scholarly journals Horizon thermodynamics in holographic cosmological models with a power-law term

2019 ◽  
Vol 100 (12) ◽  
Author(s):  
Nobuyoshi Komatsu
Keyword(s):  
Power Law ◽  
Cosmological Models ◽  
Horizon Thermodynamics

String inspired cosmological models through Lagrangian invariance

2020 ◽  
Vol 17 (06) ◽  
pp. 2050085
Author(s):  
José Antonio Belinchón ◽  
Danae Polychroni
Keyword(s):  
Perfect Fluid ◽  
Power Law ◽  
Matter Field ◽  
Scale Factor ◽  
Cosmological Models ◽  
De Sitter ◽  
Text Field ◽  
Duality Property ◽  
Constant Potential ◽  
Variable Potential

We study a string inspired cosmological with variable potential through the Lagrangian invariance method in order to determine the form of the potential. We have studied four cases by combining the different fields, that is, the dilaton [Formula: see text] the potential [Formula: see text] the [Formula: see text]-field and the matter field (a perfect fluid). In all the studied cases, we found that the potential can only take two possible forms: [Formula: see text] and [Formula: see text] where [Formula: see text] and [Formula: see text] are numerical constants. We conclude that when we take into account the Kalb–Ramond field, i.e. the [Formula: see text]-field, then it is only possible to get a constant potential, [Formula: see text] Nevertheless, if this field is not considered, then we get two possible solutions for the potential: [Formula: see text] and [Formula: see text] In all the cases, if the potential is constant, [Formula: see text] then we get a de Sitter like solution for the scale factor of the metric, [Formula: see text], which verifies the [Formula: see text]-duality property, while if the potential varies, then we get a power-law solution for the scale factor, [Formula: see text] [Formula: see text]

Galaxy Luminosity Function based on the Press-Schechter Theory

1999 ◽  
Vol 183 ◽  
pp. 275-275 ◽  
Author(s):  
H. Yoshida ◽  
M. Umemura ◽  
Y. Yoshii
Keyword(s):  
Cosmological Model ◽  
Chemical Evolution ◽  
Power Law ◽  
Luminosity Function ◽  
Density Fluctuations ◽  
Cosmological Models ◽  
Model Dependence ◽  
The Press ◽  
Galaxy Luminosity Function

We investigate the cosmological model dependence of galaxy luminosity function (GLF) obtained by the Press–Schechter (PS) prescription. We consider the power–law spectra as well as a CDM spectrum for primordial density fluctuations, assuming a variety of cosmological models. We do not consider any galaxy luminosity (chemical) evolution in this report.

VISCOUS COSMOLOGICAL MODELS IN (1 + 1) DIMENSIONS

1998 ◽  
Vol 07 (04) ◽  
pp. 567-579
Author(s):  
B. C. PAUL ◽  
S. MUKHERJEE ◽  
A. BEESHAM
Keyword(s):  
Power Law ◽  
Causal Theory ◽  
Cosmological Models ◽  
The Other ◽  
Cosmological Solutions ◽  
Theory Of Gravity

Cosmological solutions in (1 + 1) dimensions in the theory of gravity given by Mann have been obtained in the presence of dissipative phenomena. We have studied both the truncated Israel–Stewart theory and the full causal theory in these lower dimensions. In the full causal theory, we discuss two cases, one with the temperature obeying a power law behavior and the other without this assumption. Some of the solutions found in the truncated Israel–Stewart theory and in the full causal theory are comparable to those obtained by Chimento and Cossarini in (1 + 1) dimensions in Eckart theory.

scholarly journals INTERACTING COSMIC FLUIDS IN BRANS–DICKE COSMOLOGY

2010 ◽  
Vol 25 (30) ◽  
pp. 2579-2589 ◽  
Author(s):  
HOSSEIN FARAJOLLAHI ◽  
NARGES MOHAMADI ◽  
HAMED AMIRI
Keyword(s):  
Power Law ◽  
Cosmological Models ◽  
Expansion Of The Universe ◽  
The Universe

We provide a detailed description for power-law scaling FRW cosmological models in Brans–Dicke theory dominated by two interacting fluid components during the expansion of the universe.

scholarly journals Interacting cosmic fluids in power-law Friedmann–Robertson–Walker cosmological models

