COSMOLOGY WITH ADIABATIC MATTER CREATION

1994 ◽  
Vol 03 (01) ◽  
pp. 327-330 ◽  
Author(s):  
WINFRIED ZIMDAHL ◽  
DIEGO PAVÓN
Keyword(s):  
Stability Analysis ◽  
Energy Density ◽  
Early Universe ◽  
Particle Production ◽  
De Sitter ◽  
Matter Creation ◽  
Production Processes ◽  
Density Perturbations ◽  
Creation Rate

The standard Friedmann-Lemaître-Robertson-Walker (FLRW) model is modified to include particle production processes. The influence of these processes on the dynamics of the early Universe is investigated. We argue that a sufficiently high creation rate may give rise to an inflationary period. A stability analysis about this background yields growing energy density perturbations during the de Sitter stage.

scholarly journals Thermodynamic analysis of universes with the initial and final de Sitter eras

2015 ◽  
Vol 30 (31) ◽  
pp. 1550158 ◽  
Author(s):  
H. Moradpour ◽  
M. T. Mohammadi Sabet ◽  
A. Ghasemi
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Production Process ◽  
Particle Production ◽  
Apparent Horizon ◽  
Thermal Fluctuations ◽  
Mutual Interaction ◽  
De Sitter ◽  
Coincidence Problem ◽  
The Universe

Our aim is studying the thermodynamics of cosmological models including initial and final de Sitter eras. For this propose, bearing Cai–Kim temperature in mind, we investigate the thermodynamic properties of a dark energy (DE) candidate with variable energy density, and show that the state parameter of this dark energy candidate [Formula: see text] should obey the [Formula: see text] constraint, whiles there is no interaction between the fluids filled the universe, and the universe is not in the de Sitter eras. Additionally, based on the thermal fluctuation theory, we study the possibility of inducing fluctuations to the entropy of the DE candidate due to a mutual interaction between the cosmos sectors. Therefore, we find a relation between the thermal fluctuations and the mutual interaction between the cosmos sectors, whiles the DE candidate has a varying energy density. Finally, bearing the coincidence problem in mind, we derive a constraint on the vacuum energy, and investigate its relation with the entropy evolution of the DE candidate. We also point to a model with initial and final de Sitter eras in which a gravitationally induced particle production process leads to change the expansion eras, whiles the corresponding pressure is considered as the cause of current accelerated phase. We study its thermodynamics, and show that such processes may also leave thermal fluctuations into the system. We also find an expression between the thermal fluctuations and the particle production rate. Finally, we use Hayward–Kodama temperature to get a relation for the horizon entropy in models including the gravitationally induced particle production process. Our study shows that the first law of thermodynamics is available on the apparent horizon whiles, the gravitationally induced particle production process, as the DE candidate, may add an additional term to the Bekenstein limit of the horizon. The relation between the validity of the second law of thermodynamics and the gravitationally particle production process is also studied.

BRANE WORLD DYNAMICS AND ADIABATIC MATTER CREATION

2006 ◽  
Vol 15 (03) ◽  
pp. 321-334 ◽  
Author(s):  
P. GOPAKUMAR ◽  
G. V. VIJAYAGOVINDAN
Keyword(s):  
Energy Density ◽  
Open Systems ◽  
Brane World ◽  
Creation Process ◽  
Brane Worlds ◽  
Matter Creation ◽  
Standard Scenario ◽  
Brane Models ◽  
The Universe ◽  
Creation Rate

We treat the adiabatic matter creation process in various three-brane models by applying the thermodynamics of open systems. The matter creation rate is found to affect the evolution of the scale factor and energy density of the universe. We find a modification at the early stages of cosmic dynamics. In GB and RS brane worlds, by choosing appropriate parameters we obtain the standard scenario, while the warped DGP model has different solutions. During later stages, since matter creation is negligible, the evolution reduces to FRW expansion, in the RS and GB models.

NONLINEARITY OF ELECTRODYNAMICS AS A SOURCE OF MATTER CREATION IN A FLAT FRW COSMOLOGY

2007 ◽  
Vol 16 (02n03) ◽  
pp. 427-432 ◽  
Author(s):  
C. S. CÂMARA ◽  
J. C. CARVALHO ◽  
M. R. DE GARCIA MAIA
Keyword(s):  
Particle Production ◽  
Particle Creation ◽  
Second Law Of Thermodynamics ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Matter Creation ◽  
Imperfect Fluid ◽  
Creation Rate

