scholarly journals Maxwell-modified metric affine gravity

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Oktay Cebecioğlu ◽  
Salih Kibaroğlu
Keyword(s):  
Cosmological Constant ◽  
Vector Fields ◽  
Linear Connection ◽  
Constant Term ◽  
Accelerated Expansion ◽  
Gauge Fields ◽  
Field Equations ◽  
Special Linear ◽  
Gravity Equations ◽  
Affine Gravity

AbstractWe present a gauge formulation of the special affine algebra extended to include an antisymmetric tensorial generator belonging to the tensor representation of the special linear group. We then obtain a Maxwell modified metric affine gravity action with a cosmological constant term. We find the field equations of the theory and show that the theory reduces to an Einstein-like equation for metric affine gravity with the source added to the gravity equations with cosmological constant $$\mu $$ μ contains linear contributions from the new gauge fields. The reduction of the Maxwell metric affine gravity to Riemann–Cartan one is discussed and the shear curvature tensor corresponding to the symmetric part of the special linear connection is identified with the dark energy. Furthermore, the new gauge fields are interpreted as geometrical inflaton vector fields which drive accelerated expansion.

GENERALIZED GRAVITY IN CLIFFORD SPACES, VACUUM ENERGY AND GRAND UNIFICATION

2011 ◽  
Vol 08 (06) ◽  
pp. 1239-1258 ◽  
Author(s):  
CARLOS CASTRO
Keyword(s):  
Cosmological Constant ◽  
Gauge Field ◽  
Constant Term ◽  
Gauge Field Theories ◽  
Field Equations ◽  
Spectral Action ◽  
Action Model ◽  
The One ◽  
Curvature And Torsion ◽  
Vacuum Solutions

Polyvector-valued gauge field theories in Clifford spaces are used to construct a novel Cl (3, 2) gauge theory of gravity that furnishes modified curvature and torsion tensors leading to important modifications of the standard gravitational action with a cosmological constant. Vacuum solutions exist which allow a cancelation of the contributions of a very large cosmological constant term and the extra terms present in the modified field equations. Generalized gravitational actions in Clifford-spaces are provided and some of their physical implications are discussed. It is shown how the 16 fermions and their masses in each family can be accommodated within a Cl (4) gauge field theory. In particular, the Higgs fields admit a natural Clifford-space interpretation that differs from the one in the Chamseddine–Connes spectral action model of non-commutative geometry. We finalize with a discussion on the relationship with the Pati–Salam color-flavor model group SU (4)C × SU (4)F and its symmetry breaking patterns. An Appendix is included with useful Clifford algebraic relations.

scholarly journals ON THE NATURAL GAUGE FIELDS OF MANIFOLDS

2000 ◽  
Vol 15 (32) ◽  
pp. 1991-2005 ◽  
Author(s):  
A. B. PESTOV ◽  
BIJAN SAHA
Keyword(s):  
Displacement Field ◽  
Energy Momentum Tensor ◽  
Linear Connection ◽  
Momentum Tensor ◽  
Gauge Fields ◽  
Spherically Symmetric ◽  
Time Inversion ◽  
Field Equations ◽  
Gauge Invariant ◽  
Minkowski Space Time

The gauge symmetry inherent in the concept of manifold has been discussed. Within the scope of this symmetry the linear connection or displacement field can be considered as a natural gauge field on the manifold. The gauge-invariant equations for the displacement field have been derived. It has been shown that the energy–momentum tensor of this field conserves and hence the displacement field can be treated as one that transports energy and gravitates. To show the existence of the solutions of the field equations, we have derived the general form of the displacement field in Minkowski space–time which is invariant under rotation and space and time inversion. With this ansatz we found spherically-symmetric solutions of the equations in question.

scholarly journals Time Dependence of Various Cosmological Parameters in the Framework of Kaluza-Klein Space-Time

2019 ◽  
pp. 211-220
Author(s):  
Sudipto Roy ◽  
Anirban Sarkar ◽  
Pritha Ghosh
Keyword(s):  
Cosmological Constant ◽  
Time Dependence ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Accelerating Universe ◽  
Field Equations ◽  
Eos Parameter ◽  
Klein Theory ◽  
Time Variations ◽  
Kaluza Klein

A theoretical model, regarding the time dependence of several cosmological parameters, has been constructed in the present study, in the framework of Kaluza-Klein theory, using its field equations for a spatially flat metric. Time dependent empirical expressions of the cosmological constant and the equation of state (EoS) parameter have been substituted into the field equations to determine the time dependence of various cosmological parameters. Time variations of these parameters have been shown graphically. The cosmological features obtained from this model are found to be in agreement with the observed characteristics of the accelerating universe. Interestingly, the signature flipping of the deceleration parameter, from positive to negative, is predicted by this model, indicating a transformation of the universe from a state of decelerated expansion to accelerated expansion, as obtained from astrophysical observations. Time dependence of the gravitational constant (G), energy density (?), cosmological constant (?) and the EoS parameter (?) have been determined and depicted graphically in the present study.

scholarly journals ROTATING BLACK HOLES IN METRIC-AFFINE GRAVITY

2006 ◽  
Vol 15 (05) ◽  
pp. 635-668 ◽  
Author(s):  
PETER BAEKLER ◽  
FRIEDRICH W. HEHL
Keyword(s):  
Black Hole Solution ◽  
Lorentz Invariance ◽  
Linear Connection ◽  
Vacuum Field ◽  
Axially Symmetric ◽  
De Sitter ◽  
Field Equations ◽  
Rotating Black Holes ◽  
Affine Gravity ◽  
De Sitter Metric

