Friedmann–Lemaître–Robertson–Walker metric

About: Friedmann–Lemaître–Robertson–Walker metric is a research topic. Over the lifetime, 4113 publications have been published within this topic receiving 87752 citations. The topic is also known as: FLRW metric.

Tunneling of Massive/Massless Bosons From the Apparent Horizon of FRW Universe

Abstract: In this article we investigate the Hawking radiation of vector particles from the apparent horizon of a Friedmann-Robertson-Walker (FRW) universe in the framework of quantum tunneling method. Furthermore we use Proca equation, a relativistic wave equation for a massive/massless spin-1 particle (massless $\gamma$ photons, weak massive $W^{\pm}$ and $Z^{0}$ bosons, strong massless gluons and $\rho$ and $\omega$ mesons) together with a Painleve spacetime metric for the FRW universe. We solve the Proca equation via Hamilton-Jacobi (HJ) equation and the WKB approximation method. We recover the same result for the Hawking temperature associated with vector particles as in the case of scalar and Dirac particles tunnelled from outside to the inside of the apparent horizon in a FRW universe.

A square-torsion modification of Einstein-Cartan theory

Abstract: In the present paper a theory of gravity is considered in which not only curvature but also torsion is explicitly present in the Lagrangian, both with their own coupling constant. In particular, the couplings to Dirac fields and spin fluids are discussed: in the case of Dirac fields, it is discusses how the Dirac self-interactions depend on the coupling constant as a parameter that may even make these non-linearitiesmanifest at subatomic scales, showing different applications according to the value of the parameter assigned; in the case of spin fluids, FLRW cosmological models arising from the proposed theory are discussed.

Cosmological perturbations in teleparallel Loop Quantum Cosmology

Abstract: Cosmological perturbations in Loop Quantum Cosmology (LQC) are usually studied incorporating either holonomy corrections, where the Ashtekar connection is replaced by a suitable sinus function in order to have a well-defined quantum analogue, or inverse-volume corrections coming from the eigenvalues of the inverse-volume operator In this paper we will develop an alternative approach to calculate cosmological perturbations in LQC based on the fact that, holonomy corrected LQC in the flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) geometry could be also obtained as a particular case of teleparallel $F(T)$ gravity (teleparallel LQC) The main idea of our approach is to mix the simple bounce provided by holonomy corrections in LQC with the non-singular perturbation equations given by $F(T)$ gravity, in order to obtain a matter bounce scenario as a viable alternative to slow-roll inflation In our study, we have obtained an scale invariant power spectrum of cosmological perturbations However, the ratio of tensor to scalar perturbations is of order $1$, which does not agree with the current observations For this reason, we suggest a model where a transition from the matter domination to a quasi de Sitter phase is produced in order to enhance the scalar power spectrum

The graviton one-loop effective action in cosmological space-times with constant deceleration

Abstract: We consider the quantum Friedmann equations which include one-loop vacuum fluctuations due to gravitons and scalar field matter in a FLRW background with constant $\epsilon=-{\dot{H}}/{H^2}$. After several field redefinitions, to remove the mixing between the gravitational and matter degrees of freedom, we can construct the one loop correction to the Friedmann equations. Due to cosmological particle creation, the propagators needed in such a calculation are typically infrared divergent. In this paper we construct the graviton and matter propagators, making use of the recent construction of the infrared finite scalar propagators calculated on a compact spatial manifold in \cite{Janssen:2008px}. The resulting correction to the Friedman equations is suppressed with respect to the tree level contribution by a factor of $H^2/m_p^2$ and shows no secular growth.

FLRW cosmological models with quark and strange quark matters in f(R,T) gravity.

Abstract: In this paper, we have studied the magnetized quark matter (QM) and strange quark matter (SQM) distributions in the presence of $ f(R,T)$ gravity in the background of Friedmann--Lema\^itre--Robertson--Walker (FLRW) metric. To get exact solutions of modified field equations we have used $f(R,T) = R + 2 f(T)$ model given by Harko et al. with two different parametrization of geometrical parameters \textit{i.e.} the parametrization of the deceleration parameter $ q $, and the scale factor $ a $ in hybrid expansion form. Also, we have obtained Einstein Static Universe (ESU) solutions for QM and SQM distributions in $f(R,T)$ gravity and General Relativity (GR). All models in $f(R,T)$ gravity and GR for FRW and ESU Universes with QM also SQM distributions, we get zero magnetic field. These results agree with the solutions of Akta{\c{s} and Ayg\"un in $f(R,T)$ gravity. However, we have also discussed the physical consequences of our obtained models.