inverted phase separation. It could also be used to study pool boiling and two-phase heat transfer in Martian, Lunar or near-zero gravity, as well as phenomena such as Marangoni flow and convective instabilities. These studies would contribute directly to the reliability and optimization of the Moon and Mars flight programs.
Anti-de Sitter 3-dimensional Gravity with Torsion
Blagojevic, M; Vasilic, M.
2004-01-01
Using the canonical formalism, we study the asymptotic symmetries of the topological 3-dimensional gravity with torsion. In the anti-de Sitter sector, the symmetries are realized by two independent Virasoro algebras with classical central charges. In the simple case of the teleparallel vacuum geometry, the central charges are equal to each other and have the same value as in general relativity, while in the general Riemann-Cartan geometry, they become different.
General heavenly equation governs anti-self-dual gravity
Malykh, A. A.; Sheftel, M. B.
2010-01-01
We show that the general heavenly equation, suggested recently by Doubrov and Ferapontov \\cite{fer}, governs anti-self-dual (ASD) gravity. We derive ASD Ricci-flat vacuum metric governed by the general heavenly equation, null tetrad and basis of 1-forms for this metric. We present algebraic exact solutions of the general heavenly equation as a set of zeros of homogeneous polynomials in independent and dependent variables. A real solution is obtained for the case of neutral signature.
Multiculturalism and Anti-multiculturalism Phenomena in South Korea
Yong-Seung, Lee
2016-01-01
Multicultural policies in South Korea are currently showing some signs of backlash. The declaration that multiculturalism has failed has been successively announced around the world, and it is often observed that the extreme rightwing parties that support anti-multiculturalism and anti-immigration secure a significant number of votes. It is not certain how closely the phenomenon of backlash against multicultural policies in South Korea is related to global trends, yet this tendency undoubtedl...
Pilot Fullerton dons EES anti-gravity suit lower torso on middeck
1982-01-01
Pilot Fullerton dons ejection escape suit (EES) anti-gravity (anti-g) suit lower torso on forward port side middeck above potable water tank. Anti-g suit is an olive drab inner garment that complements EES.
Accuracy of unloading with the anti-gravity treadmill.
McNeill, David K P; de Heer, Hendrik D; Bounds, Roger G; Coast, J Richard
2015-03-01
Body weight (BW)-supported treadmill training has become increasingly popular in professional sports and rehabilitation. To date, little is known about the accuracy of the lower-body positive pressure treadmill. This study evaluated the accuracy of the BW support reported on the AlterG "Anti-Gravity" Treadmill across the spectrum of unloading, from full BW (100%) to 20% BW. Thirty-one adults (15 men and 16 women) with a mean age of 29.3 years (SD = 10.9), and a mean weight of 66.55 kg (SD = 12.68) were recruited. Participants were weighed outside the machine and then inside at 100-20% BW in 10% increments. Predicted BW, as presented by the AlterG equipment, was compared with measured BW. Significant differences between predicted and measured BW were found at all but 90% through 70% of BW. Differences were small (Anti-Gravity Treadmill®, with the largest differences (>5%) found at 100% BW and the greatest BW support (30 and 20% BW). These differences may be associated with changes in metabolic demand and maximum speed during walking or running and should be taken into consideration when using these devices for training and research purposes. PMID:25226319
Critical gravity as van Dam-Veltman-Zakharov discontinuity in anti de Sitter space
Myung, Yun Soo
2011-01-01
We consider critical gravity as van Dam-Vletman-Zakharov (vDVZ) discontinuity in anti de Sitter space. For this purpose, we introduce the higher curvature gravity. This discontinuity can be confirmed by calculating the residues of relevant poles explicitly. For the non-critical gravity of $0
Motivations for anti-gravity in general relativity
Energy Technology Data Exchange (ETDEWEB)
Chardin, G. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee
1996-05-01
Arguments are presented showing that it is natural to interpret the negative mass part of the Kerr solution as representing the geometry experienced by antimatter. The C, P and T discrete transformations are considered for this geometry. The C and T properties of the proposed identification are found to be in agreement with the usual representation of antimatter. In addition, a property of perfect stigmatism through Kerr wormholes which allows general relativity to mimic anti-gravity is conjectured. Kerr wormholes would then act as `super-mirrors` reversing the C, P and T images of an object seen through it. This interpretation is subjected to several experimental tests and able to provide an explanation, without any free parameter, of the `CP`-violation observed in the neutral kaon system. (K.A.). 37 refs.
Motivations for anti-gravity in general relativity
International Nuclear Information System (INIS)
Arguments are presented showing that it is natural to interpret the negative mass part of the Kerr solution as representing the geometry experienced by antimatter. The C, P and T discrete transformations are considered for this geometry. The C and T properties of the proposed identification are found to be in agreement with the usual representation of antimatter. In addition, a property of perfect stigmatism through Kerr wormholes which allows general relativity to mimic anti-gravity is conjectured. Kerr wormholes would then act as 'super-mirrors' reversing the C, P and T images of an object seen through it. This interpretation is subjected to several experimental tests and able to provide an explanation, without any free parameter, of the 'CP'-violation observed in the neutral kaon system. (K.A.)
Marriage of Electromagnetism and Gravity in an Extended Space Model and Astrophysical Phenomena
Andreev, V. A.; Tsipenyuk, D. Yu.
2013-09-01
The generalization of Einstein's special theory of relativity (SRT) is proposed. In this model the possibility of unification of scalar gravity and electromagnetism into a single unified field is considered. Formally, the generalization of the SRT is that instead of (1+3)-dimensional Minkowski space the (1+4)-dimensional extension G is considered. As a fifth additional coordinate the interval S is used. This value is saved under the usual Lorentz transformations in Minkowski space M, but it changes when the transformations in the extended space G are used. We call this model the extended space model (ESM). From a physical point of view our expansion means that processes in which the rest mass of the particles changes are acceptable now. If the rest mass of a particle does not change and the physical quantities do not depend on an additional variable S, then the electromagnetic and gravitational fields exist independently of each other. But if the rest mass is variable and there is a dependence on S, then these two fields are combined into a single unified field. In the extended space model a photon can have a nonzero mass and this mass can be either positive or negative. The gravitational effects such as the speed of escape, gravitational red shift and detection of light can be analyzed in the frame of the extended space model. In this model all these gravitational effects can be found algebraically by the rotations in the (1+4) dimensional space. Now it becomes possible to predict some future results of visible size of supermassive objects in our Universe due to new stage of experimental astronomy development in the RadioAstron Project and analyze phenomena is an explosion of the star V838 Mon.
Anti-evaporation of Schwarzschild–de Sitter black holes in F(R) gravity
International Nuclear Information System (INIS)
We studied the anti-evaporation of a degenerate Schwarzschild–de Sitter black hole (so-called Nariai space-time) in modified F(R) gravity. We analyze the perturbations in the Nariai black hole and find that anti-evaporation may occur in F(R) gravity even at a classical level. For several power-law F(R) gravities which may describe the inflation and/or dark energy eras, we presented the theory parameter bounds for the occurrence of anti-evaporation and conjectured creation of an infinite number of horizons. (paper)
Anti-de Sitter holography for gravity and higher spin theories in two dimensions
Grumiller, Daniel(Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10/136, A-1040, Vienna, Austria); Leston, Mauricio; Vassilevich, Dmitri(CMCC, Universidade Federal do ABC, Santo André, S.P., Brazil)
2013-01-01
We provide a holographic description of two-dimensional dilaton gravity with Anti-de Sitter boundary conditions. We find that the asymptotic symmetry algebra consists of a single copy of the Virasoro algebra with non-vanishing central charge and point out difficulties with the standard canonical treatment. We generalize our results to higher spin theories and thus provide the first examples of two-dimensional higher spin gravity with holographic description. For spin-3 gravity we find that th...
Merkel, A; Tournat, V; Gusev, V
2014-08-01
We report the experimental observation of the gravity-induced asymmetry for the nonlinear transformation of acoustic waves in a noncohesive granular phononic crystal. Because of the gravity, the contact precompression increases with depth inducing space variations of not only the linear and nonlinear elastic moduli but also of the acoustic wave dissipation. We show experimentally and explain theoretically that, in contrast to symmetric propagation of linear waves, the amplitude of the nonlinearly self-demodulated wave depends on whether the propagation of the waves is in the direction of the gravity or in the opposite direction. Among the observed nonlinear processes, we report frequency mixing of the two transverse-rotational modes belonging to the optical band of vibrations and propagating with negative phase velocities, which results in the excitation of a longitudinal wave belonging to the acoustic band of vibrations and propagating with positive phase velocity. We show that the measurements of the gravity-induced asymmetry in the nonlinear acoustic phenomena can be used to compare the in-depth distributions of the contact nonlinearity and of acoustic absorption.
Merkel, A; Tournat, V; Gusev, V
2014-08-01
We report the experimental observation of the gravity-induced asymmetry for the nonlinear transformation of acoustic waves in a noncohesive granular phononic crystal. Because of the gravity, the contact precompression increases with depth inducing space variations of not only the linear and nonlinear elastic moduli but also of the acoustic wave dissipation. We show experimentally and explain theoretically that, in contrast to symmetric propagation of linear waves, the amplitude of the nonlinearly self-demodulated wave depends on whether the propagation of the waves is in the direction of the gravity or in the opposite direction. Among the observed nonlinear processes, we report frequency mixing of the two transverse-rotational modes belonging to the optical band of vibrations and propagating with negative phase velocities, which results in the excitation of a longitudinal wave belonging to the acoustic band of vibrations and propagating with positive phase velocity. We show that the measurements of the gravity-induced asymmetry in the nonlinear acoustic phenomena can be used to compare the in-depth distributions of the contact nonlinearity and of acoustic absorption. PMID:25215842
Anti-Evaporation of Schwarzschild-de Sitter Black Holes in $F(R)$ gravity
Nojiri, Shin'ichi; Odintsov, Sergei D.
2013-01-01
We studied the anti-evaporation of degenerate Schwarzschild-de Sitter black hole (so-called Nariai space-time) in modified $F(R)$ gravity. The analysis of perturbations of the Nariai black hole is done with the conclusion that anti-evaporation may occur in such a theory already on classical level. For several power-law $F(R)$ gravities which may describe the inflation and/or dark energy eras we presented the theory parameters bounds for occurrence of anti-evaporation and conjectured creation ...
Anti-de Sitter gauge theory for gravity
Verwimp, Theo
2010-01-01
First a review is given of Riemann-Cartan space-time and Einstein-Cartan gravity. This gives us the necessary tools to handle the SO(2,3) Yang-Mills gauge theory for gravity. New here is the derivation of the conservation laws. Finally possible solutions of the field equations are discussed. They depend on the scale of the de Sitter length.
(Anti-) de Sitter Electrically Charged Black Hole Solutions in Higher-Derivative Gravity
Lin, Kai; Qian, Wei-Liang; Pavan, A. B.; Abdalla, E.
2016-01-01
In this paper, static electrically charged black hole solutions with cosmological constant are investigated in an Einstein-Hilbert theory of gravity with additional quadratic curvature terms. Beside the analytic Schwarzschild (Anti-) de Sitter solutions, non-Schwarzschild (Anti-) de Sitter solutions are also obtained numerically by employing the shooting method. The results show that there exist two groups of asymptotically (Anti-) de Sitter spacetimes for both charged and uncharged black hol...
Dewitt, Kenneth J.; Brockwell, Jonathan L.; Yung, Chain-Nan; Chai, An-Ti; Mcquillen, John B.; Sotos, Raymond G.; Neumann, Eric S.
1988-01-01
This paper will describe the experimental and analytical work that has been done to establish justification and feasibility for a Shuttle mid-deck experiment involving mass transfer between a gas bubble and a liquid. The experiment involves the observation and measurement of the dissolution of an isolated, immobile gas bubble of specified size and composition in a thermostatted solvent liquid of known concentration in the reduced gravity environment of earth orbit. Methods to generate and deploy the bubble have been successful both in normal gravity using mutually buoyant fluids and under reduced gravity conditions in the NASA Lear Jet. Initialization of the experiment with a bubble of a prescribed size and composition in a liquid of known concentration has been accomplished using the concept of unstable equilibrium. Subsequent bubble dissolution or growth is obtained by a step increase or decrease in the liquid pressure. A numerical model has been developed which simulates the bubble dynamics and can be used to determine molecular parameters by comparison with the experimental data. The primary objective of the experiment is the elimination of convective effects that occur in normal gravity. The results will yield information on transport under conditions of pure diffusion.
The instabilities and (anti)-evaporation of Schwarzschild-de Sitter black holes in modified gravity
L. Sebastiani; Momeni, D.; Myrzakulov, R.; Odintsov, S. D.
2013-01-01
We investigate the future evolution of Nariai black hole which is extremal limit of Schwarzschild-de Sitter one in modified gravity. The perturbations equations around Nariai black hole are derived in static and cosmological patches for general $F(R)$-gravity. The analytical and numerical study of several realistic $F(R)$-models shows the occurence of rich variety of scenarios: instabilities, celebrated Hawking evaporation and anti-evaporation of black hole. The realization of specific scenar...
Massive Higher Derivative Gravity in D-dimensional Anti-de Sitter Spacetimes
Gullu, Ibrahim; Tekin, Bayram(Department of Physics, Middle East Technical University, 06800 Ankara, Turkey)
2009-01-01
We find the propagator and calculate the tree level scattering amplitude between two covariantly conserved sources in an Anti-de Sitter background for the most general D-dimensional quadratic, four-derivative, gravity with a Pauli-Fierz mass. We also calculate the Newtonian potential for various limits of the theory in flat space. We show how the recently introduced three dimensional New Massive Gravity is uniquely singled out among higher derivative models as a (tree level) unitary model and...
Chemical potentials in three-dimensional higher spin anti-de Sitter gravity
Henneaux, Marc(Université Libre de Bruxelles, ULB-Campus Plaine CP231, 1050, Brussels, Belgium); Pérez, Alfredo; Tempo, David; Troncoso, Ricardo(Centro de Estudios Científicos (CECs), Av. Arturo Prat 514, Valdivia, Chile)
2013-01-01
We indicate how to introduce chemical potentials for higher spin charges in higher spin anti-de Sitter gravity in a manner that manifestly preserves the original asymptotic W-symmetry. This is done by switching on a non-vanishing component of the connection along the temporal (thermal) circles. We first recall the procedure in the pure gravity case (no higher spin) where the only "chemical potentials" are the temperature and the chemical potential associated with the angular momentum. We then...
Interface and transport phenomena under reduced gravity. II - Surfaces and wetting
Bewersdorff, A.; Mueller, G.; Oertel, H., Jr.; Sahm, P. R.; Sell, P.-J.; Siekmann, J.
1983-02-01
Liquids contained in propellant tanks under microgravity conditions are subject to reduced gravity forces, surface forces and boundary adhesion. Based on the principle of the minimum of the total potential energy, the basic equations of capillary hydrostatics are derived and the equilibrium configurations of the free fluid surface in rotationally symmetric containers are calculated. Tank geometries for technical purposes are discussed, as well as the role of outgassing of molten matter in materials processing in space. The Hele-Shaw cell is described as a simple and reliable instrument for terrestrial experiments on bubble dynamics under simulated microgravity and temperature gradients. Finally, the wetting kinetics of model tubes under simulated gravity and microgravity is examined.
Transport Phenomena in Stratified Multi-Fluid Flow in the Presence and Absence of Gravity
Chigier, Norman; Humphrey, William
1996-01-01
Experiments are being conducted to study the effects of buoyancy on planar density-stratified shear flows. A wind tunnel generates planar flows separated by an insulating splitter plate, with either flow heated, which emerge from a two-dimensional nozzle. The objective is to isolate and define the effect of gravity and buoyancy on a stratified shear layer. To this end, both stably and unstably stratified layers will be investigated. This paper reports on the results of temperature and velocity measurements across the nozzle exit plane and downstream along the nozzle center plane.
Study on dynamic anti-sliding stability of a high gravity dam considering complex dam foundation
Deng-hong CHEN; Du, Cheng-bin
2011-01-01
There existed some limitations when analyzing the anti-sliding seismic stability of dam-foundation system by traditional pseudo-static method and response spectrum method. The dynamic strength reduction method was used to study on the deep anti-sliding stability of a high gravity dam considering complex dam foundation under strong earthquake-induced ground action. The static analysis was firstly carried out by reducing the shear strength parameters of the dam foundation’s rock mass with equal...
Topological regularization and self-duality in four-dimensional anti-de Sitter gravity
Miskovic, Olivera; Olea, Rodrigo
2009-01-01
It is shown that the addition of a topological invariant (Gauss-Bonnet term) to the anti-de Sitter (AdS) gravity action in four dimensions recovers the standard regularization given by holographic renormalization procedure. This crucial step makes possible the inclusion of an odd parity invariant (Pontryagin term) whose coupling is fixed by demanding an asymptotic (anti) self-dual condition on the Weyl tensor. This argument allows to find the dual point of the theory where the holographic str...
Investigations of the Effects of Altered Vestibular System Function on Hindlimb Anti-Gravity Muscles
Lowery, Mary Sue
1998-01-01
Exposure to different gravitational environments, both the microgravity of spaceflight and the hypergravity of centrifugation, result in altered vestibulo-spinal function which can be reversed by reacclimation to earth gravity (2). Control of orientation, posture, and locomotion are functions of the vestibular system which are altered by changes in gravitational environment. Not only is the vestibular system involved with coordination and proprioception, but the gravity sensing portion of the vestibular system also plays a major role in maintaining muscle tone through projections to spinal cord motoneurons that control anti-gravity muscles. I have been involved with investigations of several aspects of the link between vestibular inputs and muscle morphology and function during my work with Dr. Nancy Daunton this summer and the previous summer. We have prepared a manuscript for submission (4) to Aviation, Space, and Environmental Medicine based on work that I performed last summer in Dr. Daunton's lab. Techniques developed for that project will be utilized in subsequent experiments begun in the summer of 1998. I have been involved with the development of a pilot project to test the effects of vestibular galvanic stimulation (VGS) on anti-gravity muscles and in another project testing the effects of the ototoxic drug streptomycin on the otolith-spinal reflex and anti-gravity muscle morphology.
Exact solutions of dilaton gravity with (anti)-de Sitter asymptotics
Mignemi, S.
2009-01-01
We present a technique for obtaining spherically symmetric, asymptotically (anti)-de Sitter, black hole solutions of dilaton gravity with generic coupling to a Maxwell field, starting from exact asymptotically flat solutions and adding a suitable dilaton potential to the action.
Marriage of Electromagnetism and Gravity in Extended Space Model and Astrophysical Phenomena
Andreev, V A
2013-01-01
The generalization of Einstein's special theory of relativity (SRT) is proposed. In this model the possibility of unification of scalar gravity and electromagnetism into a single united field is considered. Formally, the generalization of the SRT is that instead of (1+3)-dimensional Minkowski space the (1+4)-dimensional extension G is considered. As a fifth additional coordinate the interval S is used. This value is saved under the usual Lorentz transformations in Minkowski space M, but it changes when the transformations in the extended space G are used. We call this model the extended space model (ESM). From a physical point of view our expansion means that processes in which the rest mass of the particles changes are acceptable now. If the rest mass of a particle does not change and the physical quantities do not depend on an additional variable S, then the electromagnetic and gravitational fields exist independently of each other. But if the rest mass is variable and there is a dependence on S, then these...
Instabilities and anti-evaporation of Reissner–Nordström black holes in modified F(R) gravity
International Nuclear Information System (INIS)
We study the instabilities and related anti-evaporation of the extremal Reissner–Nordström (RN) black hole in F(R) gravity. It is remarkable that the effective electric charge can be generated for some solutions of F(R) gravity without electromagnetic field. The anti-evaporation effect occurs but it emerges only in the strong coupling limit of the effective gravitational coupling. The instabilities of RN black hole are also investigated when the electromagnetic sector is added to the action of F(R) gravity. We show the anti-evaporation occurs in the Maxwell-F(R) gravity with the arbitrary gravitational coupling constant although it does not occur in the Maxwell–Einstein gravity. Furthermore, general spherically-symmetric solution of F(R) gravity in the Einstein frame is obtained
Critical gravity as van Dam-Veltman-Zakharov discontinuity in anti de Sitter space
Myung, Yun Soo
2011-01-01
Critical gravity as van Dam-Veltman-Zakharov discontinuity in anti de Sitter spaceWe consider critical gravity as van Dam-Vletman-Zakharov (vDVZ) discontinuity in anti de Sitter space. For this purpose, we introduce the higher curvature gravity. This discontinuity can be confirmed by calculating the residues of relevant poles explicitly. For the non-critical gravity of $0
Critical phenomena of regular black holes in anti-de Sitter space-time
Fan, Zhong-Ying
2016-01-01
In General Relativity coupled to a non-linear electromagnetic field, together with a negative cosmological constant, we obtain the general static spherical symmetric black hole solution with magnetic charges, which is asymptotic to anti-de Sitter (AdS) space-times. In particular, for a degenerate case the solution becomes a Hayward-AdS black hole, which is regular everywhere in the full space-time. The existence of such a regular black hole solution preserves the weak energy condition while the strong energy condition is violated. We then derive the first law and the Smarr formula of the black hole solution. We further discuss its thermodynamic properties and study the critical phenomena in the extended phase space where the cosmological constant is treated as a thermodynamic variable as well as the parameter associated with the non-linear electrodynamics. We obtain many interesting results such as: the Maxwell's equal area law in the $P-V$ (or $S-T$) diagram is violated and consequently the critical point $(...
(Anti-) de Sitter Electrically Charged Black Hole Solutions in Higher-Derivative Gravity
Lin, Kai; Pavan, A B; Abdalla, E
2016-01-01
In this paper, static electrically charged black hole solutions with cosmological constant are investigated in an Einstein-Hilbert theory of gravity with additional quadratic curvature terms. Beside the analytic Schwarzschild (Anti-) de Sitter solutions, non-Schwarzschild (Anti-) de Sitter solutions are also obtained numerically by employing the shooting method. The results show that there exist two groups of asymptotically (Anti-) de Sitter spacetimes for both charged and uncharged black holes. In particular, it was found that for uncharged black holes the first group can be reduced to the Schwarzschild (Anti-) de Sitter solution, while the second group is intrinsically different from a Schwarzschild (Anti-) de Sitter solution even when the charge and the cosmological constant become zero.
(Anti-) de Sitter electrically charged black-hole solutions in higher-derivative gravity
Lin, Kai; Qian, Wei-Liang; Pavan, A. B.; Abdalla, E.
2016-06-01
In this paper, static electrically charged black-hole solutions with cosmological constant are investigated in an Einstein-Hilbert theory of gravity with additional quadratic curvature terms. Beside the analytic Schwarzschild (Anti-) de Sitter solutions, non-Schwarzschild (Anti-) de Sitter solutions are also obtained numerically by employing the shooting method. The results show that there exist two groups of asymptotically (Anti-) de Sitter spacetimes for both charged and uncharged black holes. In particular, it was found that for uncharged black holes the first group can be reduced to the Schwarzschild (Anti-) de Sitter solution, while the second group is intrinsically different from a Schwarzschild (Anti-) de Sitter solution even when the charge and the cosmological constant become zero.
The Asymptotic Dynamics of two-dimensional (anti-)de Sitter Gravity
Brigante, Mauro; Cacciatori, Sergio; Klemm, Dietmar; Zanon, Daniela
2002-01-01
We show that the asymptotic dynamics of two-dimensional de Sitter or anti-de Sitter Jackiw-Teitelboim (JT) gravity is described by a generalized two-particle Calogero-Sutherland model. This correspondence is established by formulating the JT model of (A)dS gravity in two dimensions as a topological gauge theory, which reduces to a nonlinear 0+1-dimensional sigma model on the boundary of (A)dS space. The appearance of cyclic coordinates allows then a further reduction to the Calogero-Sutherlan...
Plebanski-like action for general relativity and anti-self-dual gravity
Celada, Mariano; González, Diego; Montesinos, Merced
2016-05-01
We present a new B F -type action for complex general relativity with or without a cosmological constant resembling Plebanski's action, which depends on an SO (3 ,C ) connection, a set of 2-forms, a symmetric matrix, and a 4-form. However, it differs from the Plebanski formulation in the way that the symmetric matrix enters into the action. The advantage of this fact is twofold. First, as compared to Plebanski's action, the symmetric matrix can now be integrated out, which leads to a pure B F -type action principle for general relativity; the canonical analysis of the new action then shows that it has the same phase space of the Ashtekar formalism up to a canonical transformation induced by a topological term. Second, a particular choice of the parameters involved in the formulation produces a B F -type action principle describing conformally anti-self-dual gravity. Therefore, the new action unifies both general relativity and anti-self-dual gravity.
Stability of anti-de sitter space in Einstein-Gauss-Bonnet gravity.
Deppe, Nils; Kolly, Allison; Frey, Andrew; Kunstatter, Gabor
2015-02-20
Recently it has been argued that in Einstein gravity anti-de Sitter spacetime is unstable against the formation of black holes for a large class of arbitrarily small perturbations. We examine the effects of including a Gauss-Bonnet term. In five dimensions, spherically symmetric Einstein-Gauss-Bonnet gravity has two key features: Choptuik scaling exhibits a radius gap, and the mass function goes to a finite value as the horizon radius vanishes. These suggest that black holes will not form dynamically if the total mass-energy content of the spacetime is too small, thereby restoring the stability of anti-de Sitter spacetime in this context. We support this claim with numerical simulations and uncover a rich structure in horizon radii and formation times as a function of perturbation amplitude. PMID:25763946
Study on dynamic anti-sliding stability of a high gravity dam considering complex dam foundation
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Deng-hong CHEN
2011-06-01
Full Text Available There existed some limitations when analyzing the anti-sliding seismic stability of dam-foundation system by traditional pseudo-static method and response spectrum method. The dynamic strength reduction method was used to study on the deep anti-sliding stability of a high gravity dam considering complex dam foundation under strong earthquake-induced ground action. The static analysis was firstly carried out by reducing the shear strength parameters of the dam foundation’s rock mass with equal proportion. Then, the time-history seismic analysis was carried out based on the static analysis. It was proposed as one of dynamic instability criterions that the peak values of the dynamic displacements and plastic strain energy change suddenly with increasing strength reduction coefficient. The elasto-plastic behavior of the dam foundation was idealized using Drucker–Prager yield criterion based on associated flow rule assumption. Through the static, dynamic strength reduction analysis and dynamic linear elastic analysis of the overflow dam monolith of a high gravity dam, the results’ reliability of elastic-plastic time history analysis was confirmed. The results also showed that the rock mass strength of the high gravity dam foundation has higher strength reserve coefficient. The instability criterions of dynamic strength reduction method proposed were feasible. Although the static anti-slide analysis methods and standards of gravity dam based on the numerical methods are being discussed at present, the dynamic calculation method and instability criterions proposed in this paper would provide some meaningful suggestions for the dynamic analysis of the similar projects.
Reissner–Nordström Anti-de Sitter Black Holes in Mimetic F(R Gravity
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V. K. Oikonomou
2016-05-01
Full Text Available In this paper, we study under which conditions the Reissner–Nordström anti-de Sitter black hole can be a solution of the vacuum mimetic F ( R gravity with Lagrange multiplier and mimetic scalar potential. As the author demonstrates, the resulting picture in the mimetic F ( R gravity case is a trivial extension of the standard F ( R approach, and in effect, the metric perturbations in the mimetic F ( R gravity case, for the Reissner–Nordström anti-de Sitter black hole metric, at the first order of the perturbed variables are the same at the leading order.
Reissner–Nordström Anti-de Sitter Black Holes in Mimetic F(R) Gravity
Oikonomou, V. K.
2016-05-01
In this paper we study under which conditions the Reissner-Nordstr\\"om-anti de Sitter black hole can be a solution of the vacuum mimetic $F(R)$ gravity with Lagrange multiplier and mimetic scalar potential. As we demonstrate, the resulting picture in the mimetic $F(R)$ gravity case, is different in comparison to the ordinary $F(R)$ gravity case, with the two descriptions resulting to a different set of constraints that need to hold true. We also investigate the metric perturbations in the mimetic $F(R)$ gravity case, for the Reissner-Nordstr\\"om-anti de Sitter black hole metric, at first order of the perturbed variables. Interestingly enough, the resulting equations are identical to the ones corresponding to the ordinary $F(R)$ gravity Reissner-Nordstr\\"om-anti de Sitter black hole, at least at first order. We attribute this feature to the particular form of the Reissner-Nordstr\\"om-anti de Sitter metric, and we speculate for which cases there could be differences between the mimetic and non-mimetic case. Since the perturbation equations are the same for the two cases, it is possible to have black hole instabilities in the mimetic $F(R)$ gravity case too, which can be interpreted as anti-evaporation of the black hole.
A note on asymptotically anti-de Sitter quantum spacetimes in loop quantum gravity
Bodendorfer, Norbert
2015-01-01
A framework conceptually based on the conformal techniques employed to study the structure of the gravitational field at infinity is set up in the context of loop quantum gravity to describe asymptotically anti-de Sitter quantum spacetimes. A conformal compactification of the spatial slice is performed, which, in terms of the rescaled metric, has now finite volume, and can thus be conveniently described by spin networks states. The conformal factor used is a physical scalar field, which has the necessary asymptotics for many asymptotically AdS black hole solutions.
(Anti)evaporation of Dyonic Black Holes in string-inspired dilaton $f(R)$-gravity
Addazi, Andrea
2016-01-01
We discuss dyonic black hole solutions in the case of $f(R)$-gravity coupled with a dilaton and two gauge bosons. The study of such a model is highly motivated from string theory. Our Black Hole solutions are extensions of the one firstly studied by Kallosh, Linde, Ort\\'in, Peet and Van Proyen (KLOPV) in [arXiv:hep-th/9205027]. We will show that extreme solutions are unstable. In particular, these solutions have Bousso-Hawking-Nojiri-Odintsov (anti)evaporation instabilities.
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
Effect of temperature gradient on heavy quark anti-quark potential using gravity dual model
Ganesh, S
2016-01-01
The Quark-gluon plasma (QGP) is an expanding fireball, with finite dimensions. Given the finite dimensions, the temperature would be highest at the center, and close to the critical temperature, $T_c$, at the boundary, giving rise to a temperature gradient inside the QGP. A heavy quark anti-quark pair immersed in the QGP medium would see this temperature gradient. The effect of the temperature gradient on the quark anti-quark potential is analyzed using a gravity dual model. The resulting modification to the potential due to the temperature gradient is seen to have a $L^{-2}$ correction term. This could be a possible fallout of the breaking of conformal invariance at finite temperature.
Vogel, S N; Havell, E A
1990-01-01
Tumor necrosis factor alpha (TNF alpha) has been implicated as a major mediator of lipopolysaccharide (LPS)-induced phenomena. Administration to mice of a polyclonal, monospecific antibody prepared against recombinant murine TNF alpha abolished detection of LPS-induced TNF alpha activity and significantly reduced levels of LPS-induced colony-stimulating factor but failed to reduce the production of LPS-induced interferon, corticosterone, or LPS-induced hypoglycemia.
Plebanski-like action for general relativity and anti-self-dual gravity
Celada, Mariano; Montesinos, Merced
2016-01-01
We present a new $BF$-type action for complex general relativity with or without a cosmological constant resembling Plebanski's action, which depends on an SO(3,$\\mathbb{C}$) connection, a set of 2-forms, a symmetric matrix, and a 4-form. However, it differs from the Plebanski formulation in the way that the symmetric matrix enters into the action. The advantage of this fact is twofold. First, as compared to Plebanski's action, the symmetric matrix can now be integrated out, which leads to a pure $BF$-type action principle for general relativity; the canonical analysis of the new action then shows that it has the same phase space of the Ashtekar formalism up to a canonical transformation induced by a topological term. Second, a particular choice of the parameters involved in the formulation produces a $BF$-type action principle describing conformally anti-self-dual gravity. Therefore, the new action unifies both general relativity and anti-self-dual gravity.
Berthelsen, Martin Peter; Husu, Edith; Christensen, Sofie Bouschinger; Prahm, Kira Philipsen; Vissing, John; Jensen, Bente Rona
2014-06-01
Recent studies in patients with muscular dystrophies suggest positive effects of aerobic and strength training. These studies focused training on using bicycle ergometers and conventional strength training, which precludes more severely affected patients from participating, because of their weakness. We investigated the functional effects of combined aerobic and strength training in patients with Becker and limb-girdle muscular dystrophies with knee muscle strength levels as low as 3% of normal strength. Eight patients performed 10 weeks of aerobic and strength training on an anti-gravity treadmill, which offered weight support up to 80% of their body weight. Six minute walking distance, dynamic postural balance, and plasma creatine kinase were assessed 10 weeks prior to training, immediately before training and after 10 weeks of training. Training elicited an improvement of walking distance by 8±2% and dynamic postural balance by 13±4%, indicating an improved physical function. Plasma creatine kinase remained unchanged. These results provide evidence that a combination of aerobic and strength training during anti-gravity has the potential to safely improve functional ability in severely affected patients with Becker and limb-girdle muscular dystrophies. PMID:24684860
Reissner–Nordström Anti-de Sitter Black Holes in Mimetic F(R) Gravity
Oikonomou, V.K.
2016-01-01
In this paper we study under which conditions the Reissner-Nordstr\\"om-anti de Sitter black hole can be a solution of the vacuum mimetic $F(R)$ gravity with Lagrange multiplier and mimetic scalar potential. As we demonstrate, the resulting picture in the mimetic $F(R)$ gravity case, is different in comparison to the ordinary $F(R)$ gravity case, with the two descriptions resulting to a different set of constraints that need to hold true. We also investigate the metric perturbations in the mim...
Henneaux, Marc(Université Libre de Bruxelles, ULB-Campus Plaine CP231, 1050, Brussels, Belgium); Rey, Soo-Jong
2010-01-01
We investigate the asymptotic symmetry algebra of (2+1)-dimensional higher spin, anti-de Sitter gravity. We use the formulation of the theory as a Chern-Simons gauge theory based on the higher spin algebra hs(1,1). Expanding the gauge connection around asymptotically anti-de Sitter spacetime, we specify consistent boundary conditions on the higher spin gauge fields. We then study residual gauge transformation, the corresponding surface terms and their Poisson bracket algebra. We find that the...
Experimental constraints on anti-gravity and antimatter, in the context of dark energy
Ting, Yuan-Sen
2013-01-01
In a paper by Villata (2011), the possibility of a repulsive gravitational interaction between antimatter and ordinary matter was discussed. The author argued that this anti-gravity can be regarded as a prediction of general relativity, under the assumption of CPT symmetry. Stringent experimental constraints have been established against such a suggestion. The measurement of free-fall accelerations of various nuclei by the Eot-Wash group and searches for equivalence principle violation through the gravitational splitting in kaon physics consistently establish null results on any difference between the gravitational behaviour of antimatter and ordinary matter. The original arguments against antigravity were questioned by Nieto & Goldman (1991). In the light of new experiments as well as theoretical developments in the past 20 years, some of Nieto & Goldman's concerns have been addressed. While a precise measurement of the free-fall acceleration of antihydrogen will eventually lay this issue to rest, th...
Rehabilitation Exercises to Induce Balanced Scapular Muscle Activity in an Anti-gravity Posture.
Ishigaki, Tomonobu; Yamanaka, Masanori; Hirokawa, Motoki; Tai, Keita; Ezawa, Yuya; Samukawa, Mina; Tohyama, Harukazu; Sugawara, Makoto
2014-12-01
[Purpose] The purpose of this study was to compare the intramuscular balance ratios of the upper trapezius muscle (UT) and the lower trapezius muscle (LT), and the intermuscular balance ratios of the UT and the serratus anterior muscle (SA) among prone extension (ProExt), prone horizontal abduction with external rotation (ProHAbd), forward flexion in the side-lying position (SideFlex), side-lying external rotation (SideEr), shoulder flexion with glenohumeral horizontal abduction load (FlexBand), and shoulder flexion with glenohumeral horizontal adduction load (FlexBall) in the standing posture. [Methods] The electromyographic (EMG) activities of the UT, LT and SA were measured during the tasks. The percentage of maximum voluntary isometric contraction (%MVIC) was calculated for each muscle, and the UT/LT ratios and the UT/SA ratios were compared among the tasks. [Results] The UT/LT ratio with the FlexBand was not significantly different from those of the four exercises in the side-lying and prone postures. The UT/SA ratio with the FlexBall demonstrated appropriate balanced activity. [Conclusion] In an anti-gravity posture, we recommend the FlexBand and the FlexBall for inducing balanced UT/LT and UT/SA ratios, respectively. PMID:25540485
Balance control and anti-gravity muscle activity during the experience of fear at heights.