The thermodynamics of cosmological matter creation has been extensively investigated in the literature. In the context of general relativity, the particle production in the cosmological models is due to mechanisms such as an imperfect fluid with bulk viscosity or the decaying vacuum. Another interesting proposal is matter creation in cosmologies with variation of fundamental constants. In this work, we study the nonlinearity of the electrodynamics as a source of matter creation in cosmological models with flat Friedmann–Robertson–Walker (FRW) line geometry. We write the energy conservation law arising from Einstein field equations with cosmological term Λ, solve the field equations, and study how particles are created as the magnetic field B changes with cosmic epoch. We obtain solutions for the adiabatic particle creation rate, the total number of particles, and the scale factor as a function of time in three cases: Λ = 0, Λ = constant and Λ ∝ H2 (cosmological term proportional to the Hubble parameter). We find the constraints imposed by the second law of thermodynamics upon the cosmological solutions.

scholarly journals Derivative couplings in gravitational production in the early universe

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Daniel E. Borrajo Gutiérrez ◽  
Jose A.R. Cembranos ◽  
Luis J. Garay ◽  
Jose M. Sánchez Velázquez
Keyword(s):  
Early Universe ◽  
Ricci Tensor ◽  
Particle Production ◽  
Kinetic Term ◽  
Curvature Scalar ◽  
De Sitter ◽  
Goldstone Bosons ◽  
Highly Sensitive ◽  
Perturbative Regime ◽  
Background Curvature

Abstract Gravitational particle production in the early universe is due to the coupling of matter fields to curvature. This coupling may include derivative terms that modify the kinetic term. The most general first order action contains derivative couplings to the curvature scalar and to the traceless Ricci tensor, which can be dominant in the case of (pseudo-)Nambu-Goldstone bosons or disformal scalars, such as branons. In the presence of these derivative couplings, the density of produced particles for the adiabatic regime in the de Sitter phase (which mimics inflation) is constant in time and decays with the inverse effective mass (which in turn depends on the coupling to the curvature scalar). In the reheating phase following inflation, the presence of derivative couplings to the background curvature modifies in a nontrivial way the gravitational production even in the perturbative regime. We also show that the two couplings — to the curvature scalar and to the traceless Ricci tensor — are drastically different, specially for large masses. In this regime, the production becomes highly sensitive to the former coupling while it becomes independent of the latter.

scholarly journals ON VACUUM-ENERGY DECAY FROM PARTICLE PRODUCTION

2012 ◽  
Vol 27 (25) ◽  
pp. 1250150 ◽  
Author(s):  
F. R. KLINKHAMER
Keyword(s):  
Vacuum Energy ◽  
Particle Production ◽  
Energy Decay ◽  
Back Reaction ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Consistent Description ◽  
Sitter Spacetime

A simplified (but consistent) description of particle-production back-reaction effects in de Sitter spacetime is given.

scholarly journals QCD PHASE TRANSITION IN DGP BRANE COSMOLOGY

2012 ◽  
Vol 21 (08) ◽  
pp. 1250069 ◽  
Author(s):  
K. ATAZADEH ◽  
A. M. GHEZELBASH ◽  
H. R. SEPANGI
Keyword(s):  
Phase Transition ◽  
Energy Density ◽  
Early Universe ◽  
Effective Temperature ◽  
Quark Gluon Plasma ◽  
Friedmann Equation ◽  
Gluon Plasma ◽  
High Energy ◽  
Brane World ◽  
High Energy Density

In the standard picture of cosmology it is predicted that a phase transition, associated with chiral symmetry breaking after the electroweak transition, has occurred at approximately 10μ seconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider the quark-hadron phase transition in a Dvali, Gabadadze and Porrati (DGP) brane world scenario within an effective model of QCD. We study the evolution of the physical quantities useful for the study of the early universe, namely, the energy density, temperature and the scale factor before, during and after the phase transition. Also, due to the high energy density in the early universe, we consider the quadratic energy density term that appears in the Friedmann equation. In DGP brane models such a term corresponds to the negative branch (ϵ = -1) of the Friedmann equation when the Hubble radius is much smaller than the crossover length in 4D and 5D regimes. We show that for different values of the cosmological constant on a brane, λ, phase transition occurs and results in decreasing the effective temperature of the quark-gluon plasma and of the hadronic fluid. We then consider the quark-hadron transition in the smooth crossover regime at high and low temperatures and show that such a transition occurs along with decreasing the effective temperature of the quark-gluon plasma during the process of the phase transition.

Classicality of Density Perturbations in the Early Universe

1991 ◽  
pp. 39-45
Author(s):  
Robert Brandenberger ◽  
Raymond Laflamme ◽  
Milan Mijić
Keyword(s):  
Early Universe ◽  
Density Perturbations

scholarly journals Stability analysis of de Sitter solutions in models with the Gauss-Bonnet term

2019 ◽  
Vol 100 (8) ◽  
Author(s):  
Ekaterina O. Pozdeeva ◽  
Mohammad Sami ◽  
Alexey V. Toporensky ◽  
Sergey Yu. Vernov
Keyword(s):  
Stability Analysis ◽  
De Sitter ◽  
Bonnet Term
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