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An analysis of the solutions for the field equations of generalized scalar-tensor theories of gravitation is performed through the study of the geometry of the phase space and the stability of the solutions, with special interest in the…

General Relativity and Quantum Cosmology · Physics 2007-05-23 J. C. C. Souza , A. Saa

We use an alternative interpretation of quantum mechanics, based on the Bohmian trajectory approach, and show that the quantum effects can be included in the classical equation of motion via a conformal transformation on the background…

General Relativity and Quantum Cosmology · Physics 2019-11-20 G. Gregori , B. Reville , B. Larder

We solve the field equations of modified gravity for $f(R)$ model in metric formalism. Further, we obtain the fixed points of the dynamical system in phase space analysis of $f(R)$ models, both with and without the effects of radiation.…

General Relativity and Quantum Cosmology · Physics 2018-01-26 Murli Manohar Verma , Bal Krishna Yadav

From the Wheeler-Dewitt solutions, the scale factor of the initial universe is discussed. In this study, scale factors from Wheeler-Dewitt solutions, loop quantum gravity, and phantom energy dominated stages are compared. Certain…

General Relativity and Quantum Cosmology · Physics 2020-06-29 Natarajan S , Chandrmohan R , Swaminathan R

We compare two versions of deformed dispersion relations (energy vs momenta and momenta vs energy) and the corresponding time delay up to the second order accuracy in the quantum gravity scale (deformation parameter). A general framework…

High Energy Physics - Theory · Physics 2010-11-26 A. Borowiec , Kumar S. Gupta , S. Meljanac , A. Pachol

A quantum cosmological model with radiation and a dilaton scalar field is analysed. The Wheeler-deWitt equation in the mini-superspace induces a Schr\"odinger equation, which can be solved. An explicit wavepacket is constructed for a…

General Relativity and Quantum Cosmology · Physics 2015-06-11 J. C. Fabris , F. T. Falciano , P. Vargas Moniz , J. Marto , N. Pinto-Neto

Previous work in the literature had built a formalism for spatially averaged equations for the scale factor, giving rise to an averaged Raychaudhuri equation and averaged Hamiltonian constraint, which involve a backreaction source term. The…

General Relativity and Quantum Cosmology · Physics 2010-05-12 Vincenzo F. Cardone , Giampiero Esposito

We investigate various dark energy models by taking into account the thermal effects induced from Hawking radiation on the apparent horizon of the Universe, for example near a finite-time future singularity. If the dark energy density…

General Relativity and Quantum Cosmology · Physics 2021-02-17 Artyom V. Astashenok , Sergei D. Odintsov , Vasilis K. Oikonomou

We study linear cosmological perturbations in a previously introduced family of deformations of general relativity characterized by the absence of new degrees of freedom. The homogeneous and isotropic background in this class of theories is…

General Relativity and Quantum Cosmology · Physics 2010-06-08 Kirill Krasnov , Yuri Shtanov

A linear relationship between the Hubble expansion parameter and the time derivative of the scalar field is explored in order to derive exact cosmological, attractor-like solutions, both in Einstein's theory and in Brans-Dicke gravity with…

General Relativity and Quantum Cosmology · Physics 2010-10-27 Olga Arias , Tame Gonzalez , Yoelsy Leyva , Israel Quiros

We generate new spherical and time-dependent solutions of viable Horndeski gravity by disforming a solution of the Einstein equations with scalar field source and positive cosmological constant. They describe dynamical objects embedded in…

General Relativity and Quantum Cosmology · Physics 2022-10-05 Reza Saadati , Andrea Giusti , Valerio Faraoni , Fatimah Shojai

A dynamical resolution to the cosmological constant fine-tuning problem has been previously put forward, based on a scalar-tensor gravitational theory possessing de Sitter attractor solutions characterized by a small Hubble expansion rate,…

General Relativity and Quantum Cosmology · Physics 2021-08-19 Oleg Evnin , Victor Massart , Kevin Nguyen

In this paper, we present an accelerating cosmological model by constraining the free parameters using the cosmological datasets in an extended symmetric teleparallel gravity for the flat and anisotropic space-time. We employ a time…

General Relativity and Quantum Cosmology · Physics 2023-06-27 S. A. Narawade , M. Koussour , B. Mishra

In this work, we compute the universe temperature for the cosmological horizon for the FLRW metric. For this purpose, we consider a scalar field on the cosmological horizon. This scalar field satisfies the Klein-Gordon equation in a curved…

General Relativity and Quantum Cosmology · Physics 2024-05-15 Armando Meza Gaxiola , Pablo Padilla Longoria

We show that the introduction of a hyperbolic phase for Brans-Dicke (BD) field results in a flat vacuum cosmological solution of Hubble parameter H and fractional rate of change of BD scalar field, F which asymptotically approach constant…

General Relativity and Quantum Cosmology · Physics 2015-05-13 M. Arik , M. Calik , F. Cifter

We have investigated the Brans-Dicke Chameleon theory of gravity and obtained exact solutions of the scale factor $a(t)$, scalar field $\phi(t)$, an arbitrary function $f(\phi)$ which interact with the matter Lagrangian in the action of the…

General Physics · Physics 2011-09-12 Mubasher Jamil , Ibrar Hussain , D. Momeni

The timescape cosmology represents a potentially viable alternative to the standard homogeneous cosmology, without the need for dark energy. Although average cosmic evolution in the timescape scenario only differs substantially from that of…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-12 James A. G. Duley , M. Ahsan Nazer , David L. Wiltshire

We follow approach of induced matter theory for 5D vacuum BD, introduce induced matter and potential in 4D hypersurfaces, and employ generalized FRW type solution. We confine ourselves to scalar field and scale factors be functions of the…

General Relativity and Quantum Cosmology · Physics 2015-03-17 Amir F. Bahrehbakhsh , Mehrdad Farhoudi , Hossein Shojaie

In this paper, we consider the Wheeler-DeWitt equation modified by a deformation of the second quantized canonical commutation relations. Such modified commutation relations are induced by a Generalized Uncertainty Principle. Since the…

General Relativity and Quantum Cosmology · Physics 2016-03-14 Remo Garattini , Mir Faizal

The solutions of many issues, of the ongoing efforts to make deformed graphene a tabletop quantum field theory in curved spacetimes, are presented. A detailed explanation of the special features of curved spacetimes, originating from…

High Energy Physics - Theory · Physics 2014-12-16 Alfredo Iorio , Gaetano Lambiase
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