scholarly journals Baryogenesis in f(P) gravity

2021 ◽  
Vol 36 (27) ◽  
Author(s):  
Snehasish Bhattacharjee
Keyword(s):  
Modified Gravity ◽  
Time Derivative ◽  
Mathematical Expression ◽  
Baryon Asymmetry ◽  
Ricci Scalar ◽  
Model Parameter ◽  
The Universe

In this work, we investigate gravitational baryogenesis in the framework of [Formula: see text] gravity to understand the applicability of this class of modified gravity in addressing the baryon asymmetry of the universe. For the analysis, we set [Formula: see text], where [Formula: see text] is the model parameter. We found that in [Formula: see text] gravity, the CP-violating interaction acquires a modification through the addition of the nontopological cubic term [Formula: see text] in addition to the Ricci scalar [Formula: see text] and the mathematical expression of the baryon-to-entropy ratio depends not only on the time derivative of [Formula: see text] but also the time derivative of [Formula: see text]. Additionally, we also investigate the consequences of a more complete and generalized CP-violating interaction proportional to [Formula: see text] instead of [Formula: see text] in addressing the baryon asymmetry of the universe. For this type of interaction, we report that the baryon-to-entropy ratio is proportional to [Formula: see text], [Formula: see text] and [Formula: see text]. We report that for both of these cases, rational values of [Formula: see text] generate acceptable baryon-to-entropy ratios compatible with observations.

scholarly journals A Dark Energy Model with Higher Order Derivatives of H in the f(R,T) Modified Gravity Model

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Antonio Pasqua ◽  
Surajit Chattopadhyay ◽  
Ratbay Myrzakulov
Keyword(s):  
Dark Energy ◽  
Gravity Model ◽  
Modified Gravity ◽  
Hubble Parameter ◽  
Time Derivative ◽  
Cosmic Time ◽  
Late Time ◽  
Eos Parameter ◽  
Curvature And Torsion ◽  
The Universe

We consider a model of dark energy (DE) which contains three terms (one proportional to the squared Hubble parameter, one to the first derivative, and one to the second derivative with respect to the cosmic time of the Hubble parameter) in the light of the f(R,T)=μR+νT modified gravity model, with μ and ν being two constant parameters. R and T represent the curvature and torsion scalars, respectively. We found that the Hubble parameter exhibits a decaying behavior until redshifts z≈-0.5 (when it starts to increase) and the time derivative of the Hubble parameter goes from negative to positive values for different redshifts. The equation of state (EoS) parameter of DE and the effective EoS parameter exhibit a transition from ω<-1 to ω>-1 (showing a quintom-like behavior). We also found that the model considered can attain the late-time accelerated phase of the universe. Using the statefinder parameters r and s, we derived that the studied model can attain the ΛCDM phase of the universe and can interpolate between dust and ΛCDM phase of the universe. Finally, studying the squared speed of sound vs2, we found that the considered model is classically stable in the earlier stage of the universe but classically unstable in the current stage.

scholarly journals Dynamo effects in gravity

2019 ◽  
Vol 127 ◽  
pp. 02009
Author(s):  
Boris Shevtsov
Keyword(s):  
Gravitational Constant ◽  
Nonlinear Oscillations ◽  
Big Bang ◽  
Baryon Asymmetry ◽  
System Of Equations ◽  
Fractal Structures ◽  
Expansion Of The Universe ◽  
The Big Bang ◽  
The Universe ◽  
Made In

Nonlinear oscillations in the dynamic system of gravitational and material fields are considered. The problems of singularities and caustics in gravity, expansion and baryon asymmetry of the Universe, wave prohibition of collapse into black holes, and failure of the Big Bang concept are discussed. It is assumed that the effects of the expansion of the Universe are coupling with the reverse collapse of dark matter. This hypothesis is used to substantiate the vortex and fractal structures in the distribution of matter. A system of equations is proposed for describing turbulent and fluctuation processes in gravitational and material fields. Estimates of the di usion parameters of such a system are made in comparison with the gravitational constant.

