scholarly journals The (2+1) dimensional metric f (R) gravity non-minimally coupled with fermion field

2021 ◽  
Vol 2090 (1) ◽  
pp. 012065
Author(s):  
Nurgissa Myrzakulov ◽  
Gulnur Tursumbayeva ◽  
Shamshyrak Myrzakulova
Keyword(s):  
Gravitational Theory ◽  
Noether Symmetry ◽  
Fermion Field ◽  
Field Equations ◽  
Friedmann Equations ◽  
Fermion Fields ◽  
Cosmological Solutions

Abstract In this article, we examine a gravitational theory including a fermion field that is non-minimally coupled to metric f (R) gravity in (2+1) dimensions. We give the field equations for fermion fields and Friedmann equations. In this context, we study cosmological solutions of the field equations using these forms obtained by the existent of Noether symmetry.

scholarly journals Noether Gauge Symmetry of Dirac Field in (2 + 1)-Dimensional Gravity

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Ganim Gecim ◽  
Yusuf Kucukakca ◽  
Yusuf Sucu
Keyword(s):  
Gauge Symmetry ◽  
Early Time ◽  
Gravitational Theory ◽  
Dirac Field ◽  
Late Time ◽  
Field Equations ◽  
Dynamical Equations ◽  
Symmetry Approach ◽  
Cosmological Solutions ◽  
Dimensional Gravity

We consider a gravitational theory including a Dirac field that is nonminimally coupled to gravity in 2 + 1 dimensions. Noether gauge symmetry approach can be used to fix the form of coupling functionF(Ψ)and the potentialV(Ψ)of the Dirac field and to obtain a constant of motion for the dynamical equations. In the context of (2 + 1)-dimensional gravity, we investigate cosmological solutions of the field equations using these forms obtained by the existence of Noether gauge symmetry. In this picture, it is shown that, for the nonminimal coupling case, the cosmological solutions indicate both an early-time inflation and late-time acceleration for the universe.

scholarly journals EXACT SOLUTIONS FOR COSMOLOGICAL MODELS WITH A SCALAR FIELD

2002 ◽  
Vol 17 (03) ◽  
pp. 375-381 ◽  
Author(s):  
H. MOTAVALI ◽  
M. GOLSHANI
Keyword(s):  
Scalar Field ◽  
Exact Solutions ◽  
Cosmological Models ◽  
Coupling Function ◽  
Noether Symmetry ◽  
Scalar Tensor Theory ◽  
Frw Cosmology ◽  
Field Equations ◽  
Tensor Theory ◽  
Cosmological Solutions

We consider the existence of a Noether symmetry in the scalar–tensor theory of gravity in flat Friedman–Robertson–Walker (FRW) cosmology. The forms of coupling function ω(ϕ) and generic potential V(ϕ) are obtained by requiring the existence of a Noether symmetry for such theory. We derive exact cosmological solutions of the field equations from a point-like Lagrangian.

The Field Equations of Metric-Affine Gravitational Theories

1978 ◽  
Vol 33 (4) ◽  
pp. 398-401 ◽  
Author(s):  
S. J. Aldersley
Keyword(s):  
Vector Potential ◽  
Gravitational Theory ◽  
Field Equations ◽  
Gravitational Theories ◽  
Special Case ◽  
Potential Conditions

The notions of conservation of charge and dimensional consistency are used to obtain conditions which uniquely characterize the field equations of electromagnetism and gravitation in a metric-affine gravitational framework with a vector potential. Conditions for the uniqueness of the choice of field equations of a metric-affine gravitational theory (in the absence of electromagnetism) follow as a special case. Some consequences are discussed.

scholarly journals A MAXWELL-LIKE FORMULATION OF GRAVITATIONAL THEORY IN MINKOWSKI SPACE–TIME

2007 ◽  
Vol 16 (06) ◽  
pp. 1027-1041 ◽  
Author(s):  
EDUARDO A. NOTTE-CUELLO ◽  
WALDYR A. RODRIGUES
Keyword(s):  
Gravitational Field ◽  
Minkowski Space ◽  
Gravitational Theory ◽  
Space Time ◽  
Lorentzian Geometry ◽  
Field Equations ◽  
Yang Mills ◽  
Minkowski Space Time ◽  
Clifford Bundle ◽  
Gauge Fixing

Using the Clifford bundle formalism, a Lagrangian theory of the Yang–Mills type (with a gauge fixing term and an auto interacting term) for the gravitational field in Minkowski space–time is presented. It is shown how two simple hypotheses permit the interpretation of the formalism in terms of effective Lorentzian or teleparallel geometries. In the case of a Lorentzian geometry interpretation of the theory, the field equations are shown to be equivalent to Einstein's equations.

