scholarly journals Dynamically Stable Ergostars Exist: General Relativistic Models and Simulations

2019 ◽  
Vol 123 (23) ◽  
Author(s):  
Antonios Tsokaros ◽  
Milton Ruiz ◽  
Lunan Sun ◽  
Stuart L. Shapiro ◽  
Kōji Uryū
Keyword(s):  
General Relativistic ◽  
Relativistic Models

scholarly journals Relativistic Models for a GAIA-Like Astrometry Mission

2000 ◽  
Vol 180 ◽  
pp. 314-319 ◽  
Author(s):  
F. de Felice ◽  
A. Vecchiato ◽  
B. Bucciarelli ◽  
M.G. Lattanzi ◽  
M. Crosta
Keyword(s):  
Reference Frame ◽  
Fundamental Physics ◽  
Accurate Knowledge ◽  
Adopted Model ◽  
Relativistic Approach ◽  
General Relativistic ◽  
Relativistic Models ◽  
Relativistic Parameter ◽  
Relativistic Framework ◽  
Better Than

A non-perturbative general relativistic approach to global astrometry was developed by de Felice et al. (1998) to handle satellite astrometry data in a genuine relativistic framework. In this contribution, the framework above has been further exploited to account for stellar motions and parallax. Because of the relevance that accurate knowledge (to 10−5 or better) of the relativistic parameter γ has to fundamental physics, a Parametrized Post-Newtonian (PPN) model has also been implemented, which allows the direct estimation of γ along with the astrometric parameters. These models have been tested on end-to-end simulations of the mission GAIA. The results show that, within the limitation of the simulation and the assumptions of the adopted model, measurements accurate to 100 μarcsec of large arcs among stars repeated over a few years can be modelled to establish a dense reference frame with a precision of a few tens of μarcseconds. Moreover, our experiments indicate that γ can be estimated to better than 10−6.

A NONSINGULAR PERFECT FLUID CLASSICAL LEPTON MODEL OF ARBITRARILY SMALL RADIUS

2013 ◽  
Vol 22 (14) ◽  
pp. 1350088 ◽  
Author(s):  
THOMAS E. KIESS
Keyword(s):  
Electric Field ◽  
Perfect Fluid ◽  
Small Radius ◽  
Spherically Symmetric ◽  
Model Based ◽  
Perfect Fluids ◽  
General Relativistic ◽  
Relativistic Models ◽  
Lepton Model

We exhibit a classical lepton model based on a perfect fluid that reproduces leptonic charges and masses in arbitrarily small volumes without metric singularities or pressure discontinuities. This solution is the first of this kind to our knowledge, because to date the only classical general relativistic models that have reproduced leptonic charges and masses in arbitrarily small volumes are based on imperfect (anisotopic) fluids or perfect fluids with electric field discontinuities. We use a Maxwell–Einstein exact metric for a spherically symmetric static perfect fluid in a region in which the pressure vanishes at a boundary, beyond which the metric is of the Reissner–Nordström form. This construction models lepton mass and charge in the limit as the boundary → 0.

scholarly journals Proper stellar directions and astronomical aberration

2009 ◽  
Vol 5 (S261) ◽  
pp. 130-134
Author(s):  
Mariateresa Crosta ◽  
Alberto Vecchiato
Keyword(s):  
General Relativity ◽  
Proper Motion ◽  
Measurement Accuracy ◽  
Appropriate Use ◽  
System A ◽  
Correct Definition ◽  
Physical Task ◽  
General Relativistic ◽  
Relativistic Models ◽  
Definition Of

AbstractThe general relativistic definition of astrometric measurement needs an appropriate use of the concept of reference frame, which should then be linked to the conventions of the IAU Resolutions (Soffel et al., 2003), which fix the celestial coordinate system. A consistent definition of the astrometric observables in the context of General Relativity is also essential to find uniquely the stellar coordinates and proper motion, this being the main physical task of the inverse ray tracing problem. Aim of this work is to set the level of reciprocal consistency of two relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to guarantee a physically correct definition of light direction to a star, an essential item for deducing the star coordinates and proper motion within the same level of measurement accuracy.

scholarly journals Neutron star merger remnants

2020 ◽  
Vol 52 (11) ◽  
Author(s):  
Sebastiano Bernuzzi
Keyword(s):  
Neutron Star ◽  
Nuclear Matter ◽  
Gravitational Wave ◽  
Weak Interactions ◽  
Numerical Relativity ◽  
Current Understanding ◽  
Fundamental Physics ◽  
Binary Neutron Star ◽  
General Relativistic ◽  
Relativistic Models

AbstractBinary neutron star mergers observations are a unique way to constrain fundamental physics and astrophysics at the extreme. The interpretation of gravitational-wave events and their electromagnetic counterparts crucially relies on general-relativistic models of the merger remnants. Quantitative models can be obtained only by means of numerical relativity simulations in $$3+1$$ 3 + 1 dimensions including detailed input physics for the nuclear matter, electromagnetic and weak interactions. This review summarizes the current understanding of merger remnants focusing on some of the aspects that are relevant for multimessenger observations.

A SCILAB PROGRAM FOR COMPUTING GENERAL-RELATIVISTIC MODELS OF ROTATING NEUTRON STARS BY IMPLEMENTING HARTLE'S PERTURBATION METHOD

2003 ◽  
Vol 14 (03) ◽  
pp. 321-350 ◽  
Author(s):  
P. J. PAPASOTIRIOU ◽  
V. S. GEROYANNIS
Keyword(s):  
Neutron Star ◽  
Perturbation Method ◽  
Neutron Stars ◽  
Numerical Method ◽  
Programming Language ◽  
Efficient Tool ◽  
Star Models ◽  
General Relativistic ◽  
Relativistic Models ◽  
High Level

We implement Hartle's perturbation method to the computation of relativistic rigidly rotating neutron star models. The program has been written in SCILAB (© INRIA–ENPC), a matrix-oriented high-level programming language. The numerical method is described in very detail and is applied to many models in slow or fast rotation. We show that, although the method is perturbative, it gives accurate results for all practical purposes and it should prove an efficient tool for computing rapidly rotating pulsars.

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