scholarly journals Higher Order Curvature Theories of Gravity Matched with Observations: a Bridge Between Dark Energy and Dark Matter Problems

2005 ◽  
Author(s):  
S. Capozziello
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Higher Order ◽  
Theories Of Gravity

Dark matter and dark energy or alternative theories of gravity and cosmology

2008 ◽  
Author(s):  
Alexander F. Zakharov ◽  
Victor N. Pervushin ◽  
Francesco De Paolis ◽  
Gabriele Ingrosso ◽  
Achille A. Nucita ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Alternative Theories Of Gravity ◽  
Theories Of Gravity ◽  
Alternative Theories

MAXWELL BRANE COSMOLOGY WITH HIGHER-ORDER STRING CURVATURE CORRECTIONS, A NONMINIMALLY COUPLED SCALAR FIELD, DARK MATTER–DARK ENERGY INTERACTION AND A VARYING SPEED OF LIGHT

2009 ◽  
Vol 18 (02) ◽  
pp. 289-318 ◽  
Author(s):  
R. A. EL-NABULSI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Friedmann Equation ◽  
Building Blocks ◽  
Higher Order ◽  
Alternative Theory ◽  
Speed Of Light ◽  
Energy Interaction ◽  
Curvature Term

We investigate the cosmological effects of an alternative theory of gravity on the four-dimensional Randall–Sundrum braneworld of type II with a higher-order string curvature term added to the action. We discuss the possibility of a varying speed of light, which has recently attracted considerable attention, in the presence a Maxwell field and of a dynamically evolving bulk scalar field nonminimally coupled to scalar curvature in a quadratic form, together with a dark matter–dark energy interaction term. After deriving the modified Friedmann equation on the brane, as well as the scalar field equations, we then analyze the dynamical equations obtained so far. Special attention is paid to scaling solutions which could be important building blocks in constructing the models of dark energy. The constructed model exhibits several features of cosmological and astrophysical interest for both the early and the late universe, consistent with recent observations, in particular the ones concerned with celerity of light, four and five gravitational constants, black hole masses and entropies.

scholarly journals RECONSTRUCTING f(R, T) GRAVITY FROM HOLOGRAPHIC DARK ENERGY

2012 ◽  
Vol 21 (03) ◽  
pp. 1250024 ◽  
Author(s):  
M. J. S. HOUNDJO ◽  
OLIVER F. PIATTELLA
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Dark Energy ◽  
Energy Momentum Tensor ◽  
Holographic Dark Energy ◽  
Momentum Tensor ◽  
Ricci Scalar ◽  
Relativity Theory ◽  
General Relativity Theory ◽  
Theories Of Gravity

We consider cosmological scenarios based on f(R, T) theories of gravity (R is the Ricci scalar and T is the trace of the energy–momentum tensor) and numerically reconstruct the function f(R, T) which is able to reproduce the same expansion history generated, in the standard General Relativity theory, by dark matter and holographic dark energy. We consider two special f(R, T) models: in the first instance, we investigate the modification R + 2f(T), i.e. the usual Einstein–Hilbert term plus a f(T) correction. In the second instance, we consider a f(R) + λT theory, i.e. a T correction to the renown f(R) theory of gravity.

scholarly journals Non-Detection of Dark Matter Particles: A Case for Alternate Theories of Gravity

2020 ◽  
Author(s):  
Arun Kenath ◽  
C Sivaram ◽  
Avijeet Prasad ◽  
Louise Rebecca
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Modified Gravity ◽  
Newtonian Gravity ◽  
Self Energy ◽  
Overwhelming Evidence ◽  
Modified Equations ◽  
Modified Gravity Theories ◽  
Flat Rotation Curves ◽  
Theories Of Gravity

