scholarly journals BiGONLight: light propagation with bi-local operators in Numerical Relativity

2021 ◽  
Author(s):  
Michele Grasso ◽  
Eleonora Villa
Keyword(s):  
General Relativity ◽  
Light Propagation ◽  
Numerical Relativity ◽  
Luminosity Distance ◽  
Test Bed ◽  
Angular Diameter Distance ◽  
Redshift Drift ◽  
Local Operators ◽  
Dust Universe ◽  
New Framework

Abstract BiGONLight, Bilocal Geodesic Operators framework for Numerical Light propagation, is a new tool for light propagation in Numerical Relativity. The package implements the Bi-local Geodesic Operators formalism, a new framework for light propagation in General Relativity. With BiGONLight it is possible to extract observables such as angular diameter distance, luminosity distance, magnification as well as new real-time observables like parallax and redshift drift within the same computation. As a test-bed for our code we consider two exact cosmological models, the ΛCDM and the inhomogeneous Szekeres model, and a simulated dust universe. All our tests show an excellent agreement with known results.

scholarly journals Cosmology Under Milne's Shadow

2005 ◽  
Vol 22 (3) ◽  
pp. 287-291 ◽  
Author(s):  
Michał J. Chodorowski
Keyword(s):  
General Relativity ◽  
Cosmological Model ◽  
Special Relativity ◽  
Confidence Level ◽  
Reference Model ◽  
Kinematic Model ◽  
Luminosity Distance ◽  
Angular Diameter Distance ◽  
Empty Universe ◽  
Better Than

AbstractBased on the magnitude–redshift diagram for the sample of supernovae Ia analyzed by Perlmutter et al. (1999), Davis & Lineweaver (2004) ruled out the special relativistic interpretation of cosmological redshifts at a confidence level of 23σ. Here, we critically reassess this result. Special relativity is known to describe the dynamics of an empty universe, by means of the Milne kinematic model. Applying only special relativistic concepts, we derive the angular diameter distance and the luminosity distance in the Milne model. In particular, in this model we do not use the underlying metric in its Robertson–Walker form, so our exposition is useful for readers without any knowledge of general relativity. We do however, explicitly use the special relativistic Doppler formula for redshift. We apply the derived luminosity distance to the magnitude–redshift diagram for supernovae Ia of Perlmutter et al. (1999) and show that special relativity fits the data much better than that claimed by Davis & Lineweaver. Specifically, using these data alone, the Milne model is ruled out only at a 2σ level. Alhough not a viable cosmological model, in the context of current research on supernovae Ia it remains a useful reference model when comparing predictions of various cosmological models.

scholarly journals Light propagation and optical scalars in torsion theories of gravity

2019 ◽  
Vol 34 (04) ◽  
pp. 1950029
Author(s):  
Siamak Akhshabi
Keyword(s):  
Gravitational Lensing ◽  
Light Propagation ◽  
Raychaudhuri Equation ◽  
Angular Diameter Distance ◽  
Propagation Of Light ◽  
Light Rays ◽  
Theories Of Gravity ◽  
Torsion Theories ◽  
Basic Equations ◽  
Gauge Theory Of Gravity

We investigate the propagation of light rays and evolution of optical scalars in gauge theories of gravity where torsion is present. Recently, the modified Raychaudhuri equation in the presence of torsion has been derived. We use this result to derive the basic equations of geometric optics for several different interesting solutions of the Poincaré gauge theory of gravity. The results show that the focusing effects for neighboring light rays will be different than general relativity. This in turn has practical consequences in the study of gravitational lensing effects and also in determining the angular diameter distance for cosmological objects.

scholarly journals The failure of testing for cosmic opacity via the distance-duality relation

2020 ◽  
Vol 497 (1) ◽  
pp. 378-388
Author(s):  
Václav Vavryčuk ◽  
Pavel Kroupa
Keyword(s):  
Cosmological Model ◽  
Convincing Evidence ◽  
Duality Relation ◽  
Angular Diameter ◽  
Luminosity Distance ◽  
Angular Diameter Distance ◽  
Frequency Independent ◽  
Unique Interpretation ◽  
The Universe

ABSTRACT The distance-duality relation (DDR) between the luminosity distance DL and the angular diameter distance DA is viewed as a powerful tool for testing for the opacity of the Universe, being independent of any cosmological model. It was applied by many authors, who mostly confirm its validity and report a negligible opacity of the Universe. Nevertheless, a thorough analysis reveals that applying the DDR in cosmic opacity tests is tricky. Its applicability is strongly limited because of a non-unique interpretation of the DL data in terms of cosmic opacity and a rather low accuracy and deficient extent of currently available DA data. Moreover, authors usually assume that cosmic opacity is frequency independent and parametrize it in their tests by a prescribed phenomenological function. In this way, they only prove that cosmic opacity does not follow their assumptions. As a consequence, no convincing evidence of transparency of the universe using the DDR has so far been presented.

scholarly journals Numerical relativity simulation of GW150914 beyond general relativity

