Search results for "Gravitational field"

Positioning with stationary emitters in a two-dimensional space-time

2006

The basic elements of the relativistic positioning systems in a two-dimensional space-time have been introduced in a previous work [Phys. Rev. D {\bf 73}, 084017 (2006)] where geodesic positioning systems, constituted by two geodesic emitters, have been considered in a flat space-time. Here, we want to show in what precise senses positioning systems allow to make {\em relativistic gravimetry}. For this purpose, we consider stationary positioning systems, constituted by two uniformly accelerated emitters separated by a constant distance, in two different situations: absence of gravitational field (Minkowski plane) and presence of a gravitational mass (Schwarzschild plane). The physical coord…

Gravitational waves from galaxy encounters

2007

We discuss the emission of gravitational radiation produced in encounters of dark matter galactic halos. To this aim we perform a number of numerical simulations of typical galaxy mergers, computing the associated gravitational radiation waveforms as well as the energy released in the processes. Our simulations yield dimensionless gravitational wave amplitudes of the order of $10^{-13}$ and gravitational wave frequencies of the order of $10^{-16}$ Hz, when the galaxies are located at a distance of 10 Mpc. These values are of the same order as those arising in the gravitational radiation originated by strong variations of the gravitational field in the early Universe, and therefore, such gra…

Axisymmetric core collapse simulations using characteristic numerical relativity

2003

We present results from axisymmetric stellar core collapse simulations in general relativity. Our hydrodynamics code has proved robust and accurate enough to allow for a detailed analysis of the global dynamics of the collapse. Contrary to traditional approaches based on the 3+1 formulation of the gravitational field equations, our framework uses a foliation based on a family of outgoing light cones, emanating from a regular center, and terminating at future null infinity. Such a coordinate system is well adapted to the study of interesting dynamical spacetimes in relativistic astrophysics such as stellar core collapse and neutron star formation. Perhaps most importantly this procedure allo…

Numerical Hydrodynamics in General Relativity

2003

The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. With respect to an earlier version of the article the present update provides additional information on numerical schemes and extends the discussion of astrophysical simulations in general relativistic hydrodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through lineariz…

Neutrino Spin Oscillations in External Gravitational Fields

2007

Lens Effect and CMB Anisotropies: Simulations

2003

Cosmological structures deviate the photons of the Cosmic Microwave Background (CMB). The resulting deviations can be calculated moving photons in the gravitational field of realistic lens distributions obtained from numerical simulations. The main goal of this paper is answering the following question: Which types of numerical simulations are appropriate to study angular CMB deformations caused by lensing?

Spontaneous creation of circularly polarized photons in chiral astrophysical systems

2020

This work establishes a relation between chiral anomalies in curved spacetimes and the radiative content of the gravitational field. In particular, we show that a flux of circularly polarized gravitational waves triggers the spontaneous creation of photons with net circular polarization from the quantum vacuum. Using waveform catalogues we identify precessing binary black holes as astrophysical configurations that emit such gravitational radiation, and then solve the fully non-linear Einstein's equations with numerical relativity to evaluate the net effect. The quantum amplitude for a merger is comparable to the Hawking emission rate of the final black hole, and small to be directly observe…

On the Bel radiative gravitational fields

2011

We analyze the concept of intrinsic radiative gravitational fields defined by Bel and we show that the three radiative types, N, III and II, correspond with the three following different physical situations: {\it pure radiation}, {\it asymptotic pure radiation} and {\it generic} (non pure, non asymptotic pure) {\it radiation}. We introduce the concept of {\em observer at rest} with respect to the gravitational field and that of {\em proper super-energy} of the gravitational field and we show that, for non radiative fields, the minimum value of the relative super-energy density is the proper super-energy density, which is acquired by the observers at rest with respect to the field. Several {…

Computational Approach to Gravitational Waves Forms in Stellar Systems as Complex Structures through Keplerian Parameters

2009

In this paper we investigate the gravitational waves emission by stellar dynamical structures as complex systems in the quadrupole approximation considering bounded and unbounded orbits. Precisely, after deriving analytical expressions for the gravitational wave luminosity, the total energy output and gravitational radiation amplitude, we present a computational approach to evaluate the gravitational wave-forms from elliptical, circular, parabolic and hyperbolic orbits as a function of Keplerian parameters.

Reply to Comment on Measurement of quantum states of neutrons in the Earth's gravitational field

2003

Physical review / D 68(10), 108702 (2003). doi:10.1103/PhysRevD.68.108702