Results 11  20
of
215
Principles of equivalence: their role in gravitation physics and experiments that test them
 Lect. Notes Phys. 562 (2001) 195 [grqc/0103067
"... Abstract. Modern formulations of equivalence principles provide the foundation for an efficient approach to understanding and organizing the structural features of gravitation field theories. Since theories' predictions reflect differences in their structures, principles of equivalence also su ..."
Abstract

Cited by 9 (1 self)
 Add to MetaCart
(Show Context)
Abstract. Modern formulations of equivalence principles provide the foundation for an efficient approach to understanding and organizing the structural features of gravitation field theories. Since theories' predictions reflect differences in their structures, principles of equivalence also support an efficient experimental strategy for testing gravitation theories and for exploring the range of conceivable gravitation physics. These principles focus attention squarely on empirical consequences of the fundamental structural differences that distinguish one gravitation theory from another. Interestingly, the variety of such consequences makes it possible to design and perform experiments that test equivalence principles stringently but do so in markedly different ways than the most familiar experimental tests.
Solar system effects in Schwarzschild–de Sitter space–time
 Phys. Lett
"... The Schwarzschild–de Sitter space–time describes the gravitational field of a spherically symmetric mass in a universe with cosmological constant Λ. Based on this space–time we calculate Solar system effects like gravitational redshift, light deflection, gravitational time delay, Perihelion shift, g ..."
Abstract

Cited by 9 (2 self)
 Add to MetaCart
(Show Context)
The Schwarzschild–de Sitter space–time describes the gravitational field of a spherically symmetric mass in a universe with cosmological constant Λ. Based on this space–time we calculate Solar system effects like gravitational redshift, light deflection, gravitational time delay, Perihelion shift, geodetic or de Sitter precession, as well as the influence of Λ on a Doppler measurement, used to determine the velocity of the Pioneer 10 and 11 spacecraft. For Λ = Λ0 ∼ 10 −52 m −2 the cosmological constant plays no role for all of these effects, while a value of Λ ∼ −10 −37 m −2, if hypothetically held responsible for the Pioneer anomaly, is not compatible with the Perihelion shift. 1
Constraints on GaussBonnet gravity in dark energy cosmologies
"... Abstract. Models with a scalar field coupled to the GaussBonnet Lagrangian appear naturally from KaluzaKlein compactifications of pure higherdimensional gravity. We study linear, cosmological perturbations in the limits of weak coupling and slowroll, and derive simple expressions for the main ob ..."
Abstract

Cited by 9 (3 self)
 Add to MetaCart
(Show Context)
Abstract. Models with a scalar field coupled to the GaussBonnet Lagrangian appear naturally from KaluzaKlein compactifications of pure higherdimensional gravity. We study linear, cosmological perturbations in the limits of weak coupling and slowroll, and derive simple expressions for the main observable subhorizon quantities: the anisotropic stress factor, the timedependent gravitational constant, and the matter perturbation growth factor. Using present observational data, and assuming slowroll for the dark energy field, we find that the fraction of energy density associated with the coupled GaussBonnet term cannot exceed 15%. The bound should be treated with caution, as there are significant uncertainies in the data used to obtain it. Even so, it indicates that the future prospects for constraining the coupled GaussBonnet term with cosmological observations are encouraging.
Science, Technology and Mission Design for the Laser Astrometric Test Of Relativity
, 2006
"... The Laser Astrometric Test Of Relativity (LATOR) is a MichelsonMorleytype experiment designed to test the metric nature of gravitation – a fundamental postulate of Einstein’s general theory of relativity. The key element of LATOR is a geometric redundancy provided by the longbaseline optical inte ..."
Abstract

Cited by 8 (1 self)
 Add to MetaCart
The Laser Astrometric Test Of Relativity (LATOR) is a MichelsonMorleytype experiment designed to test the metric nature of gravitation – a fundamental postulate of Einstein’s general theory of relativity. The key element of LATOR is a geometric redundancy provided by the longbaseline optical interferometry and interplanetary laser ranging. By using a combination of independent timeseries of gravitational deflection of light in the immediate proximity to the Sun, along with measurements of the Shapiro time delay on interplanetary scales (to a precision respectively better than 0.1 picoradians and 1 cm), LATOR will significantly improve our knowledge of relativistic gravity and cosmology. The primary mission objective is i) to measure the key postNewtonian Eddington parameter γ with accuracy of a part in 10 9. 1 2 (1 − γ) is a direct measure for presence of a new interaction in gravitational theory, and, in its search, LATOR goes a factor 30,000 beyond the present best result, Cassini’s 2003 test. Other mission objectives include: ii) first measurement of gravity’s nonlinear effects on light to ∼0.01 % accuracy; including both the traditional Eddington
Testing General Relativity with Pulsar Timing
, 2003
"... Pulsars of very different types – isolated objects, and binaries with short and longperiod orbits, whitedwarf and neutronstar companions – provide the means to test both the predictions of general relativity and the viability of alternate theories of gravity. This article presents an overview of ..."
Abstract

