scholarly journals DYNAMICS OF PERTURBATIONS IN GURZADYAN–XUE COSMOLOGICAL MODELS

2008 ◽  
Vol 17 (02) ◽  
pp. 203-223 ◽  
Author(s):  
G. V. VERESHCHAGIN ◽  
G. YEGORIAN
Keyword(s):  
Perturbation Theory ◽  
Cosmological Model ◽  
Analytical Solutions ◽  
Cosmological Models ◽  
Time Varying ◽  
Physical Constants ◽  
Newtonian Approximation ◽  
Standard Cosmological Model

Perturbation theory within Newtonian approximation is presented for cosmological models with time-varying physical constants. Analytical solutions for perturbations dynamics are obtained for each Gurzadyan–Xue model with pressureless matter and radiation. It is found that perturbations grow during the entire expansion within GX models, including the curvature- and vacuum-dominated stage when they cease to grow in the standard cosmological model.

scholarly journals Cosmology at high redshift — a probe of fundamental physics

2021 ◽  
Vol 2021 (12) ◽  
pp. 049
Author(s):  
Noah Sailer ◽  
Emanuele Castorina ◽  
Simone Ferraro ◽  
Martin White
Keyword(s):  
Perturbation Theory ◽  
Cosmological Model ◽  
Cross Correlation ◽  
High Redshift ◽  
Matrix Formalism ◽  
Fundamental Physics ◽  
Standard Cosmological Model ◽  
Near Future ◽  
Dynamical Dark Energy ◽  
Observational Program

Abstract An observational program focused on the high redshift (2<z<6) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constraints with those achievable by current or near-future surveys such as DESI and Euclid, all under the same forecasting formalism, and compare our formalism with traditional linear methods. Our Python code FishLSS — used to calculate the Fisher information of the full shape power spectrum, CMB lensing, the cross-correlation of CMB lensing with galaxies, and combinations thereof — is publicly available.

scholarly journals EVOLUTION OF DISTRIBUTION FUNCTION FOR COSMOLOGICAL NEUTRINO

2013 ◽  
Vol 23 ◽  
pp. 379-385 ◽  
Author(s):  
HYUNG WON LEE ◽  
KYOUNG YEE KIM ◽  
REMO RUFFINI
Keyword(s):  
Distribution Function ◽  
Cosmological Model ◽  
Cosmological Models ◽  
Standard Cosmological Model ◽  
Degenerate Neutrino ◽  
The Universe ◽  
Quintessence Model

Recent experimental evidences show that the universe is accelerating. There are many modified cosmological models to explain this accelerating phase including ΛCDM, quintessence model, Brans-Dicke, f(R) gravity, and others. In this talk we want to check the possibility of explaining the current accelerating phase using standard cosmological model with degenerate neutrino. We will study the evolution of distribution function of degenerate neutrinos with standard Friedmann-Lemaître-Roberston-Walker(FLRW) background.

scholarly journals Mixed fluid cosmological model in f(R, T) gravity

2020 ◽  
Vol 98 (11) ◽  
pp. 1015-1022 ◽  
Author(s):  
Parbati Sahoo ◽  
Barkha Taori ◽  
K.L. Mahanta
Keyword(s):  
Cosmological Model ◽  
Bianchi Type ◽  
Type I ◽  
Time Varying ◽  
Eos Parameter ◽  
Barotropic Fluid ◽  
Rotationally Symmetric ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Mixed Fluid

We construct a locally rotationally symmetric (LRS) Bianchi type-I cosmological model in f(R, T) theory of gravity when the source of gravitation is a mixture of barotropic fluid and dark energy (DE) by employing a time-varying deceleration parameter. We observe through the behavior of the state finder parameters (r, s) that our model begins from the Einstein static era and goes to ΛCDM era. The equation of state (EOS) parameter (ωd) for DE varies from the phantom (ω < –1) phase to quintessence (ω > –1) phase, which is consistent with observational results. It is found that the discussed model can reproduce the current accelerating phase of the expansion of the universe.

scholarly journals FUGACITY AND REHEATING OF PRIMORDIAL NEUTRINOS

2013 ◽  
Vol 28 (40) ◽  
pp. 1350188 ◽  
Author(s):  
JEREMIAH BIRRELL ◽  
CHENG-TAO YANG ◽  
PISIN CHEN ◽  
JOHANN RAFELSKI
Keyword(s):  
Cosmological Model ◽  
Background Radiation ◽  
Chemical Nonequilibrium ◽  
Model Parameter ◽  
Standard Cosmological Model ◽  
Cmb Fluctuations ◽  
The Impact ◽  
Freeze Out

We clarify in a quantitative way the impact that distinct chemical Tc and kinetic Tk freeze-out temperatures have on the reduction of the neutrino fugacity ϒν below equilibrium, i.e. ϒν<1, and the increase of the neutrino temperature Tν via partial reheating. We establish the connection between ϒν and Tk via the modified reheating relation Tν(ϒν)/Tγ, where Tγ is the temperature of the background radiation. Our results demonstrate that one must introduce the chemical nonequilibrium parameter, i.e. the fugacity, ϒν, as an additional standard cosmological model parameter in the evaluation of CMB fluctuations as its value allows measurement of Tk.

scholarly journals A CRITIQUE OF THE STANDARD COSMOLOGICAL MODEL : TUTORIAL

2014 ◽  
Vol 24 (5) ◽  
pp. 435-461 ◽  
Author(s):  
Michal Křížek ◽  
Lawrence Somer
Keyword(s):  
Cosmological Model ◽  
Standard Cosmological Model

scholarly journals O UNIVERSO VIVO

2012 ◽  
Vol 19 (1.2) ◽  
Author(s):  
Francisco César de Sá Barreto ◽  
Luiz Paulo Ribeiro Vaz ◽  
Gabriel Armando Pellegatti Franco
Keyword(s):  
Cosmological Model ◽  
Chemical Elements ◽  
Big Bang ◽  
Living System ◽  
Irreversible Processes ◽  
Thermodynamics Of Irreversible Processes ◽  
Protons And Neutrons ◽  
Standard Cosmological Model ◽  
The Big Bang ◽  
The Universe

The standard cosmological model suggests that after the “Big Bang”, 14 billion of years ago, the universe entered a period of expansion and cooling. In the first one millionth of a second appear quarks, glúons, electrons and neutrinos, followed by the appearance of protons and neutrons. In this paper, we describe the “cosmic battle” between gravitation and energy, responsible for the lighter chemical elements and the formation of the stars. We describe the thermodynamics of irreversible processes of systems which are far away from equilibrium, a route that is followed by the universe, seen as a living system.

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.

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