Wuehr, Max; Kugler, Guenter; Schniepp, Roman; Eckl, Maria; Pradhan, Cauchy; Jahn, Klaus; Huppert, Doreen; Brandt, Thomas
2014-02-01
Fear of heights occurs when a visual stimulus causes the apprehension of losing balance and falling. A moderate form of visual height intolerance (vHI) affects about one third of the general population and has relevant consequences for the quality of life. A quantitative evaluation of balance mechanisms in persons susceptible to vHI during height exposure is missing. VHI-related changes in postural control were assessed by center-of-pressure displacements and electromyographic recordings of selected leg, arm, and neck muscles in 16 subjects with vHI while standing at heights on an emergency balcony versus standing in the laboratory at ground level. Characteristics of open- and closed-loop postural control were analyzed. Body sway and muscle activity parameters were correlated with the subjective estimates of fear at heights. During height exposure, (1) open-loop control was disturbed by a higher diffusion activity (P anti-gravity leg and neck muscles, both of which depend on the severity of evoked fear at heights. PMID:24744901
Rainbow valley of colored (anti) de Sitter gravity in three dimensions
Gwak, Seungho; Joung, Euihun; Mkrtchyan, Karapet; Rey, Soo-Jong
2016-04-01
We propose a theory of three-dimensional (anti) de Sitter gravity carrying Chan-Paton color charges. We define the theory by Chern-Simons formulation with the gauge algebra (gl_2oplus gl_2)⊗ u(N) , obtaining a color-decorated version of interacting spin-one and spin-two fields. We also describe the theory in metric formulation and show that, among N 2 massless spin-two fields, only the singlet one plays the role of metric graviton whereas the rest behave as colored spinning matter that strongly interacts at large N. Remarkably, these colored spinning matter acts as Higgs field and generates a non-trivial potential of staircase shape. At each extremum labelled by k=0,dots, [N-1/2] , the u(N) color gauge symmetry is spontaneously broken down to u(N-k)oplus u(k) and provides different (A)dS backgrounds with the cosmological constants {(N/N-2k)}^2Λ . When this symmetry breaking takes place, the spin-two Goldstone modes combine with (or are eaten by) the spin-one gauge fields to become partially-massless spin-two fields. We discuss various aspects of this theory and highlight physical implications.
Rainbow Valley of Colored (Anti) de Sitter Gravity in Three Dimensions
Gwak, Seungho; Mkrtchyan, Karapet; Rey, Soo-Jong
2015-01-01
We propose a theory of three-dimensional (anti) de Sitter gravity carrying Chan-Paton color charges. We define the theory by Chern-Simons formulation with the gauge algebra (gl(2) + gl(2)) times u(N), obtaining a color-decorated version of interacting spin-one and spin-two fields. We also describe the theory in metric formulation and show that, among N times N massless spin-two fields, only the singlet one plays the role of metric graviton whereas the rest behave as "colored spinning matter" that strongly interacts at large N.Remarkably, these colored spinning matter generates a non-trivial potential of staircase shape. At each extremum labelled by k = 0,...., [(N-1)/2], the u(N) color gauge symmetry is spontaneously broken down to u(N-k)+u(k) and provides different (A)dS(3) backgrounds with the effective cosmological constants (N/(N-2k))^2 Lambda.When this gauge symmetry breaking takes place, the spin-two Goldstone modes combine with (or are eaten by) the spin-one gauge fields to become partially massless sp...
Oxygen consumption of elite distance runners on an anti-gravity treadmill®.
McNeill, David K P; Kline, John R; de Heer, Hendrick D; Coast, J Richard
2015-06-01
Lower body positive pressure (LBPP), or 'anti-gravity' treadmills® have become increasingly popular among elite distance runners. However, to date, few studies have assessed the effect of body weight support (BWS) on the metabolic cost of running among elite runners. This study evaluated how BWS influenced the relationship between velocity and metabolic cost among 6 elite male distance runners. Participants ran three- 16 minute tests consisting of 4 stages of 4 minutes at 8, 7, 6 and 5 min·mile(-1) pace (3.35, 3.84, 4.47 and 5.36 m·s(-1)), while maintaining an aerobic effort (Respiratory Exchange Ratio ≤1.00). One test was run on a regular treadmill, one on an anti-gravity treadmill with 40% BWS and one with 20% BWS being provided. Expired gas data were collected and regression equations used to determine and compare slopes. Significant decreases in oxygen uptake (V̇O2) were found with each increase in BWS (p < 0.001). At 20% BWS, the average decrease in net VO2 was greater than proportional (34%), while at 40% BWS, the average net reduction in VO2 was close to proportional (38%). Across velocities, the slope of the relationship between VO2 and velocity (ΔV̇O2/Δv) was steeper with less support. The slopes at both the 20% and 40% BWS conditions were similar, especially when compared to the regular treadmill. Variability in VO2 between athletes was much greater on the LBPP treadmill and was greater with increased levels of BWS. In this study we evaluated the effect of body weight support on V̇O2 among elite distance runners. We have shown that oxygen uptake decreased with support, but not in direct proportion to that support. Further, because of the high variability in oxygen uptake between athletes on the LBPP treadmill, prediction equations may not be reliable and other indicators (heart rate, perceived exertion or directly measured oxygen uptake) should be used to guide training intensity when training on the LBPP treadmill. Key pointsWith increasing
Oxygen Consumption of Elite Distance Runners on an Anti-Gravity Treadmill®
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David K.P. McNeill, John R. Kline, Hendrick D. de Heer, J. Richard Coast
2015-06-01
Full Text Available Lower body positive pressure (LBPP, or ‘anti-gravity’ treadmills® have become increasingly popular among elite distance runners. However, to date, few studies have assessed the effect of body weight support (BWS on the metabolic cost of running among elite runners. This study evaluated how BWS influenced the relationship between velocity and metabolic cost among 6 elite male distance runners. Participants ran three- 16 minute tests consisting of 4 stages of 4 minutes at 8, 7, 6 and 5 min·mile−1 pace (3.35, 3.84, 4.47 and 5.36 m·s−1, while maintaining an aerobic effort (Respiratory Exchange Ratio ≤1.00. One test was run on a regular treadmill, one on an anti-gravity treadmill with 40% BWS and one with 20% BWS being provided. Expired gas data were collected and regression equations used to determine and compare slopes. Significant decreases in oxygen uptake (V̇O2 were found with each increase in BWS (p < 0.001. At 20% BWS, the average decrease in net VO2 was greater than proportional (34%, while at 40% BWS, the average net reduction in VO2 was close to proportional (38%. Across velocities, the slope of the relationship between VO2 and velocity (ΔV̇O2/Δv was steeper with less support. The slopes at both the 20% and 40% BWS conditions were similar, especially when compared to the regular treadmill. Variability in VO2 between athletes was much greater on the LBPP treadmill and was greater with increased levels of BWS. In this study we evaluated the effect of body weight support on V̇O2 among elite distance runners. We have shown that oxygen uptake decreased with support, but not in direct proportion to that support. Further, because of the high variability in oxygen uptake between athletes on the LBPP treadmill, prediction equations may not be reliable and other indicators (heart rate, perceived exertion or directly measured oxygen uptake should be used to guide training intensity when training on the LBPP treadmill.
Li, Ran; Zhao, Jun-Kun
2016-04-01
We investigate the massive vector particles' Hawking radiation from the neutral rotating Anti-de Sitter (AdS) black holes in conformal gravity by using the tunneling method. It is well known that the dynamics of massive vector particles are governed by the Proca field equation. Applying WKB approximation to the Proca equation, the tunneling probabilities and radiation spectrums of the emitted particles are derived. Hawking temperature of the neutral rotating AdS black holes in conformal gravity is recovered, which is consistent with the previous result in the literature. Supported by the National Natural Science Foundation of China under Grant No. 11205048, and the Foundation for Young Key Teacher of Henan Normal University
Prasia, P
2016-01-01
In this work we study the Quasi Normal Modes(QNMs) under massless scalar perturbations and the thermodynamics of linearly charged BTZ black holes in massive gravity in the (Anti)de Sitter((A)dS) space time. It is found that the behavior of QNMs changes with the massive parameter and also with the charge of the black hole. The thermodynamics of such black holes in the (A)dS space time is also analyzed in detail. The behavior of specific heat with temperature for such black holes gives an indication of a phase transition that depends on the massive parameter and also on the charge of the black hole.
Bugbee, William D; Pulido, Pamela A; Goldberg, Timothy; D'Lima, Darryl D
2016-01-01
The objective was to determine the safety, feasibility, and effects of anti-gravity gait training on functional outcomes (Knee Injury and Osteoarthritis Outcome Score [KOOS], the Timed Up and Go test [TUG], Numerical Rating Scale [NRS] for pain) with the AlterG® Anti-Gravity Treadmill® device for total knee arthroplasty (TKA) rehabilitation. Subjects (N = 30) were randomized to land-based vs anti-gravity gait training over 4 weeks of physical therapy after TKA. Adverse events, complications, and therapist satisfaction were recorded. All patients completed rehabilitation protocols without adverse events. KOOS, TUG, and NRS scores improved in both groups with no significant differences between groups. For the AlterG group, Sports/Recreation and Quality of Life subscales of the KOOS had the most improvement. At the end of physical therapy, TUG and NRS pain scores improved from 14 seconds to 8 seconds and from 2.8 to 1.1, respectively. Subjectively, therapists reported 100% satisfaction with the AlterG. This initial pilot study demonstrated that the AlterG Anti-Gravity Treadmill device was safe and feasible. While functional outcomes improved over time with use of the anti-gravity gait training, further studies are needed to define the role of this device as an alternative or adjunct to established rehabilitation protocols. PMID:27327921
On a canonical quantization of 3D Anti de Sitter pure gravity
Kim, Jihun; Porrati, Massimo
2015-10-01
We perform a canonical quantization of pure gravity on AdS 3 using as a technical tool its equivalence at the classical level with a Chern-Simons theory with gauge group SL(2,{R})× SL(2,{R}) . We first quantize the theory canonically on an asymptotically AdS space -which is topologically the real line times a Riemann surface with one connected boundary. Using the "constrain first" approach we reduce canonical quantization to quantization of orbits of the Virasoro group and Kähler quantization of Teichmüller space. After explicitly computing the Kähler form for the torus with one boundary component and after extending that result to higher genus, we recover known results, such as that wave functions of SL(2,{R}) Chern-Simons theory are conformal blocks. We find new restrictions on the Hilbert space of pure gravity by imposing invariance under large diffeomorphisms and normalizability of the wave function. The Hilbert space of pure gravity is shown to be the target space of Conformal Field Theories with continuous spectrum and a lower bound on operator dimensions. A projection defined by topology changing amplitudes in Euclidean gravity is proposed. It defines an invariant subspace that allows for a dual interpretation in terms of a Liouville CFT. Problems and features of the CFT dual are assessed and a new definition of the Hilbert space, exempt from those problems, is proposed in the case of highly-curved AdS 3.
Einstein Gravity from Conformal Gravity
Maldacena, Juan
2011-01-01
We show that that four dimensional conformal gravity plus a simple Neumann boundary condition can be used to get the semiclassical (or tree level) wavefunction of the universe of four dimensional asymptotically de-Sitter or Euclidean anti-de Sitter spacetimes. This simple Neumann boundary condition selects the Einstein solution out of the more numerous solutions of conformal gravity. It thus removes the ghosts of conformal gravity from this computation. In the case of a five dimensional pure ...
On a Canonical Quantization of 3D Anti de Sitter Pure Gravity
Kim, Jihun
2015-01-01
We perform a canonical quantization of pure gravity on AdS3 using as a technical tool its equivalence at the classical level with a Chern-Simons theory with gauge group SL(2,R)xSL(2,R). We first quantize the theory canonically on an asymptotically AdS space --which is topologically the real line times a Riemann surface with one connected boundary. Using the "constrain first" approach we reduce canonical quantization to quantization of orbits of the Virasoro group and Kaehler quantization of Teichmuller space. After explicitly computing the Kaehler form for the torus with one boundary component and after extending that result to higher genus, we recover known results, such as that wave functions of SL(2,R) Chern-Simons theory are conformal blocks. We find new restrictions on the Hilbert space of pure gravity by imposing invariance under large diffeomorphisms and normalizability of the wave function. The Hilbert space of pure gravity is shown to be the target space of Conformal Field Theories with continuous sp...
Applications of gauge/gravity dualities with charged Anti-de Sitter black holes
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Grass, Viviane Theresa
2010-05-17
In this thesis, we deal with different applications of the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence. The AdS/CFT correspondence, which is also more generally referred to as gauge/gravity duality, is a conjectured duality in superstring theory between strongly-coupled four-dimensional N=4 superconformal Yang-Mills theory and weakly-coupled type IIB string theory in five-dimensional AdS spacetime. This duality provides a powerful method to investigate strongly-coupled low-energy systems in four dimensions by substitutionally carrying out calculations in five-dimensional weakly-coupled supergravity. In this work, we use the AdS/CFT correspondence to explore three different strongly-coupled systems, namely a brane world accommodating a strongly-coupled field theory, a strongly-coupled fluid on a three-sphere and a strongly-coupled p-wave superfluid. In all these cases, the dual supergravity descriptions involve charged AdS black holes. The first system studied here is a Randall-Sundrum brane world moving in the background of a five-dimensional non-extremal black hole of N=2 gauged supergravity. The equations of motion of the brane are found to be equal to the Friedmann-Robertson-Walker (FRW) equations for a closed universe. The closed brane universe has special thermodynamic properties. The energy of the brane field theory exhibits a subextensive Casimir contribution, and the entropy can be expressed as a Cardy-Verlinde-type formula. We show that the equations for both quantities can take forms that strongly resemble the two FRW equations. At the horizon of the black hole, these two sets of equations are shown to even merge with each other which might suggest the existence of a common underlying theory. In addition, as a by-product result, the non-extremal black hole solutions considered here are found to admit an alternative description in terms of first-order flow equations similar to those which are well-known from the attractor mechanism of
Applications of gauge/gravity dualities with charged Anti-de Sitter black holes
International Nuclear Information System (INIS)
In this thesis, we deal with different applications of the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence. The AdS/CFT correspondence, which is also more generally referred to as gauge/gravity duality, is a conjectured duality in superstring theory between strongly-coupled four-dimensional N=4 superconformal Yang-Mills theory and weakly-coupled type IIB string theory in five-dimensional AdS spacetime. This duality provides a powerful method to investigate strongly-coupled low-energy systems in four dimensions by substitutionally carrying out calculations in five-dimensional weakly-coupled supergravity. In this work, we use the AdS/CFT correspondence to explore three different strongly-coupled systems, namely a brane world accommodating a strongly-coupled field theory, a strongly-coupled fluid on a three-sphere and a strongly-coupled p-wave superfluid. In all these cases, the dual supergravity descriptions involve charged AdS black holes. The first system studied here is a Randall-Sundrum brane world moving in the background of a five-dimensional non-extremal black hole of N=2 gauged supergravity. The equations of motion of the brane are found to be equal to the Friedmann-Robertson-Walker (FRW) equations for a closed universe. The closed brane universe has special thermodynamic properties. The energy of the brane field theory exhibits a subextensive Casimir contribution, and the entropy can be expressed as a Cardy-Verlinde-type formula. We show that the equations for both quantities can take forms that strongly resemble the two FRW equations. At the horizon of the black hole, these two sets of equations are shown to even merge with each other which might suggest the existence of a common underlying theory. In addition, as a by-product result, the non-extremal black hole solutions considered here are found to admit an alternative description in terms of first-order flow equations similar to those which are well-known from the attractor mechanism of
Lin, Kai; Pavan, A B
2016-01-01
In this paper, we investigate the scalar quasinormal modes of Ho\\v{r}ava-Lifshitz theory with $U(1)$ symmetry in static Anti-de Sitter spacetime. The static planar and spherical black hole solutions in lower energy limit are derived in non-projectable Ho\\v{r}ava-Lifshitz gravity. The equation of motion of a scalar field is obtained, and is utilized to study the quasinormal modes of massless scalar particles. We find that the effect of Ho\\v{r}ava-Lifshitz correction is to increase the quasinormal period as well as to slow down the decay of the oscillation magnitude. Besides, the scalar field could be unstable when the correction becomes too large.
DEFF Research Database (Denmark)
Malling, Anne Sofie Bøgh; Jensen, Bente Rona
2016-01-01
Recent studies indicate that the effect of training on motor performance in persons with Parkinson's disease (PDP) is dependent on motor intensity. However, training of high motor intensity can be hard to apply in PDP due to e.g. bradykinesia, rigidity, tremor and postural instability. Therefore......, the aim was to study the effect of motor intensive training performed in a safe anti-gravity environment using lower-body positive pressure (LBPP) technology on performance during dynamic balance related tasks. Thirteen male PDP went through an 8-week control period followed by 8 weeks of motor intensive...... antigravity training. Seventeen healthy males constituted a control group (CON). Performance during a five repetition sit-to-stand test (STS; sagittal plane) and a dynamic postural balance test (DPB; transversal plane) was evaluated. Effect measures were completion time, functional rates of force development...
Asymptotically warped anti-de Sitter spacetimes in topologically massive gravity
International Nuclear Information System (INIS)
Asymptotically warped AdS spacetimes in topologically massive gravity with negative cosmological constant are considered in the case of spacelike stretched warping, where black holes have been shown to exist. We provide a set of asymptotic conditions that accommodate solutions in which the local degree of freedom (the ''massive graviton'') is switched on. An exact solution with this property is explicitly exhibited and possesses a slower falloff than the warped AdS black hole. The boundary conditions are invariant under the semidirect product of the Virasoro algebra with a u(1) current algebra. We show that the canonical generators are integrable and finite. When the graviton is not excited, our analysis is compared and contrasted with earlier results obtained through the covariant approach to conserved charges. In particular, we find agreement with the conserved charges of the warped AdS black holes as well as with the central charges in the algebra.
DEFF Research Database (Denmark)
Berthelsen, Martin Peter; Husu, Edith; Christensen, Sofie Bouschinger;
2014-01-01
of their weakness. We investigated the functional effects of combined aerobic and strength training in patients with Becker and limb-girdle muscular dystrophies with knee muscle strength levels as low as 3% of normal strength. Eight patients performed 10weeks of aerobic and strength training on an anti...... affected patients with Becker and limb-girdle muscular dystrophies.......Recent studies in patients with muscular dystrophies suggest positive effects of aerobic and strength training. These studies focused training on using bicycle ergometers and conventional strength training, which precludes more severely affected patients from participating, because...
Is nonrelativistic gravity possible?
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 Eins...
Malling, Anne Sofie B; Jensen, Bente R
2016-01-01
Recent studies indicate that the effect of training on motor performance in persons with Parkinson's disease (PDP) is dependent on motor intensity. However, training of high motor intensity can be hard to apply in PDP due to e.g. bradykinesia, rigidity, tremor and postural instability. Therefore, the aim was to study the effect of motor intensive training performed in a safe anti-gravity environment using lower-body positive pressure (LBPP) technology on performance during dynamic balance related tasks. Thirteen male PDP went through an 8-week control period followed by 8 weeks of motor intensive antigravity training. Seventeen healthy males constituted a control group (CON). Performance during a five repetition sit-to-stand test (STS; sagittal plane) and a dynamic postural balance test (DPB; transversal plane) was evaluated. Effect measures were completion time, functional rates of force development, directional changes and force variance. STS completion time improved by 24% to the level of CON which was explained by shorter sitting-time and standing-time and larger numeric rate of force change during lowering to the chair, indicating faster vertical directional change and improved relaxation. DPB completion time tended to improve and was accompanied by improvements of functional medial and lateral rates of force development and higher vertical force variance during DPB. Our results suggest that the performance improvements may relate to improved inter-limb coordination. It is concluded that 8 weeks of motor intensive training in a safe LBPP environment improved performance during dynamic balance related tasks in PDP.
Quantum Gravity Inde Sitter Space And Anti-de Sitter Space
Lippert, M S
2004-01-01
In this thesis, we consider two aspects of quantum gravity—the nature of holography in anti-de Sitter space and string theory models of de Sitter space. Searching for a holographic resolution of the black hole information paradox, we pursue the identity of precursors in the context of AdS/CFT. We consider precursors that encode bulk information causally disconnected from the boundary and whose measurement involves nonlocal bulk processes. Previous arguments that these precursors are large, undecorated Wilson loops are found to be flawed. We construct a toy model of holography which encapsulates the expected properties of precursors and compare it with previous such discussions. The information contained in precursors is argued to be encoded in the high-energy sector of the theory and not observable by low-energy measurements. These considerations lead us to propose a locality bound, which indicates where locality breaks down due to black hole or stringy effects. We apply the locality bound to Hawkin...
Nakamura, K.
Bose-Einstein condensate(BEC) provides a nice stage when the nonlinearSchrödinger equation plays a vital role. We study the dynamics of multi-component repulsive BEC in 2 dimensions with harmonic traps by using the nonlinear Schrödinger (or Gross-Pitaevskii) equation. Firstly we consider a driven two-component BEC with each component trapped in different vertical positions. The appropriate tuning of the oscillation frequency of the magnetic field leads to a striking anti-gravity transport of BEC. This phenomenon is a manifestation of macroscopic non-adiabatic tunneling in a system with two internal(electronic) degrees of freedom. The dynamics splits into a fast complex spatio-temporal oscillation of each condensate wavefunctions together with a slow levitation of the total center of mass. Secondly, we examine the three-component repulsive BEC in 2 dimensions in a harmonic trap in the absence of magnetic field, and construct a model of conservative chaos based on a picture of vortex molecules. We obtain an effective nonlinear dynamics for three vortex cores, which represents three charged particles under the uniform magnetic field with the repulsive inter-particle potential quadratic in the inter-vortex distance r_{ij} on short scale and logarithmic in r_{ij} on large scale. The vortices here acquire the inertia in marked contrast to the standard theory of point vortices since Onsager. We then explore ``the chaos in the three-body problem" in the context of vortices with inertia.
Malling, Anne Sofie B; Jensen, Bente R
2016-01-01
Recent studies indicate that the effect of training on motor performance in persons with Parkinson's disease (PDP) is dependent on motor intensity. However, training of high motor intensity can be hard to apply in PDP due to e.g. bradykinesia, rigidity, tremor and postural instability. Therefore, the aim was to study the effect of motor intensive training performed in a safe anti-gravity environment using lower-body positive pressure (LBPP) technology on performance during dynamic balance related tasks. Thirteen male PDP went through an 8-week control period followed by 8 weeks of motor intensive antigravity training. Seventeen healthy males constituted a control group (CON). Performance during a five repetition sit-to-stand test (STS; sagittal plane) and a dynamic postural balance test (DPB; transversal plane) was evaluated. Effect measures were completion time, functional rates of force development, directional changes and force variance. STS completion time improved by 24% to the level of CON which was explained by shorter sitting-time and standing-time and larger numeric rate of force change during lowering to the chair, indicating faster vertical directional change and improved relaxation. DPB completion time tended to improve and was accompanied by improvements of functional medial and lateral rates of force development and higher vertical force variance during DPB. Our results suggest that the performance improvements may relate to improved inter-limb coordination. It is concluded that 8 weeks of motor intensive training in a safe LBPP environment improved performance during dynamic balance related tasks in PDP. PMID:26444077
Black Hole Critical Phenomena Without Black Holes
Liebling, S L
2000-01-01
Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I briefly review critical phenomena, discuss some recent results, and describe a model which demonstrates similar phenomena without gravity.
Directory of Open Access Journals (Sweden)
Rabounski D.
2007-07-01
Full Text Available We consider the Podkletnov effect — the weight loss of an object located over a superconducting disc in air due to support by an alternating magnetic field. We consider this problem using the mathematical methods of General Relativity. We show via Einstein’s equations and the geodesic equations in a space perturbed by a disc undergoing oscillatory bounces orthogonal to its own plane, that there is no r ˆ ole of superconductivity; the Podkletnov effect is due to the fact that the field of the background space non-holonomity (the basic non-othogonality of time lines to the spatial section, being perturbed by such an oscillating disc produces energy and momentum flow in order to compensate the perturbation in itself. Such a momentum flow is directed above the disc in Podkletnov’s experiment, so it works like negative gravity (anti-gravity. We propose a simple mechanical system which, simulating the Podkletnov effect, is an experimental test of the whole theory. The theory allows for other “anti-gravity devices”, which simulate the Podkletnov effect without use of very costly superconductor technology. Such devices could be applied to be used as a cheap source of new energy, and could have implications to air and space travel.
一种提高重力坝抗震性能的方法%Method to improve anti-seismic performance of gravity dams
Institute of Scientific and Technical Information of China (English)
周星德; 章青; 吴继敏; 刘谦敏; 刘广波; 石星星
2011-01-01
针对我国大坝多建于高烈度地震区、坝基中存在软弱结构面和缓倾角裂隙等现象,以某重力坝为研究对象,探讨了在大坝坝底铺设铅加球墨铸铁对坝体动力反应及动力深层抗滑稳定性的影响.计算结果表明,坝底铺设铅加球墨铸铁可有效降低坝体动力反应,提高重力坝动力深层抗滑稳定性,这为提高大坝抗震性能提供了一种新的途径.%Aimed at the phenomenon of China's dams mostly built on high intensity earthquake areas with weak structural surfaces and low-inclined cracks in the dam foundation, the influences of laying lead and nodular cast iron at the dam bottom on its dynamic responses and dynamic deep anti-slide stability were investigated by taking a gravity dam as an example. The results show that laying lead and nodular cast iron at the dam bottom can effectively reduce its dynamic responses and enhance its deep anti-slide stability. It may provide a new approach for raising the anti-seismic performance of gravity dams.
Loop Quantization of a Model for D=1+2 (Anti)de Sitter Gravity Coupled to Topological Matter
Constantinidis, Clisthenis P.; Oporto, Zui; Piguet, Olivier
2014-01-01
We present a complete quantization of Lorentzian D=1+2 gravity with cosmological constant, coupled to a set of topological matter fields. The approach of Loop Quantum Gravity is used thanks to a partial gauge fixing leaving a residual gauge invariance under a compact semi-simple gauge group, namely Spin(4) = SU(2) x SU(2). A pair of quantum observables is constructed, which are non-trivial despite of being null at the classical level.
Loop quantum gravity and observations
Barrau, A
2014-01-01
Quantum gravity has long been thought to be completely decoupled from experiments or observations. Although it is true that smoking guns are still missing, there are now serious hopes that quantum gravity phenomena might be tested. We review here some possible ways to observe loop quantum gravity effects either in the framework of cosmology or in astroparticle physics.
Industrial processes influenced by gravity
Ostrach, Simon
1988-01-01
In considering new directions for low gravity research with particular regard to broadening the number and types of industrial involvements, it is noted that transport phenomena play a vital role in diverse processes in the chemical, pharmaceutical, food, and biotech industries. Relatively little attention has been given to the role of gravity in such processes. Accordingly, numerous industrial processes and phenomena are identified which involve gravity and/or surface tension forces. Phase separations and mixing are examples that will be significantly different in low gravity conditions. A basis is presented for expanding the scope of the low gravity research program and the potential benefits of such research is indicated.
重力坝抗滑稳定的研究方法概述%Research on Anti Sliding Stability of Gravity Dams
Institute of Scientific and Technical Information of China (English)
赵军亮
2013-01-01
Gravity instability problems almost al because of there is not a detailed understanding of ground engineering ge-ological conditions in the early, which overlooked the weak in-terlayer in the foundation of existence and eventual y leads to the emergence of various engineering problems. This paper by analyzing the methods of gravity dams anti sliding stability m-akes a comparison of the advantages and disadvantages of var-ious methods, thus clearly gets the stability analysis of gravity dam against sliding, and provides the reference for the constru-ction of project.%重力坝失稳问题的产生几乎全部是因为在工程勘测的前期对地质地况没有进行详细的了解，以致忽视了坝基中存在的软弱夹层，最终导致了各种工程问题的产生。本文通过总结重力坝抗滑稳定的分析方法，比对各种方法的优缺点，从而清晰地得出重力坝抗滑稳定分析的趋势，为工程的建设提供了借鉴意义。
Symmetries of Quantum Nonsymmetric Gravity
Mebarki, N; Boudine, A; Benslama, A
1999-01-01
Symmetries of Quantum Nonsymmetric gravity are studied and the corresponding generators are constructed . The related equal time canonical (and non canonical) (anti) commutation relations are established.
Black hole critical phenomena without black holes
Indian Academy of Sciences (India)
Steven L Liebling
2000-10-01
Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I brieﬂy review critical phenomena, discuss some recent results, and describe a model which demonstrates similar phenomena without gravity.
Noncommutative Quantum Gravity
Faizal, Mir
2013-01-01
We discuss the BRST and anti-BRST symmetries for perturbative quantum gravity in noncommutative spacetime. In this noncommutative perturbative quantum gravity the sum of the classical Lagrangian density with a gauge fixing term and a ghost term is shown to be invariant the noncommutative BRST and the noncommutative anti-BRST transformations. We analyse the gauge fixing term and the ghost term in both linear as well as non-linear gauges. We also discuss the unitarity evolution of the theory an...
重力坝深层抗滑稳定的可靠度校准%Reliability calibration for deep strata anti-sliding stability of gravity dam
Institute of Scientific and Technical Information of China (English)
王素芳
2001-01-01
The standard doesn't give out the determinate safe index about the deep strata anti-sliding stability of gravity dam. The reliability calibration was done with JC method for the condition of shear zone tending to upstream. And yet the dam height, safety factors, etc. how to influence reliability index were studied and discussed here.%对于重力坝的深层抗滑稳定问题，规范并未给出明确的安全指标，为此采用JC法对剪切带倾向上游的情况进行了可靠度校准，并研究了坝高、安全系数等对可靠指标的影响。
矢量控制反坦克导弹重力补偿设计%Design of Gravity Compensation for Anti-Tank Missile with Vector Control
Institute of Scientific and Technical Information of China (English)
侯师; 张靖; 朱湘龙
2012-01-01
针对矢量控制的反坦克导弹,提出了一种基于导弹飞行物理过程、从导弹系统整体角度出发求取重力补偿的方法.通过仿真验证了该方法的可行性,并与传递函数法作了比较.这种方法一定程度上避免了孤立以某一主要影响因子分段求取重补指令,因此更加简便,同时可靠.%Addressing an anti-tank missile with vector control, this paper puts forward a new way to solve gravity compensation based on the physical process of the missile in flight and also considering from a whole view on the missile system. We have validated the feasibility by emulator and then drawn a conclusion that this method is more convenient and reliable than the way of transfer function methods. To a certain extent,the method avoids taking only certain primary impact factors into account and solving gravity compensation in a segmented way.
Institute of Scientific and Technical Information of China (English)
代占平; 陈炎桂; 苏永生
2013-01-01
Two methods are widely used in stability checking of gravity quay: limit state method with single factor, probability-based limit state method expressed with partial safety factors. The first method is replied in Design and Construction Code for Gravity Quay (1987) and BS 6349(1988), the second in Design and Construction Code for Gravity Quay (2009) and BS 6349 (2010). The calculation difference on overturning and anti-slide are compared between Chinese code and Britain new and old revision standard. The comparison is further detailed by taking a typical gravity block wharf as an example, so as to offer reference for the design of gravity block structure in foreign projects.%重力式码头稳定性的验证方法主要有：单一安全系数表达的极限状态设计方法；以概率论为基础，以分项系数表达的极限状态设计方法。《重力式码头设计与施工规范》（1987）和BS 6349（1988）均采用安全系数法；JTS167-2-2009《重力式码头设计与施工规范》和BS 6349（2010）均采用以概率论为基础，以分项系数表达的极限状态设计方法。重点对比分析中国与英国BS新、旧规范在抗滑、抗倾计算上的差异，结合现有重力式方块码头工程实例，根据其计算结果验证分析的准确性，供海外项目重力式方块结构设计参考。
Directory of Open Access Journals (Sweden)
Ming-chao Li
2015-10-01
Full Text Available This study used the finite element method (FEM to analyze the stress field and seepage field of a roller-compacted concrete (RCC dam, with an upstream impervious layer constructed with different types of concrete materials, including three-graded RCC, two-graded RCC, conventional vibrated concrete (CVC, and grout-enriched vibrated RCC (GEVR, corresponding to the design schemes S1 through S4. It also evaluated the anti-seepage performance of the imperious layer in the four design schemes under the normal water level and flood-check level. Stress field analysis of a retaining section and discharge section shows that the maximum tensile stress occurs near the dam heel, the maximum compressive stress occurs near the dam toe, and the stress distributions in the four schemes can satisfy the stress control criteria. Seepage field analysis shows that the uplift pressure heads in schemes S3 and S4 descend rapidly in the anti-seepage region, and that the calculated results of daily seepage flow under the steady seepage condition in these two schemes are about 30% to 50% lower than those in the other two schemes, demonstrating that CVC and GEVR show better anti-seepage performance. The results provide essential parameters such as the uplift pressure head and seepage flow for physical model tests and anti-seepage structure selection in RCC dams.
Localized gravity on FRW branes
Singh, Parampreet; Dadhich, Naresh
2002-01-01
We study the system of Schwarzschild anti de Sitter (S-AdS) bulk and FRW brane for localization of gravity; i.e. zero mass gravitons having ground state on the brane, and thereby recovering the Einstein gravity with high energy correction. It has been known that gravity is not localized on AdS brane with AdS bulk. We prove the general result that gravity is not localized for dynamic branes whenever Lambda_4 0 and black h...
复杂地基重力坝深层抗滑模拟研究%Simulation of deep anti-sliding of gravity dam on complex foundation
Institute of Scientific and Technical Information of China (English)
王振; 韩春; 宋志斌; 王延梅
2013-01-01
The anti-sliding stability of gravity dam is always related to the overall safety of reservoir,and is very important.The paper adopted discrete element method to simulate the stability of dam base of complex structure surface that included bedding and joints.It also calculated the stability of dam body under two conditions of empty and full reservoir in different geological conditions.Study shows that the stability of dam is good when the reservoir is empty,while the reservoir is full of water,the stability of dam is affect significantly by the geological condition.Multiple sliding surface form are more better than double sliding surface form for the stability of dam.The stability is related to the position of the gravity dam centre.The results can be used for the design of gravity dam under complex geological condition.%重力坝抗滑稳定性关系到水库地整体安全,极为重要.本文采用离散元法对含层理、节理等复杂结构面的坝基抗滑稳定性进行了数值模拟研究,计算了不同地质条件下水库无蓄水、水库蓄满两种工况的坝体稳定性.研究表明:水库在无蓄水时,坝体稳定性都比较好,但当水库蓄满后,坝体稳定性受地质环境影响显著,多滑动面形式比双滑动面形式更有利益坝体稳定,并且与重力坝的重心位置有关.本文提出的方法与计算结果,可供复杂地质条件下重力坝设计参考.
Institute of Scientific and Technical Information of China (English)
ZOU De-Cheng; YANG Zhan-Ying; YUE Rui-Hong
2011-01-01
@@ By using a new approach, we demonstrate the analytic expressions for slowly rotating Gauss-Bonnet charged black hole solutions with one non-vanishing angular momentum in higher-dimensional anti-de Sitter spaces.Up to linear order of the rotating parameter a, the mass, Hawking temperature and entropy of the charged black holes get no corrections from rotation.%By using a new approach, we demonstrate the analytic expressions for slowly rotating Gauss-Bonnet charged black hole solutions with one non-vanishing angular momentum in higher-dimensionalanti-de Sitter spaces. Up to linear order of the rotating parameter a, the mass, Hawking temperature and entropy of the charged black holes get no corrections from rotation.
Kerr-Newman-dS/AdS solution and anti-evaporation in higher-order torsion scalar gravity theories
Nashed, Gamal G. L.
2016-03-01
We derive a null tetrad from axially-symmetric vierbein field. The f(T)f(T)-Maxwell field equations with cosmological constant, where T is the scalar torsion, are applied to the null tetrad. An exact non-vacuum solution having three constants of integration is derived which is a solution to the f (T) -Maxwell field equations provided that f(T)=T0f(T)=T0 and fT=df(T)dT=1fT=df(T)dT=1, where T0T0 is a constant. The scalar torsion related to this solution is constant, i.e., T=T0T=T0, and differs from the classical general relativity when f(T)≈T0f(T)≈T0. We study the singularities of this solution using curvature and torsion invariants. We consider a slow rotation and show that the derived solution behaves asymptotically as de Sitter spacetime and display the existence of Nariai spacetime as a background solution. We assume a perturbation of Nariai spacetime till the first order and investigate the behavior of the black hole horizon. Finally, we explain that the anti-evaporation occurs on the classical level in the f (T) gravitational theories.
Analog Systems for Gravity Duals
Hossenfelder, S.
2014-01-01
We show that analog gravity systems exist for charged, planar black holes in asymptotic Anti-de Sitter space. These black holes have been employed to describe, via the gauge-gravity duality, strongly coupled condensed matter systems on the boundary of AdS-space. The analog gravity system is a different condensed matter system that, in a suitable limit, describes the same bulk physics as the theory on the AdS boundary. This combination of the gauge-gravity duality and analog gravity therefore ...
Directory of Open Access Journals (Sweden)
Claudia de Rham
2014-08-01
Full Text Available 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 alternative and related models of massive gravity such as new massive gravity, Lorentz-violating massive gravity and non-local massive gravity.
Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K.
2014-01-01
We present an alternative to topologically massive gravity (TMG) with the same 'minimal' bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new 'minimal massive gravity'
Gravity-Dependent Transport in Industrial Processes
Ostrach, Simon; Kamotani, Yasuhiro
1996-01-01
Gravity dependent transport phenomena in various industrial processes are investigated in order to indicate new directions for micro-gravity research that enhance the commercial success of the space program. The present article describes the commercialization possibilities of such topics associated with physicochemical transport phenomena. The topics are: coating flow, rotating electrochemical system, and convection in low Plandtl number fluids. The present study is directed to understand these phenomena, and to develop a knowledge base for their applications with emphasis to a micro-gravity environment.
