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.

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.

Fast approximate methods for modified gravity cosmological simulations

2020 ◽  
Vol 493 (2) ◽  
pp. 2085-2100
Author(s):  
Michal Vraštil ◽  
Salman Habib
Keyword(s):  
Modified Gravity ◽  
Acoustic Oscillation ◽  
Accelerated Expansion ◽  
Minimal Extension ◽  
Linear Regime ◽  
Approximate Methods ◽  
Perturbative Methods ◽  
Non Linear ◽  
Expansion Of The Universe ◽  
The Universe

ABSTRACT The accelerated expansion of the Universe poses a major theoretical puzzle. Although the assumption of a non-zero cosmological constant provides a minimal extension of general relativity that is consistent with observational data, many theories of modified gravity have been suggested as possible alternatives. Predictions of structure formation for these models in the fully non-linear regime are very expensive and it is difficult, if not impossible, to explore such a huge space of models and parameters using high-resolution N-body simulations. Even in the mildly non-linear regime, perturbative methods can become extremely complex. We explore whether simplified dynamical approximations, applicable for a certain set of cosmological probes, can be used to investigate models of modified gravity with acceptable accuracy in the latter instance. For the case of chameleon gravity, we find that these methods can indeed be used to explore the region around the baryon acoustic oscillation scale, $k\sim 0.1~h\, \text{Mpc}^{-1}$ but not much further.

scholarly journals $$\varLambda $$CDM suitably embedded in f(R) with a non-minimal coupling to matter

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
María Ortiz-Baños ◽  
Mariam Bouhmadi-López ◽  
Ruth Lazkoz ◽  
Vincenzo Salzano
Keyword(s):  
Energy Density ◽  
The Other ◽  
Accelerated Expansion ◽  
Gravitational Coupling ◽  
Minimal Coupling ◽  
Modified Theory Of Gravity ◽  
Expansion Of The Universe ◽  
The One ◽  
The Universe ◽  
Modified Theory

AbstractIn this work, we further study a metric modified theory of gravity which contains a non-minimal coupling to matter, more precisely, we assume two functions of the scalar curvature, $$f_1$$ f 1 and $$f_2$$ f 2 , where the first one generalises the Hilbert–Einstein action, while the second couples to the matter Lagrangian. On the one hand, assuming a $$\varLambda $$ Λ CDM background, we calculate analytical solutions for the functions $$f_1$$ f 1 and $$f_2$$ f 2 . We consider two setups: on the first one, we fix $$f_2$$ f 2 and compute $$f_1$$ f 1 and on the second one, we fix $$f_1$$ f 1 and compute $$f_2$$ f 2 . Moreover, we do the analysis for two different energy density contents, a matter dominated universe and a general perfect fluid with a constant equation of state fuelling the universe expansion. On the other hand, we complete our study by performing a cosmographic analysis for $$f_1$$ f 1 and $$f_2$$ f 2 . We conclude that the gravitational coupling to matter can drive the accelerated expansion of the universe.

scholarly journals Kinetic studies relating to the accelerated expansion of the Universe

2021 ◽  
Author(s):  
Wei Zhang ◽  
Cheng Deng
Keyword(s):  
General Relativity ◽  
Hubble Constant ◽  
Kinetic Studies ◽  
Physical Significance ◽  
Accelerated Expansion ◽  
Newtonian Mechanics ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Masses ◽  
The Universe

Abstract After taking into account the mass loss of galaxies and stars at the cosmic scale, the speed and acceleration of the accelerating expansion of the Universe are derived from general relativity and Newtonian mechanics, as respectively. The physical significance of the Hubble constant is proved to be the average of the masses ejected per second per unit mass in the observed range, and it is shown that the accelerated expansion of the universe doesn’t require dark energy

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.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

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 Can accelerated expansion of the universe be due to spacetime vorticity?

2018 ◽  
Vol 33 (40) ◽  
pp. 1850240
Author(s):  
Babur M. Mirza
Keyword(s):  
Magnetic Field ◽  
Accelerated Expansion ◽  
Newtonian Gravity ◽  
Hubble’S Parameter ◽  
Cosmic Expansion ◽  
Zero Curvature ◽  
Expansion Of The Universe ◽  
General Relativistic ◽  
The Universe ◽  
The Magnetic Field

We present here a general relativistic mechanism for accelerated cosmic expansion and the Hubble’s parameter. It is shown that spacetime vorticity coupled to the magnetic field density in galaxies causes the galaxies to recede from one another at a rate equal to the Hubble’s constant. We therefore predict an oscillatory universe, with zero curvature, without assuming violation of Newtonian gravity at large distances or invoking dark energy/dark matter hypotheses. The value of the Hubble’s constant, along with the scale of expansion, as well as the high isotropy of CMB radiation are deduced from the model.

Sign in / Sign up

Export Citation Format

Share Document