2008 ◽  
Vol 662 (4) ◽  
pp. 314-322 ◽  
Author(s):  
Mauricio Cataldo ◽  
Patricio Mella ◽  
Paul Minning ◽  
Joel Saavedra
Keyword(s):  
Power Law ◽  
Cosmological Models ◽  
Friedmann Robertson Walker

scholarly journals Cosmological reconstruction and energy constraints in generalized Gauss–Bonnet-scalar–kinetic–matter couplings

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Adam Z. Kaczmarek ◽  
Dominik Szczęśniak
Keyword(s):  
Scalar Field ◽  
Perfect Fluid ◽  
Power Law ◽  
Cosmological Models ◽  
Energy Conditions ◽  
Kinetic Term ◽  
De Sitter ◽  
Field Equations ◽  
Energy Constraints ◽  
Matter Fields

Abstract Recently introduced $$f(\mathcal {G},T)$$ f ( G , T ) theory is generalized by adding dependence on the arbitrary scalar field $$\phi $$ ϕ and its kinetic term $$(\nabla \phi )^2$$ ( ∇ ϕ ) 2 , to explore non-minimal interactions between geometry, scalar and matter fields in context of the Gauss–Bonnet theories. The field equations for the resulting $$f\left( \mathcal {G},\phi ,(\nabla \phi )^2,T\right) $$ f G , ϕ , ( ∇ ϕ ) 2 , T theory are obtained and show that particles follow non-geodesic trajectories in a perfect fluid surrounding. The energy conditions in the Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime are discussed for the generic function $$f\left( \mathcal {G},\phi ,(\nabla \phi )^2,T\right) $$ f G , ϕ , ( ∇ ϕ ) 2 , T . As an application of the introduced extensions, using the reconstruction techniques we obtain functions that satisfy common cosmological models, along with the equations describing energy conditions for the reconstructed $$f\left( \mathcal {G},\phi ,(\nabla \phi )^2,T\right) $$ f G , ϕ , ( ∇ ϕ ) 2 , T gravity. The detailed discussion of the energy conditions for the de Sitter and power-law spacetimes is provided in terms of the fixed kinetic term i.e. in the $$f\left( \mathcal {G},\phi ,T\right) $$ f G , ϕ , T case. Moreover, in order to check viability of the reconstructed models, we discuss the energy conditions in the specific cases, namely the $$f(R,\phi ,(\nabla \phi )^2)$$ f ( R , ϕ , ( ∇ ϕ ) 2 ) and $$f=\gamma (\phi ,X)\mathcal {G}+\mu T^{1/2}$$ f = γ ( ϕ , X ) G + μ T 1 / 2 approaches. We show, that for the appropriate choice of parameters and constants, the energy conditions can be satisfied for the discussed scenarios.

scholarly journals Anisotropic Cosmological Models with Two Fluids

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
B. Mishra ◽  
Pratik P. Ray ◽  
S. K. J. Pacif
Keyword(s):  
Dark Energy ◽  
Power Law ◽  
Momentum Tensor ◽  
Cosmological Models ◽  
De Sitter ◽  
Eos Parameter ◽  
Two Fluids ◽  
Anisotropic Dark Energy ◽  
Bulk Viscous Fluid ◽  
De Sitter Universe

Anisotropic dark energy cosmological models have been constructed in a Bianchi V space-time, with the energy momentum tensor consisting of two noninteracting fluids, namely, bulk viscous fluid and dark energy fluid. Two different models are constructed based on the power law cosmology and de Sitter universe. The constructed model was also embedded with different pressure gradients along different spatial directions. The variable equation of state (EoS) parameter and skewness parameters for both models are obtained and analysed. The physical properties of the models obtained with the use of scale factors of power law and de Sitter law are also presented.

HIGHER DERIVATIVE THEORY WITH VISCOSITY

1998 ◽  
Vol 07 (04) ◽  
pp. 499-507 ◽  
Author(s):  
B. C. PAUL ◽  
S. MUKHERJEE ◽  
A. BEESHAM
Keyword(s):  
Early Universe ◽  
Power Law ◽  
Causal Theory ◽  
Cosmological Models ◽  
The Other ◽  
Higher Derivative ◽  
Imperfect Fluid ◽  
Cosmological Solutions ◽  
Exponential Solution ◽  
Causal Theories

Cosmological solutions in a higher derivative theory have been obtained with an imperfect fluid. We consider both power law and exponential models of the early universe. We discuss cosmological models in the Eckart, truncated and full causal theories. In the full-causal theory, we distinguish between two cases, one with the temperature obeying a power law behavior and the other relaxing this assumption. The exponential solution permits a realistic scenario when the behavior of the temperature is not of the power-law type.

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