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

scholarly journals Dark Matter and the Baryon Asymmetry of the Universe

2006 ◽  
Vol 96 (4) ◽  
Author(s):  
Glennys R. Farrar ◽  
Gabrijela Zaharijas
Keyword(s):  
Dark Matter ◽  
Baryon Asymmetry ◽  
The Universe

Baryon asymmetry of the universe. A Monte Carlo study on the lattice

1987 ◽  
Vol 197 (1-2) ◽  
pp. 49-54 ◽  
Author(s):  
J. Ambjørn ◽  
M. Laursen ◽  
M.E. Shaposhnikov
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Study ◽  
Baryon Asymmetry ◽  
The Universe

scholarly journals A dark clue to seesaw and leptogenesis in a pseudo-Dirac singlet doublet scenario with (non)standard cosmology

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Partha Konar ◽  
Ananya Mukherjee ◽  
Abhijit Kumar Saha ◽  
Sudipta Show
Keyword(s):  
Dark Matter ◽  
Thermal History ◽  
Direct Detection ◽  
Critical Role ◽  
Mass Term ◽  
Baryon Asymmetry ◽  
Dark Sector ◽  
Lepton Asymmetry ◽  
History Of ◽  
The Universe

Abstract We propose an appealing alternative scenario of leptogenesis assisted by dark sector which leads to the baryon asymmetry of the Universe satisfying all theoretical and experimental constraints. The dark sector carries a non minimal set up of singlet doublet fermionic dark matter extended with copies of a real singlet scalar field. A small Majorana mass term for the singlet dark fermion, in addition to the typical Dirac term, provides the more favourable dark matter of pseudo-Dirac type, capable of escaping the direct search. Such a construction also offers a formidable scope to radiative generation of active neutrino masses. In the presence of a (non)standard thermal history of the Universe, we perform the detailed dark matter phenomenology adopting the suitable benchmark scenarios, consistent with direct detection and neutrino oscillations data. Besides, we have demonstrated that the singlet scalars can go through CP-violating out of equilibrium decay, producing an ample amount of lepton asymmetry. Such an asymmetry then gets converted into the observed baryon asymmetry of the Universe through the non-perturbative sphaleron processes owing to the presence of the alternative cosmological background considered here. Unconventional thermal history of the Universe can thus aspire to lend a critical role both in the context of dark matter as well as in realizing baryogenesis.

Construction of neutrino models with non-vanishing θ13 and leptogenesis

2015 ◽  
Vol 93 (12) ◽  
pp. 1561-1565
Author(s):  
Ng. K. Francis
Keyword(s):  
Neutrino Mass ◽  
Big Bang ◽  
Baryon Asymmetry ◽  
Daya Bay ◽  
Mass Model ◽  
Big Bang Nucleosynthesis ◽  
Great Discovery ◽  
Neutrino Mass Models ◽  
The Universe ◽  
Inflationary Models

We construct the neutrino mass models with non-vanishing θ13 and estimate the baryon asymmetry of the universe and subsequently derive the constraints on the inflaton mass and the reheating temperature after inflation. The great discovery of this decade, the detection of Higgs boson of mass 126 GeV and nonzero θ13, makes leptogenesis all the more exciting. Besides, the neutrino mass model is compatible with inflaton mass 1010–1013 GeV corresponding to reheating temperature TR ∼ 105–107 GeV to overcome the gravitino constraint in supersymmetry and big bang nucleosynthesis. When Daya Bay data θ13 ≈ 9° is included in the model, τ predominates over e and μ contributions, which are indeed a good sign. It is shown that neutrino mass models for a successful leptogenesis can be accommodated for a variety of inflationary models with a rather wide ranging inflationary scale.

