DELTA GRAVITY AND THE ACCELERATED EXPANSION OF THE UNIVERSE

2011 ◽  
Vol 20 (supp01) ◽  
pp. 65-72
Author(s):  
JORGE ALFARO
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Cosmological Constant ◽  
Equivalence Principle ◽  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Symmetric Tensors ◽  
Test Particles ◽  
Expansion Of The Universe ◽  
The Universe

We study a model of the gravitational field based on two symmetric tensors. The equations of motion of test particles are derived. We explain how the Equivalence principle is recovered. Outside matter, the predictions of the model coincide exactly with General Relativity, so all classical tests are satisfied. In Cosmology, we get accelerated expansion without a cosmological constant.

Cosmological constant

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Vacuum Fluctuations ◽  
Present Epoch ◽  
Modify Gravity ◽  
Expansion Of The Universe ◽  
The Universe

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.

INFLATION, QUINTESSENCE PROBLEM AND VARYING SPEED OF LIGHT

2002 ◽  
Vol 17 (05) ◽  
pp. 295-302
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Speed Of Light ◽  
Expansion Of The Universe ◽  
The Universe

In this paper it is shown that the present accelerated expansion of the Universe can be explained only by considering variation of the speed of light, without taking into account the cosmological constant or quintessence matter.

Heuristic determination of the cosmological constant

2021 ◽  
pp. 2150114
Author(s):  
Manuel Urueña Palomo ◽  
Fernando Pérez Lara
Keyword(s):  
Field Theory ◽  
Energy Density ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Fundamental Constants ◽  
Quantum Field ◽  
Brute Force ◽  
Expansion Of The Universe ◽  
The Universe

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

scholarly journals THE POINCARÉ CONJECTURE AND THE COSMOLOGICAL CONSTANT

2011 ◽  
Vol 03 ◽  
pp. 195-202
Author(s):  
M. D. MAIA
Keyword(s):  
Cosmological Constant ◽  
Riemannian Geometry ◽  
Extrinsic Curvature ◽  
Space Time ◽  
Local Change ◽  
Accelerated Expansion ◽  
Observable Effect ◽  
Cosmological Constant Problem ◽  
Expansion Of The Universe ◽  
The Universe

The concept of deformation of Riemannian geometry is reviewed, with applications to gravitation and cosmology. Starting with an analysis of the cosmological constant problem, it is shown that space-times are deformable in the sense of local change of shape. These deformations leave an observable signature in the space-time, characterized by a conserved tensor, associated with a tangent acceleration, defined by the extrinsic curvature of the space-time. In the applications to cosmology, we find that the accelerated expansion of the universe is the observable effect of the deformation, dispensing with the cosmological constant and its problems.

Spinning test-particles in general relativity. I

1951 ◽  
Vol 209 (1097) ◽  
pp. 248-258 ◽  
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Equations Of Motion ◽  
Covariant Form ◽  
Test Particles

A method for the derivation of the equations of motion of test particles in a given gravitational field is developed. The equations of motion of spinning test particles are derived. The transformation properties are discussed and the equations of motion are written in a covariant form.

scholarly journals Gravitational coupling and the cosmological constant

2018 ◽  
Vol 27 (08) ◽  
pp. 1850086
Author(s):  
Yousef Bisabr
Keyword(s):  
Cosmological Constant ◽  
Equivalence Principle ◽  
Weak Equivalence ◽  
Gravitational Coupling ◽  
Dynamical Mechanism ◽  
Metric Tensor ◽  
Weak Equivalence Principle ◽  
Gravitational Model ◽  
Expansion Of The Universe ◽  
The Universe

We deal with a dynamical mechanism in which a large cosmological constant, as suggested by inflationary scenarios, decays due to expansion of the universe. This mechanism has its origin in the gravitational coupling of the vacuum density. We assume that the vacuum couples anomalously to gravity that is the metric tensor that appears the gravitational part is not the same as that appears the matter part as suggested by weak equivalence principle. Instead, the two metric tensors are taken to be conformally related. We show that this provides a dynamical mechanism which works during expansion of the universe. We also consider some observational consequences of such a gravitational model.

scholarly journals Minimal extension of General Relativity: Alternative gravity model with non-minimal coupling between matter and curvature

2014 ◽  
Vol 11 (02) ◽  
pp. 1460003 ◽  
Author(s):  
Orfeu Bertolami ◽  
Jorge Páramos
Keyword(s):  
General Relativity ◽  
Lagrangian Density ◽  
Density Fluctuations ◽  
Accelerated Expansion ◽  
Minimal Extension ◽  
Minimal Coupling ◽  
Expansion Of The Universe ◽  
Scalar Theories ◽  
The Impact ◽  
The Universe

