Motion of test particles for Weyl-interaction modified gravity

2019 ◽  
Vol 28 (16) ◽  
pp. 2040014
Author(s):  
Hyung Won Lee ◽  
Asghar Qadir
Keyword(s):  
Dark Matter ◽  
Quantum Gravity ◽  
Modified Gravity ◽  
Weyl Tensor ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Satisfactory Explanation ◽  
Test Particles ◽  
Stress Energy ◽  
Hilbert Action

Since LHC has still given no signal of Supersymmetry, though the energy at which the signal was expected has been passed, one is left short of any good candidate for dark matter. We had proposed [A. Qadir, H. W. Lee and K. Y. Kim, Int. J. Mod. Phys. D 26 (2017) 1741001, 10 pp.] a modification of the Einstein–Hilbert action to explicitly display a term of matter and gravity interaction, [Formula: see text]. The hope had been that this would also resolve the problem of Quantum Gravity. However, the argument given for the purpose of quantum gravity, would more naturally lead one to expect the contraction, [Formula: see text], of the Weyl tensor with two copies of the stress–energy tensor rather than the product of the Ricci scalar and the trace of the stress–energy tensor. Here, the attempt is made to see if this prescription will provide a satisfactory explanation of the dark matter at all scales. One would then try to see if the problem of quantum gravity is resolved by the same prescription.

scholarly journals ΛCDM as a Noether symmetry in cosmology

2020 ◽  
Vol 29 (15) ◽  
pp. 2050104 ◽  
Author(s):  
D. Benisty ◽  
E. I. Guendelman ◽  
E. Nissimov ◽  
S. Pacheva
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Noether Symmetry ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Main Ingredient ◽  
Riemannian Spacetime ◽  
Stress Energy ◽  
Space Distortion ◽  
Conserved Current

The standard [Formula: see text]CDM model of cosmology is formulated as a simple modified gravity coupled to a single scalar field (“darkon”) possessing a nontrivial hidden nonlinear Noether symmetry. The main ingredient in the construction is the use of the formalism of non-Riemannian spacetime volume-elements. The associated Noether conserved current produces stress–energy tensor consisting of two additive parts — dynamically generated dark energy and dark matter components noninteracting among themselves. Noether symmetry breaking via an additional scalar “darkon” potential introduces naturally an interaction between dark energy and dark matter. The correspondence between the [Formula: see text]CDM model and the present “darkon” Noether symmetry is exhibited up to linear order with respect to gravity-matter perturbations. With the Cosmic Chronometers (CC) and the Redshift Space Distortion (RSD) datasets, we study an example for the “darkon” potential that breaks the Noether symmetry and we show that the preservation of this symmetry yields a better fit.

scholarly journals Baryon Physics and Tight Coupling Approximation in Boltzmann Codes

Universe ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 6 ◽  
Author(s):  
Masroor C. Pookkillath ◽  
Antonio De Felice ◽  
Shinji Mukohyama
Keyword(s):  
Modified Gravity ◽  
Equations Of Motion ◽  
Cosmological Parameters ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Tight Coupling ◽  
Stress Energy ◽  
Modified Gravity Theories ◽  
Coupling Approximation ◽  
Best Fit

We provide two derivations of the baryonic equations that can be straightforwardly implemented in existing Einstein–Boltzmann solvers. One of the derivations begins with an action principle, while the other exploits the conservation of the stress-energy tensor. While our result is manifestly covariant and satisfies the Bianchi identities, we point out that this is not the case for the implementation of the seminal work by Ma and Bertschinger and in the existing Boltzmann codes. We also study the tight coupling approximation up to the second order without choosing any gauge using the covariant full baryon equations. We implement the improved baryon equations in a Boltzmann code and investigate the change in the estimate of cosmological parameters by performing an MCMC analysis. With the covariantly correct baryon equations of motion, we find 1 % deviation for the best fit values of the cosmological parameters that should be taken into account. While in this paper, we study the Λ CDM model only, our baryon equations can be easily implemented in other models and various modified gravity theories.

scholarly journals Realizing interactions between dark matter and dark energy using k-essence cosmology

2019 ◽  
Vol 34 (27) ◽  
pp. 1950219 ◽  
Author(s):  
Abhijit Bandyopadhyay ◽  
Anirban Chatterjee
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Energy Tensor ◽  
Late Time ◽  
Stress Energy Tensor ◽  
Cosmic Evolution ◽  
Stress Energy ◽  
Constant Potential ◽  
State Stress

