scholarly journals Massive gravitational waves in Chern-Simons modified gravity

2014 ◽  
Vol 2014 (10) ◽  
pp. 043-043 ◽  
Author(s):  
Yun Soo Myung ◽  
Taeyoon Moon
Keyword(s):  
Gravitational Waves ◽  
Modified Gravity ◽  
Chern Simons

scholarly journals Inflationary birefringence and baryogenesis

2016 ◽  
Vol 25 (11) ◽  
pp. 1640013 ◽  
Author(s):  
Stephon Alexander
Keyword(s):  
Gravitational Waves ◽  
Lepton Number ◽  
Gauge Fields ◽  
Lepton Asymmetry ◽  
Complex Phase ◽  
Inflaton Field ◽  
Model Based ◽  
Cross Correlations ◽  
Chern Simons

A decade ago, the first leptogenesis model based on inflation was proposed, where the complex phase of the inflaton field carries lepton number [S. H. S. Alexander, M. E. Peskin and M. M. Sheikh-Jabbari, Phys. Rev. Lett. 96 (2006) 081301, arXiv:hep-th/0403069 ]. If the inflaton field is an axion, it can couple to gravitational waves and gauge fields via Chern–Simons invariants. Due to these couplings, birefringent gravitational and gauge primordial perturbations are created during inflation to generate a lepton asymmetry, establishing a possible connection between nonvanishing TB-parity-violating polarization cross-correlations and leptogenesis. We also discuss the prospect for a subset of these models which can directly source circular (V-mode) polarization in the CMB.

scholarly journals Polarized Initial States of Primordial Gravitational Waves

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 672
Author(s):  
Sugumi Kanno ◽  
Jiro Soda
Keyword(s):  
Gravitational Waves ◽  
Modified Gravity ◽  
Coherent States ◽  
Inflationary Universe ◽  
Dynamical Generation ◽  
Primordial Gravitational Waves ◽  
Initial States ◽  
Matter Fields

Polarizations of primordial gravitational waves can be relevant when considering an inflationary universe in modified gravity or when matter fields survive during inflation. Such polarizations have been discussed in the Bunch–Davies vacuum. Instead of taking into account the dynamical generation of polarizations of gravitational waves, in this paper, we consider polarized initial states constructed from S U ( 2 ) coherent states. We then evaluate the power spectrums of the primordial gravitational waves in the states.

scholarly journals Cosmological Implications of the Generalized Entropy Based Holographic Dark Energy Models in Dynamical Chern-Simons Modified Gravity

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
M. Younas ◽  
Abdul Jawad ◽  
Saba Qummer ◽  
H. Moradpour ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Modified Gravity ◽  
Dark Energy Model ◽  
State Parameter ◽  
Energy Model ◽  
Evolutionary Equation ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Chern Simons

Recently, Tsallis, Rényi, and Sharma-Mittal entropies have widely been used to study the gravitational and cosmological setups. We consider a flat FRW universe with linear interaction between dark energy and dark matter. We discuss the dark energy models using Tsallis, Rényi, and Sharma-Mittal entropies in the framework of Chern-Simons modified gravity. We explore various cosmological parameters (equation of state parameter, squared sound of speed ) and cosmological plane (ωd-ωd′, where ωd′ is the evolutionary equation of state parameter). It is observed that the equation of state parameter gives quintessence-like nature of the universe in most of the cases. Also, the squared speed of sound shows stability of Tsallis and Rényi dark energy model but unstable behavior for Sharma-Mittal dark energy model. The ωd-ωd′ plane represents the thawing region for all dark energy models.

Cosmological implications of dark energy models in modified gravity

2018 ◽  
Vol 15 (03) ◽  
pp. 1850034 ◽  
Author(s):  
Nadeem Azhar ◽  
Abdul Jawad ◽  
Sarfraz Ahmad ◽  
Iftikhar Ahmed
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Pilgrim Dark Energy ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
Qcd Ghost Dark Energy ◽  
Chern Simons

We discuss the interacting modified QCD ghost dark energy and generalized ghost pilgrim dark energy with cold dark matter in the framework of dynamical Chern–Simons modified gravity. We investigate the cosmological parameters such as Hubble parameter, deceleration parameter and equation of state. We also discuss the physical significance of various cosmological planes like [Formula: see text] and statefinders. It is found that the results of cosmological parameters as well as planes explain the accelerated expansion of the Universe and are compatible with observational data.

scholarly journals Dynamical Chern–Simons modified gravity, Gödel Universe and variable cosmological constant

2010 ◽  
Vol 693 (4) ◽  
pp. 494-497 ◽  
Author(s):  
C. Furtado ◽  
J.R. Nascimento ◽  
A.Yu. Petrov ◽  
A.F. Santos
Keyword(s):  
Cosmological Constant ◽  
Modified Gravity ◽  
Variable Cosmological Constant ◽  
Chern Simons ◽  
Gödel Universe

scholarly journals Chern-Simons modified gravity and closed timelike curves

2016 ◽  
Vol 94 (4) ◽  
Author(s):  
P. J. Porfírio ◽  
J. B. Fonseca-Neto ◽  
J. R. Nascimento ◽  
A. Yu. Petrov ◽  
J. Ricardo ◽  
...  
Keyword(s):  
Modified Gravity ◽  
Closed Timelike Curves ◽  
Chern Simons

scholarly journals Thermodynamics of Various Entropies in Specific Modified Gravity with Particle Creation

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Salman Rafique
Keyword(s):  
Modified Gravity ◽  
Equilibrium Condition ◽  
Apparent Horizon ◽  
Particle Creation ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Fluid Equation ◽  
Generalized Second Law ◽  
Thermal Equilibrium Condition ◽  
Chern Simons

We consider the particle creation scenario in the dynamical Chern-Simons modified gravity in the presence of perfect fluid equation of state p=(γ-1)ρ. By assuming various modified entropies (Bekenstein entropy logarithmic entropy, power law correction, and Renyi entropy), we investigate the first law of thermodynamics and generalized second law of thermodynamics on the apparent horizon. In the presence of particle creation rate, we discuss the generalized second law of thermodynamics and thermal equilibrium condition. It is found that thermodynamics laws and equilibrium condition remain valid under certain conditions of parameters.

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