We examine an extension of General Relativity with an explicit non-minimal coupling between matter and curvature. The purpose of this work is to present an overview of the implications of the latter to various contexts, ranging from astrophysical matter distributions to a cosmological setting. Various results are discussed, including the impact of this non-minimal coupling on the choice of Lagrangian density, on a mechanism to mimic galactic and cluster dark matter, on the possibility of accounting for the accelerated expansion of the Universe, energy density fluctuations and modifications to post-inflationary reheating. The equivalence between a model exhibiting a non-minimal coupling and multi-scalar-theories is also discussed.

scholarly journals INFLATION IN F(R, T) GRAVITATION WITH f-ESSENCE

2020 ◽  
Vol 5 (333) ◽  
pp. 106-112
Author(s):  
S.R. Myrzakul ◽  
◽  
Y.M. Myrzakulov ◽  
М. Arzimbetova ◽  
◽  
...  
Keyword(s):  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Modified Theories Of Gravity ◽  
Fermion Field ◽  
Theory Of Relativity ◽  
Modern Physics ◽  
Expansion Of The Universe ◽  
Isotropic Cosmological Model ◽  
Theories Of Gravity ◽  
The Universe

. Modified theories of gravity have become a kind of paradigm in modern physics because they seem to solve several shortcomings of the standard General Theory of Relativity (GTR) related to cosmology, astrophysics and quantum field theory. The most famous modified theories of gravity are F(R) and F(T) theories of gravity. A generalization of these two modified theories and gravitations, which was first proposed by Myrzakulov Ratbay. In this paper, we study an inhomogeneous isotropic cosmological model with a fermion field f-essence whose action has the form , where R is the scalar of curvature, and T is the torsion scalar, and Lm is the Lagrangian f-essence. A particular case is studied in detail when parameters are obtained that describe the current accelerated expansion of the Universe. The type of Lagrangian f-essence of this model is determined. The presented results show that gravity with f-essence can describe inflation in the early evolution of the Universe. A modified F(R, T) gravity with f-essence is considered. Equations of motion were obtained and the inflationary period of the early Universe was considered. To describe the inflationary period, the form of the Hubble parameter and the slow-roll parameter were determined.

scholarly journals ON THE TOPOLOGICAL NATURE OF THE COSMOLOGICAL CONSTANT

2012 ◽  
Vol 18 ◽  
pp. 109-114
Author(s):  
M. D. MAIA
Keyword(s):  
General Relativity ◽  
Cosmological Constant ◽  
Cosmic Radiation ◽  
Cosmic Time ◽  
Space Time ◽  
Time Flow ◽  
Acceleration Of The Universe ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Topological Changes

It is shown that topological changes in space-time are necessary to make General Relativity compatible with the Newtonian limit and to solve the hierarchy of the fundamental interactions. We detail how topology and topological changes appear in General Relativity and how it leaves an observable footprint in space-time. In cosmology we show that such topological observable is the cosmic radiation produced by the acceleration of the universe. The cosmological constant is a very particular case which occurs when the expansion of the universe into the vacuum occurs only in the direction of the cosmic time flow.

scholarly journals δ Gravity: Dark Sector, Post-Newtonian Limit and Schwarzschild Solution

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 96
Author(s):  
Jorge Alfaro ◽  
Pablo González
Keyword(s):  
Rotation Velocity ◽  
Accelerated Expansion ◽  
Symmetric Tensors ◽  
Dark Sector ◽  
Schwarzschild Solution ◽  
Perihelion Precession ◽  
Cosmological Inflation ◽  
Expansion Of The Universe ◽  
Matter Effect ◽  
The Universe

We present a new kind of model, which we call δ Theories, where standard theories are modified including new fields, motivated by an additional symmetry ( δ symmetry). In previous works, we proved that δ Theories just live at one loop, so the model in a quantum level can be interesting. In the gravitational case, we have δ Gravity, based on two symmetric tensors, g μ ν and g ˜ μ ν , where quantum corrections can be controlled. In this paper, a review of the classical limit of δ Gravity in a Cosmological level will be developed, where we explain the accelerated expansion of the universe without Dark Energy and the rotation velocity of galaxies by the Dark Matter effect. Additionally, we will introduce other phenomenon with δ Gravity like the deflection of the light produced by the sun, the perihelion precession, Black Holes and the Cosmological Inflation.

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