2020 ◽  
Vol 101 (10) ◽  
Author(s):  
Maria Okounkova ◽  
Leo C. Stein ◽  
Jordan Moxon ◽  
Mark A. Scheel ◽  
Saul A. Teukolsky
Keyword(s):  
General Relativity ◽  
Numerical Relativity

scholarly journals Theory of Discrete Gravity

2018 ◽  
Author(s):  
Mihir Kumar Jha
Keyword(s):  
General Relativity ◽  
Quantum Mechanics ◽  
Loop Quantum Gravity ◽  
Riemannian Metric ◽  
Space Time ◽  
Final Theory ◽  
Theory Of Everything ◽  
Single Field ◽  
Fundamental Forces ◽  
New Framework

Theory of everything (T.O.E), final theory or ultimate theory is a theoretical framework in the field of physics, which holds an ultimate key to unify all the fundamental forces of nature in a single field. In other words such theory can glue quantum mechanics with general relativity into a single framework. Many theories have been postulated over the decades but the dominant one includes string theory and loop quantum gravity. In this paper I would like to present a new framework which can unify quantum mechanics with general relativity by showing that the change in Riemannian metric or the bend in space time is always an integral multiple of planks constant and since gravity is the result due to bend in space-time, gravity itself is a discrete force

Development of a Satellite Communication Emulator for the Hyperspectral Microwave Atmosphere Sounder (HYMAS)

2015 ◽  
Vol 7 (2) ◽  
pp. 56-67 ◽  
Author(s):  
Giti Javidi ◽  
Ehsan Sheybani ◽  
Janelle Williams
Keyword(s):  
Satellite Communication ◽  
Intermediate Frequency ◽  
Test Bed ◽  
Weather And Climate ◽  
The World ◽  
Atmospheric Sounding ◽  
New Framework

Major weather facilities around the world recognize microwave atmospheric sounding is the key to developing technology for forthcoming weather and climate missions. The mission for Hyperspectral Microwave Atmospheric Sounder (HyMAS) Emulator is to produce a model for demonstrating the hyperspectral techniques that retrieve data near 118 and 183 GHz through a 52 channel Intermediate Frequency processor. This project establishes a test bed that mimics the functionality of the instrument such as how data is retrieved and processed through computers in the instrument. The computers are programmed using a new framework application called Interoperable Remote Component. This software allows flexibility to program computers on how to communicate with each other, what devices to connect to and other factors.

Fundamentals of numerical relativity for gravitational wave sources

Science ◽  
2018 ◽  
Vol 361 (6400) ◽  
pp. 366-371 ◽  
Author(s):  
Bernd Brügmann
Keyword(s):  
General Relativity ◽  
Partial Differential Equations ◽  
Gravitational Wave ◽  
Tensor Field ◽  
Body Problem ◽  
Numerical Relativity ◽  
Gravitational Interaction ◽  
Einstein Equations ◽  
Two Body Problem ◽  
General Relativistic

Einstein’s theory of general relativity affords an enormously successful description of gravity. The theory encodes the gravitational interaction in the metric, a tensor field on spacetime that satisfies partial differential equations known as the Einstein equations. This review introduces some of the fundamental concepts of numerical relativity—solving the Einstein equations on the computer—in simple terms. As a primary example, we consider the solution of the general relativistic two-body problem, which features prominently in the new field of gravitational wave astronomy.

A REVIEW ON THE GEOMETRIC FORMULATION OF TOLMAN–BONDI EQUATIONS IN GENERAL RELATIVITY

2009 ◽  
Vol 06 (04) ◽  
pp. 595-617 ◽  
Author(s):  
IVANA BOCHICCHIO ◽  
MAURO FRANCAVIGLIA ◽  
ETTORE LASERRA
Keyword(s):  
General Relativity ◽  
Symmetric Space ◽  
Exact Solutions ◽  
Structural Properties ◽  
Spherically Symmetric ◽  
Principal Curvatures ◽  
Spherical Shells ◽  
Geometric Formulation ◽  
Dust Universe

This work is focused on spherically symmetric space-times. More precisely, geometric and structural properties of spatially spherical shells of a dust universe are analyzed in detail considering recent results of our research. Moreover, exact solutions, obtained for constant Ricci principal curvatures, are inferred and qualitatively analyzed through suitable classic analogies.

Numerical relativity: challenges for computational science

Acta Numerica ◽  
1999 ◽  
Vol 8 ◽  
pp. 1-45 ◽  
Author(s):  
Gregory B. Cook ◽  
Saul A. Teukolsky
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Numerical Relativity ◽  
Hyperbolic Systems ◽  
Nonlinear Partial Differential Equations ◽  
Elliptic Systems ◽  
Computational Domain ◽  
Einstein’S Equations ◽  
Einstein's Equations ◽  
3 Dimensional

We describe the burgeoning field of numerical relativity, which aims to solve Einstein's equations of general relativity numerically. The field presents many questions that may interest numerical analysts, especially problems related to nonlinear partial differential equations: elliptic systems, hyperbolic systems, and mixed systems. There are many novel features, such as dealing with boundaries when black holes are excised from the computational domain, or how even to pose the problem computationally when the coordinates must be determined during the evolution from initial data. The most important unsolved problem is that there is no known general 3-dimensional algorithm that can evolve Einstein's equations with black holes that is stable. This review is meant to be an introduction that will enable numerical analysts and other computational scientists to enter the field. No previous knowledge of special or general relativity is assumed.

Sign in / Sign up

Export Citation Format

Share Document