Generalized geometry and non-symmetric gravity
Jurco, Branislav; Khoo, Fech Scen; Schupp, Peter; Vysoky, Jan
2015-01-01
Generalized geometry provides the framework for a systematic approach to non-symmetric metric gravity theory and naturally leads to an Einstein-Kalb-Ramond gravity theory with totally anti-symmetric contortion. The approach is related to the study of the low-energy effective closed string gravity actions.
Bergshoeff, Eric A.; Hohm, Olaf; Rosseel, Jan; Townsend, Paul K.
2011-01-01
The physical modes of a recently proposed D-dimensional "critical gravity'', linearized about its anti-de Sitter vacuum, are investigated. All "log mode'' solutions, which we categorize as "spin-2'' or "Proca'', arise as limits of the massive spin-2 modes of the noncritical theory. The linearized Ei
Sobreiro, R. F.; Tomaz, A. A.; Otoya, V. J. Vasquez
2012-01-01
Pure gauge theories for de Sitter, anti de Sitter and orthogonal groups, in four-dimensional Euclidean spacetime, are studied. It is shown that, if the theory is asymptotically free and a dynamical mass is generated, then an effective geometry may be induced and a gravity theory emerges.
Hertog, Thomas; Hollands, Stefan
2005-12-01
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.
折线台阶状基础面重力坝的抗滑稳定性分析%Anti-sliding Stability Analysis of Gravity Dam with Polyline Stepped Foundation
Institute of Scientific and Technical Information of China (English)
李东辉; 于跃; 陈宗荣; 武帅
2011-01-01
At present there is not common and perfect method for anti-sliding stability analysis of gravity dam with polyline stepped foundation. Based on the idea of sliding wedge method and anti-sliding stability analysis of gravity dam,a simple method is put forward and the computer program is developed, which takes the dam body as rigid body and slide mass is made up with wedges. This method is applied to analyze anti-sliding stability of Manwan # 4 monolith. The resuits show that the method is simple and practical with lower computational coat and higher precision.%折线台阶状基础面重力坝的抗滑稳定性分析,目前尚无统一完善的计算方法,基于滑楔法及重力坝深层抗滑稳定分析方法,提出了一种视坝体为刚体、滑动体由若干楔形体组成的简易方法,编制了计算程序,并将其应用于漫湾水电站#4坝段抗滑稳定性分析中.结果表明,该方法简便实用、计算成本低,且精度较高.
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.
Sneddon, Andrew
2013-01-01
Gravity is a cross-disciplinary research project in Fine Art at Sheffield Institute of the Arts (SIA) in partnership with Sheffield Galleries and Museums. Gravity is led by Penny McCarthy, Dr Becky Shaw and Andrew Sneddon. Gravity begins with a series of lectures designed to examine the wider context of practice and discourse. Gravity examines the contemporary condition of the art object or artefact, and the relations between maker, medium, site of production and systems of dissemination. ...
Claudia de Rham
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...
Liouville gravity from Einstein gravity
Grumiller, D.; Jackiw, R.
2007-01-01
We show that Liouville gravity arises as the limit of pure Einstein gravity in 2+epsilon dimensions as epsilon goes to zero, provided Newton's constant scales with epsilon. Our procedure - spherical reduction, dualization, limit, dualizing back - passes several consistency tests: geometric properties, interactions with matter and the Bekenstein-Hawking entropy are as expected from Einstein gravity.
Institute of Scientific and Technical Information of China (English)
赵宏; 王洁欣; 张海霞; 沈志刚; 甄崇礼; 陈建峰
2009-01-01
The nanoparticles of the hydrophobie drug of danazol with narrow size distribution are facilely prepared by controlled high-gravity anti.solvent precipitation(HGAP)process.Intensified mlcromlxlng and uniform nucleation environment are created by thc high-gravity equipment(rotating packed bed)in carrymg out the anti-solvent precipitation process to produce nanoparticles.The average particle size decreases from 55μm of the raw danazol to 190 nm of the nanoparticles,The Brunauer-Emmett-Teller(BET)surface area sharply Increases from 0.66 ,m2.g-1 to 15.08 m2.g-1.Accordingly,the dissolution rate is greatly improved.The molecular state,chemical.composition,and crystal form of the danazol nanoparticles remains unchanged after processmg according to Fourier transtorm infrared(FTIR)and X-ray difiraction(XRD).The high recovery ratio and continuous production-capa-city are highly appreciated in industry.Therefore,the HGAP method might offer a general and facile platform tor mass production of hydrophobic pharmaceutical danazol particles in nanometer range.
Directory of Open Access Journals (Sweden)
A. V. Vikulin
2015-09-01
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.
Underwater explosions and cavitation phenomena
International Nuclear Information System (INIS)
Some aspects of underwater explosions and cavitation phenomena have been studied by using a thermodynamic equation of state for water and a one-dimensional Lagrangian hydrocode. The study showed that surface cavitation is caused by the main blast wave and a bubble pulse from rebound of a release wave moving toward the center of the exploding bubble. Gravity has little effect on the surface cavitation. In nuclear explosions the bubble is bounded by a two-phase region rather than a gas-water interface. The two-phase region cavitates as the bubble expands, changing the optical absorption coefficient by many orders of magnitude and significantly affecting the optical signature. In assessing cavitation damage, it is concluded that a water jet of unstable bubble collapse erodes solid walls. The study leads to suggestions for future research
Instabilities and anti-evaporation of Reissner–Nordström black holes in modified $F(R)$ gravity
Nojiri, Shin'ichi; Odintsov, Sergei D.
2014-01-01
We study the instabilities and related anti-evaporation of the extremal Reissner–Nordström (RN) black hole in F(R) gravity. It is remarkable that the effective electric charge can be generated for some solutions of F(R) gravity without electromagnetic field. The anti-evaporation effect occurs but it emerges only in the strong coupling limit of the effective gravitational coupling. The instabilities of RN black hole are also investigated when the electromagnetic sector is added to the action o...
Dereli, T.; Yetişmişoğlu, C.
2016-06-01
We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first-order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space AdS 3) and constant torsion provide exact solutions.
Influence of hole-opening of gravity dam on its anti-seismic behavior%重力坝坝体开孔对大坝抗震性能的影响
Institute of Scientific and Technical Information of China (English)
王家骐; 张燎军; 赵路静
2015-01-01
The practical seismic damages of gravity dams often occur on the middle and upper part of the dam body, where the dam hole-opening are arranged, so that the dam head with openings become a weak spot for anti-seismic of gravity dams. Tak-ing a powerhouse dam section of a scheduling RCC gravity dam for instance, we establish a three dimensional analytical model that considers the dam-foundation-water interaction based on ADINA. In this way, the characteristics such as natural vibration characteristic, dam displacement, principal tensile stress and crack propagation of dams with or without openings, were re-searched under strong earthquake. The results show that dam hole-opening has more impacts on local stress rather than on inte-gral rigidity. So in anti-seismic design of gravity dams, we should focus on the hole-opening and take measures such as arran-ging reinforcing bars and using high grade concrete.%重力坝实际震损多出现在坝体中上部,坝身孔洞也常布置于此,地震作用下坝头孔洞附近成为抗震安全的薄弱部位. 以某待建水电站碾压混凝土重力坝厂房坝段为例,基于ADINA有限元软件建立考虑坝体-地基-库水相互作用的三维有限元动力计算模型,研究了在强震作用下考虑大坝开孔与否对坝体自振特性、坝体位移、主拉应力和裂缝开展情况的影响. 结果表明,考虑坝体开孔对大坝整体刚度影响不大,但对局部应力影响显著,抗震设计须重视坝体实际开孔情况,采取加强配筋和提高混凝土标号等措施. 研究成果可为同类工程抗震设计提供参考.
Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K
2014-01-01
We present an alternative to Topologically Massive Gravity (TMG) with the same "minimal" bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new "minimal massive gravity" has both a positive energy graviton and positive central charges for the asymptotic AdS-boundary conformal algebra.
Higher dimensional nonlinear massive gravity
Do, Tuan Q.
2016-05-01
Inspired by a recent ghost-free nonlinear massive gravity in four-dimensional spacetime, we study its higher dimensional scenarios. As a result, we are able to show the constantlike behavior of massive graviton terms for some well-known metrics such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini (anti-) de Sitter metrics in a specific five-dimensional nonlinear massive gravity under an assumption that its fiducial metrics are compatible with physical ones. In addition, some simple cosmological solutions of the five-dimensional massive gravity are figured out consistently.
S-Duality for Linearized Gravity
Nieto, J.A.
1999-01-01
We develope the analogue of S-duality for linearized gravity in (3+1)-dimensions. Our basic idea is to consider the self-dual (anti-self-dual) curvature tensor for linearized gravity in the context of the Macdowell-Mansouri formalism. We find that the strong-weak coupling duality for linearized gravity is an exact symmetry and implies small-large duality for the cosmological constant.
Topological Black Holes in Weyl Conformal Gravity
Klemm, Dietmar
1998-01-01
We present a class of exact solutions of Weyl conformal gravity, which have an interpretation as topological black holes. Solutions with negative, zero or positive scalar curvature at infinity are found, the former generalizing the well-known topological black holes in anti-de Sitter gravity. The rather delicate question of thermodynamic properties of such objects in Weyl conformal gravity is discussed; suggesting that the thermodynamics of the found solutions should be treated within the fra...
Nonlinear surface electromagnetic phenomena
Ponath, H-E
1991-01-01
In recent years the physics of electromagnetic surface phenomena has developed rapidly, evolving into technologies for communications and industry, such as fiber and integrated optics. The variety of phenomena based on electromagnetism at surfaces is rich and this book was written with the aim of summarizing the available knowledge in selected areas of the field. The book contains reviews written by solid state and optical physicists on the nonlinear interaction of electromagnetic waves at and with surfaces and films. Both the physical phenomena and some potential applications are
Dropout Phenomena at Universities
DEFF Research Database (Denmark)
Larsen, Michael Søgaard; Kornbeck, Kasper Pihl; Kristensen, Rune;
Dropout from university studies comprises a number of complex phenomena with serious complex consequences and profound political attention. Further analysis of the field is, therefore, warranted. Such an analysis is offered here as a systematic review which gives answers based on the best possible...... evidence found in the research field comprised by the three review questions to be addressed. The aims of this systematic review can, thus, be summarized like this: Which answers can be offered from research in relation to the following questions: What is dropout from university studies? Why do such...... dropout phenomena occur at universities? What can be done by the universities to prevent or reduce such dropout phenomena?...
Gravity Waves in Three Dimensions
Gurses, Metin; Tekin, Bayram
2015-01-01
We find the explicit forms of the anti-de Sitter plane, anti-de Sitter spherical, and pp waves that solve both the linearized and exact field equations of the most general higher derivative gravity theory in three dimensions. As a sub-class, we work out the six derivative theory and the critical version of it where the masses of the two spin-2 excitations vanish and the spin-0 excitations decouple.
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.
Reichhardt, Tony
1994-03-01
Mariner 10 traveled to Mercury by using Venus' gravity to bend its course in toward the sun, a correction that would otherwise required vast amounts of rocket fuel. For the first time, an interplanetary spacecraft changed course not with rocket fuel but by using a planet's gravitational field. That maneuver stands, along with the development of the rocket engine, as one of the keys that opened the solar system for exploration. The Pioneer, Voyager, and Galileo missions all used gravity assist, and in fact would not have been possible otherwise. Gravity assist is the most efficient form of space propulsion known. Various aspects of the developmental history of the gravity assist technique and the dispute over who should receive credit for inventing the technique are discussed.
Conformal Gravity from AdS/CFT mechanism
Aros, Rodrigo; Romo, Mauricio; Zamorano, Nelson
2006-01-01
We explicitly calculate the induced gravity theory at the boundary of an asymptotically Anti-de Sitter five dimensional Einstein gravity. We also display the action that encodes the dynamics of radial diffeomorphisms. It is found that the induced theory is a four dimensional conformal gravity plus a scalar field. This calculation confirms some previous results found by a different approach.
Three-dimensional tricritical gravity
Bergshoeff, Eric A.; de Haan, Sjoerd; Merbis, Wout; Rosseel, Jan; Zojer, Thomas
2012-01-01
We consider a class of parity-even, six-derivative gravity theories in three dimensions. After linearizing around anti-de Sitter space, the theories have one massless and two massive graviton solutions for generic values of the parameters. At a special, so-called tricritical, point in parameter spac
Compactification in first order gravity
Aros, Rodrigo; Romo, Mauricio; Zamorano, Nelson
2007-01-01
The Kaluza-Klein compactification process is applied in five dimensions to CS gravity, for the anti-de Sitter and Poincar\\'e groups, using the first order formalism. In this context some solutions are found and analyzed. Also, the conserved charges associated to the solutions are computed.
Criticality in Einstein-Gauss-Bonnet Gravity: Gravity without Graviton
Fan, Zhong-Ying; Lu, Hong
2016-01-01
General Einstein-Gauss-Bonnet gravity with a cosmological constant allows two (A)dS spacetimes as its vacuum solutions. We find a critical point in the parameter space where the two (A)dS spacetimes coalesce into one and the linearized perturbations lack any bilinear kinetic terms. The vacuum perturbations hence loose their interpretation as linear graviton modes at the critical point. Nevertheless, the critical theory admits black hole solutions due to the nonlinear effect. We also consider Einstein gravity extended with general quadratic curvature invariants and obtain critical points where the theory has no bilinear kinetic terms for either the scalar trace mode or the transverse modes. Such critical phenomena are expected to occur frequently in general higher derivative gravities.
Energy Technology Data Exchange (ETDEWEB)
Bourg, I.C.; Sposito, G.
2011-05-01
Ion exchange phenomena involve the population of readily exchangeable ions, the subset of adsorbed solutes that balance the intrinsic surface charge and can be readily replaced by major background electrolyte ions (Sposito, 2008). These phenomena have occupied a central place in soil chemistry research since Way (1850) first showed that potassium uptake by soils resulted in the release of an equal quantity of moles of charge of calcium and magnesium. Ion exchange phenomena are now routinely modeled in studies of soil formation (White et al., 2005), soil reclamation (Kopittke et al., 2006), soil fertilitization (Agbenin and Yakubu, 2006), colloidal dispersion/flocculation (Charlet and Tournassat, 2005), the mechanics of argillaceous media (Gajo and Loret, 2007), aquitard pore water chemistry (Tournassat et al., 2008), and groundwater (Timms and Hendry, 2007; McNab et al., 2009) and contaminant hydrology (Chatterjee et al., 2008; van Oploo et al., 2008; Serrano et al., 2009).
Rheological phenomena in focus
Boger, DV
1993-01-01
More than possibly any other scientific discipline, rheology is easily visualized and the relevant literature contains many excellent photographs of unusual and often bizarre phenomena. The present book brings together these photographs for the first time. They are supported by a full explanatory text. Rheological Phenomena in Focus will be an indispensable support manual to all those who teach rheology or have to convince colleagues of the practical relevance of the subject within an industrial setting. For those who teach fluid mechanics, the book clearly illustrates the difference be
Celada, Mariano; Montesinos, Merced
2016-01-01
$BF$ gravity comprises all the formulations of gravity that are based on deformations of $BF$ theory. Such deformations consist of either constraints or potential terms added to the topological $BF$ action that turn some of the gauge degrees of freedom into physical ones, particularly giving rise to general relativity. The $BF$ formulations have provided new and deep insights into many classical and quantum aspects of the gravitational field, setting the foundations for the approach to quantum gravity known as spinfoam models. In this review, we present a self-contained and unified treatment of the $BF$ formulations of $D$-dimensional general relativity and other related models, focusing on the classical aspects of them and including some new results.
Celada, Mariano; González, Diego; Montesinos, Merced
2016-11-01
BF gravity comprises all the formulations of gravity that are based on deformations of BF theory. Such deformations consist of either constraints or potential terms added to the topological BF action that turn some of the gauge degrees of freedom into physical ones, particularly giving rise to general relativity. The BF formulations have provided new and deep insights into many classical and quantum aspects of the gravitational field, setting the foundations for the approach to quantum gravity known as spinfoam models. In this review, we present a self-contained and unified treatment of the BF formulations of D-dimensional general relativity and other related models, focusing on the classical aspects of them and including some new results.
Gravity and low-frequency geodynamics
Teisseyre, Roman
1989-01-01
This fourth volume in the series Physics and Evolution of the Earth's Interior, provides a comprehensive review of the geophysical and geodetical aspects related to gravity and low-frequency geodynamics. Such aspects include the Earth's gravity field, geoid shape theory, and low-frequency phenomena like rotation, oscillations and tides.Global-scale phenomena are treated as a response to source excitation in spherical Earth models consisting of several shells: lithosphere, mantle, core and sometimes also the inner solid core. The effect of gravitation and rotation on the Earth's shape is anal
Bergshoeff, Eric A; Rosseel, Jan; Townsend, Paul K
2011-01-01
The physical modes of a recently proposed D-dimensional "critical gravity", linearized about its anti-de Sitter vacuum, are investigated. All "log mode" solutions, which we categorize as `spin 2' or `Proca', arise as limits of the massive spin 2 modes of the non-critical theory. The linearized Einstein tensor of a spin 2 log mode is itself a 'non-gauge' solution of the linearized Einstein equations whereas the linearized Einstein tensor of a Proca mode takes the form of a linearized general coordinate transformation. Our results suggest the existence of a holographically dual logarithmic conformal field theory.
Sawtooth phenomena in tokamaks
International Nuclear Information System (INIS)
A review of experimental and theoretical investigaions of sawtooth phenomena in tokamaks is presented. Different types of sawtooth oscillations, scaling laws and methods of interanl disruption stabilization are described. Theoretical models of the sawtooth instability are discussed. 122 refs.; 4 tabs
Bioelectrochemistry II membrane phenomena
Blank, M
1987-01-01
This book contains the lectures of the second course devoted to bioelectro chemistry, held within the framework of the International School of Biophysics. In this course another very large field of bioelectrochemistry, i. e. the field of Membrane Phenomena, was considered, which itself consists of several different, but yet related subfields. Here again, it can be easily stated that it is impossible to give a complete and detailed picture of all membrane phenomena of biological interest in a short course of about one and half week. Therefore the same philosophy, as the one of the first course, was followed, to select a series of lectures at postgraduate level, giving a synthesis of several membrane phenomena chosen among the most'important ones. These lectures should show the large variety of membrane-regulated events occurring in living bodies, and serve as sound interdisciplinary basis to start a special ized study of biological phenomena, for which the investigation using the dual approach, physico-che...
Davis, Hyman R.; Long, R. H.; Simone, A. A.
1979-01-01
Solids are separated from a liquid in a gravity settler provided with inclined solid intercepting surfaces to intercept the solid settling path to coalesce the solids and increase the settling rate. The intercepting surfaces are inverted V-shaped plates, each formed from first and second downwardly inclined upwardly curved intersecting conical sections having their apices at the vessel wall.
Pipinos, Savas
2010-01-01
This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…
Extremal Black Hole in a Nonlinear Newtonian Theory of Gravity
Good, Michael R R
2008-01-01
This work investigates an upper-limit of charge for a black hole in a nonlinear Newtonian theory of gravity. The charge is accumulated via protons fired isotropically at the black hole. This theoretical study of gravity (known as `pseudo-Newtonian') is a forced merger of special relativity and Newtonian gravity. Whereas the source of Newton's gravity is purely mass, pseudo-Newtonian gravity includes effects of fields around the mass, giving a more complete picture of how gravity behaves. Interestingly, pseudo-Newtonian gravity predicts such relativistic phenomena as black holes and deviations from Kepler's laws, but of course, provides a less accurate picture than general relativity. Though less accurate, it offers an easier approach to understanding some results of general relativity, and merits interest due to its simplicity. The method of study applied here examines the predictions of pseudo-Newtonian gravity for a particle interacting with a highly charged black hole. A black hole with a suitable charge w...
Tunneling without barriers with gravity
Kanno, Sugumi; Sasaki, Misao; Soda, Jiro
2012-01-01
We consider the vacuum decay of the flat Minkowski space to an anti-de Sitter space. We find a one-parameter family of potentials that allow exact, analytical instanton solutions describing tunneling without barriers in the presence of gravity. In the absence of gravity such instantons were found and discussed by Lee and Weinberg more than a quarter of a century ago. The bounce action is also analytically computed. We discuss possible implications of these new instantons to cosmology in the c...
Analogue gravitational phenomena in Bose-Einstein condensates
Finazzi, Stefano
2012-01-01
Analogue gravity is based on the simple observation that perturbations propagating in several physical systems can be described by a quantum field theory in a curved spacetime. While phenomena like Hawking radiation are hardly detectable in astrophysical black holes, these effects may be experimentally tested in analogue systems. In this Thesis, focusing on Bose-Einstein condensates, we present our recent results about analogue models of gravity from three main perspectives: as laboratory tests of quantum field theory in curved spacetime, for the techniques that they provide to address various issues in general relativity, and as toy models of quantum gravity. The robustness of Hawking-like particle creation is investigated in flows with a single black hole horizon. Furthermore, we find that condensates with two (white and black) horizons develop a dynamical instability known in general relativity as black hole laser effect. Using techniques borrowed from analogue gravity, we also show that warp drives, which...
Giribet, Gaston
2014-01-01
Minimal Massive Gravity (MMG) is an extension of three-dimensional Topologically Massive Gravity that, when formulated about Anti-de Sitter space, accomplishes to solve the tension between bulk and boundary unitarity that other models in three dimensions suffer from. We study this theory at the chiral point, i.e. at the point of the parameter space where one of the central charges of the dual conformal field theory vanishes. We investigate the non-linear regime of the theory, meaning that we study exact solutions to the MMG field equations that are not Einstein manifolds. We exhibit a large class of solutions of this type, which behave asymptotically in different manners. In particular, we find analytic solutions that represent two-parameter deformations of extremal Banados-Teitelboim-Zanelli (BTZ) black holes. These geometries behave asymptotically as solutions of the so-called Log Gravity, and, despite the weakened falling-off close to the boundary, they have finite mass and finite angular momentum, which w...
Threshold Gravity Determination and Artificial Gravity Studies Using Magnetic Levitation
Ramachandran, N.; Leslie, F.
2005-01-01
What is the threshold gravity (minimum gravity level) required for the nominal functioning of the human system? What dosage is required (magnitude and duration)? Do human cell lines behave differently in microgravity in response to an external stimulus? The critical need for a variable gravity simulator is emphasized by recent experiments on human epithelial cells and lymphocytes on the Space Shuttle clearly showing that cell growth and function are markedly different from those observed terrestrially. Those differences are also dramatic between cells grown in space and those in Rotating Wall Vessels (RWV), or NASA bioreactor often used to simulate microgravity, indicating that although morphological growth patterns (three dimensional growth) can be successfully simulated using RWVs, cell function performance is not reproduced - a critical difference. If cell function is dramatically affected by gravity off-loading, then cell response to stimuli such as radiation, stress, etc. can be very different from terrestrial cell lines. Yet, we have no good gravity simulator for use in study of these phenomena. This represents a profound shortcoming for countermeasures research. We postulate that we can use magnetic levitation of cells and tissue, through the use of strong magnetic fields and field gradients, as a terrestrial microgravity model to study human cells. Specific objectives of the research are: 1. To develop a tried, tested and benchmarked terrestrial microgravity model for cell culture studies; 2. Gravity threshold determination; 3. Dosage (magnitude and duration) of g-level required for nominal functioning of cells; 4. Comparisons of magnetic levitation model to other models such as RWV, hind limb suspension, etc. and 5. Cellular response to reduced gravity levels of Moon and Mars.
Fundamentals of Fire Phenomena
DEFF Research Database (Denmark)
Quintiere, James
Understanding fire dynamics and combustion is essential in fire safety engineering and in fire science curricula. Engineers and students involved in fire protection, safety and investigation need to know and predict how fire behaves to be able to implement adequate safety measures and hazard...... analyses. Fire phenomena encompass everything about the scientific principles behind fire behaviour. Combining the principles of chemistry, physics, heat and mass transfer, and fluid dynamics necessary to understand the fundamentals of fire phenomena, this book integrates the subject into a clear...... discipline. It covers thermo chemistry including mixtures and chemical reactions; Introduces combustion to the fire protection student; Discusses premixed flames and spontaneous ignition; Presents conservation laws for control volumes, including the effects of fire; Describes the theoretical bases...
Transport phenomena II essentials
REA, The Editors of
2012-01-01
REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Transport Phenomena II covers forced convention, temperature distribution, free convection, diffusitivity and the mechanism of mass transfer, convective mass transfer, concentration
Blood Flow Multiscale Phenomena
Agić, Ante; Mijović, Budimir; Nikolić, Tatjana
2007-01-01
The cardiovascular disease is one of most frequent cause deaths in modern society. The objective of this work is analyse the effect of dynamic vascular geometry (curvature, torsion,bifurcation) and pulsatile blood nature on secondary flow, wall shear stress and platelet deposition. The problem was examined as multi-scale physical phenomena using perturbation analysis and numerical modelling. The secondary flow determined as influence pulsatile pressure, vascular tube time-dependen...
Stochastic gravity: beyond semiclassical gravity
Energy Technology Data Exchange (ETDEWEB)
Verdaguer, E [Departament de Fisica Fonamental and CER en Astrofisica, Fisica de Particules i Cosmologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain)
2007-05-15
The back-reaction of a classical gravitational field interacting with quantum matter fields is described by the semiclassical Einstein equation, which has the expectation value of the quantum matter fields stress tensor as a source. The semiclassical theory may be obtained from the quantum field theory of gravity interacting with N matter fields in the large N limit. This theory breaks down when the fields quantum fluctuations are important. Stochastic gravity goes beyond the semiclassical limit and allows for a systematic and self-consistent description of the metric fluctuations induced by these quantum fluctuations. The correlation functions of the metric fluctuations obtained in stochastic gravity reproduce the correlation functions in the quantum theory to leading order in an 1/N expansion. Two main applications of stochastic gravity are discussed. The first, in cosmology, to obtain the spectrum of primordial metric perturbations induced by the inflaton fluctuations, even beyond the linear approximation. The second, in black hole physics, to study the fluctuations of the horizon of an evaporating black hole.
The Improved Anti-Sliding Calculation Method of Gravity Retaining Wall%重力式挡土墙抗滑动稳定计算方法改进研究
Institute of Scientific and Technical Information of China (English)
张云冬; 马淑芝; 汪刚
2012-01-01
针对目前重力式挡土墙抗滑稳定性计算方法中存在的缺陷,将挡土墙入土部分划分成小网格,遍历搜寻出抗倾覆稳定系数最小的点,此点就是挡士墙的实际倾覆转动点所在的位置,根据此转动点的位置,将挡墙两侧的土体划分成四个部分分别计算各部分土压力,再结合墙底与地基土摩擦力的分析,推导出改进的墙体抗滑动稳定系数的计算公式.还通过改变墙体的几何参数,分析了最小抗倾覆转动点的位置和墙体抗滑稳定性系数随墙体宽度、挡土墙入土深度等的变化规律.%The present anti-sliding stability calculations of gravity retaining wall has some defects. This paper had divided the retaining walls that buried into earth in small grid. By searching for the point of minimum stability factor against overturning. This point is the actual turning point of the retaining walls. According to the location of this turning point, both sides of the wall are divided into four sections in order to calculated the earth pressure. At the end of the analysis, combining the friction of soil and foundation wall to get the improved anti-sliding stability factor formula. This article also, analysised the location of the minimum turning point of overturning and the anti-sliding coefficient of stability, and how they change with the change of retaining walls, width and depth that buried into earth.
Clifton, T; Barrow, John D.
2006-01-01
We consider the possibility of energy being exchanged between the scalar and matter fields in scalar-tensor theories of gravity. Such an exchange provides a new mechanism which can drive variations in the gravitational 'constant' G. We find exact solutions for the evolution of spatially flat Friedman-Roberston-Walker cosmologies in this scenario and discuss their behaviour at both early and late times.
International Nuclear Information System (INIS)
We consider the possibility of energy being exchanged between the scalar and matter fields in scalar-tensor theories of gravity. Such an exchange provides a new mechanism which can drive variations in the gravitational 'constant' G. We find exact solutions for the evolution of spatially flat Friedmann-Robertson-Walker cosmologies in this scenario and discuss their behavior at both early and late times. We also consider the physical consequences and observational constraints on these models
International Nuclear Information System (INIS)
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
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
Black Hole Phase Transition in Massive Gravity
Ning, Shou-Li; Liu, Wen-Biao
2016-07-01
In massive gravity, some new phenomena of black hole phase transition are found. There are more than one critical points under appropriate parameter values and the Gibbs free energy near critical points also has some new properties. Moreover, the Maxwell equal area rule is also investigated and the coexistence curve of the black hole is given.
Transport phenomena I essentials
REA, The Editors of
2012-01-01
REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Transport Phenomena I includes viscosity, flow of Newtonian fluids, velocity distribution in laminar flow, velocity distributions with more than one independent variable, thermal con
Lawrance, R
1972-01-01
Solid State Phenomena explores the fundamentals of the structure and their influence on the properties of solids. This book is composed of five chapters that focus on the electrical and thermal conductivities of crystalline solids. Chapter 1 describes the nature of solids, particularly metals and crystalline materials. This chapter also presents a model to evaluate crystal structure, the forces between atom pairs, and the mechanism of plastic and elastic deformation. Chapter 2 demonstrates random vibrations of atoms in a solid using a one-dimensional array, while Chapter 3 examines the resista
1999-01-01
This map from the MGS Horizon Sensor Assembly (HORSE) shows middle atmospheric temperatures near the 1 mbar level of Mars between Ls 170 to 175 (approx. July 14 - 23, 1999). Local Mars times between 1:30 and 4:30 AM are included. Infrared radiation measured by the Mars Horizon Sensor Assembly was used to make the map. That device continuously views the 'limb' of Mars in four directions, to help orient the spacecraft instruments to the nadir: straight down. The map shows thermal wave phenomena that are caused by the large topographic variety of Mars' surface, as well the latitudinally symmetric behavior expected at this time of year near the equinox.
Birefringence phenomena revisited
Pereira, Dante D; Gonçalves, Bruno
2016-01-01
The propagation of electromagnetic waves is investigated in the context of the isotropic and nonlinear dielectric media at rest in the eikonal limit of the geometrical optics. Taking into account the functional dependence $\\varepsilon=\\varepsilon(E,B)$ and $\\mu=\\mu(E,B)$ for the dielectric coefficients, a set of phenomena related to the birefringence of the electromagnetic waves induced by external fields are derived and discussed. Our results contemplate the known cases already reported in the literature: Kerr, Cotton-Mouton, Jones and magnetoelectric effects. Moreover, new effects are presented here as well as the perspectives of its experimental confirmations.
MULTISCALE PHENOMENA IN MATERIALS
Energy Technology Data Exchange (ETDEWEB)
A. BISHOP
2000-09-01
This project developed and supported a technology base in nonequilibrium phenomena underpinning fundamental issues in condensed matter and materials science, and applied this technology to selected problems. In this way the increasingly sophisticated synthesis and characterization available for classes of complex electronic and structural materials provided a testbed for nonlinear science, while nonlinear and nonequilibrium techniques helped advance our understanding of the scientific principles underlying the control of material microstructure, their evolution, fundamental to macroscopic functionalities. The project focused on overlapping areas of emerging thrusts and programs in the Los Alamos materials community for which nonlinear and nonequilibrium approaches will have decisive roles and where productive teamwork among elements of modeling, simulations, synthesis, characterization and applications could be anticipated--particularly multiscale and nonequilibrium phenomena, and complex matter in and between fields of soft, hard and biomimetic materials. Principal topics were: (i) Complex organic and inorganic electronic materials, including hard, soft and biomimetic materials, self-assembly processes and photophysics; (ii) Microstructure and evolution in multiscale and hierarchical materials, including dynamic fracture and friction, dislocation and large-scale deformation, metastability, and inhomogeneity; and (iii) Equilibrium and nonequilibrium phases and phase transformations, emphasizing competing interactions, frustration, landscapes, glassy and stochastic dynamics, and energy focusing.
PREFACE Integrability and nonlinear phenomena Integrability and nonlinear phenomena
Gómez-Ullate, David; Lombardo, Sara; Mañas, Manuel; Mazzocco, Marta; Nijhoff, Frank; Sommacal, Matteo
2010-10-01
Back in 1967, Clifford Gardner, John Greene, Martin Kruskal and Robert Miura published a seminal paper in Physical Review Letters which was to become a cornerstone in the theory of integrable systems. In 2006, the authors of this paper received the AMS Steele Prize. In this award the AMS pointed out that `In applications of mathematics, solitons and their descendants (kinks, anti-kinks, instantons, and breathers) have entered and changed such diverse fields as nonlinear optics, plasma physics, and ocean, atmospheric, and planetary sciences. Nonlinearity has undergone a revolution: from a nuisance to be eliminated, to a new tool to be exploited.' From this discovery the modern theory of integrability bloomed, leading scientists to a deep understanding of many nonlinear phenomena which is by no means reachable by perturbation methods or other previous tools from linear theories. Nonlinear phenomena appear everywhere in nature, their description and understanding is therefore of great interest both from the theoretical and applicative point of view. If a nonlinear phenomenon can be represented by an integrable system then we have at our disposal a variety of tools to achieve a better mathematical description of the phenomenon. This special issue is largely dedicated to investigations of nonlinear phenomena which are related to the concept of integrability, either involving integrable systems themselves or because they use techniques from the theory of integrability. The idea of this special issue originated during the 18th edition of the Nonlinear Evolution Equations and Dynamical Systems (NEEDS) workshop, held at Isola Rossa, Sardinia, Italy, 16-23 May 2009 (http://needs-conferences.net/2009/). The issue benefits from the occasion offered by the meeting, in particular by its mini-workshops programme, and contains invited review papers and contributed papers. It is worth pointing out that there was an open call for papers and all contributions were peer reviewed
Phenomena Associated With EIT Waves
Thompson, B. J.; Biesecker, D. A.; Gopalswamy, N.
2003-01-01
We discuss phenomena associated with "EIT Wave" transients. These phenomena include coronal mass ejections, flares, EUV/SXR dimmings, chromospheric waves, Moreton waves, solar energetic particle events, energetic electron events, and radio signatures. Although the occurrence of many phenomena correlate with the appearance of EIT waves, it is difficult to mfer which associations are causal. The presentation will include a discussion of correlation surveys of these phenomena.
Born-Infeld Gravity in any Dimension
Nieto, J.A.
2004-01-01
We develop a Born-Infeld type theory for gravity in any dimension. We show that in four dimensions our formalism allows a self-dual (or anti-self dual) Born-Infeld gravity description. Moreover, we show that such a self-dual action is reduced to both the Deser-Gibbons and the Jacobson-Smolin-Samuel action of Ashtekar formulation. A supersymmetric generalization of our approach is outlined.
Massive Gravity in Ads and Minkowski Backgrounds
Porrati, M.
2004-01-01
I review some interesting features of massive gravity in two maximally symmetric backgrounds: Anti de Sitter space and Minkowski space. While massive gravity in AdS can be seen as a spontaneously broken, UV safe theory, no such interpretation exists yet in the flat-space case. Here, I point out the problems encountered in trying to find such completion, and possible mechanisms to overcome them.
Workshop on Interface Phenomena
Kreuzer, Hans
1987-01-01
This book contains the proceedings of the first Workshop on Interface Phenomena, organized jointly by the surface science groups at Dalhousie University and the University of Maine. It was our intention to concentrate on just three topics related to the kinetics of interface reactions which, in our opinion, were frequently obscured unnecessarily in the literature and whose fundamental nature warranted an extensive discussion to help clarify the issues, very much in the spirit of the Discussions of the Faraday Society. Each session (day) saw two principal speakers expounding the different views; the session chairmen were asked to summarize the ensuing discussions. To understand the complexity of interface reactions, paradigms must be formulated to provide a framework for the interpretation of experimen tal data and for the construction of theoretical models. Phenomenological approaches have been based on a small number of rate equations for the concentrations or mole numbers of the various species involved i...
Minimal Massive 3D Gravity Unitarity Redux
Arvanitakis, Alex S.; Townsend, Paul K
2015-01-01
A geometrical analysis of the bulk and anti-de Sitter boundary unitarity conditions of 3D "Minimal Massive Gravity" (MMG) (which evades the "bulk/boundary clash" of Topologically Massive Gravity) is used to extend and simplify previous results, showing that unitarity selects, up to equivalence, a connected region in parameter space. We also initiate the study of flat-space holography for MMG. Its relevant flat space limit is a deformation of 3D conformal gravity; the deformation is both non-l...
Conformal gravity holography in four dimensions.
Grumiller, Daniel; Irakleidou, Maria; Lovrekovic, Iva; McNees, Robert
2014-03-21
We formulate four-dimensional conformal gravity with (anti-)de Sitter boundary conditions that are weaker than Starobinsky boundary conditions, allowing for an asymptotically subleading Rindler term concurrent with a recent model for gravity at large distances. We prove the consistency of the variational principle and derive the holographic response functions. One of them is the conformal gravity version of the Brown-York stress tensor, the other is a "partially massless response". The on shell action and response functions are finite and do not require holographic renormalization. Finally, we discuss phenomenologically interesting examples, including the most general spherically symmetric solutions and rotating black hole solutions with partially massless hair. PMID:24702345
Gauge Theory of Gravity and Supergravity
Kaul, Romesh K.
