Radial quantization of the 3d CFT and the higher spin/vector model duality

NASA Astrophysics Data System (ADS)

Hu, Shan; Li, Tianjun

2014-10-01

We study the radial quantization of the 3dO(N) vector model. We calculate the higher spin charges whose commutation relations give the higher spin algebra. The Fock states of higher spin gravity in AdS4 are realized as the states in the 3d CFT. The dynamical information is encoded in their inner products. This serves as the simplest explicit demonstration of the CFT definition for the quantum gravity.

The Spin-Foam Approach to Quantum Gravity.

PubMed

Perez, Alejandro

2013-01-01

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

Free-Spinning-Tunnel Investigation of a 1/17 Scale Model of the Cessna T-37A Airplane

NASA Technical Reports Server (NTRS)

Bowman, James S., Jr.; Healy, Frederick M.

1958-01-01

Results of an investigation of a dynamic model in the Langley 20-foot free-spinning tunnel are presented. Erect spin and recovery characteristics were determined for a range of mass distributions and center-of-gravity positions. The effects of lateral displacement of the center of gravity, engine rotation, nose strakes, and increased rudder area were investigated.

Mercury's gravity field, tidal Love number k2, and spin axis orientation revealed with MESSENGER radio tracking data

NASA Astrophysics Data System (ADS)

Verma, A. K.; Margot, J. L.

2015-12-01

We are conducting an independent analysis of two-way Doppler and two-way range radio tracking data from the MESSENGER spacecraft in orbit around Mercury from 2011 to 2015. Our goals are to estimate Mercury's gravity field and to obtain independent estimates of the tidal Love number k2 and spin axis orientation. Our gravity field solution reproduces existing values with high fidelity, and prospects for recovery of the other quantities are excellent. The tidal Love number k2 provides powerful constraints on interior models of Mercury, including the mechanical properties of the mantle and the possibility of a solid FeS layer at the top of the core. Current gravity analyses cannot rule out a wide range of values (k2=43-0.50) and a variety of plausible interior models. We are seeking an independent estimate of tidal Love number k2 with improved errors to further constrain these models. Existing gravity-based solutions for Mercury's spin axis orientation differ from those of Earth-based radar and topography-based solutions. This difference may indicate an error in one of the determinations, or a real difference between the orientations about which the gravity field and the crust rotate, which can exist in a variety of plausible configuration. Securing an independent estimate of the spin axis orientation is vital because this quantity has a profound impact on the determination of the moment of inertia and interior models. We have derived a spherical harmonic solution of the gravity field to degree and order 40 as well as estimates of the tidal Love number k2 and spin axis orientation.

Mercury’s gravity field, tidal Love number k2, and spin axis orientation revealed with MESSENGER radio tracking data

NASA Astrophysics Data System (ADS)

Verma, Ashok Kumar; Margot, Jean-Luc

2015-11-01

We are conducting an independent analysis of two-way Doppler and two-way range radio tracking data from the MESSENGER spacecraft in orbit around Mercury from 2011 to 2015. Our goals are to estimate Mercury’s gravity field and to obtain independent estimates of the tidal Love number k2 and spin axis orientation. Our gravity field solution reproduces existing values with high fidelity, and prospects for recovery of the other quantities are excellent.The tidal Love number k2 provides powerful constraints on interior models of Mercury, including the mechanical properties of the mantle and the possibility of a solid FeS layer at the top of the core. Current gravity analyses cannot rule out a wide range of values (k2=43-0.50) and a variety of plausible interior models. We are seeking an independent estimate of tidal Love number k2 with improved errors to further constrain these models.Existing gravity-based solutions for Mercury's spin axis orientation differ from those of Earth-based radar and topography-based solutions. This difference may indicate an error in one of the determinations, or a real difference between the orientations about which the gravity field and the crust rotate, which can exist in a variety of plausible configuration. Securing an independent estimate of the spin axis orientation is vital because this quantity has a profound impact on the determination of the moment of inertia and interior models.We have derived a spherical harmonic solution of the gravity field to degree and order 40 as well as estimates of the tidal Love number k2 and spin axis orientation

Non-AdS holography in 3-dimensional higher spin gravity — General recipe and example

NASA Astrophysics Data System (ADS)

Afshar, H.; Gary, M.; Grumiller, D.; Rashkov, R.; Riegler, M.

2012-11-01

We present the general algorithm to establish the classical and quantum asymptotic symmetry algebra for non-AdS higher spin gravity and implement it for the specific example of spin-3 gravity in the non-principal embedding with Lobachevsky ( {{{{H}}^2}× {R}} ) boundary conditions. The asymptotic symmetry algebra for this example consists of a quantum W_3^{(2) } (Polyakov-Bershadsky) and an affine û(1) algebra. We show that unitary representations of the quantum W_3^{(2) } algebra exist only for two values of its central charge, the trivial c = 0 "theory" and the simple c = 1 theory.

Freedom and the State: Kant on Revolution and International Interface

DTIC Science & Technology

1999-11-11

physical and psychological nature and many of them make us selfish and disagreeable beings. In fact, Kant contends that human beings are naturally...circumstances include a "defective education, bad company,... the viciousness of a natural disposition insensitive to shame,... levity and thoughtlessness...possibility of ethical action. Unless we are capable of choosing duty over inclinations, we cannot be held responsible for our actions (GMM 49). This

The dynamics and optimal control of spinning spacecraft and movable telescoping appendages, part B: Effect of gravity-gradient torques on the dynamics of a spinning spacecraft with telescoping appendages

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Rajan, M.

1977-01-01

The effects of gravity gradient torques during boom deployment maneuvers of a spinning spacecraft are examined. Configurations where the booms extended only along the hub principal axes and where one or two booms are offset from the principal axes were considered. For the special case of symmetric deployment (principal axes booms) the stability boundaries are determined, and a stability chart is used to study the system behavior. Possible cases of instability during this type of maneuver are identified. In the second configuration an expression for gravity torque about the hub center of mass was developed. The nonlinear equations of motion are solved numerically, and the substantial influence of the gravity torque during asymmetric deployment maneuvers is indicated.

Conformal higher spin theory and twistor space actions

NASA Astrophysics Data System (ADS)

Hähnel, Philipp; McLoughlin, Tristan

2017-12-01

We consider the twistor description of conformal higher spin theories and give twistor space actions for the self-dual sector of theories with spin greater than two that produce the correct flat space-time spectrum. We identify a ghost-free subsector, analogous to the embedding of Einstein gravity with cosmological constant in Weyl gravity, which generates the unique spin-s three-point anti-MHV amplitude consistent with Poincaré invariance and helicity constraints. By including interactions between the infinite tower of higher-spin fields we give a geometric interpretation to the twistor equations of motion as the integrability condition for a holomorphic structure on an infinite jet bundle. Finally, we conjecture anti-self-dual interaction terms which give an implicit definition of a twistor action for the full conformal higher spin theory.

Transition probability spaces in loop quantum gravity

NASA Astrophysics Data System (ADS)

Guo, Xiao-Kan

2018-03-01

We study the (generalized) transition probability spaces, in the sense of Mielnik and Cantoni, for spacetime quantum states in loop quantum gravity. First, we show that loop quantum gravity admits the structures of transition probability spaces. This is exemplified by first checking such structures in covariant quantum mechanics and then identifying the transition probability spaces in spin foam models via a simplified version of general boundary formulation. The transition probability space thus defined gives a simple way to reconstruct the discrete analog of the Hilbert space of the canonical theory and the relevant quantum logical structures. Second, we show that the transition probability space and in particular the spin foam model are 2-categories. Then we discuss how to realize in spin foam models two proposals by Crane about the mathematical structures of quantum gravity, namely, the quantum topos and causal sites. We conclude that transition probability spaces provide us with an alternative framework to understand various foundational questions of loop quantum gravity.

Time-dependent dynamical behavior of surface tension on rotating fluids under microgravity environment

NASA Technical Reports Server (NTRS)

Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.

1988-01-01

Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) step functions of spin-up and spin-down in a low gravity environment, and (3) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds.

Interacting spin-2 fields in the Stückelberg picture

NASA Astrophysics Data System (ADS)

Noller, Johannes; Scargill, James H. C.; Ferreira, Pedro G.

2014-02-01

We revisit and extend the `Effective field theory for massive gravitons' constructed by Arkani-Hamed, Georgi and Schwartz in the light of recent progress in constructing ghost-free theories with multiple interacting spin-2 fields. We show that there exist several dual ways of restoring gauge invariance in such multi-gravity theories, find a generalised Fierz-Pauli tuning condition relevant in this context and highlight subtleties in demixing tensor and scalar modes. The generic multi-gravity feature of scalar mixing and its consequences for higher order interactions are discussed. In particular we show how the decoupling limit is qualitatively changed in theories of interacting spin-2 fields. We relate this to dRGT (de Rham, Gabadadze, Tolley) massive gravity, Hassan-Rosen bigravity and the multi-gravity constructions by Hinterbichler and Rosen. As an additional application we show that EBI (Eddington-Born-Infeld) bigravity and higher order generalisations thereof possess ghost-like instabilities.

Critical gravity in four dimensions.

PubMed

Lü, H; Pope, C N

2011-05-06

We study four-dimensional gravity theories that are rendered renormalizable by the inclusion of curvature-squared terms to the usual Einstein action with a cosmological constant. By choosing the parameters appropriately, the massive scalar mode can be eliminated and the massive spin-2 mode can become massless. This "critical" theory may be viewed as a four-dimensional analogue of chiral topologically massive gravity, or of critical "new massive gravity" with a cosmological constant, in three dimensions. We find that the on-shell energy for the remaining massless gravitons vanishes. There are also logarithmic spin-2 modes, which have positive energy. The mass and entropy of standard Schwarzschild-type black holes vanish. The critical theory might provide a consistent toy model for quantum gravity in four dimensions.

On Resolutions of Cosmological Singularities in Higher-Spin Gravity

NASA Astrophysics Data System (ADS)

Burrington, Benjamin; Pando Zayas, Leopoldo; Rombes, Nicholas

2014-03-01

Gravity in three dimensions is simpler than in four, due to the lack of gravitational waves, and can be recast as a Chern-Simons theory. In this context, it is straightforward to generalize Einstein's gravity, with or without cosmological constant, by changing the gauge group. Using this, we study the resolution of certain cosmological singularities, and extend the singularity resolution scheme proposed by Krishnan and Roy. We discuss the resolution of a big-bang singularity in the case of gravity coupled to a spin-4 field realized as Chern-Simons theory with gauge group SL (4 , C) . We show the existence of gauge transformations that do not change the holonomy of the Chern-Simons gauge potential and lead to metrics without the initial singularity. We argue that such transformations always exist in the context of gravity coupled to a spin-N field when described by Chern-Simons with gauge group SL (N , C) . This work was supported by the DOE under grant DE-FG02-95ER40899, a research grant from Troy University, and the Honors Summer Fellowship at the University of Michigan.

Spin-Orbit Misalignment of Two-Planet-System KOI-89 Via Gravity Darkening

NASA Astrophysics Data System (ADS)

Ahlers, Jonathon; Barnes, Jason W.; Barnes, Rory

2015-12-01

We investigate the potential causes of spin-orbit misalignment in multiplanetary systems via two-planet-system KOI-89. We focus on this system because it can experimentally constrain the outstanding hypotheses that have been proposed to cause misalignments. Using gravity darkening, we constrain both the spin-orbit angles and the angle between the planes of the orbits. Our best-fit model shows that the 85-day-orbit and 208-day-orbit planets are misaligned from the host star's rotation axis by 72° ± 3° and 73° (+11 -5°), respectively. From these results, we limit KOI-89's potential causes of spin-orbit misalignment based on three criteria: agreement with KOI-89's fundamental parameters, the capability to cause extreme misalignment, and conformance with mutually aligned planets. Our results disfavor planet-embryo collisions, chaotic evolution of stellar spin, magnetic torquing, coplanar high-eccentricity migration, and inclination resonance, limiting possible causes to star-disk binary interactions, disk warping via planet-disk interactions, Kozai resonance, planet-planet scattering, or internal gravity waves in the convective interior of the star.

Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space

NASA Astrophysics Data System (ADS)

Baryshev, Yurij

2006-03-01

Thirring-Feynman's tensor field approach to gravitation opens new understanding on the physics of gravitational interaction and stimulates novel experiments on the nature of gravity. According to Field Gravity, the universal gravity force is caused by exchange of gravitons - the quanta of gravity field. Energy of this field is well-defined and excludes the singularity. All classical relativistic effects are the same as in General Relativity. The intrinsic scalar (spin 0) part of gravity field corresponds to ``antigravity'' and only together with the pure tensor (spin 2) part gives the usual Newtonian force. Laboratory and astrophysical experiments which may test the predictions of FG, will be performed in near future. In particular, observations at gravity observatories with bar and interferometric detectors, like Explorer, Nautilus, LIGO and VIRGO, will check the predicted scalar gravitational waves from supernova explosions. New types of cosmological models in Minkowski space are possible too.

Spin Entanglement Witness for Quantum Gravity.

PubMed

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

2017-12-15

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

Spin Entanglement Witness for Quantum Gravity

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Bounding the space of holographic CFTs with chaos

DOE PAGES

Perlmutter, Eric

2016-10-13

In this study, thermal states of quantum systems with many degrees of freedom are subject to a bound on the rate of onset of chaos, including a bound on the Lyapunov exponent, λ L ≤ 2π/β. We harness this bound to constrain the space of putative holographic CFTs and their would-be dual theories of AdS gravity. First, by studying out-of-time-order four-point functions, we discuss how λ L = 2π/β in ordinary two-dimensional holographic CFTs is related to properties of the OPE at strong coupling. We then rule out the existence of unitary, sparse two-dimensional CFTs with large central charge andmore » a set of higher spin currents of bounded spin; this implies the inconsistency of weakly coupled AdS 3 higher spin gravities without infinite towers of gauge fields, such as the SL(N) theories. This fits naturally with the structure of higher-dimensional gravity, where finite towers of higher spin fields lead to acausality. On the other hand, unitary CFTs with classical W ∞[λ] symmetry, dual to 3D Vasiliev or hs[λ] higher spin gravities, do not violate the chaos bound, instead exhibiting no chaos: λ L = 0. Independently, we show that such theories violate unitarity for |λ| > 2. These results encourage a tensionless string theory interpretation of the 3D Vasiliev theory.« less

Interacting spin-2 fields in the Stückelberg picture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noller, Johannes; Ferreira, Pedro G.; Scargill, James H.C., E-mail: noller@physics.ox.ac.uk, E-mail: james.scargill@physics.ox.ac.uk, E-mail: p.ferreira1@physics.ox.ac.uk

2014-02-01

We revisit and extend the 'Effective field theory for massive gravitons' constructed by Arkani-Hamed, Georgi and Schwartz in the light of recent progress in constructing ghost-free theories with multiple interacting spin-2 fields. We show that there exist several dual ways of restoring gauge invariance in such multi-gravity theories, find a generalised Fierz-Pauli tuning condition relevant in this context and highlight subtleties in demixing tensor and scalar modes. The generic multi-gravity feature of scalar mixing and its consequences for higher order interactions are discussed. In particular we show how the decoupling limit is qualitatively changed in theories of interacting spin-2 fields.more » We relate this to dRGT (de Rham, Gabadadze, Tolley) massive gravity, Hassan-Rosen bigravity and the multi-gravity constructions by Hinterbichler and Rosen. As an additional application we show that EBI (Eddington-Born-Infeld) bigravity and higher order generalisations thereof possess ghost-like instabilities.« less

Three-dimensional fractional-spin gravity

NASA Astrophysics Data System (ADS)

Boulanger, Nicolas; Sundell, Per; Valenzuela, Mauricio

2014-02-01

Using Wigner-deformed Heisenberg oscillators, we construct 3D Chern-Simons models consisting of fractional-spin fields coupled to higher-spin gravity and internal nonabelian gauge fields. The gauge algebras consist of Lorentz-tensorial Blencowe-Vasiliev higher-spin algebras and compact internal algebras intertwined by infinite-dimensional generators in lowest-weight representations of the Lorentz algebra with fractional spin. In integer or half-integer non-unitary cases, there exist truncations to gl(ℓ , ℓ ± 1) or gl(ℓ|ℓ ± 1) models. In all non-unitary cases, the internal gauge fields can be set to zero. At the semi-classical level, the fractional-spin fields are either Grassmann even or odd. The action requires the enveloping-algebra representation of the deformed oscillators, while their Fock-space representation suffices on-shell. The project was funded in part by F.R.S.-FNRS " Ulysse" Incentive Grant for Mobility in Scientific Research.

A string theory which isn't about strings

NASA Astrophysics Data System (ADS)

Lee, Kanghoon; Rey, Soo-Jong; Rosabal, J. A.

2017-11-01

Quantization of closed string proceeds with a suitable choice of worldsheet vacuum. A priori, the vacuum may be chosen independently for left-moving and right-moving sectors. We construct ab initio quantized bosonic string theory with left-right asymmetric worldsheet vacuum and explore its consequences and implications. We critically examine the validity of new vacuum and carry out first-quantization using standard operator formalism. Remarkably, the string spectrum consists only of a finite number of degrees of freedom: string gravity (massless spin-two, Kalb-Ramond and dilaton fields) and two massive spin-two Fierz-Pauli fields. The massive spin-two fields have negative norm, opposite mass-squared, and provides a Lee-Wick type extension of string gravity. We compute two physical observables: tree-level scattering amplitudes and one-loop cosmological constant. Scattering amplitude of four dilatons is shown to be a rational function of kinematic invariants, and in D = 26 factorizes into contributions of massless spin-two and a pair of massive spin-two fields. The string one loop partition function is shown to perfectly agree with one loop Feynman diagram of string gravity and two massive spin-two fields. In particular, it does not exhibit modular invariance. We critically compare our construction with recent studies and contrast differences.

(2 + 1)-dimensional interacting model of two massless spin-2 fields as a bi-gravity model

NASA Astrophysics Data System (ADS)

Hoseinzadeh, S.; Rezaei-Aghdam, A.

2018-06-01

We propose a new group-theoretical (Chern-Simons) formulation for the bi-metric theory of gravity in (2 + 1)-dimensional spacetime which describe two interacting massless spin-2 fields. Our model has been formulated in terms of two dreibeins rather than two metrics. We obtain our Chern-Simons gravity model by gauging mixed AdS-AdS Lie algebra and show that it has a two dimensional conformal field theory (CFT) at the boundary of the anti de Sitter (AdS) solution. We show that the central charge of the dual CFT is proportional to the mass of the AdS solution. We also study cosmological implications of our massless bi-gravity model.

Duality and integrability: Electromagnetism, linearized gravity, and massless higher spin gauge fields as bi-Hamiltonian systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnich, Glenn; Troessaert, Cedric

2009-04-15

In the reduced phase space of electromagnetism, the generator of duality rotations in the usual Poisson bracket is shown to generate Maxwell's equations in a second, much simpler Poisson bracket. This gives rise to a hierarchy of bi-Hamiltonian evolution equations in the standard way. The result can be extended to linearized Yang-Mills theory, linearized gravity, and massless higher spin gauge fields.

Spinning particles, axion radiation, and the classical double copy

NASA Astrophysics Data System (ADS)

Goldberger, Walter D.; Li, Jingping; Prabhu, Siddharth G.

2018-05-01

We extend the perturbative double copy between radiating classical sources in gauge theory and gravity to the case of spinning particles. We construct, to linear order in spins, perturbative radiating solutions to the classical Yang-Mills equations sourced by a set of interacting color charges with chromomagnetic dipole spin couplings. Using a color-to-kinematics replacement rule proposed earlier by one of the authors, these solutions map onto radiation in a theory of interacting particles coupled to massless fields that include the graviton, a scalar (dilaton) ϕ and the Kalb-Ramond axion field Bμ ν. Consistency of the double copy imposes constraints on the parameters of the theory on both the gauge and gravity sides of the correspondence. In particular, the color charges carry a chromomagnetic interaction which, in d =4 , corresponds to a gyromagnetic ratio equal to Dirac's value g =2 . The color-to-kinematics map implies that on the gravity side, the bulk theory of the fields (ϕ ,gμ ν,Bμ ν) has interactions which match those of d -dimensional "string gravity," as is the case both in the BCJ double copy of pure gauge theory scattering amplitudes and the KLT relations between the tree-level S -matrix elements of open and closed string theory.

Spin-foam models and the physical scalar product

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alesci, Emanuele; Centre de Physique Theorique de Luminy, Universite de la Mediterranee, F-13288 Marseille; Noui, Karim

2008-11-15

This paper aims at clarifying the link between loop quantum gravity and spin-foam models in four dimensions. Starting from the canonical framework, we construct an operator P acting on the space of cylindrical functions Cyl({gamma}), where {gamma} is the four-simplex graph, such that its matrix elements are, up to some normalization factors, the vertex amplitude of spin-foam models. The spin-foam models we are considering are the topological model, the Barrett-Crane model, and the Engle-Pereira-Rovelli model. If one of these spin-foam models provides a covariant quantization of gravity, then the associated operator P should be the so-called ''projector'' into physical statesmore » and its matrix elements should give the physical scalar product. We discuss the possibility to extend the action of P to any cylindrical functions on the space manifold.« less

Covariant formulation of scalar-torsion gravity

NASA Astrophysics Data System (ADS)

Hohmann, Manuel; Järv, Laur; Ualikhanova, Ulbossyn

2018-05-01

We consider a generalized teleparallel theory of gravitation, where the action contains an arbitrary function of the torsion scalar and a scalar field, f (T ,ϕ ) , thus encompassing the cases of f (T ) gravity and a nonminimally coupled scalar field as subclasses. The action is manifestly Lorentz invariant when besides the tetrad one allows for a flat but nontrivial spin connection. We derive the field equations and demonstrate how the antisymmetric part of the tetrad equations is automatically satisfied when the spin connection equation holds. The spin connection equation is a vital part of the covariant formulation, since it determines the spin connection associated with a given tetrad. We discuss how the spin connection equation can be solved in general and provide the cosmological and spherically symmetric examples. Finally, we generalize the theory to an arbitrary number of scalar fields.

Manifestations of the rotation and gravity of the Earth in high-energy physics experiments

NASA Astrophysics Data System (ADS)

Obukhov, Yuri N.; Silenko, Alexander J.; Teryaev, Oleg V.

2016-08-01

The inertial (due to rotation) and gravitational fields of the Earth affect the motion of an elementary particle and its spin dynamics. This influence is not negligible and should be taken into account in high-energy physics experiments. Earth's influence is manifest in perturbations in the particle motion, in an additional precession of the spin, and in a change of the constitutive tensor of the Maxwell electrodynamics. Bigger corrections are oscillatory, and their contributions average to zero. Other corrections due to the inhomogeneity of the inertial field are not oscillatory but they are very small and may be important only for the storage ring electric dipole moment experiments. Earth's gravity causes the Newton-like force, the reaction force provided by a focusing system, and additional torques acting on the spin. However, there are no observable indications of the electromagnetic effects due to Earth's gravity.

Asymptotic symmetries of colored gravity in three dimensions

NASA Astrophysics Data System (ADS)

Joung, Euihun; Kim, Jaewon; Kim, Jihun; Rey, Soo-Jong

2018-03-01

Three-dimensional colored gravity refers to nonabelian isospin extension of Einstein gravity. We investigate the asymptotic symmetry algebra of the SU( N)-colored gravity in (2+1)-dimensional anti-de Sitter spacetime. Formulated by the Chern-Simons theory with SU( N, N) × SU( N, N) gauge group, the theory contains graviton, SU( N) Chern-Simons gauge fields and massless spin-two multiplets in the SU( N) adjoint representation, thus extending diffeomorphism to colored, nonabelian counterpart. We identify the asymptotic symmetry as Poisson algebra of generators associated with the residual global symmetries of the nonabelian diffeomorphism set by appropriately chosen boundary conditions. The resulting asymptotic symmetry algebra is a nonlinear extension of \\widehat{su(N)} Kac-Moody algebra, supplemented by additional generators corresponding to the massless spin-two adjoint matter fields.

Fine-grained state counting for black holes in loop quantum gravity.

PubMed

Ghosh, A; Mitra, P

2009-04-10

A state of a black hole in loop quantum gravity is given by a distribution of spins on punctures on the horizon. The distribution is of the Boltzmann type, with the area playing the role of the energy. In investigations where the total area was kept approximately constant, there was a kind of thermal equilibrium between the spins which have the same analogue temperature and the entropy was proportional to the area. If the area is precisely fixed, however, multiple constraints appear, different spins have different analogue temperatures and the entropy is not strictly linear in the area, but is bounded by a linear rise.

Coupled intertwiner dynamics: A toy model for coupling matter to spin foam models

NASA Astrophysics Data System (ADS)

Steinhaus, Sebastian

2015-09-01

The universal coupling of matter and gravity is one of the most important features of general relativity. In quantum gravity, in particular spin foams, matter couplings have been defined in the past, yet the mutual dynamics, in particular if matter and gravity are strongly coupled, are hardly explored, which is related to the definition of both matter and gravitational degrees of freedom on the discretization. However, extracting these mutual dynamics is crucial in testing the viability of the spin foam approach and also establishing connections to other discrete approaches such as lattice gauge theories. Therefore, we introduce a simple two-dimensional toy model for Yang-Mills coupled to spin foams, namely an Ising model coupled to so-called intertwiner models defined for SU (2 )k. The two systems are coupled by choosing the Ising coupling constant to depend on spin labels of the background, as these are interpreted as the edge lengths of the discretization. We coarse grain this toy model via tensor network renormalization and uncover an interesting dynamics: the Ising phase transition temperature turns out to be sensitive to the background configurations and conversely, the Ising model can induce phase transitions in the background. Moreover, we observe a strong coupling of both systems if close to both phase transitions.

The coupling to matter in massive, bi- and multi-gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noller, Johannes; Melville, Scott, E-mail: noller@physics.ox.ac.uk, E-mail: scott.melville@queens.ox.ac.uk

2015-01-01

In this paper we construct a family of ways in which matter can couple to one or more 'metrics'/spin-2 fields in the vielbein formulation. We do so subject to requiring the weak equivalence principle and the absence of ghosts from pure spin-2 interactions generated by the matter action. Results are presented for Massive, Bi- and Multi-Gravity theories and we give explicit expressions for the effective matter metric in all of these cases.

Massive gravity in three dimensions.

PubMed

Bergshoeff, Eric A; Hohm, Olaf; Townsend, Paul K

2009-05-22

A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general model, which also includes "topologically-massive" gravity as a special case, propagates the two spin-2 helicity states with different masses. We discuss the extension to massive N-extended supergravity, and we present a "cosmological" extension that admits an anti-de Sitter vacuum.

Combined influence of inertia, gravity, and surface tension on the linear stability of Newtonian fiber spinning

NASA Astrophysics Data System (ADS)

Bechert, M.; Scheid, B.

2017-11-01

The draw resonance effect appears in fiber spinning processes if the ratio of take-up to inlet velocity, the so-called draw ratio, exceeds a critical value and manifests itself in steady oscillations of flow velocity and fiber diameter. We study the effect of surface tension on the draw resonance behavior of Newtonian fiber spinning in the presence of inertia and gravity. Utilizing an alternative scaling makes it possible to visualize the results in stability maps of highly practical relevance. The interplay of the destabilizing effect of surface tension and the stabilizing effects of inertia and gravity lead to nonmonotonic stability behavior and local stability maxima with respect to the dimensionless fluidity and the dimensionless inlet velocity. A region of unconditional instability caused by the influence of surface tension is found in addition to the region of unconditional stability caused by inertia, which was described in previous works [M. Bechert, D. W. Schubert, and B. Scheid, Eur. J. Mech B 52, 68 (2015), 10.1016/j.euromechflu.2015.02.005; Phys. Fluids 28, 024109 (2016), 10.1063/1.4941762]. Due to its importance for a particular group of fiber spinning applications, a viscous-gravity-surface-tension regime, i.e., negligible effect of inertia, is analyzed separately. The mechanism underlying the destabilizing effect of surface tension is discussed and established stability criteria are tested for validity in the presence of surface tension.

Cubic Interactions of Massless Bosonic Fields in Three Dimensions

NASA Astrophysics Data System (ADS)

Mkrtchyan, Karapet

2018-06-01

In this Letter, we take the first step towards construction of nontrivial Lagrangian theories of higher-spin gravity in a metriclike formulation in three dimensions. The crucial feature of a metriclike formulation is that it is known how to incorporate matter interactions into the description. We derive a complete classification of cubic interactions for arbitrary triples s1 , s2 , s3 of massless fields, which are the building blocks of any interacting theory with massless higher spins. We find that there is, at most, one vertex for any given triple of spins in 3D (with one exception, s1=s2=s3=1 , which allows for two vertices). Remarkably, there are no vertices for spin values that do not respect strict triangle inequalities and contain at least two spins greater than one. This translates into selection rules for three-point functions of higher-spin conserved currents in two dimensional conformal field theory. Furthermore, universal coupling to gravity for any spin is derived. Last, we argue that this classification persists in arbitrary Einstein backgrounds.

Supplementary Investigation to Determine the Effects of Center-of-Gravity Position on the Spin, Longitudinal-Trim, and Tumbling Characteristics of a 1/20-Scale Model of the Consolidated Vultee 7002 Airplane (Flying Mock-up of XF-92)

NASA Technical Reports Server (NTRS)

Klinar, Walter J.; Jones, Ira P., Jr.

1948-01-01

A supplementary wind-tunnel investigation has been conducted to determine the effect of rearward positions of the center of gravity on the spin, longitudinal-trim, and tumbling characteristics of the 1/20-scale model of the Consolidated Vultee 7002 airplane equipped with the single vertical tail. A few tests were also made with dual vertical tails added to the model. The model was ballasted to represent, the airplane in its approximate design gross weight for two center-of-gravity positions, 3O and 35 percent of the mean aerodynamic chord. The original tests previously reported were for a center-of-gravity position of 24 percent of the mean aerodynamic chord.

Rainbow valley of colored (anti) de Sitter gravity in three dimensions

NASA Astrophysics Data System (ADS)

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.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Philippov, Alexander A.; Rafikov, Roman R., E-mail: rrr@astro.princeton.edu

The eclipsing binary DI Herculis (DI Her) is known to exhibit anomalously slow apsidal precession below the rate predicted by general relativity. Recent measurements of the Rossiter-McLaughlin effect indicate that stellar spins in DI Her are almost orthogonal to the orbital angular momentum, which explains the anomalous precession in agreement with the earlier theoretical suggestion by Shakura. However, these measurements yield only projections of the spin-orbit angles onto the sky plane, leaving the spin projection onto our line of sight unconstrained. Here we describe a method for determining the full three-dimensional spin orientation of the binary components relying on themore » use of the gravity-darkening effect, which is significant for the rapidly rotating stars in DI Her. Gravity darkening gives rise to a nonuniform brightness distribution over the stellar surface, the pattern of which depends on the stellar spin orientation. Using archival photometric data obtained during multiple eclipses over several decades, we are able to constrain the unknown spin angles in DI Her with this method, finding that the spin axes of both stars lie close to the plane of the sky. Our procedure fully accounts for the precession of stellar spins over the long time span of observations.« less

Hypercuboidal renormalization in spin foam quantum gravity

NASA Astrophysics Data System (ADS)

Bahr, Benjamin; Steinhaus, Sebastian

2017-06-01

In this article, we apply background-independent renormalization group methods to spin foam quantum gravity. It is aimed at extending and elucidating the analysis of a companion paper, in which the existence of a fixed point in the truncated renormalization group flow for the model was reported. Here, we repeat the analysis with various modifications and find that both qualitative and quantitative features of the fixed point are robust in this setting. We also go into details about the various approximation schemes employed in the analysis.

Lorentz covariance of loop quantum gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rovelli, Carlo; Speziale, Simone

2011-05-15

The kinematics of loop gravity can be given a manifestly Lorentz-covariant formulation: the conventional SU(2)-spin-network Hilbert space can be mapped to a space K of SL(2,C) functions, where Lorentz covariance is manifest. K can be described in terms of a certain subset of the projected spin networks studied by Livine, Alexandrov and Dupuis. It is formed by SL(2,C) functions completely determined by their restriction on SU(2). These are square-integrable in the SU(2) scalar product, but not in the SL(2,C) one. Thus, SU(2)-spin-network states can be represented by Lorentz-covariant SL(2,C) functions, as two-component photons can be described in the Lorentz-covariant Gupta-Bleulermore » formalism. As shown by Wolfgang Wieland in a related paper, this manifestly Lorentz-covariant formulation can also be directly obtained from canonical quantization. We show that the spinfoam dynamics of loop quantum gravity is locally SL(2,C)-invariant in the bulk, and yields states that are precisely in K on the boundary. This clarifies how the SL(2,C) spinfoam formalism yields an SU(2) theory on the boundary. These structures define a tidy Lorentz-covariant formalism for loop gravity.« less

Dynamics and stability of a tethered centrifuge in low earth orbit

NASA Technical Reports Server (NTRS)

Quadrelli, B. M.; Lorenzini, E. C.

1992-01-01

The three-dimensional attitude dynamics of a spaceborne tethered centrifuge for artificial gravity experiments in low earth orbit is analyzed using two different methods. First, the tethered centrifuge is modeled as a dumbbell with a straight viscoelastic tether, point tip-masses, and sophisticated environmental models such as nonspherical gravity, thermal perturbations, and a dynamic atmospheric model. The motion of the centrifuge during spin-up, de-spin, and steady-rotation is then simulated. Second, a continuum model of the tether is developed for analyzing the stability of lateral tether oscillations. Results indicate that the maximum fluctuation about the 1-g radial acceleration level is less than 0.001 g; the time required for spin-up and de-spin is less than one orbit; and lateral oscillations are stable for any practical values of the system parameters.

Towards conformal loop quantum gravity

NASA Astrophysics Data System (ADS)

H-T Wang, Charles

2006-03-01

A discussion is given of recent developments in canonical gravity that assimilates the conformal analysis of gravitational degrees of freedom. The work is motivated by the problem of time in quantum gravity and is carried out at the metric and the triad levels. At the metric level, it is shown that by extending the Arnowitt-Deser-Misner (ADM) phase space of general relativity (GR), a conformal form of geometrodynamics can be constructed. In addition to the Hamiltonian and Diffeomorphism constraints, an extra first class constraint is introduced to generate conformal transformations. This phase space consists of York's mean extrinsic curvature time, conformal three-metric and their momenta. At the triad level, the phase space of GR is further enlarged by incorporating spin-gauge as well as conformal symmetries. This leads to a canonical formulation of GR using a new set of real spin connection variables. The resulting gravitational constraints are first class, consisting of the Hamiltonian constraint and the canonical generators for spin-gauge and conformorphism transformations. The formulation has a remarkable feature of being parameter-free. Indeed, it is shown that a conformal parameter of the Barbero-Immirzi type can be absorbed by the conformal symmetry of the extended phase space. This gives rise to an alternative approach to loop quantum gravity that addresses both the conceptual problem of time and the technical problem of functional calculus in quantum gravity.

Wave equations in conformal gravity

NASA Astrophysics Data System (ADS)

Du, Juan-Juan; Wang, Xue-Jing; He, You-Biao; Yang, Si-Jiang; Li, Zhong-Heng

2018-05-01

We study the wave equation governing massless fields of all spins (s = 0, 1 2, 1, 3 2 and 2) in the most general spherical symmetric metric of conformal gravity. The equation is separable, the solution of the angular part is a spin-weighted spherical harmonic, and the radial wave function may be expressed in terms of solutions of the Heun equation which has four regular singular points. We also consider various special cases of the metric and find that the angular wave functions are the same for all cases, the actual shape of the metric functions affects only the radial wave function. It is interesting to note that each radial equation can be transformed into a known ordinary differential equation (i.e. Heun equation, or confluent Heun equation, or hypergeometric equation). The results show that there are analytic solutions for all the wave equations of massless spin fields in the spacetimes of conformal gravity. This is amazing because exact solutions are few and far between for other spacetimes.

Group field theories for all loop quantum gravity

NASA Astrophysics Data System (ADS)

Oriti, Daniele; Ryan, James P.; Thürigen, Johannes

2015-02-01

Group field theories represent a second quantized reformulation of the loop quantum gravity state space and a completion of the spin foam formalism. States of the canonical theory, in the traditional continuum setting, have support on graphs of arbitrary valence. On the other hand, group field theories have usually been defined in a simplicial context, thus dealing with a restricted set of graphs. In this paper, we generalize the combinatorics of group field theories to cover all the loop quantum gravity state space. As an explicit example, we describe the group field theory formulation of the KKL spin foam model, as well as a particular modified version. We show that the use of tensor model tools allows for the most effective construction. In order to clarify the mathematical basis of our construction and of the formalisms with which we deal, we also give an exhaustive description of the combinatorial structures entering spin foam models and group field theories, both at the level of the boundary states and of the quantum amplitudes.

Horndeski theories confront the Gravity Probe B experiment

NASA Astrophysics Data System (ADS)

Mukherjee, Sajal; Chakraborty, Sumanta

2018-06-01

In this work we have investigated various properties of a spinning gyroscope in the context of Horndeski theories. In particular, we have focused on two specific situations—(a) when the gyroscope follows a geodesic trajectory and (b) when it is endowed with an acceleration. In both these cases, besides developing the basic formalism, we have also applied the same to understand the motion of a spinning gyroscope in various static and spherically symmetric spacetimes pertaining to Horndeski theories. Starting with the Schwarzschild de Sitter spacetime as a warm up exercise, we have presented our results for two charged Galileon black holes as well as for a black hole in scalar coupled Einstein-Gauss-Bonnet gravity. In all these cases we have shown that the spinning gyroscope can be used to distinguish black holes from naked singularities. Moreover, using the numerical estimation of the geodetic precession from the Gravity Probe B experiment, we have constrained the gauge/scalar charge of the black holes in these Horndeski theories. Implications are also discussed.

EPRL/FK asymptotics and the flatness problem

NASA Astrophysics Data System (ADS)

Oliveira, José Ricardo

2018-05-01

Spin foam models are an approach to quantum gravity based on the concept of sum over states, which aims to describe quantum spacetime dynamics in a way that its parent framework, loop quantum gravity, has not as of yet succeeded. Since these models’ relation to classical Einstein gravity is not explicit, an important test of their viabilitiy is the study of asymptotics—the classical theory should be obtained in a limit where quantum effects are negligible, taken to be the limit of large triangle areas in a triangulated manifold with boundary. In this paper we will briefly introduce the EPRL/FK spin foam model and known results about its asymptotics, proceeding then to describe a practical computation of spin foam and semiclassical geometric data for a simple triangulation with only one interior triangle. The results are used to comment on the ‘flatness problem’—a hypothesis raised by Bonzom (2009 Phys. Rev. D 80 064028) suggesting that EPRL/FK’s classical limit only describes flat geometries in vacuum.

Towards causal patch physics in dS/CFT

NASA Astrophysics Data System (ADS)

Neiman, Yasha

2018-01-01

This contribution is a status report on a research program aimed at obtaining quantum-gravitational physics inside a cosmological horizon through dS/CFT, i.e. through a holographic description at past/future infinity of de Sitter space. The program aims to bring together two main elements. The first is the observation by Anninos, Hartman and Strominger that Vasiliev's higher-spin gravity provides a working model for dS/CFT in 3+1 dimensions. The second is the proposal by Parikh, Savonije and Verlinde that dS/CFT may prove more tractable if one works in so-called "elliptic" de Sitter space - a folded-in-half version of global de Sitter where antipodal points have been identified. We review some relevant progress concerning quantum field theory on elliptic de Sitter space, higher-spin gravity and its holographic duality with a free vector model. We present our reasons for optimism that the approach outlined here will lead to a full holographic description of quantum (higher-spin) gravity in the causal patch of a de Sitter observer.

Towards a phase diagram for spin foams

NASA Astrophysics Data System (ADS)

Delcamp, Clement; Dittrich, Bianca

2017-11-01

One of the most pressing issues for loop quantum gravity and spin foams is the construction of the continuum limit. In this paper, we propose a systematic coarse-graining scheme for three-dimensional lattice gauge models including spin foams. This scheme is based on the concept of decorated tensor networks, which have been introduced recently. Here we develop an algorithm applicable to gauge theories with non-Abelian groups, which for the first time allows for the application of tensor network coarse-graining techniques to proper spin foams. The procedure deals efficiently with the large redundancy of degrees of freedom resulting from gauge invariance. The algorithm is applied to 3D spin foams defined on a cubical lattice which, in contrast to a proper triangulation, allows for non-trivial simplicity constraints. This mimics the construction of spin foams for 4D gravity. For lattice gauge models based on a finite group we use the algorithm to obtain phase diagrams, encoding the continuum limit of a wide range of these models. We find phase transitions for various families of models carrying non-trivial simplicity constraints.

Higher spin realization of the DS/CFT correspondence

NASA Astrophysics Data System (ADS)

Anninos, Dionysios; Hartman, Thomas; Strominger, Andrew

2017-01-01

We conjecture that Vasiliev’s theory of higher spin gravity in four-dimensional de Sitter space (dS4) is holographically dual to a three-dimensional conformal field theory (CFT3) living on the spacelike boundary of dS4 at future timelike infinity. The CFT3 is the Euclidean Sp(N) vector model with anticommuting scalars. The free CFT3 flows under a double-trace deformation to an interacting CFT3 in the IR. We argue that both CFTs are dual to Vasiliev dS4 gravity but with different future boundary conditions on the bulk scalar field. Our analysis rests heavily on analytic continuations of bulk and boundary correlators in the proposed duality relating the O(N) model with Vasiliev gravity in AdS4.

Balancing Newtonian gravity and spin to create localized structures

NASA Astrophysics Data System (ADS)

Bush, Michael; Lindner, John

2015-03-01

Using geometry and Newtonian physics, we design localized structures that do not require electromagnetic or other forces to resist implosion or explosion. In two-dimensional Euclidean space, we find an equilibrium configuration of a rotating ring of massive dust whose inward gravity is the centripetal force that spins it. We find similar solutions in three-dimensional Euclidean and hyperbolic spaces, but only in the limit of vanishing mass. Finally, in three-dimensional Euclidean space, we generalize the two-dimensional result by finding an equilibrium configuration of a spherical shell of massive dust that supports itself against gravitational collapse by spinning isoclinically in four dimensions so its three-dimensional acceleration is everywhere inward. These Newtonian ``atoms'' illuminate classical physics and geometry.

A Gaussian Weave for Kinematical Loop Quantum Gravity

NASA Astrophysics Data System (ADS)

Corichi, A.; Reyes, J. M.; Ashtekar, A.

Remarkable efforts in the study of the semiclassical regime of kinematical loop quantum gravity are currently underway. In this note, we construct a ``quasicoherent'' weave state using Gaussian factors. In a similar fashion to some other proposals, this state is peaked in both the connection and the spin network basis. However, the state constructed here has the novel feature that, in the spin network basis, the main contribution for this state is given by the fundamental representation, independently of the value of the parameter that regulates the Gaussian width.

Evidence for maximal acceleration and singularity resolution in covariant loop quantum gravity.

PubMed

Rovelli, Carlo; Vidotto, Francesca

2013-08-30

A simple argument indicates that covariant loop gravity (spin foam theory) predicts a maximal acceleration and hence forbids the development of curvature singularities. This supports the results obtained for cosmology and black holes using canonical methods.

Aspects of neutrino oscillation in alternative gravity theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Sumanta, E-mail: sumantac.physics@gmail.com

2015-10-01

Neutrino spin and flavour oscillation in curved spacetime have been studied for the most general static spherically symmetric configuration. Having exploited the spherical symmetry we have confined ourselves to the equatorial plane in order to determine the spin and flavour oscillation frequency in this general set-up. Using the symmetry properties we have derived spin oscillation frequency for neutrino moving along a geodesic or in a circular orbit. Starting from the expression of neutrino spin oscillation frequency we have shown that even in this general context, in high energy limit the spin oscillation frequency for neutrino moving along circular orbit vanishes.more » We have verified previous results along this line by transforming to Schwarzschild coordinates under appropriate limit. This finally lends itself to the probability of neutrino helicity flip which turns out to be non-zero. While for neutrino flavour oscillation we have derived general results for oscillation phase, which subsequently have been applied to three different gravity theories. One, of them appears as low-energy approximation to string theory, where we have an additional field, namely, dilaton field coupled to Maxwell field tensor. This yields a realization of Reissner-Nordström solution in string theory at low-energy. Next one corresponds to generalization of Schwarzschild solution by introduction of quadratic curvature terms of all possible form to the Einstein-Hilbert action. Finally, we have also discussed regular black hole solutions. In all these cases the flavour oscillation probabilities can be determined for solar neutrinos and thus can be used to put bounds on the parameters of these gravity theories. While for spin oscillation probability, we have considered two cases, Gauss-Bonnet term added to the Einstein-Hilbert action and the f(R) gravity theory. In both these cases we could impose bounds on the parameters which are consistent with previous considerations. In a nutshell, in this work we have presented both spin and flavour oscillation frequency of neutrino in most general static spherically symmetric spacetime, encompassing a vast class of solutions, which when applied to three such instances in alternative theories for flavour oscillation and two alternative theories for spin oscillation put bounds on the parameters of these theories. Implications are also discussed.« less

LETTER TO THE EDITOR: A theorem on topologically massive gravity

NASA Astrophysics Data System (ADS)

Aliev, A. N.; Nutku, Y.

1996-03-01

We show that for three dimensional spacetimes admitting a hypersurface orthogonal Killing vector field, Deser, Jackiw and Templeton's vacuum field equations of topologically massive gravity allow only the trivial flat spacetime solution. Thus spin is necessary to support topological mass.

Thermofield duality for higher spin Rindler Gravity

DOE PAGES

Jevicki, Antal; Suzuki, Kenta

2016-02-15

In this paper, we study the Thermo-field realization of the duality between the Rindler-AdS higher spin theory and O(N) vector theory. The CFT represents a decoupled pair of free O(N) vector field theories. It is shown how this decoupled domain CFT is capable of generating the connected Rindler-AdS background with the full set of Higher Spin fields.

Recent developments in bimetric theory

NASA Astrophysics Data System (ADS)

Schmidt-May, Angnis; von Strauss, Mikael

2016-05-01

This review is dedicated to recent progress in the field of classical, interacting, massive spin-2 theories, with a focus on ghost-free bimetric theory. We will outline its history and its development as a nontrivial extension and generalisation of nonlinear massive gravity. We present a detailed discussion of the consistency proofs of both theories, before we review Einstein solutions to the bimetric equations of motion in vacuum as well as the resulting mass spectrum. We introduce couplings to matter and then discuss the general relativity and massive gravity limits of bimetric theory, which correspond to decoupling the massive or the massless spin-2 field from the matter sector, respectively. More general classical solutions are reviewed and the present status of bimetric cosmology is summarised. An interesting corner in the bimetric parameter space which could potentially give rise to a nonlinear theory for partially massless spin-2 fields is also discussed. Relations to higher-curvature theories of gravity are explained and finally we give an overview of possible extensions of the theory and review its formulation in terms of vielbeins.

Project SKYLITE: A Design Exploration.

DTIC Science & Technology

1987-09-01

5. Gravity Gradient Boom The SKYLITE satellite uses gravity gradient stabilization. This technique requires a gravity gradient boom for attitude ... attitude of the satellite. To satisfy SKYLITE mission requirements, the satellite contains an array of IR sensors for evaluation of radiation from the ...3.1 Extended GAS Canister. The Orion satellite has been designed with 7 thrusters. Six thrusters are .1 lbr rated, and used for spin up and attitude

Three-dimensional transient flow of spin-up in a filled cylinder with oblique gravity force

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1995-01-01

Three-dimensional transient flow profiles of spin-up in a fully liquid filled cylinder from rest with gravity acceleration at various direction are numerically simulated and studied. Particular interests are concentrated on the development of temporary reverse flow zones and Ekman layer right after the impulsive start of spin-up from rest, and decay before the flow reaching to the solid rotation. Relationship of these flow developments and differences in the Reynolds numbers of the flow and its size selection of grid points concerning the numerical instabilities of flow computations are also discussed. In addition to the gravitational acceleration along the axial direction of the cylindrical container, a series of complicated flow profiles accompanied by three-dimensional transient flows with oblique gravitational acceleration has been studies.

The Coupling of Gravity to Spin and Electromagnetism

NASA Astrophysics Data System (ADS)

Finster, Felix; Smoller, Joel; Yau, Shing-Tung

The coupled Einstein-Dirac-Maxwell equations are considered for a static, spherically symmetric system of two fermions in a singlet spinor state. Stable soliton-like solutions are shown to exist, and we discuss the regularizing effect of gravity from a Feynman diagram point of view.

Unimodular Einstein-Cartan gravity: Dynamics and conservation laws

NASA Astrophysics Data System (ADS)

Bonder, Yuri; Corral, Cristóbal

2018-04-01

Unimodular gravity is an interesting approach to address the cosmological constant problem, since the vacuum energy density of quantum fields does not gravitate in this framework, and the cosmological constant appears as an integration constant. These features arise as a consequence of considering a constrained volume element 4-form that breaks the diffeomorphisms invariance down to volume preserving diffeomorphisms. In this work, the first-order formulation of unimodular gravity is presented by considering the spin density of matter fields as a source of spacetime torsion. Even though the most general matter Lagrangian allowed by the symmetries is considered, dynamical restrictions arise on their functional dependence. The field equations are obtained and the conservation laws associated with the symmetries are derived. It is found that, analogous to torsion-free unimodular gravity, the field equation for the vierbein is traceless; nevertheless, torsion is algebraically related to the spin density as in standard Einstein-Cartan theory. The particular example of massless Dirac spinors is studied, and comparisons with standard Einstein-Cartan theory are shown.

KENNEDY SPACE CENTER, FLA. - This logo for the Gravity Probe B mission portrays the theory of curved spacetime and "frame-dragging," developed by Einstein and other scientists, that the mission will test. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit. Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring the effects. The experiment was developed by Stanford University, NASA’s Marshall Space Flight Center and Lockheed Martin.

NASA Image and Video Library

2003-10-30

KENNEDY SPACE CENTER, FLA. - This logo for the Gravity Probe B mission portrays the theory of curved spacetime and "frame-dragging," developed by Einstein and other scientists, that the mission will test. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit. Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring the effects. The experiment was developed by Stanford University, NASA’s Marshall Space Flight Center and Lockheed Martin.