In this paper, we exploit dynamics of a [Formula: see text]-essence scalar field to realize interactions between dark components of universe resulting in an evolution consistent with observed features of late-time phase of cosmic evolution. Stress–energy tensor corresponding to a [Formula: see text]-essence Lagrangian [Formula: see text] (where [Formula: see text]) is shown to be equivalent to an ideal fluid with two components having same equation of state. Stress–energy tensor of one of the components may be generated from a constant potential [Formula: see text]-essence Lagrangian of form [Formula: see text] ([Formula: see text] constant) and that of other from another Lagrangian of form [Formula: see text] with [Formula: see text]. We have shown that the unified dynamics of dark matter and dark energy described by a single scalar field [Formula: see text] driven by a [Formula: see text]-essence Lagrangian [Formula: see text] may be viewed in terms of diffusive interactions between the two hypothetical fluid components “1” and “2” with stress–energy tensors equivalent to that of Lagrangians [Formula: see text] and [Formula: see text], respectively. The energy transfer between the fluid components is determined by functions [Formula: see text], [Formula: see text] and their derivatives. Such a realization is shown to be consistent with the Supernova Ia data with certain constraints on the temporal behavior of [Formula: see text]-essence potential [Formula: see text]. We have described a methodology to obtain such constraints.

scholarly journals Stress-energy tensor correlators from the world-sheet

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Hanno Bertle ◽  
Andrea Dei ◽  
Matthias R. Gaberdiel
Keyword(s):  
Vertex Operator ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
World Sheet ◽  
Stress Energy ◽  
The World

Abstract The large N limit of symmetric orbifold theories was recently argued to have an AdS/CFT dual world-sheet description in terms of an sl(2, ℝ) WZW model. In previous work the world-sheet state corresponding to the symmetric orbifold stress-energy tensor was identified. We calculate certain 2- and 3-point functions of the corresponding vertex operator on the world-sheet, and demonstrate that these amplitudes reproduce exactly what one expects from the dual symmetric orbifold perspective.

ON THE ELECTROMAGNETIC PERTURBATIONS OF A MULTICONICAL SPACETIME

1996 ◽  
Vol 11 (27) ◽  
pp. 2171-2177
Author(s):  
A.N. ALIEV
Keyword(s):  
Cosmic Strings ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Stress Energy ◽  
Electromagnetic Perturbations

The electromagnetic perturbations propagating in the multiconical spacetime of N parallel cosmic strings are described. The expression for vacuum average of the stress-energy tensor is reduced to a form involving only zero-spin-weighted perturbation modes.

scholarly journals Kerr-Newman stress-tensor from minimal coupling

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Ming-Zhi Chung ◽  
Yu-tin Huang ◽  
Jung-Wook Kim
Keyword(s):  
Form Factor ◽  
Stress Tensor ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Minimal Coupling ◽  
Massive Spin ◽  
Stress Energy ◽  
Newman Black Hole ◽  
Higher Spin ◽  
The One

Abstract In this paper, we demonstrate that at leading order in post Minkowskian (PM) expansion, the stress-energy tensor of Kerr-Newman black hole can be recovered to all orders in spin from three sets of minimal coupling: the electric and gravitational minimal coupling for higher-spin particles, and the “minimal coupling” for massive spin-2 decay. These couplings are uniquely defined from kinematic consideration alone. This is shown by extracting the classical piece of the one-loop stress-energy tensor form factor, which we provide a basis that is valid to all orders in spin. The 1 PM stress tensor, and the metric in the harmonic gauge, is then recovered from the classical spin limit of the form factor.

scholarly journals Stress Energy Tensor Study in Fluid Mechanics

2019 ◽  
Author(s):  
Roman Baudrimont
Keyword(s):  
General Relativity ◽  
Fluid Mechanics ◽  
Space Time ◽  
Newtonian Fluids ◽  
Third Party ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Perfect Fluids ◽  
Stress Energy

This paper is to summarize the involvement of the stress energy tensor in the study of fluid mechanics. In the first part we will see the implication that carries the stress energy tensor in the framework of general relativity. In the second part, we will study the stress energy tensor under the mechanics of perfect fluids, allowing us to lead third party in the case of Newtonian fluids, and in the last part we will see that it is possible to define space-time as a no-Newtonian fluids.

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