2006-01-01
We present a formulation of gravity in terms of a theory based on complex SU(2) gauge fields with a general coordinate invariant action functional quadratic in the field strength. Self-duality or anti-self-duality of the field strength emerges as a constraint from the equations of motion of this theory. This in turn leads to Einstein gravity equations for a dilaton and an axion conformally coupled to gravity for the self-dual constraint. The analysis has also been extended to N=1 and 2 super ...
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...
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...
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....
(Loop) quantum gravity and the inflationary scenario
Bojowald, Martin
2015-12-01
Quantum gravity, as a fundamental theory of space-time, is expected to reveal how the universe may have started, perhaps during or before an inflationary epoch. It may then leave a potentially observable (but probably miniscule) trace in cosmic large-scale structures that seem to match well with predictions of inflation models. A systematic quest to derive such tiny effects using one approach, loop quantum gravity, has, however, led to unexpected obstacles. Such models remain incomplete, and it is not clear whether loop quantum gravity can be consistent as a full theory. But some surprising effects appear to be generic and would drastically alter our understanding of space-time at large density. These new high-curvature phenomena are a consequence of a widening gap between quantum gravity and ordinary quantum-field theory on a background. xml:lang="fr"
PREFACE Integrability and nonlinear phenomena Integrability and nonlinear phenomena
Gómez-Ullate, David; Lombardo, Sara; Mañas, Manuel; Mazzocco, Marta; Nijhoff, Frank; Sommacal, Matteo
2010-10-01
Back in 1967, Clifford Gardner, John Greene, Martin Kruskal and Robert Miura published a seminal paper in Physical Review Letters which was to become a cornerstone in the theory of integrable systems. In 2006, the authors of this paper received the AMS Steele Prize. In this award the AMS pointed out that `In applications of mathematics, solitons and their descendants (kinks, anti-kinks, instantons, and breathers) have entered and changed such diverse fields as nonlinear optics, plasma physics, and ocean, atmospheric, and planetary sciences. Nonlinearity has undergone a revolution: from a nuisance to be eliminated, to a new tool to be exploited.' From this discovery the modern theory of integrability bloomed, leading scientists to a deep understanding of many nonlinear phenomena which is by no means reachable by perturbation methods or other previous tools from linear theories. Nonlinear phenomena appear everywhere in nature, their description and understanding is therefore of great interest both from the theoretical and applicative point of view. If a nonlinear phenomenon can be represented by an integrable system then we have at our disposal a variety of tools to achieve a better mathematical description of the phenomenon. This special issue is largely dedicated to investigations of nonlinear phenomena which are related to the concept of integrability, either involving integrable systems themselves or because they use techniques from the theory of integrability. The idea of this special issue originated during the 18th edition of the Nonlinear Evolution Equations and Dynamical Systems (NEEDS) workshop, held at Isola Rossa, Sardinia, Italy, 16-23 May 2009 (http://needs-conferences.net/2009/). The issue benefits from the occasion offered by the meeting, in particular by its mini-workshops programme, and contains invited review papers and contributed papers. It is worth pointing out that there was an open call for papers and all contributions were peer reviewed
Gravitational Decoherence, Alternative Quantum Theories and Semiclassical Gravity
Hu, B L
2014-01-01
In this report we discuss three aspects: 1) Semiclassical gravity theory (SCG): 4 levels of theories describing the interaction of quantum matter with classical gravity; 2) Alternative Quantum Theories: Discerning those which are derivable from general relativity (GR) plus quantum field theory (QFT) from those which are not; 3) Gravitational Decoherence: Derivation of a master equation and examination of the assumptions which led to the claims of observational possibilities. We list three sets of corresponding problems worthy of pursuit: a) Newton-Schr\\"odinger Equations in relation to SCG; b) Master equation of gravity-induced effects serving as discriminator of 2); and c) Role of gravity in macroscopic quantum phenomena.
Neutrino oscillations under gravity: mass independent oscillation
Mukhopadhyay, Banibrata
2003-01-01
I discuss the possibility of neutrino oscillation in presence of gravity. In this respect I consider the propagation of neutrinos in the early phase of universe and around black holes. It is seen that whether the rest masses of a neutrino and corresponding anti-neutrino are considered to be same or not due to space-time curvature effect non-zero oscillation probability between the neutrino and anti-neutrino states comes out. Therefore I can conclude that under gravity neutrino oscillation tak...
International Nuclear Information System (INIS)
The author presents a series of lectures intended for students familiar with the methods used in many developments of general relativity, cosmology and supergravity. First, he deals with geometry before gravity; manifolds, tensors, spinors and their derivatives are defined. The rules of Cartan's exterior differential calculus are established. Basic formulas of Riemannian geometry are proved with the method of the moving frame (veilbein). Some aspects of the de Rham cohomology are lightly touched on; the physical meaning of the curvature tensor which leads to the Einstein equations is analyzed; Weyl's and Palitini's variational principle are introduced and compared; the extension of first integrals for field equations on curved space is discussed; and finally, a brief description of homogeneous cosmologies, in particular the anti-de Sitter space, is given
Gravity and Mirror Gravity in Plebanski Formulation
Bennett, D. L.; Laperashvili, L. V.; Nielsen, H. B.; Tureanu, A.
2012-01-01
We present several theories of four-dimensional gravity in the Plebanski formulation, in which the tetrads and the connections are the independent dynamical variables. We consider the relation between different versions of gravitational theories: Einstenian, dual, 'mirror' gravities and gravity with torsion. According to Plebanski's assumption, our world, in which we live, is described by the self-dual left-handed gravity. We propose that if the Mirror World exists in Nature, then the 'mirror...
Magueijo, J; Magueijo, Joao; Smolin, Lee
2004-01-01
Non-linear special relativity (or doubly special relativity) is a simple framework for encoding properties of flat quantum space-time. In this paper we show how this formalism may be generalized to incorporate curvature (leading to what might be called ``doubly general relativity''). We first propose a dual to non-linear realizations of relativity in momentum space, and show that for such a dual the space-time invariant is an energy-dependent metric. This leads to an energy-dependent connection and curvature, and a simple modification to Einstein's equations. We then examine solutions to these equations. We find the counterpart to the cosmological metric, and show how cosmologies based upon our theory of gravity may solve the ``horizon problem''. We discuss the Schwarzchild solution, examining the conditions for which the horizon is energy dependent. We finally find the weak field limit.
Lombard, John
2016-01-01
We introduce the construction of a new framework for probing discrete emergent geometry and boundary-boundary observables based on a fundamentally a-dimensional underlying network structure. Using a gravitationally motivated action with Forman weighted combinatorial curvatures and simplicial volumes relying on a decomposition of an abstract simplicial complex into realized embeddings of proper skeletons, we demonstrate properties such as a minimal volume-scale cutoff, the necessity of a positive-definite cosmological constant as a regulator for non-degenerate geometries, and naturally emergent simplicial structures from Metropolis network evolution simulations with no restrictions on attachment rules or regular building blocks. We see emergent properties which echo results from both the spinfoam formalism and causal dynamical triangulations in quantum gravity, and provide analytical and numerical results to support the analogy. We conclude with a summary of open questions and intent for future work in develop...
Newtonian gravity in loop quantum gravity
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.
International Nuclear Information System (INIS)
Acid deposition, commonly known as acid rain, occurs when emissions from the combustion of fossil fuels and other industrial processes undergo complex chemical reactions in the atmosphere and fall to the earth as wet deposition (rain, snow, cloud, fog) or dry deposition (dry particles, gas). Rain and snow are already naturally acidic, but are only considered problematic when less than a ph of 5.0 The main chemical precursors leading to acidic conditions are atmospheric concentrations of sulfur dioxide (SO2) and nitrogen oxides (NOx). When these two compounds react with water, oxygen, and sunlight in the atmosphere, the result is sulfuric (H2SO4) and nitric acids (HNO3), the primary agents of acid deposition which mainly produced from the combustion of fossil fuel and from petroleum refinery. Airborne chemicals can travel long distances from their sources and can therefore affect ecosystems over broad regional scales and in locations far from the sources of emissions. According to the concern of petroleum ministry with the environment and occupational health, in this paper we will discussed the acid deposition phenomena through the following: Types of acidic deposition and its components in the atmosphere Natural and man-made sources of compounds causing the acidic deposition. Chemical reactions causing the acidic deposition phenomenon in the atmosphere. Factors affecting level of acidic deposition in the atmosphere. Impact of acid deposition. Procedures for acidic deposition control in petroleum industry
Hanslmeier, Arnold; Veronig, Astrid; Messerotti, Mauro
This book contains the proceedings of the Summerschool and Workshop "Solar Magnetic Phenomena" held from 25 August to 5 September 2003 at the Solar Observatory Kanzelhoehe, which belongs to the Institute for Geophysics, Astrophysics and Meteorology of the University of Graz, Austria. The book contains the contributions from six invited lecturers, They give an overview on the following topics: observations of the photosphere and chromosphere, solar flares observations and theory, coronal mass ejections and the relevance of magnetic helicity, high-energy radiation from the Sun, the physics of solar prominences and highlights from the SOHO mission. The lectures contain about 25 to 30 pages each and provide a valuable introduction to the topics mentioned above. The comprehensive lists of references at the end of each contribution enable the interested reader to go into more detail. The second part of the book contains contributed papers. These papers were presented and discussed in the workshop sessions during the afternoons. The sessions stimulated intensive discussions between the participants and the lecturers.
AdS Waves as Exact Solutions to Quadratic Gravity
Gullu, Ibrahim; Gurses, Metin; Sisman, Tahsin Cagri; Tekin, Bayram(Department of Physics, Middle East Technical University, 06800 Ankara, Turkey)
2011-01-01
We give an exact solution of the quadratic gravity in D dimensions. The solution is a plane fronted wave metric with a cosmological constant. This metric solves not only the full quadratic gravity field equations but also the linearized ones which include the linearized equations of the recently found critical gravity. A subset of the solutions change the asymptotic structure of the anti-de Sitter space due to their logarithmic behavior.
"Anti-Gravity" Treadmills Speed Rehabilitation
2009-01-01
A former Ames Research Center engineer, Dr. Robert Whalen, invented a treadmill that he licensed to a Menlo Park, California company, Alter-G Inc. The company s G-Trainer is an enclosed treadmill that uses air pressure to help patients feel up to 80 percent lighter, easing discomfort during rehabilitation. A patient desiring more weightlessness during a workout can simply press a button and the air pressure increases, lifting the body and reducing strain and impact. The U.S. Food and Drug Administration cleared the G-Trainer for medical use in January 2008, and researchers are now assessing the G-Trainer s effectiveness in aiding patients with various neurological or musculoskeletal conditions.
Boundary Dynamics of Higher Dimensional Chern-Simons Gravity
Gegenberg, J.; Kunstatter, G.
2000-01-01
We review the relevance to the black hole entropy problem of boundary dynamics in Chern-Simons gravity. We then describe a recent derivation of the action induced on the four dimensional boundary in a five dimensional Chern-Simons gravity theory with gauge invariant, anti-deSitter boundary conditions.
Lineal gravity from planar gravity
Achúcarro, A
1993-01-01
We show how to obtain the two-dimensional black hole action by dimensional reduction of the three-dimensional Einstein action with a non-zero cosmological constant. Starting from the Chern-Simons formulation of 2+1 gravity, we obtain the 1+1 dimensional gauge formulation given by Verlinde. Remarkably, the proposed reduction shares the relevant features of the formulation of Cangemi and Jackiw, without the need for a central charge in the algebra. We show how the Lagrange multipliersin these formulations appear naturally as the remnants of the three dimensional connection associated to symmetries that have been lostin the dimensional reduction. The proposed dimensional reduction involves a shift in the three dimensional connection whose effect is to make the length of the extra dimension infinite.
Oriti, Daniele
2009-03-01
Preface; Part I. Fundamental Ideas and General Formalisms: 1. Unfinished revolution C. Rovelli; 2. The fundamental nature of space and time G. 't Hooft; 3. Does locality fail at intermediate length scales R. Sorkin; 4. Prolegomena to any future quantum gravity J. Stachel; 5. Spacetime symmetries in histories canonical gravity N. Savvidou; 6. Categorical geometry and the mathematical foundations of quantum gravity L. Crane; 7. Emergent relativity O. Dreyer; 8. Asymptotic safety R. Percacci; 9. New directions in background independent quantum gravity F. Markopoulou; Questions and answers; Part II: 10. Gauge/gravity duality G. Horowitz and J. Polchinski; 11. String theory, holography and quantum gravity T. Banks; 12. String field theory W. Taylor; Questions and answers; Part III: 13. Loop Quantum Gravity T. Thiemann; 14. Covariant loop quantum gravity? E. LIvine; 15. The spin foam representation of loop quantum gravity A. Perez; 16. 3-dimensional spin foam quantum gravity L. Freidel; 17. The group field theory approach to quantum gravity D. Oriti; Questions and answers; Part IV. Discrete Quantum Gravity: 18. Quantum gravity: the art of building spacetime J. Ambjørn, J. Jurkiewicz and R. Loll; 19. Quantum Regge calculations R. Williams; 20. Consistent discretizations as a road to quantum gravity R. Gambini and J. Pullin; 21. The causal set approach to quantum gravity J. Henson; Questions and answers; Part V. Effective Models and Quantum Gravity Phenomenology: 22. Quantum gravity phenomenology G. Amelino-Camelia; 23. Quantum gravity and precision tests C. Burgess; 24. Algebraic approach to quantum gravity II: non-commutative spacetime F. Girelli; 25. Doubly special relativity J. Kowalski-Glikman; 26. From quantum reference frames to deformed special relativity F. Girelli; 27. Lorentz invariance violation and its role in quantum gravity phenomenology J. Collins, A. Perez and D. Sudarsky; 28. Generic predictions of quantum theories of gravity L. Smolin; Questions and
Einstein Gravity, Massive Gravity, Multi-Gravity and Nonlinear Realizations
Goon, Garrett; Hinterbichler, Kurt; Joyce, Austin; Trodden, Mark
2014-01-01
The existence of a ghost free theory of massive gravity begs for an interpre-tation as a Higgs phase of General Relativity. We revisit the study of massive gravity as a Higgs phase. Absent a compelling microphysical model of spontaneous symmetry breaking in gravity, we approach this problem from the viewpoint of nonlinear realizations. We employ the coset construction to search for the most restrictive symmetry breaking pattern whose low energy theory will both admit the de Rham-Gabadadze-Tol...
Gravitational waves in geometric scalar gravity
Toniato, J D
2016-01-01
We investigate the description of gravitational waves in the geometric scalar theory of gravity (GSG). The GSG belongs to a class of theories such that gravity is described by a single scalar field and the associated physical metric describing the spacetime is constructed from a disformal transformation of Minkowski geometry. In this theory, gravitational waves have a longitudinal polarization mode, besides others modes that are observer dependent. We examine the orbital variation of a binary system due to the emission of gravitational waves, showing that GSG can also be successful in explaining this phenomena.
Minimal Massive Gravity: Conserved Charges, Excitations and the Chiral Gravity Limit
Tekin, Bayram(Department of Physics, Middle East Technical University, 06800 Ankara, Turkey)
2014-01-01
We find the excitations and construct the conserved charges ( mass and angular momentum) of the recently found Minimal Massive Gravity (MMG) in 2+1 dimensions in asymptotically Anti-de Sitter (AdS) spacetimes. The field equation of the theory does not come from an action and hence lacks the required Bianchi Identity needed to define conserved charges. But the theory, which also provides a healthy extension of the Topologically Massive Gravity in the bulk and boundary of spacetime, does admit ...
Toward Understanding Astrophysical Phenomena
Luan, Jing
2015-06-01
I hope to resume working on fast radio bursts (FRBs) in the near future. But after we completed our FRB paper, I decided to pause this project because of the lack of observational constraints. The pulsar triple system, J0733+1715, has its orbital parameters fitted to high accuracy owing to the precise timing of the central ms pulsar. The two orbits are highly hierarchical, namely Porb,1 " Porb,2, where 1 and 2 label the inner and outer white dwarf (WD) companions respectively. Moreover, their orbital planes almost coincide, providing a unique opportunity to study secular interaction associated purely with eccentricity beyond the solar system. Secular interaction only involves effect averaged over many orbits. Thus each companion can be represented by an elliptical wire with its mass distributed inversely proportional to its local orbital speed. Generally there exists a mutual torque, which vanishes only when their apsidal lines are parallel or anti-parallel. To maintain either mode, the eccentricity ratio, e1/ e2, must be of the proper value, so that both apsidal lines precess together. For J0733+1715, e1 " e2 for the parallel mode, while e 1 " e2 for the anti-parallel one. We show that the former precesses ˜10 times slower than the latter. Currently the system is dominated by the parallel mode. Although only a little anti-parallel mode survives, both eccentricities especially e1 oscillate on ˜103yr timescale. Detectable changes would occur within ˜1y. We demonstrate that the anti-parallel mode gets damped ˜10 4 times faster than its parallel brother by any dissipative process diminishing e1. If it is the tidal damping in the inner WD, we proceed to estimate its tidal quantity parameter (Q) to be ˜106, which was poorly constrained by observations. However, tidal damping may also happen during the preceding low-mass X-ray binary (LMXB) phase or hydrogen thermal nuclear flashes. But, in both cases, the inner companion fills its Roche lobe and probably suffers
Linker, Patrick
2016-01-01
A couple of quantum gravity theories were proposed to make theoretical predictions about the behavior of gravity. The most recent approach to quantum gravity, called E-theory, is proposed mathematical, but there is not formulated much about what dynamics of gravity this theory proposes. This research paper treats the main results of the application of E-theory to General relativity involving conservation laws and scattering of particles in presence of gravity. Also the low-energy limit of thi...
Gravity wave transmission diagram
Tomikawa, Yoshihiro
2016-07-01
A possibility of gravity wave propagation from a source region to the airglow layer around the mesopause has been discussed based on the gravity wave blocking diagram taking into account the critical level filtering alone. This paper proposes a new gravity wave transmission diagram in which both the critical level filtering and turning level reflection of gravity waves are considered. It shows a significantly different distribution of gravity wave transmissivity from the blocking diagram.
Analogue gravitational phenomena in Bose-Einstein condensates
Finazzi, Stefano
2012-08-01
Analogue gravity is based on the simple observation that perturbations propagating in several physical systems can be described by a quantum field theory in a curved spacetime. While phenomena like Hawking radiation are hardly detectable in astrophysical black holes, these effects may be experimentally tested in analogue systems. In this Thesis, focusing on Bose-Einstein condensates, we present our recent results about analogue models of gravity from three main perspectives: as laboratory tests of quantum field theory in curved spacetime, for the techniques that they provide to address various issues in general relativity, and as toy models of quantum gravity. The robustness of Hawking-like particle creation is investigated in flows with a single black hole horizon. Furthermore, we find that condensates with two (white and black) horizons develop a dynamical instability known in general relativity as black hole laser effect. Using techniques borrowed from analogue gravity, we also show that warp drives, which are general relativistic spacetimes allowing faster-than-light travel, are unstable. Finally, the cosmological constant issue is investigated from an analogue gravity perspective and relativistic Bose-Einstein condensates are proposed as new analogue systems with novel interesting properties.
Teaching Optical Phenomena with Tracker
Rodrigues, M.; Carvalho, P. Simeão
2014-01-01
Since the invention and dissemination of domestic laser pointers, observing optical phenomena is a relatively easy task. Any student can buy a laser and experience at home, in a qualitative way, the reflection, refraction and even diffraction phenomena of light. However, quantitative experiments need instruments of high precision that have a…
Relaxation phenomena in disordered systems
Sciortino, F.; Tartaglia, P.
1997-02-01
In this article we discuss how the assumptions of self-similarity imposed on the distribution of independently relaxing modes, as well as on their amplitude and characteristic times, manifest in the global relaxation phenomena. We also review recent applications of such approach to the description of relaxation phenomena in microemulsions and molecular glasses.
Gravity, Twistors and the MHV Formalism
Mason, Lionel
2008-01-01
We give a self-contained derivation of the MHV amplitudes for gravity and use the associated twistor generating function to define a twistor action for the MHV diagram approach to gravity. Starting from a background field calculation on a spacetime with anti self-dual curvature, we obtain a simple spacetime formula for the scattering of a single, positive helicity linearized graviton into one of negative helicity. Re-expressing our integral in terms of twistor data allows us to consider a spacetime that is asymptotic to a superposition of plane waves. Expanding these out perturbatively yields the gravitational MHV amplitudes of Berends, Giele & Kuijf. We go on to take the twistor generating function off-shell at the perturbative level. Combining this with a twistor action for the anti self-dual background, we obtain a twistor action for the MHV diagram approach to perturbative gravity. We finish by extending these results to supergravity, in particular N=4 and N=8.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC
2007-07-06
I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable {zeta} which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. I also discuss a number of novel phenomenological features of QCD. Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high centrality heavy ion collisions.
Moduli Space of Topological 2-form Gravity
Abe, Mitsuko; Nakamichi, A.; Ueno, T.
1993-01-01
We propose a topological version of four-dimensional (Euclidean) Einstein gravity, in which anti-self-dual 2-forms and an SU(2) connection are used as fundamental fields. The theory describes the moduli space of conformally self-dual Einstein manifolds. In the presence of a cosmological constant, we evaluate the index of the elliptic complex associated with the moduli space.
Energy bounds in designer gravity
Amsel, Aaron J.; Marolf, Donald
2006-09-01
We consider asymptotically anti-de Sitter gravity coupled to tachyonic scalar fields with mass at or slightly above the Breitenlohner-Freedman bound in d≥4 spacetime dimensions. The boundary conditions in these “designer gravity” theories are defined in terms of an arbitrary function W. We give a general argument that the Hamiltonian generators of asymptotic symmetries for such systems will be finite, and proceed to construct these generators using the covariant phase space method. The direct calculation confirms that the generators are finite and shows that they take the form of the pure gravity result plus additional contributions from the scalar fields. By comparing the generators to the spinor charge, we derive a lower bound on the gravitational energy when W has a global minimum and the Breitenlohner-Freedman bound is not saturated.
Löhner-Böttcher, Johannes
2016-03-01
Context: The dynamic atmosphere of the Sun exhibits a wealth of magnetohydrodynamic (MHD) waves. In the presence of strong magnetic fields, most spectacular and powerful waves evolve in the sunspot atmosphere. Allover the sunspot area, continuously propagating waves generate strong oscillations in spectral intensity and velocity. The most prominent and fascinating phenomena are the 'umbral flashes' and 'running penumbral waves' as seen in the sunspot chromosphere. Their nature and relation have been under intense discussion in the last decades. Aims: Waves are suggested to propagate upward along the magnetic field lines of sunspots. An observational study is performed to prove or disprove the field-guided nature and coupling of the prevalent umbral and penumbral waves. Comprehensive spectroscopic observations at high resolution shall provide new insights into the wave characteristics and distribution across the sunspot atmosphere. Methods: Two prime sunspot observations were carried out with the Dunn Solar Telescope at the National Solar Observatory in New Mexico and with the Vacuum Tower Telescope at the Teide Observatory on Tenerife. The two-dimensional spectroscopic observations were performed with the interferometric spectrometers IBIS and TESOS. Multiple spectral lines are scanned co-temporally to sample the dynamics at the photospheric and chromospheric layers. The time series (1 - 2.5 h) taken at high spatial and temporal resolution are analyzed according to their evolution in spectral intensities and Doppler velocities. A wavelet analysis was used to obtain the wave power and dominating wave periods. A reconstruction of the magnetic field inclination based on sunspot oscillations was developed. Results and conclusions: Sunspot oscillations occur continuously in spectral intensity and velocity. The obtained wave characteristics of umbral flashes and running penumbral waves strongly support the scenario of slow-mode magnetoacoustic wave propagation along the
Advanced diffusion processes and phenomena
Öchsner, Andreas; Belova, Irina
2014-01-01
This topical volume on Advanced Diffusion Processes and Phenomena addresses diffusion in a wider sense of not only mass diffusion but also heat diffusion in fluids and solids. Both diffusion phenomena play an important role in the characterization of engineering materials and corresponding structures. Understanding these different transport phenomena at many levels, from atomistic to macro, has therefore long attracted the attention of many researchers in materials science and engineering and related disciplines. The present topical volume captures a representative cross-section of some of the
A Soliton and a Black Hole are in Gauss-Bonnet gravity. Who wins?
Wong, Anson W. C.; Mann, Robert B.
2012-01-01
We study here the phase-transitional evolution between the Eguchi-Hanson soliton, the orbifolded Schwarzschild Anti de-Sitter black hole, and orbifolded thermal Anti de-Sitter space in Gauss-Bonnet gravity for a small Gauss-Bonnet coefficient $\\alpha$. Novel phase structure is uncovered for both negative and positive $\\alpha$ with spacetime configurations that are stable in Gauss-Bonnet gravity without being so in Einsteinian gravity. The evolutionary tracks taken towards such stable configur...
Nonlinear dynamics of parity-even tricritical gravity in three and four dimensions
Apolo, Luis; Porrati, Massimo
2012-01-01
Recently proposed "multicritical" higher-derivative gravities in Anti de Sitter space carry logarithmic representations of the Anti de Sitter isometry group. While generically non-unitary already at the quadratic, free-theory level, in special cases these theories admit a unitary subspace. The simplest example of such behavior is "tricritical" gravity. In this paper, we extend the study of parity-even tricritical gravity in d = 3, 4 to the first nonlinear order. We show that the would-be unit...
Resonant phenomena in colloidal crystals
Palberg, Thomas; Würth, Mathias; König, Peter; Simnacher, Erwin; Leiderer, Paul
1992-01-01
Colloidal crystals of completely deionized suspensions of latex speres are subjected to oscillatory and steady shear, as well as to homogeneous and inhomogeneous electric fields. Various resonant phenomena observed in such experiments are reported.
Autoregressive description of biological phenomena
Morariu, Vasile V; Pop, Alexadru; Soltuz, Stefan M; Buimaga-Iarinca, Luiza; Zainea, Oana
2008-01-01
Many natural phenomena can be described by power-laws. A closer look at various experimental data reveals more or less significant deviations from a 1/f spectrum. We exemplify such cases with phenomena offered by molecular biology, cell biophysics, and cognitive psychology. Some of these cases can be described by first order autoregressive (AR) models or by higher order AR models which are short range correlation models. The calculations are checked against astrophysical data which were fitted to a an AR model by a different method. We found that our fitting method of the data give similar results for the astrhophysical data and therefore applied the method for examples mentioned above. Our results show that such phenomena can be described by first or higher order of AR models. Therefore such examples are described by short range correlation properties while they can be easily confounded with long range correlation phenomena.
Graviton and scalar propagations on AdS(4) space in f(R) gravities
Myung, Yun Soo
2010-01-01
We investigate propagations of graviton and additional scalar on four-dimensional anti de Sitter (AdS$_4$) space using $f(R)$ gravity models with external sources. It is shown that there is the van Dam-Veltman-Zakharov (vDVZ) discontinuity in $f(R)$ gravity models because $f(R)$ gravity implies GR with additional scalar. This indicates a difference between general relativity and $f(R)$ gravity clearly.
Mathematical Model for Hit Phenomena
Ishii, Akira; Hayashi, Takefumi; Matsuda, Naoya; Nakagawa, Takeshi; Arakaki, Hisashi; Yoshida, Narihiko
2010-01-01
The mathematical model for hit phenomena in entertainments is presented as a nonlinear, dynamical and non-equilibrium phenomena. The purchase intention for each person is introduced and direct and indirect communications are expressed as two-body and three-body interaction in our model. The mathematical model is expressed as coupled nonlinear differential equations. The important factor in the model is the decay time of rumor for the hit. The calculated results agree very well with revenues of recent 25 movies.
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...
Cadiz, California Gravity Data
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...
Classical Weyl Transverse Gravity
Oda, Ichiro
2016-01-01
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,...
... medlineplus.gov/ency/article/003587.htm Urine specific gravity test To use the sharing features on this page, please enable JavaScript. Urine specific gravity is a laboratory test that shows the concentration ...
Northern Oklahoma Gravity Data
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,...
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...
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...
Does the Madden-Julian Oscillation Modulate Stratospheric Gravity Waves?
Moss, Andrew; Wright, Corwin; Mitchell, Nicholas
2016-04-01
The circulation of the stratosphere is strongly influenced by the fluxes of gravity waves propagating from tropospheric sources. In the tropics, these gravity waves are primarily generated by convection. The Madden-Julian Oscillation (MJO) dominates the intra-seasonal variability of this convection. However, the connection between the MJO and the variability of stratospheric gravity waves is largely unknown. Here we examine gravity-wave potential energy at a height of 26 km and the upper tropospheric zonal-wind anomaly of the MJO at the 200 hPa level, sorted by the relative phase of the MJO using the RMM MJO indices. We show that a strong anti-correlation exists between gravity-wave potential energy and the MJO eastward wind anomaly. We propose that this correlation is a result of the filtering of ascending waves by the MJO winds. The study provides evidence that the MJO contributes significantly to the variability of stratospheric gravity waves in the tropics.
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"
Ambjorn, Jan
1994-01-01
I discuss recent progress in our understanding of two barriers in quantum gravity: $c > 1$ in the case of 2d quantum gravity and $D > 2$ in the case of Euclidean Einstein-Hilbert gravity formulated in space-time dimensions $D >2$.
The Other Side of Gravity and Geometry: Antigravity and Anticurvature
Directory of Open Access Journals (Sweden)
M. I. Wanas
2012-01-01
Full Text Available Gravity is one of the four known fundamental interactions used to study and interpret physical phenomenae. It governs diverse phenomenae, especially those connected with large-scale structures. From more than one decade, existing gravity theories have suffered from some problems, when confronting their predictions with the results of some experiments and observations. This situation has led to many suggestions, none of which is final, so far. Here, we show that the assumption of existence of another side of gravity, a repulsive gravity or antigravity, together with its attractive side, may give a satisfactory solution to gravity problems. We caught here two pieces of evidence for the existence of antigravity in nature. The first is on the laboratory scale, the COW experiment, and the second is on the cosmic scale, SN type Ia observation. On the other hand, we show how gravity theories can predict antigravity, using a new defined geometric object called Parameterized anticurvature. This shows clearly how Einstein's geometrization philosophy can solve recent gravity problems in a satisfactory and easy way. Also, it may throw some light on the mystery of physical nature of “Dark Energy.”
Charged C-metric in conformal gravity
Lim, Yen-Kheng
2016-01-01
Using a C-metric-type ansatz, we obtain an exact solution to conformal gravity coupled to a Maxwell electromagnetic field. The solution resembles a C-metric spacetime carrying an electromagnetic charge. The metric is cast in a factorised form which allows us to study the domain structure of its static coordinate regions. This metric reduces to the well-known Mannheim-Kazanas metric under an appropriate limiting procedure, and also reduces to the (Anti-)de Sitter C-metric of Einstein gravity f...
Charged C-metric in conformal gravity
Lim, Yen-Kheng
2016-01-01
Using a C-metric-type ansatz, we obtain an exact solution to conformal gravity coupled to a Maxwell electromagnetic field. The solution resembles a C-metric spacetime carrying an electromagnetic charge. The metric is cast in a factorised form which allows us to study the domain structure of its static coordinate regions. This metric reduces to the well-known Mannheim-Kazanas metric under an appropriate limiting procedure, and also reduces to the (Anti-)de Sitter C-metric of Einstein gravity for a particular choice of parameters.
Violation of Energy Bounds in Designer Gravity
Hertog, Thomas
2006-01-01
We continue our study of the stability of designer gravity theories, where one considers anti-de Sitter gravity coupled to certain tachyonic scalars with boundary conditions defined by a smooth function W. It has recently been argued there is a lower bound on the conserved energy in terms of the global minimum of W, if the scalar potential arises from a superpotential P and the scalar reaches an extremum of P at infinity. We show, however, there are superpotentials for which these bounds do n...
Charged C -metric in conformal gravity
Lim, Yen-Kheng
2016-04-01
Using a C -metric-type ansatz, we obtain an exact solution to conformal gravity coupled to a Maxwell electromagnetic field. The solution resembles a C -metric spacetime carrying an electromagnetic charge. The metric is cast in a factorized form which allows us to study the domain structure of its static coordinate regions. This metric reduces to the well-known Mannheim-Kazanas metric under an appropriate limiting procedure, and also reduces to the (anti)de Sitter C -metric of Einstein gravity for a particular choice of parameters.
Directory of Open Access Journals (Sweden)
Bernard S. Kay
2015-12-01
Full Text Available We give a review, in the style of an essay, of the author’s 1998 matter-gravity entanglement hypothesis which, unlike the standard approach to entropy based on coarse-graining, offers a definition for the entropy of a closed system as a real and objective quantity. We explain how this approach offers an explanation for the Second Law of Thermodynamics in general and a non-paradoxical understanding of information loss during black hole formation and evaporation in particular. It also involves a radically different from usual description of black hole equilibrium states in which the total state of a black hole in a box together with its atmosphere is a pure state—entangled in just such a way that the reduced state of the black hole and of its atmosphere are each separately approximately thermal. We also briefly recall some recent work of the author which involves a reworking of the string-theory understanding of black hole entropy consistent with this alternative description of black hole equilibrium states and point out that this is free from some unsatisfactory features of the usual string theory understanding. We also recall the author’s recent arguments based on this alternative description which suggest that the Anti de Sitter space (AdS/conformal field theory (CFT correspondence is a bijection between the boundary CFT and just the matter degrees of freedom of the bulk theory.
Containment severe accident thermohydraulic phenomena
International Nuclear Information System (INIS)
This report describes and discusses the containment accident progression and the important severe accident containment thermohydraulic phenomena. The overall objective of the report is to provide a rather detailed presentation of the present status of phenomenological knowledge, including an account of relevant experimental investigations and to discuss, to some extent, the modelling approach used in the MAAP 3.0 computer code. The MAAP code has been used in Sweden as the main tool in the analysis of severe accidents. The dependence of the containment accident progression and containment phenomena on the initial conditions, which in turn are heavily dependent on the in-vessel accident progression and phenomena as well as associated uncertainties, is emphasized. The report is in three parts dealing with: * Swedish reactor containments, the severe accident mitigation programme in Sweden and containment accident progression in Swedish PWRs and BWRs as predicted by the MAAP 3.0 code. * Key non-energetic ex-vessel phenomena (melt fragmentation in water, melt quenching and coolability, core-concrete interaction and high temperature in containment). * Early containment threats due to energetic events (hydrogen combustion, high pressure melt ejection and direct containment heating, and ex-vessel steam explosions). The report concludes that our understanding of the containment severe accident progression and phenomena has improved very significantly over the parts ten years and, thereby, our ability to assess containment threats, to quantify uncertainties, and to interpret the results of experiments and computer code calculations have also increased. (au)
Teaching optical phenomena with Tracker
Rodrigues, M.; Simeão Carvalho, P.
2014-11-01
Since the invention and dissemination of domestic laser pointers, observing optical phenomena is a relatively easy task. Any student can buy a laser and experience at home, in a qualitative way, the reflection, refraction and even diffraction phenomena of light. However, quantitative experiments need instruments of high precision that have a relatively complex setup. Fortunately, nowadays it is possible to analyse optical phenomena in a simple and quantitative way using the freeware video analysis software ‘Tracker’. In this paper, we show the advantages of video-based experimental activities for teaching concepts in optics. We intend to show: (a) how easy the study of such phenomena can be, even at home, because only simple materials are needed, and Tracker provides the necessary measuring instruments; and (b) how we can use Tracker to improve students’ understanding of some optical concepts. We give examples using video modelling to study the laws of reflection, Snell’s laws, focal distances in lenses and mirrors, and diffraction phenomena, which we hope will motivate teachers to implement it in their own classes and schools.
Gravity/Fluid Correspondence For Massive Gravity
Pan, Wen-Jian
2016-01-01
In this paper, we investigate the gravity/fluid correspondence in the framework of massive gravity. Treating the gravitational mass terms as an effective energy-momentum tensor and utilizing the Petrov-like boundary condition on a time-like hypersurface, we find that the perturbation effects of massive gravity in bulk can be completely governed by the incompressible Navier-Stokes equation living on the cutoff surface under the near horizon and non-relativistic limit. Furthermore, in our models, we have concisely computed the ratio of dynamical viscosity to entropy density, and shown that it still satisfies KSS bound.
Critical Phenomena in Gravitational Collapse
Directory of Open Access Journals (Sweden)
Gundlach Carsten
1999-01-01
Full Text Available As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term 'critical phenomena'. They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. This review gives an introduction to the phenomena, tries to summarize the essential features of what is happening, and then presents extensions and applications of this basic scenario. Critical phenomena are of interest particularly for creating surprising structure from simple equations, and for the light they throw on cosmic censorship and the generic dynamics of general relativity.
Macroscopic quantum systems and gravitational phenomena
International Nuclear Information System (INIS)
Low-energy quantum systems are studied theoretically in light of possible experiments to test the interplay between quantum theory and general relativity. The research focus in this thesis is on quantum systems which can be controlled with very high precision and which allow for tests of quantum theory at novel scales in terms of mass and size. The pulsed regime of opto-mechanics is explored and it is shown how short optical pulses can be used to prepare and characterize quantum states of a massive mechanical resonator, and how some phenomenological models of quantum gravity can be probed. In addition, quantum interferometry with photons and matter-waves in the presence of gravitational time dilation is considered. It is shown that time dilation causes entanglement between internal states and the center-of-mass position and that it leads to decoherence of all composite quantum systems. The results of the thesis show that the interplay between quantum theory and general relativity affects even low-energy quantum systems and that it offers novel phenomena which can be probed in experiments. (author)
Tribology Experiment in Zero Gravity
Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.; Finckenor, M. M.