Topics in Higher-Derivative Supergravity and N = 2 Yang-Mills Theories

NASA Astrophysics Data System (ADS)

Hindawi, Ahmed Abdel-Ati

1997-09-01

In Part I of the thesis we discuss higher-derivative theories of gravity. We start by discussing the field content of quadratic higher-derivative gravity, together with a new example of a massless spin-two field consistently coupled to gravity. The full quadratic gravity theory is shown to be equivalent to a canonical second-order theory of a massive scalar field, a massive spin-two symmetric tensor field and gravity. It is shown that flat-space is the only stable vacuum, and that the spin-two field around it is always ghost-like. We give a procedure for exhibiting the new propagating degrees of freedom in a generic higher-derivative gravity, at the full non-linear level. We show that around any vacuum the elementary excitations remain the massless graviton, a massive scalar field and a massive ghost-like spin-two field. In Part II of the thesis we extend our investigations to the realm of supergravity. We consider the general form of quadratic (1, 1) supergravity in two dimensions. It is demonstrated that the theory possesses stable vacua with vanishing cosmological constant which spontaneously break supersymmetry. We then consider higher-derivative N=1 supergravity in four dimensions. We construct two classes of higher-derivative supergravity theories. They are found to be equivalent to Einstein supergravity coupled to one or two chiral superfields and have a rich vacuum structure. It is demonstrated that theories of the second class can possess a stable vacuum with vanishing cosmological constant that spontaneously breaks supersymmetry. We then proceed to show how spontaneous supersymmetry breaking in the vacuum state of higher-derivative supergravity is transmitted, as explicit soft supersymmetry-breaking terms, to the effective Lagrangian of the standard electroweak model. In Part III we use central charge superspace to give a geometrical construction of the N=2 Abelian vector-tensor multiplet consisting, under N=1 supersymmetry, of one vector and one linear multiplet. We derive the component field supersymmetry and central charge transformations, and show that there is a super-Lagrangian, the higher components of which are all total derivatives, allowing us to construct superfield and component actions.

Inconsistency of topologically massive hypergravity

NASA Technical Reports Server (NTRS)

Aragone, C.; Deser, S.

1985-01-01

The coupled topologically massive spin-5/2 gravity system in D = 3 dimensions whose kinematics represents dynamical propagating gauge invariant massive spin-5/2 and spin-2 excitations, is shown to be inconsistent, or equivalently, not locally hypersymmetric. In contrast to D = 4, the local constraints on the system arising from failure of the fermionic Bianchi identities do not involve the 'highest spin' components of the field, but rather the auxiliary spinor required to construct a consistent massive model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Jason W.; Linscott, Ethan; Shporer, Avi, E-mail: jwbarnes@uidaho.edu

We model the asymmetry of the KOI-13.01 transit lightcurve assuming a gravity-darkened rapidly rotating host star in order to constrain the system's spin-orbit alignment and transit parameters. We find that our model can reproduce the Kepler lightcurve for KOI-13.01 with a sky-projected alignment of {lambda} = 23 Degree-Sign {+-} 4 Degree-Sign and with the star's north pole tilted away from the observer by 48 Degree-Sign {+-} 4 Degree-Sign (assuming M{sub *} = 2.05 M{sub Sun }). With both these determinations, we calculate that the net misalignment between this planet's orbit normal and its star's rotational pole is 56 Degree-Sign {+-}more » 4 Degree-Sign . Degeneracies in our geometric interpretation also allow a retrograde spin-orbit angle of 124 Degree-Sign {+-} 4 Degree-Sign . This is the first spin-orbit measurement to come from gravity darkening and is one of only a few measurements of the full (not just the sky-projected) spin-orbit misalignment of an extrasolar planet. We also measure accurate transit parameters incorporating stellar oblateness and gravity darkening: R{sub *} 1.756 {+-} 0.014 R{sub Sun }, R{sub p} = 1.445 {+-} 0.016 R{sub Jup}, and i = 85.{sup 0}9 {+-} 0.{sup 0}4. The new lower planetary radius falls within the planetary mass regime for plausible interior models for the transiting body. A simple initial calculation shows that KOI-13.01's circular orbit is apparently inconsistent with the Kozai mechanism having driven its spin-orbit misalignment; planet-planet scattering and stellar spin migration remain viable mechanisms. Future Kepler data will improve the precision of the KOI-13.01 transit lightcurve, allowing more precise determination of transit parameters and the opportunity to use the Photometric Rossiter-McLaughlin effect to resolve the prograde/retrograde orbit determination degeneracy.« less

Can Gravity Probe B usefully constrain torsion gravity theories?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flanagan, Eanna E.; Rosenthal, Eran

2007-06-15

In most theories of gravity involving torsion, the source for torsion is the intrinsic spin of matter. Since the spins of fermions are normally randomly oriented in macroscopic bodies, the amount of torsion generated by macroscopic bodies is normally negligible. However, in a recent paper, Mao et al. (arXiv:gr-qc/0608121) point out that there is a class of theories, including the Hayashi-Shirafuji (1979) theory, in which the angular momentum of macroscopic spinning bodies generates a significant amount of torsion. They further argue that, by the principle of action equals reaction, one would expect the angular momentum of test bodies to couplemore » to a background torsion field, and therefore the precession of the Gravity Probe B gyroscopes should be affected in these theories by the torsion generated by the Earth. We show that in fact the principle of action equals reaction does not apply to these theories, essentially because the torsion is not an independent dynamical degree of freedom. We examine in detail a generalization of the Hayashi-Shirafuji theory suggested by Mao et al. called Einstein-Hayashi-Shirafuji theory. There are a variety of different versions of this theory, depending on the precise form of the coupling to matter chosen for the torsion. We show that, for any coupling to matter that is compatible with the spin transport equation postulated by Mao et al., the theory has either ghosts or an ill-posed initial-value formulation. These theoretical problems can be avoided by specializing the parameters of the theory and in addition choosing the standard minimal coupling to matter of the torsion tensor. This yields a consistent theory, but one in which the action equals reaction principle is violated, and in which the angular momentum of the gyroscopes does not couple to the Earth's torsion field. Thus, the Einstein-Hayashi-Shirafuji theory does not predict a detectable torsion signal for Gravity Probe B. There may be other torsion theories which do.« less

Local quenches and quantum chaos from higher spin perturbations

NASA Astrophysics Data System (ADS)

David, Justin R.; Khetrapal, Surbhi; Kumar, S. Prem

2017-10-01

We study local quenches in 1+1 dimensional conformal field theories at large- c by operators carrying higher spin charge. Viewing such states as solutions in Chern-Simons theory, representing infalling massive particles with spin-three charge in the BTZ back-ground, we use the Wilson line prescription to compute the single-interval entanglement entropy (EE) and scrambling time following the quench. We find that the change in EE is finite (and real) only if the spin-three charge q is bounded by the energy of the perturbation E, as | q| /c < E 2 /c 2. We show that the Wilson line/EE correlator deep in the quenched regime and its expansion for small quench widths overlaps with the Regge limit for chaos of the out-of-time-ordered correlator. We further find that the scrambling time for the two-sided mutual information between two intervals in the thermofield double state increases with increasing spin-three charge, diverging when the bound is saturated. For larger values of the charge, the scrambling time is shorter than for pure gravity and controlled by the spin-three Lyapunov exponent 4 π/β. In a CFT with higher spin chemical potential, dual to a higher spin black hole, we find that the chemical potential must be bounded to ensure that the mutual information is a concave function of time and entanglement speed is less than the speed of light. In this case, a quench with zero higher spin charge yields the same Lyapunov exponent as pure Einstein gravity.

Numerical Evidence for a Phase Transition in 4D Spin-Foam Quantum Gravity

NASA Astrophysics Data System (ADS)

Bahr, Benjamin; Steinhaus, Sebastian

2016-09-01

Building on recent advances in defining Wilsonian renormalization group (RG) flows, and the notion of scales in particular, for background-independent theories, we present a first investigation of the renormalization of the 4D spin-foam path integral for quantum gravity, both analytically and numerically. Focusing on a specific truncation of the model using a hypercubic lattice, we compute the RG flow and find strong indications for a phase transition, as well as an interesting interplay between the different observed phases and the (broken) diffeomorphism symmetry of the model. Most notably, it appears that the critical point between the phases, which is a fixed point of the RG flow, is precisely where broken diffeomorphism symmetry is restored, which suggests that it might allow us to define a continuum limit of the quantum gravity theory.

Numerical Evidence for a Phase Transition in 4D Spin-Foam Quantum Gravity.

PubMed

Bahr, Benjamin; Steinhaus, Sebastian

2016-09-30

Building on recent advances in defining Wilsonian renormalization group (RG) flows, and the notion of scales in particular, for background-independent theories, we present a first investigation of the renormalization of the 4D spin-foam path integral for quantum gravity, both analytically and numerically. Focusing on a specific truncation of the model using a hypercubic lattice, we compute the RG flow and find strong indications for a phase transition, as well as an interesting interplay between the different observed phases and the (broken) diffeomorphism symmetry of the model. Most notably, it appears that the critical point between the phases, which is a fixed point of the RG flow, is precisely where broken diffeomorphism symmetry is restored, which suggests that it might allow us to define a continuum limit of the quantum gravity theory.

The Bach equations in spin-coefficient form

NASA Astrophysics Data System (ADS)

Forbes, Hamish

2018-06-01

Conformal gravity theories are defined by field equations that determine only the conformal structure of the spacetime manifold. The Bach equations represent an early example of such a theory, we present them here in component form in terms of spin- and boost-weighted spin-coefficients using the compacted spin-coefficient formalism. These equations can be used as an efficient alternative to the standard tensor form. As a simple application we solve the Bach equations for pp-wave and static spherically symmetric spacetimes.

Variable gravity research facility

NASA Technical Reports Server (NTRS)

Allan, Sean; Ancheta, Stan; Beine, Donna; Cink, Brian; Eagon, Mark; Eckstein, Brett; Luhman, Dan; Mccowan, Daniel; Nations, James; Nordtvedt, Todd

1988-01-01

Spin and despin requirements; sequence of activities required to assemble the Variable Gravity Research Facility (VGRF); power systems technology; life support; thermal control systems; emergencies; communication systems; space station applications; experimental activities; computer modeling and simulation of tether vibration; cost analysis; configuration of the crew compartments; and tether lengths and rotation speeds are discussed.

A gauge-theoretic approach to gravity.

PubMed

Krasnov, Kirill

2012-08-08

Einstein's general relativity (GR) is a dynamical theory of the space-time metric. We describe an approach in which GR becomes an SU(2) gauge theory. We start at the linearized level and show how a gauge-theoretic Lagrangian for non-interacting massless spin two particles (gravitons) takes a much more simple and compact form than in the standard metric description. Moreover, in contrast to the GR situation, the gauge theory Lagrangian is convex. We then proceed with a formulation of the full nonlinear theory. The equivalence to the metric-based GR holds only at the level of solutions of the field equations, that is, on-shell. The gauge-theoretic approach also makes it clear that GR is not the only interacting theory of massless spin two particles, in spite of the GR uniqueness theorems available in the metric description. Thus, there is an infinite-parameter class of gravity theories all describing just two propagating polarizations of the graviton. We describe how matter can be coupled to gravity in this formulation and, in particular, how both the gravity and Yang-Mills arise as sectors of a general diffeomorphism-invariant gauge theory. We finish by outlining a possible scenario of the ultraviolet completion of quantum gravity within this approach.

Path integral measure and triangulation independence in discrete gravity

NASA Astrophysics Data System (ADS)

Dittrich, Bianca; Steinhaus, Sebastian

2012-02-01

A path integral measure for gravity should also preserve the fundamental symmetry of general relativity, which is diffeomorphism symmetry. In previous work, we argued that a successful implementation of this symmetry into discrete quantum gravity models would imply discretization independence. We therefore consider the requirement of triangulation independence for the measure in (linearized) Regge calculus, which is a discrete model for quantum gravity, appearing in the semi-classical limit of spin foam models. To this end we develop a technique to evaluate the linearized Regge action associated to Pachner moves in 3D and 4D and show that it has a simple, factorized structure. We succeed in finding a local measure for 3D (linearized) Regge calculus that leads to triangulation independence. This measure factor coincides with the asymptotics of the Ponzano Regge Model, a 3D spin foam model for gravity. We furthermore discuss to which extent one can find a triangulation independent measure for 4D Regge calculus and how such a measure would be related to a quantum model for 4D flat space. To this end, we also determine the dependence of classical Regge calculus on the choice of triangulation in 3D and 4D.

Spin-stabilized magnetic levitation without vertical axis of rotation

DOEpatents

Romero, Louis [Albuquerque, NM; Christenson, Todd [Albuquerque, NM; Aaronson, Gene [Albuquerque, NM

2009-06-09

The symmetry properties of a magnetic levitation arrangement are exploited to produce spin-stabilized magnetic levitation without aligning the rotational axis of the rotor with the direction of the force of gravity. The rotation of the rotor stabilizes perturbations directed parallel to the rotational axis.

Determination of the Threshold of Gravity for the Susceptibility to Kinetosis in Fish - a Centrifuge Experiment in the ZARM Drop-Tower employing gradually reduced Gravity

NASA Astrophysics Data System (ADS)

Anken, R.; Hilbig, R.

In the course of earlier experiments at diminished gravity conditions we have successfully used larval cichlid fish Oreochromis mossambicus as a vertebrate model system in investigating the basic cause of susceptibility to motion sickness kinetosis It was observed that most animals of a given batch reveal kinetoses i e performing looping responses LR or spinning movements SM at high quality microgravity 10-6g ZARM drop-tower whereas comparatively few individuals swim kinetotically at low quality microgravity LQM 0 03-0 05g during parabolic aircraft flights Anken and Hilbig Microgravity Sci Technol 15 52-57 2004 In order to gain further insights into a possible threshold of gravity for inducing motion sickness animals were subjected to drop-tower flights within a centrifuge The levels of gravity applied ranged from 0 009g until 0 3g The lowest level of gravity under which few normally swimming fish were observed ranged around 0 015g Since this is a very low level of gravity the normally swimming fish have to be considered to be either extremely sensitive to any force of gravity in order to use it as a cue for postural control or they use cues other than the residual gravity for maintaining equilibrium Most of the remaining kinetotically swimming animals showed LR whereas few exhibited SM With increasing gravity the ratio of normally swimming and spinning specimens increased accompanied by a decrease in the number of looping larvae Regarding the ratio a shift from LR to SM took place at around 0 02g At 0 3g all animals behaved

Loop-quantum-gravity vertex amplitude.

PubMed

Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo

2007-10-19

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

Magnetospheric Multiscale Mission Attitude Dynamics: Observations from Flight Data

NASA Technical Reports Server (NTRS)

Williams, Trevor; Shulman, Seth; Sedlak, Joseph; Ottenstein, Neil; Lounsbury, Brian

2016-01-01

Extensive flight data is being collected throughout the MMS mission that includes quantities that are of interest for attitude dynamics studies such as spin rate, spin axis orientation nutation rate, etc. One example of such data is the long-term evolution of the spin rates of the four spacecraft. Spikes in these rates are observed that are separated by the MMS orbital period (just under 24 hr) and occur around perigee due to gravity-gradient torque. Periodic discontinuities in spin rate are caused by the controller resetting the spin rate approximately to the nominal 3.1 RPM value at the time of each maneuver. In between, a slow decay in spin rate can be seen to occur. The paper will discuss various disturbance torque mechanisms that could potentially be responsible for this behavior: these include magnetic hysteresis, eddy currents, solar radiation pressure, and a possible interaction between gravity-gradient and wire boom flexibility effects. One additional disturbance mechanism is produced by the Active Spacecraft Potential Control (ASPOC) devices: these emit positive indium ions to keep the MMS spacecraft electrically neutral, so as not to corrupt the electric field observations that are made by some of the on-board instruments. The spin rate decays that could be produced by these various mechanisms will be quantified in the paper, and their signatures described. Comparing these with the observations from flight data then allow the most likely candidate to be determined.

Spin-Tunnel Investigation of a 1/30-Scale Model of the North American A-5 Airplane

NASA Technical Reports Server (NTRS)

Lee, Henry A.

1964-01-01

An investigation has been made to determine the erect and. inverted spin and recovery characteristics of a 1/30-scale dynamic model of the North American A-5A airplane. Tests were made for the basic flight design loading with the center of gravity at 30-percent mean aerodynamic chord and also for a forward position and a rearward position with the center of gravity at 26-percent and 40-percent mean aerodynamic chord, respectively. Tests were also made to determine the effect of full external wing tanks on both wings, and of an asymmetrical condition when only one full tank is carried.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bianchi, Eugenio; Speziale, Simone; Dona, Pietro

Intertwiners are the building blocks of spin-network states. The space of intertwiners is the quantization of a classical symplectic manifold introduced by Kapovich and Millson. Here we show that a theorem by Minkowski allows us to interpret generic configurations in this space as bounded convex polyhedra in R{sup 3}: A polyhedron is uniquely described by the areas and normals to its faces. We provide a reconstruction of the geometry of the polyhedron: We give formulas for the edge lengths, the volume, and the adjacency of its faces. At the quantum level, this correspondence allows us to identify an intertwiner withmore » the state of a quantum polyhedron, thus generalizing the notion of the quantum tetrahedron familiar in the loop quantum gravity literature. Moreover, coherent intertwiners result to be peaked on the classical geometry of polyhedra. We discuss the relevance of this result for loop quantum gravity. In particular, coherent spin-network states with nodes of arbitrary valence represent a collection of semiclassical polyhedra. Furthermore, we introduce an operator that measures the volume of a quantum polyhedron and examine its relation with the standard volume operator of loop quantum gravity. We also comment on the semiclassical limit of spin foams with nonsimplicial graphs.« less

Spin-Tunnel Investigation of a 1/20-Scale Model of the Northrop F-5E Airplane

NASA Technical Reports Server (NTRS)

Scher, Stanley H.; White, William L.

1977-01-01

An investigation has been conducted in the Langley spin tunnel to determine the spin and recovery characteristics of a 1/20-scale model of the Northrop F-5E airplane. The investigation included erect and inverted spins, a range of center-of- gravity locations and moments of inertia, symmetric and asymmetric store loadings, and a determination of the parachute size required for emergency spin recovery. The effects of increased elevator trailing-edge-up deflections, of leading-edge and trailing-edge flap deflections, and of simulating the geometry of large external stores were also determined.

Self-Organized Critical Behavior:. the Evolution of Frozen Spin Networks Model in Quantum Gravity

NASA Astrophysics Data System (ADS)

Chen, Jian-Zhen; Zhu, Jian-Yang

In quantum gravity, we study the evolution of a two-dimensional planar open frozen spin network, in which the color (i.e. the twice spin of an edge) labeling edge changes but the underlying graph remains fixed. The mainly considered evolution rule, the random edge model, is depending on choosing an edge randomly and changing the color of it by an even integer. Since the change of color generally violate the gauge invariance conditions imposed on the system, detailed propagation rule is needed and it can be defined in many ways. Here, we provided one new propagation rule, in which the involved even integer is not a constant one as in previous works, but changeable with certain probability. In random edge model, we do find the evolution of the system under the propagation rule exhibits power-law behavior, which is suggestive of the self-organized criticality (SOC), and it is the first time to verify the SOC behavior in such evolution model for the frozen spin network. Furthermore, the increase of the average color of the spin network in time can show the nature of inflation for the universe.

Coherent states, quantum gravity, and the Born-Oppenheimer approximation. I. General considerations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stottmeister, Alexander, E-mail: alexander.stottmeister@gravity.fau.de; Thiemann, Thomas, E-mail: thomas.thiemann@gravity.fau.de

2016-06-15

This article, as the first of three, aims at establishing the (time-dependent) Born-Oppenheimer approximation, in the sense of space adiabatic perturbation theory, for quantum systems constructed by techniques of the loop quantum gravity framework, especially the canonical formulation of the latter. The analysis presented here fits into a rather general framework and offers a solution to the problem of applying the usual Born-Oppenheimer ansatz for molecular (or structurally analogous) systems to more general quantum systems (e.g., spin-orbit models) by means of space adiabatic perturbation theory. The proposed solution is applied to a simple, finite dimensional model of interacting spin systems,more » which serves as a non-trivial, minimal model of the aforesaid problem. Furthermore, it is explained how the content of this article and its companion affect the possible extraction of quantum field theory on curved spacetime from loop quantum gravity (including matter fields).« less

Dynamics for a 2-vertex quantum gravity model

NASA Astrophysics Data System (ADS)

Borja, Enrique F.; Díaz-Polo, Jacobo; Garay, Iñaki; Livine, Etera R.

2010-12-01

We use the recently introduced U(N) framework for loop quantum gravity to study the dynamics of spin network states on the simplest class of graphs: two vertices linked with an arbitrary number N of edges. Such graphs represent two regions, in and out, separated by a boundary surface. We study the algebraic structure of the Hilbert space of spin networks from the U(N) perspective. In particular, we describe the algebra of operators acting on that space and discuss their relation to the standard holonomy operator of loop quantum gravity. Furthermore, we show that it is possible to make the restriction to the isotropic/homogeneous sector of the model by imposing the invariance under a global U(N) symmetry. We then propose a U(N)-invariant Hamiltonian operator and study the induced dynamics. Finally, we explore the analogies between this model and loop quantum cosmology and sketch some possible generalizations of it.

Gravity Field Characterization around Small Bodies

NASA Astrophysics Data System (ADS)

Takahashi, Yu

A small body rendezvous mission requires accurate gravity field characterization for safe, accurate navigation purposes. However, the current techniques of gravity field modeling around small bodies are not achieved to the level of satisfaction. This thesis will address how the process of current gravity field characterization can be made more robust for future small body missions. First we perform the covariance analysis around small bodies via multiple slow flybys. Flyby characterization requires less laborious scheduling than its orbit counterpart, simultaneously reducing the risk of impact into the asteroid's surface. It will be shown that the level of initial characterization that can occur with this approach is no less than the orbit approach. Next, we apply the same technique of gravity field characterization to estimate the spin state of 4179 Touatis, which is a near-Earth asteroid in close to 4:1 resonance with the Earth. The data accumulated from 1992-2008 are processed in a least-squares filter to predict Toutatis' orientation during the 2012 apparition. The center-of-mass offset and the moments of inertia estimated thereof can be used to constrain the internal density distribution within the body. Then, the spin state estimation is developed to a generalized method to estimate the internal density distribution within a small body. The density distribution is estimated from the orbit determination solution of the gravitational coefficients. It will be shown that the surface gravity field reconstructed from the estimated density distribution yields higher accuracy than the conventional gravity field models. Finally, we will investigate two types of relatively unknown gravity fields, namely the interior gravity field and interior spherical Bessel gravity field, in order to investigate how accurately the surface gravity field can be mapped out for proximity operations purposes. It will be shown that these formulations compute the surface gravity field with unprecedented accuracy for a well-chosen set of parametric settings, both regionally and globally.

Graviton propagator from background-independent quantum gravity.

PubMed

Rovelli, Carlo

2006-10-13

We study the graviton propagator in Euclidean loop quantum gravity. We use spin foam, boundary-amplitude, and group-field-theory techniques. We compute a component of the propagator to first order, under some approximations, obtaining the correct large-distance behavior. This indicates a way for deriving conventional spacetime quantities from a background-independent theory.

On the junction conditions in f(R) -gravity with torsion

NASA Astrophysics Data System (ADS)

Vignolo, Stefano; Cianci, Roberto; Carloni, Sante

2018-05-01

Junction conditions are discussed within the framework of f(R) -gravity with torsion. After deriving general junction conditions, the cases of coupling to a Dirac field and a spin fluid are explicitly dealt with. The main differences with respect to Einstein–Cartan–Sciama–Kibble theory ≤ft( f(R)=R\\right) are outlined.

New 'phase' of quantum gravity.

PubMed

Wang, Charles H-T

2006-12-15

The emergence of loop quantum gravity over the past two decades has stimulated a great resurgence of interest in unifying general relativity and quantum mechanics. Among a number of appealing features of this approach is the intuitive picture of quantum geometry using spin networks and powerful mathematical tools from gauge field theory. However, the present form of loop quantum gravity suffers from a quantum ambiguity, owing to the presence of a free (Barbero-Immirzi) parameter. Following the recent progress on conformal decomposition of gravitational fields, we present a new phase space for general relativity. In addition to spin-gauge symmetry, the new phase space also incorporates conformal symmetry making the description parameter free. The Barbero-Immirzi ambiguity is shown to occur only if the conformal symmetry is gauge fixed prior to quantization. By withholding its full symmetries, the new phase space offers a promising platform for the future development of loop quantum gravity. This paper aims to provide an exposition, at a reduced technical level, of the above theoretical advances and their background developments. Further details are referred to cited references.

Spin foam models for quantum gravity from lattice path integrals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonzom, Valentin

2009-09-15

Spin foam models for quantum gravity are derived from lattice path integrals. The setting involves variables from both lattice BF theory and Regge calculus. The action consists in a Regge action, which depends on areas, dihedral angles and includes the Immirzi parameter. In addition, a measure is inserted to ensure a consistent gluing of simplices, so that the amplitude is dominated by configurations that satisfy the parallel transport relations. We explicitly compute the path integral as a sum over spin foams for a generic measure. The Freidel-Krasnov and Engle-Pereira-Rovelli models correspond to a special choice of gluing. In this case,more » the equations of motion describe genuine geometries, where the constraints of area-angle Regge calculus are satisfied. Furthermore, the Immirzi parameter drops out of the on-shell action, and stationarity with respect to area variations requires spacetime geometry to be flat.« less

Matter scattering in quadratic gravity and unitarity

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Gravity and the Spin-2 Planar Schrödinger Equation

NASA Astrophysics Data System (ADS)

Bergshoeff, Eric A.; Rosseel, Jan; Townsend, Paul K.

2018-04-01

A Schrödinger equation proposed for the Girvin-MacDonald-Platzman gapped spin-2 mode of fractional quantum Hall states is found from a novel nonrelativistic limit, applicable only in 2 +1 dimensions, of the massive spin-2 Fierz-Pauli field equations. It is also found from a novel null reduction of the linearized Einstein field equations in 3 +1 dimensions, and in this context a uniform distribution of spin-2 particles implies, via a Brinkmann-wave solution of the nonlinear Einstein equations, a confining harmonic oscillator potential for the individual particles.

The Dawn Gravity Investigation at Vesta and Ceres

NASA Technical Reports Server (NTRS)

Konopliv, A. S.; Asmar, S.W.; Bills, B. G.; Mastrodemos, N.; Park, R. S.; Raymond, C. A.; Smith, D. E.; Zuber, M. T.

2011-01-01

The objective of the Dawn gravity investigation is to use high precision X-band Doppler tracking and landmark tracking from optical images to measure the gravity fields of Vesta and Ceres to a half-wavelength surface resolution better than 90-km and 300-km, respectively. Depending on the Doppler tracking assumptions, the gravity field will be determined to somewhere between harmonic degrees 15 and 25 for Vesta and about degree 10 for Ceres. The gravity fields together with shape models determined from Dawn's framing camera constrain models of the interior from the core to the crust. The gravity field is determined jointly with the spin pole location. The second degree harmonics together with assumptions on obliquity or hydrostatic equilibrium may determine the moments of inertia.

Causality constraints on corrections to the graviton three-point coupling

DOE PAGES

Camanho, Xián O.; Edelstein, José D.; Maldacena, Juan; ...

2016-02-03

In this paper, we consider higher derivative corrections to the graviton three-point coupling within a weakly coupled theory of gravity. Lorentz invariance allows further structures beyond the one present in the Einstein theory. We argue that these are constrained by causality. We devise a thought experiment involving a high energy scattering process which leads to causality violation if the graviton three-point vertex contains the additional structures. This violation cannot be fixed by adding conventional particles with spins J ≤ 2. But, it can be fixed by adding an in finite tower of extra massive particles with higher spins, J > 2. In AdS theories this implies a constraint on the conformal anomaly coefficients |more » $$\\frac{a-c}{c}$$|≲ $$\\frac{1}{2}$$ $${^Δ}_{gap}$$ in terms of Δgap, the dimension of the lightest single trace operator with spin J > 2. Lastly, for inflation, or de Sitter-like solutions, it indicates the existence of massive higher spin particles if the gravity wave non-gaussianity deviates significantly from the one computed in the Einstein theory.« less

Polarizations of gravitational waves in Horndeski theory

NASA Astrophysics Data System (ADS)

Hou, Shaoqi; Gong, Yungui; Liu, Yunqi

2018-05-01

We analyze the polarization content of gravitational waves in Horndeski theory. Besides the familiar plus and cross polarizations in Einstein's General Relativity, there is one more polarization state which is the mixture of the transverse breathing and longitudinal polarizations. The additional mode is excited by the massive scalar field. In the massless limit, the longitudinal polarization disappears, while the breathing one persists. The upper bound on the graviton mass severely constrains the amplitude of the longitudinal polarization, which makes its detection highly unlikely by the ground-based or space-borne interferometers in the near future. However, pulsar timing arrays might be able to detect the polarization excited by the massive scalar field. Since additional polarization states appear in alternative theories of gravity, the measurement of the polarizations of gravitational waves can be used to probe the nature of gravity. In addition to the plus and cross states, the detection of the breathing polarization means that gravitation is mediated by massless spin 2 and spin 0 fields, and the detection of both the breathing and longitudinal states means that gravitation is propagated by the massless spin 2 and massive spin 0 fields.

Numerical simulation of the helium gas spin-up channel performance of the relativity gyroscope

NASA Technical Reports Server (NTRS)

Karr, Gerald R.; Edgell, Josephine; Zhang, Burt X.

1991-01-01

The dependence of the spin-up system efficiency on each geometrical parameter of the spin-up channel and the exhaust passage of the Gravity Probe-B (GPB) is individually investigated. The spin-up model is coded into a computer program which simulates the spin-up process. Numerical results reveal optimal combinations of the geometrical parameters for the ultimate spin-up performance. Comparisons are also made between the numerical results and experimental data. The experimental leakage rate can only be reached when the gap between the channel lip and the rotor surface increases beyond physical limit. The computed rotating frequency is roughly twice as high as the measured ones although the spin-up torques fairly match.

A gauge-theoretic approach to gravity

PubMed Central

Krasnov, Kirill

2012-01-01

Einstein's general relativity (GR) is a dynamical theory of the space–time metric. We describe an approach in which GR becomes an SU(2) gauge theory. We start at the linearized level and show how a gauge-theoretic Lagrangian for non-interacting massless spin two particles (gravitons) takes a much more simple and compact form than in the standard metric description. Moreover, in contrast to the GR situation, the gauge theory Lagrangian is convex. We then proceed with a formulation of the full nonlinear theory. The equivalence to the metric-based GR holds only at the level of solutions of the field equations, that is, on-shell. The gauge-theoretic approach also makes it clear that GR is not the only interacting theory of massless spin two particles, in spite of the GR uniqueness theorems available in the metric description. Thus, there is an infinite-parameter class of gravity theories all describing just two propagating polarizations of the graviton. We describe how matter can be coupled to gravity in this formulation and, in particular, how both the gravity and Yang–Mills arise as sectors of a general diffeomorphism-invariant gauge theory. We finish by outlining a possible scenario of the ultraviolet completion of quantum gravity within this approach. PMID:22792040

Comparing T-odd and T-even spin sum rules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teryaev, O.V.

2015-04-10

Sum rules for T-even and T-odd structure functions and parton distributions are considered. The case of spin-dependent distributions related to energy-momentum tensor (EMT) is specifically addressed. The Burkardt sum rule for T-odd Sivers functions may be related to EMT provided the imaginary prescription for gluonic pole correlator is incorporated. The momentum sum rule for deuteron tensor spin structure function allows one to probe indirectly the gravity couplings to quarks and gluons.

Radar-derived asteroid shapes point to a 'zone of stability' for topography slopes and surface erosion rates

NASA Astrophysics Data System (ADS)

Richardson, J.; Graves, K.; Bowling, T.

2014-07-01

Previous studies of the combined effects of asteroid shape, spin, and self-gravity have focused primarily upon the failure limits for bodies with a variety of standard shapes, friction, and cohesion values [1,2,3]. In this study, we look in the opposite direction and utilize 22 asteroid shape-models derived from radar inversion [4] and 7 small body shape-models derived from spacecraft observations [5] to investigate the region in shape/spin space [1,2] wherein self-gravity and rotation combine to produce a stable minimum state with respect to surface potential differences, dynamic topography, slope magnitudes, and erosion rates. This erosional minimum state is self-correcting, such that changes in the body's rotation rate, either up or down, will increase slope magnitudes across the body, thereby driving up erosion rates non-linearly until the body has once again reached a stable, minimized surface state [5]. We investigated this phenomenon in a systematic fashion using a series of synthesized, increasingly prolate spheroid shape models. Adjusting the rotation rate of each synthetic shape to minimize surface potential differences, dynamic topography, and slope magnitudes results in the magenta curve of the figure (right side), defining the zone of maximum surface stability (MSS). This MSS zone is invariant both with respect to body size (gravitational potential and rotational potential scale together with radius), and density when the scaled-spin of [2] is used. Within our sample of observationally derived small-body shape models, slow rotators (Group A: blue points), that are not in the maximum surface stability (MSS) zone and where gravity dominates the slopes, will generally experience moderate erosion rates (left plot) and will tend to move up and to the right in shape/spin space as the body evolves (right plot). Fast rotators (Group C: red points), that are not in the MSS zone and where spin dominates the slopes, will generally experience high erosion rates (left plot) and will tend to move down and to the left in shape/spin space as the body evolves (right plot), barring other influences such as YORP spin-up [6]. Moderate rotators (Group B: green points) have slopes that are influenced equally by gravity and spin, lie in or near the self-correcting MSS zone (right plot), and will generally experience the lowest erosion rates (left plot). These objects comprise 12 (43%) of the 28 bodies studied, perhaps indicating some prevalence for the MSS zone. On the other hand, a sample of 1300 asteroid shape and spin parameters (small grey points), derived from asteroid lightcurve data [7], do not show this same degree of correlation, perhaps indicating the relative weakness of erosion-driven shape modification as compared to other influences. We will continue to investigate this phenomenon as the number of detailed shape models from ground-based radar and other observations continues to increase.

Lagrangian approach to the Barrett-Crane spin foam model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonzom, Valentin; Laboratoire de Physique, ENS Lyon, CNRS UMR 5672, 46 Allee d'Italie, 69007 Lyon; Livine, Etera R.

2009-03-15

We provide the Barrett-Crane spin foam model for quantum gravity with a discrete action principle, consisting in the usual BF term with discretized simplicity constraints which in the continuum turn topological BF theory into gravity. The setting is the same as usually considered in the literature: space-time is cut into 4-simplices, the connection describes how to glue these 4-simplices together and the action is a sum of terms depending on the holonomies around each triangle. We impose the discretized simplicity constraints on disjoint tetrahedra and we show how the Lagrange multipliers distort the parallel transport and the correlations between neighboringmore » simplices. We then construct the discretized BF action using a noncommutative * product between SU(2) plane waves. We show how this naturally leads to the Barrett-Crane model. This clears up the geometrical meaning of the model. We discuss the natural generalization of this action principle and the spin foam models it leads to. We show how the recently introduced spin foam fusion coefficients emerge with a nontrivial measure. In particular, we recover the Engle-Pereira-Rovelli spin foam model by weakening the discretized simplicity constraints. Finally, we identify the two sectors of Plebanski's theory and we give the analog of the Barrett-Crane model in the nongeometric sector.« less

A status report on NASA general aviation stall/spin flight testing

NASA Technical Reports Server (NTRS)

Patton, J. M., Jr.

1980-01-01

The NASA Langley Research Center has undertaken a comprehensive program involving spin tunnel, static and rotary balance wind tunnel, full-scale wind tunnel, free flight radio control model, flight simulation, and full-scale testing. Work underway includes aerodynamic definition of various configurations at high angles of attack, testing of stall and spin prevention concepts, definition of spin and spin recovery characteristics, and development of test techniques and emergency spin recovery systems. This paper presents some interesting results to date for the first aircraft (low-wing, single-engine) in the program, in the areas of tail design, wing leading edge design, mass distribution, center of gravity location, and small airframe changes, with associated pilot observations. The design philosophy of the spin recovery parachute system is discussed in addition to test techniques.

Guidance and Control of a Man-Portable Precision Munition Concept

DTIC Science & Technology

2014-06-01

challenges posed by characteristics of spin-stabilized flight dynamics such as limit cycles, center -of- gravity swerve, instability, and practical...Control Line-of-sight rate and closing velocity estimates are used to form proportional navigation commands in classical guidance schemes...Accelerometers and gyroscopes often supply additional necessary feedback. The accelerometers ensure that the airframe is maneuvering the center of gravity

Aspects of Higher Spin Symmetry and its Breaking

NASA Astrophysics Data System (ADS)

Zhiboedov, Alexander

This thesis explores different aspects of higher spin symmetry and its breaking in the context of Quantum Field Theory, AdS/CFT and String Theory. In chapter 2, we study the constraints imposed by the existence of a single higher spin conserved current on a three-dimensional conformal field theory (CFT). A single higher spin conserved current implies the existence of an infinite number of higher spin conserved currents. The correlation functions of the stress tensor and the conserved currents are then shown to be equal to those of a free field theory. Namely a theory of N free bosons or free fermions. This is an extension of the Coleman-Mandula theorem to CFT's, which do not have a conventional S-matrix. In chapter 3, we consider three-dimensional conformal field theories that have a higher spin symmetry that is slightly broken. The theories have a large N limit, in the sense that the operators separate into single-trace and multi-trace and obey the usual large N factorization properties. We assume that the only single trace operators are the higher spin currents plus an additional scalar. Using the slightly broken higher spin symmetry we constrain the three-point functions of the theories to leading order in N. We show that there are two families of solutions. One family can be realized as a theory of N fermions with an O( N) Chern-Simons gauge field, the other as a N bosons plus the Chern-Simons gauge field. In chapter 4, we consider several aspects of unitary higher-dimensional conformal field theories. We investigate the dimensions of spinning operators via the crossing equations in the light-cone limit. We find that, in a sense, CFTs become free at large spin and 1/s is a weak coupling parameter. The spectrum of CFTs enjoys additivity: if two twists tau 1, tau2 appear in the spectrum, there are operators whose twists are arbitrarily close to tau1 + tau2. We characterize how tau1 + tau2 is approached at large spin by solving the crossing equations analytically. Applications include the 3d Ising model, theories with a gravity dual, SCFTs, and patterns of higher spin symmetry breaking. In chapter 5, we consider higher derivative corrections to the graviton three-point coupling within a weakly coupled theory of gravity. We devise a thought experiment involving a high energy scattering process which leads to causality violation if the graviton three-point vertex contains the additional structures. This violation cannot be fixed by adding conventional particles with spins J ≤ 2. But, it can be fixed by adding an infinite tower of extra massive particles with higher spins, J > 2. In AdS theories this implies a constraint on the conformal anomaly coefficients (a-c)/c lesssim 1/Delta gap2 in terms of Deltagap, the dimension of the lightest single particle operator with spin J > 2. For inflation, or de Sitter-like solutions, it indicates the existence of massive higher spin particles if the gravity wave non-gaussianity deviates significantly from the one computed in the Einstein theory.

Constraining torsion with Gravity Probe B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao Yi; Guth, Alan H.; Cabi, Serkan

2007-11-15

It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) suchmore » as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein's general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.« less

FRW and domain walls in higher spin gravity

NASA Astrophysics Data System (ADS)

Aros, R.; Iazeolla, C.; Noreña, J.; Sezgin, E.; Sundell, P.; Yin, Y.

2018-03-01

We present exact solutions to Vasiliev's bosonic higher spin gravity equations in four dimensions with positive and negative cosmological constant that admit an interpretation in terms of domain walls, quasi-instantons and Friedman-Robertson-Walker (FRW) backgrounds. Their isometry algebras are infinite dimensional higher-spin extensions of spacetime isometries generated by six Killing vectors. The solutions presented are obtained by using a method of holomorphic factorization in noncommutative twistor space and gauge functions. In interpreting the solutions in terms of Fronsdal-type fields in space-time, a field-dependent higher spin transformation is required, which is implemented at leading order. To this order, the scalar field solves Klein-Gordon equation with conformal mass in ( A) dS 4 . We interpret the FRW solution with de Sitter asymptotics in the context of inflationary cosmology and we expect that the domain wall and FRW solutions are associated with spontaneously broken scaling symmetries in their holographic description. We observe that the factorization method provides a convenient framework for setting up a perturbation theory around the exact solutions, and we propose that the nonlinear completion of particle excitations over FRW and domain wall solutions requires black hole-like states.

Generalized group field theories and quantum gravity transition amplitudes

NASA Astrophysics Data System (ADS)

Oriti, Daniele

2006-03-01

We construct a generalized formalism for group field theories, in which the domain of the field is extended to include additional proper time variables, as well as their conjugate mass variables. This formalism allows for different types of quantum gravity transition amplitudes in perturbative expansion, and we show how both causal spin foam models and the usual a-causal ones can be derived from it, within a sum over triangulations of all topologies. We also highlight the relation of the so-derived causal transition amplitudes with simplicial gravity actions.

Stars Can't Spin Out of Control (Artist's Animation)

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Click on the image for QuickTime Movie of Stars Can't Spin Out of Control

This artist's animation demonstrates how a dusty planet-forming disk can slow down a whirling young star, essentially saving the star from spinning itself to death. Evidence for this phenomenon comes from NASA's Spitzer Space Telescope.

The movie begins by showing a developing star (red ball). The star is basically a giant ball of gas that is collapsing onto itself. As it shrinks, it spins faster and faster, like a skater folding in his or her arms. The green lines represent magnetic fields.

As gravity continues to pull matter inward, the star spins so fast, it starts to flatten out. The same principle applies to the planet Saturn, whose spin has caused it to be slightly squashed or oblate.

A forming star can theoretically whip around fast enough to overcome gravity and flatten itself into a state where it can no longer become a full-fledged star. But stars don't spin out of control, possibly because swirling disks of dust slow them down. Such disks can be found orbiting young stars, and are filled with dust that might ultimately stick together to form planets.

The second half of the animation demonstrates how a disk is thought to keep its star's speed in check. A developing star is shown twirling inside its disk. As it turns, its magnetic fields pass through the disk and get bogged down like a spoon in molasses. This locks the star's rotation to the slower-turning disk, so the star, while continuing to shrink, does not spin faster.

Spitzer found evidence for star-slowing disks in a survey of nearly 500 forming stars in the Orion nebula. It observed that slowly spinning stars are five times more likely to host disks than rapidly spinning stars.

Flight investigation of the effect of tail configuration on stall, spin, and recovery characteristics of a low-wing general aviation research airplane

NASA Technical Reports Server (NTRS)

Stough, H. Paul, III; Patton, James M., Jr.; Sliwa, Steven M.

1987-01-01

Flight tests were performed to investigate the stall, spin, and recovery characteristics of a low-wing, single-engine, light airplane with four interchangeable tail configurations. The four tail configurations were evaluated for effects of varying mass distribution, center-of-gravity position, and control inputs. The airplane tended to roll-off at the stall. Variations in tail configuration produced spins ranging from 40 deg to 60 deg angle of attack and turn rates of about 145 to 208 deg/sec. Some unrecoverable flat spins were encountered which required use of the airplane spin chute for recovery. For recoverable spins, antispin rudder followed by forward wheel with ailerons centered provided the quickest spin recovery. The moderate spin modes agreed very well with those predicted from spin-tunnel model tests, however, the flat spin was at a lower angle of attack and a slower rotation rate than indicated by the model tests.

Artificial Gravity as a Multi-System Countermeasure to Bed Rest Deconditioning: Preliminary Results

NASA Technical Reports Server (NTRS)

Warren, L. E.; Paloski, William H.; Young, L. R.

2006-01-01

Artificial gravity paradigms may offer effective, efficient, multi-system protection from the untoward effects of adaptation to the microgravity of space or the hypogravity of planetary surfaces. Intermittent artificial gravity (AG) produced by a horizontal short-radius centrifuge (SRC) has recently been utilized on human test subjects deconditioned by bed rest. This presentation will review preliminary results of a 41 day study conducted at the University of Texas Medical Branch, Galveston, TX bed rest facility. During the first eleven days of the protocol, subjects were ambulatory, but confined to the facility. They began a carefully controlled diet, and participated in multiple baseline tests of bone, muscle, cardiovascular, sensory-motor, immunological, and psychological function. On the twelfth day, subjects entered the bed rest phase of the study, during which they were confined to strict 6deg head down tilt bed rest for 21 days. Beginning 24 hrs into this period, treatment subjects received one hour daily exposures to artificial gravity which was produced by spinning the subjects on a 3.0 m radius SRC. They were oriented radially in the supine position so that the centrifugal force was aligned with their long body axis, and while spinning, they "stood" on a force plate, supporting the centrifugal loading (2.5 g at the feet, 1.0 g at the heart). The subject station allowed free translation over approximately 10 cm to ensure full loading of the lower extremities and to allow for anti-orthostatic muscle contractions. Control subjects were positioned on the centrifuge but did not spin. Following the bed rest phase, subjects were allowed to ambulate again, but remained within the facility for an additional 9 days and participated in multiple follow-up tests of physiological function.

What stellar orbit is needed to measure the spin of the Galactic centre black hole from astrometric data?

NASA Astrophysics Data System (ADS)

Waisberg, Idel; Dexter, Jason; Gillessen, Stefan; Pfuhl, Oliver; Eisenhauer, Frank; Plewa, Phillip M.; Bauböck, Michi; Jimenez-Rosales, Alejandra; Habibi, Maryam; Ott, Thomas; von Fellenberg, Sebastiano; Gao, Feng; Widmann, Felix; Genzel, Reinhard

2018-05-01

Astrometric and spectroscopic monitoring of individual stars orbiting the supermassive black hole in the Galactic Center offer a promising way to detect general relativistic effects. While low-order effects are expected to be detected following the periastron passage of S2 in Spring 2018, detecting higher order effects due to black hole spin will require the discovery of closer stars. In this paper, we set out to determine the requirements such a star would have to satisfy to allow the detection of black hole spin. We focus on the instrument GRAVITY, which saw first light in 2016 and which is expected to achieve astrometric accuracies 10-100 μas. For an observing campaign with duration T years, total observations Nobs, astrometric precision σx, and normalized black hole spin χ, we find that a_orb(1-e^2)^{3/4} ≲ 300 R_S √{T/4 {yr}} (N_obs/120)^{0.25} √{10 μ as/σ _x} √{χ /0.9} is needed. For χ = 0.9 and a potential observing campaign with σ _x = 10 μas, 30 observations yr-1 and duration 4-10 yr, we expect ˜0.1 star with K < 19 satisfying this constraint based on the current knowledge about the stellar population in the central 1 arcsec. We also propose a method through which GRAVITY could potentially measure radial velocities with precision ˜50 km s-1. If the astrometric precision can be maintained, adding radial velocity information increases the expected number of stars by roughly a factor of 2. While we focus on GRAVITY, the results can also be scaled to parameters relevant for future extremely large telescopes.

The Holst spin foam model via cubulations

NASA Astrophysics Data System (ADS)

Baratin, Aristide; Flori, Cecilia; Thiemann, Thomas

2012-10-01

Spin foam models are an attempt at a covariant or path integral formulation of canonical loop quantum gravity. The construction of such models usually relies on the Plebanski formulation of general relativity as a constrained BF theory and is based on the discretization of the action on a simplicial triangulation, which may be viewed as an ultraviolet regulator. The triangulation dependence can be removed by means of group field theory techniques, which allows one to sum over all triangulations. The main tasks for these models are the correct quantum implementation of the Plebanski constraints, the existence of a semiclassical sector implementing additional ‘Regge-like’ constraints arising from simplicial triangulations and the definition of the physical inner product of loop quantum gravity via group field theory. Here we propose a new approach to tackle these issues stemming directly from the Holst action for general relativity, which is also a proper starting point for canonical loop quantum gravity. The discretization is performed by means of a ‘cubulation’ of the manifold rather than a triangulation. We give a direct interpretation of the resulting spin foam model as a generating functional for the n-point functions on the physical Hilbert space at finite regulator. This paper focuses on ideas and tasks to be performed before the model can be taken seriously. However, our analysis reveals some interesting features of this model: firstly, the structure of its amplitudes differs from the standard spin foam models. Secondly, the tetrad n-point functions admit a ‘Wick-like’ structure. Thirdly, the restriction to simple representations does not automatically occur—unless one makes use of the time gauge, just as in the classical theory.

Flight investigation of the effects of an outboard wing-leading-edge modification on stall/spin characteristics of a low-wing, single-engine, T-tail light airplane

NASA Technical Reports Server (NTRS)

Stough, H. Paul, III; Dicarlo, Daniel J.; Patton, James M., Jr.

1987-01-01

Flight tests were performed to investigate the change in stall/spin characteristics due to the addition of an outboard wing-leading-edge modification to a four-place, low-wing, single-engine, T-tail, general aviation research airplane. Stalls and attempted spins were performed for various weights, center of gravity positions, power settings, flap deflections, and landing-gear positions. Both stall behavior and wind resistance were improved compared with the baseline airplane. The latter would readily spin for all combinations of power settings, flap deflections, and aileron inputs, but the modified airplane did not spin at idle power or with flaps extended. With maximum power and flaps retracted, the modified airplane did enter spins with abused loadings or for certain combinations of maneuver and control input. The modified airplane tended to spin at a higher angle of attack than the baseline airplane.

Effects of artificial gravity on the cardiovascular system: Computational approach

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Loop Quantum Gravity and the Meaning of Diffeomorphism Invariance

NASA Astrophysics Data System (ADS)

Rovelli, Carlo; Gaul, Marcus

This series of lectures gives an introduction to the non-perturbative and background-independent formulation for a quantum theory of gravitation which is called loop quantum gravity . The Hilbert space of kinematical quantum states is constructed and a complete basis of spin network states is introduced. Afterwards an application of the formalism is provided by the spectral analysis of the area operator, which is the quantum analogue of the classical area function. This leads to one of the key results of loop quantum gravity obtained in the last few years: the derivation of the discreteness of the geometry and the computation of the quanta of area. Special importance is attached to the role played by the diffeomorphism group in order to clarify the notion of observability in general relativity - a concept far from being trivial. Finally an outlock onto a possible dynamical extension of the theory is given, leading to a "sum over histories" approach, namely a so-called spin foam model . Throughout the whole lecture great significance is attached to conceptual and interpretational issues.

Static vacuum solutions on curved space-times with torsion

NASA Astrophysics Data System (ADS)

Shabani, Hamid; Ziaie, Amir Hadi

2018-06-01

The Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity naturally extends Einstein’s general relativity (GR) to include intrinsic angular momentum (spin) of matter. The main feature of this theory consists of an algebraic relation between space-time torsion and spin of matter, which indeed deprives the torsion of its dynamical content. The Lagrangian of ECKS gravity is proportional to the Ricci curvature scalar constructed out of a general affine connection so that owing to the influence of matter energy-momentum and spin, curvature and torsion are produced and interact only through the space-time metric. In the absence of spin, the space-time torsion vanishes and the theory reduces to GR. It is however possible to have torsion propagation in vacuum by resorting to a model endowed with a nonminimal coupling between curvature and torsion. In the present work we try to investigate possible effects of the higher order terms that can be constructed from space-time curvature and torsion, as the two basic constituents of Riemann-Cartan geometry. We consider Lagrangians that include fourth-order scalar invariants from curvature and torsion and then investigate the resulting field equations. The solutions that we find show that there could exist, even in vacuum, nontrivial static space-times that admit both black holes and naked singularities.

The earth's C21 and S21 gravity coefficients and the rotation of the core

NASA Technical Reports Server (NTRS)

Wahr, John M.