Within the framework of metric-affine gravity (MAG, metric and an independent linear connection constitute space–time), we find, for a specific gravitational Lagrangian and by using prolongation techniques, a stationary axially symmetric exact solution of the vacuum field equations. This black hole solution embodies a Kerr–de Sitter metric and the post-Riemannian structures of torsion and nonmetricity. The solution is characterized by mass, angular momentum, and shear charge, the latter of which is a measure for violating Lorentz invariance.

scholarly journals Revolutionary Approach for Fusion of the Classic, Relativity and Quantum field Theories: Sayed’s Acceleration Equation and Probable Violation of E=mc2

2021 ◽  
Vol 19 ◽  
pp. 134-141
Author(s):  
Sayed A. El-Mongy
Keyword(s):  
Cosmological Constant ◽  
Planck Scale ◽  
Accelerated Expansion ◽  
Vacuum Energy Density ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Field Equations ◽  
Expansion Of The Universe ◽  
Atom Nucleus ◽  
The Universe

Expansion of the universe is a divine fact in the glorious Quran. The accelerated expansion of the universe is one of the physics mysteries and challenges. This article is a try to find an answer to this ambiguity. A simple fusion and merging of the Newton, Einstein and quantum field equations were carried out to clarify this topic. Innovative equations correlating the acceleration (As), cosmological constant (Ʌ), vacuum energy density (ρ) and distance (d) was deduced. It can be concluded that Sayed`s acceleration constant (As) is proportional to (Ʌ/ρ), (1/8mc2) and (1/πd2). The derivative equation reveals a probable violation of the mass-energy formula (E= mc2); the speed of light might be 12.5% more. This disparity may be due to antimatter contribution; neutrino-antineutrino, β-β+ annihilation and/or a predicted unrecognized very light particle in the atom nucleus. The Sayed`s acceleration constant (As) and (As/Ʌ) ratio were calculated and found to be 6.33825x10-8 m/s2 and 5.7620475x10+44 m3/s2 respectively. Using Sayed`s equations, the calculated acceleration in planck scale is matched with the declared 5.56081x1051 m/s2 value. The The calculated recession velocity at 1 Mpc was found to be 6.5192677 x 108 m/s .and the cosmological constant (Ʌ) is as measured;~1.1x10-52 m-2

scholarly journals GAUGED ADS–MAXWELL ALGEBRA AND GRAVITY

2011 ◽  
Vol 26 (36) ◽  
pp. 2689-2696 ◽  
Author(s):  
R. DURKA ◽  
J. KOWALSKI-GLIKMAN ◽  
M. SZCZACHOR
Keyword(s):  
Cosmological Constant ◽  
Dynamical Model ◽  
Gauge Fields ◽  
De Sitter ◽  
Field Equations ◽  
Negative Cosmological Constant ◽  
Bf Theory ◽  
Maxwell Fields ◽  
Dynamical Field

We deform the anti-de Sitter algebra by adding additional generators [Formula: see text], forming in this way the negative cosmological constant counterpart of the Maxwell algebra. We gauge this algebra and construct a dynamical model with the help of a constrained BF theory. It turns out that the resulting theory is described by the Einstein–Cartan action with Holst term, and the gauge fields associated with the Maxwell generators [Formula: see text] appear only in topological terms that do not influence dynamical field equations. We briefly comment on the extension of this construction, which would lead to a nontrivial Maxwell fields dynamics.

scholarly journals f(T) cosmology with nonzero curvature

2021 ◽  
Vol 36 (38) ◽  
Author(s):  
Andronikos Paliathanasis
Keyword(s):  
Cosmological Constant ◽  
Cosmological Solution ◽  
Constant Term ◽  
Analytic Solutions ◽  
De Sitter ◽  
Spatial Curvature ◽  
Field Equations ◽  
Background Space ◽  
Nonzero Curvature ◽  
Text Model

We investigate exact and analytic solutions in [Formula: see text] gravity within the context of a Friedmann–Lemaître–Robertson–Walker background space with nonzero spatial curvature. For the power-law theory [Formula: see text] we find that the field equations admit an exact solution with a linear scalar factor for negative and positive spatial curvature. That Milne-like solution is asymptotic behavior for the scale factor near the initial singularity for the model [Formula: see text]. The analytic solution for that specific theory is presented in terms of Painlevé series for [Formula: see text]. Moreover, from the value of the resonances of the Painlevé series we conclude that the Milne-like solution is always unstable while for large values of the independent parameter, the field equations provide an expanding universe with a de Sitter expansion of a positive cosmological constant. Finally, the presence of the cosmological term [Formula: see text] in the studied [Formula: see text] model plays no role in the general behavior of the cosmological solution and the universe immerge in a de Sitter expansion either when the cosmological constant term [Formula: see text] in the [Formula: see text] model vanishes.

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.

Cosmological constant Λ in f(R,T) modified gravity

2016 ◽  
Vol 13 (05) ◽  
pp. 1650058 ◽  
Author(s):  
Gyan Prakash Singh ◽  
Binaya Kumar Bishi ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Modified Gravity ◽  
Bianchi Type ◽  
Field Equations ◽  
Type Iii ◽  
Expansion Scalar ◽  
Modified Theory Of Gravity ◽  
Shear Scalar ◽  
Modified Theory

In this paper, we have studied the Bianchi type-III cosmological model in the presence of cosmological constant in the context of [Formula: see text] modified theory of gravity. Here, we have discussed two classes of [Formula: see text] gravity, i.e. [Formula: see text] and [Formula: see text]. In both classes, the modified field equations are solved by the relation expansion scalar [Formula: see text] that is proportional to shear scalar [Formula: see text] which gives [Formula: see text], where [Formula: see text] and [Formula: see text] are metric potentials. Also we have discussed some physical and kinematical properties of the models.

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.

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