2015-01-01
A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates observation of such motions as controlled by interfacial and capillary forces. Two experimental configurations were used. One deals with the liquid on one solid surface, and the other with the liquid between a pair of closed spaced surfaces. Time sequence photographs of fluid motion on a solid surface yielded spreading rate data of several fluid-surface combinations. In general, a slow spreading process as governed by the tertiary junction can be distinguished from a more rapid process which is driven by surface tension controlled internal fluid pressure. Photographs were also taken through the transparent bushings of several experimental journal bearings. Morphology of incomplete fluid films and its fluctuation with time suggest the presence or absence of unsteady phenomena of the bearing-rotor system in various arrangements.
Gravitomagnetic effects in conformal gravity
Said, Jackson Levi; Adami, Kristian Zarb
2014-01-01
Gravitomagnetic effects are characterized by two phenomena: first, the geodetic effect which describes the precession of the spin of a gyroscope in a free orbit around a massive object, second, the Lense-Thirring effect which describes the precession of the orbital plane about a rotating source mass. We calculate both these effects in the fourth-order theory of conformal Weyl gravity for the test case of circular orbits. We show that for the geodetic effect a linear term arises which may be interesting for high radial orbits, whereas for the Lense-Thirring effect the additional term has a diminishing effect for most orbits. Circular orbits are also considered in general leading up to a generalization of Kepler's third law.
Dimensional Reduction in Quantum Gravity
Hooft, G 't
2009-01-01
The requirement that physical phenomena associated with gravitational collapse should be duly reconciled with the postulates of quantum mechanics implies that at a Planckian scale our world is not 3+1 dimensional. Rather, the observable degrees of freedom can best be described as if they were Boolean variables defined on a two-dimensional lattice, evolving with time. This observation, deduced from not much more than unitarity, entropy and counting arguments, implies severe restrictions on possible models of quantum gravity. Using cellular automata as an example it is argued that this dimensional reduction implies more constraints than the freedom we have in constructing models. This is the main reason why so-far no completely consistent mathematical models of quantum black holes have been found. Essay dedicated to Abdus Salam.
Whistlers and related ionospheric phenomena
Helliwell, Robert A
2006-01-01
The investigation of whistlers and related phenomena is a key element in studies of very-low-frequency propagation, satellite communication, the outer ionosphere, and solar-terrestrial relationships. This comprehensive text presents a history of the study of the phenomena and includes all the elements necessary for the calculation of the characteristics of whistlers and whistler-mode signals.An introduction and brief history are followed by a summary of the theory of whistlers and a detailed explanation of the calculation of their characteristics. Succeeding chapters offer a complete atlas of
Undergraduates' understanding of cardiovascular phenomena.
Michael, Joel A; Wenderoth, Mary Pat; Modell, Harold I; Cliff, William; Horwitz, Barbara; McHale, Philip; Richardson, Daniel; Silverthorn, Dee; Williams, Stephen; Whitescarver, Shirley
2002-12-01
Undergraduates students in 12 courses at 8 different institutions were surveyed to determine the prevalence of 13 different misconceptions (conceptual difficulties) about cardiovascular function. The prevalence of these misconceptions ranged from 20 to 81% and, for each misconception, was consistent across the different student populations. We also obtained explanations for the students' answers either as free responses or with follow-up multiple-choice questions. These results suggest that students have a number of underlying conceptual difficulties about cardiovascular phenomena. One possible source of some misconceptions is the students' inability to apply simple general models to specific cardiovascular phenomena. Some implications of these results for teachers of physiology are discussed.
Anomalous effects due to the inertial anti-gravitational potential of the sun
Khokhlov, D. L.
2007-01-01
It is introduced inertial anti-gravitational potential into the theory of gravity to stop gravitational collapse at the nuclear density and thus prevent singularities. It is considered effective gravity which includes Newtonian potential and inertial anti-gravitational potential. It is investigated footprints of the effective gravity in the solar system. The inertial anti-gravitational potential of the sun allows to explain the anomalous acceleration of Pioneer 10 and 11, the anomalous increa...
Einstein Gravity, Massive Gravity, Multi-Gravity and Nonlinear Realizations
Goon, Garrett; Joyce, Austin; Trodden, Mark
2014-01-01
The existence of a ghost free theory of massive gravity begs for an interpretation as a Higgs phase of General Relativity. We revisit the study of massive gravity as a Higgs phase. Absent a compelling microphysical model of spontaneous symmetry breaking in gravity, we approach this problem from the viewpoint of nonlinear realizations. We employ the coset construction to search for the most restrictive symmetry breaking pattern whose low energy theory will both admit the de Rham--Gabadadze--Tolley (dRGT) potentials and nonlinearly realize every symmetry of General Relativity, thereby providing a new perspective from which to build theories of massive gravity. In addition to the known ghost-free terms, we find a novel parity violating interaction which preserves the constraint structure of the theory, but which vanishes on the normal branch of the theory. Finally, the procedure is extended to the cases of bi-gravity and multi-vielbein theories. Analogous parity violating interactions exist here, too, and may be...
Transport phenomena in particulate systems
Freire, José Teixeira; Ferreira, Maria do Carmo
2012-01-01
This volume spans 10 chapters covering different aspects of transport phenomena including fixed and fluidized systems, spouted beds, electrochemical and wastewater treatment reactors. This e-book will be valuable for students, engineers and researchers aiming to keep updated on the latest developments on particulate systems.
Strings, fields and critical phenomena
International Nuclear Information System (INIS)
The connection between field theory and critical phenomena is reviewed. Emphasis is put on the use of Monte Carlo methods in the study of non-perturbative aspects of field theory. String theory is then described as a statistical theory of random surfaces and the critical behaviour is analyzed both by analytical and numerical methods. (orig.)
Nursing phenomena in inpatient psychiatry
Frauenfelder, F.; Muller-Staub, M.; Needham, I.; Achterberg, T. van
2011-01-01
Little is known about the question if the nursing diagnosis classification of North American Nursing Association-International (NANDA-I) describes the adult inpatient psychiatric nursing care. The present study aimed to identify nursing phenomena mentioned in journal articles about the psychiatric i
Institute of Scientific and Technical Information of China (English)
常晓林; 袁曦
2012-01-01
In the traditional strength reduction method, the influence of seepage is frequently overlooked. However, recent studies have shown the necessity to consider the seepage in bedrock, especially in the stability analysis of gravity dam against sliding. The relationship between the rock permeability coefficient and the volume-strain is deduced to achieve the hydro-mechanical coupling. An USDFLD subroutine in ABAQUS is developed to implement the strength reduction analysis considering hydro-mechanical cou- pling. The anti-sliding stability analysis for a typical gravity dam with double sliding faces is then per- formed to demonstrate the effect of seepage in bedrock. Finally, the proposed strength reduction method considering hydro-mechanical coupling is applied to a gravity dam. The damage process and strength reserve safety coefficient are obtained.%对传统强度折减法计算流程进行分析,指出了其中存在的不足,即对渗流的考虑不够充分.为弥补此项不足,从H-M耦合机理出发,推导了渗透系数与体积应变之间的函数关系,从而实现了H-M完全耦合.借助ABAQUS软件子程序USDFLD的二次开发,实现了H-M耦合与强度折减法的结合.以一个典型的重力坝双滑面稳定问题为例进行了对比分析,揭示了渗流对于重力坝稳定性的影响不可忽视.最后,对某重力坝单坝段进行了考虑H-M耦合的强度折减计算,得到了该坝段的渐进破坏过程和强度储备系数.
Multi-scale gravity field modeling in space and time
Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric
2016-04-01
The Earth constantly deforms as it undergoes dynamic phenomena, such as earthquakes, post-glacial rebound and water displacement in its fluid envelopes. These processes have different spatial and temporal scales and are accompanied by mass displacements, which create temporal variations of the gravity field. Since 2002, the GRACE satellite missions provide an unprecedented view of the gravity field spatial and temporal variations. Gravity models built from these satellite data are essential to study the Earth's dynamic processes (Tapley et al., 2004). Up to present, time variations of the gravity field are often modelled using spatial spherical harmonics functions averaged over a fixed period, as 10 days or 1 month. This approach is well suited for modeling global phenomena. To better estimate gravity related to local and/or transient processes, such as earthquakes or floods, and adapt the temporal resolution of the model to its spatial resolution, we propose to model the gravity field using localized functions in space and time. For that, we build a model of the gravity field in space and time with a four-dimensional wavelet basis, well localized in space and time. First we design the 4D basis, then, we study the inverse problem to model the gravity field from the potential differences between the twin GRACE satellites, and its regularization using prior knowledge on the water cycle. Our demonstration of surface water mass signals decomposition in time and space is based on the use of synthetic along-track gravitational potential data. We test the developed approach on one year of 4D gravity modeling and compare the reconstructed water heights to those of the input hydrological model. Perspectives of this work is to apply the approach on real GRACE data, addressing the challenge of a realistic noise, to better describe and understand physical processus with high temporal resolution/low spatial resolution or the contrary.
Modeling Repulsive Gravity with Creation
Indian Academy of Sciences (India)
R. G. Vishwakarma; J. V. Narlikar
2007-03-01
There is a growing interest among cosmologists for theories with negative energy scalar fields and creation, in order to model a repulsive gravity. The classical steady state cosmology proposed by Bondi, Gold & Hoyle in 1948, was the first such theory which used a negative kinetic energy creation field to invoke creation of matter. We emphasize that creation plays a very crucial role in cosmology and provides a natural explanation to the various explosive phenomena occurring in local ( < 0.1) and extra galactic universe.We exemplify this point of view by considering the resurrected version of this theory – the quasi-steady state theory, which tries to relate creation events directly to the large scale dynamics of the universe and supplies more natural explanations of the observed phenomena. Although the theory predicts a decelerating universe at the present era, it explains successfully the recent SNe Ia observations (which require an accelerating universe in the standard cosmology), as we show in this paper by performing a Bayesian analysis of the data.
Modeling Repulsive Gravity with Creation
Vishwakarma, R G
2007-01-01
There is a growing interest in the cosmologists for theories with negative energy scalar fields and creation, in order to model a repulsive gravity. The classical steady state cosmology proposed by Bondi, Gold and Hoyle in 1948, was the first such theory which used a negative kinetic energy creation field to invoke creation of matter. We emphasize that creation plays very crucial role in cosmology and provides a natural explanation to the various explosive phenomena occurring in local (z<0.1) and extra galactic universe. We exemplify this point of view by considering the resurrected version of this theory - the quasi-steady state theory, which tries to relate creation events directly to the large scale dynamics of the universe and supplies more natural explanations of the observed phenomena. Although, the theory predicts a decelerating universe at the present era, it explains successfully the recent SNe Ia observations (which require an accelerating universe in the standard cosmology), as we show in this p...
Institute of Scientific and Technical Information of China (English)
李松辉; 张国新; 张湘涛; 徐磊; 尚伟
2013-01-01
以某碾压混凝土重力坝施工为例,采用有限元仿真的计算方法,就其度汛缺口过流坝段的温控防裂措施进行了详细分析.研究表明:缺口坝段过流前,采用仓面通河水流水养护并加上混凝土过流前中期冷却至一定温度是减小温差的有效措施,可在一定程度上防止裂缝的产生.这为今后碾压混凝土重力坝工程的建设提供一定的参考.%By taking the construction of a RCC gravity dam as the study case,a detailed analysis is made on the temperature control and anti-cracking measure for its dam section of the flood discharge gap.The study shows that curing the concrete placing face directly with the river water before the flood discharge and cooling the concrete to a certain temperature at the mid-term before the discharge is an effective measure to decrease the relevant temperature difference; which can prevent the concrete cracking to a certain extent,and then provides a certain reference for the construction of RCC gravity dam in the days to come.
Bergshoeff, Eric A; Hohm, Olaf; Merbis, Wout; Townsend, Paul K
2013-01-01
We present a generally-covariant and parity-invariant "zwei-dreibein" action for gravity in three space-time dimensions that propagates two massive spin-2 modes, unitarily, and we use Hamiltonian methods to confirm the absence of unphysical degrees of freedom. We show how zwei-dreibein gravity unifies previous "3D massive gravity" models, and extends them, in the context of the AdS/CFT correspondence, to allow for a positive central charge consistent with bulk unitarity.
Aspects of multimetric gravity
International Nuclear Information System (INIS)
We present a class of gravity theories containing N ≥ 2 metric tensors and a corresponding number of standard model copies. In the Newtonian limit gravity is attractive within each standard model copy, but different standard model copies mutually repel each other. We discuss several aspects of these multimetric gravity theories, including cosmology, structure formation, the post-Newtonian limit and gravitational waves. The most interesting feature we find is an accelerating expansion of the universe that naturally becomes small at late times.
Pirkola, Patrik
2016-01-01
The surface gravity on Mars is smaller than the surface gravity on Earth, resulting in longer falling times. This effect can be simulated on Earth by taking advantage of air resistance and buoyancy, which cause low density objects to fall slowly enough to approximate objects falling on the surface of Mars. We describe a computer simulation based on an experiment that approximates Martian gravity, and verify our numerical results by performing the experiment.
Anderson, James E.; Yoto V. Yotov
2012-01-01
This paper provides striking confirmation of the restrictions of the structural gravity model of trade. Structural forces predicted by theory explain 95% of the variation of the fixed effects used to control for them in the recent gravity literature, fixed effects that in principle could reflect other forces. This validation opens avenues to inferring unobserved sectoral activity and multilateral resistance variables by equating fixed effects with structural gravity counterparts. Our findings...
Anderson, James E.
2010-01-01
The gravity model in economics was until relatively recently an intellectual orphan, unconnected to the rich family of economic theory. This review is a tale of the orphan's reunion with its heritage and the benefits that have flowed from it. Gravity has long been one of the most successful empirical models in economics. Incorporating the theoretical foundations of gravity into recent practice has led to a richer and more accurate estimation and interpretation of the spatial relations describ...
Rovelli Carlo
1997-01-01
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: (...
Trugenberger, Carlo A
2016-01-01
In a recently developed approach, geometry is modelled as an emergent property of random networks. Here I show that one of these models I proposed is exactly quantum gravity defined in terms of the combinatorial Ricci curvature recently derived by Ollivier. Geometry in the weak (classical) gravity regime arises in a phase transition driven by the condensation of short graph cycles. The strong (quantum) gravity regime corresponds to "small world" random graphs with logarithmic distance scaling.
Gravity Independent Compressor Project
National Aeronautics and Space Administration — We propose to develop and demonstrate a small, gravity independent, vapor compression refrigeration system using a linear motor compressor which effectively...
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.
Asymptotically hyperbolic black holes in Horava gravity
Janiszewski, Stefan
2014-01-01
Solutions of Hořava gravity that are asymptotically Lifshitz are explored. General near boundary expansions allow the calculation of the mass of these spacetimes via a Hamiltonian method. Both analytic and numeric solutions are studied which exhibit a causal boundary called the universal horizon, and are therefore black holes of the theory. The thermodynamics of an asymptotically Anti-de Sitter Hořava black hole are verified.
All unitary cubic curvature gravities in D dimensions
Sisman, Tahsin Cagri; Tekin, Bayram
2011-01-01
We construct all the unitary cubic curvature gravity theories based on the contractions of the Riemann tensor in D-dimensional (anti)-de Sitter spacetimes. Our construction is based on finding the equivalent quadratic action for the general cubic curvature theory and imposing ghost and tachyon freedom. To carry out the procedure we have also classified all the unitary quadratic models. We use our general results to study the recently found cubic curvature theories and the string generated cubic curvature gravity model.
Self-dual teleparallel gravity and the positive energy theorem
Chee, G. Y.
2004-01-01
A self-dual and anti-self-dual decomposition of the teleparallel gravity is carried out and the self-dual Lagrangian of the teleparallel gravity which is equivalent to the Ashtekar Lagrangian in vacuum is obtained. Its Hamiltonian formulation and the constraint analysis are developed. Starting from Witten's equation Nester's gauge condition is derived directly and a new expression of the boundary term is obtained. Using this expression and Witten's identity the proof of the positive energy th...
Remarks on harmonic maps, solitons, and dilaton gravity
Williams, Floyd L.
2003-01-01
Another connection of harmonic maps to gravity is presented. Using 1-soliton and anti-soliton solutions of the sine-Gordon equation, we construct a pair of harmonic maps that we express in terms of a particular dilaton field in Jackiw-Teitelboim gravity. This field satisfies a linearized sine-Gordon equation. We use it also to construct an explicit transformation that relates the corresponding solitonic metric to a two dimensional black hole metric.
Asymptotic dynamics in 3D gravity with torsion
Blagojevic, M; Vasilic, M.
2003-01-01
We study the nature of boundary dynamics in the teleparallel 3D gravity. The asymptotic field equations with anti-de Sitter boundary conditions yield only two non-trivial boundary modes, related to a conformal field theory with classical central charge. After showing that the teleparallel gravity can be formulated as a Chern-Simons theory, we identify dynamical structure at the boundary as the Liouville theory.
Thermodynamic constraints on fluctuation phenomena
Maroney, O. J. E.
2009-12-01
The relationships among reversible Carnot cycles, the absence of perpetual motion machines, and the existence of a nondecreasing globally unique entropy function form the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending rather than restricting the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.
Transport phenomena in multiphase flows
Mauri, Roberto
2015-01-01
This textbook provides a thorough presentation of the phenomena related to the transport of mass, momentum and energy. It lays all the basic physical principles, then for the more advanced readers, it offers an in-depth treatment with advanced mathematical derivations and ends with some useful applications of the models and equations in specific settings. The important idea behind the book is to unify all types of transport phenomena, describing them within a common framework in terms of cause and effect, respectively represented by the driving force and the flux of the transported quantity. The approach and presentation are original in that the book starts with a general description of transport processes, providing the macroscopic balance relations of fluid dynamics and heat and mass transfer, before diving into the mathematical realm of continuum mechanics to derive the microscopic governing equations at the microscopic level. The book is a modular teaching tool and can be used either for an introductory...
Emergent Phenomena via Molecular Dynamics
Rapaport, D. C.
Emergent phenomena are unusual because they are not obvious consequences of the design of the systems in which they appear, a feature no less relevant when they are being simulated. Several systems that exhibit surprisingly rich emergent behavior, each studied by molecular dynamics (MD) simulation, are described: (i) Modeling self-assembly processes associated with virus growth reveals the ability to achieve error-free assembly, where paradoxically, near-maximum yields are due to reversible bond formation. (ii) In fluids studied at the atomistic level, complex hydrodynamic phenomena in rotating and convecting fluids - the Taylor- Couette and Rayleigh-Bénard instabilities - can be reproduced, despite the limited length and time scales accessible by MD. (iii) Segregation studies of granular mixtures in a rotating drum reproduce the expected, but counterintuitive, axial and radial segregation, while for the case of a vertically vibrated layer a novel form of horizontal segregation is revealed.
Gravitational anomaly and transport phenomena
Landsteiner, Karl; Megías Fernández, Eugenio; Pena-Benítez, Francisco
2011-01-01
Quantum anomalies give rise to new transport phenomena. In particular, a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficie...
Energy Technology Data Exchange (ETDEWEB)
Soha, Aron; /UC, Davis
2006-04-01
The authors report on recent results from the Collider Detector at Fermilab (CDF) experiment, which is accumulating data from proton-antiproton collisions with {radical}s = 1.96 TeV at Run II of the Fermilab Tevatron. The new phenomena being explored include Higgs, Supersymmetry, and large extra dimensions. They also present the latest results of searches for heavy objects, which would indicate physics beyond the Standard Model.
Foot Anthropometry and Morphology Phenomena
Agić, Ante; NIKOLIĆ, VASILIJE; Mijović, Budimir
2006-01-01
Foot structure description is important for many reasons. The foot anthropometric morphology phenomena are analyzed together with hidden biomechanical functionality in order to fully characterize foot structure and function. For younger Croatian population the scatter data of the individual foot variables were interpolated by multivariate statistics. Foot structure descriptors are influenced by many factors, as a style of life, race, climate, and things of the great importance in ...
Critical phenomena in complex networks
Dorogovtsev, S. N.; Goltsev, A. V.; Mendes, J. F. F.
2007-01-01
The combination of the compactness of networks, featuring small diameters, and their complex architectures results in a variety of critical effects dramatically different from those in cooperative systems on lattices. In the last few years, researchers have made important steps toward understanding the qualitatively new critical phenomena in complex networks. We review the results, concepts, and methods of this rapidly developing field. Here we mostly consider two closely related classes of t...
Wetting phenomena in electrolyte solutions
Ibagon, Ingrid
2014-01-01
The present study analyzes wetting phenomena in electrolyte solutions. They are investigated by means of classical density functional theory. First, the wetting of a charged substrate by an electrolyte solution is studied with emphasis on the influence of the substrate charge density and of the ionic strength on the wetting transition temperature and on the order of the wetting transition. The corresponding models consist of solvent particles, anions, and cations. Two mean field approaches ar...
Spin–spin interactions in massive gravity and higher derivative gravity theories
Güllü, İbrahim; Tekin, Bayram(Department of Physics, Middle East Technical University, 06800 Ankara, Turkey)
2014-01-01
We show that, in the weak field limit, at large separations, in sharp contrast to General Relativity (GR), all massive gravity theories predict distance-dependent spin alignments for spinning objects. For all separations GR requires anti-parallel spin orientations with spins pointing along the line joining the sources. Hence total spin is minimized in GR. On the other hand, while massive gravity at small separations ( mgr⩽1.62 ) gives the same result as GR, for large separations ( mgr>1.62...
Black hole conserved charges in Generalized Minimal Massive Gravity
Directory of Open Access Journals (Sweden)
M.R. Setare
2015-05-01
Full Text Available In this paper we construct mass, angular momentum and entropy of black hole solution of Generalized Minimal Massive Gravity (GMMG in asymptotically Anti-de Sitter (AdS spacetimes. The Generalized Minimal Massive Gravity theory is realized by adding the CS deformation term, the higher derivative deformation term, and an extra term to pure Einstein gravity with a negative cosmological constant. We apply our result for conserved charge Qμ(ξ¯ to the rotating BTZ black hole solution of GMMG, and find energy, angular momentum and entropy. Then we show that our results for these quantities are consistent with the first law of black hole thermodynamics.
Born-Infeld Type Extension of (Non-)Critical Gravity
Yi, Sang-Heon
2012-01-01
We consider the Born-Infeld type extension of (non-)critical gravity which is higher curvature gravity on Anti de-Sitter space with specific combinations of scalar curvature and Ricci tensor. This theory may also be viewed as a natural extension of three-dimensional Born-Infeld new massive gravity to arbitrary dimensions. We show that this extension is consistent with holographic $c$-theorem and scalar graviton modes are absent in this theory. After showing that ghost modes in the theory can ...
Squeezing more information out of time variable gravity data with a temporal decomposition approach
DEFF Research Database (Denmark)
Barletta, Valentina Roberta; Bordoni, A.; Aoudia, A.;
2012-01-01
A measure of the Earth's gravity contains contributions from solid Earth as well as climate-related phenomena, that cannot be easily distinguished both in time and space. After more than 7years, the GRACE gravity data available now support more elaborate analysis on the time series. We propose...... to design a screening algorithm to identify regions where anomalous gravity variations deserve further investigations. It also allows to raise the amount of information one can obtain exclusively from gravity data, prior and preliminary to any subsequent specifically targeted study. This approach has been...... used to assess the possibility of finding evidence of meaningful geophysical signals different from hydrology over Africa in GRACE data. In this case we conclude that hydrological phenomena are dominant and so time variable gravity data in Africa can be directly used to calibrate hydrological models....
Extended Birkhoff's theorem in f(T) gravity
International Nuclear Information System (INIS)
f(T) theory, a generally modified teleparallel gravity, has been proposed as an alternative gravity model to account for the dark energy phenomena. Following our previous work [Xin-he Meng and Ying-bin Wang, Eur. Phys. J. (2011)], we prove that Birkhoff's theorem holds in a more general context, specifically with the off diagonal tetrad case, in this communication letter. Then, we discuss, respectively, the results of the external vacuum and internal gravitational field in the f(T) gravity framework, as well as the extended meaning of this theorem. We also investigate the validity of Birkhoff's theorem in the frame of f(T) gravity via a conformal transformation by regarding the Brans-Dicke-like scalar as effective matter, and study the equivalence between both Einstein frame and Jordan frame. (orig.)
Krasnov, Kirill
2016-01-01
Self-dual gravity is a diffeomorphism invariant theory in four dimensions that describes two propagating polarisations of the graviton and has a negative mass dimension coupling constant. Nevertheless, this theory is not only renormalisable but quantum finite, as we explain. We also collect various facts about self-dual gravity that are scattered across the literature.
Heiss, Jonny
2000-01-01
Assuming the existence of a Multidirectional Homogeneous and Constant Shower of Elementary Particles (MHCSEP) traveling at light speed in space, several basic laws of physics are derived mainly by geometrical considerations. When placing two bodies in space, obstruction of the MHCSEP creates an attractive force among them that coincides, for two bodies, with Newton's law of gravity, generating a mechanical explanation for gravity.
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.
No consistent bimetric gravity?
Deser, S.; Sandora, M.; Waldron, A
2013-01-01
We discuss the prospects for a consistent, nonlinear, partially massless (PM), gauge symmetry of bimetric gravity (BMG). Just as for single metric massive gravity, we show that consistency of BMG relies on it having a PM extension; we then argue that it cannot.
No consistent bimetric gravity?
Deser, S; Waldron, A
2013-01-01
We discuss the prospects for a consistent, nonlinear, partially massless (PM), gauge symmetry of bimetric gravity (BMG). Just as for single metric massive gravity, ultimate consistency of both BMG and the putative PM BMG theory relies crucially on this gauge symmetry. We argue, however, that it does not exist.
Kan, Nahomi; Maki, Takuya; Shiraishi, Kiyoshi
2016-10-01
We propose a model of gravity in which a General Relativity metric tensor and an effective metric generated from a single scalar formulated in geometric scalar gravity are mixed. We show that the model yields the exact Schwarzschild solution, along with accelerating behavior of scale factors in cosmological solutions.
Topological Aspects of Quantum Gravity
Weis, Morten
1998-01-01
This thesis discusses the topological aspects of quantum gravity, focusing on the connection between 2D quantum gravity and 2D topological gravity. The mathematical background for the discussion is presented in the first two chapters. The possible gauge formulations of 2D topological gravity as a BF or a Super BF theory are presented and compared against 2D quantum gravity in the dynamical triangulation scheme. A new identification between topological gravity in the Super BF formulation and t...
重力坝深层抗滑稳定的体系可靠度分析%Reliability Analysis of Anti-sliding Stability at Deep Foundation of Gravity Dams
Institute of Scientific and Technical Information of China (English)
江胜华; 侯建国; 何英明
2013-01-01
对于重力坝双斜面深层抗滑稳定,采用一次二阶矩法和等效线性化计算了滑动体、抗力体及体系的抗滑稳定可靠指标；赋予安全系数广义的含义,采用蒙特卡罗法计算重力坝双斜面深层抗滑稳定的体系可靠指标,并与一次二阶矩法和等效线性化计算的体系可靠指标作了比较,探讨了可靠度分析法与安全系数设计法之间的联系.结果表明,安全系数设计法中,一个粗略的安全系数不能真实、准确地反映重力坝深层抗滑稳定的安全度水平,建议结合可靠度分析法和安全系数设计法,在安全系数设计法中引入分项系数,采用广义的安全系数,可供重力坝设计规范修订时参考.%With regard to the wedge stability against deep sliding of gravity dams, the reliability indexes of sliding body, resistant body and the system are calculated by means of first-order second-moment method and equivalent linearization method. The traditional safety factor is endowed with general meaning, and the system reliability index is calculated using the method of Monte Carlo. The relationship between reliability theory and safety factor method is discussed. The results show that the single safety factor can not completely reflect the safety level of stability against deep sliding of gravity dams. It is suggested that with the combination of reliability theory and safety factor method, the partial factor should be introduced into the safety factor method and the general safety factor can be used in designing, which serves as a reference for the revision of Design specification for Concrete Gravity Dams.
Complex (dusty) plasmas—kinetic studies of strong coupling phenomena
International Nuclear Information System (INIS)
“Dusty plasmas” can be found almost everywhere—in the interstellar medium, in star and planet formation, in the solar system in the Earth’s atmosphere, and in the laboratory. In astrophysical plasmas, the dust component accounts for only about 1% of the mass, nevertheless this component has a profound influence on the thermodynamics, the chemistry, and the dynamics. Important physical processes are charging, sputtering, cooling, light absorption, and radiation pressure, connecting electromagnetic forces to gravity. Surface chemistry is another important aspect. In the laboratory, there is great interest in industrial processes (e.g., etching, vapor deposition) and—at the fundamental level—in the physics of strong coupling phenomena. Here, the dust (or microparticles) are the dominant component of the multi-species plasma. The particles can be observed in real time and space, individually resolved at all relevant length and time scales. This provides an unprecedented means for studying self-organisation processes in many-particle systems, including the onset of cooperative phenomena. Due to the comparatively large mass of the microparticles (10-12to10-9g), precision experiments are performed on the ISS. The following topics will be discussed: Phase transitions, phase separation, electrorheology, flow phenomena including the onset of turbulence at the kinetic level.
Dusty Plasmas - Kinetic Studies of Strong Coupling Phenomena
Morfill, Gregor
2011-10-01
``Dusty plasmas'' can be found almost everywhere - in the interstellar medium, in star and planet formation, in the solar system in the Earth's atmosphere and in the laboratory. In astrophysical plasmas the dust component accounts for only about 1% of the mass, nevertheless this component has a profound influence on the thermodynamics, the chemistry and the dynamics. Important physical processes are charging, sputtering, cooling, light absorption and radiation pressure, connecting electromagnetic forces to gravity. Surface chemistry is another important aspect. In the laboratory there is great interest in industrial processes (e.g. etching, vapor deposition) and at the fundamental physics level - the main topic here - the study of strong coupling phenomena. Here the dust (or microparticles) are the dominant component of the multi-species plasma. The particles can be observed in real time and pace, individually resolved at all relevant length and time scales. This provides an unprecedented means for studying self-organisation processes in many particle systems including the onset of cooperative phenomena. Due to the comparatively large mass of the microparticles (10-12 to 10-9 g) precision experiments are performed on the ISS. The following topics will be discussed: Phase transitions, phase separation, electrorheology, flow phenomena including the onset of turbulence at the kinetic level.
Complex (dusty) plasmas-kinetic studies of strong coupling phenomena
Energy Technology Data Exchange (ETDEWEB)
Morfill, Gregor E.; Ivlev, Alexei V.; Thomas, Hubertus M. [Max-Planck-Institut fuer Extraterrestrische Physik, D-85740 Garching (Germany)
2012-05-15
'Dusty plasmas' can be found almost everywhere-in the interstellar medium, in star and planet formation, in the solar system in the Earth's atmosphere, and in the laboratory. In astrophysical plasmas, the dust component accounts for only about 1% of the mass, nevertheless this component has a profound influence on the thermodynamics, the chemistry, and the dynamics. Important physical processes are charging, sputtering, cooling, light absorption, and radiation pressure, connecting electromagnetic forces to gravity. Surface chemistry is another important aspect. In the laboratory, there is great interest in industrial processes (e.g., etching, vapor deposition) and-at the fundamental level-in the physics of strong coupling phenomena. Here, the dust (or microparticles) are the dominant component of the multi-species plasma. The particles can be observed in real time and space, individually resolved at all relevant length and time scales. This provides an unprecedented means for studying self-organisation processes in many-particle systems, including the onset of cooperative phenomena. Due to the comparatively large mass of the microparticles (10{sup -12}to10{sup -9}g), precision experiments are performed on the ISS. The following topics will be discussed: Phase transitions, phase separation, electrorheology, flow phenomena including the onset of turbulence at the kinetic level.
Quantum theory of collective phenomena
Sewell, G L
2014-01-01
""An excellent and competent introduction to the field … [and] … a source of information for the expert."" - Physics Today""This a book of major importance…. I trust that this book will be used as a basis for the teaching of a balanced, modern and rigorous course on statistical mechanics in all universities."" - Bulletin of the London Mathematical Society""This is one of the best introductions to the subject, and it is strongly recommended to anyone interested in collective phenomena."" - Physics Bulletin ""The book may be recommended for students as a well-balanced introduction to this rich s
Nonlinear Dynamic Phenomena in Mechanics
Warminski, Jerzy; Cartmell, Matthew P
2012-01-01
Nonlinear phenomena should play a crucial role in the design and control of engineering systems and structures as they can drastically change the prevailing dynamical responses. This book covers theoretical and applications-based problems of nonlinear dynamics concerned with both discrete and continuous systems of interest in civil and mechanical engineering. They include pendulum-like systems, slender footbridges, shape memory alloys, sagged elastic cables and non-smooth problems. Pendulums can be used as a dynamic absorber mounted in high buildings, bridges or chimneys. Geometrical nonlinear
Phase transitions and critical phenomena
Domb, Cyril
2000-01-01
The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. No longer an area of specialist interest, it has acquired a central focus in condensed matter studies. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.The two review articles in this volume complement each other in a remarkable way. Both deal with what m
Measurements design and phenomena discrimination
International Nuclear Information System (INIS)
The construction of measurements suitable for discriminating signal components produced by phenomena of different types is considered. The required measurements should be capable of cancelling out those signal components which are to be ignored when focusing on a phenomenon of interest. Under the hypothesis that the subspaces hosting the signal components produced by each phenomenon are complementary, their discrimination is accomplished by measurements giving rise to the appropriate oblique projector operator. The subspace onto which the operator should project is selected by nonlinear techniques in line with adaptive pursuit strategies
Measurements design and phenomena discrimination
Energy Technology Data Exchange (ETDEWEB)
Rebollo-Neira, Laura [Department of Mathematics, Aston University, Birmingham, B4 7ET (United Kingdom)
2009-04-24
The construction of measurements suitable for discriminating signal components produced by phenomena of different types is considered. The required measurements should be capable of cancelling out those signal components which are to be ignored when focusing on a phenomenon of interest. Under the hypothesis that the subspaces hosting the signal components produced by each phenomenon are complementary, their discrimination is accomplished by measurements giving rise to the appropriate oblique projector operator. The subspace onto which the operator should project is selected by nonlinear techniques in line with adaptive pursuit strategies.
Measurements design and phenomena discrimination
Rebollo-Neira, Laura
2009-01-01
The construction of measurements suitable for discriminating signal components produced by phenomena of different types is considered. The required measurements should be capable of cancelling out those signal components which are to be ignored when focusing on a phenomenon of interest. Under the hypothesis that the subspaces hosting the signal components produced by each phenomenon are complementary, their discrimination is accomplished by measurements giving rise to the appropriate oblique projector operator. The subspace onto which the operator should project is selected by nonlinear techniques in line with adaptive pursuit strategies.
Violent phenomena in the Universe
Narlikar, Jayant V
2007-01-01
The serenity of a clear night sky belies the evidence-gathered by balloons, rockets, satellites, and telescopes-that the universe contains centers of furious activity that pour out vast amounts of energy, some in regular cycles and some in gigantic bursts. This reader-friendly book, acclaimed by Nature as ""excellent and uncompromising,"" traces the development of modern astrophysics and its explanations of these startling celestial fireworks.This lively narrative ranges from the gravitational theories of Newton and Einstein to recent exciting discoveries of such violent phenomena as supernova
Phase transitions and critical phenomena
Domb, Cyril
2001-01-01
The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies.Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations.The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable in
Precursor films in wetting phenomena
Popescu, M. N.; Oshanin, G.; Dietrich, S.; Cazabat, A. -M.
2012-01-01
The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in t...
Ultrasound-induced encapsulated microbubble phenomena
Postema, Michiel; Wamel, van Annemieke; Lancée, Charles T.; Jong, de Nico
2004-01-01
When encapsulated microbubbles are subjected to high-amplitude ultrasound, the following phenomena have been reported: oscillation, translation, coalescence, fragmentation, sonic cracking and jetting. In this paper, we explain these phenomena, based on theories that were validated for relatively big
Chern-Simons action for inhomogeneous Virasoro group as extension of three dimensional flat gravity
International Nuclear Information System (INIS)
We initiate the study of a Chern-Simons action associated to the semi-direct sum of the Virasoro algebra with its coadjoint representation. This model extends the standard Chern-Simons formulation of three dimensional flat gravity and is similar to the higher-spin extension of three dimensional anti-de Sitter or flat gravity. The extension can also be constructed for the exotic but not for the cosmological constant deformation of flat gravity
Barnich, Glenn; Giribet, Gaston; Leston, Mauricio
2015-01-01
We initiate the study of a Chern-Simons action associated to the semi-direct sum of the Virasoro algebra with its coadjoint representation. This model extends the standard Chern-Simons formulation of three dimensional flat gravity and is similar to the higher-spin extension of three dimensional anti-de Sitter or flat gravity. The extension can also be constructed for the exotic but not for the cosmological constant deformation of flat gravity.
One-loop partition function of three-dimensional flat gravity
Barnich, Glenn; Gonzalez, Hernan A.; Maloney, Alexander; Oblak, Blagoje
2015-01-01
In this note we point out that the one-loop partition function of three-dimensional flat gravity, computed along the lines originally developed for the anti-de Sitter case, reproduces characters of the BMS3 group.