1987-01-01

Observational results for the earth's C21 and S21 gravity coefficients can be used to constrain the mean equatorial rotation of the core with respect to the mantle. Current satellite gravity solutions suggest the equatorial rotation rate is no larger than 1 x 10 to the -7th times the earth's diurnal spin rate, a limit more than one order of magnitude smaller than the polar rotation rate inferred from the westward drift of the earth's magnetic field. The next generation gravity solutions should improve this constraint by more than one order of magnitude. Implications for the fluid pressure at the core-mantle boundary and for the shape of that boundary are discussed.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-10

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

Weyl and transverse diffeomorphism invariant spin-2 models in D=2+1

NASA Astrophysics Data System (ADS)

Dalmazi, Denis; dos Santos, A. L. R.; Ghosh, Subir; Mendonça, E. L.

2017-09-01

There are two covariant descriptions of massless spin-2 particles in D=3+1 via a symmetric rank-2 tensor: the linearized Einstein-Hilbert (LEH) theory and the Weyl plus transverse diffeomorphism (WTDIFF) invariant model. From the LEH theory one can obtain the linearized new massive gravity (NMG) in D=2+1 via Kaluza-Klein dimensional reduction followed by a dual master action. Here we show that a similar route takes us from the WTDIFF model to a linearized scalar-tensor NMG which belongs to a larger class of consistent spin-0 modifications of NMG. We also show that a traceless master action applied to a parity singlet furnishes two new spin-2 self-dual models. Moreover, we examine the singular replacement h_{μ ν } → h_{μ ν } - η _{μ ν }h/D and prove that it leads to consistent massive spin-2 models in D=2+1. They include linearized versions of unimodular topologically massive gravity (TMG) and unimodular NMG. Although the free part of those unimodular theories are Weyl invariant, we do not expect any improvement in the renormalizability. Both the linearized K-term (in NMG) and the linearized gravitational Chern-Simons term (in TMG) are invariant under longitudinal reparametrizations δ h_{μ ν } = partial _{μ }partial _{ν }ζ , which is not a symmetry of the WTDIFF Einstein-Hilbert term. Therefore, we still have one degree of freedom whose propagator behaves like 1/p^2 for large momentum.

Spacecraft stability and control

NASA Technical Reports Server (NTRS)

Barret, Chris

1992-01-01

The Earth's first artificial satellite, Sputnik 1, slowly tumbled in orbit. The first U.S. satellite, Explorer 1, also tumbled out of control. Today, satellite stability and control has become a higher priority. For a satellite design that is to have a life expectancy of 14 years, appropriate spacecraft flight control systems will be reviewed, stability requirements investigated, and an appropriate flight control system recommended in order to see the design process. Disturbance torques, including aerodynamic, magnetic, gravity gradient, solar, micrometeorite, debris, collision, and internal torques, will be assessed to quantify the disturbance environment so that the required compensating torques can be determined. The control torques, including passive versus active, momentum control, bias momentum, spin stabilization, dual spin, gravity gradient, magnetic, reaction wheels, control moment gyros, inertia augmentation techniques, three-axis control, and reaction control systems (RCSs), will be considered. Conditions for stability will also be considered.

Some results on a black hole with a global monopole in Poincaré gravity

NASA Astrophysics Data System (ADS)

Bezerra, Valdir B.; Ferreira, Cristine N.; Alvarenga, Elton P. J.

2018-06-01

The aim of this work is to study the thermodynamics and spin current of a system corresponding to a black hole containing a global monopole in the context of Poincaré gravity theory which is an extension of general relativity, in the sense that the intrinsic angular momentum of matter is also a source of gravitational interaction. Thus, in this work we find the solution corresponding to the spacetime under consideration by taking into account that the action which describes this system contains terms corresponding to the curvature and torsion. The metric obtained is a function of mass, solid angle deficit and the coupling constants of the quadratic terms of the curvature and torsion. In this model, the stability of the system is studied through the analysis of the Hawking temperature and the specific heat. In this context it was also studied the critical temperatures of the system considering positive or negative cosmological constant. In the vicinity of the black hole with a global monopole, where there is a logarithmic correction due to the relationship between the torsion and curvature fields, some analysis were done. We also study the AdS/dS limit where the black hole is analyzed from the topological point of view. Although the effect of spin current density at low energies is negligible, in the vicinity of strong gravitational fields it can generate an appreciable effect due to spin gravity coupling.

Non-existence of rest-frame spin-eigenstate spinors in their own electrodynamics

NASA Astrophysics Data System (ADS)

Fabbri, Luca; da Rocha, Roldão

2018-05-01

We assume a physical situation where gravity with torsion is neglected for an electrodynamically self-interacting spinor that will be taken in its rest-frame and spin-eigenstate: we demonstrate that under this circumstance no solution exists for the system of field equations. Despite such a situation might look artificial nevertheless it represents the instance that is commonly taken as the basis for all computations of quantum electrodynamics.

That gravity thing

NASA Astrophysics Data System (ADS)

Jewess, Mike

2009-05-01

Your news article "New probe plots Earth's gravity field" (March p11) reports on the European Space Agency's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) - a satellite that will measure the Earth's gravitational field. It describes the way that g, the acceleration of free fall at the Earth's surface, varies with latitude; this variation is great enough to require adjustment of pendulum clocks between latitudes and also the recalibration of all balances that do not directly compare one mass with a reference mass. The article also notes that the spin of the (effectively fluid) Earth causes it to bulge at the equator, a realization that goes back to Newton's Principia.

Gravity Probe B

NASA Image and Video Library

2003-07-12

At Vandenberg AFB, the canister enclosing the Gravity Probe B (GP-B) spacecraft is removed from the transporter. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-12

The Gravity Probe B experiment enters the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Neutron stars structure in the context of massive gravity

NASA Astrophysics Data System (ADS)

Hendi, S. H.; Bordbar, G. H.; Eslam Panah, B.; Panahiyan, S.

2017-07-01

Motivated by the recent interests in spin-2 massive gravitons, we study the structure of neutron star in the context of massive gravity. The modifications of TOV equation in the presence of massive gravity are explored in 4 and higher dimensions. Next, by considering the modern equation of state for the neutron star matter (which is extracted by the lowest order constrained variational (LOCV) method with the AV18 potential), different physical properties of the neutron star (such as Le Chatelier's principle, stability and energy conditions) are investigated. It is shown that consideration of the massive gravity has specific contributions into the structure of neutron star and introduces new prescriptions for the massive astrophysical objects. The mass-radius relation is examined and the effects of massive gravity on the Schwarzschild radius, average density, compactness, gravitational redshift and dynamical stability are studied. Finally, a relation between mass and radius of neutron star versus the Planck mass is extracted.

Teleparallel theories of gravity as analogue of nonlinear electrodynamics

NASA Astrophysics Data System (ADS)

Hohmann, Manuel; Järv, Laur; Krššák, Martin; Pfeifer, Christian

2018-05-01

The teleparallel formulation of gravity theories reveals close structural analogies to electrodynamics, which are more hidden in their usual formulation in terms of the curvature of spacetime. We show how every locally Lorentz invariant teleparallel theory of gravity with second-order field equations can be understood as built from a gravitational field strength and excitation tensor which are related to each other by a constitutive relation, analogous to the premetric construction of theories of electrodynamics. We demonstrate how the previously studied models of f (T ) and f (Tax,Tten,Tvec) gravity as well as teleparallel dark energy can be formulated in this language. The advantage of this approach to gravity is that the field equations for different models all take the same compact form and general results can be obtained. An important new such result we find is a constraint which relates the field equations of the tetrad and the spin connection.

History of Artificial Gravity. Chapter 3

NASA Technical Reports Server (NTRS)

Clement, Gilles; Bukley, Angie; Paloski, William

2006-01-01

This chapter reviews the past and current projects on artificial gravity during space missions. The idea of a rotating wheel-like space station providing artificial gravity goes back in the writings of Tsiolkovsky, Noordung, and Wernher von Braun. Its most famous fictional representation is in the film 2001: A Space Odyssey, which also depicts spin-generated artificial gravity aboard a space station and a spaceship bound for Jupiter. The O Neill-type space colony provides another classic illustration of this technique. A more realistic approach to rotating the space station is to provide astronauts with a smaller centrifuge contained within a spacecraft. The astronauts would go into it for a workout, and get their gravity therapeutic dose for a certain period of time, daily or a few times a week. This simpler concept is current being tested during ground-based studies in several laboratories around the world.

Modified gravity (MOG), the speed of gravitational radiation and the event GW170817/GRB170817A

NASA Astrophysics Data System (ADS)

Green, M. A.; Moffat, J. W.; Toth, V. T.

2018-05-01

Modified gravity (MOG) is a covariant, relativistic, alternative gravitational theory whose field equations are derived from an action that supplements the spacetime metric tensor with vector and scalar fields. Both gravitational (spin 2) and electromagnetic waves travel on null geodesics of the theory's one metric. MOG satisfies the weak equivalence principle and is consistent with observations of the neutron star merger and gamma ray burster event GW170817/GRB170817A.

KSC-2012-3641

NASA Image and Video Library

2012-07-02

CAPE CANAVERAL, Fla. – From left, U.S. Senator Bill Nelson, NASA project engineer Trent Smith and NASA astronaut Nicole Stott share a moment of levity in Kennedy Space Center's Operations and Checkout Building high bay following an event marking the arrival of NASA's first space-bound Orion capsule in Florida. Slated for Exploration Flight Test-1, an uncrewed mission planned for 2014, the capsule will travel farther into space than any human spacecraft has gone in more than 40 years. The capsule was shipped to Kennedy from NASA's Michoud Assembly Facility in New Orleans where the crew module pressure vessel was built. The Orion production team will prepare the module for flight at Kennedy by installing heat-shielding thermal protection systems, avionics and other subsystems. For more information, visit http://www.nasa.gov/orion. Photo credit: NASA/Kim Shiflett

Microwave ac Zeeman force for ultracold atoms

NASA Astrophysics Data System (ADS)

Fancher, C. T.; Pyle, A. J.; Rotunno, A. P.; Aubin, S.

2018-04-01

We measure the ac Zeeman force on an ultracold gas of 87Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple two-level theory for the ac Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed-atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We demonstrate the practical spin selectivity of the force by pushing or pulling a specific spin state while leaving other spin states unmoved.

Constraints on higher spin CFT2

NASA Astrophysics Data System (ADS)

Afkhami-Jeddi, Nima; Colville, Kale; Hartman, Thomas; Maloney, Alexander; Perlmutter, Eric

2018-05-01

We derive constraints on two-dimensional conformal field theories with higher spin symmetry due to unitarity, modular invariance, and causality. We focus on CFTs with W_N symmetry in the "irrational" regime, where c > N - 1 and the theories have an infinite number of higher-spin primaries. The most powerful constraints come from positivity of the Kac matrix, which (unlike the Virasoro case) is non-trivial even when c > N - 1. This places a lower bound on the dimension of any non-vacuum higher-spin primary state, which is linear in the central charge. At large c, this implies that the dual holographic theories of gravity in AdS3, if they exist, have no local, perturbative degrees of freedom in the semi-classical limit.

Loop Quantum Gravity.

PubMed

Rovelli, Carlo

2008-01-01

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

The role and behavior of spin in gravitational physics

NASA Technical Reports Server (NTRS)

Ray, John R.

1987-01-01

A self-consistent method of introducing spin into any Lagrangian based theory of gravitation was developed. The metric variation of the Lagrangian in the theory leads to an improved energy-momentum tensor which represents the source term in the gravitational field equations. The goal of the research is the construction of a theory general enough to be used to investigate spin effects in astrophysical objects and cosmology, and also to serve as a basis for discussion of the theoretical ideas tested by the NASA Gyroscope Experiment (aboard Gravity Probe B). Specific accomplishments in the following areas are summarized: the inclusion of electromagnetism into the variational principle for spinning matter, formulation of a self-consistent theory for the case of a fluid in which particle production processes occur, and the derivation of the Raychaudhuri equation in the case of spinning matter.

Effects of several factors on theoretical predictions of airplane spin characteristics. [dynamic models

NASA Technical Reports Server (NTRS)

Bihrle, W., Jr.; Barnhart, B.

1974-01-01

The influence of different mathematical and aerodynamic models on computed spin motion was investigated along with the importance of some of the aerodynamic and nonaerodynamic quantities defined in these models. An analytical technique was used which included the aerodynamic forces and moments acting on a spinning aircraft due to steady rotational flow and the contribution of the rotary derivatives to the oscillatory component of the total angular rates. It was shown that (1) during experimental-analytical correlation studies, the flight-recorded control time histories must be faithfully duplicated since the spinning motion can be sensitive to a small change in the application of the spin entry controls; (2) an error in the assumed inertias, yawing moments at high angle of attack, and initial spin entry bank angle do not influence the developed spin significantly; (3) damping in pitch derivatives and the center of gravity location play a role in the spinning motion; and (4) the experimental spin investigations conducted in a constant atmospheric density environment duplicate the Froude number only at the initial full-scale spin altitude (since the full-scale airplane at high altitudes experiences large density changes during the spin.)

Emergent gravity from vanishing energy-momentum tensor

DOE PAGES

Carone, Christopher D.; Erlich, Joshua; Vaman, Diana

2017-03-27

A constraint of vanishing energy-momentum tensor is motivated by a variety of perspectives on quantum gravity. We demonstrate in a concrete example how this constraint leads to a metric-independent theory in which quantum gravity emerges as a nonperturbative artifact of regularization-scale physics. We analyze a scalar theory similar to the Dirac-Born-Infeld (DBI) theory with vanishing gauge fields, with the DBI Lagrangian modulated by a scalar potential. In the limit of a large number of scalars, we explicitly demonstrate the existence of a composite massless spin-2 graviton in the spectrum that couples to matter as in Einstein gravity. As a result,more » we comment on the cosmological constant problem and the generalization to theories with fermions and gauge fields.« less

Evaporation Spectrum of Black Holes from a Local Quantum Gravity Perspective.

PubMed

Barrau, Aurélien

2016-12-30

We revisit the hypothesis of a possible line structure in the Hawking evaporation spectrum of black holes. Because of nonperturbative quantum gravity effects, this would take place arbitrarily far away from the Planck mass. We show, based on a speculative but consistent hypothesis, that this naive prediction might in fact hold in the specific context of loop quantum gravity. A small departure from the ideal case is expected for some low-spin transitions and could allow us to distinguish several quantum gravity models. We also show that the effect is not washed out by the dynamics of the process, by the existence of a mass spectrum up to a given width, or by the secondary component induced by the decay of neutral pions emitted during the time-integrated evaporation.

Entanglement entropy and correlations in loop quantum gravity

NASA Astrophysics Data System (ADS)

Feller, Alexandre; Livine, Etera R.

2018-02-01

Black hole entropy is one of the few windows into the quantum aspects of gravitation, and its study over the years has highlighted the holographic nature of gravity. At the non-perturbative level in quantum gravity, promising explanations are being explored in terms of the entanglement entropy between regions of space. In the context of loop quantum gravity, this translates into an analysis of the correlations between the regions of the spin network states defining the quantum state of the geometry of space. In this paper, we explore a class of states, motivated by results in condensed matter physics, satisfying an area law for entanglement entropy and having non-trivial correlations. We highlight that entanglement comes from holonomy operators acting on loops crossing the boundary of the region.

Higher spin Chern-Simons theory and the super Boussinesq hierarchy

NASA Astrophysics Data System (ADS)

Gutperle, Michael; Li, Yi

2018-05-01

In this paper, we construct a map between a solution of supersymmetric Chern-Simons higher spin gravity based on the superalgebra sl(3|2) with Lifshitz scaling and the N = 2 super Boussinesq hierarchy. We show that under this map the time evolution equations of both theories coincide. In addition, we identify the Poisson structure of the Chern-Simons theory induced by gauge transformation with the second Hamiltonian structure of the super Boussinesq hierarchy.

Warped conformal field theory as lower spin gravity

NASA Astrophysics Data System (ADS)

Hofman, Diego M.; Rollier, Blaise

2015-08-01

Two dimensional Warped Conformal Field Theories (WCFTs) may represent the simplest examples of field theories without Lorentz invariance that can be described holographically. As such they constitute a natural window into holography in non-AdS space-times, including the near horizon geometry of generic extremal black holes. It is shown in this paper that WCFTs posses a type of boost symmetry. Using this insight, we discuss how to couple these theories to background geometry. This geometry is not Riemannian. We call it Warped Geometry and it turns out to be a variant of a Newton-Cartan structure with additional scaling symmetries. With this formalism the equivalent of Weyl invariance in these theories is presented and we write two explicit examples of WCFTs. These are free fermionic theories. Lastly we present a systematic description of the holographic duals of WCFTs. It is argued that the minimal setup is not Einstein gravity but an SL (2, R) × U (1) Chern-Simons Theory, which we call Lower Spin Gravity. This point of view makes manifest the definition of boundary for these non-AdS geometries. This case represents the first step towards understanding a fully invariant formalism for WN field theories and their holographic duals.

Estimation of Gravitation Parameters of Saturnian Moons Using Cassini Attitude Control Flight Data

NASA Technical Reports Server (NTRS)

Krening, Samantha C.

2013-01-01

A major science objective of the Cassini mission is to study Saturnian satellites. The gravitational properties of each Saturnian moon is of interest not only to scientists but also to attitude control engineers. When the Cassini spacecraft flies close to a moon, a gravity gradient torque is exerted on the spacecraft due to the mass of the moon. The gravity gradient torque will alter the spin rates of the reaction wheels (RWA). The change of each reaction wheel's spin rate might lead to overspeed issues or operating the wheel bearings in an undesirable boundary lubrication condition. Hence, it is imperative to understand how the gravity gradient torque caused by a moon will affect the reaction wheels in order to protect the health of the hardware. The attitude control telemetry from low-altitude flybys of Saturn's moons can be used to estimate the gravitational parameter of the moon or the distance between the centers of mass of Cassini and the moon. Flight data from several low altitude flybys of three Saturnian moons, Dione, Rhea, and Enceladus, were used to estimate the gravitational parameters of these moons. Results are compared with values given in the literature.

Frame-dragging effect in the field of non rotating body due to unit gravimagnetic moment

NASA Astrophysics Data System (ADS)

Deriglazov, Alexei A.; Ramírez, Walberto Guzmán

2018-04-01

Nonminimal spin-gravity interaction through unit gravimagnetic moment leads to modified Mathisson-Papapetrou-Tulczyjew-Dixon equations with improved behavior in the ultrarelativistic limit. We present exact Hamiltonian of the resulting theory and compute an effective 1/c2-Hamiltonian and leading post-Newtonian corrections to the trajectory and spin. Gravimagnetic moment causes the same precession of spin S as a fictitious rotation of the central body with angular momentum J = M/m S. So the modified equations imply a number of qualitatively new effects, that could be used to test experimentally, whether a rotating body in general relativity has null or unit gravimagnetic moment.

Towards a bulk description of higher spin SYK

NASA Astrophysics Data System (ADS)

González, Hernán A.; Grumiller, Daniel; Salzer, Jakob

2018-05-01

We consider on the bulk side extensions of the Sachdev-Ye-Kitaev (SYK) model to Yang-Mills and higher spins. To this end we study generalizations of the Jackiw-Teitelboim (JT) model in the BF formulation. Our main goal is to obtain generalizations of the Schwarzian action, which we achieve in two ways: by considering the on-shell action supplemented by suitable boundary terms compatible with all symmetries, and by applying the Lee-Wald-Zoupas formalism to analyze the symplectic structure of dilaton gravity. We conclude with a discussion of the entropy (including log-corrections from higher spins) and a holographic dictionary for the generalized SYK/JT correspondence.

Higher spin black holes with soft hair

NASA Astrophysics Data System (ADS)

Grumiller, Daniel; Pérez, Alfredo; Prohazka, Stefan; Tempo, David; Troncoso, Ricardo

2016-10-01

We construct a new set of boundary conditions for higher spin gravity, inspired by a recent "soft Heisenberg hair"-proposal for General Relativity on three-dimensional Anti-de Sitter space. The asymptotic symmetry algebra consists of a set of affine û(1) current algebras. Its associated canonical charges generate higher spin soft hair. We focus first on the spin-3 case and then extend some of our main results to spin- N , many of which resemble the spin-2 results: the generators of the asymptotic W 3 algebra naturally emerge from composite operators of the û(1) charges through a twisted Sugawara construction; our boundary conditions ensure regularity of the Euclidean solutions space independently of the values of the charges; solutions, which we call "higher spin black flowers", are stationary but not necessarily spherically symmetric. Finally, we derive the entropy of higher spin black flowers, and find that for the branch that is continuously connected to the BTZ black hole, it depends only on the affine purely gravitational zero modes. Using our map to W -algebra currents we recover well-known expressions for higher spin entropy. We also address higher spin black flowers in the metric formalism and achieve full consistency with previous results.

Tracking Gravity Probe B gyroscope polhode motion

NASA Technical Reports Server (NTRS)

Keiser, George M.; Parkinson, Bradford W.; Cohen, Clark E.

1990-01-01

The superconducting Gravity Probe B spacecraft is being developed to measure two untested predictions of Einstein's theory of general relativity by using orbiting gyroscopes; it possesses an intrinsic magnetic field which rotates with the rotor and is fixed with respect to the rotor body frame. In this paper, the path of the rotor spin axes is tracked using this trapped magnetic flux as a reference. Both the rotor motion and the magnetic field shape are estimated simultaneously, employing the higher order components of the magnetic field shape.

Space-time philosophy reconstructed via massive Nordström scalar gravities? Laws vs. geometry, conventionality, and underdetermination

NASA Astrophysics Data System (ADS)

Pitts, J. Brian

2016-02-01

What if gravity satisfied the Klein-Gordon equation? Both particle physics from the 1920-30s and the 1890s Neumann-Seeliger modification of Newtonian gravity with exponential decay suggest considering a "graviton mass term" for gravity, which is algebraic in the potential. Unlike Nordström's "massless" theory, massive scalar gravity is strictly special relativistic in the sense of being invariant under the Poincaré group but not the 15-parameter Bateman-Cunningham conformal group. It therefore exhibits the whole of Minkowski space-time structure, albeit only indirectly concerning volumes. Massive scalar gravity is plausible in terms of relativistic field theory, while violating most interesting versions of Einstein's principles of general covariance, general relativity, equivalence, and Mach. Geometry is a poor guide to understanding massive scalar gravity(s): matter sees a conformally flat metric due to universal coupling, but gravity also sees the rest of the flat metric (barely or on long distances) in the mass term. What is the 'true' geometry, one might wonder, in line with Poincaré's modal conventionality argument? Infinitely many theories exhibit this bimetric 'geometry,' all with the total stress-energy's trace as source; thus geometry does not explain the field equations. The irrelevance of the Ehlers-Pirani-Schild construction to a critique of conventionalism becomes evident when multi-geometry theories are contemplated. Much as Seeliger envisaged, the smooth massless limit indicates underdetermination of theories by data between massless and massive scalar gravities-indeed an unconceived alternative. At least one version easily could have been developed before General Relativity; it then would have motivated thinking of Einstein's equations along the lines of Einstein's newly re-appreciated "physical strategy" and particle physics and would have suggested a rivalry from massive spin 2 variants of General Relativity (massless spin 2, Pauli and Fierz found in 1939). The Putnam-Grünbaum debate on conventionality is revisited with an emphasis on the broad modal scope of conventionalist views. Massive scalar gravity thus contributes to a historically plausible rational reconstruction of much of 20th-21st century space-time philosophy in the light of particle physics. An appendix reconsiders the Malament-Weatherall-Manchak conformal restriction of conventionality and constructs the 'universal force' influencing the causal structure. Subsequent works will discuss how massive gravity could have provided a template for a more Kant-friendly space-time theory that would have blocked Moritz Schlick's supposed refutation of synthetic a priori knowledge, and how Einstein's false analogy between the Neumann-Seeliger-Einstein modification of Newtonian gravity and the cosmological constant Λ generated lasting confusion that obscured massive gravity as a conceptual possibility.

Unusual Contact-Line Dynamics of Thick Films and Drops

NASA Technical Reports Server (NTRS)

Veretennikov, Igor; Agarwal, Abhishek; Indeikina, Alexandra; Chang, Hsueh-Chia

1999-01-01

We report several novel phenomena In contact-line and fingering dynamics of macroscopic spinning drops and gravity-driven films with dimensions larger than the capillary length. It is shown through experimental and theoretical analysis that such macroscopic films can exhibit various interfacial shapes, including multi valued ones, near the contact line due to a balance between the external body forces with capillarity. This rich variety of front shapes couples with the usual capillary, viscous, and intermolecular forces at the contact line to produce a rich and unexpected spectrum of contact-line dynamics. A single finger develops when part of the front becomes multivalued on a partially wetting macroscopic spinning drop in contrast to a different mechanism for microscopic drops of completely wetting fluids. Contrary to general expectation, we observe that, at high viscosity and low frequencies of rotation, the speed of a glycerine finger increases with increasing viscosity. Completely wetting Dow Corning 200 Fluid spreads faster over a dry inclined plane than a prewetted one. The presence of a thin prewetted film suppresses fingering both for gravity-driven flow and for spin coating. We analyze some of these unique phenomena in detail and offer qualitative physical explanations for the others.

Modeling of micro thrusters for gravity probe B

NASA Technical Reports Server (NTRS)

Jones, Kenneth M.

1996-01-01

The concept of testing Einstein's general theory of relativity by means of orbiting gyroscopes was first proposed in 1959, which lead to the development of the Gravity Probe B experiment. Einstein's theory concerns the predictions of the relativistic precession of a gyroscope in orbit around earth. According to his theory, there will be two precessions due to the warping of space-time by the earth's gravitational field: the geodetic precession in the plane of the orbit, and the frame-dragging effect, in the direction of earth rotation. For a polar orbit, these components are orthogonal. In order to simplify the measurement of the precessions, Gravity Probe B (GP-B) will be placed in a circular polar orbit at 650 km, for which the predicted precessions will be 6.6 arcsec/year (geodetic) and 42 milli-arcsec/year (frame-dragging). As the gyroscope precesses, the orientation of its spin-axis will be measured with respect to the line-of-sight to Rigel, a star whose proper motion is known to be within the required accuracy. The line-of-sight to Rigel will be established using a telescope, and the orientation of the gyroscope spin axis will be measured using very sensitive SQUID (Superconducting Quantum Interference Device) magnetometers. The four gyroscopes will be coated with niobium. Below 2K, the niobium becomes superconducting and a dipole field will be generated which is precisely aligned with the gyroscope spin-axis. The change in orientation of these fields, as well as the spin-axis, is sensed by the SQUID magnetometers. In order to attain the superconducting temperatures for the gyroscopes and the SQUID's, the experiment package will be housed in a dewar filled with liquid helium. The helium flow through a GP-B micro thruster and into a vacuum is investigated using the Direct Simulation Monte Carlo method.

Testing general relativity's no-hair theorem with x-ray observations of black holes

NASA Astrophysics Data System (ADS)

Hoormann, Janie K.; Beheshtipour, Banafsheh; Krawczynski, Henric

2016-02-01

Despite its success in the weak gravity regime, general relativity (GR) has yet to be verified in the regime of strong gravity. In this paper, we present the results of detailed ray-tracing simulations aiming at clarifying if the combined information from x-ray spectroscopy, timing, and polarization observations of stellar mass and supermassive black holes can be used to test GR's no-hair theorem. The latter states that stationary astrophysical black holes are described by the Kerr family of metrics, with the black hole mass and spin being the only free parameters. We use four "non-Kerr metrics," some phenomenological in nature and others motivated by alternative theories of gravity, and study the observational signatures of deviations from the Kerr metric. Particular attention is given to the case when all the metrics are set to give the same innermost stable circular orbit in quasi-Boyer-Lindquist coordinates. We give a detailed discussion of similarities and differences of the observational signatures predicted for black holes in the Kerr metric and the non-Kerr metrics. We emphasize that even though some regions of the parameter space are nearly degenerate even when combining the information from all observational channels, x-ray observations of very rapidly spinning black holes can be used to exclude large regions of the parameter space of the alternative metrics. Although it proves difficult to distinguish between the Kerr and non-Kerr metrics for some portions of the parameter space, the observations of very rapidly spinning black holes like Cyg X-1 can be used to rule out large regions for several black hole metrics.

Liquid-state nuclear spin comagnetometers.

PubMed

Ledbetter, M P; Pustelny, S; Budker, D; Romalis, M V; Blanchard, J W; Pines, A

2012-06-15

We discuss nuclear spin comagnetometers based on ultralow-field nuclear magnetic resonance in mixtures of miscible solvents, each rich in a different nuclear spin. In one version thereof, Larmor precession of protons and 19F nuclei in a mixture of thermally polarized pentane and hexafluorobenzene is monitored via a sensitive alkali-vapor magnetometer. We realize transverse relaxation times in excess of 20 s and suppression of magnetic field fluctuations by a factor of 3400. We estimate it should be possible to achieve single-shot sensitivity of about 5×10(-9)  Hz, or about 5×10(-11)  Hz in ≈1 day of integration. In a second version, spin precession of protons and 129Xe nuclei in a mixture of pentane and hyperpolarized liquid xenon is monitored using superconducting quantum interference devices. Application to spin-gravity experiments, electric dipole moment experiments, and sensitive gyroscopes is discussed.

Gravity Probe B

NASA Image and Video Library

2003-07-12

The Gravity Probe B experiment rests on an assembly and test stand in the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-12

The Gravity Probe B experiment is lowered onto an assembly and test stand in the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-12

The Gravity Probe B experiment is lifted from its transporter in the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-12

Enclosed in a canister, the Gravity Probe B (GP-B) spacecraft arrives on Vandenberg Air Force Base, headed for the spacecraft processing facility. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-12

A transporter carrying the Gravity Probe B experiment backs into the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Analysis of the partially filled viscous ring damper. [application as nutation damper for spinning satellite

NASA Technical Reports Server (NTRS)

Alfriend, K. T.

1973-01-01

A ring partially filled with a viscous fluid has been analyzed as a nutation damper for a spinning satellite. The fluid has been modelled as a rigid slug of finite length moving in a tube and resisted by a linear viscous force. It is shown that there are two distinct modes of motion, called the spin synchronous mode and the nutation synchronous mode. Time constants for each mode are obtained for both the symmetric and asymmetric satellite. The effects of a stop in the tube and an offset of the ring from the spin axis are also investigated. An analysis of test results is also given including a determination of the effect of gravity on the time constants in the two modes.

Topologically massive gravity and galilean conformal algebra: a study of correlation functions

NASA Astrophysics Data System (ADS)

Bagchi, Arjun

2011-02-01

The Galilean Conformal Algebra (GCA) arises from the conformal algebra in the non-relativistic limit. In two dimensions, one can view it as a limit of linear combinations of the two copies Virasoro algebra. Recently, it has been argued that Topologically Massive Gravity (TMG) realizes the quantum 2d GCA in a particular scaling limit of the gravitational Chern-Simons term. To add strength to this claim, we demonstrate a matching of correlation functions on both sides of this correspondence. A priori looking for spatially dependent correlators seems to force us to deal with high spin operators in the bulk. We get around this difficulty by constructing the non-relativistic Energy-Momentum tensor and considering its correlation functions. On the gravity side, our analysis makes heavy use of recent results of Holographic Renormalization in Topologically Massive Gravity.

Correlation of Experimental and Theoretical Steady-State Spinning Motion for a Current Fighter Airplane Using Rotation-Balance Aerodynamic Data

DTIC Science & Technology

1978-07-01

were input into the computer program. The program was numerically intergrated with time by using a fourth-order Runge-Kutta integration algorithm with...equations of motion are numerically intergrated to provide time histories of the aircraft spinning motion. A.2 EQUATIONS DEFINING THE FORCE AND MOMENT...by Cy or Cn. 50 AE DC-TR-77-126 A . 4 where EQUATIONS FOR TRANSFERRING AERODYNAMIC DATA INPUTS TO THE PROPER HORIZONTAL CENTER OF GRAVITY

String splitting and strong coupling meson decay.

PubMed

Cotrone, A L; Martucci, L; Troost, W

2006-04-14

We study the decay of high spin mesons using the gauge-string theory correspondence. The rate of the process is calculated by studying the splitting of a macroscopic string intersecting a D-brane. The result is applied to the decay of mesons in N=4 super Yang-Mills theory with a small number of flavors and in a gravity dual of large N QCD. In QCD the decay of high spin mesons is found to be heavily suppressed in the regime of validity of the supergravity description.

Straight spinning cosmic strings in Brans-Dicke gravity

NASA Astrophysics Data System (ADS)

Dos Santos, S. Mittmann; da Silva, J. M. Hoff; Cindra, J. L.

2018-03-01

An exact solution of straight spinning cosmic strings in Brans-Dicke theory of gravitation is presented. The possibility of the existence of closed time-like curves around these cosmic strings is analyzed. Furthermore, the stability about the formation of the topological defect discussed here is checked. It is shown that the existence of a suitable choice for the integration constants in which closed time-like curves are not allowed. We also study the (im)possibility of using the obtained spacetime in the rotational curves problem.

Gravity dual of spin and charge density waves

NASA Astrophysics Data System (ADS)

Jokela, Niko; Järvinen, Matti; Lippert, Matthew

2014-12-01

At high enough charge density, the homogeneous state of the D3-D7' model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.

Spin-up of a rapidly rotating star by angular momentum loss - Effects of general relativity

NASA Technical Reports Server (NTRS)

Cook, Gregory B.; Shapiro, Stuart L.; Teukolsky, Saul A.

1992-01-01

It has recently been shown that a rapidly rotating Newtonian star can spin up by radiating angular momentum. Extremely fast pulsars losing energy and angular momentum by magnetic dipole radiation or gravitational radiation may exhibit this behavior. Here, we show that this phenomenon is more widespread for rapidly rotating stars in general relativity. We construct and tabulate polytropic sequences of fully relativistic rotating stars of constant rest mass and entropy. We find that the range of adiabatic indices allowing spin-up extends somewhat above 4/3 because of the nonlinear effects of relativistic gravity. In addition, there is a new class of 'supramassive' stars which will inevitably spin up by losing angular momentum regardless of their equation of state. A supramassive star, spinning up via angular momentum loss, will ultimately evolve until it becomes unstable to catastrophic collapse to a black hole. Spin-up in a rapidly rotating star may thus be an observational precursor to such collapse.

VANDENBERG AFB, CALIF. - Logos identify the mission of this Delta II rocket that will launch the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-12

VANDENBERG AFB, CALIF. - Logos identify the mission of this Delta II rocket that will launch the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers stand by as the balloon at right is released to lift the solar array panel into position for installation on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers stand by as the balloon at right is released to lift the solar array panel into position for installation on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

Does space-time torsion determine the minimum mass of gravitating particles?

NASA Astrophysics Data System (ADS)

Böhmer, Christian G.; Burikham, Piyabut; Harko, Tiberiu; Lake, Matthew J.

2018-03-01

We derive upper and lower limits for the mass-radius ratio of spin-fluid spheres in Einstein-Cartan theory, with matter satisfying a linear barotropic equation of state, and in the presence of a cosmological constant. Adopting a spherically symmetric interior geometry, we obtain the generalized continuity and Tolman-Oppenheimer-Volkoff equations for a Weyssenhoff spin fluid in hydrostatic equilibrium, expressed in terms of the effective mass, density and pressure, all of which contain additional contributions from the spin. The generalized Buchdahl inequality, which remains valid at any point in the interior, is obtained, and general theoretical limits for the maximum and minimum mass-radius ratios are derived. As an application of our results we obtain gravitational red shift bounds for compact spin-fluid objects, which may (in principle) be used for observational tests of Einstein-Cartan theory in an astrophysical context. We also briefly consider applications of the torsion-induced minimum mass to the spin-generalized strong gravity model for baryons/mesons, and show that the existence of quantum spin imposes a lower bound for spinning particles, which almost exactly reproduces the electron mass.

Does space-time torsion determine the minimum mass of gravitating particles?

PubMed

Böhmer, Christian G; Burikham, Piyabut; Harko, Tiberiu; Lake, Matthew J

2018-01-01

We derive upper and lower limits for the mass-radius ratio of spin-fluid spheres in Einstein-Cartan theory, with matter satisfying a linear barotropic equation of state, and in the presence of a cosmological constant. Adopting a spherically symmetric interior geometry, we obtain the generalized continuity and Tolman-Oppenheimer-Volkoff equations for a Weyssenhoff spin fluid in hydrostatic equilibrium, expressed in terms of the effective mass, density and pressure, all of which contain additional contributions from the spin. The generalized Buchdahl inequality, which remains valid at any point in the interior, is obtained, and general theoretical limits for the maximum and minimum mass-radius ratios are derived. As an application of our results we obtain gravitational red shift bounds for compact spin-fluid objects, which may (in principle) be used for observational tests of Einstein-Cartan theory in an astrophysical context. We also briefly consider applications of the torsion-induced minimum mass to the spin-generalized strong gravity model for baryons/mesons, and show that the existence of quantum spin imposes a lower bound for spinning particles, which almost exactly reproduces the electron mass.

Design strategies for the International Space University's variable gravity research facility

NASA Technical Reports Server (NTRS)

Bailey, Sheila G.; Chiaramonte, Francis P.; Davidian, Kenneth J.

1990-01-01

A variable gravity research facility named 'Newton' was designed by 58 students from 13 countries at the International Space University's 1989 summer session at the Universite Louis Pasteur, Strasbourge, France. The project was comprehensive in scope, including a political and legal foundation for international cooperation, development and financing; technical, science and engineering issues; architectural design; plausible schedules; and operations, crew issues and maintenance. Since log-term exposure to zero gravity is known to be harmful to the human body, the main goal was to design a unique variable gravity research facility which would find a practical solution to this problem, permitting a manned mission to Mars. The facility would not duplicate other space-based facilities and would provide the flexibility for examining a number of gravity levels, including lunar and Martian gravities. Major design alternatives included a truss versus a tether based system which also involved the question of docking while spinning or despinning to dock. These design issues are described. The relative advantages or disadvantages are discussed, including comments on the necessary research and technology development required for each.

Prospects for Probing Strong Gravity with a Pulsar-Black Hole System

NASA Technical Reports Server (NTRS)

Wex, N.; Liu, K.; Eatough, R. P.; Kramer, M.; Cordes, J. M.; Lazio, T. J. W.

2012-01-01

The discovery of a pulsar (PSR) in orbit around a black hole (BH) is expected to provide a superb new probe of relativistic gravity and BH properties. Apart from a precise mass measurement for the BH, one could expect a clean verification of the dragging of space-time caused by the BH spin. In order to measure the quadrupole moment of the BH for testing the no-hair theorem of general relativity (GR), one has to hope for a sufficiently massive BH. In this respect, a PSR orbiting the super-massive BH in the center of our Galaxy would be the ultimate laboratory for gravity tests with PSRs. But even for gravity theories that predict the same properties for BHs as GR, a PSR-BH system would constitute an excellent test system, due to the high grade of asymmetry in the strong field properties of these two components. Here we highlight some of the potential gravity tests that one could expect from different PSR-BH systems.

Gravity field and shape of Ceres from Dawn

NASA Astrophysics Data System (ADS)

Park, Ryan; Konopliv, Alexander; Vaughan, Andrew; Bills, Bruce; Castillo-Rogez, Julie; Ermakov, Anton; Fu, Roger; Raymond, Carol; Russell, Chris; Zuber, Maria

2017-04-01

The Dawn gravity science investigation utilizes the DSN radio tracking of the spacecraft and on-board framing camera images to determine the gravity field and global shape of Ceres. The gravity science data collected during Approach, Survey, High-Altitude Mapping Orbit, and Low-Altitude Mapping Orbit phases were processed. The final gravity science solution yielded a degree and order 18 gravity field, called CERES18C, which is globally accurate to degree and order 14. Also, the final Ceres shape using the stereo-photoclinometry method is available with the height uncertainty better than 30 meters. The degree-2 gravity harmonics show that the rotation of Ceres is very nearly about a principal axis. Combining the gravity field and topography gives the bulk density of 2162.6±2.0 kg/m3. The estimated spin pole vector yields RA=(291.42744±0.00022)° and Dec=(66.76065±0.00022)° with the prime meridian and rotation rate of (170.374±0.012)° and (952.1532638±0.0000019)°/day, respectively. The low Bouguer gravity at high topographic areas, and vice versa, indicates that the topography of Ceres is compensated, which can be explained by a low-viscosity layer at depth. Further studies on Ceres interior show that low gravity-topography admittances are consistent with Airy isostasy and finite-element modeling require a decrease of viscosity with depth.

Numerical Researches on Dynamical Systems with Relativistic Spin

NASA Astrophysics Data System (ADS)

Han, W. B.

2010-04-01

It is well known that spinning compact binaries are one of the most important research objects in the universe. Especially, EMRIs (extreme mass ratio inspirals) involving stellar compact objects which orbit massive black holes, are considered to be primary sources of gravitational radiation (GW) which could be detected by the space-based interferometer LISA. GW signals from EMRIs can be used to test general relativity, measure the masses and spins of central black holes and study essential physics near horizons. Compared with the situation without spin, the complexity of extreme objects, most of which rotate very fast, is much higher. So the dynamics of EMRI systems are numerically and analytically studied. We focus on how the spin effects on the dynamics of these systems and the produced GW radiations. Firstly, an ideal model of spinning test particles around Kerr black hole is considered. For equatorial orbits, we present the correct expression of effective potential and analyze the stability of circular orbits. Especially, the gravitational binding energy and frame-dragging effect of extreme Kerr black hole are much bigger than those without spin. For general orbits, spin can monotonically enlarge orbital inclination and destroy the symmetry of orbits about equatorial plane. It is the most important that extreme spin can produce orbital chaos. By carefully investigating the relations between chaos and orbital parameters, we point out that chaos usually appears for orbits with small pericenter, big eccentricity and orbital inclination. It is emphasized that Poincaré section method is invalid to detect the chaos of spinning particles, and the way of systems toward chaos is the period-doubling bifurcation. Furthermore, we study how spins effect on GW radiations from spinning test particles orbiting Kerr black holes. It is found that spins can increase orbit eccentricity and then make h+ component be detected more easily. But for h× component, because spins change orbital inclination in a complicated way, it is more difficult to build GW signal templates. Secondly, based on the scalar gravity theory, a numerical relativistic model of EMRIs is constructed to consider the self-gravity and radiation reaction of low-mass objects. Finally, we develop a new method with multiple steps for Hamilton systems to meet the needs of numerical researches. This method can effectively maintain each conserved quantity of the separable Hamilton system. In addition, for constrained system with a few first integrals, we present a new numerical stabilization method named as adjustment-stabilization method, which can maintain all known conserved quantities in a given dynamical system and greatly improve the numerical accuracy. Our new method is the most complete stabilization method up to now.

Holography in Lovelock Chern-Simons AdS gravity

NASA Astrophysics Data System (ADS)

Cvetković, Branislav; Miskovic, Olivera; Simić, Dejan

2017-08-01

We analyze holographic field theory dual to Lovelock Chern-Simons anti-de Sitter (AdS) gravity in higher dimensions using first order formalism. We first find asymptotic symmetries in the AdS sector showing that they consist of local translations, local Lorentz rotations, dilatations and non-Abelian gauge transformations. Then, we compute 1-point functions of energy-momentum and spin currents in a dual conformal field theory and write Ward identities. We find that the holographic theory possesses Weyl anomaly and also breaks non-Abelian gauge symmetry at the quantum level.

Note about a pure spin-connection formulation of general relativity and spin-2 duality in (A)dS

NASA Astrophysics Data System (ADS)

Basile, Thomas; Bekaert, Xavier; Boulanger, Nicolas

2016-06-01

We investigate the problem of finding a pure spin-connection formulation of general relativity with nonvanishing cosmological constant. We first revisit the problem at the linearized level and find that the pure spin-connection, quadratic Lagrangian, takes a form reminiscent to Weyl gravity, given by the square of a Weyl-like tensor. Upon Hodge dualization, we show that the dual gauge field in (A )dSD transforms under G L (D ) in the same representation as a massive graviton in the flat spacetime of the same dimension. We give a detailed proof that the physical degrees of freedom indeed correspond to a massless graviton propagating around the (anti-) de Sitter background and finally speculate about a possible nonlinear pure-connection theory dual to general relativity with cosmological constant.

Gravity Field and Internal Structure of Mercury from MESSENGER

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.; Phillips, Roger J.; Solomon, Sean C.; Hauck, Steven A., II; Lemoine, Frank G.; Mazarico, Erwan; Neumann, Gregory A.; Peale, Stanton J.; Margot, Jean-Luc;

Gravity field and internal structure of Mercury from MESSENGER.

PubMed

Smith, David E; Zuber, Maria T; Phillips, Roger J; Solomon, Sean C; Hauck, Steven A; Lemoine, Frank G; Mazarico, Erwan; Neumann, Gregory A; Peale, Stanton J; Margot, Jean-Luc; Johnson, Catherine L; Torrence, Mark H; Perry, Mark E; Rowlands, David D; Goossens, Sander; Head, James W; Taylor, Anthony H

2012-04-13

Radio tracking of the MESSENGER spacecraft has provided a model of Mercury's gravity field. In the northern hemisphere, several large gravity anomalies, including candidate mass concentrations (mascons), exceed 100 milli-Galileos (mgal). Mercury's northern hemisphere crust is thicker at low latitudes and thinner in the polar region and shows evidence for thinning beneath some impact basins. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR(2) = 0.353 ± 0.017, where M and R are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of C(m)/C = 0.452 ± 0.035. A model for Mercury's radial density distribution consistent with these results includes a solid silicate crust and mantle overlying a solid iron-sulfide layer and an iron-rich liquid outer core and perhaps a solid inner core.

Gauge assisted quadratic gravity: A framework for UV complete quantum gravity

NASA Astrophysics Data System (ADS)

Donoghue, John F.; Menezes, Gabriel

2018-06-01

We discuss a variation of quadratic gravity in which the gravitational interaction remains weakly coupled at all energies, but is assisted by a Yang-Mills gauge theory which becomes strong at the Planck scale. The Yang-Mills interaction is used to induce the usual Einstein-Hilbert term, which was taken to be small or absent in the original action. We study the spin-two propagator in detail, with a focus on the high mass resonance which is shifted off the real axis by the coupling to real decay channels. We calculate scattering in the J =2 partial wave and show explicitly that unitarity is satisfied. The theory will in general have a large cosmological constant and we study possible solutions to this, including a unimodular version of the theory. Overall, the theory satisfies our present tests for being a ultraviolet completion of quantum gravity.

Effective Dark Matter Halo Catalog in f(R) Gravity.

PubMed

He, Jian-Hua; Hawken, Adam J; Li, Baojiu; Guzzo, Luigi

2015-08-14

We introduce the idea of an effective dark matter halo catalog in f(R) gravity, which is built using the effective density field. Using a suite of high resolution N-body simulations, we find that the dynamical properties of halos, such as the distribution of density, velocity dispersion, specific angular momentum and spin, in the effective catalog of f(R) gravity closely mimic those in the cold dark matter model with a cosmological constant (ΛCDM). Thus, when using effective halos, an f(R) model can be viewed as a ΛCDM model. This effective catalog therefore provides a convenient way for studying the baryonic physics, the galaxy halo occupation distribution and even semianalytical galaxy formation in f(R) cosmologies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carone, Christopher D.; Erlich, Joshua; Vaman, Diana

A constraint of vanishing energy-momentum tensor is motivated by a variety of perspectives on quantum gravity. We demonstrate in a concrete example how this constraint leads to a metric-independent theory in which quantum gravity emerges as a nonperturbative artifact of regularization-scale physics. We analyze a scalar theory similar to the Dirac-Born-Infeld (DBI) theory with vanishing gauge fields, with the DBI Lagrangian modulated by a scalar potential. In the limit of a large number of scalars, we explicitly demonstrate the existence of a composite massless spin-2 graviton in the spectrum that couples to matter as in Einstein gravity. As a result,more » we comment on the cosmological constant problem and the generalization to theories with fermions and gauge fields.« less

Gravity Probe B

NASA Image and Video Library

2003-07-18

In the spacecraft processing facility on North Vandenberg Air Force Base, workers conduct battery charge/discharge cycles as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-18

In the spacecraft processing facility on North Vandenberg Air Force Base, battery charge/discharge cycles are underway as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Spacecraft flight control system design selection process for a geostationary communication satellite

NASA Technical Reports Server (NTRS)

Barret, C.

1992-01-01

The Earth's first artificial satellite, Sputnik 1, slowly tumbled in orbit. The first U.S. satellite, Explorer 1, also tumbled out of control. Now, as we launch the Mars observer and the Cassini spacecraft, stability and control have become higher priorities. The flight control system design selection process is reviewed using as an example a geostationary communication satellite which is to have a life expectancy of 10 to 14 years. Disturbance torques including aerodynamic, magnetic, gravity gradient, solar, micrometeorite, debris, collision, and internal torques are assessed to quantify the disturbance environment so that the required compensating torque can be determined. Then control torque options, including passive versus active, momentum control, bias momentum, spin stabilization, dual spin, gravity gradient, magnetic, reaction wheels, control moment gyros, nutation dampers, inertia augmentation techniques, three-axis control, reactions control system (RCS), and RCS sizing, are considered. A flight control system design is then selected and preliminary stability criteria are met by the control gains selection.

Cartan gravity, matter fields, and the gauge principle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westman, Hans F., E-mail: hwestman74@gmail.com; Zlosnik, Tom G., E-mail: t.zlosnik@imperial.ac.uk

Gravity is commonly thought of as one of the four force fields in nature. However, in standard formulations its mathematical structure is rather different from the Yang–Mills fields of particle physics that govern the electromagnetic, weak, and strong interactions. This paper explores this dissonance with particular focus on how gravity couples to matter from the perspective of the Cartan-geometric formulation of gravity. There the gravitational field is represented by a pair of variables: (1) a ‘contact vector’ V{sup A} which is geometrically visualized as the contact point between the spacetime manifold and a model spacetime being ‘rolled’ on top ofmore » it, and (2) a gauge connection A{sub μ}{sup AB}, here taken to be valued in the Lie algebra of SO(2,3) or SO(1,4), which mathematically determines how much the model spacetime is rotated when rolled. By insisting on two principles, the gauge principle and polynomial simplicity, we shall show how one can reformulate matter field actions in a way that is harmonious with Cartan’s geometric construction. This yields a formulation of all matter fields in terms of first order partial differential equations. We show in detail how the standard second order formulation can be recovered. In particular, the Hodge dual, which characterizes the structure of bosonic field equations, pops up automatically. Furthermore, the energy–momentum and spin-density three-forms are naturally combined into a single object here denoted the spin-energy–momentum three-form. Finally, we highlight a peculiarity in the mathematical structure of our first-order formulation of Yang–Mills fields. This suggests a way to unify a U(1) gauge field with gravity into a SO(1,5)-valued gauge field using a natural generalization of Cartan geometry in which the larger symmetry group is spontaneously broken down to SO(1,3)×U(1). The coupling of this unified theory to matter fields and possible extensions to non-Abelian gauge fields are left as open questions. -- Highlights: •Develops Cartan gravity to include matter fields. •Coupling to gravity is done using the standard gauge prescription. •Matter actions are manifestly polynomial in all field variables. •Standard equations recovered on-shell for scalar, spinor and Yang–Mills fields. •Unification of a U(1) field with gravity based on the orthogonal group SO(1,5)« less

Free-Spinning-Tunnel Investigation to Determine the Effect of Spin-Recovery Rockets and Thrust Simulation on the Recovery Characteristics of a 1/21-Scale Model of the Chance Vought F7U-3 Airplane, TED No. NACA AD 3103

NASA Technical Reports Server (NTRS)

Burk, Sanger H., Jr.; Healy, Frederick M.