Cited by 8 (0 self)
 Add to MetaCart
Pulsars of very different types – isolated objects, and binaries with short and longperiod orbits, whitedwarf and neutronstar companions – provide the means to test both the predictions of general relativity and the viability of alternate theories of gravity. This article presents an overview of pulsars, then discusses the current status and future prospects of tests of equivalence principle violations and strongfield gravitational experiments. 1 1
String theoretic bounds on Lorentzviolating warped compactification
 JHEP
"... Abstract: We consider warped compactifications that solve the 10 dimensional supergravity equations of motion at a point, stabilize the position of a D3brane world, and admit a warp factor that violates Lorentz invariance along the brane. This gives a string embedding of “asymmetrically warped ” mo ..."
Abstract

Cited by 8 (1 self)
 Add to MetaCart
(Show Context)
Abstract: We consider warped compactifications that solve the 10 dimensional supergravity equations of motion at a point, stabilize the position of a D3brane world, and admit a warp factor that violates Lorentz invariance along the brane. This gives a string embedding of “asymmetrically warped ” models which we use to calculate stringy (α ′ ) corrections to standard model dispersion relations, paying attention to the maximum speeds for different particles. We find, from the dispersion relations, limits on gravitational Lorentz violation in these models, improving on current limits on the speed of graviton propagation, including those derived from field theoretic loops. We comment on the viability of models that use
ON THE RECOVERY OF GEOMETRODYNAMICS FROM TWO DIFFERENT SETS OF FIRST PRINCIPLES
, 2006
"... The conventional spacetime formulation of general relativity may be recast as a dynamics of spatial 3geometries (geometrodynamics). Furthermore, geometrodynamics can be derived from first principles. I investigate two distinct sets of these: (i) Hojman, Kuchaˇr and Teitelboim’s, which presuppose th ..."
Abstract

Cited by 6 (1 self)
 Add to MetaCart
(Show Context)
The conventional spacetime formulation of general relativity may be recast as a dynamics of spatial 3geometries (geometrodynamics). Furthermore, geometrodynamics can be derived from first principles. I investigate two distinct sets of these: (i) Hojman, Kuchaˇr and Teitelboim’s, which presuppose that the spatial 3geometries are embedded in spacetime. (ii) The 3space approach of Barbour, Foster, Ó Murchadha and Anderson in which the spatial 3geometries are presupposed but spacetime is not. I consider how the constituent postulates of the conventional approach to relativity emerge or are to be built into these formulations. I argue that the 3space approach is a viable description of classical physics (fundamental matter fields included), and one which affords considerable philosophical insight because of its ‘relationalist’ character. From these assumptions of less structure, it is also interesting that conventional relativity can be recovered (albeit as one of several options). However, contrary to speculation in the earlier 3space approach papers, I also argue that this approach is not selective over which sorts of fundamental matter physics it admits. In particular, it does not imply the equivalence principle.
A generalization of the Lorentz ether to gravity with generalrelativistic limit
"... We define a class of condensed matter theories in a Newtonian framework with a Lagrange formalism so that a variant of Noether’s theorem gives the classical conservation laws: ∂tρ + ∂i(ρv i) = 0 ∂t(ρv j) + ∂i(ρv i v j + p ij) = 0. We show that for the metric gµν defined by ˆg 00 = g 00 √ −g = ρ ˆg ..."
Abstract

Cited by 6 (4 self)
 Add to MetaCart
(Show Context)
We define a class of condensed matter theories in a Newtonian framework with a Lagrange formalism so that a variant of Noether’s theorem gives the classical conservation laws: ∂tρ + ∂i(ρv i) = 0 ∂t(ρv j) + ∂i(ρv i v j + p ij) = 0. We show that for the metric gµν defined by ˆg 00 = g 00 √ −g = ρ ˆg i0 = g i0 √ −g = ρv i ˆg ij = g ij √ −g = ρv i v j + p ij these theories are equivalent to a metric theory of gravity with Lagrangian L = LGR + Lmatter(gµν,ϕ m) − (8πG) −1 (Υg 00 − Ξδijg ij) √ −g. with covariant Lmatter, which defines a generalization of the Lorentz ether to gravity. Thus, the Einstein equivalence may be derived from simple condensed matter axioms. The Einstein equations appear in a natural limit Ξ,Υ → 0.
Quantum Electrodynamics on background external fields
"... The quantum electrodynamics in the presence of background external fields is developed. Modern methods of local quantum physics allow to formulate the theory on arbitrarily strong possibly timedependent external fields. Nonlinear observables which depend only locally on the external field are cons ..."
Abstract

Cited by 6 (1 self)
 Add to MetaCart
(Show Context)
The quantum electrodynamics in the presence of background external fields is developed. Modern methods of local quantum physics allow to formulate the theory on arbitrarily strong possibly timedependent external fields. Nonlinear observables which depend only locally on the external field are constructed. The tools necessary for this formulation, the parametrices of the Dirac operator, are investigated. Zusammenfassung In dieser Arbeit wird die Quantenelektrodynamik in äußeren elektromagnetischen Feldern entwickelt. Die modernen Methoden der lokalen Quantenphysik ermöglichen es, die Theorie so zu formulieren, dass die äußeren Felder weder statisch noch schwach sein müssen. Es werden nichtlineare Observable konstruiert, die nur lokal von den Hintergrundfeldern abhängen. Die dazu benötigten Werkzeuge, die Parametrizes des Diracoperators, werden untersucht. Contents Chapter I. Introduction 7 I.1. Formulation of the problem 7