Setare, M R
2009-01-01
In this paper we study cosmological application of holographic dark energy density in the modified gravity framework. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in spatially flat universe. Our calculation show, taking $\\Omega_{\\Lambda}=0.73$ for the present time, it is possible to have $w_{\\rm \\Lambda}$ crossing -1. This implies that one can generate phantom-like equation of state from a holographic dark energy model in flat universe in the modified gravity cosmology framework. Also we develop a reconstruction scheme for the modified gravity with $f(R)$ action.
International Nuclear Information System (INIS)
We investigate O'Raifeartaigh-type models for F-term supersymmetry breaking in gauge mediation scenarios in the presence of gravity. It is pointed out that the vacuum structure of those models is such that in metastable vacua gravity mediation contribution to scalar masses is always suppressed to the level below 1 percent, almost sufficient for avoiding FCNC problem. Close to that limit, gravitino mass can be in the range 10-100 GeV, opening several interesting possibilities for gauge mediation models, including Giudice-Masiero mechanism for μ and Bμ generation. Gravity sector can include stabilized moduli.
Phenomenological Quantum Gravity
Hossenfelder, Sabine
2009-01-01
If the history of science has taught us anything, it's that persistence and creativity makes the once impossible possible. It has long been thought experimental tests of quantum gravity are impossible. But during the last decade, several different approaches have been proposed that allow us to test, if not the fundamental theory of quantum gravity itself, so at least characteristic features this theory can have. For the first time we can probe experimentally domains in which quantum physics and gravity cohabit, in spite of our failure so far to make a convincing marriage of them on a theoretical level.
Natural phenomena hazards, Hanford Site, Washington
International Nuclear Information System (INIS)
This document presents the natural phenomena hazard loads for use in implementing DOE Order 5480.28, Natural Phenomena Hazards Mitigation, and supports development of double-shell tank systems specifications at the Hanford Site in south-central Washington State. The natural phenomena covered are seismic, flood, wind, volcanic ash, lightning, snow, temperature, solar radiation, suspended sediment, and relative humidity
Pressure Profiles in a Loop Heat Pipe Under Gravity Influence
Ku, Jentung
2015-01-01
During the operation of a loop heat pipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed.
On Critical Massive (Super)Gravity in adS(3)
Bergshoeff, Eric A.; Hohm, Olaf; Rosseel, Jan; Sezgin, Ergin; Townsend, Paul K.; Aldaya,; Barcelo, C; Jaramillo, JL
2011-01-01
We review the status of three-dimensional "general massive gravity" (GMG) in its linearization about an anti-de Sitter (adS) vacuum, focusing on critical points in parameter space that yield generalizations of "chiral gravity". We then show how these results extend to,N = 1 super-GMG, expanded about
Schwinger's Approach to Einstein's Gravity
Milton, Kim
2012-05-01
Albert Einstein was one of Julian Schwinger's heroes, and Schwinger was greatly honored when he received the first Einstein Prize (together with Kurt Godel) for his work on quantum electrodynamics. Schwinger contributed greatly to the development of a quantum version of gravitational theory, and his work led directly to the important work of (his students) Arnowitt, Deser, and DeWitt on the subject. Later in the 1960's and 1970's Schwinger developed a new formulation of quantum field theory, which he dubbed Source Theory, in an attempt to get closer contact to phenomena. In this formulation, he revisited gravity, and in books and papers showed how Einstein's theory of General Relativity emerged naturally from one physical assumption: that the carrier of the gravitational force is a massless, helicity-2 particle, the graviton. (There has been a minor dispute whether gravitational theory can be considered as the massless limit of a massive spin-2 theory; Schwinger believed that was the case, while Van Dam and Veltman concluded the opposite.) In the process, he showed how all of the tests of General Relativity could be explained simply, without using the full machinery of the theory and without the extraneous concept of curved space, including such effects as geodetic precession and the Lense-Thirring effect. (These effects have now been verified by the Gravity Probe B experiment.) This did not mean that he did not accept Einstein's equations, and in his book and full article on the subject, he showed how those emerge essentially uniquely from the assumption of the graviton. So to speak of Schwinger versus Einstein is misleading, although it is true that Schwinger saw no necessity to talk of curved spacetime. In this talk I will lay out Schwinger's approach, and the connection to Einstein's theory.
Massive gravity as a limit of bimetric gravity
Martin-Moruno, Prado; Baccetti, Valentina; Visser, Matt
2013-01-01
Massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure can lead to an interesting interplay between the "background" and "foreground" metrics in a cosmological context. 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. Thus, solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statem...
BRST symmetry of Unimodular Gravity
Upadhyay, S.; Oksanen, M.; Bufalo, R.
2015-01-01
We derive the BRST symmetry for two versions of unimodular gravity, namely, fully diffeomorphism-invariant unimodular gravity and unimodular gravity with fixed metric determinant. The BRST symmetry is generalized further to the finite field-dependent BRST, in order to establish the connection between different gauges in each of the two versions of unimodular gravity.
Toroidal solutions in Horava Gravity
Ghodsi, Ahmad
2009-01-01
Recently a new four-dimensional non relativistic renormalizable theory of gravity was proposed by Horava. This gravity reduces to Einstein gravity at large distances. In this paper by using the new action for gravity we present different toroidal solutions to the equations of motion. Our solutions describe the near horizon geometry with slow rotating parameter.
Quantized gauge-affine gravity in the superfiber bundle approach
Meziane, A.; Tahiri, M
2004-01-01
The quantization of gauge-affine gravity within the superfiber bundle formalism is proposed. By introducing an even pseudotensorial 1-superform over a principal superfibre bundle with superconnection, we obtain the geometrical Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST transformations of the fields occurring in such a theory. Reducing the four-dimensional general affine group double-covering to the Poincare group double-covering we also find the BRST and anti-BRST transformations of the f...
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
Institute of Scientific and Technical Information of China (English)
周伟; 杨利福; 常晓林; 马刚; 涂承义
2012-01-01
Based on Euler backward integration method,an integration algorithm of constitutive equation is suggested for adaptive sub-stepping schemes;and the consistent tangent matrices of modified Mohr-Coulomb criterion are derived.The UMAT subroutine of the modified Mohr-Coulomb model is developed in ABAQUS.After a uniaxial compression test,the simulation of the deep anti-sliding stability analysis of gravity dam is performed using the mentioned subroutine by strength reserve coefficient method.The simulation results show that the modified Mohr-Coulomb criterion is reliable and could effectively depict the deep sliding failure characteristics of gravity dam;the result is inclined to safe.%针对修正后的Mohr-Coulomb准则采用基于Euler向后积分的自适应子增量本构积分算法推导得到的一致性切线刚度矩阵,以ABAQUS软件为平台,编制UMAT本构程序.进行了平面应变条件下单轴受压的数值验证后,用上述程序以强度储备系数法来验证了修正后的Mohr-Coulomb准则在重力坝抗滑稳定中的可靠性,结果表明编写的修正后的Mohr-Coulomb模型能够有效地反映重力坝深层抗滑破坏的特性,结果偏安全.
Bergshoeff, Eric A.; Hohm, Olaf; Townsend, Paul K.
2012-01-01
We present a brief review of New Massive Gravity, which is a unitary theory of massive gravitons in three dimensions obtained by considering a particular combination of the Einstein-Hilbert and curvature squared terms.
Zinoviev, Yury M
2012-01-01
The equations of the relativistic causal Newton gravity law for the planets of the solar system are studied in the approximation when the Sun rests at the coordinates origin and the planets do not iteract between each other.
Bhattacharya, Swastik
2015-01-01
General theory of relativity (or Lovelock extensions) is a dynamical theory; given an initial configuration on a space-like hypersurface, it makes a definite prediction of the final configuration. Recent developments suggest that gravity may be described in terms of macroscopic parameters. It finds a concrete manifestation in the fluid-gravity correspondence. Most of the efforts till date has been to relate equilibrium configurations in gravity with fluid variables. In order for the emergent paradigm to be truly successful, it has to provide a statistical mechanical derivation of how a given initial static configuration evolves into another. In this essay, we show that the energy transport equation governed by the fluctuations of the horizon-fluid is similar to Raychaudhuri equation and, hence gravity is truly emergent.
National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (65,164 records) were gathered by various governmental organizations (and academia) using a variety of methods. The data base was received...
National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (55,907 records) were gathered by various governmental organizations (and academia) using a variety of methods. This data base was received...
National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (71 records) were gathered by various governmental organizations (and academia) using a variety of methods. This data base was received in...
National Oceanic and Atmospheric Administration, Department of Commerce — In 1985, Dr. William F. Haxby of the Lamont-Doherty Geological Observatory of Columbia University prepared this data base of free-air gravity anomalies, based on...
Bakker MR; Smit, J.
1993-01-01
We look at gravitational attraction in simplicial gravity using the dynamical triangulation method. On the dynamical triangulation configurations we measure quenched propagators of a free massive scalar field. The masses measured from these propagators show that gravitational attraction is present.
Oda, Ichiro
2016-01-01
We propose a topological model of induced gravity (pregeometry) where both Newton's coupling constant and the cosmological constant appear as integration constants in solving field equations. The matter sector of a scalar field is also considered, and by solving field equations it is shown that various types of cosmological solutions in the FRW universe can be obtained. A detailed analysis is given of the meaning of the BRST transformations, which make the induced gravity be a topological field theory, by means of the canonical quantization analysis, and the physical reason why such BRST transformations are needed in the present formalism is clarified. Finally, we propose a dynamical mechanism for fixing the Lagrange multiplier fields by following the Higgs mechanism. The present study clearly indicates that the induced gravity can be constructed at the classical level without recourse to quantum fluctuations of matter and suggests an interesting relationship between the induced gravity and the topological qu...
De Bakker, B V; Bakker, Bas de; Smit, Jan
1994-01-01
We look at gravitational attraction in simplicial gravity using the dynamical triangulation method. On the dynamical triangulation configurations we measure quenched propagators of a free massive scalar field. The masses measured from these propagators show that gravitational attraction is present.
Bhattacharya, Swastik; Shankaranarayanan, S.
2015-10-01
General theory of relativity (or Lovelock extensions) is a dynamical theory; given an initial configuration on a spacelike hypersurface, it makes a definite prediction of the final configuration. Recent developments suggest that gravity may be described in terms of macroscopic parameters. It finds a concrete manifestation in the fluid-gravity correspondence. Most of the efforts till date has been to relate equilibrium configurations in gravity with fluid variables. In order for the emergent paradigm to be truly successful, it has to provide a statistical mechanical derivation of how a given initial static configuration evolves into another. In this paper, we show that the energy transport equation governed by the fluctuations of the horizon-fluid is similar to Raychaudhuri equation and hence gravity is truly emergent.
Emergent Phenomena at Oxide Interfaces
Energy Technology Data Exchange (ETDEWEB)
Hwang, H.Y.
2012-02-16
Transition metal oxides (TMOs) are an ideal arena for the study of electronic correlations because the s-electrons of the transition metal ions are removed and transferred to oxygen ions, and hence the strongly correlated d-electrons determine their physical properties such as electrical transport, magnetism, optical response, thermal conductivity, and superconductivity. These electron correlations prohibit the double occupancy of metal sites and induce a local entanglement of charge, spin, and orbital degrees of freedom. This gives rise to a variety of phenomena, e.g., Mott insulators, various charge/spin/orbital orderings, metal-insulator transitions, multiferroics, and superconductivity. In recent years, there has been a burst of activity to manipulate these phenomena, as well as create new ones, using oxide heterostructures. Most fundamental to understanding the physical properties of TMOs is the concept of symmetry of the order parameter. As Landau recognized, the essence of phase transitions is the change of the symmetry. For example, ferromagnetic ordering breaks the rotational symmetry in spin space, i.e., the ordered phase has lower symmetry than the Hamiltonian of the system. There are three most important symmetries to be considered here. (i) Spatial inversion (I), defined as r {yields} -r. In the case of an insulator, breaking this symmetry can lead to spontaneous electric polarization, i.e. ferroelectricity, or pyroelectricity once the point group belongs to polar group symmetry. (ii) Time-reversal symmetry (T) defined as t {yields} -t. In quantum mechanics, the time-evolution of the wave-function {Psi} is given by the phase factor e{sup -iEt/{h_bar}} with E being the energy, and hence time-reversal basically corresponds to taking the complex conjugate of the wave-function. Also the spin, which is induced by the 'spinning' of the particle, is reversed by time-reversal. Broken T-symmetry is most naturally associated with magnetism, since the
Induced-charge Electrokinetic Phenomena
Bazant, M Z; Bazant, Martin Z.; Squires, Todd M.
2003-01-01
Motivated by the recent discovery of AC electro-osmosis near micro-electrodes, we predict a broad class of nonlinear electrokinetic phenomena involving induced interfacial charge. By considering various polarizable objects (metals or dielectrics) in DC and AC applied fields, we develop a simple physical picture of `induced-charge electro-osmosis' (ICEO), the fluid slip at a surface due to an electric field acting on the diffuse charge it induces. We also discuss `induced-charge electrophoresis' (ICEP), the analogous motion of a freely-suspended polarizable particle. Both differ significantly from their classical linear counterparts. We present a mathematical theory of ICEO flows in the weakly nonlinear limit of thin double layers. As an example, we calculate the time-dependent ICEO slip around a metallic sphere with a thin dielectric coating in a suddenly-applied DC field. We briefly discuss possible applications of ICEO to microfluidics and of ICEP to colloidal manipulation.
Earthquake prediction with electromagnetic phenomena
Energy Technology Data Exchange (ETDEWEB)
Hayakawa, Masashi, E-mail: hayakawa@hi-seismo-em.jp [Hayakawa Institute of Seismo Electomagnetics, Co. Ltd., University of Electro-Communications (UEC) Incubation Center, 1-5-1 Chofugaoka, Chofu Tokyo, 182-8585 (Japan); Advanced Wireless & Communications Research Center, UEC, Chofu Tokyo (Japan); Earthquake Analysis Laboratory, Information Systems Inc., 4-8-15, Minami-aoyama, Minato-ku, Tokyo, 107-0062 (Japan); Fuji Security Systems. Co. Ltd., Iwato-cho 1, Shinjyuku-ku, Tokyo (Japan)
2016-02-01
Short-term earthquake (EQ) prediction is defined as prospective prediction with the time scale of about one week, which is considered to be one of the most important and urgent topics for the human beings. If this short-term prediction is realized, casualty will be drastically reduced. Unlike the conventional seismic measurement, we proposed the use of electromagnetic phenomena as precursors to EQs in the prediction, and an extensive amount of progress has been achieved in the field of seismo-electromagnetics during the last two decades. This paper deals with the review on this short-term EQ prediction, including the impossibility myth of EQs prediction by seismometers, the reason why we are interested in electromagnetics, the history of seismo-electromagnetics, the ionospheric perturbation as the most promising candidate of EQ prediction, then the future of EQ predictology from two standpoints of a practical science and a pure science, and finally a brief summary.
Earthquake prediction with electromagnetic phenomena
International Nuclear Information System (INIS)
Short-term earthquake (EQ) prediction is defined as prospective prediction with the time scale of about one week, which is considered to be one of the most important and urgent topics for the human beings. If this short-term prediction is realized, casualty will be drastically reduced. Unlike the conventional seismic measurement, we proposed the use of electromagnetic phenomena as precursors to EQs in the prediction, and an extensive amount of progress has been achieved in the field of seismo-electromagnetics during the last two decades. This paper deals with the review on this short-term EQ prediction, including the impossibility myth of EQs prediction by seismometers, the reason why we are interested in electromagnetics, the history of seismo-electromagnetics, the ionospheric perturbation as the most promising candidate of EQ prediction, then the future of EQ predictology from two standpoints of a practical science and a pure science, and finally a brief summary
Sjogren, William L.
1987-01-01
Work on three different efforts related to gravity data analysis is discussed. The reduction of raw Doppler data from the Apollo 15 subsatellite to produce acceleration profiles as a function of latitude, longitude and altitude; an investigation related to fitting long arcs of Pioneer Venus Orbiter tracking data; and a study of gravity/topography ratios which were found to have a linear trend with longitude are discussed.
Quantum massive conformal gravity
International Nuclear Information System (INIS)
We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed. (orig.)
Quantum massive conformal gravity
Faria, F. F.
2016-01-01
We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed.
Quantum massive conformal gravity
Faria, F. F.
2016-04-01
We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed.
Quantum massive conformal gravity
Energy Technology Data Exchange (ETDEWEB)
Faria, F.F. [Universidade Estadual do Piaui, Centro de Ciencias da Natureza, Teresina, PI (Brazil)
2016-04-15
We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed. (orig.)
Autistic phenomena in neurotic patients.
Klien, S
1980-01-01
I have described a group of patients who are seemingly successful in their professional and social lives, and who seek analysis ostensibly for professional reasons or for minor difficulties in their relationship. However, sooner or later they reveal phenomena which are strikingly similar to those observed in so-called autistic children. These autistic phenomena are characterized by an almost impenetrable encapsulation of part of the personality, mute and implacable resistance to change, and a lack of real emotional contact either with themselves or the analyst. Progress of the analysis reveals an underlying intense fear of pain, and of death, disintegration or breakdown. These anxieties occur as a reaction to real or feared separation, especially when commitment to analysis deepens. In the case I have described in detail the patient used various projective processes to deflect painful emotions either into other people, including the analyst, or into their own bodies. As a consequence the various objects or organs of the body swell up and became suffused with rage as a result of having to contain the unwanted feelings. This process leads in turn to intense persecutory fears and a heightened sensitivity to the analyst's tone of voice and facial expression. It would seem that the initial hypersensitivity of part of the personality is such as to lead it to anticipate danger to such an extent that it expels feelings even before they reach awareness. The sooner the analyst realizes the existence of this hidden part of the patient the less the danger of the analysis becoming an endless and meaningless intellectual dialogue and the greater the possibilities of the patient achieving a relatively stable equilibrium. Although the analyst has to live through a great deal of anxiety with the patient I feel that ultimately the results make it worth while.
Remote sensing of natural phenomena
Directory of Open Access Journals (Sweden)
Miodrag D. Regodić
2014-06-01
Full Text Available There has always been a need to directly perceive and study the events whose extent is beyond people's possibilities. In order to get new data and to make observations and studying much more objective in comparison with past syntheses - a new method of examination called remote sensing has been adopted. The paper deals with the principles and elements of remote sensing, as well as with the basic aspects of using remote research in examining meteorological (weather parameters and the conditions of the atmosphere. The usage of satellite images is possible in all phases of the global and systematic research of different natural phenomena when airplane and satellite images of different characteristics are used and their analysis and interpretation is carried out by viewing and computer added procedures. Introduction Remote sensing of the Earth enables observing and studying global and local events that occur on it. Satellite images are nowadays used in geology, agriculture, forestry, geodesy, meteorology, spatial and urbanism planning, designing of infrastructure and other objects, protection from natural and technological catastrophes, etc. It it possible to use satellite images in all phases of global and systematic research of different natural phenomena. Basics of remote sensing Remote sensing is a method of the acquisition and interpretation of information about remote objects without making a physical contact with them. The term Daljinska detekcija is a literal translation of the English term Remote Sensing. In French it isTeledetection, in German - Fernerkundung, in Russian - дистанционие иследования. We also use terms such as: remote survailance, remote research, teledetection, remote methods, and distance research. The basic elements included in Remote Sensing are: object, electromagnetic energy, sensor, platform, image, analysis, interpretation and the information (data, fact. Usage of satellite remote research in
Emergent Gravity from Noncommutative Spacetime
Yang, Hyun Seok
2006-01-01
We showed before that self-dual electromagnetism in noncommutative (NC) spacetime is equivalent to self-dual Einstein gravity. This result implies a striking picture about gravity: Gravity can emerge from electromagnetism in NC spacetime. Gravity is then a collective phenomenon emerging from gauge fields living in fuzzy spacetime. We elucidate in some detail why electromagnetism in NC spacetime should be a theory of gravity. In particular, we show that NC electromagnetism is realized through ...
Gravity Before Einstein and Schwinger Before Gravity
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.
Discussion on the Anti-sliding Stability Safety Coefficient and Gravity Dam Safety%重力坝抗滑稳定安全系数与安全度探讨
Institute of Scientific and Technical Information of China (English)
阮超
2013-01-01
在进行深层抗滑稳定计算讨论时，涉及到的计算会变得相对复杂，会有更多的因素难以确定，并且由于在工程实践中的经验也累积较少，我们很难找到关于安全系数的一个统一标准取值。本文通过实际工程的计算给出抗滑稳定计算公式和安全系数的建议值，为以后的研究奠定基础。%In the discussion of deep anti-sliding stability calc-ulation, the computation involving wil become relatively com-plex, there wil be more difficult to determine the factors, and the experiences in engineering practice has accumulated less, it is difficult to find a unified standard value of safety factor. This paper gives the proposed value of anti sliding stability formula and safety factor by the actual engineering, lays the foundation for the further study.
Supersymmetric 3D gravity with torsion: asymptotic symmetries
Cvetkovic, B.; Blagojevic, M
2007-01-01
We study the structure of asymptotic symmetries in N=1+1 supersymmetric extension of three-dimensional gravity with torsion. Using a natural generalization of the bosonic anti-de Sitter asymptotic conditions, we show that the asymptotic Poisson bracket algebra of the canonical generators has the form of two independent super-Virasoro algebras with different central charges.
Holographic positive energy theorems in three-dimensional gravity
Barnich, Glenn; Oblak, Blagoje
2014-01-01
The covariant phase space of three-dimensional asymptotically flat and anti-de Sitter gravity is controlled by well-understood coadjoint orbits of the Virasoro group. Detailed knowledge on the behavior of the energy functional on these orbits can be used to discuss positive energy theorems.
Dynamics of Asymptotic Diffeomorphisms in (2+1)-Dimensional Gravity
Carlip, S
2005-01-01
In asymptotically anti-de Sitter gravity, diffeomorphisms that change the conformal boundary data can be promoted to genuine physical degrees of freedom. I show that in 2+1 dimensions, the dynamics of these degrees of freedom is described by a Liouville action, with the correct central charge to reproduce the entropy of the BTZ black hole.
Distance between Quantum States and Gauge-Gravity Duality.
Miyaji, Masamichi; Numasawa, Tokiro; Shiba, Noburo; Takayanagi, Tadashi; Watanabe, Kento
2015-12-31
We study a quantum information metric (or fidelity susceptibility) in conformal field theories with respect to a small perturbation by a primary operator. We argue that its gravity dual is approximately given by a volume of maximal time slice in an anti-de Sitter spacetime when the perturbation is exactly marginal. We confirm our claim in several examples. PMID:26764986
Asymptotic symmetries in 3d gravity with torsion
Blagojevic, M; Vasilic, M.
2003-01-01
We study the nature of asymptotic symmetries in topological 3d gravity with torsion. After introducing the concept of asymptotically anti-de Sitter configuration, we find that the canonical realization of the asymptotic symmetry is characterized by the Virasoro algebra with classical central charge, the value of which is the same as in general relativity: c=3l/2G.
Validating variational principle for higher order theory of gravity
Ruz, Soumendranath; Sarkar, Kaushik; Sk., Nayem; Sanyal, Abhik Kumar
2015-01-01
Metric variation of higher order theory of gravity requires to fix the Ricci scalar in addition to the metric tensor at the boundary. Fixing Ricci scalar at the boundary implies that the classical solutions are fixed once and forever to the de-Sitter or anti de-Sitter solutions. Here, we justify such requirement from the standpoint of Noether Symmetry.
Higher dimensional gravity invariant under the AdS group
Salgado, Patricio; Izaurieta, Fernando; Rodriguez, Eduardo
2003-01-01
A higher dimensional gravity invariant both under local Lorentz rotations and under local Anti de Sitter boosts is constructed. It is shown that such a construction is possible both when odd dimensions and when even dimensions are considered. It is also proved that such actions have the same coefficients as those obtained by Troncoso and Zanelli.
Akshay, Y.S.; Ananth, Sudarshan; Mali, Mahendra(Indian Institute of Science Education and Research, Pune 411008, India)
2014-01-01
We obtain a closed form expression for the Action describing pure gravity, in light-cone gauge, in a four-dimensional Anti de Sitter background. We perform a perturbative expansion of this closed form result to extract the cubic interaction vertex in this gauge.
Reality conditions for Ashtekar gravity from Lorentz-covariant formulation
Alexandrov, Sergei
2005-01-01
We show the equivalence of the Lorentz-covariant canonical formulation considered for the Immirzi parameter $\\beta=i$ to the selfdual Ashtekar gravity. We also propose to deal with the reality conditions in terms of Dirac brackets derived from the covariant formulation and defined on an extended phase space which involves, besides the selfdual variables, also their anti-selfdual counterparts.
Discussion of the Entanglement Entropy in Quantum Gravity
Ma, Chen-Te
2016-01-01
Quantum gravity needs to be satisfied by the holographic principle, and the entanglement entropy already has holographic evidences via anti-de Sitter/ Conformal field theory correspondence. Thus, we explore principles of quantum gravity via the entanglement entropy. We compute the entanglement entropy in two dimensional Einstein-Hilbert action to understand quantum geometry and area law. Then we also discuss two dimensional conformal field theory because we expect strongly coupled conformal field theory can describe perturbative quantum gravity theory. We find universal terms of the entanglement entropy is independent of a choice of an entangling surface in two dimensional conformal field theory for one interval and some cases of multiple intervals. To extend our discussion to generic multiple intervals, we use a geometric method to determine the entanglement entropy. Finally, we argue translational invariance possibly be a necessary condition in quantum gravity theory from ruing out volume law of the entangl...
Charged Black Holes in Massive Gravity's Rainbow
Hendi, S H; Panahiyan, S
2016-01-01
Violation of Lorentz invariancy in the high energy quantum gravity, motivates one to consider an energy dependent spacetime with massive deformation of standard general relativity. In this paper, we take into account an energy dependent metric in the context of a massive gravity model to obtain exact solutions. We investigate the geometry of the solutions and show that that there is a curvature singularity at the origin ($r=0$) which can be covered with an event horizon. We also calculate the conserved and thermodynamic quantities, which are fully reproduced by the analysis performed with the standard techniques. Finally, we examine the validity of the first law of thermodynamics. Next, we conduct a study regarding the positivity and negativity of total mass in de Sitter and anti de Sitter spacetime.
Conceptual Aspects of Gauge/Gravity Duality
de Haro, Sebastian; Butterfield, Jeremy
2015-01-01
We give an introductory review of gauge/gravity duality, and associated ideas of holography, emphasising the conceptual aspects. The opening Sections gather the ingredients, viz. anti-de Sitter spacetime, conformal field theory and string theory, that we need for presenting, in Section 5, the central and original example: Maldacena's AdS/CFT correspondence. Sections 6 and 7 develop the ideas of this example, also in applications to condensed matter systems, QCD, and hydrodynamics. Sections 8 and 9 discuss the possible extensions of holographic ideas to de Sitter spacetime and to black holes. Section 10 discusses the bearing of gauge/gravity duality on two philosophical topics: the equivalence of physical theories, and the idea that spacetime, or some features of it, are emergent.
Conceptual Aspects of Gauge/Gravity Duality
De Haro, Sebastian; Mayerson, Daniel R.; Butterfield, Jeremy N.
2016-07-01
We give an introductory review of gauge/gravity duality, and associated ideas of holography, emphasising the conceptual aspects. The opening sections gather the ingredients, viz. anti-de Sitter spacetime, conformal field theory and string theory, that we need for presenting, in Sect. 5, the central and original example: Maldacena's AdS/CFT correspondence. Sections 6 and 7 develop the ideas of this example, also in applications to condensed matter systems, QCD, and hydrodynamics. Sections 8 and 9 discuss the possible extensions of holographic ideas to de Sitter spacetime and to black holes. Section 10 discusses the bearing of gauge/gravity duality on two philosophical topics: the equivalence of physical theories, and the idea that spacetime, or some features of it, are emergent.
Directory of Open Access Journals (Sweden)
Maartens Roy
2004-01-01
Full Text Available The observable universe could be a 1+3-surface (the "brane" embedded in a 1+3+$d$-dimensional spacetime (the "bulk", with Standard Model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the $d$ extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak ($sim$TeV level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. General relativity cannot describe gravity at high enough energies and must be replaced by a quantum gravity theory, picking up significant corrections as the fundamental energy scale is approached. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity "leaks" into the bulk, behaving in a truly higher-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting and potentially testable implications for high-energy astrophysics, black holes and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review discusses the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models.
Noise and fluctuations in semiclassical gravity
International Nuclear Information System (INIS)
We continue our earlier investigation of the back reaction problem in semiclassical gravity with the Schwinger-Keldysh or closed-time-path (CTP) functional formalism using the language of the decoherent history formulation of quantum mechanics. Making use of its intimate relation with the Feynman-Vernon influence functional method, we examine the statistical mechanical meaning and show the interrelation of the many quantum processes involved in the back reaction problem, such as particle creation, decoherence, and dissipation. We show how noise and fluctuation arise naturally from the CTP formalism. We derive an expression for the CTP effective action in terms of the Bogolubov coefficients and show how noise is related to the fluctuations in the number of particles created. In so doing we have extended the old framework of semiclassical gravity, based on the mean field theory of Einstein equation with a source given by the expectation value of the energy-momentum tensor, to that based on a Langevin-type equation, where the dynamics of the fluctuations of spacetime is driven by the quantum fluctuations of the matter field. This generalized framework is useful for the investigation of quantum processes in the early Universe involving fluctuations, vacuum stability, and phase transition phenomena as well as the nonequilibrium thermodynamics of black holes. It is also essential to an understanding of the transition from any quantum theory of gravity to classical general relativity
EDITORIAL: Quantum phenomena in Nanotechnology Quantum phenomena in Nanotechnology
Loss, Daniel
2009-10-01
Twenty years ago the Institute of Physics launched the journal Nanotechnology from its publishing house based in the home town of Paul Dirac, a legendary figure in the development of quantum mechanics at the turn of the last century. At the beginning of the 20th century, the adoption of quantum mechanical descriptions of events transformed the existing deterministic world view. But in many ways it also revolutionised the progress of research itself. For the first time since the 17th century when Francis Bacon established inductive reasoning as the means of advancing science from fact to axiom to law, theory was progressing ahead of experiments instead of providing explanations for observations that had already been made. Dirac's postulation of antimatter through purely theoretical investigation before its observation is the archetypal example of theory leading the way for experiment. The progress of nanotechnology and the development of tools and techniques that enabled the investigation of systems at the nanoscale brought with them many fascinating observations of phenomena that could only be explained through quantum mechanics, first theoretically deduced decades previously. At the nanoscale, quantum confinement effects dominate the electrical and optical properties of systems. They also render new opportunities for manipulating the response of systems. For example, a better understanding of these systems has enabled the rapid development of quantum dots with precisely determined properties, which can be exploited in a range of applications from medical imaging and photovoltaic solar cells to quantum computation, a radically new information technology being currently developed in many labs worldwide. As the first ever academic journal in nanotechnology, {\\it Nanotechnology} has been the forum for papers detailing progress of the science through extremely exciting times. In the early years of the journal, the investigation of electron spin led to the formulation
Short Duration Reduced Gravity Drop Tower Design and Development
Osborne, B.; Welch, C.
The industrial and commercial development of space-related activities is intimately linked to the ability to conduct reduced gravity research. Reduced gravity experimentation is important to many diverse fields of research in the understanding of fundamental and applied aspects of physical phenomena. Both terrestrial and extra-terrestrial experimental facilities are currently available to allow researchers access to reduced gravity environments. This paper discusses two drop tower designs, a 2.0 second facility built in Australia and a proposed 2.2 second facility in the United Kingdom. Both drop towers utilise a drag shield for isolating the falling experiment from the drag forces of the air during the test. The design and development of The University of Queensland's (Australia) 2.0 second drop tower, including its specifications and operational procedures is discussed first. Sensitive aspects of the design process are examined. Future plans are then presented for a new short duration (2.2 sec) ground-based reduced gravity drop tower. The new drop tower has been designed for Kingston University (United Kingdom) to support teaching and research in the field of reduced gravity physics. The design has been informed by the previous UQ drop tower design process and utilises a catapult mechanism to increase test time and also incorporates features to allow participants for a variety of backgrounds (from high school students through to university researchers) to learn and experiment in reduced gravity. Operational performance expectations for this new facility are also discussed.
High Field Phenomena of Qubits
van Tol, J; Takahashi, S; McCamey, D R; Boehme, C; Zvanut, M E
2009-01-01
Electron and nuclear spins are very promising candidates to serve as quantum bits (qubits) for proposed quantum computers, as the spin degrees of freedom are relatively isolated from their surroundings, and can be coherently manipulated e.g. through pulsed EPR and NMR. For solid state spin systems, impurities in crystals based on carbon and silicon in various forms have been suggested as qubits, and very long relaxation rates have been observed in such systems. We have investigated a variety of these systems at high magnetic fields in our multi-frequency pulsed EPR/ENDOR spectrometer. A high magnetic field leads to large electron spin polarizations at helium temperatures giving rise to various phenomena that are of interest with respect to quantum computing. For example, it allows the initialization of the both the electron spin as well as hyperfine-coupled nuclear spins in a well defined state by combining millimeter and RF radiation; it can increase the T2 relaxation times by eliminating decoherence due to ...
Precursor films in wetting phenomena
International Nuclear Information System (INIS)
The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in the last decade similar films have been reported to occur in solid-on-solid systems. While the situations in which the thickness of such films is of mesoscopic size are fairly well understood, an intriguing and yet to be fully understood aspect is the spreading of microscopic, i.e. molecularly thin, films. Here we review the available experimental observations of such films in various liquid-on-solid and solid-on-solid systems, as well as the corresponding theoretical models and studies aimed at understanding their formation and spreading dynamics. Recent developments and perspectives for future research are discussed. (topical review)
Precursor films in wetting phenomena.
Popescu, M N; Oshanin, G; Dietrich, S; Cazabat, A-M
2012-06-20
The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in the last decade similar films have been reported to occur in solid-on-solid systems. While the situations in which the thickness of such films is of mesoscopic size are fairly well understood, an intriguing and yet to be fully understood aspect is the spreading of microscopic, i.e. molecularly thin, films. Here we review the available experimental observations of such films in various liquid-on-solid and solid-on-solid systems, as well as the corresponding theoretical models and studies aimed at understanding their formation and spreading dynamics. Recent developments and perspectives for future research are discussed. PMID:22627067
Investigation of some galactic and extragalactic gravitational phenomena
Directory of Open Access Journals (Sweden)
Jovanović P.
2012-01-01
Full Text Available Here we present a short overview of the most important results of our investigations of the following galactic and extragalactic gravitational phenomena: supermassive black holes in centers of galaxies and quasars, supermassive black hole binaries, gravitational lenses and dark matter. For the purpose of these investigations, we developed a model of a relativistic accretion disk around a supermassive black hole, based on the ray-tracing method in the Kerr metric, a model of a bright spot in an accretion disk and three different models of gravitational microlenses. All these models enabled us to study physics, spacetime geometry and effects of strong gravity in the vicinity of supermassive black holes, variability of some active galaxies and quasars, different effects in the lensed quasars with multiple images, as well as the dark matter fraction in the Universe. We also found an observational evidence for the first spectroscopically resolved sub-parsec orbit of a supermassive black hole binary system in the core of active galaxy NGC 4151. Besides, we studied applications of one potential alternative to dark matter in the form of a modified theory of gravity on Galactic scales, to explain the recently observed orbital precession of some S-stars, which are orbiting around a massive black hole at the Galactic center. [Projekat Ministarstva nauke Republike Srbije, br. 176003: Gravitation and the Large Scale Structure of the Universe
Thin Film Mediated Phase Change Phenomena: Crystallization, Evaporation and Wetting
Wettlaufer, John S.
1998-01-01
We focus on two distinct materials science problems that arise in two distinct microgravity environments: In space and within the space of a polymeric network. In the former environment, we consider a near eutectic alloy film in contact with its vapor which, when evaporating on earth, will experience compositionally induced buoyancy driven convection. The latter will significantly influence the morphology of the crystallized end member. In the absence of gravity, the morphology will be dominated by molecular diffusion and Marangoni driven viscous flow, and we study these phenomena theoretically and experimentally. The second microgravity environment exists in liquids, gels, and other soft materials where the small mass of individual molecules makes the effect of gravity negligible next to the relatively strong forces of intermolecular collisions. In such materials, an essential question concerns how to relate the molecular dynamics to the bulk rheological behavior. Here, we observe experimentally the diffusive motion of a single molecule in a single polymer filament, embedded within a polymer network and find anomalous diffusive behavior.
Ensemble Averaged Gravity Theory
Khosravi, Nima
2016-01-01
We put forward the idea that all the theoretically consistent models of gravity have a contribution to the observed gravity interaction. In this formulation each model comes with its own Euclidean path integral weight where general relativity (GR) automatically has the maximum weight in high-curvature regions. We employ this idea in the framework of Lovelock models and show that in four dimensions the result is a specific form of $f(R,G)$ model. This specific $f(R,G)$ satisfies the stability conditions and has self-accelerating solution. Our model is consistent with the local tests of gravity since its behavior is same as GR for high-curvature regimes. In low-curvature regime the gravity force is weaker than GR which can interpret as existence of a repulsive fifth force for very large scales. Interestingly there is an intermediate-curvature regime where the gravity force is stronger in our model than GR. The different behavior of our model in comparison with GR in both low- and intermediate-curvature regimes ...