1955-01-01

An investigation of a l/21-scale model of the Chance Vought F7U-3 airplane in the co&at-load- condition has been conducted in the Langley 20-foot free-spinning tunnel, The recovery characteristics of the model were determined by use of spin-recovery rockets for the erect and inverted spinning condition. The rockets were so placed as to provide either a yawing or rolling moment about the model center of gravity. Also included in the investigation were tests to determine the effect of simulated engine thrust on the recovery characteristics of the model. On the basis of model tests, recoveries from erect and inverted spins were satisfactory when a yawing moment of 22,200 foot-pounds (full scale) was provided against the spin by rockets attached to the wing tips; the anti-spin yawing moment was applied for approximately 9 seconds, (full scale). Satisfactory recoveries were obtained from erect spins when a rolling moment of 22,200 foot-pounds (full scale) was provided with the spin (rolls right wing down in right spin). Although the inverted spin was satisfactorily terminated when a rolling moment of equal magnitude was provided, a roll rocket was not considered to be an optimum spin-recovery device to effect recoveries from inverted spins for this airplane because of resulting gyrations during spin recovery. Simulation of engine thrust had no apparent effect on the spin recovery characteristics.

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-15

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - A worker in the spacecraft processing facility on North Vandenberg Air Force Base checks the Gravity Probe B experiment during prelaunch testing. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-12

VANDENBERG AFB, CALIF. - A worker in the spacecraft processing facility on North Vandenberg Air Force Base checks the Gravity Probe B experiment during prelaunch testing. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., rolls back from the Delta II rocket that will launch the Gravity Probe B experiment. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-12

VANDENBERG AFB, CALIF. - The mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., rolls back from the Delta II rocket that will launch the Gravity Probe B experiment. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

Fusion basis for lattice gauge theory and loop quantum gravity

NASA Astrophysics Data System (ADS)

Delcamp, Clement; Dittrich, Bianca; Riello, Aldo

2017-02-01

We introduce a new basis for the gauge-invariant Hilbert space of lattice gauge theory and loop quantum gravity in (2 + 1) dimensions, the fusion basis. In doing so, we shift the focus from the original lattice (or spin-network) structure directly to that of the magnetic (curvature) and electric (torsion) excitations themselves. These excitations are classified by the irreducible representations of the Drinfel'd double of the gauge group, and can be readily "fused" together by studying the tensor product of such representations. We will also describe in detail the ribbon operators that create and measure these excitations and make the quasi-local structure of the observable algebra explicit. Since the fusion basis allows for both magnetic and electric excitations from the onset, it turns out to be a precious tool for studying the large scale structure and coarse-graining flow of lattice gauge theories and loop quantum gravity. This is in neat contrast with the widely used spin-network basis, in which it is much more complicated to account for electric excitations, i.e. for Gauß constraint violations, emerging at larger scales. Moreover, since the fusion basis comes equipped with a hierarchical structure, it readily provides the language to design states with sophisticated multi-scale structures. Another way to employ this hierarchical structure is to encode a notion of subsystems for lattice gauge theories and (2 + 1) gravity coupled to point particles. In a follow-up work, we have exploited this notion to provide a new definition of entanglement entropy for these theories.

Interactions in higher-spin gravity: a holographic perspective

NASA Astrophysics Data System (ADS)

Sleight, Charlotte

2017-09-01

This review is an elaboration of recent results on the holographic re-construction of metric-like interactions in higher-spin gauge theories on anti-de Sitter space (AdS), employing their conjectured duality with free conformal field theories (CFTs). After reviewing the general approach and establishing the necessary intermediate results, we extract explicit expressions for the complete cubic action on AdSd+1 and the quartic self-interaction of the scalar on AdS4 for the type A minimal bosonic higher-spin theory from the three- and four- point correlation functions of single-trace operators in the free scalar O(N) vector model. For this purpose tools were developed to evaluate tree-level three-point Witten diagrams involving totally symmetric fields of arbitrary integer spin and mass, and the conformal partial wave expansions of their tree-level four-point Witten diagrams. We also discuss the implications of the holographic duality on the locality properties of interactions in higher-spin gauge theories.

Heavy spin-2 Dark Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babichev, Eugeny; UPMC-CNRS, UMR7095, Institut d’Astrophysique de Paris, GReCO,98bis boulevard Arago, F-75014 Paris; Marzola, Luca

2016-09-12

We provide further details on a recent proposal addressing the nature of the dark sectors in cosmology and demonstrate that all current observations related to Dark Matter can be explained by the presence of a heavy spin-2 particle. Massive spin-2 fields and their gravitational interactions are uniquely described by ghost-free bimetric theory, which is a minimal and natural extension of General Relativity. In this setup, the largeness of the physical Planck mass is naturally related to extremely weak couplings of the heavy spin-2 field to baryonic matter and therefore explains the absence of signals in experiments dedicated to Dark Mattermore » searches. It also ensures the phenomenological viability of our model as we confirm by comparing it with cosmological and local tests of gravity. At the same time, the spin-2 field possesses standard gravitational interactions and it decays universally into all Standard Model fields but not into massless gravitons. Matching the measured DM abundance together with the requirement of stability constrains the spin-2 mass to be in the 1 to 100 TeV range.« less

Spin Dependence in Tidal Disruption Events

NASA Astrophysics Data System (ADS)

Kesden, Michael; Stone, Nicholas; van Velzen, Sjoert

2018-01-01

A supermassive black hole (SBH) can tidally disrupt stars when its tidal field overwhelms the stars’ self-gravity. The stellar debris produced in such tidal disruption events (TDEs) evolves into tidal streams that can self-intersect. These inelastic stream collisions dissipate orbital energy, both circularizing the tidal stream and contributing to the emission observed during the TDE. Once circularized into a disk, the stellar debris can be viscously accreted by the SBH powering additional luminous emission. We explore how SBH spin can affect the tidal disruption process. Tidal forces are spin dependent, as is the minimum orbital angular momentum below which stars are directly captured by the SBH. This implies that the TDE rate will be spin dependent, particularly for more massive SBHs for which relativistic effects are more significant. SBH spin also affects TDE light curves through the initial debris orbits, the nature of the stream collisions, the viscous evolution of the accretion disk, and the possibility of launching jets. We explore the spin dependence of these phenomena to identify promising signatures for upcoming surveys expected to discover hundreds of TDE candidates in the next decade.

KOI2138 -- a Spin-Orbit Aligned Intermediate Period Super-Earth

NASA Astrophysics Data System (ADS)

Barnes, Jason W.

2015-11-01

A planet's formation and evolution are encoded in spin-orbit alignment -- the planet's inclination relative to its star's equatorial plane. While the solar system's spin-orbit aligned planets indicate our own relatively quiescent history, many close-in giant planets show significant misalignment. Some planets even orbit retrograde! Hot Jupiters, then, have experienced fundamentally different histories than we experienced here in the solar system. In this presentation, I will show a new determination of the spin-orbit alignment of 2.1 REarth exoplanet candidate KOI2138. KOI2138 shows a gravity-darkened transit lightcurve that is consistent with spin-orbit alignment. This measurement is important because the only other super-Earth with an alignment determination (55 Cnc e, orbit period 0.74 days) is misaligned. With an orbital period of 23.55 days, KOI2138 is far enough from its star to avoid tidal orbit evolution. Therefore its orbit is likely primordial, and hence it may represent the tip of an iceberg of terrestrial, spin-orbit aligned planets that have histories that more closely resemble that of the solar system's terrestrial planets.

Supersymmetric dS/CFT

NASA Astrophysics Data System (ADS)

Hertog, Thomas; Tartaglino-Mazzucchelli, Gabriele; Van Riet, Thomas; Venken, Gerben

2018-02-01

We put forward new explicit realisations of dS/CFT that relate N = 2 supersymmetric Euclidean vector models with reversed spin-statistics in three dimensions to specific supersymmetric Vasiliev theories in four-dimensional de Sitter space. The partition function of the free supersymmetric vector model deformed by a range of low spin deformations that preserve supersymmetry appears to specify a well-defined wave function with asymptotic de Sitter boundary conditions in the bulk. In particular we find the wave function is globally peaked at undeformed de Sitter space, with a low amplitude for strong deformations. This suggests that supersymmetric de Sitter space is stable in higher-spin gravity and in particular free from ghosts. We speculate this is a limiting case of the de Sitter realizations in exotic string theories.

Classroom Analysis of Rotating Space Vehicles in 2001: A Space Odyssey.

ERIC Educational Resources Information Center

Borgwald, James M.; Schreiner, Serge

1993-01-01

This article describes the use of modern science fiction movies as a vehicle to teach scientific principles. The resulting artificial gravity from a spinning space station in movie "2001" is calculated from measurements taken off of the screen. A mathematical explanation is provided. (MVL)

ECN-2409

NASA Image and Video Library

1970-06-17

Not every moment of a test pilot's day is serious business. In a moment of levity, NASA pilots Bill Dana (left) and John A. Manke try to drag Air Force test pilot Peter Hoag away from the HL-10 lifting body while Air Force Major Jerauld R. Gentry helps from the cockpit. These four men were the principal pilots for the HL-10 program. This was not the only prank involving the HL-10 and its pilots. Once "Captain Midnight" (Gentry) and the "Midnight Skulkers" sneaked into the NASA hangar and put "U.S. Air Force" on the aircraft using stick-on letters. Later, while Gentry was making a lifting-body flight, his 1954 Ford was "borrowed" from the parking lot, painted with yellow-green zinc-chromate primer, and decorated with large stick-on flowers about one foot in diameter. After Gentry returned from the flight, he was surprised to see what had happened to his car.

The response of plasma density to breaking inertial gravity wave in the lower regions of ionosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Wenbo, E-mail: Wenbo.Tang@asu.edu; Mahalov, Alex, E-mail: Alex.Mahalov@asu.edu

2014-04-15

We present a three-dimensional numerical study for the E and lower F region ionosphere coupled with the neutral atmosphere dynamics. This model is developed based on a previous ionospheric model that examines the transport patterns of plasma density given a prescribed neutral atmospheric flow. Inclusion of neutral dynamics in the model allows us to examine the charge-neutral interactions over the full evolution cycle of an inertial gravity wave when the background flow spins up from rest, saturates and eventually breaks. Using Lagrangian analyses, we show the mixing patterns of the ionospheric responses and the formation of ionospheric layers. The correspondingmore » plasma density in this flow develops complex wave structures and small-scale patches during the gravity wave breaking event.« less

Gravity Probe B

NASA Image and Video Library

2003-07-11

Workers in the spacecraft processing facility on North Vandenberg Air Force Base get ready to begin processing the Gravity Probe B experiment, including setting up mechanical and electrical ground support equipment, making necessary connections and conditioning the spacecraft battery. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity-assist engine for space propulsion

NASA Astrophysics Data System (ADS)

Bergstrom, Arne

2014-06-01

As a possible alternative to rockets, the present article describes a new type of engine for space travel, based on the gravity-assist concept for space propulsion. The new engine is to a great extent inspired by the conversion of rotational angular momentum to orbital angular momentum occurring in tidal locking between astronomical bodies. It is also greatly influenced by Minovitch's gravity-assist concept, which has revolutionized modern space technology, and without which the deep-space probes to the outer planets and beyond would not have been possible. Two of the three gravitating bodies in Minovitch's concept are in the gravity-assist engine discussed in this article replaced by an extremely massive ‘springbell' (in principle a spinning dumbbell with a powerful spring) incorporated into the spacecraft itself, and creating a three-body interaction when orbiting around a gravitating body. This makes gravity-assist propulsion possible without having to find suitably aligned astronomical bodies. Detailed numerical simulations are presented, showing how an actual spacecraft can use a ca 10-m diameter springbell engine in order to leave the earth's gravitational field and enter an escape trajectory towards interplanetary destinations.

Tensor and Spin Representations of SO(4) and Discrete Quantum Gravity

NASA Astrophysics Data System (ADS)

Lorente, M.; Kramer, P.

Starting from the defining transformations of complex matrices for the SO(4) group, we construct the fundamental representation and the tensor and spinor representations of the group SO(4). Given the commutation relations for the corresponding algebra, the unitary representations of the group in terms of the generalized Euler angles are constructed. These mathematical results help us to a more complete description of the Barret-Crane model in Quantum Gravity. In particular a complete realization of the weight function for the partition function is given and a new geometrical interpretation of the asymptotic limit for the Regge action is presented.

Testing subleading multiple soft graviton theorem for CHY prescription

NASA Astrophysics Data System (ADS)

Chakrabarti, Subhroneel; Kashyap, Sitender Pratap; Sahoo, Biswajit; Sen, Ashoke; Verma, Mritunjay

2018-01-01

In arXiv:1707.06803 we derived the subleading multiple soft graviton theorem in a generic quantum theory of gravity for arbitrary number of soft external gravitons and arbitrary number of finite energy external states carrying arbitrary mass and spin. In this paper we verify this explicitly using the CHY formula for tree level scattering amplitudes of arbitrary number of gravitons in Einstein gravity. We pay special care to fix the signs of the amplitudes and resolve an apparent discrepancy between our general results in arXiv:1707.06803 and previous results on soft graviton theorem from CHY formula.

A 3He-129Xe co-magnetometer probed by a Rb magnetometer with Ramsey-pulse technique

NASA Astrophysics Data System (ADS)

Sheng, Dong; Kabcenell, Aaron; Romalis, Michael

2013-05-01

We report the recent progress in development of a new kind of co-magnetometer, benifiting from both the long spin coherence time of a noble gas and a highly sensitive alkali metal magnetometer. Due to the Fermi-contact interaction between alkali metal electron spin and noble gas nuclear spin the effective magnetization of the noble gas is enhanced by a factor of 6 to 600, allowing near quantum-limited detection of nuclear spins. Collisions between polarized alkali atoms and noble gas also introduce a large shift to the nuclear spin precession frequency. We reduce this effect by using Ramsey pulse techniques to measure the noble gas spin precession frequency ``in the dark'' by turning off the pumping laser between Ramsey pulses. A furthur reduction of the back-hyperpolarization from the noble gas can be achieved by controlling the cell temperature on short time scale. We showed that a 3He-129Xe Ramsey co-magnetometer is effective in cancelling fluctuations of external magnetic fields and gradients and developed cells with sufficient 129Xe T2 time without surface coatings. The new co-magnetometer has potential applications for many precision measurements, such as searches for spin-gravity couplings, electric dipole moments, and nuclear spin gyroscopes. Supported by DARPA.

Cartan gravity, matter fields, and the gauge principle

NASA Astrophysics Data System (ADS)

Westman, Hans F.; Zlosnik, Tom G.

2013-07-01

Gravity is commonly thought of as one of the four force fields in nature. However, in standard formulations its mathematical structure is rather different from the Yang-Mills fields of particle physics that govern the electromagnetic, weak, and strong interactions. This paper explores this dissonance with particular focus on how gravity couples to matter from the perspective of the Cartan-geometric formulation of gravity. There the gravitational field is represented by a pair of variables: (1) a 'contact vector' VA which is geometrically visualized as the contact point between the spacetime manifold and a model spacetime being 'rolled' on top of it, and (2) a gauge connection AμAB, here taken to be valued in the Lie algebra of SO(2,3) or SO(1,4), which mathematically determines how much the model spacetime is rotated when rolled. By insisting on two principles, the gauge principle and polynomial simplicity, we shall show how one can reformulate matter field actions in a way that is harmonious with Cartan's geometric construction. This yields a formulation of all matter fields in terms of first order partial differential equations. We show in detail how the standard second order formulation can be recovered. In particular, the Hodge dual, which characterizes the structure of bosonic field equations, pops up automatically. Furthermore, the energy-momentum and spin-density three-forms are naturally combined into a single object here denoted the spin-energy-momentum three-form. Finally, we highlight a peculiarity in the mathematical structure of our first-order formulation of Yang-Mills fields. This suggests a way to unify a U(1) gauge field with gravity into a SO(1,5)-valued gauge field using a natural generalization of Cartan geometry in which the larger symmetry group is spontaneously broken down to SO(1,3)×U(1). The coupling of this unified theory to matter fields and possible extensions to non-Abelian gauge fields are left as open questions.

Kinetotic behaviour and otolith asymmetry of fish under "low quality microgravity" - a drop-tower experiment at 0.03-0.05g

NASA Astrophysics Data System (ADS)

Anken, Ralf; Knie, Miriam; Hilbig, Reinhard; Anken, Ralf

We have shown earlier that some fish of a given batch reveal motion sickness (a kinetosis) at the transition from earth gravity to diminished gravity. The percentual ratios of the various types of behaviour (normal swimming and kinetotic swimming; kinetotic specimens revealed looping responses/LR or spinning movements/SM), however, highly differed depending on the quality of diminished gravity. Whereas kinetoses were exhibited by some 90 In striking contrast to the results gained using PF specimens, according to which otolith asymmetry (differences in the size and calcium incorporation of the inner ear stones between the left and right side of the body) was significantly higher in kinetotic specimens as compared to normally swimming fish, a comparable asymmetry between kinetotically and normally swimming drop-tower samples (HQM) could statistically not be verified. The present study was designed to further elucidate the role of otolith asymmetry concerning an individually different susceptibility to kinetoses. In order to test, whether the differing results between the PF and the drop-tower experiment were based exclusively on the differing quality of diminished gravity, or, if further parameters of the PF and the drop-tower environment (e.g., vibrations and changing accelerations during PFs or the brisk compression of the drop-capsule at its release) need to be taken into consideration to explain the earlier results, drop-tower flights were performed at LQM. This simulation of PF "micro"gravity was carried out in housing larval cichlid fish (Oreochromis mossambicus) within a centrifuge at 0.03-0.05g during the drop-tower flights. The percentual ratios of the swimming behaviour at drop-tower LQM ranged between those of PF LQM and (drop-tower) HQM. This indicates that many normally swimming fish during PFs use cues other than the residual gravity (e.g., vibrations detected by the lateral line organ) for orientation. Furthermore, looping responses seem to be transitional behaviour depending on the developmental stage, whereas spinning movements occur stage-independently. Details as well as data on otoliths will be communicated at the meeting. Acknowledgement: This work was financially supported by the German Aerospace Center (DLR) (FKZ: 50 WB 0527).

Manufacturing techniques for gyroscopes in gravity probe B

NASA Technical Reports Server (NTRS)

Rasquin, J. R.

1976-01-01

The design of the fused silica gyroscope configuration is presented. The first gyroscope was made for erection and spin tests only and does not contain the angle readout loops necessary for a functioning experimental gyroscope. The rotor ball described is not coated with the ultimate material, niobium, but instead with a sandwich of titanium, cooper, and titanium for spin-up test purposes. Background, historical information, manufacturing procedures, and sketches for this gyroscope are included to provide a better understanding of the device and the techniques and special tools required to manufacture a fused silica gyroscope to the required specifications.

Relativistic spin precession in the double pulsar.

PubMed

Breton, Rene P; Kaspi, Victoria M; Kramer, Michael; McLaughlin, Maura A; Lyutikov, Maxim; Ransom, Scott M; Stairs, Ingrid H; Ferdman, Robert D; Camilo, Fernando; Possenti, Andrea

2008-07-04

The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 degrees (-0 degrees .65)(+0 degrees .66) per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%.

Canonical transformation path to gauge theories of gravity

NASA Astrophysics Data System (ADS)

Struckmeier, J.; Muench, J.; Vasak, D.; Kirsch, J.; Hanauske, M.; Stoecker, H.

2017-06-01

In this paper, the generic part of the gauge theory of gravity is derived, based merely on the action principle and on the general principle of relativity. We apply the canonical transformation framework to formulate geometrodynamics as a gauge theory. The starting point of our paper is constituted by the general De Donder-Weyl Hamiltonian of a system of scalar and vector fields, which is supposed to be form-invariant under (global) Lorentz transformations. Following the reasoning of gauge theories, the corresponding locally form-invariant system is worked out by means of canonical transformations. The canonical transformation approach ensures by construction that the form of the action functional is maintained. We thus encounter amended Hamiltonian systems which are form-invariant under arbitrary spacetime transformations. This amended system complies with the general principle of relativity and describes both, the dynamics of the given physical system's fields and their coupling to those quantities which describe the dynamics of the spacetime geometry. In this way, it is unambiguously determined how spin-0 and spin-1 fields couple to the dynamics of spacetime. A term that describes the dynamics of the "free" gauge fields must finally be added to the amended Hamiltonian, as common to all gauge theories, to allow for a dynamic spacetime geometry. The choice of this "dynamics" Hamiltonian is outside of the scope of gauge theory as presented in this paper. It accounts for the remaining indefiniteness of any gauge theory of gravity and must be chosen "by hand" on the basis of physical reasoning. The final Hamiltonian of the gauge theory of gravity is shown to be at least quadratic in the conjugate momenta of the gauge fields—this is beyond the Einstein-Hilbert theory of general relativity.

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is ready to be lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-15

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is ready to be lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - Viewed from inside, the second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-18

VANDENBERG AFB, CALIF. - Viewed from inside, the second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., where it will be mated with the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-16

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., where it will be mated with the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-15

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-18

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. Behind it can be seen the first stage of the Delta II. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-18

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. Behind it can be seen the first stage of the Delta II. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - Workers on the mobile service tower at Space Launch Complex 2, Vandenberg Air Force Base, Calif., check the Delta II rocket’s second stage as it is mated with the first stage. The Delta II is the launch vehicle for the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-18

VANDENBERG AFB, CALIF. - Workers on the mobile service tower at Space Launch Complex 2, Vandenberg Air Force Base, Calif., check the Delta II rocket’s second stage as it is mated with the first stage. The Delta II is the launch vehicle for the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - In the spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B experiment sits on an assembly and test stand where it has been subject to various prelaunch testing. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-12

VANDENBERG AFB, CALIF. - In the spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B experiment sits on an assembly and test stand where it has been subject to various prelaunch testing. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is prepared for lifting up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. It will enclose the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-16

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is prepared for lifting up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. It will enclose the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-12

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is raised to a vertical position at Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-15

VANDENBERG AFB, CALIF. - The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is raised to a vertical position at Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., where it will be mated with the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-12

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., where it will be mated with the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - Viewed from inside, the second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. Behind it is the first stage of the Delta II. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-18

VANDENBERG AFB, CALIF. - Viewed from inside, the second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. Behind it is the first stage of the Delta II. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. It will enclose the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-16

VANDENBERG AFB, CALIF. - The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. It will enclose the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted off the transporter after its arrival on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

NASA Image and Video Library

2003-09-18

VANDENBERG AFB, CALIF. - The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted off the transporter after its arrival on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

Space-time topology and quantum gravity.

NASA Astrophysics Data System (ADS)

Friedman, J. L.

Characteristic features are discussed of a theory of quantum gravity that allows space-time with a non-Euclidean topology. The review begins with a summary of the manifolds that can occur as classical vacuum space-times and as space-times with positive energy. Local structures with non-Euclidean topology - topological geons - collapse, and one may conjecture that in asymptotically flat space-times non-Euclidean topology is hiden from view. In the quantum theory, large diffeos can act nontrivially on the space of states, leading to state vectors that transform as representations of the corresponding symmetry group π0(Diff). In particular, in a quantum theory that, at energies E < EPlanck, is a theory of the metric alone, there appear to be ground states with half-integral spin, and in higher-dimensional gravity, with the kinematical quantum numbers of fundamental fermions.

Gravity Probe B

NASA Image and Video Library

2003-07-13

In the spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to remove the soft shipping cover from the Gravity Probe B experiment. Immediate processing includes setting up mechanical and electrical ground support equipment, making necessary connections and conditioning the spacecraft battery. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Gravity Probe B

NASA Image and Video Library

2003-07-11

Workers in the spacecraft processing facility on North Vandenberg Air Force Base get ready to begin processing the Gravity Probe B experiment. Mechanical and electrical ground support equipment will be set up and necessary connections made with the spacecraft. Spacecraft battery conditioning will also begin. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

KSC-03PD-3277

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3280

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3270

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3281

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3267

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3271

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3266

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

Chern-Simons Term: Theory and Applications.

NASA Astrophysics Data System (ADS)

Gupta, Kumar Sankar

1992-01-01

We investigate the quantization and applications of Chern-Simons theories to several systems of interest. Elementary canonical methods are employed for the quantization of abelian and nonabelian Chern-Simons actions using ideas from gauge theories and quantum gravity. When the spatial slice is a disc, it yields quantum states at the edge of the disc carrying a representation of the Kac-Moody algebra. We next include sources in this model and their quantum states are shown to be those of a conformal family. Vertex operators for both abelian and nonabelian sources are constructed. The regularized abelian Wilson line is proved to be a vertex operator. The spin-statistics theorem is established for Chern-Simons dynamics using purely geometrical techniques. Chern-Simons action is associated with exotic spin and statistics in 2 + 1 dimensions. We study several systems in which the Chern-Simons action affects the spin and statistics. The first class of systems we study consist of G/H models. The solitons of these models are shown to obey anyonic statistics in the presence of a Chern-Simons term. The second system deals with the effect of the Chern -Simons term in a model for high temperature superconductivity. The coefficient of the Chern-Simons term is shown to be quantized, one of its possible values giving fermionic statistics to the solitons of this model. Finally, we study a system of spinning particles interacting with 2 + 1 gravity, the latter being described by an ISO(2,1) Chern-Simons term. An effective action for the particles is obtained by integrating out the gauge fields. Next we construct operators which exchange the particles. They are shown to satisfy the braid relations. There are ambiguities in the quantization of this system which can be exploited to give anyonic statistics to the particles. We also point out that at the level of the first quantized theory, the usual spin-statistics relation need not apply to these particles.

Mathematical Model of Bubble Sloshing Dynamics for Cryogenic Liquid Helium in Orbital Spacecraft Dewar Container

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1995-01-01

A generalized mathematical model is investigated of sloshing dynamics for dewar containers, partially filled with a liquid of cryogenic superfluid helium 2, driven by both gravity gradient and jitter accelerations applicable to two types of scientific spacecrafts, which are eligible to carry out spinning motion and/or slew motion to perform scientific observations during normal spacecraft operation. Two examples are given for the Gravity Probe-B (GP-B) with spinning motion, and the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) with slew motion, which are responsible for the sloshing dynamics. Explicit mathematical expressions for the modelling of sloshing dynamics to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics will be based on the noninertial frame spacecraft bound coordinate, and we will solve the time-dependent three-dimensional formulations of partial differential equations subject to initial and boundary conditions. Explicit mathematical expressions of boundary conditions lo cover capillary force effects on the liquid-vapor interface in microgravity environments are also derived. Results of the simulations of the mathematical model are illustrated.

Quantizing higher-spin gravity in free-field variables

NASA Astrophysics Data System (ADS)

Campoleoni, Andrea; Fredenhagen, Stefan; Raeymaekers, Joris

2018-02-01

We study the formulation of massless higher-spin gravity on AdS3 in a gauge in which the fundamental variables satisfy free field Poisson brackets. This gauge choice leaves a small portion of the gauge freedom unfixed, which should be further quotiented out. We show that doing so leads to a bulk version of the Coulomb gas formalism for W N CFT's: the generators of the residual gauge symmetries are the classical limits of screening charges, while the gauge-invariant observables are classical W N charges. Quantization in these variables can be carried out using standard techniques and makes manifest a remnant of the triality symmetry of W ∞[λ]. This symmetry can be used to argue that the theory should be supplemented with additional matter content which is precisely that of the Prokushkin-Vasiliev theory. As a further application, we use our formulation to quantize a class of conical surplus solutions and confirm the conjecture that these are dual to specific degenerate W N primaries, to all orders in the large central charge expansion.

Double-trace flows and the swampland

NASA Astrophysics Data System (ADS)

Giombi, Simone; Perlmutter, Eric

2018-03-01

We explore the idea that large N, non-supersymmetric conformal field theories with a parametrically large gap to higher spin single-trace operators may be obtained as infrared fixed points of relevant double-trace deformations of superconformal field theories. After recalling the AdS interpretation and some potential pathologies of such flows, we introduce a concrete example that appears to avoid them: the ABJM theory at finite k, deformed by \\int O^2, where O is the superconformal primary in the stress-tensor multiplet. We address its relation to recent conjectures based on weak gravity bounds, and discuss the prospects for a wider class of similarly viable flows. Next, we proceed to analyze the spectrum and correlation functions of the putative IR CFT, to leading non-trivial order in 1 /N. This includes analytic computations of the change under double-trace flow of connected four-point functions of ABJM superconformal primaries; and of the IR anomalous dimensions of infinite classes of double-trace composite operators. These would be the first analytic results for anomalous dimensions of finite-spin composite operators in any large N CFT3 with an Einstein gravity dual.

Aspects of general higher-order gravities

NASA Astrophysics Data System (ADS)

Bueno, Pablo; Cano, Pablo A.; Min, Vincent S.; Visser, Manus R.

2017-02-01

We study several aspects of higher-order gravities constructed from general contractions of the Riemann tensor and the metric in arbitrary dimensions. First, we use the fast-linearization procedure presented in [P. Bueno and P. A. Cano, arXiv:1607.06463] to obtain the equations satisfied by the metric perturbation modes on a maximally symmetric background in the presence of matter and to classify L (Riemann ) theories according to their spectrum. Then, we linearize all theories up to quartic order in curvature and use this result to construct quartic versions of Einsteinian cubic gravity. In addition, we show that the most general cubic gravity constructed in a dimension-independent way and which does not propagate the ghostlike spin-2 mode (but can propagate the scalar) is a linear combination of f (Lovelock ) invariants, plus the Einsteinian cubic gravity term, plus a new ghost-free gravity term. Next, we construct the generalized Newton potential and the post-Newtonian parameter γ for general L (Riemann ) gravities in arbitrary dimensions, unveiling some interesting differences with respect to the four-dimensional case. We also study the emission and propagation of gravitational radiation from sources for these theories in four dimensions, providing a generalized formula for the power emitted. Finally, we review Wald's formalism for general L (Riemann ) theories and construct new explicit expressions for the relevant quantities involved. Many examples illustrate our calculations.

On relativistic spin network vertices

NASA Astrophysics Data System (ADS)

Reisenberger, Michael P.

1999-04-01

Barrett and Crane have proposed a model of simplicial Euclidean quantum gravity in which a central role is played by a class of Spin(4) spin networks called "relativistic spin networks" which satisfy a series of physically motivated constraints. Here a proof is presented that demonstrates that the intertwiner of a vertex of such a spin network is uniquely determined, up to normalization, by the representations on the incident edges and the constraints. Moreover, the constraints, which were formulated for four valent spin networks only, are extended to networks of arbitrary valence, and the generalized relativistic spin networks proposed by Yetter are shown to form the entire solution set (mod normalization) of the extended constraints. Finally, using the extended constraints, the Barrett-Crane model is generalized to arbitrary polyhedral complexes (instead of just simplicial complexes) representing space-time. It is explained how this model, like the Barret-Crane model can be derived from BF theory, a simple topological field theory [G. Horowitz, Commun. Math. Phys. 125, 417 (1989)], by restricting the sum over histories to ones in which the left-handed and right-handed areas of any 2-surface are equal. It is known that the solutions of classical Euclidean general relativity form a branch of the stationary points of the BF action with respect to variations preserving this condition.

Bulk and boundary unitary gravity in 3D: MMG2

NASA Astrophysics Data System (ADS)

Tekin, Bayram

2015-07-01

We construct a massive spin-2 theory in 2 +1 dimensions that is immune to the bulk-boundary unitarity conflict in anti-de Sitter space and hence amenable to holography. The theory is an extension of topologically massive gravity (TMG), just like the recently found minimal massive gravity (MMG), but it has two massive helicity modes instead of a single one. The theory admits all the solutions of TMG with a redefined topological parameter. We calculate the Shapiro time delay and show that flat-space (local) causality is not violated. We show that there is an interesting relation between the theory we present here (which we call MMG2 ), MMG, and the earlier new massive gravity (NMG): namely, field equations of these theories are nontrivially related. We study the bulk excitations and boundary charges of the conformal field theory that could be dual to gravity. We also find the chiral gravity limit for which one of the massive modes becomes massless. The virtue of the model is that one does not have to go to the chiral limit to achieve unitarity in the bulk and on the boundary, and the log-terms that appear in the chiral limit and cause instability do not exist in the generic theory.

Poincaré gauge gravity: An emergent scenario

NASA Astrophysics Data System (ADS)

Chkareuli, J. L.

2017-04-01

The Poincaré gauge gravity (PGG) with the underlying vector fields of tetrads and spin-connections is perhaps the best theory candidate for gravitation to be unified with the other three elementary forces of nature. There is a clear analogy between the local frame in PGG and the local internal symmetry space in the Standard Model. As a result, the spin-connection fields, gauging the local frame Lorentz symmetry group S O (1 ,3 )LF , appear in PGG much as photons and gluons appear in SM. We propose that such an analogy may follow from their common emergent nature allowing us to derive PGG in the same way as conventional gauge theories. In essence, we start with an arbitrary theory of some vector and fermion fields which possesses only global spacetime symmetries, such as Lorentz and translational invariance, in flat Minkowski space. The two vector field multiplets involved are proposed to belong, respectively, to the adjoint (Aμi j) and vector (eμi) representations of the starting global Lorentz symmetry. We show that if these prototype vector fields are covariantly constrained, Aμi jAij μ=±MA2 and eμieiμ=±Me2 , thus causing a spontaneous violation of the accompanying global symmetries (MA ,e are their proposed violation scales), then the only possible theory compatible with these length-preserving constraints is turned out to be the gauge invariant PGG, while the corresponding massless (pseudo)Goldstone modes are naturally collected in the emergent gauge fields of tetrads and spin-connections. In a minimal theory case being linear in a curvature we unavoidably come to the Einstein-Cartan theory. The extended theories with propagating spin-connection and tetrad modes are also considered and their possible unification with the Standard Model is briefly discussed.

Space Time Theories Confirmed

NASA Image and Video Library

2011-05-04

Francis Everitt, Principal Investigator for the Gravity Probe B Mission at Stanford University, second from left, makes a point during a press conference, Wednesday, May 4, 2011, to discuss NASA's Gravity Probe B (GP-B) mission which has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test at NASA Headquarters in Washington. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. Photo Credit: (NASA/Paul E. Alers)

Space Time Theories Confirmed

NASA Image and Video Library

2011-05-04

Francis Everitt, Principal Investigator for the Gravity Probe B Mission at Stanford University, makes a point during a press conference, Wednesday, May 4, 2011, to discuss NASA's Gravity Probe B (GP-B) mission which has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test at NASA Headquarters in Washington. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. Photo Credit: (NASA/Paul E. Alers)

Ghost Condensation and Modification of Gravity at Long distances

NASA Astrophysics Data System (ADS)

Luty, Markus

2004-05-01

This talk will describe the physics of a "ghost condensate", a new kind of cosmological fluid that can fill the universe and give rise to novel gravitational effects. The fluid has a preferred rest frame, but is nonetheless compatible with maximally symmetric spacetimes such as flat space or de Sitter. In the presence of a ghost condensate, gravity is modified in a nontrivial way at large distances and late times. New phenomena include new contributions to dark energy and dark matter, antigravity, new spin-dependent forces, and oscillatory potentials. All of this new physics can be described by a completely explicit and consistent effective field theory.

KSC-03PD-2746

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The Gravity Probe B experiment enters the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2744

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. At Vandenberg AFB, the canister enclosing the Gravity Probe B (GP-B) spacecraft is removed from the transporter. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

TESSX: A Mission for Space Exploration with Tethers

NASA Technical Reports Server (NTRS)

Cosmo, Mario L.; Lorenzini, Enrico C.; Gramer, Daniel J.; Hoffman, John H.; Mazzoleni, Andre P.

2005-01-01

Tethers offer significant potential for substantially increasing payload mass fraction, increasing spacecraft lifetime, enhancing long-term space travel, and enabling the understanding and development of gravity-dependent technologies required for Moon and Mars exploration. The development of the Tether Electrodynamic Spin-up and Survivability Experiment (TESSX) will support applications relevant to NASA's new exploration initiative, including: artificial gravity generation, formation flying, electrodynamic propulsion, momentum exchange, and multi-amp current collection and emission. Under the broad term TESSX, we are currently evaluating several different tether system configurations and operational modes. The initial results of this work are presented, including hardware development, orbital dynamics simulations, and electrodynamics design and analysis.

Ryu-Takayanagi formula for symmetric random tensor networks

NASA Astrophysics Data System (ADS)

Chirco, Goffredo; Oriti, Daniele; Zhang, Mingyi

2018-06-01

We consider the special case of random tensor networks (RTNs) endowed with gauge symmetry constraints on each tensor. We compute the Rényi entropy for such states and recover the Ryu-Takayanagi (RT) formula in the large-bond regime. The result provides first of all an interesting new extension of the existing derivations of the RT formula for RTNs. Moreover, this extension of the RTN formalism brings it in direct relation with (tensorial) group field theories (and spin networks), and thus provides new tools for realizing the tensor network/geometry duality in the context of background-independent quantum gravity, and for importing quantum gravity tools into tensor network research.

A bulk localized state and new holographic renormalization group flow in 3D spin-3 gravity

NASA Astrophysics Data System (ADS)

Nakayama, Ryuichi; Suzuki, Tomotaka

2018-04-01

We construct a localized state of a scalar field in 3D spin-3 gravity. 3D spin-3 gravity is thought to be holographically dual to W3-extended CFT on a boundary at infinity. It is known that while W3 algebra is a nonlinear algebra, in the limit of large central charge c a linear finite-dimensional subalgebra generated by Wn (n = 0,±1,±2) and Ln (n = 0,±1) is singled out. The localized state is constructed in terms of these generators. To write down an equation of motion for a scalar field which is satisfied by this localized state, it is necessary to introduce new variables for an internal space α±, β±, γ, in addition to ordinary coordinates x± and y. The higher-dimensional space, which combines the bulk space-time with the “internal space,” which is an analog of superspace in supersymmetric theory, is introduced. The “physical bulk space-time” is a 3D hypersurface with constant α±, β± and γ embedded in this space. We will work in Poincaré coordinates of AdS space and consider W-quasi-primary operators Φh(x+) with a conformal weight h in the boundary and study two and three point functions of W-quasi-primary operators transformed as eix+L‑1heβ+W‑1hΦh(0)e‑β+W‑1he‑ix+L‑1h. Here, Lnh and Wnh are sl(3,R) generators in the hyperbolic basis for Poincaré coordinates. It is shown that in the β+ →∞ limit, the conformal weight changes to a new value h‧ = h/2. This may be regarded as a Renormalization Group (RG) flow. It is argued that this RG flow will be triggered by terms ΔS ∝ β+W ‑1h + β‑W¯ ‑1h added to the action.

Discovery of a New Super-Fast Rotator

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-07-01

Recent observations of asteroid (335433) 2005 UW163 have added a new member to the mysterious category of "super-fast rotators" — asteroids that rotate faster than should be possible, given current theories of asteroid composition. Asteroids come in sizes of a few meters to a few hundred kilometers, and can spin at rates from 0.1 to nearly 1000 revolutions per day. Current theories suggest that asteroids smaller than 150m are mostly monolithic (made up of a single rock), whereas asteroids larger than 150m are usually what's known as a "rubble pile" — a collection of rock fragments from past collisions, bound together into a clump by gravity. "Rubble pile" asteroids have an important structural limitation: they can't spin faster than once every 2.2 hours without flying apart as the centripetal force overcomes the force of gravity. Asteroid 2005 UW163 violates this rule: its diameter is 690m, but it rotates once every 1.29 hours. This discovery was made by a team of scientists using telescopes at the Palomar Observatory in California to conduct a large survey of the rotation rates of nearby asteroids. The group, led by Chan-Kao Chang of Taiwan's National Central University, discovered 11 super-fast rotator candidates — of which asteroid 2005 UW163 is the first to have its rotation rate confirmed by additional observations. The category of super-fast rotators poses an interesting problem: how are they able to spin so quickly without flying apart? Either the density of these asteroids is unexpectedly high (roughly four times the density of typical "rubble pile" asteroids), or else there must be additional forces besides gravity at work to help hold the asteroid together, such as bonds between the rocks. Future observations of super-fast rotators will help us better understand the peculiar structure of these rocky neighbors. Citation: Chan-Kao Chang et al. 2014 ApJ 791 L35 doi:10.1088/2041-8205/791/2/L35

An Anzatz about Gravity, Cosmology, and the Pioneer Anomaly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murad, Paul

2010-01-28

The Pulsar 1913+16 binary system may represent a 'young' binary system where previously it is claimed that the dynamics are due to either a third body or a gravitational vortex. Usually a binary system's trajectory could reside in a single ellipse or circular orbit; the double ellipse implies that the 1913+16 system may be starting to degenerate into a single elliptical trajectory. This could be validated only after a considerably long time period. In a majority of binary star systems, the weights of both stars are claimed by analysis to be the same. It may be feasible that the trajectorymore » of the primary spinning star could demonstrate repulsive gravitational effects where the neutron star's high spin rate induces a repulsive gravitational source term that compensates for inertia. If true, then it provides evidence that angular momentum may be translated into linear momentum as a repulsive source that has propulsion implications. This also suggests mass differences may dictate the neutron star's spin rate as an artifact of a natural gravitational process. Moreover, the reduced matter required by the 'dark' mass hypothesis may not exist but these effects could be due to repulsive gravity residing in rotating celestial bodies.The Pioneer anomaly observed on five different deep-space spacecraft, is the appearance of a constant gravitational force directed toward the sun. Pioneer spacecraft data reveals that a vortex-like magnetic field exists emanating from the sun. The spiral arms of the Sun's magnetic vortex field may be causal to this constant acceleration. This may profoundly provide a possible experimental verification on a cosmic scale of Gertsenshtein's principle relating gravity to electromagnetism. Furthermore, the anomalous acceleration may disappear once the spacecraft passes out into a magnetic spiral furrow, which is something that needs to be observed in the future. Other effects offer an explanation from space-time geometry to the Yarkovsky thermal effects are discussed.« less

What's the matter with Enceladus' gravity?

NASA Astrophysics Data System (ADS)

Rivoldini, A.; Beuthe, M.; Trinh, A.

2016-12-01

Isostasy is clearly at work on Enceladus: long-wavelength gravity is positively correlated with topography, but also well compensated. If the influence of Enceladus' fast spin is taken into account, Airy isostasy implies a very thick crust (50 km) above a very thin ocean, in flat contradiction of the thin crust (20 km) implied by librations. In a desperate attempt to solve the problem, it was recently proposed to substitute flexural isostasy to Airy isostasy, using librations as a constraint on the crust thickness. However the huge lithospheric stresses required to support the load result in complete lithospheric failure. Here we propose a new isostatic model based on the sound physical principle of minimum crustal stress. We demonstrate that gravity combined with topography predicts a 20 km thick crust agreeing with - but independent from - the libration constraint. A consistent picture finally emerges from gravity-topography analysis, confirming that the south polar crust is only a few kilometres thick. Enceladus' resonant companion, Dione, is in a similar state of minimum stress isostasy. Its gravity and topography can be explained in terms of a 100 km thick isostatic crust overlying a 60 km thick global ocean, thus providing the first clear evidence for a present-day ocean within Dione.

New Matching Method for Accelerometers in Gravity Gradiometer

PubMed Central

Wei, Hongwei; Wu, Meiping; Cao, Juliang

2017-01-01

The gravity gradiometer is widely used in mineral prospecting, including in the exploration of mineral, oil and gas deposits. The mismatch of accelerometers adversely affects the measuring precision of rotating accelerometer-based gravity gradiometers. Several strategies have been investigated to address the imbalance of accelerometers in gradiometers. These strategies, however, complicate gradiometer structures because feedback loops and re-designed accelerometers are needed in these strategies. In this paper, we present a novel matching method, which is based on a new configuration of accelerometers in a gravity gradiometer. In the new configuration, an angle was introduced between the measurement direction of the accelerometer and the spin direction. With the introduced angle, accelerometers could measure the centrifugal acceleration generated by the rotating disc. Matching was realized by updating the scale factors of the accelerometers with the help of centrifugal acceleration. Further simulation computations showed that after adopting the new matching method, signal-to-noise ratio improved from −41 dB to 22 dB. Compared with other matching methods, our method is more flexible and costs less. The matching accuracy of this new method is similar to that of other methods. Our method provides a new idea for matching methods in gravity gradiometer measurement. PMID:28757584

New predictions on meson decays from string splitting

NASA Astrophysics Data System (ADS)

Bigazzi, Francesco; Cotrone, Aldo L.

2006-11-01

We study certain exclusive decays of high spin mesons into mesons in models of large Nc Yang-Mills with few flavors at strong coupling using string theory. The rate of the process is calculated by studying the splitting of a macroscopic string on the relevant dual gravity backgrounds. In the leading channel for the decay of heavy quarkonium into two open-heavy quark states, one of the two produced mesons has much larger spin than the other. In this channel the decay rate is practically independent on the spin and has a mild dependence on the mass of the heavy quarks. Moreover, it is only power-like suppressed with the mass of the produced quark-anti quark pair. We also reconsider decays of high spin mesons made up of light quarks, confirming the linear dependence of the rate on the mass of the decaying meson. As a bonus of our computation, we provide a formula for the splitting rate of a macroscopic string lying on a Dp-brane in flat space.

String Theory Methods for Condensed Matter Physics

NASA Astrophysics Data System (ADS)

Nastase, Horatiu

2017-09-01

Preface; Acknowledgments; Introduction; Part I. Condensed Matter Models and Problems: 1. Lightning review of statistical mechanics, thermodynamics, phases and phase transitions; 2. Magnetism in solids; 3. Electrons in solids: Fermi gas vs. Fermi liquid; 4. Bosonic quasi-particles: phonons and plasmons; 5. Spin-charge separation in 1+1 dimensional solids: spinons and holons; 6. The Ising model and the Heisenberg spin chain; 7. Spin chains and integrable systems; 8. The thermodynamic Bethe ansatz; 9. Conformal field theories and quantum phase transitions; 10. Classical vs. quantum Hall effect; 11. Superconductivity: Landau-Ginzburg, London and BCS; 12. Topology and statistics: Berry and Chern-Simons, anyons and nonabelions; 13. Insulators; 14. The Kondo effect and the Kondo problem; 15. Hydrodynamics and transport properties: from Boltzmann to Navier-Stokes; Part II. Elements of General Relativity and String Theory: 16. The Einstein equation and the Schwarzschild solution; 17. The Reissner-Nordstrom and Kerr-Newman solutions and thermodynamic properties of black holes; 18. Extra dimensions and Kaluza-Klein; 19. Electromagnetism and gravity in various dimensions. Consistent truncations; 20. Gravity plus matter: black holes and p-branes in various dimensions; 21. Weak/strong coupling dualities in 1+1, 2+1, 3+1 and d+1 dimensions; 22. The relativistic point particle and the relativistic string; 23. Lightcone strings and quantization; 24. D-branes and gauge fields; 25. Electromagnetic fields on D-branes. Supersymmetry and N = 4 SYM. T-duality of closed strings; 26. Dualities and M theory; 27. The AdS/CFT correspondence: definition and motivation; Part III. Applying String Theory to Condensed Matter Problems: 28. The pp wave correspondence: string Hamiltonian from N = 4 SYM; 29. Spin chains from N = 4 SYM; 30. The Bethe ansatz: Bethe strings from classical strings in AdS; 31. Integrability and AdS/CFT; 32. AdS/CFT phenomenology: Lifshitz, Galilean and Schrodinger symmetries and their gravity duals; 33. Finite temperature and black holes; 34. Hot plasma equilibrium thermodynamics: entropy, charge density and chemical potential of strongly coupled theories; 35. Spectral functions and transport properties; 36. Dynamic and nonequilibrium properties of plasmas: electric transport, Langevin diffusion and thermalization via black hole quasi-normal modes; 37. The holographic superconductor; 38. The fluid-gravity correspondence: conformal relativistic fluids from black hole horizons; 39. Nonrelativistic fluids: from Einstein to Navier-Stokes and back; Part IV. Advanced Applications: 40. Fermi gas and liquid in AdS/CFT; 41. Quantum Hall effect from string theory; 42. Quantum critical systems and AdS/CFT; 43. Particle-vortex duality and ABJM vs. AdS4 X CP3 duality; 44. Topology and non-standard statistics from AdS/CFT; 45. DBI scalar model for QGP/black hole hydro- and thermo-dynamics; 46. Holographic entanglement entropy in condensed matter; 47. Holographic insulators; 48. Holographic strange metals and the Kondo problem; References; Index.

Scattering of two spinning black holes in post-Minkowskian gravity, to all orders in spin, and effective-one-body mappings

NASA Astrophysics Data System (ADS)

Vines, Justin

2018-04-01

We demonstrate equivalences, under simple mappings, between the dynamics of three distinct systems—(i) an arbitrary-mass-ratio two-spinning-black-hole system, (ii) a spinning test black hole in a background Kerr spacetime, and (iii) geodesic motion in Kerr—when each is considered in the first post-Minkowskian (1PM) approximation to general relativity, i.e. to linear order G but to all orders in 1/c, and to all orders in the black holes’ spins, with all orders in the multipole expansions of their linearized gravitational fields. This is accomplished via computations of the net results of weak gravitational scattering encounters between two spinning black holes, namely the net O(G) changes in the holes’ momenta and spins as functions of the incoming state. The results are given in remarkably simple closed forms, found by solving effective Mathisson–Papapetrou–Dixon-type equations of motion for a spinning black hole in conjunction with the linearized Einstein equation, with appropriate matching to the Kerr solution. The scattering results fully encode the gauge-invariant content of a canonical Hamiltonian governing binary-black-hole dynamics at 1PM order, for generic (unbound and bound) orbits and spin orientations. We deduce one such Hamiltonian, which reproduces and resums the 1PM parts of all such previous post-Newtonian results, and which directly manifests the equivalences with the test-body limits via simple effective-one-body mappings.