While there is overwhelming evidence for dark matter (DM) in galaxies and galaxy clusters, all searches for DM particles have so far proved negative. It is not even clear whether only one particle is involved or a combination or particles, their masses not precisely predicted. This non-detectability raises the possible relevance of modified gravity theories – MOND, MONG, etc. Here we consider a specific modification of Newtonian gravity (MONG) which involves gravitational self-energy, leading to modified equations whose solutions imply flat rotation curves and limitations of sizes of clusters. The results are consistent with current observations including that involving large spirals. This modification could also explain the current Hubble tension. We also consider effects of dark energy (DE) in terms of a cosmological constant.

scholarly journals AN UNEVEN VACUUM ENERGY FLUID AS Λ, DARK MATTER, MOND AND LENS

2008 ◽  
Vol 23 (08) ◽  
pp. 555-568 ◽  
Author(s):  
HONG SHENG ZHAO
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Gravitational Lensing ◽  
Vacuum Energy ◽  
Casimir Effect ◽  
Theories Of Gravity ◽  
Alternative Gravity Theories ◽  
Gravity Theories ◽  
Single Field ◽  
Day By Day

Various TeVeS-inspired and f(R)-inspired theories of gravity have added an interesting twist to the search for dark matter and vacuum energy, modifying the landscape of astrophysics day by day. These theories can be together called a Non-uniform Dark Energy fluid (a Nu-Lambda fluid or a VΛ fluid); a common thread of these theories, according of an up-to-date summary by HZL1, is a non-uniform vector field, describing an uneven vacuum energy fluid. The so-called "alternative" gravity theories are in fact in the standard GR gravity framework except that the cosmological "constant" is replaced by a nontrivial non-uniform vacuum energy, which couples the effects of Dark Matter and Dark Energy together by a single field. Built initially bottom-up rather than top-down as most gravity theories, TeVeS-inspired theories are healthily rooted on empirical facts. Here we attempt a review of some sanity checks of these fast-developing theories from galaxy rotation curves, solar system constraints, and gravitational lensing. We will also discuss some theoretical aspects of these theories related to the vacuum energy, and point out some analogies with electromagnetism and the Casimir effect.

scholarly journals Interaction between Dark Matter and Dark Energy and the Cosmological Coincidence Problem

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Kourosh Nozari ◽  
Noushin Behrouz ◽  
Narges Rashidi
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Exponential Potential ◽  
Complex Velocity ◽  
Dark Sector ◽  
Coincidence Problem ◽  
Theories Of Gravity ◽  
The Stability ◽  
Quintessence Model

We consider a quintessence model of dark energy inspired by scalar-tensor theories of gravity where the scalar field is nonminimally coupled to gravity and dark matter. By considering exponential potential as self-interaction potential, the stability and existence of the critical points are discussed in details. With nonminimally coupled dark sector with gravity, we obtain scaling solutions to address the coincidence problem by considering complex velocity for dark matter. The statefinder diagnostic shows that the equation of state reachesΛCDMmodel in the future.

Effective masses in a dense fermion background — Applied to neutrinos, dark matter and dark energy

2014 ◽  
Vol 29 (21) ◽  
pp. 1444010
Author(s):  
Bruce H. J. McKellar ◽  
T. J. Goldman ◽  
G. J. Stephenson
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Effective Mass ◽  
Negative Pressure ◽  
Expectation Value ◽  
Effective Masses ◽  
Neutrino Astrophysics

If fermions interact with a scalar field, and there are many fermions present the scalar field may develop an expectation value and generate an effective mass for the fermions. This can lead to the formation of fermion clusters, which could be relevant for neutrino astrophysics and for dark matter astrophysics. Because this system may exhibit negative pressure, it also leads to a model of dark energy.

scholarly journals Improved gravitational-wave constraints on higher-order curvature theories of gravity

2021 ◽  
Vol 104 (2) ◽  
Author(s):  
Scott E. Perkins ◽  
Remya Nair ◽  
Hector O. Silva ◽  
Nicolás Yunes
Keyword(s):  
Gravitational Wave ◽  
Higher Order ◽  
Theories Of Gravity
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