A Note on Schwarzschild de Sitter Black Holes in Mimetic $F(R)$ Gravity
Oikonomou, V K
2016-01-01
In this brief note we investigate the conditions under which a Schwarzschild de Sitter black hole spacetime is a solution of the mimetic $F(R)$ gravity with Lagrange multiplier and potential. As we demonstrate, the resulting mimetic $F(R)$ gravity is a slight modification of the ordinary $F(R)$ gravity case, however the resulting perturbation equations are not in all cases identical to the ordinary $F(R)$ gravity case. In the latter case, the perturbation equations are identical to the ones corresponding to the Reissner-Nordstr\\"{o}m anti-de Sitter black hole.
A note on Schwarzschild-de Sitter black holes in mimetic F(R) gravity
Oikonomou, V. K.
2016-05-01
In this paper, we investigate the conditions under which a Schwarzschild-de Sitter black hole spacetime is a solution of the mimetic F(R) gravity with Lagrange multiplier and potential. As we demonstrate, the resulting mimetic F(R) gravity is a slight modification of the ordinary F(R) gravity case, however the resulting perturbation equations are not in all cases identical to the ordinary F(R) gravity case. In the latter case, the perturbation equations are identical to the ones corresponding to the Reissner-Nordström anti-de Sitter black hole.
Institute of Scientific and Technical Information of China (English)
申发田; 李日; 李菲; 张建强
2012-01-01
针对采用Simple结合守恒标量法进行大平板反重力充填的数值模拟计算时,当速度大于2m/s时流场就会发生偏转,产生流场不对称现象的问题,对Simple算法的流量计算方法用调和平均值法进行修正,使流场不对称现象得到改善,充型速度可提高到40m/s.%Aimed at the phenomenon of flow field asymmetry in the simulation on flow field in anti-gravity high-speed filling of thin-wall large-plate casting with the Simple method if the speed was greater than 2 m/s, the Simple algorithm for flow field was amended with harmonic mean method. The simulation results show that the symmetry of the flow field in high speed filling is greatly improved, the filling speed can increase to 40 m/s.
Airborne Gravity: NGS' Gravity Data for CN02 (2013 & 2014)
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...
Airborne Gravity: NGS' Gravity Data for EN06 (2016)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Maine, Canada, and the Atlantic Ocean collected in 2012 over 2 surveys. This data set is part of the Gravity for the Re-definition of the...
Airborne Gravity: NGS' Gravity Data for EN08 (2013)
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...
Airborne Gravity: NGS' Gravity Data for TS01 (2014)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Puerto Rico and the Virgin Islands collected in 2009 over 1 survey. This data set is part of the Gravity for the Re-definition of the...
Airborne Gravity: NGS' Gravity Data for ES01 (2013)
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...
Airborne Gravity: NGS' Gravity Data for CN03 (2014)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Nebraska collected in 2014 over one survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...
Airborne Gravity: NGS' Gravity Data for EN05 (2012)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Minnesota, Wisconsin, and Michigan collected in 2012 over 1 survey. This data set is part of the Gravity for the Re-definition of the...
Airborne Gravity: NGS' Gravity Data for CS06 (2012 & 2013)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas collected in 2012 & 2013 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical...
Airborne Gravity: NGS' Gravity Data for AN03 (2010)
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...
Airborne Gravity: NGS' Gravity Data for EN04 (2013)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Michigan and Lake Huron collected in 2012 over 1 survey. This data set is part of the Gravity for the Re-definition of the American...
Airborne Gravity: NGS' Gravity Data for AS02 (2010)
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...
Airborne Gravity: NGS' Gravity Data for CS03 (2009)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas and Louisiana collected in 2009 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical...
Airborne Gravity: NGS' Gravity Data for EN01 (2011)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Canada, and Lake Ontario collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the...
Airborne Gravity: NGS' Gravity Data for CS01 (2014)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alabama and Florida collected in 2008 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical...
Airborne Gravity: NGS' Gravity Data for PN01 (2014)
National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for California and Oregon collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical...
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.
Jain, Bhuvnesh
2010-01-01
Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the universe. We review recent developments in modified gravity theories, focusing on higher dimensional approaches and chameleon/f(R) theories. We classify these models in terms of the screening mechanisms that enable such theories to approach general relativity on small scales (and thus satisfy solar system constraints). We describe general features of the modified Friedman equation in such theories. The second half of this review describes experimental tests of gravity in light of the new theoretical approaches. We summarize the high precision tests of gravity on laboratory and solar system scales. We describe in some detail tests on astrophysical scales ranging from ~kpc (galaxy scales) to ~Gpc (large-scale structure). These tests rely on the growth and inter-relationship of perturbations in the metric potentials, density and velocity fields which can be measured using gravitational lensi...
Gravity and embryonic development
Young, R. S.
1976-01-01
The relationship between the developing embryo (both plant and animal) and a gravitational field has long been contemplated. The difficulty in designing critical experiments on the surface of the earth because of its background of 1 g, has been an obstacle to a resolution of the problem. Biological responses to gravity (particularly in plants) are obvious in many cases; however, the influence of gravity as an environmental input to the developing embryo is not as obvious and has proven to be extremely difficult to define. In spite of this, over the years numerous attempts have been made using a variety of embryonic materials to come to grips with the role of gravity in development. Three research tools are available: the centrifuge, the clinostat, and the orbiting spacecraft. Experimental results are now available from all three sources. Some tenuous conclusions are drawn, and an attempt at a unifying theory of gravitational influence on embryonic development is made.
Generalizing unimodular gravity
Saez-Gomez, Diego
2016-01-01
The so-called unimodular version of General Relativity is revisited, which assumes the trace-free part of the equations instead of the usual Einstein equations, what leads naturally to a cosmological constant that may compensate the large value of quantum fluctuations. Here we extend such formalism to some extensions of General Relativity that have drawn a lot of attention over the last years, as $f(R)$ gravity (or its equivalent scalar-tensor picture) and Gauss-Bonnet gravity. The corresponding unimodular version of such theories is constructed. From the classical point of view, the unimodular versions of such extensions are completely equivalent to their originals, but an effective cosmological constant arises naturally, what may provide a richer description of the universe evolution. Moreover, conformal transformations within unimodular gravities lead to some corrections that may affect their solutions. Here we analyze the case of Starobisnky inflation and compared with the original one.
Intrinsic Time Quantum Gravity
Yu, Hoi Lai
2016-01-01
Correct identification of the true gauge symmetry of General Relativity being 3d spatial diffeomorphism invariant(3dDI) (not the conventional infinite tensor product group with principle fibre bundle structure), together with intrinsic time extracted from clean decomposition of the canonical structure yields a self-consistent theory of quantum gravity. A new set of fundamental commutation relations is also presented. The basic variables are the eight components of the unimodular part of the spatial dreibein and eight SU(3) generators which correspond to Klauder's momentric variables that characterize a free theory of quantum gravity. The commutation relations are not canonical, but have well defined group theoretical meanings. All fundamental entities are dimensionless; and the quantum wave functionals are preferentially in the dreibein representation. The successful quantum theory of gravity involves only broad spectrum of knowledge and deep insights but no exotic idea.
Energy Technology Data Exchange (ETDEWEB)
Abele, Hartmut; Bittner, Thomas; Cronenberg, Gunther; Filter, Hanno; Jenke, Tobias; Lemmel, Hartmut; Thalhammer, Martin [Atominstitut TU Wien, Wien (Austria); Geltenbort, Peter [Institut Laue-Langevin, Grenoble (France)
2012-07-01
This talk is about a test of the Newtons Inverse Square Law of Gravity at micron distances by quantum interference with ultra-cold neutrons deep into the theoretically interesting regime. The method is based on a new resonance spectroscopy technique related to Rabi spectroscopy, but it has been adapted to gravitationally bound quantum systems. By coupling such a quantum system to mechanical vibrations, we observe resonant transitions, devoid of electromagnetic interaction. As Newtonian gravity and hypothetical Fifth Forces evolve with different phase information, the experiment has the potential to test the equivalence principle and Newtons gravity law at the micron scale. This experiment can therefore test speculations on large extra dimensions of sub-millimetre size of space-time or the origin of the cosmological constant in the universe, where effects are predicted in the interesting range of this experiment and might give a signal in an improved setup.
Observation of Celestial Phenomena in Ancient China
Sun, Xiaochun
Because of the need for calendar-making and portent astrology, the Chinese were diligent and meticulous observers of celestial phenomena. China has maintained the longest continuous historical records of celestial phenomena in the world. Extraordinary or abnormal celestial events were particularly noted because of their astrological significance. The historical records cover various types of celestial phenomena, which include solar and lunar eclipses, sunspots, "guest stars" (novae or supernovae as we understand today), comets and meteors, and all kinds of planetary phenomena. These records provide valuable historical data for astronomical studies today.
Remnant for all black objects due to gravity's rainbow
Directory of Open Access Journals (Sweden)
Ahmed Farag Ali
2015-05-01
Full Text Available We argue that a remnant is formed for all black objects in gravity's rainbow. This will be based on the observation that a remnant depends critically on the structure of the rainbow functions, and this dependence is a model independent phenomena. We thus propose general relations for the modified temperature and entropy of all black objects in gravity's rainbow. We explicitly check this to be the case for Kerr, Kerr–Newman-dS, charged-AdS, and higher dimensional Kerr–AdS black holes. We also try to argue that a remnant should form for black saturn in gravity's rainbow. This work extends our previous results on remnants of Schwarzschild black holes [1] and black rings [2].
Quantum Gravity and Matter: Counting Graphs on Causal Dynamical Triangulations
Benedetti, D
2006-01-01
An outstanding challenge for models of non-perturbative quantum gravity is the consistent formulation and quantitative evaluation of physical phenomena in a regime where geometry and matter are strongly coupled. After developing appropriate technical tools, one is interested in measuring and classifying how the quantum fluctuations of geometry alter the behaviour of matter, compared with that on a fixed background geometry. In the simplified context of two dimensions, we show how a method invented to analyze the critical behaviour of spin systems on flat lattices can be adapted to the fluctuating ensemble of curved spacetimes underlying the Causal Dynamical Triangulations (CDT) approach to quantum gravity. We develop a systematic counting of embedded graphs to evaluate the thermodynamic functions of the gravity-matter models in a high- and low-temperature expansion. For the case of the Ising model, we compute the series expansions for the magnetic susceptibility on CDT lattices and their duals up to orders 6 ...
Gravity Dual of Spatially Modulated Phase
Nakamura, Shin; Park, Chang-Soon
2009-01-01
We show that the five-dimensional Maxwell theory with the Chern-Simons term is tachyonic in the presence of a constant electric field. When coupled to gravity, a sufficiently large Chern-Simons coupling causes instability of the Reissner-Nordstrom black holes in anti-de Sitter space. The instability happens only at non-vanishing momenta, suggesting a spatially modulated phase in the holographically dual quantum field theory in 3+1 dimensions, with spontaneous current generation in a helical configuration. The three-charge extremal black hole in the type IIB superstring theory on AdS_5 x S^5 barely satisfies the stability condition.
Braneworld setup and embedding in teleparallel gravity
Directory of Open Access Journals (Sweden)
A. Behboodi
2015-01-01
Full Text Available We construct the setup of a five-dimensional braneworld scenario in teleparallel gravity. Both cases of Minkowski and Friedmann–Robertson–Walker branes embedded in anti-de Sitter bulk are studied and the effective 4D action were studied. 4-dimensional local Lorentz invariance is found to be recovered in both cases. However, due to different junction conditions, the equations governing the 4D cosmological evolution differ from general relativistic case. Using the results of Ref. [13], we consider a simple inflationary scenario in this setup. The inflation parameters are found to be modified compared to general relativistic case.
PREFACE: Physics and Mathematics of Nonlinear Phenomena 2013 (PMNP2013)
Konopelchenko, B. G.; Landolfi, G.; Martina, L.; Vitolo, R.
2014-03-01
Modern theory of nonlinear integrable equations is nowdays an important and effective tool of study for numerous nonlinear phenomena in various branches of physics from hydrodynamics and optics to quantum filed theory and gravity. It includes the study of nonlinear partial differential and discrete equations, regular and singular behaviour of their solutions, Hamitonian and bi- Hamitonian structures, their symmetries, associated deformations of algebraic and geometrical structures with applications to various models in physics and mathematics. The PMNP 2013 conference focused on recent advances and developments in Continuous and discrete, classical and quantum integrable systems Hamiltonian, critical and geometric structures of nonlinear integrable equations Integrable systems in quantum field theory and matrix models Models of nonlinear phenomena in physics Applications of nonlinear integrable systems in physics The Scientific Committee of the conference was formed by Francesco Calogero (University of Rome `La Sapienza', Italy) Boris A Dubrovin (SISSA, Italy) Yuji Kodama (Ohio State University, USA) Franco Magri (University of Milan `Bicocca', Italy) Vladimir E Zakharov (University of Arizona, USA, and Landau Institute for Theoretical Physics, Russia) The Organizing Committee: Boris G Konopelchenko, Giulio Landolfi, Luigi Martina, Department of Mathematics and Physics `E De Giorgi' and the Istituto Nazionale di Fisica Nucleare, and Raffaele Vitolo, Department of Mathematics and Physics `E De Giorgi'. A list of sponsors, speakers, talks, participants and the conference photograph are given in the PDF. Conference photograph
Terrestrial gravity data analysis for interim gravity model improvement
1987-01-01
This is the first status report for the Interim Gravity Model research effort that was started on June 30, 1986. The basic theme of this study is to develop appropriate models and adjustment procedures for estimating potential coefficients from terrestrial gravity data. The plan is to use the latest gravity data sets to produce coefficient estimates as well as to provide normal equations to NASA for use in the TOPEX/POSEIDON gravity field modeling program.
1/R gravity and Scalar-Tensor Gravity
Chiba, Takeshi
2003-01-01
We point out that extended gravity theories, the Lagrangian of which is an arbitrary function of scalar curvature $R$, are equivalent to a class of the scalar tensor theories of gravity. The corresponding gravity theory is $\\omega=0$ Brans-Dicke gravity with a potential for the Brans-Dicke scalar field, which is not compatible with solar system experiments if the field is very light: the case when such modifications are important recently.
On the no-gravity limit of gravity
Kowalski-Glikman, J.; Szczachor, M.
2012-01-01
We argue that Relative Locality may arise in the no gravity $G\\rightarrow0$ limit of gravity. In this limit gravity becomes a topological field theory of the BF type that, after coupling to particles, may effectively deform its dynamics. We briefly discuss another no gravity limit with a self dual ground state as well as the topological ultra strong $G\\rightarrow\\infty$ one.
From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity
Giesel, Kristina; Sahlmann, Hanno
2012-01-01
We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantizati...
De Aquino, Fran
2016-01-01
A new type of device for controlling gravity is here proposed. This is a quantum device because results from the behaviour of the matter and energy at subatomic length scale (10 m).-20 From the technical point of view this device is easy to build, and can be used to develop several devices for controlling gravity. Introduction Some years ago I wrote a paper [1] where a correlation between gravitational mass and inertial mass was obtained. In the paper I pointed out that the relationship betwe...
Deser, S; Ong, Y C; Waldron, A
2014-01-01
The method of characteristics is a key tool for studying consistency of equations of motion; it allows issues such as predictability, maximal propagation speed, superluminality, unitarity and acausality to be addressed without requiring explicit solutions. We review this method and its application to massive gravity theories to show the limitations of these models' physical viability: Among their problems are loss of unique evolution, superluminal signals, matter coupling inconsistencies and micro-acausality (propagation of signals around local closed timelike/causal curves). We extend previous no-go results to the entire three-parameter range of massive gravity theories. It is also argued that bimetric models suffer a similar fate.
Chiou, Dah-Wei
2015-12-01
This paper presents an "in-a-nutshell" yet self-contained introductory review on loop quantum gravity (LQG) — a background-independent, nonperturbative approach to a consistent quantum theory of gravity. Instead of rigorous and systematic derivations, it aims to provide a general picture of LQG, placing emphasis on the fundamental ideas and their significance. The canonical formulation of LQG, as the central topic of the paper, is presented in a logically orderly fashion with moderate details, while the spin foam theory, black hole thermodynamics, and loop quantum cosmology are covered briefly. Current directions and open issues are also summarized.
Institute of Scientific and Technical Information of China (English)
毛明强; 熊巨华
2014-01-01
墙前开挖区土压力和墙后土压力模式的确定是水泥土重力式挡土墙抗倾覆稳定性验算的关键，不同土压力模式下抗倾覆系数曲线形态有一定的差异。根据墙体竖向力的平衡确定抗倾覆验算点位置，根据墙体的变形特征，同时考虑由于基坑开挖引起的上覆有效土压力变化引入修正系数α修正墙前后土压力，推导了修正土压力模式下墙体的抗倾覆稳定计算公式，对比分析三种不同土压力模式下Kq曲线的形态特征及其影响因素，结果表明墙前后土压力修正模式更能反映实际状态下墙的倾覆失稳形态，其抗倾覆稳定系数也更加合理。%The mode of earth pressures acting on the front wall and behind the wall plays a key role in checking the anti-overturning stability of cement-soil gravity retaining wall after excavation. The curve of anti-overturning safety factor somewhat varies under different earth pressure modes. The turning point can be determined according to the balance of vertical force. In order to consider the characteristics of wall deformation and the change of effective vertical earth pressure, a coefficient is introduced to modify the earth pressure on the wall, meanwhile a formula for calculating the safety factor is proposed under the new mode. Through analysis of the morphological characteristics of the curve and the influencing factor under three different earth pressure modes, the calculated results show that the anti-overturning safety factor is more reasonable, and the modified method can better reveal the real state of wall overturning.
Gauge/gravity duality. From quantum phase transitions towards out-of-equilibrium physics
Energy Technology Data Exchange (ETDEWEB)
Ngo Thanh, Hai
2011-05-02
In this dissertation we use gauge/gravity duality to investigate various phenomena of strongly coupled field theories. Of special interest are quantum phase transitions, quantum critical points, transport phenomena of charges and the thermalization process of strongly coupled medium. The systems studied in this thesis might be used as models for describing condensed matter physics in a superfluid phase near the quantum critical point and the physics of quark-gluon plasma (QGP), a deconfinement phase of QCD, which has been recently created at the Relativistic Heavy Ion Collider (RHIC). Moreover, we follow the line of considering different gravity setups whose dual field descriptions show interesting phenomena of systems in thermal equilibrium, slightly out-of-equilibrium and far-from-equilibrium. We first focus on systems in equilibrium and construct holographic superfluids at finite baryon and isospin charge densities. For that we use two different approaches, the bottom-up with an U(2) Einstein-Yang-Mills theory with back-reaction and the top-down approach with a D3/D7 brane setup with two coincident D7-brane probes. In both cases we observe phase transitions from a normal to a superfluid phase at finite and also at zero temperature. In our setup, the gravity duals of superfluids are Anti-de Sitter black holes which develop vector-hair. Studying the order of phase transitions at zero temperature, in the D3/D7 brane setup we always find a second order phase transition, while in the Einstein-Yang-Mills theory, depending on the strength of the back-reaction, we obtain a continuous or first order transition. We then move to systems which are slightly out-of-equilibrium. Using the D3/D7 brane setup with N{sub c} coincident D3-branes and N{sub f} coincident D7-brane probes, we compute transport coefficients associated with massive N=2 supersymmetric hypermultiplet fields propagating through an N=4 SU(N{sub c}) super Yang-Mills plasma in the limit of N{sub f}<
Brans–Dicke gravity theory from topological gravity
International Nuclear Information System (INIS)
We consider a model that suggests a mechanism by which the four dimensional Brans–Dicke gravity theory may emerge from the topological gravity action. To achieve this goal, both the Lie algebra and the symmetric invariant tensor that define the topological gravity Lagrangian are constructed by means of the Lie algebra S-expansion procedure with an appropriate abelian semigroup S
SATELLITE GRAVITY SURVEYING TECHNOLOGY AND RESEARCH OF EARTH'S GRAVITY FIELD
Institute of Scientific and Technical Information of China (English)
Ning Jinsheng
2003-01-01
This is a summarized paper. Two topics are discussed: Firstly, the concept, development and application of four kinds of satellite gravity surveying technology are introduced; Secondly, some problems of theory and method, which must be considered in the study of the Earth's gravity field based on satellite gravity data, are expounded.
Euler Chern Simons Gravity from Lovelock Born Infeld Gravity
Izaurieta, Fernando; Rodriguez, Eduardo; Salgado, Patricio
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.
Gravity separation for oil wastewater treatment
Golomeova, Mirjana; Zendelska, Afrodita; Krstev, Boris; Krstev, Aleksandar
2010-01-01
In this paper, the applications of gravity separation for oil wastewater treatment are presented. Described is operation on conventional gravity separation and parallel plate separation. Key words: gravity separation, oil, conventional gravity separation, parallel plate separation.
Gravity Station Data for Spain
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...
Gravity Data for South America
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...
Interior Alaska Gravity Station Data
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...
Four principles for quantum gravity
Smolin, Lee
2016-01-01
Four principles are proposed to underlie the quantum theory of gravity. We show that these suffice to recover the Einstein equations. We also suggest that MOND results from a modification of the classical equivalence principle, due to quantum gravity effects.
Gravity Station Data for Portugal
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...
Scalable Gravity Offload System Project
National Aeronautics and Space Administration — A scalable gravity offload device simulates reduced gravity for the testing of various surface system elements such as mobile robots, excavators, habitats, and...
Nonlinear dynamics of drops and bubbles and chaotic phenomena
Trinh, Eugene H.; Leal, L. G.; Feng, Z. C.; Holt, R. G.
1994-01-01
Nonlinear phenomena associated with the dynamics of free drops and bubbles are investigated analytically, numerically and experimentally. Although newly developed levitation and measurement techniques have been implemented, the full experimental validation of theoretical predictions has been hindered by interfering artifacts associated with levitation in the Earth gravitational field. The low gravity environment of orbital space flight has been shown to provide a more quiescent environment which can be utilized to better match the idealized theoretical conditions. The research effort described in this paper is a closely coupled collaboration between predictive and guiding theoretical activities and a unique experimental program involving the ultrasonic and electrostatic levitation of single droplets and bubbles. The goal is to develop and to validate methods based on nonlinear dynamics for the understanding of the large amplitude oscillatory response of single drops and bubbles to both isotropic and asymmetric pressure stimuli. The first specific area on interest has been the resonant coupling between volume and shape oscillatory modes isolated gas or vapor bubbles in a liquid host. The result of multiple time-scale asymptotic treatment, combined with domain perturbation and bifurcation methods, has been the prediction of resonant and near-resonant coupling between volume and shape modes leading to stable as well as chaotic oscillations. Experimental investigations of the large amplitude shape oscillation modes of centimeter-size single bubbles trapped in water at 1 G and under reduced hydrostatic pressure, have suggested the possibility of a low gravity experiment to study the direct coupling between these low frequency shape modes and the volume pulsation, sound-radiating mode. The second subject of interest has involved numerical modeling, using the boundary integral method, of the large amplitude shape oscillations of charged and uncharged drops in the presence
Diaz, Pablo; Walton, Mark
2016-01-01
With the aim of investigating the relation between gravity and non-locality at the classical level, we study a bilocal scalar field model. Bilocality introduces new (internal) degrees of freedom that can potentially reproduce gravity. We show that the equations of motion of the massless branch of the free bilocal model match those of linearized gravity. We also discuss higher orders of perturbation theory, where there is self-interaction in both gravity and the bilocal field sectors.
Perturbative Quantization of Gravity Theories
Bern, Z.
2001-01-01
We discuss string theory relations between gravity and gauge theory tree amplitudes. Together with $D$-dimensional unitarity, these relations can be used to perturbatively quantize gravity theories, i.e. they contain the necessary information for calculating complete gravity $S$-matrices to any loop orders. This leads to a practical method for computing non-trivial gravity $S$-matrix elements by relating them to much simpler gauge theory ones. We also describe arguments that N=8 D=4 supergrav...
Introduction to Loop Quantum Gravity
Mercuri, Simone
2012-01-01
The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity.
Black holes in modified gravity theories
Energy Technology Data Exchange (ETDEWEB)
De la Cruz-Dombriz, A; Dobado, A; Maroto, A L, E-mail: dombriz@fis.ucm.e [Departamento de Fisica Teorica I, Universidad Complutense de Madrid, 28040 Madrid (Spain)
2010-05-01
In the context of f(R) gravity theories, the issue of finding static and spherically symmetric black hole solutions is addressed. Two approaches to study the existence of such solutions are considered: first, constant curvature solutions, and second, the general case (without imposing constant curvature) is also studied. Performing a perturbative expansion around the Einstein-Hilbert action, it is found that only solutions of the Schwarzschild-(Anti-) de Sitter type are present (up to second order in perturbations) and the explicit expressions for these solutions are provided in terms of the f(R) function. Finally we consider the thermodynamics of black holes in Anti-de Sitter space-time and study their local and global stability.
Ketamine: effect of literacy on emergence phenomena.
Currie, M. A.; Currie, A. L.
1984-01-01
A prospective study of the relationship between literacy rate and emergence phenomena with ketamine anaesthesia was carried out among Pathans on Pakistan's Afghan frontier. Findings support both a strong link between the literacy of the patient and the occurrence of emergence phenomena, and the acceptability and value of ketamine in this type of population.
Fluctuation theory of critical phenomena in fluids
Martynov, G. A.
2016-07-01
It is assumed that critical phenomena are generated by density wave fluctuations carrying a certain kinetic energy. It is noted that all coupling equations for critical indices are obtained within the context of this hypothesis. Critical indices are evaluated for 15 liquids more accurately than when using the current theory of critical phenomena.
Bueno, Pablo
2016-01-01
We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a D-dimensional cubic theory of gravity which satisfies the following properties: 1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; 2) the relative coefficients of the different curvature invariants involved are the same in all dimensions; 3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones: Einstein gravity, Gauss-Bonnet and cubic-Lovelock. Of course, the last two theories fail to satisfy requirement 3 as they are, respectively, topological and trivial in four dimensions. We ...
International Nuclear Information System (INIS)
The theoretical basis for gravity-wave astronomy is described, along with the energy and momentum of gravitational fields. Other topics discussed include:- burst and periodic sources of gravitational waves, the cosmological stochastic background, and the detection of gravitational waves. (U.K.)
Banerjee, Rabin; Majhi, Bibhas Ranjan
2010-01-01
Starting from the definition of entropy used in statistical mechanics we show that it is proportional to the gravity action. For a stationary black hole this entropy is expressed as $S = E/ 2T$, where $T$ is the Hawking temperature and $E$ is shown to be the Komar energy. This relation is also compatible with the generalised Smarr formula for mass.
Artificial Gravity Research Plan
Gilbert, Charlene
2014-01-01
This document describes the forward working plan to identify what countermeasure resources are needed for a vehicle with an artificial gravity module (intermittent centrifugation) and what Countermeasure Resources are needed for a rotating transit vehicle (continuous centrifugation) to minimize the effects of microgravity to Mars Exploration crewmembers.
Newburgh, Ronald
2010-01-01
It's both surprising and rewarding when an old, standard problem reveals a subtlety that expands its pedagogic value. I realized recently that the role of gravity in the range equation for a projectile is not so simple as first appears. This realization may be completely obvious to others but was quite new to me.
International Nuclear Information System (INIS)
Loop quantum gravity is one of the approaches that are being studied to apply the rules of quantum mechanics to the gravitational field described by the theory of General Relativity . We present an introductory summary of the main ideas and recent results. (Author)
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.
Noncommutative Symmetries and Gravity
Aschieri, P
2006-01-01
Spacetime geometry is twisted (deformed) into noncommutative spacetime geometry, where functions and tensors are now star-multiplied. Consistently, spacetime diffeomorhisms are twisted into noncommutative diffeomorphisms. Their deformed Lie algebra structure and that of infinitesimal Poincare' transformations is defined and explicitly constructed. This allows to construct a noncommutative theory of gravity.
From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity
Giesel, Kristina
2012-01-01
We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantization of vacuum general relativity in loop quantum gravity.
Even-dimensional topological gravity from Chern-Simons gravity
Merino, N.; Perez, Alfredo; Salgado, P.(Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción, Chile)
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 $\\phi^{a}$, which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associat...
On the stability of the cosmological solutions in f(R, G) gravity
International Nuclear Information System (INIS)
Modified gravity is one of the most promising candidates for explaining the current accelerating expansion of the Universe, and even its unification with the inflationary epoch. Nevertheless, the wide range of models capable of explaining the phenomena of dark energy imposes that current research focuses on a more precise study of the possible effects of modified gravity on both cosmological and local levels. In this paper, we focus on the analysis of a type of modified gravity, the so-called f(R, G) gravity, and we perform a deep analysis on the stability of important cosmological solutions. This not only can help to constrain the form of the gravitational action, but also facilitate a better understanding of the behavior of the perturbations in this class of higher order theories of gravity, which will lead to a more precise analysis of the full spectrum of cosmological perturbations in future. (paper)
Reality conditions for Ashtekar gravity from Lorentz-covariant formulation
Energy Technology Data Exchange (ETDEWEB)
Alexandrov, Sergei [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Postbus 80.195, 3508 TD Utrecht (Netherlands)
2006-03-21
We study the limit of the Lorentz-covariant canonical formulation where the Immirzi parameter approaches {beta} = i. We show that, formulated in terms of a shifted spacetime connection, which also plays a crucial role in the covariant quantization, the limit is smooth and reproduces the canonical structure of the self-dual Ashtekar gravity. The reality conditions of Ashtekar gravity can be incorporated by means of the Dirac brackets derived from the covariant formulation and defined on an extended phase space which involves, besides the self-dual variables, also their anti-self-dual counterparts.
Gravity and antigravity in a brane world with metastable gravitons
Gregory, R.; Rubakov, V. A.; Sibiryakov, S. M.
2000-09-01
In the framework of a five-dimensional three-brane model with quasi-localized gravitons we evaluate metric perturbations induced on the positive tension brane by matter residing thereon. We find that at intermediate distances, the effective four-dimensional theory coincides, up to small corrections, with General Relativity. This is in accord with Csaki, Erlich and Hollowood and in contrast to Dvali, Gabadadze and Porrati. We show, however, that at ultra-large distances this effective four-dimensional theory becomes dramatically different: conventional tensor gravity changes into scalar anti-gravity.
Rainbow Vacua of Colored Higher Spin Gravity in Three Dimensions
Gwak, Seungho; Mkrtchyan, Karapet; Rey, Soo-Jong
2015-01-01
We study the color-decoration of higher spin (anti)-de Sitter gravity in three dimensions. We show that the rainbow vacua, which we found recently for the colored gravity theory, also exist in the colored higher spin theory. The color singlet spin-two plays the role of metric. The difference is that when spontaneous breaking of color symmetry takes place, the Goldstone modes of massless spin-two combine with all other spins and become the maximal depth partially massless fields of the highest spin in the theory.
Gravity Localization and Effective Newtonian Potential for Bent Thick Branes
Guo, Heng; Liu, Yu-xiao; Wei, Shao-Wen; Fu, Chun-E
2010-01-01
In this letter, we first investigate the gravity localization and mass spectrum of gravity KK modes on de Sitter and Anti-de Sitter thick branes. Then, the effective Newtonian gravitational potentials for these bent branes are discussed by the two typical examples. The corrections of the Newtonian potential turns out to be $\\Delta U(r)\\sim 1/r^{2}$ at small $r$ for both cases. These corrections are very different from that of the Randall-Sundrum brane model $\\Delta U(r)\\sim 1/r^{3}$.
Black-hole dynamics in BHT massive gravity
Maeda, Hideki
2010-01-01
Using an exact Vaidya-type null-dust solution, we study the area and entropy laws for dynamical black holes defined by a future outer trapping horizon in (2+1)-dimensional Bergshoeff-Hohm-Townsend (BHT) massive gravity. We consider the theory admitting a degenerate (anti-)de Sitter vacuum and pure BHT gravity. It is shown that, while the area of a black hole decreases by the injection of a null dust with positive energy density in several cases, the Wald-Kodama dynamical entropy always increa...
Stochastic Boundary Element Analysis of Concrete Gravity Dam
Institute of Scientific and Technical Information of China (English)
张明; 吴清高
2002-01-01
Stochastic boundary integral equations for analyzing large structures are obtained from the partial derivatives of basic random variables. A stochastic boundary element method based on the equations is developed to solve engineering problems of gravity dams using random factors including material parameters of the dam body and the foundation, the water level in the upper reaches, the anti-slide friction coefficient of the dam base, etc. A numerical example shows that the stochastic boundary element method presented in this paper to calculate the reliability index of large construction projects such as a large concrete gravity dam has the advantages of less input data and more precise computational results.
Higher Derivative Gravities and Negative Entropy
Nojiri, S
2000-01-01
We investigate the black hole solutions in the $R^2$-gravity, where the action contains the square of the curvature. In case that the action does not contain the square of the Riemann tensor and in case that the $R^2$-terms are the Gauss-Bonnet (GB) combination, we find exact solutions. We investigate the thermodynamics of these theories and find the Hawking-Page like phase transition, which is the phase transition between the black hole (BH) spacetime and the pure anti-deSitter (AdS) spacetime. From the viewpoint of the AdS/CFT correspondence, such a phase transition may correspond to thermal transition of dual CFT. An interesting feature of $R^2$-gravity is the possibility of the negative (or zero) dS (or AdS) BH entropy, which depends on the parameters of the $R^2$-terms. We speculate that the appearence of negative entropy may indicate a new type instability where a transition between dS (AdS) BH with negative entropy and AdS (dS) BH with positive entropy occurs. We also apply the GB gravity to the brane ...
The standard model with gravity couplings
Chang, L N; Lay Nam Chang; Chopin Soo
1996-01-01
ABSTRACT-The Standard Model with Gravity Couplings-Lay Nam Chang(Virginia Tech) & Chopin Soo(Penn State)--- It has been shown by Ashtekar, and many others after him, that classical gravity in four dimensions can be described equally well by (anti)self-dual variables instead of the conventional variables. In this paper, we examine the coupling of matter fields to gravity from this perspective, and show that the known quark and lepton multiplets in the Standard Model of particle physics can be introduced into the theory in a manner which ensures the cancellation of perturbative chiral gauge anomalies, despite the fact that the the Ashtekar-Sen connection allows for couplings only to left-handed Weyl fermions. We also explore a global anomaly associated with the theory, and argue that its removal requires that the number of fundamental fermions in the theory must be multiples of 16. In addition, we investigate the behavior of the theory under discrete transformations P, C and T, and discuss possible violatio...
Gravity, holography and applications to condensed matter
Baggioli, Matteo
2016-01-01
Momentum relaxation is an ever-present and unavoidable ingredient of any realistic condensed matter system. In real-world materials the presence of a lattice, impurities or disorder forces momentum to dissipate and leads to relevant physical effects such as the finiteness of the DC transport properties, i.e. conductivities. The main purpose of this thesis is the introduction of momentum dissipation and its consequent effects into the framework of AdS/CMT, namely the applications of the gauge-gravity duality to condensed matter. A convenient and effective way of breaking the translational symmetry associated to such a conservation law is provided by massive gravity (MG) bulk theories. We consider generic massive gravity models embedded into asymptotically Anti de Sitter spacetime and we analyze them using holographic techniques. We study in detail their consistency and stability. We then focus our attention on the transport properties of the CFT duals. A big part of our work is devoted to the analysis of the e...
Strings from 3D gravity: asymptotic dynamics of AdS 3 gravity with free boundary conditions
Apolo, Luis; Sundborg, Bo
2015-01-01
Pure three-dimensional gravity in anti-de Sitter space can be formulated as an SL(2,R) $\\times $ SL(2,R) Chern-Simons theory, and the latter can be reduced to a WZW theory at the boundary. In this paper we show that AdS$_3$ gravity with free boundary conditions is described by a string at the boundary whose target spacetime is also AdS$_3$. While boundary conditions in the standard construction of Coussaert, Henneaux, and van Driel are enforced through constraints on the WZW currents, we find...
Quantum gravity from noncommutative spacetime
International Nuclear Information System (INIS)
We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative *-algebra) of quantum gravity.
Quantum gravity from noncommutative spacetime
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.
Gravitational backreaction of anti-D branes in the warped compactification
Koyama, Kayoko; Koyama, Kazuya
2005-01-01
We derive a low-energy effective theory for gravity with anti-D branes, which are essential to get de Sitter solutions in the type IIB string warped compactification, by taking account of gravitational backreactions of anti-D branes. In order to see the effects of the self-gravity of anti-D branes, a simplified model is studied where a 5-dimensional anti-de Sitter ({\\it AdS}) spacetime is realized by the bulk cosmological constant and the 5-form flux, and anti-D branes are coupled to the 5-fo...
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...
A Superspace Formulation of the BV Action for Higher Derivative Gravity
Khan, Mozzam
2012-01-01
In this paper we analyse perturbative higher derivative gravity which is known to possess a BRST symmetry associated with its higher derivative structure. We first analyse the anti-BRST and double BRST symmetries of this theory. We then discuss the extended BRST and extended anti-BRST symmetries of this theory using the superspace formalism. We show that even though this theory is generally invariant under extended BRST transformations under extended anti-BRST transformations it is only invar...