EFTofPNG: a package for high precision computation with the effective field theory of post-Newtonian gravity

NASA Astrophysics Data System (ADS)

Levi, Michele; Steinhoff, Jan

2017-12-01

We present a novel public package ‘EFTofPNG’ for high precision computation in the effective field theory of post-Newtonian (PN) gravity, including spins. We created this package in view of the timely need to publicly share automated computation tools, which integrate the various types of physics manifested in the expected increasing influx of gravitational wave (GW) data. Hence, we created a free and open source package, which is self-contained, modular, all-inclusive, and accessible to the classical gravity community. The ‘EFTofPNG’ Mathematica package also uses the power of the ‘xTensor’ package, suited for complicated tensor computation, where our coding also strategically approaches the generic generation of Feynman contractions, which is universal to all perturbation theories in physics, by efficiently treating n-point functions as tensors of rank n. The package currently contains four independent units, which serve as subsidiaries to the main one. Its final unit serves as a pipeline chain for the obtainment of the final GW templates, and provides the full computation of derivatives and physical observables of interest. The upcoming ‘EFTofPNG’ package version 1.0 should cover the point mass sector, and all the spin sectors, up to the fourth PN order, and the two-loop level. We expect and strongly encourage public development of the package to improve its efficiency, and to extend it to further PN sectors, and observables useful for the waveform modelling.

Quantum and semiclassical spin networks: from atomic and molecular physics to quantum computing and gravity

NASA Astrophysics Data System (ADS)

Aquilanti, Vincenzo; Bitencourt, Ana Carla P.; Ferreira, Cristiane da S.; Marzuoli, Annalisa; Ragni, Mirco

2008-11-01

The mathematical apparatus of quantum-mechanical angular momentum (re)coupling, developed originally to describe spectroscopic phenomena in atomic, molecular, optical and nuclear physics, is embedded in modern algebraic settings which emphasize the underlying combinatorial aspects. SU(2) recoupling theory, involving Wigner's 3nj symbols, as well as the related problems of their calculations, general properties, asymptotic limits for large entries, nowadays plays a prominent role also in quantum gravity and quantum computing applications. We refer to the ingredients of this theory—and of its extension to other Lie and quantum groups—by using the collective term of 'spin networks'. Recent progress is recorded about the already established connections with the mathematical theory of discrete orthogonal polynomials (the so-called Askey scheme), providing powerful tools based on asymptotic expansions, which correspond on the physical side to various levels of semi-classical limits. These results are useful not only in theoretical molecular physics but also in motivating algorithms for the computationally demanding problems of molecular dynamics and chemical reaction theory, where large angular momenta are typically involved. As for quantum chemistry, applications of these techniques include selection and classification of complete orthogonal basis sets in atomic and molecular problems, either in configuration space (Sturmian orbitals) or in momentum space. In this paper, we list and discuss some aspects of these developments—such as for instance the hyperquantization algorithm—as well as a few applications to quantum gravity and topology, thus providing evidence of a unifying background structure.

Propagation peculiarities of mean field massive gravity

DOE PAGES

Deser, S.; Waldron, A.; Zahariade, G.

2015-07-28

Massive gravity (mGR) describes a dynamical “metric” on a fiducial, background one. We investigate fluctuations of the dynamics about mGR solutions, that is about its “mean field theory”. Analyzing mean field massive gravity (m¯GR) propagation characteristics is not only equivalent to studying those of the full non-linear theory, but also in direct correspondence with earlier analyses of charged higher spin systems, the oldest example being the charged, massive spin 3/2 Rarita–Schwinger (RS) theory. The fiducial and mGR mean field background metrics in the m¯GR model correspond to the RS Minkowski metric and external EM field. The common implications in bothmore » systems are that hyperbolicity holds only in a weak background-mean-field limit, immediately ruling both theories out as fundamental theories; a situation in stark contrast with general relativity (GR) which is at least a consistent classical theory. Moreover, even though both m¯GR and RS theories can still in principle be considered as predictive effective models in the weak regime, their lower helicities then exhibit superluminal behavior: lower helicity gravitons are superluminal as compared to photons propagating on either the fiducial or background metric. Thus our approach has uncovered a novel, dispersive, “crystal-like” phenomenon of differing helicities having differing propagation speeds. As a result, this applies both to m¯GR and mGR, and is a peculiar feature that is also problematic for consistent coupling to matter.« less

Nonsingular, big-bounce cosmology from spinor-torsion coupling

NASA Astrophysics Data System (ADS)

Popławski, Nikodem

2012-05-01

The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical big-bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic.

Turbulent black holes.

PubMed

Yang, Huan; Zimmerman, Aaron; Lehner, Luis

2015-02-27

We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.

Gravity resonance spectroscopy constrains dark energy and dark matter scenarios.

PubMed

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

2014-04-18

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

Black hole solutions in d = 5 Chern-Simons gravity

NASA Astrophysics Data System (ADS)

Brihaye, Yves; Radu, Eugen

2013-11-01

The five dimensional Einstein-Gauss-Bonnet gravity with a negative cosmological constant becomes, for a special value of the Gauss-Bonnet coupling constant, a Chern-Simons (CS) theory of gravity. In this work we discuss the properties of several different types of black object solutions of this model. Special attention is paid to the case of spinning black holes with equal-magnitude angular momenta which posses a regular horizon of spherical topology. Closed form solutions are obtained in the small angular momentum limit. Nonperturbative solutions are constructed by solving numerically the equations of the model. Apart from that, new exact solutions describing static squashed black holes and black strings are also discussed. The action and global charges of all configurations studied in this work are obtained by using the quasilocal formalism with boundary counterterms generalized for the case of a d = 5 CS theory.

The Bragg Reflection Polarimeter On the Gravity and Extreme Magnetism Small Explorer Mission

NASA Astrophysics Data System (ADS)

Allured, Ryan; Griffiths, S.; Daly, R.; Prieskorn, Z.; Marlowe, H.; Kaaret, P.; GEMS Team

2011-09-01

The strong gravity associated with black holes warps the spacetime outside of the event horizon, and it is predicted that this will leave characteristic signatures on the polarization of X-ray emission originating in the accretion disk. The Gravity and Extreme Magnetism Small Explorer (GEMS) mission will be the first observatory with the capability to make polarization measurements with enough sensitivity to quantitatively test this prediction. Students at the University of Iowa are currently working on the development of the Bragg Reflection Polarimeter (BRP), a soft X-ray polarimeter sensitive at 500 eV, that is the student experiment on GEMS. The BRP will complement the main experiment by making a polarization measurement from accreting black holes below the main energy band (2-10 keV). This measurement will constrain the inclination of the accretion disk and tighten measurements of black hole spin.

KSC-03PD-3279

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers stand by as the balloon at right is released to lift the solar array panel into position for installation on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3275

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3282

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3268

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3276

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3265

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3269

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

KSC-03PD-3278

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASAs Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einsteins general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

Time evolution as refining, coarse graining and entangling

NASA Astrophysics Data System (ADS)

Dittrich, Bianca; Steinhaus, Sebastian

2014-12-01

We argue that refining, coarse graining and entangling operators can be obtained from time evolution operators. This applies in particular to geometric theories, such as spin foams. We point out that this provides a construction principle for the physical vacuum in quantum gravity theories and more generally allows construction of a (cylindrically) consistent continuum limit of the theory.

Cosmology from a gauge induced gravity

NASA Astrophysics Data System (ADS)

Falciano, F. T.; Sadovski, G.; Sobreiro, R. F.; Tomaz, A. A.

2017-09-01

The main goal of the present work is to analyze the cosmological scenario of the induced gravity theory developed in previous works. Such a theory consists on a Yang-Mills theory in a four-dimensional Euclidian spacetime with { SO}(m,n) such that m+n=5 and m\\in {0,1,2} as its gauge group. This theory undergoes a dynamical gauge symmetry breaking via an Inönü-Wigner contraction in its infrared sector. As a consequence, the { SO}(m,n) algebra is deformed into a Lorentz algebra with the emergency of the local Lorentz symmetries and the gauge fields being identified with a vierbein and a spin connection. As a result, gravity is described as an effective Einstein-Cartan-like theory with ultraviolet correction terms and a propagating torsion field. We show that the cosmological model associated with this effective theory has three different regimes. In particular, the high curvature regime presents a de Sitter phase which tends towards a Λ CDM model. We argue that { SO}(m,n) induced gravities are promising effective theories to describe the early phase of the universe.

A Tether-Based Variable-Gravity Research Facility Concept

NASA Technical Reports Server (NTRS)

Sorensen, Kirk

2006-01-01

The recent announcement of a return to the Moon and a mission to Mars has made the question of human response to lower levels of gravity more important. Recent advances in tether technology spurred by NASA s research in MXER tethers has led to a re-examination of the concept of a variable-gravity research facility (xGRF) for human research in low Earth orbit. Breakthroughs in simplified inertial tracking have made it possible to consider eliminating the despun section of previous designs. This, in turn, improves the prospect of a facility based entirely around a tether, with the human module on one end and a countermass on the other. With such a configuration, propellantless spinup and spindown is also possible based on the conservation of angular momentum from a gravity-gradient configuration to a spinning configuration. This not only saves large amounts of propellant but vastly simplifies crew and consumable resupply operations, since these can now be done in a microgravity configuration. The importance of the science to be obtained and the performance improvements in this new design argue strongly for further investigation.

Higher-spin theory and holography

NASA Astrophysics Data System (ADS)

Gaberdiel, Matthias; Vasiliev, Mikhail

2013-05-01

This special issue of Journal of Physics A: Mathematical and Theoretical reviews recent developments in higher-spin gauge theories and their applications to holographic dualities. The analysis of higher-spin theories has a very long history, but it took until the mid 1980s for the first consistent higher-spin interactions to be constructed by Bengtsson, Bengtsson and Brink [1] and Berends, Burgers and van Dam [2]. Somewhat later it was shown by Fradkin and Vasiliev [3] that consistent higher-spin gauge theories that involve gravity should necessarily be defined on a curved background. The first consistent interacting higher-spin theories were then formulated at the classical level by Vasiliev in the early 1990s [4]. These higher-spin theories involve an infinite number of massless higher-spin fields that support higher-spin gauge symmetries, and indeed, are largely characterized by this underlying gauge symmetry. The simplest examples are provided by higher-spin theories on (anti)-de Sitter spaces, and in a sense, this anticipated the AdS/CFT correspondence. Indeed, in the tensionless limit of string theory, the massive excitations of string theory become massless, and hence define higher-spin gauge fields. On the other hand, from the dual gauge theory perspective, this is the limit in which the field theory becomes free, and therefore has many conserved higher-spin currents. By the usual AdS/CFT dictionary, these are dual to the higher-spin gauge symmetries of the bulk description. Following this line of argument, Sundborg [5] and Witten [6] suggested in 2001 that a duality relating a higher-spin theory on AdSd to a weakly coupled (d - 1)-dimensional conformal field theory should exist. A concrete proposal was then made by Klebanov and Polyakov [7] who conjectured that the simplest version of a higher-spin gauge theory on AdS4 should be dual to the 3d O(N ) vector model. Recently, much support for this conjecture was obtained by Giombi and Yin [8], and in turn, this has triggered a significant amount of activity in this general area. Among other things, the constraints that are implied by the higher-spin symmetries were analysed (see the paper by Maldacena and Zhiboedov in this issue [9]), and a fairly concrete proposal for how higher-spin theories are related to string theory was made (see the paper by Chang, Minwalla, Sharma and Yin in this issue [10]). Furthermore, a lower dimensional version of the conjecture was put forward by Gaberdiel and Gopakumar [11] that was subsequently also checked in some detail. These dualities hold the promise of offering insights into the inner workings of the AdS/CFT correspondence since they are complex enough to capture the essence of the duality, while at the same time being sufficiently simple in order to allow for a detailed analysis. Moreover, the methods specifically developed in higher-spin theory may be useful for understanding a general mechanism underlying holography, both in higher-spin models and beyond (see the paper by Vasiliev in this issue [12]). Another fascinating aspect of these higher-spin theories lies in the fact that the higher-spin symmetries mix generically fields of different spin, and in particular, the spin-2 metric and higher-spin excitations are related to one another by gauge transformations. As a result, higher-spin theories require a modification of the standard framework of Riemannian geometry since the usual diffeomorphism-invariant tensors are not gauge invariant any longer. In particular, higher-spin theories may therefore open the way towards understanding fundamental concepts of space-time geometry; for example, they may well have key lessons in store for how string theory resolves space-time singularities. In this issue we have collected together a number of review papers, summarizing the aforementioned recent developments, as well as research papers indicating current directions of interest in the study of higher-spin gauge theories. We hope that it will be useful, both for beginners interested in an introduction to the subject, and for experts already working in the field. Three of the reviews deal with the holographic dualities mentioned above: the paper by Giombi and Yin [13] reviews the situation for AdS4/CFT3, while the review by Gaberdiel and Gopakumar [14] deals with the lower-dimensional AdS3/CFT2 version. In addition, the review by Jevicki, Jin and Ye [15] explains a possible way of proving the duality using collective fields. There are two reviews on the construction of black holes in higher-spin gauge theories: the review by Iazeolla and Sundell [16] reviews the situation for 4d higher-spin theories, while the review by Ammon, Gutperle, Kraus and Perlmutter [17] deals with the three-dimensional case for which much progress has been made recently. Finally, the review of Sagnotti [18] explains various general aspects of higher-spin gauge theories. The research papers deal with different aspects of current developments; some are concerned with the holographic duality, while others develop the general theory of higher-spin fields. References [1] Bengtsson A K H, Bengtsson I and Brink L 1983 Cubic interaction terms for arbitrarily extended supermultiplets Nucl. Phys. B 227 41 [2] Berends F A, Burgers G J H Van Dam H 1984 On spin three self interactions Z. Phys. C 24 247 [3] Fradkin E S Vasiliev M A 1987 On the gravitational interaction of massless higher-spin fields Phys. Lett. B 189 89 [4] Vasiliev M A 1992 More on equations of motion for interacting massless fields of all spins in 3+1 dimensions Phys. Lett. B 285 225 [5] Sundborg B 2001 Stringy gravity, interacting tensionless strings and massless higher spins Nucl. Phys. Proc. Suppl. 102 113 (arXiv:hep-th/0103247) [6] Witten E 2001 Spacetime reconstruction Talk at the John Schwarz 60th Birthday Symp. (http://theory.caltech.edu/jhs60/witten/1.html) [7] Klebanov I R Polyakov A M 2002 AdS dual of the critical O (N ) vector model Phys. Lett. B 550 213 (arXiv:hep-th/0210114) [8] Giombi S Yin X 2010 Higher spin gauge theory and holography: the three-point functions J. High Energy Phys. JHEP09(2010)115 (arXiv:0912.3462 [hep-th]) [9] Maldacena J Zhiboedov A 2013 Constraining conformal field theories with a higher spin symmetry J. Phys. A: Math. Theor. 46 214011 (arXiv:1204.3882 [hep-th]) [10] Chang C-M, Minwalla A, Sharma T Yin X 2013 ABJ triality: from higher spin fields to strings J. Phys. A: Math. Theor. 46 214009 (arXiv:1207.4485 [hep-th]) [11] Gaberdiel M R Gopakumar R 2011 An AdS3 dual for minimal model CFTs Phys. Rev. D 83 066007 (arXiv:1011.2986 [hep-th]) [12] Vasiliev M A 2013 Holography, unfolding and higher-spin theory J. Phys. A: Math. Theor. 46 214013 (arXiv:1203.5554 [hep-th]) [13] Giombi S Yin X 2013 The higher spin/vector model duality J. Phys. A: Math. Theor. 46 214003 (arXiv:1208.4036 [hep-th]) [14] Gaberdiel M R Gopakumar R 2013 Minimal model holography J. Phys. A: Math. Theor. 46 214002 (arXiv:1207.6697 [hep-th]) [15] Jevicki A, Jin K Ye Q 2013 Perturbative and non-perturbative aspects in vector model/higher spin duality J. Phys. A: Math. Theor. 46 214005 (arXiv:1212.5215 [hep-th]) [16] Iazeolla C Sundell P 2013 Biaxially symmetric solutions to 4D higher-spin gravity J. Phys. A: Math. Theor. 46 214004 (arXiv:1208.4077 [hep-th]) [17] Ammon M, Gutperle M, Kraus P Perlmutter E 2013 Black holes in three dimensional higher spin gravity: a review J. Phys. A: Math. Theor. 46 214001 (arXiv:1208.5182 [hep-th]) [18] Sagnotti A 2013 Notes on strings and higher spins J. Phys. A: Math. Theor. 46 214006 (arXiv:1112.4285 [hep-th])

Fisher metric, geometric entanglement, and spin networks

NASA Astrophysics Data System (ADS)

Chirco, Goffredo; Mele, Fabio M.; Oriti, Daniele; Vitale, Patrizia

2018-02-01

Starting from recent results on the geometric formulation of quantum mechanics, we propose a new information geometric characterization of entanglement for spin network states in the context of quantum gravity. For the simple case of a single-link fixed graph (Wilson line), we detail the construction of a Riemannian Fisher metric tensor and a symplectic structure on the graph Hilbert space, showing how these encode the whole information about separability and entanglement. In particular, the Fisher metric defines an entanglement monotone which provides a notion of distance among states in the Hilbert space. In the maximally entangled gauge-invariant case, the entanglement monotone is proportional to a power of the area of the surface dual to the link thus supporting a connection between entanglement and the (simplicial) geometric properties of spin network states. We further extend such analysis to the study of nonlocal correlations between two nonadjacent regions of a generic spin network graph characterized by the bipartite unfolding of an intertwiner state. Our analysis confirms the interpretation of spin network bonds as a result of entanglement and to regard the same spin network graph as an information graph, whose connectivity encodes, both at the local and nonlocal level, the quantum correlations among its parts. This gives a further connection between entanglement and geometry.

Terrestrial Sagnac delay constraining modified gravity models

NASA Astrophysics Data System (ADS)

Karimov, R. Kh.; Izmailov, R. N.; Potapov, A. A.; Nandi, K. K.

2018-04-01

Modified gravity theories include f(R)-gravity models that are usually constrained by the cosmological evolutionary scenario. However, it has been recently shown that they can also be constrained by the signatures of accretion disk around constant Ricci curvature Kerr-f(R0) stellar sized black holes. Our aim here is to use another experimental fact, viz., the terrestrial Sagnac delay to constrain the parameters of specific f(R)-gravity prescriptions. We shall assume that a Kerr-f(R0) solution asymptotically describes Earth's weak gravity near its surface. In this spacetime, we shall study oppositely directed light beams from source/observer moving on non-geodesic and geodesic circular trajectories and calculate the time gap, when the beams re-unite. We obtain the exact time gap called Sagnac delay in both cases and expand it to show how the flat space value is corrected by the Ricci curvature, the mass and the spin of the gravitating source. Under the assumption that the magnitude of corrections are of the order of residual uncertainties in the delay measurement, we derive the allowed intervals for Ricci curvature. We conclude that the terrestrial Sagnac delay can be used to constrain the parameters of specific f(R) prescriptions. Despite using the weak field gravity near Earth's surface, it turns out that the model parameter ranges still remain the same as those obtained from the strong field accretion disk phenomenon.

Lorentz violation and gravity

NASA Astrophysics Data System (ADS)

Bailey, Quentin G.

2007-08-01

This work explores the theoretical and experimental aspects of Lorentz violation in gravity. A set of modified Einstein field equations is derived from the general Lorentz-violating Standard-Model Extension (SME). Some general theoretical implications of these results are discussed. The experimental consequences for weak-field gravitating systems are explored in the Earth- laboratory setting, the solar system, and beyond. The role of spontaneous Lorentz-symmetry breaking is discussed in the context of the pure-gravity sector of the SME. To establish the low-energy effective Einstein field equations, it is necessary to take into account the dynamics of 20 coefficients for Lorentz violation. As an example, the results are compared with bumblebee models, which are general theories of vector fields with spontaneous Lorentz violation. The field equations are evaluated in the post- newtonian limit using a perfect fluid description of matter. The post-newtonian metric of the SME is derived and compared with some standard test models of gravity. The possible signals for Lorentz violation due to gravity-sector coefficients are studied. Several new effects are identified that have experimental implications for current and future tests. Among the unconventional effects are a new type of spin precession for a gyroscope in orbit and a modification to the local gravitational acceleration on the Earth's surface. These and other tests are expected to yield interesting sensitivities to dimensionless gravity- sector coefficients.

Women in Surgery: Bright, Sharp, Brave, and Temperate

PubMed Central

McLemore, Elisabeth C; Ramamoorthy, Sonia; Peterson, Carrie Y; Bass, Barbara L

2012-01-01

Women make up an increasing proportion of students entering the medical profession. Before 1970, women represented 6% or less of the medical student population. In drastic contrast, nearly half of first-time applicants to medical schools in 2011 were women. However, the ratio of women to men is less balanced among graduates from surgical residencies and among leadership positions in surgery. Less than 20% of full professor, tenured faculty, and departmental head positions are currently held by women. However, this disparity may resolve with time as more women who entered the field in the 1980s emerge as mature surgeons and leaders. The aim of this article is to review the history of women in surgery and to highlight individual and institutional creative modifications that can promote the advancement of women in surgery. A secondary aim of the article is to add some levity to the discussion with personal anecdotes representing the primary author's (ECM) personal opinions, biases, and reflections. PMID:23012600

Gauge/Gravity correspondence and black hole attractors in various dimensions

NASA Astrophysics Data System (ADS)

Li, Wei

This thesis investigates several topics on Gauge/Gravity correspondence and black hole attractors in various dimensions. The first chapter contains a brief review and summary of main results. Chapters 2 and 3 aim at a microscopic description of black objects in five dimensions. Chapter 2 studies higher-derivative corrections for 5D black rings and spinning black holes. It shows that certain R 2 terms found in Calabi-Yau compactifications of M-theory yield macroscopic corrections to the entropies that match the microscopic corrections. Chapter 3 constructs probe brane configurations that preserve half of the enhanced near-horizon supersymmetry of 5D spinning black holes, whose near-horizon geometry is squashed AdS2 x S 3. There are supersymmetric zero-brane probes stabilized by orbital angular momentum on S3 and one-brane probes with momentum and winding around a U(1)L x U(1)R torus in S3. Chapter 4 constructs and analyzes generic single-centered and multi-centered black hole attractor solutions in various four-dimensional models which, after Kaluza-Klein reduction, admit a description in terms of 3D gravity coupled to a sigma model whose target space is symmetric coset space. The solutions correspond to certain nilpotent generators of the coset algebra. The non-BPS black hole attractors are found to be drastically different from their BPS counterparts. Chapter 5 examines three-dimensional topologically massive gravity with negative cosmological constant in asymptotically AdS 3 spacetimes. It proves that the theory is unitary and stable only at a special value of Chern-Simons coupling, where the theory becomes chiral. This suggests the existence of a stable, consistent quantum gravity theory at the chiral point which is dual to a holomorphic boundary CFT 2. Finally, Chapter 6 studies the two-dimensional N = 1 critical string theory with a linear dilaton background. It constructs time-dependent boundary state solutions that correspond to D0-branes falling toward the Liouville wall. It also shows that there exist four types of stable, falling D0-branes (two branes and two anti-branes) in Type 0A projection and two unstable ones in Type 0B projection.

KSC-03PD-2745

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. A transporter carrying the Gravity Probe B experiment backs into the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2748

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The Gravity Probe B experiment is lowered onto an assembly and test stand in the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2749

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The Gravity Probe B experiment rests on an assembly and test stand in the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2747

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The Gravity Probe B experiment is lifted from its transporter in the spacecraft processing facility on North Vandenberg Air Force Base. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2742

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Enclosed in a canister, the Gravity Probe B (GP-B) spacecraft arrives on Vandenberg Air Force Base, headed for the spacecraft processing facility. Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2743

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Enclosed in a canister, the Gravity Probe B (GP-B) spacecraft arrives at the spacecraft processing facility on North Vandenberg Air Force Base . Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2881

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Logos identify the mission of this Delta II rocket that will launch the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2880

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Logos identify the mission of this Delta II rocket that will launch the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

General results for higher spin Wilson lines and entanglement in Vasiliev theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hegde, Ashwin; Kraus, Per; Perlmutter, Eric

Here, we develop tools for the efficient evaluation of Wilson lines in 3D higher spin gravity, and use these to compute entanglement entropy in the hs[λ ] Vasiliev theory that governs the bulk side of the duality proposal of Gaberdiel and Gopakumar. Our main technical advance is the determination of SL(N) Wilson lines for arbitrary N, which, in suitable cases, enables us to analytically continue to hs[λ ] via N→ -λ. We then apply this result to compute various quantities of interest, including entanglement entropy expanded perturbatively in the background higher spin charge, chemical potential, and interval size. This includesmore » a computation of entanglement entropy in the higher spin black hole of the Vasiliev theory. Our results are consistent with conformal field theory calculations. We also provide an alternative derivation of the Wilson line, by showing how it arises naturally from earlier work on scalar correlators in higher spin theory. The general picture that emerges is consistent with the statement that the SL(N) Wilson line computes the semiclassical W N vacuum block, and our results provide an explicit result for this object.« less

General results for higher spin Wilson lines and entanglement in Vasiliev theory

DOE PAGES

Hegde, Ashwin; Kraus, Per; Perlmutter, Eric

2016-01-28

Here, we develop tools for the efficient evaluation of Wilson lines in 3D higher spin gravity, and use these to compute entanglement entropy in the hs[λ ] Vasiliev theory that governs the bulk side of the duality proposal of Gaberdiel and Gopakumar. Our main technical advance is the determination of SL(N) Wilson lines for arbitrary N, which, in suitable cases, enables us to analytically continue to hs[λ ] via N→ -λ. We then apply this result to compute various quantities of interest, including entanglement entropy expanded perturbatively in the background higher spin charge, chemical potential, and interval size. This includesmore » a computation of entanglement entropy in the higher spin black hole of the Vasiliev theory. Our results are consistent with conformal field theory calculations. We also provide an alternative derivation of the Wilson line, by showing how it arises naturally from earlier work on scalar correlators in higher spin theory. The general picture that emerges is consistent with the statement that the SL(N) Wilson line computes the semiclassical W N vacuum block, and our results provide an explicit result for this object.« less

Massive spin-2 scattering and asymptotic superluminality

NASA Astrophysics Data System (ADS)

Hinterbichler, Kurt; Joyce, Austin; Rosen, Rachel A.

2018-03-01

We place model-independent constraints on theories of massive spin-2 particles by considering the positivity of the phase shift in eikonal scattering. The phase shift is an asymptotic S-matrix observable, related to the time delay/advance experienced by a particle during scattering. Demanding the absence of a time advance leads to constraints on the cubic vertices present in the theory. We find that, in theories with massive spin-2 particles, requiring no time advance means that either: (i) the cubic vertices must appear as a particular linear combination of the Einstein-Hilbert cubic vertex and an h μν 3 potential term or (ii) new degrees of freedom or strong coupling must enter at parametrically the mass of the massive spin-2 field. These conclusions have implications for a variety of situations. Applied to theories of large- N QCD, this indicates that any spectrum with an isolated massive spin-2 at the bottom must have these particular cubic self-couplings. Applied to de Rham-Gabadadze-Tolley massive gravity, the constraint is in accord with results obtained from a shockwave calculation: of the two free dimensionless parameters in the theory there is a one parameter line consistent with a subluminal phase shift.

The rotational dynamics of Titan from Cassini RADAR images

NASA Astrophysics Data System (ADS)

Meriggiola, Rachele; Iess, Luciano; Stiles, Bryan. W.; Lunine, Jonathan. I.; Mitri, Giuseppe

2016-09-01

Between 2004 and 2009 the RADAR instrument of the Cassini mission provided 31 SAR images of Titan. We tracked the position of 160 surface landmarks as a function of time in order to monitor the rotational dynamics of Titan. We generated and processed RADAR observables using a least squares fit to determine the updated values of the rotational parameters. We provide a new rotational model of Titan, which includes updated values for spin pole location, spin rate, precession and nutation terms. The estimated pole location is compatible with the occupancy of a Cassini state 1. We found a synchronous value of the spin rate (22.57693 deg/day), compatible at a 3-σ level with IAU predictions. The estimated obliquity is equal to 0.31°, incompatible with the assumption of a rigid body with fully-damped pole and a moment of inertia factor of 0.34, as determined by gravity measurements.

Penrose limits and spin chains in the GJV/CS-SYM duality

NASA Astrophysics Data System (ADS)

Araujo, Thiago; Itsios, Georgios; Nastase, Horatiu; Colgáin, Eoin Ó.

2017-12-01

We examine Penrose limits of the duality proposed by Guarino, Jafferis and Varela between a type IIA massive background of the type of a warped, squashed AdS 4 × S 6, and a 2+1 dimensional IR fixed point of N=8 super Yang-Mills deformed by Chern-Simons terms to N=2 supersymmetry. One type of Penrose limit for closed strings corresponds to a large charge closed spin chain, and another, for open strings on giant graviton D-branes, corresponds to an open spin chain on sub-determinant operators. For the first limit, we find that like in the ABJM case, there are functions f a ( λ) that interpolate between the perturbative and nonperturbative (string) regions for the magnon energy. For the second, we are unable to match the gravity result with the expected field theory result, making this model more interesting than ones with more supersymmetry.

The Barrett-Crane model: asymptotic measure factor

NASA Astrophysics Data System (ADS)

Kamiński, Wojciech; Steinhaus, Sebastian

2014-04-01

The original spin foam model construction for 4D gravity by Barrett and Crane suffers from a few troubling issues. In the simple examples of the vertex amplitude they can be summarized as the existence of contributions to the asymptotics from non-geometric configurations. Even restricted to geometric contributions the amplitude is not completely worked out. While the phase is known to be the Regge action, the so-called measure factor has remained mysterious for a decade. In the toy model case of the 6j symbol this measure factor has a nice geometric interpretation of V-1/2 leading to speculations that a similar interpretation should be possible also in the 4D case. In this paper we provide the first geometric interpretation of the geometric part of the asymptotic for the spin foam consisting of two glued 4-simplices (decomposition of the 4-sphere) in the Barrett-Crane model in the large internal spin regime.

Projective Ponzano-Regge spin networks and their symmetries

NASA Astrophysics Data System (ADS)

Aquilanti, Vincenzo; Marzuoli, Annalisa

2018-02-01

We present a novel hierarchical construction of projective spin networks of the Ponzano-Regge type from an assembling of five quadrangles up to the combinatorial 4-simplex compatible with a geometrical realization in Euclidean 4-space. The key ingredients are the projective Desargues configuration and the incidence structure given by its space-dual, on the one hand, and the Biedenharn-Elliott identity for the 6j symbol of SU(2), on the other. The interplay between projective-combinatorial and algebraic features relies on the recoupling theory of angular momenta, an approach to discrete quantum gravity models carried out successfully over the last few decades. The role of Regge symmetry-an intriguing discrete symmetry of the 6j which goes beyond the standard tetrahedral symmetry of this symbol-will be also discussed in brief to highlight its role in providing a natural regularization of projective spin networks that somehow mimics the standard regularization through a q-deformation of SU(2).

Investigation of Spinning and Tumbling Characteristics of a 1/20-Scale Model of the Consolidated Vultee XFY-1 Airplane in the Free-Spinning Tunnel, TED No. NACA DE 370

NASA Technical Reports Server (NTRS)

Lee, Henry A.

1952-01-01

An investigation has been conducted in the Langley 20-foot free-spinning tunnel on a l/20-scale model of the Consolidated Vultee XFY-1 airplane with a windmilling propeller simulated to determine the effects of control setting and movements upon the erect spin and recovery characteristics for a range of airplane-loading conditions. The effects on the model's spin-recovery characteristics of removing the lower vertical tail, removing the gun pods, and fixing the rudders at neutral were also investigated briefly. The investigation included determination of the size parachute required for emergency recovery from demonstration spins. The tumbling tendencies of the model were also investigated. Brief static force tests were made to determine the aerodynamic characteristics in pitch at high angles of attack. The investigation indicated that the spin and recovery characteristics of the airplane with propeller windmilling will be satisfactory for all loading conditions if recovery is attempted by full rudder reversal accompanied by simultaneous movement of the stick laterally to full with the spin (stick right in a right spin) and longitudinally to neutral. Inverted spins should be satisfactorily terminated by fully reversing the rudder followed immediately by moving the stick laterally towards the forward rudder pedal and longitudinally to neutral. Removal of the gun pods or fixing the rudders at neutral will not adversely affect the airplane's spin-recovery characteristics, but removal of the lower vertical tail will result in unsatisfactory spin-recovery characteristics. The model-test results showed that a 13.3-foot wing-tip conventional parachute (drag coefficient approximately 0.7) should be effective as an emergency spin-recovery device during demonstration spins of the airplane. It was indicated that the airplane should not tumble and that no unusual longitudinal-trim characteristics should be obtained for the center-of-gravity positions investigated.

Free-Spinning-Tunnel Tests of a 0.057-Scale Model of the Chance Vought XF7U-1 Airplane

NASA Technical Reports Server (NTRS)

Daughtridge, Lee T., Jr.

1948-01-01

An investigation of the spin and recovery characteristics of a 0.057-scale model of the Chance Vought XF7U-1 airplane has been conducted in the Langley 20-foot free-spinning tunnel. The effects of control settings and movements on the erect and inverted spin and recovery characteristics were determined, as were also the effects of extending the wing slats, of center-of-gravity movement, and-of variation in the mass distribution. The investigation also included wing-tip spin-recovery-parachute tests, pilot-escape tests, and rudder-control-force tests. The investigation indicated that the spin and recovery characteristics of the airplane will be satisfactory for all conditions. It was found that a single 4.24-foot (full-scale) parachute when opened alone from the outboard wing tip or two 8.77-foot (full-scale) parachutes when opened simultaneously, one from each wing tip, would effect satisfactory emergency recoveries (the drag coefficients of the parachutes, based on the surface area of the parachute, were 0.83 and 0.70 for the 4.24- and 8.77-foot parachutes, respectively). The towline length in both cases was 25 feet (full scale). Tests results showed that, if the pilot should have to leave the airplane during a spin, he should jump from the outboard side (left side in a right spin) of the cockpit. The rudder-control force necessary for recovery from a spin was found to be rather high but appeared to be within the upper limits of a pilot's capabilities.

Arabella

NASA Technical Reports Server (NTRS)

1973-01-01

Arabella, a common cross spider, spins an earthly web aboard the second Skylab mission in 1973 after initial disoriented attempts. The experiment, Web Formation in Zero Gravity, part of the Skylab Student Project, was submitted by Judith Miles, a junior at Lexington High School in Lexington, Massachusetts. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments, including the Skylab Student Project.

Fermionic Tunneling Effect and Hawking Radiation in a Non Commutative FRW Universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouhalouf, H.; Aissaoui, H.; Mebarki, N.

2010-10-31

The formalism of a non commutative gauge gravity is applied to an FRW universe and the corresponding modified metric, veirbein and spin connection components are obtained. Moreover, using the Hamilton-Jacobi method and as a pure space-time deformation effect, the NCG Hawking radiation via a fermionic tunneling transition through the dynamical NCG horizon is also studied.

Group field theory and tensor networks: towards a Ryu–Takayanagi formula in full quantum gravity

NASA Astrophysics Data System (ADS)

Chirco, Goffredo; Oriti, Daniele; Zhang, Mingyi

2018-06-01

We establish a dictionary between group field theory (thus, spin networks and random tensors) states and generalized random tensor networks. Then, we use this dictionary to compute the Rényi entropy of such states and recover the Ryu–Takayanagi formula, in two different cases corresponding to two different truncations/approximations, suggested by the established correspondence.

Multipolar electromagnetic fields around neutron stars: general-relativistic vacuum solutions

NASA Astrophysics Data System (ADS)

Pétri, J.

2017-12-01

Magnetic fields inside and around neutron stars are at the heart of pulsar magnetospheric activity. Strong magnetic fields are responsible for quantum effects, an essential ingredient to produce leptonic pairs and the subsequent broad-band radiation. The variety of electromagnetic field topologies could lead to the observed diversity of neutron star classes. Thus, it is important to include multipolar components to a presumably dominant dipolar magnetic field. Exact analytical solutions for these multipoles in Newtonian gravity have been computed in recent literature. However, flat space-time is not adequate to describe physics in the immediate surroundings of neutron stars. We generalize the multipole expressions to the strong gravity regime by using a slowly rotating metric approximation such as the one expected around neutron stars. Approximate formulae for the electromagnetic field including frame dragging are computed from which we estimate the Poynting flux and the braking index. Corrections to leading order in compactness and spin parameter are presented. As far as spin-down luminosity is concerned, it is shown that frame dragging remains irrelevant. For high-order multipoles starting from the quadrupole, the electric part can radiate more efficiently than the magnetic part. Both analytical and numerical tools are employed.

Radiation induced rotation of interplanetary dust particles - A feasibility study for a space experiment

NASA Technical Reports Server (NTRS)

Ratcliff, K. F.; Misconi, N. Y.; Paddack, S. J.

1980-01-01

Irregular interplanetary dust particles may acquire a considerable spin rate due to two non-statistical dynamical mechanisms induced by solar radiation. These arise from variations in surface albedo discussed by Radzievskii (1954) and from irregularities in surface geometry discussed by Paddack (1969). An experiment is reported which will lead to an evaluation in space of the effectiveness of these two spin mechanisms. The technique of optical levitation in an argon laser beam provides a stable trap for particles 10-60 microns in diameter. The objective is to design an optical trap for dielectric particles in vacuum to study these rotation mechanisms in the gravity-free environment of a Spacelab experiment.

Observation of Diamond Nitrogen-Vacancy Center Photoluminescence under High Vacuum in a Magneto-Gravitational Trap

NASA Astrophysics Data System (ADS)

Ji, Peng; Hsu, Jen-Feng; Lewandowski, Charles W.; Dutt, M. V. Gurudev; D'Urso, Brian

2016-05-01

We report the observation of photoluminescence from nitrogen-vacancy (NV) centers in diamond nanocrystals levitated in a magneto-gravitational trap. The trap utilizes a combination of strong magnetic field gradients and gravity to confine diamagnetic particles in three dimensions. The well-characterized NV centers in trapped diamond nanocrystals provide an ideal built-in sensor to measure the trap magnetic field and the temperature of the trapped diamond nanocrystal. In the future, the NV center spin state could be coupled to the mechanical motion through magnetic field gradients, enabling in an ideal quantum interface between NV center spin and the mechanical motion. National Science Foundation, Grant No. 1540879.

Simulation of a flexible spinning vehicle

NASA Technical Reports Server (NTRS)

Baudry, W. A.

1972-01-01

Results are presented of experimental investigation of the controlled and uncontrolled dynamical behavior of a rotating or artificial gravity space station including flexible body effects. A dynamically scaled model was supported by a spherical air bearing which provided a nearly moment free environment. Reaction jet system were provided for spin-up and spin-down and for damping of wobble motion. Two single-gimbal gyros were arranged as a control moment gyro wobble damping system. Remotely controllable movable masses were provided to simulate mass shift disturbances such as arise from crew motions. An active mass balance wobble damping system which acted to minimize the wobble motions induced by crew motions was also installed. Flexible body effects were provided by a pair of inertia augmentation booms. Inertia augmentation booms are contemplated for use on rotating space stations to cause the spin axis moment of inertia to be the largest of the three moments of inertia as is necessary to assure gyroscopic stability. Test runs were made with each of the control systems with the booms locked (rigid body) and unlocked (flexible body).

The Interior Angular Momentum of Core Hydrogen Burning Stars from Gravity-mode Oscillations

NASA Astrophysics Data System (ADS)

Aerts, C.; Van Reeth, T.; Tkachenko, A.

2017-09-01

A major uncertainty in the theory of stellar evolution is the angular momentum distribution inside stars and its change during stellar life. We compose a sample of 67 stars in the core hydrogen burning phase with a {log} g value from high-resolution spectroscopy, as well as an asteroseismic estimate of the near-core rotation rate derived from gravity-mode oscillations detected in space photometry. This assembly includes 8 B-type stars and 59 AF-type stars, covering a mass range from 1.4 to 5 M ⊙, I.e., it concerns intermediate-mass stars born with a well-developed convective core. The sample covers projected surface rotation velocities v\\sin I\\in [9,242] km s-1 and core rotation rates up to 26 μHz, which corresponds to 50% of the critical rotation frequency. We find deviations from rigid rotation to be moderate in the single stars of this sample. We place the near-core rotation rates in an evolutionary context and find that the core rotation must drop drastically before or during the short phase between the end of the core hydrogen burning and the onset of core helium burning. We compute the spin parameter, which is the ratio of twice the rotation rate to the mode frequency (also known as the inverse Rossby number), for 1682 gravity modes and find the majority (95%) to occur in the sub-inertial regime. The 10 stars with Rossby modes have spin parameters between 14 and 30, while the gravito-inertial modes cover the range from 1 to 15.

f(T) teleparallel gravity and cosmology.

PubMed

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

2016-10-01

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

Asteroid Deflection: How, Where and When?

NASA Astrophysics Data System (ADS)

Fargion, D.

2008-10-01

To deflect impact-trajectory of massive and spinning km^3 asteroid by a few terrestrial radiuses one need a large momentum exchange. The dragging of huge spinning bodies in space by external engine seems difficult or impossible. Our solution is based on the landing of multi screw-rockets, powered by mini-nuclear engines, on the body, that dig a small fraction of the soil surface to use as an exhaust propeller, ejecting it vertically in phase among themselves. Such a mass ejection increases the momentum exchange, their number redundancy guarantees the stability of the system. The slow landing (below ≃ 40 cm s^{-1}) of each engine-unity at those very low gravity field, may be achieved by safe rolling and bouncing along the surface. The engine array tuned activity, overcomes the asteroid angular velocity. Coherent turning of the jet heads increases the deflection efficiency. A procession along its surface may compensate at best the asteroid spin. A small skin-mass (about 2×10^4 tons) may be ejected by mini-nuclear engines. Such prototypes may also build first safe galleries for humans on the Moon. Conclusive deflecting tests might be performed on remote asteroids. The incoming asteroid 99942 Apophis (just 2% of km^3) may be deflected safely a few Earth radiuses. Its encounter maybe not just a hazard but an opportunity, learning how to land, to dig, to build and also to nest safe human station inside. Asteroids amplified deflections by gravity swing may be driven into longest planetary journeys, beginning i.e. with the preliminary landing of future missions on Mars' moon-asteroid Phobos or Deimos.

Constraints on the perturbed mutual motion in Didymos due to impact-induced deformation of its primary after the DART impact

NASA Astrophysics Data System (ADS)

Hirabayashi, Masatoshi; Schwartz, Stephen R.; Yu, Yang; Davis, Alex B.; Chesley, Steven R.; Fahnestock, Eugene G.; Michel, Patrick; Richardson, Derek C.; Naidu, Shantanu P.; Scheeres, Daniel J.; Cheng, Andrew F.; Rivkin, Andrew S.; Benner, Lance A. M.

2017-12-01

Binary near-Earth asteroid (65803) Didymos is the target of the proposed NASA Double Asteroid Redirection Test (DART), part of the Asteroid Impact & Deflection Assessment (AIDA) mission concept. In this mission, the DART spacecraft is planned to impact the secondary body of Didymos, perturbing mutual dynamics of the system. The primary body is currently rotating at a spin period close to the spin barrier of asteroids, and materials ejected from the secondary due to the DART impact are likely to reach the primary. These conditions may cause the primary to reshape, due to landslides or internal deformation, changing the permanent gravity field. Here, we propose that if shape deformation of the primary occurs, the mutual orbit of the system would be perturbed due to a change in the gravity field. We use a numerical simulation technique based on the full two-body problem to investigate the shape effect on the mutual dynamics in Didymos after the DART impact. The results show that under constant volume, shape deformation induces strong perturbation in the mutual motion. We find that the deformation process always causes the orbital period of the system to become shorter. If surface layers with a thickness greater than ∼0.4 m on the poles of the primary move down to the equatorial region due to the DART impact, a change in the orbital period of the system and in the spin period of the primary will be detected by ground-based measurement.

A tilted and warped inner accretion disc around a spinning black hole: an analytical solution

NASA Astrophysics Data System (ADS)

Chakraborty, Chandrachur; Bhattacharyya, Sudip

2017-08-01

Inner accretion disc around a black hole provides a rare, natural probe to understand the fundamental physics of the strong gravity regime. A possible tilt of such a disc, with respect to the black hole spin equator, is important. This is because such a tilt affects the observed spectral and timing properties of the disc X-ray emission via Lense-Thirring precession, which could be used to test the theoretical predictions regarding the strong gravity. Here, we analytically solve the steady, warped accretion disc equation of Scheurer and Feiler, and find an expression of the radial profile of the disc tilt angle. In our exact solution, considering a prograde disc around a slowly spinning black hole, we include the inner part of the disc, which was not done earlier in this formalism. Such a solution is timely, as a tilted inner disc has recently been inferred from X-ray spectral and timing features of the accreting black hole H1743-322. Our tilt angle radial profile expression includes observationally measurable parameters, such as black hole mass and Kerr parameter, and the disc inner edge tilt angle Win, and hence can be ideal to confront observations. Our solution shows that the disc tilt angle in 10-100 gravitational radii is a significant fraction of the disc outer edge tilt angle, even for Win = 0. Moreover, tilt angle radial profiles have humps in ˜10-1000 gravitational radii for some sets of parameter values, which should have implications for observed X-ray features.

Cosmic space and Pauli exclusion principle in a system of M0-branes

NASA Astrophysics Data System (ADS)

Capozziello, Salvatore; Saridakis, Emmanuel N.; Bamba, Kazuharu; Sepehri, Alireza; Rahaman, Farook; Ali, Ahmed Farag; Pincak, Richard; Pradhan, Anirudh

An emergence of cosmic space has been suggested by Padmanabhan [Emergence and expansion of cosmic space as due to the quest for holographic equipartition, arXiv:hep-th/1206.4916] where he proposed that the expansion of the universe originates from a difference between the number of degrees of freedom on a holographic surface and the one in the emerged bulk. Now, a natural question that arises is how this proposal would explain the production of fermions and an emergence of the Pauli exclusion principle during the evolution of the universe? We try to address this issue in a system of M0-branes. In this model, there is a high symmetry and the system is composed of M0-branes to which only scalar fields are attached that represent scalar modes of the graviton. Then, when M0-branes join each other and hence form M1-branes, this symmetry is broken and gauge fields are formed. Therefore, these M1-branes interact with the anti-M1-branes and the force between them leads to a break of a symmetry such as the lower and upper parts of these branes are not the same. In these conditions, gauge fields which are localized on M1-branes and scalars which are attached to them symmetrically, decay to fermions with upper and lower spins which attach to the upper and lower parts of the M1-branes anti-symmetrically. The curvature produced by the coupling of identical spins has the opposite sign of the curvature produced by non-identical spins which lead to an attractive force between anti-parallel spins and a repelling force between parallel spins and hence an emergence of the Pauli exclusion principle. By approaching M1-branes to each other, the difference between curvatures of parallel spins and curvatures of anti-parallel spins increases, which leads to an inequality between the number of degrees of freedom on the surface and the one in the emerged bulk and hence lead to an occurrence of the cosmic expansion. By approaching M1-branes to each other, the square of the energy of the system becomes negative and hence tachyonic states arise. To remove these states, M1-branes compactify, the sign of gravity changes and anti-gravity emerges which leads to the branes moving away from each other. By joining M1-branes, M3-branes are produced which are similar to an initial system that oscillates between compacting and opening branches. Our universe is placed on one of these M3-branes and by changing the difference between the amount of couplings between identical and non-identical spins, it contracts or expands.

Book Review:

NASA Astrophysics Data System (ADS)

Kiefer, C.

2005-10-01

The most difficult unsolved problem in fundamental theoretical physics is the consistent implementation of the gravitational interaction into a quantum framework, which would lead to a theory of quantum gravity. Although a final answer is still pending, several promising attempts do exist. Despite the general title, this book is about one of them - loop quantum gravity. This approach proceeds from the idea that a direct quantization of Einstein's theory of general relativity is possible. In contrast to string theory, it presupposes that the unification of all interactions is not needed as a prerequisite for quantum gravity. Usually one divides theories of quantum general relativity into covariant and canonical approaches. Covariant theories employ four-dimensional concepts in its formulation, one example being the path integral approach. Canonical theories start from a classical Hamiltonian version of the theory in which spacetime is foliated into spacelike hypersurfaces. Loop quantum gravity is a variant of the canonical approach, the oldest being quantum geometrodynamics where the fundamental configuration variable is the three-metric. Loop quantum gravity has developed from a new choice of canonical variables introduced by Abhay Ashtekar in 1986, the new configuration variable being a connection defined on a three-manifold. Instead of the connection itself, the loop approach employs a non-local version in which the connection is integrated over closed loops. This is similar to the Wilson loops used in gauge theories. Carlo Rovelli is one of the pioneers of loop quantum gravity which he started to develop with Lee Smolin in two papers written in 1988 and 1990. In his book, he presents a comprehensive and competent overview of this approach and provides at the same time the necessary technical background in order to make the treatment self-contained. In fact, half of the book is devoted to 'preparations' giving a detailed account of Hamiltonian mechanics, quantum mechanics, general relativity and other topics. According to the level of the reader, this part can be skipped or studied as interesting material on its own. The penetrating theme of the whole book (its leitmotiv) is background independence. In non-gravitational theories, dynamical fields are formulated on a fixed background spacetime that plays the role of an absolute structure in the theory. In general relativity, on the other hand, there is no background structure - all fields are dynamical. This was a confusing point already during the development of general relativity and led Albert Einstein in 1913 erroneously to give up general covariance before recognizing his error and presenting his final correct field equations that are of course covariant. This story is instructive, circling around the famous 'hole problem', and is told in detail in Rovelli's book. Its solution is that points on a bare manifold do not make sense in physics; everything, including the gravitational field, is dragged around by a diffeomorphism - there is just no background available, only the fields exist. In loop quantum gravity, physical space (called 'quantum geometry') itself is formed by loop-like quantum states: a suitable orthonormal basis is provided by spin-network states (a spin-network is a graph with edges and nodes, where spins are assigned to the edges), and the quantum geometry is a superposition of such states. Time and space in the usual sense have disappeared. In the second half of his book, Rovelli discusses at length the major successes of this approach. First of all, the formalism yields a unique kinematical Hilbert space for the quantum states obeying the Gauss and diffeomorphism constraints. The situation with the Hamiltonian constraint is more subtle. The need for a Hilbert-space structure in quantum gravity is, however, not discussed. After all, the Hilbert-space structure in quantum mechanics is tied to the presence of an external time and the conservation of probability with respect to this external time. But in quantum gravity there is no background structure, in particular no external time. Secondly, there exist two important operators that are connected, respectively, with area and volume in the classical limit. These operators have a discrete spectrum and thus provide elementary 'quanta' of area and volume. This gives a vague hint of a discrete structure at the Planck scale, about which there were speculations for many decades. In spite of these promising results, loop quantum gravity is still far away from a physical theory. This is also reflected in this volume where the technical treatment prevails and where physical applications are relegated to about 20 pages. These applications deal with quantum cosmology and black holes. The part on loop quantum cosmology summarizes briefly recent results about a possible singularity avoidance and a new mechanism for inflation. These results are not derived from loop quantum gravity but from imposing the discrete structure of the full theory directly on the quantum cosmological models. The part on black holes discusses the derivation of the Bekenstein-Hawking entropy from counting the number of relevant spin-network states. Since the theory contains a free parameter (the 'Barbero-Immirzi parameter'), the best one can do is to determine this parameter by demanding that the result be the Bekenstein-Hawking entropy. The book does not yet contain the results of recent papers, published in 2004, that correct the earlier entropy calculations presented here. From the new value of the Barbero-Immirzi parameter, the appealing connection with quasi-normal modes, as discussed in the book, may be lost. The book concludes with a brief discussion of the major open issues. Among these are the following: a well-defined and physically sensible semiclassical limit, the precise form of the Hamiltonian, the role of unification (most of the work in loop quantum gravity deals only with pure gravity) and, last but not least, the issue of quantitative and testable predictions. Whether loop quantum gravity will become a physical theory is not clear. Nor is this clear for string theory or any other approach. However, loop quantum gravity provides a fascinating line of research and has much conceptual appeal. The present volume gives both an introduction and a review of this approach, making it suitable for advanced students as well as experts. It is certainly of interest for the readers of Classical and Quantum Gravity.

