Search results for "GRAVITATION"

On the canonical structure of higher-derivative field theories. The gravitational WZW-model

1992

Abstract A general expression for the symplectic structure of a higher-derivative lagrangian field theory is given. General relativity and the gravitational WZW-model are considered in this framework. In the second case we work out explicitly the Poisson bracket for both chiral solutions giving rise, in two different ways, to the classical exchange algebra of the SL q (2) group.

On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

2004

I discuss various ways in which CPT symmetry may be violated, and their phenomenology in current or immediate future experimental facilities, both terrestrial and astrophysical. Specifically, I discuss first violations of CPT symmetry due to the impossibility of defining a scattering matrix as a consequence of the existence of microscopic or macroscopic space-time boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological horizons due to the presence of a (positive) cosmological constant in the Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry, which may characterize certain approaches to quantum gravity, and third, I describe models of CPT non…

Matter, quantum gravity, and adiabatic phase

1990

Based on the observation that particle masses are much smaller than the Planck mass, a framework for the matter-gravity system in which matter follows gravitation adiabatically is examined in a path-integral approach. It is found that the equations that the resulting gravitational wave function satisfies involve, in addition to the expectation value of the matter stress tensor, an adiabatically induced gauge field which can lead to interesting topological structures in superspace. Such a non-trivial geometric contribution modifies the semiclassical quantization condition and can change the conserved quantities associated with the symmetries of the system. © 1990 The American Physical Societ…

Post-post-Newtonian effects on a clean nearly-Newtonian binary

1983

Etude du taux de changement temporel moyen de l'energie newtonienne et du moment d'une binaire presque newtonienne, ponctuelle. On trouve qu'il faut ajouter quelques termes post-post newtoniens non seculaires aux flux radiatifs seculaires standards. Les termes post-post newtoniens tendent vers zero pour l'observateur du centre de masse newtonien dans le cas de l'energie mais pas dans le cas du moment. Du fait de la longue periode de ces termes ils sont observationnellement significatifs, c'est-a-dire qu'ils vont apparaitre comme s'ils etaient des effets seculaires

The Weber-Wheeler-Bonnor pulse and phase shifts in gravitational soliton interactions

1997

Abstract The WWB cylindrical pulse solution and the equivalent G 2 solution are analyzed particularly as the wave is reflected off the axis. Apparent phase shifts are revealed that are relevant to the discussion of whether or not phase shifts occur in gravitational soliton interactions.

Soldner, Einstein, gravitational light deflection and factors of two

2021

Einstein’s gravitational field equations and the bianchi identities

2002

In his highly acclaimed biography of Einstein, Abraham Pais gave a fairly detailed analysis of the many difficulties his hero had to overcome in November 1915 before he finally arrived at generally covariant equations for gravitation (Pais 1982, 250–261).

1972

The present paper demonstrates theoretically as well as experimentally, that the gravitational field of the earth produces very pronounced changes in the equilibrium concentration of dissolved macromolecules with height, under near critical conditions. Thus it could be observed for the system polystyrene/cyclohexane that the equilibrium concentration at the bottom of a tube is approximately three times that at a height of 10 cm, under such conditions. In the case of polymolecular samples the sedimentation is associated with a corresponding fractionation. Die vorliegende Arbeit zeigt sowohl theoretisch als auch experimentell, das das Schwerefeld der Erde unter annahernd kritischen Bedingunge…

The relativity experiment of MORE: Global full-cycle simulation and results

2015

BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. In particular, the Mercury Orbiter Radio science Experiment (MORE) intends, as one of its goals, to perform a test of General Relativity. This can be done by measuring and constraining the parametrized post-Newtonian (PPN) parameters to an accuracy significantly better than current one. In this work we perform a global numerical full-cycle simulation of the BepiColombo Radio Science Experiments (RSE) in a realistic scenario, focussing on the relativity experiment, solving simultaneously for all the parameters of interest for RSE in a global least squares fit …

Gravitational-wave Constraints on the Equatorial Ellipticity of Millisecond Pulsars

2020

We present a search for continuous gravitational waves from five radio pulsars, comprising three recycled pulsars (PSR J0437-4715, PSR J0711-6830, and PSR J0737-3039A) and two young pulsars: the Crab pulsar (J0534+2200) and the Vela pulsar (J0835-4510). We use data from the third observing run of Advanced LIGO and Virgo combined with data from their first and second observing runs. For the first time, we are able to match (for PSR J0437-4715) or surpass (for PSR J0711-6830) the indirect limits on gravitational-wave emission from recycled pulsars inferred from their observed spin-downs, and constrain their equatorial ellipticities to be less than 10-8. For each of the five pulsars, we perfor…