A statistical approach to strange diffusion phenomena
International Nuclear Information System (INIS)
The study of particle (and heat) transport in fusion plasmas has revealed the existence of what might be called 'unusual' transport phenomena. Such phenomena are: unexpected scaling of the confinement time with system size, power degradation (i.e. sub-linear scaling of energy content with power input), profile stiffness (also known as profile consistency), rapid transient transport phenomena such as cold and heat pulses (travelling much faster than the diffusive timescale would allow), non-local behaviour and central profile peaking during off-axis heating, associated with unexplained inward pinches. The standard modelling framework, essentially equal to Fick's Law plus extensions, has great difficulty in providing an all-encompassing and satisfactory explanation of all these phenomena. This difficulty has motivated us to reconsider the basics of the modelling of diffusive phenomena. Diffusion is based on the well-known random walk. The random walk is captured in all its generality in the Continuous Time Random Walk (CTRW) formalism. The CTRW formalism is directly related to the well-known Generalized Master Equation, which describes the behaviour of tracer particle diffusion on a very fundamental level, and from which the phenomenological Fick's Law can be derived under some specific assumptions. We show that these assumptions are not necessarily satisfied under fusion plasma conditions, in which case other equations (such as the Fokker-Planck diffusion law or the Master Equation itself) provide a better description of the phenomena. This fact may explain part of the observed 'strange' phenomena (namely, the inward pinch). To show how the remaining phenomena mentioned above may perhaps find an explanation in the proposed alternative modelling framework, we have designed a toy model that incorporates a critical gradient mechanism, switching between rapid (super-diffusive) and normal diffusive transport as a function of the local gradient. It is then demonstrated
Transient phenomena in electrical power systems
Venikov, V A; Higinbotham, W
1964-01-01
Electronics and Instrumentation, Volume 24: Transient Phenomena in Electrical Power Systems presents the methods for calculating the stability and the transient behavior of systems with forced excitation control. This book provides information pertinent to the analysis of transient phenomena in electro-mechanical systems.Organized into five chapters, this volume begins with an overview of the principal requirements in an excitation system. This text then explains the electromagnetic and electro-mechanical phenomena, taking into account the mutual action between the components of the system. Ot
Fourteenth International Conference on Ultrafast Phenomena
Kobayashi, Takayoshi; Kobayashi, Tetsuro; Nelson, Keith A; Silvestri, Sandro; Ultrafast Phenomena XIV
2005-01-01
Ultrafast Phenomena XIV presents the latest advances in ultrafast science, including ultrafast laser and measurement technology as well as studies of ultrafast phenomena. Pico-, femto-, and atosecond processes relevant in physics, chemistry, biology and engineering are presented. Ultrafast technology is now having a profound impact within a wide range of applications, among them imaging, material diagnostics, and transformation and high-speed optoelectronics. This book summarizes results presented at the 14th Ultrafast Phenomena Conference and reviews the state of the art in this important and rapidly advancing field.
Sixteenth International Conference on Ultrafast Phenomena
Corkum, Paul; Nelson, Keith A; Riedle, Eberhard; Schoenlein, Robert W; Ultrafast Phenomena XVI
2009-01-01
Ultrafast Phenomena XVI presents the latest advances in ultrafast science, including both ultrafast optical technology and the study of ultrafast phenomena. It covers picosecond, femtosecond and attosecond processes relevant to applications in physics, chemistry, biology, and engineering. Ultrafast technology has a profound impact in a wide range of applications, amongst them biomedical imaging, chemical dynamics, frequency standards, material processing, and ultrahigh speed communications. This book summarizes the results presented at the 16th International Conference on Ultrafast Phenomena and provides an up-to-date view of this important and rapidly advancing field.
Synchronization Phenomena and Epoch Filter of Electroencephalogram
Matani, Ayumu
Nonlinear electrophysiological synchronization phenomena in the brain, such as event-related (de)synchronization, long distance synchronization, and phase-reset, have received much attention in neuroscience over the last decade. These phenomena contain more electrical than physiological keywords and actually require electrical techniques to capture with electroencephalography (EEG). For instance, epoch filters, which have just recently been proposed, allow us to investigate such phenomena. Moreover, epoch filters are still developing and would hopefully generate a new paradigm in neuroscience from an electrical engineering viewpoint. Consequently, electrical engineers could be interested in EEG once again or from now on.
Computational transport phenomena for engineering analyses
Farmer, Richard C; Cheng, Gary C; Chen, Yen-Sen
2009-01-01
Computational Transport PhenomenaOverviewTransport PhenomenaAnalyzing Transport PhenomenaA Computational Tool: The CTP CodeVerification, Validation, and GeneralizationSummaryNomenclatureReferencesThe Equations of ChangeIntroductionDerivation of The Continuity EquationDerivation of The Species Continuity EquationDerivation of The Equation Of MotionDerivation of The General Energy EquationNon-Newtonian FluidsGeneral Property BalanceAnalytical and Approximate Solutions for the Equations of ChangeSummaryNomenclatureReferencesPhysical PropertiesOverviewReal-Fluid ThermodynamicsChemical Equilibrium
Terrestrial Microgravity Model and Threshold Gravity Simulation using Magnetic Levitation
Ramachandran, N.
2005-01-01
What is the threshold gravity (minimum gravity level) required for the nominal functioning of the human system? What dosage is required? Do human cell lines behave differently in microgravity in response to an external stimulus? The critical need for such a gravity simulator is emphasized by recent experiments on human epithelial cells and lymphocytes on the Space Shuttle clearly showing that cell growth and function are markedly different from those observed terrestrially. Those differences are also dramatic between cells grown in space and those in Rotating Wall Vessels (RWV), or NASA bioreactor often used to simulate microgravity, indicating that although morphological growth patterns (three dimensional growth) can be successfully simulated using RWVs, cell function performance is not reproduced - a critical difference. If cell function is dramatically affected by gravity off-loading, then cell response to stimuli such as radiation, stress, etc. can be very different from terrestrial cell lines. Yet, we have no good gravity simulator for use in study of these phenomena. This represents a profound shortcoming for countermeasures research. We postulate that we can use magnetic levitation of cells and tissue, through the use of strong magnetic fields and field gradients, as a terrestrial microgravity model to study human cells. Specific objectives of the research are: 1. To develop a tried, tested and benchmarked terrestrial microgravity model for cell culture studies; 2. Gravity threshold determination; 3. Dosage (magnitude and duration) of g-level required for nominal functioning of cells; 4. Comparisons of magnetic levitation model to other models such as RWV, hind limb suspension, etc. and 5. Cellular response to reduced gravity levels of Moon and Mars. The paper will discuss experiments md modeling work to date in support of this project.
Terrestrial Microgravity Model and Threshold Gravity Simulation sing Magnetic Levitation
Ramachandran, N.
2005-01-01
What is the threshold gravity (minimum gravity level) required for the nominal functioning of the human system? What dosage is required? Do human cell lines behave differently in microgravity in response to an external stimulus? The critical need for such a gravity simulator is emphasized by recent experiments on human epithelial cells and lymphocytes on the Space Shuttle clearly showing that cell growth and function are markedly different from those observed terrestrially. Those differences are also dramatic between cells grown in space and those in Rotating Wall Vessels (RWV), or NASA bioreactor often used to simulate microgravity, indicating that although morphological growth patterns (three dimensional growth) can be successiblly simulated using RWVs, cell function performance is not reproduced - a critical difference. If cell function is dramatically affected by gravity off-loading, then cell response to stimuli such as radiation, stress, etc. can be very different from terrestrial cell lines. Yet, we have no good gravity simulator for use in study of these phenomena. This represents a profound shortcoming for countermeasures research. We postulate that we can use magnetic levitation of cells and tissue, through the use of strong magnetic fields and field gradients, as a terrestrial microgravity model to study human cells. Specific objectives of the research are: 1. To develop a tried, tested and benchmarked terrestrial microgravity model for cell culture studies; 2. Gravity threshold determination; 3. Dosage (magnitude and duration) of g-level required for nominal functioning of cells; 4. Comparisons of magnetic levitation model to other models such as RWV, hind limb suspension, etc. and 5. Cellular response to reduced gravity levels of Moon and Mars.
Holographic bound in covariant loop quantum gravity
Tamaki, Takashi
2016-01-01
We investigate puncture statistics based on the covariant area spectrum in loop quantum gravity. First, we consider Maxwell-Boltzmann statistics with a Gibbs factor for punctures. We establish formulae which relate physical quantities such as horizon area to the parameter characterizing holographic degrees of freedom. We also perform numerical calculations and obtain consistency with these formulae. These results tell us that the holographic bound is satisfied in the large area limit and correction term of the entropy-area law can be proportional to the logarithm of the horizon area. Second, we also consider Bose-Einstein statistics and show that the above formulae are also useful in this case. By applying the formulae, we can understand intrinsic features of Bose-Einstein condensate which corresponds to the case when the horizon area almost consists of punctures in the ground state. When this phenomena occurs, the area is approximately constant against the parameter characterizing the temperature. When this ...
Akhavan, Amin; Nemati, Azadeh; Shirzad, Ahmad
2016-01-01
We show that the problem of ghosts in critical gravity and its higher dimensional extensions can be resolved by giving dynamics to the symmetric rank two auxiliary field existing in the action of these theories. These New Bi-Gravities, at linear level around the AdS vacuum, are free of Boulware-Deser ghost, kinetic ghost and tachyonic instability within the particular range of parameters. Moreover, we show that the energy and entropy of AdS-Schwarzschild black hole solutions of these new models are positive in the same range of parameters. This may be the sign that these new models are also free of ghost instabilities at the non-linear level.
Murad, P. A.
2003-01-01
Newtonian gravitation adequately predicts planet and satellite motion. Gravitational anomalies and the wish to travel at relativistic speeds, however, imply that gravity should be integrated within a unification framework that may include electricity and magnetism. Thus, new theories are needed that predict currently accepted phenomenon as well as anomalies to prepare the necessary groundwork for experimental validation needed for advanced technology propulsion schemes and far-term missions. A primary deficiency is that we are obviously limited within the confines of our own solar system and a different gravity model may be applicable elsewhere in the cosmos. The model proposed here follows previous ideas proposed by Murad, Dyatlov, and Jefimenko for a universal gravitation model with an intrinsic radial force term coupled with angular momentum. Including angular momentum may explain several spin symmetries seen in some anomalous gyroscopic experiments and throughout the universe regarding planets that orbit around the sun: moons that orbit larger planetary bodies: and the rotation about each planetary axis.
Gomberoff, Andres
2006-01-01
The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward. This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.
Gravity from Spacetime Thermodynamics
Padmanabhan, T
2002-01-01
The Einstein-Hilbert action (and thus the dynamics of gravity) can be obtained by combining the principle of equivalence, special relativity and quantum theory in the Rindler frame and postulating that the horizon area must be proportional to the entropy. This approach uses the local Rindler frame as a natural extension of the local inertial frame, and leads to the interpretation that the gravitational action represents the free energy of the spacetime geometry. As an aside, one obtains an insight into the peculiar structure of Einstein-Hilbert action and a natural explanation to the questions:(i) Why does the covariant action for gravity contain second derivatives of the metric tensor? (ii) Why is the gravitational coupling constant is positive ? Some geometrical features of gravitational action are clarified.
International Nuclear Information System (INIS)
Superstrings being consistent theories that include gravity have to produce classical gravity within limits provided by unambiguous quantum effects. Through the study of a hard scattering process - clearly provided by string theory - it is shown that infinite genus calculations give indeed rise to a classical limit, when 'large' distances are explored, as well as quantum effects. These are dominant at distances of the order of the string length (related to the Planck length) but may extend much beyond that region hinting indeed to gravitational instabilities. Below the string length even space-time loses meaning as a classical concept. A new position-momentum uncertainty relation is produced that assigns to the string length the meaning of a minimum observable distance. (orig.)
Christiansen, Nicolai; Meibohm, Jan; Pawlowski, Jan M; Reichert, Manuel
2015-01-01
We investigate the ultraviolet behaviour of quantum gravity within a functional renormalisation group approach. The present setup includes the full ghost and graviton propagators and, for the first time, the dynamical graviton three-point function. The latter gives access to the coupling of dynamical gravitons and makes the system minimally self-consistent. The resulting phase diagram confirms the asymptotic safety scenario in quantum gravity with a non-trivial UV fixed point. A well-defined Wilsonian block spinning requires locality of the flow in momentum space. This property is discussed in the context of functional renormalisation group flows. We show that momentum locality of graviton correlation functions is non-trivially linked to diffeomorphism invariance, and is realised in the present setup.
Christiansen, N.; Knorr, B.; Meibohm, J.; Pawlowski, J. M.; Reichert, M.
2015-12-01
We investigate the ultraviolet behavior of quantum gravity within a functional renormalization group approach. The present setup includes the full ghost and graviton propagators and, for the first time, the dynamical graviton three-point function. The latter gives access to the coupling of dynamical gravitons and makes the system minimally self-consistent. The resulting phase diagram confirms the asymptotic safety scenario in quantum gravity with a nontrivial UV fixed point. A well-defined Wilsonian block spinning requires locality of the flow in momentum space. This property is discussed in the context of functional renormalization group flows. We show that momentum locality of graviton correlation functions is nontrivially linked to diffeomorphism invariance, and is realized in the present setup.
International Nuclear Information System (INIS)
Quantum theory and general relativity will only be unified when theory meets experiment. Physics in the 20th century was built on two great revolutions: the general theory of relativity and quantum mechanics. These two theories have profoundly changed the way we think about space, time and the meaning of reality, and both have been verified to extraordinary precision. However, the two theories are also completely incompatible with one another. Three of the four known forces in nature - the electromagnetic, weak and strong interactions - are described by quantum field theories. These theories, which make up the highly successful Standard Model of particle physics, explain fundamental interactions in terms of the exchange of field particles between elementary matter particles. Gravity, on the other hand, does not fit into this framework. Einstein's elegant description of gravity is classical, and gravitational forces result from the curvature of the space-time continuum. But there is something deeply unsettling about this whole picture. Ever since Maxwell unified electricity and magnetism with a single set of equations, finding a general theory that can describe everything that we observe in the physical world has been one of the primary goals in theoretical physics. A unified description of the electromagnetic and weak interactions was achieved in the 1960s, but a true theory of quantum gravity would be a giant step towards this goal. Moreover, a theory of quantum gravity is needed to understand what happens in circumstances when both gravitational and quantum effects are large - such as in the very early universe. (U.K.)
Antimatter gravity with muonium
kaplan, Daniel M.; Fischbach, Ephraim; Kirch, Klaus; Mancini, Derrick C.; Phillips, James D.; Phillips, Thomas J.; Reasenberg, Robert D; Roberts, Thomas J.; Terry, Jeff
2016-01-01
The gravitational acceleration of antimatter, $\\bar{g}$, has never been directly measured and could bear importantly on our understanding of gravity, the possible existence of a fifth force, and the nature and early history of the universe. Three avenues appear feasible for such a measurement: antihydrogen, positronium, and muonium. The muonium measurement requires a novel monoenergetic, low-velocity, horizontal muonium beam directed at an atom interferometer. The precision three-grating inte...
Gravity, Time, and Lagrangians
Huggins, Elisha
2010-01-01
Feynman mentioned to us that he understood a topic in physics if he could explain it to a college freshman, a high school student, or a dinner guest. Here we will discuss two topics that took us a while to get to that level. One is the relationship between gravity and time. The other is the minus sign that appears in the Lagrangian. (Why would one…
Intrinsic Time Quantum Gravity
Yu, Hoi Lai
2016-01-01
Correct identification of the true gauge symmetry of General Relativity being 3d spatial diffeomorphism invariant(3dDI) (not the conventional infinite tensor product group with principle fibre bundle structure), together with intrinsic time extracted from clean decomposition of the canonical structure yields a self-consistent theory of quantum gravity. A new set of fundamental commutation relations is also presented. The basic variables are the eight components of the unimodular part of the s...
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.
Covariant Loop Quantum Gravity
Rovelli, Carlo; Vidotto, Francesca
2014-11-01
Preface; Part I. Foundations: 1. Spacetime as a quantum object; 2. Physics without time; 3. Gravity; 4. Classical discretization; Part II. The 3D Theory: 5. 3D Euclidean theory; 6. Bubbles and cosmological constant; Part III. The Real World: 7. The real world: 4D Lorentzian theory; 8. Classical limit; 9. Matter; Part IV. Physical Applications: 10. Black holes; 11. Cosmology; 12. Scattering; 13. Final remarks; References; Index.
Alesci, Emanuele; Cianfrani, Francesco
2015-01-01
Quantum Reduced Loop Gravity provides a promising framework for a consistent characterization of the early Universe dynamics. Inspired by BKL conjecture, a flat Universe is described as a collection of Bianchi I homogeneous patches. The resulting quantum dynamics is described by the scalar constraint operator, whose matrix elements can be analytically computed. The effective semiclassical dynamics is discussed, and the differences with Loop Quantum Cosmology are emphasized.
Aastrup, Johannes; Grimstrup, Jesper M.
2009-01-01
We present a separable version of Loop Quantum Gravity (LQG) based on an inductive system of cubic lattices. We construct semi-classical states for which the LQG operators -- the flux, the area and the volume operators -- have the right classical limits. Also, we present the Hamilton and diffeomorphism constraints as operator constraints and show that they have the right classical limit. Finally, we speculate whether the continuum limit, which these semi-classical states probe, can be defined...
Ashour, Amani; Faizal, Mir; Ali, Ahmed Farag; Hammad, Fayçal
2016-05-01
In this work, we investigate the thermodynamics of black p-branes (BB) in the context of Gravity's Rainbow. We investigate this using rainbow functions that have been motivated from loop quantum gravity and κ -Minkowski non-commutative spacetime. Then for the sake of comparison, we examine a couple of other rainbow functions that have also appeared in the literature. We show that, for consistency, Gravity's Rainbow imposes a constraint on the minimum mass of the BB, a constraint that we interpret here as implying the existence of a black p-brane remnant. This interpretation is supported by the computation of the black p-brane's heat capacity that shows that the latter vanishes when the Schwarzschild radius takes on a value that is bigger than its extremal limit. We found that the same conclusion is reached for the third version of rainbow functions treated here but not with the second one for which only standard black p-brane thermodynamics is recovered.
Granular Superconductors and Gravity
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.
Levin, J J
1995-01-01
The union of high-energy particle theories and gravitation often gives rise to an evolving strength of gravity. The standard picture of the earliest universe would certainly deserve revision if the Planck mass, which defines the strength of gravity, varied. A notable consequence is a gravity-driven, kinetic inflation. Unlike standard inflation, there is no potential nor cosmological constant. The unique elasticity in the kinetic energy of the Planck mass provides a negative pressure able to drive inflation. As the kinetic energy grows, the spacetime expands more quickly. The phenomenon of kinetic inflation has been uncovered in both string theory and Kaluza-Klein theories. The difficulty in exiting inflation in these cases is reviewed. General forms of the Planck field coupling are shown to avoid the severity of the graceful exit problem found in string and Kaluza-Klein theories. The completion of the model is foreshadowed with a suggestion for a heating mechanism to generate the hot soup of the big bang.
Energy Technology Data Exchange (ETDEWEB)
Agrawal, Aniket [Indian Institute of Technology Delhi, New Delhi (India)
2012-07-01
Recently, Chiao predicted the quantum incompressibility of a falling Rydberg atom. A Hydrogen-like atom was considered in a very high n,l=m=n-1 state to calculate the effects of tidal gravitational forces on these states. The high values of quantum numbers ensure that gravitational effect is measurable on the *stretch* state. We consider a similar atom and derive the energy of a particular level under the influence of Newtonian gravity. A change in the frequency of observed transition is predicted for a freely falling Hydrogen atom. This change is calculated both in Newtonian gravity and in curved space. We see that the change in energy of the electron under gravity also depends on its principal quantum number. Thus there will be a shift in the frequency of the photon emitted by an electron making an ordinary transition from the state n=100, l=99, m=99 to the state n=99, l=98, m=98. Though this shift is quite less to be observed on Earth, it is measurable in satellites in a highly elliptical orbit about the earth, by spectroscopic methods. A similar result was derived by Chiao recently using a different argument. We conclude that the effect described by Chiao will be masked to a very large extent by the effect calculated above. Such perturbations might be important in emission spectra of white dwarfs and neutron stars.
Conditioning and breakdown phenomena in accelerator tubes
International Nuclear Information System (INIS)
Important breakdown mechanisms in accelerator tubes are reviewed, and discharge phenomena in NEC tubes are deduced from the surface appearance of the electrodes and insulators of a used tube. Microphotos of these surfaces are shown
CISM Course on Rolling Contact Phenomena
Kalker, Joost
2000-01-01
Preface.- Rolling Contact Phenomena - Linear Elasticity.- Finite Element Methods for Rolling Contact.- Plastic Deformation in Rolling Contact.- Non-Steady State Rolling Contact and Corrugations.- Modelling of Tyre Force and Moment Generation.- Rolling Noise.- Lubrication
Classifying prion and prion-like phenomena.
Harbi, Djamel; Harrison, Paul M
2014-01-01
The universe of prion and prion-like phenomena has expanded significantly in the past several years. Here, we overview the challenges in classifying this data informatically, given that terms such as "prion-like", "prion-related" or "prion-forming" do not have a stable meaning in the scientific literature. We examine the spectrum of proteins that have been described in the literature as forming prions, and discuss how "prion" can have a range of meaning, with a strict definition being for demonstration of infection with in vitro-derived recombinant prions. We suggest that although prion/prion-like phenomena can largely be apportioned into a small number of broad groups dependent on the type of transmissibility evidence for them, as new phenomena are discovered in the coming years, a detailed ontological approach might be necessary that allows for subtle definition of different "flavors" of prion / prion-like phenomena.
Periglacial phenomena affecting nuclear waste disposal
Directory of Open Access Journals (Sweden)
Niini, H.
1997-12-01
Full Text Available Slow future changes in astronomic phenomena seem to make it likely that Finland nll suffer several cold periods during the next 100,000 years. The paper analyses the characteristics of the periglacial factors that are most likely to influence the long-term safety of high-level radioactive waste disposed of in bedrock. These factors and their influences have been divided into two categories, natural and human. It is concluded that the basically natural phenomena are theoretically better understood than the complicated phenomena caused by man. It is therefore important in future research into periglacial phenomena, as well as of the disposal problem, to emphasize not only the proper applications of the results of natural sciences, but especially the effects and control of mankind's own present and future activities.
Sorption phenomena of PCBs in environment
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The relationship between the properties of PCBs and the behavior of soil and sediment is reviewed. The sorption phenomena of PCBs in the environment are described with different models. The research progress on the sorption mechanisms is also discussed.
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...
Noise Induced Phenomena in Population Dynamics
Valenti, D.; Giuffrida, A; Denaro, G.; Pizzolato, N; Curcio, L; Spagnolo, B.; Mazzola, S.; Basilone, G.; Bonanno, A.
2015-01-01
Noise through its interaction with the nonlinearity of the living systems can give rise to counter-intuitive phenomena. In this paper we shortly review the noise induced effects in different ecosystems. The transient dynamics of these ecosystems are analyzed through generalized Lotka-Volterra equations in the presence of multiplicative noise, which models the interaction between the species and the environment. We find noise induced phenomena such as quasi-deterministic oscillations, stochast...
The resonance phenomena and state of health
Sikura A.Y.
2010-01-01
The question of dependence of the state of health is examined from the resonance phenomena in the liquid environments of organism, roles herein physical loadings. It is rotined that resonance waves can compensate structural violations on a tissue, system levels. The oppressive operating is the same compensated on the organism of man. The physical loading in a complex with other external resonance phenomena causes substantial resonance vibrations in all systems of organism. It is necessary to ...
Gauge/gravity duality. A road towards reality
International Nuclear Information System (INIS)
In this dissertation we use gauge/gravity duality to investigate various phenomena of strongly coupled systems. In particular, we consider applications of the duality to real-world systems such as condensed matter systems and the quark-gluon plasma created by heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Gauge/gravity duality which originates from string theory relates strongly coupled gauge theories to weakly coupled gravity theories. This duality allows for computations of non-perturbative results on the field theory side by perturbative calculations on the gravity side. As we have learned in the recent years, the duality is especially suitable to describe hot and dense plasmas as well as real-time processes related to transport properties or spectral functions. Unfortunately, so far there is no dual gravity description modeling every aspect of a strongly coupled real-world system. However, there are many gravity duals which describe several phenomena. The general idea of this thesis is to study different gravity duals in order to develop a gravity description of hot and dense plasmas. In particular, we focus on physics in thermal equilibrium and close to equilibrium. Motivated by the experimentally observed mesonic resonances in the quark-gluon plasma, we first study quasinormal modes of a gravity dual which contains such resonances. The quasinormal modes on the gravity side are identified with the poles of the Green's function on the field theory side. By studying these quasinormal modes, we observe how quasiparticle resonances develop in a hot and dense plasma. We find interesting trajectories of quasinormal frequencies which may be found experimentally as the temperature and density is varied. In addition, we find an instability in the quasinormal mode spectrum at large chemical potential or magnetic field. At large chemical potential, this instability triggers the condensation of a field which breaks
Gauge/gravity duality. A road towards reality
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
A Simple Theory of Quantum Gravity
Horndeski, Gregory W
2015-01-01
A novel theory of Quantum Gravity is presented in which the real gravitons manifest themselves as holes in space. In general, these holes propagate at the speed of light through an expanding universe with boundary denoted by U, which is comprised of pulsating cells. These holes can form bound and semi-bound states. The geometry of U is non-Euclidean on a small scale, but there are indications that it can become Euclidean on a large scale. The motions of elementary particles through U are governed by probability 4 and 7-vectors, which are related to the momentum vectors in Minkowski space. The connection of this theory to Newtonian gravity is discussed, and an expression for the gravitational redshift of photons is derived which relates the redshift to the probability that a photon absorbs a virtual graviton. The theory also provides a possible explanation of dark matter and dark energy as gravitational phenomena, which do not require the introduction of any new particles. A quantum cosmology is presented in w...
Second DOE natural phenomena hazards mitigation conference
International Nuclear Information System (INIS)
This conference has been organized into ten presentation sessions which include an overview of the DOE Natural Phenomena Guidelines, Seismic Analysis, Seismic Design, Modifying Existing Facilities, DOE Orders, Codes, and Standards (2 sessions), Seismic Hazard (2 sessions), and Probabilistic Risk Assessment (2 sessions). Two poster sessions were also included in the program to provide a different forum for communication of ideas. Over the past fourteen years, Lawrence Livermore National Laboratory, Nuclear Systems Safety Program, has been working with the US Department of Energy, Office of Safety Appraisals and their predecessors in the area of natural phenomena hazards. During this time we have developed seismic, extreme wind/tornado, and flood hazard models for DOE sites in the United States. Guidelines for designing and evaluating DOE facilities for natural phenomena have been developed and are in interim use throughout the DOE community. A series of state-of-the practice manuals have also been developed to aid the designers. All of this material is listed in the Natural Phenomena Hazards Bibliography included in these proceedings. This conference provides a mechanism to disseminate current information on natural phenomena hazards and their mitigation. It provides an opportunity to bring together members of the DOE community to discuss current projects, to share information, and to hear practicing members of the structural engineering community discuss their experiences from past natural phenomena, future trends, and any changes to building codes. Each paper or poster presented is included in these proceedings. We have also included material related to the luncheon and dinner talks
Gravity Resonance Spectroscopy and Einstein-Cartan Gravity
Abele, Hartmut; Ivanov, Andrei; Jenke, Tobias; Pitschmann, Mario; Geltenbort, Peter
2015-01-01
The qBounce experiment offers a new way of looking at gravitation based on quantum interference. An ultracold neutron is reflected in well-defined quantum states in the gravity potential of the Earth by a mirror, which allows to apply the concept of gravity resonance spectroscopy (GRS). This experiment with neutrons gives access to all gravity parameters as the dependences on distance, mass, curvature, energy-momentum as well as on torsion. Here, we concentrate on torsion.
Gravity-Matter Entanglement in Regge Quantum Gravity
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 correc...
Smooth quantum gravity: Exotic smoothness and Quantum gravity
Asselmeyer-Maluga, Torsten
2016-01-01
Over the last two decades, many unexpected relations between exotic smoothness, e.g. exotic $\\mathbb{R}^{4}$, and quantum field theory were found. Some of these relations are rooted in a relation to superstring theory and quantum gravity. Therefore one would expect that exotic smoothness is directly related to the quantization of general relativity. In this article we will support this conjecture and develop a new approach to quantum gravity called \\emph{smooth quantum gravity} by using smoot...
Teleparallel Complex Gravity as Foundation for Noncommutative Gravity
Nishino, Hitoshi; Rajpoot, Subhash
2001-01-01
We present a teleparallel complex gravity as the foundation for the formulation of noncommutative gravity theory. The negative energy ghosts in the conventional formulation with U(1,3) local Lorentz connection no longer exists, since the local Lorentz invariance is broken down to U(1,3) global Lorentz symmetry. As desired, our teleparallel complex gravity theory also passes the key classical test of perihelion advance of Mercury. Based on this result, we present a lagrangian for the noncommut...
New massive gravity and AdS(4) counterterms.
Jatkar, Dileep P; Sinha, Aninda
2011-04-29
We show that the recently proposed Dirac-Born-Infeld extension of new massive gravity emerges naturally as a counterterm in four-dimensional anti-de Sitter space (AdS(4)). The resulting on-shell Euclidean action is independent of the cutoff at zero temperature. We also find that the same choice of counterterm gives the usual area law for the AdS(4) Schwarzschild black hole entropy in a cutoff-independent manner. The parameter values of the resulting counterterm action correspond to a c=0 theory in the context of the duality between AdS(3) gravity and two-dimensional conformal field theory. We rewrite this theory in terms of the gauge field that is used to recast 3D gravity as a Chern-Simons theory. PMID:21635026
Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales
Chum, J.; Lastovicka, J.; Sindelárová, T.; Buresová, D.; Hruska, F.
2008-04-01
Compared to investigations of the influence of gravity and planetary waves on the ionosphere, the effects of infrasound (periods from about 0.01 s to several minutes) variations have not been studied very much in the last 20 years. Here we present some recent results on peculiar transient phenomena occurring at infrasound timescales, as observed by HF Doppler sounding in the Czech Republic. After a brief description of the measuring equipment for continuous HF Doppler sounding of the ionosphere, we deal with the observations of short-time transient changes that are observed in the Doppler spectrograms in time intervals of a minute or less, and therefore cannot be observed by ionosondes. First, we present examples of S-shaped traces and examine the diurnal and seasonal variation of their occurrence. We show that S-shape phenomena appear to be concentrated near sunset and sunrise. We also discuss the possible source of these disturbances and their relationship to gravity and infrasound waves. Then we show rare patterns with Doppler shifts corresponding to quasi-linear shape (QLS) phenomena in the time-frequency space. Their slope may be positive or negative. We present some of their properties and discuss the possible origin of such a phenomenon. Several potential sources of QLSs were excluded, such as aircrafts, satellites, bolides, meteors, meteorites, thunderstorms or geomagnetic storms. We speculate that QLSs may correspond to the radio waves in the Z-mode reflected at the upper hybrid resonance frequency.
Scaling phenomena in gravity and Yang-Mills theories, or black hole formation and its unitarization
International Nuclear Information System (INIS)
This talk was based on an earlier paper of the author and others (arXiv:0804.1464) and on a general discussion of the problems of black hole physics in the context of string theory. Adequate reference can be found in this paper. Here we only present a short summary of the seminar. (Abstract Copyright [2009], Wiley Periodicals, Inc.)
Isaac Newton's scientific method turning data into evidence about gravity and cosmology
Harper, William L.
2014-01-01
Isaac Newton's Scientific Method examines Newton's argument for universal gravity and his application of it to resolve the problem of deciding between geocentric and heliocentric world systems by measuring masses of the sun and planets. William L. Harper suggests that Newton's inferences from phenomena realize an ideal of empirical success that is richer than prediction. Any theory that can achieve this rich sort of empirical success must not only be able to predict the phenomena it purports to explain, but also have those phenomena accurately measure the parameters which explain them. Harper explores the ways in which Newton's method aims to turn theoretical questions into ones which can be answered empirically by measurement from phenomena, and to establish that propositions inferred from phenomena are provisionally accepted as guides to further research. This methodology, guided by its rich ideal of empirical success, supports a conception of scientific progress that does not require construing it as progr...
Geometric scalar theory of gravity
Energy Technology Data Exchange (ETDEWEB)
Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D. [Instituto de Cosmologia Relatividade Astrofisica ICRA - CBPF Rua Dr. Xavier Sigaud 150 - 22290-180 Rio de Janeiro - Brazil (Brazil); Moschella, U., E-mail: novello@cbpf.br, E-mail: eduhsb@cbpf.br, E-mail: Ugo.Moschella@uninsubria.it, E-mail: egoulart@cbpf.br, E-mail: jsalim@cbpf.br, E-mail: toniato@cbpf.br [Università degli Studi dell' Insubria - Dipartamento di Fisica e Matematica Via Valleggio 11 - 22100 Como - Italy (Italy)
2013-06-01
We present a geometric scalar theory of gravity. Our proposal will be described using the ''background field method'' introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor — which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models — does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ''geometric'' pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.
Holographic bound in covariant loop quantum gravity
Tamaki, Takashi
2016-07-01
We investigate puncture statistics based on the covariant area spectrum in loop quantum gravity. First, we consider Maxwell-Boltzmann statistics with a Gibbs factor for punctures. We establish formulas which relate physical quantities such as horizon area to the parameter characterizing holographic degrees of freedom. We also perform numerical calculations and obtain consistency with these formulas. These results tell us that the holographic bound is satisfied in the large area limit and the correction term of the entropy-area law can be proportional to the logarithm of the horizon area. Second, we also consider Bose-Einstein statistics and show that the above formulas are also useful in this case. By applying the formulas, we can understand intrinsic features of Bose-Einstein condensate which corresponds to the case when the horizon area almost consists of punctures in the ground state. When this phenomena occurs, the area is approximately constant against the parameter characterizing the temperature. When this phenomena is broken, the area shows rapid increase which suggests the phase transition from quantum to classical area.
Macroscopic quantum phenomena from the large N perspective
Energy Technology Data Exchange (ETDEWEB)
Chou, C H [department of Physics, National Cheng Kung University, Tainan, Taiwan 701 (China) and National Center for Theoretical Sciences (South), Tainan, Taiwan 701 (China); Hu, B L; Subasi, Y, E-mail: hubeilok@gmail.com [Joint Quantum Institute and Maryland Center for Fundamental Physics, University of Maryland, College Park, Maryland 20742 (United States)
2011-07-08
Macroscopic quantum phenomena (MQP) is a relatively new research venue, with exciting ongoing experiments and bright prospects, yet with surprisingly little theoretical activity. What makes MQP intellectually stimulating is because it is counterpoised against the traditional view that macroscopic means classical. This simplistic and hitherto rarely challenged view need be scrutinized anew, perhaps with much of the conventional wisdoms repealed. In this series of papers we report on a systematic investigation into some key foundational issues of MQP, with the hope of constructing a viable theoretical framework for this new endeavour. The three major themes discussed in these three essays are the large N expansion, the correlation hierarchy and quantum entanglement for systems of 'large' sizes, with many components or degrees of freedom. In this paper we use different theories in a variety of contexts to examine the conditions or criteria whereby a macroscopic quantum system may take on classical attributes, and, more interestingly, that it keeps some of its quantum features. The theories we consider here are, the O(N) quantum mechanical model, semiclassical stochastic gravity and gauge / string theories; the contexts include that of a 'quantum roll' in inflationary cosmology, entropy generation in quantum Vlasov equation for plasmas, the leading order and next-to-leading order large N behaviour, and hydrodynamic / thermodynamic limits. The criteria for classicality in our consideration include the use of uncertainty relations, the correlation between classical canonical variables, randomization of quantum phase, environment-induced decoherence, decoherent history of hydrodynamic variables, etc. All this exercise is to ask only one simple question: Is it really so surprising that quantum features can appear in macroscopic objects? By examining different representative systems where detailed theoretical analysis has been carried out, we find that
Cascading Gravity is Ghost Free
de Rham, Claudia; Tolley, Andrew J
2010-01-01
We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity.
Cosmological tests of modified gravity.
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. PMID:27007681
Astrophysical aspects of Weyl gravity
Kazanas, Demosthenes
1991-01-01
This paper discusses the astrophysical implications and applications of Weyl gravity, which is the theory resulting from the unique action allowed under the principle of local scale invariance in Einstein gravity. These applications include galactic dynamics, the mass-radius relation, the cosmological constant, and the 'Modified Newtonian Dynamics' proposed by Milgrom (1983). The relation of Weyl gravity to other scale-invariant theories is addressed.
Schwarzschild Solution from WTDiff Gravity
Oda, Ichiro
2016-01-01
We study classical solutions in the Weyl-transverse (WTDiff) gravity. The WTDiff gravity is invariant under both the local Weyl (conformal) transformation and the volume preserving diffeormorphisms (transverse diffeomorphisms) and is known to be equivalent to general relativity at least at the classical level. In particular, we find that in a general space-time dimension, the Schwarzschild metric is a classical solution in the WTDiff gravity when it is expressed in the Cartesian coordinate system.