Effects of De-spinning and Lithosphere Thickening on the Lunar Fossil Bulge

NASA Astrophysics Data System (ADS)

Zhong, S.; Qin, C.; Phillips, R. J.

2016-12-01

The Moon has abnormally large degree-2 anomalies in gravity and shape (or bulge). The degree-2 gravity coefficients C20 and C22 are, respectively, 22 and 7 times greater than expected from the Moon's current orbital and rotational states. One prevalent hypothesis, called the fossil bulge hypothesis, interprets the current degree-2 shape as a remnant of the bulge that froze in when the Moon was closer to the Earth with stronger tidal and rotational potentials. However, the dynamic feasibility of the freeze-in process has never been quantitatively examined. In this study, we explore, using numerical models of viscoelastic deformation with time-dependent rotational potential and lithospheric rheology, how the degree-2 bulge would evolve with time as the early Moon cools and migrates away from the Earth. Our model includes two competing effects: 1) a thickening lithosphere with time through cooling, which helps maintain the bulge, and 2) de-spinning through tidal locking, which tends to reduce the bulge. In our model, a strong lithosphere is represented by the topmost layer that is orders of magnitude more viscous than the mantle. The benchmark results show that our numerical model can compute the bulge size accurately. Our calculations start with a bulge size that is in hydrostatic equilibrium with the initial rotational rate. The bulge reduces with time as the Moon spins down, while the lithosphere can support certain amount of bulge as it thickens. We find that the final size of the bulge is controlled by the relative time scales of the two processes. At limiting cases, if the time scale of de-spinning were much larger than that of lithosphere thickening, the bulge size would be largely maintained. Conversely, the bulge size would be reduced significantly. We will consider more realistic time scales for these two processes, as well as effects of other subsequent processes after lunar magma ocean crystallization, such as large impacts and mare volcanism.

GMI Instrument Spin Balance Method, Optimization, Calibration and Test

NASA Technical Reports Server (NTRS)

Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

2014-01-01

The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3-year mission life. Therefore, GMI must be very precisely balanced about the spin axis and center of gravity (CG) to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

Binary Mixture of Perfect Fluid and Dark Energy in Modified Theory of Gravity

NASA Astrophysics Data System (ADS)

Shaikh, A. Y.

2016-07-01

A self consistent system of Plane Symmetric gravitational field and a binary mixture of perfect fluid and dark energy in a modified theory of gravity are considered. The gravitational field plays crucial role in the formation of soliton-like solutions, i.e., solutions with limited total energy, spin, and charge. The perfect fluid is taken to be the one obeying the usual equation of state, i.e., p = γρ with γ∈ [0, 1] whereas, the dark energy is considered to be either the quintessence like equation of state or Chaplygin gas. The exact solutions to the corresponding field equations are obtained for power-law and exponential volumetric expansion. The geometrical and physical parameters for both the models are studied.

KSC-03PD-2754

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, workers conduct battery charge/discharge cycles as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2751

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, workers conduct battery charge/discharge cycles as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2752

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, workers conduct battery charge/discharge cycles as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2750

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, battery charge/discharge cycles are underway as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2753

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, workers conduct battery charge/discharge cycles as part of the battery conditioning process on Gravity Probe B. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03pd2743

NASA Image and Video Library

2003-07-11

VANDENBERG AFB, CALIF. - Enclosed in a canister, the Gravity Probe B (GP-B) spacecraft arrives at the spacecraft processing facility on North Vandenberg Air Force Base . Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einstein’s general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Once in orbit, for 18 months each gyroscope’s spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASA’s Marshall Space Flight Center.

Fate of the Hoop Conjecture in Quantum Gravity.

PubMed

Anzà, Fabio; Chirco, Goffredo

2017-12-08

We consider a closed region R of 3D quantum space described via SU(2) spin networks. Using the concentration of measure phenomenon we prove that, whenever the ratio between the boundary ∂R and the bulk edges of the graph overcomes a finite threshold, the state of the boundary is always thermal, with an entropy proportional to its area. The emergence of a thermal state of the boundary can be traced back to a large amount of entanglement between boundary and bulk degrees of freedom. Using the dual geometric interpretation provided by loop quantum gravity, we interpret such phenomenon as a pregeometric analogue of Thorne's "hoop conjecture," at the core of the formation of a horizon in general relativity.

KSC-03PD-2868

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. A worker in the spacecraft processing facility on North Vandenberg Air Force Base checks the Gravity Probe B experiment during prelaunch testing. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

Miles Discusses Experiment With NASA Personnel

NASA Technical Reports Server (NTRS)

1972-01-01

Lexington, Massachusetts high school student, Judith Miles, discusses her proposed Skylab experiment with Keith Demorest (right) and Henry Floyd, both of Marshall Space Flight Center (MSFC). In her experiment, called the 'Web Formation in Zero Gravity', called for spiders to be released into a box and their actions recorded to determine how well they adapt to the absence of gravity. Spiders are known to adapt quickly to other changes in the environment but nothing was known of their ability to adapt to weightlessness. At the same time spiders were weaving webs in Earth orbit, similar spiders were spinning webs in identical boxes on Earth under full gravity conditions. Miles was among the 25 winners of a contest in which some 3,500 high school students proposed experiments for the following year's Skylab Mission. Of the 25 students, 6 did not see their experiments conducted on Skylab because the experiments were not compatible with Skylab hardware and timelines. Of the 19 remaining, 11 experiments required the manufacture of equipment.

Initial Satellite Formation Flight Results from the Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Williams, Trevor; Ottenstein, Neil; Palmer, Eric; Farahmand, Mitra

2016-01-01

This paper will describe the results that have been obtained to date concerning MMS formation flying. The MMS spacecraft spin at a rate of 3.1 RPM, with spin axis roughly aligned with Ecliptic North. Several booms are used to deploy instruments: two 5 m magnetometer booms in the spin plane, two rigid booms of length 12.5 m along the positive and negative spin axes, and four flexible wire booms of length 60 m in the spin plane. Minimizing flexible motion of the wire booms requires that reorientation of the spacecraft spin axis be kept to a minimum: this is limited to attitude maneuvers to counteract the effects of gravity-gradient and apparent solar motion. Orbital maneuvers must therefore be carried out in essentially the nominal science attitude. These burns make use of a set of monopropellant hydrazine thrusters: two (of thrust 4.5 N) along the spin axis in each direction, and eight (of thrust 18 N) in the spin plane; the latter are pulsed at the spin rate to produce a net delta-v. An on-board accelerometer-based controller is used to accurately generate a commanded delta-v. Navigation makes use of a weak-signal GPS-based system: this allows signals to be received even when MMS is flying above the GPS orbits, producing a highly accurate determination of the four MMS orbits. This data is downlinked to the MMS Mission Operations Center (MOC) and used by the MOC Flight Dynamics Operations Area (FDOA) for maneuver design. These commands are then uplinked to the spacecraft and executed autonomously using the controller, with the ground monitoring the burns in real time.

Gapless topological order, gravity, and black holes

NASA Astrophysics Data System (ADS)

Rasmussen, Alex; Jermyn, Adam S.

2018-04-01

In this work we demonstrate that linearized gravity exhibits gapless topological order with an extensive ground state degeneracy. This phenomenon is closely related both to the topological order of the pyrochlore U (1 ) spin liquid and to recent work by Hawking and co-workers, who used the soft-photon and graviton theorems to demonstrate that the vacuum in linearized gravity is not unique. We first consider lattice models whose low-energy behavior is described by electromagnetism and linearized gravity, and then argue that the topological nature of these models carries over into the continuum. We demonstrate that these models can have many ground states without making assumptions about the topology of spacetime or about the high-energy nature of the theory, and show that the infinite family of symmetries described by Hawking and co-workers is simply the different topological sectors. We argue that in this context black holes appear as topological defects in the infrared theory, and that this suggests a potential approach to understanding both the firewall paradox and information encoding in gravitational theories. Finally, we use insights from the soft-boson theorems to make connections between deconfined gauge theories with continuous gauge groups and gapless topological order.

Background-independent condensed matter models for quantum gravity

NASA Astrophysics Data System (ADS)

Hamma, Alioscia; Markopoulou, Fotini

2011-09-01

A number of recent proposals on a quantum theory of gravity are based on the idea that spacetime geometry and gravity are derivative concepts and only apply at an approximate level. There are two fundamental challenges to any such approach. At the conceptual level, there is a clash between the 'timelessness' of general relativity and emergence. Secondly, the lack of a fundamental spacetime renders difficult the straightforward application of well-known methods of statistical physics to the problem. We recently initiated a study of such problems using spin systems based on the evolution of quantum networks with no a priori geometric notions as models for emergent geometry and gravity. In this paper, we review two such models. The first model is a model of emergent (flat) space and matter, and we show how to use methods from quantum information theory to derive features such as the speed of light from a non-geometric quantum system. The second model exhibits interacting matter and geometry, with the geometry defined by the behavior of matter. This model has primitive notions of gravitational attraction that we illustrate with a toy black hole, and exhibits entanglement between matter and geometry and thermalization of the quantum geometry.

Dynamic wormhole solutions in Einstein-Cartan gravity

NASA Astrophysics Data System (ADS)

Mehdizadeh, Mohammad Reza; Ziaie, Amir Hadi

2017-12-01

In the present work, we investigate evolving wormhole configurations described by a constant redshift function in Einstein-Cartan theory. The matter content consists of a Weyssenhoff fluid along with an anisotropic matter which together generalize the anisotropic energy momentum tensor in general relativity in order to include the effects of intrinsic angular momentum (spin) of particles. Using a generalized Friedmann-Robertson-Walker spacetime, we derive analytical evolving wormhole geometries by assuming a particular equation of state for energy density and pressure profiles. We introduce exact asymptotically flat and anti-de Sitter spacetimes that admit traversable wormholes and respect energy conditions throughout the spacetime. The rate of expansion of these evolving wormholes is determined only by the Friedmann equation in the presence of spin effects.

jsc2018m000314_Spinning_Science_Multi-use_Variable-g_Platform_Arrives_at_the_Space_Station-MP4

NASA Image and Video Library

2018-05-09

Spinning Science: Multi-use Variable-g Platform Arrives at the Space Station --- The Multi-use Variable-gravity Platform (MVP) Validation mission will install and test the MVP, a new hardware platform developed and owned by Techshot Inc., on the International Space Station (ISS). Though the MVP is designed for research with many different kinds of organisms and cell types, this validation mission will focus on Drosophila melanogaster, more commonly known as the fruit fly. This platform will be especially important for fruit fly research, as it will allow researchers to study larger sample sizes of Drosophila melanogaster than in other previous hardware utilizing centrifuges and it will be able to support fly colonies for multiple generations.

Constraints on Mass, Spin and Magnetic Field of Microquasar H 1743-322 from Observations of QPOs

NASA Astrophysics Data System (ADS)

Tursunov, A. A.; Kološ, M.

2018-03-01

The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in many microquasars can provide a powerful tool for testing of the phenomena occurring in strong gravity regime. QPOs phenomena can be well related to the oscillations of charged particles in accretion disks orbiting Kerr black holes immersed in external large-scalemagnetic fields. In the present paper we study the model ofmagnetic relativistic precession and provide estimations of the mass and spin of the central object of the microquasar H 1743-322 which is a candidate for a black hole. Moreover, we discuss the possible values of external magnetic field and study its influence on the motion of charged particles around rotating black hole.

UNIVERSE IN A BLACK HOLE IN EINSTEIN–CARTAN GRAVITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popławski, Nikodem, E-mail: NPoplawski@newhaven.edu

The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space onmore » the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.« less

Universe in a Black Hole in Einstein-Cartan Gravity

NASA Astrophysics Data System (ADS)

Popławski, Nikodem

2016-12-01

The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein-Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space on the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.

On the origin of Poincaré gauge gravity

NASA Astrophysics Data System (ADS)

Chkareuli, J. L.

2017-06-01

We argue that the origin of Poincaré gauge gravity (PGG) may be related to spontaneous violation of underlying spacetime symmetries involved and appearance of gauge fields as vector Goldstone bosons. In essence, we start with an arbitrary theory of some vector and fermion fields which possesses only global spacetime symmetries, such as Lorentz and translational invariance, in flat Minkowski space. The two vector field multiplets involved are assumed to belong, respectively, to the adjoint (Aμij) and vector (eμi) representations of the starting global Lorentz symmetry. We propose that these prototype vector fields are covariantly constrained, Aμij Aijμ = ±MA2 and eμi eiμ = ±Me2 , that causes a spontaneous violation of the accompanying global symmetries (MA,e are their presumed violation scales). It then follows that the only possible theory compatible with these length-preserving constraints is turned out to be the gauge invariant PGG, while the corresponding massless (pseudo)Goldstone modes are naturally collected in the emergent gauge fields of tetrads and spin-connections. In a minimal theory case being linear in a curvature we unavoidably come to the Einstein-Cartan theory. The extended theories with propagating spin-connection and tetrad modes are also considered and their possible unification with the Standard Model is briefly discussed.

Sloshing dynamics on rotating helium dewar tank

NASA Technical Reports Server (NTRS)

Hung, R. J.

1993-01-01

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics were based on the non-inertia frame spacecraft bound coordinate, and solve time dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers were derived. Results were widely published in the open journals.

Numerical studies of the surface tension effect of cryogenic liquid helium

NASA Technical Reports Server (NTRS)

Hung, R. J.

1994-01-01

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose of performing scientific observation during the normal spacecraft operation is investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics has been based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers, have been derived.

Influence of the geometric configuration of accretion flow on the black hole spin dependence of relativistic acoustic geometry

NASA Astrophysics Data System (ADS)

Tarafdar, Pratik; Das, Tapas K.

Linear perturbation of general relativistic accretion of low angular momentum hydrodynamic fluid onto a Kerr black hole leads to the formation of curved acoustic geometry embedded within the background flow. Characteristic features of such sonic geometry depend on the black hole spin. Such dependence can be probed by studying the correlation of the acoustic surface gravity κ with the Kerr parameter a. The κ-a relationship further gets influenced by the geometric configuration of the accretion flow structure. In this work, such influence has been studied for multitransonic shocked accretion where linear perturbation of general relativistic flow profile leads to the formation of two analogue black hole-type horizons formed at the sonic points and one analogue white hole-type horizon which is formed at the shock location producing divergent acoustic surface gravity. Dependence of the κ-a relationship on the geometric configuration has also been studied for monotransonic accretion, over the entire span of the Kerr parameter including retrograde flow. For accreting astrophysical black holes, the present work thus investigates how the salient features of the embedded relativistic sonic geometry may be determined not only by the background spacetime, but also by the flow configuration of the embedding matter.

Faster paleospin and deep-seated uncompensated mass as possible explanations for Ceres' present-day shape and gravity

NASA Astrophysics Data System (ADS)

Mao, Xiaochen; McKinnon, William B.

2018-01-01

We show that Ceres' measured degree-2 zonal gravity, J2, is smaller by about 10% than that derived assuming Ceres' rotational flattening, as measured by Dawn, is hydrostatic. Irrespective of Ceres' radial density variation, as long as its internal structure is hydrostatic the J2 predicted from the shape model is consistently larger than measured. As an explanation, we suggest that Ceres' current shape may be a fossil remnant of faster rotation in the geologic past. We propose that up to ∼7% of Ceres' previous spin angular momentum has been removed by dynamic perturbations such as a random walk due to impacts or a loss of satellite that slowed Ceres spin as it tidally evolved outward. As an alternative, we also consider a formal degree-2 admittance solution, from which we infer a range of possible non-hydrostatic contributions to J2 from uncompensated, deep-seated density anomalies. We show that such density anomalies could be due to low order convection or upwelling. The normalized moments-of-inertia derived for the two explanations - faster paleospin and deep-seated density anomalies - range between 0.353 ± 0.009 and 0.375 ± 0.001 for a spherically equivalent Ceres, which can be used as constraints on more complex Ceres interior models.

Hyperunified field theory and gravitational gauge-geometry duality

NASA Astrophysics Data System (ADS)

Wu, Yue-Liang

2018-01-01

A hyperunified field theory is built in detail based on the postulates of gauge invariance and coordinate independence along with the conformal scaling symmetry. All elementary particles are merged into a single hyper-spinor field and all basic forces are unified into a fundamental interaction governed by the hyper-spin gauge symmetry SP(1, D_h-1). The dimension D_h of hyper-spacetime is conjectured to have a physical origin in correlation with the hyper-spin charge of elementary particles. The hyper-gravifield fiber bundle structure of biframe hyper-spacetime appears naturally with the globally flat Minkowski hyper-spacetime as a base spacetime and the locally flat hyper-gravifield spacetime as a fiber that is viewed as a dynamically emerged hyper-spacetime characterized by a non-commutative geometry. The gravitational origin of gauge symmetry is revealed with the hyper-gravifield that plays an essential role as a Goldstone-like field. The gauge-gravity and gravity-geometry correspondences bring about the gravitational gauge-geometry duality. The basic properties of hyperunified field theory and the issue on the fundamental scale are analyzed within the framework of quantum field theory, which allows us to describe the laws of nature in deriving the gauge gravitational equation with the conserved current and the geometric gravitational equations of Einstein-like type and beyond.

A d-dimensional stress tensor for Minkd+2 gravity

NASA Astrophysics Data System (ADS)

Kapec, Daniel; Mitra, Prahar

2018-05-01

We consider the tree-level scattering of massless particles in ( d+2)-dimensional asymptotically flat spacetimes. The S -matrix elements are recast as correlation functions of local operators living on a space-like cut ℳ d of the null momentum cone. The Lorentz group SO( d + 1 , 1) is nonlinearly realized as the Euclidean conformal group on ℳ d . Operators of non-trivial spin arise from massless particles transforming in non-trivial representations of the little group SO( d), and distinguished operators arise from the soft-insertions of gauge bosons and gravitons. The leading soft-photon operator is the shadow transform of a conserved spin-one primary operator J a , and the subleading soft-graviton operator is the shadow transform of a conserved spin-two symmetric traceless primary operator T ab . The universal form of the soft-limits ensures that J a and T ab obey the Ward identities expected of a conserved current and energy momentum tensor in a Euclidean CFT d , respectively.

The f ( R ) halo mass function in the cosmic web

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braun-Bates, F. von; Winther, H.A.; Alonso, D.

An important indicator of modified gravity is the effect of the local environment on halo properties. This paper examines the influence of the local tidal structure on the halo mass function, the halo orientation, spin and the concentration-mass relation. We use the excursion set formalism to produce a halo mass function conditional on large-scale structure. Our simple model agrees well with simulations on large scales at which the density field is linear or weakly non-linear. Beyond this, our principal result is that f ( R ) does affect halo abundances, the halo spin parameter and the concentration-mass relationship in anmore » environment-independent way, whereas we find no appreciable deviation from \\text(ΛCDM) for the mass function with fixed environment density, nor the alignment of the orientation and spin vectors of the halo to the eigenvectors of the local cosmic web. There is a general trend for greater deviation from \\text(ΛCDM) in underdense environments and for high-mass haloes, as expected from chameleon screening.« less

Symmetry operators and decoupled equations for linear fields on black hole spacetimes

NASA Astrophysics Data System (ADS)

Araneda, Bernardo

2017-02-01

In the class of vacuum Petrov type D spacetimes with cosmological constant, which includes the Kerr-(A)dS black hole as a particular case, we find a set of four-dimensional operators that, when composed off shell with the Dirac, Maxwell and linearized gravity equations, give a system of equations for spin weighted scalars associated with the linear fields, that decouple on shell. Using these operator relations we give compact reconstruction formulae for solutions of the original spinor and tensor field equations in terms of solutions of the decoupled scalar equations. We also analyze the role of Killing spinors and Killing-Yano tensors in the spin weight zero equations and, in the case of spherical symmetry, we compare our four-dimensional formulation with the standard 2  +  2 decomposition and particularize to the Schwarzschild-(A)dS black hole. Our results uncover a pattern that generalizes a number of previous results on Teukolsky-like equations and Debye potentials for higher spin fields.

Lorentz-violating modification of Dirac theory based on spin-nondegenerate operators

NASA Astrophysics Data System (ADS)

Reis, J. A. A. S.; Schreck, M.

2017-04-01

The Standard Model extension (SME) parametrizes all possible Lorentz-violating contributions to the Standard Model and general relativity. It can be considered as an effective framework to describe possible quantum-gravity effects for energies much below the Planck energy. In the current paper, the spin-nondegenerate operators of the SME fermion sector are the focus. The propagators, energies, and solutions to the modified Dirac equation are obtained for several families of coefficients including nonminimal ones. The particle energies and spinors are computed at first order in Lorentz violation and, with the optical theorem, they are shown to be consistent with the propagators. The optical theorem is then also used to derive the matrices formed from a spinor and its Dirac conjugate at all orders in Lorentz violation. The results are the first explicit ones derived for the spin-nondegenerate operators. They will prove helpful for future phenomenological calculations in the SME that rely on the footing of quantum field theory.

Irreversibility and higher-spin conformal field theory

NASA Astrophysics Data System (ADS)

Anselmi, Damiano

2000-08-01

I discuss the properties of the central charges c and a for higher-derivative and higher-spin theories (spin 2 included). Ordinary gravity does not admit a straightforward identification of c and a in the trace anomaly, because it is not conformal. On the other hand, higher-derivative theories can be conformal, but have negative c and a. A third possibility is to consider higher-spin conformal field theories. They are not unitary, but have a variety of interesting properties. Bosonic conformal tensors have a positive-definite action, equal to the square of a field strength, and a higher-derivative gauge invariance. There exists a conserved spin-2 current (not the canonical stress tensor) defining positive central charges c and a. I calculate the values of c and a and study the operator-product structure. Higher-spin conformal spinors have no gauge invariance, admit a standard definition of c and a and can be coupled to Abelian and non-Abelian gauge fields in a renormalizable way. At the quantum level, they contribute to the one-loop beta function with the same sign as ordinary matter, admit a conformal window and non-trivial interacting fixed points. There are composite operators of high spin and low dimension, which violate the Ferrara-Gatto-Grillo theorem. Finally, other theories, such as conformal antisymmetric tensors, exhibit more severe internal problems. This research is motivated by the idea that fundamental quantum field theories should be renormalization-group (RG) interpolations between ultraviolet and infrared conformal fixed points, and quantum irreversibility should be a general principle of nature.

Gravitoelectromagnetic perturbations of Kerr-Newman black holes: stability and isospectrality in the slow-rotation limit.

PubMed

Pani, Paolo; Berti, Emanuele; Gualtieri, Leonardo

2013-06-14

The most general stationary black-hole solution of Einstein-Maxwell theory in vacuum is the Kerr-Newman metric, specified by three parameters: mass M, spin J, and charge Q. Within classical general relativity, one of the most important and challenging open problems in black-hole perturbation theory is the study of gravitational and electromagnetic fields in the Kerr-Newman geometry, because of the indissoluble coupling of the perturbation functions. Here we circumvent this long-standing problem by working in the slow-rotation limit. We compute the quasinormal modes up to linear order in J for any value of Q and provide the first, fully consistent stability analysis of the Kerr-Newman metric. For scalar perturbations the quasinormal modes can be computed exactly, and we demonstrate that the method is accurate within 3% for spins J/J(max) ≲ 0.5, where J(max) is the maximum allowed spin for any value of Q. Quite remarkably, we find numerical evidence that the axial and polar sectors of the gravitoelectromagnetic perturbations are isospectral to linear order in the spin. The extension of our results to nonasymptotically flat space-times could be useful in the context of gauge-gravity dualities and string theory.

Behavior of a test gyroscope moving towards a rotating traversable wormhole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Chandrachur; Pradhan, Parthapratim, E-mail: chandrachur.chakraborty@tifr.res.in, E-mail: pppradhan77@gmail.com

2017-03-01

The geodesic structure of the Teo wormhole is briefly discussed and some observables are derived that promise to be of use in detecting a rotating traversable wormhole indirectly, if it does exist. We also deduce the exact Lense-Thirring (LT) precession frequency of a test gyroscope moving toward a rotating traversable Teo wormhole. The precession frequency diverges on the ergoregion, a behavior intimately related to and governed by the geometry of the ergoregion, analogous to the situation in a Kerr spacetime. Interestingly, it turns out that here the LT precession is inversely proportional to the angular momentum ( a ) ofmore » the wormhole along the pole and around it in the strong gravity regime, a behavior contrasting with its direct variation with a in the case of other compact objects. In fact, divergence of LT precession inside the ergoregion can also be avoided if the gyro moves with a non-zero angular velocity in a certain range. As a result, the spin precession frequency of the gyro can be made finite throughout its whole path, even very close to the throat, during its travel to the wormhole. Furthermore, it is evident from our formulation that this spin precession not only arises due to curvature or rotation of the spacetime but also due to the non-zero angular velocity of the spin when it does not move along a geodesic in the strong gravity regime. If in the future, interstellar travel indeed becomes possible through a wormhole or at least in its vicinity, our results would prove useful in determining the behavior of a test gyroscope which is known to serve as a fundamental navigation device.« less

Satellite Laser Ranging in the 1990s: Report of the 1994 Belmont Workshop

NASA Technical Reports Server (NTRS)

Degnan, John J. (Editor)

1994-01-01

An international network of 43 stations in 30 countries routinely collects satellite ranging data which is used to study the solid Earth and its interactions with the oceans, atmosphere, and Moon. Data products include centimeter accuracy site positions on a global scale, tectonic plate motions, regional crustal deformation, long wavelength gravity field and geoid, polar motion, and variations in the Earth's spin rate. By calibrating and providing precise orbits for spaceborne microwave altimeters, satellite laser ranging also enables global measurement of sea and ice surface topography, mean sea level, global ocean circulation, and short wavelength gravity fields and marine geoids. It provides tests of general relativity and a means or subnanosecond time transfer. This workshop was convened to define future roles and directions in satellite laser ranging.

KSC-03PD-2741

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the spacecraft processing facility on North Vandenberg Air Force Base get ready to begin processing the Gravity Probe B experiment, including setting up mechanical and electrical ground support equipment, making necessary connections and conditioning the spacecraft battery. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2740

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the spacecraft processing facility on North Vandenberg Air Force Base get ready to begin processing the Gravity Probe B experiment, including setting up mechanical and electrical ground support equipment, making necessary connections and conditioning the spacecraft battery. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2867

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B experiment sits on an assembly and test stand where it has been subject to various prelaunch testing. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2739

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the spacecraft processing facility on North Vandenberg Air Force Base get ready to begin processing the Gravity Probe B experiment, including setting up mechanical and electrical ground support equipment, making necessary connections and conditioning the spacecraft battery. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

Chirality and gravitational parity violation.

PubMed

Bargueño, Pedro

2015-06-01

In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented. © 2015 Wiley Periodicals, Inc.

2D quantum gravity from quantum entanglement.

PubMed

Gliozzi, F

2011-01-21

In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

Space-Based Gravitational-Wave Observations as Tools for Testing General Relativity

NASA Technical Reports Server (NTRS)

Will, Clifford M.

2004-01-01

We continued a project, to analyse the ways in which detection and study of gravitational waves could provide quantitative tests of general relativity, with particular emphasis on waves that would be detectable by space-based observatories, such as LISA. This work had three foci: 1) Tests of scalar-tensor theories of gravity that, could be done by analyzing gravitational waves from neutron stars inspiralling into massive black holes, as detectable by LISA; 2) Study of alternative theories of gravity in which the graviton could be massive, and of how gravitational-wave observations by space-based detectors, solar-system tests, and cosmological observations could constrain such theories; and 3) Study of gravitational-radiation back reaction of particles orbiting black holes in general relativity, with emphasis on the effects of spin.

Cell Partition in Two Polymer Aqueous Phases

NASA Technical Reports Server (NTRS)

Harris, J. M.

1985-01-01

Partition of biological cells in two phase aqueous polymer systems is recognized as a powerful separation technique which is limited by gravity. The synthesis of new, selective polymer ligand conjugates to be used in affinity partition separations is of interest. The two most commonly used polymers in two phase partitioning are dextran and polyethylene glycol. A thorough review of the chemistry of these polymers was begun, particularly in the area of protein attachment. Preliminary studies indicate the importance in affinity partitioning of minimizing gravity induced randomizing forces in the phase separation process. The PEG-protein conjugates that were prepared appear to be ideally suited for achieving high quality purifications in a microgravity environment. An interesting spin-off of this synthetic work was the observation of catalytic activity for certain of our polymer derivatives.

KSC-03PD-2872

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2870

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is raised to a vertical position at Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2883

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted off the transporter after its arrival on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2879

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., rolls back from the Delta II rocket that will launch the Gravity Probe B experiment. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2878

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The second stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2869

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The first stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2884

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2882

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The second stage of the Delta II launch vehicle for the Gravity Probe B experiment arrives at the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

Space Station Biological Research Project

NASA Technical Reports Server (NTRS)

Johnson, Catherine C.; Hargens, Alan R.; Wade, Charles E.

1995-01-01

NASA Ames Research Center is responsible for the development of the Space Station Biological Research Project (SSBRP) which will support non-human life sciences research on the International Space Station Alpha (ISSA). The SSBRP is designed to support both basic research to understand the effect of altered gravity fields on biological systems and applied research to investigate the effects of space flight on biological systems. The SSBRP will provide the necessary habitats to support avian and reptile eggs, cells and tissues, plants and rodents. In addition a habitat to support aquatic specimens will be provided by our international partners. Habitats will be mounted in ISSA compatible racks at u-g and will also be mounted on a 2.5 m diameter centrifuge except for the egg incubator which has an internal centrifuge. The 2.5 m centrifuge will provide artificial gravity levels over the range of 0.01 G to 2 G. The current schedule is to launch the first rack in 1999, the Life Sciences glovebox and a second rack early in 2001, a 4 habitat 2.5 in centrifuge later the same year in its own module, and to upgrade the centrifuge to 8 habitats in 2004. The rodent habitats will be derived from the Advanced Animal Habitat currently under development for the Shuttle program and will be capable of housing either rats or mice individually or in groups (6 rats/group and at least 12 mice/group). The egg incubator will be an upgraded Avian Development Facility also developed for the Shuttle program through a Small Business and Innovative Research grant. The Space Tissue Loss cell culture apparatus, developed by Walter Reed Army Institute of Research, is being considered for the cell and tissue culture habitat. The Life Sciences Glovebox is crucial to all life sciences experiments for specimen manipulation and performance of science procedures. It will provide two levels of containment between the work volume and the crew through the use of seals and negative pressure. The glovebox will accommodate use by two crew persons simultaneously and the capability for real time video down-link and data acquisition. In house testbeds and Phase B studies of the centrifuge validated the concepts of vibration isolation and autobalancing systems to meet the ISSA microgravity requirements. The vibration isolation system is effective above the centrifuge rotation frequency while the autobalancing system on the rotor removes vibration at and below the rotation rate. Torque of the Station, induced by spin-up/spindown of the centrifuge, can be minimized by controlling spin-up/spin-down rates. The SSBRP and ISSA will provide the opportunity to perform long-term, repeatable and high quality science. The long duration increments available on the Station will permit multigeneration studies of both plants and animals which have not previously been possible. The u-g habitat racks and the eight habitat centrifuge will accommodate sufficient number of specimens to permit statistically significant sampling of specimens to investigate the time course of adaptation to altered gravity environments. The centrifuge will, for the first time, permit investigators to use gravity itself as a tool to investigate fundamental processes, to investigate the intensity and duration of gravity to maintain normal structure and function, to separate the effects of u-g from other environmental factors and to examine artificial gravity as a potential countermeasure for the physical deconditioning observed during space flight.

PHOS Experiment: Thermal Response of a Large Diameter Pulsating Heat Pipe on Board REXUS-18 Rocket

NASA Astrophysics Data System (ADS)

Creatini, F.; Guidi, G. M.; Belfi, F.; Cicero, G.; Fioriti, D.; Di Prizio, D.; Piacquadio, S.; Becatti, G.; Orlandini, G.; Frigerio, A.; Fontanesi, S.; Nannipieri, P.; Rognini, M.; Morganti, N.; Filippeschi, S.; Di Marco, P.; Fanucci, L.; Baronti, F.; Mameli, M.; Marengo, M.; Manzoni, M.

2015-09-01

In the present work, the results of two Closed Loop Pulsating Heat Pipes (CLPHPs) tested on board REXUS-1 8 sounding rocket in order to get experimental data over a relatively broad reduced gravity period (about 90 s) are thoroughly discussed. The CLPHPs are partially filled with refrigerant FC-72 and have, respectively, an inner tube diameter larger (3 .0 mm) and slightly smaller (1 .6 mm) than a critical diameter defined on Earth gravity conditions. On ground, the small diameter CLPHP works as a real Pulsating Heat Pipe (PHP): the typical capillary slug flow pattern forms inside the device and the heat exchange is triggered by self-sustained thermally driven oscillations of the working fluid. Conversely, the large diameter CLPHP behaves like a two-phase thermosyphon in vertical position while does not operate in horizontal position as the working fluid stratifies within the tube and surface tension is not able to balance buoyancy. Then, the idea to test the CLPHPs under reduced gravity conditions: as soon as gravity reduces, buoyancy becomes less intense and the typical capillary slug flow pattern can also forms within a tube with a larger diameter. Moreover, this allows to increase the heat transfer rate and, consequently, to decrease the overall thermal resistance. Even though it was not possible to experience the expected reduced gravity conditions due to a failure of the yo-yo de-spin system, the thermal response to the peculiar acceleration field (hyper-gravity) experienced on board are thoroughly described.

Experimental Searches for Exotic Short-Range Forces Using Mechanical Oscillators

NASA Astrophysics Data System (ADS)

Weisman, Evan

Experimental searches for forces beyond gravity and electromagnetism at short range have attracted a great deal of attention over the last decade. In this thesis I describe the test mass development for two new experiments searching for forces below 1 mm. Both modify a previous experiment that used 1 kHz mechanical oscillators as test masses with a stiff conducting shield between them to suppress backgrounds, a promising technique for probing exceptionally small distances at the limit of instrumental thermal noise. To further reduce thermal noise, one experiment will use plated silicon test masses at cryogenic temperatures. The other experiment, which searches for spin-dependent interactions, will apply the spin-polarizable material Dy3Fe5O 12 to the test mass surfaces. This material exhibits orbital compensation of the magnetism associated with its intrinsic electron spin, minimizing magnetic backgrounds. Several plated silicon test mass prototypes were fabricated using photolithography (useful in both experiments), and spin-dependent materials were synthesized with a simple chemical recipe. Both silicon and spin-dependent test masses demonstrate the mechanical and magnetic properties necessary for sensitive experiments. I also describe sensitivity calculations of another proposed spin-dependent experiment, based on a modified search for the electron electric dipole moment, which show unprecedented sensitivity to exotic monopole-dipole forces. Inspired by a finite element model, a study attempting to maximize detector quality factor versus geometry is also presented, with experimental results so far not explained by the model.

Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658.

PubMed

Reis, R C; Reynolds, M T; Miller, J M; Walton, D J

2014-03-13

The co-evolution of a supermassive black hole with its host galaxy through cosmic time is encoded in its spin. At z > 2, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. It is not known, however, whether below z ≈ 1 these black holes continue to grow by coherent accretion or in a chaotic manner, though clear differences are predicted in their spin evolution. An established method of measuring the spin of black holes is through the study of relativistic reflection features from the inner accretion disk. Owing to their greater distances from Earth, there has hitherto been no significant detection of relativistic reflection features in a moderate-redshift quasar. Here we report an analysis of archival X-ray data together with a deep observation of a gravitationally lensed quasar at z = 0.658. The emission originates within three or fewer gravitational radii from the black hole, implying a spin parameter (a measure of how fast the black hole is rotating) of a = 0.87(+0.08)(-0.15) at the 3σ confidence level and a > 0.66 at the 5σ level. The high spin found here is indicative of growth by coherent accretion for this black hole, and suggests that black-hole growth at 0.5 ≤ z ≤ 1 occurs principally by coherent rather than chaotic accretion episodes.

New vertices and canonical quantization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexandrov, Sergei

2010-07-15

We present two results on the recently proposed new spin foam models. First, we show how a (slightly modified) restriction on representations in the Engle-Pereira-Rovelli-Livine model leads to the appearance of the Ashtekar-Barbero connection, thus bringing this model even closer to loop quantum gravity. Second, we however argue that the quantization procedure used to derive the new models is inconsistent since it relies on the symplectic structure of the unconstrained BF theory.

Asymptotic Charges at Null Infinity in Any Dimension

NASA Astrophysics Data System (ADS)

Campoleoni, Andrea; Francia, Dario; Heissenberg, Carlo

2018-03-01

We analyse the conservation laws associated with large gauge transformations of massless fields in Minkowski space. Our aim is to highlight the interplay between boundary conditions and finiteness of the asymptotically conserved charges in any space-time dimension, both even and odd, greater than or equal to three. After discussing non-linear Yang-Mills theory and revisiting linearised gravity, our investigation extends to cover the infrared behaviour of bosonic massless quanta of any spin.

Introduction to the AdS/CFT Correspondence

NASA Astrophysics Data System (ADS)

Nąstase, Horaǧiu

2015-09-01

Preface; Introduction; Part I. Background: 1. Elements of quantum field theory and gauge theory; 2. Basics of general relativity. Anti-de Sitter space; 3. Basics of supersymmetry; 4. Basics of supergravity; 5. Kaluza-Klein dimensional reduction; 6. Black holes and p-branes; 7. String theory actions and spectra; 8. Elements of conformal field theory; 9. D-branes; Part II. Basics of AdS/CFT for N = 4 SYM vs AdS5 × S5: 10. The AdS/CFT correspondence: motivation, definition and spectra; 11. Witten prescription and 3-point correlator calculations; 12. Holography in Lorentzian signature: Poincaré and global; 13. Solitonic objects in AdS/CFT; 14. Quarks and the Wilson loop; 15. Finite temperature and N = 4 SYM plasmas; 16. Scattering processes and gravitational shockwave limit; 17. The pp-wave correspondence; 18. Spin chains; Part III. AdS/CFT Developments and Gauge-Gravity Dualities: 19. Other conformal cases; 20. The 3 dimensional ABJM model vs. AdS4 × CP3; 21. Gravity duals; 22. Holographic renormalization; 23. RG flow between fixed points; 24. Phenomenological gauge-gravity duality I: AdS/QCD; 25. Phenomenological gauge-gravity duality II: AdS/CMT; 26. Gluon scattering: the Alday-Maldacena prescription; 27. Holographic entanglement entropy: the Ryu-Takayanagi prescription.

Conformal anomaly and off-shell extensions of gravity

NASA Astrophysics Data System (ADS)

Meissner, Krzysztof A.; Nicolai, Hermann

2017-08-01

The gauge dependence of the conformal anomaly for spin-3/2 and spin-2 fields in nonconformal supergravities has been a long standing puzzle. In this paper we argue that the "correct" gauge choice is the one that follows from requiring all terms that would imply a violation of the Wess-Zumino consistency condition to be absent in the counterterm, because otherwise the usual link between the anomaly and the one-loop divergence becomes invalid. Remarkably, the "good" choice of gauge is the one that confirms our previous result [K. A. Meissner and H. Nicolai, Phys. Lett. B 772, 169 (2017)., 10.1016/j.physletb.2017.06.031] that a complete cancellation of conformal anomalies in D =4 can only be achieved for N -extended (Poincaré) supergravities with N ≥5 .

The dynamics of particle disks. III - Dense and spinning particle disks. [development of kinetic theory for planetary rings

NASA Technical Reports Server (NTRS)

Araki, Suguru

1991-01-01

The kinetic theory of planetary rings developed by Araki and Tremaine (1986) and Araki (1988) is extended and refined, with a focus on the implications of finite particle size: (1) nonlocal collisions and (2) finite filling factors. Consideration is given to the derivation of the equations for the local steady state, the low-optical-depth limit, and the steady state at finite filling factors (including the effects of collision inelasticity, spin degrees of freedom, and self-gravity). Numerical results are presented in extensive graphs and characterized in detail. The importance of distinguishing effects (1) and (2) at low optical depths is stressed, and the existence of vertical density profiles with layered structures at high filling factors is demonstrated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Jason W., E-mail: jwbarnes@uidaho.ed

Main-sequence stars earlier than spectral-type approxF6 or so are expected to rotate rapidly due to their radiative exteriors. This rapid rotation leads to an oblate stellar figure. It also induces the photosphere to be hotter (by up to several thousand kelvin) at the pole than at the equator as a result of a process called gravity darkening that was first predicted by von Zeipel. Transits of extrasolar planets across such a non-uniform, oblate disk yield unusual and distinctive lightcurves that can be used to determine the relative alignment of the stellar rotation pole and the planet orbit normal. This spin-orbitmore » alignment can be used to constrain models of planet formation and evolution. Orderly planet formation and migration within a disk that is coplanar with the stellar equator will result in spin-orbit alignment. More violent planet-planet scattering events should yield spin-orbit misaligned planets. Rossiter-McLaughlin measurements of transits of lower-mass stars show that some planets are spin-orbit aligned, and some are not. Since Rossiter-McLaughlin measurements are difficult around rapid rotators, lightcurve photometry may be the best way to determine the spin-orbit alignment of planets around massive stars. The Kepler mission will monitor approx10{sup 4} of these stars within its sample. The lightcurves of any detected planets will allow us to probe the planet formation process around high-mass stars for the first time.« less

Rayleigh-Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries

NASA Technical Reports Server (NTRS)

Titarchuk, Lev

2002-01-01

Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the approximation of very small pressure gradients is reduced to the problem of the classical oscillator in the rotational frame of reference which was previously introduced and applied for the interpretation of kHZ QPO observation by Osherovich & Titarchuk.

Subsonic Dynamics of Stardust Sample Return Capsule

NASA Technical Reports Server (NTRS)

Mitcheltree, Robert A.; Fremaux, Charles M.

1997-01-01

Subsonic dynamic stability tests performed in the NASA Langley 20-Foot Vertical Spin-Tunnel on a 0.238 scale model of the Stardust Sample Return Capsule are discussed. The tests reveal that the blunted 60 degree half-angle cone capsule is dynamically unstable at low subsonic conditions due to the aft location of the center-of-gravity (0.351 body diameters back from the nose). The divergent behavior of the capsule continued when the center-of-gravity was moved to 0.337 and 0.313 body diameters back from the nose. When the center-of-gravity was moved further forward to 0.290 body diameters back from the nose, the vehicle established itself in a limit cycle with amplitude around 10 degrees. Two afterbody modifications were examined which proved unsuccessful in alleviating the instability of the original design. Finally, the addition of different sized parachutes was examined as a means to stabilize the vehicle. The parachute tests indicate that a parachute with equivalent full scale drag area of at least 2.24 ft. is necessary to assure large perturbations are damped.

Benefits of ESA Gravity-Related Hands-on Programmes for University Students' Careers

NASA Astrophysics Data System (ADS)

Callens, Natacha; Ha, Lily; Galeone, Piero

2016-10-01

The Education Office of the European Space Agency (ESA) offers university students, from ESA Member and Cooperating States, the opportunity to perform investigations in physical sciences, life sciences, and technology, under different gravity conditions through three educational programmes. The "Fly Your Thesis!" (FYT) programme makes use of parabolic flights and the "Drop Your Thesis!" (DYT) programme utilizes a drop tower as microgravity carriers, while the "Spin Your Thesis!" (SYT) programme uses a large centrifuge to create hypergravity. To date, more than hundred university students had the chance to participate in the design, development, and performance of one or more experiments during dedicated campaigns. In the following paper, we examine demographics of past participants of the ESA Education Office gravity-related opportunities over the past seven years and evaluate the benefits of these educational programmes for the participants' studies and careers. Student teams that participated in one of the programmes between 2009 and 2013 were contacted to fill in a questionnaire. The feedback from the students demonstrate significant benefits extending far beyond the primary educational objectives of these programmes.

Development of a rotating gravity gradiometer for earth orbit applications (AAFE)

NASA Technical Reports Server (NTRS)

Forward, R. L.; Bell, C. C.; Lahue, P. M.; Mallove, E. F.; Rouse, D. W.

1973-01-01

Some preliminary mission studies are described along with the design, fabrication, and test of a breadboard model of an earth orbital, rotating gravity gradiometer with a design goal of 10 to the minus 11th power/sec sq (0.01 EU) in a 35-sec integration time. The proposed mission uses a Scout vehicle to launch one (or two orthogonally oriented) spin-stabilized satellites into a 330-km circular polar orbit some 20 days before an equinox. During the short orbital lifetime, the experiment would obtain two complete maps of the gravity gradient field with a resolution approaching 270 km (degree 75). The breadboard model of the gradiometer demonstrated a combined thermal and electronic noise threshold of 0.015 EU per data channel. The design changes needed to reduce the noise to less than 0.01 EU were identified. Variations of the sensor output signal with temperature were experimentally determined and a suitable method of temperature compensation was developed and tested. Other possible error sources, such as sensor interaction with satellite dynamics and magnetic fields, were studied analytically and shown to be small.

Quantum gravity in three dimensions, Witten spinors and the quantisation of length

NASA Astrophysics Data System (ADS)

Wieland, Wolfgang

2018-05-01

In this paper, I investigate the quantisation of length in euclidean quantum gravity in three dimensions. The starting point is the classical hamiltonian formalism in a cylinder of finite radius. At this finite boundary, a counter term is introduced that couples the gravitational field in the interior to a two-dimensional conformal field theory for an SU (2) boundary spinor, whose norm determines the conformal factor between the fiducial boundary metric and the physical metric in the bulk. The equations of motion for this boundary spinor are derived from the boundary action and turn out to be the two-dimensional analogue of the Witten equations appearing in Witten's proof of the positive mass theorem. The paper concludes with some comments on the resulting quantum theory. It is shown, in particular, that the length of a one-dimensional cross section of the boundary turns into a number operator on the Fock space of the theory. The spectrum of this operator is discrete and matches the results from loop quantum gravity in the spin network representation.

Pulsating Heat pipe Only for Space (PHOS): results of the REXUS 18 sounding rocket campaign

NASA Astrophysics Data System (ADS)

Creatini, F.; Guidi, G. M.; Belfi, F.; Cicero, G.; Fioriti, D.; Di Prizio, D.; Piacquadio, S.; Becatti, G.; Orlandini, G.; Frigerio, A.; Fontanesi, S.; Nannipieri, P.; Rognini, M.; Morganti, N.; Filippeschi, S.; Di Marco, P.; Fanucci, L.; Baronti, F.; Mameli, M.; Manzoni, M.; Marengo, M.

2015-11-01

Two Closed Loop Pulsating Heat Pipes (CLPHPs) are tested on board REXUS 18 sounding rocket in order to obtain data over a relatively long microgravity period (approximately 90 s). The CLPHPs are partially filled with FC-72 and have, respectively, an inner tube diameter larger (3 mm) and slightly smaller (1.6 mm) than the critical diameter evaluated in static Earth gravity conditions. On ground, the small diameter CLPHP effectively works as a Pulsating Heat Pipe (PHP): the characteristic slug and plug flow pattern forms inside the tube and the heat exchange is triggered by thermally driven self-sustained oscillations of the working fluid. On the other hand, the large diameter CLPHP works as a two- phase thermosyphon in vertical position and doesn't work in horizontal position: in this particular condition, the working fluid stratifies within the device as the surface tension force is no longer able to balance buoyancy. Then, the idea to test the CLPHPs in reduced gravity conditions: as the gravity reduces the buoyancy forces becomes less intense and it is possible to recreate the typical PHP flow pattern also for larger inner tube diameters. This allows to increase the heat transfer rate and, consequently, to decrease the overall thermal resistance. Even though it was not possible to experience low gravity conditions due to a failure in the yoyo de-spin system, the thermal response to the peculiar acceleration field (hyper-gravity) experienced on board are thoroughly described.

Probing Planckian Corrections at the Horizon Scale with LISA Binaries

NASA Astrophysics Data System (ADS)

Maselli, Andrea; Pani, Paolo; Cardoso, Vitor; Abdelsalhin, Tiziano; Gualtieri, Leonardo; Ferrari, Valeria

2018-02-01

Several quantum-gravity models of compact objects predict microscopic or even Planckian corrections at the horizon scale. We explore the possibility of measuring two model-independent, smoking-gun effects of these corrections in the gravitational waveform of a compact binary, namely, the absence of tidal heating and the presence of tidal deformability. For events detectable by the future space-based interferometer LISA, we show that the effect of tidal heating dominates and allows one to constrain putative corrections down to the Planck scale. The measurement of the tidal Love numbers with LISA is more challenging but, in optimistic scenarios, it allows us to constrain the compactness of a supermassive exotic compact object down to the Planck scale. Our analysis suggests that highly spinning, supermassive binaries at 1-20 Gpc provide unparalleled tests of quantum-gravity effects at the horizon scale.

KSC-03PD-2755

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. In the spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to remove the soft shipping cover from the Gravity Probe B experiment. Immediate processing includes setting up mechanical and electrical ground support equipment, making necessary connections and conditioning the spacecraft battery. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

KSC-03PD-2738

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers in the spacecraft processing facility on North Vandenberg Air Force Base get ready to begin processing the Gravity Probe B experiment. Mechanical and electrical ground support equipment will be set up and necessary connections made with the spacecraft. Spacecraft battery conditioning will also begin. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center.

Probing Planckian Corrections at the Horizon Scale with LISA Binaries.

PubMed

Maselli, Andrea; Pani, Paolo; Cardoso, Vitor; Abdelsalhin, Tiziano; Gualtieri, Leonardo; Ferrari, Valeria

2018-02-23

Several quantum-gravity models of compact objects predict microscopic or even Planckian corrections at the horizon scale. We explore the possibility of measuring two model-independent, smoking-gun effects of these corrections in the gravitational waveform of a compact binary, namely, the absence of tidal heating and the presence of tidal deformability. For events detectable by the future space-based interferometer LISA, we show that the effect of tidal heating dominates and allows one to constrain putative corrections down to the Planck scale. The measurement of the tidal Love numbers with LISA is more challenging but, in optimistic scenarios, it allows us to constrain the compactness of a supermassive exotic compact object down to the Planck scale. Our analysis suggests that highly spinning, supermassive binaries at 1-20 Gpc provide unparalleled tests of quantum-gravity effects at the horizon scale.