General form of the analytic function f(T) in diverse dimension for a static planar spacetime

2019 ◽  
Vol 28 (12) ◽  
pp. 1950158 ◽  
Author(s):  
Gamal Nashed
Keyword(s):  
Black Hole ◽  
Analytic Function ◽  
Black Hole Solution ◽  
Static Solution ◽  
Gravitational Theory ◽  
Interesting Property ◽  
Constant Function ◽  
Field Equations ◽  
Adm Mass ◽  
Laws Of Thermodynamics

We derive an exact static solution in diverse dimension, without any constraints, to the field equations of [Formula: see text] gravitational theory using a planar spacetime with two unknown functions, i.e. [Formula: see text] and [Formula: see text]. The black hole solution is characterized by two constants, [Formula: see text] and [Formula: see text], one is related to the mass of the black hole, [Formula: see text], and the other is responsible to make the solution deviate from the teleparallel equivalent of general relativity (TEGR). We show that the analytic function [Formula: see text] depends on the constant [Formula: see text] and becomes constant function when [Formula: see text] which corresponds to the TEGR case. The interesting property of this solution is the fact that it makes the singularity of the Kretschmann invariant much softer than the TEGR case. We calculate the energy of this black hole and show that it is equivalent to ADM mass. Applying a coordinate transformation, we derive a rotating black hole with nontrivial values of the torsion scalar and [Formula: see text]. Finally, we examine the physical properties of this black hole solution using the laws of thermodynamics and show that it has thermodynamical stability.

scholarly journals Compact stars in f(ℛ,𝒢,𝒯 ) gravity

2021 ◽  
Vol 36 (24) ◽  
pp. 2150165
Author(s):  
M. Ilyas
Keyword(s):  
Test Particle ◽  
Gravitational Theory ◽  
Momentum Tensor ◽  
Conservation Equation ◽  
Compact Objects ◽  
Compact Stars ◽  
Energy Conditions ◽  
Field Equations ◽  
Physical Features ◽  
The Impact

This work is to introduce a new kind of modified gravitational theory, named as [Formula: see text] (also [Formula: see text]) gravity, where [Formula: see text] is the Ricci scalar, [Formula: see text] is Gauss–Bonnet invariant and [Formula: see text] is the trace of the energy–momentum tensor. With the help of different models in this gravity, we investigate some physical features of different relativistic compact stars. For this purpose, we develop the effectively modified field equations, conservation equation, and the equation of motion for test particle. Then, we check the impact of additional force (massive test particle followed by a nongeodesic line of geometry) on compact objects. Furthermore, we took three notable stars named as [Formula: see text], [Formula: see text] and [Formula: see text]. The physical behavior of the energy density, anisotropic pressures, different energy conditions, stability, anisotropy, and the equilibrium scenario of these strange compact stars are analyzed through various plots. Finally, we conclude that the energy conditions hold, and the core of these stars is so dense.

scholarly journals New cosmological solutions in hybrid metric-Palatini gravity from dynamical symmetries

2021 ◽  
pp. 2150100
Author(s):  
Andronikos Paliathanasis
Keyword(s):  
Conservation Laws ◽  
Integrable Systems ◽  
Functional Form ◽  
Analytic Solutions ◽  
Momentum Conservation ◽  
Field Equations ◽  
Dynamical Symmetries ◽  
Cosmological Solutions ◽  
Liouville Integrable

We investigate the existence of Liouville integrable cosmological models in hybrid metric-Palatini theory. Specifically, we use the symmetry conditions for the existence of quadratic in the momentum conservation laws for the field equations as constraint conditions for the determination of the unknown functional form of the theory. The exact and analytic solutions of the integrable systems found in this study are presented in terms of quadratics and Laurent expansions.

scholarly journals A PATH-INTEGRAL APPROACH FOR BOSONIC EFFECTIVE THEORIES FOR FERMION FIELDS IN FOUR AND THREE DIMENSIONS

2000 ◽  
Vol 15 (05) ◽  
pp. 755-770 ◽  
Author(s):  
LUIZ C. L. BOTELHO
Keyword(s):  
Path Integral ◽  
Infrared Region ◽  
Three Dimensions ◽  
Integral Approach ◽  
Ultraviolet Region ◽  
Fermion Field ◽  
Massive Fermion ◽  
Bosonic Field ◽  
Fermion Fields ◽  
Effective Theories

We study four-dimensional effective bosonic field theories for (A) massive fermion field in the infrared region and (B) massive fermion in the ultraviolet region by using an appropriate fermion path integral chiral variable change and (C) Polyakov's Fermi–Bose transmutation in the 3D-Abelian Thirring model and its triviality as a quantum field theory.

scholarly journals Conformal gravity with electrodynamics for fermion fields and their symmetry breaking mechanism

2014 ◽  
Vol 11 (03) ◽  
pp. 1450019 ◽  
Author(s):  
Luca Fabbri
Keyword(s):  
Scalar Fields ◽  
Specific Form ◽  
Conformal Gravity ◽  
Field Equations ◽  
Cosmological Constant Problem ◽  
Conformal Theory ◽  
Fermion Fields ◽  
Breaking Mechanism ◽  
Cosmological Constants ◽  
Dirac Spinors

In this paper, we consider an axial torsion to build metric-compatible connections in conformal gravity, with gauge potentials; the geometric background is filled with Dirac spinors: scalar fields with suitable potentials are added eventually. The system of field equations is worked out to have torsional effects converted into spinorial self-interactions: the massless spinors display self-interactions of a specific form that gives them the features they have in the non-conformal theory but with the additional character of renormalizability, and the mechanisms of generation of mass and cosmological constants become dynamical. As a final step we will address the cosmological constant problem and the coincidence issue.

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