scholarly journals Hamiltonian formalism for nonlocal gravity models

2022 ◽  
Author(s):  
Pawan Joshi ◽  
Utkarsh Kumar ◽  
Sukanta Panda
Keyword(s):  
Ricci Tensor ◽  
Degrees Of Freedom ◽  
Hamiltonian Formalism ◽  
Riemann Tensor ◽  
Ricci Scalar ◽  
Gravity Models ◽  
Lagrangian Formalism ◽  
Acceleration Of The Universe ◽  
Nonlocal Action ◽  
The Universe

Nonlocal gravity models are constructed to explain the current acceleration of the universe. These models are inspired by the infrared correction appearing in Einstein–Hilbert action. Here, we develop the Hamiltonian formalism of a nonlocal model by considering only terms to quadratic order in Riemann tensor, Ricci tensor and Ricci scalar. We show how to count degrees of freedom using Hamiltonian formalism including Ricci tensor and Ricci scalar terms. In this model, we have also worked out with a choice of a nonlocal action which has only two degrees of freedom equivalent to GR. Finally, we find the existence of additional constraints in Hamiltonian required to remove the ghosts in our full action. We also compare our results with that of obtained using Lagrangian formalism.

scholarly journals The Perturbation of Material Density in f(R) Modified Gravity of Polynormal Exponential Form

10.29007/xqpk ◽  
2020 ◽  
Author(s):  
Van On Vo
Keyword(s):  
Cosmological Model ◽  
Modified Gravity ◽  
Linear Perturbation ◽  
Exponential Form ◽  
Material Density ◽  
Gravitational Model ◽  
Standard Cosmological Model ◽  
The Difference ◽  
Evolutionary Aspects ◽  
The Universe

In this paper, we investigate the linear perturbation of the material density of the universe in f(R) modified gravity of polynomial exponential form on the scale of distance below the cosmic horizon (sub-horizon). The results show that the model for the evolutionary aspects of the universe is slightly different from that in the standard cosmological model of ΛCDM. They can be used to show the difference between this modified gravitational model with the standard cosmological model of ΛCMD and other cosmological models. We also investigate the ration Ψ/ Φ and Geff / GN in the model and show that they are within allowable limits of experiments.

scholarly journals Primordial black holes from the QCD epoch: linking dark matter, baryogenesis, and anthropic selection

2020 ◽  
Vol 501 (1) ◽  
pp. 1426-1439
Author(s):  
Bernard Carr ◽  
Sebastien Clesse ◽  
Juan García-Bellido
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Selection Effect ◽  
Mass Function ◽  
Baryon Asymmetry ◽  
Primordial Black Holes ◽  
Cosmological Horizon ◽  
Chandrasekhar Limit ◽  
The Universe ◽  
Characteristic Mass

ABSTRACT If primordial black holes (PBHs) formed at the quark-hadron epoch, their mass must be close to the Chandrasekhar limit, this also being the characteristic mass of stars. If they provide the dark matter (DM), the collapse fraction must be of order the cosmological baryon-to-photon ratio ∼10−9, which suggests a scenario in which a baryon asymmetry is produced efficiently in the outgoing shock around each PBH and then propagates to the rest of the Universe. We suggest that the temperature increase in the shock provides the ingredients for hotspot electroweak baryogenesis. This also explains why baryons and DM have comparable densities, the precise ratio depending on the size of the PBH relative to the cosmological horizon at formation. The observed value of the collapse fraction and baryon asymmetry depends on the amplitude of the curvature fluctuations that generate the PBHs and may be explained by an anthropic selection effect associated with the existence of galaxies. We propose a scenario in which the quantum fluctuations of a light stochastic spectator field during inflation generate large curvature fluctuations in some regions, with the stochasticity of this field providing the basis for the required selection. Finally, we identify several observational predictions of our scenario that should be testable within the next few years. In particular, the PBH mass function could extend to sufficiently high masses to explain the black hole coalescences observed by LIGO/Virgo.

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