KSC-03PD-2875

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., where it will be mated with the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2874

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. It will enclose the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2873

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is prepared for lifting up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. It will enclose the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2871

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The first stage of the Delta II launch vehicle for the Gravity Probe B experiment is ready to be lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2885

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Viewed from inside, the second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2889

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Workers on the mobile service tower at Space Launch Complex 2, Vandenberg Air Force Base, Calif., check the Delta II rockets second stage as it is mated with the first stage. The Delta II is the launch vehicle for the Gravity Probe B experiment, developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2876

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The interstage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif., where it will be mated with the second stage. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

Computational Analysis of Artificial Gravity as a Possible Countermeasure to Spaceflight Induced Bone Loss

NASA Technical Reports Server (NTRS)

Mulugeta, L.; Werner, C. R.; Pennline, J. A.

2015-01-01

During exploration class missions, such as to asteroids and Mars, astronauts will be exposed to reduced gravity for extended periods. Data has shown that astronauts lose bone mass at a rate of 1% to 2% a month in microgravity, particularly in lower extremities such as the proximal femur. Exercise countermeasures have not completely eliminated bone loss from long duration spaceflight missions, which leaves astronauts susceptible to early onset osteoporosis and greater risk of fracture. Introduction of the Advanced Resistive Exercise Device and other large exercise devices on the International Space Station (ISS), coupled with improved nutrition, has further minimized bone loss. However, unlike the ISS, exploration vehicles will have very limited volume and power available to accommodate such capabilities. Therefore, novel concepts like artificial gravity systems are being explored as a means to provide sufficient load stimulus to the musculoskeletal system to mitigate bone changes that may lead to early onset osteoporosis and increased risk of fracture. Currently, there is minimal data available to drive further research and development efforts to appropriately explore such options. Computational modeling can be leveraged to gain insight on the level of osteoprotection that may be achieved using artificial gravity produced by a spinning spacecraft or centrifuge. With this in mind, NASA's Digital Astronaut Project (DAP) has developed a bone remodeling model that has been validated for predicting volumetric bone mineral density (vBMD) changes of trabecular and cortical bone both for gravitational unloading condition and the equivalent of 1g daily load stimulus. Using this model, it is possible to simulate vBMD changes in trabecular and cortical bone under different gravity conditions. In this presentation, we will discuss our preliminary findings regarding if and how artificial gravity may be used to mitigate spaceflight induced bone loss.

I-Love-Q relations for neutron stars in dynamical Chern Simons gravity

NASA Astrophysics Data System (ADS)

Gupta, Toral; Majumder, Barun; Yagi, Kent; Yunes, Nicolás

2018-01-01

Neutron stars are ideal to probe, not only nuclear physics, but also strong-field gravity. Approximate universal relations insensitive to the star’s internal structure exist among certain observables and are useful in testing general relativity, as they project out the uncertainties in the equation of state. One such set of universal relations between the moment of inertia (I), the tidal Love number and the quadrupole moment (Q) has been studied both in general relativity and in modified theories. In this paper, we study the relations in dynamical Chern–Simons gravity, a well-motivated, parity-violating effective field theory, extending previous work in various ways. First, we study how projected constraints on the theory using the I-Love relation depend on the measurement accuracy of I with radio observations and that of the Love number with gravitational-wave observations. Provided these quantities can be measured with future observations, we find that the latter could place bounds on dynamical Chern–Simons gravity that are six orders of magnitude stronger than current bounds. Second, we study the I–Q and Q-Love relations in this theory by constructing slowly-rotating neutron star solutions to quadratic order in spin. We find that the approximate universality continues to hold in dynamical Chern–Simons gravity, and in fact, it becomes stronger than in general relativity, although its existence depends on the normalization of the dimensional coupling constant of the theory. Finally, we study the variation of the eccentricity of isodensity contours inside a star and its relation to the degree of universality. We find that, in most cases, the eccentricity variation is smaller in dynamical Chern–Simons gravity than in general relativity, providing further support to the idea that the approximate self-similarity of isodensity contours is responsible for universality.

The gravity field and orientation of Mercury after the MESSENGER mission

NASA Astrophysics Data System (ADS)

Mazarico, E.; Genova, A.; Goossens, S. J.; Lemoine, F. G.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.; Solomon, S. C.

2015-12-01

After more than four years in orbit about Mercury, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the planet's surface north of Shakespeare crater (54.44° N, 210.12° E,) on 30 April 2015. One of the main goals of the mission was to determine the gravity field of Mercury in order to learn about Mercury's interior. Together with ground-based radar measurements of the obliquity and forced librations, MESSENGER-derived gravity models helped revise models of Mercury's interior. Nevertheless, the refinement of Mercury's orientation with the latest data from MESSENGER can further improve the interior modeling of the planet. The last eight months of the mission provided a special opportunity to conduct low-altitude measurements, with extensive radio tracking coverage below 200 km altitude north of ~30°N. MESSENGER's Mercury Laser Altimeter (MLA) mapped the topography of Mercury's northern hemisphere with a sub-meter vertical precision, an along-track sampling of ~500 m, and a longitudinal resolution (~0.1°) limited by the number of spacecraft orbits (~4,000). The combination of gravity and topography helps determine crustal thickness and interior properties. Altimetric ranges provide geodetic constraints to improve the spacecraft orbit determination, and thus the gravity field model. In particular, whereas the MESSENGER spacecraft was not tracked at each periapsis passage, MLA operated nearly continuously (outside of thermally challenging periods). From an analysis of the entire radiometric and altimetric datasets acquired by MESSENGER, a new gravity field to degree and order 100 has been obtained, resolving features down to ~75 km horizontal scale. The altimetric data help reduce the uncertainties in the determination of the pole position. A reanalysis of the Mercury flybys also constrains the spin rate over the longest available time span.

Stability of the Einstein static universe in Einstein-Cartan theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atazadeh, K., E-mail: atazadeh@azaruniv.ac.ir

The existence and stability of the Einstein static solution have been built in the Einstein-Cartan gravity. We show that this solution in the presence of perfect fluid with spin density satisfying the Weyssenhoff restriction is cyclically stable around a center equilibrium point. Thus, study of this solution is interesting because it supports non-singular emergent cosmological models in which the early universe oscillates indeterminately about an initial Einstein static solution and is thus past eternal.

Rotating boson stars and Q-balls. II. Negative parity and ergoregions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleihaus, Burkhard; Kunz, Jutta; List, Meike

2008-03-15

We construct axially symmetric, rotating boson stars with positive and negative parity. Their flat space limits represent spinning Q-balls. Q-balls and boson stars exist only in a limited frequency range. The coupling to gravity gives rise to a spiral-like frequency dependence of the mass and charge of boson stars. We analyze the properties of these solutions. In particular, we discuss the presence of ergoregions in boson stars and determine their domains of existence.

Leptogenesis from spin-gravity coupling following inflation.

PubMed

Mohanty, Subhendra; Prasanna, A R; Lambiase, G

2006-02-24

The energy levels of the left- and the right-handed neutrinos are split in the background of gravitational waves generated during inflation, which, in presence of lepton-number-violating interactions, gives rise to a net lepton asymmetry at equilibrium. Lepton number violation is achieved by the same dimension five operator which gives rise to neutrino masses after electroweak symmetry breaking. A net baryon asymmetry of the same magnitude can be generated from this lepton asymmetry by electroweak sphaleron processes.

A user's guide to the Flexible Spacecraft Dynamics and Control Program

NASA Technical Reports Server (NTRS)

Fedor, J. V.

1984-01-01

A guide to the use of the Flexible Spacecraft Dynamics Program (FSD) is presented covering input requirements, control words, orbit generation, spacecraft description and simulation options, and output definition. The program can be used in dynamics and control analysis as well as in orbit support of deployment and control of spacecraft. The program is applicable to inertially oriented spinning, Earth oriented or gravity gradient stabilized spacecraft. Internal and external environmental effects can be simulated.

On the Uniqueness and Consistency of Scattering Amplitudes

NASA Astrophysics Data System (ADS)

Rodina, Laurentiu

In this dissertation, we study constraints imposed by locality, unitarity, gauge invariance, the Adler zero, and constructability (scaling under BCFW shifts). In the first part we study scattering amplitudes as the unique mathematical objects which can satisfy various combinations of such principles. In all cases we find that locality and unitarity may be derived from gauge invariance (for Yang-Mills and General Relativity) or from the Adler zero (for the non-linear sigma model and the Dirac-Born-Infeld model), together with mild assumptions on the singularity structure and mass dimension. We also conjecture that constructability and locality together imply gauge invariance, hence also unitarity. All claims are proved through a soft expansion, and in the process we end re-deriving the well-known leading soft theorems for all four theories. Unlike other proofs of these theorems, we do not assume any form of factorization (unitarity). In the second part we show how tensions arising between gauge invariance (as encoded by spinor helicity variables in four dimensions), locality, unitarity and constructability give rise to various physical properties. These include high-spin no-go theorems, the equivalence principle, and the emergence of supersymmetry from spin 3/2 particles. We also complete the fully on-shell constructability proof of gravity amplitudes, by showing that the improved "bonus'' behavior of gravity under BCFW shifts is a simple consequence of Bose symmetry.

Self-force correction to geodetic spin precession in Kerr spacetime

NASA Astrophysics Data System (ADS)

Akcay, Sarp

2017-08-01

We present an expression for the gravitational self-force correction to the geodetic spin precession of a spinning compact object with small, but non-negligible mass in a bound, equatorial orbit around a Kerr black hole. We consider only conservative backreaction effects due to the mass of the compact object (m1), thus neglecting the effects of its spin s1 on its motion; i.e., we impose s1≪G m12/c and m1≪m2, where m2 is the mass parameter of the background Kerr spacetime. We encapsulate the correction to the spin precession in ψ , the ratio of the accumulated spin-precession angle to the total azimuthal angle over one radial orbit in the equatorial plane. Our formulation considers the gauge-invariant O (m1) part of the correction to ψ , denoted by Δ ψ , and is a generalization of the results of Akcay et al. [Classical Quantum Gravity 34, 084001 (2017), 10.1088/1361-6382/aa61d6] to Kerr spacetime. Additionally, we compute the zero-eccentricity limit of Δ ψ and show that this quantity differs from the circular orbit Δ ψcirc by a gauge-invariant quantity containing the gravitational self-force correction to general relativistic periapsis advance in Kerr spacetime. Our result for Δ ψ is expressed in a manner that readily accommodates numerical/analytical self-force computations, e.g., in the radiation gauge, and paves the way for the computation of a new eccentric-orbit Kerr gauge invariant beyond the generalized redshift.

The holographic dual of the Penrose transform

NASA Astrophysics Data System (ADS)

Neiman, Yasha

2018-01-01

We consider the holographic duality between type-A higher-spin gravity in AdS4 and the free U( N) vector model. In the bulk, linearized solutions can be translated into twistor functions via the Penrose transform. We propose a holographic dual to this transform, which translates between twistor functions and CFT sources and operators. We present a twistorial expression for the partition function, which makes global higher-spin symmetry manifest, and appears to automatically include all necessary contact terms. In this picture, twistor space provides a fully nonlocal, gauge-invariant description underlying both bulk and boundary spacetime pictures. While the bulk theory is handled at the linear level, our formula for the partition function includes the effects of bulk interactions. Thus, the CFT is used to solve the bulk, with twistors as a language common to both. A key ingredient in our result is the study of ordinary spacetime symmetries within the fundamental representation of higher-spin algebra. The object that makes these "square root" spacetime symmetries manifest becomes the kernel of our boundary/twistor transform, while the original Penrose transform is identified as a "square root" of CPT.

Tolerance in the Ramsey interference of a trapped nanodiamond

NASA Astrophysics Data System (ADS)

Wan, C.; Scala, M.; Bose, S.; Frangeskou, A. C.; Rahman, ATM A.; Morley, G. W.; Barker, P. F.; Kim, M. S.

2016-04-01

In the scheme recently proposed by M. Scala et al. [Phys. Rev. Lett. 111, 180403 (2013), 10.1103/PhysRevLett.111.180403], a gravity-dependent phase shift is induced on the spin of a nitrogen-vacancy (NV) center in a trapped nanodiamond by the interaction between its magnetic moment and the quantized motion of the particle. This provides a way to detect spatial quantum superpositions by means of only spin measurements. Here, the effect of unwanted coupling with other motional degrees of freedom is considered, and we show that it does not affect the validity of the scheme. Both this coupling and the additional error source due to misalignment between the quantization axis of the NV center spin and the trapping axis are shown not to change the qualitative behavior of the system, so that a proof-of-principle experiment can be neatly performed. Our analysis, which shows that the scheme retains the important features of not requiring ground-state cooling and of being resistant to thermal fluctuations, can be useful for several schemes which have been proposed recently for testing macroscopic superpositions in trapped microsystems.

Unitarity of spin-2 theories with linearized Weyl symmetry in D=2+1 dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalmazi, D.

2009-10-15

Here we prove unitarity of the recently found fourth-order (in derivatives) self-dual model of spin-2 by investigating the analytic structure of its propagator. The model describes massive particles of helicity +2 (or -2) in D=2+1 dimensions and corresponds to the quadratic truncation of a higher derivative topologically massive gravity about a flat background. It is an intriguing example of a theory where a term in the propagator of the form 1/[{open_square}{sup 2}({open_square}-m{sup 2})] does not lead to ghosts. The crucial role of the linearized Weyl symmetry in getting rid of the ghosts is pointed out. We use a peculiar pairmore » of gauge conditions which fix the linearized reparametrizations and linearized Weyl symmetries separately.« less

The NUTS CubeSat Project: Spin-Offs and Technology Development

NASA Astrophysics Data System (ADS)

Birkeland, R.; Stein, T. A.; Tommer, M.; Beermann, B.; Petrasch, J.; Gjersvik, A.

2015-09-01

The development of CubeSats allows for the conception and implementation of new approaches and technologies. In this paper we present a spin-off and technology innovation resulting from the NTNU Test Satellite (NUTS). NUTS is a 2U CubeSat under development by students of the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. The satellite is due to launch in 2017 and is based upon in-house developments. We will describe the innovative carbon-fibre frame, radio systems and proposals for an infrared camera for atmospheric gravity waves observations. A NUTS spinoff, the Cosmic Particle Telescope (CPT-SCOPE), will be presented in greater detail since it has been selected for the BEXUS 20 campaign in autumn 2015. CPT-SCOPE is a Norwegian-German compact radiation monitor prototype developed by students.

Quantum back-action-evading measurement of motion in a negative mass reference frame

NASA Astrophysics Data System (ADS)

Møller, Christoffer B.; Thomas, Rodrigo A.; Vasilakis, Georgios; Zeuthen, Emil; Tsaturyan, Yeghishe; Balabas, Mikhail; Jensen, Kasper; Schliesser, Albert; Hammerer, Klemens; Polzik, Eugene S.

2017-07-01

Quantum mechanics dictates that a continuous measurement of the position of an object imposes a random quantum back-action (QBA) perturbation on its momentum. This randomness translates with time into position uncertainty, thus leading to the well known uncertainty on the measurement of motion. As a consequence of this randomness, and in accordance with the Heisenberg uncertainty principle, the QBA puts a limitation—the so-called standard quantum limit—on the precision of sensing of position, velocity and acceleration. Here we show that QBA on a macroscopic mechanical oscillator can be evaded if the measurement of motion is conducted in the reference frame of an atomic spin oscillator. The collective quantum measurement on this hybrid system of two distant and disparate oscillators is performed with light. The mechanical oscillator is a vibrational ‘drum’ mode of a millimetre-sized dielectric membrane, and the spin oscillator is an atomic ensemble in a magnetic field. The spin oriented along the field corresponds to an energetically inverted spin population and realizes a negative-effective-mass oscillator, while the opposite orientation corresponds to an oscillator with positive effective mass. The QBA is suppressed by -1.8 decibels in the negative-mass setting and enhanced by 2.4 decibels in the positive-mass case. This hybrid quantum system paves the way to entanglement generation and distant quantum communication between mechanical and spin systems and to sensing of force, motion and gravity beyond the standard quantum limit.

Quantum back-action-evading measurement of motion in a negative mass reference frame.

PubMed

Møller, Christoffer B; Thomas, Rodrigo A; Vasilakis, Georgios; Zeuthen, Emil; Tsaturyan, Yeghishe; Balabas, Mikhail; Jensen, Kasper; Schliesser, Albert; Hammerer, Klemens; Polzik, Eugene S

2017-07-12

Quantum mechanics dictates that a continuous measurement of the position of an object imposes a random quantum back-action (QBA) perturbation on its momentum. This randomness translates with time into position uncertainty, thus leading to the well known uncertainty on the measurement of motion. As a consequence of this randomness, and in accordance with the Heisenberg uncertainty principle, the QBA puts a limitation-the so-called standard quantum limit-on the precision of sensing of position, velocity and acceleration. Here we show that QBA on a macroscopic mechanical oscillator can be evaded if the measurement of motion is conducted in the reference frame of an atomic spin oscillator. The collective quantum measurement on this hybrid system of two distant and disparate oscillators is performed with light. The mechanical oscillator is a vibrational 'drum' mode of a millimetre-sized dielectric membrane, and the spin oscillator is an atomic ensemble in a magnetic field. The spin oriented along the field corresponds to an energetically inverted spin population and realizes a negative-effective-mass oscillator, while the opposite orientation corresponds to an oscillator with positive effective mass. The QBA is suppressed by -1.8 decibels in the negative-mass setting and enhanced by 2.4 decibels in the positive-mass case. This hybrid quantum system paves the way to entanglement generation and distant quantum communication between mechanical and spin systems and to sensing of force, motion and gravity beyond the standard quantum limit.

Bodily Tides Near Spin-Orbit Resonances

DTIC Science & Technology

2012-01-01

radial term may cause an equipotential - surface variation of about 10 cm. This magnitude is large enough to be observed by future missions and should...U (r) = ∞∑ l=2 Ul(r) = ∞∑ l=2 kl ( R r )l+1 Wl(R, r∗), (2) R now being the mean equatorial radius of the primary, R = (R, φ, λ) being a surface point...rheology. For a homogeneous incompressible spherical primary of density ρ, surface gravity g, and rigidity μ, the static Love number of degree l is

Numerical studies of surface tensions

NASA Technical Reports Server (NTRS)

Hung, R. J.

1995-01-01

Liquid-vapor (bubble) interface disturbances caused by various types of accelerations, including centrifugal, lateral and axial impulses, gravity gradient and g-jitter accelerations associated with spinning and slew motion in microgravity, are reviewed. Understanding of bubble deformations and fluctuations is important in the development of spacecraft orbital and attitude control techniques to secure its normal operation. This review discusses bubble deformations and oscillations driven by various forces in the microgravity environment. The corresponding bubble mass center fluctuations and slosh reaction forces and torques due to bubble deformations are also reviewed.

Vortical susceptibility of finite-density QCD matter

DOE PAGES

Aristova, A.; Frenklakh, D.; Gorsky, A.; ...

2016-10-07

Here, the susceptibility of finite-density QCD matter to vorticity is introduced, as an analog of magnetic susceptibility. It describes the spin polarization of quarks and antiquarks in finite-density QCD matter induced by rotation. We estimate this quantity in the chirally broken phase using the mixed gauge-gravity anomaly at finite baryon density. It is proposed that the vortical susceptibility of QCD matter is responsible for the polarization of Λ and Λ¯ hyperons observed recently in heavy ion collisions at RHIC by the STAR collaboration.

Subleading soft theorem for multiple soft gravitons

NASA Astrophysics Data System (ADS)

Chakrabarti, Subhroneel; Kashyap, Sitender Pratap; Sahoo, Biswajit; Sen, Ashoke; Verma, Mritunjay

2017-12-01

We derive the subleading soft graviton theorem in a generic quantum theory of gravity for arbitrary number of soft external gravitons and arbitrary number of finite energy external states carrying arbitrary mass and spin. Our results are valid to all orders in perturbation theory when the number of non-compact space-time dimensions is six or more, but only for tree amplitudes for five or less non-compact space-time dimensions due to enhanced contribution to loop amplitudes from the infrared region.

6D thick branes from interacting scalar fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dzhunushaliev, Vladimir; Folomeev, Vladimir; Singleton, Douglas

2008-02-15

A thick brane in six dimensions is constructed using two scalar fields. The field equations for 6D gravity plus the scalar fields are solved numerically. This thick brane solution shares some features with previously studied analytic solutions, but has the advantage that the energy-momentum tensor which forms the thick brane comes from the scalar fields rather than being put in by hand. Additionally the scalar fields which form the brane also provide a universal, nongravitational trapping mechanism for test fields of various spins.

Are black holes springlike?

NASA Astrophysics Data System (ADS)

Good, Michael R. R.; Ong, Yen Chin

2015-02-01

A (3 +1 )-dimensional asymptotically flat Kerr black hole angular speed Ω+ can be used to define an effective spring constant, k =m Ω+2. Its maximum value is the Schwarzschild surface gravity, k =κ , which rapidly weakens as the black hole spins down and the temperature increases. The Hawking temperature is expressed in terms of the spring constant: 2 π T =κ -k . Hooke's law, in the extremal limit, provides the force F =1 /4 , which is consistent with the conjecture of maximum force in general relativity.

Convection measurement package for space processing sounding rocket flights. [low gravity manufacturing - fluid dynamics

NASA Technical Reports Server (NTRS)

Spradley, L. W.

1975-01-01

The effects on heated fluids of nonconstant accelerations, rocket vibrations, and spin rates, was studied. A system is discussed which can determine the influence of the convective effects on fluid experiments. The general suitability of sounding rockets for performing these experiments is treated. An analytical investigation of convection in an enclosure which is heated in low gravity is examined. The gravitational body force was taken as a time-varying function using anticipated sounding rocket accelerations, since accelerometer flight data were not available. A computer program was used to calculate the flow rates and heat transfer in fluids with geometries and boundary conditions typical of space processing configurations. Results of the analytical investigation identify the configurations, fluids and boundary values which are most suitable for measuring the convective environment of sounding rockets. A short description of fabricated fluid cells and the convection measurement package is given. Photographs are included.

Application of inertial instruments for DSN antenna pointing and tracking

NASA Technical Reports Server (NTRS)

Eldred, D. B.; Nerheim, N. M.; Holmes, K. G.

1990-01-01

The feasibility of using inertial instruments to determine the pointing attitude of the NASA Deep Space Network antennas is examined. The objective is to obtain 1 mdeg pointing knowledge in both blind pointing and tracking modes to facilitate operation of the Deep Space Network 70 m antennas at 32 GHz. A measurement system employing accelerometers, an inclinometer, and optical gyroscopes is proposed. The initial pointing attitude is established by determining the direction of the local gravity vector using the accelerometers and the inclinometer, and the Earth's spin axis using the gyroscopes. Pointing during long-term tracking is maintained by integrating the gyroscope rates and augmenting these measurements with knowledge of the local gravity vector. A minimum-variance estimator is used to combine measurements to obtain the antenna pointing attitude. A key feature of the algorithm is its ability to recalibrate accelerometer parameters during operation. A survey of available inertial instrument technologies is also given.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pereira, S.H.; Pinho, A.S.S.; Silva, J.M. Hoff da

In this work the exact Friedmann-Robertson-Walker equations for an Elko spinor field coupled to gravity in an Einstein-Cartan framework are presented. The torsion functions coupling the Elko field spin-connection to gravity can be exactly solved and the FRW equations for the system assume a relatively simple form. In the limit of a slowly varying Elko spinor field there is a relevant contribution to the field equations acting exactly as a time varying cosmological model Λ( t )=Λ{sub *}+3β H {sup 2}, where Λ{sub *} and β are constants. Observational data using distance luminosity from magnitudes of supernovae constraint the parametersmore » Ω {sub m} and β, which leads to a lower limit to the Elko mass. Such model mimics, then, the effects of a dark energy fluid, here sourced by the Elko spinor field. The density perturbations in the linear regime were also studied in the pseudo-Newtonian formalism.« less

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free

NASA Astrophysics Data System (ADS)

Bianconi, Ginestra; Rahmede, Christoph

2015-09-01

In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension . We show that in d = 2 CQNM are homogeneous networks while for d > 2 they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the -faces of the -dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the -faces.

Effective field theory of broken spatial diffeomorphisms

DOE PAGES

Lin, Chunshan; Labun, Lance Z.

2016-03-17

We study the low energy effective theory describing gravity with broken spatial diffeomorphism invariance. In the unitary gauge, the Goldstone bosons associated with broken diffeomorphisms are eaten and the graviton becomes a massive spin-2 particle with 5 well-behaved degrees of freedom. In this gauge, the most general theory is built with the lowest dimension operators invariant under only temporal diffeomorphisms. Imposing the additional shift and SO(3) internal symmetries, we analyze the perturbations on a FRW background. At linear perturbation level, the observables of this theory are characterized by five parameters, including the usual cosmological parameters and one additional coupling constantmore » for the symmetry-breaking scalars. In the de Sitter and Minkowski limit, the three Goldstone bosons are supermassive and can be integrated out, leaving two massive tensor modes as the only propagating degrees of freedom. In conclusion, we discuss several examples relevant to theories of massive gravity.« less

Artificial gravity field, astrophysical analogues, and topological phase transitions in strained topological semimetals

NASA Astrophysics Data System (ADS)

Yu, Zhiming; Guan, Shan; Yao, Yugui; Yang, Shengyuan

Effective gravity and gauge fields are emergent properties intrinsic for low-energy quasiparticles in topological semimetals. Here, taking two Dirac semimetals as examples, we demonstrate that applied lattice strain can generate warped spacetime, with fascinating analogues in astrophysics. Particularly, we study the possibility of simulating black-hole/white-hole event horizons and gravitational lensing effect. Furthermore, we discover strain-induced topological phase transitions, both in the bulk materials and in their thin films. Especially in thin films, the transition between the quantum spin Hall and the trivial insulating phases can be achieved by a small strain, naturally leading to the proposition of a novel piezo-topological transistor device. Our result not only bridges multiple disciplines, revealing topological semimetals as a unique table-top platform for exploring interesting phenomena in astrophysics and general relativity; it also suggests realistic materials and methods to achieve controlled topological phase transitions with great potential for device applications.

KSC-03PD-2886

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. Viewed from inside, the second stage of the Delta II launch vehicle for the Gravity Probe B experiment is lifted up the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. Behind it is the first stage of the Delta II. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

KSC-03PD-2887

NASA Technical Reports Server (NTRS)

2003-01-01

VANDENBERG AFB, CALIF. The second stage of the Delta II launch vehicle for the Gravity Probe B experiment is moved into the mobile service tower on Space Launch Complex 2, Vandenberg Air Force Base, Calif. Behind it can be seen the first stage of the Delta II. The Gravity Probe B will launch a payload of four gyroscopes into low-Earth polar orbit to test two extraordinary predictions of Albert Einsteins general theory of relativity: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earths rotation drags space and time around with it). Once in orbit, for 18 months each gyroscopes spin axis will be monitored as it travels through local spacetime, observing and measuring these effects. The experiment was developed by Stanford University, Lockheed Martin and NASAs Marshall Space Flight Center. The targeted launch date is Dec. 6, 2003.

Preliminary Planning for NEAR's Low-Altitude Operations at 433 Eros

NASA Technical Reports Server (NTRS)

Antreasian, P. G.; Helfrich, C. L.; Miller, J. K.; Owen, W. M.; Williams, B. G.; Yeomans, D. K.; Scheeres, D. J.; Dunham, D. W.; Farquhar, R. W.; McAdams, J. V.

1999-01-01

On February 14, 2000, an orbit insertion burn will place NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft (S/C) into orbit around asteroid 433 Eros. NEAR will initially orbit Eros with distances ranging from 500 to 100 km in order to characterize the shape, gravity and spin of Eros. Once the physical parameters of Eros are determined reasonably well, the plan is to establish an orbit of the NEAR S/C with increasingly lower altitudes as the one year orbital mission progresses while further characterizing the gravity and shape of Eros. Towards the end of the NEAR mission, after the shape, gravity and spin of Eros have been well characterized, the scientific interest of obtaining very close observations (< 5 km) can be realized. The navigation during this phase relies on a combination of NASA's Deep Space Network (DSN) radio metric tracking, laser ranging (LIDAR) data from the S/C to the surface of Eros, and onboard optical imaging of landmarks on Eros. This paper will provide preliminary plans for mission design and navigation during the last two months of the orbit phase, where several close passes to the surface will be incorporated to enhance the science return. The culmination of these close passes will result in the eventual landing of the S/C on the surface of Eros. Several considerations for these plans are given by Antreasian, et at. [1998]. The objective for the end of the mission will be to land the S/C autonomously using the surface relative information obtained from the onboard LIDAR instrument. The goal will be to soft land the S/C in such a way as to keep it operational. With the use of an onboard LIDAR landing algorithm as discussed by Antreasian et at. [1998], it is believed that the S/C impact velocity can be kept well under 7 m/s which is a requirement for allowing the S/C to remain operational.

Reorientation Histories of the Terrestrial Planets

NASA Astrophysics Data System (ADS)

Keane, J. T.; Matsuyama, I.

2016-12-01

The nature of how a planet spins is controlled by the planet's inertia tensor. In a minimum energy rotation state, planets spin about the maximum principal axis of inertia. Yet, the orientation of this axis is not often constant with time. The redistribution of mass within a planet due to both interior processes (e.g. convection, intrusive volcanism) and surface processes (e.g. extrusive volcanism, impacts) can significantly alter the planet's inertia tensor, resulting in the reorientation of the planet. This form of reorientation is also known as true polar wander. Reorientation can directly alter the topography and gravity field of a planet, generate tectonic stresses, change the insolation geometry (affecting climate and volatile stability), and modify the orientation of the planet's magnetic field. Yet, despite its significance, the reorientation histories of many planets is not well constrained. In this work, we present a new technique for using spacecraft-derived, orbital gravity measurements to directly quantify how individual large geologic features reoriented Mercury, Venus, the Moon, and Mars. When coupled with the geologic record for these respective planets, this enables us to determine the reorientation history for each planet. These mark the first comprehensive, multi-episode reorientation chronologies for these planets. The reorientation histories for the Moon and Mercury are similar; the orientation of both planets is strongly controlled by the presence of large remnant bulges (tidal/rotational for the Moon, and likely thermal for Mercury), but significantly modulated by subsequent, large impacts and volcanic events—resulting in 15° of total reorientation after their formation. Mars experienced larger reorientation due to the formation of the Tharsis rise, punctuated by smaller reorientation events from large impacts. Lastly, Venus's diminutive remnant figure and large volcanic edifices result in the largest possible reorientation events, but the exact reorientation chronology is clouded by the uncertainties of Venus's geologic record. The methodology presented here is completely general, and can be applied to any future global gravity maps of other planets or planetary satellites.

Reference Frames and the Physical Gravito-Electromagnetic Analogy

NASA Astrophysics Data System (ADS)

Costa, Luis Filipe P. O.; Herdeiro, C. A. R.

2009-05-01

The interest on the physical analogies between General Relativity and Electromagnetism has been revived by the recent Gravity Probe-B and the upcoming Lares missions, aiming to measure the so-called gravito-magnetic effects. These effects are presently believed to be at the origin of observed jets in quasars, galactic nuclei, neutron stars and black holes, as well as the precession of black holes' accretion disks. Gravitomagnetism has been studied mainly in a first order approximation ( e.g. [arXiv:gr-qc/0207065]) which, making use of certain similarities between linearized gravity and electromagnetism, applies intuition and well known results from electromagnetic phenomena to the description of the less familiar gravitational ones. However, there is no consensus at present on the limit of validity of such approach. Using a new exact approach based on tidal tensors [Phys. Rev. D 78, 024021 (2008)], we show that the existence of the aforementioned similarities depends crucially on the reference frame. Whereas a stationary observer will find remarkable similarities between the gravitational and electromagnetic interactions, if the fields are not stationary in the observer's rest frame, however, the two interactions differ significantly, so that the gravito-electromagnetic equations commonly found in literature are no longer valid. The tidal tensor formalism allows for a comparison between gravity and electromagnetism in terms of quantities common to both theories (tidal forces), making transparent both the similarities and key differences between the two interactions. It also unveils a new analogy based on exact, covariant, and fully general equations, which allows to extend the intuition from electromagnetism to the understanding of non-linear gravitational phenomena, such as the spin interaction between two celestial bodies, and Hawking's [Phys Rev. Lett. 26, 1344 (1971)] spin-dependent upper bound for the energy released by gravitational radiation when two black holes collide. Funded by Fundação para a Ciència e a Tecnologia, Grant SFRH/BD/41370/2007

Variations on holography from modifications of gravity in anti-de sitter

NASA Astrophysics Data System (ADS)

Apolo Velez, Luis Alberto

In this thesis we study aspects of the AdS/CFT correspondence that result from modifications of gravity in the bulk and lead to novel features in the dual theories at the boundary. The variations on the holographic theme studied in this thesis are model-independent since we have not assumed a particular UV-completion of gravity. Our results can be applied to a wide class of models that include higher-spin theories and compactifications of string theory on AdS backgrounds. The modifications of the bulk physics studied in this thesis include massive gravitons, higher-derivative terms in the Einstein-Hilbert action, and new boundary conditions for gravity. We begin by showing that it is possible to construct duals with a massive graviton in the bulk by deforming the dual theory at the boundary. This procedure does not break the translation invariance of the dual theory and might be useful in the study of certain condensed matter systems. We then construct the most general class of parity-even tricritical gravities in three and four dimensions. These higher-derivative theories are not unitary and characterized by the logarithmic fall-off of their linearized perturbations. They are conjectured to be dual to rank-3 logarithmic conformal field theories. We will show that, at linear order in the equations of motion, it is possible to truncate the theory to a unitary subsector. We also show that tricritical gravities in three and four dimensions suffer from a linearization instability that forbids unitary truncations beyond linear order. Finally we consider the role of boundary conditions in the AdS3/CFT2 correspondence. We show that free boundary conditions that lead to enhanced asymptotic symmetry groups are dual to 2D theories of quantum gravity in either the conformal or lightcone gauges. In particular we match the generators of symmetries in the bulk and boundary theories and show that a proper identification of the generator of Virasoro transformations in the bulk leads to a vanishing total central charge. We also show that this identification is consistent with the constraint equations of 2D gravity.

The Gravity Field, Orientation, and Ephemeris of Mercury from MESSENGER Observations After Three Years in Orbit

NASA Technical Reports Server (NTRS)

Mazarico, Erwan M.; Genova, Antonio; Goossens, Sander; Lemoine, Gregory; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.; Solomon, Sean C.

2014-01-01

We have analyzed three years of radio tracking data from the MESSENGER spacecraft in orbit around Mercury and determined the gravity field, planetary orientation, and ephemeris of the innermost planet. With improvements in spatial coverage, force modeling, and data weighting, we refined an earlier global gravity field both in quality and resolution, and we present here a spherical harmonic solution to degree and order 50. In this field, termed HgM005, uncertainties in low-degree coefficients are reduced by an order of magnitude relative to the earlier global field, and we obtained a preliminary value of the tidal Love number k(sub 2) of 0.451+/-0.014. We also estimated Mercury's pole position, and we obtained an obliquity value of 2.06 +/- 0.16 arcmin, in good agreement with analysis of Earth-based radar observations. From our updated rotation period (58.646146 +/- 0.000011 days) and Mercury ephemeris, we verified experimentally the planet's 3: 2 spin-orbit resonance to greater accuracy than previously possible. We present a detailed analysis of the HgM005 covariance matrix, and we describe some near-circular frozen orbits around Mercury that could be advantageous for future exploration.

Anti-gravity: The key to 21st century physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noyes, H.P.

1993-01-01

The masses coupling constants and cosmological parameters obtained using our discrete and combinatorial physics based on discrimination between bit-strings indicate that we can achieve the unification of quantum mechanics with relativity which had become the goal of twentieth century physics. To broaden our case we show that limitations on measurement of the position and velocity of an individual massive particle observed in a colliding beam scattering experiment imply real, rational commutation relations between position and velocity. Prior to this limit being pushed down to quantum effects, the lower bound is set by the available technology, but is otherwise scale invariant.more » Replacing force by force per unit mass and force per unit charge allows us to take over the Feynman-Dyson proof of the Maxwell Equations and extend it to weak gravity. The crossing symmetry of the individual scattering processes when one or more particles are replaced by anti-particles predicts both Coulomb attraction (for charged particles) and a Newtonian repulsion between any particle and its anti-particle. Previous quantum results remain intact, and predict the expected relativistic fine structure and spin dependencies. Experimental confirmation of this anti-gravity prediction would inaugurate the physics of the twenty-first century.« less

Anti-gravity: The key to 21st century physics

NASA Astrophysics Data System (ADS)

Noyes, H. P.

1993-01-01

The masses coupling constants and cosmological parameters obtained using our discrete and combinatorial physics based on discrimination between bit-strings indicate that we can achieve the unification of quantum mechanics with relativity which had become the goal of twentieth century physics. To broaden our case we show that limitations on measurement of the position and velocity of an individual massive particle observed in a colliding beam scattering experiment imply real, rational commutation relations between position and velocity. Prior to this limit being pushed down to quantum effects, the lower bound is set by the available technology, but is otherwise scale invariant. Replacing force by force per unit mass and force per unit charge allows us to take over the Feynman-Dyson proof of the Maxwell Equations and extend it to weak gravity. The crossing symmetry of the individual scattering processes when one or more particles are replaced by anti-particles predicts both Coulomb attraction (for charged particles) and a Newtonian repulsion between any particle and its anti-particle. Previous quantum results remain intact, and predict the expected relativistic fine structure and spin dependencies. Experimental confirmation of this anti-gravity prediction would inaugurate the physics of the twenty-first century.

Dimensional flow in discrete quantum geometries

NASA Astrophysics Data System (ADS)

Calcagni, Gianluca; Oriti, Daniele; Thürigen, Johannes

2015-04-01

In various theories of quantum gravity, one observes a change in the spectral dimension from the topological spatial dimension d at large length scales to some smaller value at small, Planckian scales. While the origin of such a flow is well understood in continuum approaches, in theories built on discrete structures a firm control of the underlying mechanism is still missing. We shed some light on the issue by presenting a particular class of quantum geometries with a flow in the spectral dimension, given by superpositions of states defined on regular complexes. For particular superposition coefficients parametrized by a real number 0 <α

Miles Discusses Skylab Experiment With NASA Personnel

NASA Technical Reports Server (NTRS)

1972-01-01

Lexington, Massachusetts high school student, Judith Miles, discusses her proposed Skylab experiment with engineers and scientists during a design review of the experiment equipment. At left is Ron Pavlue of Kennedy Space Flight Center (KSC), holding a box is Keith Demorest of Marshall Space Flight Center (MSFC). Right of Miles is Dr. Raymond Gause, also of MSFC, who is Miles' scientific advisor. In her experiment, called the 'Web Formation in Zero Gravity', spiders were released into a box and their actions recorded to determine how well they adapt to the absence of gravity. Spiders are known to adapt quickly to other changes in the environment but nothing was known of their ability to adapt to weightlessness. At the same time spiders were weaving webs in Earth orbit, similar spiders were spinning webs in identical boxes on Earth under full gravity conditions. Miles was among the 25 winners of a contest in which some 3,500 high school students proposed experiments for the following year's Skylab mission. Of the 25 students, 6 did not see their experiments conducted on Skylab because the experiments were not compatible with Skylab hardware and timelines. Of the 19 remaining, 11 experiments required the manufacture of equipment.

Probing the effects of Lorentz-symmetry violating Chern-Simons and Ricci-Cotton terms in higher derivative gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pereira-Dias, B.; Hernaski, C. A.; Helayeel-Neto, J. A.

The combined effects of the Lorentz-symmetry violating Chern-Simons and Ricci-Cotton actions are investigated for the Einstein-Hilbert gravity in the second-order formalism modified by higher derivative terms, and their consequences on the spectrum of excitations are analyzed. We follow the lines of previous works and build up an orthonormal basis of projector-like operators for the degrees of freedom, rather than for the spin modes of the fields. With this new basis, the attainment of the propagators is remarkably simplified and the identification of the physical and unphysical modes becomes more immediate. Our conclusion is that the only tachyon- and ghost-free modelmore » is the Einstein-Hilbert action added up by the Chern-Simons term with a timelike vector of the type v{sup {mu}=}({mu},0-vector). Spectral consistency imposes that the Ricci-Cotton term must be switched off. We then infer that gravity with Lorentz-symmetry violation imposes a drastically different constraint on the background if compared to ordinary gauge theories whenever conditions for the suppression of tachyons and ghosts are imposed.« less

Einstein gravity 3-point functions from conformal field theory

NASA Astrophysics Data System (ADS)

Afkhami-Jeddi, Nima; Hartman, Thomas; Kundu, Sandipan; Tajdini, Amirhossein

2017-12-01

We study stress tensor correlation functions in four-dimensional conformal field theories with large N and a sparse spectrum. Theories in this class are expected to have local holographic duals, so effective field theory in anti-de Sitter suggests that the stress tensor sector should exhibit universal, gravity-like behavior. At the linearized level, the hallmark of locality in the emergent geometry is that stress tensor three-point functions 〈 T T T 〉, normally specified by three constants, should approach a universal structure controlled by a single parameter as the gap to higher spin operators is increased. We demonstrate this phenomenon by a direct CFT calculation. Stress tensor exchange, by itself, violates causality and unitarity unless the three-point functions are carefully tuned, and the unique consistent choice exactly matches the prediction of Einstein gravity. Under some assumptions about the other potential contributions, we conclude that this structure is universal, and in particular, that the anomaly coefficients satisfy a ≈ c as conjectured by Camanho et al. The argument is based on causality of a four-point function, with kinematics designed to probe bulk locality, and invokes the chaos bound of Maldacena, Shenker, and Stanford.

Skyrmions, Skyrme stars and black holes with Skyrme hair in five spacetime dimension

NASA Astrophysics Data System (ADS)

Brihaye, Yves; Herdeiro, Carlos; Radu, Eugen; Tchrakian, D. H.

2017-11-01

We consider a class of generalizations of the Skyrme model to five spacetime dimensions ( d = 5), which is defined in terms of an O(5) sigma model. A special ansatz for the Skyrme field allows angular momentum to be present and equations of motion with a radial dependence only. Using it, we obtain: 1) everywhere regular solutions describing localised energy lumps ( Skyrmions); 2) Self-gravitating, asymptotically flat, everywhere non-singular solitonic solutions ( Skyrme stars), upon minimally coupling the model to Einstein's gravity; 3) both static and spinning black holes with Skyrme hair, the latter with rotation in two orthogonal planes, with both angular momenta of equal magnitude. In the absence of gravity we present an analytic solution that satisfies a BPS-type bound and explore numerically some of the non-BPS solutions. In the presence of gravity, we contrast the solutions to this model with solutions to a complex scalar field model, namely boson stars and black holes with synchronised hair. Remarkably, even though the two models present key differences, and in particular the Skyrme model allows static hairy black holes, when introducing rotation, the synchronisation condition becomes mandatory, providing further evidence for its generality in obtaining rotating hairy black holes.

Extremal higher spin black holes

NASA Astrophysics Data System (ADS)

Bañados, Máximo; Castro, Alejandra; Faraggi, Alberto; Jottar, Juan I.

2016-04-01

The gauge sector of three-dimensional higher spin gravities can be formulated as a Chern-Simons theory. In this context, a higher spin black hole corresponds to a flat connection with suitable holonomy (smoothness) conditions which are consistent with the properties of a generalized thermal ensemble. Building on these ideas, we discuss a definition of black hole extremality which is appropriate to the topological character of 3 d higher spin theories. Our definition can be phrased in terms of the Jordan class of the holonomy around a non-contractible (angular) cycle, and we show that it is compatible with the zero-temperature limit of smooth black hole solutions. While this notion of extremality does not require supersymmetry, we exemplify its consequences in the context of sl(3|2) ⊕ sl(3|2) Chern-Simons theory and show that, as usual, not all extremal solutions preserve supersymmetries. Remarkably, we find in addition that the higher spin setup allows for non-extremal supersymmetric black hole solutions. Furthermore, we discuss our results from the perspective of the holographic duality between sl(3|2) ⊕ sl(3|2) Chern-Simons theory and two-dimensional CFTs with W (3|2) symmetry, the simplest higher spin extension of the N = 2 super-Virasoro algebra. In particular, we compute W (3|2) BPS bounds at the full quantum level, and relate their semiclassical limit to extremal black hole or conical defect solutions in the 3 d bulk. Along the way, we discuss the role of the spectral flow automorphism and provide a conjecture for the form of the semiclassical BPS bounds in general N = 2 two-dimensional CFTs with extended symmetry algebras.

Asteroid spin-rate studies using large sky-field surveys

NASA Astrophysics Data System (ADS)

Chang, Chan-Kao; Lin, Hsing-Wen; Ip, Wing-Huen; Prince, Thomas A.; Kulkarni, Shrinivas R.; Levitan, David; Laher, Russ; Surace, Jason

2017-12-01

Eight campaigns to survey asteroid rotation periods have been carried out using the intermediate Palomar Transient Factory in the past 3 years. 2780 reliable rotation periods were obtained, from which we identified two new super-fast rotators (SFRs), (335433) 2005 UW163 and (40511) 1999 RE88, and 23 candidate SFRs. Along with other three known super-fast rotators, there are five known SFRs so far. Contrary to the case of rubble-pile asteroids (i.e., bounded aggregations by gravity only), an internal cohesion, ranging from 100 to 1000 Pa, is required to prevent these five SFRs from flying apart because of their super-fast rotations. This cohesion range is comparable with that of lunar regolith. However, some candidates of several kilometers in size require unusually high cohesion (i.e., a few thousands of Pa). Therefore, the confirmation of these kilometer-sized candidates can provide important information about asteroid interior structure. From the rotation periods we collected, we also found that the spin-rate limit of C-type asteroids, which has a lower bulk density, is lower than for S-type asteroids. This result is in agreement with the general picture of rubble-pile asteroids (i.e., lower bulk density, lower spin-rate limit). Moreover, the spin-rate distributions of asteroids of 3< D < 15 km in size show a steady decrease along frequency for f > 5 rev/day, regardless of the location in the main belt. The YORP effect is indicated to be less efficient in altering asteroid spin rates from our results when compared with the flat distribution found by Pravec et al. (Icarus 197:497-504, 2008. doi: 10.1016/j.icarus.2008.05.012). We also found a significant number drop at f = 5 rev/day in the spin-rate distributions of asteroids of D < 3 km.

Bobbing and kicks in electromagnetism and gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gralla, Samuel E.; Harte, Abraham I.; Wald, Robert M.

2010-05-15

We study systems analogous to binary black holes with spin in order to gain some insight into the origin and nature of 'bobbing' motion and 'kicks' that occur in this system. Our basic tool is a general formalism for describing the motion of extended test bodies in an external electromagnetic field in curved spacetime and possibly subject to other forces. We first show that bobbing of exactly the type as observed in numerical simulations of the binary black hole system occurs in a simple system consisting of two spinning balls connected by an elastic band in flat spacetime. This bobbingmore » may be understood as arising from the difference between a spinning body's 'lab frame centroid' and its true center of mass, and is purely 'kinematical' in the sense that it will appear regardless of the forces holding two spinning bodies in orbit. Next, we develop precise rules for relating the motion of charged bodies in a stationary external electromagnetic field in flat spacetime with the motion of bodies in a weakly curved stationary spacetime. We then consider the system consisting of two orbiting charges with magnetic dipole moment and spin at a level of approximation corresponding to 1.5 post-Newtonian order. Here we find that considerable amounts of momentum are exchanged between the bodies and the electromagnetic field; however, the bodies store this momentum entirely as ''hidden'' mechanical momentum, so that the interchange does not give rise to any net bobbing. The net bobbing that does occur is due solely to the kinematical spin effect, and we therefore argue that the net bobbing of the electromagnetic binary is not associated with possible kicks. We believe that this conclusion holds in the gravitational case as well.« less

Entanglement of purification: from spin chains to holography

NASA Astrophysics Data System (ADS)

Nguyen, Phuc; Devakul, Trithep; Halbasch, Matthew G.; Zaletel, Michael P.; Swingle, Brian

2018-01-01

Purification is a powerful technique in quantum physics whereby a mixed quantum state is extended to a pure state on a larger system. This process is not unique, and in systems composed of many degrees of freedom, one natural purification is the one with minimal entanglement. Here we study the entropy of the minimally entangled purification, called the entanglement of purification, in three model systems: an Ising spin chain, conformal field theories holographically dual to Einstein gravity, and random stabilizer tensor networks. We conjecture values for the entanglement of purification in all these models, and we support our conjectures with a variety of numerical and analytical results. We find that such minimally entangled purifications have a number of applications, from enhancing entanglement-based tensor network methods for describing mixed states to elucidating novel aspects of the emergence of geometry from entanglement in the AdS/CFT correspondence.

A flight investigation of the spinning of the NY-1 airplane with varied mass distribution and other modifications, and an analysis based on wind-tunnel tests

NASA Technical Reports Server (NTRS)

Scudder, Nathan F

1934-01-01

This report presents the results of an investigation of the spinning characteristics of NY-1 naval training biplane. The results of flight tests and an analysis based on wind-tunnel test data are given and compared. The primary purpose of the investigation was the determination in flight of the effect of changes in mass distribution along the longitudinal axis, without change of mass quantity or centroid. Other effects were also investigated, such as those due to wing loading, center-of-gravity position, dihedral of wings, control setting, and the removal of a large portion of the fabric from the fin and rudder. The wind tunnel test results used in the numerical analysis were obtained in the 7 by 10 foot wind tunnel through an angle-of-attack.

Gravitational effective action at second order in curvature and gravitational waves

NASA Astrophysics Data System (ADS)

Calmet, Xavier; Capozziello, Salvatore; Pryer, Daniel

2017-09-01

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential.

Satellite attitude prediction by multiple time scales method

NASA Technical Reports Server (NTRS)

Tao, Y. C.; Ramnath, R.

1975-01-01

An investigation is made of the problem of predicting the attitude of satellites under the influence of external disturbing torques. The attitude dynamics are first expressed in a perturbation formulation which is then solved by the multiple scales approach. The independent variable, time, is extended into new scales, fast, slow, etc., and the integration is carried out separately in the new variables. The theory is applied to two different satellite configurations, rigid body and dual spin, each of which may have an asymmetric mass distribution. The disturbing torques considered are gravity gradient and geomagnetic. Finally, as multiple time scales approach separates slow and fast behaviors of satellite attitude motion, this property is used for the design of an attitude control device. A nutation damping control loop, using the geomagnetic torque for an earth pointing dual spin satellite, is designed in terms of the slow equation.

Correlation between vestibular and autonomous function after 6 months of spaceflight: Data of the SPIN and GAZE-SPIN experiments.

