scholarly journals Barrow entropy corrections to Friedmann equations

2021 ◽  
Vol 103 (12) ◽  
Author(s):  
Ahmad Sheykhi
Keyword(s):  
Friedmann Equations ◽  
Entropy Corrections

scholarly journals On asymptotic solutions of Friedmann equations

2012 ◽  
Vol 219 (3) ◽  
pp. 1273-1286 ◽  
Author(s):  
Ž. Mijajlović ◽  
N. Pejović ◽  
S. Šegan ◽  
G. Damljanović
Keyword(s):  
Asymptotic Solutions ◽  
Friedmann Equations

Cosmological consequences of modified Friedmann equations according to holographic equipartition law

2021 ◽  
Vol 36 (10) ◽  
pp. 2150069
Author(s):  
Abdul Jawad ◽  
Sidra Saleem ◽  
Saba Qummer
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Om Diagnostic ◽  
Generalized Second Law ◽  
Friedmann Equations ◽  
Equation Of State Parameter ◽  
Equipartition Law

We examine thermodynamically an extra driving term for the flat universe by applying Sharma Mittal entropy to Padmanabhan’s holographic equipartition law. Deviations from the Bekenstein–Hawking entropy by using this law, we generate an extra driving in the acceleration equation. By using the constant and parametrized equation of state parameter, we investigate the different cosmological parameters like deceleration parameter, squared speed of sound, Om-diagnostic and statefinder parameter through graphical approach. We observe compatible results with current observational data in both models. Generalized second law of thermodynamics also remains valid in both cases.

scholarly journals Effective fluid FLRW cosmologies of minimal massive gravity

2015 ◽  
Vol 30 (18) ◽  
pp. 1550087
Author(s):  
Nejat Tevfik Yılmaz
Keyword(s):  
Ideal Fluid ◽  
Massive Gravity ◽  
General Solutions ◽  
Friedmann Equations

By using a solution ansatz we partially decouple the metric and the Stückelberg sectors of the minimal massive gravity (MMGR). In this scheme for a diagonal physical metric we find the general solutions for the scalars of the theory and the particular fiducial (background) metric which leads to these solutions. Then we adopt this general formalism to construct the derivation of new Friedmann–Lemaitre–Robertson–Walker (FLRW) cosmologies of the theory in the presence of a so-called effective ideal fluid which arises from our solution ansatz as a modifying, non-physical source for the Einstein and the corresponding Friedmann equations.

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 Noncommutative Friedmann equations in effective LQC

2020 ◽  
Vol 29 (06) ◽  
pp. 2050039
Author(s):  
Luis Rey Díaz-Barrón ◽  
Abraham Espinoza-García ◽  
S. Pérez-Payán ◽  
J. Socorro
Keyword(s):  
Scalar Field ◽  
Effective Potential ◽  
Quantum Cosmology ◽  
Equations Of Motion ◽  
Loop Quantum Cosmology ◽  
Friedmann Equations ◽  
Noncommutative Version ◽  
Previous Proposal ◽  
Free Scalar ◽  
Raychaudhuri Equations

In this work, we construct a noncommutative version of the Friedmann equations in the framework of effective loop quantum cosmology, extending and applying the ideas presented in a previous proposal by some of the authors. The model under consideration is a flat FRW spacetime with a free scalar field. First, noncommutativity in the momentum sector is introduced. We establish the noncommutative equations of motion and obtain the corresponding exact solutions. Such solutions indicate that the bounce is preserved, in particular, the energy density is the same as in the standard LQC. We also construct an extension of the modified Friedmann equations arising in effective LQC which incorporates corrections due to noncommutativity, and argue that an effective potential is induced. This, in turn, leads us to investigate the possibility of an inflationary era. Finally, we obtain the Friedmann and the Raychaudhuri equations when implementing noncommutativity in the configuration sector. In this case, no effective potential is induced.

scholarly journals Bounce Cosmology in Generalized Modified Gravities

Universe ◽  
2019 ◽  
Vol 5 (3) ◽  
pp. 74 ◽  
Author(s):  
Georgios Minas ◽  
Emmanuel Saridakis ◽  
Panayiotis Stavrinos ◽  
Alkiviadis Triantafyllopoulos
Keyword(s):  
Scalar Field ◽  
Special Relativity ◽  
Tangent Bundle ◽  
General Class ◽  
Degrees Of Freedom ◽  
Geometrical Structure ◽  
Tensor Structure ◽  
Nonlinear Connection ◽  
Friedmann Equations ◽  
Very Special Relativity

We investigate the bounce realization in the framework of generalized modified gravities arising from Finsler and Finsler-like geometries. In particular, a richer intrinsic geometrical structure is reflected in the appearance of extra degrees of freedom in the Friedmann equations that can drive the bounce. We examine various Finsler and Finsler-like constructions. In the cases of general very special relativity, as well as of Finsler-like gravity on the tangent bundle, we show that a bounce cannot easily be obtained. However, in the Finsler–Randers space, induced scalar anisotropy can fulfil bounce conditions, and bouncing solutions are easily obtained. Finally, for the general class of theories that include a nonlinear connection, a new scalar field is induced, leading to a scalar–tensor structure that can easily drive a bounce. These features reveal the capabilities of Finsler and Finsler-like geometries.

scholarly journals Cosmic acceleration from quantum Friedmann equations

2020 ◽  
Vol 37 (8) ◽  
pp. 085006
Author(s):  
Thibaut Demaerel ◽  
Christian Maes ◽  
Ward Struyve
Keyword(s):  
Cosmic Acceleration ◽  
Friedmann Equations

Polymer quantization effects on gauge-flation

2018 ◽  
Vol 15 (10) ◽  
pp. 1850169
Author(s):  
M. Mardaani ◽  
K. Nozari
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Quantum Gravity ◽  
Gauge Field ◽  
Quantum Cosmology ◽  
Loop Quantum Gravity ◽  
Loop Quantum Cosmology ◽  
Abelian Gauge ◽  
Friedmann Equations ◽  
Cosmological Inflation

Polymer quantum mechanics, as a non-standard representation of quantum mechanics, is based on a symmetric sector of loop quantum gravity known as loop quantum cosmology. In this work, by analyzing the Hamiltonian and Friedmann equations in the standard Hilbert space and polymer Hilbert space, we show that polymer quantization is a successful formalism for a non-Abelian gauge field driving the cosmological inflation, the so-called gauge-flation, in order to remove initial singularity and also keeping the inflationary trajectories in this model as attractors of dynamics after the bounce.

scholarly journals A dynamical study of the Friedmann equations

2001 ◽  
Vol 22 (4) ◽  
pp. 371-384 ◽  
Author(s):  
Jean-Philippe Uzan ◽  
Roland Lehoucq
Keyword(s):  
Dynamical Study ◽  
Friedmann Equations

scholarly journals Modified Friedmann equations from DSR-GUP

2020 ◽  
Vol 129 (5) ◽  
pp. 50002
Author(s):  
Özgür Ökcü ◽  
Christian Corda ◽  
Ekrem Aydiner
Keyword(s):  
Friedmann Equations
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