NASA Astrophysics Data System (ADS)

Wuyts, Floris; Clement, Gilles; Naumov, Ivan; Kornilova, Ludmila; Glukhikh, Dmitriy; Hallgren, Emma; MacDougall, Hamish; Migeotte, Pierre-Francois; Delière, Quentin; Weerts, Aurelie; Moore, Steven; Diedrich, Andre

In 13 cosmonauts, the vestibulo-autonomic reflex was investigated before and after 6 months duration spaceflight. Cosmonauts were rotated on the mini-centrifuge VVIS, which is installed in Star City. Initially, this mini-centrifuge flew on board of the Neurolab mission (STS-90), and served to generate intermittent artificial gravity during that mission, with apparent very positive effects on the preservation of the orthostatic tolerance upon return to earth in the 4 crew members that were subjected to the rotations in space. The current experiments SPIN and GAZE-SPIN are control experiments to test the hypothesis that intermittent artificial gravity in space can serve as a counter measure against several deleterious effects of microgravity. Additionally, the effect of microgravity on the gaze holding system is studied as well. Cosmonauts from a long duration stay in the International Space Station were tested on the VVIS (1 g centripetal interaural acceleration; consecutive right-ear-out anti-clockwise and left-ear-out clockwise measurement) on 5 different days. Two measurements were scheduled about one month and a half prior to launch and the remaining three immediately after their return from space (typically on R+2, R+4, R+9; R = return day from space). The ocular counter roll (OCR) as a measure of otolith function was measured on before, during and after the rotation in the mini centrifuge, using infrared video goggles. The perception of verticality was monitored using an ultrasound system. Gaze holding was tested before, during and after rotation. After the centrifugation part, the crew was installed on a tilt table, and instrumented with several cardiovascular recording equipment (ECG, continuous blood pressure monitoring, respiratory monitoring), as well as with impedance measurement devices to investigate fluid redistribution throughout the operational tilt test. To measure heart rate variability parameters, imposed breathing periods were included in the test protocol. The subjects were subjected to a passive tilt test of 60 degrees, during 15 minutes. The results show that cosmonauts clearly have a statistically significantly reduced ocular counter rolling during rotation upon return from space, when compared to the pre-flight condition, indicating a reduced sensitivity of the otolith system to gravito intertial acceleration. None of the subjects fainted or even approached presyncope. However, the resistance in the calf, measured with the impedance method, showed a significant increased pooling in the lower limbs. Additionally, this was statistically significantly correlated (p=0.024) with a reduced otolith response, when comparing for each subject the vestibular and autonomic data. This result shows that the vestibulo-autonomic reflex is reduced after 6 months of spaceflight. When compared with Neurolab, the otolith response in the current group of crew members that were not subjected to in-flight centrifugation is significantly reduced, corroborating the hypothesis that in-flight artificial gravity may be of great importance to mitigate the deleterious effects of microgravity. Projects are funded by PRODEX-BELSPO, ESA, IBMP

The Interior of Enceladus from Gravity and Topography

NASA Astrophysics Data System (ADS)

Iess, L.

2015-12-01

The combination of gravity and topography has been the method of choice to obtain quantitative information on the interior of Enceladus, but its application was challenging because of the small mass of the moon and the short gravitational interaction time with the Cassini spacecraft. The main observable quantity used in the estimation of the gravity field was the spacecraft range rate, measured by the antennas of NASA's Deep Space Network to an accuracy of about 0.03 mm/s (at 60 s integration time). In spite of these challenges and thanks to the careful design of three gravity flybys, Cassini was able to catch the essential features of Enceladus's gravity field, in particular to estimate its quadrupole and detect the sought-for hemispherical asymmetry [1]. Crucial for the correct fit of the Doppler data was the inclusion in the dynamical model of the drag acceleration from the plume's neutral particles. Although the largest quadrupole coefficients indicate only a mild deviation from hydrostatic equilibrium (J2/C22=3.55±0.05), a reliable determination of the MOIF uses J3 to separate the hydrostatic and non-hydrostatic components of the quadrupole field. The application of this method results in a MOIF (0.336) compatible with a differentiated structure. (An admittance analysis leads to a similar value.) The magnitude and the sign of J3 indicate that the gravity anomaly associated to the striking topographic depression (-1 km) in the southern polar regions is largely compensated by denser material at depth. The obvious (but not the only) interpretation points to a liquid water mass, denser than the surrounding ice and sandwiched between the ice shell and the rocky core. The gravity field and the topography provide also rough estimate of the size of the water mass and the depth at which it is located. Starting from the consideration that the hydrostatic J2/C22 ratio for a fast rotator like Enceladus is about 3.25 and not 10/3, a recent work [2] offers some adjustments to this picture. [1] L. Iess, D.J. Stevenson, et al.: "The Gravity Field and Interior Structure of Enceladus", Science, 344, 78-80 (2014) DOI: 10.1126/science.1250551 [2] W.B. McKinnon: "Effect of Enceladus's rapid synchronous spin on interpretation of Cassini gravity", GRL, 42, 2137-2143 (2015) DOI:10.1002/2015GL063384

Analysis of nucleon electromagnetic form factors from light-front holographic QCD: The spacelike region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sufian, Raza Sabbir; de Teramond, Guy F.; Brodsky, Stanley J.

We present a comprehensive analysis of the space-like nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front holographic QCD. We show that the inclusion of the higher Fock componentsmore » $$|{qqqq\\bar{q}}$$ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD results for the proton and neutron form factors at any momentum transfer range, including asymptotic predictions, and show that our results agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30$$\\%$$ in the proton and about 40$$\\%$$ in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The free parameters needed to describe the experimental nucleon form factors are very few: two parameters for the probabilities of higher Fock states for the spin-flip form factor and a phenomenological parameter $r$, required to account for possible SU(6) spin-flavor symmetry breaking effects in the neutron, whereas the Pauli form factors are normalized to the experimental values of the anomalous magnetic moments. As a result, the covariant spin structure for the Dirac and Pauli nucleon form factors prescribed by AdS$$_5$$ semiclassical gravity incorporates the correct twist scaling behavior from hard scattering and also leads to vector dominance at low energy.« less

Analysis of nucleon electromagnetic form factors from light-front holographic QCD: The spacelike region

DOE PAGES

Sufian, Raza Sabbir; de Teramond, Guy F.; Brodsky, Stanley J.; ...

2017-01-10

We present a comprehensive analysis of the space-like nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front holographic QCD. We show that the inclusion of the higher Fock componentsmore » $$|{qqqq\\bar{q}}$$ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD results for the proton and neutron form factors at any momentum transfer range, including asymptotic predictions, and show that our results agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30$$\\%$$ in the proton and about 40$$\\%$$ in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The free parameters needed to describe the experimental nucleon form factors are very few: two parameters for the probabilities of higher Fock states for the spin-flip form factor and a phenomenological parameter $r$, required to account for possible SU(6) spin-flavor symmetry breaking effects in the neutron, whereas the Pauli form factors are normalized to the experimental values of the anomalous magnetic moments. As a result, the covariant spin structure for the Dirac and Pauli nucleon form factors prescribed by AdS$$_5$$ semiclassical gravity incorporates the correct twist scaling behavior from hard scattering and also leads to vector dominance at low energy.« less

On the Determination of the Spin of the Black Hole in Cyg X-1 from X-Ray Reflection Spectra

NASA Technical Reports Server (NTRS)

Fabian, A. C.; Wilkins, D.; Miller, J. M.; Reis, R. C.; Reynolds, C. S.; Cackett, E. M.; Nowak, M. A.; Pooley, G.; Pottschmidt, K.; Sanders, J. S.;

Validity of the "Laplace Swindle" in Calculation of Giant-Planet Gravity Fields

NASA Astrophysics Data System (ADS)

Hubbard, William B.

2014-11-01

Jupiter and Saturn have large rotation-induced distortions, providing an opportunity to constrain interior structure via precise measurement of external gravity. Anticipated high-precision gravity measurements close to the surfaces of Jupiter (Juno spacecraft) and Saturn (Cassini spacecraft), possibly detecting zonal harmonics to J10 and beyond, will place unprecedented requirements on gravitational modeling via the theory of figures (TOF). It is not widely appreciated that the traditional TOF employs a formally nonconvergent expansion attributed to Laplace. This suspect expansion is intimately related to the standard zonal harmonic (J-coefficient) expansion of the external gravity potential. It can be shown (Hubbard, Schubert, Kong, and Zhang: Icarus, in press) that both Jupiter and Saturn are in the domain where Laplace's "swindle" works exactly, or at least as well as necessary. More highly-distorted objects such as rapidly spinning asteroids may not be in this domain, however. I present a numerical test for the validity and precision of TOF via polar "audit points". I extend the audit-point test to objects rotating differentially on cylinders, obtaining zonal harmonics to J20 and beyond. Models with only low-order differential rotation do not exhibit dramatic effects in the shape of the zonal harmonic spectrum. However, a model with Jupiter-like zonal winds exhibits a break in the zonal harmonic spectrum above about J10, and generally follows the more shallow Kaula power rule at higher orders. This confirms an earlier result obtained by a different method (Hubbard: Icarus 137, 357-359, 1999).

Feasibility analysis of gravitational experiments in space

NASA Technical Reports Server (NTRS)

Everitt, C. W. F.

1977-01-01

Experiments on gravitation and general relativity suggested by different workers in the past ten or more years are reviewed, their feasibility examined, and the advantages of performing them in space were studied. The experiments include: (1) the gyro relativity experiment; (2) experiments to test the equivalence of gravitational and inertial mass; (3) an experiment to look for nongeodesic motion of spinning bodies in orbit around the earth; (4) experiments to look for changes of the gravitational constant G with time; (5) a variety of suggestions; laboratory tests of experimental gravity; and (6) gravitational wave experiments.

PREFACE: Loops 11: Non-Perturbative / Background Independent Quantum Gravity

NASA Astrophysics Data System (ADS)

Mena Marugán, Guillermo A.; Barbero G, J. Fernando; Garay, Luis J.; Villaseñor, Eduardo J. S.; Olmedo, Javier

2012-05-01

Loops 11 The international conference LOOPS'11 took place in Madrid from the 23-28 May 2011. It was hosted by the Instituto de Estructura de la Materia (IEM), which belongs to the Consejo Superior de Investigaciones Cientĺficas (CSIC). Like previous editions of the LOOPS meetings, it dealt with a wealth of state-of-the-art topics on Quantum Gravity, with special emphasis on non-perturbative background-independent approaches to spacetime quantization. The main topics addressed at the conference ranged from the foundations of Quantum Gravity to its phenomenological aspects. They encompassed different approaches to Loop Quantum Gravity and Cosmology, Polymer Quantization, Quantum Field Theory, Black Holes, and discrete approaches such as Dynamical Triangulations, amongst others. In addition, this edition celebrated the 25th anniversary of the introduction of the now well-known Ashtekar variables and the Wednesday morning session was devoted to this silver jubilee. The structure of the conference was designed to reflect the current state and future prospects of research on the different topics mentioned above. Plenary lectures that provided general background and the 'big picture' took place during the mornings, and the more specialised talks were distributed in parallel sessions during the evenings. To be more specific, Monday evening was devoted to Shape Dynamics and Phenomenology Derived from Quantum Gravity in Parallel Session A, and to Covariant Loop Quantum Gravity and Spin foams in Parallel Session B. Tuesday's three Parallel Sessions dealt with Black Hole Physics and Dynamical Triangulations (Session A), the continuation of Monday's session on Covariant Loop Quantum Gravity and Spin foams (Session B) and Foundations of Quantum Gravity (Session C). Finally, Thursday and Friday evenings were devoted to Loop Quantum Cosmology (Session A) and to Hamiltonian Loop Quantum Gravity (Session B). The result of the conference was very satisfactory and enlightening. Not only was it a showroom for the research currently being carried out by many groups throughout the world, but there was also a permanent look towards the future. During these days, the CSIC Campus witnessed many scientific conversations triggered by the interaction amongst the people and groups that participated in LOOPS'11 Madrid and which, in many cases, will crystallise into new results and advances in the field. The conference would not have been possible without the generous help of a number of national and international institutions. The organizers would like to acknowledge the financial support provided by the Spanish Ministry of Science and Innovation (Ministerio de Ciencia e Innovación), the Spanish Research Council, CSIC (Consejo Superior de Investigaciones Cientĺficas), The BBVA Foundation (Fundación BBVA), The CONSOLIDER-CPAN project, the Spanish Society for Gravitation and Relativity (SEGRE), The Universidad Carlos III of Madrid (UC3M), and the European Science Foundation (ESF). The ESF, through the Quantum Gravity and Quantum Geometry network, provided full support for a number of young participants that have contributed to these proceedings: Dario Benedetti (Albert Einstein Institute, Potsdam, Germany), Norbert Bodendorfer (Institute for Theoretical Physics III, FAU Erlangen Nürnberg, Germany), Mariam Bouhmadi López (CENTRA, Centro Multidisciplinar de Astrofĺsica, Lisbon), Timothy Budd (Institute for Theoretical Physics, Utrecht University, The Netherlands), Miguel Campiglia (Institute for Gravitation and the Cosmos, Penn State University, USA), Gianluca Delfino (School of Mathematical Sciences, University of Nottingham, UK), Maite Dupuis (Institute for Theoretical Physics III, FAU Erlangen Nürnberg, Germany), Michał Dziendzikowski (Institute of Theoretical Physics, Warsaw University, Poland), Muxin Han (Centre de Physique Théorique de Luminy, Marseille, France), Philipp Höhn (Institute for Theoretical Physics, Utrecht University, The Netherlands), Jacek Puchta (Centre de Physique Théorique de Luminy, Marseille, France), James Ryan (Albert Einstein Institute, Potsdam, Germany), Lorenzo Sindoni (Albert Einstein Institute, Golm, Germany), David Sloan (Institute for Theoretical Physics, Utrecht University, The Netherlands), Johannes Tambornino (Laboratoire de Physique, ENS Lyon, France), Andreas Thurn (Institute for Theoretical Physics III, FAU Erlangen Nürnberg, Germany), Francesca Vidotto (Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, France), and Matteo Smerlak (Albert Einstein Institute, Golm, Germany). We would like to conclude this preamble by thanking all the attendants of the conference for their high and enthusiastic participation. The presence of a large number of past and present Loop Quantum Gravity practitioners, as well as a significant number of top researchers in other approaches to quantum gravity, provided ample opportunities for fruitful scientific exchanges and a very lively atmosphere. It is encouraging to see that, 25 years after the inception of Loop Quantum Gravity, there is a vibrant young community of researchers entering the field. Let us hope that, with their help, the quantization of general relativity can be successfully accomplished in the near future. The Editors Conference photograph

Representing massive gravitons, as a way to quantify early universe magnetic field contributions to space-time, created by non linear electrodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beckwith, Andrew Walcott, E-mail: Rwill9955b@gmail.com

We review a relationship between cosmological vacuum energy and massive gravitons as given by Garattini and also the nonlinear electrodynamics of Camara et.al (2004) for a non singular universe and NLED. . In evaluating the Garattini result, we find that having the scale factor close to zero due to a given magnetic field value in, an early universe magnetic field affects how we would interpret Garattini’s linkage of the ‘cosmological constant’ value and non zero graviton mass.. We close as to how these initial conditions affect the issue of an early universe initial pressure and its experimental similarities and differencesmore » with results by Corda and Questa as to negative pressure at the surface of a star. Note, that in theDupays et.al. article , the star in question is rapidly spinning, which is not. assumed in the Camara et.al article , for an early universe. Also, Corda and Questa do not assume a spinning star. We conclude with a comparison between the Lagrangian Dupays and other authors bring up for non linear electrodynamics which is for rapidly spinning neutron stars , and a linkage between the Goldstone theorem and NLED. Our conclusion is for generalizing results seen in the Dupays neutron star Lagrangian with conditions which may confirm C. A. Escobar and L. F. Urrutia’s work on the Goldstone theorem and non linear electrodynamics, for some future projects we have in mind. If the universe does not spin, then we will stick with the density analogy given by adapting density as proportional to one over the fourth power of the minimum value of the scale factor as computed by adaptation of the Camara et.al.(2004) theory for non spinning universes. What may happen is that the Camara (2004) density and Quintessential density are both simultaneously satisfied, which would put additional restrictions on the magnetic field, which is one of our considerations, regardless if a universe spins, akin to spinning neutron stars. The spinning universe though may allow for easier reconciliation of the ‘Goldstone’ behavior of gravity and NLED though.« less

Comments on gravitoelectromagnetism of Ummarino and Gallerati in "Superconductor in a weak static gravitational field" vs other versions

NASA Astrophysics Data System (ADS)

Behera, Harihar

2017-12-01

Recently reported [Eur. Phys. J. C., 77, 549 (2017). https://doi.org/10.1140/epjc/s10052-017-5116-y] gravitoelectromagnetic equations of Ummarino and Gallerati (UG) in their linearized version of general relativity (GR) are shown to match with (a) our previously reported special relativistic Maxwellian Gravity equations in the non-relativistic limit and with (b) the non-relativistic equations derived here, when the speed of gravity c_g (an undetermined parameter of the theory here) is set equal to c (the speed of light in vacuum). Seen in the light of our new results, the UG equations satisfy the Correspondence Principle (cp), while many other versions of linearized GR equations that are being (or may be) used to interpret the experimental data defy the cp. Such new findings assume significance and relevance in the contexts of recent detection of gravitational waves and the gravitomagnetic field of the spinning earth and their interpretations. Being well-founded and self-consistent, the equations may be of interest and useful to researchers exploring the phenomenology of gravitomagnetism, gravitational waves and the novel interplay of gravity with different states of matter in flat space-time like UG's interesting work on superconductors in weak gravitational fields.

On the local structure of spacetime in ghost-free bimetric theory and massive gravity

NASA Astrophysics Data System (ADS)

Hassan, S. F.; Kocic, Mikica

2018-05-01

The ghost-free bimetric theory describes interactions of gravity with another spin-2 field in terms of two Lorentzian metrics. However, if the two metrics do not admit compatible notions of space and time, the formulation of the initial value problem becomes problematic. Furthermore, the interaction potential is given in terms of the square root of a matrix which is in general nonunique and possibly nonreal. In this paper we show that both these issues are evaded by requiring reality and general covariance of the equations. First we prove that the reality of the square root matrix leads to a classification of the allowed metrics in terms of the intersections of their null cones. Then, the requirement of general covariance further restricts the allowed metrics to geometries that admit compatible notions of space and time. It also selects a unique definition of the square root matrix. The restrictions are compatible with the equations of motion. These results ensure that the ghost-free bimetric theory can be defined unambiguously and that the two metrics always admit compatible 3+1 decompositions, at least locally. In particular, these considerations rule out certain solutions of massive gravity with locally Closed Causal Curves, which have been used to argue that the theory is acausal.

DC electrostatic gyro suspension system for the Gravity Probe B experiment

NASA Astrophysics Data System (ADS)

Wu, Chang-Huei

1994-12-01

The Gravity Probe B experiment is a satellite-based experiment primarily designed to test two aspects of Einstein's General Theory of Relativity by observing the spin axis drift of near-perfect gyroscopes in a 650-km circular polar orbit. The goal of this experiment is to measure the drift angles to an accuracy of 0.3 milli-arcsec after one year in orbit. As a result, electrostatically suspended free-spinning gyroscopes operating at a very low temperature became the final choice for their ultra-low Newtonian torque-induced drift rate. The Conventional AC current-driven suspension system faces two fundamental difficulties for ground gyro testing. Field emission causes rotor charging and arcing with an imperfect electrode or rotor surfaces because the electric field intensity needed to support a solid rotor in the 1-g field is more than 107 V/m. The system not only becomes unstable at a high rotor charge, which can be more than 500 volts, but may also lose control in case of arcing. Both the high voltage AC suspension signal and the high frequency (1 MHz) signal for rotor position sensing interfere with the superconducting SQUID magnetometer for spin axis readout through inductive coupling. These problems were resolved by using DC voltage to generate a suspension force and a low frequency position sensor. In addition to the Input/Output linearization algorithm developed to remove the system nonlinearity for global stability and dynamic performance, we also minimized the electric field intensity to reduce rotor charging. Experimental results verified the desired global stability and satisfactory dynamic performance. The problem of rotor charging is virtually eliminated. More importantly, the DC system is compatible with the SQUID readout system in the Science Mission configuration. Consequently, experiments in low magnetic field at a sub-micro-gauss level for SQUID design verification and trapped flux distribution study were finally realizable in ground environment. The second part of the research focused on design issues for the Science Mission in a micro-g environment. The unique requirement of the GP-B experiment is to minimize suspension-induced torque and subsequent spin axis drift. A nonlinear control law which employs stiffened spring and stiffened damping coefficients was developed to achieve both low RMS noise in steady-state operation and quick response for situations like a micrometeoroid impact. Rotor voltage measurement and in-flight sensor bias correction schemes were developed to ensure system stability and absolute centering accuracy. Simulation results verified the system performances and confirmed that a suspension system induced rotor spin axis drift lower than 0.1 milli arcsec/year can be reached.

Skylab

NASA Image and Video Library

1972-08-21

Lexington, Massachusetts high school student, Judith Miles, discusses her proposed Skylab experiment with Keith Demorest (right) and Henry Floyd, both of Marshall Space Flight Center (MSFC). In her experiment, called the “Web Formation in Zero Gravity”, called for spiders to be released into a box and their actions recorded to determine how well they adapt to the absence of gravity. Spiders are known to adapt quickly to other changes in the environment but nothing was known of their ability to adapt to weightlessness. At the same time spiders were weaving webs in Earth orbit, similar spiders were spinning webs in identical boxes on Earth under full gravity conditions. Miles was among the 25 winners of a contest in which some 3,500 high school students proposed experiments for the following year’s Skylab Mission. Of the 25 students, 6 did not see their experiments conducted on Skylab because the experiments were not compatible with Skylab hardware and timelines. Of the 19 remaining, 11 experiments required the manufacture of equipment.

Models & Searches of CPT Violation: a personal, very partial, list

NASA Astrophysics Data System (ADS)

Mavromatos, Nick E.

2018-01-01

In this talk, first I motivate theoretically, and then I review the phenomenology of, some models entailing CPT Violation (CPTV). The latter is argued to be responsible for the observed matter-antimatter asymmetry in the Cosmos, and may owe its origin to either Lorentz-violating background geometries, whose effects are strong in early epochs of the Universe but very weak today, being temperature dependent in general, or to an ill-defined CPT generator in some quantum gravity models entailing decoherence of quantum matter as a result of quantum degrees of freedom in the gravity sector that are inaccessible to the low-energy observers. In particular, for the latter category of CPTV, I argue that entangled states of neutral mesons (Kaons or B-systems), of central relevance to KLOE-2 experiment, can provide smoking-gun sensitive tests or even falsify some of these models. If CPT is ill-defined one may also encounter violations of the spin-statistics theorem, with possible consequences for the Pauli Exclusion Principle, which I only briefly touch upon.

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free

PubMed Central

Bianconi, Ginestra; Rahmede, Christoph

2015-01-01

In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension . We show that in d = 2 CQNM are homogeneous networks while for d > 2 they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the -faces of the -dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the -faces. PMID:26356079

Perfect discretization of reparametrization invariant path integrals

NASA Astrophysics Data System (ADS)

Bahr, Benjamin; Dittrich, Bianca; Steinhaus, Sebastian

2011-05-01

To obtain a well-defined path integral one often employs discretizations. In the case of gravity and reparametrization-invariant systems, the latter of which we consider here as a toy example, discretizations generically break diffeomorphism and reparametrization symmetry, respectively. This has severe implications, as these symmetries determine the dynamics of the corresponding system. Indeed we will show that a discretized path integral with reparametrization-invariance is necessarily also discretization independent and therefore uniquely determined by the corresponding continuum quantum mechanical propagator. We use this insight to develop an iterative method for constructing such a discretized path integral, akin to a Wilsonian RG flow. This allows us to address the problem of discretization ambiguities and of an anomaly-free path integral measure for such systems. The latter is needed to obtain a path integral, that can act as a projector onto the physical states, satisfying the quantum constraints. We will comment on implications for discrete quantum gravity models, such as spin foams.

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free.

PubMed

Bianconi, Ginestra; Rahmede, Christoph

2015-09-10

In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension d. We show that in d = 2 CQNM are homogeneous networks while for d > 2 they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the δ-faces of the d-dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the δ-faces.

Generalized soldering of {+-}2 helicity states in D=2+1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalmazi, D.; Mendonca, Elias L.

2009-07-15

The direct sum of a couple of Maxwell-Chern-Simons gauge theories of opposite helicities {+-}1 does not lead to a Proca theory in D=2+1, although both theories share the same spectrum. However, it is known that by adding an interference term between both helicities we can join the complementary pieces together and obtain the physically expected result. A generalized soldering procedure can be defined to generate the missing interference term. Here, we show that the same procedure can be applied to join together {+-}2 helicity states in a full off-shell manner. In particular, by using second-order (in derivatives) self-dual models ofmore » helicities {+-}2 (spin-2 analogues of Maxwell-Chern-Simmons models) the Fierz-Pauli theory is obtained after soldering. Remarkably, if we replace the second-order models by third-order self-dual models (linearized topologically massive gravity) of opposite helicities, after soldering, we end up exactly with the new massive gravity theory of Bergshoeff, Hohm, and Townsend in its linearized approximation.« less

Translation invariant time-dependent solutions to massive gravity II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mourad, J.; Steer, D.A., E-mail: mourad@apc.univ-paris7.fr, E-mail: steer@apc.univ-paris7.fr

2014-06-01

This paper is a sequel to JCAP 12 (2013) 004 and is also devoted to translation-invariant solutions of ghost-free massive gravity in its moving frame formulation. Here we consider a mass term which is linear in the vielbein (corresponding to a β{sub 3} term in the 4D metric formulation) in addition to the cosmological constant. We determine explicitly the constraints, and from the initial value formulation show that the time-dependent solutions can have singularities at a finite time. Although the constraints give, as in the β{sub 1} case, the correct number of degrees of freedom for a massive spin twomore » field, we show that the lapse function can change sign at a finite time causing a singular time evolution. This is very different to the β{sub 1} case where time evolution is always well defined. We conclude that the β{sub 3} mass term can be pathological and should be treated with care.« less

On trajectories of rolling marbles in cones and other funnels

NASA Astrophysics Data System (ADS)

White, Gary D.

2013-12-01

We report on theoretical and experimental results for a ball that rolls without slipping on a surface of revolution, whose symmetry axis is aligned with a uniform gravitational field, particularly investigating both near-circular orbits and scattering-type orbits in cones. The experimental data give support for the theoretical treatment, a non-trivial application of Newton's second law that expands on our previous work and related work of others. Our findings refine those from a recent article in this journal, and largely replicate those obtained from an earlier Lagrangian approach, adding some new details and commentary. While the orbits of marbles rolling in cones do not match inverse-square-law orbits quantitatively (e.g., instead of Kepler's 3rd law, we have T2∝R), we argue that students should experience these qualitative phenomena—precession of orbits, escape velocity behavior, spin-orbit coupling, conservation laws for angular momentum, energy, and spin projection—as much for the fun and kinesthetic impressions as for the raw learning. We also report on a heretofore largely ignored variable in the exploration of rolling orbits in a gravity well: the marble's spin about its own axis as it rolls. Experimenters can, intentionally or not, vary this initial condition and produce different orbital periods for a given orbital radius—a distinctly non-celestial behavior. Careful selection of the initial spin direction and speed for a particular cone can result in marble orbits that mimic the planetary ellipses.

Noncommutative Wilson lines in higher-spin theory and correlation functions of conserved currents for free conformal fields

NASA Astrophysics Data System (ADS)

Bonezzi, Roberto; Boulanger, Nicolas; De Filippi, David; Sundell, Per

2017-11-01

We first prove that, in Vasiliev’s theory, the zero-form charges studied in Sezgin E and Sundell P 2011 (arXiv:1103.2360 [hep-th]) and Colombo N and Sundell P 20 (arXiv:1208.3880 [hep-th]) are twisted open Wilson lines in the noncommutative Z space. This is shown by mapping Vasiliev’s higher-spin model on noncommutative Yang-Mills theory. We then prove that, prior to Bose-symmetrising, the cyclically-symmetric higher-spin invariants given by the leading order of these n-point zero-form charges are equal to corresponding cyclically-invariant building blocks of n-point correlation functions of bilinear operators in free conformal field theories (CFT) in three dimensions. On the higher spin gravity side, our computation reproduces the results of Didenko V and Skvortsov E 2013 J. High Energy Phys. JHEP04(2013)158 using an alternative method amenable to the computation of subleading corrections obtained by perturbation theory in normal order. On the free CFT side, our proof involves the explicit computation of the separate cyclic building blocks of the correlation functions of n conserved currents in arbitrary dimension d>2 using polarization vectors, which is an original result. It is shown to agree, for d=3 , with the results obtained in Gelfond O A and Vasiliev M A 2013 Nucl. Phys. B 876 871-917 in various dimensions and where polarization spinors were used.

Secular obliquity variations for Ceres

NASA Astrophysics Data System (ADS)

Bills, Bruce; Scott, Bryan R.; Nimmo, Francis

2016-10-01

We have constructed secular variation models for the orbit and spin poles of the asteroid (1) Ceres, and used them to examine how the obliquity, or angular separation between spin and orbit poles, varies over a time span of several million years. The current obliquity is 4.3 degrees, which means that there are some regions near the poles which do not receive any direct Sunlight. The Dawn mission has provided an improved estimate of the spin pole orientation, and of the low degree gravity field. That allows us to estimate the rate at which the spin pole precesses about the instantaneous orbit pole.The orbit of Ceres is secularly perturbed by the planets, with Jupiter's influence dominating. The current inclination of the orbit plane, relative to the ecliptic, is 10.6 degrees. However, it varies between 7.27 and 11.78 degrees, with dominant periods of 22.1 and 39.6 kyr. The spin pole precession rate parameter has a period of 205 kyr, with current uncertainty of 3%, dominated by uncertainty in the mean moment of inertia of Ceres.The obliquity varies, with a dominant period of 24.5 kyr, with maximum values near 26 degrees, and minimum values somewhat less than the present value. Ceres is currently near to a minimum of its secular obliquity variations.The near-surface thermal environment thus has at least 3 important time scales: diurnal (9.07 hours), annual (4.60 years), and obliquity cycle (24.5 kyr). The annual thermal wave likely only penetrates a few meters, but the much long thermal wave associated with the obliquity cycle has a skin depth larger by a factor of 70 or so, depending upon thermal properties in the subsurface.

Spin Complicates Eccentric BH-NS Mergers

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-08-01

When a neutron star (NS) has a glancing encounter with a black hole (BH), its spin has a significant effect on the outcome, according to new simulations run by William East of Stanford University and his collaborators. Spotting an Eccentric Merger. In a traditional BH-NS merger, the two objects orbit each other quasi-circularly as they spiral in. But there's another kind of merger that's possible in high-density environments like galactic nuclei or globular clusters: a dynamical capture merger, in which a NS and BH pass each other just close enough that the gravity of the black hole "catches" the NS, leading the two objects to merge with very eccentric orbits. During an eccentric merger, the NS can be torn apart -- at which point some fraction of the tidally-disrupted material will escape the system, while some fraction instead accretes back onto the BH. Knowing these fractions is important for being able to model the expected electromagnetic signatures for the merger: the unbound material can power transients like kilonovae, whereas the accreting material may be the cause of short gamma-ray bursts. The amount of material available for events like these would change their observable strengths. Testing the Effects of Spin. To see whether NS spin has an impact on the behavior of the merger, East and collaborators use a general-relativistic hydrodynamic code to simulate the glancing encounter of a BH and a NS with dimensionless spin between a=0 (non-spinning) and a=0.756 (rotation period of 1 ms). They also vary the separation of the first encounter. The group finds that changing the NS's spin can change a number of outcomes of the merger. To start with, it can affect whether the NS is captured by the BH, or if the encounter is glancing and then both objects carry on their merry way. And if the NS is trapped by the BH and torn apart, then the higher the NS's spin, the more matter outside of the BH ends up unbound, instead of getting trapped into an accretion disk around the BH. As a result of these simulations, the authors argue that the spin of NSs in dynamical capture mergers is crucially important for correctly modeling the observational signatures that might come out of them. Citation: William E. East et al. 2015 ApJ, 807, L3.

Otolith Asymmetry and kinetotic Behaviour of Fish in Parabolic Flights and under simulated Parabolic Flight "Micro"Gravity - a Drop-Tower Experiment

NASA Astrophysics Data System (ADS)

Knie, M.; Hilbig, R.; Anken, R.

We have shown earlier that some fish of a given batch reveal motion sickness a kinetosis at the transition from earth gravity to diminished gravity The percentual ratios of the various types of behaviour normal swimming and kinetotic swimming kinetotic specimens revealed looping responses LR or spinning movements SM however highly differed depending on the quality of diminished gravity Anken and Hilbig Microgravity Sci Technol 15 52-57 2004 Whereas kinetoses were exhibited by some 90 of the individuals who had experienced flights at high quality microgravity HQM 10-6g ZARM drop-tower only some 15-25 depending on the batch of all animals had shown a kinetotic behaviour during parabolic aircraft flights PFs low quality microgravity LQM 0 03-0 05g Probably LQM is sufficient for most fish to be perceived - in relation to the individual shape or weight of otoliths and thus the performance of the vestibular system - and used as a cue for postural control In striking contrast to the results gained using PF specimens according to which otolith asymmetry differences in the size and calcium incorporation of the inner ear stones between the left and right side of the body was significantly higher in kinetotic specimens as compared to normally swimming fish a comparable asymmetry between the kinetotically and normally swimming drop-tower samples could statistically not be verified Anken et al Adv Space Res submitted The present study was designed to further elucidate the role of otolith asymmetry concerning an individually different

The Experiment that Came from the Cold: Results from the Recovered REXUS 12 Suaineadh Spinning Web Experiment

NASA Astrophysics Data System (ADS)

Sinn, T.; McRobb, M.; Wujek, A.; Skogby, J.; Rogberg, F.; Wang, J.; Vasile, M.; Tibert, G.; Mao, H.

2015-09-01

The Suaineadh experiment had the purpose to deploy a 2m x 2m web in milli gravity conditions by using the centrifugal forces acting on corner sections of a web that is spinning around a central hub. Continuous exploration of our solar system and beyond requires ever larger structures in space. But the biggest problem nowadays is the transport of these structures into space due to launch vehicle payload volume constrains. By making the space structures deployable with minimum storage properties, this constrain may be bypassed. Deployable concepts range from inflatables, foldables, electrostatic to spinning web deployment. The advantage of the web deployment is the very low storage volume and the simple deployment mechanism. These webs can act as lightweight platforms for the construction of large structures in space without the huge expense of launching heavy structures from Earth. The Suaineadh experiment was launched onboard the sounding rocket REXUS12 in March 2012. After achieving the required altidue, the Suaineadh experiment was ejected from the rocket in order to be fully free flying. A specially designed spinning wheel in the ejected section was then used to spin up the experiment until the required rate is achieved for web deployment to commence. Unfortunately during re-entry, the probe was lost and also a recovery mission in August 20 1 2 was only able to find minor components of the experiment. After 18 month, in September 201 3 , the experiment was found in the wilderness of Northern Sweden. In the following months all data from the experiment could be recovered. The images and accelerometer~ data that has been analysed showed the deployment of the web and a very interesting three dimensional behaviour that differs greatly from on ground two dimensional prototype tests. This paper will give an overview on the recovered data and it will present the analysed results of the Suaineadh spinning web experiment.

Quarks, Symmetries and Strings - a Symposium in Honor of Bunji Sakita's 60th Birthday

NASA Astrophysics Data System (ADS)

Kaku, M.; Jevicki, A.; Kikkawa, K.

1991-04-01

The Table of Contents for the full book PDF is as follows: * Preface * Evening Banquet Speech * I. Quarks and Phenomenology * From the SU(6) Model to Uniqueness in the Standard Model * A Model for Higgs Mechanism in the Standard Model * Quark Mass Generation in QCD * Neutrino Masses in the Standard Model * Solar Neutrino Puzzle, Horizontal Symmetry of Electroweak Interactions and Fermion Mass Hierarchies * State of Chiral Symmetry Breaking at High Temperatures * Approximate |ΔI| = 1/2 Rule from a Perspective of Light-Cone Frame Physics * Positronium (and Some Other Systems) in a Strong Magnetic Field * Bosonic Technicolor and the Flavor Problem * II. Strings * Supersymmetry in String Theory * Collective Field Theory and Schwinger-Dyson Equations in Matrix Models * Non-Perturbative String Theory * The Structure of Non-Perturbative Quantum Gravity in One and Two Dimensions * Noncritical Virasoro Algebra of d < 1 Matrix Model and Quantized String Field * Chaos in Matrix Models ? * On the Non-Commutative Symmetry of Quantum Gravity in Two Dimensions * Matrix Model Formulation of String Field Theory in One Dimension * Geometry of the N = 2 String Theory * Modular Invariance form Gauge Invariance in the Non-Polynomial String Field Theory * Stringy Symmetry and Off-Shell Ward Identities * q-Virasoro Algebra and q-Strings * Self-Tuning Fields and Resonant Correlations in 2d-Gravity * III. Field Theory Methods * Linear Momentum and Angular Momentum in Quaternionic Quantum Mechanics * Some Comments on Real Clifford Algebras * On the Quantum Group p-adics Connection * Gravitational Instantons Revisited * A Generalized BBGKY Hierarchy from the Classical Path-Integral * A Quantum Generated Symmetry: Group-Level Duality in Conformal and Topological Field Theory * Gauge Symmetries in Extended Objects * Hidden BRST Symmetry and Collective Coordinates * Towards Stochastically Quantizing Topological Actions * IV. Statistical Methods * A Brief Summary of the s-Channel Theory of Superconductivity * Neural Networks and Models for the Brain * Relativistic One-Body Equations for Planar Particles with Arbitrary Spin * Chiral Property of Quarks and Hadron Spectrum in Lattice QCD * Scalar Lattice QCD * Semi-Superconductivity of a Charged Anyon Gas * Two-Fermion Theory of Strongly Correlated Electrons and Charge-Spin Separation * Statistical Mechanics and Error-Correcting Codes * Quantum Statistics

Modern Quantum Field Theory II - Proceeeings of the International Colloquium

NASA Astrophysics Data System (ADS)

Das, S. R.; Mandal, G.; Mukhi, S.; Wadia, S. R.

1995-08-01

The Table of Contents for the book is as follows: * Foreword * 1. Black Holes and Quantum Gravity * Quantum Black Holes and the Problem of Time * Black Hole Entropy and the Semiclassical Approximation * Entropy and Information Loss in Two Dimensions * Strings on a Cone and Black Hole Entropy (Abstract) * Boundary Dynamics, Black Holes and Spacetime Fluctuations in Dilation Gravity (Abstract) * Pair Creation of Black Holes (Abstract) * A Brief View of 2-Dim. String Theory and Black Holes (Abstract) * 2. String Theory * Non-Abelian Duality in WZW Models * Operators and Correlation Functions in c ≤ 1 String Theory * New Symmetries in String Theory * A Look at the Discretized Superstring Using Random Matrices * The Nested BRST Structure of Wn-Symmetries * Landau-Ginzburg Model for a Critical Topological String (Abstract) * On the Geometry of Wn Gravity (Abstract) * O(d, d) Tranformations, Marginal Deformations and the Coset Construction in WZNW Models (Abstract) * Nonperturbative Effects and Multicritical Behaviour of c = 1 Matrix Model (Abstract) * Singular Limits and String Solutions (Abstract) * BV Algebra on the Moduli Spaces of Riemann Surfaces and String Field Theory (Abstract) * 3. Condensed Matter and Statistical Mechanics * Stochastic Dynamics in a Deposition-Evaporation Model on a Line * Models with Inverse-Square Interactions: Conjectured Dynamical Correlation Functions of the Calogero-Sutherland Model at Rational Couplings * Turbulence and Generic Scale Invariance * Singular Perturbation Approach to Phase Ordering Dynamics * Kinetics of Diffusion-Controlled and Ballistically-Controlled Reactions * Field Theory of a Frustrated Heisenberg Spin Chain * FQHE Physics in Relativistic Field Theories * Importance of Initial Conditions in Determining the Dynamical Class of Cellular Automata (Abstract) * Do Hard-Core Bosons Exhibit Quantum Hall Effect? (Abstract) * Hysteresis in Ferromagnets * 4. Fundamental Aspects of Quantum Mechanics and Quantum Field Theory * Finite Quantum Physics and Noncommutative Geometry * Higgs as Gauge Field and the Standard Model * Canonical Quantisation of an Off-Conformal Theory * Deterministic Quantum Mechanics in One Dimension * Spin-Statistics Relations for Topological Geons in 2+1 Quantum Gravity * Generalized Fock Spaces * Geometrical Expression for Short Distance Singularities in Field Theory * 5. Mathematics and Quantum Field Theory * Knot Invariants from Quantum Field Theories * Infinite Grassmannians and Moduli Spaces of G-Bundles * A Review of an Algebraic Geometry Approach to a Model Quantum Field Theory on a Curve (Abstract) * 6. Integrable Models * Spectral Representation of Correlation Functions in Two-Dimensional Quantum Field Theories * On Various Avatars of the Pasquier Algebra * Supersymmetric Integrable Field Theories and Eight Vertex Free Fermion Models (Abstract) * 7. Lattice Field Theory * From Kondo Model and Strong Coupling Lattice QCD to the Isgur-Wise Function * Effective Confinement from a Logarithmically Running Coupling (Abstract)

Perspectives on handedness, life and physics.

PubMed

Axelsson, Sven

2003-08-01

In contrast to motion, matter will be conserved in all eternity. Structure and function will arise by the angular momentum of spinning spherical particles and their composites. Symmetry prevails in physics by equal amounts of left- and right-hand spinning entities, while life is asymmetric in this respect. Very rare deviations from the ubiquitous one-sided handedness in biology will probably explain the inert degradation resistant proteins in 'mad cow' type diseases. Velocities of physical events seems to be a most important feature and will explain for instance brain function and the true nature of neurodegenerative diseases. This biophysics of mind will in turn provide answers to many disputable aspects of physics such as the true nature of waves and gravity. Many current concepts in quantum physics will be invalidated, among them the uncertainty principle, the relativity to a fixed speed of light, the energy equation and the expansion of the Universe. Instead, decay and formation will balance each other in a continuum of matter in an intuitively cyclic Multiverse.

Radiation-induced rotation of small celestial bodies

NASA Technical Reports Server (NTRS)

Misconi, N. Y.; Oliver, John; Mzariegos, Roberto

1992-01-01

The rotation was studied of particles in a simulated space environment via a technique known as Laser Particle Levitation. The combination of both a high vacuum and optical laser levitation to negate the effects of Earth's gravity, simulate the space environment. The rotation mechanism under study is known as the 'Windmill Effect,' which is a spin mechanism that suggests that the interaction of the photon field from a star with the surface irregularities of cosmic dust will cause them to spin due to the imbalance in the directionality of the scattered photons which necessitates a non-zero angular momentum. This conclusion is based on the random nature of the orientation of the sites of surface irregularities. The general object is to study the behavior of particles in orbits around the Earth, both natural and man made, as well as interplanetary and circumstellar particles. To meet this objective, an apparatus was constructed which was designed to allow optical levitation in a vacuum.

Space station impact experiments

NASA Technical Reports Server (NTRS)

Schultz, P.; Ahrens, T.; Alexander, W. M.; Cintala, M.; Gault, D.; Greeley, R.; Hawke, B. R.; Housen, K.; Schmidt, R.

1986-01-01

Four processes serve to illustrate potential areas of study and their implications for general problems in planetary science. First, accretional processes reflect the success of collisional aggregation over collisional destruction during the early history of the solar system. Second, both catastrophic and less severe effects of impacts on planetary bodies survivng from the time of the early solar system may be expressed by asteroid/planetary spin rates, spin orientations, asteroid size distributions, and perhaps the origin of the Moon. Third, the surfaces of planetary bodies directly record the effects of impacts in the form of craters; these records have wide-ranging implications. Fourth, regoliths evolution of asteroidal surfaces is a consequence of cumulative impacts, but the absence of a significant gravity term may profoundly affect the retention of shocked fractions and agglutinate build-up, thereby biasing the correct interpretations of spectral reflectance data. An impact facility on the Space Station would provide the controlled conditions necessary to explore such processes either through direct simulation of conditions or indirect simulation of certain parameters.

Gravitating lepton bag model

NASA Astrophysics Data System (ADS)

Burinskii, A.

2015-08-01

The Kerr-Newman (KN) black hole (BH) solution exhibits the external gravitational and electromagnetic field corresponding to that of the Dirac electron. For the large spin/mass ratio, a ≫ m, the BH loses horizons and acquires a naked singular ring creating two-sheeted topology. This space is regularized by the Higgs mechanism of symmetry breaking, leading to an extended particle that has a regular spinning core compatible with the external KN solution. We show that this core has much in common with the known MIT and SLAC bag models, but has the important advantage of being in accordance with the external gravitational and electromagnetic fields of the KN solution. A peculiar two-sheeted structure of Kerr's gravity provides a framework for the implementation of the Higgs mechanism of symmetry breaking in configuration space in accordance with the concept of the electroweak sector of the Standard Model. Similar to other bag models, the KN bag is flexible and pliant to deformations. For parameters of a spinning electron, the bag takes the shape of a thin rotating disk of the Compton radius, with a ring-string structure and a quark-like singular pole formed at the sharp edge of this disk, indicating that the considered lepton bag forms a single bag-string-quark system.

Gravitating lepton bag model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burinskii, A., E-mail: burinskii@mail.ru

The Kerr–Newman (KN) black hole (BH) solution exhibits the external gravitational and electromagnetic field corresponding to that of the Dirac electron. For the large spin/mass ratio, a ≫ m, the BH loses horizons and acquires a naked singular ring creating two-sheeted topology. This space is regularized by the Higgs mechanism of symmetry breaking, leading to an extended particle that has a regular spinning core compatible with the external KN solution. We show that this core has much in common with the known MIT and SLAC bag models, but has the important advantage of being in accordance with the external gravitationalmore » and electromagnetic fields of the KN solution. A peculiar two-sheeted structure of Kerr’s gravity provides a framework for the implementation of the Higgs mechanism of symmetry breaking in configuration space in accordance with the concept of the electroweak sector of the Standard Model. Similar to other bag models, the KN bag is flexible and pliant to deformations. For parameters of a spinning electron, the bag takes the shape of a thin rotating disk of the Compton radius, with a ring–string structure and a quark-like singular pole formed at the sharp edge of this disk, indicating that the considered lepton bag forms a single bag–string–quark system.« less

Space Time Theories Confirmed

NASA Image and Video Library

2011-05-04

Clifford Will, Professor of Physics at Washington University in St. Louis, makes a point during a press conference, Wednesday, May 4, 2011, to discuss NASA's Gravity Probe B (GP-B) mission which has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test at NASA Headquarters in Washington. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. Photo Credit: (NASA/Paul E. Alers)

Space Time Theories Confirmed

NASA Image and Video Library

2011-05-04

Clifford Will, Professor of Physics at Washington University in St. Louis, foreground, answers questions during a press conference, Wednesday, May 4, 2011, to discuss NASA's Gravity Probe B (GP-B) mission which has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test at NASA Headquarters in Washington. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. Photo Credit: (NASA/Paul E. Alers)

Space Time Theories Confirmed

NASA Image and Video Library

2011-05-04

Rex Geveden, President of Teledyne Brown Engineering, makes a point during a press conference, Wednesday, May 4, 2011, to discuss NASA's Gravity Probe B (GP-B) mission which has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test at NASA Headquarters in Washington. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. Photo Credit: (NASA/Paul E. Alers)

Cosine problem in EPRL/FK spinfoam model

NASA Astrophysics Data System (ADS)

Vojinović, Marko

2014-01-01

We calculate the classical limit effective action of the EPRL/FK spinfoam model of quantum gravity coupled to matter fields. By employing the standard QFT background field method adapted to the spinfoam setting, we find that the model has many different classical effective actions. Most notably, these include the ordinary Einstein-Hilbert action coupled to matter, but also an action which describes antigravity. All those multiple classical limits appear as a consequence of the fact that the EPRL/FK vertex amplitude has cosine-like large spin asymptotics. We discuss some possible ways to eliminate the unwanted classical limits.

Null result for violation of the equivalence principle with free-fall rotating gyroscopes

NASA Astrophysics Data System (ADS)

Luo, J.; Nie, Y. X.; Zhang, Y. Z.; Zhou, Z. B.

2002-02-01

The differential acceleration between a rotating mechanical gyroscope and a nonrotating one is directly measured by using a double free-fall interferometer, and no apparent differential acceleration has been observed at the relative level of 2×10-6. It means that the equivalence principle is still valid for rotating extended bodies, i.e., the spin-gravity interaction between the extended bodies has not been observed at this level. Also, to the limit of our experimental sensitivity, there is no observed asymmetrical effect or antigravity of the rotating gyroscopes as reported by Hayasaka et al.

Evidence for a Past High-Eccentricity Lunar Orbit

NASA Technical Reports Server (NTRS)

Garrick-Betthell, Ian; Wisdom, Jack; Zuber, Maria T.

2007-01-01

The large differences between the Moon's three principal moments of inertia have been mystery since Laplace considered them in 1799. Here we present calculations that show how past high eccentricity orbits can account for the moment differences, represented by the low-order lunar gravity field and libration parameters. One of our solutions is that the Moon may have once been in a 3:2 resonance of the orbit period to spin-period, similar to Mercury's present state. The possibility of past high-eccentricity orbits suggests a rich dynamical history and may influence our understanding of the early thermal evolution of the Moon.

Electrical torques on the electrostatic gyro in the gyro relativity experiment

NASA Technical Reports Server (NTRS)

Eby, P.; Darbo, W.

1980-01-01

A comprehensive discussion and calculation of electrical torques on an electrostatic gyro as they relate to the gyroscope experiment to test general relativity is presented. Drift rates were computed for some typical state of the art rotors, including higher harmonics in the rotor shape. The effect of orbital averaging of gravity gradient forces, roll averaging of torques, and the effect of spin averaging on the effective shape of the rotor were considered. The electrical torques are reduced sufficiently in a low g environment to permit a measurement of the relativistic drifts predicted by general relativity.

An Introduction to Rockets - or - Never Leave Geeks Unsupervised

NASA Technical Reports Server (NTRS)

Mellett, Kevin

2006-01-01

An introduction to rockets along with a brief history Newton's third law is presented. The contents include: 1) What is a Rocket?; 2) A Brief History; 3) Newton's Third Law; 4) A Brief History; 5) Mission Requirements; 6) Some Orbital Measurements; 7) Self Eating Watermelon; 8) Orbital Inclinations; 9) 28.5 Equatorial Orbit; 10) 51.6 Orbit (ISS); 11) Polar Orbit; 12) Geostationary Orbit; 13) Liquid Rocket; 13) Liquids vs. Solids; 14) Liquids; 15) Systems Integration; 16) Integration (NFL!); 17) Guidance Systems; 18) Vectored Thrust; 19) Spin Stabilization; 20) Aerodynamic Stability (Fire Arrows); and 21) Center of Gravity & Center of Pressure.